Transducers are electric or electronic devices that transform energy from one manifestation into another. The term transducer is commonly used in two senses; the sensor, used to detect a parameter in one form and report it in another (usually an electrical or digital signal), and an actuator may be described as opposite to a sensor-it converts electrical signal into generally nonelectrical energy. An example of a transducer is a loudspeaker which converts an electrical signal into a variable magnetic field and, subsequently, into acoustic waves.

Types of Transducers

Electromagnetic Transducers:

  • Antenna – converts electromagnetic waves into electric current and vice versa.
  • Cathode ray tube (CRT) – converts electrical signals into visual form
  • Fluorescent lamp, light bulb – converts electrical power into visible light
  • Magnetic cartridge – converts motion into electrical form
  • Pick up (music technology) – converts motion into electrical form
  • Photodetector or Photoresistor (LDR) – converts changes in light levels into resistance changes
  • Tape head – converts changing magnetic fields into electrical form
  • Hall effect sensor – converts a magnetic field level into electrical form only.

Electrochemical Transducers:

  • pH probes
  • Electro-galvanic fuel cell

Electromechanical (actuators) Transducers:

  • Electroactive polymers
  • Galvanometer
  • MEMS
  • 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

Electroacoustic Transducers:

  • Geophone – convert a ground movement (displacement) into voltage
  • Gramophone pick-up
  • Hydrophone – converts changes in water pressure into an electrical form
  • Loudspeaker, earphone – converts changes in electrical signals into acoustic form
  • Microphone – converts changes in air pressure into an electrical signal
  • Piezoelectric crystal – converts pressure changes into electrical form (and electrical signals into acoustic/mechanical form)
  • Sonar transponder
  • Tactile transducer

Photoelectric Transducers:

  • Laser diode, light-emitting diode – convert electrical power into forms of light
  • Photodiode – converts changing light levels into electrical form
  • Photo Resistor – converts changing light levels into electrical form
  • Phototransistor – converts changing light levels into electrical form
  • Photomultiplier tube – converts changing light levels into electrical form

Electrostatic Transducers:

  • Electrometer

Thermoelectric Transducers:

  • RTD Resistance Temperature Detector
  • Thermocouple
  • Peltier cooler
  • Thermistor (includes PTC resistor and NTC resistor)

Radioacoustic Transducers:

  • Geiger-Muller tube used for measuring radioactivity.
  • Receiver (radio)