[volt-nuts] Fluke 883AB differential voltmeter

Dr. Frank Stellmach drfrank.stellmach at freenet.de
Fri Mar 19 21:57:12 UTC 2010

>>..Final problem was it would not zero properly.
The zero circuit uses two diodes to make a +/- 0.6V supply driving the offset pot.
The unit was offset so that you could not reach zero and the offset pot had fairly little range.
Adjusting the chopper didn't help.
I replaced the diodes with three 1.2V reference chips (making a -1.2 to +2.4V supply).
This centered the zero adjustment and gave better range...

Hi Mark,

this problem seems to be related to the mechanical, reed contact chopper.

This device had to be replaced very often, when I worked in a cal lab about 30 years ago..

I wonder if the unit realy works oK after your modification.

Try to replace the mechanical contact by a FET., like in later Fluke designs..


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