USA Cal Club: Round 2

[bitseeker]

Welcome, Jester. Since you've read the first and last pages, you have some basic info, where to get and put data files, can check out the log files that have been submitted thus far, and a link to the latest manual about the club's calibration equipment, getting started, how to hook everything up, etc.

Reading this thread at least from about page 6 or 7 will get you to the point that folks started talking about their experience with the kit. It's recommended to read from there forward. There are tangential posts, so you can effectively skim over stuff that's not relevant (i.e., you won't actually read every post in the thread).

Between the manual and this thread, you'll find most of what you seek. Info on the reference devices might be either in this thread or the thread for Round 1. I don't recall.

Your DMMs will be fine and it's good that yours all agree. We don't all have uber-resolution equipment. If you can log for a few days at least, that'd be good. If you're able to go longer, that can be accommodated.

Contact vindoline after you've gone through the manual and the thread, if you'd like to join the rotation. Note that the list is long, so it can take quite some time for the kit to get to everyone. But, don't dismay. It eventually gets to everyone.

[CatalinaWOW]

I will add just a bit to bitseekers comments.  Many of us in the club have older equipment, not recently calibrated and are looking for some indication of where our equipment stands without sending in for an expensive calibration.  Your equipment list sounds like it will fit in quite well with others in the club.

For those with the knowledge and interest the ensemble of measurements can provide even more information about performance.  But none of the exotic analysis is required.

The primary reference sent around is a standard design and it is possible to build your own copy.  It is not inexpensive or easy to fully calibrate the result.  TiN has graciously done a lot of work to build and characterize this reference, and access to it is a major benefit of the club.  You may wish to look into any number of lower cost and lower performance references for your local use.  When you are not operating in the 8-10 digit precision world you can get by very well with lesser devices.

As you will pick up as you read the thread, patience will be required.  It has taken a year or more for a circuit around the club membership and while there is reason to hope for somewhat faster cycling, growing club membership will like counter any gains in that area.  Fortunately most of our older instruments have stabilized enough that the long interval isn't critical.

[Jester]

I just speed read through the 30 or so pages of round 2, so I now have a feel for progress so far.

First off special thanks to: cellularmitosis, TiN and vindoline for their extraordinary efforts. Also to everyone else that contributed along the way.

I would like to participate to either the end of round 2 or get in line for round 3. I will PM vindoline.

What I plan to do:
1) Prepare while waiting:
  A) get a GPIB logging system up an running well in advance *  complete
  B) log data using my Data Precision calibrator, even though it appears to drift more than all of my best 5 DMM’s  in progress
  C) previous step will also give me some idea of temperature swings
  D) fabricate a four sided metal box to allow me to easily slip out Data Precision** (presently on bottom of heap)  complete

Objectives:
a)  begin logging drift history of my DMM’s relative to each other and occasionally with the cal club references.
b)  calibrate at minimum the 10V range of my 5 DMM’s
c)  explore the possibility of upgrading my calibrator ** with improved: reference, resistors and op amps, I will start a new thread asking for advice.

*Question:
Regarding data logging, I’m left with the impression that different participants used different data logging programs and windows created a fair bit of problems related to GPIB drivers and updates. I have had multiple GPIB instruments successfully communicating in the past with a clone HP to USB adapter however I also experienced numerous problems in the past as well, in fact the last time I tried to use some excel macros that were working fine they no longer worked. I have wasted too much time on this in the past and prefer to learn from that and move on. To that end I’m inclined to setup a Raspberry Pie as a dedicated reliable data logger. I have never used a RP so if this idea holds merit if someone can suggest what model I should order, suitable operating system (or do they already come with an OS?)  and data logger software that would allow logging 2 or 3 DMM’s at the same time for the sake of time efficiency

Thanks,
J

EDIT--> UPDATE
My Data Precision 8200 calibrator has about 10 pieces of equipment on top of it, making removal a real PITA, so I decided to weld up a 12 gauge steel box that houses the calibrator making it easy to slip out without moving everything above. Mission accomplished....

I was able to get three instances of the Nx-1997 HP34401A Standalone software running and logging 3 DMM's on a Win 10 tablet, when I tried to log a 4th channel for temperature Win10 had a conniption so I put together a quick and dirty temperature logger that logs to a microSD card. I will let it run for a day or two and see how the data looks.

[Conrad Hoffman]

You have way too many meters! We have the same situation- my 8200 is also under pretty much everything else and is very difficult to get out for calibration. BTW, IMHO the 8200 is a really excellent device. Even though it only uses a lowly 399 reference, mine stays within a couple ppm for years at a time. The only negative is mine gets dirty intermittent switches and I have to clean them every now and then. Even with that they're never perfect for long. It would be great to have the GPIB board, but I don't.

[Jester]

You have way too many meters! We have the same situation- my 8200 is also under pretty much everything else and is very difficult to get out for calibration. BTW, IMHO the 8200 is a really excellent device. Even though it only uses a lowly 399 reference, mine stays within a couple ppm for years at a time. The only negative is mine gets dirty intermittent switches and I have to clean them every now and then. Even with that they're never perfect for long. It would be great to have the GPIB board, but I don't.

My 8200 seems to drift very slowly (I think). with my 3x 34401A's connected in parallel the difference between the three meters is only about 30ppm, however a few years ago after a fresh calibration of the 8200 the difference between the 8200 an all three meters was quite small, now it is significant, I need to set the 8200 to 10.00129 to get the meters displaying 10.00000V

It's possible that all three meters have drifted, but that seems highly unlikely. So my assumption at this point is that the 8200 is drifting down. I'm getting ready to start logging the 8200's reference relative to the 34401A. I would like to eventually get the 8200 to drift less than the 34401A's possibly by upgrading the: reference, resistors and opamps. Looks like this will take quite some time. I managed to get data logging of my 3x 34401A's going yesterday, so a small step in the right direction.

When you have a dirty switch, is it obvious?
Cycling the switches on mine seems to be okay, nothing I have noticed. I have noticed that on rare occasion mine gets in a snit and outputs a value that is off by a bit, however cycling the +0- switch seems to reset the problem, seems fine after that.

[Conrad Hoffman]

Dirty switch can be the occasional "off by a bit" and does no harm. Mine is far worse and just cycling the switches doesn't fix it. Once I had a resistor go bad and you want to be very careful of what you use for replacements in the whole reference/amplifier/summer system, especially at the top end. I think I used a Vishay metal foil part. If you have a lot of drift you might want to inspect for previous repairs and cleanliness.

[SirAlucard]

You have way too many meters!

How dare you say such a thing! Oh wait this isn't TEA.

[Grandchuck]

Been quiet here for a while.  What is the status?  Any ideas about a 3rd round?

[SirAlucard]

Has been quiet here, Lately I've been thinking about setting up my 3478a with it's own raspberry pi for data logging, however I'm not really super verbose with the need to know information. My idea is sound and theoretically it should work without issue. My issue is knowing the actual coding that needs to be done to get it to work. Currently I have a 3478a connected up with an arduino that connects to the GPIB port and I'm capable of talking to it and reading from it through usb no problem. So the idea is to connect that USB into a raspberry pi that'll run a script for grabbing the data from the meter. Then send that data over to a graphana server that I have running for temperature logging for the server, in which I just followed a simple guide I don't actually know how to use Graphana. Allowing me to log anything I'd wish to log. With the idea of logging temperature humidity and voltage/amperage over a long period of time. I'll likely post this elsewhere trying to find help with it, as the hardware side of things I can do no problem, it's the software that I'm clueless with, but I don't really know where to post it.

So hopefully if we do get around to a round 3 I can keep a better log over time.

[bitseeker]

I remember there was a thread about Pi logging, but I haven't kept up on the latest.

Ah, yes. Here it is: https://www.eevblog.com/forum/metrology/raspberry-pi23-logging-platform-for-voltnuts/

There were some issues regarding Linux drivers for GPIB, but I think that was resolved quite some time ago. Anyway, have a look if there's anything useful there.

A common setup of open source tools might be good to define for general use.

[Fred_47]

Will there be a round 3?

Any hint about when it will start?

[Grandchuck]

Is round 2 over?

Will there be a round 3?

[RandallMcRee]

I recently talked to Vindoline.

He is currently too busy to take on another round (so that must mean that the previous round is over).

I agreed to be the next "moderator of rounds" if no one better able and qualified is up for it.

So please PM me if you would like to be the "king of rounds" or "A-number-one-calibrator" or ?

Thanks,
Randall McRee
Davis, CA

[Grandchuck]

I recently talked to Vindoline.

He is currently too busy to take on another round (so that must mean that the previous round is over).

I agreed to be the next "moderator of rounds" if no one better able and qualified is up for it.

So please PM me if you would like to be the "king of rounds" or "A-number-one-calibrator" or ?

Thanks,
Randall McRee
Davis, CA

TiN has graciously re-certified the club FX voltage reference and donated a characterized 10k ohm reference resistor:
https://xdevs.com/article/usac_2023/
https://xdevs.com/review/ln4040b/

[Conrad Hoffman]

I find those L&N resistors perfectly decent so long as you know the temperature. Mine tend to be a bit leaky, so probably should be double bagged or used dry at low currents. Definitely interested in a 3rd go at some point.

[alm]

I find those L&N resistors perfectly decent so long as you know the temperature. Mine tend to be a bit leaky, so probably should be double bagged or used dry at low currents. Definitely interested in a 3rd go at some point.

I also have some leaky ones, but I'd prefer not to go dry, because the oil at least adds to the heat capacity and slows down any temperature changes. So removing the oil would probably exacerbate the relatively high tempco and make the coupling of the thermometer to the resistive element much worse.

Removing the oil would cut down on shipping weight if that helps, though.

[bdunham7]

Is this going forward?  I have some spare time and can help with organization and shipping if others are busy. 

[Grandchuck]

It is going forward.  Randall McRee has agreed to be in charge.

[Rax]

Going through the thread and getting up to speed, but if still possible, I'd like to take a turn with this.

[Rax]

You have way too many meters! We have the same situation- my 8200 is also under pretty much everything else and is very difficult to get out for calibration. BTW, IMHO the 8200 is a really excellent device. Even though it only uses a lowly 399 reference, mine stays within a couple ppm for years at a time. The only negative is mine gets dirty intermittent switches and I have to clean them every now and then. Even with that they're never perfect for long. It would be great to have the GPIB board, but I don't.

My 8200 seems to drift very slowly (I think). with my 3x 34401A's connected in parallel the difference between the three meters is only about 30ppm, however a few years ago after a fresh calibration of the 8200 the difference between the 8200 an all three meters was quite small, now it is significant, I need to set the 8200 to 10.00129 to get the meters displaying 10.00000V

It's possible that all three meters have drifted, but that seems highly unlikely. So my assumption at this point is that the 8200 is drifting down. I'm getting ready to start logging the 8200's reference relative to the 34401A. I would like to eventually get the 8200 to drift less than the 34401A's possibly by upgrading the: reference, resistors and opamps. Looks like this will take quite some time. I managed to get data logging of my 3x 34401A's going yesterday, so a small step in the right direction.

When you have a dirty switch, is it obvious?
Cycling the switches on mine seems to be okay, nothing I have noticed. I have noticed that on rare occasion mine gets in a snit and outputs a value that is off by a bit, however cycling the +0- switch seems to reset the problem, seems fine after that.

Jester - check my thread on fixing the switches on the 8200 ("Data Precision 8200 calibrator - repair and other fun stuff"). It's not hard and it fixes them 100% - my conclusion is this happens due to the hardening and degradation of the grease used in the switch - though I wish I'd have put some fresh grease myself when reassembling them. The only conditioning I did inside is deoxit on all contacts, which hopefully lubes the moving parts a bit.

But well worth the effort.

The drift you're seeing seems very high to me, maybe the unit needs actual repair.

Apologies to everyone for posting this here, but hopefully we're merging it into the thread where it belongs.

[CatalinaWOW]

A heads up for those who don't lurk the forum regularly.  There is a new thread for Round 3.

https://www.eevblog.com/forum/metrology/usa-cal-club-round-3/