Audi A6´05 323 Service page 25

Crash sensors for side airbag, rear,
G256 and G257
(C-pillar)
Both crash sensors for side airbag G256 and G257,
which are fitted near the C-pillar (left and right), are
conventional acceleration sensors, which were
already used for the previous Audi A6 model.
How the crash sensors work
A crash sensor essentially comprises a housing,
evaluation electronics and a micro-mechanical
acceleration sensor.
Basically, the acceleration sensor is structured
like a capacitor.
Some of the capacitor plates are fixed. The
counterparts of these are movable and work like a
seismic mass.
If the seismic mass is pushed into recording
direction during an accident, the capacity of the
capacitor changes. This information is evaluated
by the evaluation electronics and is then digitally
processed and transmitted to the airbag control
unit.
Pressure sensors, on the other hand, react to a
change in pressure conditions. The resistance of the
micromechanical sensor unit is monitored and
evaluated.
Evaluation electronics
Idle position
Movable capacitor plate
Capacitor plate
fixed
Evaluation electronics
Acceleration sensor
Crash
Direction of detection
326_003
326_025
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