Electronics > Repair
Repair : HP 3245A precision DC/AC source
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alanambrose:
OK still alpha standard code but V0.2 here:

http://anagram.net/Nuts/3245A/calibration/app/V0.2/

As you know you can't do DCI cal without DCV so it'll beep at you when it wants the leads changed over on the meter.

A.
Kleinstein:
Using more smaples at a single point is a good idea - though I would expect the 3458 to give a good reading rather fast. I would still look at the first samples too - they may point to possible settling time after a step in settling. Especially after a large step the voltage can take some time - possibly even more than 10 s to reach it's final value. The most obvieous case would be coming from a high voltage to a a rather small value (e.g. 1 V). Possible source for this could be thermal effects in dividers and dielectric absorbtion.

There is absolutely no need to ignore the alst 3 measurements - if you would do that, no need to take that data.
alanambrose:
Hi Kleinstein,

Could you explain what you are referring to? The cal executable I provided has a 'SETTLETIMEINMS' parameter (which defaults to 1,000 ms) and a meter 'NPLC' parameter which defaults to 100 - so there's an adjustable wait time to allow the 3245A to settle and an adjustable amount of meter averaging - so the user can (a) experiment and (b) decide for themselves. The official cal procedure is written as though the cal is done by hand (and doesn't suggest a set amount of wait time, but I think, leaves it up to the user to judge) and specifies on page 4-5 'RESET, ACAL, and NPLC 100 on the HP 3458A'.

>>> There is absolutely no need to ignore the alst 3 measurements - if you would do that, no need to take that data.

Sorry I don't see where the 'last 3 measurements are ignored' - are we looking at the same thing?

Alan
TiN:
Alan, he was referring to my post with that suggestion.
What I meant is to use average of few readings already after settle time elapsed, with few first readings disregarded. I often see that voltages measured are not accurate to last bits if just first reading is taken, even NPLC 100. Sounds fishy, but it could play a bit at very last digits of accuracy.

Even after 2 recals using 1s of settling time, I still cannot get 10.00000 reading from 3458A, while gen set to 10.00000. Have to set it 10.00002 or so, to get exact 10V. It's nitpicking, but hey, we doing this for fun here, right? :)

Also I don't think LTZ have anything to do with better calibration accuracy, but I can't prove it, since I never tried it with original LM399 in came condition test.
TiN:
CSV data with version 0.2:

Perf check
Pre-cal check
Calibration
Post-cal check
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