| 摘要 |
PURPOSE:To detect defects of materials to be inspected by disposing a flaw detecting head consisting of a primary coil and plural secondary coils assuming a cylindrical shape in proximity to the material to be inspected, drawing out the signals by the eddy currents generated in the material time serially and detecting the signals synchronously. CONSTITUTION:AC voltage of a fixed oscillation frequency is applied from an oscillator 7 to a primary coil 16 assuming a sylindrical shape of a flaw detection head 15 disposed in proximity to a material 1 to be inspected, via a power amplifier 8. The magnetic flux generated by the coil 16 intersects the material 1. If any flaw exists in the material 1, the value of the eddy current changes and the voltage corresponding to the flaw is induced in plural pieces of secondary coils 17 disposed along the inside circumference of the coil 16. The output of the oscillator 7 is applied via a sampling pulse generator 14 to a multiplexer 10 after frequency division 13, so that the outputs of the coils 17 are drawn out time serially. The outputs are applied via an amplifier 11 to a synchronous detector 12, and the output of a phase shifter 9 is applied to the detector 12. The flaw existing in the material 1 is detected by the converted DC voltage. |
