| 摘要 |
PROBLEM TO BE SOLVED: To detect a displacement with high resolution, and also with high accuracy even under a severe temperature environment. SOLUTION: An axis of rotation 3 is provided in a housing 1 with the axis freely and angularly displaceable, the axis of rotation 3 is fixed to an arm 4, and a permanent magnet piece 5 is fixed to the arm 4. In the housing 1, a pair of Hall elements HE1, HE2 are disposed and fixed in the vicinity of the both end parts of a movement rangeθa of the permanent magnet piece 5. The Hall element HE1, HE2 is a linear function of a bias voltage applied, and their output voltage fluctuates in response to the strength of a magnetic field. The output of each Hall element HE1, HE2 is added by an adding circuit 32, the added result is given to the one input of an attenuator 41, its differenceΔE from a reference voltage is found, and the bias voltage is changed so that the differenceΔE becomes zero. In this way, the output voltage of each Hall element HE1, HE2 can be obtained as the output voltage corresponding to the displacement of the permanent magnet piece 5 as an almost linear function.
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