Is it possible to measure the voltage of 2 different batteries on arduino? Currently I am able to use a resistor divider / voltage divider of 2x 10K resistors to an analog pin to read the voltage of the battery supplying the arduino.
Currently the system looks like 6v battery -> 5v power regulator to Arduino -> resistor divider attached to 6v (unregulated) battery. GND is common throughout.
How could I measure the voltage of another battery given that it will be on a different circuit? e.g. different ground loop.