How does a differential pressure transmitter work?

A differential pressure (DP) transmitter measures the difference between two pressures applied to high and low pressure ports. The sensing element (capacitive, piezoresistive, or strain gauge) converts pressure difference to an electrical signal (typically 4-20 mA). DP transmitters are versatile instruments used for flow measurement (with orifice plates), level measurement (hydrostatic head), and filter monitoring (across filter differential).