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Thursday, December 16, 2010

Transducer





                      A transducer is a device that converts one type of energy to another. The conversion can be to/from electrical, electro-mechanical, electromagnetic, photonic, photovoltaic, or any other form of energy. While the term transducer commonly implies use as a sensor/detector, any device which converts energy can be considered a transducer.

Types

Transducers may be categorized by application: sensor, actuator, or combination.

A sensor is used to detect a parameter in one form and report it in another form of energy (usually an electrical and/or digital signal). For example, a pressure sensor might detect pressure (a mechanical form of energy) and convert it to electricity for display at a remote gauge.

An actuator accepts energy and produces movement (action). The energy supplied to an actuator might be electrical or mechanical (pneumatic, hydraulic, etc.). An electric motor and a loudspeaker are both actuators, converting electrical energy into motion for different purposes.

Combination transducers have both functions; they both detect and create action. For example, a typical ultrasonic transducer switches back and forth many times a second between acting as an actuator to produce ultrasonic waves, and acting as a sensor to detect ultrasonic waves.

Applications

Electromagnetic:
  • 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
  • Photodetector or photoresistor or light dependent resistor (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:
  • 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 → signal)
  • Pickup (music technology) – converts motion of metal strings into an electrical signal (magnetism → electricity (signal))
  • Tactile transducer – converts solid-state vibrations into electrical signal (vibration → ? → signal)
  • Piezoelectric crystal – converts solid-state electrical modulations into an electrical signal (vibration → electrical current → signal)
  • Geophone – converts a ground movement (displacement) into voltage (vibrations → motion of conductor/coil → magnetic field → signal)
  • Gramophone pickup – (air pressure → motion → magnetic field → signal)
  • Hydrophone – converts changes in water pressure into an electrical form
  • Sonar transponder (water pressure → motion of conductor/coil → magnetic field → signal)
  • Photoelectric:xxfhm
  • Laser diode, light-emitting diode – converts electrical power into forms of light
  • Photodiode, photoresistor, phototransistor, photomultiplier tube – converts changing light levels into electrical form

Electrostatic:
  • Electrometer

Thermoelectric:
  • Resistance temperature detector (RTD)
  • Thermocouple
  • Peltier cooler
  • Thermistor (includes PTC resistor and NTC resistor)

Radioacoustic:
  • Geiger–Müller tube – used for measuring radioactivity
  • Receiver (radio)


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Hai friends…welcome to my blog. This blog is exclusively for instrumentation engineering students which will provide sources for their reference and studies. As you all know Instrumentation is now a fast emerging and developing field in Engineering. This blog has different categories like PLC, SCADA, DCS, Sensors and Transducers, Computer control of process, Industrial Instrumentation, etc.

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