Patent ID: 8547089

Claim:
A method of non-destructively testing a magnetisable conducting object mechanically shielded by a magnetisable layer, comprising the steps of: abruptly changing a field strength of a primary magnetic field that is applied exterior to the magnetisable layer thereby inducing eddy currents in the object, receiving a vanishing secondary magnetic field generated by eddy currents induced by the changed field strength of the primary magnetic field, analyzing a temporal field strength of the received secondary magnetic field for deriving characteristics of the magnetisable conducting object, and applying a transient tertiary magnetic field exterior to the magnetisable layer when the field strength of the primary magnetic field abruptly changes, wherein the orientation of the primary and tertiary magnetic field, respectively, are mutually opposite and the tertiary magnetic field is strong enough for substantially neutralizing temporal relaxation processes in the magnetisable layer thereby allowing the testing.