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
- posted
18 years ago
multimeter conversion
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18 years ago
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Yes. You need a "shunt".
This is in effect a low value resistor that goes between the terminals of the meter. In effect it shunts (diverts) some of the current "around" rather than through the meter. If you had a shunt that diverted 50% of the current it would read 0-1A.
How they work...
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18 years ago
E = Imeter x Rmeter = Ishunt x Rshunt
Im = ( Is x Rs ) / Rm . . . Rs = Rm / ((Im+Is)/Im) - 1
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18 years ago
To use a shunt: run the current through the shunt and measure the VOLTS across the shunt
the shunt must have very low resistance and the voltage reading will be very low -- millivolts or microvolts. You can calculate the current, or you can go to the trouble of labeling the meter movement with a scale to read directly in amps.
You need to get your hands on a shunt, which can be bought from supply houses on the internet.
Of course, it would be easier just to get a multimeter that includes an ammeter range that's high enough for the measurement you want to make. You can get multimeters with 10 amp range for less than 20 bucks.