"Jeff Liebermann" wrote in message
...

http://www.eznec.com/Amateur/RMS_Power.pdf
On Pg 6 it says:
"The RMS value of power is not the equivalent heating power and,
in fact, it doesn't represent any useful physical quantity."
and:
"The RMS power is different than the average power, and therefore
isnt the equivalent heating power. In fact, the RMS value of the
power doesnt represent anything useful."

It would seem that the author finds average power different from,
more useful than, and closer to heating power. Perhaps we should
change the name from "true-RMS voltmeter" to "true heating average
voltmeter"?

Jeff, you're misreading this. The author is saying //exactly// what I said.
(It's unfortunate he doesn't use a sine wave for his example, but the math
would then require integral calculus.)

Average power /is/ the heating power. (The rationale is that a resistor's
temperature is determined by the average power applied to it.) When we know
the RMS value of any repetitive waveform, we can compute its heating power by
squaring that voltage (current) and dividing (multiplying) by the resistor's
value.

Voltmeters (of all sorts) are usually calibrated to show the RMS value //of a
sine wave//. If the waveform differs, the value shown is wrong. One of the
advantages of a true-RMS meter is that all readings are "equivalent" in an
easily-comprehended way, regardless of the waveform -- even if that
"equivalency" has little practical usefulness. (If you want to know the
details of a waveform, you use a 'scope.)

I remember a Popular Electronics quiz with questions about how a voltmeter (at
that time, a moving-coil device) would read, depending on the waveform
supplied. A key point was that the deflection was proportional to the average
current flowing through the coil, but the meter was usually calibrated for the
RMS value of a sinewave.