Oxygen Sensor: Description and Operation

Oxygen Sensor:

The oxygen sensor is located on the exhaust manifold to detect the concentration of oxygen in the exhaust gases. It consists of a zirconia element (with a thin platinum surface coating) which generates a voltage, lead wire which carries the voltage, and cover and housing which protect the zirconia element from damage. The zirconia element, by its property, generates a voltage when a difference in oxygen concentration exists between its faces. As its temperature rises, the change of the voltage is amplified by catalytic reaction of the platinum. The oxygen sensor makes use of this property. Atmosphere is introduced into the oxygen sensor, the inside of the zirconia element is exposed to the atmosphere and outside to exhaust gases. Thus the difference in concentration between the inside and the outside of the zirconia element varies with the oxygen concentration in the exhaust gases. The large concentration difference results in about 1 volt and small difference results in about O volts. To put it in other words, if the amount of oxygen in the exhaust gases is less (air-fuel mixture is richer than the stoichiometric mixture), about 1 volt is generated and if more (air-fuel mixture is leaner than the stoichiometric mixture), almost none is generated. In this way, the oxygen sensor detects whether the oxygen concentration is high or low (or the mixture is richer or leaner than the stoichiometric Mixture).