Electrical Transducer: Basics, Types, Requirements
Electrical Transducers: An Introduction
What is meant by transducers?
A transducer is a device which converts the energy from one form to another form. This energy may be mechanical, electrical, optical or thermal.
Before proceeding further, let us see couple of transducers (loudspeaker, microphone) familiar in our daily life.
A loudspeaker is a transducer that converts low-frequency electric current into audible sounds.
A microphone is a transducer that performs the reverse function, i.e. that of converting sound pressure variations into voltage or current.
Thus the Loudspeaker and microphone can be considered as complementary transducers.
Transducers may be used as both inputs to electronic circuits and outputs from them.
In the above example, a loudspeaker is an output transducer designed for use in conjunction with an audio system. Whereas, a microphone is an input transducer designed for use with a recording system.
What is meant by electrical transducer?
The transducers that gives electrical energy as output is known as electrical transducers.
In other words, The Electrical transducers are the devices that convert energy in the form of sound, light, heat, etc., into an equivalent electrical signal, or vice versa.
The output electrical signal may be voltage, current,or frequency. Production of these electrical signals is based upon resistive, inductive, capacitive effects.
For measuring non electrical quantities, a detector is used which usually converts the physical quantity into a displacement, that activates the electrical transducers.
Classification of Electrical Transducer:
A sharp distinction among the types of transducers is difficult. The transducers may be classified according to their application, method of energy conversion, nature of the output signal and so on. All these classifications generally result in overlapping areas.
In one way, the electrical transducers are classified as;
(1) Active Transducers
(2) Passive Transducers
It is also known as self-generating type transducers. They develop their own voltage or current as the output signal. The energy required for production fo this output signal is obtained from the physical phenomenon being measured.
Examples of active transducers: Thermocouple, Piezoelectric transducers, Photovoltaic cell, Moving coil generator, Photoelectric cell.
It is also called as externally powered transducers. They derive the power required for energy conversion from an external power source.
The passive transducers are further classified into Resistive type, Inductive type and capacitive type.
Thermistor, Photoconductive cell, Resistance strain gauge
LVDT- Linear Variable Differential Transformer
Photoemissive cell, Hall effect based devices.
Apart from these classification, some kind of transducers are known as opto-electronic transducers. They use the principle of converting light energy into electrical energy. Some of the examples of opto-electronic transducers are photoconductive cell, photovoltaic cell, solar cell, photomultiplier tube and photomultiplier.
Basic requirements of the Electrical transducer:
Some of the basic requirements of the transducers are given below:
When the same input signal is applied to the transducer at different times under the same environmental conditions, it should give identical output signals.
The transducers should have linear input-output characteristics.
The transducer circuit should have overload protection so that it will withstand overloads.
- High stability and reliability
The transducers output signal should not get affected by environmental variations(disturbances) like temperature, vibration etc. It should give minimum error in measurements.
- Good dynamic response
In real-time applications, the input signal will vary with time ( ie, the input signal is dynamic in nature). The transducer should respond as quick as possible for any change in the input signal.
- Convenient instrumentation
The transducers output signal should be measured either directly or after suitable amplification.
- Mechanical characteristics
When the transducer is subjected to various mechanical strains during working conditions, its performance should not degrade. It should withstand the mechanical strains.