Techniques and Mechanisms in Gas Sensing

This book continues the Adam Hilger series on sensors. One of the earlier volumes in the series, "Solid State Gas Sensors", set out the operating principles of the three types of solid-state gas detection devices that are currently in widespread use. The present book is designed to cover all the remaining techniques in gas sensing that are well established commercially and to take up new aspects of the mechanisms of some of the solid-state devices that were not covered earlier. The two volumes are thus intended to be complementary, between them covering all the major large-volume gas sensing methods that are current or emerging. The present volume includes descriptions of new designs of solid electrolyte sensors (for oxygen) and semiconductor gas sensors based on the response characteristics of a wide range of inorganic oxides and of metallo-organic materials. Separate chapters are devoted to considerations of the role of oxide species on semiconducting oxides and to spectroscopic methods of studying surface reactions. The contribution of liquid electrolyte electrochemical sensors is thoroughly treated. Other well-established techniques that are covered include the use of colour change methods, the exploitation of magnetic effects, infra-red spectroscopic methods and a range of methods of humidity sensing. Techniques that are expected to provide advantages in the future are described in chapters devoted to field-effect transistor based gas sensors, surface acoustic wave devices, fibre optic gas sensors and the exploitation of pattern recognition methods. This last chapter is of great relevance for any of the techniques where the response of fundamental device is prone to interference. The methods described point the way to increased reliability of measuring individual analytes and to the possibliity of simultaneous treatment of several analytes in a gas mixture.