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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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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 !
 

RCinFLA

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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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BradtheRad

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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.
 

Andy G

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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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