Oxygen Sensor: Description and Operation

Fig. 31 Exhaust gas sensor:

The exhaust gas sensor, Fig. 31, consists of a closed end tube of ceramic zirconia contained in an open ended holder. Porous platinum electrodes cover the inner and outer surfaces of the tube. The closed end and outer surface of the tube contact the exhaust gasses, while the inner surface of the tube contacts air. The electrical signal is generated corresponding to the difference between the oxygen pressure at the outer surface (exhaust gas) and the oxygen pressure at the inner surface (air), which remains constant. The electrical signal is monitored by the fuel system, which adjusts air/fuel ratios accordingly.