| 摘要 |
PURPOSE:To compensate input current deviation of each Hall element and Hall constant deviation by changing an amplifying property of buffer amplifier for composition and extraction of output signals of a plurality of the Hall elements arranged free to rotate relative to a magnetic field. CONSTITUTION:A transit is provided with a telescope 21 free to swing around horizontal axes 21a, 21b and for instance, detection of vertical angle, magnetic field forming member 30 and signal detecting member 40 are installed. A disc 32 of the member 30 is provided with magnets 34 and 36, forming a magnetic field normal to the reference axis and swing axis 21a of the telescope. The Hall element 3 of the member 40 is mounted around the center of the swing axis 21a horizontally and the Hall elements 5 vertically. Outputs of elements 3, 5 are delivered to a Hall voltage detecting circuit and a voltage detecting circuit extracts a combined voltage less input current deviations of elements 3, 5 and Hall constant value deviation. A vaviable resistance compensates an input current deviation and other variable resistance the constant value deviation. By processing an extracted voltage from the voltage detecting circuit, an accurate detection of swing angles of the elements 3, 5 become possible.
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