EEVblog Electronics Community Forum
Electronics => Metrology => Topic started by: cellularmitosis on May 15, 2017, 02:20:29 pm
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Volt nuts, unite!
Inspired by the overseas DMM calibration club thread (https://www.eevblog.com/forum/metrology/dmm-voltsohm-calibration-club-anyone-interested/), I'd like for us to organize a US-based club.
The most valuable aspect of a reference is its history. As Conrad Hoffman has said, "I'd rather have an ancient reference with a lot of history, than a brand new one with zero history!" [1 (https://www.eevblog.com/forum/metrology/old-fashioned-zener-10v-reference/msg1139452/#msg1139452)]. I'd love to see a few references which develop a thorough history by being shipped to many forum members over the course of years.
I can't claim to bring much to the table myself -- I'm more of an aspiring volt-nut. I have a 4.5, 5.5, ,and 6.5-digit meter (UT61E, HP 3478A, Keithley 196), and a couple of pre-made voltage references (a Geller Labs SVR-T and a PentaRef). Still working on getting all of these devices to datalog to a computer :)
I'd also like to encourage the creation of simple (https://www.eevblog.com/forum/metrology/old-fashioned-zener-10v-reference/) hand-made (https://www.eevblog.com/forum/metrology/lt1021cmh-based-mini-reference/) references among the group as well. I've got a handful of LM399's on hand, am in the process of building a small peltier oven to measure tempco's, and have a few of the cheap AD587 boards from ebay on order, just for kicks.
I don't want this club to be exclusionary in any way. If you'd like one of the roving references to pay you a visit and you can post some measurements to this thread, you're in the club.
I'd be happy to maintain a github page or two with all of the csv files of data, etc. I'm a programmer by trade, so I'm happy to help with any sort of python scripting for logging or analyzing data, plotting, etc.
Who's interested?
To get the ball rolling, my current offer is this: If you'd like to take some measurements of my Geller Labs reference, I'll pay for shipping (both ways).
Other members, please feel free to chime in with what you can bring to the club and how you'd like to participate!
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(reserved)
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Count me in. I've got (2) 3458As, DMM7510, K2010, (2) 731Bs, 731A, and a variety of other stuff laying around.
Only my 7510/2010 have recent cals, both of my 3458As are rebuilds and cal'ed off my unknown 731B. I REALLY need to get about half my stuff to @CalMachine's for cal, this will happen very soon.
EDIT:
Plus I've got (3) KX boards that have been burning in for the past few months.
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Interested. Just built a standard resistance box of decent quality I could pass around. Planning on building a KX LTZ1000 reference soon and adding a 34465a or maybe even a 34470a to the shop.
Edit, new 34465a just delivered.
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Haven't done any reference stuff in years, but I keep my three 731s and a Analogic 8200 tuned up. (What's inside a 8200? Ha, an LM399!) They were last calibrated over a decade ago, but still agree within a few ppm. What I need is a customer willing to pay for a cal on one of the 731s, but so far no luck. Peoples interest in extreme accuracy has faded in our digital world.
My best meter is an ancient HP 3455 6.5 digit that also has very low drift. For inter-comparisons I've got a Fluke 845. I can also scale, having several KVDs and a Fluke 752 divider. Anyway, count me in for any kind of round robin measurements.
BTW, if anybody wants a traveling capacitance reference added in, I've got some very stable high value C0G caps and a GR1615 bridge.
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I'm in! :-+ :-DMM :-BROKE :-/O :scared:
In my home lab I have got a Datron 1082 7.5 Digit meter, Keithley 237 HV SMU, Lecroy LC584AL Scope, Fluke 81 FGen, and a GR DAS-47AL Voltage Reference. I've got 1 KX board built, and plan on building the other one here in the next few days. I will also have my own designs and projects to contribute in the future.
I've also got a fully accredited cal lab available to me.
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Would like to participate!
I have a host of five volt references that I have been playing with: MAX6530, LTC6655B-5LS8 (4), LT6654, MAX6126, ADR4550, ADR450. Current favorite is the 6655B which seems best for long term drift. Would like to calibrate some of these. I'm interested in averaging one or more to create a more stable reference. Possibly an ovenized reference.
Have a calibratory D105-5 supposedly = 4.9999971 volts at 19.4 degrees! Hmmm, bought this before knowing about thread at eevblog.
Keithley 2015 6.5 digit meter, on 24x7. Seems quite stable, would like to know how stable.
Also, a HaoQiXin LRC cal box. Some miscellaneous reference capacitors and a 0.1% UT822C LCR meter.
Thanks, Randy
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Count me in as well. I have a 8842A Fluke 5 1/2 digit meter, Keithley 2015 6 1/2 and the Fluke 8845A 6 1/2. I also have the DMMcheck plus (It's out of cal now) reference as well as one of those cheap chinese AD584-M (2).
I am only really just now getting into high resolution measurements, up until this point I was just happy making sure my collection of handhelds (bunch of vintage and modern Flukes) were in spec. Recently I was doing some zener effect characterization and I find I really need to explore this field more. It seems like a lot of fun.
I am on a lookout for a 7 1/2 or an 8 1/2 meter as well as building Tin's KX reference, or whatever other reference we decide to share.
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I think I'm in. Don't really have the volt-nut disease but some of the symptoms are coming to the fore. I have several 3468, a couple of 3478, 3456 and others and would like to be able to evaluate their accuracy.
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I'm in, but like some others I can't contribute measurements that are comparable with yours. The best equipment I have are ~ 5.5 digit Keithley 197s.
I humbly suggest you alter your goals to carve out a well-detailed place for people who can benefit from but not strongly contribute to the roving calibration devices. Perhaps those who can benefit from but not contribute to, can pay for shipping to and from someone who can contribute.
For example, the mail path might look like:
- A 7.5 digit measurer reports results, contributing and thus not paying for shipping.
- A 5.5 digit calibrator reports results (for posterity only), pays for shipping from and to the next person.
- A 8.5 digit measurer reports results, contributing and thus not paying...
- A 6.5 digit calibrator calibrates, and pays for two ways of shipping...
In this way, those of us without the ability to contribute to a high reliability history of the unit can contribute to the history: by using and forwarding the device.
Or maybe this is a horrible idea, what do I know.
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:-+ Wonderful! Thanks everyone for replying.
CalMachine: I've just been made aware of your generous calibration service offer -- needless to say, you'll soon be receiving some business from me :)
technogeeky: That's a very considerate proposal, but I'm more interested in general participation and enthusiasm than the value of each member's contribution. After all, why would anyone with an 8.5 digit meter "waste their time" with me? If they are willing to extend a hand to the 6.5-digit guys, I'm happy to extend a hand to the 5.5-digit fellows. I've learned so much from this community over the past few years, I have no qualms with sponsoring some shipping in order to give back to it.
Speaking of shipping... I need to figure out a solution there (USPS flat rate? Parcel post? Perhaps I can keep it under 13 ounces and use First Class?). PM me if you have any experience or tips on that front.
I'll start sending out some PM's to coordinate things this evening. Thanks again everyone for responding!
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I am in, and will help where possible. The list of my equipment is in my signature.
My short list of in-cal instruments
Qty 2 Fluke 731B
DMM7510
Fluke 5450A
Home-made 100M, 10G, 100G knock-offs of KE5155
I did a calibration of my 236 a year or so ago. I calibrated and adjusted it against a much better calibrated current source.
I would be willing to ship the high value resistors around but not any of the other calibrated gear. The resistors were calibrated at 10V and that is how they should be used. Its convenient for using them with the 731Bs.
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CalMachine: I've just been made aware of your generous calibration service offer -- needless to say, you'll soon be receiving some business from me :)
Definitely! Feel free to send me a PM if you have any questions.
Speaking of shipping... I need to figure out a solution there (USPS flat rate? Parcel post? Perhaps I can keep it under 13 ounces and use First Class?). PM me if you have any experience or tips on that front.
I'll start sending out some PM's to coordinate things this evening. Thanks again everyone for responding!
What are you trying to ship at 13 ounces or less? Most test gear is going to be decently heavy to the point where you either need to know how to pack it properly, to avoid damage in shipping... or strap the units in their boxes to a pallet and ship it freight (more expensive by exponentially more safe for the equipment)
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I am not interested in being responsible someone else's actual test gear. A travelling reference is what I was thinking of. I think at least some others are of that inclination. I know some of those can be large and heavy, but some of those under discussion are very light and portable.
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I'll play! I'd love to check the accuracy of my Keithley 196 6.5 digit meter!
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There's no reason a decent voltage reference has to be large or heavy. I'd also like to include one or more standard capacitors and resistors that I can supply, which should also be small. Just guessing, everything should fit in less than a cubic foot and ship USPS or FedEx ground for under $25.
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I guess I was thinking more along the lines of test equipment and not small prototypes. I do apologize!
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Ok! Here's the route I've planned for my little SVR-T to go on it's journey!
Still arranging the shipping details (prepaid shipping labels, etc).
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@cellularmitosis: Just saw the thread. Thanks for getting it started. This is a great turnout! More than I was expecting for the kickoff.
I have two calibrated meters, but they're handhelds: U1252B @ 50,000 counts and U1282A @ 60,000 counts. Not sure how useful they'll be in adding to the reference's data history as compared to the higher-res equipment others have.
For bench DMMs, I have several 6.5-digit ones (Keithley 196, Keithley 2700, Agilent 34401A, Agilent 34410A), but they don't have recent calibrations.
Since I don't have experience with voltage standards, calibration, etc., this'll be a new adventure and I look forward to participating, learning, and contributing what I can. Plus, it'll be interesting to see how far off my uncalibrated equipment has gotten.
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That's odd, no voltnuts in the middle of the country.
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That's odd, no voltnuts in the middle of the country.
This is the time of year that farmers watch the corn grow.
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That's odd, no voltnuts in the middle of the country.
Fringe lunatics.
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Volt nuts, unite!
Inspired by the overseas DMM calibration club thread (https://www.eevblog.com/forum/metrology/dmm-voltsohm-calibration-club-anyone-interested/), I'd like for us to organize a US-based club.
The most valuable aspect of a reference is its history. As Conrad Hoffman has said, "I'd rather have an ancient reference with a lot of history, than a brand new one with zero history!" [1 (https://www.eevblog.com/forum/metrology/old-fashioned-zener-10v-reference/msg1139452/#msg1139452)]. I'd love to see a few references which develop a thorough history by being shipped to many forum members over the course of years.
I can't claim to bring much to the table myself -- I'm more of an aspiring volt-nut. I have a 4.5, 5.5, ,and 6.5-digit meter (UT61E, HP 3478A, Keithley 196), and a couple of pre-made voltage references (a Geller Labs SVR-T and a PentaRef). Still working on getting all of these devices to datalog to a computer :)
I'd also like to encourage the creation of simple (https://www.eevblog.com/forum/metrology/old-fashioned-zener-10v-reference/) hand-made (https://www.eevblog.com/forum/metrology/lt1021cmh-based-mini-reference/) references among the group as well. I've got a handful of LM399's on hand, am in the process of building a small peltier oven to measure tempco's, and have a few of the cheap AD587 boards from ebay on order, just for kicks.
I don't want this club to be exclusionary in any way. If you'd like one of the roving references to pay you a visit and you can post some measurements to this thread, you're in the club.
I'd be happy to maintain a github page or two with all of the csv files of data, etc. I'm a programmer by trade, so I'm happy to help with any sort of python scripting for logging or analyzing data, plotting, etc.
Who's interested?
To get the ball rolling, my current offer is this: If you'd like to take some measurements of my Geller Labs reference, I'll pay for shipping (both ways).
Other members, please feel free to chime in with what you can bring to the club and how you'd like to participate!
Way-to-go @cellularmitosis. What a response in such a short time!. I suggest you or someone in your group put together a simple set of measurement instructions so that everyone does it the same way and you end up with more meaningful results. Things such as temperature, humidity, air drafts, equipment warm-up times, types of connectors, etc, etc can and do affect the outcome. Also, the number of power-line-cycles or averaging maths may be beneficial. All this is second nature to voltnuts but may not be obvious to novices.
enut11 (Australia).
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Thanks enut! Great ideas!
Yeah, I actually just got in a couple of BME280 and Si7021 boards for measuring the lab temperature and humidity. My intention was to include those sensors with the voltage standard, so that everyone was using the same environmental sensors when taking measurements. However, I'm not sure I'll have time to get that working before I mail out the SVR-T, at least for this first round!
Similarly, I also have a couple of pomona hook-grabbers on order as well, with the idea that I could include the cabling in the setup. I've weighed similar cables and I think I should be able to fit everything in under 13 ounces, which will keep the shipping cheap.
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Hello,
Why not use a simple passive PT1000 or 10K NTC which can be measured in the Ohms range?
Or do you want to deliver a unit which can be read out by USB/RS232?
With best regards
Andreas
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I've probably got a platinum RTD I could throw in.
Cabling is important and I'd suggest untinned copper wire with no connectors. Measuring with a meter can be useful, but since everything in my lab is calibrated to my voltage standards anyway, I'm going to measure the difference with a Fluke 845, giving me far more effective digits (though my reference hasn't been measured in forever) than if I used my meter.
Hopefully we'll loop the package around more than once.
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I'd also like to encourage the creation of simple (https://www.eevblog.com/forum/metrology/old-fashioned-zener-10v-reference/) hand-made (https://www.eevblog.com/forum/metrology/lt1021cmh-based-mini-reference/) references among the group as well.
cellular,
Do you think Conrad's reference (linked as the 'simple' one above) is a good starting point to try my hand at building a reference?
I have some 2DW232 & 233 parts ordered thru Technix - I assume I could use those in this circuit?
I also looked at Julian's thread which looked very promising.
Just trying to find my feet here as I am a noob.
Thanks, Iain
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The reference I posted performs decently but isn't the equal of various others discussed here. IMO, it's still pretty good and the real value of it is to teach you the basics of how most compensated references work, get some experience with zeroing in on the minimum TC point and just get comfortable with the topic. If you want to do it for near zero money, substitute the compensated zener diode with a plain cheap zener in series with a regular diode.
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to teach you the basics of how most compensated references work
Sounds ideal for me to try, thanks
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Andreas: yes, I was hoping for the simplicity of USB data logging, at least for temperature.
iainwhite: I'm just a noob myself -- I think Conrad's circuit with a 2DW232 would be an ideal place to start!
Conrad: Indeed, cabling is critical, as I am discovering this evening!
My "mailer" cardboard boxes arrived today, so I thought I'd take some measurements with my Keithley 196 to decide which cables I should include with the reference, but my results were disappointingly inconsistent.
I've tried a bunch of cabling variations and am getting different readings. More importantly, the readings wander around by as much as 150uV, seemingly just from getting up and walking around the room.
I think I have an idea of what the problem is: I stuck a temperature probe directly into the Ohms sense jack and it read over 105F. Can you say "thermal gradient"?
Across all the various setups I tried, the overall span of readings went from around 10.00104 V to around 10.00150 V.
Setups I tried included:
- Cheap Chinese mini-pincer to banana jack: https://www.amazon.com/gp/product/B00O9WGHQ6/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1 (https://www.amazon.com/gp/product/B00O9WGHQ6/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1)
- Mini-hook to banana cables from Frankie's ebay store (short, appear to be bare copper hooks, similar to these: http://www.ebay.com/itm/Silicone-Test-Leads-50cm-with-Sprung-Hooks-and-Banana-Plugs-1-Pair-Red-Black-/200979921195 (http://www.ebay.com/itm/Silicone-Test-Leads-50cm-with-Sprung-Hooks-and-Banana-Plugs-1-Pair-Red-Black-/200979921195))
- Banana to banana DIY cables, using pomona 6733 silicone 18AWG and cheap ebay gold plated "logico" banana jacks: http://www.ebay.com/itm/LOGICO-10-Pcs-24K-Gold-Plated-Audio-banana-plug-Speaker-Wire-Jack-Connector-/131584318536?hash=item1ea3095c48:g:GEoAAOSwt5hYZG0X (http://www.ebay.com/itm/LOGICO-10-Pcs-24K-Gold-Plated-Audio-banana-plug-Speaker-Wire-Jack-Connector-/131584318536?hash=item1ea3095c48:g:GEoAAOSwt5hYZG0X)
- Banana to mini-hook DIY cables, using pomona 6733 wire, pomona 4555 mini-hooks, and "logico" banana jacks
- Banana to mini-hook DIY cables, using CAT5 (stranded), pomona 4555 mini-hooks, and Cinch solutions 108-0753-001 banana plugs https://www.digikey.com/product-detail/en/cinch-connectivity-solutions-johnson/108-0753-001/J149-ND/5927 (https://www.digikey.com/product-detail/en/cinch-connectivity-solutions-johnson/108-0753-001/J149-ND/5927)
I filed down one of the "logico" jacks and surprise! They do not appear to be copper (the body definitely isn't -- it shines like steel after filing off the plating. the springs miiiiight be some sort of really light looking copper alloy).
The Cinch banana plugs I salvaged from from a defunct banana DMM breakout project I worked on a while ago. They are brass with nickel-silver springs: http://www.belfuse.com/resources/Johnson/productinformation/pi-108-0753-001.pdf (http://www.belfuse.com/resources/Johnson/productinformation/pi-108-0753-001.pdf)
I'm definitely open to advice here, but I suspect I'm fighting an uphill battle here -- a 105F to 75F gradient across my cables is just asking for trouble.
I think I'll go ahead and mail out the reference with some solid CAT5, the pomona mini-grabbers, and the screw-banana plugs.
(I really, really need to get GPIB up and running. Trying to describe the behavior of a DMM using sentences just doesn't cut it.)
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(argh, forgot the forum doesn't honor EXIF rotation tags on photos, d'oh!)
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Placing an ice cube on one of the banana plugs brings the reading down to 10.00084 V (about a 400uV drop).
(edit: oops, attached the wrong photo)
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I think you need to open up your Keithley dmm. I cannot think of anything that should cause it to get that warm. Unless they use the front panel as a heat sink :-DD
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Yeah, that's way too warm for precision work. I've had very consistent results with un-tinned solid copper phone wire. The stuff they sell here as "bell wire" is similar and works well. Every time I add a connector of any type, including copper alligator clips, errors start building up. Thus, I just clean the ends of the wires with Scotchbrite and screw them under the banana jacks. If the meter only has push-in banana jacks, you'll have to attach something and keep them at the same temperature. IMO, confidence at the 1 ppm level isn't going to happen with plated connectors.
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Thanks for the feedback, guys. This morning (after the 196 was turned off all night, and lab temp down to 71.0F), I removed the top cover and powered it up. Initial reading was 10.00031, then climbed to around 35 to 45 within the first minute. That's 1,000uV down from where I was last night! 20 minutes later it is wandering around 54 to 62 (edit: just checked on my lunch break and it is around 10.00072 to 78 V at 73.1F lab temp).
I'll get the SVR-T shipped out within the next day or two, and while it is in transit I'll start another thread for investigation / repair of the 196. Hopefully, by the time the SVR-T returns to Austin, I'll have a more stable and GPIB enabled setup :)
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That's a very peculiar temp gradient, indeed. Looking forward to the repair and what may be causing the issue.
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Coming your way, Muxr!
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Good stuff, thank you cellularmitosis!
I can measure with my 2015 Kei and my 8845A Fluke and report the figures, and send it along. As far as I know neither of them have been calibrated any time recently, however at least they are both surprisingly close to each other when compared to my AD584KH reference (TempCo 15 ppm/C, Long Term Stability 25 ppm/1000 Hrs), either dead on or off by a few uV depending on the measured voltage of the reference.
Will report here when I get the package.
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Finally got around to writing a script to data log and plot my measurements on the Keithley 2015. I can include this for the traveling reference as well.
This is an example of it running for about 7 hours. Summarizes max/min readings, mean and the standard deviation.
(http://i.imgur.com/2q2nkMS.png)
Also looking to datalog temperature in the future as well. Not sure how to go about it. Perhaps I just build an arduino module around SI7051 and query it over UART, that should be easy enough. If anyone has any other suggestions they are welcome.
Also I am using a very simple Python script to log data over rs232, which just saves it to a cvs file. And then another script which uses Python's Pandas and Seaborn to draw the graph. If anyone is interested I can share it (needs some cleanup still).
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I can do GPIB to some of my equipment. What's a good interval between measurements?
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I can do GPIB to some of my equipment. What's a good interval between measurements?
I am experimenting with polling once a second.
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Interested in the script. Also have a 2015 and GPIB but scpi is foreign to me. Some guidance would be helpful.
Thanks,
Randy
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Interested in the script. Also have a 2015 and GPIB but scpi is foreign to me. Some guidance would be helpful.
Thanks,
Randy
Cool, I'll clean it up and post it on github and link here (tonight or tomorrow).
I have it broken into two scripts. Logging and plotting.
Logging: is super simple.. I have one of those rs232 USB adapters.. so I just connect to it via /dev/stty device that the system recognised (this is on Mac OS, but should work on Linux just the same, perhaps even on a raspberry pi, you can also do it in Windows I am sure but I wouldn't know how). As long as you can read GPIB from Python you should be able to do the same thing.
You only really need to execute one command: serial.write(':FETCh?\r\n'), wait a bit (I wait a second) and fetch the data.
I just simply write this alongside the timestamp into a comma separated file. That's it. The added benefit is FETCh command works for any measurement you have selected on your instrument. So no need to change the script if you do Ohms, VDC, VDI.. it should all work the same. Also I believe this command is the same for all Keithley instruments and Agilent and Fluke should have similar if not identical.
The trickier part at least for me was plotting this data. But basically the second script just takes this CSV file that's been recorded or is being recorded to by the first script (can do it in real time), crunches it using Pandas statistical time series framework library and plots it with Seaborn to make it look "pretty". The end result is a .png file. This was a lot of trial and error to get the graph to exactly where I want it, but that above is the end result. I think I am just going to also add the duration delta between start data point and end datapoint to my summary before I post it.
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Oh look what just arrived.
(http://i.imgur.com/Xjtg8p8.jpg)
I am feeding it 15VDC per instructions on Geller's website and letting it warm up for an hour:
(http://i.imgur.com/xHD8xJr.png)
Then I will measure it for 24 hours or so. Post office is closed Monday, Tuesday I have meetings all day long but will be shipping it out to the next person (technogeeky) wednesday.
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THIS IS SO COOL!!!
(http://i1.kym-cdn.com/photos/images/newsfeed/000/242/631/382.gif)
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Looks great! I would love to be able to log data like that from my Keithley 196 but it only has a GPIB connection. All of the solutions I've seen have been hopelessly complex and expensive.
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vindoline, when I get GPIB working on my 196, I'll share the solution with you. Since GPIB is a 5V bus, I should be able to bit bang a solution, which means the whole solution should be less than $10.
I'm currently waiting on these boards to arrive: https://github.com/pepaslabs/atmega-gpib
Then it is just a matter of writing the firmware :)
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Muxr, I forgot to mention, if you have time, please also take some data with the temperature compensation jumper removed. Might as well!
Also, I just realized I forgot to secure the trimpot screw before mailing it out. If you have a dab of hot snot or nail polish handy, feel free to do so!
I'm also working on a simple lab temperature / humidity logging system. I have a BME280 and Si7012 breakout boards and my plan is to log to PC via a serial to USB adapter. It sounds like we are all working on similar problems! This thread will be a great place to share solutions.
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For environmental data logging I use this;
http://www.onsetcomp.com/products/data-loggers/mx1101 (http://www.onsetcomp.com/products/data-loggers/mx1101)
Not the cheapest solution but very high resolution, some really cool logging features and supper easy export of data in various formats. Native excel export can be used to overlay plots from other data.
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This is exciting, thanks for suggestions everyone:
Muxr, I forgot to mention, if you have time, please also take some data with the temperature compensation jumper removed. Might as well!
Good idea, will do!
Also, I just realized I forgot to secure the trimpot screw before mailing it out. If you have a dab of hot snot or nail polish handy, feel free to do so!
10-4
I'm also working on a simple lab temperature / humidity logging system. I have a BME280 and Si7012 breakout boards and my plan is to log to PC via a serial to USB adapter. It sounds like we are all working on similar problems! This thread will be a great place to share solutions.
Good call, humidity is also important.
As to the results so far. Looks like I am influencing the results somehow.
(http://i.imgur.com/hQZfgyX.png)
The reference is on the other side of my desk where I use my computer. I went to bed about 3am.. you can see a slight rise and a pretty uniform trend after that.. so my presence looks to be interfering somehow. Also I have no clue what those spikes are about. That was just around the time I returned back to my office. Perhaps EMI interference.
The unit is powered of my linear E3611A PSU.. I am going to go out and buy me a box of Royal Danish.. empty the cookies and ground it.. place the unit inside of it (after I apply nail polish to the trimpot) and repeat the test. See if I can minimize the environmental interference.
In either case, this thing is looking much better than my cheapo AD584KH reference.. and it's great to be able to log and plot this data (the script is coming today.. I just finished adding a few more features as you see in the summary section).
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I've posted the capture and plotting script on github.. https://github.com/sirmo/muxrplot
All the install and usage instructions are there as well. Let me know if you run into any issues.
edit: I should also add, for the folks on GPIB, you would need to modify this function only to use GPIB instead:
https://github.com/sirmo/muxrplot/blob/master/mplot/logger.py#L94
I can look into adding GPIB functionality as well.
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Thanks Muxr, I'm no programmer, but this looks like I could make it work. The major hurdle for me is going to be on the hardware side.
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Thanks Muxr, I'm no programmer, but this looks like I could make it work. The major hurdle for me is going to be on the hardware side.
No problem vindoline! I actually made a dedicated thread for the script, so feel free to ask questions there, (so we don't derail this topic). https://www.eevblog.com/forum/metrology/mplot-logging-and-plotting-script-for-long-term-measurements/ (https://www.eevblog.com/forum/metrology/mplot-logging-and-plotting-script-for-long-term-measurements/)
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(http://i.imgur.com/I1CkcpJ.png)
I did another 15hour run. I am somehow introducing some significant noise when I am in the office. The grounded Royal Dansk box has helped with big spikes, but there is still a good amount of other noise.
Perhaps I am introducing noise to the Kei2015 or my PSU. Perhaps it's my computer monitors adding noise?
After I ship out the unit I will do some base level measurements of the noise floor with just the two probe leads connected. I also have some BNC couplings on order to improve the shielding.
edit: changed the probes, using the red and black twisted pair that came with the reference. The meter is looking more stable, so hopefully this solves the issue.
edit2:
ok things are looking much much better with the provided red and black twisted pair:
(http://i.imgur.com/zRx69cA.png)
Standard deviation is less than 3 uV, which is really good at this stage. With old probes it was over 10 uV half hour in. Also the mean is looking much closer to where it was calibrated. I will let this one run for about 12 hours and then repeat with the heater (jumper) off.
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Very interesting! Those red/black probes use high-quality pomona grabbers on one end, but the banana jack ends are just cheap ebay plugs.
In the above graph where there is a quiet section in the middle, was that when you put the reference inside of the tin? Or was that when you left the room?
Have you done a comparison of inside / outside the tin?
On my end, I finally managed to get a more reasonable result with my Keithley 196 and a few LM399's I've been playing around with. Previously, if I took three steps to the side, the value would climb by about 40 counts, and then come back down if I moved to stand directly in front of the meter again.
I noticed that the reading jumped if I connected an oscilloscope lead to the board (in fact, just connecting the ground pin changed the value), so I suspected an EMI problem. However, putting the board inside an aluminum caldero didn't seem to change this 40 count drift at all.
I was surprised to find that simply putting a 0.1uF ceramic cap directly across the (zener) output of the board has reduced that drift to 1 or 2 counts, even when it isn't shielded at all. (I was surprised because I don't see such a cap in e.g. the Keithley 196 reference schematic!). That change (combined with removing the lid of my 196, which seems to be running hot), has the output of this board staying within 1 or 2 counts all day today (from a zeroed point this morning).
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Very interesting! Those red/black probes use high-quality pomona grabbers on one end, but the banana jack ends are just cheap ebay plugs.
In the above graph where there is a quiet section in the middle, was that when you put the reference inside of the tin? Or was that when you left the room?
That whole graph is in the tin box. The one with a few giant spikes previous to that one was without the box.. so I've been using the tin box with all the subsequent graphs I posted. The quiet period in that graph you're referring to begins like 2-3 hours after I went to bed. This is why I was suspecting maybe one of my monitors was causing interference. Because that's actually how my computer's energy settings are configured:
(http://i.imgur.com/kgCVUJf.png)
So it aligns about perfectly. So I am guessing as soon as the monitors (2) went to sleep the noise stopped. And I am assuming the measuring leads from the the DMM and the tin box were picking up interference.
Now that I actually have a way to do long term logging and plotting, I can experiment and eliminate the interference. I will probably setup some of my instruments on the other side of my office at some point, for these types of experiments, and just use a Raspberry Pi to log to. But for now it looks like switching to the twisted pair leads you provided is giving me much better results.
I just checked the current progress of the test, and it looks like I got a big spike again, but overall noise is much lower as reflected by the standard deviation figure as well. 2.7 uV is the best I've gotten so far.
(http://i.imgur.com/BUMcOjj.png)
On my end, I finally managed to get a more reasonable result with my Keithley 196 and a few LM399's I've been playing around with. Previously, if I took three steps to the side, the value would climb by about 40 counts, and then come back down if I moved to stand directly in front of the meter again.
I noticed that the reading jumped if I connected an oscilloscope lead to the board (in fact, just connecting the ground pin changed the value), so I suspected an EMI problem. However, putting the board inside an aluminum caldero didn't seem to change this 40 count drift at all.
I was surprised to find that simply putting a 0.1uF ceramic cap directly across the (zener) output of the board has reduced that drift to 1 or 2 counts, even when it isn't shielded at all. (I was surprised because I don't see such a cap in e.g. the Keithley 196 reference schematic!). That change (combined with removing the lid of my 196, which seems to be running hot), has the output of this board staying within 1 or 2 counts all day today (from a zeroed point this morning).
Interesting. It will be good to see other folks do some measurements with this traveling reference and compare our findings.
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Just compared those spikes before and after the tin box and they are much lower. When you used the aluminum caldero did you ground it?
I have both my lid and the bottom part of the cookie tin box grounded with alligator clip jumpers from the tin box to one of my oscilloscope BNC connectors grounds (it's conveniently close).
Also the other thing I should mention. I have the negative port of my PSU also jumpered to earth's ground. So the actual DUT/voltage reference is grounded as well. I noticed you were powering yours of batteries, perhaps try grounding the negative lead as well.
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@technogeeky she's on her way to you.
So the final two tests (both about 17 hours long). First one is with the temperature compensation jumper on:
(http://i.imgur.com/aICtcGr.png)
And this one is with temperature compensation off (I even tried using slow measurement mode):
(http://i.imgur.com/5kftvG3.png)
You can see the number of pops or spikes is much greater. Haven't isolated those yet.. could be my instrument, environmental interference or the reference itself.. will be interesting to see more results.
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@technogeeky she's on her way to you.
So the final two tests (both about 17 hours long).
You can see the number of pops or spikes is much greater. Haven't isolated those yet.. could be my instrument, environmental interference or the reference itself.. will be interesting to see more results.
Spikes excluded, the drift is not much different on these two graphs.
Cheers
Alex
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If I am not too late, I also would like to participate.
I got a calibrated K2000 as well as K2015, 34401a, DMM check plus, two dial-a-volt standards and now repairing K2002.
I am in Northern New Jersey. Feel free to PM me.
Sent from my iPhone using Tapatalk
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@cellularmitosis: On this first go-round, is the primary goal to get lots of samples made via the members to see how the standard behaves and holds up? Is calibration of the standard taking place as well or will that happen on a future trip around the loop?
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@technogeeky she's on her way to you.
Roger.
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vindoline, when I get GPIB working on my 196, I'll share the solution with you. Since GPIB is a 5V bus, I should be able to bit bang a solution, which means the whole solution should be less than $10.
I'm currently waiting on these boards to arrive: https://github.com/pepaslabs/atmega-gpib
Then it is just a matter of writing the firmware :)
I just had a quick look at this project. Looks great! If you get this working, I'll definitely make a batch! Please keep us updated.
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nikonoid: we can probably work something out -- the reference will be working its way through jersey. I can email out a couple of updated shipping labels to stitch you in the loop.
bitseeker: well, the goals of this first round are more about getting people involved and working the kinks out of the system. Getting us all to go through the motions -- from that will emerge a set of scripts, practices, hardware, knowledge, etc. which are known-good which we can use in future rounds, with other references (hopefully many references from many forum members!). But yes, it is also about establishing the beginnings of a known history for this particular reference. My ultimate vision here is something like a small fleet of references which circle around the country every so often, which establishes a "relative" history or drift, and then occasionally sending them to someone like CalMachine to have a (paid-for) professional spot check, which ties that drift to a known value.
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I just had a quick look at this project. Looks great! If you get this working, I'll definitely make a batch! Please keep us updated.
vindoline, the boards are in! Now time to get serious about that firmware...
(I'd be happy to mail you a board for free -- I ordered like 10 of them through dirtypcb's).
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I just had a quick look at this project. Looks great! If you get this working, I'll definitely make a batch! Please keep us updated.
vindoline, the boards are in! Now time to get serious about that firmware...
(I'd be happy to mail you a board for free -- I ordered like 10 of them through dirtypcb's).
heh, I use dirtypcb's too :) Good to see their blue looks good, I usually order red. Digging the project by the way! Most of my gear has rs232 or ethernet support but I do have a few that could really use a GPIB adapter.
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Looking good! :-+
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I received the kit this weekend. I'll try to make some measurements on Monday and Tuesday and have it on its way by Wednesday.
Let me know if you want me to insert some more shipping labels, or change the next hop!
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bitseeker: well, the goals of this first round are more about getting people involved and working the kinks out of the system. Getting us all to go through the motions -- from that will emerge a set of scripts, practices, hardware, knowledge, etc. which are known-good which we can use in future rounds, with other references
...
Sounds good! Thanks again for getting this started.
vindoline, the boards are in! Now time to get serious about that firmware...
(I'd be happy to mail you a board for free -- I ordered like 10 of them through dirtypcb's).
You might give the firmware from Emanuele's Arduino GPIB project (http://egirland.blogspot.com/2014/03/arduino-uno-as-usb-to-gpib-controller.html) a try. At least it could be a good starting point.
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(http://i.imgur.com/I1CkcpJ.png)
I did another 15hour run. I am somehow introducing some significant noise when I am in the office. The grounded Royal Dansk box has helped with big spikes, but there is still a good amount of other noise.
Perhaps I am introducing noise to the Kei2015 or my PSU. Perhaps it's my computer monitors adding noise?
After I ship out the unit I will do some base level measurements of the noise floor with just the two probe leads connected. I also have some BNC couplings on order to improve the shielding.
edit: changed the probes, using the red and black twisted pair that came with the reference. The meter is looking more stable, so hopefully this solves the issue.
edit2:
ok things are looking much much better with the provided red and black twisted pair:
(http://i.imgur.com/zRx69cA.png)
Standard deviation is less than 3 uV, which is really good at this stage. With old probes it was over 10 uV half hour in. Also the mean is looking much closer to where it was calibrated. I will let this one run for about 12 hours and then repeat with the heater (jumper) off.
Does that SVR-T have a capacitor on its output? I had to use about 0.22uF to prevent an HP 3455A reading differently when the leads were swapped... and they are susceptible to RFI from cellphones too. A nice metal box, cap on the output and twisted pair from the SVR to meter should get rid of most of the noise and hopefully, the spikes.
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Does that SVR-T have a capacitor on its output? I had to use about 0.22uF to prevent an HP 3455A reading differently when the leads were swapped... and they are susceptible to RFI from cellphones too. A nice metal box, cap on the output and twisted pair from the SVR to meter should get rid of most of the noise and hopefully, the spikes.
I don't think it has a capacitor at the output. Lars here posted the schematic: https://www.eevblog.com/forum/metrology/best-out-of-the-box-10v-reference/msg1162989/#msg1162989 (https://www.eevblog.com/forum/metrology/best-out-of-the-box-10v-reference/msg1162989/#msg1162989) I didn't investigate it closely. I did eventually move to the twisted pair which helped with general noise (see the latest results: https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1222185/#msg1222185 (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1222185/#msg1222185)). The spikes were largely gone with the temperature compensation jumper on as well.
I've been characterising some AD584 references since, also an LT1021 based DMM Check Plus, and I am not getting those spikes. Overall noise and tempco was better on SVR-T though (not counting the spikes).
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I posted in the Kx thread, but thought I would post here as well--
if anyone needs a spare Kx Ref board, I have one. $17 + shipping....from OSH
https://xdevs.com/article/kx-ref/ (https://xdevs.com/article/kx-ref/)
Hope to contruct one, run it a while and then send it around in the future.
Thanks,
Randall
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If you still have it, I will take it.
Sent from my iPhone using Tapatalk
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I recently came across this development board for temperature and humidity readings.
http://www.mouser.com/ProductDetail/Texas-Instruments/HDC1010EVM/?qs=KuuZdrM3jLxa5c3Zf%2fmjNA%3d%3d (http://www.mouser.com/ProductDetail/Texas-Instruments/HDC1010EVM/?qs=KuuZdrM3jLxa5c3Zf%2fmjNA%3d%3d)
While not the most precise instrument out there, it has OK specs and ease of USB port. This could be a temp/humidity sensor to travel with voltage standard.
Does anyone have direct experience with these?
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A good suggestion.
I don't have experience with that one but note that TI has several with similar specs. This one, the 1080, has identical specs with a wider temperature range, same price:
http://www.ti.com/tool/hdc1080evm (http://www.ti.com/tool/hdc1080evm)
It's also $29 at digikey or the TI store. Datasheet mentions exporting data as a CSV which is universal, but primitive. The problem then might be aligning the time axis, i.e. making sure that the temperature time reading is correctly aligned with your GPIB time, if that makes sense.
Regardless, the suggestion of putting a (small) usb circuit in the mailing for measuring temp&humidity (T&H?) is a good one.
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Agreed, that would be a great thing to have. As for time alignment, hopefully the temp and humidity aren't changing very fast and anything better than a minute would probably be OK.
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The voltage reference is on the way to the next hop. Unfortunately, my two 220,000 count multimeters couldn't be repaired in time (and I couldn't justify holding the voltage reference any longer)... so I didn't get much benefit from it other than to confirm a few handhelds.
Thanks for the opportunity though!
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The voltage reference is on the way to the next hop. Unfortunately, my two 220,000 count multimeters couldn't be repaired in time (and I couldn't justify holding the voltage reference any longer)... so I didn't get much benefit from it other than to confirm a few handhelds.
Thanks for the opportunity though!
No worries, thanks for participating!
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Gents,
I've made some progress on a "lab logger" -- a little board which logs the ambient temperature and relative humidity of your lab.
The idea is to have an Si7021 + ATtiny85 + FTDI chip on a board small enough that it can be shipped cheaply along with any references. Plug it via USB cable, start the script, and you're capturing temp + humidity in a CSV file.
Prototype stage 1 was getting this to work with an Arduino (an ATmega 328), using the Arduino's built-in USB-serial converter. I got that working last week.
Prototype stage 2 was getting this to work using an ATtiny85, using an FTDI FT230X for USB. I've just gotten that working today.
The next step is to design a little board for it.
Anyway, just wanted to share the progress :)
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Looking good CM, one question though. Is the plan for this to be a stand alone solution, or do we need a computer tethered to dump the data to? It seems to me that it would be ideal if we could capture the data to an sd card or some other form of local storage.
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I assumed it was to be used with a PC. If you're logging the voltage reference measurements to a PC, then it's easy to correlate that data with the temperature and humidity using the PC's clock.
If your DMM has a built-in real-time clock (none of mine do) and onboard logging capability, then the temp/humidity board would need an RTC as well. From an earlier post, fine synchronization between the devices isn't necessary, but you'd probably want them to be roughly within the same minute.
Was there an idea earlier about using a Raspberry Pi to do all the logging?
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I assumed it was to be used with a PC. If you're logging the voltage reference measurements to a PC, then it's easy to correlate that data with the temperature and humidity using the PC's clock.
If your DMM has a built-in real-time clock (none of mine do) and onboard logging capability, then the temp/humidity board would need an RTC as well. From an earlier post, fine synchronization between the devices isn't necessary, but you'd probably want them to be roughly within the same minute.
Was there an idea earlier about using a Raspberry Pi to do all the logging?
I would imagine you would collect the data from the sensor the same way you would from the DMM.. the host collecting the data would be responsible for logging the timestamp, at the same time you sample the USB serial device for each. Whether it be <GPIB->USB_serial> or <temp_sensor->USB_serial>, the principle is the same.
Temp/humidity doesn't move that much, but if synchronization is critical you can record separate timestamps for both temp and DMM intervals.. library like Pandas (like the one I used in the script I shared: https://www.eevblog.com/forum/metrology/mplot-logging-and-plotting-script-for-long-term-measurements/ (https://www.eevblog.com/forum/metrology/mplot-logging-and-plotting-script-for-long-term-measurements/)) is smart enough to interpolate the two measurements.
Regarding the Raspberry Pi I did something similar today as well for my lab. I am planning on using this little Rpi 2 (I had laying around) as a sort of a sampling concentrator for 2-3 of my bench DMMs. I also hooked up one of those Bosch BM280 temp/humidity/pressure sensors to it so that I can measure the ambient temp/humidity/pressure.
(http://i.imgur.com/u7dX0Mg.jpg)
(http://i.imgur.com/VgQmbg8.png)
edit: what it looks like with all the data plugged in:
(http://i.imgur.com/AvOXWJk.png)
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I have been using my BME280 in a similar way. It communicates via telnet and can support multiple connections.
To mount my sensor near the equipment, I used a spare SD card holder and a spare ps/2 extension cable. This way I can disconnect it and not worry about reconnecting it wrong. The locking tab can be used with a zip tie to hang it out of the way.
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So much engineering :) I have mine just dangling around at Pi3 ;D
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Too much stuff to risk shorting out one of my RPi. That would leave me with a half dozen or so...
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The Gellar labs reference has arrived, is powered and is warming up. It has a very pronounced warmup signature. After it has been on for a couple of hours, I will post the graph and some numbers.
My DMM7510 was warmed up 12+ hours before powering the reference.
The reference is inside a metal enclosure but the front panel is not installed. After warmup, I will install the front panel.
cheers!
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Too much stuff to risk shorting out one of my RPi. That would leave me with a half dozen or so...
That's a good point. Thanks for sharing the tip with the SD card sleeve, will do something similar as well!
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I have been using my BME280 in a similar way. It communicates via telnet and can support multiple connections.
By the way, instead of having to leverage telnet you can run a simple Restful service with Flask. At least this is what I did, this is the simple server script:
from flask import Flask
from flask_restful import Resource, Api
import bme280
app = Flask(__name__)
api = Api(app)
def convert_to_f(c):
return ((c * 9)/5) + 32
class Banner(Resource):
def get(self):
return "/bme280 returns a json dict with metrics"
class Bme280(Resource):
def _get_metrics(self):
temperature, pressure, humidity = bme280.readBME280All()
return {'temperature_c': temperature,
'temperature_f': convert_to_f(temperature),
'pressure': pressure,
'humidity': humidity}
def get(self):
return self._get_metrics()
api.add_resource(Banner, '/')
api.add_resource(Bme280, '/bme280')
if __name__ == '__main__':
app.run(debug=True, host='0.0.0.0')
"import bme280" being the following module: https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/python/bme280.py (https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/python/bme280.py)
You just run it with: "sudo python server.py" where server.py is the name of the script I pasted.
Consuming the service becomes trivial (this is from a different machine on my network):
(http://i.imgur.com/2kCeLtN.png)
For added security, you could wrap it in ssh or configure Flask to use https.
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I have a very inexpensive UGsimple GPIB to USB card. It comes with VBA and Visual Studio compatible libraries.
Would anyone have a suggestions for logging with that card under Windows environment.
I am using HP 34401a, Keithley 2000 and Keithley 2002.
Even if you do not have it for Windows, any logging script for these would be great, especially scripts that were already used in this thread, so my results are consistent. Thanks.
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I have a very inexpensive UGsimple GPIB to USB card. It comes with VBA and Visual Studio compatible libraries.
Would anyone have a suggestions for logging with that card under Windows environment.
I am using HP 34401a, Keithley 2000 and Keithley 2002.
Even if you do not have it for Windows, any logging script for these would be great, especially scripts that were already used in this thread, so my results are consistent. Thanks.
There is a Linux driver and a python script for that device: https://github.com/haata/ugsimple-usb-gpib
I am actually going to order one and see if I can make it work with an rpi.. because I do have a few GPIB only devices I would like to start using for data acquisition.
Again I prefer Linux here because I can log all the data on a "remote" raspberry pi and just access it wirelessly. Or I can turn the Rpi into a wireless REST gateway which is easy to query from scripts like above. Will let you know how it goes.. with some instructions if I get it working.
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I have a UG plus and was trying to set up to log various meters. So far no success. The card hangs anytime I try to use one of the libraries, and hangs frequently with the provided simple GUI. I have given up and ordered a NI USB-GPIP-HS card which should arrive any day now.
I am not sure what is wrong with the UG, but others have had problems and I decided I had other fish to fry. A brief look inside showed three ICs, two buffers and a totally unmarked device.
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Regarding the Raspberry Pi I did something similar today as well for my lab. I am planning on using this little Rpi 2 (I had laying around) as a sort of a sampling concentrator for 2-3 of my bench DMMs. I also hooked up one of those Bosch BM280 temp/humidity/pressure sensors to it so that I can measure the ambient temp/humidity/pressure.
This is exactly what I would like to do - get my GPIB only Keithley 196 connected to a Raspberry Pi for datalogging. Then I could access the data from my Mac for plotting, analysis, etc. I need to figure out the physical hardware layer (GPIB -> RPi) as well as the software aspect. I am not a programmer though! I think CellularMitosis is working on a GPIB to USB adapter board. I'm sure he'll report on his progress when he has a chance.
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I took the cheap/easy way out and bought a Prologix USB/GPIB box some years ago. Works well for what I code, but is not software compatible with any other solution like NI.
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UGSimple USB to GPIB Controller is only $29, if I can get it working I will share my findings. If not Cellularmitosis is also working on an Atmega solution that's worth a try. I am sure we'll come up with an affordable enough solution.
On a side note I should in the future also be able to provide additional data from a new tool in my voltnut inflicted lab. I saw a decent deal on a pretty beat up 3458A so I decided to bite the bullet. So far I haven't found any issues other than cosmetic ones, but will have to run a longer test to determine drift etc.. I can already tell I will need to replace the fan, as it does have a bit of a high pitch sound to it.
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@Muxr
Thanks for the sample code. I only chose telnet as an emulation of the Fluke 1620. Moving forward, I would look at other ways to communicate with it. The 1620 may be accurate, but its implementation is horrible. Dropped characters from the result string made me use the RPi.
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On a side note I should in the future also be able to provide additional data from a new tool in my voltnut inflicted lab. I saw a decent deal on a pretty beat up 3458A so I decided to bite the bullet.
That one looks like it's been down the road a few times, on the back of the truck. Hopefully it's OK inside. That'll be nice to have in the loop, for sure.
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On a side note I should in the future also be able to provide additional data from a new tool in my voltnut inflicted lab. I saw a decent deal on a pretty beat up 3458A so I decided to bite the bullet.
That one looks like it's been down the road a few times, on the back of the truck. Hopefully it's OK inside. That'll be nice to have in the loop, for sure.
Aye it's really been through a ringer, probably a dumpster dive but so far it behaves alright. I have not found any issues with it yet in terms of functionality, but will need to hook up GPIB and a decent set of references before I can tell if it has drift issues. It looks in agreement with my Keithley 2015 at least. Passed the self tests and went through ACAL once it warmed up without issues.
The guard post was also yanked. Man who does this to an instrument? On the other hand, it's the reason I got it for a decent price, so I can't really complain too much. Here is another picture: it has a big gash by the number keypad. Maybe I find a new face panel on Ebay in the future.
(http://i.imgur.com/Snb0wBw.jpg)
The screen is actually surprisingly bright, better than all my Keithley and Fluke 8845A/8846A DMMs I have.
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Good find on the meter. Depending on how comfortable you are moving the front and rear posts around you could get the front ones looking new again.
I typically replace the front panel if only because the mounting screws behind the front cover are broken because of impacts to the terminals.
Also, the front rear switch might need replacing depending on its age.
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Good find on the meter. Depending on how comfortable you are moving the front and rear posts around you could get the front ones looking new again.
I typically replace the front panel if only because the mounting screws behind the front cover are broken because of impacts to the terminals.
Also, the front rear switch might need replacing depending on its age.
Once I do some tests and issue finding.. will look into doing some preventative maintenance.. first order will probably be the NVRAM calibration data backup (I hear it can be done via GPIB). Also will need to replace the fan as well. Thanks for the tips on the other issues.
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Muxr
I saw a decent deal on a pretty beat up 3458A so I decided to bite the bullet.
From now on, it's only going downhill, trust me ;)
You can get brand new front panel plastic from the Keysight, MPN: 03458-40212. It's relatively cheap (100$) + 30$ for the display window (which says Key-sigh on it :).
Binding posts block is $230 however. :-/O
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Congrats on the meter! Fantastic! :clap:
That $29 GPIB adapter sounds like a great deal, definitely the cheapest I've seen so far! I'm tempted to order one just to see if it solves my problem (I have the Galvant Industries open source GPIB board, which works with my HP 3478A, but not with my Keithley 196).
I just got the board design finished and ordered from dirtypcbs. Should be here in about 3 weeks.
I decided to throw in a button with the idea that you can use it to log a generic "event".
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Muxr
I saw a decent deal on a pretty beat up 3458A so I decided to bite the bullet.
From now on, it's only going downhill, trust me ;)
There are worse hobbies I suppose ;D
You can get brand new front panel plastic from the Keysight, MPN: 03458-40212. It's relatively cheap (100$) + 30$ for the display window (which says Key-sigh on it :).
Binding posts block is $230 however. :-/O
Thanks TiN! Will give them a call about the face panel!
Congrats on the meter! Fantastic! :clap:
That $29 GPIB adapter sounds like a great deal, definitely the cheapest I've seen so far! I'm tempted to order one just to see if it solves my problem (I have the Galvant Industries open source GPIB board, which works with my HP 3478A, but not with my Keithley 196).
I just got the board design finished and ordered from dirtypcbs. Should be here in about 3 weeks.
Thanks CM! I ordered one today, will definitely keep you guys posted if I have any luck with it once I get it.
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Here are the results of the Gellar Labs reference being monitored via DMM7510
First the graph of the voltage vs time. You can see the popcorn noise. One of the individual popcorn events is rather large.
Next, the statistics view. The average is almost exactly 10V. So, the deviation from 10V, is just about exacly the deviation from 10V of the DMM7510. That deviation is just a couple of PPM. I will dig out the calibration report of the DMM7510.
The standard deviation is 77.16 uV. This standard deviation is an order of magnitude larger than the standard deviation of my Fluse 731Bs. My conclusion is that the Gellar reference is noisier than the 731B.
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Here are the results of the Gellar Labs reference being monitored via DMM7510
...
1) Glad it got to you safely.
2) Wow, what an instrument that is!
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The stats were not posted properly. Here they are
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Great find on the meter MUXR. Just to make us really sick do mind sharing how good a deal you got?
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Great find on the meter MUXR. Just to make us really sick do mind sharing how good a deal you got?
Don't think it will make you feel sick. I think it was priced fairly. Largely as is, and pretty beat up, I talked the seller down to $2800, he accepted. It's still a lot for largely a gamble on an abused piece of gear. But at the end of the day it's a great instrument, and I really wanted to be able to evaluate drift on the references I am working on with an 8 1/2 digit meter.
Not going to lie either, it's the most expensive used item I bought on Ebay. The heart did skip a beat when I placed the order. ;)
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The stats were not posted properly. Here they are
Thanks VintageNut! Did you happen to take note of the temperature and humidity during the run? Also this was as is, with the temp. compensation jumper on?
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If you have good A3 (seems only me get very lucky with bad/dead A3 every meter I got :D), than it's very well worth the money.
Looking forward for your data plots.
Btw, any schedule you guys have for rotating standards?
Little bird tells me that I might have a voltage reference and a resistor to participate in USA club rover ::).
I might also be on short trip to Oregon next month...
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There isn't a fixed schedule that I'm aware of. We're in a loop and each person, when they're done, just ships everything to the next one in order. CM posted a neat little map (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1211533/#msg1211533) last month.
I haven't counted the posts in this thread thus far to figure out how far around it is right now (I'd guess New York or thereabouts). However, I do see what appears to be an upcoming stop in Oregon. So, I guess you could jump into the loop there by coordinating with CM or whomever is at that stop. If that timing doesn't work out, you could just send your additions from Oregon to whichever is the upcoming stop at that point in time.
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If you have good A3 (seems only me get very lucky with bad/dead A3 every meter I got :D), than it's very well worth the money.
Looking forward for your data plots.
Thanks TiN, your articles were instrumental in learning about this piece of equipment. I read about your ordeals with A3 in particular. Hopefully I get lucky. It will take me awhile to determine how drifty this unit is. I need to build some more references including a few KX LTZ1000 (which will take some time to age as well). I am also building some 1027 based ones.
Btw, any schedule you guys have for rotating standards?
There is no set schedule, so far Cellularmitosis has been kind enough to send out his SVR-T reference together with all prepaid labels for the entire loop of the trip to people who have expressed interest. I think this is a test run to see how well this works.
Maybe we should start a GoogleDocs Spreadsheet to keep track of each reference so that we can have multiple in flight.
Little bird tells me that I might have a voltage reference and a resistor to participate in USA club rover ::).
I might also be on short trip to Oregon next month...
I am in FL.. too far :( but would love to participate in measuring and plotting of one of your references. I can cover the shipping costs.
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Ok, my UGSimple arrived moments ago. With shipping it was $36 (certainly one of the cheaper GPIB solutions). It was trivial to get it working on my Raspberry Pi. http://www.ebay.com/itm/171631337518?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/171631337518?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
- I hooked it up to my HP 3458A
- cloned the python repo from here: https://github.com/haata/ugsimple-usb-gpib (https://github.com/haata/ugsimple-usb-gpib)
I just needed to install pyusb python module "sudo pip install pyusb" (if you don't have pip you can either use easy_install or just install pip first "sudo apt-get install python-pip")
There is an example script as part of the project I just modified it to use HP 3458A commands (which I must say are weird, they are different than your usual scpi gpib commands I've seen on other DMMs.)
Here is the script:
from ugsimple.GPIB import UGSimpleGPIB
if __name__ == '__main__':
# Initialize the UGSimpleGPIB USB adapter
# Requires root permissions (or add the udev rule)
mygpib = UGSimpleGPIB()
#mygpib = UGSimpleGPIB(debug_mode=True)
# Firmware / Device Information
print ( mygpib.firmware_version() )
print ( mygpib.manufacturer_id() )
print ( mygpib.series_number() )
# List Connected Devices
print( mygpib.query_devices() )
# GPIB address of the device
addy = 22
# sending the command to 3458A
mygpib.write(addy, "TARM SGL,1")
# reading from device
data = mygpib.read(addy)
print data
print ('%.08f' % float(data))
And this is what it looks like in action (I use the "watch" command here which executes the script periodically") "watch sudo python example2.py":
(http://i.imgur.com/NqmIhgW.png)
edit: I should add, I ran into a few syntax errors (on the device) while running this occasionally, so maybe this little module has some issues with synchronization. So high frequency polling is likely out of the question. But for my once a second or once every 2 seconds polling it looks like it will be sufficient enough.
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That is awkward way to say at least :)
Why not just add loop in python app like:
for cnt in range (0, 100000):
# make 100k samples
# sending the command to 3458A
mygpib.write(addy, "TARM SGL,1")
# reading from device
data = mygpib.read(addy)
print data
print ('[%d] %.08f' % (cnt, float(data)) )
I like HP 3458 protocol, it's much easier to remember DCV 100 than SCPI stuff like :SENS:VOLT:DC:RANG 100 etc :D. But SCPI has it's power, when you take existing tested app and just run on another SCPI-compatible meter, with just few minor tweaks.
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That is awkward way to say at least :)
Why not just add loop in python app like:
It's just for a quick demo, keeping it short. ;) Adding it to my plotting/logging script with a loop and error handling now.
As far as HP3458A commands go, they are just not familiar. I see your point, they do seem easy to code.
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Well , here is my spaghetti python (http://trash.xdevs.com/nvs_ltzs.py) which I use to log meters together.
This specific one reads BME280 I2C sensor locally from Pi, have classes for Keithley 2510 (unused), Keithley 2001/2002 SCPI, Keithley 182 (proprietary protocol), HP 3245A and HP 3458A.
It also logs temperature of 3458A every 100th sample and runs ACAL if temp changes more than 0.5c either direction.
Surely, python experts will puke from the code, but hey, it works for me so far :D.
Output CSV is processed by D3js on my site, to make chart like this one (https://xdevs.com/keis12/).
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Well , here is my spaghetti python (http://trash.xdevs.com/nvs_ltzs.py) which I use to log meters together.
This specific one reads BME280 I2C sensor locally from Pi, have classes for Keithley 2510 (unused), Keithley 2001/2002 SCPI, Keithley 182 (proprietary protocol), HP 3245A and HP 3458A.
It also logs temperature of 3458A every 100th sample and runs ACAL if temp changes more than 0.5c either direction.
Surely, python experts will puke from the code, but hey, it works for me so far :D.
Output CSV is processed by D3js on my site, to make chart like this one (https://xdevs.com/keis12/).
I write Python (Golang and Lua) for a living and work on some fairly large projects, which enforce some pretty strict rules in terms of code style etc (cloud applications, stuff like OpenStack).. but all the rules can get pretty annoying.. especially if you have people on the team who like to nitpick on pull requests (which we do), for personal stuff quick hacks are more fun ;) is how I feel about it. Spaghetti code is sometimes easier to follow, compared to highly abstracted and encapsulated code, which is easier to maintain but you have to understand it first.
Your graphs look really nice I must say. :-+ Thanks for sharing.
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Ok, my UGSimple arrived moments ago. With shipping it was $36 (certainly one of the cheaper GPIB solutions).
If it works well, that is a nice price. The syntax error worries me, since I want GPIB equipment to be able to log days without intervention. I am actually moving away from using my current NI-GPIB-USB with linux-gpib because of the occasional glitch. Guess you have to build some sort of error recovery mechanism (including resetting the instruments to a known state) with this. Might also that adding some delays can help if the hardware is not well designed. Obviously does not help if it is a signal integrity issue.
The software setup certainly sounds more convenient than messing with linux-gpib. Their claim about Labview setup is the usual nonsense from the small manufacturers. Yes, you can interface with it from Labview, but you can not use it through VISA, and all those instrument (e.g. IVI) drivers that are the main reason for putting up with Labview will not work either. Not that I am recommending any hobbyist with a decent programming knowledge to use Labview.
According to the listing the current version does not support binary transfers. No big deal for DMMs, but would be a limitation for some other instruments like scopes. I also expect that they are just driving the outputs with standard logic gates, not true GPIB drivers. So I expect problems at larger number of instruments and cable length: I believe proper GPIB supports up to 15 instruments and up to 20 meter of cable. This unit might become (more) unreliable with even a couple of instruments.
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Ok, my UGSimple arrived moments ago. With shipping it was $36 (certainly one of the cheaper GPIB solutions).
If it works well, that is a nice price. The syntax error worries me, since I want GPIB equipment to be able to log days without intervention. I am actually moving away from using my current NI-GPIB-USB with linux-gpib because of the occasional glitch. Guess you have to build some sort of error recovery mechanism (including resetting the instruments to a known state) with this. Might also that adding some delays can help if the hardware is not well designed. Obviously does not help if it is a signal integrity issue.
The software setup certainly sounds more convenient than messing with linux-gpib. Their claim about Labview setup is the usual nonsense from the small manufacturers. Yes, you can interface with it from Labview, but you can not use it through VISA, and all those instrument (e.g. IVI) drivers that are the main reason for putting up with Labview will not work either. Not that I am recommending any hobbyist with a decent programming knowledge to use Labview.
According to the listing the current version does not support binary transfers. No big deal for DMMs, but would be a limitation for some other instruments like scopes. I also expect that they are just driving the outputs with standard logic gates, not true GPIB drivers. So I expect problems at larger number of instruments and cable length: I believe proper GPIB supports up to 15 instruments and up to 20 meter of cable. This unit might become (more) unreliable with even a couple of instruments.
You make great points. I have run into a few syntax errors but it seems to only happen when the instrument is fresh (just reset). The driver itself which is written in python as well appears to be pretty experimental, so I might be able to fix some of these problems or at least add some error recovery/retry and perhaps push a PR to the master for the author to merge.
The biggest appeal of this unit as you said is the low price and how lightweight the software stack is.
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Only happens when the instrument is just reset. That does not sound like signal integrity to me, but more like something like insufficient time between asserting the address signal and sending the data. Hence my idea that a strategically placed delay, despite being a band-aid, makes things more stable. Unfortunately my knowledge of GPIB is not deep enough to go into more detail. I know the Prologix people spent quite a lot of time tweaking their products to work with every instrument.
Does it exhibit the same problem with instruments other than the 3458A (assuming you have those)?
The problem with retrying is that you do not know what state the instrument is in. Did it process part of the commands? Do you need to clear an error? Did it stop sampling? Hence my idea of just resetting an instrument and starting from scratch. Obviously this is something you would do in the application layer, not in the driver.
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Ok I lied when I said it only happened after a fresh reset. It happens intermittently. Now that I have it plugged into my logger/plotter I am able to tell exactly how often it occurs. The issue is much less frequent if I set the polling interval to 2 seconds. Will keep it running and tweak some settings. I have an unrelated work project to finish with a deadline next week, so won't be able to dig into this further until that's done.
For now I am just gracefully handling the errors. The good readings themselves at least aren't being impacted, from what I can tell. And I am able to get at least somewhat useful captures. But I feel like I am going to have to modify the (python) driver itself. Some cursory research also points to a potential bug in the usb.core python library that may have been resolved with a newer version. Will look into this deeper next week.
(http://rev.muxr.org/hp3458a_5v_voltage_standard_com_2.png)
edit: not a single error in the last 3 hours..
(http://i.imgur.com/j7PzMPw.gif)
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The driver itself which is written in python as well appears to be pretty experimental
I'd say that's quite an understatement. I couldn't get it to work for any but the most primitive use cases. The "programmer" of the Linux code doesn't have much or any documentation (he certainly didn't share any) and apparently lost interest after he dumped the code. I gave up on it and got me a pre-enjoyed PCI based GPIB adaptor which is supported by the Linux GPIB library.
The UGSimple hardware isn't all that great either. It doesn't follow the IEEE488 standard (doesn't use driver chips and won't be able to supply sufficient current); might work with a single modern instrument, but don't expect much more. There's cheap, as in exploiting the laborers in low wage countries, using cheap components, reducing the margin and utilizing the economy of scale and then there is cheap as in cutting corners ...
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Speaking of Linux GPIB and (earlier) Raspberry Pi, it appears that there's been discussion of using them along with an 82357 (genuine HPAK and Beiming clone). One of the recent posts, from last year, indicate it may not be too stable with NI's USB adapter.
https://www.eevblog.com/forum/reviews/using-a-raspberry-pi-with-linux-gpib-and-a-beiming-or-agilent-usb-gpib-adapter/ (https://www.eevblog.com/forum/reviews/using-a-raspberry-pi-with-linux-gpib-and-a-beiming-or-agilent-usb-gpib-adapter/)
That'd be a neat setup for logging.
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I use a few RPi and NI GPIB-USB-HS adapters. They work quite well together logging data over long periods of time. The biggest issue I have is wearing out the SD card and I eventually have to replace it 2-3 times a year. I used to have an Agilent clone and gave up on it not properly loading firmware.
I recommend spending the extra money on the NI model. Get the HS model and not the B.
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I have an UGSimple adapter and it seems to work ok with hp 34401a using their windows utility. However on Keithlies it is working sporadically at best.
Anybody had a luck using UGSimple on Keithley 2000 or 2002, perhaps using RPi3?
Sent from my iPhone using Tapatalk
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Too bad the UGSimple adapter does (currently) not appear to be sufficient even for fairly simple logging.
I had problems with the NI GPIB-USB-B hanging somewhat frequently with linux-gpib on amd64. It would require unplugging the USB cable to reset the adapter to get it to work again. Kind of sucks when it happens during an overnight logging run. Found at least one similar report on the linux-gpib mailing list: the conclusion was that it was probably some particular sequence of events that upset the GPIB-USB-B, but that it was hard to reproduce. NI seem to have given up on supporting USB devices on Linux.
So I am planning to switch to VXI-11 (ethernet) compatible interfaces (got the hardware, have to change my software). It does not need any drivers and hence should be more stable, apart from the one with corrupt EEPROM that I still have to fix :P. The old devices can only do 10 Mbit/s ethernet and will be slower, especially compared to the USB-HS, but I imagine that few people on this forum ever max out the transfer rate of GPIB. The HP E2050a can be found fairly cheap (I think I paid around $50+shipping). Other options are the Agilent E5810A and Tektronix AD007. Software support is pure python, so should be easy to maintain.
There are also the NI GPIB-ENET(/100), but it does not support VXI-11, so software support will be more complicated. You would either need whatever NI-VISA version still supports that hardware or some unmaintained Python code (https://pypi.python.org/pypi/gpib-devices/0.0.4). Not something I would rely on, but I have not tried it.
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I wouldn't quite call it useless, but it's pretty flaky. I've hacked around most of the issues and I am actually getting good captures with it on my 3458A. The driver definitely needs attention but in the absence of that these are my workarounds:
- First of all, for some reason I can't have the polling of the instrument in a python loop. I tried multiple things, like destroying objects on each iteration etc.. when you keep polling in a loop there is some residual state or a memory leak caused by the driver which causes the USB subsystem to become locked out. You basically get a USB device driver busy after a while and you are no longer able to poll. The workaround for this is to execute a system process each time you poll.. ugly and annoying but this resolved the issue, I haven't had USB device busy since I did that.
process = os.popen('/usr/bin/python ad_hoc_hp3458a.py')
list_returned = process.read().split('\n')
process.close()
return float(list_returned[-2])That basically executes the following script and converts the second to last line into float.
from ugsimple.GPIB import UGSimpleGPIB
import time
import sys
class Delay(object):
""" introduces a delay into a while loop
with a timeout
"""
def __init__(self):
self.i = 0
self.timeout = 50
def delay(self):
self.i += 1
if self.i == 1:
# no delay on the first run
return self.i
time.sleep(0.1)
if self.i > self.timeout:
sys.exit(1)
return self.i
if __name__ == '__main__':
# Initialize the UGSimpleGPIB USB adapter
# Requires root permissions (or add the udev rule)
mygpib = UGSimpleGPIB(debug_mode=False)
# List Connected Devices
print mygpib.query_devices()
# GPIB address of the device
addy = 22
data = ''
d = Delay()
# sending the command to 3458A
mygpib.write(addy, "TARM AUTO")
# reading from device
while data == '':
print d.delay()
data = mygpib.read(addy)
print 'data: {}'.format(data)
print ('%.08f' % float(data))
The notable change from the example script the python driver ships with is that I discovered that their read() function is non blocking. Which means if the instrument doesn't respond in time the result just gets abandoned. This caused a lot of missed readings in the past, and since I implemented this hack.. I have not missed a single reading.
I do still get occasional syntax errors, but the polling never gets interrupted, and the readings aren't corrupted by it. It is definitely flakey, and your mileage may vary with other instruments I haven't yet tested it with. But it is a workable solution. I am getting useful captures from it.
For instance see an attached 20hour run:
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I got back into town yesterday to find this waiting for me :-+ :
(https://www.eevblog.com/forum/metrology/usa-calibration-club/?action=dlattach;attach=325765;image)
The Keithley 196 has been powered up for over a week now, so it should be as stable as it will get. I've powered up the reference at 15.00 V with the Power Designs 4010 and let it settle for 24 hours.
(https://www.eevblog.com/forum/metrology/usa-calibration-club/?action=dlattach;attach=325767;image)
(https://www.eevblog.com/forum/metrology/usa-calibration-club/?action=dlattach;attach=325769;image)
All my data will have to be taken manually, as my GPIB solution is a work in progress... I will report back soon with some measurements, graphs, etc. and send it on it's way to the next club member!
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That's certainly a nice thing to find when getting home. ;D Looking forward to seeing how everything works out.
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I just had a quick look at this project. Looks great! If you get this working, I'll definitely make a batch! Please keep us updated.
vindoline, the boards are in! Now time to get serious about that firmware...
(I'd be happy to mail you a board for free -- I ordered like 10 of them through dirtypcb's).
Hi CellularMitosis, I've built up the board you were so kind to send. Is this board designed to be able to be programmed via the USB? I have an Arduino I can use as well. I'd like to be able to confirm that I built it up OK. That FTDI chip was the smallest thing I've ever soldered!
(https://www.eevblog.com/forum/metrology/usa-calibration-club/?action=dlattach;attach=325802;image)
No rush, but have you made any progress getting your K196 talking via GPIB yet?
Thanks again!
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Nice job for a first-timer soldering that tiny pin pitch. :clap:
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Glad the reference arrived! Nice collection of gear by the way :)
Sadly, I have had to behave like an adult quite a lot recently, and have not made much progress on the firmware. However, if you have a linux box handy, you can simply plug the USB cable in and run 'dmesg' from the command line, and you should see a message about a new FTDI device being recognized. If that works, the only untested part would be the ATmega chip, but because it is wired straight up to both the centronics connector and the FTDI chip, there's very little chance that it isn't connected.
I completely forgot to put an ICSP header on the board -- you'll have to remove the chip anytime you want to reprogram it (sorry!).
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Or remove it only once to program a bootloader in it.
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Glad the reference arrived! Nice collection of gear by the way :)
Sadly, I have had to behave like an adult quite a lot recently, and have not made much progress on the firmware. However, if you have a linux box handy, you can simply plug the USB cable in and run 'dmesg' from the command line, and you should see a message about a new FTDI device being recognized. If that works, the only untested part would be the ATmega chip, but because it is wired straight up to both the centronics connector and the FTDI chip, there's very little chance that it isn't connected.
I completely forgot to put an ICSP header on the board -- you'll have to remove the chip anytime you want to reprogram it (sorry!).
Thanks. I plugged the adapter into my Mac OS X machine and the USB adapter info showed up in the console. So it looks like a success! Like a lot of us, the gear is mostly from eBay cheap and repaired/refurbished by me.
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Or remove it only once to program a bootloader in it.
I'll give that a try!
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OK, the SVR-T is on its way to Conrad! I'll post my measurement results as soon as I have a chance to do some analysis - hopefully this weekend. Thanks for the fun!
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Posting a lookout and warming up the meter!
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Getting my act together for the arrival in Oregon I finally got GPIB logging working. After a few weeks of frustration fighting the LQ Electronics USB battle I bought a National Instruments one (under $200 on Ebay) and other than the requirement for multiple reboots during installation of the various NI drivers it has been a dream. A few minutes with EZ-GPIB and I was logging 3 voltmeters.
The attached shows about 12 hours watching a AD581 with a 1996 date code with one HP3457A and two HP3478As. Still need to rig up temperature logging as the voltage shows the long overnight drift down in temperature followed by a sudden drop as I opened the windows to the lab to let the cool morning air in. Once that is in place will decide if I need to do more for temperature compensation.
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If the tools haven't been mentioned before, I found http://www.ke5fx.com/gpib/readme.htm (http://www.ke5fx.com/gpib/readme.htm) to be very useful in my GPIB programming.
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I didn't know Prologix.exe in the GPIB Toolkit can work with "an otherwise-unsupported TCP/IP or serial adapter." I'll have to check that out.
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Had non hobby related commitments today. Some conclusions from looking at this first run.
1. There isn't enough noise on this source to allow extending the resolution of the HP3478s by averaging measurements.
2. There is enough to extend the 7.5 digits from the HP3457. Still have some work to do to see if the stability is good enough for this to translate into precision, but so far it seems promising.
Plenty of interesting things to do. Hope I get time.
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A small and mysterious box was on the dinner table when I arrived home tonight. More reports to follow! :-DMM
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Ooh, intriguing. Looking forward to the forthcoming reports. :-+
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A quick measurement shows that even though my last traceable calibration was over 13 years ago, I'm showing the standard within 3 ppm of 10V on the 3455A. The standard seems to warm up within a few minutes, compared to the rest of my equipment that takes a couple hours for good stability. I'm going to use the 845 null meter and compare the standard with my "golden" 731A. It occurs to me that I can put a DVM on the output of the 845 and do some data logging on that. Need to check the long term drift of the 845.
The big problem in my lab is temperature. It's about 20C right now. I heat with wood, and heating season is over, so it's not so easy to warm things up. Need to find a small heater and see if I can stabilize things a bit higher over the next few days. RH is controlled at 60%. Idea- I can lower the RH setting which will also heat up the room.
Do we have an idea of the tempco of the standard? Line regulation? I can check the latter easily enough.
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Unfortunately, I didn't have my temp measurement rig setup when I had it. So can't really speak on the Tempco.
SVR-T has the NTC based temperature compensation in its trim circuit, and I did notice much less temperature related drift with the jumper on.
SVR (non T version) without NTC is rated at 5 ppm / ºC.
http://www.gellerlabs.com/svr%20series.htm (http://www.gellerlabs.com/svr%20series.htm)
edit: post where I shared my measurements with trim jumper on and off: https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1222185/#msg1222185 (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1222185/#msg1222185)
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Hi, I've finally had a chance to look at the SVR-T measurements that I made last week. First off, I'm an organic chemist, not an ee - I still have a lot to learn about this metrology stuff! My good meter is an old Keithley 196 6.5 digit. The only thing I know about its calibration history is that I haven't done it! It is in nice shape and seems very stable to me. The 196 has GPIB, however I don't have an automated measurement system working yet - it's in the planning stage for now.
I powered the SVR-T at 15.00 v from a very stable and quiet Power Designs 4010 precision power source. I let everything stabilize overnight before I took any data. For the cable connection between the SVR-T and the 196 I tried the various solutions "in the box" from cellularmitosis as well as my own teflon insulated twisted pair from plenum grade Cat5e and standard RG-59 coax with Pomona BNC to banana plug adapters. I was unable to discern any difference between any of them. In the end I used the coax cable for the measurements.
What I did was each morning for 3 days I took manual readings of the K196 every 30 seconds for 15 min. I checked the lab temperature on my Fluke thermometer at the beginning and end of each run. For the third run I decided to record the temperature every 30 sec also.
Looking at the 3rd day plot with the temperature, it appears that the slight voltage drift may be correlated with the temperature fluctuation. Like Conrad, my lab is in my basement. Its temp and humidity is not well controlled and I took no measures to prevent drafts on the SVR-T. It looks like that might be a good idea.
I also took 10 min of data on day 3 with the Keithley 196 averaging filter ON. It did seem to smooth out the data somewhat, but not entirely. I'm still working on understanding how this filter works, so I didn't use it for the main part of the experiment.
Overall, the SVR-T appears to be very stable and quiet. In the time I had it up and running it's value changed less than 10 PPM.
Graphs of the data are below for your enjoyment.
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Hi, one of the other projects/interests I have is noise measurement. A while back I built up the "Curiously Low Noise Amplifier" from Charles Wenzel's website (http://www.techlib.com/electronics/audioamps.html#curiously%20low%20noise (http://www.techlib.com/electronics/audioamps.html#curiously%20low%20noise)). This is a JFET front end low noise preamp with a gain of x100. The output is measured on an HP3400A thermally responding true RMS AC voltmeter using a simple RC filter to give an equivalent noise bandwidth of 500 kHz. The SVR-T measured about 4 mV rms which corresponds to 40 uV noise on the SVR-T output. That sounds pretty good to me!
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First off, I'm an organic chemist, not an ee - I still have a lot to learn about this metrology stuff!
No worries. I'm an EE and I enjoyed organic chemistry, too.
My good meter is an old Keithley 196 6.5 digit. The only thing I know about its calibration history is that I haven't done it! It is in nice shape and seems very stable to me. The 196 has GPIB, however I don't have an automated measurement system working yet - it's in the planning stage for now.
You're in good company. CM and I also have a 196, probably with very similar history (I know I haven't calibrated mine, either). Great job with the manual logging!
Hi, one of the other projects/interests I have is noise measurement. A while back I built up the "Curiously Low Noise Amplifier" from Charles Wenzel's website (http://www.techlib.com/electronics/audioamps.html#curiously%20low%20noise (http://www.techlib.com/electronics/audioamps.html#curiously%20low%20noise)). This is a JFET front end low noise preamp with a gain of x100. The output is measured on an HP3400A thermally responding true RMS AC voltmeter using a simple RC filter to give an equivalent noise bandwidth of 500 kHz. The SVR-T measured about 4 mV rms which corresponds to 40 uV noise on the SVR-T output. That sounds pretty good to me!
That is very cool. Added to my to-do list. ;D
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Long ago I had (I think) a 195. Same brown case. The voltage regulator ran astoundingly hot. I don't know if the 196 suffers from the same thing, but I added an extra piece of aluminum sheet to get the temp down a bit. Just something to check.
When I get home tonight I'll try some noise measurements.
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Indeed, I found a surprise when I stuck a temperature probe into one of the input jacks of my 196 (it read about 106F).
I ran the unit using a Kill-a-watt, and it only draws 14 watts, which seems reasonable. I suppose a 14-watt light bulb probably would raise the temperature of a sealed plastic case to 106F...
I've been brainstorming about moving the transformer and regulators outside of the case to see if I can get the temp down, or possibly hacking the case and adding a large double-sided heat sink. My concern is that the banana jacks will see a ~30F gradient, which could be inducing a large EMF (or perhaps only if they aren't both being heated evenly?).
I just scored a 34401a off of ebay so I'm now in the position to see if I can device some experiments to quantify the effect of this somewhat high internal temperature (and I'll have a reference to check the performance of any mods against)
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btw, great job everyone on the data you're collecting!
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Congrats on the new score, CM. I really like these old, fanless devices.
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I just scored a 34401a off of ebay so I'm now in the position to see if I can device some experiments to quantify the effect of this somewhat high internal temperature (and I'll have a reference to check the performance of any mods against)
Grats on the score! Looking forward to your measurements.
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Hi, I've finally had a chance to look at the SVR-T measurements that I made last week.
Thanks for going to the effort to log these by hand!
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The secret underground lair uses some elderly but useful equipment, like the big Tek scopes and the 1A7A high gain diff plug in. Here's a photo of the ref signal, AC coupled, 10 uV/div and 2 mS/div, with the filters set for a bandwidth of 1 kHz. I've got the ref in a shallow aluminum box that I can use as a guard. It took me a while to rid myself of some low frequency spikes/pulses. Not sure what's generating them in the house, but enough shielding got rid of them. Interestingly, my 731A has a lot more 60 Hz hum, but lower high frequency noise than the ref.
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So cool!
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The secret underground lair uses some elderly but useful equipment, like the big Tek scopes and the 1A7A high gain diff plug in. Here's a photo of the ref signal, AC coupled, 10 uV/div and 2 mS/div, with the filters set for a bandwidth of 1 kHz. I've got the ref in a shallow aluminum box that I can use as a guard. It took me a while to rid myself of some low frequency spikes/pulses. Not sure what's generating them in the house, but enough shielding got rid of them. Interestingly, my 731A has a lot more 60 Hz hum, but lower high frequency noise than the ref.
thanks.
how about a scope-shot at slow scan, say 2 Sec/div ?
regards.
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Nice scope shot Conrad! Now that I have a bit more lab space, I may keep an eye out for an old Tek with plugins. For a long time I've been interested in building a homemade diff amp and seeing what kind of performance I can get from the Rigol!
It looks like the first "upgrade" to the SVR-T might be a nice shielded enclosure to keep out RF and drafts.
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If you are short on space, getting a Tek AM502 differential amplifier plugin plus one of the smaller TM500/5000 mainframes might be an option. The circuit is probably very similar to the 1A7A (except solid state), it is basically a TM500 version of the 7A22. They have a BNC out that you can plug into any scope. Due to the smaller size and versatility they do tend to be more expensive. You might be able to pick up an 1A7A + mainframe for less than the plugin :P.
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I was mostly looking for medium frequency popcorn noise, and didn't see any. Doing slow scans on the analog scope with a hand-held camera isn't practical. I'm getting ready to do data-logging and can see that time scale there, or if I have the time and the stuff still works, I have some paper chart recorders that would have been used for this sort of thing in the past. I'm hoping to be done with whatever I can do over the weekend and ship to the next destination on Monday.
I like the 1A7A because it fits my fat fingers well. The AM502 is definitely an option, and there are similar plug-ins for the 7000 mainframe series. The solid state diff amps should have better specs, particularly bandwidth, than the 1A7A. The 1A7A is also getting scarce and expensive when they turn up, and it uses Nuvistors. There is also the ADA400 for the newer scopes with power connectors around the BNCs, but IMO the thing is far less convenient than a dedicated plug-in. You could build your own version for very little.
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The downside of those older amplifiers with discrete components is drift due to temperature differentials. Only an issue if you want to do long term logging of noise for some reason. The ADA400 would be better in this regard. But more expensive and less convenient (need either a compatible Tektronix scope or buy/build a power supply like the Tek 1103).
I was mostly looking for medium frequency popcorn noise, and didn't see any. Doing slow scans on the analog scope with a hand-held camera isn't practical. I'm getting ready to do data-logging and can see that time scale there, or if I have the time and the stuff still works, I have some paper chart recorders that would have been used for this sort of thing in the past. I'm hoping to be done with whatever I can do over the weekend and ship to the next destination on Monday.
How about connecting a DSO to the Y output that the 500-series scope presumably has? Or does that sound to modern? ;)
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That would work. I hate to admit this in public, but I don't even own a DSO, though I could probably borrow one if necessary. And yes, one would certainly not use any of my antiquities for drift measurements.
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Guess another old-fashioned way to do this measurement is with a storage CRT, although I am not sure if there ever were any storage CRTs in the 500 series, never mind the space.
I meant drift of the offset of the differential amplifiers, so if you are trying to measure the noise over hours using some sort of external data recorder (trying to characterize noise of temperature, for example), the offset voltage may cause the signal to drift off screen unless you stop and readjust the offset/balance regularly. That is where more modern IC-based solutions like the ADA400 would be superior, since the temperature across that IC will be much more equal. I was not suggesting using these amplifiers to measure the ppm-level output drift of the references.
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There was the 549. We had storage 5000 series where I worked long ago, and I've got a 350 MHz 7000 mainframe in the garage with storage, but old storage scopes are prone to CRT trouble, with no replacements to be had. If there's anything where a DSO is light years ahead, it's certainly storage and slow waveform work.
The big question is what time-frame are we interested in? I've seen popcorn noise and random jumps at pretty much any interval, but if you just stare at the scope for quite a few minutes, misbehavior should be obvious. Next step is longer term data collection at second or a few second intervals.
Drifting off-topic, many Fluke & HP gadgets used NiCad batteries for isolated operation and to keep the power up during a power failure. The 845 null meter and 731 references do it. Unfortunately, they had primitive charging methods and also used the batteries as a voltage clamp/regulator. I discovered the batteries in my "golden" 731A were shot, though they were still clamping the voltage to something reasonable. My other two units were noisy because the batteries were missing. Though I've made new battery packs in the past, they eventually suffer the same fates. NiMH batteries don't work well in this application because they can't take as heavy a trickle charge indefinitely. What seems to work well is to replace the batteries with a good sized capacitor, say 2000 uF or so, paralleled with a zener that clamps at about 14.5 volts. The combination provides the filtering and voltage limiting similar to the battery, though obviously not the remote power operation. I've never seen significant hysteresis when powering up the 731 references, so avoiding a power failure at all costs isn't very important, at least at ppm levels. Maybe different at tenth ppm levels.
Having fixed that, the SVT is only slightly noisier than my 731 references, and far less susceptible to hum, especially if powered from a regulated wall wart.
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Conrad, what about a series resistor with the NiMH batteries to bring the current down to a safe level for their chemistry? I was considering doing that with my Keithley 228A, which has a very dead NiCd backup battery, though it's not used for clamping/filtering, just backup power.
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Apparently NiMH can take a small trickle charge with little trouble, but I never see them used in float applications. Most things I'd need batteries for require 12 1/2AA size, with tabs. Too expensive and probably hard to pick a resistor that balances circuit requirements and trickle requirements. If I absolutely needed battery backup, I'd be more apt to use an external lead acid gel cell. Those too, have limited life. I used to have a bank of them for my standard cell oven, but disposed of that a few years ago.
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Speaking of batteries, a few days ago I ordered a set of VRLA batteries (lead acid but safe for office/lab use). http://www.ebay.com/itm/2-LOT-NEW-YUASA-12V-9ah-VRLA-UPS-Backup-Battery-Replaces-Werker-WKA12-7-5-F2-/191886670473?hash=item2cad563a89:g:EYQAAOSwe-FU455l (http://www.ebay.com/itm/2-LOT-NEW-YUASA-12V-9ah-VRLA-UPS-Backup-Battery-Replaces-Werker-WKA12-7-5-F2-/191886670473?hash=item2cad563a89:g:EYQAAOSwe-FU455l)
My intention was to use them as a power supply for noise measurements.
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Apparently NiMH can take a small trickle charge with little trouble, but I never see them used in float applications.
Hello,
after my experiences with my LTZ1000 references:
The limit is somewhere 20-40mA for AA cells.
Above around 60mA they get cooked.
For 1/2AA cells the values might be lower.
What I use is a L200 CC/CV regulator.
Charge current limited to C/10 (200mA) and voltage limited to around 1.45V/cell.
Since I use a diode to prevent discharging back. The actual voltage is around 18.1V.
And has to be adjusted so that the floating current does not get too high.
(max 60 mA including the 20mA for the LTZ1000 reference).
Unfortunately the T.C. of the cell voltage is negative so the whole works only for room temperature.
With best regards
Andreas
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Finally, after getting my adult "make a living" stuff under control, I got back to the SVT. Wanting a less intrusive power supply than my big Kepco bench supplies, I found a 24 VDC wall wart (got a case of 'em) and made a nice little LM317 regulator board to for 15 VDC. Isolated, stable and quiet. I'll put that in the box when I ship it.
Original plan was to use the 845 null detector and record the output. It's surprisingly noisy and probably needs a major tune-up. Then it occurred to me that the 845 isn't needed. The little HP 3478A, that I already wrote a data logging program for, has a very sensitive lower range, 0.001 mV. Just fine as the null detector. For a first go I put the SVT back to back with my Fluke 731A and recorded about ten minutes worth of samples at one second intervals. Since the SVT is known to be nearly dead on from others measurements, I'll assume my 731A is about 2.5 ppm low. This agrees with measurements of both using my HP 3455A. I'll do a longer run tomorrow.
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Great idea using the lower DMM range differentially against a more stable reference!
I just realized one could do the same to measure two LM399's against each other, or two LTZ1000's (assuming they match within the lowest range on your meter).
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Alright; it looks like I can finally play.
I got one of my HP3456As working (no calibration), and have 3 Agilent 34401A (6.5 digit as well, cal expired Oct 1, 2016) that I just bought at the Blackberry/RIM auction. Also have an assortment of GPIB parts, but no proven GPIB data-logging solution yet. I hope to wrap the GPIB part in the next 4-8 weeks, depending on how complex it turns out to be.
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I have a bit of cyclic wander over an hour or two, probably the dehumidifier turning on and off. Or something else TBD. The room temperature has been dead stable at 73F. Smallish, half a ppm or so. Right now I'm running some casual temperature tests with a cardboard box and desk lamp. Here's the datalogger screen I wrote for the HP3478A. It's reasonably functional, though by no means bug free. It's written in PowerBASIC for the Prologix GPIB unit. No graphing, just gets me a csv file for Excel.
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This has been fun! I'll ponder the data for the next few days, but whatever temperature sensitivity there is, is darn small, buried in whatever other variations exist in my system. When we have a really good cal on the SVT, we can all adjust, but my guess is it's near dead on, and I'm running about 2.5 ppm low on my "golden" 731A.
I couldn't include the wall wart, as it would have put the package well over the limit. I did include the small regulator board with the mating DC connector, should anybody want to use it, and a small capacitance standard on a dual banana. Normally I'd do a shielded box with two BNCs, but few people would be able to take advantage of that. Instead, the cap is tagged with a three terminal measurement done on my GR 1615 that one can use with common bridges that measure independent of the front panel. It's a very good NP0 from Corning. I had wanted to throw in a resistance standard, but the weight was again too high, and I didn't have enough measurement history on it yet to feel comfortable sending it. Maybe next round.
I should be able to hit the post office tomorrow, so Dr. Diesel is next!
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Ohh, more goodies to test!
Thanks so much Conrad!
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my guess is it's near dead on, and I'm running about 2.5 ppm low on my "golden" 731A.
Thanks Conrad! I'm just curious - why do you guess the SVR-T is "dead on" and your standard has drifted? It's always that chicken and egg question!
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Somewhere back in this thread I thought the SVT got measured with a far better meter than I've got, and it was very close. Though I have three Fluke 731s that I can intercompare, it's been more than 13 years since the last traceable cal on my best one. I call that the "golden" unit because I modified it for near zero TC and it's the one that gets sent out. They're good, but I'd be astounded if they were that good. In the years since getting a cal, I've compared to various new Agilent 6.5 digit meters purchased at the day job. I'm always within a couple ppm, but I don't know how good those meter were when received- the chicken and egg problem!
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Somewhere back in this thread I thought the SVT got measured with a far better meter than I've got, and it was very close. Though I have three Fluke 731s that I can intercompare, it's been more than 13 years since the last traceable cal on my best one. I call that the "golden" unit because I modified it for near zero TC and it's the one that gets sent out. They're good, but I'd be astounded if they were that good. In the years since getting a cal, I've compared to various new Agilent 6.5 digit meters purchased at the day job. I'm always within a couple ppm, but I don't know how good those meter were when received- the chicken and egg problem!
FWIW, my comparison of my SVR-T and my Fluke 731B is here: https://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582 (https://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582)
Orin.
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Thanks, your graph and my results show the same signature wander, albeit very small. I need to do the same test between my different 731s, but the SVT is definitely on a similar level of performance.
edit- unit is now in the hands of the USPS and on the way to Dr. Diesel.
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OK, this is officially bad. I spent most of Independence Day farting around with old lab equipment (and doing a whole lot of yak shaving (https://en.wiktionary.org/wiki/yak_shaving)), but I got myself setup to the point where I have GPIB interfaced equipment working! :-+
The reason this is officially bad, is it's now caused me to wonder, "Which of my 6.5 digit meters is more accurate?", "What does it mean to 'calibrate' a meter?", "Why wouldn't my meters all read 0.0 microvolts DC with shorted leads?", and a whole host of other gateway-to-madness questions...
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I spent some of the day tweaking my two other references to match my "golden" unit, and then doing data collection between two of them. Things are good, sub ppm wander, but now I need to know the cause of it. Thermal issues with the leads, leakage currents in the measurement setup, temperature variations, the dehumidifier turning on and off, with the associated air currents from the fan, HF interference from the LED lights in the ceiling and on and on. Also started improving my GPIB logging program, since this was the first time I actually used it. I neglected to account for the midnight rollover on the data timestamp, plus I should display the measurement count so I have some idea how far along a given run is. Should probably fix the abort button as well. It will be great when the SVT hits the cal lab so we can all see where we really are.
BTW, I have a couple HP3455A 6.5 digit meters. The one I use regularly works as expected, zeros correctly and reads the same for both polarities. The one on the shelf meets all specs, but it has a slight polarity difference. As for accuracy, they're old and don't have very sophisticated references, but will still hold 1-2 ppm after warm-up for years at a time. In general, you should be able to adjust almost any 6.5 digit meter to near perfection, it's just a matter of how long and under what conditions it stays that way. ;D
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edit- unit is now in the hands of the USPS and on the way to Dr. Diesel.
This might just work out, if my schedule holds my two 3458A's will be at @CalMachine's this Thursday.
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In general, you should be able to adjust almost any 6.5 digit meter to near perfection
Oh dear, now you've said it....
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OK, this is officially bad. I spent most of Independence Day farting around with old lab equipment (and doing a whole lot of yak shaving (https://en.wiktionary.org/wiki/yak_shaving)), but I got myself setup to the point where I have GPIB interfaced equipment working! :-+
The reason this is officially bad, is it's now caused me to wonder, "Which of my 6.5 digit meters is more accurate?", "What does it mean to 'calibrate' a meter?", "Why wouldn't my meters all read 0.0 microvolts DC with shorted leads?", and a whole host of other gateway-to-madness questions...
Or another variant - if you have two meters that track each other to 10 microvolts over time and temperature, and another that has a constant difference (All same make, different models), which is right and does the tracking indicate that they are really stable, or just have the same kind of errors?
I understand exactly. This is where I am also. After spending a few days logging my crude standards and calibrating their sensitivity to supply voltage and temperature I am starting to worry about some of that real volt nut stuff. I started out thinking that knowing to 100 microvolts would make me happy. I now think I can know within 10 microvolts what the standard is saying when it arrives and am working my way down to one and maybe even a third. I think I have a path, but don't know if I am really that deep in the disease.
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BTW, I have a couple HP3455A 6.5 digit meters. The one I use regularly works as expected, zeros correctly and reads the same for both polarities. The one on the shelf meets all specs, but it has a slight polarity difference. As for accuracy, they're old and don't have very sophisticated references, but will still hold 1-2 ppm after warm-up for years at a time.
Early 3455A used a selected LMx99, just like 90% of the other 6.5 digit meters out there. Only the proprietary selection process may be different (I do not know the p/n they used, since they considered the reference module as not field repairable). So no reason to expect the stability of their reference to be any worse than more modern meters. Of course the supporting/input/ADC circuit may be different, and may also affect drift.
Funnily, they replaced the LMx99 with a custom heated zener in later 3455A units, which (or a very similar part) was also used in early 3456A units, but subsequently replaced by a selected LMx99 again in later 3456A units. Not sure what the story behind that was. I do know that they retroactively tightened the spec of the 3456A after they gained more confidence in their reference, so maybe the switching between LMx99 and the custom reference was also related to long term stability data collected over years that proved the LMx99 to be more stable than their custom zener.
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Look what just showed up.
I'm gone till Monday, but will get right on it when I get back.
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Woohoo!
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BTW, I have a couple HP3455A 6.5 digit meters. The one I use regularly works as expected, zeros correctly and reads the same for both polarities. The one on the shelf meets all specs, but it has a slight polarity difference. As for accuracy, they're old and don't have very sophisticated references, but will still hold 1-2 ppm after warm-up for years at a time. In general, you should be able to adjust almost any 6.5 digit meter to near perfection, it's just a matter of how long and under what conditions it stays that way. ;D
3455As and AD587 (Geller SVR(-T)s) don't get along well if you reverse the polarity unless you put a pretty big capacitor on the SVR output or are very careful about shielding and guarding.
I would see 9.9998X with the polarity normal and -9.989XX with the polarity reversed (I don't recall the X digits, they depended on temperature drift in the 'lab'). I saw this on two different 3455As. I did not see it on a 3456A.
I could see 120mV pk-pk at 570kHz when I looked at the signal with a 10X scope probe, so I suspected AM radio pickup.
It took 0.33 uF on the SVR output to make the 3455A read the same magnitude with the polarity reversed.
The guarding alternative was to use shielded twisted pair from the power supply to the SVR and from the SVR to the 3455A (shield grounded at the power supply, connected straight through at the SVR and connected to the Guard terminal at the 3455A). This got the difference in magnitude down to 15 counts. It still needed 4.7 nF capacitance to get the magnitudes within one count with the polarity reversed.
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I didn't see any particular problem with the SVT and my 3455A- the results agreed with the Fluke 845A and the 3478A and the three 731s, just with less resolution. The last digit of the 3455A will wander a couple counts. I don't have the data logging set up for the 3455A, but that would be the smart thing to do. Too many projects, too little time. The problem with my other 3455A seems to occur with any voltage source, so I'm assuming it's inherent in the unit. It's not a huge amount, just a few counts, but too much for my OCD. I don't remember there being any adjustment to trim it out, so one might have to select components or something.
The whole shielding/guarding thing has pitfalls. That's why I used a wall wart and the regulator board to power the SVT, as I don't know the ground isolation of my big bench supplies. It's the current paths you don't know that will throw things off. On that note, last night I did a run comparing two of my 731s. A couple periods of maybe 5-15 minutes had 1/4 ppm steps I need to track down. It could have been air currents on the connections, or even popcorn type noise in a reference. The trials and tribulations of a voltnutter.
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3455As and AD587 (Geller SVR(-T)s) don't get along well if you reverse the polarity unless you put a pretty big capacitor on the SVR output or are very careful about shielding and guarding.
My theory would be the higher capacitance from low terminal to ground due to the guard being connected to low by default would cause this issue. But disconnecting guard from low and connecting a separate wire from guard to SVR ground should fix that. Sounds like you had to go through much more trouble. Another option is the 3455 injecting current into the circuit. I remember Bob Pease complaining about that, so it could definitively have been the 3455. Adding some large-ish values series resistors might help and should have a negligible effect on the voltage measurement.
The last digit of the 3455A will wander a couple counts. I don't have the data logging set up for the 3455A, but that would be the smart thing to do. Too many projects, too little time. The problem with my other 3455A seems to occur with any voltage source, so I'm assuming it's inherent in the unit. It's not a huge amount, just a few counts, but too much for my OCD. I don't remember there being any adjustment to trim it out, so one might have to select components or something.
The service manual has a procedure for isolating DCV noise. Unlike modern manuals, it tells you to use a known good board, but subsequently explains how to do the tests if you do no have access to a known good board. This thread (https://www.eevblog.com/forum/testgear/hp-3455a-last-digit-jitter-in-hi-res-auto-cal-mode/) suggests that it might be dielectric absorption in the integration capacitor. Could well be an aging issue. The 3455 is much more sensitive to that than the newer meters. It is one issue that they explicitly fixed in the 3456 design. No argument that investigating it would take time ;).
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The two or three digit wander* in Hi-Res mode with Auto-Cal on the 3455A is due to dielectric absorption in the integrating capacitor. I suspect it was better when the meter/capacitor was new. Other than the (physically huge) Russian teflon capacitors that can be found on ebay, I've not found anything better than the original capacitor. With a couple of 39nF teflon capacitors in parallel instead of the original 82nF polypro, my last digit jitter is around one count.
*EDIT: This wander is in time with the clicking of the auto-cal relays.
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Is the HP3455A wander due to dielectric absorption only present when measuring a voltage? No voltage = no voltage on the cap and nothing to absorb?
My HP3478A is particularly noisy on the 30 mV range- can anybody tell me what's normal with a shorted input? The manual on that one does suggest turning off the auto-zero if change injection into the DUT is a problem.
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Is the HP3455A wander due to dielectric absorption only present when measuring a voltage? No voltage = no voltage on the cap and nothing to absorb?
My HP3478A is particularly noisy on the 30 mV range- can anybody tell me what's normal with a shorted input? The manual on that one does suggest turning off the auto-zero if change injection into the DUT is a problem.
i have a HP3468A, which with inputs shorted is +- 1uv (Least significant digit goes 1/2/1/2/1/2 .....) on 30mv range.
regards.
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The 3468A has a 30 mV range?
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The 3468A has a 30 mV range?
sorry, my *bad*, 300mv. :palm:
regards.
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Is the HP3455A wander due to dielectric absorption only present when measuring a voltage? No voltage = no voltage on the cap and nothing to absorb?
It's present when you have Auto-Cal on as the meter is continually measuring a set of references which include a +10V reference and a -10V reference.
So when the meter measures the +10V reference then your input, your input reads a count or two high.
When the meter measures the -10V reference then your input, your input reads a count or two low.
If you log the readings, you can see a pattern as in the attached graph. You'll see the same pattern (based about 0V) if you short the input.
If you turn Auto-Cal off, you'll just see at most one count jitter, but it will drift badly.
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I must have the best 3455A ever made, or it's broken. It wanders by about 1 count after a good warm-up. I've never paid much attention to what it does with auto cal off.
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I just went back through the posts in this thread and made an index: https://goo.gl/GHyj67
I'll try to keep it updated as we go along!
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While waiting on my GPIB "spy" board and logic analyzers to arrive, I got my 34401A logging via RS-232 this evening.
It turns out you can put it into "talk only" mode, which makes it super easy to get started logging data from this meter. See my post here: https://www.eevblog.com/forum/testgear/34401a-interface-to-pc-rs232-or-gpib/msg1257501/#msg1257501 (https://www.eevblog.com/forum/testgear/34401a-interface-to-pc-rs232-or-gpib/msg1257501/#msg1257501)
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Finally some data! I was unable to get extended runs without power outages due the storm pounding the midwest has seen over the past week. I've attached two graphs (LibreOffice Graphing is a huge PITA, any other Linux suggestions?) one capturing the entirety of the spikes and one narrowed down a bit. I need to track down what is causing the spikes, something enviromental as both 3458As see it, might be my shop air compressor. Note I did not offset the the two readings for graph readability and both are back from a fresh cal. I utilized the included PS in a consistency attempt, fed via an old Heath linear PS set at 20V.
Cabling was solid twisted ethernet cable, utilizing the 3458A screw terminal, no banana. Connection at the DUT was copper Mueller Electric Co BU-34C, crimped, not soldered, which I'll forward on when I ship the reference to the next participant.
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Forgot to mention, 3458A setup, from the PI lognut scripts, hacked to read both 3458As and a Maxim ds18b20 temp probe.
# Setup HP 3458A
inst.write("PRESET NORM")
inst.write("OFORMAT ASCII")
inst.write("DCV 10")
inst.write("TARM HOLD")
inst.write("TRIG AUTO")
inst.write("NPLC 200")
inst.write("AZERO ON")
inst.write("LFILTER ON")
inst.write("NRDGS 1,AUTO")
inst.write("MEM OFF")
inst.write("END ALWAYS")
inst.write("NDIG 9")
inst.write("DELAY 0")
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Finally some data! I was unable to get extended runs without power outages due the storm pounding the midwest has seen over the past week. I've attached two graphs (LibreOffice Graphing is a huge PITA, any other Linux suggestions?) one capturing the entirety of the spikes and one narrowed down a bit. I need to track down what is causing the spikes, something enviromental as both 3458As see it, might be my shop air compressor. Note I did not offset the the two readings for graph readability and both are back from a fresh cal. I utilized the included PS in a consistency attempt, fed via an old Heath linear PS set at 20V.
Cabling was solid twisted ethernet cable, utilizing the 3458A screw terminal, no banana. Connection at the DUT was copper Mueller Electric Co BU-34C, crimped, not soldered, which I'll forward on when I ship the reference to the next participant.
Do you have your 3458As on top of each other?
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Do you have your 3458As on top of each other?
Yup. Every 100 samples I take the internal 3458A temps, just too much for the graph. On average the higher reading 3458A #1 is 1.06C lower in temp.
I need to quantify/test this, but I thought I noticed after a couple of the power outages the deviation between the two being much (after a 4 hour warm up) less before the first ACAL. This wasn't captured by the logging as an ACAL is initiated at first run.
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Dr.Diesel,
Try Gnumeric spreadsheet.
Much faster than libre or what have you.
I too was using libre and it was such a tedious task.
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Beautiful data dr.diesel! I don't think we'll get better measurement confidence than this - 2 freshly call'd 3458As. Looks like the SVR-T is within 0.5 ppm of 10.00000 volts!
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Beautiful data dr.diesel! I don't think we'll get better measurement confidence than this - 2 freshly call'd 3458As. Looks like the SVR-T is within 0.5 ppm of 10.00000 volts!
Indeed! Bravo!
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Headed your way @CalMachine. :-+
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:scared:
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The "goodie bag" keeps growing in size!
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Indeed. Seems the cal pack will need an inventory checklist.
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I have L&N 4030-10KOhm to throw in :-DMM.
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TiN, you have contributed so much to the volt nut community. :clap: I would be honored to add you as an honorary member of the USA Cal Club.
I'll PM you to get your address, and look into international shipping options :-+
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Well, resistor is in USA now, so you guys go in the planned routing, and I'll jump in for the round two.
Hopefully we will have few voltage references too. I heard some modules are cooking ;).
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Sounds good :D
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I'd really love to see Raspberry Pi included in round two with data storage.
Maybe somebody could even donate Agilent/knockoff GPIB dongle, so we can have automated datalogging for common meters.
Seeing calibration clubs without data attached to each measurement + environmentals + used gear details defeats whole purpose for me, to be honest. :-//
It's bit too much, asking for people who use/own meters like 3458/8508/2002 spending their time on so-so reusability and history access.
I wanted to make a dedicated website for this very purpose, of storing/accessing data with history,... but well, need moar time. :palm:
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Yeah, I agree with you on a lot of those points, and I've been enjoying working on some solutions to these problems, but the going is slow.
I have a first-draft of a temperature / humidity logger which works over USB. I plan on including this in round two, or maybe even just distributing the boards to forum members so that we all have environment logging ready at hand. https://github.com/pepaslabs/lab-logger
My current mission in life is to bring a cheap and open GPIB solution to this community. We have a wonderful gift of all of this cheap used test & measurement gear on ebay, yet most hobbyists are ham-strung by lack of a solid PC connection. And if you can't log data, it is pretty difficult to be a volt-nut.
(My latest weapon in this crusade has just arrived from OSHPark -- I made a "spy" board which allows me to insert logic analyzers into a GPIB connection).
I'm still working on a plotting solution. Muxr's python-based script is a great start -- I just need to figure out how to make Pandas process two independent CSV files at once.
My hope is that in a couple of months (by the time round 1 is finished?), this little club will be in a much better spot with regard to solutions to all of these challenges.
(A perhaps more distant pipe-dream is to start a youtube channel and make some videos about metrology and volt-nutting. Perhaps I could start by making a video guide to the LTZ1000 thread. That should keep me busy for a while... ::) )
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I'd really love to see Raspberry Pi included in round two with data storage.
Maybe somebody could even donate Agilent/knockoff GPIB dongle, so we can have automated datalogging for common meters.
Seeing calibration clubs without data attached to each measurement + environmentals + used gear details defeats whole purpose for me, to be honest. :-//
It's bit too much, asking for people who use/own meters like 3458/8508/2002 spending their time on so-so reusability and history access.
I wanted to make a dedicated website for this very purpose, of storing/accessing data with history,... but well, need moar time. :palm:
That's a great idea.
I have come up with a solution for logging for my own needs and tried to share my findings but not everyone has the same background and time to get it going. Plus for my needs I use REST micro services on my distributed network in the lab, in order to keep instruments in different locations connected.
But I can try working on a traveling rig we can use. I wasn't aware of the 82357B USB/GPIB clones to be honest, so I don't mind donating it and the rPi to the club.
I have some ideas on how to make it fairly easy for anyone to get it working. I could build a simple self hosted web interface on the Pi to simplify the process. I do have a full time job and other side projects, so it won't be any time soon though.
I'm still working on a plotting solution. Muxr's python-based script is a great start -- I just need to figure out how to make Pandas process two independent CSV files at once.
I purposely wanted to keep the python example simple so that it's easier to extend. But take a look at the version I've been developing: https://gist.github.com/sirmo/4126a9450a769a3cc9d011beb6a7eded
I just need to clean it up a bit and make it smart so that the old single column format still works with it (and then I'll merge it).
It doesn't load multiple CSV files but it feeds off multiple columns in the CSV. Value from the DMM, Temp, Humidity, Pressure (see attachment)
Not sure if that's what you're looking for.
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Muxr, that's fantastic!
I just realized that I made a github mistake -- I made pull requests against my own fork of your repo, so they never made it your way!
These two PR's allow the columns to be arbitrarily named:
https://github.com/cellularmitosis/muxrplot/pull/2
https://github.com/cellularmitosis/muxrplot/pull/3
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Muxr, that's fantastic!
I just realized that I made a github mistake -- I made pull requests against my own fork of your repo, so they never made it your way!
These two PR's allow the columns to be arbitrarily named:
https://github.com/cellularmitosis/muxrplot/pull/2
https://github.com/cellularmitosis/muxrplot/pull/3
Sweet! will merge them tomorrow, thanks!
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I set up a little area for the reference to sit in the lab and I brought a 3458A over to log! I do not have any ambient temperature logging device hooked up, currently.... but I did plot the internal oven temp along with the voltage reference, so that will give you a somewhat idea of what ambient was doing.
My graphing skills are still very lacking, so... without spending too much time making it look all pretty, here are the overnight logging results. Each 1000 measurements was ~ 140 minutes. The right-hand axis is ºC
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Wow, just a few microvolts shy from "bang on!" :-DMM
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Quickly threw a BME280 sensor on the RPi3 and logged a few hours this morning. Definitely somethin funky going on with the BME280.
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Quickly threw a BME280 sensor on the RPi3 and logged a few hours this morning. Definitely somethin funky going on with the BME280.
I see what you mean. Those dips. Rpi3 likes to use some power when the CPU spins up.. I would maybe try a different power supply for the Rpi3. Maybe the voltage droop is causing the BME280's readings to dip. Shot in the dark.
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Another way to check if there may be a power issue with the RPi3 is to plug a monitor into the HDMI port. A lightning bolt icon will flash in the corner of the screen anytime the power supply is insufficient for the Pi's needs.
https://raspberrypi.stackexchange.com/questions/57963/what-does-the-lightning-bolt-mean
(I don't know if this is linux distribution-dependent.)
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My current mission in life is to bring a cheap and open GPIB solution to this community. We have a wonderful gift of all of this cheap used test & measurement gear on ebay, yet most hobbyists are ham-strung by lack of a solid PC connection. And if you can't log data, it is pretty difficult to be a volt-nut.
The clones from eBay are nice, but OSHW solution would be great. I have this somewhere on my long TODO list.
The idea is to replicate the Keysight E5810B. If you look at the firmware it is based on the AM335x CPUs (i.e. Beagle Bone Black). This neat SoC has a real time peripheral-microcontroller called PRU, can bitbang a pin at 100 MHz rate AFAIR. This is for example used in LinuxCNC/MachineKit for accurate step/dir signals for the stepper drivers.
If I understand E5810B correctly (I never saw any teardown) it uses PRU to bitbang the GPIB transceivers (SN75160B and SN75162B) directly - very neat, no CPLD or obsolete NI chips needed. It could potentially enable high speed GPIB (like GPIB-USB-HS, with DMA) and of course, as it is a decent SoC, an Ethernet gateway (VXI11) and attaching extra I2C or SPI sensors is easy. The whole thing is fully open-source (Linux, linux-gpib, GCC compiler, TI provides the PRU tools).
The GPIB cape wouldn't be very expensive, just the 2 layer PCB, GPIB connector, pin headers, transceivers and some misc components. I guess $20 + the cost of BeagleBoneBlack ($45). The difficulty lies in the low level understanding of both GPIB and VXI11 (for the Ethernet bridge) to implement everything.
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From what I read some time ago, the PRU isn't all that easy to deal with. Hopefully, the tools support for it is good now. I've got a BBB ready to put on a GPIB cape. It'd be pretty cool.
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Quickly threw a BME280 sensor on the RPi3 and logged a few hours this morning. Definitely somethin funky going on with the BME280.
I see what you mean. Those dips. Rpi3 likes to use some power when the CPU spins up.. I would maybe try a different power supply for the Rpi3. Maybe the voltage droop is causing the BME280's readings to dip. Shot in the dark.
I'm using a 2.5A wall wort that are generally sold with the RPi3s. I've got a little monitor hooked up to it and I'm monitoring the script through the command prompt. There are not any power draw issues coming from the RPi3, that I've observed. I was getting some pretty funky readings, so I had to put the reference in a Faraday cage. I'm supplying the provided voltage regulator with 23 V and I'm using the copper twisted pair wires that Dr. Diesel sent along with the package.
Here is a 3 hour run from this afternoon. Still observing odd spikes on the BME280, but I'm not really that worried about it, though. It's only happening for 1 measurement.
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Hmm, that's interesting. Fortunately, the temp trend is the important part.
A few months ago, I saw this comparison of some different hygrometer sensors. It includes the BME280, which seems to be very good.
http://www.kandrsmith.org/RJS/Misc/Hygrometers/calib_many.html (http://www.kandrsmith.org/RJS/Misc/Hygrometers/calib_many.html)
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Hmm, that's interesting. Fortunately, the temp trend is the important part.
A few months ago, I saw this comparison of some different hygrometer sensors. It includes the BME280, which seems to be very good.
http://www.kandrsmith.org/RJS/Misc/Hygrometers/calib_many.html (http://www.kandrsmith.org/RJS/Misc/Hygrometers/calib_many.html)
This is fantastic! I wished I would have seen this a few months ago :P
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There's so much good stuff out there, you can't hope to see everything. Fortunately, resources such as this forum enable us to benefit from each other's eyes. :-+
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Here is a log of the weekend! Should be headed your way within the next day or 2, CatalinaWOW.
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Timing is perfect. I am out of town but will be back shortly. Should be able to get things warmed up a stabilized soon enough to minimize any delay.
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Thanks for posting your graph CalMachine -- I've been doing some logging from a 34401A and have noticed similar issues that appear in your graph. If I'm away at work or in bed asleep, things are pretty stable. But then I walk into the room where the meter is, wake up the laptop display, etc, and I see sharp offsets which are large in comparison to the periods of stability. Humans seem to be problematic to precision data logging efforts!
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Thanks for posting your graph CalMachine -- I've been doing some logging from a 34401A and have noticed similar issues that appear in your graph. If I'm away at work or in bed asleep, things are pretty stable. But then I walk into the room where the meter is, wake up the laptop display, etc, and I see sharp offsets which are large in comparison to the periods of stability. Humans seem to be problematic to precision data logging efforts!
Ofcourse! I wish I had the time to get a better test environment set up. Judging from the graph, the test environment looks pretty noisy... The 3458A ACAL threshold was set to 0.4 ºC and ACAL'd itself a total of 4 times throughout the weekend @
22/7/17 20:15:21
23/7/17 03:08:26
23/7/17 15:15:25
24/7/17 00:54:05
I wasn't able to match any correlation between the observed noise spikes and ACAL events. I will be working reducing noise around here!
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Noise comes in many forms. Remember that you are an infrared radiator. When I do capacitance measurements on the standards bridge (1615A) or even the old 716C, just holding my hand under the DUT to adjust the knobs will cause a value shift if the DUT tempco is significant. There are also RF sources we never had to deal with like CFLs and LED lamps. They're not usually well filtered. Best solution is a Faraday cage around the lab, then fill the lab with temperature controlled Fluorinert!
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You guys are scaring me. I probably have noise galore in my lab: PCs, switching power supplies, CFL bulbs, Wi-Fi routers, unshielded ESP modules, etc. :o Maybe my graphs will have more popcorn than this guy :popcorn:
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You guys are scaring me. I probably have noise galore in my lab: PCs, switching power supplies, CFL bulbs, Wi-Fi routers, unshielded ESP modules, etc. :o Maybe my graphs will have more popcorn than this guy :popcorn:
I wouldn't be that worried. The lab I work at has many large industrial businesses, TV stations, power lines, and cell towers in the vicinity. Here in the next few months with the new lab coming, I'll have a completely shielded and much tighter environmentally controlled lab. I'm excited!
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OK, I'm enhancing my calm. I think I may be next after CatalinaWOW, so I'll find out soon enough.
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The happy box arrived today. It is percolating away on its first run as I type.
The photo shows the reference set up in my basement lab. The arrival of the reference coincided with a historic heat wave here in Southern Oregon so it is a little warmer than usual in the hideout. This may also affect my plans. A careful look at the photo will show a TI temperature and pressure measurement dongle. Normal Oregon temperatures let me get a range of temperatures around normal room ambient just by sticking things outside the window, leaving the measurement system inside. Trial runs while waiting for the gold standard showed this worked well. I balanced the materials in the leads and was able to convince myself that thermo-electric effects were negligible at the level of accuracy that I am capable of. Temperatures ranged from 55 F to 95 F (13 C to 35 C). Unless the weather bureau lies the range I will see before I send this on will be more like 65 F to 110 F (18 C to 43 C). Not a nice balanced range around normal lab temperatures. I will send the temp/humidity dongle along when I send the reference out. It appears as a serial port so should be easy for anyone to interface. Before I ship this stuff out I will post the EZGPIB code I am using. Needs a little polish before public viewing.
The two key instruments in the setup are an HP 3457 and an HP 3456. Both have unknown calibration histories with most recent signs of calibration more than a decade ago. I am pleased to see that they are both fairly close. If I wasn't coming down with the Voltnut disease I would be ecstatic and not go any further. Unfortunately.....
I am also attaching a short sample of my test run on the reference. First column is date and time in MS julian date format. Next column is temp (C) and the next is relative humidity. The sensor is not formally calibrated but tracks well with multiple thermometers and thermocouples I have. I don't have as much information on the humidity sensor, but it tracks a couple of other measurements I have. Next column is an HP 3478 monitoring the supply voltage. Currently it is supplying the voltage regulator that Conrad provided to help provide consistency in measurements, but I also plan to to a couple of voltage sensitivity runs bypassing Conrad's regulator. Next is the HP 3457 which is being operating in 100 PLC mode and using the extra sensitivity register to get 7.5 digit information. Finally the HP 3456. Also operating at max PLC, but clearly the extra digits are missing.
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Catalina,
Can You please post the calculated temperature coefficients of the three instruments based on the text file.
0.007131491465747643
9.653462320521867E-05
0.00020292057647497002
?
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I will be happy to post TCs once I have a sufficient data set. The short sample posted covered only a few minutes, far shorter than the thermal time constant of the instruments, and possibly short wrt the voltage reference/sensor system so I don't believe that anything found in this sample is meaningful. It will be interesting to sort out the instrument TCs from any TC in the voltage reference. My own references are not particularly stable (I am new on this volt nut trail) but in trial runs I found that the readings from all three instruments tracked each other much more tightly than the movement in my references. Using Occam's I concluded that the instruments were probably very stable since the likelihood that the three different instruments had the same TC was low. Not zero since they all are the same manufacturer, but they are of somewhat different eras and market intents.
Also recognize that for temperature differences of the size seen (0.1 degree) the temperature sensed is unreliable relative to the instruments. The photograph shows that the instruments are stacked and thus likely have a bottom to top gradient, and are separated from the sensor by half a meter or so.
The final issue is not evident from what I have posted. My HP 3456 has an odd thermal sensitivity. When it is exposed to a strong negative thermal gradient it shuts off. Since I normally open these windows in the cool morning hours to bank cool air against the hot afternoon it frequently shuts down. This had occurred the morning of this short sample and so the instrument had just been turned on and was still stabilizing. I expect the data from the longer run started yesterday evening will show this. I am leaving the windows closed this morning so will get a full twenty four hour run in.
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The 3456A shutting down does not sound normal. Could be a bad connection that is stressed due to the thermal gradient.
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The 3456A shutting down does not sound normal. Could be a bad connection that is stressed due to the thermal gradient.
I think it is in the switch itself, perhaps mechanical in the latch mechanism. I will be diving into it once I send the club reference on. Maybe I will get lucky and it is just a loose push on terminal.
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First results are in. A day late due to a rookie mistake that resulted in erasing the first days data collection. So now what I have is the run showing temperature sensitivity of the reference. I can also glean some stuff about my instruments. Both the 3456 and 3457 are a bit off, not surprising given how long it has been since they were calibrated. There is also an indication that the 3457 is a bit drifty. This surprised me as it had not shown up in my trial runs. Will look more into that in the rerun of day one which is going now.
The real surprise was the temperature sensitivity of the reference. It is not too bad below 30C, but definitely wanders at higher temperatures. Fortunately most labs will not have to deal with that.
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It is quite obvious that the heater resistor is too low of a value for the higher temperatures, the LTZ is losing temperature regulation, it needs at least a 13K or higher to operate at higher temperatures. Remember, it is not the ambient temperature that the LTZ works from but its internal temperature, the heater resistor must be high enough to allow the LTZ to servo its internal temperature at whatever ambient temperature it is in.
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It is quite obvious that the heater resistor is too low of a value for the higher temperatures, the LTZ is losing temperature regulation, it needs at least a 13K or higher to operate at higher temperatures. Remember, it is not the ambient temperature that the LTZ works from but its internal temperature, the heater resistor must be high enough to allow the LTZ to servo its internal temperature at whatever ambient temperature it is in.
Last week I ran test to insure the 13K/1K ratio was not going to be an issue with the LTZ1000A at my intended operating temp of 35 deg C. My testing showed I was okay up to about 43 deg C, any higher I would run out of headroom.
LTZ1000A heater current at 15v;
23 deg C = 22mA
35 deg C = 15mA
40 deg C = 10mA
43 Deg C = 8mA
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@CatalinaWOW reply #241
I have to ask about the DUT. Is it an SVR-T or LTZ? Edwin says something about LTZ. If it is an SVR-T I should say it is very good to be an simple NTC compensated AD587LQ with just a few ppm over 17-39C. The NTC just compensates the first and second order and just over a narrow temperature range it is very effective, normally 20-30°. The spec for the SVR.-T also is +-1ppm/C. The third order term found in the AD587 is not compensated at all.
I also guess you just temperature cycled the DUT not the DVMs? Or did all your setup (room) vary 17-39C? How long was the measurement time?
I have to ask what you mean by both instruments are a little bit off? As I see the HP3456 at 23C is within 1ppm that is very close for me. Guess the fluctuation over some days may be more for an HP3456 and also depending on how long it has been on.
@CalMachine reply #228
Is the blue line the SVR-T? If so it seems to vary from 2-7ppm above 10V. Earlier you had closer and less variation. Is the environment the same. In the lab you work? I find this very intersting as it shows how difficult it is to be sure of a result.
As I understand you use a calibrated HP3458 as Dr. Diesel also did (calibrated at your work?). His result was very close to spot on within 2ppm if I remember correct. Both for the DUT and DMMs. How was the calibration of your 3458?
@-To the owner of the SVR-T (if it is one SVR?) How old is it? Any serial number? Think I saw 911 on some picture? If so I guess it from about 2012-13. Has it been powered most of the time or not?
I think the round robin is really nice but ask for more detailed info about DUT and used setup on every post if possible to easier compare result. Ok, I know I am not better at this and it not easy to know what we as audience needs. Pictures and texts for the DUT and measuring device is nice.
Lars
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Yeah, in a future round we will want to do a star pattern rather than round robin, to detect drift during transit.
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@lars
I love questions, they focus my ignorance. I can describe the reference I am testing - owner is cellularmitosis I believe.
Geller Labs Reference - model number is not obvious in the available view. I don't want to disturb it during a run.
The number 977 is inked on the board. (Or possibly 911 if written Euro-style, but the characters in question look more North American than the Euro style 1.) Don't know if this is the serial number.
The key chip is clearly marked AD587LQ with a date code of 0054. I haven't found a data sheet admitting to the existence of an LQ grade so don't know what that means.
The DUT was exposed to normal diurnal temperature swing (started at approximately peak daytime temperature, and went 14 hours, a little past where temperatures began rising the next day. NPLC for 3457 was 100, 3456 was at default value of 10 (another mistake that has been corrected for the current run.) The DVMs were all thermally isolated from these changes in a room whose temperature was 26 C +/- about a degree. Measurements were taken about every 8 seconds. The plotted data is the running average of 11 of these measurements.
My comment about the instruments being off was a lazy reference to the difference in readings and the difference from the stated perfection of the reference. I have not yet even plotted error bands or the range specified by HP.
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Yeah, the AD587LQ is no longer manufactured. They do still offer a hermetic CERDIP version (AD587UQ), but is specified over the wider industrial temperature range, rather than the commercial temperature range.
Andreas has hinted before that the UQ has a less desireable tempco curve, because its was designed to operate over a wider temp range.
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If it could come to the Bay Area, I would love to get my hands on it for a couple of weeks. I have some local friends with well-characterized 732As that would give us some interesting numbers.
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If it could come to the Bay Area, I would love to get my hands on it for a couple of weeks. I have some local friends with well-characterized 732As that would give us some interesting numbers.
Sounds great! I'll tack you onto the end of the route. Can you shoot me a PM with your address?
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If it could come to the Bay Area, I would love to get my hands on it for a couple of weeks. I have some local friends with well-characterized 732As that would give us some interesting numbers.
Sounds great! I'll tack you onto the end of the route. Can you shoot me a PM with your address?
If it's of any interest, I could compare against my very good SVR-T and/or 731B.
https://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582 (https://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582)
The 731B is currently within 1ppm of 10V on the 34461A at a temperature of 25C. Realistically, that measurement setup reflects the 34461A'a tempco. A SVR-T vs. 731B setup as in the above post is far more interesting.
Orin.
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If it's of any interest, I could compare against my very good SVR-T and/or 731B.
Definitely! Can you send me a PM with your address?
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@CalMachine reply #228
Is the blue line the SVR-T? If so it seems to vary from 2-7ppm above 10V. Earlier you had closer and less variation. Is the environment the same. In the lab you work? I find this very intersting as it shows how difficult it is to be sure of a result.
As I understand you use a calibrated HP3458 as Dr. Diesel also did (calibrated at your work?). His result was very close to spot on within 2ppm if I remember correct. Both for the DUT and DMMs. How was the calibration of your 3458?
Lars
Correct, the blue line is the SVR-T. The environmental conditions were fairly constant. My 2 first logs were of only a few hours each, while the last log was close to 60 hours. I also didn't have a line transient suppressor available for use with the power supply for the reference... so whatever noise from the grid/nearby SMPS wasn't being filtered.
You hit the nail on the head! It is very difficult to measure in the PPM world, accurately. Sure, you're meter might be stable and measuring a reference/source with little noise and deviation between measurements.. but, that doesn't give you any kind of indication of system biases that might be present, skewing your result.
His meters performed pretty flawlessly!! It was my first time having the pleasure of calibrating a modified oven'd 3458A. I believe the 3458A I used was last calibrated in March.
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If it's of any interest, I could compare against my very good SVR-T and/or 731B.
Definitely! Can you send me a PM with your address?
Will do.
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I now have measurements enough to keep me thinking for a long time now.
It will be on the way to you kj7e in this afternoons post.
I added a thumb drive to store data and to hold the drivers for the temp and humidity sensor I threw in.
Just for giggles I measured the precisely measured capacitor that is in the box with my $20 LCR meter (https://www.eevblog.com/forum/testgear/ (https://www.eevblog.com/forum/testgear/)$20-lcr-esr-transistor-checker-project/). Just a bit over 1 part in 1000 error in the reading. Very nice work madires and others who have contributed to this.
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Oh, good idea to check the $20 tester. I'll have to remember to do that as well.
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I now have measurements enough to keep me thinking for a long time now.
It will be on the way to you kj7e in this afternoons post.
I added a thumb drive to store data and to hold the drivers for the temp and humidity sensor I threw in.
Just for giggles I measured the precisely measured capacitor that is in the box with my $20 LCR meter (https://www.eevblog.com/forum/testgear/ (https://www.eevblog.com/forum/testgear/)$20-lcr-esr-transistor-checker-project/). Just a bit over 1 part in 1000 error in the reading. Very nice work madires and others who have contributed to this.
Perfect timing, these showed up today.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/93C69317-4783-409A-85FC-34B11112340B.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/93C69317-4783-409A-85FC-34B11112340B.jpg.html)
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:popcorn:
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Brief summary of what I found just before I sent the SVR-T on down the line.
Line regulation ~ 4.9 microvolts/Volt , compares very favorably with specification of < 100 microvolts/volt
Max temp slope over lab temp range is about .6 ppm/deg. Compares well to specification of <5 ppm/deg although spec is over a significantly larger range.
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As a volt-noob whose turn with the roving transfer standard is coming up soon, I have a few questions to start preparing.
1. What's the minimum input impedance that's acceptable for the included voltage standard? The defaults for my 6.5-digit bench meters in multi-megaohm, but if I run three or four of them in parallel, will that load down the standard too much? If I, instead, switch them to gigaohm range, will that be too noisy?
2. Since banana plugs were indicated to be suboptimal for connecting to the standard, how many leads are in the package? How do they connect to DMMs that don't have binding posts, just banana jacks?
3. CatalinaWOW's line regulation figures look like I won't have to worry too much about the power supply for the voltage standard. However, I do have a Power Designs 2010 and an HP 6114A to run it.
4. @cellularmitosis: Were you able to get your K196 logging via GPIB?
5. Has anyone in the loop used https://www.eevblog.com/forum/metrology/raspberry-pi23-logging-platform-for-voltnuts (https://www.eevblog.com/forum/metrology/raspberry-pi23-logging-platform-for-voltnuts) for logging? I don't know if I'll be able to try it out prior to the package arriving. If not, I'll just log with my laptop.
Any recommendations or links to information on how best to perform the first run is also much appreciated.
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I created an inventory of what is in the box, and then cleverly put my only copy in the box. Maybe kj7e can post it.
By memory there are four banana plugs with screw caps. Two of these are connected to a twisted pair of solid copper wire with mini grabbers on the end. Two more are loose. There are two twisted pairs of copper wire with bare leads on the end. Twisted pair with banana plugs and mini-grabbers for attaching the supplied voltage regulator. The regulator has a twisted pair and the appropriate plug to power the SVR-T.
I also am a noob, but don't think that hooking multiple meters up should be a problem. The output is directly from the AD587 which specs load regulation as 100 microvolts/mA. The meters will be drawing microamps so errors from hooking the voltmeters up should be small fractions of a microvolt.
While stability of the power supply will not be important in terms of controlling line regulation, isolation from line transients will be useful. I spent a little time looking at the SVR-T output through a spectrum analyzer. Most of the time the noise was quite white down to just a couple of Hz, but occasionally a burst of 120 Hz showed up. I didn't try to track down the source - I figured that more good would be done by sending the thing down the line. Another thing that was showing up when I zeroed in on the very low frequency material was a very low level set of peaks (about 85 dB down) about 8 Hz apart. I will spend some time tracking these down as time goes by.
I did further reduce my data a pretty up a plot. I can't explain why, but the recommended 15 volt input does seem to be in a sweet spot with extra low response to source voltage.
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Thanks for the rundown. It sounds like I can hook up two DMMs with the parts in the kit and perhaps some alligator-to-banana adapters. I'll take a look at the twisted pairs when I get the package to see if I can replicate them for hooking up other meters.
Nice graph. It is quite a flat response around 15V. That's likely the reason it was chosen as the recommended supply voltage. I shall power the standard accordingly.
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5. Has anyone in the loop used https://www.eevblog.com/forum/metrology/raspberry-pi23-logging-platform-for-voltnuts (https://www.eevblog.com/forum/metrology/raspberry-pi23-logging-platform-for-voltnuts) for logging? I don't know if I'll be able to try it out prior to the package arriving. If not, I'll just log with my laptop.
Any recommendations or links to information on how best to perform the first run is also much appreciated.
I use the LogNut image on an RPi3 here at the shop. It's what I used for the 3458A logging of the reference.
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Excellent. Which GPIB interface do you use with it, CalMachine?
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I am using the NI-USB-GPIB-HS dongle with it
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Cool. I've got an 82357B (a real one from what I can discern from its internals), which seems to have been a bit of a pain for the LogNut project recently. Hopefully, it'll work OK. I'd also like to try to get the interface working with the BeagleBone Black as I have a 7" LCD cape for it, which would look great with a live graph. Ah, too many projects.
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4. @cellularmitosis: Were you able to get your K196 logging via GPIB?
Not yet. I am currently working on getting multiple 8-channel logic analyzers to work in unison with Pulseview (the open-source logic analyzer GUI). The Sigrok developers were kind enough to supply me with a patch, and I'm currently working on muxing the output of two analyzers into a single dump file so that it can be viewed in their GUI. Once I get that working, then I can start to figure out all of the idiosyncrasies of my GPIB attempts (e.g., why can the UGSimple write to the K196, but not read from it? etc).
I'll keep you posted!
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Wow, that sounds like quite a project in itself. Cheers!
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Hi bitseeker,
Recently I've had some success logging my Keithley 196 via GPIB. I built up the Arduino based GPIB adapter described here: http://egirland.blogspot.cz/2014/03/arduino-uno-as-usb-to-gpib-controller.html (http://egirland.blogspot.cz/2014/03/arduino-uno-as-usb-to-gpib-controller.html)
I think the only changes I made to the Arduino code is to make sure the GPIB ID matches my K196, that the USB port matches my Mac, and to set the "++auto" mode to true.
On my Mac, I'm using muxr's logging and plotting scripts described here: https://www.eevblog.com/forum/metrology/mplot-logging-and-plotting-script-for-long-term-measurements/ (https://www.eevblog.com/forum/metrology/mplot-logging-and-plotting-script-for-long-term-measurements/)
It took me quite some time to figure out how to to install and configure these, but it was the first time I did anything with Python. I had to make a few small changes to the code, but I don't remember what off the top of my head.
Now I'm trying to get the RPi solution working, but I'm totally lost with it.
Good luck and have fun!
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To read from the 196 with a Prologix-compatible GPIB interface, you would probably need something like:
++addr 16
++auto 1
F0R0X
16 should be the GPIB address as set on the 196 through the front panel. This should output a continuous stream of readings. See the Keithley 196 manual for more details.
If you want to trigger a single reading at a time, you could send T5X, and it will only perform a single reading on receiving the X command.
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Thank yo alm. My setup is "working" at the moment, but for all the wrong reasons! My Mac (via Python) is reading the responses from the K196 fine. I'm having trouble getting the Mac to talk to the K196 though. I'm not certain if the issue is with Python on the Mac or in the Arduino code. However, with the Arduino GPIB in auto mode, any characters sent to it (including gibberish) result in the current meter reading being returned.
The odd part is that if I use the serial terminal built into the Arduino IDE, everything seems to work fine. My best guess at this point is that it's some kind of line ending mismatch.
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So sending something like R1X does not effect a range change? Note that the meter will do nothing until you send the eXecute command. Do you see any errors on the 196 display when you send a command, like IddC?
I would start by power cycling the meter and resetting the DMM to factory defaults through the front panel (program 37). This will also reset the GPIB address to 7. You could try if changing the line termination to only LF (Y3X) via the Arduino IDE makes a difference. Not sure what the Arduino IDE does as far as line terminations are concerned. Maybe try sending something like "R1X\r\n" from Python?
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Hi alm, the meter has been power cycled, but I've never reset it to defaults. I can send "R1X" etc. from the Arduino terminal and it works. When I try and have python send the same message, it's not working. So I'm assuming something is getting mangled between the python and arduino. I can check this evening about the error codes. I know I've seen them, but I don't recall under what circumstances.
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Thank yo alm. My setup is "working" at the moment, but for all the wrong reasons! My Mac (via Python) is reading the responses from the K196 fine. I'm having trouble getting the Mac to talk to the K196 though. I'm not certain if the issue is with Python on the Mac or in the Arduino code. However, with the Arduino GPIB in auto mode, any characters sent to it (including gibberish) result in the current meter reading being returned.
The odd part is that if I use the serial terminal built into the Arduino IDE, everything seems to work fine. My best guess at this point is that it's some kind of line ending mismatch.
I'm using a Prologix Ethernet based interface with python and I have my K196 working fine. This is my initialisation sequence that I send to the device each time.
# Configure the Keithley 196
gpib.select(K196_A_ADDR)
gpib.write("K0X") # enable EOI and bus hold off
gpib.write('F0X') # DC Volts
gpib.write('R3X') # 30V range
gpib.write('Z0X') # Zero disabled
gpib.write('S3X') # 6.5d rate
gpib.write('B0X') # reading from ADC
gpib.write('G1X') # data format without prefixes
gpib.write('P0X') # Digital running average filter disabled
gpib.write('N1X') # Internal Filter for high sensitivity measurements enabled
gpib.write('A1X') # enable Auto/Cal Multiplex
gpib.write('T0X') # continous on talk
When I do a read, I'm using the prologix "++read eoi" command to wait for end of input to be asserted. The "K" command is something to look at. :-/O
I understand you are building your own GPIB interface, that's cool. I believe the older instruments are a bit picky sometimes with the signalling. Also ensure that you have sufficient line drive capability from the Arduino as I've heard that some older instruments load the bus more than they should. :-//
If it helps, my code (very hacky scripts at the moment as I'm trying to get stuff going before cleaning it up) is here: https://github.com/AshleyRoll/GBIPLogger There is also some plotting code I'm working on there for my Australian Voltnut stuff.
Good luck!
Ash.
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Do you mean some devices load the bus more than allowed by IEEE 488.1, or that they load it more than a wimpy micro that does not conform to IEEE 488 can drive? GPIB drivers are supposed to be pretty beefy and able to drive up to 20m of cable and up to fifteen devices at the same time.
By the way, you could skip X on all but the last command, or even write it as a single string (K0F0R3Z0...X).
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Do you mean some devices load the bus more than allowed by IEEE 488.1, or that they load it more than a wimpy micro that does not conform to IEEE 488 can drive? GPIB drivers are supposed to be pretty beefy and able to drive up to 20m of cable and up to fifteen devices at the same time.
By the way, you could skip X on all but the last command, or even write it as a single string (K0F0R3Z0...X).
It is hear-say from Prologix when I asked them about drive capabilities. Sorry I should have been clearer. The told me that some older devices load the bus more than the spec allows.
Basically they have an Atmel device directly driving the bus, but claim it should be able to drive lots of devices. I currently have 4 older Keithley devices (K705 matrix switch, K740 temperature logger, K196) and a newer K2015 in my bus, but all short 1m cables, in a daisy chain.
I was worried about cable drive capabilities, but is seems to be working ok for me. (I've had my system logging for days at a time without incident), however I'd be wary about driving the cables directly from microcontroller I/O if I was building an interface. Not just for drive capability, but also for protection.
And yes, thanks, I could combine all the commands together in a line as you suggest, but I'd rather have the comments on each line so I can remember what I'm doing later.. only get executed once so I'm not worried about speed :)
Ash.
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The 244 octal 3state bus driver is able to drive 8 gpib units. AVR cpu can drive not more as 4 units directly.
Pic cpu is superior to 244 driver.
What fool AVR:
GPIB high is stated at 2V min and low at 0.8V max.
AVR cpu have 3V min for high and 1.5V max for low at 5V and when driving -20ma the voltage is 0.9V max from Datasheet.
If instead the AVR cpu is running at 3V, things changes, 2V min for high and 1V max for low. Driving -10ma the voltage is then 0,6V
and the limit of 10mA instead of 20mA reduced the number of devices to max 4.
If you use AVR without drivers, then (avr) Arduino must be 3.3V powered for driving it directly, otherwise 74..244 drivers are needed for 5V operation.
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The 244 octal 3state bus driver is able to drive 8 gpib units. AVR cpu can drive not more as 4 units directly.
Pic cpu is superior to 244 driver.
What fool AVR:
GPIB high is stated at 2V min and low at 0.8V max.
AVR cpu have 3V min for high and 1.5V max for low at 5V and when driving -20ma the voltage is 0.9V max from Datasheet.
If instead the AVR cpu is running at 3V, things changes, 2V min for high and 1V max for low. Driving -10ma the voltage is then 0,6V
and the limit of 10mA instead of 20mA reduced the number of devices to max 4.
If you use AVR without drivers, then (avr) Arduino must be 3.3V powered for driving it directly, otherwise 74..244 drivers are needed for 5V operation.
Thanks Nisma, exactly what I was concerned about. I didn't get far enough to check the logic level voltages though. good info.
If I was going to design an interface, I'd spend the extra on proper GPIB drivers - for instance there are a pair of devices specifically designed for it from TI:
http://www.ti.com/product/SN75160B (http://www.ti.com/product/SN75160B) - data lines
http://www.ti.com/product/sn75161b (http://www.ti.com/product/sn75161b) - control signals
there are 2 variants of the control signals chip - 161 and 162, the 162 will deal with multi controller busses as you can control the REN and IFC lines independently of the others to assert certain states.
These are only a few dollars each on DigiKey. I'm sure there are other options as well. Just the first ones I came across.
I'm probably pushing the limits on the capabilities of the non-buffered interfaces. Seems like most of these are just for one or two instruments. Also longer cable lengths are going to make this worse..
Ash.
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The open source gpib interface from University of Ljubljana use that driver.
Hovewer this drivers are slow if you want use the hs mode.
The special feature of this drivers is the defined impedance at power off and the missing glitch during power on/off,
when GPIB devices are switched on and off during measurement in order to prepare next measurement
setup where the specification allows 30 devices on one bus, but only 2/3 can be powered at the same time.
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I would not worry about about high-speed mode. For starters, there is no way that something like an Arduino or 8-bit AVR would be able to keep up with it. I believe the Prologix devices are limited to 500 kB/s (at least they were when I acquired about them a couple of years ago). Even the old IEEE 488.1 supports up to 1.8 MB/s. I also doubt most voltnut equipment would be able to ever exceed 1.8 MB/s. Maybe if you are into RF. And then only if the equipment is modern enough to support HS488.
where the specification allows 30 devices on one bus, but only 2/3 can be powered at the same time.
I thought the specification allowed only fifteen (http://digital.ni.com/public.nsf/allkb/CD66538B9541F474862570820047B175). And at least two-thirds have to be powered on.
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Initially the specs was 30 max and max 2/3 powered on (21 total) because the used driver was MC3441A and that had a better fanout.
Then the specs was reduced to 20 max on and max 2/3 powered on at same time because the 75160/1 drivers that hp and other have created for gpib had
a fanout of 14, this is then 15 devices max including controller and the max speed was specified 250Kbyte/sec .
For 1Mbyte/sec and more, the specs say, that all device must be powered on.
hs488 is not difficult to implement into arduino or any other cpu.
After setting up the data transmitters (addressing the sender, addressing the receivers), the controller enters the system into the data transmission mode (ATN = "0"). Recipients are ready to receive the RFD message by setting the NRFD line to high (NRFD = "0"). The sender then sets the NRFD line low (NRFD = "1") for a moment, informing the recipients of the possibility of an accelerated data transmission, and then sends the DIO message (DAV = "1") after setting the first data byte on the DIO bus. If all data recipients have the ability to receive data expeditiously, they inform the sender by leaving the NRFD line high, and then leaving the first byte (NDAC = "0") to leave the NDAC line high. The second data byte and the next are already sent in an accelerated manner without the participation of NRFD and NDAC lines. The sender sets the byte on the DIO bus and then after the programmable delay time (T 11 ) sends a DAV message (ie set low line DAV) to the programmable reception time (T 12 ) during which all receivers must receive a byte from the DIO bus. Data transmission is therefore without acknowledgment of receipt. The recipient may set the NDAC line low to pause the transmission of further bytes. It can also set the NRFD line low, thereby forcing the sender to cancel the accelerated transmission cycle. Both of these mechanisms allow the recipient to adjust the average bit rate to its receiving capacity. It is, however, necessary for the device to have the appropriate input buffer to which data byte groups can be sent at the maximum rate at the time necessary to reach the NRFD or NDAC signal to the sender. Delay times (T 11 ) and reception (T 12 ) can be set by the user. These depend on the total length of the cables and the number of devices in the system. The data transfer rate between two devices connected by a 2 m cable during an accelerated transmission cycle can reach 8 MB / s. For a full system consisting of 15 devices connected by 15 m total cables, the baud rate can reach 1.5 MB / s.
It have to be noticed that some device support only speeds up to 7.2mb/s.
The increased data rate requires several additional conditions:
The power supply of all devices connected to the bus must be switched on,
I / O buffers of all devices must be three-state,
The signal line capacity of each device must be less than 50 pF.
The HS488 procedure only concerns data transmission (ie programming texts, measurement results, STBs). IEEE-488 instructions and instructions are always transmitted using the full transmission cycle.
Interesting mostly on RF setups, that is correct.
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CatalinaWoW reminded me that I hadn't yet set up a github repo where we can post CSV data and such.
I've just created a github organization: https://github.com/USACalClub
and a first repository: https://github.com/USACalClub/data
Send me a PM and I'll add you to the org!
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Github Update: TiN just informed me about datashort! https://xdevs.com/datashort/ :clap:
He has graciously offered to host CSV data for all of us. I can see how this might be a better option than github -- not everyone is familiar with how to use git. Perhaps we should all use that instead? PM him (or me) for details on how to access his ftp upload.
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No need PM, uploads are free for all, over FTP with login and password datashort. All data automatically mirrored with https URL. Make sure to use passive mode for ftp. Welcome to create specific folders, for example USACalClub/Round1_Nut1 etc.
Meaningful file naming also helpful.
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I've only used command-line git, so I don't know if Github has a friendlier way of managing files and revisions. Basic operations in git are OK, but the concept of working with decentralized revision tracking can take some getting used to.
Thank you, TiN, for the FTP space.
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I'll add my thanks to TiN for the space. I have logged in and browsed, but was unsuccessful in creating a USA_Cal_Club directory and adding my data. I am not an FTP maven so am sure I am doing something wrong. Will look into it. I have added my data to the Github so some progress has been made.
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Were you using an FTP client (I use lftp on Linux)? Web browsers will usually only be able to download from FTP, not upload.
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Getting back to metrology and actual calibration, I'd propose that if there are enough individuals that would like to be able to calibrate their high end DMMs and other precision equipment, why not share the price of a high end calibrator. Either a new one from Fluke (>>$30000) or a working used one from eBay. I've seen decent calibrators in the $15000 range. I guess the logistics of shipping a large calibrator around the nation is the problem, but perhaps someone could host it regionally and club members could make the trip to use it. Working out share prices would also be a problem, but considering how much Cal labs charge, it could still be worth it. I know I'd be willing to fork up $500~1000. I could host in the Northwest region (Seattle area).
If there are 50 people all willing to pay $500 the budget would be $25000. Leaving it in 12 regions (TBD) for a month at a time should give every member a chance to use it. It would also be a chance to get together with like minded engineers and Volt-nut enthusiasts.
There would also have to be a maintenance fee for shipping costs, and eventual recertification.
Ah well, the more I write, the more I realize that this would never work. Sure wish I could get my hands on a really great multifunction calibrator just once in a while without going to the poor farm. Still posting this just for the heck of it.
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No worries, Dr. T. It's a good thought experiment and probably still worthwhile with enough participants in a metro region (i.e., no need to ship the calibrator around).
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Sharing the calibrator would be pretty much out of the question and voltnuts would simply send their stuff to the calibrator-location. Aside from that this lab would also need a few Voltage standards and at least a 3458A and a KVD to be really useful. So we need more TiNs around the world. ;D
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I have logged in and browsed, but was unsuccessful in creating a USA_Cal_Club directory and adding my data. I am not an FTP maven so am sure I am doing something wrong. Will look into it.
I logged in, found that someone already created a USA_Cal_Club directory, added a test file to it, and subsequently removed said test file.
CatalinaWOW, be sure to use an FTP client in order to have full functionality. On Mac and Linux, I use the command-line ftp client. On Windows, I use WinSCP, which supports FTP, SFTP, SCP, and WebDAV.
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I was using the command line FTP client from Windows. It has been 25 years since my last use of FTP so lots of rust. I will try WinSCP to see if it makes it easier.
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I use FileZilla on the Mac but it is also available for other platforms. It is constantly updated and it is what I use to upload everything to xDevs and KO4BB.
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Group funded calibrator (if we talking real calibrator, like 5440/57xx/480x) is really worst idea possible :). Even w/o shipping (somebody drops it and bye-bye for those ppm's), just usage scenario does not work well. To reach proper stability and uncertainty most of these must be ran 24/7 at stable controlled environment, and supported by set of high-performance standards. It's a full-time job on it's own to maintain lab with calibration capability even just for basic DCV/Ohm/ACV stuff calibrator provide. Leave alone learning and tweaking procedures and measurements for every obscure DUT abovementioned voltnuts have. Also maintenance of calibrator is not an easy task, even if you send it to Fluke for their standard 3K$ cal. Just open service manual for 5700A and check what are the performance test and calibration procedures? :) Has no 5790A, 792A, stash of expensive transfer standards? No performance tests for you :D.
What works though is local voltnut gatherings (2-4 people) for extended time (at least a week, best if 2-3 weeks) around a crazy voltnut which has calibrator, supporting gear and history in calibrated gear. That justify for visitors to bring their stuff and run it for days/week to get it all nice and stable.
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Group funded calibrator (if we talking real calibrator, like 5440/57xx/480x) is really worst idea possible :).
What works though is local voltnut gatherings (2-4 people) for extended time (at least a week, best if 2-3 weeks) around a crazy voltnut which has calibrator, supporting gear and history in calibrated gear. That justify for visitors to bring their stuff and run it for days/week to get it all nice and stable.
TiN - I already acknowledged this was a bad idea at the end of my post. However, I deal mostly with 3.5 - 5.5 digit DMMs, not in the Volt-Nut realm. Weeks of stable operation in a controlled environment is not really needed at the 4.5 digit level. I was just frustrated that I have no low cost way to fully calibrate many of my low end DMMs. I'm not paying a cal service for old multimeters for hobbyist use.
Now in regards to gatherings of Volt-Nuts with all this cal gear, who are you, where are you, who would organize these voltnut gatherings? Is there really an EEVblog forum member willing to share his high end equipment? I would if I had it, but then I'm retired now and have time. I'm talking about a true multifunction Calibrator.
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Group funded calibrator (if we talking real calibrator, like 5440/57xx/480x) is really worst idea possible :).
What works though is local voltnut gatherings (2-4 people) for extended time (at least a week, best if 2-3 weeks) around a crazy voltnut which has calibrator, supporting gear and history in calibrated gear. That justify for visitors to bring their stuff and run it for days/week to get it all nice and stable.
TiN - I already acknowledged this was a bad idea at the end of my post. However, I deal mostly with 3.5 - 5.5 digit DMMs, not in the Volt-Nut realm. Weeks of stable operation in a controlled environment is not really needed at the 4.5 digit level. I was just frustrated that I have no low cost way to fully calibrate many of my low end DMMs. I'm not paying a cal service for old multimeters for hobbyist use.
Now in regards to gatherings of Volt-Nuts with all this cal gear, who are you, where are you, who would organize these voltnut gatherings? Is there really an EEVblog forum member willing to share his high end equipment? I would if I had it, but then I'm retired now and have time. I'm talking about a true multifunction Calibrator.
There are quite a few of us in the Seattle area... I have a Fluke 731B for example. No 3458A yet unfortunately, just a 34461A.
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I'm not paying a cal service for old multimeters for hobbyist use.
Well, than why would you pay for somebody's calibrator just to check stash of your 4.5d meters :)
Heck, it's cheaper just to buy new meter of that level, than get setup for a calibration :).
Who would organize these voltnut gatherings?
Interested parties organize themselves. At least I want to believe that, as I know that happened before, being on such calibration "party" last year, when I calibrated both of my K2002's and stash of references. Even though cost of such (due to airplane fares from TW to USA) was close to sending meters to Keithley/Fluke for calibration, it was manyfold much more fun to play with gear, instead of getting just expensive piece of paper with numbers. Would I do it again? Heck yes, TBD next year! :)
Is there really an EEVblog forum member willing to share his high end equipment?
That depends too. Usually hardcore voltnuts are fond of their gear, and are happy to show off a bit. :-DD
I'd be happy to accept visitor for few days to hangout, calibrate some meter, play with the references and chat about ppm-hunts over the cup of tea/beer/something else. :=\. But that's unlikely to happen in my current geo.
But I'd expect the owner of expensive set/MFC would expect guest party to be at same level , so both sides can benefit. Meaning that meetup with everyone bringing 8.5d meter to verify with one member's MFC is likely possible, unlike having guests with ten 4.5 handhelds, which just mean work for calibrator owner :) After all cross-comparisons are key aspect in metrology. No matter how great and stable is the equipment, there are always statistic laws at play. And all of this is not cheap, so resulting cal club member list will be rather short anyway.
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Now in regards to gatherings of Volt-Nuts with all this cal gear, who are you, where are you, who would organize these voltnut gatherings? Is there really an EEVblog forum member willing to share his high end equipment? I would if I had it, but then I'm retired now and have time. I'm talking about a true multifunction Calibrator.
I'd gladly take the time to share my equipment, including travel and hotel expenses.
The Volt-Nut community here is growing stronger, lots of good equipment is being restored, stable homebrew stuff being born, looking forward to the future. :-+
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Now in regards to gatherings of Volt-Nuts with all this cal gear, who are you, where are you, who would organize these voltnut gatherings? Is there really an EEVblog forum member willing to share his high end equipment? I would if I had it, but then I'm retired now and have time. I'm talking about a true multifunction Calibrator.
I'd gladly take the time to share my equipment, including travel and hotel expenses.
The Volt-Nut community here is growing stronger, lots of good equipment is being restored, stable homebrew stuff being born, looking forward to the future. :-+
Dr! Perhaps we should think about hosting a midwest cal get together :-+
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My door is always open to volt-nutters and audio people, but nobody wants to come to Rochester even in good weather and I've taken a vow of poverty, so don't get out much.
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My data is now copied into TiNs repository. I will continue to post graphs of conclusions here, but will leave the raw data elsewhere.
Thanks for the WinSCP suggestion. Made the operation simple. Which has a downside. One more area where the motivation to learn has been eroded. Years of mandatory exposure to Windows in the corporate world has allowed me to be deficient in Linux and command line operations. I am slowly switching to Linux for all of the usual reasons, but still find most tasks far easier in the system with decades of training behind me.
On that note I have used Libre Calc and Excel for data reduction. Neither is particularly good. Libre Calc is very slow on large files, particularly graphs. Excel is far faster, but crashes periodically. Apparently has a memory leak somewhere which catches up on large files. On to try Gnumeric. Too bad there is no single tool set that is ideal for everything.
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Catalina,
Can You please post the calculated temperature coefficients of the three instruments based on the text file.
0.007131491465747643
9.653462320521867E-05
0.00020292057647497002
?
Room ambient temperature fluctuations were not sufficient to get a meaningful temperature coefficient for the 3478 and the 3456. The quantization was too large with respect to the noise and any changes due to temperature. I am still trying to tease out a temperature coefficient for the 3457, but don't have an answer yet that I consider meaningful. There does appear to be a very slight negative coefficient, but it is a fraction of a part per million per deg at most, and I am not yet ready to say that anything I have seen is statistically significant.
A simple inversion of the test on the SVR-T isn't in the cards because the thermal time constant of the meters cannot be assumed to be short relative to the overnight temperature changes. I had evidence that the thermal time constant of the SVR-T is in the order of 10 minutes so the overnight temperature changes were tracked reasonably. From my experience with other somewhat similar pieces of equipment I would expect the thermal time constant of the 3457 to be more on the order of an hour.
Based on the small size of the tempco, I have put any further investigations of this on the back burner while I chase other things of more impact and interest to me.
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Thanks for the WinSCP suggestion. Made the operation simple. Which has a downside. One more area where the motivation to learn has been eroded. Years of mandatory exposure to Windows in the corporate world has allowed me to be deficient in Linux and command line operations. I am slowly switching to Linux for all of the usual reasons, but still find most tasks far easier in the system with decades of training behind me.
Glad WinSCP worked OK for you. Although I have a dedicated Linux box (or two) at home, on my Windows and Mac systems I also have Linux virtual machines. The Mac also has a Windows virtual machine. So, it's easy to switch to whichever environment works best for a particular task or project. Sometimes, though, it can be a bit of a brain juggle getting the fingers to use the correct hotkeys in the correct OS.
On that note I have used Libre Calc and Excel for data reduction. Neither is particularly good. Libre Calc is very slow on large files, particularly graphs. Excel is far faster, but crashes periodically. Apparently has a memory leak somewhere which catches up on large files. On to try Gnumeric.
I also tend to use Excel more than Calc since I often work with files on the order of 100K to 1M rows. However, despite the additional speed, I've occasionally had Excel crunching all night (8 threads at 100%) and still not finish. Need mo' pow-ah!
Too bad there is no single tool set that is ideal for everything.
Yep. C'est la vie. I've even used one tool solely as an intermediary to get data into a format that will load into another tool. As the old saying goes, the great thing about standards is that there are so many to choose from.
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For serious data analysis (1M rows is no longer some casual experimentation), I would suggest a more professional tool like MATLAB (https://www.mathworks.com/products/matlab.html) (or one of its open-source clones like Octave (https://www.gnu.org/software/octave/) or Scilab (http://www.scilab.org/)), R (https://www.r-project.org/) or Python with the standard scientific packages (https://www.scipy.org/). Performance should be much better if you use them properly (vectorized calculations are much quicker than loops in all of the tools). And it is much easier to figure out:
tolerance = measured_value * gain_error + temperature * gain_tempco * measured_value + offset_error + temperature * offset_tempco
than:
=$A3 * Constants!$C$44 + $X3 * Constants!$C$46 * $A3 + Constants!$C$45 + $X3 * Constants!$C$47
Plotting a million random points takes a few of seconds with R or SciPy/Matplotlib on Python 3. Pretty much instantly in Octave.
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Thanks, alm. I'll check out Octave and Scilab.
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I've started on Octave. I've had some experience with Matlab and find that it takes a different mindset in formulating problems. No problem once you get it, but it is frustrating until that clicks. Just like any large package.
I actively resisted using Matlab before I retired, simply because I wanted my work accessible to the broadest population, and my corporation did not fund a Matlab license for every engineer, let alone technicians and managers of technical work. But spreadsheets were on every machine, even secretaries and other totally non math oriented positions. They also didn't allow freeware such as Octave.
Situations like this are one of the reasons that Excel compatibles survive in the face of more powerful tools. You will reach a more sophisticated audience using Matlab and similar, but a much broader audience with Excel. (Also note that someone proficient in Excel can make equations much more readable than your example above, not as good as the Matlab version, but significantly better. And comments are quite possible in both, a great aid when the author can be bothered to include them.)
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It looks like feedback.loop also uses Octave.
https://youtu.be/jcCC867gKXE?t=26m47s
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Yes, it is possible to do better with Excel. But I would argue what I posted is fairly typical for a large fraction of the Excel spreadsheets I have seen. I admit that I have not been in a company with people with advanced Excel skills that spend all day in it, like you might have in some financial firms. But I have worked with plenty of scientists and engineers, and what I posted was fairly typical. Actually the worksheet named "Constants" might have been Sheet2 or the constants might have been shoved somewhere below the data. Excel just invites this kind of code by hiding away features like named ranges. Even a lazy scientist programming in MATLAB would at least have named the temperature t and the voltage v. I am not sure if I have ever seen someone else use the Excel comment feature except for collaboration.
I took a course which used Excel for some moderately complicated equations based on a dozen or so of input parameters. After looking at a student's Excel worksheet and seeing the results were all messed up, the instructor proclaimed that it is impossible to debug an Excel worksheet. I proceeded to find the bugs in their worksheet, but it was definitely much harder than debugging a MATLAB program that did the same.
If you have zero programming experience, then MATLAB/Octave/Scilab might be a fairly steep learning curve. But if you have any experience with procedural programming, you should be able to get started quickly. Learning how to (mostly) get around loops through clever programming or the intricacies of indexing takes a bit longer. Many solutions you find for MATLAB will be applicable to Octave or Scilab with some minor modifications.
For me Excel (or other spreadsheets) is fine for simple problems with at most a dozen columns, a few hundred rows and no complicated math. But as soon as it becomes more complicated, I move it to a proper programming language. What if you want to do the same analysis for a hundred CSV files (common case for me). Sure, you could write some VBA, but at that point you have pretty much lost all advantages Excel had about being less complicated.
Just to be clear, MATLAB/Octave/Scilab are not my favorite tools either. I think the language is pretty ugly. But I recognize them as professional tools and have written a fair amount of code for them (mostly MATLAB). Excel mostly strikes me as a toy, despite said toy being used by millions of professionals.
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I have to agree with the accessibility of Excel, and I use it a lot. It just doesn't take much effort to get things labeled, colored and commented. Heck, comments help me remember what I did. You can also extend things greatly by enabling the advanced analysis features and adding some VBA code. That said, I usually do a first tab with background and instructions and half the people I give it to respond with, "OK, I see the text, but where's the spreadsheet?"
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The question came up because of the performance of Excel with a large number of rows. Do you have a way to get reasonable performance with 1M samples? In my admittedly old Excel 2007 it refuses to plot more than 32k points (making me do the decimation, instead of doing it itself like every other math package). And scrolling past this graph with 32k points (not many in my book) takes a couple of seconds per redraw cycle. While Octave was able to plot 1M points (decimated, obviously) in a fraction of a second, never mind moving the window.
How do you even decimate data without aliasing in Excel? Something like the MATLAB/Octave decimate (http://www.mathworks.com/help/signal/ref/decimate.html) function that low-pass filters the signal before resampling.
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Don't know what the limits are, but I just created a column of 70,000 data points, summed them and graphed them, with no trouble at all. Took just over zero seconds. Running Windows 10 and Office 2016 on a 4.2 GHz i7-7700. No doubt one smarter than me could write some VBA code to filter and decimate.
edit- OK, I put some Excel data smoothing filters up in a separate thread. They seem to work well on voltage history.
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Package arrived, Ill setup and begin some tests this evening.
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cellularmitosis, any specific tests you would like me to look at? I have a 2 hour warm up drift plot of the Geller ref and a 10 hour plot. I am able to confirm my 34465A as sent from Keysight consistently reads about 5 to 8 ppm low from various references, including the Geller. Ill work on posting the data I have so far today.
Edit, doing a noise comparison, LM399 based PDVS1 vs AD587LQ Geller vs LT1021 Doug Malone vs LTZ1000A KX Ref. Photos and data forthcoming.
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cellularmitosis, any specific tests you would like me to look at? I have a 2 hour warm up drift plot of the Geller ref and a 10 hour plot. I am able to confirm my 34465A as sent from Keysight consistently reads about 5 to 8 ppm low from various references, including the Geller. Ill work on posting the data I have so far today.
Edit, doing a noise comparison, LM399 based PDVS1 vs AD587LQ Geller vs LT1021 Doug Malone vs LTZ1000A KX Ref. Photos and data forthcoming.
Sounds great! Yeah, I would have just suggested whatever tests you are familiar with, voltage, tempco, noise, hysteresis. The specific tests aren't critical in this round -- this is more about giving people a real object to engage with, and to start grappling with solving all of the challenges which come with it ("how do I record and plot data? How stable is my lab temp? What are my EMI issues?"). I know that for me, just mailing off this box has kicked into motion several projects which I've been mentally toying with for years!
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Who is the last person if the food chain? :)
Perhaps somebody can list the loop members and sequence, for us outsiders? :)
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After kj7e comes bitseeker and then RandallMcRee, which completes the original route.
However, we've had a few more jump on the bandwagon! nikonoid, martinr33, and orin.
Finally, I've also recruited someone (Vacuuminded) from the volt-nuts mailing list! He should be introducing himself in the thread soon :)
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More members. Yay! :-+ Welcome aboard, everyone.
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Should certainly be interesting.
Since the recent hot spell (max of 29 deg C in the lab), my 731B has been reading a little low on the 34461A, so tonight I fired up both the Fluke 8845A and my SVR-T. The results were surprising.
Using 100PLC and stats to average 100 readings:
| 34461A | 8845A |
| 731B | 9.999967 | 9.999980 |
| SVR-T | 9.999969 | 9.999981 |
The last time I compared them seriously was back in 2013:
https://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582 (https://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582)
If anything, they've drifted closer! The 731B has been powered almost continuously (we've had some pretty long power outages) and the SVR-T unpowered. I certainly didn't expect them to be so close.
The 61A is two years since its last cal and the 45 is a year old.
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Cool! I've found that power cycling the 731s is less of a problem than one might think. In fact, I don't even have batteries in mine anymore, just a large capacitor and parallel zener diode to emulate a battery's filtering and voltage regulating action. They won't work correctly without that, or a battery. I do the same thing on my 845 null detector.
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My Excel skills are lacking, I can send someone my raw data if they could overlay the temp and voltage plots.
There really was not much of a warm up needed for the Geller reference, 2 hour plot;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/2_H_warmup_587lq.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/2_H_warmup_587lq.jpg.html)
10 hour plot, A/C was on but the room held steady within 1dec C. You can still see the influence of the A/C cycling. I cant explain the two spikes, possibly overhead lights being switched on or off;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/10_H_587lq.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/10_H_587lq.jpg.html)
Temp over the same 10 hour time frame;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/10H%20temp%20plot.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/10H%20temp%20plot.jpg.html)
Ill have the noise comparison of the various references later. I would like to also do a tempco comparison if time permits.
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I would like to also do a tempco comparison if time permits.
No need to rush on my account. Feel free to do the tempco, too.
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Sent a PM to get the 10 hour.
Thanks,
Conrad
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Sent a PM to get the 10 hour.
Thanks,
Conrad
Email sent.
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Does anyone have/want to do a low ohms test.
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I have two micro ohm meters (510a,Simpson). It might be a good test.
Sent from my iPhone using Tapatalk
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I have two micro ohm meters (510a,Simpson). It might be a good test.
Sent from my iPhone using Tapatalk
Cool, glad I'm not the only one.
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What kind of resistors are currently in the traveling kit? Anything of interest to micro ohm meter owners?
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There were none when it arrived here and I didn't add any. The only reference parts are the voltage reference and a well calibrated capacitor.
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Ah, OK. I may have been thinking of the capacitor that was added, incorrectly recalling it as a resistor.
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Looking through the specs of most milliohm meters. 1m - 1k will be sufficient for most.
Resistors following the 1.9x decade scheme aren't very common. Especially as you go down in resistance.
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I was going to put in a 100 ohm resistor, but the weight of the package is right at the limit. I also didn't get the unit aged and measured as well as I'd like. Need a bigger box next time!
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Ran 15-30 deg C tempco tests, one with the tempco comp jumper on and one off. The package will be mailed to bitseeker in the morning. More charts forthcoming.
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Thanks, I'll keep my eyes peeled for it.
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Ran 15-30 deg C tempco tests, one with the tempco comp jumper on and one off. The package will be mailed to bitseeker in the morning. More charts forthcoming.
Fantastic!
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Hi Jason and all involved in this! Such an excellent idea! Hi my name is Chris, and I have a problem. <hi chris> :P
Been a long time lurker of eevblog, but at the prompting of someone on the voltnuts mailing list and Jason, finally created an account and am posting here. Not sure just how much I can contribute to this effort, but if it works out that I can be added to the list I'd certainly like to be involved! Pretty low on the food chain far as precision measurements go, but slowly getting there. I presently have a recently calibrated (Simco, fwiw..) 3456A, and am repairing/partially rebuilding a recently acquired 3455A, which may be a perfect platform for experimenting with a more stable reference. I could only DREAM of the legendary 3458A or similar that so many of you have!
I am a long time tinkerer of tube type electronics (thus the screen name) and mechanical stuff, very passionate about vintage test equipment and ham radio/communications equipment. This has awoken my inner OCD and need for extreme accuracy!
Need to go back through this long thread and re-read everything but this is all extremely impressive and a very interesting idea!
Regards,
Chris
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Great to have you on-board! I'll add you to the end of this go-round.
Don't worry about your ability to "contribute" -- we are all helping each other! Glad to have you participating :)
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Welcome to the club and the active side of the forum, Chris!
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Hi Chris, is that some Collins gear in your photo?
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Hi Jason and all involved in this! Such an excellent idea! Hi my name is Chris, and I have a problem. <hi chris> :P
Been a long time lurker of eevblog, but at the prompting of someone on the voltnuts mailing list and Jason, finally created an account and am posting here. Not sure just how much I can contribute to this effort, but if it works out that I can be added to the list I'd certainly like to be involved! Pretty low on the food chain far as precision measurements go, but slowly getting there. I presently have a recently calibrated (Simco, fwiw..) 3456A, and am repairing/partially rebuilding a recently acquired 3455A, which may be a perfect platform for experimenting with a more stable reference. I could only DREAM of the legendary 3458A or similar that so many of you have!
Hi Chris! ;)
As to that 3455A... how is the jitter in the low digit in hi-res mode with auto-cal on when fed with 10V? If it's more than +/- 1 digit, then it's probably dielectric absorption in the integrating capacitor. I've only heard of one without this problem so far. I've put some Russian teflon capacitors in mine and it's much improved.
Orin.
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Has the package already passed the East Coast yet?
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Has the package already passed the East Coast yet?
Yup, but it'll be running through NJ again to visit nikonoid. PM me if you want to jump in!
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I got a little box today. :-+ More when I get it up and running.
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Bitseeker, A WWII hacked up command set transmitter, (not sure who contract built that one), 12V command set dynamotor power supply, and a Hallicrafters "UHF" (really VHF) receiver of the same era. I have a serious problem when it comes to accumulating boatanchors! Barely visible behind me is also a B&W 5100B transmitter.
Orin, I cannot honestly answer the 3455A jitter question, as I discovered the +12V regulator has a fault both producing some very ugly ripple, and loading down the power supply by an extra 200mA. I located a NOS replacement but it is hanging in limbo at a Houston post office. No idea when it will arrive. I'm half tempted to use a TO-220 regulator and just bolt it to the dang chassis, haha!
Do you know offhand which capacitor(s) you had this issue with? All electrolytics have now been replaced, but no others have been touched.
Regards,
Chris
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Gentlemen!
After getting a 16-channel logic analyzer, I have finally made a break-through on my DIY GPIB project! I can now stream readings from a Keithley 196!
I'll start a thread for this in the project sub-forum, so that I don't derail this thread. But since I had posted about this earlier in this thread, I thought I'd mention my progress here as well.
https://www.eevblog.com/forum/projects/atmega-gpib-yet-another-diy-gpib-to-usb-project/ (https://www.eevblog.com/forum/projects/atmega-gpib-yet-another-diy-gpib-to-usb-project/)
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That's great news, cellularmitosis! Thanks for starting a thread on it. I haven't tried logging with my 196 yet and am curious what the deal was with yours. I'll check out the thread.
Back on the calibration front, I was delayed on getting started and then had some GPIB issues with my 34401A. It's all working now. With both the 34401A and 34410A connected to my laptop via 82357B, I'm running a logging test on a 6114A supply warming up at 15VDC. Warm up was approximately 50 minutes to flatten out. It's an all-HP volt party.
The 34410A is marked as having been calibrated on 25 Aug. 2009. The 34401A is unknown. However, they're currently reading within 4 to 5 counts of one another at 15V (i.e., 400-500 µV).
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I'm on the tail end of a recent heat wave, so it's been a bit toasty in the lab the past few days. Fortunately, today's been a bit better and, from the two-hour period I was logging the reference, stable as far as temperature and humidity.
It's funny that you can see when I was in the lab to start and restart the logging each hour (BenchVue log timeout). I add to the humidity and lower the room's temperature. Who'd a thunk it.
Question: How much of the resolution captured via GPIB is for real on these meters? For example, the raw data had values such as 10.0000512. :o Surely, it can't do 8.5 digits even at 100 PLC. I formatted the stats below to 6.5 digits and added one extra decade for the standard deviation (so it wouldn't be zero).
Here are some stats (second hour only) and graphs from today's logging. I'll upload raw data to the xdev's share.
34401A
| Range | 10VDC |
| NPLC | 100 |
| Average | 10.00028 |
| Std Dev | 0.000003 |
| Min | 10.00027 |
| Max | 10.00029 |
34410A
| Range | 10VDC |
| NPLC | 100 |
| Average | 10.00005 |
| Std Dev | 0.000003 |
| Min | 10.00004 |
| Max | 10.00006 |
Attachments
T&H-Hour1&2.png: Temperature and humidity during the two-hour duration. Captured from the TI dongle and logged via EZGPIB.
34401A-Hour1.png: First hour of logging the 10V reference via 34401A.
34401A-Hour2.png: Second hour of logging the 10V reference via 34401A.
34410A-Hour1.png: First hour of logging the 10V reference via 34410A.
34410A-Hour2.png: Second hour of logging the 10V reference via 34410A.
34401A-34410A-10VDC.jpg: DMMs at work.
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Interesting!
So, because they show the same std deviation, does that indicate both meters are close in terms of stability and noise, and that the measurement overall was a high quality one? That would give you good confidence that the 34401A is about 230uV high relative to the 34410A?
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I, too, was quite surprised that they both fluctuated by only one count from the average. To minimize noise, I twisted the Pomona leads, disconnected every electronic device in the room except for the participating instruments and my laptop, turned off all the lights, and left the room during logging. I used an integration time of 100 PLC, but still didn't expect the DMMs to be so similar.
I haven't yet dug into the specifics of the data collected during the earlier runs, but if I recall correctly, someone posted that the SVR-T's output is pretty much right on. So, yes, I take that to mean that the 34401A is a bit high.
Hey, it just occurred to me to check the cal message in the menus, since there's no sticker. Bingo! 14 July 2003. Six years older calibration than the 34410A.
Here's some stats from 1 hour of the 34401A logging the output of the 6114A that was powering the SVR-T at 15V.
| Average | 15.0219 V |
| Std Dev | 0.00009 V |
| Max | 15.0221 V |
| Min | 15.0217 V |
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There were three programs on the thumb drive to log temp/humidity from the TI module using EZGPIB. One of them always returned -1 due to a conversion problem and only logged to the console. Another one logged to a file. The third one output the correct values and only logged to the console. Two or all three didn't log the date/time, logged as fast as possible (which seemed excessive), and had hard coded values for things such as the COM port, which made configuration more difficult.
I made a new one, TiSensorLogger.488, that logs date, time, and sensor values once per second to both the console and a file. There's a section near the beginning of the source code with configuration variables to set the COM port and location/name for the log file.
The log file that's created has a header row and is tab-delimited for easy loading into Excel, Libre Office Calc, etc. If the file already exists, data is appended to it.
I've added the program to the thumb drive in the package as well as attached here for anyone who has their own module and uses EZGPIB.
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Awesome work! Thanks! 8)
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I still do not have my logging working. I am planning to use some of what you bitseeker did. Thanks.
Sent from my iPhone using Tapatalk
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nikonoid, I used a version of BenchVue from last year on my laptop for the meter logging as it was relatively straightforward. The only downside was that the logging times out after an hour, at which point you have to start a new file. The current version of BenchVue only has a trial mode and I'm not sure what the limitations are during the trial period.
At some point, I'd like to move logging operations to my Pi or BBB.
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Orin, I cannot honestly answer the 3455A jitter question, as I discovered the +12V regulator has a fault both producing some very ugly ripple, and loading down the power supply by an extra 200mA. I located a NOS replacement but it is hanging in limbo at a Houston post office. No idea when it will arrive. I'm half tempted to use a TO-220 regulator and just bolt it to the dang chassis, haha!
Regards,
Chris
Chris,
This is a reply to your pm about the 12V power supply in the 3455A outguard. Pre-regulator (J5 pin 2) is 18.6V and about 1.2V ripple. Post-regulator (J5 pin 5) is 11.9V and 200mV noise. Nothing really surprising there. 'scope shots attached at same vertical resolution*... not much point posting a higher resolution shot of the post-regulator noise.
Orin.
*multiply scope readings by 10 - someone forgot to set the scope probe setting.
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Since the heatwave has passed, I did another run with the same meters. As before, I logged for two hours, but only pay attention to the second because the meters aren't really stable during the first hour even though I warm everything up half an hour prior to starting.
All logging at 100 NPLC as before. Data files will be uploaded to the xdev's share.
34401A
| Average | 10.00027 |
| Std Dev | 0.000002 |
| Max | 10.00028 |
| Min | 10.00026 |
34410A
| Average | 10.00026 |
| Std Dev | 0.000006 |
| Max | 10.00027 |
| Min | 10.00024 |
Based on the temp/humidity logging over the entire two hours, the temp was rising slowing from 27.0 to 27.7°C. The 34410A's voltage was similarly rising, unlike the 34401A. The next time the roving standard comes around I hope to have the ability to do all-night logging to better see the stability.
During this run, I also had a Keithley 2700 attached to the SVR-T. I don't have it set up for logging right now, but it was even closer to 10V than the 34410A. Right now, the displayed values are as follows:
34410A: 10.00010
34401A: 10.00026
K2700: 10.00007 (Cal unknown)
Here are some other meters I hooked up for a quick check. The Keithley 196 and Fluke 8100A warmed up for about half an hour. The handheld Keysights and Greenlee warmed up for about five minutes.
K196: 10.00035 (Cal unknown)
F8100A: 10.002 (Cal unknown)
U1272A: 9.978 (Cal exp. 6/2013)
U1282A: 9.998 (Cal exp. 12/2017)
U1252B: 10.000 (Cal exp. 10/2017)
DM-820A: 10.00 (Cal unknown)
As for the 9764.02 pF capacitor in the box, here are the values I got.
34410A: 9.7689 nF
U1272A: 9.691 nF
U1282A: 9.789 nF
U1252B: 9.764 nF
DM-820A: 9.77 nF
M12864: 9711 pF
The M12864 is a version of the "$20 transistor tester".
Note: I've updated the TiSensorLogger.488 program on the USB stick and attached to my post (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1296589/#msg1296589). Changes include the following:
- Code tidying
- Flush bad data prior to the start of logging (the first temp and humidity samples are always wrong)
- Configurable logging interval (in seconds)
- Throw an error if unable to connect to COM port
- Blink right-most LED on EZGPIB UI while logger is running
@RandallMcRee: I'll be dropping the package off at the Post Office on Monday. You'll probably get it Tuesday or Wednesday.
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A note on the capacitor- the value is for the device plugged into standard banana jacks, with the fixed capacitance of the jacks subtracted out. That means I would have measured the open circuit capacitance of my 1615A, probably about 1.2 pF if I remember right, and subtracted that from the reading. The banana method is OK, but not nearly as good as a cap in a shielded box with two shielded connectors. The problem is almost nobody has a bridge or other method of doing the proper shielded measurement.
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Thanks for the reminder, Conrad. I didn't check for null on the meters that I measured the cap on. They all have banana jacks and I just plugged the thing in. I guess I can go back and see if they're already zero when open circuit and subtract accordingly. The U1252B was bang on based on the value on the little tag. :-+
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I used our HP4284A for my reported value of the capacitor. Open/Short corrections were done beforehand, as well.
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I already packed everything up. The value I posted was from the little tag. I believe yours was on the larger paper, correct? If so, then where did the value on the little tag come from? I don't remember how much you had noted via the HP 4284A, but I think it was a higher value.
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Pretty sure I put a toe tag on the cap with the 1615A value. I have access to several GR 1000 pF standards that agree pretty well, so I trust the 1615 is well calibrated, if not traceable.
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Yes, the toe tag read 9764.02 pF
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@RandallMcRee: When you receive the package, can you post the capacitor value on the larger tag (the one that isn't 9764.02 pF)? Thanks!
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Package received.
Capacitor tags:
Large tag: 9776.11 pF, D=0.000081 measured @1V 1Khz w/ HP4284A
Small tag: Cs=9764.02 pF, D=0.000092 (73F at end)
More later.
Randy
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Thanks, Randy. So, the large tag is from CalMachine and the small one from Conrad.
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I am sort of infected with the volt nut disease. But often run into cognitive dissonance. I grew up in the slide rule era. Discussing the third digit of capacitor readings, or the fifth and sixth digits of voltage readings still seems a bit bit surreal to me. All of the attention required to temperature, humidity, terminal material, aging and stabilization times continually reminds me why in the more general world of electronics things beyond the second digit are rarely important.
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Yeah, having recently finished the measurements logging, looking at 3.5- and 4.5-digit meters is rather serene. Hardly any fluctuations, no worry about noise, and moving in/out/around the room doesn't cause a disturbance. I don't know if I could handle more than 6.5. ^-^
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I am sort of infected with the volt nut disease. But often run into cognitive dissonance. I grew up in the slide rule era. Discussing the third digit of capacitor readings, or the fifth and sixth digits of voltage readings still seems a bit bit surreal to me. All of the attention required to temperature, humidity, terminal material, aging and stabilization times continually reminds me why in the more general world of electronics things beyond the second digit are rarely important.
I was thinking about the notion of ppm the other day and came up with the following visualization to put it into perspective for myself:
Think about the length of a football field. 1 ppm is roughly the thickness of a sheet of paper.
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I am sort of infected with the volt nut disease. But often run into cognitive dissonance. I grew up in the slide rule era. Discussing the third digit of capacitor readings, or the fifth and sixth digits of voltage readings still seems a bit bit surreal to me. All of the attention required to temperature, humidity, terminal material, aging and stabilization times continually reminds me why in the more general world of electronics things beyond the second digit are rarely important.
I was thinking about the notion of ppm the other day and came up with the following visualization to put it into perspective for myself:
Think about the length of a football field. 1 ppm is roughly the thickness of a sheet of paper.
or say a scale 1KM long, 1ppm is 1mm on that scale.
regards.
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Think about the length of a football field. 1 ppm is roughly the thickness of a sheet of paper.
Good visualization aide.
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D'oh, I just saw that I forgot to try out my HP 3469A on the SRV-T. Next time. :-DMM
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I am sort of infected with the volt nut disease. But often run into cognitive dissonance. I grew up in the slide rule era. Discussing the third digit of capacitor readings, or the fifth and sixth digits of voltage readings still seems a bit bit surreal to me. All of the attention required to temperature, humidity, terminal material, aging and stabilization times continually reminds me why in the more general world of electronics things beyond the second digit are rarely important.
I was thinking about the notion of ppm the other day and came up with the following visualization to put it into perspective for myself:
Think about the length of a football field. 1 ppm is roughly the thickness of a sheet of paper.
A bit off topic but that reminded of this, fold said sheet of paper 103 times = the thickness of the universe;
https://www.youtube.com/watch?v=AAwabyyqWK0 (https://www.youtube.com/watch?v=AAwabyyqWK0)
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I just got an HP 3468A. The internal battery was from 1985 and dead. I soldered in a CR123. The device is at Error 1, and was before. I tried following the Service Manual on Calibration. On the first step with the leads shorted, It said Zero Done. I attached the 3.0 volt source and pressed CAl and then SGL TRIG and this is where I got the problem. It says invalid Voltage for Cal. Can anyone help me?
Second, is the device usable un-calibrated?
I did find nice adapters to convert to shielded leads on Amazon.
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I just got an HP 3468A. The internal battery was from 1985 and dead. I soldered in a CR123. The device is at Error 1, and was before. I tried following the Service Manual on Calibration. On the first step with the leads shorted, It said Zero Done. I attached the 3.0 volt source and pressed CAl and then SGL TRIG and this is where I got the problem. It says invalid Voltage for Cal. Can anyone help me?
Second, is the device usable un-calibrated?
I did find nice adapters to convert to shielded leads on Amazon.
Welcome Marty, I may suggest posting this question as a new topic in the Test Equipment section, here https://www.eevblog.com/forum/testgear/ (https://www.eevblog.com/forum/testgear/)
I'm sure those who have run into the same situation will respond.
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In my case silence is good. I have been busy getting all the bits and bobs to do what they are supposed to be doing:
New prologix gpib converter woking on both computers :-+
EZGPIB working :-+
Installed CatalinaWows Temp-Humidity sensor :-+
Modified his script to work on my laptop :-+
Logging started :-+
Preliminary data confirms what we already know: Keithley 6.5 digit meters (K2015) have 1ppm/degree TCR and even older, uncalibrated meters like to show 10.00007 at 23C.
Perhaps someone can point me to a good (non-excel, prob. not python) windows or cloud way to show csv data graphically. Previous tools are all work-related and forbidden. I see that TiN has d3.js on xdevs but not sure how that works. Pointers?
o-o,
Randy
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You can use the LibreOffice (http://www.libreoffice.org/) suite. Calc is similar to Excel (but free) for loading up and graphing your log file.
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I have found Libre Office slow for large files like these log files. Octave, an open source Matlab look alike is recommended by many. I have loaded it and am coming up to speed so can't really personally recommend it.-
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Gnumeric is much quicker than Ope Office if You are using Linux
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Perhaps someone can point me to a good (non-excel, prob. not python) windows or cloud way to show csv data graphically.
Hello,
I often use plotter from Ulrich Bangert.
(does also some statistics and analysis).
http://www.ulrich-bangert.de/html/downloads.html (http://www.ulrich-bangert.de/html/downloads.html)
with best regards
Andreas
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Thanks, Andreas. I've been intending to try Plotter (saw when programming EZGPIB), but it slipped my mind.
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Trying Plotter, now. Should have thought of it since I'm using EZGPIB.
Ulrich Bangert seems like a stellar individual. I was really sorry to read that he had passed away. There is no emoticon to express my feeling of loss.
The run that I was doing crashed out after 9,656 samples with some software exception. Is the EZGPIB code available somewhere to debug? (It has happened consistently).
Thanks again,
Randy
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The EZGPIB source code doesn't seem to be available currently. Ulrich's brother has control of the source code, and may be amenable to releasing it. I haven't contacted him for fear that I can't do justice to it.
I have run logs longer than 9,656 samples, so the problem may not be purely with EZGPIB.
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Plotter output from run1. Strong temperature dependence as expected. Obviously, I need some help with Plotter....
First plot is voltage which only varied from 10.00004 to 10.00007 volts. Second plot is temperature. Around 5pm I covered the reference with poly batting to dcrease the influence of air currents, but the temperature sensor remained uncovered. I think the big temp event is me closing an open window (not sure when it *was* opened--not by me anyway).
CatalinaWow--yes, my script could be at fault, memory leak perhaps? Hard to know, without better debugging. I would be interested in helping maintain it, though I'm a Java guy.
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Randy, what error did you receive when the logging crashed? Which script file were you running? If you're using TiSensorLogger.488, then there could be a bug that I introduced as well.
I logged for a little over two hours at a time, so my logs were between 8k and 9k. But if CatalinaWOW was able to run longer, then it could be something in the script or perhaps a driver issue. Details on the error may help reveal more.
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The EZGPIB error was in german and I id not capture it. Next time!
Here is the script--
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OK, I only noticed two things in the script:
- Lines 63-64: A '1' is being sent to the HDC1010 and the returned value stored as temphex. However, '1' is humidity. The value doesn't appear to be used before it's overwritten on line 86. I assume this portion of code is just to fetch and discard the first value, which I found to be garbage data when I was working with the HDC1010. So, this issue is more an FYI for the sake of consistency.
- Line 71: The header is being output with a comma as the delimiter. However, when the captured values are sent to the file buffer (lines 81, 102, 103, 110), EZGPIB_FileAddToBuffer() uses tab as the delimiter. So the header and data use different delimiter characters. Do you see that being the case in your log file?
Other than that, the script code looks fine.
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Oh, one other thing to note about EZGPIB is that each time EZGPIB_FileWrite() is called, it opens and closes the file. Since the script does this on every loop, if something goes awry with the file or the file subsystem, an error could be generated.
The EZGPIB docs have a note in the revision log about how you can restructure the code to buffer all the output during logging and write it at the end of the session. However, you may not want to do that if power is an issue, otherwise the data could be lost.
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EZGPIB crashed again on yesterdays run, I did a screen capture this time....
I have noticed that the prologix adapter I picked up on ebay does not have the latest firmware. So will update firmware and try again, later.
Will do a separate post on the measurement itself.
Randy
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So here is the data from my second run. It's an experiment. You can judge for yourself whether there is any value to it.
I have recently finished an LT1027-based ovenized reference. There are five LT1027D chips averaged. The averaged output is about 5.00005 volts. I constructed an LTC1043 /2 circuit (and a *2, but that was not used in experiment). The geller was the input to the 1043/2 and the output was 4.99999 volts. The geller, the LTC1043 circuit and the LT1027 ref are all hooked up to the same power supply (Analaog Devices +-15v power brick).
So I simply hooked the K2015 to LT1027 averaged vout (+) and geller out to (-). The difference was about 0.05 mV. So I logged this difference.
The idea was simply to see if there was or was not a temperature correlation (hoping not). As you can see it was a bit ad-hoc!
Mean of run was 4.91e-5 and SD was 7.47e-6.
Output seems to show no, or negative correlation with temperature. But, there are concerning unexplained voltage spikes (noise of some sort I guess). Anyway here are the pics,
(Ran into data limits--will need to break up this post)
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Pics of setup
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Pics of setup without polyfill.
More on the LT1027 based "ovenized" reference. There are five LTC1027 refs in LCC package (no humidity sensitivity). Three on each side. (One was disconnected because it was unstable). These are mounted on a piece of 0.25 inch silvered copper bar. This bar is ground. There are three drilled holes in which are mounted heater resistors. The heater is the simple wenzel TL431 set to 35C. I just surrounded this circuit board with thermal blanket and polyfill -- it worked well enough that I nave not so far mounted it into the bud box.
Randy
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Very cool! :-+
Can you log while you are asleep or otherwise out of the room and see if the spikes are still present?
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No one in the room. I setup the logging and went to bed!
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I've always thought the 1043 was a neat part. Just curious, have you hooked both inputs to the same reference (not ground) and logged data for a while?
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Ummm, as I came up from my lab, I remarked to my wife--I need another 6.5 digit meter. My remark came about exactly because it seemed the quickest way to see how that 1043 circuit was doing--I have no way of precision logging more than one source at the moment. What I have been doing is flipping from back to front on the meter....sigh.
Wife was not amused. Discussion about budget. No new meter coming. |O
So, I've logged reference outputs only. Have not done the same on 1043 outputs. I do have good logs of the exepected standard deviation on my LTZ1000 references and LT1027. So I could hook up the 1043 and look at the SD. Should be correlated, right?
Also I completely trust that datasheet.
Seriously, I've compared the 1043-implemented instrumentation amplifier (first page of datasheet) with an AD8429 IIRC. The 1043 showed better CMRR, which was nice.
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I've always thought the 1043 was a neat part.
Hello,
The 1043 is a neat part.
But you must not load the output. (and a 1nF capacitor at the input or a buffer keeps EMI away).
A output buffer amplifier is mandatory. (I see none on the perf board).
Unfortunately the buffer amplifier limits the accuracy of the LTC1043. (offset temperature drift)
https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg528192/#msg528192 (https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg528192/#msg528192)
with best regards
Andreas
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The Geller Labs reference has finally made its way back to me :D
We have a few people whom have jumped on the train, and for them I'd like to try something slightly different. Until now, we've used a ring or round-robin pattern of mailing the reference -- it goes straight from one person to the next.
For the next few hops, I'd like to try a star pattern, where the reference is sent back to me after each hop. I'll use this to try an get an idea of the repeatability of the reference after each shipping hop -- i.e. does shipping induce any hysteresis?
I'll take some measurements over the next few days and then send it on its way again!
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How about keeping a powered logger with it to track temperature, humidity and pressure as well as 3D acceleration (bumps) in transit? Are there any regulations against shipping powered devices?
Sent from my iPhone using Tapatalk
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Backing up a bit, to log while in transit requires power. For domestic shipments via USPS, household dry-cell batteries are OK. See 348.22.b:
https://pe.usps.com/text/pub52/pub52c3_026.htm#ep900090
Lithium-based cells (rechargeable or non) have restrictions. See 349.221 and 349.222:
https://pe.usps.com/text/pub52/pub52c3_027.htm#ep900090
It's also interesting to note that 349.221.b.2 and 349.222.b.2 state that, "the equipment must be equipped with an effective means of preventing it from being inadvertently turned on or activated." So, no running devices that use lithium batteries.
However, a similar requirement isn't listed for dry-cell batteries.
Disclaimer: IANAL
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... "the equipment must be equipped with an effective means of preventing it from being inadvertently turned on or activated."
So, no running devices that use lithium batteries. ...
Sorry if I am nitpicking and I am not a native speaker, but wouldn't this mean that if you would advertently turn on the equipment, it is allowed ?
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Yes, semantically they are referring specifically to inadvertent activation. However, I don't think they intended for it to mean that it is therefore OK to activate it beforehand since the end result is the same, a running device powered by a lithium battery. Even though I'm a native English speaker, I'm not a lawyer, so my interpretation isn't worth much. ;D
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Hey there, fellow cal clubbers. What's new with the roving standard, etc.?
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Sorry I fell off the face of the earth! Life got in the way of my hobbies. I’ll make time this week to get the reference into the hands of the last few people who jumped on the band wagon.
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Welcome back to planet Earth. We were afraid you may have become an ex-pat to some wonderful new planet and left us all behind. ;D
Yeah, real life does have a way of interfering with important stuff like tinkering with electronics and T&M equipment. No worries. Glad to have you back.
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I'd like to throw my name back into the ring, too. I was one of the first people to get my hands on it, but I couldn't make use of it so I just forwarded it quickly. I have finally fixed at least one of my precision multimeters so I can make a useful measurement of it now. Well, useful for me. I doubt it's good enough to help any of you guys.
Let me know if it's coming back to this quarter of the country, and if someone can intercept.
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I believe everyone who was in Round 1 will be participating in each subsequent round. There were a few late additions to Round 1, which is what cellularmitosis is taking care of now.
Last I recall, for Round 2, the route will be changing from a loop to a star/hub, returning to cellularmitosis after visiting each point/spoke to check for post-shipping variation.
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If we decide to do a round 2, a testing standard definitely needs to be developed.
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bitseeker very generously paid all of the postage for the first round. I know it wasn't a huge sum, but he shouldn't have to carry the whole load. Early in the thread there were some suggestions about how to cover postage costs. At the very least I would suggest that in the next round each participant pay postage to the next location.
The easiest implementation for this might cause privacy issues for some, as it would require a complete name and address for each participant. Would this be a problem for anyone in the club?
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bitseeker very generously paid all of the postage for the first round. I know it wasn't a huge sum, but he shouldn't have to carry the whole load.
I believe cellularmitosis covered the postage. In any case, I agree that we should distribute that burden.
Early in the thread there were some suggestions about how to cover postage costs. At the very least I would suggest that in the next round each participant pay postage to the next location.
The easiest implementation for this might cause privacy issues for some, as it would require a complete name and address for each participant. Would this be a problem for anyone in the club?
It depends if the route for Round 2 is chain or star. A chain does leak address information, but that can be minimized by everyone creating their own label to the person after them.
For Round 1, since all the postage was pre-paid, each person along the path could see the mailing labels for all the destinations after them. Forum names were used on the labels (which caused a USPS employee to write a "?" on the label that was addressed to me ;D), but real addresses, of course, had to appear there.
In my case, the address information leakage is OK as inbound mail is held at the post office. If anyone wants to send me free goodies, let me know. :-DD
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At the very least I would suggest that in the next round each participant pay postage to the next location.
The easiest implementation for this might cause privacy issues for some, as it would require a complete name and address for each participant. Would this be a problem for anyone in the club?
I agree that we should share in the costs. My address is no secret. Anyone is welcome to visit, as long as they like large dogs... :box:
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I REALLY need to get my GPIB datalogging worked out before it comes around though! :scared:
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At the very least I would suggest that in the next round each participant pay postage to the next location.
The easiest implementation for this might cause privacy issues for some, as it would require a complete name and address for each participant. Would this be a problem for anyone in the club?
I agree that we should share in the costs. My address is no secret. Anyone is welcome to visit, as long as they like large dogs... :box:
Never met a dog I didn't like.
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If we decide to do a round 2, a testing standard definitely needs to be developed.
I'm all for learning about such things. Let the defining begin.
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If we decide to do a round 2, a testing standard definitely needs to be developed.
I'm all for learning about such things. Let the defining begin.
It's up for discussion, what is the goal for round 2? A few first thoughts:
- Is anyone actually using this as a cal standard? What can we reasonably expect from this as a mobile transfer standard?
- The reference has two separate outputs posts, are we all utilizing the same one?
- Cabling consistancy
- Meter setup, NPLC, Math, temp, polling frequency
- Documentation file format
- Other notable potential environmental factors?
If this goes around again, and we end up with say 20 datasets, how do we make this data useful to the group, or the reference?
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Lack of transparency still an issue, from non-participant POV :-//.
Cabling consistancy
Resolve by shipping with cable set.
Meter setup, NPLC, Math, temp, polling frequency
I'd expect settings best for accuracy for specific meter?
Temperature should be fixed to metrology level range : +20-+24C.
Is there a photo of whole current setup?
Round two should be testing current setup by somebody who has reference standard with lower uncertainty, so travel box can be verified that it's still in spec (whatever that is?) and comparisons made by previous members from run 1 are in line.
So essentially it should be few "golden members" with calibrated equipment to verify travel box, and "green members" who compare their gear to travel box.
I have L&N 4030B 10KOhm resistor to donate for 2nd round, which was measured by 3458A/002 (https://xdevs.com/ln4030-10k_t1/) over a month.
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First, my apologies to cellularmitosis for not correctly thanking him for the first round postage.
Second, I have no concerns about sharing real world name and address information with other members of the club. The only risk is to those who use the information as my lab and shops DO have materials known to cause cancer and other hazards to health.
Finally, I will clearly be a green user, but would like to contribute something to this. While I can't provide traceability, my measurements can possibly make assertions about noise and stability. One suggestion would be that in addition to the raw data each user provide brief summary information of the results. Things like mean, standard deviation, shift from prior observation for each instrument used.
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Lack of transparency still an issue, from non-participant POV :-//.
What would help with transparency? What can we provide?
Cabling consistancy
Resolve by shipping with cable set.
Some cables were included in the package, though I suspect that not only do we want to use them specifically, we also want to use the same ones for the same purpose each time (i.e., pair 1 between power supply and standard, pair 2 between standard and DMM1, pair 3 between standard and DMM2, etc.).
Meter setup, NPLC, Math, temp, polling frequency
I'd expect settings best for accuracy for specific meter?
I posted some of my settings with summary data in the thread (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1294815/#msg1294815). Additional info as well as raw data is in the log files uploaded to xDevs. Sampling was at the maximum rate that BenchVue would capture, which I assume is based on the instrument's NPLC.
Temperature should be fixed to metrology level range : +20-+24C.
That sounds prudent. Unfortunately, for me, there was a heat wave when the standard arrived, so my time with it was well above this temp range.
Is there a photo of whole current setup?
Taking photos of all the items in the roving package crossed my mind, but alas, I did not take them before sending everything to the next participant. Perhaps cellularmitosis can take a photo inventory before sending it out again.
Finally, I will clearly be a green user, but would like to contribute something to this. While I can't provide traceability, my measurements can possibly make assertions about noise and stability. One suggestion would be that in addition to the raw data each user provide brief summary information of the results. Things like mean, standard deviation, shift from prior observation for each instrument used.
I, too, am a green user. Summary info of setup and results from Round 1 are in the following posts.
- Initial setup and checking the power supply for powering the standard (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1294580/#msg1294580)
- First run summary and graphs (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1294815/#msg1294815)
- Second run summary and graphs (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1298543/#msg1298543) (post-heatwave, but still a few degrees higher temp than desired)
Raw data is in the xDevs share that was set up for our cal club (/USA_Cal_Club/Round1). CatalinaWOW and I created individual subdirectories in there for our results.
Recommendations on improvements to methodology, recording, reporting, etc. are most welcome.
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I'm green and am using it for calibration, not being able to justify using a local lab right now. I make no effort to hide myself, hoping it will attract people that need machine or design work, though the result of that has been zero for years, save for a huge amount of junk mail. :palm:
In any case I'd be happy to pay for postage. The last package was already at the limit for weight, so I couldn't add much of anything. It would be nice if we had a bit of freedom there.
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Ideally here is what I would want to have in a kit, in no particular order.
1) 10V Voltage Standard (Geller Labs)
2) Metal shield for Voltage Standard
3) Power supply for Voltage Standard
4) GPIB to USB controller. Smallest and lightest available (initially this would only be driving one instrument at a time).
5) Temperature/Humidity sensor (BME 280) and cabling. We may also consider two sensors (one inside voltage standard shield, another next to DMM being evaluated).
6) Raspberry Pi with software that already supports: GPIB, Temperature Sensor, and wide and hopefully growing number of DMMs. It will provide HTTP interface, common logging format and whatever else we need, including posting files to public server.
7) Low thermal leads leads for voltage standard (possibly just pure copper wire with Teflon insulation). It must be easy to connect to both voltage standard and banana plugs, since many participants do not have binding posts). Maybe use Pomona 5405 and pure copper crocodile clips. Some input from more experienced members is needed here.
8 ) 10k Ohms resistor. 10K is probably the best value. Anything much higher than that is harder to measure precisely. Ideally this resistor should be small and light (easier and safer to ship), have 4 wire low thermal connection and wiring, have fairly low thermal coefficient because many members cannot control temperature and be time stable. Maybe this could be a custom wire wound or z-foil resistor in small metal case with copper wires permanently attached. Help of experienced members is needed here too.
9) Low thermal short, to measure zero offset for volts and resistance, and also noise. Fluke 884X, plus possibly draft guard for it.
10) Padded case, like cheap Pelican copy from harbor freight: https://www.harborfreight.com/watertight-protective-case-small-63518.html (https://www.harborfreight.com/watertight-protective-case-small-63518.html). Alternatively we can take a look at custom padding for Small or Medium flat rate box from USPS.
11) If the Voltage Standard is capable of driving 1mA without loss of precision and resistance standard is not compromised by continuous 1mA current, we can also have 1mA current standard, making sure required cabling is included.
Essentially everything but your meter will be included in the package, guaranteeing the highest consistency possible.
Items that we do not yet have are fairly inexpensive and I will be happy to contribute to the cause.
Since everything is already prepared the time per hop will also be minimal. What do you guys think?
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Ideally here is what I would want to have in a kit, in no particular order.
1) 10V Voltage Standard (Geller Labs)
2) Metal shield for Voltage Standard
3) Power supply for Voltage Standard
4) GPIB to USB controller. Smallest and lightest available (initially this would only be driving one instrument at a time).
5) Temperature/Humidity sensor (BME 280) and cabling. We may also consider two sensors (one inside voltage standard shield, another next to DMM being evaluated).
6) Raspberry Pi with software that already supports: GPIB, Temperature Sensor, and wide and hopefully growing number of DMMs. It will provide HTTP interface, common logging format and whatever else we need, including posting files to public server.
7) Low thermal leads leads for voltage standard (possibly just pure copper wire with Teflon insulation). It must be easy to connect to both voltage standard and banana plugs, since many participants do not have binding posts). Maybe use Pomona 5405 and pure copper crocodile clips. Some input from more experienced members is needed here.
8 ) 10k Ohms resistor. 10K is probably the best value. Anything much higher than that is harder to measure precisely. Ideally this resistor should be small and light (easier and safer to ship), have 4 wire low thermal connection and wiring, have fairly low thermal coefficient because many members cannot control temperature and be time stable. Maybe this could be a custom wire wound or z-foil resistor in small metal case with copper wires permanently attached. Help of experienced members is needed here too.
9) Low thermal short, to measure zero offset for volts and resistance, and also noise. Fluke 884X, plus possibly draft guard for it.
10) Padded case, like cheap Pelican copy from harbor freight: https://www.harborfreight.com/watertight-protective-case-small-63518.html (https://www.harborfreight.com/watertight-protective-case-small-63518.html). Alternatively we can take a look at custom padding for Small or Medium flat rate box from USPS.
11) If the Voltage Standard is capable of driving 1mA without loss of precision and resistance standard is not compromised by continuous 1mA current, we can also have 1mA current standard, making sure required cabling is included.
Essentially everything but your meter will be included in the package, guaranteeing the highest consistency possible.
Items that we do not yet have are fairly inexpensive and I will be happy to contribute to the cause.
Since everything is already prepared the time per hop will also be minimal. What do you guys think?
If this route is followed then items 1-3 should be permanently wired together to avoid any cabling variations. Thinking about that leads to concerns about how to investigate possible future contributions of error from each of the three elements.
Supplying GPIB controller has both benefits and problems. The major benefit I see is assuring everyone has a chance at data logging. The problem is that compatibility with various instruments varies, and will force those who have already resolved those issues to do further debug. If the controller is only single instrument capable it also precludes simultaneous logging of multiple instruments. Not good. But these issues are somewhat resolved if the Rasberry Pi is included.
Item 7 is resolved if items 1-3 are permanently wired. The travelling kit already includes a pair of binding posts with a banana pin out.
A pelican case ups the shipping bill automatically through both size and weight. I do think it is worth biting the bullet to go to a standard sized USPS package. We should be able to fit a medium box easily (~$15) but might be able to get into the small (~$8) one.
I do like the idea of a standard data format (must be extensible for multiple instruments and future adds like current and resistance).
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What is our purpose? I'd think if the device is well characterized, its performance should be predictable. Are we mostly measuring the test environment to confirm that the measurements change as expected? Or, are we doing a long term evaluation of the device, with the added variable of doing it in multiple locations? I'm not trying to promote any particular thing, but I think it's important to be able to clearly state the goals.
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Conrad, I think we are doing multiple things.
First of foremost we are collecting a rich and consistent dataset. By writing a little bit of a software we can determine a number of things, like:
1) When device reaches our "calibrated" members, then other members can see where they stand in terms of calibration.
2) We can compare noise generated by our equipment. Is K2000 generally better than 34401a? Is my K2000 noisier than some else's K2000.
3) When standard returns to calibrated members with very stable equipment in stable environment we can judge stability of the standard itself and any problems the shipping might have caused, power up/downs temperature in transit, mechanical stress.
4) We have a lot of old aged equipment. In my experience old equipment runs better than manufacturers specs that had to be conservative and include "new device" drift. If we run this club for several years and have large enough membership, we might be able to ascertain if our equipment is better then spec and how much. For example if 34401a 10V spec is 40ppm per year, we might discover that typical drift for old instrument is 2ppm. In my mind that would be a useful information.
These are all examples how we can crowdsource the data, so that every contributor can benefit from data that others collected.
As logging from multiple instruments is concerned, I believe seeing something about instruments sometimes affecting each other, with noise, extra cabling or mismatched impedance. Logging them individually may take more time, but would be more consistent.
For GPIB, I started with a $30 logger from Amazon that "sometimes" worked. Then I bought old HP 82357a for $80 (original, not fake) and it supports every device I have, no fiddling required. It supports multiple devices too if needed.
Between GPIB, low thermal short, raspberry pi, 10k resistor, etc. we are probably looking at around $200. Shared metered members, it will be compatible to postage cost. I am certainly willing to contribute. We can PayPal contributions to CM.
With proper prep, round 2 will be great.
Sent from my iPhone using Tapatalk
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I'd say verifying any spec even at 6.5 digit meter, like K2000/34401 mentioned need a standard bit better than AD587 or attached environment data for both calibrated condition and DUT setup.
And since there is multiple mentions about shipping cost, seems like 20$ of whatever it is now is bit much for participants (?), that already rules better gear out?
Leave alone noise, which is tricky to get correctly even at one location by single member. How would you know that member's B K2000 noise larger because of his meter , not the Wifi router nearby under the desk? Sure, member B can evaluate possible noise sources and try to obtain lowest noise possible on his setup, but for that he need no cal club reference..
Most valuable outcome in my opinion is going after 3) to estimate how much stress/condition cycling affect the DUT. And this means that all non-calibrated members would just need to be a transit points, with their time on the gear (doing whatever they see fit for their own benefits), and all major data collected by high-end gear (more stable than a DUT box) at calibrated members.
Anyhow, I have few ideas for next year calibration club, on which i'll share the details as right time comes (other that it wouldn't be low-cost, that's I already know :scared: ).
My offer of L&N 4030B stands (free of charge :) ), I bought it specifically for community and it's just collecting dust somewhere in USA right now.
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Yeah, that 4030B is collecting dust. So are a few of his other things. Sorry! :palm:
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Howdy gents!
I hooked up the SVR-T this weekend and took about 20 hours of data with my 34401A (and a Si7021 temp/humidity sensor), and now I've got the reference packaged up and ready to ship after work tomorrow -- I believe nikonoid was next in line.
I plan on doing a "star" configuration this time around, where the reference will hop back to me in between each participant. I'll take at least 8 hours of data each time it comes back to me, so that we can start to get a better handle on the repeatability / consistency of these measurements.
As far as shipping costs go, that's great if anyone would like to pitch in. How about this: I'll pay to ship it to you, you pay to ship it back? So far, I've spent about $50 in shipping over 6 months, so this is a pretty cheap endeavor :)
Lots of great discussion in this thread, and I totally agree that it is time to start tightening up the process, in terms of trying to get each participant's setup as similar as possible, etc. I've got some ideas I'll be trying out in that vein.
More details to follow soon! Excited to get back into the swing of volt nutting 8)
(attached: ~20 hours of 34401A data, slow 6-digit mode, 10 GOhm input impeadance, plotted with a 100-sample rolling average filter, units are microvolts)
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Also, I decided to take the plunge and start working on a resistance transfer standard, so I ordered a few VHP202Z's.
I decided to go with a 10k and 20k resistor in series, so it should be useful to calibrate the 10k, 20k, or 30k range of a meter, which I think will cover all of the meters we are likely to use. For example, a 34401A would use the 10k value, the Keithley 196 would use the 30k value, and I believe the Fluke meters use a 20k scale.
I got three pieces of each, so that I can mail out one unit while keeping the other two in-house, which should allow me to figure out which one drifted.
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Very cool, CM. I think TiN has a 10K resistor to add to the mix as well.
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Sorry I fell off the face of the earth! Life got in the way of my hobbies. I’ll make time this week to get the reference into the hands of the last few people who jumped on the band wagon.
I've been kind of in the same boat.. work projects took over all of my brain time. Catching up on all the stuff I missed. Good thing is my references should have all aged. ;)
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I got the package today. Logging starts tomorrow :)
Sent from my iPhone using Tapatalk
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I just sent this message to nikonoid, but I thought I'd echo it here for the benefit of the next recipients.
I've included a little Arduino shield which uses an Si7021 temperature and humidity sensor.
Here's the Python script I use to read the data from the Arduino and log the data in CSV format:
https://gist.github.com/cellularmitosis/421781b4f89636b612378f33d705f8c3
(also attached to this post)
Usage:
The script takes one argument, which is the serial port it should read from.
For example, using this script on linux might look like:
./Si7021-logger.py /dev/ttyACM0
The script will print output like so:
timestamp,temp_c,humidity
1500422021.565,25.4043,68.5087
1500422022.565,25.4257,68.5239
1500422023.565,25.4150,68.5239
...
That's a timestamp (seconds since the 1970), temperature in celsius, and humidity in percent.
On Linux, your serial port will probably look like /dev/ttyACM0 or /dev/ttyUSB0. On Mac, it might look like /dev/tty.usbserial-DN02TIYO.
On Linux, after you plug in the Arduino, you can run the dmesg command to figure out which device name it got associated with. I don't know of the equivalent of dmesg on Mac, so I just open the Arduino IDE to figure it out. I'm guessing you can do the same on Windows, but I haven't tried it.
Since the output of the script is in CSV format, you can just redirect the output of the script to a file in order to log to a file, e.g.:
./Si7021-logger.py /dev/ttyACM0 > temp-log.csv
If you'd like to watch the output while also logging to a file, you can use the tee command:
./Si7021-logger.py /dev/ttyACM0 | tee temp-log.csv
Technical info:
The Arduino spits out 9 bytes of binary at a time: a 32-bit floating point temperature, a 32-bit floating point humidity, and an 8-bit CRC.
The Python script reads in 9 bytes and checks that the CRC is valid. If it isn't valid, it tries reading another byte until the CRC works, so even if the script starts up in the middle of a 9-byte sequence, the script will recover after throwing away the first reading.
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For the curious, here's the Arduino sketch:
https://gist.github.com/cellularmitosis/4bc0de74b6c3dd03d57ef5ce09c51896
Drop the crc files into the same folder as your Arduino sketch and it should compile correctly in the Arduino IDE.
After I implemented this, I found out about Fletcher's checksum, which is much simpler, and will do just fine for an application like this. I'll give that a shot for my next project. https://en.wikipedia.org/wiki/Fletcher%27s_checksum
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That's neat. Is it just the shield (with cable and sensor) that you put into the package or the Uno as well? I have a variety of Arduinos, so either way is OK with me. I just wasn't clear which it was.
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Yup, it was light weight enough that I just threw the whole thing in there.
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OK, cool. If space/weight become a limiting factor, I'm sure the whole thing could be made much smaller/lighter.
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I finally have first round of preliminary results:
K2002 had been powered continuously. It sits between K2001 and another K2002 and consistently shows same internal temperature as when it was calibrated by CalMachine.
After warm up for few hours the reference read at +1.5ppm, however now that I had it powered continuously for 5 days it slowly drifted up to about +4.5ppm. This reference may need to be warmed up for longer than few hours to perform better. This is sort of a bad news for a traveling reference.
All readings were done at 10 PLC with digital filtering off. I had drawn the 20 sample moving average line to compensate for low NPLC count and no filtering. Attached is an 8 hours run. ‘TEMP?’ is the internal temperature difference with the internal calibration temperature. The 10v reference was put inside of metal foil container along with temperature/humidity sensor (‘TEMP’ and ‘HUMID%’). As you can see my temperature difference throughout the run was under 0.5 C.
I am not sure why the shape of K2002 internal temperature change is different from the shape for Arduino temp sensor.
I am going to do another run with foil container placed on the top of warm meter to create a different temperature point for the reference.
Is there anything else you would like me to test before passing the reference on?
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Wow, a 5-day warmup. However, if we plot the characteristic warmup drift of the reference over time, it could be taken into account when comparing the output voltage to other instruments, no?
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Very interesting to hear about the 1.5 to 4.5 ppm drift over 5 days. Feel free to keep the reference for a few more days -- I'd be interested to see how well it has really settled out.
I'll be looking specifically for a similar drift over the 5 days when the reference returns to me.
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I am finally done with the reference. It went back to CM today.
After going through my records I was able to attribute a large portion of 1.5mm => 4.5ppm drift to temperature. My room temperature is fairly stable, in most cases not exceeding +/-0.5C per day, staying pretty much around 70F every day.
With that in mind the initial testing was done in open air (Run1 attachment). Then seeing a large amount of noise I enclosed the reference in foil baking tray and covered with sheet metal (Run4 - temperature not recorded, bug in a script). This did not help noise much. Then for (Run 5), the tray with reference and also temp sensor were standing on an off Keithley 2000, but to the left of working K2002, blowing some warm air in its direction. For Run 6, the tray was relocated atop of working K2001 (see photo attached). This increased temperature somewhat. Just to test the temperature hypothesis, I let the reference be off for 24 hours (still seating on warm K2001). Then after day off I turned reference back on and is returned to expected voltage very quickly (Run 7).
It is possible that I was seeing a temperature dependency around 1ppm/C.
To make sure that noise or temperature variation are not contributing through performance of the Keithley 2002, I recorded output of Fluke 732a for 14 hours with the same setup and script (Run732a).
I have to find a place to upload Excel sessions. They are too big to fit here.
CM, please run a long session over few days to confirm. Thanks.
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I have to find a place to upload Excel sessions. They are too big to fit here.
You can put them on xdevs. See CM's post followed by TiN's starting at https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1276612/#msg1276612 (https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1276612/#msg1276612). On the FTP server, you'll see a directory for our cal club and subdirectories that CatalinaWOW and I made with our data.
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Thanks, bitseeker.
I just found the "datashort" and uploaded files there. It is raw data plus a charts in excel.
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Excellent!
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nikonoid, I've received the SVR-T and have started logging.
I'm glad to see that we are using the same "q-tip" trick and the same cable, so the differences between our setups are minimized. I also applied a shot of deoxit, both before I sent you the unit and again today.
I'll keep you posted!
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Hey, I have a special deal for you guys :-DMM
In theory I can provide xDevs.com FX 10V reference to USA Club, if somebody willing to donate LTZ1000A and set of LTZ resistors for the cause.
Rest of the parts, calibration and shipping I'll provide myself. :)
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TiN I would be happy to take that deal!
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Cellular, I can chip in for the cost.
Sent from my iPhone using Tapatalk
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I may have an extra VHD200 13k/1k network for the LTZ1000(A)? heater divider. Not sure how well that would fit on the FX board.
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Got a new toy, early Christmas gift to myself.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/76ED9514-85CC-4CC0-A327-DA043455757A.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/76ED9514-85CC-4CC0-A327-DA043455757A.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/E7A8B748-8298-4E4F-93F1-C8A71F1CEAD7.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/E7A8B748-8298-4E4F-93F1-C8A71F1CEAD7.jpg.html)
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I hit the "Thanks" button only because I could not find the 'JEALOUS' one.
Looking forward to some quality logging data from that puppy.
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I can also chip in for TiN's generous offer.
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Just saw TiN's offer.
I just bought some precision resistors for another project. Have some extra, so for LTZ1000A resistors in particular I can offer
two 100K RNC90Y (10ppm) and one naked Zfoil 10K (.2ppm). But there may be better on offer.
http://www.newark.com/vishay-foil-resistors/y0089100k000tp0l/metal-film-resistor-100kohm-300mw/dp/35M4599 (http://www.newark.com/vishay-foil-resistors/y0089100k000tp0l/metal-film-resistor-100kohm-300mw/dp/35M4599)
http://www.newark.com/vishay-foil-resistors-vpg/y070610k0000t9l/through-hole-metal-foil-resistor/dp/39T1673 (http://www.newark.com/vishay-foil-resistors-vpg/y070610k0000t9l/through-hole-metal-foil-resistor/dp/39T1673)
I homebuilt a reference using this ebay sellers NOS LTZ1000A (you can see my review below!):
https://www.ebay.com/itm/NEW-Genuine-Linear-Technology-LTZ1000ACH-Ultra-Precision-Reference-/253083175317?hash=item3aeceec995#rwid (https://www.ebay.com/itm/NEW-Genuine-Linear-Technology-LTZ1000ACH-Ultra-Precision-Reference-/253083175317?hash=item3aeceec995#rwid)
Money, ok too...but would prefer to donate parts. My family bought a lot of Christmas presents. Nothing left!
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VHD will fit perfectly. Worlds reference, I like it :)
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Okay, I can provide VHD200 13K/1K.
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TiN I would be happy to take that deal!
CM, I would also be happy to contribute funds to the effort. Sadly, I have no parts to offer...
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Sounds like a "stone soup" reference, I like it! One created by and owned by the community.
kj7e's VHD200 13k/1k is as good as it gets for R4/R5 -- fantastic! 8)
I can supply:
- LTZ1000ACH, used, not yet tested for popcorn noise :o
- R1: Vishay RNC90Z 120R (2ppm/C)
- R2, R3: Vishay RNC90Y 69.8K (5ppm/C)
TiN just messaged me and suggested the cheapest route might be for me to collect the parts and ship them together to him, then he can assemble, calibrate and ship it back to us. He's out of town for the holidays, will be back Jan 7, and can ship it back to us in February.
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Indeed, that was also idea of the club, no ? This would hopefully boost quality of future rotate runs in 2018, until somebody donates portable JJA :popcorn:.
I'd prefer hermetic 100-120ohm for good stability though. :)
February is due because it would be waste to calibrate any LTZ1000 reference without pre-aging for 200-400 hours first.
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Wow, lots of activity all of a sudden. What else is needed for this reference? I can chip in as well, CM.
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For what we are trying to accomplish here, lets buy the best possible components that TiN suggests (i.e. hermetic resistors). It will probably be cheapest and quickest to place a single order and have it shipped directly to TiN.
Cellular, how is your logging going?
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For what we are trying to accomplish here, lets buy the best possible components that TiN suggests (i.e. hermetic resistors). It will probably be cheapest and quickest to place a single order and have it shipped directly to TiN.
Sounds good. However, we will have to wait for new vishay resistors to be made.
Cellular, how is your logging going?
I used this evening to make some more tweaks to muxr's plotting script, here are the results so far: (attached)
I was a bit disappointed -- the voltage is wandering around by quite a bit. Also, we had a huge cold front roll in through Austin, and my A/C was set to "cool", so the temperature in my apartment left regulation until I came home from work and kicked on the heater. This, of course, caused a huge dive in humidity. So, not ideal conditions, but interesting data!
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By way of comparison, here is an updated set of plots from Nov 4th, just before I mailed the reference out to nikonoid. You can see how much better the reference was behaved! (note that the std-dev is 4x smaller)
for reference, here's the current set of scripts I'm using to log and plot data: https://gist.github.com/cellularmitosis/11e73bfc15f64f3d3f3c9a02e3d112ad
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Hello,
for me it looks that there is something defect. (noise increased by a factor of 5).
Perhaps the reference falling out of the socket? Or something with the wiring?
with best regards
Andreas
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CM, this is very strange. After a quick initial warmup it was much more stable than this. You can download my sessions from the server.
One difference that I noticed is humidity. My environment is very dry (around 30%). Your humidity is much higher at around 75%. Humidity can take a while to sip into reference and resistors and humidity can also affect things dimensionally.
I also ran the reference inside of shielded tray that protected it from noise and air drafts.
Another thing is that RH (Relative humidity with relative being a key word) is temperature dependent. Same concentration of water in air results in different RH percentage at different temperatures. Maybe someone more knowledgeable can weight in on what is more important in affecting reference, RH% or concentration of water in air.
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Yeah, I agree this is strange, and something must be wrong with the setup. Perhaps copper oxide has snuck up on me?
Last night I swapped over to the alternate cable (using the Pomona gold-plated grabbers and some nickel-plated banana plugs), but overnight the data still looked pretty noisy.
This morning before I left for work I hooked up one of the taobao LM399 boards (https://www.eevblog.com/forum/metrology/cheap-ebay-ad584-voltage-references-my-experiences/msg1274955/#msg1274955 (https://www.eevblog.com/forum/metrology/cheap-ebay-ad584-voltage-references-my-experiences/msg1274955/#msg1274955)). Previously I've seen these be stable within 10uV for several hours, so that should be a good test.
I also realized my room placement isn't ideal -- the meter is near a sliding glass door, and it looks like the temperature regulation in that area isn't as tight as near the AC thermostat.
I have also recently acquired a Keithley 2015, so I can throw that into the mix for a day and see what the data looks like.
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Ok, I think it's an issue with the SVR-T itself.
First, here's a graph of the SVR-T using the alternate cable. The standard deviation is 54uV, so no improvement there.
Second, a graph of the LM399 board. The standard deviation is 3uV, and the only variable which changed was which board was connected to the meter.
Time for some further investigation!
EDIT: Wow, take a look at the first humidity graph and guess what time I took my shower this morning :)
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Once again, the 'myth' of hermetic resistors vs humidity, yes hermetic is essentially immune to humidity at a very high price point. Nobody of significance, Keysight, Fluke, ect., are using hermetic resistors in the LTZ circuits because it isn't necessary. But if you want to spend a whole lot more money on hermetics to find this out, be my guest, it isn't my money you're spending. There are many LTZ circuits that have gone into far more difficult environments than a 3458A and they don't use hermetic resistors, they work just fine. Yes some resistors are very sensitive to humidity but well made resistors should be no problem in LTZ circuits.
Check your circuits, you've likely got other factors that are out weighing humidity effects and if humidity is causing a problem, you should take the time to find out just what is being sensitive to it and not just grabbing at straws.
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Could it have been an appliance? The first thing I do when I get up is preheat the water in the Keurig. If you have an electric water heater, that could explain noise at that time frame.
Lights, dimmers, and all other electrified items in the house are suspect.
It will be interesting if you see a pattern.
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CM, I reviewed my sessions and the last one (Log 7) was the noisiest, with few spikes as high as 60uV. My data was recorded at 10 NPLC, so you expect it to be somewhat noisy. The Log 6 was better than 7, but worse than any other recording.
There was nothing special happening to reference between experiments, so I am not sure why last one shows the most noise. I remember I had short power outages during the week of logging, but I am not sure on what day they took place. The power supply I was using for it was Hantec lab supply. It is not HP quality, but good enough for the purpose.
By the way, on Standard Deviation measure is only applicable to noise when statistical mean of your measurements is stable and not changing. Therefore StDev over large sessions with temperature variations is fairly meaningless. You would need to isolate much shorter subsections of your session and calculate StDev over them.
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nikonoid, interesting that a smaller version of the noise showed up before shipping. What a mystery!
I tried reseating the temperature compensation jumper, and also reseated the reference IC, but it looks like that hasn't helped.
Ideas for further debugging:
- remove the temperature compensation jumper
- remove the IC from the board and put it into a temporary protoboard circuit
- throw the unit into the freezer and thermally shock it a few times
- solder leads directly to the output terminals (rather than using grabbers)
any other ideas I might try?
EDIT: adding a zoomed-in 10-minute window
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any other ideas I might try?
Use Deoxit for the socket or replace it. (after testing the reference outside the PCB).
By the way: do you have a possibility to measure 1/f-noise.
It looks somewhat like the popcorn noise that I have on one of my LT1027 references.
https://www.eevblog.com/forum/metrology/t-c-hysteresis-measurements-on-brand-new-lt1027dcls8-5-voltage-reference/msg972153/#msg972153 (https://www.eevblog.com/forum/metrology/t-c-hysteresis-measurements-on-brand-new-lt1027dcls8-5-voltage-reference/msg972153/#msg972153)
with best regards
Andreas
Edit: added zoomed measurement of popcorn noise
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I took the AD587 off of the board, placed it into a machine socket, and clipped 15V and the meter leads to it, and I am shocked at how stable and low noise the output is. And this is without any capacitors or other circuitry at all! Just the IC in a socket!
Here's ~20 minutes of data (attached).
EDIT: adding photo of connections
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Those alligator clips bother me. :P
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3 hours in, this looks pretty well behaved. If you flip and reverse the voltage graph, it looks like you can see some correlation with the temperature graph.
Now I'm curious which component on the board is causing the noise. I can run without the temperature compensation jumper, which will eliminate several components.
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Ideas for further debugging:
- remove the temperature compensation jumper
any other ideas I might try?
I was wondering if that little 2-pin jumper could have developed a poor contact?
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CM, I am glad to hear that chip itself is doing good. I think this is the only part that is difficult to replace. I feel bad the board started misbehaving while I had it. The whole time it was not a subject to any stress, electrically or mechanically. I did not remove the chip or the jumper.
Good luck with troubleshooting. Let me know if I can somehow help.
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nikonoid, please don't feel bad! I am sure it isn't your fault, and anyways, I adopted the viewpoint that this board would serve as "training wheels" for the community, before we moved on to something more serious like an LM399 or LTZ1000.
I reflowed all of the solder joints and gave the board a once over with some IPA. This seems to have helped a bit, but the performance is nowhere near as good as the bare IC.
I actually just thought of one other variable -- I added a piece of electrical tape across the output solder pads, to reduce the likelihood that the bare copper clips would accidentally short across both output pads. I wonder if the tape adhesive is acting an intermittent conductive path, causing the strange output?
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I wonder if the tape adhesive is acting an intermittent conductive path, causing the strange output?
Only one way to find out! I would generally use kapton tape for this application.
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Horowitz and Hill *do* mention that electrical tape is evil and ought never to be used. Ever.
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I can go ahead and place an order for a 120 ohm VHP202Z for our community LTZ1000 reference. http://www.vishaypg.com/docs/63120/hzseries.pdf (http://www.vishaypg.com/docs/63120/hzseries.pdf)
Here's what I was thinking of ordering: Y6071120R000F0L
That's Y6071 (VHP202Z), 120R000 (120 Ohm), F (1% tolerance), 0 (lead finish), L (bulk packaging).
If anyone else would like one for themselves, let me know and I can add it to this order and mail it out to you. The last time I ordered some VHP202Z they were about $28 each. Texas Components was able to deliver them in about two weeks.
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CM, I have a good contact here in CA for any custom Vishay parts if needed, jut be prepared to wait 15-17 weeks.
Thought someone would like to see this, just having some fun with the new Keithley DMM7510 and testing the prototype LTC1150/LT1010 10v buffer. The VHD200 ratio set divider network I have on order for this is still two months out :(.
www.youtube.com/watch?v=APHFnoTWEKE (https://www.youtube.com/watch?v=APHFnoTWEKE)
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Wow, that meter is awesome! Thanks for making the video -- really neat to get to see someone put it through its paces. Also nice to see the sort of stability I'm (eventually) aiming for!
Thanks kj7e
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Just spent some time catching up on this thread, wow lots of things in the pipes!
Was any resolution reached with the new noise issue? I'm curious if that simple piece of electrical tape was the root cause!
Finally rounded up a small PC and am up and (I think) running with the NI GPIB card. So far have procured one GPIB cable. Now just to figure out what program(s) I need for logging and control, and start learning how to use them! Hoping to be up to speed and ready before the reference makes it's way here!
Regards,
Chris
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Chris, are you under UNIX or Windows on that PC?
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You don't need those over priced Vishay parts, you're not going to get an equivalent return for your money in performance.....unless you like spending more money than needed.
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Chris, are you under UNIX or Windows on that PC?
Windows 7 Pro, 32 bit.
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Hi Chris,
I haven't solved it yet. This weekend I'm going to take one more shot at scrubbing the board (perhaps with acetone), then try replacing the caps, etc. I was hoping to not have to replace components, as that might throw out whatever history we have thus far, but we'll see!
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The failure documented here is pretty typical of a chip / board destroyed by having been powered by reverse voltage. The reason the chip appears to be okay is because when powered off board, the trim input is not being tested.
The AD587 was first trimmed to very near 10V by two resistors about the trimmer, to Vout regulated, and common respectively. After hours or semiautomated testing, the series resistor for the Vishay compensating thermistor was determined. The small correction current developed by this very fine correction was applied to the trim pin. Hours of final testing and calibration followed.
So, I think what has happened is that internal trim circuit is damaged (destroyed). The reason there may be some correlation to the jumper is that the jumper connects the trim.
Because the fine temperature trim was unique to each individual AD587, once an AD587 of a SVR-T board was destroyed, there was no repair. So, it was okay to use the thermal epoxy to get good thermal coupling between the thermistor and thermistor series resistor to the board itself.
Another reason the chip might be showing some signs of life is that for SVR-T boards, the AD587 was preselected, generally for an uncorrected tempco of better than about 3 ppm/c. After correction, the SVR-T board tempco was typically better than 0.3 ppm/c. Without the internal damaged trim circuit, there apparently remains a pretty good "raw" output, which however, can no longer be trimmed because the trim circuit is damaged.
We never spent much time looking at reverse powered boards, because all of the passive off chip components were likely okay. These boards just went in the trash.
I took the AD587 off of the board, placed it into a machine socket, and clipped 15V and the meter leads to it, and I am shocked at how stable and low noise the output is. And this is without any capacitors or other circuitry at all! Just the IC in a socket!
Here's ~20 minutes of data (attached).
EDIT: adding photo of connections
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:-BROKE
Very interesting! Thanks for weighing in on this Joe. (for those unfamiliar, Joe is the designer of the SVR-T)
Welp, it looks like it is time for this humble gang of volt nuts to graduate to heated zeners! ;D
I have several taobao LM399 boards on hand which we could start using immediately. I also rush-ordered a set of LTZ1000 boards which I recently designed, which should arrive on Thursday, so we could start using one of those after Christmas. And TiN's "FX" reference should be ready in February.
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(for those unfamiliar, Joe is the designer of the SVR-T)
Just to clarify (from that what I know).
The SVR was designed and sold by Joe.
The SVR-T cirquit was a further development of Lars (then also sold by Joe).
with best regards
Andreas
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Joe, thank you for your comments on this.
My biggest challenge for the last run was not the tempco, but noise on 10V.
I attached is last log of 16 hours. It was logged at 10PLC, so some averaging is needed to cleanup the results (20 moving average).
(https://www.eevblog.com/forum/metrology/usa-calibration-club/?action=dlattach;attach=379920;image)
(https://www.eevblog.com/forum/metrology/usa-calibration-club/?action=dlattach;attach=379922;image)
Temperature by Voltage correlation graph from that run shows almost no temperature dependency. If it is there and masked by the noise, it is certainly nowhere near 3ppm/C.
(https://www.eevblog.com/forum/metrology/usa-calibration-club/?action=dlattach;attach=379924;image)
What could possibly create a noise on the output? Could somehow the damaged trim circuit manifest itself as noise on voltage read?
Please let us know what you think.
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Sad to hear that the SVR-T board is probably toast (sort of). This also gives us direction for any subsequent traveling standard. The nature of its use is that it will be connected and disconnected many, many times by many people. Which is a recipe for error no matter the skill level and intentions of those involved. So we should probably incorporate idiot proofing to the extent possible. Definitely a diode bridge on power inputs. Outputs are tougher since protection techniques will generally compromise performance, but we can probably come up with some ideas.
This comment does not point fingers at any individual. As I understand the data history the noise increase does not correspond to a setup change. Perhaps the cause is a power spike, ESD or some variant of the purple plague. So protection will not eliminate all possibility of damage or degradation, just reduce the chances.
There may also still be merit in circulating the SVR-T with trim circuit disconnected. It appears that the device has pretty good performance on its own.
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Yeah I should reiterate that I am not upset about this at all. The big win is that this cal club has a lot of interest and participation, and a few broken eggs is no big deal at all. And, I would much rather have a mishap early on than have it happen when years of calibration history are at stake.
Yeah, I don’t think it is toast, but rather I now need to use an external op amp for the offset trim and temperature compensation circuitry. That will be an enjoyable design exercise! However that also invalidates any history we have thus far, so this is a good time to make a break and switch to another reference.
In terms of the things we’ve learned so far, input protection is a good one. Good binding posts and having everyone use the same cables are another big one. A shielded enclosure is another. In general, doing everything we can to make everyone’s setup as identical as possible.
As you say, output protection is a trickier one, because a buffer inevitably introduces some amount of error, it perhaps we can overcome the danger of exposing the unbuffered output by coming up with a ritual to follow. In the airline industry, using checklists in time of emergency has revolutionized their safety records, and now doctors are starting to adapt that practice to avoid operating room mishaps (see the book “Checklist Manifesto”). We might have a ritual where you always start by connecting the buffered output first, and then as the last step you swap one lead from the buffered to the unbuffered output post, to minimize the chance of an output short, etc.
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Nikonoid, I like that temperature - voltage correlation graph. I need to learn how to make those!
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Chris, are you under UNIX or Windows on that PC?
Windows 7 Pro, 32 bit.
There is an existing ezGPIB tool. I created my own VisualStudio code. It is very ugly, since I did not have time to write it nicely. It covers some functions for Keithley 2002 and some for HP3458a. I might do a rewrite later when I get time. If you like a copy, let me know and I will it PM to you.
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Nikonoid, I like that temperature - voltage correlation graph. I need to learn how to make those!
Cellular, this is very easy. It is called XY plot or scatter plot. Excel, as well as any other platform, has them.
Since voltage is pretty noisy in a way that is not correlated to temperature, it is beneficial to run voltage readings though pretty heavy averaging filter before plotting it against temp. In Excel for each cell you can just average 20 previous: R23 =AVERAGE(I4:I23)
You can even make Excel plot trend line for you and display formula for trend line. Slope coefficient will give you the best PPM/C approximation and R^2 will be indicative of the quality of correlation (100% excellent, 30% BAD).
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Sad to hear that the SVR-T board is probably toast (sort of). This also gives us direction for any subsequent traveling standard. The nature of its use is that it will be connected and disconnected many, many times by many people. Which is a recipe for error no matter the skill level and intentions of those involved. So we should probably incorporate idiot proofing to the extent possible. Definitely a diode bridge on power inputs. Outputs are tougher since protection techniques will generally compromise performance, but we can probably come up with some ideas.
I'm bummed, too, about the news of the SVR-T. But I'm thankful that Joe could stop by to clear up the mystery.
This comment does not point fingers at any individual. As I understand the data history the noise increase does not correspond to a setup change. Perhaps the cause is a power spike, ESD or some variant of the purple plague. So protection will not eliminate all possibility of damage or degradation, just reduce the chances.
Agreed. It's an opportunity to learn and make improvements.
There may also still be merit in circulating the SVR-T with trim circuit disconnected. It appears that the device has pretty good performance on its own.
Interesting idea. Could a new trim circuit be made for it?
Yeah I should reiterate that I am not upset about this at all. The big win is that this cal club has a lot of interest and participation, and a few broken eggs is no big deal at all. And, I would much rather have a mishap early on than have it happen when years of calibration history are at stake.
It's still unfortunate that it occurred when you so generously made the SVR-T available to the club. It's true, though, that's it's good to shake out the issues early on, rather than after we've got years of history on record.
Yeah, I don’t think it is toast, but rather I now need to use an external op amp for the offset trim and temperature compensation circuitry. That will be an enjoyable design exercise! However that also invalidates any history we have thus far, so this is a good time to make a break and switch to another reference.
That's good news if it can be put back in service with some external trim, even if only for a stationary reference that you can use for comparison.
In terms of the things we’ve learned so far, input protection is a good one. Good binding posts and having everyone use the same cables are another big one. A shielded enclosure is another. In general, doing everything we can to make everyone’s setup as identical as possible.
Check.
...perhaps we can overcome the danger of exposing the unbuffered output by coming up with a ritual to follow. In the airline industry, using checklists in time of emergency has revolutionized their safety records, and now doctors are starting to adapt that practice to avoid operating room mishaps (see the book “Checklist Manifesto”). We might have a ritual where you always start by connecting the buffered output first, and then as the last step you swap one lead from the buffered to the unbuffered output post, to minimize the chance of an output short, etc.
In fact, airline pilots have checklists for standard operations, regardless how many times they've gone through the same procedures for takeoff, landing, etc. I'm happy to follow any checklists that will ensure the safety of the equipment as well as the consistency and quality of the data.
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Nikonoid, I like that temperature - voltage correlation graph. I need to learn how to make those!
Cellular, this is very easy. It is called XY plot or scatter plot. Excel, as well as any other platform, has them.
Since voltage is pretty noisy in a way that is not correlated to temperature, it is beneficial to run voltage readings though pretty heavy averaging filter before plotting it against temp. In Excel for each cell you can just average 20 previous: R23 =AVERAGE(I4:I23)
You can even make Excel plot trend line for you and display formula for trend line. Slope coefficient will give you the best PPM/C approximation and R^2 will be indicative of the quality of correlation (100% excellent, 30% BAD).
I would suggest taking averages centered around the point of interest. R23=AVERAGE(I13:I33). It doesn't matter when the mean is not moving, but if there is a slope to the data errors are reduced. We are post processing the data so there is no concern about getting data out of the future.
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There may also still be merit in circulating the SVR-T with trim circuit disconnected. It appears that the device has pretty good performance on its own.
Interesting idea. Could a new trim circuit be made for it?
My understanding of Joe's post is that it's the trim circuit on the chip itself that is damaged, so nothing can be done, other than running with the trim circuit disconnected and accepting the uncorrected tempco.
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There may also still be merit in circulating the SVR-T with trim circuit disconnected. It appears that the device has pretty good performance on its own.
Interesting idea. Could a new trim circuit be made for it?
My understanding of Joe's post is that it's the trim circuit on the chip itself that is damaged, so nothing can be done, other than running with the trim circuit disconnected and accepting the uncorrected tempco.
Yeah, that was my understanding as well. I was just wondering if an external trim of some sort was a possibility. Volt-noob questions. :)
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YEah, I meant an external trim + tempco compensation
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You can't be sure if rest of the chip is still meets the spec, as damage for trim circuit might affect other areas of the die, and now every time you get questionable data, you'll be asking yourself if it's your or the chip. I'd ditch the chip, or replace it and retrim properly, or better yet use multiple units of same reference design, so you can relate data between them to see if any single unit doing funny business. That is how I maintain confidence in ppm-level measurements using four 8.5d meters. If all of them show same data deviations, then I know it is coming from the DUT and not the meter.
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Cellular, in respect to copper clips used in the kit, I just saw a very useful modification from Rob Renz. It should be pretty easy to do. Watch video below from 4:30 till 5:30.
https://m.youtube.com/watch?v=o13e5LWsPTI (https://m.youtube.com/watch?v=o13e5LWsPTI)
Sent from my iPhone using Tapatalk
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Oh that is really clever nikonoid!
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About the SVR and SVR-T: I designed the temperature compensation for the SVR-T but credit really should go to Joe for all hours he spent to supply calibrated boards to the Volt nut community at a really low price! Of course I am proud of the simple compensation with two components that adds both first and second order temperature compensation to the AD587LQ
About the SVR-T that have circulated in US:
With a bare IC that is stable and only 61ppm off I really wonder if the IC have been reverse powered. I have once toasted an AD587LQ in an SVR-T. That IC only outputted 0.4V and the supply pin took a lot more current (around 10mA if I remember correct). After that incident I always have put a 1N5819 or similar in series with the 15V. The about 0.2V drop only gives a small part of a ppm different output voltage normally. I have chosen the 1N5819 as it can stand 40v reverse voltage, have a reasonable low voltage drop at 2mA and is cheap.
For me next step in testing would be the bare IC plus a 10Mohm resistor from the trim-pin 5. With the 10Mohm connected to the output (pin 6) the voltage should be about 170ppm lower and if stable I shouldn’t suspect the trim-pin of the IC. A further test would be to connect to ground (pin 4) and see if the voltage is about 400ppm higher.
If you put the IC back on the board without jumper and the output is still noisy another possibility for noise is the pin 8. This pin has about 4kohm resistance. A resistance to ground here of 4Gohm will offset the output about 1ppm. Maybe I should take away the capacitor as a test.
If the IC output isn’t noisy a possibility is to measure the about 7V from the trim circuit (without the jumper). Measure on the jumper pin, see if it is noisy. I guess the attenuation from the trim pin to output is about 20 times so the noise should not be more than about 20ppm p-p measured with the DMM.
Lars
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lars, thanks for your reply. Do you happen to still have a copy of the circuit schematic which you designed? The original is currently returning a 404.
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Hello,
I still have a copy from Lars.
with best regards
Andreas
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I recently acquired an HP34401A, appears to be fully functional and in perfect condition but was last calibrated in 97. Definitely interested in locating others in the SF bay area that have calibration sources to compare with. Currently gathering parts to build up an LTZ1000A which will also need calibration.
Really sort of new to this level of accuracy, just hope its a mild case.
Craig
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Welcome, Craig! We will restart the USA Cal Club soon with an upgraded reference :)
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Welcome, Craig, to both the forum and the cal club. Things like this always start out mild. Then, who knows... ;D
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Thanks guys, winter is my work in the lab time been itching to do a project or two.
Finally figured out how to make the HP34401 Talk RS232, was driving me nuts till I figured out it needs a line feed at the end of the line and Putty sends a CR.
What are you guys using to plot the readings, I have Excel 2003 but there has to be some open source plotting app that is better?
Craig
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I either use a modified version of a script which one of our users posted (Muxr), or I use google sheets if I need to manipulate the data first and it is something small and quick.
https://github.com/cellularmitosis/logs/tree/master/plotting-scripts
The nice thing about the 34401A is that you can put it into “talk only” mode, where it just broadcasts every measurement automatically. I wish every meter did that by default.
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Im ready, networked in all my gear (that has LAN). 2x LTZ1000A references running, freshly cal'ed 34465A, new DMM7510, HP 3456A, HP 3457A, HP 3478A and a Keithley 191 since the last round (stupid eBay).
The HP 3457A with a cal date of 2000 still seems to be in spec!
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/85D9AD1D-3FDD-4765-A0DB-6F6BCDF3AEED.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/85D9AD1D-3FDD-4765-A0DB-6F6BCDF3AEED.jpg.html)
The HP 3456A with a cal date of 1990 also still seems to be in spec!
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/9F434934-8EDB-4E8E-9DBD-7F9EC8E86EA8.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/9F434934-8EDB-4E8E-9DBD-7F9EC8E86EA8.jpg.html)
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Nice collection!
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I would commit several small-level crimes to have a DMM7510 on my bench.
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Im ready, networked in all my gear (that has LAN). 2x LTZ1000A references running, freshly cal'ed 34465A, new DMM7510, HP 3456A, HP 3457A, HP 3478A and a Keithley 191 since the last round (stupid eBay).
Yeah, I think it's safe to say that you're good and ready! Nice collection! :-+
I would commit several small-level crimes to have a DMM7510 on my bench.
Just a hint of TEA? ;D
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BTW
Put myself down for a new DMMCheckPlus from VoltageStandard.com (as discussed in this thread:
https://www.eevblog.com/forum/testgear/group-buy-proposal-voltagestandard-dmmcheck-plus/ (https://www.eevblog.com/forum/testgear/group-buy-proposal-voltagestandard-dmmcheck-plus/)
Would be nice to send it around if that is of interest to the group.
Thanks,
Randy
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Thanks for the update. Other members note that this offer is likely to be the last chance to buy a DMM Check. It has been discontinued once. Don't know how long the door will remain open, but the signs say just a few weeks or so.
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I have DMMCheck Plus that I got 3 years ago and have not adjusted it since. I like it a lot. If you are getting one, I highly recommend getting it with the enclosure. It is very good and functional and goes long way to keeping your unit safe and protected.
I fired mine up 30 minutes ago and having a specified tempco of about -3ppm/C, it is only 2ppm too low according to my calibrated Keithley 2002, when I apply temperature correction. It now fluctuates by about 1ppm up and down as the temperature is cycling.
I consider this quite awesome for a low cost reference. I would like to +1 the recommendation.
Sent from my iPhone using Tapatalk
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Looks like no more pre-orders until March.
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I had a DMMCheckPlus but sold it, since and regretted it.
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I just remembered I bought a PentaRef from him about 3 years ago. At the time, I didn't really have the ability to try and characterize its drift or tempco. Might be time to dig it back up!
I think he will also give it a spot-check for like $20 -- might be worth throwing it in a temperature regulated box and using that as a poor-man's voltage transfer (as a cheap sanity-check against a "real" calibration service). If he maintains a 3458A in calibration, it might be worthwhile!
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I hadn't seen why the DMMCheck models were discontinued. Was it lack of demand, to focus on voltage references exclusively, or something else?
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Doug cited costs at one point. Just not very profitable in the end.
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Ah, I see. That makes sense as there is a lot to them.
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Looks like no more pre-orders until March.
I successfully put in an order just before I made my last post here. Must have made it just under the wire.
It is also worth double checking to see if the web site put you off. By searching for the DMMCheck it brings you that product page, which can then be entered into the shopping cart.
Off on a tangent, I wonder if the various people who have attempted to enter in this business have investigated the elasticity of demand for this product. The total market is clearly small, but perhaps it is not much smaller at 150% or even 200% of the current prices. This gets even further from the BOM costs which apparently drive somes folks attitude towards pricing, but there is surely a significant fraction of the market for these things that understands that not all of the value is in the BOM.
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I think you made it just before orders got suspended. Hopefully, I interpreted it correctly. Here's the current message:
For the time being we have stopped accepting DMMCheck Plus orders but will start accepting them again in March, closer to when we will be shipping product.
Maybe they didn't want the backlog to get too big. Anyway, March isn't that far away.
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Seems like I won an auction for 10 VRE3050 voltage references. I want two. The rest are available to club members for what I paid plus shipping.
https://www.ebay.com/itm/132499240091 (https://www.ebay.com/itm/132499240091)
Let me know.
Randy
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Seems like I won an auction for 10 VRE3050 voltage references. I want two. The rest are available to club members for what I paid plus shipping.
https://www.ebay.com/itm/132499240091 (https://www.ebay.com/itm/132499240091)
Let me know.
Randy
Randy, I'm game for two.
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Are you guys making transfer standards with these or something else?
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I intend just to track it personally, out of curiosity.
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Seems like I won an auction for 10 VRE3050 voltage references. I want two. The rest are available to club members for what I paid plus shipping.
https://www.ebay.com/itm/132499240091 (https://www.ebay.com/itm/132499240091)
Let me know.
Randy
Sent you a PM.
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The VRE3050 seems interesting just from a price-point persepective. Look:
https://www.digikey.com/product-detail/en/apex-microtechnology/VRE3050JS/1240-1002-5-ND/2036537 (https://www.digikey.com/product-detail/en/apex-microtechnology/VRE3050JS/1240-1002-5-ND/2036537)
Like, what? they are embedded in some deep pocket military stuff? But I think myself and others just want to know how they compare to an LTZ1000.
I'll ping people when I actually get these in hand. They're being shipped from the UK and I actually don't know what my outlay is in USD. (But its around $5-6 per *not* $90).
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DigiKey wants $90 :o
Yeah, you did good on that auction. I remember some folks were comparing them to the LTZ1000 and some others, but I don't recall the specifics. There's a thread somewhere around here.
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Seems like I won an auction for 10 VRE3050 voltage references. I want two. The rest are available to club members for what I paid plus shipping.
Hello,
for me it would be only interesting how noisy they are.
I hope you can measure 1/f (0.1 .. 10 Hz) noise.
The 2 pieces (VRE3050AS) that I bought from DigiKey were around 9-10uVpp
which is much against the typical 3uVpp of 5V buried zener devices.
Of course it can be that I picked 2 "mondays devices".
Especially since I bought them shortly after APEX had bought Thaler Corporation.
But my personal opinion is that you get a better price/performance ratio
with AD586LQ (if you pay the DigiKey prices).
with best regards
Andreas
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Andreas, I have recently acquired a low-frequency LNA amp from Pipelie, so I can perform that measurement.
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Hello Jason,
fine.
It would also be interesting how this LNA measures the ADC#21 (arrived AUSTIN today) reference voltage.
here a typical example with my LNA.
with best regards
Andreas
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AHHh it has already arrived! I won’t be back in town until tuesday :scared: :scared: :scared:
Something to look forward to :)
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Jason, these arrived today.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/824D3524-6C84-43B7-9003-96DC4F9C64BD.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/824D3524-6C84-43B7-9003-96DC4F9C64BD.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/8AF460C0-AF5C-46AF-AF56-35CEE90488DA.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/8AF460C0-AF5C-46AF-AF56-35CEE90488DA.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/D844C7C1-C9A5-461C-B418-47866BAD56A7.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/D844C7C1-C9A5-461C-B418-47866BAD56A7.jpg.html)
Gotta love quality parts. Offer is still good if you need one for a one of TiN's 10v references.
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Kj7e, that’s great! I just mailed my hermetic resistors to Andreas to measure the tempco (I have made measurements but my setup is a bit crude, so it will be good to see how his measurements compare).
When they are shipped back, I will use the ones with the best tempco for TiN’s FX reference.
If you would like to ship your VHD200 to me, I can make some measurements while the rest of the resistors are in Germany.
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Kj7e, actually... since you have a 7.5 digit meter, it would make more sense for me to ship a copy of my temperature control box to you, and then you could measure the tempco. Have you set up and logging with your meter yet?
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Let me know what the parameters are, start temp, end temp, slope (deg C/Min). I should be able to duplicate the effort here with what I have on hand.
Yes, I can log the temp and data from the 7510.
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My resistors ETA is no earlier than May...
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This rimes... another talent :)
Sent from my iPhone using Tapatalk
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TIN, between kj7e and myself we should have R1 through R5 as hermetic resistors.
Are you waiting on the 7V-10V resistors?
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TIN, between kj7e and myself we should have R1 through R5 as hermetic resistors.
Are you waiting on the 7V-10V resistors?
No, those I already have. I ordered LTZ sets for all FX boards and few extras for fun.
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Let me know what the parameters are, start temp, end temp, slope (deg C/Min). I should be able to duplicate the effort here with what I have on hand.
Yes, I can log the temp and data from the 7510.
Great, I have just gotten back to Austin. Soon, I’ll make graphs for the measurements I’ve done and make a post in Andreas’ TC thread, which will include parameters for each measurement.
But the gist of it is that I used 10 steps of 1C each, from 25C to 35C, to measure the tempco near 25C. The best results came from using a 5 minute settling period at each step, and 30 minute plateaus at the top and bottom of each 25-to-35 or 35-to-25 excursion. Time permitting, I tried to allow three up and down ramps for each resistor, because there was some overall drift of the system, and multiple ramps helps identify that source of error.
I was able to get in some light reading while I was out of town :)
Edit: feeling a bit wicked with this post >:D >:D >:D
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Edit: feeling a bit wicked with this post >:D >:D >:D
OT:
Yes, stay at home, don't go out, since this number is gone ;)
Can help, if you answe me now ... ^-^
But beware in the mountains too!
Don't you know David Paulides "Missing 411"?
If not, YT to him. >:D
;) ;) ;D
:-+
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Great, I have just gotten back to Austin. Soon, I’ll make graphs for the measurements I’ve done and make a post in Andreas’ TC thread, which will include parameters for each measurement.
But the gist of it is that I used 10 steps of 1C each, from 25C to 35C, to measure the tempco near 25C. The best results came from using a 5 minute settling period at each step, and 30 minute plateaus at the top and bottom of each 25-to-35 or 35-to-25 excursion. Time permitting, I tried to allow three up and down ramps for each resistor, because there was some overall drift of the system, and multiple ramps helps identify that source of error.
Okay, just fooling around yesterday I ran from 12C to 45C and back down. Never saw more than a 200mOhm shift on the 13K side and that was only at once over 35C. For the most part the plot is just a flat line. I'll post a quick and dirty screen shot of the plots later when I get down to my home office/lab.
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I was able to get in some light reading while I was out of town :)
Edit: feeling a bit wicked with this post >:D >:D >:D
LOL! Nice place for such reading. :-+
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Just a quick TC plot of the 13K side on the VHD200, 5C-45C temp plot;
At 25C, measured -100mOhm (13,000k zero). On the cold side, the plot peaks just over 25mOhm at 17.5C then is a nearly flat down to 5C. Above 25C the resistances falls slightly and gets a bit bumpy, I tried this three times and see the same results, not nearly as smooth as I thought it would be. Dips to -300mOhm at 37.5C then starts to come back up. So if we take the two most extreme points there is a 400mOhm NTC over 20C or 1.5ppm/C. Ill test the 1K side next, the main thing is how close the 13:1 ratio remains.
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Great, I have just gotten back to Austin.
...
I was able to get in some light reading while I was out of town :)
Edit: feeling a bit wicked with this post >:D >:D >:D
:-DD
When I first saw the picture, I preferred to think that you were dragging metrology equipment behind you in a sled and making measurements at different altitudes and pressures or something. Something something true dedication to the craft.
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I actually have a really selfish question regarding the next round of calibration send-arounds. My best multimeter equipment is a pair of Keithley 197s that I have worked somewhat hard to restore to life. One of them is very stable (all the way to ~ 5.5 digits or 220,000 counts), the other is not so stable and isn't even repaired yet. That said, I only need to calibrate one to check the other.
But one of my problems is that these meters use the 1.9 multiplier as the calibration points. So, at least in regard to the kind of calibrations that are possible without a super accurate voltage multiplier, the ranges that I have a chance of calibrating are the 200mV range (with 190.000mV) and the 2V range (with 1.90000V). Given that the reference we are talking about is 10V, I don't see a way to calibrate the higher ranges.
My current plan was to buy a bag of resistors to try and make a divider down from the best average value of the calibrator down to these two voltages, and try to get as close as possible to whatever ratio is required. Unfortunately the best equipment I have for this is also the Keithley 197's resistance ranges, so that seems like putting the cart before the horse.
The other possibility is that I can shoot for some value other than 1.9x that's easier to make with standard resistors (or resistors any of you guys have lying around), since the meter goes to 220,000 counts. I'm not sure I understand the impact this will have on the calibration, but I believe it's possible in principle. Since the procedure is to hook up a source whose voltage you know, and then make the display agree with that voltage you know, there is no reason I couldn't calibrate it at 2.0V. I assume this works in principle too for e.g. the 20V range: I could just try to calibrate it with 10V and make the display read 10V but I think would be a bad idea for a reason I don't understand (if anyone could tell me exactly why this is a bad idea, please do!)
In any case, does anyone have any advice here? Sending them off to be calibrated seems a bit silly, considering the cost of that is several times what I paid for the instruments in the first place. But if I could figure out a way to leverage the reference you're sending around, it would at least be a starting point.
The other reason I'm interested in this in particular on the low ranges, is that I think I once actually calibrated the 1.9V range on the 2nd meter (and hence mis-calibrated, because the meter is still broken). I would love, in particular, to fix that range.
Thanks a bunch!
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If you wanted, I would be willing to check it against my 7510 which was cal'ed in late September. I calibrated my Keithley 191 with the same 1.9 cal points, just used a decade box and the 7510 to reference the known value to match on the 191.
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technogeeky, I maintain a set of text files which describe the metal foil resistors for sale by the ebay seller "hifi-szjxic":
https://ssl.pepas.com/hifi/
In your case, if you wanted to make an LM399-based transfer standard, you might need to divide 6.95V down to 1.9V, for which you would need a voltage divider of ratio 0.273381.
Using https://ssl.pepas.com/hifi/resistor-ratios-z-all.txt (which just lists his "Z-foil" resistors), several combinations of resistors make ratios which come very close:
0.273303167421 [1x RNC90Z 604R00 BR Vishay RNC90 Series Metal Foil Resistors Y1189604R000BR0​L] [1x RNC90Z 2K2100 BR Vishay RNC90 Series Metal Foil Resistors Y11892K21000BR0​L]
0.273303167421 [1x RNC90Z 6K0400 BR Vishay RNC90 Series Metal Foil Resistors Y11896K04000BR0​L] [1x RNC90Z 22K100 BR Vishay RNC90 Series Metal Foil Resistors Y118922K1000BR0​L]
0.273303167421 [1x RNC90Z 6K0400 BR Vishay RNC90 Series Metal Foil Resistors Y11896K04000BR0​L] [1x VTA56Z 22K100 1.0%Z Metal Foil Resistors 0.25w Y009522K1000F0L]
0.273388375526 [1x RNC90Z 150R00 BR Vishay RNC90 Series Metal Foil Resistors Y1189150R000BR0​L] [1x Z201 548R67 0.1% Vishay Z-Foil Series Metal Foil Resistors Y1453548R670B0L]
0.273417721519 [1x RNC90Z 432R00 FR Vishay RNC90 Series Metal Foil Resistors Y1189432R000FR0​L] [1x RNC90Z 1K5800 BR Vishay RNC90 Series Metal Foil Resistors Y11891K58000BR0​L]
Edit: to find those resistors on ebay, just search for the description on ebay.com, e.g. "RNC90Z 432R00 FR Vishay RNC90 Series Metal Foil Resistors".
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Hey guys! So I've only currently have two DMMs a Cheap-O Innova 3300, and a AMPROBE AM-520, obviously I can't yet afford anything better. However I am a bit of a stickler when it comes to accuracy. Is it worth trying to calibrate these to be as accurate as possible? Or just wait until I get something better and just use these as is.
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Hey there!
From a financial perspective, it definitely wouldn't make sense to pay a cal shop to calibrate these (that would be at least $200 per meter).
But the next time we start up a round of the cal club, you are welcome to join in! Generally you'll be just paying for one leg of shipping a small transfer standard. It looks like one is a 2,000-count meter and the other a 4,000-count, so anyone who has had a recent calibration would more than meet any uncertainty requirements to say if your meter was "bang on".
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Hey guys! So I've only currently have two DMMs a Cheap-O Innova 3300, and a AMPROBE AM-520, obviously I can't yet afford anything better. However I am a bit of a stickler when it comes to accuracy. Is it worth trying to calibrate these to be as accurate as possible? Or just wait until I get something better and just use these as is.
You might want to think hard before you enter these waters. Others have found this an expensive habit to support.
Fortunately, the first steps are free. You say you are a stickler for accuracy. Have you fully defined what you mean by that? If your meters meet their specification will you be happy? Do you understand how the specifications are written and what they mean over the ranges of the meter? Do you want each displayed digit of the meter to be correct? Under what operating conditions? Will performance verification at a small number of operating points be satisfactory to you? What do you mean by correct? Most of these questions don't have absolute answers, they are mostly determined by your personal needs and desires. After you have answered these and other questions you will be better prepared to go further down this road.
If you do you will find much friendly support on this and other calibration threads.
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Hey guys! So I've only currently have two DMMs a Cheap-O Innova 3300, and a AMPROBE AM-520, obviously I can't yet afford anything better. However I am a bit of a stickler when it comes to accuracy. Is it worth trying to calibrate these to be as accurate as possible? Or just wait until I get something better and just use these as is.
You might want to think hard before you enter these waters. Others have found this an expensive habit to support.
Fortunately, the first steps are free. You say you are a stickler for accuracy. Have you fully defined what you mean by that? If your meters meet their specification will you be happy? Do you understand how the specifications are written and what they mean over the ranges of the meter? Do you want each displayed digit of the meter to be correct? Under what operating conditions? Will performance verification at a small number of operating points be satisfactory to you? What do you mean by correct? Most of these questions don't have absolute answers, they are mostly determined by your personal needs and desires. After you have answered these and other questions you will be better prepared to go further down this road.
If you do you will find much friendly support on this and other calibration threads.
Lets just say at this point I'd be extremely happy in knowing that the readouts of my DMMs are showing me what I should be seeing. So if a 5.204 volt source where being measured, it'd come out as 5.204. The Innova 3300 has been rather old, so I calibrated it to the AM-520 reading because both did not want to agree, they were separated by a couple hundred millivolts. However I'd sleep better knowing that if read by accurate DMMs they'd all give the same output.
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Seems like I won an auction for 10 VRE3050 voltage references. I want two. The rest are available to club members for what I paid plus shipping.
https://www.ebay.com/itm/132499240091 (https://www.ebay.com/itm/132499240091)
Let me know.
Randy
Hi Randy, any update on the VRE3050's? Thanks.
-John
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Sure. I have received several emails from an intermediate shipping agency saying “on the way”, “don’t panic” and “still on the way”
Randall
Sent from my iPhone using Tapatalk
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Hey guys! So I've only currently have two DMMs a Cheap-O Innova 3300, and a AMPROBE AM-520, obviously I can't yet afford anything better. However I am a bit of a stickler when it comes to accuracy. Is it worth trying to calibrate these to be as accurate as possible? Or just wait until I get something better and just use these as is.
You might want to think hard before you enter these waters. Others have found this an expensive habit to support.
Fortunately, the first steps are free. You say you are a stickler for accuracy. Have you fully defined what you mean by that? If your meters meet their specification will you be happy? Do you understand how the specifications are written and what they mean over the ranges of the meter? Do you want each displayed digit of the meter to be correct? Under what operating conditions? Will performance verification at a small number of operating points be satisfactory to you? What do you mean by correct? Most of these questions don't have absolute answers, they are mostly determined by your personal needs and desires. After you have answered these and other questions you will be better prepared to go further down this road.
If you do you will find much friendly support on this and other calibration threads.
Lets just say at this point I'd be extremely happy in knowing that the readouts of my DMMs are showing me what I should be seeing. So if a 5.204 volt source where being measured, it'd come out as 5.204. The Innova 3300 has been rather old, so I calibrated it to the AM-520 reading because both did not want to agree, they were separated by a couple hundred millivolts. However I'd sleep better knowing that if read by accurate DMMs they'd all give the same output.
Your AM-520 is specified to be accurate to +/- 1% and 3 LSD. So when hooked to your 5.204 volt source and reading plus or minus 104 millivolts is "correct" (with a little more allowance for LSD). In addition, they probably didn't work to get drift and temperature sensitivity to values that are factors smaller than this, so even if you adjusted your AM-520 to read exactly 5.204 with a source that is somehow know to be "exactly" 5.204, you couldn't realistically expect it to read that value next week or even tomorrow morning. Of course you might have gotten lucky and your AM-520 may have zero temperature coefficient and zero drift. But until you have a long series of measurements of a known stable source you can't know that.
I didn't look up the specs for your other meter, but 3 to 5 percent accuracy allowances are not uncommon, frequently with the added caveat that it is 3 or 5 percent of full scale. It is entirely possible that your two meters can disagree by a couple hundred millivolts and both be within specification.
This is the kind of thinking I was recommending you go through before you dive into this pool.
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Sure. I have received several emails from an intermediate shipping agency saying “on the way”, “don’t panic” and “still on the way”
Randall
Sorry--that was a little glib. Here's the tracking info. Hopefully, LAX means LA international which is not *too* far. Not compared to the UK anyway.
This is the first time I've looked at the tracking info since I don't believe in getting my expectations up. Often, the package sits at my local post office for a day or more.
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The VRE3050Bs have arrived in California. Ready to be sent out to you all...
I sent a PM to those that asked for them...if you have not received a PM from me--but asked for a unit--please send me a PM.
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Would anyone be interested in a simple VRE3050 PCB via OSHPark?
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Hello,
> simple
I would at least look that I have a stress-less mounting. (perhaps on the polyimide part of a flex pcb)
I never thought that with a ceramic package I would get 200uV change with mechanical stress.
(tested with SMD-Version VRE3050AS)
with best regards
Andreas
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I never thought that with a ceramic package I would get 200uV change with mechanical stress.
Why not? Ceramic can be a great piezo-electric resonator ;)
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I'd hope they're using alumina, which AFAIK has no piezoelectric effect. If something else...?
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Making good progress on a temperature regulation board which gets thermal-epoxied onto the bottom of a Hammond 1590B. Soon the cal club will restart with temperature-regulated LTZs! :-+
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On another note, I'm also trying to cobble together some resistance transfer standards for the club.
I know the (used) meters which are popular among hobbyists have ranges based on either 10x, 20x, or 30, so I'll build e.g. the 10k standard with a 10k and 20k resistor in series, so that values of 10k, 20k, or 30k can be read from it.
Question for the group: :-/O
Should I just make these the nominal value and keep it simple, or should I go with a slightly smaller / larger value and add a trimming circuit? (e.g. should my 10K be 10K +/-0.1% or 9.99K + trimming circuit?)
(The example trimming circuit I had in mind to mimic was the ESI SRX-10k (see attached)).
Another way to phrase this question: are there any meters out there which have digital calibration, yet don't allow you to enter in an exact value? I.e. is there a meter which forces you to calibrate against a 10.00000k resistor?, and won't let you type in 10.00123k?
I'm leaning towards just sticking with nominal values, because that simplifies the design, and keeps the cost down (including 4-wire connections for both the trimmed and un-trimmed values in each standard would get expensive when Pomona 3770's are $10 a pop).
Which brings up another question: for a 4-wire connection, is it important to have low-thermal-emf jacks for all four leads, or just two of them? My intuition says that the sense leads are voltage-mode, but the force leads are current-mode, so a few uV of thermal EMF on the force leads doesn't matter at all (so use the Pomona 3770's on the sense leads, and use cheaper brass jacks on the force leads). Thoughts?
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derp, I forgot to attach the pictures of the heater progress:
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I'd go with no adjustments. Adjustments are another variable and can change during shipment or temperature cycling. They sow the seeds of doubt. AFAIK, there are no meters where you can't enter a specific value.
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Question for the group: :-/O
Should I just make these the nominal value and keep it simple, or should I go with a slightly smaller / larger value and add a trimming circuit? (e.g. should my 10K be 10K +/-0.1% or 9.99K + trimming circuit?)
Which brings up another question: for a 4-wire connection, is it important to have low-thermal-emf jacks for all four leads, or just two of them? My intuition says that the sense leads are voltage-mode, but the force leads are current-mode, so a few uV of thermal EMF on the force leads doesn't matter at all (so use the Pomona 3770's on the sense leads, and use cheaper brass jacks on the force leads). Thoughts?
I would not add any trimmer, and make the adjustment resistor small. That way its stability is not important. You will anyway not have an exact (I mean <0.1ppm or so) accurate value. And what I would not do anyhow is readjust the standard, I would leave it as is and watch anual drift. Tells you much more. All relevant precision meters accept deviations from nominal to be entered.
And while you do not need EMF posts for the force connections, I would go with all low EMF, just for the sake of avoiding any connection errors. Actually, all precision meters have EMF compensation anyhow, so you could argue you can go with no low-EMF but standard binding posts.
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I also vote for fixed resistor references (no trimmers) for simplicity, stability, and ease of use. Having 10k and 20k in series is a good idea for some flexibility.
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@cellularmitosis: Would you mind sharing the Heater-PCB? Looks nice for Hammond-cases. Is it a single supply design?
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@cellularmitosis: Would you mind sharing the Heater-PCB? Looks nice for Hammond-cases. Is it a single supply design?
Yup, designed to run off of the same 12V battery pack which will power the LTZ board:
https://github.com/pepaslabs/1590b-isothermal
https://oshpark.com/shared_projects/qRlewBCr
However, I'd hold off just a bit before ordering this board -- I haven't really verified its functionality fully yet. I hooked it up the other night and logged the temperature, and it seemed to behave a bit strangely, in a way which I don't think I can simply shrug off as "bad PID constants". So its possible there's a bug in the circuit.
Tonight I'm going to hook up the serial TTL output and see what the PID loop is doing, then I'll know for sure.
Also, there are a few changes I had planned already: 1) the LED is actually using the reset pin, which I think needs to actually be a reset pin if you want the bootloader to work correctly. 2) I think I'd like to move to using two FETs and just one current shunt, rather than one FET with power resistors above and below it.
But if you just want something to hack on, go for it!
(attached graphs are... overnight if I recall (at least 8 hours)).
Edit: I managed to get the pinout backwards on the 78L05. Which means I've been feeding my attiny85 about 8 volts. Oops.
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On another note, I'm also trying to cobble together some resistance transfer standards for the club.
I got lucky on ebay and scored a GenRad 1434 for super cheap which we can use as a donor for our resistance transfer standards!
The 1434 appears to be a later, cost-saving model compared to the 1432 and 1433:
- The case is physically smaller.
- They pulled some clever tricks with the rotary switch to get away with only 6 resistors per decade (see schematic).
- Mechanically, the switches are vastly inferior to the older models.
My 1434 arrived with no knobs, one of the switches was stuck, and a few others are not so easy to turn. The resistors look fine, but mechanically, this design does not appear to stand the test of time. So its a perfect donor for our club!
Each decade has two ceramic cards with three resistors each, of a 2-value (20R, 200R, 2k, 20k, 200k). Through clever switching, they can turn 6 2-values into 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10-values.
This is ideal for our desired 1, 2, 3-value transfer standards, as we can simply parallel 2 of the 2-values to make a 1-value, then put that in series with the other 2-value to make 1, 2, and 3.
The 200k resistors follow the same scheme, but are on individual bobbins rather than cards.
These cards are just the right size to fit into the smallest water-tight aluminum case which Hammond makes, the 1550WQ. I'll order some of those along with some silicone oil, and include a thermistor in each case. I think we can get away without active temperature control for these, as there should be enough thermal mass that the typical +/-1F swing of a typical air-conditioned lab should be smoothed out. I can also characterize the tempco of the resistors so that we can provide a correction curve using the paired thermistor.
I'm super excited!
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Over the past year I've been a bit indulgent with my ebay habit, so I also have a 1432 and 1433 to show for comparison. Mini-teardown time!
See also EEVBlog 461:
https://www.youtube.com/watch?v=fKrvtYS_6fI (https://www.youtube.com/watch?v=fKrvtYS_6fI)
I also got incredibly luck with the 1432 ($39 shipped!), but paid dearly for the 1433 ($200 shipped).
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Does your 1432 have brass , or silver contacts?
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I got lucky on ebay and scored a GenRad 1434 for super cheap which we can use as a donor for our resistance transfer standards!
The 1434 appears to be a later, cost-saving model compared to the 1432 and 1433:
Yeah, that's significantly different from the older ones I'm accustomed to seeing. Wow, good to know.
I also got incredibly luck with the 1432 ($39 shipped!), but paid dearly for the 1433 ($200 shipped).
I see. But the 1433 is such a nice design, both mechanically and aesthetically. You could look at them, instead, as having cost $120 each — a bit easier to swallow, perhaps.
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Does your 1432 have brass , or silver contacts?
bottom decades appear to be silver, top two decades (10k, 1k) are bare copper.
Yeah, that's significantly different from the older ones I'm accustomed to seeing. Wow, good to know.
It looks like things went even further downhill once IET took over. https://www.eevblog.com/forum/metrology/teardown-standard-resistors/msg1295900/#msg1295900 (https://www.eevblog.com/forum/metrology/teardown-standard-resistors/msg1295900/#msg1295900)
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Yeah, that's significantly different from the older ones I'm accustomed to seeing. Wow, good to know.
It looks like things went even further downhill once IET took over. https://www.eevblog.com/forum/metrology/teardown-standard-resistors/msg1295900/#msg1295900 (https://www.eevblog.com/forum/metrology/teardown-standard-resistors/msg1295900/#msg1295900)
That is how the ESI DB-62 is set up.
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I'm curious-- Why don't you just repair this decade box, and add knobs? -- This could be a transfer standard as well-- just get someone with good equipment (3458A or better) to calibrate each value.
So the honest answer is that I'm just having fun ;D but if I had to justify it, I'd say that by the time I spend money on a few replacement switches (I've already tried some silicone spray and it didn't help), on knobs, etc, I'd just have another decade box, which I already have two of. Plus, by hacking this into transfer standards, this opens up the possibility of trying to improve the performance, e.g. encasing in silicone oil, possibly adding a 25C heater, perhaps even a copper tempco-compensation resistor (if the tempco's turn out to be negative).
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Yeah, though it's probably still better than the little IET RC box I have with the thumbwheel switches.
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I have a garbage condition 1433. It has few good switches with very low and stable contact resistance. CM, I can easily donate a switch.
Now we can fit it with just 4 binding posts to limit the need for expensive low emf posts.
This decade has 11 positions and each of them can be wired individually with a different resistor going directly to common. This can give us these values from the same box:
10ohm, 20, 100, 200, 1k, 2k, 10k, 20k, 100k, 200k, and 1M.
This sequence covers full range on most meters and also allows us to check linearity of a meter, by having known non full scale values.
I also have some resistors from 1433. Tempco of these resistors is not the best, but not horrible also.
Another thing to consider is that 1433 switch has 4 individual wiper blades. If we can separate them as 2 and 2 we can bring 4 terminal kelvin connections right to the contact, eliminating contact resistance at all.
This would be fairly compact and light traveling 4 terminal resistance standard covering much of a useful range.
Is this something you would want to try? I have a milling machine and can help with making precision holes in a casing.
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Sorry mate, definitely appreciate the offer, but I have already sacrificed her in the name of science :)
https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1449156/#msg1449156 (https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1449156/#msg1449156)
Tempco of these resistors appears to be in the neighborhood of -5 to -6ppm/C, so its not ideal for a transfer standard anyway (unless we tried to ovenize the whole thing which is an interesting idea... ;) )
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This is ideal for our desired 1, 2, 3-value transfer standards, as we can simply parallel 2 of the 2-values to make a 1-value, then put that in series with the other 2-value to make 1, 2, and 3.
Edwin Pettis was kind enough to point out that there are many meters which call for e.g. 1.9x values for Ohms calibration, and that I'd probably want the value to be just under the 1x, 2x, 3x nominal values for maximum compatibility. He inspired me to start digging into the service manuals of a bunch of meters and figure out what they require.
I've started working on a few tables with this info and other general info about meters which hobbyist volt-nuts are likely to have: https://github.com/USACalClub/gear/blob/master/dmms/README.md
If you have a meter you'd like me to add to this growing list, give me a shout, especially if you have a meter which has possibly problematic calibration requirements (e.g., it looks like the Keithley 192 had no "over-range" ability -- its max reading was 1.999999, so a transfer standard sitting at 2.000123 wouldn't work).
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Nice tables, CM! I thought the K199 was 5.5 digits. Oh, I see you have it in both sections.
Is the HP 3458A pending?
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Nice tables, CM! I thought the K199 was 5.5 digits. Oh, I see you have it in both sections.
Is the HP 3458A pending?
Oops, thanks!
Yeah, this table grows a bit haphazardly, as finding info out about one meter leads to discovering another. By the time I started adding a 8.5-digit section, I realized I was a bit off-track from filling out the 6.5-digit section :)
Edit: oh yeah, and I remembered that someone created a similar table here on the forum with details about all of the 8.5-digit meters. I should link to that for starters.
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Links to additional reference materials are certainly welcome. There's also the DMM comparison spreadsheet thread. Although not specifically targeting metrology, it has a lot of good feature info.
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Nice tables, CM! I thought the K199 was 5.5 digits. Oh, I see you have it in both sections.
Is the HP 3458A pending?
Oops, thanks!
Yeah, this table grows a bit haphazardly, as finding info out about one meter leads to discovering another. By the time I started adding a 8.5-digit section, I realized I was a bit off-track from filling out the 6.5-digit section :)
I was going to say isn't there already a pretty extensive list of DMMs, which include handhelds as well as bench DMMs. In fact wouldn't this list suffice? https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/ (https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/)
I mean I suppose your listing is different, and it is nice to see what they look like.
Edit: oh yeah, and I remembered that someone created a similar table here on the forum with details about all of the 8.5-digit meters. I should link to that for starters.
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Just in case any one here needs a bench DMM upgrade for cheap;
https://www.ebay.com/itm/HP-AGILENT-KEYSIGHT-3456A-DIGITAL-VOLTMETER/253463397941?_trkparms=pageci%3A9afa0f65-27d0-11e8-9345-74dbd1808459%7Cparentrq%3A2676f9851620a8608e4b4673fff982b5%7Ciid%3A1&_trksid=p2481888.c100651.m4497 (https://www.ebay.com/itm/HP-AGILENT-KEYSIGHT-3456A-DIGITAL-VOLTMETER/253463397941?_trkparms=pageci%3A9afa0f65-27d0-11e8-9345-74dbd1808459%7Cparentrq%3A2676f9851620a8608e4b4673fff982b5%7Ciid%3A1&_trksid=p2481888.c100651.m4497)
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Maybe. Their listings always start at $9.99 with the balance made up for in the shipping. Due to the low apparent starting price, they tend to get lots of bids that often drive the total cost too high.
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I was going to say isn't there already a pretty extensive list of DMMs, which include handhelds as well as bench DMMs. In fact wouldn't this list suffice? https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/ (https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/)
I mean I suppose your listing is different, and it is nice to see what they look like.
Edit: oh yeah, and I remembered that someone created a similar table here on the forum with details about all of the 8.5-digit meters. I should link to that for starters.
Ah, thanks so much! I think that spreadsheet only had handhelds when I last saw it.
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I was going to say isn't there already a pretty extensive list of DMMs, which include handhelds as well as bench DMMs. In fact wouldn't this list suffice? https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/ (https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/)
I mean I suppose your listing is different, and it is nice to see what they look like.
Edit: oh yeah, and I remembered that someone created a similar table here on the forum with details about all of the 8.5-digit meters. I should link to that for starters.
Ah, thanks so much! I think that spreadsheet only had handhelds when I last saw it.
When I went through it I was pretty sure it had bench meters too. It also looks like he includes a separate list of bench and hand held meters.
Maybe. Their listings always start at $9.99 with the balance made up for in the shipping. Due to the low apparent starting price, they tend to get lots of bids that often drive the total cost too high.
Yea those shipping prices are always killer. I always love finding items that are $.99 Buy it now, with $150 shipping. They really shouldn't be allowed to do that. I think that's how they get away with having to pay Ebay's 15% of sale price.
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I see $59 for shipping from Texas to CA, that's not unrealistic for a 3456, its big heavy. A heck of a good 6.5 digit meter though. Looks clean and the bid is only $35 (as of now) with less than two days to go.
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Yep, definitely a good meter to keep an eye on. Just wanted to be sure folks were aware of the shipping. I've shipped HP 856x and 859x spectrum analyzers across the country for less, but anyway, YMMV.
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So has anyone worked out how they got it to display "+ 500000" with the SHIFT and EXT TRIGGER LEDs lit?
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I'm going to bed ( and on my phone) , but it might be one of the error codes.
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So has anyone worked out how they got it to display "+ 500000" with the SHIFT and EXT TRIGGER LEDs lit?
Shift + ~V = AC+DC volt mode. It's supposedly measuring some kind of voltage in auto-ranging mode via external trigger, but I'm not sure what the 500000 is indicating since there's no decimal point displayed.
For self-testing, a negative number on the display indicates the self-test number (1–12) that failed. The AC converter is test 12.
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So has anyone worked out how they got it to display "+ 500000" with the SHIFT and EXT TRIGGER LEDs lit?
Shift + ~V = AC+DC volt mode. It's supposedly measuring some kind of voltage in auto-ranging mode via external trigger, but I'm not sure what the 500000 is indicating since there's no decimal point displayed.
For self-testing, a negative number on the display indicates the self-test number (1–12) that failed. The AC converter is test 12.
I'll have to dig one of mine out and see if I can make it display that - perhaps setting one of the registers? If not, I'd be expecting to have to do repair work on this unit.
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So has anyone worked out how they got it to display "+ 500000" with the SHIFT and EXT TRIGGER LEDs lit?
Shift + ~V = AC+DC volt mode. It's supposedly measuring some kind of voltage in auto-ranging mode via external trigger, but I'm not sure what the 500000 is indicating since there's no decimal point displayed.
For self-testing, a negative number on the display indicates the self-test number (1–12) that failed. The AC converter is test 12.
I'll have to dig one of mine out and see if I can make it display that - perhaps setting one of the registers? If not, I'd be expecting to have to do repair work on this unit.
Your close, I just played with mine, all you have to do is enter 500000 and not store it, the display will show +500000 with out a decimal. Since there is no input to the unit, I suspect he is just trying to show a displayed value. I see nothing to indicate there is a fault and it is listed a guaranteed with returns accepted.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/C97F7CD3-2AD2-4E3B-BF69-403E2A18059A.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/C97F7CD3-2AD2-4E3B-BF69-403E2A18059A.jpg.html)
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How peculiar (showing that instead of a measurement). Thanks for solving the mystery, kj7e.
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Is anybody here bidding on this? I'm thinking of it, but I won't if anyone else is...
My way is always to put in a bid in the last two seconds. I think the current bidders aren't following this forum's ebay bidding thread ::)
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Yeah, most eBay bidders don't know how to bid properly. C'est la vie.
I'm not bidding on that listing, so no worries here.
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Is anybody here bidding on this? I'm thinking of it, but I won't if anyone else is...
Not me.
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Is anybody here bidding on this? I'm thinking of it, but I won't if anyone else is...
My way is always to put in a bid in the last two seconds. I think the current bidders aren't following this forum's ebay bidding thread ::)
Good luck! Hope the price does not go up much. If you do get it and need some help I have the full original manual in hard copy plus extra spare caps for the power supply rails.
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Is anybody here bidding on this? I'm thinking of it, but I won't if anyone else is...
Not me.
I'll abstain from bidding :) From the "sold items" search, it looks like a lot of these are listed as $100 or best offer and most of them sold for a best offer, so this meter will still be a good deal in the future for the patient + persistent.
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Hmmm
I'll abstain from bidding :) From the "sold items" search, it looks like a lot of these are listed as $100 or best offer and most of them sold for a best offer, so this meter will still be a good deal in the future for the patient + persistent.
So you're saying its already past its sell-by date? I mean, not a good deal at, what is it--$41 + (yikes) 63.65 in shipping?
Yes, you are right, as usual.
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Yep, t'was what I was jibber-jabbering about. But, of course, different folks have different tolerance for price flexibility. It had exceeded my limits, had I been in the market for one. YMMV
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I just picked up a 3456A for $115 delivered. When it arrived it was the grungist piece of gear I'd ever seen - filthy and sticky ( :scared: )all over the outside. Inside it was spotless! Soap, hot water, IPA and magic sponges took care of everything! So far all I've done is a prophylactic re-capping of the power supply. I'm still getting used to it, but I think it's more stable than my Keithley 196. Now that I have two meters, I'll never know which one is right :-DD
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Hmmm
I'll abstain from bidding :) From the "sold items" search, it looks like a lot of these are listed as $100 or best offer and most of them sold for a best offer, so this meter will still be a good deal in the future for the patient + persistent.
So you're saying its already past its sell-by date? I mean, not a good deal at, what is it--$41 + (yikes) 63.65 in shipping?
Yes, you are right, as usual.
Ha, no no I just meant I’ll restrain myself from snatching up another piece of gear so that I don’t ruin your good deal with a bidding war :). I think it looks like a great deal.
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I just picked up a 3456A for $115 delivered. When it arrived it was the grungist piece of gear I'd ever seen - filthy and sticky ( :scared: )all over the outside. Inside it was spotless! Soap, hot water, IPA and magic sponges took care of everything! So far all I've done is a prophylactic re-capping of the power supply. I'm still getting used to it, but I think it's more stable than my Keithley 196. Now that I have two meters, I'll never know which one is right :-DD
Good deal, vindoline. Glad to hear it was only a mess on the outside. To know which is right, fortunately you're part of the cal club. :-+
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Ok, I've slogged through a ton of old manuals and I've got a pretty decent crack at what the resistance reference requirements are for a large selection of old 6.5 and 5.5-digit meters:
https://github.com/USACalClub/gear/blob/master/dmms/README.md
Attached is a spreadsheet which summarizes all of the different sets of required references, and which meters require then.
Second attachment is an attempt at consolidating those into a smaller number of mailable "kits" which could be produced, and the meters which would be supported.
This was an interesting exercise. Requirements vary widely, and many particulars of the limits are often unspecified (e.g. many meters allow specifying arbitrary calibration values, but some of them don't state what the limits are of how far your artifact can deviate from nominal). Another example was that I had trouble figuring out which meters allow you to just calibrate the Ohms function, and which meters allow you to just calibrate one range of the Ohms function.
With the consolidated set, a few meters would get left out in the cold (assuming they can't calibrate just one range):
- Fluke 8846A (needs a 1G resistor, maybe it allows skipping this value?)
- Keithley 193 (maybe this can use 1.9x values instead?)
- Fluke 45 (the manual states this can use 1.9x values as an alternative)
- Fluke 8808A (appears to require 1R, 10R, 50R, 100R, 150R, 500R, 1k, 1.5k, 5k, 10k, 15k, 50k, 100k, 150k, 500k, 1M, 1.5M, 5M, 10M, 15M, 20M, 50M, and 100M)
(So, potentially, most of those which will be "left out" might be able to use alternate values anyway.)
Also, if anyone has an recommendations for very high value resistors (10M, 100M, 1G) which could be used, let me know (I have no experience here). Wirewound is probably out, and metal foils don't go that high either.
A relaxed requirement there would be a resistor which is stable enough that it can be used to simply transfer the meter's existing calibration back onto itself (e.g., read the value of the resistor before you start calibration, then enter that same value during calibration). If a resistor were immersed in a controlled 25C oil bath (+/- 0.01C), we could probably get away with fairly modest resistors for these high values. The point of including these "relaxed requirement" resistors is that some meters force you to calibrate all of the ranges, so if you are missing 100M, you are stuck. Being able to improve your calibration on 1k, 10k, etc, and simply copy your existing calibration for 100M is better than not being able to do any calibration.
Let me know if I've left off any important meters from the list so far! And as always, I'm very interested to hear any feedback here, as I'm pretty inexperienced here.
Thanks!
https://docs.google.com/spreadsheets/d/1VGwU2JbYxnRlgqtmr-_dVEWjddAojWWOSKOFVCrEPf8/edit?usp=sharing
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2001 wants 20K (can eat 10K too though, 4wire) and 1Meg (2wire).
2002 wants 1Meg, 200k, 20k, 2k, 200, 20 (all 4-wire).
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K2002 accepts adjustment resistors starting from 95x
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Yeah, most eBay bidders don't know how to bid properly. C'est la vie.
I'm not bidding on that listing, so no worries here.
Looks like it ended up going for well over $200 with shipping, so much for getting it cheap.
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Someone just listed about ten HP 3455a (6.5 digits) units for $75. Unfortunately he wants $88 for shipping.
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Oh, the joys of hyper-inflated shipping. It does seem to make for higher overall closing prices. Math is harder while bidding. >:D
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The point of including these "relaxed requirement" resistors is that some meters force you to calibrate all of the ranges, so if you are missing 100M, you are stuck. Being able to improve your calibration on 1k, 10k, etc, and simply copy your existing calibration for 100M is better than not being able to do any calibration.
That's a good idea to get through a calibration if you can't skip ranges.
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Someone just listed about ten HP 3455a (6.5 digits) units for $75. Unfortunately he wants $88 for shipping.
I know its a very subjective opinion, but the more I play with my 3456A the more I think its worth. Personally I feel $150 - $200 for a clean, working 3456A is a bargain. Maybe Conrad can comment on the 3455A.
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I've got two 3455a units, one that's perfect and has been rock stable for years, the other that has a tiny asymmetry between positive and negative voltages that I've never gotten quite perfect. Since I don't have any other models, I can't say much about different or missing features. One thing I like about the units is you can switch them so they read AC+DC for RMS situations where it matters. OK, it doesn't matter that often. One thing I don't like is they're not very good for low ohms work. The 3478a is way better for that. I've used them both with a Prologix GPIB to USB adapter and they log very nicely.
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Hello calibration club!
Looking for a new (to me) 6.5 to 7.5 digit meter and I see this on ebay:
eBay auction: #https://www.ebay.com/itm/Keithley-2700-Digital-Multimeter-Data-Acquisition-Mainframe-Integra-Series-GOOD/132549221634?epid=1401732325&hash=item1edc8c9d02:g:Jy8AAOSw-RFaXmr3
Its for a Keithley 2700. Is that meter useful without a scanner card? So I could use it stand-alone until such time as a scanner card came into my possession??
Any other suggestions welcome, especially in the 7.5 digit arena up to ~$1000.
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I have K2001 in that price range. Can do the calibrate with data (non official, using my standards and calibrated 8.5d meters as reference) prior to shipment as a bonus.
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Its for a Keithley 2700. Is that meter useful without a scanner card? So I could use it stand-alone until such time as a scanner card came into my possession??
Yes, you can use the K2700 without a scanner card. It's then like a K2000. However, if you don't need the scanning capability, you may want to consider TiN's offer for a K2001 since you're keen on a 7.5.
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I have K2001 in that price range. Can do the calibrate with data (non official, using my standards and calibrated 8.5d meters as reference) prior to shipment as a bonus.
Wow, sounds good. Will pm you!
Sent from my iPhone using Tapatalk
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I picked up a 3457A from ManateeMafia, who has a lab which is remote-controlled by TiN. TiN did a fully remote calibration of the 3457A using a 57xxA Fluke calibrator, SSH, a ras-pi, webcams, and chat. It was really pretty impressive! I've been meaning to make a short post about it -- it was a pretty cool experience.
In other news, I have some good news for the cal club! I contacted Doug at voltagestandard.com asking how much he would charge to measure an LTZ against his 3458A, and he decided to donate a measurement to the cal club! I'm about to mail a reference over to him, and I think I'll start mailing that reference around the club after it comes back from him.
Also, my hermetic resistors are on their way back from Andreas, after which I can send a set over to TiN to finish his cal club FX reference.
I know this club has been dormant for a while, but cool things should be coming pretty soon :)
Edit: I had also contacted the two cal shops in Austin, asking how much they would charge to hook an LTZ up to a 3458a for an hour and give me a CSV file, and both of them basically said "go away".
Edit 2: Ah, blast! Recently, on ebay, an old 731B went for something like $35, because the description was something like "this was donated to our church, I don't know what it is and most of the screws are missing". I just realized that I should have jumped on that, because even if it was a gutted 731B, I could have stuffed an LTZ in there and then at least a cal lab would look at it, because it is an "official" piece of equipment, rather than a DIY job.
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I have K2001 in that price range. Can do the calibrate with data (non official, using my standards and calibrated 8.5d meters as reference) prior to shipment as a bonus.
Wow, sounds good. Will pm you!
Sent from my iPhone using Tapatalk
DO IT!
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Doug is a supper guy, I had a similar experience with him and my home built resistor standard.
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Also, my hermetic resistors are on their way back from Andreas, after which I can send a set over to TiN to finish his cal club FX reference.
Great, this will be first external FX reference to go in wild.
My resistor order is due July, so schedule slips on those units. I'll have update for rest FX units soon.
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Actually, even if you need scanning, you can get a scanner card for 2001. Sometimes they sell for as little as $50.
It is a very good offer, especially for a unit that was verified working correctly and calibrated.
Sent from my iPhone using Tapatalk
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Oh, yeah. I forgot you can get scanner cards for the 2000 and 2001. The 2700 can use two cards, but the card models are different than for 200x.
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I know this club has been dormant for a while, but cool things should be coming pretty soon :)
Now I'm feeling the pressure to finish my various voltnut projects so I have something to compare! :scared:
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@cellularmitosis: Please do a post about the remote-controlled-lab from TiN/ManateeMafia. Im curious how this works. :popcorn:
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I know this club has been dormant for a while, but cool things should be coming pretty soon :)
Now I'm feeling the pressure to finish my various voltnut projects so I have something to compare! :scared:
I keep running into similar thoughts. "Oh wait, I need to go back in time and age this thing for 3 months so that I can use it..."
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@cellularmitosis: Please do a post about the remote-controlled-lab from TiN/ManateeMafia. Im curious how this works. :popcorn:
Actually, I might have to turn the mic over to TiN and ManateeMafia! I was shown a few pictures in the xdevs chatroom, and it was briefly described, but I am a bit scant on details, and I am very curious!
What other sort of unobtanium gear do they have in that lab? How did MM and TiN come to this arrangement? Perhaps TiN wanted to take advantage of some foreign ebay deals, but didn't want to pay for overseas shipping, so MM agreed to host the equipment in exchange for being allow to occasionally crack the lid and breathe in some vintage metrology fumes? ;D I'm also curious about how good TiN's estimate of his uncertainties has gotten -- I think he paid $$$ to have fluke calibrate something directly one time, and I'd imagine that's about as good as it gets (surely they have a JJ on premises?).
And on how many continents does TiN have calibration history accumulating now??? :scared: :-DD
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I wish i could come in to your "USA" calibration club. :rant: :'( ;D
(have several px'es to throw in ... :palm: )
;) ::)
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I wish i could come in to your "USA" calibration club. :rant: :'( ;D
(have several px'es to throw in ... :palm: )
;) ::)
I've shipped to Andreas and it wasn't that expensive. I say you are in :-+
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foreign ebay deals, but didn't want to pay for overseas shipping
That is not how it started, and never was a goal. But few deals might slipped thru eventually. MM just couldn't resist when I packed both of my K2002's, stash of KX LTZ REF's and showed up at the airport ;D. That's how it started, and now we help each other to dispose whatever cash available on more rusty broken equipment. :palm:
I'd prefer to have mic off, when not relevant :). In general picture, we do rotations for our volt and ohm standards on periodic term (with intervals longer than desired, after all this is just hobby). For what we do, there is near zero value of any single time calibration, no matter how good it is. Because you anchor internal lab calibrations to that standard, but are completely at the mercy of unknown drift rate. So need to have at least three calibrations in same conditions with good uncertainty to establish good confidence in transfers. This is our main goal since 2015 or so, using best standards we can get hands on to minimize chances of errors. And thousands of kilometers between us cost pretty penny too.
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I wish i could come in to your "USA" calibration club. :rant: :'( ;D
(have several px'es to throw in ... :palm: )
;) ::)
I've shipped to Andreas and it wasn't that expensive. I say you are in :-+
Yes, that would be very nice. :-+
Seriously, I already have some offers from some nice forum participants for calibrating after burn in. After that, i would spend one to let go it around to the club, if that makes any sense. But Andreas (€: and others, of course) makes much better things than me for such a project. :)
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Been in contact with a member here regarding a second pair of eyes on my 10v reference box. I've done all I can with it, time to send it off and have someone else measure and play with it some. Hope he will post his measurements here.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/4AE1673D-86D2-45AD-A4E6-8B30ABF39ACB.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/4AE1673D-86D2-45AD-A4E6-8B30ABF39ACB.jpg.html)
I may have gone a little overboard on the shipping container :o
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/551DC223-C353-473F-9AC6-C24A18A570F3.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/551DC223-C353-473F-9AC6-C24A18A570F3.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/37BD754B-9DCF-42CF-87BF-6608705545C3.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/37BD754B-9DCF-42CF-87BF-6608705545C3.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/03C4AC63-5E4B-45F7-8D9A-C3814E953D7B.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/03C4AC63-5E4B-45F7-8D9A-C3814E953D7B.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/AE43F2B4-6BAE-46FD-AFEA-4446E1C0F78F.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/AE43F2B4-6BAE-46FD-AFEA-4446E1C0F78F.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/936DF293-0838-4885-837E-55280B5B6EB4.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/936DF293-0838-4885-837E-55280B5B6EB4.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/11948879-3532-4CF2-9A9E-E912EC8C10F0.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/11948879-3532-4CF2-9A9E-E912EC8C10F0.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/C5C9F496-8090-4AED-B83D-B337CA874979.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/C5C9F496-8090-4AED-B83D-B337CA874979.jpg.html)
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Wow, beautiful packing job! And that 3456 looks mighty nice.
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tres cool! 8) 8) 8)
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planning on becoming a fluke competitor? :-+
best regards.
-zia
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kj7e
It's amazing, considering that my hobby projects never get to this stage :-DD.
time to send it off and have someone else measure and play with it some. Hope he will post his measurements here.
I wonder who would that be :bullshit:.
This build definately deserves full review and testing. :-DMM
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Does the pushbike provide emergency power to the reference?
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Does the pushbike provide emergency power to the reference?
Funny you mention that, I live in the mountains at elevation. We see ice and snow and only have one utility power line path to the homes up here. We loose power a few times a year, so I have my home office on a large UPS and two generators for the home. The push bike provides me with emergency power, Ill put it 50-100 miles with 4,000'-10,000' ele gain a week. I also have a Beta 300RR for more extreme enduro/trials riding (not quite as good as Tim Coleman).
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I also have a Beta 300RR for more extreme enduro/trials riding (not quite as good as Tim Coleman).
OT
Supernice. :-+
Have a Honda Transalp PD10 (Nickname: Transe) :=\
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(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/C5C9F496-8090-4AED-B83D-B337CA874979.jpg)
A M A Z I N G , is it an SRAM Eagle 12 speed?
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Yes, with an oval 32 front.
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Teaser, I got word it arrived safely this morning, I was told this photo was taken after about 20 min of warm up...
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Oi oi, it's -3ppm off :-/O :-DMM
Thanks for update.
I wonder who is next in food chain for this awesome box ^-^
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I told him to keep it for a week or two and play with it. So it looks like my DMM7510 may be a few PPM off one of his 3458's, so which is right :scared:
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Of course fancy blingy DMM7510. Never trust those rusty HP's out there :D.
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You guys crack me up! ;D
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Also, my hermetic resistors are on their way back from Andreas, after which I can send a set over to TiN to finish his cal club FX reference.
Hermetic resistors are en route to TiN! ;D ;D ;D \$\Omega\$ \$\Omega\$ \$\Omega\$
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I told him to keep it for a week or two and play with it. So it looks like my DMM7510 may be a few PPM off one of his 3458's, so which is right :scared:
Buy a second 7510 ;D
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I told him to keep it for a week or two and play with it. So it looks like my DMM7510 may be a few PPM off one of his 3458's, so which is right :scared:
Buy a second 7510 ;D
I'm waiting for the 8510 >:D
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Whew! I read the entire thread and I am already hooked. I have an HP3455A, a Doug Malone 5v ref, a L&N 10K resistor and lots of unfinished projects! :scared: Can I join the USA calibration club?
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Yes! PM me your address :)
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So how does shipping to people actually work? Also cellularmitosis is your offer on the Geller Labs reference still available?
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The Geller labs ref is still sick, so that’s out of rotation.
My plan this time around was to ship in a star pattern (the ref returns to me on each hop). I had in mind that if you have an instrument which was calibrated recently, I’ll pay for shipping both ways. Otherwise, I’ll pay for shipping one way.
I made a small accessory board which has an output buffer, and I think I’ll install that this weekend and try to get this thing shipped out on Monday.
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I read back a few pages but didn't see any references to logging temperature during transit. After hunting for a paper by Franco Rota on the noise diode sources he built for the 13th EME conference without success last night, I'm a bit annoyed with google. I *know* I have a copy, but no idea where.
Is that being done? If not, the MSP430 typically has an internal temperature sensor. So it would be dead simple to build a battery powered data logger that just rode around with a reference and logged the ambient temperature. Not much more effort to log BP and RH. Probably more work to select the sensors. If the container is insulated, one would need only a few measurements per hour, so battery life would be very long as in months or years.
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After hunting for a paper by Franco Rota on the noise diode sources he built for the 13th EME conference without success last night, I'm a bit annoyed with google. I *know* I have a copy, but no idea where.
You mean this one?
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There was another copy in color. Same material, but the other copy had some additional information appended to the PDF. I'm sure that google returned a link somewhere in all the pages. After chasing it a while I punted and just used this for now.
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Ah, damnit! I think I just threw away the ~3 months of ageing on the board which I was about to send out.
I decided to trim the board a bit to fit inside of one of the TEKO cases, and accidentally connected VCC to the 2n3904 base, rather than the collector. The circuit drew about 45mA, which I knew was odd, but by the time I traced down what was going on, the LTZ had been running too hot for about a minute.
It looks like it has shifted about 100uV down from where it was before the accident, and a new ageing cycle has surely begun.
The good news is that this means there's no reason for me not to assemble one of the newer PX ref boards which has an output buffer built-in.
The whole reason I wanted to bodge in an output buffer to this older board revision PX ref was that I wanted to be able to take advantage of the several months of ageing it had accumulated.
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Hello Jason,
shi(f)t happens.
You can try to restore the old value (at least for a part) by power cycling the LTZ board several times.
Power off, let the LTZ cool down and switch on again for several cycles.
I think Frank had the Idea of putting the cirquit into the freezer. (didnt try that up to now).
Of course you will not get the same voltage as before but the shift will decrease somewhat.
Up to now I had about -2 to -5 ppm after cycling.
And yes, after such a accident I usually have about double the ageing rate as before for about 6 months.
good luck
Andreas
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I decided to trim the board a bit to fit inside of one of the TEKO cases, and accidentally connected VCC to the 2n3904 base, rather than the collector.
The TEKO's are somehow dangerous things.
^-^
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Time to fire up TECbox again.
(https://xdevs.com/doc/_Passives/usac_resistor/vhp_calclub_1.jpg) (https://xdevs.com/doc/_Passives/usac_resistor/vhp_calclub.jpg).
:popcorn:
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cellularmitosis, can you help to post/link me to resistor test measurement results on the ones you sent me?
They currently running my tempco test, so I am curious to compare data.
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Yes! :-+
The number of dots on each resistor indicates which number it is.
My results start here: https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1434052/#msg1434052 (https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1434052/#msg1434052)
Andreas results start here: https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1441601/#msg1441601 (https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1441601/#msg1441601)
His summary of results is here:
https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1457580/#msg1457580 (https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1457580/#msg1457580)
https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1458463/#msg1458463 (https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1458463/#msg1458463)
The epoxy package resistor wasn't tested.
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By the way, over the past week I have been fooling around with various setups to try and squash my EMI demons. Just this evening I seem to have succeeded.
The winning combination seems to be three turns around a large cylindrical ferrite, inside of a TEKO case (however, with the ferrites, the board is nearly immune to noise even outside of the case). I can no longer move the last digit by moving around my hands, touching the case, touching the meter, touching the battery, etc. :-DMM
I haven't posted about this yet because I wanted to show the video footage I was recording, but I needed to figure out how to do picture-in-picture video editing. I've just figured out how to do that: here's a sample of testing a battery for "hand-waving" sensitivity: https://youtu.be/Ifm13AZ-QFM (https://youtu.be/Ifm13AZ-QFM)
(site note: this little guy is just about small enough to fit inside of a 34401A... >:D )
edit: the ferrites: https://www.amazon.com/gp/product/B016FC6HX0 (https://www.amazon.com/gp/product/B016FC6HX0)
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When I do ppm bridge measurements with the 1615, I do that same few turn trick. I use a tape wound core because lower frequencies are involved. Haven't tried it for DC metrology yet.
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What inductance does the 3 turn choke have?
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Hello,
surprising good results. Would be interesting what frequencies your daemons contain.
EMI-Ferrites usually have no resonant frequency like a inductor.
They are lossy and convert the EMI into heat and thus have a broader frequency range.
with best regards
Andreas
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rhb, I'll try to use my cheap LCR tester to see what the inductance is.
Another thing I was surprised by (which I'll try to post more detailed info about) was that squashing the EMI changed the DC value (I've observed this before when placing a ref inside of my dutch oven faraday cage). This made me realize that if the EMI is different across two environments, that could translate into additional DC uncertainty. Perhaps I should also be looking at the AC value on my multimeter as I test the various configurations of ferrites and such.
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Welcome to why I want long time series and went to the trouble of doing a rigorous analysis of the thermal noise amplitude spectrum. I've still not got to the 1/f noise. You can't do anything about 1/f and thermal noise, but EMI is aliased and can produce significant errors. Taking a long measurement series and examining the FFT should reveal the presence of aliased EMI, though not the frequency. AM radio stations will be the biggest source of EMI in an integrating ADC. Unfortunately, with a 3 Hz Nyquist, the audio modulation will spread the noise all across the spectrum. The only indication it is present is that it does not match the amplitude-frequency curve of the 1/f or thermal noise.
My lab is in complete disarray. I got an HP 5386A yesterday and an 8648C today (w/ a 34401A on the way ;-). In addition I pulled out all the computers so I could get a couple more machines in and on the UPS'.
In a search on a completely unrelated topic, google threw up some AD584 boards for $3. God only knows why. Probably an ad service they offer. But I couldn't resist, so I ordered 3 for the grand sum of $8.85. I'm going to put them in an enclosure with the LM399s you gave me and see what happens. These are the J parts, so I assume that the better units have been graded off. One of the things that amazed me was the AD584 costs 3x+ more from Digikey than the eBay boards. For what I want to do, the drift and TC don't matter so long as I can quantify it accurately.
If I can trim the output voltage using an MCU and PWM DAC driving a JFET wired up as a variable resistor, I should manage to annoy a few people.
Have Fun!
Reg
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What inductance does the 3 turn choke have?
I took a look at this tonight, testing the inductance of just one lead of the twisted pair, using a cheap LCR meter.
Results:
No ferrite: 2.4uH
0 turns: 3.1uH
1 turn: 5.3uH @ 721kHz
2 turns: 9.2uH @ 693kHz
3 turns: 14.9uH @ 657kHz
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My expectation for apiece of straight wire of that gage would be about 1nH per cm length of wire.
Calibrate the aligator clip leads by measuring 0 cm long piece of wire.
Note that even without the ferrite You have one complete turn of undefined cross sectional area.
same logic applies to the notionally one turn through the ferrite.
I seem to recall inductance varies as square of turns.so the measurement should go in increments of 1 to 4 to 9 ... something very off.
How long is that piece of twisted pair?
EDIT: that should be 10nH not 1nH
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Hello Jason,
shi(f)t happens.
You can try to restore the old value (at least for a part) by power cycling the LTZ board several times.
Power off, let the LTZ cool down and switch on again for several cycles.
I think Frank had the Idea of putting the cirquit into the freezer. (didnt try that up to now).
Of course you will not get the same voltage as before but the shift will decrease somewhat.
Up to now I had about -2 to -5 ppm after cycling.
And yes, after such a accident I usually have about double the ageing rate as before for about 6 months.
good luck
Andreas
The LTZ1000 output shows hysteresis, when temperature excursion is greater than about 30°C off from the nominal oven set temperature.
This hysteresis / offset might be permanent, or the output might slowly creep back towards its initial value, that depends on the individual LTZ1000 chip.
Slowly means on a years time scale.
There's the patent by Pickering, which might mitigate this hysteresis by temperature cycling the LTZ1000 oven temperature.. but I doubt that it works inside the DATRON / WAVETEK 7001 device, as the oven temperature is set to about 45°C, so the lower cycling temperature is room temperature only, which is too less to have an effect.
Anyhow, I run all my seven LTZ1000 at 12k/1k, or at about 45..55°C, and also encountered such oven temperature runaways.
In one case, that led to a permanent shift of -5ppm.
So I cycled the whole circuit (not powered, inside a plastic bag) to -23°C in the freezer, then let the oven run (outside the freezer) at 80°C, then back to -7°C, to 60°C, 10°C, 60°C, 21°C.
That set the output back to its initial value within less than 1 ppm.
Afterwards, the drift rate was again as high as -1.5ppm/ year for the first year, so it's obvious, that the initial ageing process starts over after that cycling process.
I think, I should publish the long term drift measurements for my references....
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Inductance of a toroid is L = K * N**2 where K is a material specific constant. [1]
The inductance of 1" of straight #19 wire is ~28 nH [2]
For a close wound aircore inductor L = (r*N)**2/(9*r+10*l) [3]
L - microHenries
r - radius in inches
l - length in inches
[1] "Solid State Design for the Radio Amateur", Hayward and DeMaw, ARRL 1977 p 250
[2] "Grounding and Shielding", Morrison, Wiley 2016, p 35
[3] "ARRL Electronics Data Book", DeMaw. ARRL 1977 p 26
Finding that information was surprisingly difficult in more recent publications. Ultimately I went back to what I used 40 years ago.
The test frequency is rather unusual. It's also in the AM broadcast band. You may have an EMI problem measuring inductance.
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Though I have a collection of known Amidon parts (great company), I also have a lot of surplus stuff. If you wind an arbitrary number of turns, say 10-50, and measure value and loss, you can often pin down the materials quite well, even to a specific manufacturer if they have a colored coating.
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Let's pick up this thread over here! https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/ (https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/)
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What inductance does the 3 turn choke have?
I took a look at this tonight, testing the inductance of just one lead of the twisted pair, using a cheap LCR meter.
Results:
No ferrite: 2.4uH
0 turns: 3.1uH
1 turn: 5.3uH @ 721kHz
2 turns: 9.2uH @ 693kHz
3 turns: 14.9uH @ 657kHz
For fun, I got some of those cores and put one with 3 turns of ordinary solid hookup wire on the network analyzer (VNWA). Two runs, 1 to 1001 KHz and 1 to 501MHz.
In my case, it looks like it would do best at blocking FM radio with an impedance of 1085 ohms, not so well elsewhere.
There was only about 4 inches of wire not on the core, so lower inductances are to be expected.
Edit: added picture of core and fixture.