I am designing a MOSFET based H-Bridge to handle high current. I would like to place a SHUNT resistor in the circuit in order to detect over current. The voltage across the shunt resistor is to be read by a PIC micro controller (so the + voltage side cannot exceed 5V). The only place in the circuit i can think to add the shunt resistor is after the H-Bridge, however this means placing a tiny load on the source side of a MOSFET (as shown in image). Will this be a problem when considering the load is only 0.0001 Ohms? and is there a better place to position the shunt resistor?
That is the location where it is commonly placed.
If your shunt is really only 0.1 mohm, you will need to ensure you use a 'Kelvin' connection to measure the voltage across it. You will have to connect GND of the micro controller at the bottom (GND) connection of the sense resistor, else the additional wiring resistance will swamp your readings.
You will also need to be careful about inductive spikes, and perhaps need a decoupling capacitor on the 24 V to make your whole system work.