Electronics > Metrology

ADR1001 - Ovenized Voltage Reference System

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sahko123:
nobody else will be able to get one for a while so guess not

iMo:
An update..
Note:
34401A, 100NPLC, 10M input
7.1.23 powered off for 10minutes
24.1.23 powered off for 20minutes
18.2.23 powered off for 16 hours
5.3.23 powered off for 20minutes
17.3.23 - the first "metro-LAB_A measurement", powered off for 3h
18.4.23 - the first "metro-LAB_B measurement", powered off for 1h

Another great day - my first LAB_B measurement (thanks!), this time with a HP3458A and a trusty Fluke 8508A. This time my box spent almost a day in the lab B prior to the measurement, the measurement with thr Fluke 8508A has been provided together with a quick check with a hot 732C (0.6uV uncertainty as per last report) and it proved to be spot on within some +/- half of a uV with my test leads :) Below some shots while playing with the meters, it has been a great fun :)
PS: fixed the part numbers :)

Dr. Frank:
Hello,
I recommend for the next time when you have access to this lab, to use statistics and voltage reversal to get proper measurements, i.e. including Standard Deviation and e.m.f. removal.
See my example here:
https://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/msg4792004/#msg4792004

On my 3458A, I always use its built-in statistics function with 10 .. 16 times NPLC 100 measurements for each polarity, i.e. about 2x 30 secs. 30 secs give the lowest StD of about 2x10-8, judging from Allan Deviation statistics, and as can be seen in my protocol (e.g. 80nV/7.176V ~ 0.011 ppm StD).

The difference of these averaged measurements divided by 2 gives the mean value of the reference, w/o e.m.f.
Their sum divided by 2 gives the e.m.f. value, so you can estimate, how good your electrical connections are.

Frank   

iMo:
@Frank - thanks, I'll do next time. I tried the reversal with both (therefore my shots show negative numbers). For precise measurements as you do one needs some time I had not.. My box spent 19 hours there, not me , unfortunately :). The goal with the first LAB measurements had been to get some basic numbers and refresh the contacts. Next LAB A/B measurements in summer (this year hopefully) and I will try harder with the built in math too..

iMo:
Out of curiosity I wrote a short python prog which reads my .csv files, extracts T_amb and raw 34401A voltage, and takes last 5000 samples (NPLC100) of the longer over-night measurements only, thus the measurements are evaluated upon samples acquired during the very morning while the meter has been warmed-up for at least 6-8 hours. Below the results for comparison, together with the LAB A/B values. I will know more after the second LAB A/B measurements..
PS: the original graph I've been posting here contains some shorter measurements (not good) which made the January pretty hairy. Also I do there adjusting for gain/offset/TC_dmm, but the difference is rather small - taking in account the unknown uncertainty of my measurements  :P
Edit: removed the TC graph (not related)

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