I have a pressure sensor (output -> Wheatstone bridge) connected to an amplification stage, as shown here:
As you can see, four points in total are attached to the ADC of my MCU (STM32L476ZGT3.) The reason for that is to check the noise at different points.
The MCU is soldered and it works fine - I am able to program it and get responses.
I started soldering the sensor module step by step. The pressure sensor does its job: I see differences (mV) when I increase/decrease the pressure - it has a full scale = 52.5 mV.
Afterwards I soldered the first amplifier circuit (AD623) and here my problem came. At the output pin, I cannot see any difference when the pressure changes. I see constantly the ref value = 1.65V.
What can be the issue? The pinout is correct, there are no shortcircuits, supplies are fine with no noise.