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Why does the voltmeter measure the rms value of voltage?

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renzworldc

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digital voltmeter

why does the voltmeter measure the rms value of voltage and not the peak or avrg. value???
 

digital voltmeter

RMS is all about comparing apples to apples, irrespective of what signal waveform is applied. The RMS of a DC signal will be the DC signal, taking the RMS of an AC, PWM, sawtooth or complex signal allows us to compare their 'real value' when comparing between them.

Most of the cheaper meters don't measure true RMS. They just estimate it from an pseudo RMS.
True RMS gives a real comparison to DC equivalence, which is better given modern meters extremely high input impedance.

For example a AC signal with a 40V noise signal imposed on top may register a Peak voltage or pseudo RMS way different to its real equivalence.

BTW the average of a true sine wave would be 0, as it would be symmetric around 0V over 2Π radians.
 

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