Optical thickness sensor calibrating method for contactless determination of thickness of e.g. paper web, involves compressing material web against upper and lower sensor plates by air cushions, where plates are provided on side of web

摘要

The method involves changing upper and lower air cushions (26, 28) by changing pressure at a material web (20) in a defined area for separately calibrating an optical thickness sensor on the web towards material web sides. The cushions are correlated with sensor plate distance. The air cushions on one of the sides of the web are deactivated during change of the air cushions on the other side of the material web so that the web is compressed against upper and lower sensor plates (22, 24) in flat manner by the air cushions, where the sensor plates are provided on the latter side of the web.