CA1102579A - Method of measuring the amount of substance associated with a material in the presence of a contaminant - Google Patents
Method of measuring the amount of substance associated with a material in the presence of a contaminantInfo
- Publication number
- CA1102579A CA1102579A CA320,074A CA320074A CA1102579A CA 1102579 A CA1102579 A CA 1102579A CA 320074 A CA320074 A CA 320074A CA 1102579 A CA1102579 A CA 1102579A
- Authority
- CA
- Canada
- Prior art keywords
- band
- absorption
- lies
- intensity
- substance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of measuring the amount of substance associated with a material in the presence of a contaminant comprises choosing a first band of radiation which lies outside the absorption band of the substance but within the abosrption band of the contaminant. The first band is directed at the material; a first detector is positioned to receive the radiation after impinging the material. The first detector converts the radiation received into a first electrical signal. A second band of radiation, which is chosen to lie within the absorption band of the substance, is also within an absorption band of the contaminant. The second band is directed at the material; a second detector is positioned to receive the radiation after impinging the material. The second detector produces a second electrical signal in response to the radiation received. The second electrical signal is subtracted from the first electrical signal.
A method of measuring the amount of substance associated with a material in the presence of a contaminant comprises choosing a first band of radiation which lies outside the absorption band of the substance but within the abosrption band of the contaminant. The first band is directed at the material; a first detector is positioned to receive the radiation after impinging the material. The first detector converts the radiation received into a first electrical signal. A second band of radiation, which is chosen to lie within the absorption band of the substance, is also within an absorption band of the contaminant. The second band is directed at the material; a second detector is positioned to receive the radiation after impinging the material. The second detector produces a second electrical signal in response to the radiation received. The second electrical signal is subtracted from the first electrical signal.
Description
i7~3 ~ACKGROUND OF THE INVENTION
The present invention relates to a method for measuring the amount of substance associated with a material in the presence of a contaminant, and more particularly to a method for measuring the amount of water associated with a paper material in the presence of carbon.
Methods for detecting moisture in paper material are well known in the prior art, see e.g. United States Patent No. 3,614,450. Typically, an infrared source emits two bands of electromagnetic radiation. A first band (usually 1.8 microns - so called reference channel) is insensitive to absorption by the moisture. A second band (usually 1.94 mQcrons - so called measure channel) is sensitive to absorption by the moisture. The two bands of radiation are directed at the paper material. Detectors are positioned to receive the bands of radiation after they have been reflected from the paper or transmitted through the paper. The detectors convert the radiation received into electrical signalsO The ratio of the signal of the reference channel to the measure channel is indicative of the moisture content of the paper material. A fundamental assumption of this method is that neither the reference channel nor the measure channel is sensitive to absorption by other compounds in the paper material.
As ecological demands increase, the use of recycled paper also increases. This has ocurred most frequently in the news print industry.
Used newspaper is recycled with new pu]p to produce fresh news print. The use of recycled news print in the manufacturing process introduces contaminant, namely carbon from the printing ink, into the process. The presence of car~on effects the measurement of moisture of the paper material in that the bands ~both reference channel and measure channel) of electromagnetic radiation are absorbed by the carbon. Thus, the ratio of the signals of the reference channel to the measure channel would not be determinitive of the -1_ ~
. .'' '' ''', : ' .
.
, .
-. ~ :
moisture content of the paper material.
Heretofore, one way to correct for the presence of carbon is todetermine a ~iori the influence of carbon on the ratio of the signals for a particular moisture level. For example a 7% level of moisture for a par~icular paper material, a ratio of the signals without carbon was determined to be 2.2 and as carbon was introduced the ratio of the signals - detected, for the same level of moisture, became 2.00 For a different level of moisture, the ratio of the signals would also vary as the amount of carbon present in the paper materialO In this manner, a family of curves was pre-determined and usually stored in a com-puter. The amount of carbon present in the paper material was determined from the change in the signal strength of the reference channel. Since the reference channel was insensitive to the presence of water, the change in signal strength of the reference channel could be attributed to the presence of carbon. With knowledge of the ratio of the signals and the amount of deviation of the signal strength in the reference channel, indicating the amount of carbon present, the moisture level of the paper material could thus be calculated from the family of pre-determined curves. The drawback of this method, of course, is that a large amount of data had to be pre-determined and stored in a medium which is easily and quickly accessible.
Moreover, the method that was developed was based upon empirical results and not upon theoretical basisO As a result, it was limited in its accuracy and in its range of application.
SUMMARY OF THE INVENTION
A method of measuring the amount of substance associated with a material in the presence of a contaminant, wherein the contaminant has an electromagnetic radiation absorption characteristic different from the electromagnetic radiation absorption characteristic of the substance, .: - . : : : . ... :.: :
. .
- '' ~ . ' ' ' .' ' ':
: - :
"' . - ' '' S7~
comprises emitting a first band of electromagnetic radiation. The first band is directed at the material and is characterized in that it lies outside an absorption band of the substance but within an absorption band of the con-taminant. The first band is detected, after it has impinged on the material, by a detector which produces a first electrical signal in response to the radiation detected. A second band of electromagnetic radiation is also emitted and is aligned to impinge the material. The second band is character-ized in that it lies within an absorption band of the substance and also lies within an absorption band of the contaminant. The second band is detected, after it has impinged the material, by a receiver which generates a second electrical signal, in response to the radiation detected. The second electrical signal is subtracted from the first electrical signal.
According to the invention there is provided a method of measuring the amount of substance associated with a material in the presence of a con-taminant, said contaminant having an electromagnetic radiation absorption characteristic different from the electromagneti& radiation absorption characteristic of said substance, wherein said method comprising the steps of: emitting a first band of electromagnetic radiation, wherein said first band lies outside an absorption band of said substance, and lies within an ; 20 absorption band of said contaminant; directing said first band to lmpinge said material; detecting said first band after reflecting from said material;
generating a first electrical signal, in response to said first band detect-ed; emanating a second band of electromagnetic radiation, wherein said second band lies within an absorption band of said substance, and also lies wlthin an absorption band of said contaminant; aligning said second band to impinge said material; receiving said second band after reflecting from said material; producing a second electrical signal, in response to said second band received; and calculating the amount of substance in accordance with the ;:
, ~t - ~, ' ~ ' 5~9 formula:
amount of substance = A+B(M + M)-C(N ~ N) where A, B, C are calibration constants; M = intensity of second band received without material divided by intensity of second band received with material; N = intensity of first band detected without material divided by intensity of first band detected with material.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic side view of an apparatus using the method of the present invention.
Figure 2 is a schematic side view of another apparatus using the method of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
The present invention relates to a method of measuring the amount of substance associated with a material, in the presence of a contaminant.
The contaminant has an electromagnetic radiation absorption characteristic different from that of the substance. In the method of the present invention, a first band of electromagnetic radiation is emitted from a source. The first band has the characteristic of being within an absorption band of the contaminant, but outside an absorption band of the substance. The Eirst band is directed to impin~e the material. A detector is positioned to receive the first band after impinging the material. A first electrical signal in response to the first radiation detected is generated by the detector. A
second band of electromagnetic radiation is produced and is also aligned to impinge the material. The second band has the characteristic of being within an absorption band of the substance and within an absorption band of the con-taminant. The second band is detected by a receiver after the second band has impinged the material. The receiver generates a second electrical signal in response to the second band of radiation detected. The second electrical ~4~
. : . .
.. . , .' . ~
.
: - - ~ - - : ; -' 7g signal is subtracted from the first electrical signal.
A particular application of the method of the present invention is in the measurement of moisture of paper material in the presence of carbon.
This can be best understood by referring to Figure 1, which is a schematic 4a ~1~257~
side view of an apparatus 10 using the method of the present invention. h paper material 12, substantially in a sheet form, moves in a direction shown by arrow 14. The paper material 12 can be the manufactured product of a Fourdrinier machine (not shown). As is well known in paper making technology, the control of the amount of moisture or water in the paper is critical in controlling quality and economic return. In the paper matcrial 12 of Figure 1, however, the paper material 12 also contains carbon particles 16 (greatly exaggerated). A first source 18 emits a first band of electro-magnetic radiation, directed towards the paper material 12 in a direction along the dotted line 20. The first band, after impinging the paper material 12 reflects from it and travels in the direction along the dotted line 22 and is received by a fir9t receiver 24. The first receiver 24 converts the first band received into a first electrical signal 26. The first band is chosen such that it lies within an electromagnetic absorption band of carbon but lies outside of an electromagnetic absorption band of water. Typically, this is at about 1.8 microns. A second source 28 emits a second band of ~ electromagnetic radiation, directed towards the paper material 12 in a ; direction along the dotted line 30. The second band, after impinging the paper material 12, reflects from it and travels in the direction along the dotted line 32 and is received by a second receiver 34. The second receiver 34 convert9 the 9econd band received into a second electrical signal 36. The second band is chosen such that it lies within an electromagnetic absorption band of water and is also within an electromagnetic absorption band of carbon. Typically, this is about 1.94 microns. The second electrical signal 36 is subtracted from a first electrical signal 26 by a computer 380 The result is determinitive of the amount of moisture in the paper material 12.
In general, the first source 18 and the second source 28 can be any - 5 _ , .
..
, - , , :, :, ,,~ - - :: - , : . . .
5~9 source emitting the desired electromagnetic radiation. They can even be the same source, e.g. an infrared lamp. The dotted lines 20 and 30 can coincide and thus the first band and second band would impinge the same area on~
the paper material 12. In fact, for accuracy, this is preferred. In the event the dotted lines 20 and 30 coincide such that the first band and the second band impinge the same area on the paper material 12, then the dotted lines 22 and 32 would also coincide. In that event, the first receiver 24 and the second receiver 34 are positioned to receive both bands with a beam splitter such as that disclosed in United States Patent No. 3,641,349.
The first receiver 24 and the second receiver 34 can be any suitable detector, such as photodiode. The apparatus 10 of FYgure 1 uses the method of the present invention in which the measurement of the amount of moisture of the paper material 12 is accomplished by reflecting bands of electro-magnetic radiation from the paper material 12. In this application, known as reflectance measurement, the calculation of the amount of moisture associated with the paper material 12 in the presence of carbon, by subtracting the second signal 36 from the first signal 26, can be further simpli ~ed to:
' amount of moisture = A + B (M + -) - C (N + 1) M N
where A~ B~ C are constantsof the apparatus 10 obtained from initial calibration, M is the intensity of second band (1094 micron) received without the paper material 12 (eOg. replace the paper material 12 by a reflector) divided by the intensity of the 9econd band received with the paper material 12 ( i.e. the intensity of second band received during the measurement process), and N is the intensity of the first band (1.8 micron) received without the paper material 12(eOg.
_ 6 -: ~ --: ~ , ,. . - . ' , ~ ' 1~ ii79 replace the paper material by a reflector) divided by the intensity of the first band received with the paper material 12 (i.e. the intensity of first band received during the measurement process).
The measurement of the intensity of the first band and the second band are made usually during standardization, i.eO when the apparatus 10 moves off-sheet from the paper material 12. These measurements are made to correct for errors caused by dirt build-up, source aging etc.
Referring to Figure 2, there is shown a schematic side view of another apparatus 40 using the method of the present invention. A paper material 42, substantially in a sheet form, moves in a direction shown by arrow 44. The paper material 42 contains carbon particles 46 (greatly exaggerated). A first source 48 emits a first band of electromagnetic radiation, directed towards the paper material 42 in a direction along the dotted line 50. me first band, after impinging the paper material 42, transmits through it, and travels in the direction along the dotted line 52 and is received by a first receiver 54. The first receiver 54 converts the first band received into a first electrical signal 56. The first band is chosen such that it lies within an electromagnetic absorption band of carbon but lies outside of an electromagnetic absorption band of water.
Typically, this is at about 1.8 microns. A second source 58 emits a second band of electromagnetic radiation, directed towards the paper material 42 in a direction along the dotted line 60. The second band~ after impinging the paper material 42, transmits through it and travels in the direction along -the dotted line 62 and is received by a second receiver 64. m e second receiver 64 converts the second band received into a second electrical signal 66c The second band is chosen such that it lies within an electro-.: .. - , . . ... .. : - : .
magnetic absorption band of water and is also within an electromagnetic absorption band of carbon. Typically, this is at about 1094 microns. The second electrical signal 66 is subtracted from a first electrical signal 56 by a computer 68. The result is determinitive of the amount of moisture in the paper material 42.
The apparatus 40 of Figure 2 is similar to that disclosed and shown in United States Patent No. 3,793,524. The apparatus 40 comprises a first diffusing plate 41 to one side of the paper material 42, while a second diffusing plate 43 is to the other side of the paper material 42. In addition the sources 48, 58 and the receivers 54, 64 are off-set from one another, iOe. no amount of radiation is received directly by the receivers 54 and 64 from the sources 48 and 58. The advantages of the diffusing plates 41 and 43, and the off-set geometry are discussed fully in United States Patent ~o. 3,793,524. In general, the first source 48 and the second source 58 can be any source emitting the desired electromagnetic radiation.
They can even by the same source, e.gO an infrared lampO The dotted lines 50 and 60 can coincide and thus the first band and second band would impinge the same area on the paper material 420 In fact, for accuracy, this is preferred. In the event the dotted lines 50 and 60 coincide such that the first band and the second band impinge the same area on the paper material 42, then the dotted lines 52 and 62 would also coincideO In that event, the first receiver 54 and the second receiver 64 are positioned to receive both bands with a beam splitter, such as that disclosed in United States Patent No. 3,641~349. The first receiver 54 and the second receiver 64 can be any 9uitable detector such as photodiode. The apparatus 40 of Figure 2 uses the method of the present invention in which the measurement of the amount of moisture of the paper material 42 is accomplished by transmitting bands of electromagnetic radiation through the paper ~aterial 42. In this i79 application, known as transmittance measurement, the calculation of the amount of moisture associated with the paper material 42 in the presence of carbon, by subtracting the second signal 66 from the first signal 56, can be further simplified to:
amount of moisture = A + B ~M - C ~N
where A, B, C are constants of the apparatus 40 obtained from initial calibration;
M is the intensity of the second band (1.94 micron) received without the paper material 42 (e.gO
remove the paper material 42 and measure the intensity of the second band) divided by the intensity of the second band received with the paper material 42 (i.e. the intensity of the second band received during the measurement process); and N is the intensity of the first band (1.8 micron) received without the paper material 42`(e.gA
remove the paper material 42 and measure the intensity of the second band) divided by the intensity of the first band received with the paper material 42 (i.e. the intensity of the first band received during the measurement process).
me measurements of the intensity of the first band and the second band are made usually during standardization, iOe. when the apparatus 40 moves off_sheet from the paper material 420 These measurements are made to correct for errors caused by dirt build-up, source aging etc.
It should be appreciated that the method of the present invention is not limited in its application to the determination of the amount of .. . . . . . .
.. - ............... . . . , - .
.... .
.
5;~
moisture associated with paper material in the presence of carbon, either through reflectance measurement or transmittance measurementO The method of the present invention can be used to determine the amount of any substance associated with a material in the presence of a contaminant. For example, the method of the present invention can also be used to determine the amount of plastic in a plastic film in the presence of carbon, or to determine the amount of water in a paper material in the presence of other colored dyes.
The theoretical basis for the method of the present invention is as follows: The amount of monochromatic light reflected or transmitted from a diffusing sheet depends on the absorption coefficient K and the scattering coefficient S. It shall be assumed that, in accordance with Beer's Iaw, the absorption depends on the concentration of substance in the sheet, the concentration of contaminant, and the concentration of some unknown (albeit small amount). In addition, it is assumed that the absorption coefficients are additive so that the total absorption coefficient K is the sum:
K = K (substance ) + K (contaminant) + K (other) + KS + KC + Ko From the theory of Kubelka and Munk (Kubelka, Paul, "New Contributions to the Optics of Intensely Light-Scattering Materials~ Part I'l, Journ.
Opt. Soc, Am., 38, 1945.), the total absorption coefficient can also be related to reflectance R and scattering coefficient S. Thus:
M MS + KMC + KMo 2 _ (M +~~r) ~ S
N NS + KNC + KN0 = 2 (N + -N) ~ SN
where M and N are the ratio of measure and reference bands respectively as previously discussed.
.. . . . ..
. . : : - . : : -. " . ~, . - ,- : ~ .
: . :' -', ~ ' : .. ' If it is assumed that the contaminant absorbs equally at the reference channel and at the measure channel, i.e. KMC = KNC then the difference of the two equations yields:
(KMS ~ KNS) + (KMo ~ KN0) = 2M (M + M) ~ 2 (N + N) ~ (SM S~) since (KMs- KNs) is proportional to the amount of substance, and the terms (KMo - KN0)~ 2 ~ 2 and (SM ~ SN) are constants, the equation becomes:
amount of substance = A + B (M + M) ~ C (N + 1) where A, B and C are constants determined by calibration.
In the case of light transmitted through the sheet, the effect of the light scattered from the sheet and then reflected from the diffusing plates to impinge the sheet, must be considered~ mus, the theory of Kubelka and Munk must be rewritten to include multiple passes and to take into account the off-set geometry. m e analysis, thereafter, however, is the same. The coefficient of absorption K can be determined for the measured channel and the reference channel. me difference is taken and the resultant is proportional to the amount of substance.
It should be appreciated that the method of the present invention does not require a large amount of a priori data. Moreover, it i9 accurate and has a wi~e range of applicability to correct for the presence of any contaminant.
. .
, , ' : , ' ,: ' ' ' ': ' . ' ' . . ' , ' : : -, . ' - ~ -
The present invention relates to a method for measuring the amount of substance associated with a material in the presence of a contaminant, and more particularly to a method for measuring the amount of water associated with a paper material in the presence of carbon.
Methods for detecting moisture in paper material are well known in the prior art, see e.g. United States Patent No. 3,614,450. Typically, an infrared source emits two bands of electromagnetic radiation. A first band (usually 1.8 microns - so called reference channel) is insensitive to absorption by the moisture. A second band (usually 1.94 mQcrons - so called measure channel) is sensitive to absorption by the moisture. The two bands of radiation are directed at the paper material. Detectors are positioned to receive the bands of radiation after they have been reflected from the paper or transmitted through the paper. The detectors convert the radiation received into electrical signalsO The ratio of the signal of the reference channel to the measure channel is indicative of the moisture content of the paper material. A fundamental assumption of this method is that neither the reference channel nor the measure channel is sensitive to absorption by other compounds in the paper material.
As ecological demands increase, the use of recycled paper also increases. This has ocurred most frequently in the news print industry.
Used newspaper is recycled with new pu]p to produce fresh news print. The use of recycled news print in the manufacturing process introduces contaminant, namely carbon from the printing ink, into the process. The presence of car~on effects the measurement of moisture of the paper material in that the bands ~both reference channel and measure channel) of electromagnetic radiation are absorbed by the carbon. Thus, the ratio of the signals of the reference channel to the measure channel would not be determinitive of the -1_ ~
. .'' '' ''', : ' .
.
, .
-. ~ :
moisture content of the paper material.
Heretofore, one way to correct for the presence of carbon is todetermine a ~iori the influence of carbon on the ratio of the signals for a particular moisture level. For example a 7% level of moisture for a par~icular paper material, a ratio of the signals without carbon was determined to be 2.2 and as carbon was introduced the ratio of the signals - detected, for the same level of moisture, became 2.00 For a different level of moisture, the ratio of the signals would also vary as the amount of carbon present in the paper materialO In this manner, a family of curves was pre-determined and usually stored in a com-puter. The amount of carbon present in the paper material was determined from the change in the signal strength of the reference channel. Since the reference channel was insensitive to the presence of water, the change in signal strength of the reference channel could be attributed to the presence of carbon. With knowledge of the ratio of the signals and the amount of deviation of the signal strength in the reference channel, indicating the amount of carbon present, the moisture level of the paper material could thus be calculated from the family of pre-determined curves. The drawback of this method, of course, is that a large amount of data had to be pre-determined and stored in a medium which is easily and quickly accessible.
Moreover, the method that was developed was based upon empirical results and not upon theoretical basisO As a result, it was limited in its accuracy and in its range of application.
SUMMARY OF THE INVENTION
A method of measuring the amount of substance associated with a material in the presence of a contaminant, wherein the contaminant has an electromagnetic radiation absorption characteristic different from the electromagnetic radiation absorption characteristic of the substance, .: - . : : : . ... :.: :
. .
- '' ~ . ' ' ' .' ' ':
: - :
"' . - ' '' S7~
comprises emitting a first band of electromagnetic radiation. The first band is directed at the material and is characterized in that it lies outside an absorption band of the substance but within an absorption band of the con-taminant. The first band is detected, after it has impinged on the material, by a detector which produces a first electrical signal in response to the radiation detected. A second band of electromagnetic radiation is also emitted and is aligned to impinge the material. The second band is character-ized in that it lies within an absorption band of the substance and also lies within an absorption band of the contaminant. The second band is detected, after it has impinged the material, by a receiver which generates a second electrical signal, in response to the radiation detected. The second electrical signal is subtracted from the first electrical signal.
According to the invention there is provided a method of measuring the amount of substance associated with a material in the presence of a con-taminant, said contaminant having an electromagnetic radiation absorption characteristic different from the electromagneti& radiation absorption characteristic of said substance, wherein said method comprising the steps of: emitting a first band of electromagnetic radiation, wherein said first band lies outside an absorption band of said substance, and lies within an ; 20 absorption band of said contaminant; directing said first band to lmpinge said material; detecting said first band after reflecting from said material;
generating a first electrical signal, in response to said first band detect-ed; emanating a second band of electromagnetic radiation, wherein said second band lies within an absorption band of said substance, and also lies wlthin an absorption band of said contaminant; aligning said second band to impinge said material; receiving said second band after reflecting from said material; producing a second electrical signal, in response to said second band received; and calculating the amount of substance in accordance with the ;:
, ~t - ~, ' ~ ' 5~9 formula:
amount of substance = A+B(M + M)-C(N ~ N) where A, B, C are calibration constants; M = intensity of second band received without material divided by intensity of second band received with material; N = intensity of first band detected without material divided by intensity of first band detected with material.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic side view of an apparatus using the method of the present invention.
Figure 2 is a schematic side view of another apparatus using the method of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
The present invention relates to a method of measuring the amount of substance associated with a material, in the presence of a contaminant.
The contaminant has an electromagnetic radiation absorption characteristic different from that of the substance. In the method of the present invention, a first band of electromagnetic radiation is emitted from a source. The first band has the characteristic of being within an absorption band of the contaminant, but outside an absorption band of the substance. The Eirst band is directed to impin~e the material. A detector is positioned to receive the first band after impinging the material. A first electrical signal in response to the first radiation detected is generated by the detector. A
second band of electromagnetic radiation is produced and is also aligned to impinge the material. The second band has the characteristic of being within an absorption band of the substance and within an absorption band of the con-taminant. The second band is detected by a receiver after the second band has impinged the material. The receiver generates a second electrical signal in response to the second band of radiation detected. The second electrical ~4~
. : . .
.. . , .' . ~
.
: - - ~ - - : ; -' 7g signal is subtracted from the first electrical signal.
A particular application of the method of the present invention is in the measurement of moisture of paper material in the presence of carbon.
This can be best understood by referring to Figure 1, which is a schematic 4a ~1~257~
side view of an apparatus 10 using the method of the present invention. h paper material 12, substantially in a sheet form, moves in a direction shown by arrow 14. The paper material 12 can be the manufactured product of a Fourdrinier machine (not shown). As is well known in paper making technology, the control of the amount of moisture or water in the paper is critical in controlling quality and economic return. In the paper matcrial 12 of Figure 1, however, the paper material 12 also contains carbon particles 16 (greatly exaggerated). A first source 18 emits a first band of electro-magnetic radiation, directed towards the paper material 12 in a direction along the dotted line 20. The first band, after impinging the paper material 12 reflects from it and travels in the direction along the dotted line 22 and is received by a fir9t receiver 24. The first receiver 24 converts the first band received into a first electrical signal 26. The first band is chosen such that it lies within an electromagnetic absorption band of carbon but lies outside of an electromagnetic absorption band of water. Typically, this is at about 1.8 microns. A second source 28 emits a second band of ~ electromagnetic radiation, directed towards the paper material 12 in a ; direction along the dotted line 30. The second band, after impinging the paper material 12, reflects from it and travels in the direction along the dotted line 32 and is received by a second receiver 34. The second receiver 34 convert9 the 9econd band received into a second electrical signal 36. The second band is chosen such that it lies within an electromagnetic absorption band of water and is also within an electromagnetic absorption band of carbon. Typically, this is about 1.94 microns. The second electrical signal 36 is subtracted from a first electrical signal 26 by a computer 380 The result is determinitive of the amount of moisture in the paper material 12.
In general, the first source 18 and the second source 28 can be any - 5 _ , .
..
, - , , :, :, ,,~ - - :: - , : . . .
5~9 source emitting the desired electromagnetic radiation. They can even be the same source, e.g. an infrared lamp. The dotted lines 20 and 30 can coincide and thus the first band and second band would impinge the same area on~
the paper material 12. In fact, for accuracy, this is preferred. In the event the dotted lines 20 and 30 coincide such that the first band and the second band impinge the same area on the paper material 12, then the dotted lines 22 and 32 would also coincide. In that event, the first receiver 24 and the second receiver 34 are positioned to receive both bands with a beam splitter such as that disclosed in United States Patent No. 3,641,349.
The first receiver 24 and the second receiver 34 can be any suitable detector, such as photodiode. The apparatus 10 of FYgure 1 uses the method of the present invention in which the measurement of the amount of moisture of the paper material 12 is accomplished by reflecting bands of electro-magnetic radiation from the paper material 12. In this application, known as reflectance measurement, the calculation of the amount of moisture associated with the paper material 12 in the presence of carbon, by subtracting the second signal 36 from the first signal 26, can be further simpli ~ed to:
' amount of moisture = A + B (M + -) - C (N + 1) M N
where A~ B~ C are constantsof the apparatus 10 obtained from initial calibration, M is the intensity of second band (1094 micron) received without the paper material 12 (eOg. replace the paper material 12 by a reflector) divided by the intensity of the 9econd band received with the paper material 12 ( i.e. the intensity of second band received during the measurement process), and N is the intensity of the first band (1.8 micron) received without the paper material 12(eOg.
_ 6 -: ~ --: ~ , ,. . - . ' , ~ ' 1~ ii79 replace the paper material by a reflector) divided by the intensity of the first band received with the paper material 12 (i.e. the intensity of first band received during the measurement process).
The measurement of the intensity of the first band and the second band are made usually during standardization, i.eO when the apparatus 10 moves off-sheet from the paper material 12. These measurements are made to correct for errors caused by dirt build-up, source aging etc.
Referring to Figure 2, there is shown a schematic side view of another apparatus 40 using the method of the present invention. A paper material 42, substantially in a sheet form, moves in a direction shown by arrow 44. The paper material 42 contains carbon particles 46 (greatly exaggerated). A first source 48 emits a first band of electromagnetic radiation, directed towards the paper material 42 in a direction along the dotted line 50. me first band, after impinging the paper material 42, transmits through it, and travels in the direction along the dotted line 52 and is received by a first receiver 54. The first receiver 54 converts the first band received into a first electrical signal 56. The first band is chosen such that it lies within an electromagnetic absorption band of carbon but lies outside of an electromagnetic absorption band of water.
Typically, this is at about 1.8 microns. A second source 58 emits a second band of electromagnetic radiation, directed towards the paper material 42 in a direction along the dotted line 60. The second band~ after impinging the paper material 42, transmits through it and travels in the direction along -the dotted line 62 and is received by a second receiver 64. m e second receiver 64 converts the second band received into a second electrical signal 66c The second band is chosen such that it lies within an electro-.: .. - , . . ... .. : - : .
magnetic absorption band of water and is also within an electromagnetic absorption band of carbon. Typically, this is at about 1094 microns. The second electrical signal 66 is subtracted from a first electrical signal 56 by a computer 68. The result is determinitive of the amount of moisture in the paper material 42.
The apparatus 40 of Figure 2 is similar to that disclosed and shown in United States Patent No. 3,793,524. The apparatus 40 comprises a first diffusing plate 41 to one side of the paper material 42, while a second diffusing plate 43 is to the other side of the paper material 42. In addition the sources 48, 58 and the receivers 54, 64 are off-set from one another, iOe. no amount of radiation is received directly by the receivers 54 and 64 from the sources 48 and 58. The advantages of the diffusing plates 41 and 43, and the off-set geometry are discussed fully in United States Patent ~o. 3,793,524. In general, the first source 48 and the second source 58 can be any source emitting the desired electromagnetic radiation.
They can even by the same source, e.gO an infrared lampO The dotted lines 50 and 60 can coincide and thus the first band and second band would impinge the same area on the paper material 420 In fact, for accuracy, this is preferred. In the event the dotted lines 50 and 60 coincide such that the first band and the second band impinge the same area on the paper material 42, then the dotted lines 52 and 62 would also coincideO In that event, the first receiver 54 and the second receiver 64 are positioned to receive both bands with a beam splitter, such as that disclosed in United States Patent No. 3,641~349. The first receiver 54 and the second receiver 64 can be any 9uitable detector such as photodiode. The apparatus 40 of Figure 2 uses the method of the present invention in which the measurement of the amount of moisture of the paper material 42 is accomplished by transmitting bands of electromagnetic radiation through the paper ~aterial 42. In this i79 application, known as transmittance measurement, the calculation of the amount of moisture associated with the paper material 42 in the presence of carbon, by subtracting the second signal 66 from the first signal 56, can be further simplified to:
amount of moisture = A + B ~M - C ~N
where A, B, C are constants of the apparatus 40 obtained from initial calibration;
M is the intensity of the second band (1.94 micron) received without the paper material 42 (e.gO
remove the paper material 42 and measure the intensity of the second band) divided by the intensity of the second band received with the paper material 42 (i.e. the intensity of the second band received during the measurement process); and N is the intensity of the first band (1.8 micron) received without the paper material 42`(e.gA
remove the paper material 42 and measure the intensity of the second band) divided by the intensity of the first band received with the paper material 42 (i.e. the intensity of the first band received during the measurement process).
me measurements of the intensity of the first band and the second band are made usually during standardization, iOe. when the apparatus 40 moves off_sheet from the paper material 420 These measurements are made to correct for errors caused by dirt build-up, source aging etc.
It should be appreciated that the method of the present invention is not limited in its application to the determination of the amount of .. . . . . . .
.. - ............... . . . , - .
.... .
.
5;~
moisture associated with paper material in the presence of carbon, either through reflectance measurement or transmittance measurementO The method of the present invention can be used to determine the amount of any substance associated with a material in the presence of a contaminant. For example, the method of the present invention can also be used to determine the amount of plastic in a plastic film in the presence of carbon, or to determine the amount of water in a paper material in the presence of other colored dyes.
The theoretical basis for the method of the present invention is as follows: The amount of monochromatic light reflected or transmitted from a diffusing sheet depends on the absorption coefficient K and the scattering coefficient S. It shall be assumed that, in accordance with Beer's Iaw, the absorption depends on the concentration of substance in the sheet, the concentration of contaminant, and the concentration of some unknown (albeit small amount). In addition, it is assumed that the absorption coefficients are additive so that the total absorption coefficient K is the sum:
K = K (substance ) + K (contaminant) + K (other) + KS + KC + Ko From the theory of Kubelka and Munk (Kubelka, Paul, "New Contributions to the Optics of Intensely Light-Scattering Materials~ Part I'l, Journ.
Opt. Soc, Am., 38, 1945.), the total absorption coefficient can also be related to reflectance R and scattering coefficient S. Thus:
M MS + KMC + KMo 2 _ (M +~~r) ~ S
N NS + KNC + KN0 = 2 (N + -N) ~ SN
where M and N are the ratio of measure and reference bands respectively as previously discussed.
.. . . . ..
. . : : - . : : -. " . ~, . - ,- : ~ .
: . :' -', ~ ' : .. ' If it is assumed that the contaminant absorbs equally at the reference channel and at the measure channel, i.e. KMC = KNC then the difference of the two equations yields:
(KMS ~ KNS) + (KMo ~ KN0) = 2M (M + M) ~ 2 (N + N) ~ (SM S~) since (KMs- KNs) is proportional to the amount of substance, and the terms (KMo - KN0)~ 2 ~ 2 and (SM ~ SN) are constants, the equation becomes:
amount of substance = A + B (M + M) ~ C (N + 1) where A, B and C are constants determined by calibration.
In the case of light transmitted through the sheet, the effect of the light scattered from the sheet and then reflected from the diffusing plates to impinge the sheet, must be considered~ mus, the theory of Kubelka and Munk must be rewritten to include multiple passes and to take into account the off-set geometry. m e analysis, thereafter, however, is the same. The coefficient of absorption K can be determined for the measured channel and the reference channel. me difference is taken and the resultant is proportional to the amount of substance.
It should be appreciated that the method of the present invention does not require a large amount of a priori data. Moreover, it i9 accurate and has a wi~e range of applicability to correct for the presence of any contaminant.
. .
, , ' : , ' ,: ' ' ' ': ' . ' ' . . ' , ' : : -, . ' - ~ -
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of measuring the amount of substance associated with a material in the presence or a contaminant, said contaminant having an electromagnetic radiation absorption characteristic different from the electromagnetic radiation absorption character-istic of said substance, wherein said method comprising the steps of:
emitting a first band of electromagnetic radiation, wherein said first band lies outside an absorption band of said substance, and lies within an absorption band of said contaminant;
directing said first band to impinge said material;
detecting said first band after reflecting from said material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within an absorption band of said substance, and also lies within an absorption band of said contaminant;
aligning said second band to impinge said material;
receiving said second band after reflecting from said material;
producing a second electrical signal, in response to said second band received; and calculating the amount of substance in accordance with the formula:
amount of substance = A+B(M+?)-C(N+?) where A, B, C are calibration constants;
M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
emitting a first band of electromagnetic radiation, wherein said first band lies outside an absorption band of said substance, and lies within an absorption band of said contaminant;
directing said first band to impinge said material;
detecting said first band after reflecting from said material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within an absorption band of said substance, and also lies within an absorption band of said contaminant;
aligning said second band to impinge said material;
receiving said second band after reflecting from said material;
producing a second electrical signal, in response to said second band received; and calculating the amount of substance in accordance with the formula:
amount of substance = A+B(M+?)-C(N+?) where A, B, C are calibration constants;
M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
2. A method of measuring the amount of substance associated with a material in the presence of a contaminant, said contaminant having an electromagnetic radiation absorption characteristic different from the electromagnetic radiation absorption character-istic of said substance, wherein said method comprising the steps of:
emitting a first band of electromagnetic radiation, wherein said first band lies outside an absorption band of said substance, and lies within an absorption band of said contaminant;
directing said first band to impinge said material;
detecting said first band after transmitting through said material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within an absorption band of said substance, and also lies within an absorption band of said contaminant;
aligning said second band to impinge said material;
receiving said second band after transmitting through said material;
producing a second electrical signal, in response to said second band received; and calculating the amount of substance in accordance with the formula:
amount of substance = A+B?M-C?N
where A, B, C are calibration constants;
M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
emitting a first band of electromagnetic radiation, wherein said first band lies outside an absorption band of said substance, and lies within an absorption band of said contaminant;
directing said first band to impinge said material;
detecting said first band after transmitting through said material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within an absorption band of said substance, and also lies within an absorption band of said contaminant;
aligning said second band to impinge said material;
receiving said second band after transmitting through said material;
producing a second electrical signal, in response to said second band received; and calculating the amount of substance in accordance with the formula:
amount of substance = A+B?M-C?N
where A, B, C are calibration constants;
M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
3. A method of measuring the amount of water associated with a paper material in the presence of carbon, wherein said method comprising the steps of:
emitting a first band of electromagnetic radiation, wherein said first band lies outside the electromagnetic absorption band of water but lies within the electromagnetic absorption band of carbon;
directing said first band to impinge said paper material;
detecting said first band after reflecting from said paper material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within the electromagnetic absorption band of water and lies within the electromagnetic absorption band of carbon;
aligning said second band to impinge said paper material;
receiving said second band after reflecting from said paper material;
producing a second electrical signal, in response to said second band received; and calculating the amount of water in accordance with the formula:
moisture = A+B(M+?)-C(N+?) where A, B, C are calibration constants M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
emitting a first band of electromagnetic radiation, wherein said first band lies outside the electromagnetic absorption band of water but lies within the electromagnetic absorption band of carbon;
directing said first band to impinge said paper material;
detecting said first band after reflecting from said paper material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within the electromagnetic absorption band of water and lies within the electromagnetic absorption band of carbon;
aligning said second band to impinge said paper material;
receiving said second band after reflecting from said paper material;
producing a second electrical signal, in response to said second band received; and calculating the amount of water in accordance with the formula:
moisture = A+B(M+?)-C(N+?) where A, B, C are calibration constants M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
4. The method of Claim 3 wherein said first band of electromagnetic radiation lies at about 1.8 microns.
5. The method of Claim 4 wherein said second band of electromagnetic radiation lies at about 1.94 microns.
6. A method of measuring the amount of water associated with a paper material in the presence of carbon, wherein said method comprising the steps of:
emitting a first band of electromagnetic radiation, wherein said first band lies outside the electromagnetic absorption band of water but lies within the electromagnetic absorption band of carbon;
directing said first band to impinge said paper material;
detecting said first band after transmitting through said paper material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within the electromagnetic absorption band of water and lies within the electromagnetic absorption band of carbon;
aligning said second band to impinge said paper material;
receiving said second band after transmitting through said paper material;
producing a second electrical signal, in response to said second band received; and calculating the amount of water in accordance with the formula:
moisture = A+B?M-C?N
where A, B, C are calibration constants M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
emitting a first band of electromagnetic radiation, wherein said first band lies outside the electromagnetic absorption band of water but lies within the electromagnetic absorption band of carbon;
directing said first band to impinge said paper material;
detecting said first band after transmitting through said paper material;
generating a first electrical signal, in response to said first band detected;
emanating a second band of electromagnetic radiation, wherein said second band lies within the electromagnetic absorption band of water and lies within the electromagnetic absorption band of carbon;
aligning said second band to impinge said paper material;
receiving said second band after transmitting through said paper material;
producing a second electrical signal, in response to said second band received; and calculating the amount of water in accordance with the formula:
moisture = A+B?M-C?N
where A, B, C are calibration constants M = intensity of second band received without material divided by intensity of second band received with material;
N = intensity of first band detected without material divided by intensity of first band detected with material.
7. The method of Claim 6 wherein said first band of electromagnetic radiation lies at about 1.8 microns.
8. The method of Claim 7 wherein said second band of electromagnetic radiation lies at about 1.94 microns.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87477778A | 1978-02-03 | 1978-02-03 | |
| US874,777 | 1978-02-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1102579A true CA1102579A (en) | 1981-06-09 |
Family
ID=25364556
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA320,074A Expired CA1102579A (en) | 1978-02-03 | 1979-01-22 | Method of measuring the amount of substance associated with a material in the presence of a contaminant |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS54114294A (en) |
| CA (1) | CA1102579A (en) |
| FR (1) | FR2416466A1 (en) |
| GB (1) | GB2013881B (en) |
| SE (1) | SE7900926L (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4602160A (en) * | 1983-09-28 | 1986-07-22 | Sentrol Systems Ltd. | Infrared constituent analyzer and control system |
| JPS6242035A (en) * | 1985-08-19 | 1987-02-24 | Yunisoku:Kk | Drying degree detecting device for leaf tobacco |
| JPH0372346U (en) * | 1989-11-20 | 1991-07-22 | ||
| DE19520035C1 (en) * | 1995-03-31 | 1996-11-07 | Gta Sensorik Gmbh | Contactless measurement of surface moisture of objects |
| JP2014016373A (en) * | 2013-10-30 | 2014-01-30 | Fujifilm Corp | Method of measuring component amount in coating film |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3614450A (en) * | 1969-02-17 | 1971-10-19 | Measurex Corp | Apparatus for measuring the amount of a substance that is associated with a base material |
| US3851175A (en) * | 1972-10-27 | 1974-11-26 | Measurex Corp | Moisture gauge with opacity type compensation |
| CA1000406A (en) * | 1972-10-27 | 1976-11-23 | Measurex Corporation | Moisture gauge with opacity type compensation |
| US4006358A (en) * | 1975-06-12 | 1977-02-01 | Measurex Corporation | Method and apparatus for measuring the amount of moisture that is associated with a web of moving material |
-
1979
- 1979-01-09 GB GB7900768A patent/GB2013881B/en not_active Expired
- 1979-01-22 CA CA320,074A patent/CA1102579A/en not_active Expired
- 1979-01-22 FR FR7901523A patent/FR2416466A1/en active Granted
- 1979-02-02 JP JP1133179A patent/JPS54114294A/en active Pending
- 1979-02-02 SE SE7900926A patent/SE7900926L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2416466A1 (en) | 1979-08-31 |
| GB2013881A (en) | 1979-08-15 |
| SE7900926L (en) | 1979-08-04 |
| GB2013881B (en) | 1982-06-16 |
| JPS54114294A (en) | 1979-09-06 |
| FR2416466B1 (en) | 1983-06-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4306151A (en) | Method of measuring the amount of substance associated with a material in the presence of a contaminant | |
| US4297874A (en) | Apparatus for measuring a percentage of moisture and weighing of a sheet-like object | |
| CA1260628A (en) | Method and apparatus for sensing or determining one or more properties or the identity of a sample | |
| CA1132364A (en) | Method and apparatus for measuring the moisture content of paper | |
| CA1193660A (en) | Microwave moisture sensor | |
| KR880010326A (en) | Temperature compensated humidity sensor | |
| SE7906518L (en) | PROCEDURE TO MEET THE CONTENT OF A SUBSTANCE IN A MIXTURE OF A MULTIPLE SUBJECT (MATERIAL) WHICH MIX IS THE FORM OF A THIN MOVIE, EXAMPLE OF MEASURING THE WATER CONTENT OF PAPER | |
| US5185644A (en) | Sensor for water film on a plate in printing machines | |
| CA1102579A (en) | Method of measuring the amount of substance associated with a material in the presence of a contaminant | |
| EP0119630A3 (en) | Method and apparatus for coating detection and surface evaluation | |
| US5774228A (en) | Deterioration diagnosis method and device of electrical machine and apparatus | |
| JPH08178870A (en) | Spectroscopic method and device for measuring minute absorbing amount or reflecting amount of material sample | |
| US4769544A (en) | System and process for measuring fiberglass | |
| US3260850A (en) | Measuring the water content of photographic layers | |
| EP0066434B1 (en) | Determination of heat transfer from a surface | |
| JPS56115905A (en) | Measuring method for thickness of transparent film and device therefor | |
| US3662170A (en) | Method and apparatus for measuring the thickness moisture profile of fibrous webs | |
| JPS5796203A (en) | Contactless displacement detector employing optical fiber | |
| US4764023A (en) | Heat transfer rate measurement using the optical properties of a dissolving coating | |
| GB1566398A (en) | Thickness measurements | |
| JPS5761905A (en) | Measuring device of surface coarseness | |
| JPS55155204A (en) | Measuring instrument for thickness of film | |
| JPS5644802A (en) | System and method of measuring film thickness and coating varnish film thickness | |
| JPH0850007A (en) | Method and apparatus for evaluating film thickness | |
| JPS57111435A (en) | Measuring device for absorption intensity of infrared ray by atr method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |