Abstract: A coil assembly for a magnetic actuator is described, the coil assembly comprising: —a tubular coil holder (100) comprising a first (110) and second open distal end (120); —the first open distal end comprising an outer circular rim (112) and an inner circular rim (114) separated by a circular groove (116); —the second open distal end comprising an outer circular rim (122); the tubular coil holder further comprising a central circular rim (130) arranged substantially halfway between the inner circular rim of the first open distal end and the outer circular rim of the second open distal end; —a coil (140) formed of a single wire (150) the coil comprising a first coil section (142) arranged in a first winding area (144) between the inner circular rim of the first open distal end and the central circular rim, and a second coil section (146) in a second winding area (148) between the central circular rim and the outer circular rim of the second distal end; the first coil section and the second coil section being w

Abstract: A speed sensor has a static part and a dynamic part arranged concentrically inside the static part. The static part has two permanent magnets and the dynamic part has two further permanent magnets. The magnet is oriented reversely to the further magnets. The magnets are tuned to each other so that gravity on the dynamic part is counteracted by the magnetic force on the dynamic part. As a result, the weight of the dynamic part need not be carried by springs and the dynamic part can move freely so that the full stroke can be used for measuring accelerations and the natural frequency is low. The static part further includes a measuring coil for measuring the displacement of the dynamic part and for the radial positioning of the dynamic part this part is connected to the static part by means of leaf springs.