I've created this small circuit to translate voltage drop over a shunt resistor into a usable range for arduino (5v atmega32u4) adc.
This is to measure current out of and into (charging) a 12v battery on a boat. The shunt is low side (connected to Bat-). My circuit has Bat- as Ground, Vin at high side of shunt. The shunt is 75mV at 100A.
The circuit seems to work nicely (though center was ~0.8v below the expected 2.5?)
Question(s): It should probably be some form of protection in there. If I float Vin, output goes >9v and uC-pins would be unhappy. Is a zener diode enough?
Anything else that's missing? 0.1u caps on input and output?