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February 24th 04, 10:54 PM

On Tue, 24 Feb 2004 14:30:02 -0600 (CST),
(Richard Harrison) wrote:

I make lots of mistakes, but fortunately, I don`t think I made any of
consequence in this thread. I probably didn`t go into enough detail, but
I was just an engineer, not a professor.

Best regards, Richard Harrison, KB5WZI

Hi Richard,

The one I noted (mistake) was in your reference:
It is derived from the average of the squared current over a half cycle
which necessarily forces both a doubling, and a symmetry that is not
demanded of native RMS determinations. It then follows that the
commonplace illustration of the mains Sine wave completes the
illusion. Few EE students migrated beyond this simplicity because the
world is nasty place to measure power.

RMS by and of its mathematical nature through the squaring operation
negates any requirement for "half cycle" determinations (no issue of
negatives). It also preserves the natural order (of two forced by the
half). If you think about it, any biased sine wave impinging upon a
load imparts the power loss of the bias at the 180Â° portion of the
Sine cycle. RMS copes with this, the notion of half cycles does not.

The simple determination of RMS is the graphical integration of the
area under the curve. There are as many "correction factors" for RMS
as there are shapes, and they all derive from this simple concept.

When the computational horsepower requirement becomes enormous (there
are many here that give up too easily with complexity); it is the
provence of the "Old School" to suggest that since RMS is all based on
the notion of power, you simply measure the caloric result and ignore
shape altogether. This may be done with thermo-electric piles or
other measurable property transformers that perform the complexity of
integration through physics*. I can anticipate those who dearly
embrace the complexity that they shudder to face (such contradictions
of their love-hate relationships) when I hear Crest, or pulse/power
factor (or duty cycle) uttered. Clearly the problem will have
migrated from Power to some other consideration, but is dressed as an
RMS debate.

73's
Richard Clark, KB7QHC

* The Chaberlain and Hookum meter; the Sangamo meter, the Wright
Demand meter; the GE Demand meter; the Edison chemical meter (where
the weight of a cathodic reduction revealed 1.224 grams = one
ampere-hour)...

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