Electronic Measurement Systems. Theory and Practice 2nd edn

An ambitious title indeed, bearing in mind that electronic techniques are employed in virtually all serious measurement situations. The author has attempted to present a comprehensive review of the whole field of measurement. He starts off by giving a systems view, where functional structures of measurement systems are reviewed, followed by an examination of signal structures or types: transient, (rather curiously termed `unique' by the author), periodic, samples and stochastic. System organization is also considered, centralized and distributed. Unusually for an introductory review chapter, the reader is then inundated with the fine details of IEE 488, and various bus systems. Some of the building blocks of electronic systems are presented in the next chapter. This is more than a simple catalogue; it gives thumb-nail sketches of the modes of operation of all the main building blocks: operational amplifiers and related analogue circuits, A/D and D/A converters, digital circuits and programmable logic, without going into too much detail. The Wheatstone bridge sits rather uneasily as the final topic in this chapter. The chapter which follows comes closer to the kernel of the design of a measurement system: specification. The author first considers factors such as resolution, accuracy, sensitivity, linearity, offset and drift, reliability and throughput. The treatment is very brief and is largely carried out by way of examples. Consideration is then given to the use of feedback to improve the performance of electronic systems. Finally a microprocessor-based measurement system is described. There then follows a chapter giving a review of elementary reliability theory. This is obviously an area in which the author has a particular interest; the flavour of this chapter is rather more exciting. From this point onwards, the reader begins to meet a dedicated instrumentation practitioner. The chapter on transducers which follows aims to review the whole range of available sensors or transducers and there is an attempt to categorize transducer types. Inevitably, because of the breadth of the field, such a treatment will swing between the detailed and the superficial, as no single author can be expected to have the same level of expertise in all areas; this chapter is no exception. However, as a first reference point for an engineer embarking on a new design in an unfamiliar field, it provides a useful starting point for further investigations. There are gaps, however, and a second opinion may be needed from other sources. Offset and drift are given rather more detailed consideration in the chapter which follows. Some sources of offset and drift in bipolar and MOS transistors are described; rather surprisingly there is no consideration of the Seebeck effect in amplifier circuits, which can be a significant source of errors, although it has been previously described in the discussion on transducers. In the chapter on guarding and shielding we have the practical man speaking: techniques for improving the performance of a measurement system in practical situations are presented. Although the treatment of each aspect is short, the measurement practitioner will find this chapter useful. Noise is the subject of the next two chapters. In the first, methods of calculating the noise performance of a system are described, and a common fallacy regarding the use of `noise figure' is demolished. The second is a review of some of the physical effects which give rise to noise in circuits. The manufacturing technology of semiconductor circuits has now improved to such an extent that the noise performance predicted by consideration of Johnson noise and shot noise is very close to that observed in practical circuits. However, noise arising from surface or trapping effects, observed as 1/f noise, is still not completely understood, and is often the over-riding source of error in some measurements. It is disappointing therefore that so little consideration is given to this form of noise. The chapters which follow serve to round off the whole work. The chapter on interfacing to sensors is actually a closely focused treatment of methods of taking the output from a Wheatstone bridge using electronic circuits. Although the linearization of a bridge by feedback is introduced, the explanation is not clear for such an important technique. The final chapter is a very brief view of ergonomic aspects of instrument design. Although many aspects of the measurement of physical quantities have been covered, it is surprising to find that there is no mention of the charge amplifier and its use in interfacing to charge-producing or capacitive sensors. A reader new to the field will therefore not learn that piezo-electric accelerometers are measured using charge amplifiers, nor that the measurement of radioactivity is effectively ignored. One could go on to catalogue other examples of important measurement principles which have not been treated: the feedback accelerometer, for example, one of the cornerstones of space instrumentation and inertial navigation. However, to do so would be to ignore the main purpose of this book, which is intended as an undergraduate text. In this sense, the title is misleading, as it implies a greater and deeper coverage than that which the reader will find. Is it therefore useful as a course textbook? Here the reviewer must give a qualified `yes'. It serves to bring together in their proper perspective many elements which will have been treated to greater depth in other lecture courses. It is also suitable for undergraduates on other science based courses, especially in disciplines which make extensive use of electronic measurements. It could also provide useful reference material for technicians who are often called to provide instrumentation for scientific research. However it will not replace standard works such as Lion's 1959 book on transducers, or Oliver and Cage's 1971 book on electronic measurements and instrumentation, for example, for breadth and depth.