Thanks.
I knew I had to check.

Cristiano

On 19 May 2011 18:24, Olin Lathrop <olin_piclist@embedinc.com> wrote:

> Cristiano Cesaretto wrote:
> > regard the analog to digital converter, page 270 of the 18F4550
> > datasheet says: "The maximum recommended impedance for analog sources
> > is 2.5 KOhm". Does it mean using a 10K potentiometer is not advisable?
>
> No, that means a 10K pot is the largest you can use and stay within the
> recommendation.  This is assuming both ends of the pot are tied to a low
> impedance, like Vdd and Vss.
>
> Remember that the worst case output impedance added by a pot is 1/4 its
> value.  When the wiper is in the center, it becomes a resistor divider wi=
th
> 1/2 the pot value in each leg.  Those two legs in parallel make the total
> 1/4 the pot value.
>
>
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