| 摘要 |
PROBLEM TO BE SOLVED: To realize high sensitivity of a proximity sensor. SOLUTION: An MI (magnetic impedance) element 1 is arranged inside an exciting coil 2 and the magnetic flux T of an eddy current from a metallic body F is detected by the MI element 1. The oscillation frequency of an exciting oscillation circuit 5 is set so that eddy-current magnetic flux T of which the phase is delayed by 90°from exciting magnetic flux S. A timing control circuit 7 generates a sampling pulse in a prescribed period of which the center is a point of time that an exciting current from the circuit 5 becomes zero. Outputs from the MI element 1 are integrated in a pulse output period by the operation of a gate circuit 9 and a positive/negative sampling/holding circuit 10 corresponding to the sampling pulse. The integrated result is accumulated in a differential amplifier circuit 11 and compared with a prescribed threshold by a comparator 12. COPYRIGHT: (C)2003,JPO
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