Lambda Sensors detect and measure the presence of oxygen in exhaust gases. It then compares this information with the air sample found inside the sensor. This information is relayed to the fuel injection control unit (computer) in order to calculate the optimal air/fuel ratio mix.
The fuel injection control unit does not use the sensor signal when:
- The engine is cold – because during this period the mixture will be rich.
- In fast acceleration or in full load.
- During cut-oﬀ, as the mixture, will be poor.
The Lambda Sensor generates millivolts according to the quantity of oxygen in the exhaust gases.
The “heart“of the Lambda Sensor is the thimble-shaped part made of a ceramic material called zirconium dioxide
This thimble-shaped part is also covered on both sides with an extremely thin layer of microporous platinum. This part works as a galvanic cell (battery).
When the zirconium dioxide is heated to above 300°C (572°F) it becomes an electrical conductor, allowing the oxygen ions to move from the internal platinum layer (in contact with the atmosphere) to the external platinum layer (in contact with the exhaust gases).
The generation of a high millivoltage means that practically all oxygen that was injected in the combustion chamber has been consumed.
On the other hand, the generation of a low millivoltage means that there is more oxygen in the combustion chamber than is needed for combustion, leading to a surplus of oxygen in the exhaust gases.
The fuel injection control unit registers the generated millivoltage and adjusts the air/fuel mixture to be as close to the ideal ratio as possible.
The Lambda Sensor is one of the most important sensors in the engine management system. The sensor is critical and serves to control the air/fuel ratio, making it possible for vehicles to comply with the emissions standards set by law worldwide.
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Reference: Information Adapted from Hella Sensors Info Brochure
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