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[SOLVED] Question is what voltage will a DMM show at inverter output terminals?

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Andy G

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Jan 25, 2010
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i want to know what will be the reading on a DMM or analog multimeter at the output terminals of a modified sine wave or square wave inverter?
I am using a commercial Chinese inverter and my DMM shows 200 volts when the inverter is supposed to give 220V AC
Thanks !

Your inverter is likely a modified sinewave inverter. These are actually modified square wave output of three discrete voltages. For 240 vac modified sinewave inverter the output is about -305v, 0v, +305v. This yields about 240 vrms.

As to your meter. Unless it specifically states that it is a true rms meter then it is a simple averaging AC voltmeter. The AC is rectified and averaged through an R-C filter. The meter is then calibrated to read the equivalent rms reading assuming the input is a sinewave. When waveform is not a sinewave the AC voltmeter is inaccurate.

A modified sinewave inverter will read low on an averaging AC voltmeter.
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    Andy G

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I've used inexpensive inverters. Both square and modified sine.

My ordinary analog meter reads about 91 volts.

They gave my DMM fits. Sometimes it showed nonsensical readings. With a true sinewave inverter it gave normal readings.

Thanks very much indeed to "RCinFLA" with the detailed clear explanation,the output voltage will show low on an ordinary DMM or analog multimeter
cheers !!

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