GB960922A - Improvements in and relating to measuring apparatus - Google Patents

Abstract

960,922. Photo-electric measuring. BRITISH IRON & STEEL RESEARCH ASSOCIATION, and DIGITAL ENGINEERING CO. Ltd. Feb 14, 1963 [Nov. 14, 1961; March 23, 1962], Nos. 40663/61 and 11209/62. Headings G1A and G1M. The invention relates to means for measuring the length of moving objects, which may emit radiation, such as hot steel billets. According to the invention in its broadest aspect two time intervals are measured, a first between the times when the front edge of an object passes first and second points spaced apart a known distance and a second between times when the front andtrailing edges of the object pass the first point. The object length can then be computed by means using these time intervals. In a particular embodiment a hot billet B moving in the direction of the arrow is sensed by a photo-cell PC1 as it passes a first point and a pulse from the cell is fed to control unit CU and to start the operation of two integrators, I1 and I2. When the front edge of the billet reaches a second point viewed by cell PC2 unit LU is pulsed to stop the charge of integrator I2 and to disconnect it. Finally when the rear edge of the billet reaches cell PC1 the charging of I1 is terminated and the control unit allows both integrated voltages to be fed to dividing unit DU the output of which is a voltage proportional to billet length indicated at ID. When the division has been effected a signal is passed back to the control unit to reset the apparatus for another measurement. To minimize errors due to variation in the object's velocity of travel a plurality of detector cells may be placed at intervals of L units along the direction of travel and the length of the object determined as L times the number of cells affected less one, plus L times the ratio of the time interval between the passage of a leading edge over a cell and the next succeeding passage of trailing edge over a cell and the time interval between the front edge passing two adjacent cells. In the arrangement the length of each object may be measured a number of times and registration made conditional on substantial agreement of the results. Another way to minimize speed variation is to make the distance between the two points substantially the same as the expected length of the objects. The objects may intercept radiation normally falling on the photo-cells or means other than photo-cells be used to detect the passage of the ends of an object.