Sensors

Platinum is used for a variety of sensor applications, including oxygen sensors in car exhaust systems. Oxygen sensors are used to help run a gasoline engine more efficiently. The oxygen content is related to the amount of unburned fuel remaining in the engine. The sensor is made of a porous platinum coating on both the inside and the outside of the zirconia tube. The outside is exposed to the exhaust, whereas the inside remains exposed to normal air.

The zirconia tube is heated by the exhaust and becomes an ionic conductor. As the oxygen content in the atmosphere of each platinum sensor is different, there will be a potential difference between them. This difference is monitored, and changes are used to control the fuel flow through the engine to ensure that the gas/fuel mixture allows for complete combustion of the fuel.