>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).

Thanks.
Google says that here's the original for anyone interested.

        http://www.national.com/an/AN/AN-265.pdf

Here's a comment in passing re April 14 1997 Electronic Design article.

        http://www.pupman.com/listarchives/1999/January/msg00460.html

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