Basis weight gauge standardizing system

Claim 1

A method of standardizing a basis weight gaUge for measuring the weight per unit area of a sheet material such gauge having a radiation source and radiation detector with a gap therebetween for directing radiation along a path towards said material and for detecting the amount of radiation transmitted through said material, said transmitted radiation being a measure of the basis weight of said material substantially in accordance with Beer''s law, said gauge also including standard means having a predetermined and stable basis weight and movable to be interposed in said radiation path, said method including the following steps: a. providing at least one reference sample of a material having a measured basis weight; b. placing said reference sample in said gap and obtaining a measurement of the radiation transmitted through said sample; c. constructing a first calibration curve from said measurement of said sample of material of known basis weight said curve relating the independent variable, basis weight, as a function of the dependent variable, transmitted radiation, substantially in accordance with Beer''s law; d. constructing a second calibration curve by the simulation of dirt in said radiation path whereby said second curve is displaced from first curve; e. placing said standard in said gap and measuring an initial shift due to said dirt simulation; f. obtaining a function of said calibration curve displacement as a function of one of said two variables of said calibration curves; g. updating said displacement function for the effects of current ambient conditions including the effects of air density changes due to temperature variation and other temperature effects and dirt buildup in the radiation path including the steps of, 1. obtaining a current value of the transmitted radiation with no sheet material in said radiation path but with said standard in said path to obtain a current standard shift, 2. updating said displacement function by relating said current standard shift to said initial standard shift; and h. placing said sheet material in said gap and measuring the current transmitted radiation and relating said updated displacement function to said first calibration curve along with such current measurement to obtain a standardized basis weight value.

Claim 2

A method of standardizing a basis weight gaUge for measuring the weight per unit area of a sheet material such gauge having a radiation source and radiation detector with a gap therebetween for directing radiation along a path towards said material and for detecting the amount of radiation transmitted through said material, said transmitted radiation being a measure of the basis weight of said material substantially in accordance with Beer''s law, said gauge also including standard means having a predetermined and stable basis weight and movable to be interposed in said radiation path, said method including the following steps: a. providing at least one reference sample of a material having a measured basis weight; b. placing said reference sample in said gap and obtaining a measurement of the radiation transmitted through said sample; c. constructing a first calibration curve from said measurement of said sample of material of known basis weight said curve relating the independent variable, basis weight, as a function of the dependent variable, transmitted radiation, substantially in accordance with Beer''s law; d. constructing a second calibration curve by the simulation of dirt in said radiation path whereby said second curve is displaced from first curve; e. placing said standard in said gap and measuring an initial shift due to said dirt simulation; f. obtaining a function of said calibration curve displacement as a function of one of said two variables of said calibration curves; g. updating said displacement function for the effects of current ambient conditions including the effects of air density changes due to temperature variation and other temperature effects and dirt buildup in the radiation path including the steps of, 1. obtaining a current value of the transmitted radiation with no sheet material in said radiation path but with said standard in said path to obtain a current standard shift, 2. updating said displacement function by relating said current standard shift to said initial standard shift; and h. placing said sheet material in said gap and measuring the current transmitted radiation and relating said updated displacement function to said first calibration curve along with such current measurement to obtain a standardized basis weight value.

Claim 11

A method of standardizing a basis weight gauge for measuring the weight per unit area of a sheet material such gauge having scanning means for scanning said material and for carrying a radiation source and radiation detector with a gap therebetween for directing radiation along a path towards said material and for detecting the amount of radiation transmitted through said material said transmitted radiation being a measure of the basis weight of said material in accordance with Beer''s law, said gauge also including standard means having a predetermined and stable basis weight within the range of basis weights of the sheet material to be measured and movable to be interposed in said radiation path, said method including the following steps: a. providing several reference samples of said material having measured basis weights, Q; b. placing said reference samples in said gap and obtaining measurements, Is, of the radiation transmitted through said samples and additionally simUlating dirt in said radiation path and obtaining measurements, Isb, of the radiation received by said detector after attenuation by said dirt simulation and said samples; c. removing said samples and obtaining a measurement, Iab, of attenuation of said radiation caused by substantially only said dirt simulation and air in said radiation path; d. measuring the received radiation, Iao, with only air in said radiation path; e. constructing a first calibration curve of the form where Q1 is the basis weight of a selected known sample, Mu 1 is the mass absorption coefficient which is determined by where I2, I1 are measures of the received radiation for said Q1 sample and a Q2 sample said equation being derived from the foregoing equation; f. constructing a second calibration curve of the form whereby said second curve is displaced from first curve; g. placing said standard in said radiation path and measuring radiation received, Ifo, and additionally simulating said same dirt in said radiation path and measuring radiation received Ifb, the difference between the ratios Ifb/Iab and Ifo/Iao representing an initial standard shift, C0; h. obtaining a function Delta Ro of the difference between said ratios Isb/Iab and Is/Iao of said two calibration curves and making straight line approximations of such function of the type a1 + b1 Q, a2 + b2Q, etc; i. updating said displacement function, Delta Ro for the effects of current ambient conditions including the effects of air density changes due to temperature variation and other temperature effects and dirt buildup in the radiation path including the steps of,

Claim 12

A method of standardizing a basis weight gauge for measuring the weight per unit area of a sheet material such gauge having scanning means for scanning said material and for carrying a radiation source and radiation detector with a gap therebetween for directing radiation along a path towards said material and for detecting the amount of radiation transmitted through said material said transmitted radiation being a measure of the basis weight of said material in accordance with Beer''s law, said gauge also including standard means having a predetermined and stable basis weight within the range of basis weights of the sheet material to be measured and movable to be interposed in said radiation path, said method including the following steps: a. providing several reference samples of said material having measured basis weights, Q; b. placing said reference samples in said gap and obtaining measurements, Is, of the radiation transmitted through said samples and additionally simUlating dirt in said radiation path and obtaining measurements, Isb, of the radiation received by said detector after attenuation by said dirt simulation and said samples; c. removing said samples and obtaining a measurement, Iab, of attenuation of said radiation caused by substantially only said dirt simulation and air in said radiation path; d. measuring the received radiation, Iao, with only air in said radiation path; e. constructing a first calibration curve of the form where Q1 is the basis weight of a selected known sample, Mu 1 is the mass absorption coefficient which is determined by where I2, I1 are measures of the received radiation for said Q1 sample and a Q2 sample said equation being derived from the foregoing equation; f. constructing a second calibration curve of the form whereby said second curve is displaced from first curve; g. placing said standard in said radiation path and measuring radiation received, Ifo, and additionally simulating said same dirt in said radiation path and measuring radiation received Ifb, the difference between the ratios Ifb/Iab and Ifo/Iao representing an initial standard shift, C0; h. obtaining a function Delta Ro of the difference between said ratios Isb/Iab and Is/Iao of said two calibration curves and making straight line approximations of such function of the type a1 + b1 Q, a2 + b2Q, etc; i. updating said displacement function, Delta Ro for the effects of current ambient conditions including the effects of air density changes due to temperature variation and other temperature effects and dirt buildup in the radiation path including the steps of,

Claim 13

A method of standardizing a basis weight gauge for measuring the weight per unit area of a sheet material such gauge having a radiation source and radiation detector with a gap therebetween for directing radiation along a path towards said material and for detecting the amount of radiation transmitted through said material, said transmitted radiation being a measure of the basis weight of said material substantially in accordance with Beer''s law, said gauge also including standard means having a predetermined and stable basis weight and movable to be interposed in said radiation path, said method including the following steps: obtaining a calibration function relating basis weight as a function of transmitted radiation; obtaining a displacement function of said calibration function, which is indicative of the change in measured basis weight, and obtaining an initial displacement of the measured basis weight of said standard means by artificially shifting said calibration function, updating said displacement function by obtaining a current displacement of said standard means and by comparing said current displacement to said initial displacemeNt; and placing said sheet material in said gap and obtaining its basis weight by relating said updated displacement function to said calibration function.

Claim 14

A method of standardizing a basis weight gauge for measuring the weight per unit area of a sheet material such gauge having a radiation source and radiation detector with a gap therebetween for directing radiation along a path towards said material and for detecting the amount of radiation transmitted through said material, said transmitted radiation being a measure of the basis weight of said material substantially in accordance with Beer''s law, said gauge also including standard means having a predetermined and stable basis weight and movable to be interposed in said radiation path, said method including the following steps: obtaining a calibration function relating basis weight as a function of transmitted radiation; obtaining a displacement function of said calibration function, which is indicative of the change in measured basis weight, and obtaining an initial displacement of the measured basis weight of said standard means by artificially shifting said calibration function, updating said displacement function by obtaining a current displacement of said standard means and by comparing said current displacement to said initial displacemeNt; and placing said sheet material in said gap and obtaining its basis weight by relating said updated displacement function to said calibration function.