| 摘要 |
PURPOSE:To make it possible to detect an absolute position over a wide range with high accuracy, by together providing two or more kinds of patterns to a rod and calculating the position detection signal in accordance with the positional relation of a detection head to the rod at every pattern. CONSTITUTION:When a rod part 3 displaces to the axial direction thereof and a rectangular pattern 3a enters the coils A-D of a first head 1, an eddy current flows to the pattern 3a corresponding to the penetrating quantity of said head 1. The change in magnetic resistance due to this eddy current loss is generated in the magnetic circuits of the coils A-D. AC signals each having a peak level corresponding to said magnetic resistance is induced in these secondary coil. By this method, the relative position of the rod part 3 can be detected as an absolute value in the range of one pitch length P1 of the pattern 3a. Further, the head 1 responds only to the pattern 3a by maskings 5, 6 and a second detection head 2 responds only to the pattern 3b. In the same way, the position of the rod part 3 in the range of one pitch length P2 the pattern 3b is calculated. By the combination of both positions, the position in a magnified range is obtained.
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