Sensors (Transducer) Introduction By Sintayehu Challa

Transcription

1 Sensors (Transducer) Introduction

2 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 NEQ Force, Light, Temp, etc Sensors EQ Voltage, Current Resistance, Inductance, Capacitance,

3 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.

4 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

5 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

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10 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

11 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

12 Primary and Secondary Sensor Sensors can be selected on the methods of application can be classified as primary and secondary sensors. NEQ Load Cell NEQ Strain gauge EQ Weight (Primary (Secondary Resistance Sensors) Sensors)

13 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 NEQ Force, Light, Temp, etc Active Sensors EQ Voltage, Current

14 Passive Sensor Passive sensors require external power source for energy conversion NEQ Force, Light, Temp, etc Passive Sensors EQ Resistance, Inductance, Capacitance,

15 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.

16 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

17 Contd. 3. Voltage Generating Sensor Thermocouples and Thermopiles Photovoltaic Cells Piezoelectric Transducer 4. Sensor Based on variable Magnetic Coupling The LVDT Synchros and Resolvers

18 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

19 Modern car

20 Sensors are used for 1. Measurement of motion 2. Measurement of Temperature 3.Measurement of light etc

21 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

22 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

23 Linear displacement The most known Liner displacement measuring sensors are Linear potentiometer Strain gauge Variable capacitor sensors Magnetic sensors