JP7071723B2 - Circuit for measuring complex permittivity, device for measuring complex permittivity, and method for measuring complex permittivity - Google Patents

Description

The present invention relates to a circuit for measuring a complex dielectric constant for measuring the complex dielectric constant of a dielectric containing a liquid, a complex dielectric constant measuring device, and a method for measuring the complex dielectric constant, and in particular, the complex dielectric constant with respect to frequency is known. The present invention relates to a circuit for measuring a complex dielectric constant having a comb-shaped electrode substrate having a comb-shaped electrode formed on the substrate thereof, and a method for measuring the complex dielectric constant using the circuit.

Electrical properties such as the dielectric constant and conductivity of a substance reflect the internal structure of the substance, so as a means of knowing the structure of the substance and changes in the internal state, for example, the cause of deterioration of the lubricating oil or the electrolyte of the storage battery. It is attracting attention in a wide range of fields, such as elucidation and means for measuring changes in ingredients online in food production lines.

It is well known that the dielectric relaxation phenomenon, in which the dielectric constant of a dielectric decreases as the measurement frequency increases, can be considered at the same time as changes in the dielectric constant and conductivity of a substance by using the concept of complex dielectric constant.

There are several measurement methods for measuring the complex permittivity of a substance, such as the dielectric spectroscopy method and the flat plate capacitor method, and the optimum method is appropriately selected according to the state and shape of the dielectric to be measured, as well as the measurement frequency. ing.

FIG. 1 is an explanatory diagram of the measurement principle of the flat plate capacitor method, in which the upper surface electrode 11 and the lower surface electrode 12 face each other in parallel with the dielectric 10 to be measured interposed therebetween to form a capacitor. The flat plate capacitor method is a method of measuring the complex dielectric constant of the dielectric 10 to be measured from the measured value of admittance at a predetermined frequency of the capacitor of FIG. 1, and the area of the upper surface electrode 11 and the lower surface electrode 12 of FIG. 1 is A [ If m ² ] and the distance between the electrodes are d [m], first, the capacitance C ₀ [F] without the dielectric to be measured is given by Eq. (1). In equation (1), ε ₀ is the permittivity of vacuum or atmosphere, which is 8.854 × 10 ^-12 [F / m].

Since the complex permittivity ε * of the measured dielectric is defined by Eq. (2), the capacitance C * of the capacitor in Fig. 1 is given by Eq. (3), and the admittance of this capacitance C * is given. Expressed as a parallel circuit of R _p and C _p , they are given by Eqs. (5) and (6), respectively, via Eq. (4). The flat plate capacitor method is a method of obtaining the real part ε ₁ and the imaginary part ε ₂ of the complex permittivity ε * from R _p and C _p by Eqs. (7) and (8), respectively.

Ω ₀ in Eqs. (4), (6), and (8) is an angular frequency with respect to the frequency f ₀ , and ω ₀ = 2π f ₀ , which is the same in the following calculation formula.

The complex permittivity ε * given by Eqs. (2) to (8) and its real part ε ₁ and imaginary part ε ₂ are the values obtained by dividing the complex permittivity of the material by the permittivity ε ₀ of the vacuum, respectively. It is correct to call each of them the complex relative permittivity, but in the following explanation, we will simply call them the complex permittivity for the sake of simplicity. In the following explanation, different expressions such as complex permittivity, complex permittivity ε *, complex permittivity ε ₁₁ , and ε ₁₂ are used, but the complex permittivity is expressed by Eq. (2). As is shown, since it is a complex number having a real part and an imaginary part, both are simple expressions of this.

(Prior techniques and their problems)
In Patent Document 1, the complex impedance of the lubricating oil is measured by using the flat plate capacitor method, the real part of the admittance of the reciprocal is regarded as the resistance component, and the conductivity is obtained, and the imaginary part of the reciprocal of the complex impedance is capacitive. A method of detecting the deterioration / deterioration of oil from changes in conductivity and dielectric constant by determining the dielectric constant as a component is disclosed.

However, in the method described in Patent Document 1, the distance between the counter electrodes changes due to a change in pressure or temperature applied to the lubricating oil, or dust or the like is caught between the counter electrodes, so that correct measurement can be performed. There is a problem that it disappears. Further, since the structure of the counter electrode becomes three-dimensional, there is a problem that the sensor portion becomes large.

In Non-Patent Document 1, as a method of removing the drawbacks of the flat plate capacitor method, a comb-shaped electrode is formed on one surface of a dielectric substrate to form a two-terminal dielectric sensor, and the measurement is performed so as to cover the comb-shaped electrode. A method of contacting a dielectric and measuring the admittance at that time to measure the dielectric constant and the conductivity of the dielectric to be measured is shown. In this, in order to obtain the capacitance C _mut due to the dielectric constant of the dielectric to be measured, the capacitance C _base due to the substrate material of the comb-shaped electrode is subtracted from the capacitance C _tot of the entire dielectric sensor. Although a method has been shown, no method has been shown for determining the complex dielectric constant of the object to be measured, including the contribution of the complex dielectric constant of the substrate material. Further, in Non-Patent Document 1, it is assumed that only this comb-shaped electrode, which is necessary for obtaining the capacitance C _mut due to the dielectric constant of the dielectric to be measured, is floating in the air. In order to obtain C _air , a method of measuring using a liquid whose conductivity is almost negligible and whose dielectric constant is known has been shown.
-There is a problem that the measurement accuracy is lowered because the characteristic change due to the measurement frequency of the sample used as the standard liquid is not corrected and the influence of the change with time is not corrected.
-Furthermore, in the method described in Non-Patent Document 1, since the influence of the thickness of the substrate is not taken into consideration in the capacitance C _base caused by the substrate material of the comb-shaped electrode, if a thin substrate is used. If this is the case, the effective complex permittivity value will be small, and if any object is close to the back side of the substrate, it will be affected by the dielectric properties of the close object and the measurement accuracy will be reduced. There is.
-Furthermore, in the method described in Non-Patent Document 1, the influence of the thickness of the measured dielectric in contact so as to cover the comb-shaped electrode is not taken into consideration, so the measurement is performed based on the thickness of the measured dielectric. There is a problem that the value changes.
-In addition, a dedicated measuring device is used for impedance or admittance measurement disclosed in Patent Document 1 and Non-Patent Document 1, and in particular, when a dielectric sensor is to be mounted on an individual storage battery or the like. Difficult to use.

Japanese Unexamined Patent Publication No. 2009-2693

The Handbook of Dielectric Analysis and Cure Monitoring; Lambient Technologies

The present invention solves the drawbacks of the conventional flat plate capacitor method, that is, the distance between the counter electrodes changes and dust is caught between the counter electrodes, resulting in a decrease in measurement accuracy, and the conventional method. Considering the drawbacks of the comb-shaped electrode method, that the measurement frequency of the sample used as the standard liquid and the influence of changes over time are not corrected, and the influence of the thickness of the substrate of the comb-shaped electrode and the thickness of the sample to be measured are taken into consideration. With the problem of solving the problems that the measurement accuracy is lowered due to the fact that the measurement is not performed and that it is necessary to measure using a dedicated measuring device, the complex dielectric constant as the material constant of the material to be measured is highly accurate. Provided is a measurable complex dielectric constant measuring circuit, a complex dielectric constant measuring device, and a method for measuring a complex dielectric constant.

According to the present invention
A complex dielectric characterized in that a comb-shaped electrode having an electrode pitch at least smaller than the thickness of the dielectric substrate is formed on one surface of a dielectric substrate made of a dielectric material having a known complex dielectric constant at a predetermined frequency. A dielectric sensor for rate measurement can be obtained.

According to the present invention
A means for obtaining the first equivalent parallel capacitance and the first equivalent parallel resistance from the admittance of the dielectric sensor according to claim 1 at a predetermined frequency in the atmosphere.
The second equivalent parallel capacitance and the second from the admittance of the dielectric sensor at the predetermined frequency in a state where the electrode surface of the dielectric sensor is covered with a dielectric to be measured having a thickness at least larger than the pitch of the comb electrode. As a means to find the equivalent parallel resistance of
A means for obtaining an additional parallel capacity from the first equivalent parallel capacity and the second equivalent parallel capacity,
A means for obtaining an additional parallel resistance from the first equivalent parallel resistance and the second equivalent parallel resistance,
Using the values of the additional parallel capacitance, the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex permittivity of the dielectric substrate, the dielectric to be measured is used. As a means to obtain the complex permittivity of
A device for measuring a complex permittivity is obtained.

According to the present invention
The step of obtaining the first equivalent parallel capacitance and the first equivalent parallel resistance from the admittance of the dielectric sensor according to claim 1 at a predetermined frequency in the atmosphere.
The second equivalent parallel capacitance and the second from the admittance of the dielectric sensor at the predetermined frequency in a state where the electrode surface of the dielectric sensor is covered with a dielectric to be measured having a thickness at least larger than the pitch of the comb electrode. And the process of finding the equivalent parallel resistance of
The process of obtaining the additional parallel capacitance from the first equivalent parallel capacitance and the second equivalent parallel capacitance,
The step of obtaining the additional parallel resistance from the first equivalent parallel resistance and the second equivalent parallel resistance,
The dielectric to be measured is measured using the additional parallel capacitance, the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex permittivity of the dielectric substrate. The process of finding the complex permittivity of the body and
A method for measuring a complex permittivity is obtained, which comprises.

According to the present invention
The two dielectric sensors having the same characteristics and having the same characteristics connected in parallel, and the dielectric sensor connected in parallel with one of the two dielectric sensors having a comb-shaped electrode covered with a dielectric to be measured. An oscillator for applying an AC voltage of a predetermined frequency, a difference detector for detecting the difference between the currents flowing through the two dielectric sensors with respect to the AC voltage, and an output signal of the AC voltage and the difference detector. A means for obtaining an additional admittance of a dielectric sensor in which one of the comb-shaped electrodes is covered with the dielectric to be measured by dividing the AC voltage by the output of the phase detector and the phase detector for detecting the phase difference. A means for obtaining an additional parallel capacitance and an additional parallel resistance from the phase difference between the AC voltage detected by the phase detector and the output of the difference detector, and the additional admittance of the dielectric sensor, and the additional parallel capacitance. As a means for obtaining the complex dielectric constant of the dielectric to be measured by using the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex dielectric constant of the dielectric substrate. , A device for measuring a complex dielectric constant is obtained.

According to the present invention
A step of applying an AC voltage having a predetermined frequency to the dielectric sensors connected in parallel with one of the two dielectric sensors having a comb-shaped electrode covered with a dielectric to be measured.
The step of detecting the difference between the currents flowing through the two dielectric sensors with respect to the AC voltage, and
The step of detecting the phase difference between the AC voltage and the output signal of the difference detector, and
A step of obtaining an additional admittance of a dielectric sensor in which one of the comb-shaped electrodes is covered with the dielectric to be measured by dividing the AC voltage by the output of the difference detector.
A step of obtaining an additional parallel capacitance and an additional parallel resistance from the phase difference between the AC voltage detected by the phase detector and the output of the difference detector and the additional admittance of the dielectric sensor.
The complex dielectric of the dielectric to be measured using the additional parallel capacitance, the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex permittivity of the dielectric substrate. The process of finding the rate and
A method for measuring a complex permittivity is obtained, which comprises .

According to the present invention, the value of the complex dielectric constant of the measured dielectric is correctly measured, including the influence of the complex dielectric constant of the dielectric substrate, the influence of the thickness of the substrate, and the influence of the thickness of the measured dielectric. can do.

Further, according to the present invention, it is possible to obtain the admittance change ΔY due to the object to be measured for obtaining the complex permittivity with a simple circuit, and a measuring instrument for measuring the admittance becomes unnecessary.

It is explanatory drawing of the measurement principle of a plate capacitor method. It is a top view which shows the outline of the structural example of the dielectric sensor made of the comb-shaped electrode substrate of this invention. FIG. 2 is a schematic cross-sectional view of the dielectric sensor made of the comb-shaped electrode substrate of the present invention shown in FIG. FIG. 3 is a schematic cross-sectional view showing a state in which the electrode surface of the dielectric sensor made of the comb-shaped electrode substrate of the present invention shown in FIG. 3 is covered with the dielectric to be measured. It is the calculation result of Rp and Cp for the thickness of the substrate when there is no dielectric to be measured. It is the calculation result of Rp and Cp for the thickness of the dielectric to be measured. It is explanatory drawing of the method of finding the admittance ΔY when the admittance ΔY is added to one of two equal admittances. It is explanatory drawing of the method of finding the admittance ΔY when the admittance ΔY is added to one of two equal admittances. It is a circuit block diagram which shows the circuit structure example which obtains the additional admittance ΔY which was constructed using the dielectric sensor of this invention. It is a top view which shows an example of another electrode composition of the comb-shaped electrode substrate of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, such embodiments do not limit the technical scope of the invention.

(Explanation of the structure of the comb-shaped electrode substrate of the present invention and the measurement principle of the complex permittivity)
FIG. 2 is a plan view showing an outline of a structural example of a dielectric sensor made of the comb-shaped electrode substrate of the present invention. In FIG. 2, a plurality of strip-shaped electrodes 21 and 22 are formed on one surface of the dielectric substrate 20, and every other strip-shaped electrode is connected to the common electrodes 23 and 24, respectively, and the measurement terminals 25 and 22 are respectively. It is connected to 26. Therefore, the dielectric sensor made of the two-terminal comb-shaped electrode substrate of the present invention shown in FIG. 2 can be considered as one capacitor when viewed from the measurement terminal 25 and the measurement terminal 26.

FIG. 3 is a schematic cross-sectional view of the dielectric sensor made of the comb-shaped electrode substrate of the present invention shown in FIG. 2, wherein the band-shaped electrodes 21 and 22 are formed on one surface of a dielectric substrate 20 such as glass epoxy. There is.

FIG. 4 is a schematic cross-sectional view showing a state in which the electrode surface of the dielectric sensor made of the comb-shaped electrode substrate of the present invention shown in FIG. 3 is covered with the dielectric to be measured, and the band-shaped electrodes 21 and 22 are made of glass epoxy. It is formed on one surface of the dielectric substrate 20 such as the above, and the comb-shaped electrode portion is covered with the dielectric 47 to be measured.

In FIGS. 2, 3, and 4, the shapes, dimensions, etc. of the strip-shaped electrodes are shown schematically and differ from the actual ones in order to facilitate understanding of the structure.

In FIGS. 2 to 4, the capacitance C ₀₁ assuming that the comb-shaped electrode is floating in the air is given by Eq. (9).

Here, Se and de are the effective electrode area and the effective electrode spacing determined by the shape and dimensions of the comb-shaped electrode, respectively, and although it is difficult to obtain them separately, the ratio of Se and de is a constant. ..

Next, assuming that this comb-shaped electrode is buried in a material having a complex permittivity ε ₁ *, the capacitance C ₁ * is given by Eq. (10).

Similarly, the capacitance C ₂ * when this comb-shaped electrode is buried in a material having a complex permittivity ε ₂ * is given by Eq. (11).

Therefore, as shown in FIG. 4, the capacitance when the lower half of the comb-shaped electrode is covered with a material having a complex dielectric constant ε ₁ * and the upper half is covered with a material having a complex dielectric constant ε ₂ *. C ₁₂ * is considered to be given by the sum of half of the capacitance C ₁ * of Eq. (10) and half of the capacitance C ₂ * of Eq. (11), and is given by Eq. (12).

As shown in Fig. 4, the capacitance C ₁₂ of the capacitor represented by Eq. (12) is considered to be the capacitance when the electrode surface of the comb-shaped electrode substrate is covered with the dielectric to be measured. , This admittance Y ₂ is given by Eq. (13), and further, as shown by Eq. (13), when the admittance Y ₂ is expressed by the parallel circuit of the resistor R _p2 and the capacitor C _p2 , R _p2 and C _p2 Are given by Eqs. (14) and (15), respectively.

On the other hand, when the admittance Y ₁ of a single comb-shaped electrode substrate is represented by a parallel circuit of resistance R _p1 and capacitance C _p1 , R _p1 and C _p1 are the dielectrics to be measured in Eqs. (14) and (15). It is obtained by setting ε ₂₁ = 1 and ε ₂₂ = 0 using the complex permittivity of vacuum as the complex permittivity, and is given by Eqs. (16) and (17), respectively.

Therefore, the change in parallel capacitance and the change in parallel resistance when the electrode surface of the comb-shaped electrode substrate alone and the electrode surface of the comb-shaped electrode substrate are covered with the dielectric to be measured are shown as the additional parallel capacitance ΔC _p and the additional parallel resistance ΔR _p , respectively. Then, it is given by the equations (18) and (19), respectively.

Therefore, if C ₀₁ and the complex permittivity ε ₁₁ and ε ₁₂ of the dielectric substrate are known, and if ΔR _p and ΔC _p are known, the complex permittivity ε ₂₁ and ε ₂₂ of the measured dielectric will be, respectively. It can be obtained from Eqs. (20) and (21).

If C ₀₁ is unknown, if the complex permittivity ε ₁₁ and ε ₁₂ of the dielectric substrate are known, it can be obtained by Eq. (17) by measuring the parallel capacitance C _p1 of the comb-shaped electrode substrate alone. Can be done.

As described in the procedures of Eqs. (9) to (21), in the present invention, it is necessary to know the complex permittivity of the dielectric substrate in advance, but the complex permittivity of the dielectric substrate is the above-mentioned (1). By the procedure of Eqs. to (8), counter electrodes of area A are formed on both sides of the substrate material having a known thickness D, the admittance Y at the desired frequency is measured, and the parallel equivalent circuit constants R _p and C _p . By obtaining, the values of the complex permittivity ε ₁₁ and ε ₁₂ of the dielectric substrate at a desired frequency can be easily obtained.

By the above procedure, the complex of the dielectric to be measured is complex in consideration of the influence of the complex dielectric constant of the dielectric substrate, which was impossible by the measurement method using the comb-shaped electrode substrate described in Non-Patent Document 1. The dielectric constant can be measured.

(Confirmation of the characteristics required for the thickness of the comb-shaped electrode substrate and the thickness of the dielectric to be measured)
In the above explanation, it is assumed that the comb-shaped electrode is buried in an object having a complex permittivity ε ₁ * or an object having a complex permittivity ε ₂ *, and the thickness of the dielectric substrate and the thickness of the measured dielectric are measured. It is implicitly assumed to be thick enough. However, in practice, it is desirable that the thickness of the dielectric substrate or the dielectric to be measured is thin, so in order to confirm how thick the dielectric substrate is suitable, the complex dielectric of the actually measured dielectric substrate is used. It was calculated by the finite element method using the value of the rate and the value of glycerin, which is generally known as the value of the complex permittivity as the dielectric to be measured.

Figure 5 shows the calculation results of R _p and C _p for the thickness of the dielectric substrate when there is no dielectric to be measured. Using an epoxy substrate with ε ₁₁ = 5.5 and ε ₁₂ = 0.1 as the substrate material, the conductor The width is 0.25 mm, the electrode spacing is 0.25 mm, the electrode length is 7 mm, and the number of electrode pairs is eight.

Figure 6 shows the calculation results of R _p and C _p for the thickness of the dielectric to be measured when glycerin of ε ₂₁ = 34 and ε ₂₂ = 0.47 is used as the dielectric to be measured, and the thickness of the dielectric substrate is shown in FIG. The diameter is fixed to 1 mm, and the same shaped electrode as in Fig. 5 is used.

From the results shown in FIGS. 5 and 6, the values of R _p and C _p in the region where the thickness of the dielectric substrate and the thickness of the measured dielectric are larger than the pitch of the comb-shaped electrodes (= conductor width + electrode spacing). Shows almost constant values, and the thickness of the dielectric substrate and the thickness of the dielectric to be measured must be at least equal to or greater than the pitch of the comb-shaped electrode, and is preferably about twice the pitch of the comb-shaped electrode. It turns out that it is good to say. By doing so, the influence of the thickness of the dielectric substrate and the influence of the thickness of the dielectric to be measured, which are unclear by the method of Non-Patent Document 1, are eliminated, and the influence is close to the back side of the dielectric substrate. It is possible to measure the complex permittivity of the dielectric to be measured with high accuracy without the influence of the material.

(Equivalent circuit of the dielectric sensor of the present invention and how to obtain a specific admittance ΔY)
FIG. 7 and FIG. 8 are explanatory diagrams of a method of finding ΔY when the admittance ΔY is added to one of two equal admittances, and FIG. 7 shows two admittances Y ₁ and Y ₂ connected in parallel. When the voltage V is applied to the circuit, the currents I ₁ and I ₂ flowing through the respective admittances are shown, and I ₁ and I ₂ are given by Eq. (22).

FIG. 8 shows a circuit when Y ₂ = Y ₁ + ΔY in FIG. 7, and the current ΔI flowing through ΔY is given by Eq. (23). From Eq. (23), it can be seen that the voltage V is a real number and ΔI and ΔY are complex numbers, so that the phase of ΔI and the phase of ΔY are equal.

Further, from Eq. (23), the additional admittance ΔY is given by Eq. (24).

That is, if the currents I ₁ and I ₂ flowing through the admittances Y ₁ and Y ₂ are detected and the current ΔI of the difference between them is obtained, ΔY can be obtained from Eq. (24).

Here, if the additional admittance ΔY is set as ΔY = 1 / ΔR _p + jω ₀ ΔC _p , then ΔR _p and ΔC _p are given by equations (25) and (26), and ΔR _p . And ΔC _p can be obtained, and the complex permittivity of the dielectric to be measured can be obtained by using Eqs. (20) and (21). In equations (25) and (26), θ is the phase of the added admittance ΔY, and as described above, is equal to the phase of the current ΔI of the difference.

As described above, in the present invention, when the comb-shaped electrode surface of the dielectric sensor is covered with a dielectric material to be measured having a predetermined thickness, the additional admittance ΔY to the additional parallel capacitance ΔC _p and the additional parallel resistance Δ Obtain R _p and use the value of the complex permittivity of the previously known dielectric substrate and the capacitance assuming that the comb-shaped electrode is floating in the air to determine the complex permittivity of the dielectric to be measured. Can be asked.

(Circuit configuration example for obtaining additional admittance △ Y)
FIG. 9 is a circuit block diagram showing a circuit configuration example for obtaining additional admittance ΔY configured by using the dielectric sensor which is the comb-shaped electrode substrate of the present invention, and shows a configuration example of a circuit for measuring complex dielectric constant. In FIG. 9, one terminal of the two dielectric sensors 92 and 93 having the same characteristics is connected, and further connected to an oscillation circuit 91 that outputs an AC voltage V having a frequency f ₀ , and the other of the respective dielectric sensors. Terminals are connected to current-voltage conversion circuits 94 and 95. The output voltages of the current-voltage conversion circuits 94 and 95 are connected to the differential amplifier 96 (difference detector), respectively, and the output of the differential amplifier 96 and the output of the oscillation circuit 91 are connected to the phase detection circuit 97. The output signal of the phase detection circuit (phase detector) 97 representing the phase θ of the additional admittance ΔY is connected to the phase signal terminal 98, and the output signal of the differential amplifier circuit 96 representing the additional admittance ΔY is the additional admittance ΔY signal. It is connected to terminal 99.

In the circuit of FIG. 9, when the comb-shaped electrode portion of one of the two dielectric sensors 92 and 93 is covered with the measured dielectric, a difference occurs in the current flowing through the dielectric sensors 92 and 93. The output voltage of the current-voltage conversion circuits 94 and 95 changes accordingly. Therefore, the output voltage of the differential amplifier 96 is a value proportional to the difference in this current. As described in the above equations (23) and (24), this current difference ΔI is proportional to the added admittance ΔY, and the phases of ΔI and ΔY with respect to the applied voltage V are equal. Therefore, if the proportionality constant of the circuit system is known, the additional admittance ΔY, that is, the additional parallel resistance ΔR _p , using the equations (25) and (26) from the differential amplifier 96 output and the phase detection circuit 97 output. And the additional parallel capacitance ΔC _p is obtained, and the complex dielectric constant of the dielectric to be measured can be obtained by the above equations (20) and (21). The complex dielectric constant of the dielectric to be measured is input to an arithmetic processing means such as an integrated circuit or a general-purpose computer device that digitally processes the output of the differential amplifier 96 and the output of the phase detection circuit 97 to perform the calculation by the above-mentioned arithmetic expression. Is required. The complex permittivity measuring device of the present invention is configured to include the complex permittivity measuring circuit shown in FIG. 9 and the arithmetic processing means for obtaining the complex permittivity by calculation, and includes the complex dielectric constant measuring circuit and the arithmetic processing means. May be configured integrally or as a combination of separate components.

According to the present invention, the real part and the imaginary part of the complex permittivity ε * of the measured dielectric can be measured separately, but only the real part changes greatly depending on the characteristics of the measured dielectric, and the imaginary part is imaginary. There are cases where the part hardly changes, or conversely, the imaginary part changes significantly even though the change in the real part is small. In this case, the change in the absolute value of the complex dielectric constant ε *, that is, the change in the absolute value of the admittance difference ΔY between the two dielectric sensors, or the difference in the current flowing through the two dielectric sensors. Changes in the characteristics of the dielectric to be measured, which are practically useful, can also be measured by changing the absolute value of ΔI.

In the above description, as shown in FIG. 2, the structure of the comb-shaped electrode substrate has been described in the case where a plurality of strip-shaped electrodes are formed on one surface of the dielectric substrate to form a two-terminal structure. The configuration of is not necessarily limited to the band-shaped electrode.

FIG. 10 is a plan view showing another example of the electrode configuration of the comb-shaped electrode substrate of the present invention, in which concentric linear electrodes 101 and 102 are formed on one surface of the dielectric substrate 100, and FIG. 10 shows. As shown, the linear electrodes on both sides are connected to each other to form a two-terminal structure, which is connected to the connection terminals 103 and 104.

The complex permittivity measuring circuit, the complex permittivity measuring device, and the complex permittivity measuring method in the present invention include, for example, elucidating the cause of deterioration of the electrolytic solution of lubricating oil and storage battery, and monitoring changes in components in a food production line. Can be used for.

The present invention is not limited to the above-described embodiment, and there are design changes within a range that does not deviate from the gist including various modifications and modifications that can be conceived by a person having ordinary knowledge in the field of the present invention. Of course, it is also included in the present invention.

10: Dielectric to be measured
11: Top electrode
12: Bottom electrode
20: Dielectric substrate
21: Band-shaped electrode
22: Band-shaped electrode
23: Common electrode
24: Common electrode
25: Measurement terminal
26: Measurement terminal
47: Dielectric to be measured
91: Oscillator circuit
92, 93: Dielectric sensor of the present invention
94, 95: Current-voltage conversion circuit
96: Differential amplifier
97: Phase detection circuit
98: Phase signal terminal
99: Additional admittance △ Y signal terminal
100: Dielectric substrate
101, 102: Linear electrode
103, 104: Connection terminal

Claims (4)

From the admittance in the atmosphere of a dielectric sensor in which a comb-shaped electrode having an electrode pitch at least smaller than the thickness of the dielectric substrate is formed on one surface of a dielectric substrate made of a dielectric material having a known complex dielectric constant at a predetermined frequency. A means for obtaining the first equivalent parallel capacitance and the first equivalent parallel resistance,
The second equivalent parallel capacitance and the second from the admittance of the dielectric sensor at the predetermined frequency in a state where the electrode surface of the dielectric sensor is covered with a dielectric to be measured having a thickness at least larger than the pitch of the comb electrode. As a means to find the equivalent parallel resistance of
A means for obtaining an additional parallel capacity from the first equivalent parallel capacity and the second equivalent parallel capacity,
A means for obtaining an additional parallel resistance from the first equivalent parallel resistance and the second equivalent parallel resistance,
Using the values of the additional parallel capacitance, the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex permittivity of the dielectric substrate, the dielectric to be measured is used. As a means to obtain the complex permittivity of
A device for measuring complex permittivity. From the admittance in the atmosphere of a dielectric sensor in which a comb-shaped electrode having an electrode pitch at least smaller than the thickness of the dielectric substrate is formed on one surface of a dielectric substrate made of a dielectric material having a known complex dielectric constant at a predetermined frequency. The process of finding the first equivalent parallel capacitance and the first equivalent parallel resistance,
The second equivalent parallel capacitance and the second from the admittance of the dielectric sensor at the predetermined frequency in a state where the electrode surface of the dielectric sensor is covered with a dielectric to be measured having a thickness at least larger than the pitch of the comb electrode. And the process of finding the equivalent parallel resistance of
The process of obtaining the additional parallel capacitance from the first equivalent parallel capacitance and the second equivalent parallel capacitance,
The step of obtaining the additional parallel resistance from the first equivalent parallel resistance and the second equivalent parallel resistance,
The dielectric to be measured is measured using the additional parallel capacitance, the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex permittivity of the dielectric substrate. The process of finding the complex permittivity of the body and
A method for measuring a complex permittivity, which comprises. Two dielectric sensors having the same characteristics are formed on one surface of a dielectric substrate made of a dielectric material having a known complex dielectric constant at a predetermined frequency, in which a comb-shaped electrode having an electrode pitch at least smaller than the thickness of the dielectric substrate is formed. In parallel,
With the comb-shaped electrode of one of the two dielectric sensors covered with the dielectric to be measured, an oscillator for applying an AC voltage of a predetermined frequency to the dielectric sensors connected in parallel, and an oscillator.
A difference detector that detects the difference between the currents flowing through the two dielectric sensors with respect to the AC voltage, and
A phase detector that detects the phase difference between the AC voltage and the output signal of the difference detector, and
A means for obtaining the additional admittance of a dielectric sensor in which one of the comb-shaped electrodes is covered with the dielectric to be measured by dividing the AC voltage by the output of the difference detector.
A means for obtaining an additional parallel capacitance and an additional parallel resistance from the phase difference between the AC voltage detected by the phase detector and the output of the difference detector and the additional admittance of the dielectric sensor.
The complex dielectric of the dielectric to be measured using the additional parallel capacitance, the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex permittivity of the dielectric substrate. The means to find the rate,
A device for measuring complex permittivity. Two dielectric sensors having the same characteristics are formed on one surface of a dielectric substrate made of a dielectric material having a known complex dielectric constant at a predetermined frequency, in which a comb-shaped electrode having an electrode pitch at least smaller than the thickness of the dielectric substrate is formed. In parallel,
A step of applying an AC voltage of a predetermined frequency to the two dielectric sensors connected in parallel with the comb-shaped electrode of one of the two dielectric sensors covered with the dielectric to be measured.
A step of detecting the difference between the currents flowing through the two dielectric sensors with respect to the AC voltage by a difference detector, and
A step of detecting the phase difference between the AC voltage and the output signal of the difference detector by a phase detector, and
A step of obtaining an additional admittance of a dielectric sensor in which one of the comb-shaped electrodes is covered with the dielectric to be measured by dividing the AC voltage by the output of the difference detector.
A step of obtaining an additional parallel capacitance and an additional parallel resistance from the phase difference between the AC voltage detected by the phase detector and the output of the difference detector and the additional admittance of the dielectric sensor.
The complex dielectric of the dielectric to be measured using the additional parallel capacitance, the additional parallel resistance, the capacitance when the comb-shaped electrode alone is assumed to be floating in the atmosphere, and the complex permittivity of the dielectric substrate. The process of finding the rate and
A method for measuring a complex permittivity, which comprises.

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