Kabushiki Kaisha Kobe Seiko Sho

Hiroaki Yasukuni

Yoshiro Nishimoto

Shoji Nasu

Masayoshi Iwasaki

A signal processing method in an electromagnetic induction test. A test object is subjected to an electromagnetic induction by use of N (N.gtoreq.1) kinds of test frequencies to obtain M (M.ltoreq.2N) kinds of phase detection outputs corresponding to respective states of the test object. The phase detection outputs are then sampled at a plurality of measuring points so that there exists n (n&lt;M) kinds of disturbance factors of which a portion contribute to the electromagnetic induction test. The phase detection outputs have a variance greater than a variance of a target parameter of the test object and contribute to the electromagnetic induction test. A first coordinate axis Z, is determined in a direction in which a variance of a distribution of the group of the measuring points comes to be a maximum in an M-dimensional space formed with the coordinate axes associated with the M kinds of the phase detection outputs. The remaining coordinate axes are likewise determined. Based on the coordinate of each of the measuring points viewed from the coordinate axis Z.sub.n+1, a measuring is effected to determine a presence or an absence of a defect, a physical quantity, and a geometric quantity on a surface of the test object.

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Kobe, Japan

Hiroaki Yasukuni