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 develope d to measure the moisture content profile through paper (z-direction) for t he purpose of understanding the mechanisms of internal heat and mass transf er within a thick handsheet during drying. The impedance of a wet paper sam ple between a pair of electrodes was measured at 100 kHz. The results demon strated that the measured impedance was strongly related to the moisture co ntent 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 re peatability of the tests was satisfactory. The effects of temperature and f requency on the impedance were also studied and some of the results are ill ustrated in this paper.