Oxygen sensors

Recent progress in the development of oxygen sensors mainly for automotive use is reviewed, together with a description of our trial. Three types of oxygen sensors, i.e., concentration cell (zirconia sensors), oxide semiconductor (TiO2 sensors) and electrochemical pumping oxygen sensors (limiting current sensors) are now available for control of the air—fuel ratio of engines. Introduction of thin-film and micromachining technology to the fabrication of oxygen sensors is now in progress and will aid the development of a new generation of sensors.