Patent ID: 8487610

Claim:
A magnetiser for an in-line pipe inspection tool, the magnetiser comprising: a ferromagnetic base member; a pair of driving magnets mounted at spatially separate locations on the base member, the directions of magnetisation of the magnets extending in opposite senses to each other, towards and away from the base member respectively, to create a magnetic circuit that includes a flux path between the driving magnets which passes through the base member; and a flux enhancing magnet mounted on the base member adjacent to one or both of the driving magnets and having a direction of magnetisation substantially aligned with the direction of magnetic flux on the flux path, the flux enhancing magnet being magnetically coupled to the adjacent driving magnet(s) to drive flux around the magnetic circuit and thereby enhance the magnitude of a magnetic field exhibited by the magnetic circuit outside the magnetizer; wherein a thickness in the direction of magnetisation of one or both of the driving magnets increases with distance away from the flux enhancing magnet.