How to use a pressure sensor (transducer)?
This looks like the device modulates the power supply by drawing current in a data pattern.  To measure this you can place a small series impedance (resistor) in series and use a differential opamp to measure it.  To remove the DC offset of the normal device current you can add a high pass filter C1 and R6.
Something like this:







simulate this circuit &ndash; Schematic created using CircuitLab

Note: You'll need to set your gain, this is just for topology.

Or you can do the same on the ground side, and then just measure it with a single ended opamp.