> Hi Russell, this is a air-pump, pressure monitoring, temperature.
> Basically I need to be sure that VAC is not lower than 200V (say) or
> higher than 240 before activating the pumps, the valves, or else.
> So precision is not *that* important, but still somehow.

OK. Nice simple application.
Finding the peak voltage over N cycles and averaging it would very
likely be good enough. Loading the transformer lightly to damp effects
of noise, capacitive coupling etc may be a good idea. Use of standard
values, probably calculated and then checked in practice, would
probably be good enough. A diode, resistor and capacitor would allow a
single reading, but in this case code sounds preferable to even a few
components.

As described the voltage sounds to be bipolar wrt to ground. If so,
you need to be sure your ADC input will handle that (I won't go and
look up the datasheet). If not, then a discussion of simple extra
circuitry may be about to happen:-).



             Russell
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