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Crash Sensors

If a collision should occur, intelligent sensors trigger off the occupant restraint systems at the correct moment. The crash sensors must be able to detect a collision and convert it into corresponding signals within a matter of milliseconds. The nerve centre of this system is the airbag control unit, which decides whether to activate it and, depending on the nature and severity of the crash, deploys the airbags and belt tensioners. The control unit installed centrally in the vehicle contains sensors which determine the pattern and severity of a frontal or side impact at an early stage. Additional, remote crash sensors are also located on the vehicle to assist with crash detection.

The measurement principle employed by the crash sensors is usually based on the effect of inertia. When a vehicle is stopped abruptly by an impact, all bodies or objects which are not firmly fixed to the vehicle will continue to move at the impact speed.
The sensors’ design enables them to measure this acceleration and relay it to the control unit as usable data.
Many Volkswagen models are fitted with ultra-fast pressure sensors in the front doors to detect a collision from the side. When the vehicle is hit from the side, the outer door panel is pushed inwards, creating excess pressure inside the door. If the change in air pressure exceeds a certain limit, the sensor will relay a corresponding signal to the airbag control unit. Acceleration sensors are furthermore fitted in the vicinity of the C-posts so that collisions from the side can also be detected in time.