# convert current meter

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

1. ### palitoGuest

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

Thanks,
Pat

2. ### John FieldsGuest

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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 - KD5YIGuest

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

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.

John

4. ### Pat KilgoreGuest

I gave up. I bought a better meter.

Thanks for the replies