| 摘要 |
<p>A speed detecting device for detecting the speed of movement of a pick-up is disclosed. The device incorporates a plurality of coils (27, 28) and a magnetic circuit arrangement. The magnetic circuit arrangement may be of various forms but includes gaps in which lines of flux exist and through which the coils pass on movement of the pick-up (1). Crossing the lines of flux by the coils generates in each coil an electric signal representative of the speed of relative movement between the coils and the magnetic circuit arrangement and the coils are arranged such that an extraneous magnetic field passing through the coils will produce an error signed with an electrical sense relative to the speed detecting signal in one coil which is opposite to that produced in the other coil or in other coils.
<??>Embodiments of the magnetic circuit arrangement are disclosed comprising first and second magnetic circuit members (20, 21) and permanent magnets (23, 24). The coils may be positioned over the magnets or over portions of the magnetic circuit spaced from the magnets. Movement of the pick-up may result in movement of the coils or of the magnetic circuit arrangement. </p> |
