analog to digital conversion

[rahulkrishna]

Hi All,

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?

Regards 

[Martin35804 · Accepted solution]

Hi,

12-bit adc gives you 4096 steps for full range of the adc. This range is usually mapped by a ration to a measurement range of a particular sensor. If you are more interested in low voltage range you should redefine the sensor range according your needs so you will get measurements our of the sensor only within that short range but with full 4096 adc range. That means you will get higher resolution out of the sensor but smaller range.

And for getting a stable value you can introduce sort of moving averages math function.