TECHNIQUES FOR MEASUREMENT OF OXYGEN AND AIR-TO-FUEL RATIO USING ZIRCONIA SENSORS

The various techniques for measurement of oxygen concentration/partial pressure using sensors employing zirconia electrolytes are reviewed. Zirconia-based air-to-fuel ratio sensors used in combustion applications are also discussed. A solid electrolyte cell incorporating two electrodes on each opposing side may be used as a potentiometric oxygen sensor; this requires a reference gas and provides a logarithmic output. An oxygen pump-gauge device normally consists of two solid electrolyte cells assembled to enclose an internal volume. Pump-gauge devices can be operated in various modes requiring simple electronic circuitry. Devices operating in steady state modes incorporate a diffusion path between the internal volume and the sample gas and provide an output proportional to the oxygen concentration in the sample gas. Pump-gauges operating in oscillatory modes may be fully sealed or may incorporate a diffusion path; they enable both oxygen concentration and partial pressure to be determined.