Page 376 - Understanding Automotive Electronics

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DIAGNOSTICS 10

Figure 10.18
Airbag Deployment
System

Under normal driving conditions the acceleration at the accelerometer
locations is less than 1 g. However, during a collision at a sufficiently high speed
the signal increases rapidly. Signal processing can be employed to enhance the
collision signature in relation to the normal driving signal. Such signal
processing must be carefully designed to minimize time delay of the output
relative to the collision deceleration signal.
After being processed, the deceleration signal is compared with a
threshold level. As long as the processed signal is less than this threshold the
driver circuit remains deactivated. However, when this signal exceeds the

UNDERSTANDING AUTOMOTIVE ELECTRONICS 363