Keysight 34401A

[Keith956]

If your meters have all been warmed up for at least an hour, I sincerely hope it is the bottom 2.

You would think so, but actually the top 2 went for cal. I did send the two that readings furthest from the mean of the 4, and the cal lab tests first and only adjusts if out of tolerance.

The cal house report stated (amongst many other things) that on the 10V DC range,  the test tolerance was 400uV. (that tolerance is the HP quoted 1 year figure of +/- (0.0035% of reading  + 0.0005% of range).

1 meter read 10.00021V with 10.00000V applied, the other 10.00013V. So both are 'in spec'.

So, with one pair of meters out of cal for around 10 years, the other in cal, both pairs are within the manufacture's spec. Which reinforces my opinion that  getting this particular meter calibrated only makes sense if you need to prove your readings are within spec.

[cemelec]

Following my original post, I thought I'd follow up with my further testing. Basically I wanted to know how well a NOS 5 year old Keysight 34401A would hold its calibration.

I mentioned I might get a voltage calibrator, And Andreas suggested this:

https://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-2-mini-detail

So after checking various sources, YouTube, EEVblog and Ian Johnsons website,  I went ahead and spent some of my lockdown savings on the PDVS2mini.

This enabled me to do some low voltage DC testing, the results are in the attached PDF and Excel files (both the same data)

the 34401A is certainly within the 1 year Keysight spec.

Obviously the results are totally dependant on the PDVS2mini accuracy, but the PDVS2mini build quality is top class, the manufacturing and test processes top class, and final calibration carried out using very high end test equipment, so I have absolutely no doubts on that.

Its not a rigorous calibration process, for which I neither have the equipment or the knowledge, but so far I'm happy

It only covers DC up to 10 volts, but I don't see any reason for ACV, current and resistance to have drifted

Hope its of interest to someone!