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Planar sensor diagram
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As the new, stricter, NLEV (national low emission vehicle), California's LEV (low emission vehicle), ULEV (ultra low emission vehicle) and SULEV (super ultra low emission vehicle) standards all begin to take effect, it has necessitated newer and more exact air/fuel monitoring technologies. Critical to conformance of these new clean air standards is reducing emissions on cold vehicle start up. This has required the advent of the new Planar Air/Fuel sensors and the 5 wire Wide Band oxygen sensor.
PLANAR SENSORS
A Planar sensor may also be referred to as an Air/Fuel Sensor. The Planar design and operation is very similar to the zirconia sensor with the main exception being the design of the internal element itself. In the traditional zirconia sensor the sensor head was a thimble style design. The new planar style is a flat strip (or geometrical plane, thus referred to as planar). The zirconia ceramic, platinum electrode and heater are laminated together on a single wafer. Like its predecessor, the zirconia sensor, it constantly monitors and sends a voltage to the ECU based on the oxygen content in the exhaust gas versus outside reference air. The ECU uses this information to maintain a stoichiometric air/fuel ratio. The difference in the Planar sensor is it’s smaller and lighter as well as less susceptible to contamination. It also has an improved internal heater which brings it to operating temperature much faster (apx. 10 seconds), thus reducing cold engine emissions. |
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