| 摘要 |
PROBLEM TO BE SOLVED: To provide a magnetic metal sensor for detecting a micro magnetic metal piece surely with high accuracy and high speed. SOLUTION: A magnetic metal sensor 2 comprises a core 22 forming a substantially U-shaped open magnetic path, and coils 23, 24 of same polarity wound around the core 22. The coils 23, 24 are applied with a uniform field in the magnetic sensitive direction by a magnet 25. The sensor 2 is disposed such that the opening of the U-shaped core 22 faces a part to be detected where a plurality of metal pieces are arranged in parallel at an intervalλand the sensor 2 moves relatively to the arranging direction of the metal pieces. Interval g' of the coils 23, 24 in the moving directon is set to satisfy a relationship g'=(n+1/2)λ, where n is an integer of 0 or above. Difference of detection signal between the coils 23, 24 deviates positively or negatively from a threshold value, i.e., a detection signal at the time of no response of the metal piece.
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