[volt-nuts] 732A drift

[Randy Evans]

I hope someone can help with a strange anomaly on either my 3458A or the
732A.  The 732A 10V output as measured on my 3458A seems relatively stable
over time (it bounces around about +/-1 uV but is it the 732 or the 3458?).
 However, the 1.000 VDC output drifts downward at a rate around 1-2 uV per
second as soon as I plug the 3458A into the 732 output. If I remove the
3458A and connect it back up after a few 10s of seconds, the reading goes
back to what it started at and then drifts downward again.  The 1.018V
output also drifts downward but at a much slower rate and not as much.  Now
the question is: is it the 732 or the 3458A?  I tried to see it on my
Agilent 34401A DMM but it really doesn't have the resolution, but I do seem
to see it on the 1.000VDC output.  If it is the 732A, what would cause it
to drift downward like that?  Since the 3458A has an input impedance of
>10Gohm on the 1 and 10 V ranges, I wouldn't think the 732 would even see
the difference of whether the 3458A is connected of not, but it clearly
makes a difference as to how long its connected and how long it's been
disconnected.

Any one have any conjectures?

Also, what will turn on the "In Cal" light?  What does it mean if it
doesn't come on?

Thanks,

Randy