Callegaro L. Electrical Impedance Principles, Measurement, and Applications

CRC Press Taylor & Francis Group, 308 p, 2013.Motivation The interest in the accurate measurement of electrical impedance is shared by scientists and engineers from different backgrounds.Impedance measurements can be performed on an impedance standard, to perform a calibration and issue a calibration certificate. Electromechanical appliances and electronic components can be characterized by impedance measurement to identify the parameters of their equivalent electrical model. Properties such as resistivity, permittivity, and permeability of material samples can be derived from impedance measurements conducted with proper electrical fixtures. Biological quantities related to a tissue, or even to a living being, can be related to their impedance. Sensors of many physical quantities can have electrical impedance as their output.Impedance spectroscopy permits to follow the evolution of an ongoing electrochemical reaction; impedance tomography is an imaging technique.Despite such a broad range of existing applications, and the potential for new ones, high school and university courses show a marginal interest in the subject of impedance measurement. Often, impedance measurement techniques are described as minor variations of the corresponding DC resistance measurements; recent publications may cite obsolete measurement techniques.Difficulties When performing an impedance measurement, the experimenter faces conceptual and practical difficulties that are not encountered in resistance measurements. Voltages and currents become geometry-dependent quantities, and different parts of the measurement circuit can interact in unexpected ways because of mutual capacitances and inductances. Even commercial impedance meters ask for careful wiring techniques, which may involve several conductors. The measurement result can be expressed in a variety of representations, related by non-trivial mathematical transformations, prone to be misinterpreted.Outline Chapter 1 recollects the main definitions of the quantities related to impedance, some theorems of particular interest, and the issue of impedance representation. Chapter 2 introduces the problem of impedance definition and electromagnetic ways to distinguish the impedance to be measured from the environment. Chapter 3 gives a list of devices, appliances, circuits, and instruments employed as building blocks of impedance measurement setups. Chapter 4 attempts a classification of main impedance measurement methods, and the importantly gives details on their implementation when a specific impedance definition is chosen. The increasing use of mixed-signal electronics in impedance measurement setups is discussed in Chapter 5.Chapter 6 gives a list of applications and some details on the measurement of electromagnetic properties of materials.Chapters 7 to 9 are devoted to impedance metrology. After Chapter 7, an introduction, Chapter 8 is devoted to artifact impedance standards, the material basis of measurement traceability. Chapter 9 deals with primary metrology: the realization and reproduction of SI impedance units.Limitations The science of impedance measurement spans more than 150 years, and even a condensed recollection of all important theoretical results, measurement methods, and implementations is beyond the scope of the book and, frankly, of the author’s capacity. A large part of circuits reported are principle schematics; equations expressing a measurement model are reported without an explicit derivation. No operative measurement procedures or troubleshooting techniques are reported. No hint about the expression of measurement uncertainty is given.References and further reading As a partial compensation for the reader for the limitations listed above, every time this limitation was particularly apparent the author tried to include references to excellent papers reporting the pregnant details omitted in the book.The choice of references included does not follow any systematic criterion, and no attempt for completeness has been pursued. Whenever possible, milestone or recent papers in the English language, published in peer-reviewed journals, have been preferred over conference papers and technical notes.Just a bunch of references to review papers and books are present because only a few have been published in the recent past. When a historical reference is given, it is usually the first one the author is aware of; the choice does not imply serious historical research.Acknowledgments I wish to thank my colleagues, Walter Bich and Massimo
Ortolano (Politecnico di Torino, Italy), for their critical reviewing.