I'm into a small PIC  project measuring AC line power consumption
of different loads that can be highly reactive/inductive.

I need to measure power the same way the power companies do.
They _do_ measure RMS, don't they?

Also I wonder: If I just measure current, utilizing a toroid and a load
resistor,  and let the PIC do the root-mean-squaring over considerable
time - will that give me a fair approximation of power consumtion?

I seem to remember that I need the RMS of both the current and the
voltage, and the phase relationship betwixt the two?
(Yes, I _have_ ordered "The Art of Electronics")

Anyway, I only need to mimic the way the power company's inductive
rotating disk measures power.  I also just need the hour average,
so there's plenty of time.

All hints will be appreciated


Gus