Sensors and Transducers: Introduction

CHAPTER ‒8

SENSORS AND TRANSDUCERS

SENSORS AND TRANSDUCERS

Measurement is an important subsystem of a mechatronics system. Its main function is to collect the information on system status and to feed it to the micro‒processors for controlling the whole system.

Measurement system comprises of sensors, transducers and signal processing devices.

Sensors in manufacturing are basically employed to automatically carry out the production operations as well as process monitoring activities. Sensor technology has the following important advantages in transforming a conventional manufacturing unit into a modern one.

1. Sensors alarm the system operators about the failure of any of the sub units of manufacturing system. It helps operators to reduce the downtime of complete manufacturing system by carrying out the preventative measures.

2. Reduces requirement of skilled and experienced labours.

3. Ultra‒precision in product quality can be achieved.

Sensor

It is defined as an element which produces signal relating to the quantity being measured. According to the Instrument Society of America, sensor can be defined as "A device which provides a usable output in response to a specified measured."

Here, the output is usually an "electrical quantity" and measured is a "physical quantity, property or condition which is to be measured". Thus in the case of, say, a variable inductance displacement element, the quantity being measured is displacement and the sensor transforms input of displacement into a change in inductance.

Transducer

It is defined as an element when subjected to some physical change experiences a related change or an element which converts a specified measured into a usable output by using a transduction principle.

It can also be defined as a device that converts a signal from one form of energy to another form.

A wire of constant an alloy (copper‒nickel 55‒45% alloy) can be called as a sensor because variation in mechanical displacement (tension or compression) can be sensed as change in electric resistance. This wire becomes a transducer with appropriate electrodes and input‒output mechanism attached to it. Thus we can say that "sensors are transducers".