scalerobotics:

Thanks for the reply. The schematic is very simple. It is a 10 turn 50k POT, one side tied to 5.013 Vdd, the other side tied to Vss. The center tap of the POT is connected to AN0 of the PIC16F873A. I currently have a 2.2uf cap tied to Vss at AN0.

The readings on the display are stable, I'm able to adjust the POT fully clockwise and counterclockwise and get a reading of 0 to 1023 on the display.

The problem is between 0.000 and 0.063 Vdc in on AN0 the ADC count is 0, and at 2.500 Vdc the ADC count is 505. At 5.00 Vdc the ADC count is correct, it reads 1023.

The 16F873A datasheet, table 17-14, A/D converter characteristics, parameter A25 states the analog voltage input is Vss-0.3V to Vref+0.3V.

I have set via the ADCON the VREF- to = Vss, and VREF+ to = VDD, and I have set the ADC to 10 bit. I would expect ADCin to give a ADCcount of 0 at 0.000V and a count of 1 at 0.048V, 512 at 2.500V, and 1023 at 5.00V.

Thanks,
Ron