(Please excuse my intentional ambiguity)
I have created a "frequency-shifter" that takes input in the form of an un-grounded AC sine wave, and outputs a square wave at a multiplied frequency. The system consists of an Arduino Nano plus some supporting hardware.
Currently I can control the frequency multiplier from a physical potentiometer on the project board. However, I would like to begin changing the multiplier based on analog input from a sensor.
Here is the issue... my entire Arduino system is grounded to one leg of the incoming AC sine wave. The analog signal I want to read references a ground on an external system and I am unable to connect the two ground references.
Is there an Arduino/Software method I can use to read this analog signal? Will I need additional hardware?