| The on-line moisture measurement in paper has gained increased importance in respect of constant quality, low energy consumption, and high production rates. Several different technologies have been available in the on-line moisture gages, for example, infrared ray, microwave, and capacitance method and others. Compared with other methods, infrared technology has the advantages of higher accuracy, broader range of moisture, and the better suitbility of lighter weight paper sheets. Even so, conventional infrared moisture gages are inaccurate for lightweight paper sheets (particularly those lighter than 25g/m~2) in the papermaking process where environment conditions are worse and the sensor head mounting states are changing during the scanning of the sensor heads, and therefore the computer based moisture control technologies have been hindered from being effectively employed in the production of above lightweight paper. The measurement inaccuracy is attributed to less moisture in lightweingt paper sheets in comparison with heavier paper sheets, and higher sensitivity to the changes of features of gage, paper morphology, environment conditons, and other factors in the on-line measurement. So how to resolve these problems in the implementation and applications of moisture gage is the key to gain the accurate moisture measurement.Because of the lack of better theory describing the infrared properties of paper containing moisture, which is the basis of analzing the transfer characteristics of infrared moisture measurements in paper, for a long time, people had to roughly ultilize Beer's law to demonstrate the mechanism of infrared moisture measurement in paper. But paper is a kind of strong scattering substance, which disobeys the presupposes of Beer's law, Beer's law tells us little about the interreactions of light with paper and the interrelations of measurement outputs with various influence quantities, for example, paper morphology, the basis weight, and other...
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