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Fluke AC/DC diff. voltmeter malfunction

Discussion in 'Electronic Equipment' started by R. D. Davis, Jun 1, 2004.

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  1. R. D. Davis

    R. D. Davis Guest

    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?
  2. Guest

    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.
  3. Tweetldee

    Tweetldee Guest

    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.
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