Method and apparatus for compensating for different depths of sun currents induced in the object tested for imperfections

摘要

A method for testing an electrically conductive test object with regard to an imperfection therein uses a transducer supplied with drive signals of two different frequencies so that via inductive coupling between the transducer and the test object, signal information is received from the transducer which can be processed to indicate the presence of an imperfection. The invention is characterized in that the transducer is designed and supplied with drive signals in such wise that the effect of the different depth penetration of currents induced in the test object at the two frequencies can be compensated for.