> I'm monitoring five external lines for change in voltage level with the 74's
> ADC but have to consider the effects of induced voltage from lightning
> strikes.  I was thinking of using either MOV's or optoisolators but I'm not
> very familar with either.
I don't know what voltages are on your
lines, but MOV's are normally associated with rather high voltages.  I
don't think you get 5V MOV's.  You could try using a zener diode
instead.
Optoisolators can also work quite well as far as isolation is concerned,
but they will affect you voltage measurement.  You would have to bias the
transistor so that you get exactly a unity gain across the device - and
that would proably be temperature dependant, so it may drift.

Niki
steenkmp@firga.sun.ac.za