18F2525 ADC Accuracy

[mungam753]

I am seeing a number jump of 144 to 155 on my analog conversions of 5VDC with a 740 millivolt input. I don't see the input changing but the conversion seems to be not as accurate as I would like it to be. I am using a 10 bit result and a 4mhz crystal.
Is this normal or do I have some settings hosed up?

[Bruce]

It's very normal to see AD values jump if you're not using a filter circuit on the input.

Try a filter something like this;

AD input
o-----/\/\/\/\---1K--- external analog input
|---| |---0.1uF---gnd

There are other simple tricks like using sleep mode, and filters on Vref for noisy power rails.

[mungam753]

I am testing right now and it seems to have cut the jumping around in half. I thank you for your help as this has been driving my nuts for the last week.