The systematic experiment

Book Review Books that provide general coverage of experimental techniques and instrumentation operating principles are useful as teaching tools for undergraduate engineering students and as references for practicing engineers and scientists. The Systematic Experiment, a recently published book of this type, is reviewed in this issue of the Journal. The Systematic Experiment, J. C. Gibbings, editor, Cambridge University Press, Cambridge, U.K., 1986, 352 pages, $19.95 (paperback). The Systematic Experiment is structured to be an introduction to methodologies for the planning and execution of scientific experiments for undergraduate engineering students as well as a reference text for practitioners. Chapter 1 is mostly introductory, giving a historical perspective of the importance of experimentation to the advancement of science. Chapter 2 gives procedures and guidelines for the planning of experiments. While many of the considerations discussed in it are obvious, this chapter nevertheless provides a useful checklist for preliminary planning of experiments. Particularly useful items include the assessment and determination of the most important variables, critical path analysis, and the use of Gantt charts for planning experimental programs. Considerations regarding the design of the experimental rig are also discussed. Chapter 3 focuses on the statistical design of experiments. This chapter provides an introduction to the statistical assessment of different experimental strategies for determining the effects of several variables on a specific system parameter. The examples provided, however, are abstract, and some undergraduate students may struggle to follow them and/or relate them to real physical systems. This section also introduces the use of Yates analysis as a simple method of assessing statistical trends in data. Chapter 4 describes the benefits of dimensional analysis in planning experiments, showing how this technique can be used to reduce the number of parameters in the problem, eliminating those that will not strongly affect the results. The fundamentals of dimensional analysis are described briefly in Appendix 1. The latter portion of Chapter 4 presents a detailed discussion of the use of scale models to experimentally examine the behavior of large systems. Chapter 5 covers the general aspects of making measurements with various types of instrumentation and equipment. The sensitivity, resolution, and dynamic response of the instrumentation and the degree to which it interferes with the physical mechanism of interest are all discussed. The operating principles of a number of different types of instrumentation are briefly described, including techniques for measuring length, time, speed, mass, force, torque, and pressure. The latter portion of this chapter is dedicated to methods of measurement in fluid flows, including the use of hot-wire and hot-film anemometers, Pitot static tubes, laser-Doppler anemometry

systems, orifice-plate flowmeters, thermocouples, and pyrometers. Chapter 6 discusses, in some detail, the use of photographic techniques in experiments. Topics covered include optical elements, lens resolution, film resolution, exposure time, picture tonal quality, film characteristics, front lighting versus backlighting, and special aspects of color photography. Many of these topics are described in considerable analytical detail. A discussion of interfacing experimental equipment to microcomputers is provided in Chapter 7. Early portions of this chapter are very basic introductions to computer logic, hardware, and software. Later sections cover the interface adapters needed to let equipment communicate with integrated circuits, analog-to-digital and digital-to-analog conversion, multiplexers, and the use of serial versus parallel ports. This chapter concludes with a glossary of technical terms related to computer applications. Chapter 8 is devoted entirely to the description of different types and sources of error. Fundamentals of error analysis are presented in Appendix 2. Chapter 9 discusses the analysis and interpretation of experimental results, with reference to a specific light bulb experiment example. The accuracy of calculations used in reducing data and graphical analysis and the interpretation of trends in plotted data are discussed in some detail. Chapter 10 covers basic elements of technical report preparation. While there are many nuggets of useful information in this book, as a text for undergraduates it is somewhat disappointing. Material on more basic measurement techniques and instrumentation is extremely brief, while the coverage of photographic methodologies seems disproportinately long, unless one has a special interest in that area. This unevenness of coverage may be unavoidable given the fact that the book represents the combined efforts of several authors. It nevertheless detracts from the book's usefulness as an instructional aid. In addition, although the book provides a useful introduction to the use of statistical methods in the planning of experiments, there is little, if any, discussion of the use of sensitivity and error analysis in the planning stages, which would seem to be of fundamental importance. It is difficult, at best, to write a book on experimental methods that pleases everyone, since each investigator has his or her own special interests and biases. While some aspects of the book seem weak, it does have strong areas, which may make it useful to some investigators. Its introductory discussion of photographic techniques, for example, is particularly good. The usefulness of this book may therefore depend on the reader's interests and the depth of coverage desired.

Experimental Thermal and Fluid Science 1989; 2:122 © 1989 by Elsevier Science Publishing Co., Inc., 655 Avenue of the Americas, New York, NY 10010

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VAN P. CAREY Mechanical Engineering Department University of California at Berkeley

0894-1777/89/$3.50