| 摘要 |
PURPOSE:To improve the flaw detection accuracy by applying an exciting current varied in the test frequency to a plurality of detection coils. CONSTITUTION:A plurality of detection coils 121, 122...12n are arranged in the proximity of work 11 and separately connected to single frequency eddy current flaw detectors 131, 132...13n. The detection coils are wound on the same bobbin. The length, diameter and the number of turns of the coils are determined so that test frequencies f1, f2...fn are roughly equal in the response range on the surface of the work 11 thereby enabling the removal of noise factors in the signal processing process. An induction voltage from the detection coils is separated into components of test frequencies with bandpass filters 161, 162... 16n to detect the phases thereof. The phases detected are computed linearly with an adder/subtractor 19 and the results are indicated on a display 20. |
