I have a board(BoardA) with a MCU which are powered from a battery. the board also has a buffer circuit for the ADC.
I would like to measure a signal from an other board(BoardB) which is powered from an plug. One possible solution is to connect the two grounds and measure the signal.
Let say because of some reason I am not able to connect the two grounds. How can I achieve accurate measurement? If first I measure the ground on the BoardB, so In this case I can have the potential difference between the grounds on the BoardB and BoardA, the I can measure the signal on the BoardB.
Can I achieve accurate measurement with this solution? What can be the disadvantages?