Moisture gauge with opacity type compensation

Claim 1

In a method of measuring the moisture content of a moving sheet of paper being manufactured by a paper machine with a dual wavelength radiation type gauge that provides a first output signal, R, representative of the ratio of the absorption of radiation in a band highly sensitive to absorption by water and in a nearby band that is relatively less sensitive to absorption by water, the steps comprising: generating a second signal, L, functionally related to the opacity of said moving sheet of paper; and combining said second signal with said first signal to produce a third signal, W, indicative of the water weight per unit area of said moving sheet of paper in accordance with the relationship W - Wo (R - Ro) ( Alpha L + Beta )/( 1 + ( Alpha / theta ) (R - Ro)) where Wo, Ro, Alpha , Beta , and theta are constants whereby said moisture measurement is relatively insensitive to fiber variations.

Claim 4

A method of measuring the amount of moisture in a moving sheet of paper manufactured by a paper machine with a radiation type gauge that supplies an output signal, R, proportional to the ratio of radiation received having a wavelength that is outside of the absorption band of water and a wavelength received that lies within the absorption band of water and provides a second signal, L, indicative of the attenuation of the non-water sensitive radiation by the paper, the steps comprising: preparing two sets of paper samples having different fiber constituents, the individual samples of each set having different known water weight; supplying said samples, one at a time, to said moisture gauge and obtaining a ratio reading, R, and said second signal attenuation reading, L, therefrom for each sample, determining the intersection point of a curve generated from a plot of the ratio measurement, R, against the known water weights, W, for samples in said first set of samples with a curve determined by a plot of the ratio signal, R, versus water weight, W, for samples in said second set of samples; determining the slope of each of said curves; determining the attenuation value, Lo, associated with said intersection point for each set of samples; determining a set of constants associated with a curve generated from a plot of said slope measurement against said Lo points; and utilizing said constants to provide a relationship between said water weight, W, said ratio signal, R, and said attenuation signal, L.

Claim 5

A method of measuring the amount of moisture in a moving sheet of paper manufactured by a paper machine with a radiation type gauge that supplies an output signal, R, proportional to the ratio of radiation received having a wavelength that is outside of the absorption band of water and a wavelength received that lies within the absorption band of water and provides a second signal, L, indicative of the attenuation of the non-water sensitive radiation by the paper, the steps comprising: preparing two sets of paper samples having different fiber constituents, the individual samples of each set having different known water weight; supplying said samples, one at a time, to said moisture gauge and obtaining a ratio reading, R, and said second signal attenuation reading, L, therefrom for each sample, determining the intersection point of a curve generated from a plot of the ratio measurement, R, against the known water weights, W, for samples in said first set of samples with a curve determined by a plot of the ratio signal, R, versus water weight, W, for samples in said second set of samples; determining the slope of each of said curves; determining the attenuation value, Lo, associated with said intersection point for each set of samples; determining a set of constants associated with a curve generated from a plot of said slope measurement against said Lo points; and utilizing said constants to provide a relationship between said water weight, W, said ratio signal, R, and said attenuation signal, L.