| 摘要 |
PURPOSE:To reduce the loss of an electromagnetic ultrasonic transducer so as to improve the sensitivity, by providing a ferromagnetic core provided with grooves on the surface of a magnetic pole and putting plural rectangular coils on the core and unnecessary two sides of the rectangular coils in the grooves. CONSTITUTION:The transducer is composed of two magnet blocks 11, a small magnet 11', two cores 13, in which grooves 15 are formed at fixed pitches, and plural coils 14. The two magnets 11 are set in such a way that the upper sides are fixed by supports and the bottom sides are stuck to the cores 13. The small magnet 11' is put between the two cores 13. Two sides of the coils 14, which are unnecessary for producing Lorentz forces running beside the coils 14, are put in the grooves 15 of the cores 13. Moreover, wound directions of adjacent two coils are opposite to each other. In such structure, a magnetic flux B produced by the magnets 11 through the cores 13 is normal to the surface of an object 10 to be inspected. In addition, AC magnetic fluxex produced by the coils are condensed to the object 10 to be inspected, because the cores are provided.
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