Re: Wattmeter

Bill Noble wrote:

> if you really wanted isolation, wouldn't it be best to put a lightbulb of
> suitable voltage/wattage inside a plastic box (to keep out light) and run a
> fiber optic cable from the bulb to some suitable remote location - then use
> light intensity and a nomograph on your computer to calculate wattage.

This will calculate the RMS current, not the power. The power is the
square root of the average of the current x voltage product. An
Wattmeter must take scaled samples of the voltage and the current in the
load, multiply them, average the result, and take the square root.
Any other approach will not work correctly with arbitrary waveforms.

Antonio Carlos M. de Queiroz