I am looking to use a Raspberry Pi to power and read the current from a current-to-voltage converter. I am currently using two batteries to power the operational amplifier, as shown in the schematic below. Please ignore the potentiometer, it is an attempt at mimicking a sensor and is for illustrative purposes only. I would like to measure the current going through the sensor in just one direction.
However, I am finding that the 9V batteries I'm using to give the op-amp a negative voltage are running low pretty quickly, so I would like to power the op amp through the Raspberry Pi.
The sensor has a constant voltage input of 50 mV and a variation in output voltage from the op amp of 1 mV (even with the gain). The sensor is similar to a thermocouple or resistance temperature detector in terms of its small changes in current.
I am unsure if using a resistance divider or similar (as shown here: http://tangentsoft.net/elec/vgrounds.html) will wash out the signal. E.g. Voltage division with 2.5 V going into the op amp when I'm looking for mV changes.
Is there a way to redesign the circuit to operate from a single supply voltage source? Thanks!