Method and apparatus including a flux leakage and eddy current sensor

Abstract

A technique for detecting flaws in a metal product which uses a combined eddy current and magnetic flaw detection technique. A first magnetic field having flux lines parallel to the surface of the test object and a second field having flux lines perpendicular to the surface of the test object are generated. The resultant magnetic field is affected by faults in the metal test object. A magnetic field detector adjacent the test object detects the resultant magnetic field and produces an output signal which is processed by a circuit to provide a pair of component signals representing the portion of the output signal corresponding to the individual components of the resultant magnetic field, thus providing an indication of the type of faults that are present in the test object. One, or both, of the individual magnetic fields can be generated by an electromagnet which is driven by an alternating current to thereby produce a rotary resultant magnetic field, thereby allowing greater flexibility in detecting all types of flaws.