This paper presents a newly developed coat weight sensor, IQMultiCoat. The presented sensor is a single-sided, direct-reading measurement of coat weight on paper or board. The sensor directs a broad band of infrared energy onto the sheet. Main components of the applied coating mixture have a charasteristic absorbtion spectras. By analyzing the backscattered infrared signal at multiple wavelengths in the near infrared (NIR) and middle infrared (MIR), the amount of specific substances, such as, clay, calcium carbonate or latex, is read directly. The total coat weight on one side of the sheet is then calculated based on the coating color recipe. Optionally the sensor simultaneously measures surface the moisture content of the sheet. The paper discusses the sensor's main operating principles, introduces laboratory test results from the development phase and presents results of trial runs on a pilot coater.
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