Olin Lathrop said:
>> Put a .01 uF capacitor from the PIC pin to ground, and allow extra
>> time for settling.
>
> That won't do anything about the inaccuracies caused by the internal
> leakage and a high external source impedence.

It will accurately convert the voltage at the PIC pin if you do what I said.

If the internal leakage(which is quite small, btw) affects the voltage
because the impedance of the source is high, so be it, but you will get an
accurate reading of what's at the pin which you wouldn't otherwise.

Also, some of the leakage is to the voltage on the sampling cap, so if the
input voltage stays pretty much the same from one reading to the next,
leakage is minimized.

Anyway, the horrors one otherwise gets when converting from a high
impedance source are done away with.

Cheers,

Bob

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads