The pressure sensor two-wire system is relatively simple, one line is connected to the positive terminal of the power supply, and the other line is the signal line connected to the negative terminal of the power supply through the instrument.
The pressure sensor three-wire system adds a line on the basis of the two-wire system, and this line is directly connected to the negative terminal of the power supply, which is more troublesome than the two-wire system.
The four-wire pressure sensor is definitely two power inputs, and the other two are signal outputs. Four-wire system is mostly voltage output rather than 4~20mA output, 4~20mA called pressure transmitter, most made of two-wire system.