Provide a sketch of how you actually have the components connected - otherwise we'd just be guessing
Good day all I am trying to implement current measurement using the shunt resistor method. I have a device that's powered with 3V and draws 30mA while in normal operation. I'm trying to monitor that current with an Arduino Nano. I'm using a low-side setup like the left hand circuit in the diagram attached and a 1 Ohm resistor to generate a 30mV drop across it. When I measure the voltage across the resistor with my meter I get the expected 30mV. But as soon as I couple the ground from the circuit to the arduino ground, the measurement drops to 6mV. I'm not sure whats causing this. Could it be that the arduino ground is somehow offsetting the circuit?I've not been able to find much info on this and am quite stumped at the moment. I may try using a voltage follower to provide isolation.