MCP 3204 ADC output fluctuation

[paddy]

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

 

[GPG]

No picture.

 

[paddy]

Sorry!!!
Please find attached schematic.

 

[GPG]

The fluctuation is approximately +/- 30 counts than expected.

Do you mean 30x LSB?
Some reading: http://www.analog.com/library/analogDialogue/archives/46-06/staying_well_grounded.html

 

[paddy]

+/- 30 count means if the expected adc output is 2048 then I am getting adc output anywhere in between 2000 to 2100 and it is continuously fluctuating.