Monitor One internal ADC reference voltage

Hardware
1

Hi,
Just starting to evaluate the Monitor One and it looks like although the internal voltage divider on 0-10V input is using 0.1% resistors, the voltage reported by the unit (raw data coming from ADC) is off by about 5%. The voltage on the internal voltage divider node is spot on.
What is the reference voltage source for the ADC? Is it actually the 3.3V voltage supply?
If so, what is the officially recommended method for getting the accurate analog input reading on Monitor One?

Thanks!

2

The voltage reference on the Tracker SoM is 3V3.

On the Tracker SoM (nRF52840), it is possible to switch to using the MCU internal voltage reference using analogSetReference. The MCU has an internal 0.6V precision reference, and the ADC is set to a 1/6 gain when internal is selected. Since this is a 3.6V maximum, not 3.3V, it's scaled in software so 3.3V = 4095 still.

3

Thank you! Will check this out right away.