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Re: Wattmeters

Original poster: father dest <dest@xxxxxxxxxxx>

hi, Steve.

Tl> Original poster: Steve Conner <steve@xxxxxxxxxxxx>

>Wow, that is a pretty severe test.

as you know - "coilers do it with more energy per bang", and some
coilers like to do it with all they find - with caps, transformers,
wattmeters :-)))

>Your meter must be good if it passed that.

yes, coz it was made in USSR! :-p

>>in generally - how wide is the spectrum of the current drawing by real
>>TCs - without mains filters, power correctors?

> My DRSSTC draws small current peaks of about 25A from the 240v line,
> even though the real power draw is only 500W. It's the usual story
> with a bridge rectifier feeding a big capacitor (3300uF in my case)

i mentioned the frequency spectrum.

> I found a nice simple wattmeter designed by Bob Pease, that uses two
> transistors as the multiplier. I posted it to the list a while ago
> but nobody was interested. Hey, what if I post it again ;)))

> http://www.elecdesign.com/Articles/ArticleID/2190/2190.html

>I have a suspicion that the Kill-A-Watts clip when they are hit with
>loads that draw very high peak currents, which would make them read
>too low.

but this wattmeter also clip (maybe not so much) on high peak current:

http://www.elecdesign.com/Articles/ArticleID/2191/2191.html

"If you calibrate this at about 2 A, the calibration will be right on
at  6 A, about 1% high at 1 or 2 or 3 A, about 1% low for 12 A dc,
about 2% low for 12-A sine waves, and about  5% low for 15-A
sinusoidal ac loads, or as much as 10% or 20% where the rectifiers are
pulling significant  peak currents at the sine peaks."

imo shunt`s size would be a bit large:

"22-gauge copper bus...
paralleling 12 9-in. lengths of that wire"

is the input RC of the DMM an integrator? and what`s the integration`s
period - it is optimal for 50hz on any DMM?
i`m just kidding ;-)

-------
All I saw was a bright white flash, an explosion like a high-powered
gunshot, and the thick smell of ozone and electrical damage.
(c) Richard Quick  22-01-95 00:13:00