Hi first poster genfory!
You don't say what sensor, or what you are doing with the signal other than 'use an Arduino'. That's ok, I will be similarly general.
Why are you using a 3 amp device with a 24 volt system (+12 to -12.) Perhaps you can start out with a single op-amp run between +5 volts and ground. It will be MUCH easier to experiment with, and less likely to give you 'mysterious problems'.
The signal will then always be between 0 and 1023 as read by an analog pin of the Arduino. You can easily adjust the gain from unity to many thousand times with resistors on the pins of the op-amp.