Transducer Types, Parts, Working, Applications With Examples

What is a transducer?

The transducer may be defined as any device that convert the energy from one form to another.

What is a transducer used for?

Most of the transducers either convert electrical energy in to mechanical displacement and convert some non electrical physical quantities like temperature, Light, Pressure , Force , Sound etc to an electrical signals.

In an electronics instrument system the function of transducers is of two types.

1. To detect or sense the pressure, magnitude and change in physical quantity being measured.

2. To produce a proportional electrical signal.

1. Sensing Element

The physical quantity or its rate of change is sensed and responded to by this part of the transistor.

2. Transduction Element

The output of the sensing element is passed on to the transduction element. This element is responsible for converting the non-electrical signal into its proportional electrical signal.

Classification of Transducers

Transducer types

The Classification of Transducers is done in many ways.

Some of the criteria for the classification are based on

the area of application
Method of energy conversion
Nature of output signal
According to Electrical principles involved
Electrical parameter used
principle of operation
Typical applications.

Classification of Transducer/ types of transducers

Based upon the transduction principle used

2. Primary & Secondary transducers

3.Active & Passive transducers

4. Analog & Digital transducers

5.Transducers & Inverse transducers

1. Based upon the transduction principle:-

Resistance transducers

Potentimeter devices, Resistance strain gauge, Pirani guage or hot wire meter, Resistance thermometer, Thermister, Resistance hygrometer, Photoconductive cell.

Capacitance transducers

Variable capacitance pressure gauge, Capacitor microphone, Dielectric gauge.

Inductance Transducers

Magnetic circuit transducer, Reluctance pick-up, Differential transformer, Eddy current guage, Magneto striction gauge.

Voltage & Current transducers

Hall effect transducer, Ionisation chamber, Photoemissive cell,Photomultiplier tube.

Self generating transducers

Thermocouple, Thermopile, Moving coil generator, Piezoelectric transducer, Photovoltaic.

2. Primary & Secondary transducers

Some transducers contain mechanical as well as electrical devices

. The mechanical device converts the physical quantity to be measured into a mechanical signal.

Such mechanical devices are called as primary transducers, because they deal with the physical quantity to be measured.

• The electrical device then converts this mechanical signal into a corresponding electrical signal. Such electrical device are known as secondary transducers.

Example of Primary and secondary transducer Primary transducer Displacement voltage Secondary transducer

3. Active & Passive Transducer

Transducers that don’t require an auxiliary power source to produce their output are known as ‘Active transducers’ or self generating type.

eg: Moving coil, Piezoelectric crystal, Thermocouple, Photovoltaic cell.

On the other hand transducer that can’t work on the absence of external power supply are called ‘passive transducers’.

eg: Resistive, Capacitive, Inductive.

4. Analog & Digital transducers

Analoge transducers converts input quantity into an analog output which is continous function of time.

eg: strain gauge, LVDT, Thermocouple. Thermister.

Digital transducer converts input quantity into an electrical output is in the form of pulses

eg: Glass scale, Metallic scale.

5. Transducers & Inverse Transducers

inverse transducers are just the opposite of transducers in function. Inverse transducers converts electrical quantity in non electrical quantity.

Just think about a current coil moving in magnetic field which is an inverse transducer.

eg: Peizoelectrical crystal.

Basically, there are two types of transducers, electrical, and mechanical.

Electrical Transducer

An electrical transducer is a sensing device by which the physical, mechanical or optical quantity to be measured is transformed directly by a suitable mechanism into an electrical voltage/current proportional to the input measurand.

Transducer Properties

An electrical transducer must have the following parameters:

Linearity: The relationship between a physical parameter and the resulting electrical signal must be linear.

Sensitivity: This is defined as the electrical output per unit change in the physical parameter (for example V/°C for a temperature sensor).

High sensitivity is generally desirable for a transducer.

Dynamic Range: The operating range of the transducer should be wide, to permit its use under a wide range of measurement conditions.

Repeatability: The input/output relationship for a transducer should be predictable over a long period of time. This ensures reliability of transducer.

Physical Size: The Electrical Transducer Definition must have minimal weight and volume, so that its presence in the measurement system does not disturb the existing conditions

What is the main difference between sensor and transducer?

Difference Between a Transducer & Sensor

Transducers	Sensors
It converts energy from one form to another.	It senses physical quantities and converts it into a readable form.
Eg: Cable extension transducer, linear transducer and microphones	Eg:Thermistors, pressure switches and motion sensors