if that was so, i think you could assume 2 puffs of smoke for correct operation, one for under voltage, and 3 puffs for over voltage. surely the easiest way would to be by using a transformer to drop the line voltage by a ratio of the windings, and as for the current the use of a CT coil around the live conductor to give a mili-amp current for the ratio again. then what you have to ask yourself is are you going to display the values in the RMS value (the useful value) or the mean value..... why are you wishing to do these measurements?!?! to make KWh meter or something??

Chris