JPS63274850A - Method and device for measuring characteristic of low conductive sheet or wheel-shaped material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a measuring method and apparatus for measuring the properties of highly wettable, low electrically conductive planar or foil-like materials.

BACKGROUND OF THE INVENTION Determining the properties of sheets and foil-like materials that move rapidly on a production line has proven difficult with conventional measurement equipment. Contact transducers are mainly used, such as humidity sensors for plywood based on resistance measurements or sheet-based gravimetric scales. Typically, contact transducers, such as toxin sensors, are susceptible to high measurement errors due to vertical movement of the material. Transducers that use penetrating radiation, such as gamma rays, are often slow to respond, expensive, and moreover, highly hazardous due to the ionizing radiation used. In contrast, non-penetrating radiation such as infrared radiation only conveys surface information from the immediate surface of the material.

Using radio frequency radiation eliminates many of the aforementioned drawbacks and sources of error. Also, non-contact measurements of the material are possible, and the measurements transmit information about the interior of the material sheet. Due to the low cost construction of the transducer arrangement itself, a large number of transducers can be arranged in parallel, thereby achieving fast measurements for the entire line. Furthermore, simultaneous determination of material properties is possible by measuring multiple factors related to the propagation of radio waves in the material. However, even when using an RF transducer, the transducer must be close enough to the material to obtain a sufficiently strong signal when measuring thin sheets or foils.
Movement of the sheet or foil relative to the transducer can cause large errors during measurements.

[Problems to be Solved by the Invention] The object of the present invention is to overcome the drawbacks of the above-mentioned techniques and to provide an entirely new measuring method and device for determining the properties of sheet or foil-like materials of low conductivity and high wettability. That's true.

[Means for Solving Problems] In the present invention, the transducer is electromagnetic! ? ! It is based on the principle that the TEM transfer line resonator is constructed from parts located on both sides of the material forming together with a central conductor. Here, such a structure supports a large number of resonant wave modes, the Q and the resonant frequency of which depend on the material since its dielectric constant is different from that of air. By selecting the appropriate mode, these measurement signals can be maximized and
The effect of material movement on the signal is minimized.

In particular, the method according to the invention comprises: ground planes being provided on both sides of the material to be measured, and one or more central connectors being provided approximately parallel to the material between the ground planes and the material being measured;
A quasi-TEM transfer line resonator self-7 is formed, and a voltage vfiSRE is applied to the quasi-TEM transfer line resonator.
Energy is supplied so that the quasi-TEM mode spreads parallel to the material being measured, and the resonator supports both transverse and longitudinally oriented resonant modes, the resonant frequency and Q of which depend on the properties of the material being measured. , characterized in that the Q associated with the resonant frequencies are measured and these frequencies determine the complex permittivity and related variables of the material being measured.

Furthermore, the device according to the invention is provided in such a way that the material to be measured passes between the central conductors, whereby the central conductor is connected to the material to be measured in such a way as to bring the material to be measured into longitudinal and transverse resonance modes. It is characterized by being almost parallel to the

The present invention provides considerable benefits.

As a result, the measurement method according to the invention and its corresponding device operating in an RF envelope can be applied to one sheet or foil-like material.
It can be used to determine individual or multiple properties simultaneously. The material can be any low conductivity material such as plywood, plastic or cellulose sheet, or paperware. The material passes through the transducer without contacting it. This allows for rapid automatic measurements. Relatively large displacements perpendicular to the plane of the material sheet or foil do not significantly influence the measurement results.

[Example 1] A transducer according to the invention used for measuring the properties of a sheet or foil-like material of low electrical conductivity is
As shown in FIGS. The illustrated transducer consists of two ground planes 3, which in this example are two central conductors 2 (strips, pipes, etc.) and an insulated conductor 2 which is also used to support the central conductors. The material 1 to be measured is located in the center of the central conductor, the material plane parallel to the ground plane. The ground plane and the central conductor together form an electromagnetic resonator, and the electromagnetic waves propagate parallel to the level of the material being measured.

The resonator shown in FIGS. 1 and 2 resonates when the wavelength is twice the length of the central conductor 2. The resonator shown in FIGS.

The dielectric sheet between the central conductors 2 changes the wavelength and consequently also the resonant frequency of the structure. The material attenuates the electromagnetic field detected from changes in the resonator Q.

Information from the characteristics of the resonance is obtained by connecting the resonator to the measurement circuit via a coupling pin or loop 5.

When the distance between the central conductors of the resonators according to FIGS. 1 to 5 increases without changing the spacing from the ground plane 3, the sensitivity of the transducer increases with respect to the vertical displacement of the material 1 to be measured. descend. However, the Q and measurement sensitivity are also reduced. On the other hand, if the spacing of the central conductor 2 from the ground plane increases without changing the mutual distance of the central conductors, the measurement sensitivity increases and the Q decreases. Sensitivity to vertical movement of the material is unaffected. A sufficient value for Q is approximately 500, such that the spacing of the central conductor 2 to the ground plane 3 is approximately 0 wavelengths.
．． 12 times, and the mutual distance between the central conductors is approximately 0.1 of the wavelength.
This can be obtained by selecting a factor of 5. The measurement sensitivity provided by the transducer is then relatively high and the sensitivity to vertical movement of the material is low.

A quasi-TEM transfer line resonator with multiple center conductors, such as the resonators shown in FIGS. 1-5, supports multiple resonant modes at different potential couplings of the center conductors. With respect to a resonator with two central conductors, it is described as a resonator that supports even modes in which the central conductors are at equal potential, and odd modes in which the central conductors are at opposite potentials. With slightly different discontinuous capacitances, the resonant frequencies of the same number of even and odd modes are generally slightly displaced.

Correspondingly, the electromagnetic field pattern differs significantly in the plane perpendicular to the wave propagation direction for even and odd resonant modes. The field pattern for the even mode is shown in FIG. 4, and the corresponding field pattern for the odd mode is shown in FIG. When the thin sheet or foil to be measured is placed in the center of the central conductor 2, the electric field at the position of the sheet to be measured is parallel to the plane of the sheet 1 and perpendicular to the sheet 1 for the odd modes. Therefore, the correlated change in the resonant frequency and Q of the resonator compared to the unloaded resonator produced by the sheet being measured is significantly higher in the even modes than in the odd modes.

Furthermore, the change in the measurement signal caused by vertical movement of the sheet being measured is much smaller than in the odd mode. In the example shown in FIG. 6, an even mode correlated frequency change appears in the resonator according to the invention compared to the change in an unloaded resonator when the plywood sheet in the resonator is moved vertically. The vertical axis is the relative change in resonant frequency and the horizontal axis is the displacement of the seat position from the midpoint of the transducer. The illustrated transducer size A is typically 100μ, size B is 125μ, and size C is 100μ.

For example, to measure the humidity of a plywood sheet, the following approach is provided. Measurements are made using the resonator shown in FIGS. 1-5 to determine the change in resonant frequency and the losses caused by the sheet, ie the dielectric Qc. It is shown that the following equations are valid for different resonance modes.

(1/Qc)-/((fo-ft)/fo
)-c''/((C-death (c--1)) where fa is the resonant frequency of the unloaded resonator and fl is the frequency between the central conductors as shown by Figures 4 and 5. is the resonant frequency with the sheet inserted in , where C′ is the real part of the sheet permittivity and C11 is the imagined part of the sheet permittivity.The constant n is 0 for even modes and for odd modes As a result, the variables calculated from the left side of the equation do not depend on the thickness of the material sheet, such as plywood. Furthermore, in general the variables depend slightly on the material density. However, the variables are material,
For example, it depends on the humidity of the tree and provides a method for determining the humidity. The formula also calculates the actual permittivity of the material sheet or foil by measuring the variables on the left for both the even (n-0) and odd (n=1) modes and then calculating the ratio of these variables. It shows that a portion can be obtained. By again using any of the variables obtained for the different resonant modes, the imaginary part of the dielectric constant is determined, and the result is also independent of the measured sheet thickness.

Both the resonant frequency and the measurement range of the transducer are influenced by the shape of the central conductor 2 of the resonator.

For example, a star central conductor with a butterfly-shaped cross-section according to FIG. 3 results in a resonant frequency that is half the length of a strip-shaped central conductor with the same length. A lower resonant frequency, for example, increases the distance between the center conductors and reduces the sensitivity to vertical movement of the material. The measurement area of the transducer extends outside the edges of the center conductor to a distance of approximately one-third of the correlation distance between the center conductors and is thus compared to a strip-shaped center conductor of constant width. The measurement area of the butterfly-shaped central conductor becomes shorter and wider. 1st
The central conductor 2 shown in FIGS. 5 to 5 is electrically open-circuited at both ends. However, the central conductor 2 can be shorted to the ground plane 3 at both ends or at one end without significantly changing the operation. The ground plane 3 extends cross-sectionally by at least a third wavelength outside the end of the central conductor and blocks radiation from the resonator.

Using normal techniques, the resonant frequency and Q should be at least 1
Measurements are taken 50 times per second, facilitating the determination of properties of relatively fast moving materials. By forming the central conductor as described above, the measurement area of the transducer is influenced, facilitating focused determination of material properties. Such things determine the humidity of plywood sheets because, for example, the sheets are thin, the dielectric constant approaches that of air when dry, and the sheets are often very waved after drying. is important. In addition, the sheet transfer speed on the production line is relatively high, up to 3m/$, and the humidity information can be transmitted across the entire 1.5m of the line at 30X30cj.
Taking into account that it is desirable to have a resolution of 1,000 yen, a measurement rate of 50 times per second is required as described above.

In particular, the method according to the invention is characterized in that ground planes are provided on both sides of the material to be measured, one or more central conductors are provided approximately parallel to the material between the ground plane and the material to be measured, and a quasi-T
Forming an EM transfer line resonator, the quasi-TEM transfer line resonator is supplied with electromagnetic RF energy so that the quasi-TEM modes propagate parallel to the material being measured and the resonator is aligned both laterally and longitudinally. The resonant frequency and Q are determined according to the properties of the material being measured, the Q associated with the resonant frequency is measured, and these frequencies determine the complex dielectric constant of the material being measured and the variables involved. and the measurement sensitivity is characterized in that the resonant frequency and/or Q of the resonant mode parallel to the plane of the material being measured reduces errors caused by vertical movement of the material being measured with respect to the resonator. and further characterized in that the resonant frequencies of two or more resonant modes are measured at least substantially simultaneously, and the difference between the two resonant frequencies is determined to represent a humidity proportional to the humidity of the material being measured. It is characterized by

The change in the resonant frequency caused by the material 1 being measured is
Different for different resonance modes. Thus, the frequency change for even modes is directly proportional to the variable CR-1, and for odd modes the change in frequency is directly proportional to the variable (CR-1)/C-R(
relative to Fig. 7). When the humidity of the material 1 being measured is high, the actual part of the lightning dielectric constant C'R is also high. Then, according to the above equation, small changes in the humidity of the wettable material 1 do not result in significant frequency changes for the odd modes. In contrast, the resonant frequency change for even modes is also large, compensating for the effects of error factors. Sources of such errors are, for example, the vertical movement of the measured object 1 with respect to the transducer, the mutual distance between the central conductors 20, and also changes in the size of the transducer parts due to temperature changes.

If the humidity of the material being measured is high and the humidity change is small,
Measurement errors as mentioned above are reduced. To reduce measurement errors, the resonant frequencies of both resonant modes are measured simultaneously. The different resonant modes are then distinguished in such a measurement device from the different resonant frequency variations of the modes. Error correction is simply performed by subtracting the resonant frequencies of the modes from each other. However, the compensation is not perfect because the effects of error sources at different modes' resonant frequencies are not equal. The effect of compensation depends on how the influence of the error source is equally distributed in different resonant modes. By suitably choosing the correlation distance between the central conductor 2 and the distance of the ground plane 3 from the central conductor 2, the influence of error sources is reduced. This example shows that the error in measuring paper wetness is
The distance between the center conductors 2 is chosen to be 5ca+ and the spacing of the ground plane 3 from the center conductor 2 to 60III1. : Reduced by one-third by compensation when selected. The wetness of the paper averaged 58%, with a variation range of ±2.5%.

As mentioned above, the measurement frequency used is 350MHz
Met. Information from the resonance characteristics is coupled to the RF signal at pin 5.
or by feeding the corresponding coupling loop and then measuring the resonant frequency. The resonant frequency is found, for example, by sweeping through the frequency range of the resonator and then determining the amplitude maximum of the signal.

[Brief explanation of the drawing]

1 is a side view of a measuring transducer consisting of two ground planes, two central conductors and an insulating spacer support, and FIG. 2 is a bottom view of the measuring transducer according to FIG. 3 is a view of the bottom of the central conductor strip of a butterfly-type measurement transducer;
FIG. 4 shows the electric field in the direction of wave propagation for even modes of a measurement resonator with two central conductors, and FIG.
6 shows the associated resonant frequency variation of the measuring resonator according to FIGS. 1 to 5 as a function of the plywood sheet position for the odd modes of a measuring resonator with two central conductors; FIG. , FIG. 73 graphically illustrates the associated frequency variation of odd resonant modes as a function of dielectric constant. DESCRIPTION OF SYMBOLS 1... Sheet or foil-like material, 2... Central conductor, 3... Ground plane, 5... Coupling pin.

Claims (6)

[Claims] (1) A ground plane is provided on both sides of the material to be measured, and a line approximately parallel to the material is provided between the ground plane and the material to be measured.
A central conductor of more than If the resonator supports both transverse and longitudinal resonant modes, and the resonant frequency and Q are according to the properties of the material being measured, the resonant frequency and associated Q are measured, and these frequencies depend on the complexity of the material being measured. A measurement method for determining the properties of highly wettable, low conductivity sheet or foil-like materials, characterized in that it is used to determine the dielectric constant and related variables. (2) that the resonant frequency and/or Q of the resonant mode parallel to the plane of the material being measured reduces errors caused by vertical movement of the material being measured with respect to the resonator, improving measurement sensitivity; A measuring method according to claim 1, characterized in that: (3) The resonant frequencies of two or more resonant modes are measured at least substantially simultaneously, and the difference between the two resonant frequencies is determined to represent a humidity proportional to the humidity of the material being measured. The measuring method described in Range 1. (4) two or more ground planes, two or more conductors disposed between the ground planes to form a quasi-TEM transfer line resonator, and one or more coupling pins for supplying electromagnetic RF energy to the resonators; The material to be measured is arranged to pass between the central conductors, such that the central conductor is approximately parallel to the material to be measured to place the material to be measured in longitudinal and transverse resonance modes. An apparatus for measuring the properties of highly wettable, low electrically conductive sheet or foil-like materials, characterized in that: (5) The ground plane surrounding the material to be measured is flat;
5. Device according to claim 4, characterized in that it is substantially parallel to the central conductor. (6) Device according to claim 4 or 5, characterized in that there are two central conductors.