> Gee Russel, quite brillant on your part for working that out!

Thanks.
It might even be right :-)

The man who designed it was very clever.
It's an opto implemenmtation of a "Gilbert cell".
Its main problenm is probably the matching of the optos.
But it should do a reasonable job as a comparison instrument.

        RM

Hello Russel,

I think you get the point. There is a basic application note from
National Semiconductor AN265 from february 1984 "Electronic Watt-Hour-Meter"
which uses matched transistor pairs (LM394)for the multiplier (no optos).

Googling for the original article  from oct. 1994 gives no usefull result
for me,
but it seems that the author, Steve Woodward is at UNC, Chapel Hill.

Now looking for a hardcopy...

Thomas

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