Detection of inhomogeneities in magneto-conductive objects

This paper describes an effective method to detect inhomogeneities in magneto-conductive objects using very cheap but still rather sensitive sensors based on the giant magneto resistive effect (GMR) [6]. These sensors measure the magnetic field leakage near the surface of a magneto-conductive object. For a pilot survey, some test specimens were prepared with artificial inhomogeneities in a ferromagnetic specimen. In order to get the distribution of the magnetic field leakage near the specimen´s surface, it was mechanically scanned. The measurement results allow to indicate the exact position of the inhomogeneities inside the specimen and also magnetizable spiral drills inside the ferromagnetic specimen can be detected this way.