USA Cal Club Round 3

[RandallMcRee]

It's time for round 3 of the US Calibration Club!

After some informal discussion there are a few ground rules that are proposed:
   Each member should have the kit for two weeks, or less, exclusive of transit time;
   If you are away, do not accept the kit (inform Randall by email), you will get the next available slot when you are ready;
   The kit recipient is responsible for USPS priority mail costs in both directions;
   It is hub and spoke, so the kit is returned to, at the moment, Randall, and sent by him to you;
   There are two options: round 2 kit only (kit2) or kit2 plus a resistor set (rkit3), they may ship separately, still trying to figure that out
   
Priority mail costs $17.10 $14.75 for kit2 in a medium flat rate box, resistor set, rkit3 is another $17.10 now $14.75
Both kits in large flat rate box: $22.80 now: $19.90

Other nice-to-haves:
   Please post in this thread any questions, comments, etc,
   Please indicate any pertinent details about your measurement setup, make and model of the DMM, last cal, if any, cables, temperature, etc.
   Please post data to xdevs.com in the USA Cal Club folder (TBD).
   
PDF instructions from round1/2 from bitseeker:
https://drive.google.com/file/d/1AoXDJ-ybEtL40Hh-SGyr5oJMXcGVgf-l/view

Instructions for uploading data to xdevs:
https://www.eevblog.com/forum/metrology/usa-cal-club-getting-started-user-guide/msg2527656/#msg2527656

EEVblog starting page for kit2:
https://www.eevblog.com/forum/metrology/usa-cal-club-getting-started-user-guide/msg2527122/#msg2527122

Intro to rkm resistor box:
https://www.eevblog.com/forum/metrology/creating-some-high-precision-resistors-for-calibration-purposes/msg4550849/#msg4550849

TiN calibrated my Keithley 2002 and recertified the FX reference in kit2:
https://xdevs.com/article/usac_2023/

TiN also donated a L&N 10K standard for the club that forms the kernel of rkit3:
https://xdevs.com/article/usac_2023/#ln4040b

LET ME KNOW IF YOU WANT TO PARTICIPATE! send PM or reply here...

Thanks,
Randall
updated to reflect postal price change, 5/24/2023

[RandallMcRee]

Let's begin.  I generated a random permutation of those who signed up... and here it is:

CatalinaWow
rax
edavid
rockstedy40
SilverSolder
rsjsouza
jjoonathan
bdunham7
conrad hoffman
cscaccetti
uski
AeroETech
Smokey
maxwell3e10
1audio
RoadDog
rhb
ycui7
rockstedy40
mower
zepto
chuckb
CurtisSeizert

I will be contacting you by DM to get your contact details, etc. as the weeks roll by.

Thanks,
Randall

[Rax]

I'm in, please.

[bdunham7]

Me two.

[CatalinaWOW]

I'll join the fun. 

I would suggest investigating a large flat rate box or even just a non-standard priority box for the kit3 option.  It seems likely the charges would be less than two medium boxes, and cuts the chances for something to go wrong in the post office in half (nah, that never happens. ).

I am assuming that the precision resistors that went around with the kit in Round 2 will still be there.  Comparison data on those relative to the new resistance standard will be useful to those not wanting to do the kit3 option.

[Conrad Hoffman]

Count me in, but in a few months. Don't want to be at the front of the list so I can be more prepared this time. Translation- so I have time to tune up all my broken, ailing and neglected stuff!

[rsjsouza]

I might be interested as well, but I would need time to dive into my old/broken/new-to-me Fluke 8505A and see if I can get it up and running... Ah, and get the old PC with the GPIB interface running...

[jjoonathan]

Please put me on the list!   

[cscaccetti]

Would like to be on the list! Thanks.

[RandallMcRee]

I'll join the fun. 

I would suggest investigating a large flat rate box or even just a non-standard priority box for the kit3 option.  It seems likely the charges would be less than two medium boxes, and cuts the chances for something to go wrong in the post office in half (nah, that never happens. ).

I am assuming that the precision resistors that went around with the kit in Round 2 will still be there.  Comparison data on those relative to the new resistance standard will be useful to those not wanting to do the kit3 option.

Hi CatalinaWow--one of the reasons that I am going to the resistor setup is because those resistors are somewhat suspect. What I noticed is that their value depends on whether or not you measure them before or after using the PX reference in which they are embedded. So, presumably, a temperature effect. So I thought to eliminate that and add more range as well. I don't have the equipment necessary to characterize their tempco, so I am sort of ignoring them. Forgive me!

[CatalinaWOW]

I'll join the fun. 

I would suggest investigating a large flat rate box or even just a non-standard priority box for the kit3 option.  It seems likely the charges would be less than two medium boxes, and cuts the chances for something to go wrong in the post office in half (nah, that never happens. ).

I am assuming that the precision resistors that went around with the kit in Round 2 will still be there.  Comparison data on those relative to the new resistance standard will be useful to those not wanting to do the kit3 option.

Hi CatalinaWow--one of the reasons that I am going to the resistor setup is because those resistors are somewhat suspect. What I noticed is that their value depends on whether or not you measure them before or after using the PX reference in which they are embedded. So, presumably, a temperature effect. So I thought to eliminate that and add more range as well. I don't have the equipment necessary to characterize their tempco, so I am sort of ignoring them. Forgive me!

I think it is appropriate for you to ignore them.  By putting yourself in charge of Round 3 you have more than enough to do.  But since the data, presumably including the temp sensor data for room ambient  is all posted those who might choose this route can do the work themselves.   There should be enough data sets to provide at least some good information.   I haven't decided which way I will go.  But if I decide to go the analysis route I will certainly post the results.

[Smokey]

I don't have anything better at the moment than an old way out of cal 6-1/2 digit Keithley, but I love the idea.  Now I'll get updates when you guys do cool stuff.

[SilverSolder]

I'd like to join in on this round, if I may!

[rockstedy40]

Hello everyone.  I’m new to this group, and am amazed at the incredible engineering going on here.  Thanks to all that have made this round 3 possible.  I’d like to get in on this round also, as I have an HP 3456A and Fluke 45 I’s like to check.

I was thinking about making a Hammon divider to get a decent 1V reference.  I noticed in the round 2 thread, post #261, TIN stated that the FX could sink or source up to 20 mA (but at that level there would be no Kelvin compensation).   Would a 2mA load affect the output accuracy of the FX? Or should I design the Hammon divider for a lower parallel connection current?

Thanks
Bob

[RandallMcRee]

Hello everyone.  I’m new to this group, and am amazed at the incredible engineering going on here.  Thanks to all that have made this round 3 possible.  I’d like to get in on this round also, as I have an HP 3456A and Fluke 45 I’s like to check.

I was thinking about making a Hammon divider to get a decent 1V reference.  I noticed in the round 2 thread, post #261, TIN stated that the FX could sink or source up to 20 mA (but at that level there would be no Kelvin compensation).   Would a 2mA load affect the output accuracy of the FX? Or should I design the Hammon divider for a lower parallel connection current?

Thanks
Bob

Yes, 2 ma does affect the output accuracy.  But if you search for Conrad Hoffman’s article on diy metrology you will find techniques that don’t rely on having access to an ultra accurate voltage when making a hamon divider.  However, you should be able to calibrate your hp3456 I believe since IIRC you need just a 10v source and a 10k resistor. 

[guenthert]

Hello everyone.  I’m new to this group, and am amazed at the incredible engineering going on here.  Thanks to all that have made this round 3 possible.  I’d like to get in on this round also, as I have an HP 3456A and Fluke 45 I’s like to check.

I was thinking about making a Hammon divider to get a decent 1V reference.  I noticed in the round 2 thread, post #261, TIN stated that the FX could sink or source up to 20 mA (but at that level there would be no Kelvin compensation).   Would a 2mA load affect the output accuracy of the FX? Or should I design the Hammon divider for a lower parallel connection current?

Thanks
Bob

Yes, 2 ma does affect the output accuracy.

Well, any current draw will cause an voltage drop across the leads (iirc the FX has sense wires to the terminals, so there the drop should be small, albeit unknown.  For e.g. the Fluke 731b, a 1mA current (10kOhm load) causes a drop of 5ppm at the 10V output).  You will need to decide, whether that error is acceptable for your purpose.

[..]
However, you should be able to calibrate your hp3456 I believe since IIRC you need just a 10v source and a 10k resistor.

You might be thinking of the 3458A.  For the (older) 3456A the calibration procedure relies on several reference values (calls for Fluke's 731b as DCV standard, not HP's own 735A, even though it is used with a reference divider as stand-in for a standard cell, ouch  ) and adjusting up to 14 potentiometers (fortunately accessible from the front).

[SilverSolder]

[...] Conrad Hoffman’s article on diy metrology [...]

That article led me down a very deep rabbit hole....  into the meaning of precision, accuracy, limitations - at the frontier of what can be known. 

Fascinating stuff.

[rockstedy40]

Randall, you are correct in that I don’t need to use a precision voltage source to set the Hammon divider, thanks for reminding me about that.

The HP3456A does require a separate voltage for each decade :-(  But with the FX I can cal the 10V range.  With the FX and a 0.1x Hammon divider I can cal the 1V range (accounting for the loading of the divider on the FX by measuring the FX output first with the just calibrated 10V range).  Using the 0.1x divider and a 100V source I could also set the 100V range (albeit with less accuracy based on the stability of the 100V source).  I was also thinking about making a x0.01 Hammon divider, and using the FX to cal the 0.1V range.

I realize that these methods are not up to the typical metrology accuracy, but they should allow me to get close enough for my hobby work.

Thanks for all your inputs.

[AeroETech]

Please count me in.  I have a Keithley 2010 and a Keysight 34420A.  They were both calibrated just over a year ago.

I also have an Amphenol IRTD-400 (M2801) that is within Cal, so I can confirm the temperature logger.  My probe's specified accuracy is +/-0.025 Degrees C, but when it was recently calibrated, it checked out to within 0.003 Degrees C at 0C and 0.008 Degrees C at 420C

[alm]

The HP3456A does require a separate voltage for each decade :-(  But with the FX I can cal the 10V range.  With the FX and a 0.1x Hammon divider I can cal the 1V range (accounting for the loading of the divider on the FX by measuring the FX output first with the just calibrated 10V range).  Using the 0.1x divider and a 100V source I could also set the 100V range (albeit with less accuracy based on the stability of the 100V source).  I was also thinking about making a x0.01 Hammon divider, and using the FX to cal the 0.1V range.

I realize that these methods are not up to the typical metrology accuracy, but they should allow me to get close enough for my hobby work.

These methods have been the standard methods for decades. If you read the freely available book "Calibration - Philosophy in Practice" 1st edition by Fluke (just search for the PDF), then you'll read about using similar techniques, though with a worse voltage divider, when they describe the Fluke 7105A system. They calibrated the Fluke 750A decade to 1.018XV divider using the Fluke 720A Kelvin-Varley divider, and then use the Fluke 750A Kelvin divider to adjust the Fluke 335A calibrator, which is merely used as a stable voltage source, relative to the standard cell. A more modern way would be to use the Fluke 752A Hamon voltage divider to calibrate a calibrator using the exact method your describe.

Of course the uncertainty depends on how good your procedure is and how stable your divider and voltage source are over the duration of the calibration. But with excellent execution, this method can get you lower uncertainties than almost any other method (except by using even better dividers).

[uski]

I would love to join please, too, but put me towards the end. The reason is that I am getting an LTZ1000A reference going, and would like to compare it at the beginning to get an initial calibration, and then for the next round I can compare again and see how it ages.

I also have a few multimeters that would happily compare themselves with a good known source.

Thanks

[RandallMcRee]

Updated post #2 with a list of folks who responded.

CatalinaWOW is the first victim uh participant.

It all fits into one large flat rate box, so postage is $22.80 each way.

Thanks,
Randall

[CatalinaWOW]

I started warming up and checking test gear today.  Will be doing test runs tomorrow.  Hope to send the stuff back to Randall about three days after it arrives.  If I and the rest of us can keep this cadence up those at the end of the list won't have to wait more than a year.

[Exeter]

Very interesting concept.

[Rax]

I started warming up and checking test gear today.  Will be doing test runs tomorrow.  Hope to send the stuff back to Randall about three days after it arrives.  If I and the rest of us can keep this cadence up those at the end of the list won't have to wait more than a year.

I'd (please) not completely blast it from the front door straight to the back - I was under the impression a couple of weeks of using it is fine. The list is not that long, currently (and I assume it's being updated). I am second in line and would hope I'd get a bit of heads up before it's heading my way. Most people have actually asked to be pushed towards the end of the line.

I do appreciate the expenditure, I just hope we're keeping things on a similar timeline to what was presented.