A transducer is an electronic device that converts energy from one form to another form. It is a device that is capable of converting the physical quantity(i.e. Mechanical, thermal, chemical, optical, etc) into a proportional electrical quantity such as voltage or current. Transducers are also known as PICKUPS. Common types of transducers include microphones, loudspeakers, thermometers, pressure sensors, and antennas.
Transducers can be divided into two parts:
1. Sensing element: Sensing element is a detector which is responsible for sensing the element.
2. Transduction element: Transduction element is used to
transform the output of the sensing element to electrical output.
The efficiency of the transducer: It is defined as the ratio of
the power output in the desired form to the total power input. Mathematically,
if P represents the total power input and Q represents the power output in the
desired form, then the efficiency E, as the ratio between 0 and1, is given by:
E=Q/P
Transducers
are not 100% efficient; some power is always lost in the conversion process.
Usually, this loss is manifested in the form of heat.
Transducers
maybe categorized by application: sensor, actuator, or combination.
Sensor: A sensor is used to detect a parameter in one form of energy and report it to another form of energy. For example, a pressure sensor might detect pressure( a mechanical form of energy) and convert it into electricity for display at a remote gauge.
Actuator: An actuator accepts energy and produces movement(action). The energy
supplied to the actuator might be electrical or mechanical, pneumatic or
hydraulic, etc. For example, electric motors and a loudspeaker, converting
electrical energy into motion for different purposes.
Combination: Combination transducers have both
functions, they both detect and create action. For example, a typical
ultrasonic transducer switches back many times a second between acting as an
actuator and acting as a sensor.
Classification of Transducers:
1.
Primary
and secondary transducers
2.
Analog
and digital transducers
3.
Active
and passive transducers
4.
Transducers
and inverse type
1. Primary and secondary transducers
Primary transducers
consist of mechanical as well as electrical devices. The mechanical
devices of the transducer change the physical input quantities into a
mechanical signal. This mechanical device is known as the primary
transducers. Example - bourdon tube.
The
secondary transducer converts the mechanical signal into an electrical signal.
The magnitude of the output signal depends on the input mechanical signal.
Example - LVDT.
2.
Analog and digital transducers
Analog transducers is a transducer converting input quantity to analog output
in the form of pulses. Examples - strain gauge, LVDT, thermocouple, thermistor,
etc.
A Digital transducer is a transducer that can convert the input to electrical output in form of pulses. The digital signals work on high or low power.
3. Active and passive transducers
Transducers which do not need any external power source to produce output are known as active transducers. The required energy is obtained from physical quantity being measured i.e. tachometers. Example- piezoelectric sensors, photovoltaic cells, etc.
Transducers
which need external power to produce output i.e. linear potentiometers are
known as passive transducers. Example- strain gauge, thermistor,
etc.
4. Transducers and inverse transducers
A device that converts the non-electrical quantity into an electrical quantity
is known as the transducer.
A transducer that converts the electric quantity into a physical quantity, such
types of transducers are known as the inverse transducer. The transducer
has high electrical input and low non-electrical output.
Applications
of Transducers
Electromagnetic:
● Antenna: Converts electromagnetic waves into electric current and vice
versa
● Cathode Ray Tube: It converts an electrical signal into visual form.
● A Fluorescent Lamp, Light bulb: It converts electrical power into
visible light.
● Tape head: It converts changing magnetic fields
into electrical form.
● Hall effect sensor: It converts a magnetic field level into electrical
form only.
Electrochemical
● pH probes
● Hydrogen sensor
Electroacoustic:
● Loudspeaker, earphone: It converts electrical signals into
sound.
● Microphone: It converts sound into an electrical signal
● Piezoelectric crystal: It converts changes in water pressure
into an electrical form.
Electromechanical:
● Galvanometer
● Rotary motor
● Vibration power generator
● Potentiometer
● Load cell
● Strain gauge
Photoelectric:
● Laser diode
● Light-emitting diode
● Photodiode, photoresistor,
photomultiplier tube
Thermoelectric:
● Resistance temperature
detector
● Thermocouple
● thermistor
Radio Acoustic:
● Geiger Muller Tube
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