EXTENSION MEASURING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide an extension measuring apparatus using an optical rotation sensor. SOLUTION: The extension measuring apparatus comprises: a first rotary body having a first circumference at a predetermined distance from a rotary axis and rotating about the rotary axis; a plurality of first magnets disposed on a surface of the first rotary body along the first circumference with the north or south pole oriented to the surface; a rotation sensor disposed outside the rotary body so as to be opposed to the first circumference and provided with first and second proximity sensors each detecting the state of a magnetic field; a wire attached to an object; a wire reeling part on which the wire is reeled; a tension maintaining part for reeling and unreeling the wire by rotating the wire reeling part so as to maintain the constant tension of the wire; and a fixing part for fixing a reference member and the wire reeling part. In the extension measuring apparatus, the first and second rotary bodies rotate according to the reeled or unreeled amount of the wire at the tension maintaining part. COPYRIGHT: (C)2009,JPO&INPIT