Page 388 - Understanding Automotive Electronics

2735 | CH 11 Page 375 Tuesday, March 10, 1998 1:30 PM

FUTURE AUTOMOTIVE ELECTRONIC SYSTEMS 11

The sensor configuration is shown in Figure 11.6. This sensor uses yttria
(Y O )-stabilized zirconia (ZrO ) as a diffusion element that is preheated to a
2
2
3
desired operating temperature. In actual operation, a voltage, V , is applied
s
across this element, and a current, I , flows. The theory of operation is beyond
p
the scope of this book, though it is based on the diffusion of various ions
through the element. Nevertheless, current I varies linearly with λ, as shown in
p
Figure 11.7. A measurement of the current (which is straightforward) yields a
measurement of λ.
Whether this sensor concept will be broadly applied in engine control is
yet to be determined. However, the control strategy based on air/fuel ratio
measurements has the benefit of providing emission control without requiring a
three-way catalytic converter, and at the same time achieves relatively good fuel
economy.

Figure 11.6
Linear Air/Fuel
Sensor
Configuration

FPO

UNDERSTANDING AUTOMOTIVE ELECTRONICS 375