In Four Wheel Drive (4WD) vehicles, all wheels may slip and the speed reference for the ABS system cannot be measured with wheel speed sensors. Deceleration/acceleration information comes from a longitudinal accelerometer, which is either a stand alone sensor or a PCB mountable component integrated within the ABS controller or in a separate sensor cluster.
The measuring range is typically 1 to 2g. The offset stability should be better than 100mg over the temperature range and life time while the frequency range is typically 50Hz. The sensitive axis must be along the longitudinal axis of the car. Murata has a product range that covers all directions in respect to the sensitive axis compared to the sensor unit and PCB assembly. If a sensor with more demanding specification is used also hill descend control, automatic stop-start and electronic parking brake functions can use the same sensor data.