USA Cal Club: Round 2

[bitseeker]

I hear ya...on both counts.

[vindoline]

I figure that there are basically two types of people in the USA Cal Club:
1) those who want to use the refs to check and callibrate their equipment, and
2) those with serious high end 8.5 digit meters who want to check our references!

I'm firmly in the former camp and I figured that I may as well bite the bullet and use TiN's FX reference to "callibrate" the 10V range on my two best multimeters  .
So, before I sent out the gear to bitseeker, I adjusted my HP3456A (easy front panel trim pot) and Fluke 8506A (awkward "software" calibration in the mid-range of the 20 v range  ) to 9.999 960

I then collected data for several hours with these two meters measuring the PX and FX references as well as a couple of experimental references I've made based on the JVR and 2DW233 circuits. The plots are attached.

[hwj-d]

Thanks vindoline.

Hm, so your HP3456A shows the pretty same as my dmm6500, but with 5.5 Digit 10µV resolution. With 18-19°C your Lab is little too cold.

[vindoline]

With 18-19°C your Lab is little too cold.

You should see it in the winter! It gets down to about 8C! 

[bitseeker]

Package arrived today, but had meetings until just a few minutes ago, so I haven't even opened it, yet. The box arrived in good shape. That's about all I can report for now.

What all is on the agenda for this first round of the calibration set? Log measurements for each DCV and the resistors (along with temp)? For how long should each be measured? Any particular NPLC?

Just asking in order to make the data useful across members and over time.

[TiN]

I would love if members can upload all results and measurement setup photo (too see wires connection, power source, etc) to FTP.
Posted details and logins here in the post.
This will allow to track how measurements change from different people and shipping locations. So we can make a graph in the end of overall reference values to see spread.
Let's fight lack of transparency on these Cal Clubs 

[bitseeker]

Will do. I uploaded results last round to your FTP. I'll add setup photo as well.

[bitseeker]

I'm in the process of getting everything set up. This was a good way to force one to clear some space on the bench.

vindoline packed everything really well. Inside the flat rate USPS box was another box with a Nanuk label and inside that was the actual Nanuk armored box and inside that are all the goodies.

I unstacked my 34401A and 34410A, put them side by side for even operating temperature, and hooked them up to my laptop via 82357B. Remote control was working fine.

Then, as I started looking at all the parts of the cal kit, I read on the FX reference that it should be plugged in and allowed to settle for 24 hours or more at constant air temperature. Unfortunately, as happened during round 1, the refs arrived at the onset of a heat wave. So, it won't get constant temp for the next few days. I'll try it out anyway.

As for power, I have a HP 6114A precision supply, but the FX ref needs +12 and -12. So, I'll try running it with an HP E3631A and use the 6114A for the PX ref (should I use its included regulator?).

So far, most things seem like they go in obvious locations. Thanks, vindoline, for marking polarity on the various connectors and making effective use of genders, too, to avoid mistakes. Nevertheless, I'm attaching photos of the PX reference setup, just to confirm that I have it right before powering up.

As for the Arduino and temp sensor (a.k.a., Tempduino), they go together in an obvious fashion (pic attached), but I'm not sure how to log from it. Does it just output to the serial monitor in the Arduino IDE?

On the FX power cable, there's an I2C/RPi connector and a pair of banana plugs for temp. I'm not sure if I should be using them in some fashion. Please advise.

Finally, there are two more cables, one with alligator clips and one with a header on one end and bare on the other. I'm not sure what they're for.

[TiN]

On the FX power cable, there's an I2C/RPi connector and a pair of banana plugs for temp. I'm not sure if I should be using them in some fashion. Please advise.

That is more of an optional feature. There are MAX6610 Temp sensor and EEPROM on FX PCB, but power and ground for them are 100% isolated from analog section with LTZ and output. So there is separate fanout for that power into Pi3 header, +5V for MAX6610, and +3.3V for I2C EEPROM, and digital ground. I thought of idea to have each member to record their results and write in short form (e.g. used meter, readout value, current calibrated value of ref, ambient temp, date) into I2C EEPROM, so we can have data stored within reference, no matter where it goes. But didn't do software bit for that. If you connect I2C SDA/SCL to RPi you should detect I2C EEPROM (24C64 chip), but right now nothing written in it. None of this is needed for LTZ1000 or 10V output operation, that just works from +/- 12V power supplied to banana plugs. Make sure to connect grounds properly (blue are grounds), red is +, black is -.

[hwj-d]

...
As for power, I have a HP 6114A precision supply, but the FX ref needs +12 and -12. So, I'll try running it with an HP E3631A and use the 6114A for the PX ref (should I use its included regulator?).
...

Hi bitseeker,

nice to see all that stuff by you now. Vindoline makes a good packaging job. 
Yes, use the included regulator as on your picture for the px. This guaranteed equal conditions in terms of voltage. Give the regulator something like 15V. The bare and clips ended wires are only for connecting power to the regulator. The Ref output and the little connectors to the header are high quality ones only connect together, not to others. I don't use the 'tempduino', because the temp in my lab are always the same at 21.7 to 22.0°C. But you need some python script at the back-end.
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg2084380/#msg2084380
(edit: oh, i see, you are there ...  )

[bitseeker]

Thanks for the background info on those optional features, TiN.

HW, OK I'll use the regulator for consistency. I didn't realize that the tempduino was from the previous round as it was added after my turn that time. Thanks for the pointer. I'll try the Python code from that discussion.

[bitseeker]

Oof, it was almost 40 °C today. My AC can't maintain an otherwise modest 26-27 with that much heat outside.

[SirAlucard]

I figure that there are basically two types of people in the USA Cal Club:
1) those who want to use the refs to check and callibrate their equipment, and
2) those with serious high end 8.5 digit meters who want to check our references!

I'm definitely in the "want to use the refs to check and callibrate their equipment" camp. Eventually I'll get to #2, maybe.

[VNUTDENYER]

Is it possible to be added to end of current list, not random, as need time to implement GPIB control of 3478A/1410A?  Thanks for any consideration.

Dick 

[ArthurDent]

Still alive, still following the list, and still aging my LTZ1000A.

[vindoline]

Is it possible to be added to end of current list, not random, as need time to implement GPIB control of 3478A/1410A?  Thanks for any consideration.

Dick

Hi VNUTDENYER! Welcome to the club. You're added to the list!

[VNUTDENYER]

Thanks much.  Hope  to add useful data in return for measuring mine.

[KK6IL]

I've got a recently acquired 3456 with unknown history and a DIY LM399 calibrator calibrated at a cal lab in 2006, and recently measured as 9.99931 as an average of two HP 6.5 or more digits out of cal voltmeters.

I'd also like to be placed near the end of the list to give me time to build a much better LM339 reverence than I built before.  Reading here, I see details I could have done better.

In addition to the 2 unused LM399H's Ive had since the dark ages, I've ordered a few used LM399H's from ebay.  Being pulls from equipment, they may have many hours of operation and be more stable than what I have now - only time will tell.

Or if anyone here lives near San Diego and has a known accurate voltmeter, I could get a head start.

John

[bitseeker]

Greetings folks, sorry for the late update. The heat wave is over and then I was traveling for a bit. Got everything except the tempduino (looking for an old-fashioned USB cable) set up tonight and it's now beginning stabilization.

Meanwhile, I reacquainted myself with BenchVue and took a screenshot of it logging from the two DMMs. I don't know the characteristics of these references and don't remember the behavior of the meters, so it was interesting to see them settling in opposite directions. Once everything levels off, my plan is to log the data in this configuration, then swap meters and log again to see how similar they are.

The PX ref is sitting on top of an old Keithley 870 since the power lead is too short to get to the HP 6114A.

So, here's the setup:

HP 6114A @ 15V -> PX vreg @ 11.93V -> PX ref -> Agilent 34401A -> GPIB cable -> Agilent 34410A
HP E3631A @ ±12V -> FX ref -> Agilent 34410A -> Agilent 82357B -> laptop

I don't have low-noise cables (except for a Triax one), so I used the shortest Pomona banana leads I have for the FX output connection.

[TiN]

Looking promising, log some ppms and we can run some analysis on CSV

We need another 10V ref in the pack, so FX can be logged in opposition, then one could get sub-ppm resolution even with 34401A. 

[bitseeker]

After dropping during the first hour or so, during the second hour the 34410A at 100 PLC shows the FX between 10.0000349 and 10.0000409. I'll take a look at the CSV after the log is done to see how much resolution is in there.

Going to bed now, but will leave the refs powered overnight and see where they are tomorrow.

[TiN]

That makes your 34410A +8 ppm off, if everything else assumed stable.
Well within even 24 hour specifications of 34410A. 

[bitseeker]

Wow, that's pretty cool considering it hasn't been adjusted in ages.

OK, noob question now. How did you arrive at 8 ppm? 1 ppm of 10V is 0.00001V. The FX ref's sticker showed 10.000000 @ 23 °C. So, at max, it's +0.00004 or 4 ppm. Where did I go astray?

[TiN]

Sure, 10V is only nominal output (specification). Actual real output comes from sticker, field EMF, T₂₃.
Now I got traceable calibration to SI Volt just 2 weeks ago, which corrected "xDevs Volt" by -0.22 ppm . Thread about that exercise will be published soon.

With huge leap of faith, we assume that FX ref was not drifted/shifted from shipping stresses/etc, and stayed ~0.1ppm from my measurements. If we entertain that idea, than this FX should provide EMF = 9.9999568 +/-0.63 ppm.

Rest is simple, 10.0000379 (I took average between two numbers you provided, as without raw data files we can't do any better) / 9.9999568 = +8.1 ppm high.
But I wouldn't bet more than $10 on this number  .

[bitseeker]

Got it. Thanks for the background info and summary, TiN!

I've logged a couple hours in the same configuration after the refs had been powered on for about 12 hours. Then, I swapped the meters and am capturing a couple more hours. Currently on the second hour.

So far, the 34401A is closer (~10.000229) to the FX ref than the 34410A was.

I'll be uploading the data files to the FTP for further analysis.

How shall I handle the reference resistors in the PX box? Just take a 4-wire reading with each DMM or record a log? If a log, for how long?