| 摘要 |
PURPOSE:To prevent a high voltage from being induced in a detecting coil, by providing a transformer where the primary side is connected in series to an exciting coil and the secondary side is connected in series to the detecting coil. CONSTITUTION:The eddy current due to the action between the magnetic field and the ultrasonic wave arriving at the surface of materials 1 is detected by a detecting coil 6 and is inputted to an amplifier 12 through a secondary winding 16 of a transformer 14. At this time, since the primary side of the transformer 14 is cut off by a discharge tube 11, the circuit of the detecting coil 6, the secondary winding 16, and the amplifier 12 are not affected by the state of the primary side at all. When the voltage between terminals of a capacitor becomes a certain value or more, discharge occurs in the discharge tube 11 to constitute a serial resonance circuit, and a high frequency pulse current is flowed in an exciting coil 5 and the primary winding of the transformer 14. Since the exciting coil 5 is provided near the surface of materials 1, an eddy current is generated in materials 1, and an ultrasonic wave is generated by the interaction between the eddy current and the magnetic field. |
