Detection of small resistances on an operational component.

[MD68]

[UNSOLVED] Sorry it was a mistake to ask.

I should have known better.

 

[MD68]

No idea what you're on about.

 

[chuckey]

As above feed the Arduino input from the unknown resistor via a resistor (10 K?) and use diode on the Arduino side to stop the 16V getting into its inputs (or any negative voltage). the resistor will decrease your sensitivity (slightly) so can be compensated for in the constant current generator.
I am not sure that biasing the op amps input to 1V is correct, You have a Volt drop across Rx, Vak, Vce and Ri sense. Check the volt drops with your current and with extreme ends of Rx values and make sure that the amp has a bit of head room in each direction.
Frank

 

[MD68]

Thanks all for completely confusing me to hell.

If an OP reads this can you delete the thread or something? I'll figure it out myself somehow.