JP6176332B2 - Measuring method and apparatus for basis weight and moisture content - Google Patents

Description

  The present invention relates to a method and apparatus for measuring on-line the basis weight (weight per square meter) and moisture content of a sheet-like material such as paper, non-woven fabric, and film, particularly a paper sheet.

  In the paper manufacturing process, it is very important to measure the basis weight online, and the basis weight is an important management item in terms of paper quality and commerce. Not only the basis weight but also the moisture content is an important item. Conventionally, it is common to use a BM meter (Basis Weight & Moisture Measurement System) to determine the basis weight of paper from the transmission attenuation amount of β rays and the moisture of paper from the absorption amount of near infrared rays. The basis weight measured by the BM meter is considered to have the highest reliability.

  In order to measure the basis weight, β rays obtained from a radiation source such as Kr85 (krypton) or Pm147 (promesum) are used. If the basis weight is large, the attenuation amount of β rays is large, and if the basis weight is small, the attenuation amount is small. Therefore, the transmission amount of the β rays and the basis weight are in an inversely proportional relationship. In order to determine the basis weight accurately, a calibration curve indicating the relationship between the amount of β-ray transmission and the basis weight is used.

  Normally, three types of reference light, measurement light, and correction light are used as near infrared rays for measuring moisture. The reference light has a wavelength of 1.8 μm, and this wavelength light is not attenuated by moisture. The measurement light has a wavelength of 1.9 μm, and this wavelength light is attenuated by moisture. The correction light has a wavelength of 2.1 μm, and this wavelength light is not affected by cellulose. By examining the relationship between the amount of attenuation of the measurement light due to moisture and the amount of moisture in advance as a calibration curve, an accurate amount of moisture can be obtained.

  Since the basis weight measurement of the conventional BM meter uses β rays, a radiation source such as krypton 85 or promesum 147 must be used as a radiation source. Radiation sources can adversely affect the human body. For this reason, it is necessary to set up a no-access area so as not to get close to the radiation source at the time of measurement, and to obligate people who frequently work in the vicinity to carry a film batch and to check the radiation dose regularly. In addition, it is necessary to appoint a chief engineer who can handle radiation, and sufficient attention and expertise are required for handling radiation.

  As a method for avoiding such problems caused by using a radiation source, the present inventors have proposed a method for measuring the basis weight and moisture of a sheet-like substance such as paper without using radiation (Patent Document 1). reference.). The proposed method uses a microwave dielectric resonator to simultaneously measure the basis weight and moisture, and as an application of a device that measures the dielectric anisotropy of a sample, such as the fiber orientation of a paper, It shows that the basis weight and water content can be measured simultaneously in addition to the orientation. According to the proposed method, the basis weight is obtained from the resonance frequency shift amount that is the difference between the resonance frequency when there is no sample and the resonance frequency when the sample is placed, and the moisture content is the resonance frequency when there is no sample. Is obtained from the amount of change in resonance peak level, which is the difference between the peak level at 1 and the peak level at the resonance frequency when the sample is placed.

  Furthermore, the present inventors have also proposed a specific method for obtaining the basis weight and the moisture content or moisture content (see Patent Document 2). The specific method of the proposal is schematically shown as follows.

  When a microwave resonator is used, the resonance frequency shift amount Δf and the resonance peak level change amount ΔP appear as shown in FIG. When the thickness of the sample is T, the resonance frequency shift amount Δf is proportional to ((dielectric constant−1) × T), and the resonance peak level change amount ΔP is proportional to (dielectric loss factor × T).

On the other hand, considering a model in which paper is separated into an absolutely dry part and water as shown in FIG. 6 and assuming that the volume of the absolute dry part being measured is V1 and the volume of water is V2, the following equation is established.
Δf = Kf (V1 · ε′1 + V2 · ε′2) (3)
ΔP = Kp (V1 · ε ″ 1 + V2 · ε ″ 2) (4)
Here, Kf and Kp are proportional constants for matching the dimensions, ε′1 is the dielectric constant-1 of the absolutely dry paper, ε′2 is the dielectric constant of water, ε ″ 1 is the dielectric loss factor of the absolutely dry paper , Ε ″ 2 is the dielectric loss rate of water (which also depends on the frequency, the degree of binding, and the temperature).

V1 and V2 are obtained by solving the above simultaneous equations (3) and (4) using the measured data of Δf and ΔP. And between V1, V2, absolute dry basis weight (BD), moisture content (WT),
Absolutely dry basis weight (BD) = β · V1 (5)
Water content (WT) = γ · V2 (6)
Since β is a specific gravity of paper in an absolutely dry state and γ is a specific gravity of water, the absolute dry basis weight is obtained from V1, and the water content is obtained from V2. This is the method proposed in Patent Document 2.

JP 2006-349425 A (US Pat. No. 7,423,435 B2) WO2011 / 092889 (US-2013-0025350-A1)

JIS P8124 (established in 1956, revised in 2011) JIS P8127 (established in 1958, revised in 2010)

  An object of the present invention is to provide a new method and apparatus for determining the basis weight and moisture content of paper using a microwave resonator by a method different from the method described in Patent Document 2.

The basis weight / water content measuring method of the present invention includes the following steps S1 to S3.
(Step S1) Resonance frequency f1 and resonance peak level P1 in the microwave resonator in the first state where the sample is not installed, and resonance frequency f2 and resonance in the microwave resonator in the second state where the sample is installed Measuring the peak level P2, and obtaining a resonance frequency shift amount Δf (= f1-f2) and a peak level change amount ΔP (= P1-P2);
(Step S2) Calibration curve showing relationship between ΔP and water content WT (1)
WT = F (ΔP) (1)
(F (ΔP) is a function of ΔP)
And the step of obtaining the moisture content WT of the sample from ΔP obtained in step S1, and (step S3) The following equation (2) showing the relationship between Δf, WT and BD
Δf = A · BD + B · WT (2)
(A and B are constants.)
The step of obtaining the absolute dry basis weight BD of the sample from Δf obtained in step S1 and WT obtained in step S2.

  The WT for determining the calibration curve (1) and the BD and WT for determining the constants A and B are used for a plurality of standard samples using a device other than a microwave resonator, for example, a BM meter, or a microwave. It is obtained separately by a method that does not use a device other than the resonator and the microwave resonator. The calibration curve (1) is obtained from the separately obtained WT and the measured value ΔP obtained for the corresponding standard sample using the microwave resonator, and the constants A and B are obtained from the separately obtained BD and WT. The Δf obtained by applying the equation (2) is obtained as a combination of constants A and B such that the corresponding standard sample is closest to the measured value Δf obtained using the microwave resonator.

  As a device other than the microwave resonator for separately obtaining BD and WT, for example, a BM meter can be used. Although the BM meter uses a radiation source, even if a BM meter is used, the BM meter is used only when measuring a standard sample for determining a calibration curve and constants A and B in the present invention. Once the calibration curve and the constants A and B are determined, a measurement device equipped with a microwave resonator is only used for the subsequent actual sample measurement, and a BM meter is no longer necessary. Therefore, in the present invention, there is no problem described above by using a radiation source.

  As an example of a method in which neither a microwave resonator nor an apparatus other than a microwave resonator such as a BM meter is used, the absolute dry basis weight is “paper and paperboard? Basis weight measurement method, JIS P8124 (established in 1956, revised in 2011) ) "(See Non-Patent Document 1), the method described in the method for measuring the absolute dry basis weight specified in Appendix A, and the moisture content is" paper and paperboard-lot moisture test method-using a dryer " Method, JIS P8127 (established in 1958, revised in 2010) ”(see Non-Patent Document 2). These Japanese Industrial Standard measurement methods are all off-line measurement methods and are performed when the BM meter is verified.

The absolute dry basis weight measurement method based on the measurement method of the Japanese Industrial Standard is performed as follows.
(1) The area of the collected sheet sample is measured in advance.
(2) The sample is put in a heated dryer and the water content is sufficiently removed until there is no change in weight, and the sample weight is immediately measured.
(3) The absolute dry basis weight is obtained by dividing the sample weight after drying by the sample area measured before heating.
The moisture measurement method based on the measurement method of Japanese Industrial Standard is performed as follows.
(1) The area and weight of the collected sheet sample are measured in advance.
(2) In the same manner as the method for measuring the absolute dry basis weight, the sample is put in a heated drier and the water content is sufficiently removed until there is no change in weight, and the sample weight is immediately measured.
(3) When calculating | requiring a moisture content, it calculates with the following (a) formula, when calculating | requiring a moisture content, it calculates with the following (b) formula.
Moisture content = [(sample weight before heating−sample weight after heating) / (sample weight before heating)] × 100 (a)
Water content = (sample weight before heating−sample weight after heating) / (sample area before heating) (b)

  In the above two measurement methods, when measuring the weight of the sample, the change in moisture contained in the sample is caused by measurement error, so it is sufficient to use a weighing bottle to prevent moisture change during weight measurement. It is necessary to pay attention.

Here, the process of deriving equation (2) will be described. Rewriting V1 and V2 as BD (absolute dry basis weight) and WT (water content) based on (5) and (6), respectively, for the expression (3), the following expression (3A) is obtained.
Δf = Kf ((BD / β) · ε′1 + (WT / γ) · ε′2) (3A)
Here, the constant part of the expression (3A) is summarized to be the expression (2).
Δf = A · BD + B · WT (2)

The expression (1) is a general expression in which a calibration curve indicating the relationship between ΔP and the amount of water WT is a function of ΔP. In one embodiment, as a specific example of the calibration curve, the following approximate expression WT = a · ΔP ³ + b · ΔP ² + c · ΔP (1A)
Use the one represented by. In this case, the calibration curve is determined by applying the WT acquired separately for a plurality of standard samples and the measured value ΔP obtained for the corresponding standard sample using the microwave resonator to the equation (1A), and by using constants a and b , C is determined.

In another embodiment, the air dry basis weight (g / m ² ) and moisture content (%) are further determined using the following formula. The absolutely dry basis weight means the basis weight when the moisture content is 0%.
Air dry basis weight = absolute dry basis weight BD + water content WT (7)
Moisture content = moisture content WT x 100 / air dry basis weight (8)

In this specification, “water content” and “water content” are used as equivalent terms as terms related to the amount of water. “Moisture content” and “water content” have the following relationship from the equations (7) and (8).
Moisture content = (water content WT / (absolute dry basis weight BT + water content WT)) × 100

  The basis weight / moisture content measuring device of the present invention detects a microwave resonator, a microwave excitation device that generates an electric field vector in the microwave resonator, and transmitted energy or reflected energy by the microwave resonator. The detection device, the resonance frequency f1 of the microwave resonator in the first state where no sample is installed from the detection device, the peak level P1 at the position of the resonance frequency f1, and the second state where the sample is installed A data processing device that takes in the resonance frequency f2 of the microwave resonator and the peak level P2 at the position of the resonance frequency f2, and calculates the absolute dry basis weight and moisture content of the sample; A detailed configuration of the data processing apparatus will be described later.

  ADVANTAGE OF THE INVENTION According to this invention, when measuring the basic weight and moisture content (water content) of sheet-like substances, such as paper, using a microwave resonator, it can measure safely, without using a radiation.

It is a block diagram which shows one preferable embodiment of a basic weight / moisture content measuring apparatus. It is a top view which shows the dielectric resonator used in one Example. It is a vertical sectional view of the same resonator. It is a wave form diagram which shows the change of the resonance curve in a dielectric resonator by the presence or absence of a sample. It is a top view which shows an example of the orientation meter measurement part which has arrange | positioned five dielectric resonators. It is a figure which shows an example of the orientation pattern obtained from the five dielectric resonators shown in FIG. It is sectional drawing which shows a moisture model. It is a graph which shows an example of the calibration curve showing the correlation of (DELTA) P and a moisture content. It is a block diagram which shows the circuit which processes the signal from five dielectric resonators. It is a time chart which shows the signal processing in the block diagram of FIG. It is a block diagram which shows in detail the signal processing circuit about one dielectric resonator in the circuit of FIG. It is a flowchart which shows the procedure which calculates | requires (DELTA) fr. It is a flowchart which shows the procedure which calculates | requires (DELTA) Pr. It is a flowchart which shows the procedure which determines a constant. It is a flowchart which shows an example of sample measurement operation | movement. It is a graph which shows the correlation with the moisture content measured value by BM meter, and the measurement result in a microwave resonator. It is a graph which shows the correlation with the absolute dry basis weight measured value by BM meter, and the measurement result in a microwave resonator. It is a graph which shows the correlation with the measurement result in an air dry basis weight measured with a BM meter, and a microwave resonator.

  First, the outline | summary of the apparatus which measures basic weight and a moisture content (or moisture content) is demonstrated.

When measuring the basis weight and water content of paper instead of measuring the fiber orientation of paper using a microwave resonator, it is necessary to cancel the anisotropy of the dielectric constant. As a canceling method, for example, there is a method using one microwave resonator. The microwave resonator may be a cavity resonator or a dielectric resonator. In this case, in the case of a cavity resonator, a cylindrical cavity resonator or a spherical cavity resonator is used to select a resonance mode in which the electric field vector is not biased in a certain direction, such as the TE ₀₁₁ mode in which the electric field vector is looped. To do. In the case of a dielectric resonator, the electric field vector of the evanescent wave is not oriented in a certain direction, but an electric field distribution directed in all directions using a cylindrical dielectric resonator, or an electric field distribution in a loop shape, etc. Of course, it is desirable to select a resonance mode that provides an electric field distribution. In this case, the basis weight and the moisture content can be calculated using the resonance frequency shift amount and the resonance peak level change amount obtained by the resonator when there is no sample and when there is no sample as it is.

  When measuring the basis weight and water content as an application of a device that measures the dielectric anisotropy of a sample such as the fiber orientation of paper online, there is a problem that it is influenced by the dielectric anisotropy of the sample. is there. Since the dielectric constant is a tensor, the value varies depending on the direction. However, since the basis weight and the moisture amount are scalar amounts, the value does not vary depending on the direction. The problem is how to cancel this dielectric anisotropy when measuring the basis weight or moisture content.

  A method for canceling the dielectric anisotropy of the sample with an apparatus for measuring the dielectric anisotropy of the sample will be described. 2A and 2B show schematic views of a rectangular microwave dielectric resonator. FIG. 2A is a plan view, and FIG. 2B is a vertical sectional view at a position passing through the antennas 2a and 2b. The dielectric resonator 1 is excited by one antenna 2a and outputs from the other antenna 2b. The resonator 1 and the antennas 2 a and 2 b are accommodated in the shield case 4.

  Most of the resonance energy is confined inside the resonator 1, but a part of the resonance energy oozes out as an evanescent wave. In the case of a rectangular dielectric resonator, by appropriately selecting the resonance mode, the electric field distribution protruding on the surface of the resonator becomes parallel to the long side direction. Here, it is used in such a resonance mode in which the electric field distribution is parallel to the long side direction. When almost all the electric field vectors of the evanescent wave 6 are parallel, it is possible to measure the dielectric anisotropy of the sample 8, that is, the orientation.

  When the sample 8 is arranged close to or in contact with the upper surface of the dielectric resonator 1, the resonance frequency is shifted to the lower frequency side as shown in FIG. 3 corresponding to the dielectric constant of the evanescent wave 6 in the electric field vector direction. Let the resonance frequency shift amount be Δf. The resonance frequency shift amount is defined as a value obtained by subtracting the resonance frequency f2 when there is a sample from the resonance frequency f1 when blank when there is no sample.

  When the sample 8 is arranged close to or in contact with the upper surface of the dielectric resonator 1, the peak level at the resonance frequency position decreases corresponding to the dielectric loss rate of the sample simultaneously with the shift of the resonance frequency. The amount of change in peak level is ΔP. The peak level change amount is defined as a value obtained by subtracting the peak level P2 at the resonance frequency position when there is a sample from the peak level P1 at the resonance frequency position when blank when there is no sample. When the dielectric constant of the sample is ε ′, the dielectric loss rate is ε ″, and the thickness of the sample is T, the frequency shift amount Δf is proportional to (ε′−1) × T, and the peak level change amount ΔP is ε ″ × It is proportional to T.

  When measuring the orientation, the anisotropy of the dielectric constant may be observed. Therefore, the dielectric anisotropy can be obtained by arranging a plurality of rectangular dielectric resonators so that their directions are different from each other and detecting the amount of resonance frequency shift in each resonator.

  FIG. 4 shows a layout example when, for example, five rectangular dielectric resonators 1a to 1e are arranged so as to have different directions (θ) from the reference direction. The five resonators 1a to 1e are preferably arranged close to each other so that a place as close as possible can be measured. In this example, five resonators 1a to 1e are arranged in a circle having a diameter of 200 mm. The reference direction can be arbitrarily determined, but here, as an example, the moving direction (MD direction) of the sample is set as the reference direction.

  The alignment pattern corresponding to this is shown in FIG. This is based on polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, and the direction (θ) of the resonators 1a to 1e is the angle θ, and the resonance frequency shift amount Δf detected by each resonator. Is plotted as r, and elliptic approximation is performed. Since the major axis direction of the ellipse indicates the maximum direction of the frequency shift amount, the dielectric constant of the sample is maximum in this direction. Therefore, fibers or molecular chains are arranged in this direction. The major axis direction of the ellipse is the orientation angle (φ). On the other hand, the degree of orientation can be expressed by the difference or ratio between the major axis a and the minor axis b of the approximate ellipse.

  The invention described in Patent Document 1 was conceived as a secondary method and method for determining the fiber orientation or molecular orientation of a sheet-like material such as paper from the anisotropy of dielectric constant, and measuring the orientation. At the same time, the basis weight can be measured. Therefore, when measuring the basis weight which is a scalar amount, the direction dependency of the dielectric constant becomes an obstacle. When the resonance frequency shift amount is plotted on the polar coordinates, when the sample is not non-oriented, the value varies depending on the dependency of the sample on the dielectric constant direction as shown in FIG. However, since the basis weight is a scalar, it does not have direction dependency.

  A first method for canceling the direction dependency of the resonance frequency shift amount due to the anisotropy of the dielectric constant is a method of simply averaging the resonance frequency shift amounts of a plurality of resonators.

As a second method for canceling the direction dependency, the resonance frequency shift amount Δf is plotted on the polar coordinates as shown in FIG. 5, and the radius of a circle having the same area as that of an ellipsoid obtained by ellipse approximation is determined as the dielectric of the sample. This is a method of obtaining a converted shift amount Δfr in which the mechanical anisotropy is canceled. For example, a plurality of rectangular dielectric resonators (the number is n) arranged on only one surface side of a sheet-like sample are on the same plane so that their long side directions are different from the reference direction (θ). The resonance frequencies f2 _{1 to} f2 _n of the respective resonators arranged above are measured, and the resonance frequency shift amounts Δf _{1 to} Δf _n of the respective rectangular dielectric resonators are obtained for a certain sample. The shift amounts Δf _{1 to} Δf _n are, as defined above, the difference between the resonance frequency f1 when there is no sample and the resonance frequencies f2 _{1 to} f2 _n of each rectangular dielectric resonator when there is a sample. Next, on the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, the direction (θ) is plotted as the angle θ, and the shift amounts Δf _{1 to} Δf _n are plotted as r. As described above, an ellipse is drawn by the ellipse approximation process, and the area of the ellipse is obtained. When the radius of a circle having the same area as that of the ellipse is obtained, this radius corresponds to the resonance frequency shift amount in which anisotropy is canceled.

When the basis weight / moisture content measurement method according to an embodiment of the present invention is carried out with an apparatus for measuring the dielectric anisotropy of a sample, a plurality of (number of units) arranged only on one side of the sample as microwave resonators. n)) are arranged on the same plane so that the long side directions of the resonators are directed in different directions (θ). Then, plotting on polar coordinates (r, θ) where the direction (θ) is the angle θ, the resonance frequency shift amounts Δf _{1 to} Δf _n of those resonators are r, the angle is θ, and the distance from the origin is r. Then, an ellipse is drawn by the ellipse approximation process, and a radius Δfr of a circle having the same area as that of the ellipse is obtained, and that Δfr is set as Δf in the equation (2). Further, peak level changes ΔP _{1 to} ΔP _n of those resonators are obtained, and any one of the following (A) to (C) ΔPr is set as ΔP in the equation (1).
(A) ΔPr composed of any one of ΔP _{1 to} ΔP _n .
(B) ΔPr composed of an average value of ΔP _{1 to} ΔP _n .
(C) Plotting on the polar coordinates (r, θ) where the direction (θ) is the angle θ, ΔP ₁ to ΔP _n is r, the angle is θ, and the distance from the origin is r, and the ellipse is approximated by ellipse approximation processing. ΔPr calculated as a radius of a circle having the same area as the ellipse.

  In the following description, description will be made on the assumption that the frequency shift amount Δf in which the dielectric anisotropy is canceled by any one of the methods described above.

  The operation of determining the calibration curve and the operation of determining the constants A and B in the equation (2) indicating the relationship between Δf, WT and BD can be executed by using an appropriate program on the computer.

  First, for a plurality of standard samples, the absolute dry basis weight BD and the moisture content WT are measured by a BM meter as an example. On the other hand, Δf and ΔP are measured for these standard samples by a measuring apparatus equipped with a microwave resonator.

  It was found that the function WT = F (ΔP) representing the calibration curve does not become a linear function of ΔP. It can be approximated by a quadratic function or a cubic function. Therefore, for example, approximation is performed with a cubic function such as the expression (1A), and the constants a, b, and c are determined by the least square method by applying the measured values WT and ΔP.

Further, the calibration curve may be approximated by a quadratic function. In this case, the constant a is set to zero and the constants b and c are determined by the least square method. An example of the calibration curve obtained by approximating the calibration curve with a quadratic function is shown in FIG. ΔP on the horizontal axis is a measurement value obtained by a measurement apparatus equipped with a microwave resonator, and the vertical axis is a measurement value of the water content WT by a BM meter. The calibration curve in FIG. 7 shows a high value of 0.9897 for the determination coefficient R ² (R is a correlation coefficient), indicating that the calibration curve is highly reliable.

  The water content WT can be approximated by multiple regression equations using ΔP and explanatory variables other than ΔP. As an explanatory variable other than ΔP, for example, the dielectric loss of the absolutely dry portion of the sample can be mentioned.

  The operation of determining the constants A and B in the equation (2) showing the relationship between Δf, WT and BD is performed as follows. For a certain set of constants A and B (A, B), for example, Δf is calculated by applying quantities BD and WT obtained from a BM meter. The difference between the calculated value Δf and the measured value Δf measured using the microwave resonator is calculated for a plurality of standard samples, and the variance or standard deviation of the difference in Δf is obtained. The variance or standard deviation is calculated in the same manner for another set of A and B (A, B). Among the various sets A and B (A, B), the set A and B (A, B) having the smallest variance or standard deviation is determined as the constants A and B in the equation (2). As an example of such a calculation program, a program called “solver” (one of the functions of spreadsheet software “Excel” manufactured by Microsoft Corporation) can be used.

  One embodiment of the basis weight / water content measuring apparatus of the present invention will be described with reference to FIG. The same basis weight / water content measuring apparatus includes a microwave resonator 100, a microwave excitation device 102 that generates an electric field vector in the resonator 100, and a detection device 104 that detects transmitted energy or reflected energy by the resonator 100. The resonance frequency f1 of the microwave resonator 100 in the first state where no sample is installed from the detection device 104, the peak level P1 at the position of the resonance frequency f1, and the microwave resonance in the second state where the sample is installed A data processing device 106 that takes in the resonance frequency f2 of the vessel 100 and the peak level P2 at the position of the resonance frequency f2 and calculates the absolute dry basis weight and moisture content of the sample.

  The data processing device 106 is realized by a computer dedicated to the measuring device or a computer such as a personal computer connected to the outside. The data processing apparatus 106 includes a Δf / ΔP calculation unit 108, a constant / calibration curve determination unit 112, a constant / calibration curve storage unit 114, and an absolutely dry basis weight / water content calculation unit 120.

  The Δf · ΔP calculation unit 108 calculates the resonance frequency shift amount Δf (= f1−f2) and the peak level change amount ΔP (= P1−P2) from the resonance frequencies f1 and f2 and the peak levels P1 and P2 acquired from the detection device 104. calculate.

The constant / calibration curve determination unit 112 is a calibration that indicates the relationship between ΔP and the moisture content WT from the moisture content WT separately obtained for a plurality of standard samples and the ΔP calculated by the Δf / ΔP computation unit 108 for the corresponding standard samples. The following formula (2) showing the relationship between Δf, WT, and BD as absolute lines BD and WT obtained separately for a plurality of standard samples
Δf = A · BD + B · WT (2)
A combination of constants A and B is obtained such that Δf obtained by applying to the above is the closest to Δf calculated by the Δf · ΔP calculating unit 108 for the corresponding standard sample.

  The constant / calibration curve storage unit 114 holds the constants A and B determined by the constant / calibration curve determination unit 112 and the calibration curve.

  The absolute dry basis weight / moisture amount calculation unit 120 applies ΔP calculated by the Δf · ΔP calculation unit 108 to the calibration curve held in the constant / calibration curve storage unit 114 to obtain the moisture amount WT of the sample, WT calculated in this way, Δf calculated by Δf · ΔP calculation unit 108 and constants A and B held in constant / calibration curve storage unit 114 are applied to equation (2) to calculate the absolute dry basis weight of the sample. Ask.

  The constant / calibration curve determination unit 112 uses the absolute dry basis weight / moisture measuring device 110 other than the microwave resonator for a plurality of standard samples, or the microwave resonator is not a microwave resonator. Acquired by a method not using the absolutely dry basis weight / moisture measuring device 110. Such an absolutely dry basis weight / moisture measuring device 110 is not particularly limited, but an example thereof is a BM meter.

In the preferred embodiment, the constant / calibration curve determination unit 112 converts the calibration curve into the following approximate expression: WT = a · ΔP ³ + b · ΔP ² + c · ΔP (1A)
To determine the constants a, b, and c. In this case, the constant / calibration curve storage unit 114 stores the constants a, b, and c determined by the constant / calibration curve determination unit 112 as corresponding to the calibration curve. Is obtained by applying the constants a, b, and c held in the constant / calibration curve storage unit 114 to the equation (1A) as a calibration curve.

  In another preferred embodiment, the data processing device 106 further includes an air-dry basis weight / water content calculating unit 122 that calculates an air-dry basis weight and a water content.

  In still another preferred embodiment, the microwave resonator 100 is a plurality of rectangular dielectric resonators disposed only on one side of the sample, and the long side directions of these resonators are different directions (θ). Are arranged on the same plane so as to face. In this case, the Δf / ΔP calculation unit 108 calculates the above-described Δfr and ΔPr in which the anisotropy is canceled, and the absolutely dry basis weight / water content calculation unit 120 calculates the Δfr calculated by the Δf / ΔP calculation unit 108. And ΔPr are used for calculation.

  An embodiment of the measuring apparatus of the present invention is specifically shown in FIGS. This is an embodiment for realizing the present invention with an apparatus for measuring the dielectric anisotropy of a sample. Five dielectric resonators 1a to 1e are arranged, and using the signal processing circuit shown in the block diagram of FIG. 8, the signal is processed based on the time chart shown in FIG. 9 to measure the resonance frequency and the resonance peak level. To do.

  A signal output from a microwave sweeper oscillator 21, which is one of the microwave oscillation means, is distributed to the dielectric resonators 1a to 1e via the isolators 22a to 22e. The outputs from the resonators 1a to 1e are converted into voltages by the respective detection diodes 23a to 23e, and the respective peak detection and averaging processing circuit units 25a are passed through the respective amplification and A / D conversion circuit units 24a to 24e. Enter -25e.

  The resonance frequency is measured as follows. As shown in FIG. 9, the microwave sweeper oscillator 21 sweeps the frequency. For example, the frequency can be continuously increased by sweeping the frequency at 250 MHz at 10 msec centering on 4 GHz. By the frequency sweep, the peak detection and averaging processing circuit units 25a to 25e can obtain a resonance curve from the microwave transmission intensity. The resonance curve is obtained as data of 100,000 pieces / 10 msec, and the peak position is obtained in a short time from the data by hardware according to VHDL (VHSIC Hardware Description Language). The peak detection and averaging processing circuit units 25a to 25e detect the start pulse portion from the sweep signal 21s, measure the time until the resonance level reaches the peak, and obtain the resonance frequency from the time by proportional calculation.

  In this method, since the sweep start timing can be detected by the start pulse portion that is the rising edge of the sweep signal, the time until reaching the peak level is measured, and the resonance frequency is measured by calculating from the sweep speed of 250 MHz in 10 msec. The This is repeated, for example, at a period of 50 msec, and is set to one resonance frequency on an average of 20 times. Thus, the sweep time for one time is as very short as 10 msec, and the signal is amplified at a high speed to perform digital processing.

  FIG. 10 shows in more detail the detection system circuit for one dielectric resonator in the circuit shown in FIG. The detection system circuit for the other dielectric resonators is the same. The amplification and A / D conversion circuit unit 24a described above includes, for example, an amplification circuit 31 and an A / D converter unit LSI32. The digital output from the amplification and A / D conversion circuit unit 24a enters the peak detection and average value processing circuit unit 25a. For example, the peak detection and averaging processing circuit unit 25a includes a peak detection LSI and an averaging processing LSI. To be precise, the peak detection LSI has a resonance peak level detection circuit. In this LSI, both resonance frequency and resonance peak level are detected as resonance peak detection, and the averaging processing LSI performs averaging processing of the resonance frequency and resonance peak level obtained for each sweep.

  A microcomputer 26 is connected to the subsequent stage of the peak detection and averaging processing circuit units 25a to 25e, and signals from the respective dielectric resonator detection systems are input to the microcomputer 26. The microcomputer 26 collectively transmits the resonance frequency and resonance peak level from the peak detection and averaging processing circuit units 25a to 25e to the personal computer 27 in the subsequent stage. The microcomputer 26 also has a control function for controlling and operating each of the amplification and A / D conversion circuit units 24a to 24e and the peak detection and averaging processing circuit units 25a to 25e for each dielectric resonator system. .

  The personal computer 27 performs the function of the data processing device 106 that calculates the output from the microcomputer 26 and obtains the basis weight and water content to display or store the data as data.

  Here, in FIG. 10, since the output after amplification in the amplification and A / D conversion circuit unit 24a includes ripple due to noise, the amplification circuit 31 feeds back an RC circuit composed of the capacitor C1 and the resistor R2. Inserted into the line, absorbs and reduces ripple voltage, and obtains DC voltage with little fluctuation.

  The functions of the data processing apparatus realized by the personal computer 27 are those shown in FIG.

  The case where five rectangular dielectric resonators are used will be described more specifically.

  FIG. 11 shows a procedure for calculating Δfr.

The resonance frequency of the blank is obtained for each dielectric resonator and is defined as f ₀₁ , f ₀₂ , f ₀₃ , f ₀₄ , and f ₀₅ , respectively.

The resonance frequency of the sample is determined for each dielectric resonator and is set to f _s1 , f _s2 , f _s3 , f _s4 , and f _s5 , respectively.

For each dielectric resonator, the resonance frequency shift amount Δf is calculated and set as Δf ₁ , Δf ₂ , Δf ₃ , Δf ₄ , Δf ₅ , respectively. However,
Δf ₁ = f ₀₁ −f _s1
Δf ₂ = f ₀₂ −f _s2
Δf ₃ = f ₀₃ −f _s3
Δf ₄ = f ₀₄ −f _s4
Δf ₅ = f ₀₅ −f _s5

Five points of Δf are displayed in polar coordinates, ellipse approximation is performed, and the area S of the ellipse is calculated. A radius r of a circle having the same area as the ellipse is obtained, and this is set as a conversion shift amount Δfr.
Δfr = (S / π) ^1/2

  This Δfr is the resonance frequency shift amount in which the dielectric anisotropy is canceled.

  Since the peak level is not as anisotropic as the dielectric constant, the amount of change in the peak level for one dielectric resonator with or without a sample may be adopted as ΔP, and the peak level for five dielectric resonators may be adopted. You may employ | adopt the average value of variation | change_quantity as (DELTA) P. Even if such a ΔP is employed, no significant error occurs. However, if further anisotropy is to be canceled, it can be performed in the same manner as canceling the anisotropy of the dielectric constant. The procedure in that case is shown in FIG.

For each dielectric resonator, the peak levels P _{01 to} P ₀₅ at the resonance frequency position of the blank are measured. The peak levels P _{S1 to} P _S5 at the resonance frequency position when there is a sample for each resonator are measured. Peak level change amounts ΔP _{1 to} ΔP ₅ are determined for each resonator. ΔP _{1 to} ΔP ₅ are displayed on polar coordinates, and the area of the ellipse is obtained by ellipse approximation processing. The radius of a circle having the same area as that of the ellipse is obtained, and the radius of the circle is set as a converted peak level change ΔPr obtained by canceling the dielectric anisotropy of the sample.

  Although the method for determining the calibration curve and the constants A and B has already been described, the procedure is shown again in FIG.

  With respect to a plurality of standard samples having different basis weights or moisture amounts, the resonance frequency shift amount Δf and the peak level change amount ΔP are measured by a measuring device using a microwave resonator, and, for example, an absolutely dry basis weight (BD) is measured with a BM meter. Measure moisture content (WT).

  The calibration curve is obtained from, for example, the amount of water (WT) measured by a BM meter and the peak level change ΔP obtained using a microwave resonator for the corresponding standard sample. Constants a, b, and c are determined assuming that the calibration curve is approximated by a cubic function such as the expression (1A).

  The constants A and B in the relational expression (2) for obtaining the absolute dry basis weight were calculated by applying the absolute dry basis weight (BD) and the water content (WT) measured by a BM meter, for example, to the expression (2) Δf Is determined as a combination of constants A and B that are closest to the measured value Δf obtained using the microwave resonator for the corresponding standard sample.

  FIG. 14 shows the operation for obtaining the absolute dry basis weight and moisture content, and further the air dry basis weight and moisture content in this example.

  Using a microwave resonator obtained by measuring a standard sample for determining the constants A, B, a, b, and c, the resonance frequency and resonance peak level in the microwave resonator when there is no sample are measured. The sample is arranged by the same microwave resonator and the resonance frequency and the resonance peak level are measured (step S1).

  A resonance frequency shift amount Δfr and a resonance peak level change amount ΔPr relating to the presence / absence of the sample are obtained (step S2).

  The constants A, B, a, b, and c are fetched from the memory constant storage unit 114 and substituted into the above equations (1A) and (2). (Step S3).

  The amount of water WT is calculated by substituting ΔPr as ΔP into the equation (1A) (step S4).

  The absolute dry basis weight BD is calculated by substituting Δfr as Δf and WT calculated in step S4 into the equation (2) (step S5).

  Further, the air-dried basis weight and moisture content are calculated using the above equations (7) and (8) (step S6).

(Measurement Example 1)
The vertical axis of FIG. 15 shows the result of obtaining the moisture content for a plurality of samples by the apparatus of the embodiment of the present invention on an actual paper machine, and the result of measuring the moisture content by a BM meter for the sample is shown in FIG. Shown on the axis. When both moisture contents are approximated by a linear function, the determination coefficient R ² has a high value of 0.9897. From this, it is understood that the water content can be measured with high accuracy according to the present invention.

(Measurement example 2)
The result of having obtained the absolute dry basis weight with the apparatus of the Example of this invention in the actual paper machine about several samples is shown on the vertical axis | shaft of FIG. 16, and the result of having measured the absolute dry basis weight with the BM meter about the same sample. This is shown on the horizontal axis of FIG. When the absolute basis weight is approximated by a linear function, the determination coefficient R ² has a high value of 0.9829. From this, it is understood that the absolutely dry basis weight can be measured with high accuracy by the present invention.

(Measurement Example 3)
For a plurality of samples, the result of obtaining the air dry basis weight by the apparatus of the embodiment of the present invention in an actual paper machine is shown on the vertical axis of FIG. 17, and the result of measuring the air dry basis weight by a BM meter for the sample is shown in FIG. Is shown on the horizontal axis. When the air dry basis weight is approximated by a linear function, the determination coefficient R ² has a high value of 0.9853. From this, it is understood that the air-dried basis weight can be measured with high accuracy according to the present invention.

1, 1a to 1e Dielectric resonator 2a, 2b Antenna 6 Evanescent wave 8 Sample 27 Personal computer 100 Microwave resonator 102 Microwave excitation device 104 Detection device 106 Data processing device 108 Δf · ΔP calculation unit 110 Absolutely dry basis weight・ Moisture measuring device 112 Constant / calibration curve determination unit 114 Constant / calibration curve storage unit 120 Absolute dry basis weight / water content calculation unit 122 Air dry basis weight / water content calculation unit

Claims (8)

(Step S1) Resonance frequency f1 and resonance peak level P1 in the microwave resonator in the first state where the sample is not installed, and resonance frequency f2 and resonance in the microwave resonator in the second state where the sample is installed Measuring the peak level P2, and obtaining a resonance frequency shift amount Δf (= f1-f2) and a peak level change amount ΔP (= P1-P2);
(Step S2) Calibration curve showing relationship between ΔP and water content WT (1)
WT = F (ΔP) (1)
(F (ΔP) is a quadratic or higher function of ΔP)
And the step of obtaining the moisture content WT of the sample from ΔP obtained in step S1, and (step S3) The following equation (2) showing the relationship between Δf, WT and BD
Δf = A · BD + B · WT (2)
(A and B are constants.)
A basis weight / moisture content measurement method including a step of obtaining an absolute dry basis weight BD of the sample from Δf obtained in step S1 and WT obtained in step S2,
The WT for determining the calibration curve (1) and the BD and WT for determining the constants A and B are obtained using a device other than the microwave resonator for a plurality of standard samples, or the microwave resonator Separately obtained by a method that does not use the device other than the microwave resonator,
The calibration curve (1) is obtained from the WT acquired separately and the measured value ΔP obtained for the corresponding standard sample using the microwave resonator,
As for the constants A and B, Δf obtained by applying BD and WT obtained separately to the equation (2) is closest to the measured value Δf obtained using the microwave resonator for the corresponding standard sample. Basis weight / moisture content measurement method obtained as a combination of constants A and B. The calibration curve (1) has the following approximate expression: WT = a · ΔP ³ + b · ΔP ² + c · ΔP (1A)
The basis weight / moisture content measurement method according to claim 1, wherein the basis weight is determined by determining constants a, b, and c. Furthermore, the basic weight and moisture content measuring method of Claim 1 or 2 which calculates | requires to an air dry basic weight and a moisture content using the following formula | equation.
Air dry basis weight = absolute dry basis weight BD + moisture content WT
Moisture content = moisture content WT x 100 / air dry basis weight A plurality of rectangular dielectric resonators disposed only on one surface side of the sample as the microwave resonators are disposed on the same plane so that the long side directions of the resonators are directed in different directions (θ). ,
Plotting on polar coordinates (r, θ) where the direction (θ) is the angle θ, the resonance frequency shift amounts Δf _{1 to} Δf _n of those resonators are r, the angle is θ, and the distance from the origin is r, An ellipse is drawn by an ellipse approximation process, and a radius Δfr of a circle having the same area as the area of the ellipse is obtained. The Δfr is defined as Δf in claim 1;
4. The peak level change amounts ΔP _{1 to} ΔP _n of these resonators are obtained, and any one of the following (A) to (C) ΔPr is set as ΔP in claim 1. The basis weight / moisture content measuring method described in 1.
(A) ΔPr composed of any one of ΔP _{1 to} ΔP _n .
(B) ΔPr composed of an average value of ΔP _{1 to} ΔP _n .
(C) Plotting on the polar coordinates (r, θ) where the direction (θ) is the angle θ, ΔP ₁ to ΔP _n is r, the angle is θ, and the distance from the origin is r, and the ellipse is approximated by ellipse approximation processing. ΔPr calculated as a radius of a circle having the same area as the ellipse. A microwave resonator (100);
A microwave excitation device (102) for generating an electric field vector in the resonator (100);
A detection device (104) for detecting transmitted energy or reflected energy by the resonator (100);
The resonance frequency f1 of the microwave resonator (100) in the first state where no sample is placed from the detection device (104), the peak level P1 at the position of the resonance frequency f1, and the second state where the sample is placed A data processing device (106) that takes in the resonance frequency f2 of the microwave resonator (100) and the peak level P2 at the position of the resonance frequency f2 and calculates the absolute dry basis weight and moisture content of the sample. And
The data processing device (106)
Δf for calculating a resonance frequency shift amount Δf (= f1−f2) and a peak level change amount ΔP (= P1−P2) from the resonance frequencies f1 and f2 and the peak levels P1 and P2 captured from the detection device (104). A ΔP calculation unit (108);
Calibration curve (1) showing the relationship between ΔP and moisture content WT from the moisture content WT separately acquired for a plurality of standard samples and the ΔP calculated by the Δf · ΔP calculation unit (108) for the corresponding standard sample
WT = F (ΔP) (1)
(F (ΔP) is a quadratic or higher function of ΔP)
The absolute dry basis weights BD and WT acquired separately for a plurality of standard samples are expressed by the following equation (2) indicating the relationship between Δf, WT and BD:
Δf = A · BD + B · WT (2)
A constant / calibration curve determination unit (112) that obtains a combination of constants A and B such that Δf obtained by applying to is the closest to Δf calculated by the Δf · ΔP calculation unit (108) for the corresponding standard sample. )When,
A constant / calibration curve storage unit (114) for holding the constants A and B determined by the constant / calibration curve determination unit (112) and a calibration curve;
The amount of water WT of the sample was obtained by applying ΔP calculated by the Δf · ΔP calculating unit (108) to a calibration curve held in the constant / calibration curve storage unit (114), and was obtained as such. WT, Δf calculated by the Δf · ΔP calculation unit (108) and constants A and B held in the constant / calibration curve storage unit (114) are applied to the equation (2) to completely dry the sample. Absolute dry basis weight / moisture content calculation unit (120) for determining basis weight,
A basis weight / water content measuring device. The constant / calibration curve determination unit (112) converts the calibration curve into the following approximate expression: WT = a · ΔP ³ + b · ΔP ² + c · ΔP (1A)
To determine the constants a, b, and c,
The constant / calibration curve storage unit (114) stores the constants a, b and c determined by the constant / calibration curve determination unit (112) as corresponding to the calibration curve.
The absolute dry basis weight / moisture amount calculation unit (120) uses the constants a, b, and c held in the constant / calibration curve storage unit (114) as applied to the equation (1A) as a calibration curve. 6. The basis weight / water content measuring device according to claim 5, wherein the water content WT is obtained by using. The basis weight according to claim 5 or 6, wherein the data processing device (106) further comprises an air-dry basis weight / moisture percentage calculation unit (122) for obtaining an air-dry basis weight and a moisture percentage using the following formula.・ Moisture measuring device.
Air dry basis weight = absolute dry basis weight BD + moisture content WT
Moisture content = moisture content WT x 100 / air dry basis weight The microwave resonator (100) is a plurality of rectangular dielectric resonators disposed only on one side of the sample, and the long side directions of the resonators are the same so that they are in different directions (θ). Are arranged on a plane,
The Δf · ΔP calculating section (108) calculates Δfr and ΔPr according to claim 4.
8. The absolute dry basis weight / water content calculation unit (120) performs an operation using Δfr and ΔPr calculated by the Δf / ΔP calculation unit (108). 9. The basis weight / water content measuring device described.