hi. i need to design a prototype of a  power meter utilizing an analog multiplier integrated circuit that I developed a few months ago. the integrated circuits arrived a few days ago and I still havent tested them, but it doesnt matter for now.

The only idea I found was to put the siganls v(t) and i(t) at the multiplier inputs, and put the output v(t)*i(t) into a low-pass filter. i didnt understand yet what is the purpose of the filter.

anyone please could give me some ideas, tips of books, articles or ANYTHING that could help me developing such prototype or even suggest a topology for it ?

thanks.