MEASUREMENT OF SPEED AND/OR LENGTH

摘要

Method and apparatus for determining both relative speed between two bodies and length measurement of linearly moving material (21), particularly of moving strip or sheet material. A pair of non contacting detectors in a sensing head (11) derive two time sequences of signals characteristic of physical variations of material passing through two locations spaced apart (d) in direction of movement. The time delay between the two sequences of signals for which the two sequences most closely match one another is determined by a correlation unit (12) as a measure of time for material to travel between the two said locations to provide speed determination on a speed display unit (14). Length determination is made by determining instantaneous material speed values (by above-mentioned method) throughout a time interval during which the material passes the detectors and integrating these speed values over the time interval to obtain the length of material.