A transducer
is an electrical device that is used to convert one form of energy into
another form. In general, these devices deal with different types of
energies such as mechanical, electrical energy, light energy, chemical energy, thermal energy, acoustic energy, electromagnetic energy, and so on.
For instance, consider a mic we use in daily life in telephones, mobile phones, that converts the sound into electrical signals and then amplifies it into the preferred range. Then, alters the electrical signals into audio signals at the o/p of the loudspeaker. Nowadays fluorescent bulbs are used for lighting, changes the electrical energy into light energy.The best examples of the transducer are mic, fluorescent bulb, and the speaker can be considered as a transducer.
The input quantity is the non-electrical quantity, and the output electrical signal is in the form of the current, voltage or frequency.
1. Classification based on the Principle of Transduction
The transducer is classified by the transduction medium. The transduction medium may be resistive, inductive or capacitive depends on the conversion process that how input transducer converts the input signal into resistance, inductance and capacitance respectively.
2. Primary and Secondary Transducer
Primary Transducer – This type transducers consist of a mechanical as well as Electrical. Mechanical devices of the transducer change the physical input quantity into mechanical signal.This mechanical device is called Primary Transducers.
Secondary Transducer - The secondary transducer converts the mechanical signal into an electrical signal. The magnitude of the output signal depends on the input mechanical signal.
Example of Primary and Secondary Transducer
Consider the Bourdon’s Tube shown in the figure below. The tube act as a primary transducer. It detects the pressure and converts it into a displacement from its free end. The displacement of the free ends moves the core of the linear variable displacement transformer. The movement of the core induces the output voltage which is directly proportional to the displacement of the tube free end.
Thus, the two type of transduction occurs in the Bourdon’s tube. First, the pressure is converted into a displacement and then it is converted into the voltage by the help of the L.V.D.T
3. Passive and Active Transducer
The transducer is classified as the Active and Passive transducer.
Active Transducer – The transducer which does not require the external power source is known as the active transducer. Such type of transducer develops theirs owns voltage or current, hence known as a self-generating transducer. The output signal is obtained from the physical input quantity.
The physical quantity like velocity, temperature, force and the
intensity of light is induced with the help of the transducer. The
piezoelectric crystal, photo-voltaic cell, tacho generator,
thermocouples, photovoltaic cell are the examples of the active
transducers.
Examples – Consider the examples of a piezoelectric crystal. The crystal is sandwiched between the two metallic electrodes, and the entire sandwiched is fastened to the base. The mass is placed on the top of the sandwiched.
The piezo crystal has the special property because of which when the force is applied to the crystal, they induce the voltage. The base provides the acceleration due to which the voltage is generated. The mass applies on the crystals induces an output voltage. The output voltage is proportional to the acceleration.
Passive Transducer – The transducer which requires
the power from an external supply source is known as the passive
transducer. They are also known as the external power transducer. The
capacitive, resistive and inductive transducers are the example of the
passive transducer.
4. Analog and Digital Transducer
The transducer can also be classified by their output signals. The output signal of the transducer may be continuous or discrete.
Analog Transducer – The Analog transducer changes the input quantity into a continuous function. The strain gauge, L.V.D.T, thermocouple, thermistor are the examples of the analogue transducer.
Digital Transducer – These transducers convert an input quantity into a digital signal or in the form of the pulse. The digital signals work on high or low power.
Encoder is a example of Digital Transducers....
5. Transducer and Inverse Transducer
Transducer – The device which converts the non-electrical quantity into an electric quantity is known as the transducer.
Inverse Transducer – The transducer which converts the electric quantity into a physical quantity, such type of transducers is known as the inverse transducer. The transducer has high electrical input and low non-electrical output.
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