I went back and read the entire thread, and realized I was incorrect when I told ibralfy that it was necessary to sample often (that was *my* requirement). Aratti, you are correct when you imply that you don't a high sample rate. 20 or 30 samples between each LCD update should be enough.

But ibralfy, if you sample slowly, you need to make certain that you aren't sampling at a sub-harmonic of the line frequency.