cancel
Showing results for 
Search instead for 
Did you mean: 

ADC values fluctuating

PAcha.1
Associate

The project I am working on presently need to capture dc voltage with precision of 1mv. I am using STM32f446RE development board. As mentioned in the datasheet STM32F446RE have inbuilt ADC of 12-bit resolution and reference voltage is 3.3v. Thus theoretical resolution is 3.3/2^12 = 0.0008056640625 is expected, but I am getting the voltage fluctuations of about 25mV. Please let me know how what the best resolution is possible using inbuilt ADC and also the means 

This discussion is locked. Please start a new topic to ask your question.
1 ACCEPTED SOLUTION

Accepted Solutions
AScha.3
Super User

first - read ds of your cpu , adc real performance ->

AScha3_0-1690270783548.png

so from this can expect about 0,8mV *7 -> +/- 6mV best resolution.

+ input has to be low impedance, best 100nF cap at input adc pin to gnd. (mlcc cer cap)

+ long sampling time , min. 7.5 

+ averaging , maybe 2000 x samples , will show, how far you can come down :)

+ otherwise need preamp

If you feel a post has answered your question, please click "Accept as Solution".

View solution in original post

1 REPLY 1
AScha.3
Super User

first - read ds of your cpu , adc real performance ->

AScha3_0-1690270783548.png

so from this can expect about 0,8mV *7 -> +/- 6mV best resolution.

+ input has to be low impedance, best 100nF cap at input adc pin to gnd. (mlcc cer cap)

+ long sampling time , min. 7.5 

+ averaging , maybe 2000 x samples , will show, how far you can come down :)

+ otherwise need preamp

If you feel a post has answered your question, please click "Accept as Solution".