TEMPERATURE INSENSITIVE WEB MOISTURE SENSOR AND METHOD

摘要

An infrared web moisture sensor (10) which is substantially temperature and basis weight insensitive comprises a source (16) of infrared radiation for directing an infrared beam (24) through the web (12) and an infrared detecting unit (18) on the other side of the web which measures the transmission of the infrared beam through the web at three separate wavelength regions. The transmission in the first wavelength region is primarily sensitive to the moisture content of the web. The transmission in the second wavelength region is less sensitive to the moisture content. The transmission in the third wavelength region provides an indication of the web temperature. Temperature insensitivity is achieved by selecting the temperature response of a measurement band pass filter (42) and a reference band pass filter (40) based on the maximum basis weight and the maximum moisture content of the web and compensating for any remaining temperature sensitivity with a temperature correction band pass filter (48).