Zirconia oxygen sensor
No free O2 ==> 0.8 V
Free O2 ==> 0.0 V
The oxygen sensor in your automobile's exhaust system keeps the car efficient and the air clean. How does it work?
There are two types of oxygen sensors, zirconia (zirconium dioxide) and titania (titanium dioxide). General Motors automobiles use the zirconia type described herein.
When the zirconia sensor is hot, it responds to the presence or absence of oxygen in the vicinity.
If there is a dearth of free oxygen, as when unburnt fuel is present in the exhaust, the sensor generates a voltage of somewhat over 0.8 volts.
If there is free oxygen present, the sensor generates zero voltage.
The automobile's computer automatically adjusts
the flow of fuel to keep the sensor reading approximately 0.4 volts, thereby
keeping the fuel mixture ideal.