Sensor Technology:
NOx OBD Application
The NGK NOx sensor for reducing NOx tail pipe emission is a stand alone component. This means no further calibration is required. Easy system integration can be done by CAN Bus.
It can also be used for On-Board Diagnosis (OBD).
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No additional hardware in engine ECU required.
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Software-control driven by microcontroller.
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Bidirectional digital data transmission to/from engine ECU via CAN Bus.
The NOx sensor provides three signals in parallel:
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Binary λ
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Wide range λ-signal
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NOx signal
Design Concept of the sensor:
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Binary λ-signal: The binary λ-signal is obtained by measuring voltage between reference and main pump electrode (=Nernstian voltage), Wide range λ-signal: The exhaust gas penetrates into the first cavity and the main pumping cell controls O2 concentration at low ppm levels. In this condition, NOx will not be decomposed but all rich gases, such as HCs, CO and H2 will be oxidised. The resulting pumping current is proportional to the wide range λ-signal.
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NOx signal: The exhaust gas with less oxygen and without rich gas will penetrate into the second chamber. In the second chamber, Oxygen concentration is further reduced in order to decompose NO into Oxygen and Nitrogen, using the catalytic activity of a measuring electrode. This generated oxygen is measured as the NOx signal.
