Re: Wattmeter

I wrote:

> An electronic
> Wattmeter must take scaled samples of the voltage and the current in the
> load, multiply them, average the result, and take the square root.

Oops... There is no square root. The average power is just the average
of the V*I product.

The square root appears in the computation of RMS values:
Xrms = sqrt(average of X(t)^2)
For sinusoidal values of the same frequency, the average power is:
P=Vrms*Irms*cos(angle between V and I)
But this is valid only for sinusoidal signals.

Antonio Carlos M. de Queiroz