JP5169733B2 - Basis weight measuring method and apparatus - Google Patents

Description

The present invention relates to a method and an apparatus for measuring the thickness or basis weight (mass per 1 m ² ) of a sheet-like substance such as paper, non-woven fabric, and film by utilizing microwave resonance.

  In the paper manufacturing process, it is very important to measure basis weight (weight per square meter) and moisture online, and it is an important management item in terms of paper quality and commerce.

  Conventionally, the basis weight of paper is generally obtained from a β-ray transmission attenuation amount using a BM meter. The β ray for measuring the basis weight uses a radiation source such as Kr (krypton) 85 or Pm (promesum) 147. If the basis weight is large, the attenuation amount of the β-ray is large, and if the basis weight is small, the attenuation amount is small. Therefore, the transmission amount of the β-ray and the basis weight are in an inversely proportional relationship. Is required.

  The water content of paper is generally determined from near infrared absorption. Three types of wavelengths are normally used as near infrared rays for measuring moisture. They have a wavelength of 1.8 μm as reference light (wavelength that is not attenuated by the amount of water), a wavelength of 1.9 μm (wavelength that is attenuated by the amount of water), and a wavelength of 2.1 μm as correction light (not affected by the amount of cellulose). Wavelength). By examining the relationship between the near-infrared attenuation and the amount of moisture as a calibration curve in advance, accurate moisture can be obtained.

  In conventional basis weight measurement using β rays, a radiation source such as Kr85 or Pm147 must be used as a radiation source, which may adversely affect the human body. Therefore, it is necessary to provide a no-entry area so as not to get close to the radiation source at the time of measurement, and to carry a film batch for people who frequently work in the vicinity, and to check the radiation dose received regularly. Furthermore, it is necessary to decide the chief engineer who can handle radiation, and sufficient care and expertise are required for handling.

As a method for avoiding such problems, the present inventors have proposed a method and a measuring apparatus for measuring the basis weight of sheet-like substances such as paper and even moisture without using radiation (Patent Document 1). reference.). The contents of Patent Document 1 are incorporated herein by reference. In the measurement apparatus, when a plurality of dielectric resonators that generate an electric field vector having a unidirectional component are arranged on the same plane and assume an in-sample plane parallel to the plane and crossing the sample, these dielectric resonators The electric field vectors of the dielectric resonators are arranged so as to be different from each other in the sample inner plane.
JP 2006-349425 A (US Pat. No. 7,423,435 B2)

  The invention described in Patent Document 1 is basically an on-line application of a device for measuring the dielectric anisotropy of a sample such as the fiber orientation of paper, and in addition to the fiber orientation, the basis weight and further the moisture content can be measured simultaneously. It is what I did. Therefore, when measuring the basis weight or the moisture content, there is a problem that the sample is influenced by the dielectric anisotropy of the sample. 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.

  The invention described in Patent Document 1 proposes a method of simply averaging the measurement results of dielectric resonators arranged in different directions. The simple averaging processing method is a particularly convenient processing method in on-line measurement because the processing is simple and the burden on the data processing apparatus is light and processing can be performed at high speed. On the other hand, it has been found that the simple averaging processing method causes an error depending on the sample, for example, when measuring a sample having a very high degree of orientation.

  Therefore, the present invention provides a method and apparatus capable of expanding the range in which the dielectric anisotropy can be canceled with higher accuracy than the simple averaging process, assuming that high-speed processing is possible so as to be applicable to online measurement. It is intended to provide.

  1A and 1B are schematic views of a rectangular microwave dielectric resonator. 1A is a plan view and FIG. 1B is a vertical sectional view thereof. The rectangular 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. The present invention is used in such a resonance mode where 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 shifts to the lower frequency side as shown in FIG. 2 corresponding to the dielectric constant of the evanescent wave 6 in the electric field vector direction. At the same time, the resonance peak level decreases corresponding to the dielectric loss factor of the 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 resonance frequency shift amount Δf is proportional to (ε′−1) × T, and the peak level change amount ΔP is It is proportional to ε ″ × T.

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

  FIG. 3 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 shift amount of the resonance frequency detected by each resonator. Plotting Δf as r and performing ellipse approximation. Since the major axis direction of the ellipse indicates the maximum direction of the shift amount of the resonance frequency, 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 of Patent Document 1 was originally conceived as a secondary method and method for determining the fiber orientation or molecular orientation of a sheet-like substance 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. Therefore, as a method of canceling the direction dependency of the anisotropy of the dielectric constant, that is, the shift amount of the resonance frequency (the value obtained by subtracting the resonance frequency when there is a sample from the resonance frequency when there is no sample). The shift amount of the resonance frequency of the plurality of resonators is simply averaged.

  When the shift amount of the resonance frequency is plotted on the polar coordinates, when the sample is not non-oriented, the value varies slightly depending on the dielectric constant direction dependency of the sample as shown in FIG. However, since the basis weight is a scalar, it does not have direction dependency. Therefore, as a method of canceling the direction dependency, attention was paid to the area of the ellipsoid obtained by plotting the shift amount Δf of the resonance frequency on the polar coordinates and approximating the ellipse.

Therefore, the basis weight measuring method of the present invention is the same so that a plurality of rectangular dielectric resonators arranged on only one surface side of the sheet-like sample are directed in different directions (θ) from the reference direction. This is a method of measuring the resonance frequencies f _{1 to} f _n of the respective resonators arranged on a plane and calculating the basis weight of the sample by the following steps (S1) to (S6).
(S1) A step of obtaining shift amounts Δf _{1 to} Δf _n of each rectangular dielectric resonator for the sample.
(S2) On the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, the direction (θ) is the angle θ and the shift amounts Δf _{1 to} Δf _n are plotted as r, and the ellipse approximation process is performed. Step to draw an ellipse.
(S3) A step of obtaining an area of the ellipse.
(S4) A step of obtaining a radius of a circle having the same area as the area of the ellipse, and setting the radius of the circle as a converted shift amount Δfr obtained by canceling the dielectric anisotropy of the sample.
(S5) A step of preparing in advance a first relationship indicating a relationship between Δfr and basis weight.
(S6) A step of obtaining the basis weight of the sample from Δfr obtained in step S4 using the first relationship prepared in step S5.

The principle of basis weight (thickness) measurement is described in detail in Patent Document 1. Assuming that the sample has no dielectric anisotropy, the shift amount Δf, which is the difference between the resonance frequency f ₀ when there is no sample and the resonance frequency f _s when there is a sample, is proportional to the basis weight b. Therefore, for a sample having electric anisotropy, if the converted shift amount Δfr in which the electric anisotropy is canceled can be obtained, the converted shift amount Δfr is proportional to the basis weight b.

  In general, when the refractive index anisotropy of a crystal is shown, a refractive index ellipsoid is used, and even in a polymer film, the three-dimensional refractive index plot is an ellipsoidal shape, and the dielectric constant is also a second-order tensor. It becomes an ellipsoid three-dimensionally. From this, it can be said that it is theoretically appropriate to display and discuss the orientation as an ellipse. Considering a circle having the same area as that of this ellipse, the radius of this circle is just the shape in which the direction dependency of the shift amount (Δf) of the resonance frequency is eliminated, and the original shift amount excluding anisotropy is obtained. It corresponds.

An example of the first relationship between Δfr and basis weight prepared in step (S5) is a calibration curve showing the relationship between Δfr and basis weight. The calibration curve can be created by the following steps S11 to S13 using a plurality of standard samples having the same dielectric constant and density as the sample to be measured and different basis weights.
(S11) A step of obtaining the basis weight of each standard sample by a known method.
(S12) A step of obtaining Δfr of each standard sample by steps (S1) to (S4).
(S13) A step of creating a calibration curve indicating a first relationship between the basis weight determined for a plurality of standard samples and Δfr.

  In this case, in the step (S6) for obtaining the basis weight, the calibration curve created in step (S13) is applied to Δfr of the sample obtained in step (S4).

Another example of the first relationship between Δfr and basis weight prepared in step (S5) is the following equation (2) showing the relationship between Δfr and basis weight b.
Δfr = A · b (2)
It is.

This relational expression can be created by the following steps S21 to S23 using a standard sample having the same dielectric constant and density as the sample to be measured.
(S21) A step of obtaining a basis weight b of the standard sample by a known method.
(S22) A step of obtaining Δfr of the standard sample by steps (S1) to (S4).
(S23) Using Δfr and basis weight b obtained for the standard sample, the constant A is set to A = b / Δfr
Step to find by.
In this case, in the step (S6) for obtaining the basis weight, Δfr of the sample obtained in step (S4) and the constant A obtained in step (S23) are applied to the equation (2).

  In addition to determining the basis weight, the present invention further includes determining the moisture content or the moisture content as the moisture content. The measurement principle of the water content and the water content is described in detail in Patent Document 1, but the outline is as follows. Let ΔP (= P0−Ps) be the difference between the resonance peak level P0 and the sample resonance peak level Ps when there is no sample (blank). Since ΔP is proportional to a value ε ″ · t obtained by multiplying the dielectric loss rate ε ″ of the sample and the thickness t of the sample, the moisture content can be measured from ΔP in a sample having a constant thickness t. . For measurement of a sample with a non-constant thickness, when the sample moisture is very small, that is, when ε ′ is constant, the dielectric loss rate ε ″ is ΔP regardless of the sample thickness t. Since it is proportional to / Δf, the moisture content can be measured from ΔP / Δf. Since this explanation is based on the assumption that the sample does not have dielectric anisotropy, if the sample has dielectric anisotropy, converted ΔPr and ΔPr / Δfr with the dielectric anisotropy canceled are derived. If possible, the moisture content and moisture content can be determined using them.

The method for canceling the dielectric anisotropy when obtaining the moisture content or moisture content of the sample is the same as the method for canceling the dielectric anisotropy when obtaining the basis weight. That is, the peak levels P _{1 to} P _n at the resonance frequency positions of the respective resonators are measured, and the moisture content or moisture content is calculated by the following steps (S31) to (S36).
(S31) A step of obtaining peak level variations ΔP _{1 to} ΔP _n of each rectangular dielectric resonator for the sample.
(S32) On the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, the direction (θ) is the angle θ, and the peak level change amounts ΔP _{1 to} ΔP _n are plotted as r. A step of drawing an ellipse by approximation processing.
(S33) A step of obtaining an area of the ellipse.
(S34) A step of obtaining a radius of a circle having the same area as the area of the ellipse, and setting the radius of the circle as a converted peak level change amount ΔPr obtained by canceling the dielectric anisotropy of the sample.
(S35) A step of preparing in advance a calibration curve or a relational expression indicating a second relationship between ΔPr and the water content or the water content.
(S36) A step of obtaining the moisture content or moisture content of the sample from ΔPr obtained in step S34 using the second relationship prepared in step S35.

  Here, the peak level change amount means a difference in resonance peak level of each rectangular dielectric resonator when there is no sample and when there is no sample.

The basis weight measuring apparatus according to the present invention includes a plurality (in which the surface facing the sample has a rectangular shape and is disposed only on one surface side of the sample, and each long side direction faces a different direction (θ) from the reference direction. n) a plurality of rectangular dielectric resonators, a microwave excitation device for generating an electric field vector in each dielectric resonator, and a detection device for detecting transmitted energy or reflected energy by each dielectric resonator, As shown in FIG. 5, the storage device 13 storing the first relationship indicating the conversion shift amount of the resonance frequency with respect to the basis weight obtained for the standard sample having the same dielectric constant and density as the measurement target sample, and the measurement target Data processing for calculating the basis weight of the sample to be measured based on the resonance frequency of each resonator when the sample is measured and the first relationship stored in the storage device And a location 10.

As shown in FIG. 5 and FIG. 6, the data processing apparatus 10 calculates the shift amount for obtaining the resonance frequency shift amounts Δf _{1 to} Δf _n of each resonator as the basis weight calculation means 11 for calculating the basis weight. On the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, the direction (θ) of each resonator is the angle θ and the shift amount Δf _1- When plotting Δf _n as r, the radius of a circle having the same area as the ellipse drawn by the ellipse approximation process is obtained, and the converted shift amount calculating means 15 using the converted shift amount Δfr as the converted shift amount Δfr is obtained. The basis weight calculating means 16 for calculating the basis weight from the converted shift amount Δf and the first relationship stored in the storage device 13 is provided.

When the basis weight measuring device of the present invention is further provided with a function for obtaining the moisture content or moisture content, the storage device 13 contains the moisture content obtained for the standard sample having the same dielectric loss factor and thickness as the sample to be measured. A second relationship indicating the converted peak level change amount with respect to the amount or moisture content is also stored. Then, as shown in FIG. 5, the data processing apparatus 10 has the second relationship stored in the storage device and the peak levels P _{1 to} P _n at the resonance frequency positions of the resonators when the measurement target sample is measured. And a moisture content calculating means 12 for calculating the moisture content or moisture content of the sample to be measured.

As shown in FIG. 7, the moisture amount calculation means 12 includes a peak level change amount calculation means 17 that calculates peak level change amounts ΔP _{1 to} ΔP _n of each rectangular dielectric resonator for the measurement target sample, and an angle. The peak level change amounts ΔP _{1 to} ΔP _n obtained by the peak level change amount calculation means 17 on the polar coordinates (r, θ) where r is the distance from the origin and r and the direction (θ) of each resonator is the angle θ. Is plotted as r, the radius of a circle having the same area as that of the ellipse drawn by the ellipse approximation process is obtained, and the converted peak level change amount calculating means 18 is set as the converted peak level change amount ΔPr, and the calculated peak level change amount is calculated. A water content / content rate calculating means 19 for calculating the water content or the water content from the converted peak level change amount ΔPr obtained by the means 18 and the second relationship stored in the storage device 13 is provided.

The second relationship can be obtained in the same manner as the first relationship. When the second relationship is a calibration curve indicating the relationship between ΔPr and moisture content or moisture content, the calibration curve has the same dielectric loss factor and density as the sample to be measured, and the moisture content or moisture content of each other. A plurality of standard samples having different values can be used, and can be obtained by the following steps S41 to S43.
(S41) A step of obtaining the moisture content or moisture content of each standard sample by a known method.
(S42) A step of obtaining ΔPr of each standard sample by steps (S31) to (S34).
(S43) A step of creating a calibration curve indicating the second relationship between the moisture content or moisture content obtained for a plurality of standard samples and ΔPr.

  In this case, in the step (S36) for obtaining the water content or the water content rate, the calibration curve created in the step (S43) is applied to ΔPr of the sample obtained in the step (S34).

When the second relationship is a relational expression between ΔPr and the water content or the water content c, the relational expression is the following formula (3):
ΔPr = B · c (3)
It becomes. This equation (3) can be obtained by the following steps S51 to S53 using a standard sample having the same dielectric loss factor and density as the sample to be measured.
(S51) A step of obtaining the moisture content or moisture content c of the standard sample by a known method.
(S52) A step of obtaining ΔPr of the standard sample by the steps (S31) to (S34).
(S53) Using ΔPr obtained for the standard sample and the water content or water content c, the constant B is set to B = c / ΔPr
Step to find by.

  In this case, ΔPr of the sample obtained in step (S34) and the constant B obtained in step (S53) are applied to equation (3) in the step (S36) for obtaining the water content or the water content.

  In a preferred embodiment of the present invention, an amplifier circuit connected to each detector and amplifying each output includes a time delay element, and each of the plurality of resonators includes a microwave oscillator connected thereto. And a resonator detection system comprising an amount variable electric signal attenuation / amplification means inserted between the output of the amplifier circuit and the resonance peak level detection circuit for detecting the resonance peak level. The output from the resonance peak level detection circuit of each resonator detection system is compared with a target resonance peak level set separately, and the attenuation or amplification degree for the variable electric signal attenuation / amplification means is set so as to approach the target resonance peak level. Computation means for computing and outputting a signal to be changed is provided.

In the present invention, the amount of shift Δf _{1 to} Δf _n of the resonance frequency of each rectangular dielectric resonator is obtained, plotted on polar coordinates, and subjected to ellipse approximation processing, and the radius of a circle having the same area as that of the ellipse is obtained. The radius of the circle is defined as a conversion shift amount Δfr that cancels the dielectric anisotropy of the sample. Since the basis weight is obtained from the calculated conversion shift amount Δfr using the relationship between Δfr and basis weight, the dielectric anisotropy can be canceled rather than simply averaging the shift amounts Δf _{1 to} Δf _n. And the required basis weight accuracy is improved.

  In the present invention, the concept of canceling the dielectric anisotropy of a sample is schematically shown in FIG. Here, half of the major axis of the ellipse is 100, and half of the minor axis is 70. Δf corresponds to a radius in the case of a circle and a distance from the center in the case of an ellipse. The directions of the five measurement points were plotted as 18 °, 90 °, 162 °, 234 °, and 306 °. In FIG. 8, the hatched portion represents the area of a circle having the same area as the ellipse. The level on the vertical axis represents the leveled Δf, in this case 83.67. On the other hand, the average of 5 points is 80.80, which is not the same value.

  Next, taking the case of five resonators as an example, FIGS. 9A to 9C show a comparison between simply averaging five Δf and finding the radius of a circle having the same area as in the present invention. Show. When the major axis is 4000 and the minor axis is 4000, a circle is represented. In this case, there is no difference between the two. Next, if the major axis is 4000 and the minor axis is 3800, the difference is 15. Further, it can be seen that when the minor axis is 3600, the difference becomes as large as 28.1, and as the ellipse becomes elongated, that is, as the degree of orientation increases, the difference between the two increases.

  This difference also depends on the number of resonators. When the number of resonators is large, the difference tends to be small, but when the number is decreased, for example, three, the difference tends to be larger.

  Further, in the method of simply performing the averaging process, for example, in the case of five dielectric resonators, the average value result changes only by shifting the five arrangement angles from the reference direction. This means that even if the orientation angle is tilted from 5 degrees to 10 degrees from the 0 degree direction, even if the basis weight is the same, the five-point average values are different, which is an error factor. Since the basis weight does not change even if the orientation angle is changed, the average value should not change. From this point, it can be said that it is not correct to simply perform the average value processing.

  A specific example of the measuring device will be shown. Five dielectric resonators 1a to 1e are arranged, and the signal is processed based on the time chart shown in FIG. 11 using the signal processing circuit shown in the block diagram of FIG. 10, and the resonance frequency is measured.

  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. 11, the microwave sweeper oscillator 21 sweeps the frequency. For example, the frequency is 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 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. 12 shows the detection system circuit for one dielectric resonator in the circuit shown in FIG. 10 in more detail. 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 25 a to 25 e, 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 sections 25a to 25e to the personal computer 27 at 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. .

  A personal computer 27 is connected to the microcomputer 26. The personal computer 27 calculates the output from the microcomputer 26 and obtains the basis weight and further the water content or the water content and displays or stores it as data. The personal computer 27 implements the functions of the data processing device 10 and the storage device 13 shown in FIGS. The personal computer 27 also has a function of measuring the orientation direction and amount.

  Here, in FIG. 12, since the output after amplification in the amplification and A / D conversion circuit unit 24a includes ripple due to noise, the amplification circuit 31 uses an RC circuit composed of the capacitor C1 and the resistor R2 as a feedback line. To reduce the ripple voltage and obtain a DC voltage with little fluctuation. For this reason, the capacitor C1 is essential in the present amplifier circuit.

  Such C1 and R2 are so-called time delay elements, and therefore a delay (time constant) occurs in the amplifier circuit. Japanese Patent Application Laid-Open Publication No. 2004-228688 describes in detail a problem and a solution when a resonator output is input to a circuit using such an amplifier circuit at a high sweep speed of 10 msec. An example of a signal processing circuit that solves such a problem is shown in FIG.

  FIG. 13 is a block diagram of a circuit of a dielectric resonator of an orientation meter showing a state in which a programmable attenuator is inserted in a circuit for processing a signal from the dielectric resonator shown in FIG. In the figure, the same reference numerals as those shown in FIG. 10 indicate the same functions in the same parts. Since the personal computer 27 has a function for controlling such a programmable attenuator added in software, it is functionally different from that in FIG. When five dielectric resonators are used as shown in FIG. 10, programmable attenuators 33a to 33e are inserted in the circuits of the five dielectric resonators as shown in FIG.

  That is, the microwaves emitted from the microwave sweeper oscillator 21 are distributed and enter five programmable attenuators 33a to 33e, where they are attenuated by an amount determined by an electrical signal 34s sent from the personal computer 27 to each programmable attenuator. The The attenuated microwaves are input to the five dielectric resonators 1a to 1e through the isolators 22a to 22e. The resonance level is detected by the antenna on the opposite side, and the transmission intensity is converted into a voltage by the detection diodes 23a to 23e. Thereafter, the signal passes through the amplification and A / D conversion circuit units 24a to 24e and is sent to the peak detection and averaging processing circuit units 25a to 25e. Similar to the operation of the circuit of FIG. 10, the resonance frequency and the peak level are measured in the peak detection LSI.

  The resonance peak level voltage is sent to the personal computer 27 via the microcomputer 26, and is compared with the target resonance peak level voltage, and according to the deviation (target resonance peak level voltage−current peak level voltage). The attenuation amount of the programmable attenuators 33a to 33e is determined, and the attenuation amount of the programmable attenuators 33a to 33e is changed by outputting a digital signal from the personal computer 27, and adjusted to the target resonance peak level voltage. That is, the personal computer 27 is a calculation means for performing a calculation based on the difference calculation by comparing with the target resonance peak level voltage. This process is performed for each dielectric detector system, and for the five systems in the example of FIG.

  Note that the target resonance peak level voltage is set as high as possible with a slight margin in the input voltage range of the amplification and A / D conversion circuits 24a to 24e so that there is no input overshoot. . For example, the value is 90% of the maximum input voltage. Note that the input voltage to the A / D conversion also involves the magnitude of the previous amplification.

  As described above, the measured resonance frequency and resonance peak level voltage are sent to the personal computer 27 via the microcomputer 26. The personal computer 27 compares the preset target resonance peak level voltage with the actually measured resonance peak level voltage, and controls the attenuation of the programmable attenuators 33a to 33e according to the deviation. In short, if the peak voltage is higher than the target voltage, the attenuation is increased, and if it is lower, the attenuation is decreased and the microwave power is increased.

  If this is repeated automatically, in a short cycle, and continuously, a constant resonance peak level voltage can be always obtained.

  When control is performed to keep the resonance peak voltage constant, the moisture content of the sample is obtained based on the difference between the resonance peak level when the sample is present and the resonance peak level when there is no sample. It can't be simple. That is, in an example of such a case, control is performed so that the resonance peak level is the same and constant when there is no sample and when there is no sample. In that case, the average value of each dielectric resonator of the attenuation value of the program attenuator of each dielectric resonator based on making the resonance peak level constant is the difference between when the sample is present and when there is no sample. Can be considered as a difference in resonance peak level.

The case where five rectangular dielectric resonators are used will be described more specifically.
FIG. 14 shows a procedure for calculating the basis weight.

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 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, an 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

Since this Δfr is a shift amount in which the dielectric anisotropy is canceled, the relationship between the converted shift amount Δfr and the actual basis weight was examined for various papers. The result is shown in FIG. From this result, the relationship between Δfr and basis weight b is
Δfr = 62.193 × b
I found out that Using the above formula and the calculated Δfr, the basis weight b to be obtained is
b = Δfr / 62.193
As required.

FIG. 15 shows a procedure for calculating the water content.
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. A relationship between ΔPr and moisture content is obtained in advance, and the moisture content of the sample is obtained from the relationship and ΔPr obtained for the sample.

  When obtaining the moisture content, the converted resonance frequency shift amount Δfr is also obtained at the same time, and ΔPr / Δfr is used instead of ΔPr.

  FIG. 17 shows an example in which the basis weight and water content are calculated by the procedure shown in FIGS. 14 and 15 and displayed on the actual measurement screen. In FIG. 17, the basis weight and the moisture content are displayed as the rice basis weight, and the moisture content is obtained and displayed. The orientation angle is φ shown in FIG. 4, and the orientation degree is the difference (ab) between the major axis and the minor axis of the ellipse shown in FIG.

Changes in basis weight measured using this method at the time of grade change (basis weight change) are shown in FIGS. The amount of water has hardly changed. In Figure 18, it shows the change in basis weight when the basis weight changes from 60.0 g / m ² of SATEN stencil to 49.3 g / m ² was made. It can be seen that the basis weight is almost the same as the target value. Further, FIG. 19 shows the data when the basis weight changes from TACK base paper 54.3 g / m ² to 99.5 g / m ^2. It can also be seen that the basis weight can be displayed almost as the target value. Thus, cancellation of anisotropy enabled more accurate basis weight measurement.

  The present invention can be used to measure the basis weight of sheet-like substances including paper, nonwoven fabric, and film.

It is a top view which shows the dielectric resonator used by this invention. 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 a block diagram which shows the data processor and memory | storage device in the measuring apparatus of one Example. It is a block diagram which shows the basic weight calculation means and memory | storage device in the data processor in the measuring apparatus of the Example. It is a block diagram which shows the moisture content calculation means and memory | storage device in the data processor in the measuring apparatus of the Example. It is a figure which shows typically the method of canceling the dielectric anisotropy of a sample. When there are five resonators, it is a diagram showing a comparison between a case where five Δf are simply averaged and a case where a radius of a circle having the same area is obtained. It is a table | surface which shows the result of FIG. 9A by a numerical value. It is a figure which shows the ellipse which makes a major axis the circle and its radius. 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 block diagram which shows the signal processing circuit which put the programmable attenuator in the signal processing circuit of FIG. It is a flowchart which shows the procedure which measures basic weight. It is a flowchart which shows the procedure which measures a moisture content. It is a graph which shows the relationship between (DELTA) f which canceled the anisotropy, and actual basic weight. It is a figure which shows the example which displayed the basic weight on the actual measurement screen. It is a figure which shows the change of the basic weight at the time of the grade change (basic weight change) in an Example. It is a figure which shows the change of the other basic weight at the time of the grade change (basis weight change) in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a-1e Dielectric resonator 2a, 2b Antenna 4 Shield container 6 Evanescent wave 8 Sample 10 Data processing device 11 Basis weight calculation means 12 Water content calculation means 13 Storage device 14 Shift amount calculation means 15 Conversion shift amount calculation means 16 Basis weight calculation means 17 Peak level change amount calculation means 18 Converted peak level change amount calculation means 19 Water content / water content rate calculation means 21 Microwave sweeper oscillator 22a-22e Isolators 23a-23e Detection diodes 24a-24e Amplification and A / D conversion circuit unit 25a to 25e Peak detection and averaging processing circuit unit 26 Microcomputer 27 Personal computer 33a to 33e Programmable attenuator

Claims (7)

A plurality of rectangular dielectric resonators arranged on only one surface side of the sheet-like sample are arranged on the same plane so that the long side directions thereof are different from the reference direction (θ), and the respective resonators are arranged. A basis weight measurement method in which the resonance frequencies f _{1 to} f _n are measured, and the basis weight of the sample is calculated by the following steps (S1) to (S6).
(S1) A step of obtaining a shift amount Δf _{1 to} Δf _n of the resonance frequency of each rectangular dielectric resonator for the sample.
(S2) On the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, the direction (θ) is the angle θ and the shift amounts Δf _{1 to} Δf _n are plotted as r, and the ellipse approximation process is performed. Step to draw an ellipse.
(S3) A step of obtaining an area of the ellipse.
(S4) A step of obtaining a radius of a circle having the same area as the area of the ellipse, and setting the radius of the circle as a converted shift amount Δfr obtained by canceling the dielectric anisotropy of the sample.
(S5) A step of preparing in advance a first relationship indicating a relationship between Δfr and basis weight.
(S6) A step of obtaining the basis weight of the sample from Δfr obtained in step S4 using the first relationship prepared in step S5.
Here, the shift amount of the resonance frequency means a difference in resonance frequency between the rectangular dielectric resonators when there is no sample and when there is no sample. The first relationship between Δfr and basis weight prepared in step (S5) is a calibration curve showing the relationship between Δfr and basis weight;
The step (S5) uses a plurality of standard samples having the same dielectric constant and density as the sample to be measured and different basis weights from each other,
(S11) obtaining a basis weight of each standard sample by a known method;
(S12) obtaining Δfr of each standard sample by the steps (S1) to (S4);
(S13) including a step of creating a calibration curve indicating a first relationship between the basis weight determined for a plurality of standard samples and Δfr,
The basis weight measurement method according to claim 1, wherein the calibration curve created in step (S13) is applied to Δfr of the sample obtained in step (S4) in the step (S6) for obtaining basis weight. The first relationship between Δfr and basis weight prepared in step (S5) is the following formula (1) showing the relationship between Δfr and basis weight b.
Δfr = A · b (1)
And
The step (S5) uses a standard sample having the same dielectric constant and density as the sample to be measured.
(S21) obtaining the basis weight b of the standard sample by a known method;
(S22) obtaining Δfr of the standard sample by the steps (S1) to (S4);
(S23) Using Δfr and basis weight b obtained for the standard sample, the constant A is set to A = b / Δfr
Including the step of
2. The basis weight measurement according to claim 1, wherein in step (S6) for obtaining basis weight, Δfr of the sample obtained in step (S4) and constant A obtained in step (S23) are applied to formula (1). Method. Further, the peak levels P _{1 to} P _n at the resonance frequency positions of the respective resonators are measured, and the moisture content or moisture content of the sample is also calculated by the following steps (S31) to (S36). The basis weight measuring method according to any one of the above.
(S31) A step of obtaining peak level variations ΔP _{1 to} ΔP _n of each rectangular dielectric resonator for the sample.
(S32) On the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, the direction (θ) is the angle θ, and the peak level change amounts ΔP _{1 to} ΔP _n are plotted as r. A step of drawing an ellipse by approximation processing.
(S33) A step of obtaining an area of the ellipse.
(S34) A step of obtaining a radius of a circle having the same area as the area of the ellipse, and setting the radius of the circle as a converted peak level change amount ΔPr obtained by canceling the dielectric anisotropy of the sample.
(S35) A step of preparing in advance a calibration curve or a relational expression representing a second relationship indicating the relationship between ΔPr and the moisture content or moisture content.
(S36) A step of obtaining the moisture content or moisture content of the sample from ΔPr obtained in step S34 using the second relationship prepared in step S35.
Here, the peak level change amount means a difference in resonance peak level of each rectangular dielectric resonator when there is no sample and when there is no sample. Plural (n) rectangular dielectric resonators having a rectangular surface facing only the sample and disposed only on one surface side of the sample, and the long sides of the sample facing different directions (θ) from the reference direction When,
A microwave excitation device for generating an electric field vector in each dielectric resonator;
A detection device for detecting transmission energy or reflection energy by each dielectric resonator;
A storage device that stores a first relationship indicating a conversion shift amount of a resonance frequency with respect to a basis weight determined for a standard sample having the same dielectric constant and density as the measurement target sample;
A data processing device that calculates the basis weight of the measurement target sample based on the resonance frequency of each resonator when the measurement target sample is measured and the first relationship stored in the storage device; And the data processing device, as basis weight calculation means for calculating basis weight,
A shift amount calculating means for obtaining a shift amount Δf _{1 to} Δf _n of the resonance frequency of each resonator;
On the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, the direction (θ) is the angle θ, and the shift amounts Δf _{1 to} Δf _n obtained by the shift amount calculating means are plotted as r. A converted shift amount calculating means for obtaining a radius of a circle having the same area as the ellipse sometimes drawn by the ellipse approximation process and setting it as a converted shift amount Δfr;
A basis weight measuring device comprising basis weight calculating means for calculating a basis weight from the converted shift amount Δf obtained by the converted shift amount calculating means and the first relationship stored in the storage device. The storage device also stores the second relationship indicating the moisture content or the converted peak level change amount with respect to the moisture content obtained for the standard sample having the same dielectric loss factor and thickness as the measurement target sample,
The data processing device measures the sample to be measured based on the peak levels P _{1 to} P _n at the resonance frequency positions of the resonators when the sample to be measured is measured and the second relationship stored in the storage device. It also has a moisture content calculating means for calculating the moisture content or moisture content of
The moisture amount calculation means includes a peak level change amount calculation means for calculating peak level change amounts ΔP _{1 to} ΔP _n of each rectangular dielectric resonator with respect to the measurement target sample;
On the polar coordinates (r, θ) where the angle is θ and the distance from the origin is r, and the direction (θ) is the angle θ, the peak level change amounts ΔP _{1 to} ΔP _n obtained by the peak level change amount calculating means are a converted peak level change amount calculating means for obtaining a radius of a circle having the same area as the ellipse drawn by the ellipse approximation process when plotted as r and making it a converted peak level change amount ΔPr;
A moisture content / content rate calculating means for calculating a moisture content or a moisture content rate from the converted peak level change amount ΔPr obtained by the converted peak level change amount calculating means and the second relationship stored in the storage device; The basis weight measuring device according to claim 5 provided. An amplification circuit connected to each detector and amplifying each output includes a time delay element,
Each of the plurality of dielectric resonators is inserted between a microwave oscillator connected thereto and a resonance peak level detection circuit that is connected to the amplifier circuit and detects a resonance peak level from the output thereof. A dielectric resonator detection system comprising a variable amount electric signal attenuation / amplification means is configured,
The output from the resonance peak level detection circuit of each dielectric resonator detection system is compared with a separately set target resonance peak level, and the degree of attenuation with respect to the variable electric signal attenuation / amplification means so as to approach the target resonance peak level or The basis weight measuring device according to claim 5 or 6, further comprising a calculation means for calculating and outputting a signal for changing the amplification degree.