PURPOSE: To achieve the reduction of dead zone by providing a filter for inhibiting the passage of signals near the frequencies of the currents flowed to an ultrasonic wave generating coil in an eddy current detecting circuit.
CONSTITUTION: An initial pulse waveform 33 based on the current directly induced in a detecting coil 7 appears in a display device 22. Next, when there is am internal defect 16, a defect waveform 24 appears, following to which the bottom waveform 25 from the bottom appears. Here, if the width of the initial pulse waveform 23 is large, i,e., if a dead zone is large in ultrasonic flaw detection, the defect waveform 24 or bottom waveform 25 is concealed and this is inconvenient, but if a band- pass filter 20 which selectively inhibits the passage of the signal of the frequency of the initial pulse waveform 23 is provided, the initial pulse waveform 23 may be considerably reduced and the dead zone considerably reduced.
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KAWASHIMA KATSUHIRO
MUROTA SHIYOUJI
NAKAMORI YUKIO
| JP44015948A |