Quote Originally Posted by passion1 View Post
Paul

Please excuse my ignorance , but what do you mean with:
"Try converting the rails first"?
Passion,

The low rail means ground - connect a wire directly from your circuit ground to AN3 and convert (you should get 0)

The high rail means your PIC supply voltage - connect a wire directly from your 5V supply (the same one connected to your VDD pin on your PIC) to AN3 and convert (you should get 255)

If you do not get these values, then something else is going on.

The 100 pF is for AN3 (I use ceramic ). I had replied about the VDD and VSS caps before I saw your next reply giving impedance info and asking again. I followed with the 100 pF recommendation, which is for AN3. However, although good practice to have these, I do not think the lack of these are your problem.

Let us know how the rails convert.

Good Luck