I need to measure a potentiometer where the voltage supplied is very noisy and cannot be filtered.
I run into this a lot in my work, but currently I'm trying to measure a steering angle potentiometer on an autonomous ATV using an external Arduino. The problem is that an inaccessible onboard computer is providing the power to the potentiometer, and sensing it for it's own calculations, meaning I cannot supply my own voltage to power the pot. Because of the strong EMI from the engine, the computer/pot ground varies +-1v from the ground rail powering the Arduino(or whatever other sensor I might add). So I need a high impedance way to sense the voltage ratio across the potentiometer without disturbing it. The nominal voltage difference between the ends of the pot is 5V and the wiper swings from 1 to 4V relative to pot ground.
I feel like the obvious solution is to get some kind of differential amplifier/measurement boards with synchronized sampling and do the division in software, but is there a better/more elegant/cheaper way? If not, can anyone recommend differential measurement boards for the Arduino?
I would prefer not to make a custom board, but if I can do it in perfboard, that wouldn't be too bad.
This is like a noisy version of Measuring external voltage on Arduino