Introduction to sensors and transducers

Introduction to sensors and transducers:

1. Sensor:

A device detecting the presence of parameter or measured variable and converting it into suitable form is called a sensor. It is a device which converts one physical parameter into other.

2. Transducer:

It is information receiving device, in a form of quantity. It converts the information in the same or other quantity, for indication, recording or control. The device used for conversion of a non electrical quantity into electrical quantity is called transducer.

A transducer is a device which converts non-electrical or physical quantity into electrical quantity. In most of the electrical system the output is not in the form of electrical form, but in non-electrical form. So if we want to measure that output using electrical methods we are required to use transducers.

Transducer = sensor + transduction

Transduction means conversion of input information, into some suitable form.

E.g. Glass. Thermometer is a sensor as it converts temperature into displacement of mercury column (non-electrical) and thermistor is a transducer as it converts temperature into resistance change (electrical).

Block diagram of transducer is shown in figure below:

[caption id="" align="aligncenter" width="490"]block diagram of transducer block diagram of transducer[/caption]

1) Sensing element:

Sensing element senses the physical or non-electrical quantity like temperature, pressure, etc. or its rate of change.

2) Transduction element:

The output of the sensing element goes to the transduction element. This transduction element is responsible for conversion of non-electrical or physical quantity into its equivalent electrical quantity.

In some cases this transduction element performs both the action of sensing as well as transduction. For example if we consider thermocouple, it generates emf (electrical quantity) corresponding to the heat generated at the ends of two dissimilar metals.

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