High resolution system and method for measurement of traveling web

摘要

A system and method that combine an array of fast under wire water weigh sensors with a scanning system provides an accurate measurement of the entire sheet down to 1 in. by 1 in. resolution. Because CD profiles are obtained instantaneously, MD and CD variations are completely decoupled, even if CD profiles are taken at longer intervals apart. The technique allows monitoring the basis weight of a sheet of material that is formed in a process that employs a de-watering machine that includes a water permeable moving fabric supporting wet stock and a dry end which technique includes the steps of: a) positioning an array of water weight sensor elements (array) underneath and adjacent to the fabric wherein the array is positioned in a cross direction to the moving fabric; b) positioning a scanning sensor at the dry end to measure the dry basis weight of the sheet of material; c) operating the machine and measuring the water weights of the sheet of material with the array and measuring the dry basis weight of the sheet of material with the scanning sensor at the dry end; d) developing a functional relationship between water weight of the sheet as measured by the array and the basis weight of the sheet which is formed after being substantially de-watered; end; and e) periodically, adjusting the functional relationship using readings from the scanning sensor to compensate for variations due to process parameters. The technique can further include the step of correlating positional readings of the scanning sensor with measurements from the corresponding element in the array to obtain separate calibration for each individual element of the array and step e comprises adjusting the functional relationship obtained in step d and the calibration obtained in to compensate for variations due to process parameters.