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Re: Wattmeters

Original poster: Steve Conner <steve@xxxxxxxxxxxx>



wattmeter showed me the same 460w. 

Wow, that is a pretty severe test. Your meter must be good if it passed that.


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)


why don`t you take a cheap four-quadrant multiplier (ex. AD633) and
make a simple wattmeter scheme, so  that even a beginner could make
it?  there`s a "Terry filter", but you could make a "Steve meter"

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

If anyone is interested, I figured out how to make it work with an analog meter, and read properly on signals with a DC component. (such as a half rectified SSTC) I could go ahead and develop it and maybe do a PCB. The LM394 dual transistor is expensive, but Grandpa Bob says that two 2N3904s work almost as well...

Steve