A method and apparatus for measuring the relaxed length of a moving web includes forming a plurality of detectable marks along the length of the web at a repeated length interval. First and second detectors positioned along the web path are separated by a known distance S. A first tensioning force is...http://www.google.de/patents/US4984458?utm_source=gb-gplus-sharePatent US4984458 - System for measuring the relaxed length of a moving web
