| 摘要 |
PURPOSE:To enable the accurate detection of a position in an invariably stable manner by a method wherein two couples of magnetic sensors each comprising two magnetic sensors connected in series are connected in parallel and the cross point of the respective midpoint potentials of these couples is detected. CONSTITUTION:In a magnetic sensor circuit 38, magnetic sensors 38a and 38b, and 38c and 38d, are connected in series respectively, and the couples of these magnetic sensors connected in series respectively are connected in parallel to each other. When a seat belt is put on completely, accordingly, the fore end part of a magnet 32 faces the circuit 38 in proximity thereto and thereby midpoint potentials VC1 and VC2 of the magnetic sensors are varied. These midpoint potentials are compared by a comparator 39b, and they coincide with each other when a distance between the fore end part of the magnet 32 and the circuit 38 takes a prescribed value. At this point of time, a coincidence signal is sent to a control circuit 39c. Thereby the state of fitting of the seat belt can be known certainly. According to this constitution, the temperature characteristic of the magnetic sensors is canceled even when an ambient temperature is varied, and therefore the invariably accurate detection of a position is enabled free from the effect of the ambient temperature.
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