Advancement of gas sensor technology over the past few decades has led to significant progress in pollution control and thereby, to environmental protection. An excellent example is the control of automobile exhaust emissions, made possible by the use of oxygen gas sensors. Since early 1970's there have been sustained studies on oxygen sensors and has led to development of sensors for various applications with varying performance characteristics. Solid electrolyte based potentiometric, amperometric and metal oxide based semiconducting resistive type sensors are used for high temperature applications. For solution-based pollution monitoring, dissolved oxygen sensors based on Clark electrodes have played a major role. More recently, for biological and medical applications, optical oxygen sensors are beginning to have an impact. In this review, we focus on both high temperature as well as dissolved oxygen sensors and compare the different methods of oxygen sensing, discuss underlying principles, and outline the designs and specific applications. (C) 2003 Kluwer Academic Publishers.
