Front passenger seat occupancy detection

The front passenger seat occupancy detection detects whether the seat is occupied or not. The seat occupancy mat consists of conductor paths and pressure sensors. The conductor paths are connected to the electronic evaluation unit.

Fig 1: Identifying Seat Occupancy Mat With Pressure Sensors

Courtesy of BMW OF NORTH AMERICA, INC.

When a weight is placed on the seat, resistance in the seat occupancy mat changes. The seat occupancy electronics evaluate this change in resistance ("seat occupied" or "seat unoccupied" status).

The seat is recognized as being not occupied up to a weight of approx. 12 kg. The seat occupancy detection function, however, also depends on the type of seat. For example, the material tension in a leather seat or a taut sports seat is already interpreted as pressure on the sensors. In such cases, a weight below 12 kg can trigger the "seat occupied" condition.

The signal is sent across a direct line to the MRS control unit. The signal is only required for the seat belt warning. For example, if the passenger's seat is recognized as being occupied without the seat belt buckle switch sending a signal, a fasten belt warning will be emitted.