Seat belt tension sensor

摘要

A sensor of Giant magneto-resistive (GMR) type is attached to a seat belt anchor bracket. A seat belt passes through an opening in the bracket and is doubled back and sewn to form a loop. A magnet positioned on a sliding carriage is biased away from the sensor by springs. A seat belt loops around the carriage, and when tension is applied to the belt, the carriage with the magnet is drawn against the springs toward the GMR sensor. The GMR sensor measures the magnetic field present at the sensor and a microprocessor determines belt tension based on the known spring constants and the strength of measured magnetic field which is correlated with displacement of the magnet.