Quote Originally Posted by rwskinner
I have a 100 amp shunt which out puts 1 mv per amp. I will be using this shunt to measure current in a 24 volt dc circuit. My question is, even though the max voltage across the two leads on the shunt is limited to 100mv, I actually still have 23 to 24 volts on each side of the shunt which would damage the PIC's ADC.

How is the best method for measuring the voltage drop of the shunt with a Pic's ADC?
You will need an op amp to "condition" the voltage.A 10 bit A/D will not register any current until you are at over 4 amps of current draw! If you can float the PIC supply, you can attach the ground side of the circuit to the lower voltage side of the shunt.Your voltage input pin then attaches to the higher potential side.If you use the 24 volt system to power your circuit, you can put the shunt on the negative battery lead to the circuit under measurement. Connect the PIC/op amp to the battery negative ahead of the shunt, and your current measurement input on the other side of the shunt.
Iffff...your maximum current drain is not that much, get a more sensitive shunt,say 10mV per amp, you may not need as much amplification, and will have less noise issues.