On 8/14/2007, Arfa Daily posted this:
"CBFalconer" wrote in message
...
Arfa Daily wrote:

... snip ...

OK. I'm not sure that 'RMS' is the right term to attach to any
value derived from a ragged-arsed waveform, as it is a mathematical
function normally associated with symetrical waveforms, which the
draw by a SMPS may very well not be, but I see what you're saying.

What I am trying to say is that a chip which is designed to produce
an RMS reading from a sine wave, may well produce a meaningful
figure from a non-sinusoidal waveform also, but *only* if it is
still symetrical.

Oh? Try a square wave, for example. Nice and symetrical. You are
over-simplifying.


Explain ?

Arfa

My interpretation: you seem to be saying that some meters produce an
RMS value by applying a simple factor to the peak value of the voltage,
and you seem to be saying that it works for any symmetrical wave form.
For a sine wave, as I mentioned elsewhere in this thread, this factor
would be (root 2)/2. CBFalconer mentioned a square wave as a
counter-example. Square waves are obviously quite symmetrical, but for
them, the magic factor is 1, assuming a perfect square wave. There's no
such thing, of course, but the factor is still pretty close to 1.

--
Gene E. Bloch (Gino)
letters617blochg3251
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