Abstract: A rotary head for scanning the surface of elongated test materials (62) by eddy current transducers (60) is additionally provided with means for magnetization of the test material (62) over an intended test range making it now possible to achieve sensitive testing of non-bare ferromagnetic bars and wires, testing for "smeared cracks" where surface has closed above the material separation, and testing of welded austenitic pipes. For the magnetization, parts of the housing (10) as well as a rotating hollow shaft (40) are employed in the conduction of magnetic flux, and special measures are taken for the homogenization of the magnetic field in the test range.

Abstract: A contactless magnetic bearing system comprises a passive axial bearing element which serves to exert axial stabilizing forces on the rotor and at the same time exerts radial destablizing forces thereon, a controlled or active radial bearing element for counteracting these radial destabilizing forces and a passive radial bearing element which supports and journals the rotor at a position axially spaced from the two first-mentioned bearing elements. The axial destabilizing forces produced by the passive radial bearing are counteracted by the much stronger axial forces exerted by the passive axial bearing element.

Abstract: A contactless magnetic bearing between two members, not necessarily relatively rotatable, comprises at least one magnet on one member cooperating with two ferromagnetic parts on the other member to exert a stabilizing effect in the direction of one degree of freedom due to oppositely directed mgnetic fluxes in the two parts parallel to the direction of the degree of freedom. The destabilizing effect in a direction transverse to the direction of the one degree of freedom can be countered by a lateral bearing, preferably an active bearing whose coil is arranged in the magnetic field of the magnet or magnets.