The Body Control Systems North America (BCS-NA) division of TRW Automotive offers contactless magnetic sensors, including the Seat Track Position Sensor (STPS) for advanced multi-stage airbag system applications.  This device provides an input to the deployment algorithm when the seat is too close to the airbag so operation in a de-powered mode is enabled.

The patented design is contactless, self-contained and completely sealed against any environment.  It employs a simple, low-cost magnetic circuit.  The 2-wire Hall effect-based sensor is easily packaged on the seat track and can be arranged such that no external ferrous target is needed. 

The STPS operates with a large sensing air gap.  Shielding against external fields is provided by a patented clip-in bracket with audible engagement confirmation.  The large sensing face reduces the flux density in the working air gap, and consequently reduces the chance of fouling the air gap with ferrous track or foreign debris.  Excellent field performance on several OEM platforms has demonstrated that this device has proven, real-world functionality and overall value.

Other magnetic-based sensors are available from BCS-NA, including a linear version of the STPS that provides a radiometric output throughout full seat travel.