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Seeking Advice on DIY Calibration for 34401A Multimeter
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wmundstock:
Hello everyone,

I'm experiencing some discrepancies between my Rigol DM3068 and a 34401A multimeter, and given the Rigol is pretty new, I am thinking its a decent reference. I would like both meters agree on the readings.
I'm considering attempting a DIY calibration for the 34401A and have a few questions for those who might have experience or insights:

- Is DIY calibration a feasible task?
- The calibration menu, after disabling the security feature, is showing 000 for everything. Should I expect to see previous calibration values there? Does this mean the calibration was  "reset"?
- I understand that running the zero calibration might overwrite existing calibration values. Can someone confirm if this is the case? I am worried to start the zeroing and then make the readings worse.
- Is it necessary to calibrate every range of every function, or can I focus on the functions/ranges that need more attention?

Any advice or tips would be greatly appreciated as I navigate this process.

Notes:
- The HP is older model, with firmware 05-01-01.
- For DC reference voltage planning to use a chinece circuit bought from aliexpress.
- For resistors planning to use a chinece circuit bought from aliexpress.
- For AC voltage, planning to use a function generator with sine wave.
- I do not have means to generate DC voltage higher than 30v nor AC voltage higher than 10v or so. Would need to build/buy something.
- I do not know what I could use to generate current, maybe a power supply with low voltage and current limit?

Thank you in advance for your help!
J-R:
IMHO, short answer: leave the 34401A alone.

Longer answer: none of the references you mentioned seem adequate for calibrating a DMM and I would suspect the 34401A could be better than the Rigol (do you mean the DM3068?).  So I would ship the 34401A out for calibration + data.
coromonadalix:
the right answer is no,  34401a  and some others are software calibrated .... unless i see the contrary

Yes i would send the 34401a to calibration,  the lm399 in it is supposed to aged well enough,  and as a minimum  you need at least 6.5 digit precision reference or higher to do the tasks

What you are proposing mak absolutely no sense at all and you could destroy all the goodness of the 34401

I had 3x 34401a in the past, sent one to cal after a psu capacitos change (all of them),  and compared it with the 2 others once done, and they were still pretty good againt it for minumum 20 years old stuff
wmundstock:
Thank you for the comments J-R and coromonadalix!


--- Quote from: J-R on March 17, 2024, 10:43:23 pm ---IMHO, short answer: leave the 34401A alone.

--- End quote ---


--- Quote from: coromonadalix on March 18, 2024, 12:56:47 am ---What you are proposing mak absolutely no sense at all and you could destroy all the goodness of the 34401

--- End quote ---

I thought I could get some feedback like this. Long live the goodness of the 34401! I am glad I asked before I messed it up.... sometimes I just cant leave things alone.



--- Quote from: J-R on March 17, 2024, 10:43:23 pm ---(do you mean the DM3068?)

--- End quote ---
Yes, fixed in the original post.



--- Quote from: J-R on March 17, 2024, 10:43:23 pm ---I would suspect the 34401A could be better than the Rigol

--- End quote ---
That crossed my mind at some point, but I have no reference to make such assumption.

bdunham7:

--- Quote from: wmundstock on March 17, 2024, 08:48:28 pm --- I would like both meters agree on the readings.

--- End quote ---

Can you give some specific examples of how much particular readings are off and the source being used?  How long are you letting the 34401A warm up and what is the ambient temperature when you do these tests?
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