A sensor is an input device that provides a usable output in response to the input measurand. A sensor is also commonly called a sensing element, primary sensor, or primary detector. The measurand is the physical parameter to be measured.
An input transducer produces an electrical output that is representative of the input measurand. Its output is conditioned and ready for use by the receiving electronics like PLC or DCS.
The receiving electronics can be an indicator, controller, computer, PLC, DCS etc. The term “transmitter,†as commonly used with industrial process control instrumentation, has a more narrow deï¬nition than those of a sensor or transducer:
A transmitter is a transducer that responds to a measured variable by means of a sensing element and converts it to a standardized transmission signal (like 4-20mA) that is a function only of the measured variable.