some time ago I initialized a discussion on a pressure sensor in the german Arduino forum (https://forum.arduino.cc/index.php?topic=706606.msg4748386#msg4748386) as I was not able to get some bytes out of this sensor (RS485). I sent it to a forum member, who had no success, too. So I thought, perhaps is something wrong with the sensor itself. Unfortunetely it was too late to give it back to the vendor. So I opened the sensor and found the sensor itself and a microcontroller board (see attachment), the type of the µC (not on picture, on the back) was not to decipher. The actual sensor has 4 leads, connected to I-, I+, S-, S+. Though the I's may stand for "current", it could also be a Wheatstone bridge. Between every 2 leads I measure about 2,2 kOhm.
Any other guesses?
Seems like it probably is a wheatstone bridge. I’d apply 24v to the board and measure the voltage across the +/- pairs. If it is a bridge, that should tell you which of the +/- pairs is the “excite” and which is the “sense.” And then apply the “excite” voltage to the sensor and measure the voltage across the “sense” pair at zero pressure, rated pressure, and a few points in between. If the board is dead and there is no voltage across either of the +/- pairs, then pick a pair, apply 5v, and measure the voltage across the other pair at various pressures.
I couldn't veryfy the assumption "Wheatstone bridge". When applying a voltage (5V) to the S+/S- -terminals, the resulting voltage across I+/I- is 1.22 V. This voltage is changing only very little (about 10 µV) when applying pressure to the sensor. Applying a voltage to the I+/I- -leads results in 0 V across S+/S-. I assume this sensor is broken.
The core component of a silicon based pressure sensor is a wheatstone bridge, which this appears to be. They are sometimes linearised on the board, sometimes by microprocessor lookup as the pressure respnse is not linear. The response is measured in mV, if it is changing then I don’t think your sensor is broke. What then comes out of the other end of the board could be a 4-20mA signal, a 0-10V, 0-5V, or a comms bus, suggest you review either the label or any original paperwork. 24V supply suggests HVAC type application, which tend to use 0-10V in Europe, can you put a 'scope on the output?