The difference between a differential pressure switch and a differential pressure transmitter lies in what they do with the recorded pressure information:
The differential pressure switch behaves like a light switch that switches on or off when the pressure difference between two points reaches a set threshold.
The differential pressure transmitter provides continuous measurements and detailed data for more precise process control. The output signal is usually 0-10V, 4-20mA or bus (e.g. Modbus, Wireless Modbus or EtherCAT P)