| 摘要 |
PURPOSE:To shorten a working time through simplification of inspection and to miniaturize a device, by methode wherein a surface fault and an internal fault are found by one probe. CONSTITUTION:If coils 4A and 4B are excited by an output of a pulse generating circuit 8 under an exciting condition of a DC coil 2, an eddy current of each frequency component is generated on a surface of a material 1 to be tested, an ultrasonic wave is produced resulting from the mutual action with a DC magnetic field. The ultrasonic wave is reflected by a fault in the material 1 to be tested or a bottom, it reaches the surface of the material to be tested again, and an eddy current is produced in a reverse action to that of the ultrasonic wave at a producing time on the surface of the material to be tested. The eddy current is detected by coils 5A and 5B, a differential voltage thereof is tuning-amplified (9) as a fault signal, and a given process is conducted by a signal processing circuit 10 to display it as an internal fault signal by means of a display device 11. A difference in a detecting voltage between the coils 5A and 5B, produced in consequence of a fault in the surface of the material 1 to be tested, is signal-processed (13) through an N-BPF12 to display it as a surface fault by means of the display device 11. |
