Hi - if you don't need to sample continuously, a trick I have done (to=20
measure battery voltage) is to have the resistor divider ( 3.3V -> 330K=20
-> 15ohm -> GND) not go to ground, but to another PIC pin.  When=20
sampling, the PIC pin is set to ground.  When not sampling, it is set to=20
high (3.3V), so no current flows.  So if you can sample say every=20
100msec, and each sample time takes a few millisec (say 5), you've cut=20
your power to 5/100=3D 5% of what it is now.

Cheers
J




alan smith wrote:
> I have a sensor, that when its activated, it goes from a 15ohm to
> open circuit.  This is a battery powered device, so low current is
> critical. It will bounce back and forth, as its a motion detector of
> sorts.
>
> The approach I was going to take (and build up to test later) is to
> put a 330K resistor in series being fed by the box 3.3V power, and
> connect the A/D of the PIC between the sensor and the resistor.
> Normally it will pull some small amount of current and thus a voltage
> drop to measure, and on a open circuit if course it should read
> zero.
>
> Any other ideas on measuring for an open circuit with very low power
> consumption?
>
>
>
--=20
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