MCP 3204 ADC output fluctuation

[paddy_p]

Hi,

Greetings of the day!!

I am using MCP 3204 ADC interfaced with PIC18F4520. The reference voltage of MCP 3204 is from voltage divider network of resistor and set to 500mV. Potentiometer value is 1K and resistor of 1.2K.
Input signal range is 0-500mV.

Even though the input signal and reference signal is stable, there is fluctuation in output of MCP 3204. The fluctuation is approximately +/- 30 counts than expected.

I do not have oscilloscope to check the noise, but I have measured voltages and that are stable.

Please find attached schematic and suggest.

Thanks,
Paddy
View attachment Test.pdf

 

[wizpic]

It would more than likely it will be noise that could be causing it, if the signal is 500mV why use a resistor divider just place the signal straight in.
Have a look at this
**broken link removed**

I've done this but using arduino and the reading where spot on and stable

looking at your drawing your v ref will not be stable and not the best method to create a stable v ref plus what's the idea of the resistor across the op-amp I presume to boost it as I only had a quick look