| 摘要 |
PROBLEM TO BE SOLVED: To correct measurement errors caused by the wear and shortening of the circumferential length of a contact roller brought into contact with a travelling work and to maintain stable accuracy in length measurements. SOLUTION: The length measuring system for computing the length of feeding of the continuously traveling work W by bringing the contract roller 12 into contact with the work and multiplying the number of pulse signals outputted from an encoder synchronized with the rotation of the contact roller 12 and counted by a board 20 by a previously set resolution of length measurement is provided with a computing device 22 constituted of a means for measuring the circumferential length of the contact roller by image processing on an image photographed by a camera 24, a means for computing the resolution of length measurement by dividing the circumferential length of measurement by the number of pulses outputted during one rotation of the contact roller, a means for comparing the circumferential length this time with the last circumferential length, and a means for updating values up to the point by the resolution of length measurement obtained from the circumferential length this time in the case that the difference of the circumferential length is equal to a predetermined error or more.
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