DMM Volts/Ohm Calibration Club - anyone interested?

[TiN]

I have to put a warning note, as my LM399 circuit values need corrections. Schematic also require few bodgewires to have proper operation with two LM399's.

LTZ one is good though.

[ez24]

Based on the posted responses so far, the original idea to fund the calibration of a member's high end DMM and use this to calibrate roving standards did not get enough support.

So, we need a source of parts and someone with metrology experience to build the cal standard.

Also useful would be a headcount of those interested in participating as well as country of residence.
enut11 (Australia)

Interesting.  I hope you can get this to work.   As someone said, customs could be a problem.  How about limit the devices to countries or regions, ie one for the US, one for Australia, one for Europe, etc.  Also shipping out of the US is very expensive.  Most in the know use shipping agents.   But start with one in your country (Australia) and if it works, try another one (in the US).

Maybe you can take a survey?  How much would a device cost? 

Good luck

[tautech]

Based on the posted responses so far, the original idea to fund the calibration of a member's high end DMM and use this to calibrate roving standards did not get enough support.

So, we need a source of parts and someone with metrology experience to build the cal standard.

Also useful would be a headcount of those interested in participating as well as country of residence.
enut11 (Australia)

Interesting.  I hope you can get this to work.   As someone said, customs could be a problem.  How about limit the devices to countries or regions, ie one for the US, one for Australia, one for Europe, etc.  Also shipping out of the US is very expensive.  Most in the know use shipping agents.   But start with one in your country (Australia) and if it works, try another one (in the US).

Maybe you can take a survey?  How much would a device cost? 

Good luck

The way around Customs is with Canet documentation.
Read this:
http://www.uscib.org/what-is-a-carnet-ud-1843/

This how touring bands/groups disclose the contents of their shipments of equipment.

[Nuno_pt]

I have to put a warning note, as my LM399 circuit values need corrections. Schematic also require few bodgewires to have proper operation with two LM399's.

LTZ one is good though.

TiN I've send an PM to plesa asking if he could provide the mods that he made to get the boards working.

Would it be feasible like in TiN 2xLM399 board to have 10V - 20V - 30V, maybe with one more LM? That way we could have 1A - 2A - 3A.

Mickle T. have made an DIY Calibrator here < https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg982223/#msg982223 >, with DCV 0.1, 1, 10, 100 V. DCI 10 mA, 1 A. Ohms 1k, 10k, 100k, 1M, in 3 small boxes.

If you could have the 10, 20, 30V, it could reach almost every DMM, K2000/15/1, HP 3456/7, 34401, etc....

[enut11]

OK, there seems to be interest from the EU, some from the USA but nil from Australia. It could mean that potential members are just too busy to get involved or have no need for this service. 

I am still hoping for more to come on board. Meanwhile I think that I will have to acquire metrology level building skills and will probably start with an LM399 voltage reference. Lots of Forum reading to catch up on...

TiN, how do I get hold of a couple of your dual-399 project PCBs?
enut11

[t2kv]

+1 for interest from Australia (Sydney).
(Subscribed to the thread, but forgot to jump in.)

[Dr. Frank]

If you get enough people, someone in the group will always have a new and/or recently calibrated meter.

We could use a wiki page. Eyeryone who joins the group could add his dmm, including the calibration dates, to this wikipage. We send two or three standards in a circle always around, and everyone could enter the meassurements into the wiki page. If someone gets the standard, he can check his DMM against the others.

We do this in our country, and the shipping costs are low. Once a year we send a standard over the ocean to another measurement club and they send us vice versa their standard. In this way we could do a cross check.

I would join such a "measurement club" here in germany/europe. And I can offer hosting the wiki. Anyone interested?

That common site would be a good idea, and a necessity for the exchange / circle-comparison of calibration data. I doubt, anyhow, that it's feasible to disclose publicly, visible to everybody, such confidential data, e.g. about individual possession of expensive instruments.

The technical exchange could only work properly, if travelling standards / calibrators of highest quality would be available. DMMCheckers and alike, or lower grade resistors are not suitable.

Reasons for my opinion:
1. Even if one member only wants to "check" his lower grade instruments, like e.g. 5 1/2 .. 6 1/2 DMMs, anyhow, sufficient T.U.R. is needed, so you easily end up with 1ppm uncertainty.
2. These standards, as they are exposed to rough environment on their travel, have to be extra stable and rugged, otherwise you won't have the chance that you ever get consistent values, after their return to the place of origin. Therefore, this excludes any simple or cheap solutions for these standards, probably also LM399's.
3. This initiative for sure aims also at volt-nuts, who already operate at the <= 1ppm uncertainty level.
If the travelling standards are less stable / uncertain than that, it would be completely uninteresting for these people.

Under these preconditions, I'm basically interested in such a group.

There already have been several personal  volt-nuts meetings with high grade equipment.
I personally prefer such events, over anonymous parcel shipping.

Frank

[Nuno_pt]

OK, there seems to be interest from the EU, some from the USA but nil from Australia. It could mean that potential members are just too busy to get involved or have no need for this service. 

Most of the guys that do this already have there own references build, and already sent them to others, like Dr. Frank said they do it in Germany, also Andreas told that we could send a reference out to others.

Has for me I'm probably going to make an TSB (Traveler Standard Box) with LM399 (here probably will use Mickle T. design for this) or LTZ with output of 7V, 10V and 10K 0.005% 3ppm/C PWW resistor from Edwin, when would be done will look for people to send it out.

I am still hoping for more to come on board. Meanwhile I think that I will have to acquire metrology level building skills and will probably start with an LM399 voltage reference. Lots of Forum reading to catch up on...

TiN, how do I get hold of a couple of your dual-399 project PCBs?
enut11

To get the boards you just have to go to TiN's website and download the Gerber files, but the 2xLM399 from TiN has some problem in the resistors networks look at the last page of the LM399 thread, also when TiN assemble one he put lots of bodge wires to make it work, also on the last page.

I don't know if TiN will do another board revision to fix this (because of his other projects and work), I know that @plesa has assemble 2 or 4 boards with UBX Vishay resistors and many PWW pots from Bourns.

A new design probably would be best to have 4xLM399 in one board since that way the noise is attenuate by a factor of 2, and is still economically acceptable, since you can get 4 LM399 from LT for free, 2 A version and 2 non-A.

 

[Nuno_pt]

The technical exchange could only work properly, if travelling standards / calibrators of highest quality would be available. DMMCheckers and alike, or lower grade resistors are not suitable.

Dr. Frank, here would the 0.01% or 0.005% 3ppm/C PWW resistors from Edwin or be acceptable?
Or must be Vishay VHP 101 or 202?
What values? 10k would be enough, or others are needed?
Also agree on DMMCheckers.

Reasons for my opinion:
1. Even if one member only wants to "check" his lower grade instruments, like e.g. 5 1/2 .. 6 1/2 DMMs, anyhow, sufficient T.U.R. is needed, so you easily end up with 1ppm uncertainty.

Would it be acceptable to do the measurements in 6 1/2 DMM? I've here 2 on way to 3, but don't know about the calibration state.

2. These standards, as they are exposed to rough environment on their travel, have to be extra stable and rugged, otherwise you won't have the chance that you ever get consistent values, after their return to the place of origin. Therefore, this excludes any simple or cheap solutions for these standards, probably also LM399's.

Also if it was 2 or 4xLM399?

3. This initiative for sure aims also at volt-nuts, who already operate at the <= 1ppm uncertainty level.
If the travelling standards are less stable / uncertain than that, it would be completely uninteresting for these people.

Agree, that for the already Volt-nuts, it would be uninteresting, but for newcomers would be good to learn with people that are already on this for long time.

Under these preconditions, I'm basically interested in such a group.

I would like to start somewhere.

There already have been several personal  volt-nuts meetings with high grade equipment.
I personally prefer such events, over anonymous parcel shipping.

Frank

I also prefer to meet in person, but given my case as an example, since I don't have any Volt-nut here in Portugal, after reading all the groups, for example it's easy to send my TS to you in Germany, then catch a flight to Germany, and maybe renting a car, etc..., the same could happen to others, if you've some people in your country or maybe neighbor country, it's ok to meet in person, but if not shipping is good.

No disrespect mean Dr. Frank.

Nuno

[HighVoltage]

I am interested in meeting in person but I also can help out, by sending a Geller Labs 10V reference, to those who are interested in seeing it on their equipment. I do have several of these 10V Geller Labs references and would make one available for traveling. But best to send it without the 24V DC power supply. You would have to power it with your own adapter or a lab PSU with 4 mm Banana plugs.

I would check the 10V reference on my 3458A, 34470A and DMM7510 before shipping and again when I receive it back.
May be even adjusting it as close as possible to 10.00000V
What I should do, is to install a PT100 RTD so we can also record the internal reference temperature when taking readings.



   

[VK5RC]

Apologies for late entry into this post, I just found it.
enut11
I am interested, in Australia, have a 3458A (out of cal). I am not at 1ppm level by quite some way.
Robert

[lukier]

A new design probably would be best to have 4xLM399 in one board since that way the noise is attenuate by a factor of 2, and is still economically acceptable, since you can get 4 LM399 from LT for free, 2 A version and 2 non-A.

I sense you have a laissez faire approach to samples. I wouldn't abuse sample programs like that and also encourage others to do so, in quantity. LM399 is a bit pricey, but not extremely and can be had cheaper on eBay.

There are really people that need these samples, in the academia, in startups and other legit business etc. There is a reason why being a volt-nut is an expensive hobby

[Kleinstein]

In a reference for calibration purpose the noise is not that important, as one can spend a little more (e.g. 2 or 4 times) time on averaging. So I don't think there is a real need to have more than one LM399 for noise reasons, unless you need a fast measurements or go beyond 8 digits.

It might be a reasonable Idea two have two references for a kind of self check - but this would be more like getting independent readings or average and difference.

For price of the LM399 circuit it really depends of one also includes the 7 V to 10 V circuit. The resistors for the 7 to 10 V step might be the more expensive part. The other parts should not be really expensive.

[enut11]

+1 for interest from Australia (Sydney).
(Subscribed to the thread, but forgot to jump in.)

Hi t2kv. Thanks for joining in. I am a novice volts-nut. What is your expertise? What type of DMM do you want to calibrate? I live in Wollongong, NSW and have an HP3456A (uncalibrated). enut11

Apologies for late entry into this post, I just found it.
enut11
I am interested, in Australia, have a 3458A (out of cal). I am not at 1ppm level by quite some way.
Robert

Hi VK5RC. Thanks for joining in. Having a 3458A is a good start, even if it is uncalibrated! What area do you live in? enut11

[t2kv]

Hi t2kv. Thanks for joining in. I am a novice volts-nut. What is your expertise?

I'm whatever the rank below novice is. I've done a bunch of little experiments comparing properties of commercial voltage standards in the 0.05-0.02% range, and built a resistance standard from 0.01% and 0.005% resistors.

What type of DMM do you want to calibrate?

One I haven't bought yet; I'm out hunting for a 6.5 digit multimeter at the moment.
The best I have at the moment is 4.5 digits, which is a bit embarrassing in the metrology section of the forum.

Hi VK5RC. Thanks for joining in. Having a 3458A is a good start, even if it is uncalibrated! What area do you live in? enut11

Based on the username, I'm guessing he is probably in SA. 

[hammy]

I'm whatever the rank below novice is.

 
We could split up Novice in Low/Mid/High 

[bitseeker]

I have several 6.5-digit bench DMMs (and lower-resolution handhelds) and am intrigued by the club concept, but need to see how it all comes together. The tradeoff will be cost vs. time required to perform the calibration and adjustment process myself as compared to occasionally using a local lab.

[VK5RC]

enut11,  I live in suburban Adelaide.
Regards Rob

[enut11]

I'm whatever the rank below novice is.

 
We could split up Novice in Low/Mid/High 

Maybe not such a crazy idea, at least we would know where we all stand wrt expertise.
Also, novices may be content with access to calibrated lower standards, such as DMMcheck or similar, while they are coming up to speed with knowledge and building skills.
enut11

http://www.voltagestandard.com/DMMCheck_Plus.html

[Alex Nikitin]

As an option - would it be an interest in a simple 10V/7V/10K travelling box, with 24V DC supply requirement, only two quality terminals and a 3-position switch (10V/10K/7V) ?

10K resistor would be hard-wired directly to the terminals so for the resistance standard the switch just disconnects the voltage reference, no contact resistance involved. This could be a very small, fairly accurate (probably under 10ppm for 90 days is achievable using LM399 and a good wire-wound resistor) and cheap unit. The 7V output would allow for a 7V to 10V transfer accuracy check limited only by the meter's ADC linearity error (so about 1ppm or better for decent 6.5+ digits units). 10K position also can be used to check the thermal offsets in the interconnects as long as the input current of the meter at 0V is low (1nA would create 10uV or 1ppm@10V error).

Cheers

Alex

P.S. from 10V and 10K anyone can derive other required DC references (i.e. 1K, 100K, 1M, 100mV, 1V, 100V, 1000V, 1mA, 10mA, 100mA, 1A etc) with a pretty good accuracy using the Hamon transfer method - as long as the resistors used in Hamon dividers have a reasonable short-term stability (and a low voltage coefficient for HV).

[Nuno_pt]

Alex, I'm looking at the same thing, but the difference will be 5 Pomona connectors, 7V directly from the Zener (maybe trimmer with Bourns PWW pot), 10V buffer from an LTC2057 (also trimmer), and 10k PWW from Edwin Pettis 0.005% 3ppm/C.

This would be box in a IP67 plastic or aluminum box, RPi Zero & BME280 inside to log, for power I was thinking maybe from battery (12V or 24V) or an wallwart could be use.

No switching involve from ranges.

[Alex Nikitin]

Alex, I'm looking at the same thing, but the difference will be 5 Pomona connectors, 7V directly from the Zener (maybe trimmer with Bourns PWW pot), 10V buffer from an LTC2057 (also trimmer), and 10k PWW from Edwin Pettis 0.005% 3ppm/C.

This would be box in a IP67 plastic or aluminum box, RPi Zero & BME280 inside to log, for power I was thinking maybe from battery (12V or 24V) or an wallwart could be use.

No switching involve from ranges.

It would be a lot more money  . And you shouldn't trim 7V from Zener (and 10V should not have a user accessible trim IMHO). Accurate multimeters would allow you to enter the actual value for 10V / 10K calibration, and not accurate meters won't need that accurate value anyway. Also you don't need a very expensive 0.005% 10K resistor. Even 0.1% will do nicely as long as the quality is good and the actual value is measured with good accuracy. Right now I can build one as I've described, with Pomona terminals and a Hammond aluminium box, for less than £70 even buying all parts from Digikey/Farnell.

Cheers

Alex

[enut11]

Cheap enough for each member to build his own and circulate it amongst the group.
Would a number of roving standards provide more useful information?

[3roomlab]

i had an idea once to want to fit out the insides of a pelican case with some resistors and standards to send to someone to help me determine some values, i didn't get around to do it.

so i think i will just put this idea in this thread, maybe the case is something like a box in a box suspended/shock-proofed? special air cushion? small enough that makes shipping affordable? or maybe not? i am guessing this equipment will be doing lots n lots of traveling, and things get hairy if it breaks due to rough cargo handling, it will really waste lots of time and effort. there could be live accelerometers to keep track of the journey so that the next user can help check if it went thru hell? then possibly look for damages and repair if any.

its just a thought

[ManateeMafia]

This case looks like it could be a good candidate. The lid is removable and perhaps add over the top plate a custom pcb with cutouts for binding posts switches, etc...

The plastic handle would probably have to go.

http://www.budind.com/view/Small+Metal+Electronics+Enclosures/Transi-Cases