Transducers are electrical devices which convert energy from one form to another. Normally, these devices deal with energies like electrical, mechanical, chemical, thermal, electromagnetic, acoustic and many other.

Common examples include microphones, loudspeakers, thermometers, and antennas; all are transducers that transform one type of energy into another.


In transducers, the efficiency is considered to be an important factor. Transducer efficiency can be defined as the ratio of power output to the total input power. If F represents the power input and P represents the output power, then the efficiency is given by E= P/F and this ratio ranges between 0 and 1.

However, no transducer is 100% efficient and some power is always lost in the process of conversion. Usually, this power is lost in the form of heat.

Types of transducers:

Transducers can be classified based on various criteria given below-

1. Based on the quantity to be measured

  • Pressure transducers (e.g. a diaphragm)
  • Temperature transducers(e.g. a thermocouple)
  • Displacement transducers (e.g. LVDT)
  • Flow transducers

2.  Based on the principle of operation

  • Photovoltaic ( e.g. a solar cell )
  • Chemical
  • Piezoelectric
  • Mutual Induction


3. Based on Whether an External Power Source is required or not

  • Active Transducer

Transducers that do not require any power source for their working are active transducers. They work on the principle of energy conversion. They produce an electrical signal proportional to the input. A common example is a thermocouple.

  • Passive Transducers

This type of transducer requires an external power source to operate. With the small change in capacitance, resistance or any other electrical parameters, passive transducers create the output signal.Then it is converted into the equivalent voltage or current signal. A photocell is an example of a passive transducer.

Working of transducers-

The working of a transducer can be understood by the mic of telephones that we use in our daily life. The mic converts sound into electrical signals and amplify it to the required range. Then this electrical signal is transmitted at the output which gets transformed from the electrical signal into sound by a transducer.


Another example to understand the working of transducers is when it is used in a fish-finder. It is used in the echo sounder system.  It converts electrical pulses into sound. In other words, it sends out sound waves and gets back the echo that is interpreted by the echo sounder. The transducer receives transmit pulse that are high voltage electrical pulses from the echo sounder. Then it converts the transmitted pulses into sound. The sound travels through the water as a pressure wave and when it strikes an object like a rock or a fish, the wave bounces back.

When this wave bounces back, the transducer acts as a microphone and converts it into electrical energy. The echo sounder calculates the time difference between the transmitted pulse and the echo returning from the objects, then this information is displayed on the screen that can be easily understood by the user.


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