Transducers are used to convert one form of energy into another.
There are two primary types of transducers: sensors and actuators. An electronic thermometer, for example, is a sensor that detects heat energy and reports temperature. A transducer is needed to convert the heat energy into an electrical signal that can be displayed on a gauge or meter. Actuators, on the other hand, receive an electrical input signal and perform a physical action. Transduction occurs when the signal is converted into a force.
Transducers are found in most automation, measurement and control applications. They are commonly used to report force, pressure, position or current values. They are also used to convert signals for measurement.