Difference between Sensor & Transducer

Transducer 1

What is Transducer?

Transducer 2

The non-electrical quantity is converted into an electrical form by using electrical method. The techniques like measurement, manipulation and control are done in transducer. The device when actuated, transforms energy from one form to another is called a transducer.

Transducers classification:

The transducer classifications shown are:

  • Active & Passive Transducer
  • Based on Principle
  • Primary & Secondary Transducer
  • Analog & Digital Transducer
  • Transducer & Inverse Transducer

Active & Passive Transducer:

Active transducer is defined as transducer that does not require an external energy source. Example: Thermocouple, Piezoelectric Pick up & Photovoltaic.

Passive Transducer is defined as transducer which requires external energy to produce its output is called a passive transducer. Example: Potentiometric Transducer, RTD, Thermistor, Capacitor microphone, LVDT.

Based on the principle:

The transducer can be still subdivided into inputs/output & transduction.

Inputs / Outputs Transducer:

Input Transducer:

A physical quantity or parameter in a certain form is converted by an input transducer into a signal that can be read and understood. One kind of input transducer is the microphone. It absorbs the sound waves that are produced and transforms them into an electrical signal.

Output transducer:

The electrically formed signals that are received are transformed into a different energy form or version.

Mechanical Transducer:

A physical quantity can be changed into its mechanical equivalent.

Example: Bourdon tube

Electrical Transducer:

A physical quantity can be transformed into its electrical equivalent.

Example: Thermocouple


Transductionis based on how the input quantity is transform into resistance, inductance, or capacitance a transducer is either categorized as resistive, inductive, or capacitive. They can be divided into the following categories: piezoelectric, thermoelectric, magneto-restrictive, electro-kinetic, and optical.

Primary and Secondary transducer:

Primary Transducer:

The detecting or sensing component that reacts to a change in physical phenomena is known as a primary transducer.

Secondary Transducer:

The first transducer’s output, which takes the form of mechanical movement, is transformed into electrical output by the secondary transducer.

Analog and Digital Transducer:

Analog Transducer:

Analog transducers are ones with continuous time-domain output. As a result, the electrical output signal will essentially be a continuous function of time. RTD, Thermocouple, LVDT, RVDT, and thermistor are a few examples of analogue transducers.

Digital Transducer:

Digital Transducers are transducers that transform an input quantity into an electrical output signal that is in the form of a pulse. The output is discrete because it is not continuous but rather takes the shape of pulses. Shaft encoders, limit switches, digital tachometers, and other devices are examples of digital transducers.

Shaft encoder:

The angular position and velocity are measured using a shaft encoder, and the output is digital in form. It is widely utilised in rotating machinery control for robotics, including cranes.

Transducers and Inverse Transducers:


Transducers are devices which convert a non-electrical quantity into an electrical quantity.

Inverse Transducer:

Inverse transducers are devices that change an electrical quantity into a non-electrical quantity.

What is sensor?

A sensor is a device which senses the presence of various quantity and converts it into a signal which is in readable format.

Sensor is a device which responds with a change in physical phenomenon. The classification of sensor is based on conversion principle, based on quantity being measured and the technology used. The types of energy that can be sensed is classified as Mechanical, electrical, gravitational, thermal etc. Resolution in sensor defines its ability to detect a change in sensed element during measurement. 

The sensing of any quantity is liable to errors. The two types of errors are Static error and Dynamic error.

  • Static error: It is a type of error caused while sensing due to reading problems. The parallax of needle in meter scale is an example of this type of error. One major advantage of digital readouts is parallax error doesn’t exist.
  • Dynamic error: This error is caused due to the difference in quantity as it really is and the amount to be measured, caused by the loading of measuring instrument itself. A typical example is a false voltage reading across a high- resistance potential divider with a voltmeter whose resistance is not high enough.

Classification of sensors:

Sensors are mainly classified into two as

  • Active sensors
  • Passive sensors.

Active sensor:

These type of sensors self generating and it does not require any external power supply. Photovoltaic cell, piezoelectric devices thermocouples are examples of Active sensors.

Passive sensor:

These types of sensors require an external power supply and are not self generating. A diaphragm used to convert the pressure is an example of passive sensor.

What is the difference between transducer and sensor?

DefinitionA Sensor is defined as a device which measures a physical characteristic such as sound, temperature, light intensity and transforms into an easily readable format.A transducer is defined as an electronics conversion which converts any physical form to electrical form
ComponentsSensorsSensor and signal conditioning
FunctionGenerates the relevant electrical impulses after detecting the changes.Conversion of one form of energy to another form.
ExamplesProximity sensor, Magnetic sensor, Ultrasonic sensor, etc..Thermistor, Thermocouple, LVDT etc..

Is transducer a detector?

Sensors or detectors are a type of electrical transducers which can sense and convert energy (heat energy, light energy etc) from one form to another. Thus we can conclude that all sensors are transducers but all transducers are not sensors in all cases. Almost input transducers are sensors and output transducers are Actuators or Effectors.

Is Thermocouple a transducer or a sensor?

Peltier effect is the working principle of Thermocouple. The structure of    thermocouple consists of two metallic ends joined together to form two junctions of different temperature. Peltier emf is generated due to the temperature difference in two junctions. A reference temperature is connected to one end for reference and unknown is connected to other end. Since it senses the temperature it is a sensor and it converts temperature into emf, hence it is a Transducer. Thermocouple acts as an active transducer.

The output from the sensor will be in the same format, and the measurement will be transformed into an electrical signal by a transducer.

Is every sensor a transducer?

All sensors can be called as transducers but not all transducers need not be sensors. For example, a thermocouple is a type of transducer which directly converts to an electrical output whereas a thermistor can be said as a type of sensor which sense the change in temperature.

Difference between sensor and actuator:

A device that transforms energy into motion is called an actuator. As a result, it belongs to a certain class of transducer. A sensor is an object that receives signals and reacts to them.

What is another word for sensor?

Sensor can also be called as detector.

List some of sensor with its application.

  • Pressure Sensors – measures the pressure of gas and liquids.
  • Temperature Sensors – Measures temperature
  • Humidity Sensors – measures moisture in air

Can a device be both a sensor and a transducer?          

Yes, some sensors are accurate tools when calibrated properly.

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