Page 55 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Catalytic Converter Functionality Diagnosis by Means of Oxygen or AirRuel Ratio Sensors 37

exhaust gas in a rather complex manner. For relatively small concentrations of reducing agents
(CO, H2), the response of the sensor becomes significantly slower.

Migration pattern

Diffusion chamber
Vs - electrode

Vs + electrode

Fig. 14 (from [l], p. 175)

Fig. I4 shows a universal air/hel ratio heated exhaust gas oxygen sensor (UEGO) presented
by the NGK Spark Plug company. The main characteristic of the sensor is the output
proportionality for large ranges of air/hel ratio. It also exhibits faster response, improved
accuracy and superior aging characteristics.

Sensor developments crucial to measurement and exhaust emission control are presented in
[18]. A sensor with improved characteristics over the HEGO and UEGO sensors is the so
called NEEGO sensor (Non IGydihriirm Exhaust Gas Oxygen Sensor) presented in [ 191.
However this sensor is still under investigation and has not been applied yet in real OBD
measurements.