Transducer is a device that converts variations into a measurable physical quantity, for example, pressure into electrical signals or even the other way round. The most commonly used transducers are strain gauge, hydraulic and pneumatic. Strain gauge is the most commonly used in several industries like automobile, medical and weighing etc. Load cells are also a type of force transducer. This process of conversion of force into electrical signals is called transduction. Transducers can be segregated into two broad categories namely; mechanical transducers and electrical transducers. Mechanical transducers convert physical quantities to mechanical quantities whereas, electrical transducers convert physical quantities to electrical quantities. The different types of transducers are:

  • Sensor: It is a type of transducer that reacts to a signal from a physical system. Usually, a signal is produces which gives out information from the system and this information is further used by a control system.
  • Actuator: It is a device that is responsible for the movement and controlling of a system. It can be controlled manually or through signals from controller system. It is operated by a source of energy and the energy is converted into motion. This source of energy can be anything from mechanical force to a pneumatic pressure.
  • Bidirectional Transducer: A bidirectional transducer can convert physical energy to electrical signals and also vice versa. A relevant example of bidirectional transducer is an antenna which can convert radio waves into electrical signals which can be used by a receiver.

There are different types of transducers, both analogue and digital available with an option of input and output to choose from. The type of input or output to be chosen really depends on the type of signal that is being controlled. Devices performing input function are usually called sensors since a physical change in their characteristic is sensed. On the other hand, the devices that perform output function are called actuators and control external devices like a control system. All these sensors can be subcategorized into active sensors and passive sensors. Active sensors require an external power source to function whereas, passive sensors do not require any such power source to function. Active sensors can produce amplified signals whereas, passive sensors are direct sensors that can change their physical properties.