34410A Calibration question

[opa627bm]

I am trying to adjust 2 34410A that was calibrated back in 2014, during the AC flatness adjustment, it seems I cannot get the read out to match the calibration value. is that normal?
https://youtube.com/shorts/BFdKmX4rV20?feature=share

[alm]

I've never calibrated this meter, but it's a flatness adjustment, so something is adjusted in this process to maximize the flatness from 10 Hz to 1kHz. I could imagine that does not mean having to be spot on at all frequencies, but rather minimize the error across the range.

If you complete and save AC voltage adjustments including the the low frequency AC flatness and normal AC flatness steps, does it comfortably meet the 24h specs in the AC voltage performance verification tests the service manual tells you to run after adjustment, and in particular the optional AC voltage tests that also test low frequency flatness?

The adjustment procedure is to supply a value, enter the actual value and wait for the succeeded message. It does not tell you to verify that it reads any particular value. That comes later in the performance verification with different signals.

[opa627bm]

Thank you for the reply, I will run the verification tomorrow. Since I only have two of this meter, I was too lazy to write a script for it, but for the flatness adjustment, there are ~ 100 steps total, so I probably should automate it.

Also, For the DCA adjustment, in the high current range, (1A and 2A) the read out will shift for 15 min before stabilize (assume is the CSR heat up causing drift) , so do you do spot calibration or you wait 15 min for each step ?

[alm]

You could try just the 1V and 10V 10 Hz and 1kHz ACV performance verification points after saving the AC gain and LF flatness. The service manual is a bit unclear here: it tells you run ACV performance verification after LF flatness, and then again after normal flatness. But obviously testing frequencies above 1 kHz after just the LF flatness adjustment doesn't make sense.

I don't see anything about it in the calibration manual, but I would wait for thermal stabilization in the higher current and 1000 V ranges. How long this takes depends on the meter. You could take a number of successive samples from the meter, or make a plot if it has a graphical display (e.g. 3446x/7x). If there's a clear linear trend in those samples, then I'd argue the system is not stable yet.