On Tue, 24 Feb 2004 18:28:57 -0600, "Steve Nosko"
wrote:
I assumed Richard's intent here is that you only have to do the
calculation for one full period of the periodic component to derive the RMS
value - and if it is symmetrical, then only one half period will suffice.
This all assumes a symmetrical AC shape. .. I see no reason why this would
not be true.

And then you offer in contradiction:

However a DC biased periodic shape requires another squaring and root
operation if you capture all the components. It gets a bit more harry

Such is reality. There is no such thing as symmetry, except on the
academic page. However, I am not so pedantic as to suggest that
shortcuts don't abound; simply pedantic enough to point out you don't
make claims to accuracy (admittedly none were offered that I was
responding to) through fudge factors when so many alternatives remove
doubt.

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.

Here I'll take issue with the ONE WORD "graphical". You can integrate
if you can describe the function of the wave shape mathematically.

Of course, but it is eminently doubtful if you can actually express it
mathematically. Far more here own o'scopes than works of multiple
regression. Graphical analysis is first year engineering stuff out of
drafting class.

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

Yikes! Not sure where you went on that last bit, Richard C...
Now, I ask. Do the power meters on the outside of our houses take all those
factors into consideration and REALLY show TRUE watt hours? I have one in
the basement and I think I figured out why I was seeing twice the reading I
should have (letting a light bulb sit on for awhile) ... I counted the
teeth to get the ratio of the gear train, just to find that it is printed
(somewhat cryptically) on the face) (I made a two wire / three wire
connection error)

Hi Steve,

Yikes? Look at your own response to shudder. ;-)

You offer the doubt and then correct your error in the space of three
sentences. From that I must suppose it was a rhetorical question, but
the "yikes" heading it promises more clarity in response to what you
apparently complain of. After all, a complex, compound sentence with
ellipses and nested parenthetical statements? You lose points for
unpaired braces and lack of punctuation throughout and at the end.

Do the power meters on the outside of our houses take all those
factors into consideration and REALLY show TRUE watt hours?
For at least a Century now.

The power companies offer as close to pure symmetry as you could buy.
They also offer long term time accuracy to far better than any source
short of WWVL.

73's
Richard Clark, KB7QHC