i just realised a first project with my Arduino MKR WAN 1300. I am powering the Arduino with two AA cells and wanted to have an information about the battery voltage. As the supply voltage of the arduino is not stabilised, I think that the measurement of ADC_BATTERY will always print out roughly 3.3V because the measured voltage is the same as the reference voltage. Is that correct?
My idea would be, after consulting the analog reference documentation (https://www.arduino.cc/reference/en/language/functions/analog-io/analogreference/), to use one of the internal references, such as AR_INTERNAL, being at 2.23V. Is this voltage stabilised, meaning that it is not proportional to the battery supply voltage? Or will I have the same problems and I have to build my own stabilised reference voltage (e.g. using a zener diode and a resistor)?
There is a thread about this: https://forum.arduino.cc/index.php?topic=568862.0 (https://forum.arduino.cc/index.php?topic=568862.0)
I am using the 1.0V reference to be safe, and it seems to be ok.
I use the 1V refernce and it works fine eevn when the battery runs down to around 2.1v in testing. The code thread above gives a good result which i crossed checked against a separate meter.
3,3V is just the battery voltage.