DC Meter To Read AC ma: Possible ?

Jan 04, 2007 1 Replies

Hello:



I wish to set the heat-anticipator on a heating thermostat by mesuring the current flow thru the circuit when energized.



It's probably about 400 or so ma, ac



But, I only have a meter that reads in dc ma.



Any way around this ?



Any conversion factor ?



Or, would it just blow my meter (dial type) ?



Thanks, B.


If you have ac volts ranges, you can stick a suitable resistor into series with the circuit and measure the voltage drop - and use the resistor value to convert to current. eg a one ohm one watt resistor will drop 0.4v ac when 400mA ac is flowing through it. A ten ohm resistor would drop 4v ac under the same circumstances but would need to be a couple of watts rating or more.

Or you can stick the meter at the centre of a full-wave bridge rectifier. But you would have to calibrate it, say using fixed resistors and a known supply voltage. It would be highly non-linear - particularly at low readings..

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