HP3421A

[Jeff]

Have acquired a used HP3421A (to replace an older unit that died), and am having difficulty getting this unit to measure at AC voltages below ~60mV. The prior unit had no problem before it went on us. Generally, once you input a voltage higher than this (give or take), it begins to read more accurately (it needs cal. as its a bit off, but ok for now). Any thoughts?

Thanks,

Jeff

[Christoph Klug]

Dear Jeff,

may be your new HP4321 needs a new calibratio procedure. It would be possible, that the internal lithium battery cell now is failured, and the stored calbiration data are lost....

Best regards - Christoph Klug