Yamaha 2002 TDM900 Service Manual page 26

O sensor
2
The O sensor has been adopted to enable the catalyst to function at a high degree of efficiency by
2
maintaining the air-fuel mixture near the stoichiometric ratio (14.7 : 1). This sensor, which is a zirconia
type, utilizes the oxygen ion conductivity of the solid electrolyte for detecting the oxygen concentration
levels. In actual operation, a zironia tube made of solid electrolyte is exposed in the exhaust gas, so
that the exterior of the zirconia tube is in contact with the exhaust gas and the interior is in contact with
the atmosphere whose oxygen concentration level is known. When a difference in the oxygen con-
centration level is created between the outside and the inside of the zirconia tube, the oxygen ion
passes through the zirconia element and generates an electromotive force. The electromotive force
increases when the oxygen concentration level is low (rich air-fuel ratio) and the electromotive force
decreases when the oxygen concentration level is high (lean air-fuel ratio). As electromotive force is
generated in accordance with the concentration of the exhaust gas, the resultant voltage is input into
the ECU in order to correct the duration of the injection of fuel.
Inner cover
1
Outer cover
2
Zirconia tube
3
A Exhaust gas
B Atmosphere
1-15
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