Currently within converting production lines, generally the thickness of the coating layer is assessed by the gravimetric method, thus only indirectly. And most of the multi-film production lines contain only a sensor for the total thickness evaluation. With an increasing oil price on the long ran, the requirements are to actually measure individual and thin layers down to few urn. Optical contactless devices are increasingly attractive for high level measurement tasks even under production conditions. But those are often restricted to transmission measurements which exclude a) many converting applications, particularly with substrates difficult to penetrate, and b) in multi-films, only a combined evaluation of layers with the same material is possible. For the first time, ISIS sentronics presents the newly developed optical thin-layer StraDex sensor which works in reflection mode with the advantages to a) measure a coating thickness directly even in the presence of a thick unpenetratable substrate and b) each individual layer in a multi-layer film. In addition the robustness for rapid and harsh production conditions and the capability to measure down to 4 μm is highlighted. The basic working principle is revealed and compared to our current technology. Results are shown from both technologies under laboratory and production conditions.
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