Oxygen Sensor: Description and Operation

Oxygen (O2) Sensor:

The Oxygen 02 sensor is located on the exhaust manifold to detect the concentration of oxygen in the exhaust gases. It consists of a zirconia element, lead wire with a cover, and a housing which protect the zirconia element from damage. The zirconia element, by its properties generates a voltage when a difference in oxygen concentration exists between its faces. As its temperature rises, the change in voltage is amplified by catalytic reaction of the platinum.

The inside of the zirconia element is exposed to the atmosphere and the 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. A large concentration difference results in about 1 volt and a small difference results in about 0 volt. In other words, if the amount of oxygen in the exhaust gases is low (air-fuel mixture is rich) about 1 volt is generated, and if it is high (air-fuel mixture is lean) almost none is generated. In this way, the oxygen sensor detects whether the oxygen concentration is high or low.