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convert current meter

Discussion in 'Electronic Basics' started by palito, Jun 20, 2005.

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  1. palito

    palito Guest

    Is it possible to convert an analog meter that measures up to 500mA to read
    up to 1 amp and also 1.5 amps.

    This is to measure the draw on a 12 volt DC circuit. Motor is supposed to
    draw 0.91A

  2. John Fields

    John Fields Guest

    It's possible, and all that's required is to place a resistance in
    parallel with the meter which, in the 1 amp case, diverts 1/2 of the
    current around the meter and through the resistor, and in the 1.5 amp
    case, diverts 2/3 of the current.

    In order to determine the value of the resistor, however, we'll need
    to know the internal resistance of the meter. If you have a
    manufacturer and a part number for the meter we may be able to find
    that information on the web. If you don't, then unless it's written
    on the meter somewhere, you'll have to measure it. Do you have any
    test equipment available?
  3. John - KD5YI

    John - KD5YI Guest

    If you can supply the meter with 500 mA, do so, and put a resistor in
    parallel with the meter. Adjust the resistor's value until the meter reads
    250 mA. It will take a low value of resistor (maybe .1 Ohms), most likely.

    For the 1.5 amps case, do the same but adjust the resistor until the meter
    reads 1/3 scale.

    If you can't adjust the meter to read exactly 500 mA, set a convenient value
    (as high as possible) then adjust the resistor to read half of the value.
    This doubles the meter's range.

    Good luck.

  4. Pat Kilgore

    Pat Kilgore Guest

    I gave up. I bought a better meter.

    Thanks for the replies
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