I have a 5 V system and I want to monitor the current in different parts of the system. I am planning to place a small value resistor on the positive power rail and feed the rail voltage and the voltage after the sense resistor to the microcontroller ADC peripheral. The maximum current is 0.2 A, and the sense resistor I am thinking of is 0.5 Ω.
I always see people use a differential op-amp to amplify the signal. Can I not use the op-amp and directly read the voltage using the ADC?