One requirement of mine wanted to read very low voltages from around 6mv from a sensor. The Vref is 5V and using S12x ADC in 12 bit mode. My problem is the ADC count is fluctuating and at lower voltages it goes to "0" and then a value of 30 etc. I am confused, I have seen some of the previous posts regarding the same problem but could not get a clear idea of how i have to solve this problem. At higher voltages also i see the last two bits varying something like if it 24.34 24.38 24.40 and etc. How should be the properties of the input source to achieve stable output?