Development of an impedance method to measure the moisture content of a wet paper web

As part of a project on paper drying, an impedance method has been developed to measure the moisture content profile through paper (z-direction) for the purpose of understanding the mechanisms of internal heat and mass transfer within a thick handsheet during drying. The impedance of a wet paper sample between a pair of electrodes was measured at 100 kHz. The results demonstrated that the measured impedance was strongly related to the moisture content of the handsheet, independent of thickness within the tested moisture content range (7 to 60%) and dry thickness range (120 to 260 mu m). The repeatability of the tests was satisfactory. The effects of temperature and frequency on the impedance were also studied and some of the results are illustrated in this paper.