Patent ID: 8358125

Claim:
A method for determining geometric characteristics of an anomaly in a region near the surface of an electrically conducting test object, the anomaly changing the electrical conductivity of the test object, the method comprising: exciting eddy currents of different frequencies in the region of the anomaly in the test object, to produce a magnetic field component B y,0 which is perpendicular to a direction in which the anomaly extends along the test object; scanning said magnetic field component B y,0 in the vicinity of the anomaly; and deducing the geometric characteristics of the anomaly exclusively from the distribution of the magnetic field component B y,0 ; wherein said anomaly comprises at least one crack in the test object, and wherein deducing the geometric characteristics comprises determining a crack depth; and wherein determining a crack depth comprises first determining the position of the crack on the surface of the test object, and second scanning and evaluating the distribution of the magnetic field component B y,0 transversely with respect to the longitudinal direction of the crack.