On Mon, 17 Oct 2005 16:39:25 GMT, chuck wrote:

Hello Owen,

Seems both average-responding and trms meters use rectifiers, so a
square wave input with perfect symmetry should result in BOTH meters
reading the same: an amount equal to the peak square wave voltage. Am I
confused on this?

Leaving aside the rectifier point which is arguable:

If we accept that the RMS responding instrument reads correctly on all
types of waveforms, the issue is with the average responding
instrument.

The average responding instrument is (usually) calibrated for the form
factor of a sine wave, and its scaling in RMS is only valid for
waveforms with the same form factor.

There are two cases to consider, the square wave, and the square wave
with the fundamental removed. The form factor of both are different to
the form factor of a sine wave, and more importantly to each other, so
the average responding meter does not provide an accurate ratio of the
(true) power of each wave.

Does that make sense?

Owen
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