Sensors (Transducer) - Electrical and Computer Engineering · Sensors (Transducer) ... direction representing a change in Position of a body or point with respect to a reference point

Sensors (Transducer)

Introduction

By Sintayehu Challa

ECEG535:-Instumentation Eng'g By Sintayehu Challa

What are Sensors?

� Basically the quantities to be measured are

Non-Electrical quantities such as temperature, pressure,displacement,humidity,

fluid flow, speed etc, but these quantities can not measured directly

SensorsNEQ EQ

Force, Light,

Temp, etc

Voltage, Current

Resistance, Inductance,

Capacitance,


Contd.

� Sensors (Sensing Device) by which a Physical,

Mechanical or Optical Quantity is changed to (transformed) directly with a suitable mechanism into Electrical Signal.

� Simply

Sensing device is to detect Non-Electrical

quantity to a measurable output Electrical quantity.


What advantage to use Sensors?

1. Friction effects is reduced to the minimum

possibility.

2. Very small power is required for controlling the system.

3. The Electrical output can be amplified to any desired level.

4. etc


What are the Basic Requirement of

Sensors?

Sensors should meet the following requirement

1. Ruggedness:-It should be capable of withstanding overload and some safety arrangement should be provided for overload protection.

2. Linearity

3. Repeatability

4. High Output Signal quality

5. High reliability and stability

6. Good dynamic Response

7. No Hysteresis effect

8. etc






Classification of sensors

The sensor may be classified as in various

forms such as

1. On the basis of Electrical principles

2. On the method of application

3. On the method of energy conversion

4. On the nature of output signal

5. etc


Contd.

In general the classification of sensor is

given by

1. Primary and Secondary Sensor

2. Active and Passive Sensor

3. Analog and Digital Sensor


Primary and Secondary Sensor

Sensors can be selected on the methods of

application can be classified as primary and secondary sensors.

Load Cell

(Primary

Sensors)

NEQ

Weight Resistance

Strain gauge

(Secondary

Sensors)

NEQEQ


Active and Passive Sensor

Sensors can be selected as the basis of

Energy Conversion can be classified as

Active and Passive sensors

1. Active sensors are also called self generating sensors

Active

Sensors

NEQ EQ

Force, Light,

Temp, etc

Voltage, Current


Passive Sensor

� Passive sensors require external power

source for energy conversion

Passive

Sensors

NEQ EQ

Force, Light,

Temp, etc

Resistance, Inductance,

Capacitance,


Analog and Digital Sensors

Sensors on the basis of nature of output

signal may be classified as analog and Digital Sensor

1. Analog Sensor converts input signal into output signal, which is a continuous function of time.

2. Digital Sensor converts input signal into output signal of the form of pulses or Discrete form or Sampled form.


Categories of input sensors

1. Resistive Sensors

� Direct Resistance Change used to Sense

Position or Angle

� Resistive Temperature Sensor

� Resistive Strain Gauges

� Photoconductors

� Resistive Relative Humidity Sensor

2. Variable Capacitor Sensors


Contd.

3. Voltage Generating Sensor

� Thermocouples and Thermopiles

� Photovoltaic Cells

� Piezoelectric Transducer

4. Sensor Based on variable Magnetic Coupling4. Sensor Based on variable Magnetic Coupling

� The LVDT

� Synchros and Resolvers


Selection of Sensors

The most useful steps for selection of sensor

1. Define the nature of quantity under measurement

2. You must know the range of magnitudes and

frequency that the measurement is expected to exhibit.

3. Examine the available Sensor principles for measurement of desired quantity.

4. The selected sensor should be able to withstand

the environmental conditions

5. etc


Modern car


Sensors are used for

1. Measurement of motion

2. Measurement of Temperature

3.Measurement of light

etc


Measurement of Motion

� Sensors are used to measure motion

� Motion is the change in the physical position of an object, and Encompasses several variables.

� sensors which measure the following types of motion

� Linear displacement

� Angular displacement


Displacement

Displacement is the magnitude and direction representing a change in Position of a body or point with respect to a reference point.There are two types of displacement sensor, these are

� Liner displacement is a displacement in a fixed position

� Angular displacement is the angle turned through

by a body about the given axis


Linear displacement

The most known Liner displacement

measuring sensors are

�Linear potentiometer

�Strain gauge

�Variable capacitor sensors

�Magnetic sensors

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Sensors (Transducer) - Electrical and Computer Engineering · Sensors (Transducer) ... direction representing a change in Position of a body or point with respect to a reference point