Valmet IQ Coat Weight Measurement

The accurate coat weight and high-resolution profiles measured by Valmet IQ Coat Weight Measurement (IQ Coat Weight) provide a solid foundation for Valmet’s machine-direction and cross-direction coat weight controls.

The scanning sensor can be utilized in applications including calcium carbonate and clay-based coatings. The sensor is suitable for multi-station coaters or single-station film coaters. Fully digital signal processing and factory pre-calibration ensure superior sensor accuracy. Utilizing Valmet’s patented technology, IQ Coat Weight is the most sophisticated measurement solution for modern two-sided simultaneous film coating and excellent for folding boxboard coater applications.


IQ Coat Weight is a single-sided, direct-reading measurement of coating color weight on paper or board applications. Infrared energy generated by the sensor is preferentially absorbed at specific wavelengths by constituents in the sheet. By analyzing the back scattered infrared signal at sixteen wavelengths in the near-infrared (NIR) and middle infrared (MIR), the amount of a marker agent, - clay, calcium carbonate or latex- is measured directly. The coating weight on one side of the sheet is then precisely calculated. Optionally the sensor is able to simultaneously measure the surface moisture content of the sheet.

Possible coating color on the other side of the sheet does not interfere with the sensor reading. This makes it possible to accurately and independently measure film coatings that are applied simultaneously on both sides. These measurements are made with two single-sided sensors on the same scanner.
On a multi-station coater, coat weight is measured by a single sensor after each coating application. For better precision, an additional IQ Coat Weight sensor on the base sheet measures marker agent content from recycled broke.

A superior signal to noise ratio and excellent accuracy is achieved by using dedicated processors with DSP technology in each sensor head. The sensor’s internal standardization, built-in diagnostics, and temperature stabilization techniques ensure accurate readings even in hot and dirty environments. Normal sheet flutter does not affect the sensor’s readings.


  • Accurate, high resolution (1 cm) profiles on the first scan ensure precise MD and CD coat weight controls and excellent quality soon after process upsets, like startup, grade change or breaks.
  • For coated board applications, the direct coat weight measurement accuracy is better than traditional oven-dry basis weight differential methods.
  • On two-sided film coating applications, both sides can be measured simultaneously, allowing paper makers to adjust coating applications for the best sheet properties on each side.
  • No additional sensors are needed to measure direct percent moisture.
  • The single-sided sensor can be located in tight locations on a one-sided scanner.