ADC sampling noise

Fabricio_2021
Posts: 1
Joined: Wed Dec 16, 2020 5:44 pm

ADC sampling noise

Postby Fabricio_2021 » Wed Dec 16, 2020 6:04 pm

Hi,

I'm trying to read an analog input using analogRead() with a simple circuit (voltage divider),
IMG_20201216_133513.jpg
IMG_20201216_133513.jpg (175.07 KiB) Viewed 3832 times
ADC_test.jpg
ADC_test.jpg (46.21 KiB) Viewed 3832 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
Posts: 45
Joined: Thu Aug 22, 2019 3:48 am

Re: ADC sampling noise

Postby Aussie Susan » Thu Dec 17, 2020 2:45 am

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
Posts: 42
Joined: Tue Dec 01, 2020 10:56 am

Re: ADC sampling noise

Postby ESP_Jan » Thu Dec 17, 2020 3:28 am

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

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