JP2013083606A - Dielectric constant sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply find out a dielectric constant of a target.SOLUTION: A dielectric constant sensor includes: an application electrode 10 for applying AC voltage to the target; a first electrode 12 directly contacting with the target to detect a first current generated by the AC voltage; a second electrode 14 contacting with the target through an insulator to detect a second current generated by the AC voltage; and a calculation part 36 for calculating a dielectric constant of the target on the basis of a first signal corresponding to the first current and a second signal corresponding to the second current.

Description

  The present invention relates to a dielectric constant sensor, for example, a dielectric constant sensor that measures a dielectric constant using an electrode in contact with an object and an electrode in contact with the object through an insulator.

  For example, a sensor that measures the moisture content of soil by measuring the relative permittivity of soil by using the fact that the relative permittivity of water is very large is used. The relationship between the moisture content of the soil and the relative permittivity is almost proportional, but even if it is slightly out of proportion, the soil moisture content can be measured from the relative permittivity by performing calibration in advance. . Thus, a sensor that simply measures the relative permittivity is known. A soil solution conductivity measuring device that measures the electrical conductivity of soil with improved measurement accuracy is known (for example, Patent Document 1).

JP 2001-215203 A

  For example, when the dielectric constant of an object such as soil is measured, conductivity may be increased due to moisture contained in the object. In such a case, for example, it is difficult to easily measure the capacitance between two electrodes. Therefore, it is difficult to easily obtain the dielectric constant of the object.

  This dielectric constant sensor is intended to easily obtain the dielectric constant of an object.

  For example, an application electrode that applies an AC voltage to the object, a first electrode that is in direct contact with the object and detects a first current generated by the AC voltage, and the object and an insulator are interposed. In contact with the second electrode for detecting a second current generated by the AC voltage, a first signal corresponding to the first current, and a second signal corresponding to the second current. A dielectric constant sensor comprising: a calculation unit that calculates a dielectric constant of an object.

  This dielectric constant sensor is intended to easily obtain the dielectric constant of an object.

FIG. 1 is a schematic diagram of a dielectric constant sensor according to a comparative example. FIG. 2A and FIG. 2B are diagrams showing an equivalent circuit between the application electrode and the first electrode. FIG. 3 is a schematic diagram illustrating the dielectric constant sensor according to the first embodiment. FIG. 4 is a functional block diagram of the main body of the dielectric constant sensor according to the first embodiment. FIG. 5 is a cross-sectional view of the buried portion of the dielectric constant sensor according to the first embodiment. 6A and 6B are block diagrams of the detection circuit. FIG. 7 is a diagram illustrating a correlation between the first signal and the second signal at each relative dielectric constant of the soil. FIG. 8 is a flowchart showing the operation of the calculation unit. FIG. 9 is a diagram illustrating FIG. 7 in detail, and is a diagram illustrating a second signal with respect to the first signal. FIG. 10 is a flowchart illustrating the operation of the calculation unit of the dielectric constant sensor according to the second embodiment. FIG. 11 is a diagram in which a range 50 is provided in FIG. FIG. 12 is a diagram illustrating the correlation between the first signal and the relative permittivity. FIG. 13 is a cross-sectional view of the buried portion of the permittivity sensor according to the third embodiment and a functional block diagram of the main body. FIG. 14 is a flowchart illustrating the operation of the calculation unit of the dielectric constant sensor according to the third embodiment. FIG. 15 is a diagram showing the correlation between the resistivity of the soil and the first signal at each dielectric constant. FIG. 16 is a flowchart illustrating the operation of the calculation unit of the dielectric constant sensor according to the fourth embodiment. FIG. 17A is a cross-sectional view of the buried portion of the fifth embodiment, and FIG. 17B is a cross-sectional view of the buried portion of the first modification of the fifth embodiment. 18A is a cross-sectional view of the buried portion of the second modification of the fifth embodiment, and FIG. 18B is a schematic diagram of the buried portion of the third modified example of the fifth embodiment.

  First, a method for measuring the capacitance of an object (in this example, soil) using two electrodes will be described. FIG. 1 is a schematic diagram of a dielectric constant sensor according to a comparative example. As shown in FIG. 1, the dielectric constant sensor 100 mainly includes an application electrode 10, a first electrode 12, a voltage application circuit 31, and a detection circuit 32. The application electrode 10 and the first electrode 12 are fixed to the support 18 and are in contact with the soil 28. An AC voltage is applied to the application electrode 10 from the voltage application circuit 31 via the cable 20. The current flowing through the first electrode 12 is detected by the detection circuit 32 via the cable 22 and output as a first signal. The impedance and capacitance between the application electrode 10 and the first electrode 12 are Z and C, respectively. At this time, Z = 1 / (2πf · C). Thereby, if the frequency and detection current of an applied voltage and an alternating voltage are calculated | required, the electrostatic capacitance C between the application electrode 10 and the 1st electrode 12 can be measured. Since the capacitance C is proportional to the dielectric constant of the soil 28, the dielectric constant (or relative dielectric constant) of the soil 28 can be measured.

  FIG. 2A and FIG. 2B are diagrams showing an equivalent circuit between the application electrode and the first electrode. As shown in FIG. 2A, a capacitor C and a resistor R are connected in parallel between the application electrode 10 and the first electrode 12. The capacitance C depends on the relative dielectric constant of the soil, and the resistance R depends on the conductivity of the soil 28. Here, for example, when the water content of the soil 28 is large and the resistance R is small, it is difficult to accurately measure the capacitance C. For example, when each of the application electrode 10 and the first electrode 12 is covered with an insulator, a capacitor C ′ may be added in series between the application electrode 10 and the first electrode 12 as shown in FIG. it can. Thereby, the direct current resistance can be increased. However, alternating current flows through the capacitor C ′. For this reason, it is difficult to accurately measure the capacitance C. For example, in both the equivalent circuits of FIG. 2A and FIG. 2B, when the detected current increases, it is difficult to distinguish between the effect of increasing the relative dielectric constant of the soil 28 and the effect of increasing the conductivity. .

  Therefore, the first electrode 12 that is in direct contact with the soil 28 and the second electrode 14 that is in contact with the soil 28 via an insulator are provided. Thereby, a capacitance C ′ is added in series between the second electrode 14 and the soil 28. As described above, both the first current detected at the first electrode 12 and the second current detected at the second electrode 14 increase regardless of whether the relative permittivity of the soil 28 increases or the conductivity increases. To do. However, if one of the first current and the second current has a relatively large effect on conductivity and the other has a relatively small effect on conductivity, the relative permittivity is based on the first current and the second current. It can be calculated. Examples using the above method will be described below.

  Example 1 is an example of a dielectric constant sensor that measures the dielectric constant of soil. FIG. 3 is a schematic diagram illustrating the dielectric constant sensor according to the first embodiment. As shown in FIG. 3, the dielectric constant sensor 102 includes an embedded part 26 and a main body part 30. The buried part 26 is buried in the soil 28. The main body 30 is installed outside the soil 28. The buried portion 26 includes the application electrode 10, the first electrode 12, the second electrode 14, and the support 18. The support 18 is made of, for example, a water-impermeable material, and it is preferable that the support 18 is not submerged. The support 18 is preferably an insulator so that the application electrode 10, the first electrode 12, and the second electrode 14 are not short-circuited. As the support 18, for example, a resin such as acrylic or Duracon can be used. Since the support 18 is installed in the soil 28, the support 18 has a cylindrical shape with a sharp tip. The shape of the support 18 may be other shapes.

  An application electrode 10, a first electrode 12, and a second electrode 14 are provided along the surface of the support 18. The application electrode 10, the first electrode 12, and the second electrode 14 have, for example, a ring shape so as to surround the support 18.

FIG. 4 is a functional block diagram of the main body of the dielectric constant sensor according to the first embodiment. As shown in FIG. 4, the main body 30 includes a voltage application circuit 31, detection circuits 32 and 34, a calculation unit 36, and a memory 38. The voltage application circuit 31 outputs an alternating current to the application electrode 10 via the cable 20 according to an instruction from the calculation unit 36. The AC voltage is, for example, several MHz. The detection circuit 32 detects the first current flowing through the first electrode 12 via the cable 22 and outputs a first signal corresponding to the first current to the calculation unit 36. The detection circuit 34 detects the second current flowing through the second electrode 14 via the cable 24 and outputs a second signal corresponding to the second current to the calculation unit 36. CPU (Central
Processing Unit) functions as the calculation unit 36. The calculation unit 36 calculates the dielectric constant of the soil 28. The memory 38 stores data for the calculation unit 36 to calculate the dielectric constant of the soil 28 and the like.

  FIG. 5 is a cross-sectional view of the buried portion of the dielectric constant sensor according to the first embodiment. As shown in FIG. 5, the application electrode 10 and the second electrode 14 are embedded in a support 18 that is an insulator. That is, the application electrode 10 and the second electrode 14 are in contact with the soil 28 via an insulator. The first electrode 12 is exposed to the soil 28 and is in direct contact with the soil 28. The application electrode 10 applies an alternating voltage to the soil 28. The first electrode 12 detects a first current generated by an AC voltage. The second electrode 14 detects a second current generated by the AC voltage. The voltage application circuit 31 and the detection circuits 32 and 34 are the same as those in FIG. The second electrode 14 is embedded in the support 18 and is in contact with the soil 28 through an insulator that forms the support 18. The second electrode 14 may be in contact with the soil 28 via an insulator having non-permeability different from that of the support 18.

  6A and 6B are block diagrams of the detection circuit. As shown in FIG. 6A, the detection circuit 32 includes a current-voltage conversion circuit 41 and a rectification and integration circuit 46. The current-voltage conversion circuit 41 converts the alternating first current flowing from the first electrode 12 into a voltage. The current-voltage conversion circuit 41 includes an operational amplifier 42 and a resistor R2. The first electrode 12 is electrically connected to the negative input of the operational amplifier 42, and the positive input is grounded. A feedback resistor R2 is connected between the output of the operational amplifier 42 and the negative input. The rectification and integration circuit 46 outputs the amplitude of the AC voltage signal converted by the current-voltage conversion circuit 41 as the first signal. As shown in FIG. 6B, the detection circuit 34 includes a current-voltage conversion circuit 43 and a rectification and integration circuit 48. The current-voltage conversion circuit 43 includes an operational amplifier 44 and a resistor R4. The configuration and function of each member are the same as those of the detection circuit 32 in FIG.

  FIG. 7 is a diagram illustrating a correlation between the first signal and the second signal at each relative dielectric constant of the soil. As shown in FIG. 7, when the relative permittivity k of the soil 28 is 3, 10, 20, 30 and 40, the relationship between the first signal and the second signal when the resistivity of the soil 28 is changed is a finite element. It is the result calculated using the method. Each point is a calculated point and a straight line connecting the points is a linear interpolation line. The correlation diagram between the first signal and the second signal as shown in FIG. 7 can be obtained using measurement or simulation. The relationship between the first signal and the second signal is stored in the memory 38, for example.

  FIG. 8 is a flowchart showing the operation of the calculation unit. As shown in FIG. 8, the calculation part 36 acquires a 1st signal and a 2nd signal from the detection circuits 32 and 34, respectively (step S10). Next, the calculation unit 36 calculates the relative dielectric constant k of the soil 28 based on the first signal and the second signal (step S16). For example, the calculation unit 36 acquires the data in FIG. 6 from the memory 38 and calculates the relative dielectric constant k. Next, the calculation unit 36 outputs the relative dielectric constant k (step S18). For example, the calculation unit 36 outputs the relative permittivity k of the soil 28 to the moisture calculation unit, so that the moisture calculation unit can calculate the moisture content of the soil.

An example of the relative dielectric constant calculation method in step S16 will be described. FIG. 9 is a diagram illustrating FIG. 7 in detail, and is a diagram illustrating a second signal with respect to the first signal. Measuring point _P i when the relative dielectric constant k is _{k i, m, P i,} m + 1, the measurement points _P i + 1 when the relative dielectric constant k _{k i + 1, m, P} i + 1, m + 1 and the relative dielectric constant k is k _{i +} measuring point when the _{2 P} i + _{2, m,} is _{P i + 2, m + 1} are indicated by dots. The line connecting the points is a linear interpolation line. The measurement point may be a calculation point. Consider a case where the first signal detected by the detection circuit 32 is S1 and the second signal detected by the detection circuit 34 is S2. A Y-axis value Y ′ _i corresponding to the first signal S1 is obtained from an interpolation line between points P _{i, m} and P _{i, m + 1} that sandwich the first signal S1 on the X-axis. Similarly, a Y-axis value Y ′ _{i + 1} corresponding to the first signal S1 is obtained from an interpolation line between points P _{i + 1, m} and P _{i + 1, m + 1} that sandwich the first signal S1 on the X-axis. The dielectric constant k _{is, k = [(Y'i +} 1 -S2) × k i - (Y'i -S2) × k i + 1] / can be obtained from _{(Y'i + 1 -Y' i)} . As described above, the relative permittivity can be obtained by linear interpolation from the measurement point (or calculation point). The relative dielectric constant may be obtained by another interpolation method such as subline interpolation.

  According to the first embodiment, the calculation unit 36 calculates the relative dielectric constant of the soil 28 based on the first signal corresponding to the first current and the second signal corresponding to the second current. As shown in FIG. 6, the first signal from the first electrode 12 that is in direct contact with the soil 28 and the second signal from the second electrode 14 that is in contact with the soil through the insulator are the relative dielectric constants of the soil 28. A different relationship. Thereby, the dielectric constant k can be calculated based on the first signal and the second signal. Therefore, even if the resistivity of the soil 28 is low, the relative permittivity can be measured more accurately. According to the first embodiment, a signal obtained by converting the first current into a voltage is used as the first signal, and a signal obtained by converting the second current into a voltage is used as the second signal, but the first signal and the second signal are These may be signals corresponding to the amplitudes of the first current and the second current, respectively.

  Referring to FIG. 6, the difference between the relative dielectric constants is small in the range where the first signal and the second signal are small. Therefore, the relative permittivity obtained from FIG. 6 has low accuracy. On the other hand, the range in which the first signal and the second signal are small is the range in which the resistance value of the soil 28 is large. This is a measurable range. Example 2 is an example in which this is applied.

  FIG. 10 is a flowchart illustrating the operation of the calculation unit of the dielectric constant sensor according to the second embodiment. FIG. 11 is a diagram in which a range 50 is provided in FIG. FIG. 12 is a diagram illustrating the correlation between the first signal and the relative permittivity.

  Referring to FIG. 10, the calculation unit 36 acquires the first signal and the second signal (step S10). Next, the calculation unit 36 determines whether the range of the first signal and the second signal is a predetermined range (step S12). For example, in FIG. 11, when the range of the first signal and the second signal is the range 50, it is determined as Yes. In the case of Yes, the calculation unit 36 calculates the relative dielectric constant k based on the first signal (step S14). For example, using FIG. 12, the relative dielectric constant k is calculated from the first signal. In the case of No in step S12, the relative dielectric constant k is calculated based on the first signal and the second signal, as in step S16 of FIG. Next, the calculation unit 36 outputs the relative dielectric constant k (step S18). Then exit. Note that step S10 is performed in the case of No in step S12, and in the case of Yes in step S12, the calculation unit 36 may acquire only the first signal out of the first signal and the second signal.

  According to the second embodiment, the calculation unit 36 uses the second signal as in step S14 when the first signal and the second signal are within a predetermined range (Yes in step S12 in FIG. 10). First, the relative dielectric constant is calculated based on the first signal. On the other hand, when the first signal and the second signal are outside the predetermined range (No in step S12 in FIG. 10), the relative dielectric constant is calculated based on the first signal and the second signal as in step S16. As a result, when the relative permittivity can be calculated accurately with the first signal without using the second signal, the relative permittivity can be calculated with the first signal. In addition, when the relative permittivity can be calculated with high accuracy using the first signal and the second signal, the relative permittivity can be calculated with the first signal and the second signal. Therefore, the relative dielectric constant can be calculated with higher accuracy. The predetermined range is preferably a range where the resistance value of the soil 28 is high. For example, it is preferable that the first signal is smaller than the predetermined value and the second signal is smaller than the predetermined value. Further, instead of FIG. 12, the relative permittivity can be calculated using the correlation between the second signal and the relative permittivity. Therefore, in step S14, the relative permittivity may be calculated based on the other of the first signal and the second signal without using any one of the first signal and the second signal.

  Example 3 is an example in which the resistance value of the soil 28 is measured, and the calculation method of the relative permittivity is selected based on the magnitude of the resistance value. FIG. 13 is a cross-sectional view of the buried portion of the permittivity sensor according to the third embodiment and a functional block diagram of the main body. As shown in FIG. 13, in the third embodiment, the buried portion 26 includes a resistance electrode 19 that is in direct contact with the soil 28 as compared to FIG. 5 of the first embodiment. The resistance electrode 19 applies a direct current or a low-frequency voltage to the soil 28. Compared with FIG. 4 of the first embodiment, the main body 30 includes a resistance measurement power source 37, a resistance measurement circuit 33, and a switch 35. The resistance measurement power source 37 supplies a DC voltage or a low-frequency voltage to the resistance electrode 19. Here, the low frequency voltage may be a voltage having a frequency sufficiently lower than the AC voltage applied by the application electrode 10. When the first electrode 12 detects the first current, the switch 35 electrically connects the first electrode 12 to the detection circuit 32. When the first electrode 12 detects the resistance value of the soil 28, the switch 35 electrically connects the first electrode 12 to the resistance measurement circuit 33. The resistance measurement circuit 33 measures the resistance value of the soil 28 between the resistance electrode 19 and the first electrode 12 by a direct current or a low frequency current flowing from the first electrode 12. Other configurations are the same as those of the first embodiment, and the description thereof is omitted.

  FIG. 14 is a flowchart illustrating the operation of the calculation unit of the dielectric constant sensor according to the third embodiment. Referring to FIG. 14, the calculation unit 36 acquires the resistance value of the soil 28 from the resistance measurement circuit 33 (step S20). For example, the resistance electrode 19 applies a DC voltage to the soil 28. A switch 35 connects the first electrode 12 to the resistance measurement circuit 39. The resistance measurement circuit 39 calculates the resistance value of the soil 28 from the current flowing through the first electrode 12 and outputs it to the calculation unit 36. Next, the calculation unit 36 acquires the first signal and the second signal (step S10). Next, the calculation unit 36 determines whether the resistance value of the soil 28 is greater than or equal to the threshold resistance value Rth (step S22). In the case of Yes, the calculation unit 36 calculates the relative dielectric constant k based on the first signal using FIG. 12 (step S14). In the case of No in step S12, the relative dielectric constant k is calculated based on the first signal and the second signal, as in step S16 of FIG. Next, the calculation unit 36 outputs the relative dielectric constant k (step S18). Then exit.

  According to the third embodiment, when the resistance value of the soil 28 is equal to or greater than the threshold value (in the case of Yes in step S22 in FIG. 14), the calculation unit 36 does not use the second signal as in step S14, Based on this, the relative dielectric constant is calculated. On the other hand, when the resistance value is smaller than the threshold value (in the case of No in step S22), the calculation unit 36 calculates the relative dielectric constant based on the first signal and the second signal as in step S16. Thereby, when the resistance value of the soil 28 is high and the relative permittivity can be calculated accurately with the first signal without using the second signal, the relative permittivity is calculated with the first signal. On the other hand, when the resistance value of the soil 28 is low and the relative permittivity can be calculated with high accuracy using the first signal and the second signal, the relative permittivity can be calculated with the first signal and the second signal. Therefore, the relative dielectric constant can be calculated with higher accuracy. In Example 3, the resistance electrode 19 and the first electrode 12 were used as the third electrode for measuring the resistance value of the soil 28, but a dedicated electrode for measuring the resistance instead of the first electrode 12. May be used. In step S14, the relative permittivity may be calculated based on the other of the first signal and the second signal without using one of the first signal and the second signal.

  When the resistivity of the soil 28 is very large, the relative dielectric constant of the soil can be accurately obtained from the first signal as shown in FIG. However, if the resistivity of the soil 28 is not sufficiently high, the relative permittivity cannot be obtained with high accuracy using FIG. 12, and the correlation diagram between the first signal and the second signal in FIG. However, there are cases where the relative dielectric constant cannot be obtained with high accuracy. In Example 4, when the resistance value of the soil 28 is equal to or greater than a predetermined value, the relative permittivity of the soil 28 is obtained from the correlation between the resistivity of the soil 28 and the first signal.

  FIG. 15 is a diagram showing the correlation between the resistivity of the soil and the first signal at each dielectric constant. The resistivity is an arbitrary unit. As shown in FIG. 15, in the region where the resistivity is large, the first signal is constant with respect to the resistivity at any relative dielectric constant. In this case, the relative dielectric constant can be accurately calculated from the first signal using FIG. On the other hand, when the resistivity decreases, the first signal changes with respect to the resistivity. In this region, the relative permittivity cannot be accurately calculated from the first signal by using FIG. For example, in the example of FIG. 15, if the resistivity is 600 or less, the relative permittivity cannot be calculated from the first signal with high accuracy. On the other hand, in the range where the resistivity is 200 or more, the relative permittivity can be accurately calculated based on the resistivity and the first signal in FIG.

  FIG. 16 is a flowchart illustrating the operation of the calculation unit of the dielectric constant sensor according to the fourth embodiment. The configuration of the dielectric constant sensor is the same as that of the third embodiment, and the description is omitted. As shown in FIG. 16, compared with FIG. 14 of Example 3, in the case of Yes in step S22, a relative dielectric constant is calculated based on the resistance value of the soil 28 and the first signal (step S24). For example, the relative dielectric constant is calculated from the relationship between the resistivity and the first signal in FIG. Since the resistivity can be calculated from the resistance value, the horizontal axis in FIG. 15 may be the resistance value. Further, the determination based on the resistance value in step S22 may be determined based on the resistivity.

  According to the fourth embodiment, when the resistance value is equal to or greater than the threshold, the calculation unit 36 calculates the relative permittivity based on the first signal and the resistance value without using the second signal as in step S24 of FIG. To do. On the other hand, when the resistance value is smaller than the threshold, the calculation unit 36 calculates the relative dielectric constant based on the first signal and the second signal as in step S16. Thereby, when the resistivity of the soil 28 is high as described above, the relative dielectric constant can be calculated with higher accuracy than when the relative dielectric constant is calculated from the first signal as in the third embodiment. Note that the relative dielectric constant can also be calculated using the correlation between the second signal and the resistivity instead of FIG. Therefore, in step S24, either the first signal or the second signal is not used, and the dielectric constant may be calculated based on the other of the first signal and the second signal and the resistance value.

  Example 5 is an example in which the arrangement of each electrode is changed. FIG. 17A is a cross-sectional view of the buried portion of the fifth embodiment. In FIG. 5 of the first embodiment, the application electrode 10, the first electrode 12, and the second electrode 14 are arranged on the support 18 in order from the top. Referring to FIG. 17A, as in the fifth embodiment, the application electrode 10, the second electrode 14, and the first electrode 12 may be arranged on the support 18 in order from the top. FIG. 17B is a cross-sectional view of the buried portion of the first modification of the fifth embodiment. Referring to FIG. 17B, as in Modification 1 of Example 5, the second electrode 14, the application electrode 10, and the first electrode 12 may be arranged on the support 18 in order from the top. Thus, the arrangement of each electrode can be changed as appropriate.

  FIG. 18A is a cross-sectional view of the buried portion of the second modification of the fifth embodiment. In FIG. 5 of the first embodiment, the application electrode 10 is embedded in the support 18. With reference to Fig.18 (a), like the modification 2 of Example 5, the application electrode 10 may be exposed to the soil 28 and may be in contact with the soil directly. FIG. 18B is a schematic diagram of the buried portion of the third modification of the fifth embodiment. In FIG. 3 of the first embodiment, the application electrode 10, the first electrode 12, and the second electrode 14 are provided on a cylindrical support 18 and have a ring shape. Referring to FIG. 18B, as in Modification 3 of Example 5, the application electrode 10, the first electrode 12, and the second electrode 14 may be flat. Thus, the shape of each electrode can be changed as appropriate.

  In the first to fifth embodiments, the soil is described as an example of the target object. However, the target object may be other than the soil. Moreover, although the relative dielectric constant has been described as an example of the dielectric constant to be measured, the dielectric constant may be calculated. Moreover, if the resistance value of the soil 28 between electrodes (for example, between the resistance electrode 19 and the first electrode 12) can be detected using the third electrode, the resistivity of the soil 28 can be calculated, and the conductivity of the soil 28 is also calculated. it can. Therefore, the determination based on the resistance value and the calculation based on the resistance value are substantially the same as the determination and calculation based on the resistivity and the determination and calculation based on the conductivity.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

The following additional remarks are disclosed regarding the embodiment including Examples 1 to 5.
Appendix 1:
An application electrode for applying an AC voltage to the object, a first electrode for directly contacting the object and detecting a first current generated by the AC voltage, and an object for contact with the object through an insulator; Based on the second electrode for detecting the second current generated by the AC voltage, the first signal corresponding to the first current, and the second signal corresponding to the second current, A dielectric constant sensor comprising: a calculation unit that calculates a dielectric constant.
Appendix 2:
When the first signal and the second signal are within a predetermined range, the calculation unit does not use either the first signal or the second signal, and the first signal and the second signal The dielectric constant is calculated based on the other, and when the first signal and the second signal are outside the predetermined range, the dielectric constant is calculated based on the first signal and the second signal. The dielectric constant sensor according to appendix 1.
Appendix 3:
A third electrode for measuring a resistance value of the object; and the calculation unit does not use one of the first signal and the second signal when the resistance value is greater than or equal to a threshold value. The dielectric constant is calculated based on the other of one signal and the second signal, and the dielectric constant is calculated based on the first signal and the second signal when the resistance value is smaller than a threshold value. The dielectric constant sensor according to appendix 1.
Appendix 4:
A third electrode for measuring a resistance value of the object; and the calculation unit does not use one of the first signal and the second signal when the resistance value is greater than or equal to a threshold value. The dielectric constant is calculated based on the other of one signal and the second signal and the resistance value. When the resistance value is smaller than a threshold value, the dielectric constant is calculated based on the first signal and the second signal. The dielectric constant sensor according to supplementary note 1, wherein:
Appendix 5:
5. The dielectric constant sensor according to any one of appendices 1 to 4, wherein the object is soil.
Appendix 6:
The dielectric constant sensor according to any one of appendices 1 to 5, wherein the application electrode is in contact with the object through the insulator.
Appendix 7:
The dielectric constant sensor according to any one of appendices 1 to 5, wherein the application electrode is in direct contact with the object.

DESCRIPTION OF SYMBOLS 10 Application electrode 12 1st electrode 14 2nd electrode 18 Support body 19 Electrode for resistance 26 Buried part 28 Soil 30 Main-body part 36 Calculation part

Claims (5)

An application electrode for applying an AC voltage to the object;
A first electrode that is in direct contact with the object and detects a first current generated by the AC voltage;
A second electrode that is in contact with the object through an insulator and detects a second current generated by the AC voltage;
A calculation unit that calculates a dielectric constant of the object based on a first signal corresponding to the first current and a second signal corresponding to the second current;
A dielectric constant sensor comprising:   When the first signal and the second signal are within a predetermined range, the calculation unit does not use either the first signal or the second signal, and the first signal and the second signal The dielectric constant is calculated based on the other, and when the first signal and the second signal are outside the predetermined range, the dielectric constant is calculated based on the first signal and the second signal. The dielectric constant sensor according to claim 1. Comprising a third electrode for measuring a resistance value of the object;
The calculation unit calculates the dielectric constant based on the other of the first signal and the second signal without using one of the first signal and the second signal when the resistance value is equal to or greater than a threshold value. The dielectric constant sensor according to claim 1, wherein when the resistance value is smaller than a threshold value, the dielectric constant is calculated based on the first signal and the second signal. Comprising a third electrode for measuring a resistance value of the object;
When the resistance value is greater than or equal to a threshold value, the calculation unit does not use one of the first signal and the second signal, and based on the other of the first signal and the second signal and the resistance value. The dielectric constant sensor according to claim 1, wherein a dielectric constant is calculated, and when the resistance value is smaller than a threshold value, the dielectric constant is calculated based on the first signal and the second signal.   The dielectric constant sensor according to claim 1, wherein the object is soil.

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