Transducer

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This article briefly elucidates transducers. It also enlightens classification of transducers along with their applications.

Definition

A transducer is a device that converts one form of energy to another. Energy types include (but are not limited to) electrical, mechanical, electromagnetic (including light), chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a transducer. Transducers are widely used in measuring instruments.

Applications

Electromagnetic:
- Antenna – converts propagating electromagnetic waves to and from conducted electrical signals
- Magnetic cartridge – converts relative physical motion to and from electrical signals
- Tape head – converts changing magnetic fields to and from electrical signals
- Hall effect sensor – converts a magnetic field level into an electrical signal
- Disk read-and-write head – converts magnetic fields on a magnetic medium to and from electrical signals

Electrochemical:
- pH probes
- Electro-galvanic fuel cell
- Hydrogen sensor
Electromechanical (electromechanical output devices are generically called actuators):
- Electroactive polymers
- Galvanometer
- Microelectromechanical systems
- Rotary motor, linear motor
- Vibration powered generator
- Potentiometer when used for measuring position
- Load cell – converts force to mV/V electrical signal using strain gauge
- Accelerometer
- Strain gauge
- String potentiometer
- Air flow sensor
- Tactile sensor

Electroacoustic:
- Loudspeaker, earphone – converts electrical signals into sound (amplified signal → magnetic field → motion → air pressure)
- Microphone – converts sound into an electrical signal (air pressure → motion of conductor/coil → magnetic field → electrical signal)
- Pickup (music technology) – converts motion of metal strings into an electrical signal (magnetism → electrical signal)
- Tactile transducer – converts electrical signal into vibration ( electrical signal → vibration)
- Piezoelectric crystal – converts deformations of solid-state crystals (vibrations) to and from electrical signals
- Geophone – converts a ground movement (displacement) into voltage (vibrations → motion of conductor/coil → magnetic field → signal)
- Gramophone pickup – (air pressure → motion → magnetic field → electrical signal)
- Hydrophone – converts changes in water pressure into an electrical signal
- Sonar transponder (water pressure → motion of conductor/coil → magnetic field → electrical signal)

Electro-optical (Photoelectric):
- Fluorescent lamp – converts electrical power into incoherent light
- Incandescent lamp – converts electrical power into incoherent light
- Light-Emitting Diode – converts electrical power into incoherent light
- Laser Diode – converts electrical power into coherent light
- Photodiode, photoresistor, phototransistor, photomultiplier tube – converts changing light levels into electrical signals
- Photodetector or photoresistor or light dependent resistor (LDR) – converts changes in light levels into changes in electrical resistance
- Cathode ray tube (CRT) – converts electrical signals into visual signals