Fluke 8840A doesn't go to zero

[ashwinsawant]

Hello everyone, I got a used Fluke 8840A from Ebay. It seems to be able to measure voltage, however once I disconnect the probes, it continues to show a slightly lower voltage reading and it takes a long time to 'discharge'. For example, see the attached images: Image01 shows 1.6V across a battery, Image02 taken 30 seconds after disconnecting the probes from the battery shows 1.4V and Image03 taken 30 minutes thereafter shows 1.3V! If I touch the probes to one another, the reading goes to zero as expected, but then spontaneously rises to around 200 mV.
Has anyone else experienced this kind of a problem before? I am wondering where the fault might lie.

[cncjerry]

short the probes and it goes to zero.  Completely normal.  It has to do with the high impedance input of the meter.  Nothing to drain down the integrating capacitor in the ADC.

[ashwinsawant]

Thank you. I learned something new today, and saved myself unnecessary hassle and expenditure. I love this forum.

[tooki]

Hahaha the asset tag that says "HP 8840A"!!!  

[mzacharias]

To expound on this just a bit further - The 8840A  input impedance is about 10 gig-ohms on DC function up to 20 volts.  Voltage ranges above that are standard 10 meg impedance. For lower DC voltages you can almost consider this a "Touch-Hold" feature. If you ever find this annoying or want to defeat it, manually switch to the 200 volt range.

Come to think of it - I'm not sure if the AC 20 volt range works the same - I'm guessing not...