Definition of Transducer, Sensor, and Actuator

SENSOR EXAMPLE

There are many devices which have close meaning, eg: transducer, sensor, detector, and actuator. What is difference of each device?

A transducer is a device that converts a signal from one physical form to a corresponding signal having a different physical form. There for it is an energy converter. This means that the input signal always has energy or power.

There are six different kind of signal:

• Mechanical
• Thermal
• Magnetic
• Electric
• Optical
• Chemical

Any device converting signal of one kind to signal of a different kind is considered to be a transducer. The output signals can be of any useful physical form. The transducer can placed as input transducer or output transducer. An input transducer converts physical signal to electric signal while an output transducer converts electric signal to physical signal.

Another name of input and output transducers are sensor and actuator. Sensor is used to refer to the input transducer while actuator refers to the output transducer. Sensors are intended to acquire information, usually designed to handle LOW power and intended to consume energy as low as possible. Actuators are designed to power conversion and to handle (relatively) HIGH power.

Sensors monitor a measurand (a quantity to be measured) by taking advantage of how it affects a material or geometric property that causes a change in a measurable quantity (energy form). This quantity is either directly or indirectly converted into a form that is useful for processing. Functional design “around” the sensing mechanism may be required in order to yield a usable output signal.

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Sensor Classification:

Sensor can be classified by transduction principle, measurand, physical law, detection method, etc.
Transduction Principle

• Active sensor: a sensor that requires external power to operate. It converts form of input energy into form of output energy by using additional energy. Examples: the carbon microphone, thermistors, strain gauges, capacitive and inductive sensors, etc. Other name: modulating sensor, parametric sensors (output is a function of a parameter - like resistance)

• Passive sensor: a sensor that generates its own electric signal and does not require a power source. It converts form of input energy into form of output energy without additional energy. Examples: thermocouples, magnetic microphones, piezoelectric sensors. Other name: self-generating sensors

Measurand:

• Electric sensors

• Magnetic

• Electromagnetic

• Acoustic • Chemical

• Optical

• Heat, Temperature

• Mechanical

• Radiation

• Biological

• Etc.

Physical law:

• Photoelectric

• Magnetoelectric

• Thermoelectric

• Photoconductive

• Magnitostrictive

• Electrostrictive

• Photomagnetic

• Thermoelastic

• Thermomagnetic

• Thermooptic

• Electrochemical

• Magnetoresistive

• Photoelastic

• Etc.

Application area:

• Consumer products

• Military applications

• Infrastructure

• Energy

• Heat

• Manufacturing

• Transportation

• Automotive

• Avionic

• Marine

• Space

• Scientific

• Etc.

Reference Books About Sensor:

Wireless Sensor Networks...     by Terrance J. Dishongh $79.20	BioMEMS (Microsystems)          $126.44	Handbook of Transducers by Harry N. Norton $78.75