I need to sense current in the range of 0-500mA with resolution of 1mA.
My current plan is to use a shunt resistor, a differential op amp stage to amplify the signal and then one more stage to span it to my PIC ADC.

My voltage applied to measure current is 60VDC.

Should I use 1Ohm shunt resistor or 0.1ohm shunt resistor?

which circuit configuration is good to follow in my situation?

Thanks.

 

Through what load are you measuring this current?

Can you put the shunt resistor in the common (return) circuit of the load?

 

Through what load are you measuring this current?

It is a testing specimen.(a solution) I need to measure the current flowing through that when 60VDC is applied. Current can vary from 1mA to 500mA.

Can you put the shunt resistor in the common (return) circuit of the load?

Shunt resistor I can place in the higher side or lower side of the load. But I prefer in the lower side. (I hope that is more simple!).
My system will be having 8 similar current sensing 'channels'.Each of them are ON/OFF using MOSFETs. So the return paths will be having varying currents at different times. So keeping ground steady is tough. So I thought of going for a differential amp.
Please correct if I am wrong.

Thanks