Next generation optical caliper sensor technology, PaperCon '09 Conference

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Caliper measurement and control is a vital part of papermaking. But this measurement can be a challenge. Over the years, various mechanical and optical sensors have been invented to achieve the best combination of accuracy, no sheet damage and reliable operation.

Some caliper sensors utilize laser triangulation. There are several inherent accuracy problems in this method. One particular problem is due to light interaction with semitranslucent cellulose fibers or coatings of the paper being measured. This can allow the light to penetrate the paper body instead of being reflected from the true paper surface. Consequently, the distance to the actual paper surface cannot be determined accurately. Gradedependent and processdependent calibrations or other compensations may be required when utilizing a laser caliper sensor.