[volt-nuts] Guidance requested.

Illya Tsemenko illya at xdevs.com
Sun Jul 9 17:23:22 EDT 2017

If this is for hobby nut purposes, I'd go next:

1. Test 3458A to make sure it's all nice and stable. Refer to SN18 procedure as example test.

2. Test 732A to make sure it's stable on 10V. Absolute output at this point doesn't really matter, drift is what matters.

3. Get some decent 10KOhm resistance standard. You'd like something with <2ppm/K TCR and <5ppm/year stability. In worst case get few (4-10pcs) VPG Foil VHP hermetic 10K resistors (even 1% are fine, you need stability, not absolute accuracy). 

4. Test resistors, make them transportable in a nice sturdy box. Prep some decent wiring sets.

5. Find happy lad who'd be ready to measure your 732A/10K resistance standard for beer/juice/whatever suitable. Log temperatures during test to guardband uncertainty a little.

6. Get your 10V and 10K standards back, let them rest for week or so, under power.

7. Calibrate your 3458A against these standards. You should get <4ppm DCV, <8ppm Ohms pretty easily now.

8. Calibrate your 4808 vs 3458A

9. Calibrate 720A.

10. Modify/calibrate 7081's and keep an eye on all gear to maintain deltas for next 2-5-10 years.

---- On Mon, 10 Jul 2017 05:01:41 +0800 David C. Partridge <david.partridge at perdrix.co.uk> wrote ----

So I have: 


 1) A Datron 4808 (not calibrated recently AFAIK, and no way to check), 

 2) A 3458A which is about 6 months out of calibration (sadly not by 


 3) Three 7081s two of which are also 6 months out of calibration against 

the 3458A, 

 4) A 720A. 


The readings of the output of the Datron for the 1V, and 10V, 100V and 100V 

ranges on the 3458A (NPLC100) are: 


 1.00000177V (high limit 1.00000480V), 

 9.9999964V (low limit 9.9999720V, 

 99.999380V and climbing slowly (low limit 99.999550V) In spec some five or 

so minutes later. 

 999.98xxxV (and falling) (low limit 99.99450V) So definitely out of spec 


To be fair both the 4808 and 3458A have only been on for about 8 hours - 

things may improve :). 


The two "recently out of calibration" 7081s disagree with the 3458A but I've 

not made a record of their readings (a job for tomorrow). The other 7081 is 

not in consideration at present as its of unknown provenance. 


I also have out of calibration Cropico VS10 and Fluke 732A. 


I'm going to run the 720A through its self-calibration tomorrow. 


I can't begin to afford to send the 4808 to Fluke or the 3458A to Keysight 

for calibration. Even local cal. labs are a bit pricey, and I'm not over 

sure I trust them to get this sort of equipment correctly calibrated, given 

that they normally only handle PAT testers, 3.5 or 4.5 digit DMMs, and maybe 

the odd 6.5 digit meter. 


So please how best to proceed from here? 






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