"R. William Kichman" wrote:

> > Maybe this has been covered before, but please bear with me...
> >
> > I need to measure AC current at 60 Hertz, 0 to 35 amps to approx. 0.1A or so
> > precision.  How might I most easily do such measurement using a
> > microcontroller?  I understand that a voltage measurement across a precision
> > resistor, or a few wraps of coated wire around a conductor will allow a
> > current to be calculated, but with AC, isn't the measurement time varying?
> > Won't the A/D read a constantly varying event and get something between 0A
> > and peak current?
> > What am I missing here?
> > Any links to URLs with similar projects would be welcome.
> > Thanks for your time.
> >
> > Bill K.

You need a current transformer.  The output should be rectified/filtered into a DC
voltage
which the PIC can read with it's A-D.  A simple 8 bit A-D will get you 255 levels,

so you can expect to get .13725 amp resolution.  (I'd scale it to .2 amp.)
At the low end some non linearity can occur due to the rectifiers.
(But do you REALLY need to know the absolute value of the current  at the low
end?)


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