RE: nRF52832 - Analog read with higher impedance divisor

Jared — Wed, 22 May 2024 12:44:47 GMT

Hi there,

I think this will be fine, but the only way to know is to actually test it.

Higher resistors in the divisor can lead to more noise susceptibility and the longer increased acquisition time. I think the resistor values that you've chosen can work but you might need to adjust the capacitor as well. How did you choose that capacitor size, have you already tested it?

Also, we have written a blogpost regarding this topic here:

However, often the easiest way to determine a suitable capacitor si+ze for a custom voltage divider or any connected external circuit with impedance higher than 1kΩ, is to use trial and error method. Start with mounting e.g. 100 nF capacitor between the ADC input pin and ground. If you do not get adequate ADC accuracy with low sample rate (<1Hz), increase the size until error disappears. The trade-off is that if you have large capacitor, the maximum sampling frequency is lower then when you have a small capacitor. Typically you are limited to 1Hz - 10Hz maximum sampling frequency when using a capacitor.

regards

Jared