PURPOSE: To detect various shape defects, by synthesizing a signal having a low frequency and a signal having a high frequency, which are synchornized with each other, to flow them to a probe coil and detecting the change of the impedance for each frequency component.
CONSTITUTION: Square waves which are synchronized with each other and are different in frequency are outputted from an oscillator 11 and are converted to corresponding sine waves on a basis of signals transmitted to locking oscilators 13 and 14 through a changeover switch 12 and are synthesized by frequency mixer 15 and 16. The synthesized signal selected by a mode changeover switch 17 is amplified and is applied to a test coil 19. The change of the impedance of the test coil 19 which is generated by the interaction upon the eddy current induced in an object 30 to be examined is detected for each frequency of a specific phase angle level with detection timing pulses 11aW11d outputted from an oscillator 11 of a signal detecting circuit 22. Thus, the examination is performed by plural signals simultaneously, and various shape defects are detected simultaneously.
NAKADA EIJI
HOSOKAWA TAKAHITO
ABE NOBUAKI
YONEZAWA MAKOTO
FURUSAWA KAZUHIRO
TOKUSHU TORYO KK
| JPS50129090A | 1975-10-11 | |||
| JPS5233791A | 1977-03-15 | |||
| JP57093853B |
| US4303885A | 1981-12-01 |