What are the differences between differential pressure, absolute pressure, and pressure transmitters?

A differential pressure transmitter is primarily used to measure pressure differences and convert them into standard signals, usually in the form of 4–20 mA. It is mainly used for flow measurement (throttle devices, differential pressure flow meters) and level measurement (storage tanks). Pressure transmitters are primarily used to measure pressure values, converting them into 4–20 MA signals; they can be used to measure pressure in any application. For measuring low pressure values (for example, at several dozen KPa, the detection accuracy of pressure transmitters is not sufficient; in such cases, differential pressure transmitters can be used as a substitute). Absolute pressure transmitters are used primarily to measure absolute pressure values, which are calculated as standard atmospheric pressure plus gauge pressure (with consistent units), and they display these values directly. Their function is similar to that of pressure transmitters.

Generally, differential pressure and pressure transmitters are based on atmospheric pressure, while absolute pressure transmitters measure against the level of absolute vacuum