ADC sampling noise

[Fabricio_2021]

Hi,

I'm trying to read an analog input using analogRead() with a simple circuit (voltage divider),

IMG_20201216_133513.jpg (175.07 KiB) Viewed 3831 times

ADC_test.jpg (46.21 KiB) Viewed 3831 times

as you see in the screenshot, there are non stable values given by the ESP32, I have read in the documentation that adding a capacitor and multisampling, the values could improve.
Did you have the same problems when use the ADC?

Any suggestion?

Regards,

Fabricio

[Aussie Susan]

I certainly do have the same issue.
Personally I use multiple sampling - sample 128 samples adding each to a total value and then dividing that by 128.
Susan

[ESP_Jan]

Hi Fabricio,

the voltage devider just devides the input voltage. So if there is any noise in the input voltage the reading will also contain it.
You can reduce this noise and fluctuations by adding a capacitor across the input voltage.
Also USB power is not entirely clean and without fluctuations.

Please also note you are deviding the 3.3V from the linear regulator.

Hope this information helps,
Jan