Experimental data must be valid to the desired degree of accuracy, consistent with the purpose of the experiment. Our objective here is to present a mathematical basis for obtaining valid data and basic concepts in measurement and instrumentation. This differs from some other excellent books on the subject, which tend to either describe specific instruments in detail or emphasize the design of experiments and statistical methods. The data must be valid, however, before statistical analysis is applicable.
The sources of noise and loading are identified and documented in order to obtain valid data in a measurement. To this end, a measuring system is examined in terms of (1) physical laws describing the interaction between a transducer and its environment, (2) modeling, basic methods of measurement, errors and uncertainty, (3) arrangement of components in a system and the interaction between components, and (4) system dynamics. These related attributes are presented in the first four chapters. The subsequent chapters are oriented toward current engineering practice and applications.
The conventional functional stages of a measuring system are described in the next two chapters. The transducer/detector stage for non-self-generating transducers is presented in Chapter 5. It takes the viewpoint that if a physical law describing a transducer relates several variables, then it can be used to measure each of the variables if only one of the variables is desired, and all others are undesired and are sources of noise. The intermediate stage for signal conditioning and the terminal stage for data utilization are treated in Chapter 6
Current engineering practice for measurements of motion, flow, and temperature are described in greater detail in Chapters 7, 8, and 9. Some topics of interest, such as acoustics, are omitted in order to limit the size of the book. There is no unique method to classify transducers. Evidently, many phenomena or physical laws can be used to measure a variable, such as a temperature. The other side of the coin is that the same phenomenon can also be used to measure many variables. For example, a strain gage is susceptible to both strain and temperature. Thus, a resistance wire can be a strain gage or a temperature sensor. The deduction is that any object that has a property influenced by a variable is potentially a transducer for that variable. By viewing measurement from physical laws and effects, the current practice in measurement can be extrapolated to future needs. For example, if a physical law relates flow, temperature, tubulence, and drag force in an equation, then heat transfer, turbulence, or drag force can be utilized for the construction of a flow transducer. Again, the equation also points at the possible sources of noise in a flow measurement.
The laboratory experiments in Chapter 10 complement the text material. Basic, general-purpose laboratory instruments are the equipment required, and the capital investment for the equipment is nominal for an engineering laboratory. The experiments are given in sufficient detail to minimize the instructional time. Some topics are used as demonstrations in order to cover the scope of a broad study, but many other suitable experiments, such as an air gage, a transistor amplifier, or digital techniques, are not included in order to limit the size of the book.
This book is suitable for a concurrent lecture and laboratory course at the junior level in engineering. The prerequisite is basic electrical network. The concurrent laboratory may be the first laboratory course in the engineering department. It is difficult to synchronize the lectures and the laboratory at times, and we wish to ask the instructor and students for their indulgence. When the experiments are used for an independent laboratory course, the laboratory session is preceded by a lecture, and the other chapters are used as references. The book is suitable for a senior or beginning graduate level course in measurement and instrumentation if students have prior laboratory experience.
The book includes a wide scope of material, and the selection of topics is fairly flexible. Chapters 1 and 2 and parts of Chapter 3 give the framework for a course in measurement. The instructor may wish to select topics from other chapters to utilize the background of students. Our experience is that it is difficult to teach a meaningful lecture course on the subject to students with no prior laboratory experience, or without an associated laboratory course.
We wish to acknowledge our indebtedness to friends and students for their suggestions, to the authors listed in the references, and to those who have contributed to this area. Particular thanks are due to Professors Kurt S. Lion and Peter K. Stein, who pioneered in the field of measurement.
Francis S. Tse
Ivan E. Morse