I'm trying to implement an instrumentation amplifier to measure pressure from an MPX2050 transducer. After deriving resistor values to give me a suitable gain and adding an adjustable reference voltage I moved on to simulation and everything was looking good.
After building the circuit on the breadboard, it was amplifying differential signals as expected. However, I found the circuit was not rejecting common mode signals. I've tried rebuilding the circuit, testing the breadboard for shorts, replacing the op amps and at this stage I'm out of ideas. Do you guys have any ideas on what might be the cause or how to fix it?
Op amps: OP27G
Pressure transducer: MPX2050
EDIT: Thanks for the help guys. I've reuploaded the breadboard layout with labels. I completely agree with you guys saying I should use an off the shelf instrumentation amp, however, it's a college project and we're limited to using this configuration.
I can understand tolerance issues being a cause of reduced CMRR, but I'm getting pretty much zero common mode rejection. Connecting the 68k resistor directly to ground doesn't affect the output.