Power factor measurement

[dhouston]

... I don't think a KILOWATT does either.

The Kill-A-Watt sampling rate is about 2kHz which is on the low side. I exchanged email with one of their engineers way back when it was introduced. And, I don't recall what the sampling rate was in the Microchip AN220 (I did read it long, long ago.) but believe it was even higher. With electronics, you can get some very non-sinusoidal loads. Harmonics are why you need high sampling rates. AN220 says, "The CS5460 power/energy measurement IC measures instantaneous voltage and current four thousand times a second."

IIRC, there were also some excellent articles on the Rensselaer Polytechnic Institute site and there was a really good article on non-linear loads written by a fellow in New Zealand whose name escapes me.