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Difference between Active Transducer and Passive Transducer
In electronics, a device that coverts energy from one form to some other form is known as a transducer. For example, a loudspeaker converts electrical energy into sound, hence it is a transducer. Another common examples of transducers include microphone, thermometer, pressure sensor, antenna and other position sensors, etc.
Based on excitation system, transducers are broadly classified into the following two types namely,
Active Transducer
Passive Transducer
The most fundamental difference between active and passive transducer is that an active transducer does not need any external power supply to generate output, whereas a passive transducer needs an additional source of power to operate.
This article is meant for explaining the differences between active transducer and passive transducer. But before discussing the differences, let us first know a bit about active transducer and passive transducer individually.
What is an Active Transducer?
The type of transducer which can generate an output signal in the form of voltage or current without the need of external power supply is known as active transducer. In other words, the active transducer is one that requires an additional power supply to work.
Since the active transducer can generate its output itself, hence it is also known as self-generating transducer. The active transducer obtains the energy required to produce the output signal from the physical quantity that is to be measured.
A common example of active transducer is the piezo electric crystal. This is because when an external force is applied to the piezo electric crystal, it produces an output voltage, and for this it does not require any additional source of power. Another common examples of active transducers are tachogenerators, thermos-couples, etc.
What is a Passive Transducer?
The type of transducer that requires some additional source of power to produce the output is known as passive transducer. Therefore, a passive transducer requires an external power source to work. Passive transducers generate output signals when electrical parameters such as resistance, inductance, and capacitance change.
A common examples of a passive transducer is a linear potentiometer that is used to measure the displacement. It is a passive transducer because it requires an external power source to work, i.e. to measure linear displacement. Another example of passive transducer is a thermistor.
After discussing about the basics of active transducer and passive transducer, let us now discuss the key differences between them.
Difference between Active Transducer and Passive Transducer
The important differences between active transducer and passive transducer are listed in the following table −
Parameter |
Active Transducer |
Passive Transducer |
|---|---|---|
Basic description |
The type of transducer which does not require external power supply to produce the output signal is known as an active transducer. |
The type of transducer that requires an addition source of power to work is known as a passive transducer. |
Working energy |
Active transducer draws the energy required to work directly from the physical quantity which is to be measured. |
Passive transducer draws energy to work from an external source of power. |
Design |
Active transducers have simple design and construction. |
The design and construction of passive transducer is complex. |
External power supply |
Active transducer does not require external power supply. |
Passive transducer requires additional power supply. |
Need of output amplification |
Active transducer produces an output signal of very low amplitude. Therefore, it requires amplification. |
Passive transducer naturally produces an output signal of high amplitude, hence it does not require amplification of output signal. |
Output |
Active transducer generally produces its output in the form of voltage or current. |
Passive transducer produces its output as the change in passive circuit parameters such as resistance, inductance, and capacitance. |
Also known as |
Active transducer is also known as self-generating transducer. |
Passive transducer is also known as externally powered transducer. |
Examples |
The common examples of active transducers include piezo-electric crystals, thermocouple, tachogenerator, photovoltaic cell, etc. |
Examples of passive transducers are potentiometer, thermistor, differential transformer, photomultiplier tube, etc. |
Conclusion
In conclusion, the active transducer is a type of transducer that converts one form of energy into another without need of external power supply. On the other hand, the passive transducer is one that also converts one form of energy into another but requires an additional source of power to perform this conversion.
Both active and passive transducers are widely used to convert physical quantities such as pressure, displacement, humidity, etc. into the corresponding quantities which are easy to measure.
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