Hello everyone.
Im sorry that I forgot to mention the application, I was just so caught up with the problem at hand!

All I am trying to do is measure the voltdrop across a pair of bars in a commutator of a Large DC motor. In doing this I can know if there are any shorts in the windings.

The way this was done previously is;
The test technician applies a current of anything of between 200 and 300A to the commutator with the brushes at about 90 deg from each other. As I mentioned previously, the supply is about 10V/300A and the resistence of the armature is about 0.0148 ohms.
The technician then uses a millivilt meter to measure the volt drop between each pair of bars. The readings should not vary much if there are no shorts or open cct windings.
Now I need to impliment this test digitaly and save the readings.

That is the reason I need to masure the volt drop between bars.

Kai, I plan to use the INA117, but my worry is the current.
I dont need to measure the currrent but I am worried that large currents from the test supply (300A) might flow into my low current control cct. I think that im not "the sharpest tool in the shed", maybe that is why i dont understand this problem.

Is there a chance that dangerous currents from the 10v/300A test supply will flow through the resistors in the INA117 down to the ground of my control cct? With this in mind, do you guys feel that I should use isolation in the form of an isolation amplifire?

Thank you all for taking the time,
sun