Instrumentation and Control Systems

Instrumentationand

Control Systems

Dr. V. Sugumaran Dr. V. MuralidharanM.Tech., (Gold Medalist), Ph.D., M.Tech., Ph.D.,

SMBS, VIT University, Chennai Campus, Department of Mechanical Engineering,Chennai, Tamil Nadu , Vandalur

Chennai, Tamil Nadu

Ravi C. TejaB.Tech., M.S. (USA)

System Control and MechatronicsChalmers University of Technology, Sweden

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INSTRUMENTATION AND CONTROL SYSTEMS

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FOREWORD

Mastery of instrumentation is a challenge. The physics of measured process, principlesof sensing, different possible sensors, and the process environment are all to be well understood and a well thought out selection made to match the application. The

book is a good balance in the sense that it does justice to all the relevant aspects. Sukumarhas organized it in a well thought out manner. Starting with the basics of measurement, thebook progresses through the need and scope of standardization and the modules of aninstrumentation scheme methodically; subsequently the schemes are dealt with in depth.Their selection and organization is from an application angle. All major application segmentsare discussed in adequate depth and detail. I am sure that the book will prove to be a valuableasset to the student community as well as the interested professionals.

Dr T.R. PadmanabhanProfessor Emeritus, School of EngineeringAmrita University, Ettimadai, Coimbatore

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PREFACE

nstrumentation and control systems are essential activities in every branch of science and technology. We need to know our body temperature, the blood pressure, temperature of the induction stove, speed of our car/bike, salt content level in the water, etc. Also, we need to control systems for water level control,

temperature control in oven, refrigerator and air conditioners. Therefore, the study of instrumentation and control systems is essential for engineering and technology students. There are a number of books available in the market on ‘Instrumentation’ and ‘Control systems’, separately. In many universities, Instrumentation and Control Systems are combined as a single subject and offered. Very few books are available in the market to meet this requirement. Students always express the need for a comprehensive text on Instrumentation and Control Systems. A small effort is taken in this direction by a group of Engineers to bring this book.

The book is divided into three parts. Part I (Chapters 1 to 7) introduces the fundamental concepts required to understand the subject. This part discusses about standards, uncertainty management, errors in the measurements and how to tackle them, characteristics of instruments, signal conditioning units, and signal presentation units. Also, if one needs to use computers for measurement and control purposes, the necessary fundamentals are presented with some sample codes.

Part II (Chapters 8 to 18) deals with individual measurement/instrumentation techniques. One can approach this part in two ways: based on type of transducers and listing the applications and the other way is to list the sensors for each of the parameters. In this book, the second approach is used, as it will be easy for the learners to get a comprehensive idea about various options available to measure a particular parameter. Part II specifically examines the principles, construction, working, advantage, disadvantage and applications of transducers for measuring displacement, strain, liquid level, force, torque, pressure, flow, density, vibration, temperature and PH.

Part III (Chapters 19 to 24) introduces control systems concepts. It gives a frame work for mathematical modeling, block diagram, signal flow diagram, time and frequency domain analysis, and stability analysis. The book is aimed at the students taking courses in ‘Instrumentation and Control’ at undergraduate and post graduate levels and the working professionals in this field.

—Authors

I

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ACKNOWLEDGEMENTS

e take this opportunity to thank Poojya Swamiji, Abhayamrita Chitanya, the driving force AMRITA, for his timely support during our critical periods. We have learnt how to help people and to whom to help, from Swamiji.

The first author conceived the idea of writing this book during his interaction with Dr T.R. Padmanabhan regarding the subject matter. The interaction was mainly informal discussions for clarifying doubts from Dr Padmanabhan. During that time he was Dean-Engineering, Amrita School of Engineering, who had already written many books in engineering including Industrial Instrumentation. He inspired many (including authors) not only by his words, but also by his dedicated actions. The pages are not sufficient to describe the enjoyable timely small stories, the way he conducted short and effective meetings and so on. May we take this opportunity to pay our accolade to a real teacher who took a lot of pain in training us for no gains.

A very similar and a saintly person there, is our Guide, Dr K.I. Ramachandran, who magnanimously and in good nature guided us. We have learnt how to give freedom to the students from him. We are extremely grateful and wish to place on record our deep sense of indebtedness and gratitude to Prof. K.I. Ramachandran, the intellectual power house, for his valuable guidance, generosity, encouragement and immense help.

Our heartiest gratitude to Dr Joshi C. Haran, Chairman-Mechanical Engineering, who laid the foundation in engineering fundamentals and insisted perfection in every minutest detail. We sincerely thank him for all that he has done to us. The authors are grateful to Dr B.K. Vinayagam, Head (Department of Mechatronics, SRM University) with whom the authors enjoyed working.

Our gratitude and sincere thanks to all people who are directly and indirectly involved in compilation of the material presented in this book.

The help rendered by Mrs. Meena Sugumaran, Mrs. Manju Muralidharan, Mr. Dhruv and Ms. Niranjana Manickam during the manuscript preparation is warmly acknowledged. We cherish the association with the Publisher while bringing out this book (in just 5 years they brought out this book). This section will be incomplete if we forget to thank the patience and efforts rendered by our family members to bring out this book.

—Authors

W

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CONTENTS

Foreword (vii)

Preface (ix)

PART I

CHAPTER 1 Introduction 3–17

1.1 Measurement 4

1.2 Why Measurement? 4

1.3 Why an Engineer should Learn Measurements? 8

1.4 What do we Measure and when do we Measure? 8

1.5 How do we Measure? 9

1.6 What is an Instrument? 9

1.7 Generalized Measurement System 9

1.8 Types of Instruments 11

1.9 Experimental Test Plan 15

1.10 Review Questions 16

CHAPTER 2 Standards 18–35

2.1 Introduction 18

2.2 Standard 19

2.3 Standard Organizations 19

2.4 A Brief history of standards 20

2.5 Definition of Base Units 22

2.6 Classes of SI units 24

2.7 Units for Dimensionless Quantities 28

2.8 SI Prefixes (Decimal Multiples and Submultiples of SI Units) 28

2.9 Non-SI Units Accepted for use with SI Units 29

2.10 SI Unit Rules and Style Conventions 29

2.11 Classification of Standards 34

2.12 Review Questions 35

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( )Acknowledgements x

CHAPTER 3 Characteristics of an Instrument 36–53

3.1 Introduction 37

3.2 Static Terms 37

3.3 Dynamic terms 49

3.4 Impedance 51

3.5 Review Questions 52

CHAPTER 4 Uncertainty Management 54–72

4.1 Introduction 55

4.2 Uncertainty in Measurement 55

4.3 Propagation of Uncertainty/Error 56

4.4 Statistical Tools 57

4.5 How to Calculate Standard Deviation? 61

4.6 Sources of Error 64

4.7 Classification of Sources of Error 64

4.8 Methods of Reducing Error Source 67

4.9 Measurement Arithmetic 69

4.10 Rules for Rounding 70

4.11 Significant Digits 70

4.12 Arithmetic Operations 71

4.13 Presenting Data 72

4.14 Review Questions 72

CHAPTER 5 Computer Fundamentals for Measurements andControl 73–91

5.1 Introduction 74

5.2 A Quick Tour Inside CPU Box 74

5.3 Getting Started…Digital Signals Out… 76

5.4 Analog Signals Out 81

5.5 Taking Signals into the Computer 82

5.6 The Basics of Making Accurate Measurements 89

5.7 Review Questions 91

CHAPTER 6 Signal Conditioning 92–111

6.1 Introduction 93

6.2 Amplifiers 94

6.3 Operational Amplifiers (OP-Amps) 97

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6.4 Filters 103

6.5 Divider Circuit 106

6.6 Charge Amplifiers 106

6.7 Wheatstone Bridge 107

6.8 Rectifiers 108

6.9 Scaling Devices 109

6.10 Review Questions 111

CHAPTER 7 Signal Presentation 112–130

7.1 Introduction 112

7.2 Electrical Display Units 113

7.3 Moving Coil Meters (Permanent Magnet Moving Coil Meters) 113

7.4 Digital Meters 120

7.5 Liquid Crystal Diode (LCD) 123

7.6 Oscilloscope 124

7.7 Recorders 126

7.8 Review Questions 130

PART II

CHAPTER 8 Displacement Measurement 133–180

8.1 Basics of Motion 133

8.2 The Need for Displacement Measurement 135

8.3 How do we Measure Displacement? 135

8.4 Potentiometer 136

8.5 Other Types of Potentiometers 143

8.6 For Rotary Measurement 146

8.7 Potentiometer for Large Displacements 146

8.8 Capacitance Type Transducer 147

8.9 Measurement of Rotational Motion Using Capacitive Transducer 153

8.10 Inductance Type Transducers 156

8.11 Piezoelectric Transducer 166

8.12 Nozzle Flapper 167

8.13 Synchro-pair (Transmitter-transformer Pair) 169

8.14 Resolver 171

8.15 Microsyn 172

8.16 Linear Inductosyn 173

8.17 Laser Interferometer 174

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Instrumentation and Control Systems

Publisher : Laxmi Publications ISBN : 9789383828500Author : V.Sugumaran,V.Muralidharan, Ravi C.Teja

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