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Re: Average, RMS and Power Factor made easy!



Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-uswest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<free0076-at-flinders.edu.au>

> Sounds like a variation of the electrodynamometer. I agree that it's not
> hard to measure real power but the statement made was based on my own area
> where they just use eddy currents to push a little aluminium wheel around.
> The eddy currents are induced by an inductor in series with the supply
> (maybe shunted?) and I have been told by an A-class electrician whom I
> have respect for that they are usually like that in Australia, they don't
> even care what RMS voltage you get fed when they measure the integrated
> current. I'll ask him again though when I see him.

The meters here are like this too. This was the "clever mechanism" that
I mentioned. An electrodynamometer only produces a movement against a
spring, showing an indication of average power with a pointer. Something
more complex is required to integrate the power measurement and measure
energy. 
I didn't had at hand the schematic of those disk meters (that are rather
difficult to explain, anyway). Looking at the meter here I see above 
the disk a coil of thin wire, and below it two coils of thick wire. 
I found the site below, that shows how these meters are built:
http://www.usbr.gov/power/data/fist/fist3~10/3~10_con.htm

Antonio Carlos M. de Queiroz