Fluke AC/DC diff. voltmeter malfunction

Jun 01, 2004 2 Replies
R

Picked up a cheap Fluke AC/DC differential voltmeter, model 887AB/AN, at a hamfest this past weekend that's acting a little flakey. When it's switched to battery operation, the meter deflects full scale and remains that way until switched off. Any ideas? Is this a typical failure with these? I haven't attempted to connect a power cord to it yet since it has a few disconnected wires coming from the area where the transformer, AC plug, etc. is and I haven't obtained a schematic, calibration info., etc. for it yet.



The battery pack is said to be good, and I was told that it should be charged once every week or two... not sure for how long though; will the batteries be overcharged if charged for too long?


Copyright (C) 2004 R. D. Davis The difference between humans & other animals: All Rights Reserved an unnatural belief that we're above Nature & her other creatures, using dogma to justify such www.rddavis.org 410-744-4900 beliefs and to justify much human cruelty.
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U

Pegging of the needle on a meter is often due to an open shunt resistor. I am not familiar with this unit, but that is the first thing I would look for.

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T

Disturbed wiring in the power supply area could mean any of several troubles... in the power supply area. And that's where your battery pack connects. You need to get a manual, or at least, the schematic for the unit and start troubleshooting. The normal battery pack in those meters were NiCads, and the normal charging period for those instruments was 16 hours. Don't leave it on charge for much longer than 16 hours.. it will definitely damage the batteries or seriously shorten their lives. As I remember, there was no end-of-charge detection in those old meters.. just a resistor to limit charging current.

Dave M Good judgment comes from experience, and a lot of that comes from bad judgement.
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