### Transducer types and its applications

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

Strain gauge

Photoelectric:

Laser diode

Light-emitting diode

Photodiode, photoresistor, photomultiplier tube

Thermoelectric:

Resistance temperature detector

Thermocouple

thermistor

Geiger Muller Tube