On-Machine Visible Dirt Measurement on Moving Sheets and the Relationships to Standard Laboratory Methods

摘要

There has been a proliferation of new sensors to measure on-machine dirt specks, which employ different technologies and methodologies to perform measurements. The differences of the on-machine technologies are discussed in terms of the Tappi and ISO standard laboratory methods with respect to dirt detection using light reflected from, or light transmitted through, the sheet. Also discussed are the requirements of measuring statistically representative areas of sheet, the difference between the dirt physical size and EBA (Equivalent Black Area) size and the implication of these issues when specifying cleanliness acceptance criteria.