Different types of transducer

The transducer is used in electronic communication systems to convert signals of different physical forms to an electronic signal. While the sensor is a device that senses a physical quantity and it converts it into an analog type quantity which can be measured electricity such as voltage, capacitance, inductance, and ohmic resistance.

One of the main key difference between the sensor and transducer is that the transducer converts the physical quantity or nonelectrical into another signal or electrical signal whereas the sensor senses the physical changes occur in the surrounding.

Classification based on the source of energy:

The transducer is of many different types of transducer, they can be classified based on various criteria as:
  • Active transducer
  • Passive transducer
1. Active transducer:

In the active transducer, the energy from the input is used as a control signal in the process of transferring energy from the power supply to proportional output. Such type of transducer develops theirs owns voltage or current hence known as a self-generating transducer. This output signal is obtained from the physical input quantity.

Piezoelectric transducer: When an external force is applied to this transducer, the produced voltage that can be measured easily. This change is measured by its corresponding value of sound or vibration.

Piezoelectric transducer applications:
  • This sensor can be used as a knock sensor in automotive engine management systems for noticing knock of the engine
  • This sensor is used for the measurement of pressure and acceleration
  • This transducer is mainly used to detect the sticks drummer impact in electronic drums pads 
Thermopile transducer: The voltage change developed across a junction of two dissimilar metals is knowns by its corresponding value of temperature heat or flow.

Moving coil type: The change in voltage generated in a magnetic field can be measured using its corresponding value of vibration or velocity.

Photovoltaic cell: The voltage change that occurs across the PN junction due to light radiation is known as the corresponding solar cell value or light intensity

2. Passive transducer:

A transducer which requires an external power source for their operation is called a passive transducer. They produce an output signal in the form of some variation in resistance-capacitance or any other electrical parameter like inductance which then has to be converted to an equivalent current or voltage signal. A transducer which requires an external power source for their operation is called a passive transducer.

Resistive transducer:
  • Resistive thermometers
  • Resistive displacement transducer
  • Resistive strain transducer
  • Resistive pressure transducer
  • Resistive moisture transducer
Capacitive transducer:
  • Capacitive displacement transducer
  • Capacitive moisture  transducer
  • Capacitive thickness transducer
  • Inductive displacement transducer
Inductive transducer:
  • Eddy current inductive transducer
  • Moving core inductive transducer

Classification based on physical quantity:

The second classification of the transducer is based on the physical quantity converted. The end use of the transducer after the conversion.

Following some list of transducer based on physical quantity:
Flow transducer - flow meter
  • Pressure transducer - Bourdon gauge
  • Force transducer  - Dynamometer
  • Acceleration transducer  - Accelerometer
  • Temperature transducer  - Thermocouple
  • Displacement transducer  - LVDT

Type of transducer based on the principle of operation:
  • Chemical
  • Mutual induction
  • Photovoltaic
  • Piezoelectric 
  • Hall effect
  • Photoconductor
Primary and secondary transducer:
  • Primary transducer: This transducer consists the mechanical as well as the electrical devices. The mechanical devices of the transducer change the physical input quantities into a mechanical signal or device. This mechanical device is known as the primary transducer.
  • Secondary transducer: The secondary transducer converts the mechanical signal into a form of an electrical signal. The magnitude of the output signal depends on the input mechanical signal.

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