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