Our customer approached us to reverse engineer a product after reviewing our steel sensor capabilities. Initially this led to a shock sensor project but as the project progressed, it developed into an entirely new solution that would result in a full sensor package.

HSI Sensing developed a sensor package to included two different buckle sensors: A magnetic shield in a dome housing to detect any tampering of the magnetic fields surrounding the shock sensor and finally the shock sensor.

This new seat belt sensor is now used on private and commercial jets to detect if the belt is buckled. When buckled, the sensor tells the control unit to arm the airbag system in the strap of each belt. The sensor is also designed to sense only the ferrous buckle “connector” and not sense the nonferrous components. For child booster chairs, there is an extender and this nonferrous connector does not activate the airbag system.

HSI Sensing’s seatbelt sensor product incorporates a finely tuned steel sensor that detects the specific makeup of the supplied connectors. The sensor can detect the difference between a ferrous (iron containing) buckle and a non-ferrous one (not containing iron). The magnetic bubble is altered by the iron in the buckle activating the switch. The non-ferrous buckle does not elicit a reaction from the magnetic bubble and will not activate the switch.

The switch used in this seatbelt sensor package is the HSR-004, mainly due to its small size. It is only required to carry a signal load and has a center gap making it optimal for the sensor arrangement.