Measurement and Instrumentation in Engineering

Principles and Basic Laboratory Experiments

Francis S. Tse, Ivan E. Morse

• Publisher: CRC Press
• Year: 2018
• ISBN:
  9781351432764
• Edition: 1
• Topic: Tecnología e ingeniería
• Subtopic: Ingeniería eléctrica y telecomunicaciones

Presenting a mathematical basis for obtaining valid data, and basic concepts inmeasurement and instrumentation, this authoritative text is ideal for a one-semesterconcurrent or independent lecture/laboratory course.Strengthening students' grasp of the fundamentals with the most thorough, in-depthtreatment available, Measurement and Instrumentation in Engineeringdiscusses in detail basic methods of measurement, interaction between a transducer andits environment, arrangement of components in a system, and system dynamics...describes current engineering practice and applications in terms of principles andphysical laws... enables students to identify and document the sources of noise andloading... furnishes basic laboratory experiments in sufficient detail to minimizeinstructional time... and features more than 850 display equations, over 625 figures, and end-of-chapter problems.This impressive text, written by masters in the field, is the outstanding choice forupper-level undergraduate and beginning graduate-level courses in engineeringmeasurement and instrumentation in universities and four-year technical institutes formost departments.

1

The Place of Measurement, Instrumentation, and Laboratory

1-1. INTRODUCTION

Innumerable measurements are made everyday with countless instruments. The field of measurement, instrumentation, and laboratory means different things to different people in our pluralistic society. The subject is more difficult to teach than a “traditional” laboratory course, because students tend to associate the subject with specific instruments instead of with a more general approach to the study. Hence the roles of measurement, instrumentation, and laboratory are discussed in this chapter rather than in the preface. The discussion is in greater detail than in the usual textbook introduction. Hopefully, the digression will bring into sharper focus the organization of the topics to be presented.

The book is intended as an undergraduate text and/or a supplement for a laboratory course. The objectives are (1) to examine the methodology of measurement to judge the validity of test data, (2) to present principles by which the hardware can be understood, (3) to follow the principles with applications, and (4) to suggest a sequence of laboratory exercises aimed at acquiring a working familiarity with basic laboratory instruments.

The methodology for obtaining valid measurements is discussed in the early chapters. Although numerous measurements are made, the same methodology is used regardless of the type of measurement or the instrumentation.

A measurement must be valid. When an engineer has experimental data, the first question should be: Are the data worth analyzing? Or, phrased another way: Are the data valid? What accuracy can be expected? How much of your reputation are you willing to bet? These are difficult questions, but they must be answered satisfactorily before the data analysis.

The discussions in the early chapters should enable the reader to understand the general principles of the hardware. The engineer should know what an instrument can and cannot do in an application. Few of us need to be convinced of the importance of instrumentation or reminded of proliferation of electronic instruments in recent years. The field is literally overflowing with hardware. These devices cannot be mastered by one person in a lifetime. Yet there is the uneasy feeling that the information is important and that one’s own knowledge can become obsolete. By discussing principles first, we will not be overwhelmed by details. Furthermore, we will find a means to organize the knowledge, which may otherwise appear as pieces of unrelated information.

Subsequent chapters deal with more specific measurements, such as pressure and temperature. Principles are emphasized rather than instrumentation technology. As an introductory course, the perspective presented will be more useful to readers than will the detailed coverage of specific topics.

A group of laboratory exercises is included in Chapter 10. The methodology and principles provide the necessary background for the exercises. There is no substitute for hands-on experience. Furthermore, familiarity with equipment is a prerequisite for meaningful measurements. Only simple and basic exercises are suggested. Since skill is transferable, the reader should be able to advance from the basic to more complex problems.

This book is intended as a teaching text at the junior or senior level. It is neither a compendium of transducers nor an operating manual for specific instruments. Excellent information in this regard can be found in the literature or obtained from vendors of instruments. Statistics is treated only superficially, since the text focuses on the “front end” of experimentation. Statistics can be applied after it has been ascertained that data are worth analyzing. There are excellent books available on statistical analysis and the design of experiments.

It is assumed that readers are somewhat conversant with basic subjects such as electrical networks. Alternatively, the instructor can give a brief introduction to the subjects as needed. The background of measurement is drawn from a broad range of subjects, which are separate studies in themselves. In reality, engineers must be conversant with the fields in which they intend to make measurements. For example, it is futile to measure temperature without an understanding of the heat transfer process. If the error due to the heat transfer is unknown, the temperature measured must be questioned.

With the advent of computers, digital processing of experimental data is fast becoming an important field. This is a more advanced subject but will not invalidate the basic information presented in this book.

1-2. SIGNIFICANCE OF MEASUREMENT AND INSTRUMENTATION

Measurement is the common thread that runs through the fabric of all science and engineering. In this section we briefly relate measurement and experimentation to the development of science, research, engineering design, and the manufacture of goods. Measurement and experimentation can also be justified on their own merits.

The development of science can be traced through experimentation, observation, the generalization of facts, and subsequent formulation of hypotheses and theories. Experiments supply the facts. It is easy enough to collect a massive amount of data. An accumulation of facts, however, is no more a science than a pile of bricks is a house. The facts must be simplified and stripped of “nonessentials” such that each item of information fits into the framework of a physical law. A law is observable experimentally, and a theory seeks to explain the law. A measurement must be valid; invalid data will lead to a faulty theory and then be verified by other erroneous experiments. After all, a theory only represents knowledge at a given time. Theories, as devised by human beings, impose on science. They do not impose on nature, for nature dictates the laws.

Measurement is a vital link in the chain of events in research and development. The chain begins with a definition of the problem and objectives, and ends with the utilization of information. The events can be involved, but the chain is only as strong as its weakest link. Valid measurement is no less important than any other phase of the work.

Experimentation is an integral phase of engineering design. Theories predict the performance of a design. Experimentation measures what actually happens. Theoretical analysis and experimental verification are complementary, and together they form the basis of our design method.

Measurement is necessary for proper operation, maintenance, and control of equipment and processes in manufacturing. Proper maintenance and control are the prerequisites for efficient production, which is the ultimate payoff in manufacturing. Without the means for measurement, automation would not be feasible. In fact, the industrial revolution was made possible through the introduction of mechanical ...