> Can you suggest the simplest way to achieve that result?

For the hardware I would prefer a mains-powered PIC that does the A/D 
and transmits the (possibly processed) result to the main PIC by 
optocoupler. Eliminates the transformer (bulky, uncalibrated, might 
change the waveform) in exchange for an extra PIC, optocoupler and a 
C-based power supply.

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Wouter van Ooijen

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Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu

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