Oxygen Sensor: Description and Operation

Heated Oxygen Sensor:

The oxygen (O2) sensor, which is mounted in the exhaust flow, monitors the amount of oxygen in the exhaust gas. The sensor has a closed tube made of ceramic zirconia. The inner surface of the tube is is exposed to atmosphere while the outer surface is exposed to the exhaust gas. The differences in oxygen content makes the sensor generate an electrical current. To enhance the generating capacity of the zirconia, the tube is coated with platinum.
A richer A/F mixture equates to a higher voltage (Approx. 1 volt).
A leaner A/F mixture equates to a lower voltage (Approx 0.1 volt).
The ECU interprets the voltage change as the stoichiometric point and will attempt to control the injector duration, ignition timing and several other systems to maintain that condition.
To enable the sensor to reach operating temperature, a heating element is incorporated inside the housing. The heater enables the 02 sensor to reach operating temperature in a matter of seconds, as opposed to minutes as with non heated models. The main advantages of a heated sensor are, better driveability and lower emissions during warm-up.