Method and apparatus for calibrating a sensor for the measurement of material thickness or surface weight

A method for measuring the layer thickness and/or the surface weight of a material sheet and of calibrating a sensor, the method comprising:

• moving a sensor transverse (y) to a longitudinally (x) transported material sheet and detecting transmission values and/or reflection values of the material sheet;
• determining the layer thickness and/or the surface weight of the material sheet or the respective distribution over the material sheet by calculation using the detected transmission values and/or reflection values and a calibration value or a calibration curve;
• and
• calibrating the sensor wherein the average calibration value, having been determined using the calibration sample, is used for determining the layer thickness and/or the surface weight or used for the recalibration of the calibration curve.

An apparatus for determining the layer thickness and/or surface weight of a material sheet, the apparatus comprising:

• a material sheet transportation device for transporting a material sheet in a longitudinal direction (x);
• and
• a sensor unit arranged at the material sheet transportation device, the sensor unit comprising:
• a sensor for detecting transmission values and/or reflection values of the material sheet,
• a sensor moving unit for moving the sensor in a transverse direction (y) to the material sheet;
• a sensor calibration station, at which the sensor is positioned outside the material sheet measurement path, wherein the sensor is positioned laterally offset to the material sheet to be measured;
• and
• a support device for supporting a two-dimensional or areal calibration sample, wherein in the sensor calibration station the sensor is moveable relative to the calibration sample being held in the support device and/or the calibration sample is moveable relative to the sensor.