JPH0644022B2 - Method and apparatus for measuring complex conductivity - Google Patents

Description

The present invention relates to a method for measuring a complex conductivity, in which a plurality of sinusoidal signals are applied to an electrode system including a plurality of point electrodes to measure a complex conductivity, and Regarding the device.

[Problems of conventional technology]

FIG. 6 is a diagram showing a conventional example of a complex conductivity measuring device.

The total current in a substance consists of a "conduction current" and a "displacement current", where the conduction current is characterized by "conductivity" and the displacement current is characterized by "dielectric constant". In this specification, the ease of passing an electric current, which is a combination of both, is expressed below by the term "electrically conductive".

As shown in FIG. 6, a conventional electric conductivity measuring device applies a sine wave signal to a measuring electrode having a finite shape, and measures the impedance of a measured object using a bridge or a resonance circuit. Then, the loss angle δ, the effective resistance γ, and the electric capacitance C are obtained from the measured values, and the edge effect is corrected,
The electrical conductivity is measured by calculating the electric conductivity δ and the dielectric constant ε.

In such conventional electrical conductivity measurement, the conductivity at low frequency is low for the DUT having a small resistivity, on the contrary,
The dielectric constant at high frequency was the object of measurement for each of the measured objects having a large resistivity. In this case, the structure of the electrode used for measurement and the method of measurement were also different.

[Problems to be solved by the invention]

By the way, when water penetrates into the soil, there are cases where the water content is small and the dielectric constant is excellent, and there are cases where the water content is large and the electrical conductivity is excellent. Conventionally, it has been difficult to perform the measurement across such an object to be measured with the same electrode because the structure of the electrode used for the measurement and the measurement method are different as described above.

Further, in the conventional measurement of the dielectric constant, since an electrode having a constant shape such as a concentric cylindrical shape is widely used, the edge effect that appears depending on the shape of the electrode cannot be ignored, and the shape of the electrode prevents the penetration of water. There are two drawbacks that it affects the change of the electrical conductivity of the measured object, such as interference.

The present invention is to solve the above problems, and by using a dot-shaped electrode, the structure of the electrode system does not affect the fluctuation of the electrode conductivity of the DUT, and the same electrode can be used. The purpose is to simultaneously measure the electric conductivity and the permittivity of an object to be measured, which can be considered to spread infinitely, as complex electric conductivity.

[Means for solving problems]

Therefore, the method for measuring the complex conductivity of the present invention is a method for measuring the complex conductivity by arranging a plurality of point electrodes in the DUT and applying a current signal to measure the complex conductivity. , A plurality of sinusoidal signals are applied to one of the electrode systems, the potential difference of the other is measured, the ratio of the current value of the applied signal to the voltage value of the measured signal, the angular velocity of the applied signal, and the coefficient determined by the arrangement of the dot electrodes. From the above, it is characterized by calculating the complex conductivity of the measured object that can be considered to spread infinitely, the measuring device is a point electrode for applying a current signal, a point electrode for measuring the potential difference, A means for deriving the current value of the applied signal and the angular velocity, a means for deriving the voltage value of the measurement signal, a means for setting a coefficient determined by the arrangement of the point electrodes, and a ratio of the current value of the applied signal and the voltage value of the measurement signal. The ratio, the angular velocity, and the coefficient It is characterized in that it comprises a calculating means for calculating a Luo conductivity and dielectric constant.

[Action]

In the method and apparatus for measuring the complex conductivity of the present invention, since a plurality of sinusoidal signals are applied to the electrode system composed of a plurality of point electrodes, the problem of the edge effect due to the shape of the electrodes is eliminated,
It is easy to calculate the complex conductivity of the DUT that can be regarded as infinitely spreading, from the ratio of the current value of the applied signal to the voltage value of the measured signal, the angular velocity of the applied signal, and the coefficient determined by the arrangement of the point electrodes. The complex conductivity can be measured. The measuring device is composed of point electrodes and an arithmetic means, and the arithmetic means obtains the ratio between the current value of the applied signal and the voltage value of the measured signal, and determines the applied signal as the conductivity using the angular velocity and the coefficient. Anything that calculates the dielectric constant may be used.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram showing an arrangement example of a point electrode system for explaining a method for measuring a complex conductivity according to the present invention, and FIG. 2 is a current signal and a potential signal when the potential signal is matched with a real axis. FIG. 3 is a diagram showing the phase relationship with and FIG. 3 is a diagram showing the configuration of one embodiment of the apparatus for measuring fluorine conductivity according to the present invention.

In FIG. 1, 1 to 4 are point electrodes, respectively,
The electrodes 1 and 4 (hereinafter, this electrode is referred to as a current electrode) apply a sinusoidal current to the object to be measured, and
(Hereinafter, this electrode is referred to as a potential electrode) measures the potential difference at two points representing the point of interest. In the present invention, the complex conductivity is obtained from the sinusoidal current signal applied from the point electrodes, the voltage measured, and the placement coefficient of the electrodes.

Next, the measurement principle of the present invention will be described.

The potential difference between the potential poles 2 and 3 when a sinusoidal signal having a current value is applied from the current poles 1 and 4 is Becomes However, σ ^* is a complex conductivity, and assuming that the angular frequency of the applied current signal is ω, the conductivity σ and the permittivity ε have the following relationship.

σ ^* = σ + jωε (2) Further, K is a coefficient determined by the arrangement of the point electrodes, and in a substance that can be regarded as infinitely wide, Is. γ _{i, j} represents the distance between the electrode i and the electrode j, respectively. , Indicates that it is a complex number representation of a sinusoidal signal, Is. In FIG. 2, the current signal, the potential signal, and φ in the equation (1) represent the phase difference between these signals.

Assuming that the values of the conductivity σ and the permittivity ε are the same for a plurality of input frequencies, the above (1),
From equations (2) and (4), Becomes However, R _i = V _i / I _i (6), φ is the phase difference (= “loss angle”) between the current signal and the voltage signal in FIG. 2, and the subscript _i is the response to the input angular frequency ω _i . Is shown.

Since equation (5) holds for each of n types of sine waves with different frequencies, And apply the least squares method to equation (7),
The conductivity σ and the permittivity ε are obtained as follows.

However, And [] is Is a symbol that represents.

In the above equation (8), the right side includes only the coefficient K determined by the shape of the point electrode system, the angular frequency ω of the input signal, and the ratio R of the applied current I and the measured voltage V. Among these, K and ω are known parameters depending on the measurement conditions, and therefore by measuring R, the conductivity σ and the permittivity ε can be obtained.

By arranging the point electrodes in this way, applying a sinusoidal current signal from one side, and measuring the potential difference on the other side, the conductivity σ and the permittivity ε can be obtained by using known parameters. As the measuring device, the structure shown in FIG. 3 can be adopted.

In FIG. 3, 11 is a current signal generation source, 12 is a changeover switch, 13 is an object to be measured, 14 is a measuring unit, and 15 is a measuring unit.
Reference numerals 19 and 19 denote a calculation unit, 16 denotes a current value derivation unit, 17 denotes an angular velocity derivation unit, and 18 denotes a coefficient setting unit. Current signal source 11
Generates a sinusoidal current signal of angular velocities ω ₁ and ω ₂ to be applied to the point electrode, and switches which of these signals is applied to the point electrode installed in the object 13 to be measured. Is the changeover switch 12. Measuring unit 14
Is for measuring the voltage signal of the point electrode. The electrode value derivation unit 16 and the angle degree derivation unit 17 are provided in the current signal generation source 1
Each value corresponding to the current signal generated by 1 is derived. For example, the value may be set in advance corresponding to the current signal generation source 11 and selected according to the position of the changeover switch 12. Good. Also, the coefficient setting unit 1
8 is for measuring the coefficient corresponding to the arrangement of the point electrodes installed in the measured object 13. Computing unit 15
Is to obtain the ratio between the voltage value and the current value, and the calculation unit 19 calculates the above equation (8) from the output of the calculation unit 15, the angular velocity and the coefficient to obtain the conductivity σ and the dielectric constant ε. It is what you want.

FIG. 4 is a diagram showing the configuration of another embodiment of the present invention applied when a square wave signal is applied, and FIG. 5 is another embodiment of the present invention applied when an arbitrary waveform signal is applied. It is a figure which shows an example structure. In the figure, the same reference numerals as in FIG. 3 indicate the same components, 14 'and 21 are measuring units 16', 17 'are setting units, 20 and 22 are calculating units, and 23 is an angular velocity detecting unit.

As a method of applying a plurality of sine wave current signals, it is also one method to prepare a plurality of sine wave current generating means as described above, and switch and apply them, but a square wave signal waveform or an arbitrary signal Of course, corrugations may be used. In this case, after directly or once recording the applied current signal waveform and the measured potential waveform, Fourier coefficients are obtained for a plurality of frequencies of interest, and if the amplitude ratio is obtained, the equation (8) is similarly used. Complex conductivity can be determined.
Examples thereof are shown in FIGS. 4 and 5. In these cases, since the Fourier coefficient is calculated as described above,
As a matter of course, a calculation means for that is required, and the calculation means shown in FIGS.
In the figure, a configuration in which these means are incorporated (calculation means 20
~ 23). Further, in the example shown in FIG. 4, the current value to be applied and the specific value of the angular velocity are set as known values in advance, but the example shown in FIG. 5 is also applied to the current signal to be applied. It is configured to obtain the Fourier coefficient.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, even when a square wave input current is applied,
It goes without saying that a signal setting system similar to the case of using an arbitrary waveform for the angular velocity and the current value may be adopted.

〔The invention's effect〕

As is clear from the above description, according to the present invention, since the point electrode is used, the edge effect due to the shape of the electrode does not appear. The change in the electrical conductivity of the DUT is not hindered by the shape of the electrode. By changing the arrangement of the electrodes, it is possible to obtain the effect that the measurement range of the object to be measured can be arbitrarily set.

In addition, because the measurement method that focuses on multiple sinusoidal signals is used, there is no need to measure the phase difference (loss angle) between the applied current and the measured voltage. V
It is possible to obtain the effect that a direct-reading type AC meter of RMS value indication or average value indication can be used for measurement of.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement example of a point electrode system for explaining a method for measuring a complex conductivity according to the present invention, and FIG. 2 is a current signal and a potential signal when the potential signal is matched with a real axis. FIG. 3 is a diagram showing a phase relationship with FIG. 3, FIG. 3 is a diagram showing a configuration of one embodiment of a complex conductivity measuring device according to the present invention, and FIG. 4 is a diagram showing the present invention applied when a square wave signal is applied. FIG. 5 is a diagram showing the configuration of another embodiment, FIG. 5 is a diagram showing the configuration of another embodiment of the present invention applied when an arbitrary waveform signal is applied, and FIG. 6 is a conventional example of a complex conductivity measuring device. FIG. 1 to 4 ... Point electrodes, 11 ... Current signal generation source, 12 ...
... Changeover switch, 13 ... Object to be measured, 14 ...
Measuring unit, 15 and 19 ... Calculation unit, 16 ... Current value deriving unit, 17 ... Angular velocity deriving unit, 18 ... Coefficient setting unit.

Claims (6)

[Claims] 1. A method of measuring complex conductivity in which a plurality of point electrodes are arranged in an object to be measured and a current signal is applied to the complex conductivity, wherein a plurality of electrodes are provided on one side of an electrode system. A sinusoidal signal is applied, the potential difference of the other is measured, and it is assumed that it will spread infinitely from the ratio of the current value of the applied signal to the voltage value of the measured signal, the angular velocity of the applied signal, and the coefficient determined by the arrangement of the point electrodes. A method of measuring complex conductivity, comprising calculating the complex conductivity of an object to be measured. 2. The method for measuring complex conductivity according to claim 1, wherein a plurality of sinusoidal signals are simultaneously applied by the rectangular wave signal, and the Fourier coefficient is obtained for signal processing. 3. The method for measuring complex conductivity according to claim 1, wherein a plurality of sinusoidal signals are simultaneously applied by arbitrary signal waveform signals, and Fourier coefficients are obtained to perform signal processing. 4. A complex conductivity measuring device for measuring a complex conductivity by arranging a plurality of point electrodes in an object to be measured and applying a current signal, wherein the point signal to which a current signal is applied. Electrodes, point electrodes for measuring the potential difference, means for deriving the current value and angular velocity of the applied signal, means for deriving the voltage value of the measured signal, means for setting a coefficient determined by the arrangement of the point electrodes, and current for the applied signal An apparatus for measuring a complex conductivity, comprising a calculating means for obtaining a ratio between a value and a voltage value of a measurement signal, and calculating a conductivity and a dielectric constant from the ratio, the angular velocity and the coefficient. 5. The method according to claim 4, wherein the means for deriving the current value and the angular velocity of the applied signal derives the current value and the angular velocity by obtaining a Fourier coefficient from the current waveform of the applied signal. Complex conductivity measuring device. 6. The means for deriving the voltage value of the measurement signal derives the voltage value by obtaining a Fourier coefficient from the voltage waveform of the measurement signal.
Item 7. A device for measuring complex conductivity according to the item.