Recognizing external ground on analog input

Hello there,

I was wondering how I can get an arduino analog to recognize a ground from another power source without making a common ground. Is there an IC or some other method I could use to control this?

Every reliable wire bound communication requires 2 wires.

Digital signals can be isolated by optocouplers, analog signals don't work well this way.

In general, all grounds should be common. There are very few exceptions to this. Why do you have separate grounds?

And optical isolator can have isolated grounds on each side.

For AC signals a transformer can provide isolation and for "slow switching" a relay can provide isolation.

You can get isolating voltage transmitters - they are not a simple IC tho. Your project may give us a clue as to why you need to do this

Example

Sorry, that does not make much sense. Have another try at explaining your actual requirement. :grin: