| 摘要 |
PURPOSE:To make it possible to measure an absolute position regardless of disturbance while preventing the drift of a zero point, by providing correction function wherein the position where the outputs of a plurality of magnetic field detectors are equal or the magnitude relation between said outputs reverses is set as the origin. CONSTITUTION:A linear scale is constituted by mounting a closed magnetic path 14 having alnico magnets 12, 13 inserted therein as means applying magnetic fluxes and magnetic field detectors 16, 17 arranged so as to be faced to magnetic paths respectively having different polarities between two magnetically soft plates 10, 11 comprising Permalloy or magnetic stainless steel. In this case, when a main shaft 15 moves to a positive (+) direction, the output of one detector 16 increases whereas the output of the other detector 17 reduces. Therefore, even if there is a position (a) where the outputs of both detectors take the same value and the output levels thereof change by disturbance or temp., because the outputs of the detectors 16, 17 simultaneously change, the position a' of a zero point coming to reference is not drifted.
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