| 摘要 |
PROBLEM TO BE SOLVED: To provide a proximity sensor which can be constituted to be very thin because a detection coil and a signal processing part are composed of one board, by which an object to be detected can be judged with high accuracy and at high speed even when the material of the object to be detected is a nonmagnetic material such as a medal, a coin or the like because a frequency is detected and which is low-cost and small. SOLUTION: A detection coil 11 composed of a printed coil and the signal processing part 12 are formed integrally on a printed-wiring board 10. The signal processing part is provided with an oscillation circuit whose oscillation frequency is changed according to the impedance of the detection coil, a plurality of frequency discrimination parts which detect the oscillation frequency of the oscillation circuit, a judgment means by which the state of the object to be detected is judged on the basis of the detection result of the frequency discrimination parts, and an output means which outputs an output signal on the basis of the judgment result of the judgment means. A through hole 17 is formed in the central part of the detection coil, and the object to be detected such as the medal or the like can be passed. The plurality of frequency discrimination parts are used, the object to be detected is judged comprehensively on the basis of a discrimination result, and the object to be detected can be judged with high accuracy and at high speed. Since the proximity sensor is formed of one board, the sensor which is small and thin can be constituted.
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