Soil physical property measuring method

Abstract

To stably measure various physical property values of soil.SOLUTION: A measuring method of physical property values of soil in the ground, includes: a step of inserting a measurement probe 10 into each of water and air, the reference objects with known dielectric constants, applying a frequency signal, calculating two reference values from respective reflection signals, and storing the reference values in a memory; an entry step of inserting the measurement probe 10 into the ground, an actual measurement step of applying the frequency signal to the probe 10 in the ground and detecting a reflection signal from the probe 10; and a calculation step of calculating a relative dielectric constant and an electrical conductivity of the soil on the basis of the reflection signal detected in the actual measurement step and the two reference values.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for measuring physical properties of soil using a probe.

Background Art

[0002] In order to obtain the physical properties of an object, electricity (electric power) or an electrical signal is applied to the object, and its response (the level of current flow, or the reflection / transmission of the electrical signal) is measured. For example, if direct current electricity (electric power) is applied to an object and the current value (resistance) is measured, the electrical conductivity of the object can be obtained. Also, for example, by applying an electrical signal such as a frequency signal or a pulse signal to an object and measuring its reflection characteristics and / or transmission characteristics, the relative permittivity, electrical conductivity, etc. of the object can be obtained. As a type of device for measuring the electrical response characteristics of such an object, a network analyzer is used. Types of network analyzers include scalar network analyzers and vector network analyzers. A scalar network analyzer mainly measures the amplitude of a frequency signal. A vector network analyzer measures both the amplitude and the phase of a frequency signal.

[0003] When measuring an object using a network analyzer, generally, a transmitting-side contact (probe) that injects a frequency signal generated by the network analyzer into the object and a receiving-side contact (probe) that receives the transmitted signal (transmission response) after the frequency signal has passed through (transmitted through) the object and delivers it to the network analyzer are arranged on the object to construct a circuit network for measurement. In addition, when measurement of the characteristics of the transmitted signal is not required, an open-end type circuit network with the receiving-side probe omitted may be used, and the reflection signal (reflection response) of the transmitting-side contact (probe) may be measured.

[0004] Information on transmission characteristics and / or reflection characteristics measured by a network analyzer is referred to as S-parameters. S-parameters mainly include transmission characteristics and reflection characteristics. When the management symbol of the transmitting-side contact (probe) is "1" and the management symbol of the receiving-side contact (probe) is "2", the reflection characteristic (S11) means the signal characteristic in which the frequency signal applied from the transmitting-side contact (probe) to the object is reflected back to the transmitting-side contact (probe), and the transmission characteristic (S21) means the signal characteristic in which the frequency signal applied from the transmitting-side contact (probe) to the object is transmitted to the receiving-side contact (probe). In the case of a vector network analyzer, each measured value is a complex quantity of a real number and an imaginary number, and the amplitude and phase are calculated from the complex quantity.

[0005] When using a network analyzer, it becomes possible to calculate physical property values such as those of soil (see Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to measure the relative permittivity and electrical conductivity of soil using a probe for measurement.

Means for Solving the Problems

[0008] The present invention related to the above object is a method for measuring physical property values of soil in the ground, comprising the steps of: inserting a probe for measurement into each of water and air, which are reference objects with known dielectric constants, applying a radio frequency signal, calculating two reference values from each reflection signal, and storing them in a memory; an entering step of entering the probe for measurement into the ground; an actual measurement step of applying a radio frequency signal to the probe in the ground and detecting a reflection signal from the probe; and a calculation step of calculating the relative dielectric constant and electrical conductivity of the soil based on the reflection signal detected in the actual measurement step and the two reference values.

[0009] In relation to the above soil physical property value measurement method, in the actual measurement step, it may be characterized in that the radio frequency signal of a specific frequency selected from a plurality of frequencies is applied.

[0010] In relation to the above soil physical property value measurement method, it may be characterized in that a response detection device for applying electricity to the probe and detecting the reflection signal of the soil is positioned in the ground.

[0011] In relation to the above soil physical property value measurement method, the probe may include a first electrode surface in contact with the soil, a second electrode surface in contact with the soil, an isolation surface that isolates the first electrode surface and the second electrode surface with an insulator, a first wiring electrically connected to the first electrode surface, and a second wiring electrically connected to the second electrode surface.

[0012] In relation to the above soil physical property value measurement method, the frequency of the radio frequency signal applied to the probe in the actual measurement step may be from 30 MHz to 0.3 GHz or 0.3 GHz or higher.

Effects of the Invention

[0013] According to the present invention, it is possible to achieve an excellent effect of being able to measure the relative dielectric constant and electrical conductivity of soil.

Brief Description of the Drawings

[0014]

Figure 1

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Figure 19

Embodiments for Carrying Out the Invention

[0015] The physical property measuring device according to the embodiment of the present invention will be described below with reference to the drawings. Here, the case of measuring soil as an object is exemplified, but the object is not limited to soil.

[0016] FIG. 1 shows an overall view of the physical property measuring device 1 according to the embodiment. The physical property measuring device 1 also serves as a digital soil hardness meter. This physical property measuring device 1 includes a conical probe 10 that is penetrated from the tip into the ground, a shaft portion 300 that is continuous with the rear of the conical probe 10, a stress detection device 400 that is disposed at the rear end of the shaft portion 300 and detects the stress (penetration reaction force) that the conical probe 10 receives from the soil, an operation handle 500 that is disposed on the stress detection device 400 side, and a control device 600 that is disposed near the operation handle 500. A weight 310 is disposed on the shaft portion 300. The stress detection device 400 is, for example, a load cell, detects the reaction force transmitted from the conical probe 10 to the shaft portion 300, converts the reaction force data into digital values, and transmits it to the control device 600 via the communication line 480.

[0017] Inside the shaft portion 300, a signal detection device 200 electrically connected to the conical probe 10 is accommodated. The signal detection device 200 is connected to the control device 600 by a communication line 280 and a power supply line 282. The signal detection device 200 is a kind of response detection device that detects various response characteristics (such as electrical resistance value, signal reflection response, signal transmission response, etc.) of direct current electricity (power) or alternating current electricity (power) applied to the soil via the conical probe 10. The signal detection device 200 of the present embodiment acquires a signal (reflection signal) regarding the response characteristics (here, reflection characteristics) of the electrical signal applied to the soil via the conical probe 10 based on the measurement instruction signal transmitted from the control device 600 via the communication line 280, and further digitally converts the reflection signal and transmits it to the control device 600. Note that the signal detection device 200 may perform various calculations such as S parameters when converting to a digital signal.

[0018] Details will be described later, but the control device 600 has a built-in height sensor capable of detecting displacement in the height direction, and can measure the penetration depth of the conical probe 10 from the ground surface U. This height sensor may be provided on the conical probe 10, the signal detection device 200, etc.

[0019] The user grips the operation handle 500, positions the physical property measurement device 1 so that the shaft portion 300 and the conical probe 10 are perpendicular (or vertical) to the ground surface U, and penetrates the conical probe 10 into the ground from its tip. The stress detection device 400 is a so-called load cell, and detects the reaction force from the soil acting on the conical probe 10 via the shaft portion 300 in conjunction with the penetration depth. At the same time, the signal detection device 200 acquires the reflection signal (S parameter) of the soil using the conical probe 10 in conjunction with the penetration depth. As a result, the depth information from the ground surface U in the soil, the reaction force information from the soil, and the S parameter of the soil can be measured in a linked state.

[0020] Note that although the stress detection device 400 has been exemplified in the case of a load cell, for example, as shown in FIG. 11, a structure that detects the reaction force by using the amount of expansion and contraction of the spring 402 can also be adopted. In that case, a displacement sensor 404 capable of measuring the amount of expansion and contraction of the spring 402 may be used to transmit the displacement amount or the stress conversion value based on the displacement amount to the control device 600 via the communication line 480. Instead of the displacement sensor 404, the amount of expansion and contraction of the spring may be judged visually or the like.

[0021] Furthermore, in addition to the purpose of calculating the soil hardness, the stress detection device 400 also has a function of measuring the contact pressure between the first electrode surface 33 and the second electrode surface 53 of the conical probe 10 described later and the measurement object (soil). When the contact pressure is lower than a predetermined threshold value, the measurement error can be reduced by interrupting the measurement of the reflection signal (S parameter) or excluding the data.

[0022] FIG. 2 and FIG. 3 show an enlarged view of the conical probe 10 and the signal detection device 200.

[0023] The conical probe 10 includes a base 70, a cone 20 provided on the base 70 and having the shape of a headed cone (a cone having a vertex), and a connector portion 80. This cone 20 also serves as a penetration cone for measuring soil hardness. Although various shapes of the cone 20 can be selected, in the present embodiment, it is adapted to the penetration type soil hardness meter method in the soil environmental analysis method supervised by the Japanese Society of Soil Science and Plant Nutrition and is made to match the penetration cone of the SR-II type soil resistance measuring device. That is, the tip angle is 30 degrees, and the area of the circular bottom surface is 2 cm 2It is set to [[VALUE]] and the diameter of the shaft portion 300 is set to 12 mm. Also, for example, when adapting to a mountain-type hardness tester, the tip angle of the cone 20 is 12 degrees and 40 minutes, and the diameter of the bottom surface of the regular circle is 18 mm. Further, when adapting to the portable cone penetration test, which is the ground investigation method of the Japan Geotechnical Society, the tip angle of the cone 20 is set to 30 degrees, the diameter of the bottom surface of the regular circle is 28.6 mm, and the diameter of the shaft portion 300 is set to 16 mm. Also, when adapting to the Swedish sounding test in the simple dynamic cone penetration test, for example, the tip angle of the cone 20 is 60 degrees, the diameter of the bottom surface of the regular circle is 25 mm, and the diameter of the shaft portion 300 is 16 mm. Furthermore, when adapting to the electric cone penetration test, the tip angle of the cone 20 is 60 degrees, the diameter of the bottom surface of the regular circle is 35.3 mm to 36.0 mm, and the diameter of the shaft portion 300 is 35.3 mm to 36.0 mm. When adapting to the soil rod penetration test of the National Institute of Technology and Evaluation, for example, the tip angle of the cone 20 is 60 degrees, the diameter of the bottom surface of the regular circle is 15 mm, and the diameter of the shaft portion 300 is 10 mm. That is, the tip angle of the cone 20 is preferably set in the range of 10 degrees or more and 70 degrees or less. Also, the diameter of the shaft portion 300 is desirably 10 mm or more and desirably 40 mm or less. Also, the length of the shaft portion 300 is desirably 15 cm and more preferably 30 cm or more. In the present embodiment, the case where the cone 20 has a headed cone shape (cone shape having a vertex) is exemplified, but the present invention is not limited to this, and a truncated cone shape (frustum shape having no vertex) may be used. Also, it is not limited to a cone, and a pyramid shape such as a triangular pyramid or a quadrangular pyramid may be used.

[0024] As shown in FIGS. 3 and 4, as components constituting the cone 20, it has a first electrode body 30, an insulator 40, and a second electrode body 50. That is, when the cone 20 is an overall cone, the first electrode body 30, the insulator 40, and the second electrode body 50 are partial cones constituting a part of the overall cone. Hereinafter, when explaining the direction and orientation, the tip side in the axial direction of the cone 20 (lower side in the usage mode) may be referred to as the front, and the rear end side in the axial direction (upper side in the usage mode) may be referred to as the rear.

[0025] (First Electrode Body)

[0026] As shown in FIG. 4(A), the first electrode body 30 is made of a conductive metal (e.g., stainless steel) and has a first conical portion 32 and a first shaft portion 36. The first conical portion 32 has a shape of a headed cone (a conical shape having a vertex), and the entire conical surface thereof becomes a first electrode surface 33 that contacts the soil. The surface area of the first electrode surface 33 is set to be the same as that of the second electrode surface 53 described later. The first electrode surface 33 includes an annular region K1 that extends in a circumferential direction in a band shape near the bottom of the cone (see FIG. 3(C)). Here, the case where the first conical portion 32 has a shape of a headed cone is exemplified, but the present invention is not limited thereto, and it may be a frustum cone shape (a cone (trapezoid shape) having no vertex). Further, the shape of the first conical portion 32 is not limited to a cone, and may be a pyramid shape such as a triangular pyramid or a quadrangular pyramid.

[0027] The first shaft portion 36 is a rod-shaped member having a circular cross-section that continuously extends rearward from the first lower bottom surface 34 of the first conical portion 32. The first shaft portion 36 is arranged coaxially with the central axis of the first conical portion 32. The region near the rear end including at least the rear end of the first shaft portion 36 is cylindrical, and the tip of the first wiring T1 (central contact portion 84) of the connector portion 80 is inserted into the internal space 36A thereof and electrically connected (see FIG. 3(B)). Therefore, the first shaft portion 36 serves as a part of the first wiring T1 that guides the radio frequency signal to the first electrode surface 33 (see FIG. 6).

[0028] A male thread 36B is formed around the first shaft portion 36 and is screwed with the female thread 46A of the separator 40. By screwing the male thread 36B of the first shaft portion 36 and the female thread 46A of the separator 40, a front engagement structure J1 is configured in which the separator 40 is axially engaged with the front first electrode body 30 (see FIG. 3(B)). Note that the coupling method of the front engagement structure J1 is not limited to a screw structure, and various coupling structures such as a claw engagement, a step engagement, a pin engagement, and a press-fit engagement (friction engagement) can be adopted.

[0029] The first lower bottom surface 34 of the first conical portion 32 is in contact with the isolation-side upper bottom surface 45 of the isolator 40, and serves to transmit the axial reaction force received by the first electrode surface 33 from the soil to the isolator 40. In order to prevent water from entering through the fine gap between the first lower bottom surface 34 and the isolation-side upper bottom surface 45, it is preferable to interpose or apply a waterproof material (for example, a waterproof insulating adhesive or a sealing material) between them.

[0030] In this embodiment, the first shaft portion 36 is formed on the first electrode body 30, and the first shaft portion 36 is inserted into the isolator 40 to realize the front engagement structure J1. However, the present invention is not limited to this. The isolator 40 may be provided with a front-side shaft portion extending to the front side, and this front-side shaft portion may be inserted into the first electrode body 30 to realize the front engagement structure J1.

[0031] (Second Electrode Body)

[0032] As shown in FIG. 4(C), the second electrode body 50 is made of a conductive metal (for example, stainless steel) and has a second conical portion 52. The second conical portion 52 has a frustum of a cone shape (a truncated cone shape without a vertex), and the entire conical surface thereof serves as the second electrode surface 53 that contacts the soil. The second electrode surface 53 is an annular region K2 that extends in a band shape around the central axis of the second conical portion 52 (see FIG. 3(C)). The axial length (height of the cone) of the second conical portion 52 is set to be smaller than the axial length (height of the cone) of the first conical portion 32. Thereby, the axial distance of the second electrode surface 53 (axial bandwidth W2 of the annular region K2) is smaller than the axial distance of the first electrode surface 33. In this embodiment, the surface area of the second electrode surface 53 is set to be the same as that of the first electrode surface 33. Note that the shape of the second conical portion 52 is not limited to a frustum of a cone, and may be a frustum of a pyramid shape such as a frustum of a triangular pyramid or a frustum of a quadrangular pyramid.

[0033] The second conical portion 52 has a second axial hole 57 that is a hole penetrating in the axial direction. The second axial hole 57 is formed coaxially with the central axis of the second conical portion 52, and both ends thereof open to the second upper bottom surface 55 and the second lower bottom surface 54. A female thread 57A is formed on the inner peripheral surface of the second axial hole 57 and is screwed with a rear male thread 47A of the isolation shaft portion 47 of the isolator 40. By screwing the female thread 57A of the second conical portion 52 and the rear male thread 47A of the isolator 40, a rear engagement structure J2 is configured in which the isolator 40 is axially engaged with the rear second electrode body 50 (see Fig. 3(B)). Note that the coupling method of the rear engagement structure J2 is not limited to the screw structure, and various coupling structures such as claw engagement, step engagement, pin engagement, and press-fit engagement (friction engagement) can be adopted.

[0034] The second axial hole 57 also serves as a place through which the first wiring T1 (central contact portion 84) that guides the radio frequency signal to the first electrode body 30 passes. Specifically, the isolation shaft portion 47 serving as an insulator is interposed between the second axial hole 57 and the first wiring T1, thereby insulating and isolating the two.

[0035] The second upper bottom surface 55 of the second conical portion 52 is in contact with the isolation-side lower bottom surface 44 of the isolator 40 and serves to receive the axial reaction force of the soil transmitted therefrom. In order to prevent water from entering through the fine gap between the second upper bottom surface 55 and the isolation-side lower bottom surface 44, it is preferable to interpose or apply a waterproof material (for example, a waterproof insulating adhesive or a sealing material) between them. The second lower bottom surface 54 of the second conical portion 52 is in contact with the base 70 and serves to transmit the axial reaction force of the soil received by the second upper bottom surface 55 to the base 70. In order to prevent water from entering through the fine gap between the second lower bottom surface 54 and the base 70, it is preferable to interpose or apply a waterproof material (for example, a waterproof insulating adhesive or a sealing material) between them.

[0036] On the second lower bottom surface 54 of the second conical portion 52, connector engaging portions 54A are formed at a plurality of locations (here, four locations) that are equally spaced along the circumferential direction. The connector engaging portions 54A are in a concave shape (recess) and engage with the engaging protrusions 89 formed on the base 82 of the connector portion 80 in the circumferential direction (see Fig. 3(B)). Also, electrical connection is ensured by the contact between the connector engaging portions 54A and the engaging protrusions 89 of the connector portion 80. Furthermore, the second lower bottom surface 54 serves to ensure electrical connection in the same manner by contacting the base 82 of the connector portion 80. Note that the connector engaging portions 54A and / or the base 82 may be fixed to the second lower bottom surface 54 with solder or the like. The base 82 and the engaging protrusions 89 of the connector portion 80 constitute a part of the second wiring T2 (see Fig. 6).

[0037] On the second lower bottom surface 54 of the second conical portion 52, female screw holes 54B are formed at a plurality of locations (here, four locations) that surround the second axial hole 57 at equal intervals in the circumferential direction. With the positions of the female screw holes 54B and the screw holes 78 formed through a plurality of locations of the base 70 aligned, a headed screw 90 is inserted from the rear toward the front and screwed into the female screw holes 54B, thereby connecting the second electrode body 50 and the base 70 in the axial direction and the circumferential direction. That is, the female screw holes 54B, the screw holes 13, and the headed screw 90 constitute a base engaging structure J3 for engaging the base 12 and the second electrode body 50 (see Fig. 3(B)). Note that the coupling method of the base engaging structure J3 is not limited to the screw structure, and various coupling structures such as claw engagement, step engagement, pin engagement, press-fit engagement (friction engagement), etc. can be adopted.

[0038] In this embodiment, the isolation shaft portion 47 of the isolator 40 is inserted into the inner peripheral surface of the second axial hole 57 of the second electrode body 50 to realize the rear engagement structure J2, but the present invention is not limited thereto. The second electrode 50 may be provided with a front-side shaft portion that extends to the front side, and this front-side shaft portion may be inserted into the recess formed in the isolator 40 to realize the rear engagement structure J2.

[0039] (Isolator)

[0040] As shown in Fig. 4(B), the separator 40 is made of an insulating material (such as a resin like plastic such as polyvinyl chloride), and has a separating cone portion 42 and a separating shaft portion 47.

[0041] The separating cone portion 42 has a truncated cone shape (a frustum of a cone shape without a vertex), and the entire conical surface thereof becomes a separating surface 43 that contacts the soil. The separating surface 43 becomes an annular region K3 that extends in a band shape around the central axis of the separating cone portion 42 (see Fig. 3(C)). This separating surface 43 serves to electrically isolate (insulate) the first electrode surface 33 and the second electrode surface 53. The shape of the separating cone portion 42 is not limited to a frustum of a cone, and may be a frustum of a pyramid shape such as a frustum of a triangular pyramid or a frustum of a quadrangular pyramid. The axial distance (axial bandwidth W3) of the separating surface 43 is smaller than the axial distance of the first electrode surface 33. Similarly, the axial distance (axial bandwidth W3) of the separating surface 43 is smaller than the axial distance (axial bandwidth W2) of the second electrode surface 53. The area of the separating surface 43 is smaller than the area of the first electrode surface 33. Similarly, the area of the separating surface 43 is smaller than the area of the second electrode surface 53.

[0042] The isolation shaft portion 47 is a rod-shaped member with a circular cross-section that extends continuously rearward from the isolation-side lower bottom surface 44 of the isolation cone portion 42. The isolation shaft portion 47 is arranged coaxially with the central axis of the isolation cone portion 42. Both the isolation cone portion 42 and the isolation shaft portion 47 are formed with an isolation shaft hole 46 that serves as a common through-hole penetrating the whole in the axial direction, and an internal thread 46A is formed on the inner peripheral surface thereof. The first shaft portion 36 of the first electrode body 30 is inserted into the isolation shaft hole 46, and its male thread 36B is screwed with the female thread 46A. By screwing the male thread 36B of the first shaft portion 36 and the female thread 46A of the isolation body 40, a front engagement structure J1 is formed in which the isolation body 40 is axially engaged with the front first electrode body 30 (see Fig. 3(B)). This isolation shaft hole 46 also serves as a place through which the first wiring T1 (central contact portion 84) that guides the radio frequency signal to the first electrode body 30 passes. Also, since the first wiring T1 (central contact portion 84) is surrounded by the isolation body 40 that serves as an insulating material, it is insulated from the second electrode body 50. Note that the axial length of the first shaft portion 36 of the first electrode body 30 is set to be larger than the axial length (cone height) of the isolation cone portion 42. As a result, the first shaft portion 36 penetrates the isolation cone portion 42 and is inserted into the interior of the isolation shaft portion 47.

[0043] A male thread 47A is formed around the isolation shaft portion 47, and it is inserted into the second shaft hole 57 of the second electrode body 50 and screwed with its female thread 57A. By screwing the male thread 47A of the isolation shaft portion 47 and the female thread 57A of the second electrode body 50, a rear engagement structure J2 is formed in which the isolation body 40 is axially engaged with the rear second electrode body 50 (see Fig. 3(B)). The isolation-side upper bottom surface 45 of the isolation cone portion 42 serves to receive the axial reaction force of the soil transmitted from the first lower bottom surface 34 of the first electrode body 30. The isolation-side lower bottom surface 44 of the isolation cone portion 42 serves to transmit the axial reaction force of the soil received by the isolation-side upper bottom surface 45 to the second electrode body 50.

[0044] (Base)

[0045] As shown in Fig. 5(A), the base 70 is made of an insulating material (such as a resin like plastic such as polyvinyl chloride), and has a reduced-diameter portion 74 and a connecting shaft portion 76.

[0046] The diameter-reducing portion 74 has a frustum-of-a-cone shape (a truncated cone shape without a vertex), and its vertex faces the rear side. The lower bottom surface 75 of the frustum-of-a-cone shape in the diameter-reducing portion 74 covers substantially the entire second lower bottom surface 54 of the second electrode body 50. As a result, the lower bottom surface 75 serves to receive the axial reaction force of the soil transmitted from the second electrode body 50. The upper bottom surface of the frustum-of-a-cone shape in the diameter-reducing portion 74 is directly connected to the connecting shaft portion 76. That is, the diameter-reducing portion 74 covers the second lower bottom surface 54 of the second electrode body 50 and exhibits an insulating function, and at the same time, plays a role of reducing the diameter of the entire base 70 to the connecting shaft portion 76 having a smaller diameter than the second lower bottom surface 54. Here, the diameter is gradually reduced by the frustum-of-a-cone shape, but it may be reduced stepwise by a step formed by a disk shape or the like.

[0047] The connecting shaft portion 76 is a shaft (rod) member having a circular cross-section with a smaller diameter than the second lower bottom surface 54 of the second electrode body 50. The connecting shaft portion 76 is arranged coaxially with the central axis of the diameter-reducing portion 74. A male thread 76A is formed on the outer peripheral surface of the connecting shaft portion 76. As shown in FIG. 3(B), a female thread 310A is formed near the tip of the inner peripheral surface of the cylindrical shaft portion 300. The connecting shaft portion 76 is inserted into the shaft portion 300, so that the female thread 310A and the male thread 76A are screwed together. That is, by screwing the male thread 76A of the connecting shaft portion 76 and the female thread 310A of the shaft portion 300, a shaft engagement structure J4 is configured in which the conical probe 10 is axially engaged with the shaft portion 300. The coupling method of the shaft engagement structure J4 is not limited to the screw structure, and various coupling structures such as claw engagement, step engagement, pin engagement, and press-fit engagement (friction engagement) can be adopted.

[0048] A wiring shaft hole 77, which is a hole penetrating the entire diameter-reducing portion 74 and the connecting shaft portion 76 in the axial direction, is formed. Both the central contact portion 84 and the shell portion 86 of the connector portion 80 are coaxially inserted into the wiring shaft hole 77. Note that the shell portion 86 constitutes a part of the second wiring T2, and the central contact portion 84 constitutes a part of the first wiring T1 (see FIG. 6).

[0049] At the center of the lower bottom surface 75 of the reduced-diameter portion 74, a base accommodation recess 75A is formed. In the present embodiment, the base accommodation recess 75A is a square depression and communicates with the wiring shaft hole 77. The base 82 of the connector portion 80 is accommodated in this base accommodation recess 75A. As a result, the base 82 is axially sandwiched between the base 70 and the second electrode body 50. Note that the depth of the base accommodation recess 75A is set to be the same as or slightly smaller than the thickness of the base 82, so that when the base 70 and the second electrode body 50 are coupled, the base 82 can be pressed toward the second electrode body 50 side.

[0050] In the reduced-diameter portion 74 and the connecting shaft portion 76, screw holes 78 that penetrate the whole in the axial direction are formed at a plurality of locations (here, four locations) that circumferentially surround the wiring shaft hole 77 at equal intervals. With the positions of the female screw holes 54B of the second electrode body 50 and the screw holes 78 of the base 70 aligned, a headed screw 90 is inserted from the rear to the front and screwed into the female screw holes 54B, whereby the second electrode body 50 and the base 70 are connected in the axial and circumferential directions.

[0051] At least a part of the conical surface formed around the reduced-diameter portion 74 contacts the tip surface of the shaft portion 300. The remaining portion of the conical surface becomes the rear isolation surface 73 that is exposed to the outside. The rear isolation surface 73 becomes an annular region K4 that extends in a band shape around the central axis of the reduced-diameter portion 74 (see Fig. 3(C)). This rear isolation surface 73 serves to electrically isolate (insulate) the second electrode surface 53 and the shaft portion 300. Note that the shape of the reduced-diameter portion 74 is not limited to a truncated cone and may be a cylindrical (disk) shape.

[0052] (Connector portion)

[0053] As shown in Fig. 5(B), the connector portion 80 has a coaxial connector structure to which a coaxial cable can be connected, and in the present embodiment, it has an SMA-standard receptacle structure. Note that as the standard of the coaxial connector, in addition to SMA, BNC standard, TNC standard, N standard, SMB standard, SMC standard, etc. can also be adopted. Further, the connector portion 80 may have any shape as long as the impedance is matched. Also, instead of the receptacle structure, a plug structure may be adopted.

[0054] The connector portion 80 includes a conductive base 82 that is square plate-shaped with an opening 82A formed therein, a conductive and cylindrical shell portion 86 erected on the rear surface of the base 82, a conductive and rod-shaped center contact portion 84 coaxially disposed inside the shell portion 86, and a cylindrical insulating portion 83 disposed in the gap between the inner peripheral surface of the shell portion 86 and the outer peripheral surface of the center contact portion 84. The opening 82A of the base 82 and the inner peripheral surface of the shell portion 86 form a continuous surface. The insulating portion 83 is held on the inner peripheral surface of the shell portion 86. The center contact portion 84 is held on the inner peripheral surface of the insulating portion 83. The insulating portion 83 insulates and isolates the shell portion 86 and the center contact portion 84 from each other.

[0055] A female thread 86A is formed on the outer peripheral surface of the shell portion 86. The female thread 86A is screwed with a male thread of the SMA plug standard of a mating connector (transmission connector portion 270 of the signal detection device 200) connected thereto. Engagement protrusions 89 protruding axially are formed at the four corners of the front surface of the base 82. The engagement protrusions 89 engage with a connector engagement portion 54A formed on the second lower bottom surface 54 of the second electrode body 50. The front surface of the base 82 abuts against the second lower bottom surface 54 of the second electrode body 50 and is electrically connected thereto. The front end of the center contact portion 84 is housed in the internal space 36A of the first shaft portion 36 of the first electrode body 30 and is electrically connected thereto (see FIG. 3(B)).

[0056] The shell portion 86, the base 82, and the engagement protrusions 89 in the connector portion 80 form part of a second wiring T2 connected to the second electrode body 50. The center contact portion 84 forms part of a first wiring T1 connected to the first electrode body 30. In this embodiment, the first wiring T1 serves as a signal supply wiring that supplies a pulsed or wavy electrical signal to the first electrode body 30, and the second wiring T2 serves as a ground (GND) wiring for setting the second electrode body 50 as a reference potential. That is, the first wiring T1 and the second wiring T2 form a signal transmission path D through which a pulsed or wavy electrical signal and its reflected signal are transmitted (see FIG. 6).

[0057] In the present embodiment, although the case where the shell portion 86 forms part of the connector portion 80 has been exemplified, the present invention is not limited thereto. For example, the shell portion 86 may extend integrally rearward from the second bottom surface 54 of the second conical portion 52 of the second electrode body 50. That is, the shell portion 86 may constitute part of the second wiring T2, and it is sufficient to surround the periphery of the first wiring T1, including the case where it does not function as a connector.

[0058] (Signal detection device)

[0059] As shown in FIG. 6, the signal detection device 200 is composed of various electronic components and electric circuits, and includes a power supply unit 205 connected to a power supply line 282 to receive power supply from the outside, a signal generation unit 210 that generates an electric signal such as a pulse signal or a frequency signal, a signal transmission path D that guides the electric signal from the signal generation unit 210 to a transmission connector unit 270, a signal reception unit 220 provided in the middle of the signal transmission path D to receive the electric signal flowing through the signal transmission path D, an AD conversion unit 250 that converts the analog reception signal received by the signal reception unit 220 into a digital reception signal, a calculation unit 255 that calculates various characteristic values (for example, S parameters) of the signal and generates parameter information using the digital reception signal converted by the AD conversion unit 250, and an input / output unit 260 that outputs the digital reception signal and / or the parameter information to a communication line 280 and receives a command signal from the outside. The signal reception unit 220 is configured to receive at least one of a transmission-side electric signal flowing from the signal generation unit 210 toward the transmission connector unit 270 and a reflection-side electric signal flowing from the transmission connector unit 270 toward the signal generation unit 210, and here, both are received.

[0060] In the present embodiment, the transmission connector unit 270 has a coaxial connector structure (SMA standard plug structure) and is connected to the connector unit 80. Note that these functional components operate by the power of the power supply unit 205.

[0061] The calculation unit 255 also serves to control the signal generation unit 210 and the signal reception unit 220 with reference to the command signal from the control device 600. The calculation unit 255 is, for example, a microcontroller (MPU), and as a functional block, it has a characteristic value calculation processing unit 255A and a frequency sweep processing unit 255B. The characteristic value calculation processing unit 255A calculates various characteristic values (e.g., S parameters) of the signal using the digital reception signal converted by the AD conversion unit 250 and generates parameter information. Furthermore, the characteristic value calculation processing unit 255A can further calculate the physical property values (relative permittivity and electrical conductivity) of the soil using the calculated parameter information. The frequency sweep processing unit 255B changes the frequency of the electrical signal generated by the signal generation unit 210 in multiple steps or sweeps the frequency during the unit measurement process. As a result, for the underground soil with unknown composition and volumetric water content, various characteristic values (e.g., S parameters) can be calculated using electrical signals of various frequencies, so that the optimal frequency can be selected retrospectively from the measurement results. Note that all or part of this calculation unit 255 can also be provided on the control device 600 side.

[0062] The signal generation unit 210 can generate a step pulse-shaped electrical signal for measurement by the TDR method (time domain reflectometry) and sinusoidal electrical signals with various frequencies for S parameter measurement. When expressing the frequency of the sinusoidal electrical signal in terms of radio wave classification, for example, this signal generation unit 210 preferably can generate at least part, preferably all, of the electrical signals in the long wave band (30 kHz to 300 kHz), medium wave band (300 kHz to 3 MHz), short wave band (3 MHz to 30 MHz), ultra-short wave band (30 MHz to 0.3 GHz), and microwave band (0.3 GHz or higher). In particular, in the signal generation unit 210 of this embodiment, since it can generate at least part of the electrical signals in the microwave band, especially in the extremely ultra-short wave band from 0.3 GHz to 3 GHz, it is characterized by the ability to measure physical properties with high precision. Note that the signal generation unit 210 of this embodiment is capable of generating signals with frequencies from 50 kHz to 1.5 GHz.

[0063] The signal receiving unit 220 specifically includes a transmission signal separation unit 230 that serves as a power splitter for separating the transmission-side electrical signal flowing through the signal transmission path D, a transmission signal receiving unit 235 that receives the transmission-side electrical signal separated by the transmission signal separation unit 230, a reflection signal separation unit 240 that serves as a directional coupler for separating the reflection-side electrical signal flowing through the signal transmission path D, and a reflection signal receiving unit 245 that receives the reflection-side electrical signal separated by the reflection signal separation unit 240. Each analog reception signal received by the transmission signal receiving unit 235 and the reflection signal receiving unit 245 is converted into a digital reception signal by the AD conversion unit 250.

[0064] Note that the signal detection device 200 of the present embodiment exemplifies the case of functioning as a scalar network analyzer or a vector network analyzer with the above circuit structure, but the present invention is not limited thereto, and the signal receiving unit can also be configured with other structures. Further, the signal receiving unit 220 of the signal detection device 200 of the present embodiment exemplifies the case of separately separating and receiving the transmission-side electrical signal and the reflection-side electrical signal, but it is also possible to simultaneously receive the transmission-side electrical signal and the reflection-side electrical signal in a mixed state, such as in a digital oscilloscope circuit. Further, part or all of the functions of the calculation unit 255 that calculates the S parameters and generates parameter information may be provided on the control device 600 side described later.

[0065] In the present embodiment, the case where the signal detection device 200 and the conical probe 10 are electrically connected in a coaxial cable structure is exemplified, but the present embodiment is not limited thereto, and they may be connected by non-coaxial wiring.

[0066] Note that the signal detection device 200 is appropriately calibrated as necessary. As calibration methods, for example, SOLT (Short-Open-Load-Thru) calibration, Offset Short calibration, LRL (Line-Reflect-Line) / TRL (Thru-Reflect-Line) / LRM (Line-Reflect-Match) calibration, etc. can be adopted.

[0067] (Control device)

[0068] As shown in FIG. 7, the control device 600 is a so-called computer, and includes a CPU 641, a RAM 642, a ROM 643, an input device 644, a display device 645, a height sensor 646, a power supply 647, an input / output interface 648, and a bus 649.

[0069] The CPU 641 is a so-called central processing unit, and various programs are executed to realize various functions. The RAM 642 is a so-called RAM (random access memory), and is used as a work area of the CPU 641. The ROM 643 is a so-called ROM (read only memory), and stores a basic OS and various programs (for example, a measurement program) executed by the CPU 641.

[0070] The input device 644 is a button, a touch panel type input key, a keyboard, or a mouse, and inputs various information. The display device 645 is a display, and displays various measurement progress and measurement results. The height sensor 646 detects the height of the physical property measurement device 1 (the conical probe 10) by an acceleration probe, a GPS sensor, a gyro sensor, or the like.

[0071] The power supply 647 supplies power for each component to operate. The input / output interface 648 has a power supply line 282 and a communication line 280 connected thereto, supplies power for operating the signal detection device 200 and the stress detection device 400 from the power supply 647, outputs a control signal for controlling the signal detection device 200 and the stress detection device 400, or inputs a digital signal transmitted from the signal detection device 200 and the stress detection device 400. The bus 649 is a wiring that integrally connects the CPU 641, the RAM 642, the ROM 643, the input device 644, the display device 645, the height sensor 646, the power supply 647, the input / output interface 448, etc. to perform communication.

[0072] When the basic OS and various programs (soil measurement programs) stored in the ROM 643 are executed by the CPU 641, the functional blocks shown in FIG. 8(A) are implemented.

[0073] That is, the control device 600 includes, as functional blocks, a height determination unit 660, an S parameter acquisition unit 662, a physical property conversion unit 664, a hardness acquisition unit 666, a data display unit 668, and a frequency selection unit 669.

[0074] The height determination unit 660 determines the height of the physical property measurement device 1 (the depth from the ground surface U of the conical probe 10) with the start of measurement as the reference height, and generates a measurement execution command each time a predetermined depth that is at a certain interval (for example, 1 cm interval) is reached. Based on the measurement execution command from the height determination unit 660, the S parameter acquisition unit 662 controls the signal detection device 200 to acquire the S parameter information of the soil. The S parameter acquisition unit 662 preferably issues a sweep command to the calculation unit 255 of the signal detection device 200 to cause it to be swept at a plurality of types of frequencies or a predetermined bandwidth during one measurement cycle. In the case of soil existing underground, since its soil quality and water content are unknown, the optimal frequency of the electrical signal during measurement is often unknown. Therefore, the S parameter acquisition unit 662 acquires the S parameter information of a plurality of frequencies or bandwidths that can handle various soils from the signal detection device 200. The frequency selection unit 669 refers to all the S parameter information in the sweep frequency band, and afterwards determines the optimal frequency to determine the corresponding S parameter. Note that it is preferable to include the microwave band in a part of the plurality of frequencies or bandwidths.

[0075] The physical property conversion unit 664 calculates various physical property values of the soil (for example, relative dielectric constant, water content, etc.) using the S-parameter information selected by the frequency selection unit 669. Here, an example is shown in which the frequency selection unit 669 specifies an optimal frequency in advance and narrows down the S-parameter information before the conversion process in the physical property conversion unit 664, but the present invention is not limited to this. For example, based on all the S-parameter information obtained by sweeping the frequency, all various physical property values of the soil (for example, relative dielectric constant, water content) can also be calculated. As a result, since various physical property values of the soil that vary depending on the frequency are obtained, the frequency selection unit 669 may also determine an optimal physical property value (optimal frequency) from among those physical property values retrospectively.

[0076] Based on the measurement execution command from the height determination unit 660, the hardness acquisition unit 666 acquires stress information from the stress detection device 400 and calculates the hardness of the soil. The data display unit 668 causes the display device 645 to display various physical property values and hardness values of the soil corresponding to the depth in the ground.

[0077] The detailed calculation block in the physical property conversion unit 664 is as follows.

[0078] (1) Y-parameter calculation unit In the Y-parameter calculation unit 664A, the Y-parameter (admittance matrix) is calculated from the S-parameter (scattering matrix). In the present embodiment, since only the signal input side by the first electrode body 30 and the second electrode body 50 exists with respect to the soil, S in the S-parameter 12 , S 21 , S 22 becomes 0, and the calculation using the reflection characteristic (S 11 ) is performed. Specifically, the Y-parameter calculates the input-side admittance characteristic (Y 11 ) assuming that the output signal side is in a short-circuit state. The calculation formula in this case is Y 11 = (1 - S 11 ) / (1 + S 11) It should be noted that since the Y parameter (admittance matrix) is the inverse matrix of the Z parameter (impedance matrix), the Z parameter may be calculated from the S parameter, and then the Y parameter may be calculated from this Z parameter.

[0079] (2) Reference proportionality constant and reference stray capacitance calculation unit In the reference proportionality constant and reference stray capacitance calculation unit 664B, the Y parameters of two reference objects with known permittivities (for example, air (permittivity ε = 1) and water (permittivity ε = 78 at 25 °C water temperature)) are measured, and the reference proportionality constant C0 and the reference stray capacitance Cr are calculated from the capacitance method.

[0080] Y 11 When the real part and the imaginary part of are defined as Y 11 = G + jB (G: conductance, B: susceptance), substituting this into the relationship between the conductance G and the capacitance Cp, we get Y 11 = G + jωCp. The conductance G is a value related to the electrical conductivity of the reference object, and the capacitance Cp is a value related to the relative permittivity of the reference object. Here, by using the Y parameter calculation unit 664A to calculate the Y parameter of the reference object, the capacitance Cp (air) and the capacitance Cp (water) are obtained, and by calculating the two equations Cp (air) = ε (air) * C0 + Cr and Cp (water) = ε (water) * C0 + Cr obtained from the relationship between these capacitances and permittivities, the reference proportionality constant C0 and the reference stray capacitance Cr are calculated. This calculation result is stored in the memory of the control device 600.

[0081] (3) Relative permittivity and electrical conductivity calculation unit In the relative permittivity and electrical conductivity calculation unit 664C, the Y parameter (Y 11 ) of the soil, which is the measurement object obtained from the Y parameter calculation unit 664A, and the reference proportionality constant C0 and the reference stray capacitance Cr stored by the reference proportionality constant and reference stray capacitance calculation unit 664B are used to calculate the relative permittivity and electrical conductivity of the soil. The real part and the imaginary part of the soil Y 11 are Y 11When defined as \(Y = G + jB\) (\(G\): conductance, \(B\): susceptance), replacing this with the relationship between the conductance \(G\) and the capacitance \(C_p\), we get \(Y\) 11 \(= G(\text{soil})+j\omega C_p(\text{soil})\). This conductance \(G(\text{soil})\) is a value related to the electrical conductivity \(k(\text{soil})\) of the soil, and the capacitance \(C_p(\text{soil})\) is a value related to the relative permittivity \(\varepsilon'(\text{soil})\) of the soil. Using the reference proportionality constant \(C_0\) and the reference floating capacitance \(C_r\), the relational expressions \(\varepsilon'(\text{soil})=(C_p(\text{soil}) - C_r) / C_0\) and \(k(\text{soil})=\varepsilon_0\times G(\text{soil}) / C_0\) (\(\varepsilon_0\): permittivity of vacuum) can be obtained. Thus, the relative permittivity \(\varepsilon'(\text{soil})\) and the electrical conductivity \(k(\text{soil})\) are calculated. Although not particularly shown here, it is also possible to calculate the volumetric water content of the soil from the relative permittivity and / or electrical conductivity calculation unit.

[0082] Fig. 7(B) shows the flowchart of the soil measurement program, and Fig. 8 shows its actual measurement mode. As shown in Fig. 8(A), when the measurement start button is pressed with the conical probe 10 in contact with the ground surface U, the measurement starts at step S100, and the height information becomes the reference position (0-depth). After that, as shown in Fig. 8(B), when the measurer penetrates the conical probe 10 into the ground, at step S102, it is determined whether the conical probe 10 has reached a predetermined nth depth (for example, the first depth). If it has not reached the nth depth (NO), this step S102 is repeated. On the other hand, if it is determined at step S102 that the nth depth has been reached (YES), the process proceeds to step S104 to measure the S parameter of the soil, and also proceeds to step S106 to measure the hardness of the soil. At this time, the control device 600 may notify the measurer that the nth depth has been reached by an alert on the display screen or a sound. The measurer may temporarily stop the penetration into the ground when receiving the notification regarding reaching the nth depth. After the measurement at the nth depth is completed, the process proceeds to step S108, where the nth value is updated to n + 1, and then returns to step S102. At this time, the control device 600 may notify the measurer by an alert on the display screen or a sound that the previous measurement (measurement at the nth depth) has ended, and the measurer who has received the notification can resume the penetration of the conical probe 10 into the ground as shown in Fig. 8(C). At step S102, it is determined whether the next nth depth (for example, the second depth) has been reached, and if it has been reached, steps S104 to S108 are repeated. Note that the set value of the nth depth may utilize the depth table information set in advance, or the set information such as the unit depth value H (for example, at 5 cm intervals) may be used to adopt n*H (cm) as the determination depth from the ground surface U.

[0083] FIG. 9 shows a flowchart of a modified example of the soil measurement program. Here, an example is illustrated where the measurer penetrates the conical probe 10 into the ground at a constant speed (for example, 2 cm / second). When the measurer presses the measurement start button, the measurement starts at step S200. According to the cycle period of the program (for example, 0.5 seconds), the in-ground depth information of the conical probe 10 is acquired at step S202, the S parameter of the soil is measured at step S204, the hardness of the soil is measured at step S206, and the data is saved in a state where the depth information, the S parameter information, and the hardness information are associated. That is, in the case of the soil measurement program of FIG. 9, according to the so-called logging method, the depth information, the S parameter information, and the hardness information can always be collected per unit time.

[0084] According to the physical property measurement device 1 of the present embodiment, an electric signal can be applied to the soil while pressing the first electrode surface 33 and the second electrode surface 53 formed on a part of the conical surface of the conical probe 10 against the soil to measure the physical property value. As a result, it is possible to improve the measurement accuracy of the reflection signal of the soil. At this time, since there is an isolation surface 43 that insulates and isolates the first electrode surface 33 and the second electrode surface 53 on a part of the conical surface, a short circuit between the first electrode surface 33 and the second electrode surface 53 is suppressed, and it is possible to further improve the measurement accuracy of the reflection signal.

[0085] In particular, in the present embodiment, the first electrode surface 33, the second electrode surface 53, and the isolation surface 43 include an annular region along the circumferential direction of the conical surface. Therefore, the angular dependence characteristic in the circumferential direction when applying an electric signal to the soil can be reduced, and the variation in the measurement work by the measurer can be suppressed.

[0086] In the conical probe 10, the first cone portion 32 of the first electrode body 30, the isolation cone portion 42 of the isolation body 40, and the second cone portion 52 of the second electrode body 50 are connected in this order from the tip toward the rear end. At the same time, the isolation cone portion 42 has a front engagement structure J1 that can be axially engaged with the first cone portion 32 and a rear engagement structure J2 that can be axially engaged with the second cone portion 52. Therefore, while each of the first cone portion 32, the isolation cone portion 42, and the second cone portion 52 receives the external force from the soil acting on the conical probe 10, the whole is integrated, so that the rigidity and durability of the conical probe 10 can be enhanced.

[0087] The first cone portion 32 of the first electrode body 30 includes a rod-shaped first shaft portion 36 that extends axially and rearward from the first bottom surface 34 thereof, and this first shaft portion 36 forms at least a part of the first wiring T1. Further, a second shaft hole 57 is formed in the second cone portion 52 of the second electrode body 50, and the first wiring T1 (first shaft portion 36) passes through the second shaft hole 57. By configuring the first wiring T1 to pass through the inside of the conical probe 10 in this way, the electrical signal transmitted through the first wiring T1 is less likely to be disturbed. In particular, when the first wiring T1 (first shaft portion 36) passes through the second shaft hole 57, an isolation shaft portion 47 serving as an insulator is interposed. As a result, it is possible to further improve the measurement accuracy of the reflected signal of the soil.

[0088] Further, a base 70 made of an insulating material is disposed behind the second electrode body 50, and a shaft portion 300 is connected via this base 70. Thereby, the second electrode body 50 and the shaft portion 300 are insulated. Further, a second wiring T2 (the shell portion 86 of the connector portion 80) connected to the second electrode body 50 passes through a wiring shaft hole 77 formed inside the base 70. By configuring the second wiring T2 to pass through the inside of the base 70, the electrical signal (reference potential) transmitted through the second wiring T2 is less likely to be disturbed. As a result, it is possible to further improve the measurement accuracy of the reflected signal of the soil.

[0089] In the physical property measurement device 1, the signal generation unit 210 of the signal detection device 200 can generate a frequency signal (especially a frequency signal in the microwave band). As a result, since the signal detection device 200 can detect the reflection characteristics of the high-frequency signal, an optimal frequency can be selected for various soils (objects), and more accurate S-parameters can be measured.

[0090] In the physical property measurement device 1, the signal detection device 200 is housed in the shaft portion 300, and the distance from the conical probe 10 is shortened. As a result, all or part of the signal detection device 200 enters the ground during measurement. As a result, since the signal transmission path D is short, disturbance of the electrical signal during transmission is suppressed, and the measurement accuracy can be improved. It is desirable that the distance of the signal transmission path D from the signal generation unit 210 to the first electrode surface 33 and the second electrode surface 53 is 20 cm or less, more desirably 10 cm or less.

[0091] As a result of the signal detection device 200 being housed in the shaft portion 300, the entire signal detection device 200 is also shielded from the outside by the shaft portion 300, so that the influence of disturbance can be reduced. Further, in the signal detection device 200, since the measurement result is digitally converted and then transmitted to the control device 600, the influence of noise in the communication line 280 can be avoided.

[0092] Since the stress detection device 400 of the physical property measurement device 1 can measure the contact surface pressure between the first electrode surface 33 and the second electrode surface 53 of the conical probe 10 and the measurement object (soil), when the contact surface pressure is lower than a predetermined threshold value, the measurement of the reflection signal (S-parameter) can be interrupted or the data can be excluded to reduce the measurement error.

[0093] In the physical property measurement device 1, since the conical probe 10 also serves as a penetration cone for measuring the hardness of the soil, the hardness of the soil can be calculated by the stress detection device 400. Therefore, the hardness of the soil and the physical property values (relative dielectric constant and electrical conductivity) of the soil can be measured simultaneously in a single penetration measurement operation.

[0094] (Modification of the embodiment)

[0095] In this embodiment, the case where the signal detection device 200 is housed in the shaft portion 300 has been illustrated, but the present invention is not limited thereto. For example, as shown in FIG. 12, the signal detection device 200 may be disposed outside the shaft portion 300 (here, the rear end side of the shaft portion 300). In this case, the conical probe 10 and the signal detection device 200 may be connected by a coaxial cable 290 inserted into the shaft portion 300.

[0096] Also, in this embodiment, the case where the first conical portion 32 (first electrode surface 33) of the first electrode body 30 has a head cone shape and extends to the tip of the cone 20 of the conical probe 10 has been illustrated, but the present invention is not limited thereto. For example, as shown in FIG. 13, the first conical portion 32 may have a frustum shape. In this case, it is preferable to provide a front isolation body 900 made of an insulator in front of the first electrode body 30.

[0097] Also, in this embodiment, the case where the first electrode surface 33 and / or the second electrode surface 53 includes an annular region along the circumferential direction of the conical surface of the cone 20 has been illustrated, but the present invention is not limited thereto. For example, as shown in FIG. 14, the first electrode body 30, the isolation body 40, and the second electrode body 50 may occupy a non-annular range that is a part of the cone 20. In this case, it is desirable that the first electrode surface 33 and the second electrode surface 53 formed on the conical surface of the cone 20 be line-symmetric with respect to a specific diameter when viewed from the axial direction.

[0098] Furthermore, in this embodiment, the case where the calculation unit 255 of the signal detection device 200 calculates the S parameter as a characteristic value of the reflected signal has been illustrated, but the present invention is not limited thereto. For example, time domain calculation as the TDR method (time domain reflectometry) may be performed. In this case, the signal generation unit 210 may generate a step pulse-shaped electrical signal for the TDR method. On the other hand, the S parameter (S11) obtained by sweeping the frequency may be subjected to inverse Fourier transform processing to convert the reflection characteristic based on the frequency standard into the reflection characteristic based on the time domain standard, and the reflection characteristic based on the time domain standard may be calculated.

[0099] Further, in the present embodiment, the case where the signal detection device 200 measures the reflection characteristics of the soil when an electrical signal is applied is illustrated, but the present invention is not limited thereto. For example, as shown in FIG. 15, a pair of conical probes 10 are brought into contact with an object, and the transmission characteristics of a telecommunication signal (see arrow Z) transmitted from one conical probe 10 to the other conical probe 10 may be acquired. By doing so, it is also possible to calculate the transmission characteristics in S-parameters, Z-parameters, Y-parameters, etc., and it is also possible to perform calculations by the time-domain transmission method (TDT method). Further, in the present embodiment, the case where an alternating electrical signal is applied as the electrical signal is illustrated, but the present invention is not limited thereto, and a DC electrical signal may be applied to the first electrode surface and the second electrode surface, and the current value (resistance component) may be measured by a response detection device to measure the electrical conductivity of the object.

[0100] Furthermore, in the present embodiment, the case where the conical probe 10 has two electrode surfaces (electrode bodies), i.e., the first electrode surface 33 (first electrode body 30) and the second electrode surface 53 (second electrode body 50), is illustrated, but the present invention is not limited thereto, and it may be provided with three or more electrode surfaces (electrode bodies). For example, as shown in FIG. 16, the conical probe 10 may include a cone of a first group G1 having a first electrode surface 331 (first electrode body 301), a first isolation surface 431 (first isolation body 401), and a second electrode surface 531 (second electrode body 501), and a cone of a second group G2 having a first electrode surface 332 (first electrode body 302), a second isolation surface 432 (second isolation body 402), and a second electrode surface 532 (second electrode body 502). In this case, a first signal transmission path D1 (first wiring T11, second wiring T21) may be provided for the first group G1, and a second signal transmission path D2 (first wiring T12, second wiring T22) may be provided for the second group G2. Further, when the first group G1 and the second group G2 are arranged in parallel in the axial direction, an intermediate isolation surface 43T (intermediate isolation body 40T) may be provided therebetween. According to this conical probe 10, for example, when an electrical signal is supplied to the first signal transmission path D1 of the first group G1, the transmission signal to the second signal transmission path D2 of the second group G2 can be detected.

[0101] Also, like the physical property measuring device 1 of the modified example shown in FIGS. 17 and 18, it is preferable to dispose a temperature sensor 290 constituted by a thermistor or the like inside or in the vicinity of the shaft portion 300 or the conical probe 10. In this modified example, the temperature of the object (soil) is indirectly measured by bringing the temperature sensor 290 into contact with the second electrode body 30 made of a metal having high thermal conductivity, but the temperature sensor 290 may be brought into direct contact with the object (soil). The wiring of the temperature sensor 290 is connected to the signal detection device 200 via a wiring hole 70X formed in the base 70. Similarly, it is preferable to dispose an inclination sensor 292 inside or in the vicinity of the shaft portion 300 or the conical probe 10. In this modified example, the inclination sensor 292 is mounted on the substrate of the signal detection device 200. As shown in FIG. 18, the signal receiving unit 220 in the signal detection device 200 preferably has a temperature signal receiving unit 280 that receives the detection signal (current value or resistance value) of the temperature sensor 290 and an inclination signal receiving unit 282 that receives the detection signal of the inclination sensor 292. These signals are converted into digital reception signals by the AD conversion unit 250 as necessary and transmitted from the input / output unit 280 to the communication line 280. According to this physical property measuring device 1, the temperature of the object can be measured simultaneously, and further, the change in the posture of the physical property measuring device 1 can be measured simultaneously. For example, it is also possible to detect whether the central axis of the conical probe 10 or the shaft portion 300 is inclined with respect to the vertical direction during measurement.

[0102] In addition, in this embodiment, the case where the physical property measuring device 1 also serves as a soil hardness meter has been exemplified, but the present invention is not limited to this. For example, in the physical property measuring device 1 of the modified example shown in FIGS. 19(A) and (B), the conical probe 10 is fixedly embedded at an arbitrary depth in the ground, and the conical probe 10 measures the change over time of the physical property values of the soil. In this case, the control device 600 functions as a so-called data logger, and further, it is also desirable to perform wireless communication with an external communication terminal (not shown) by the wireless communication unit 990. In this way, it becomes possible to measure, monitor, and record the change over time of the physical property values of the soil remotely. In this physical property measuring device 1, it is preferable to include the temperature sensor 290 and the inclination sensor 292 shown in FIGS. 17 and 18. The angle fluctuation data of the conical probe 10 obtained from the inclination sensor 292 can be utilized for predicting slope collapse of the ground, etc. As shown in FIG. 19(B), the conical probe 10 and the signal detection device 200 embedded in the ground with the shaft portion omitted and the control device 600 installed on the ground may be connected by the communication line 280 and the power supply line 282.

[0103] Note that the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

Explanation of Reference Numerals

[0104] 1 Physical property measuring device 10 Conical probe 20 Cone 30 First electrode body 32 First cone portion 33 First electrode surface 36 First shaft portion 40 Isolator 42 Isolation cone portion 43 Isolation surface 46 Isolation shaft hole 47 Isolation shaft portion 50 Second electrode body 52 Second cone portion 53 Second electrode surface 57 Second shaft hole 70 Base 74 Reduced diameter portion 76 Connecting shaft part 80 Connector part 82 Base 83 Insulating part 84 Central contact part 86 Shell part 200 Signal detection device (response detection device) 205 Power supply part 210 Signal generation part 220 Signal reception part 230 Transmission signal separation part 235 Transmission signal reception part 240 Reflection signal separation part 245 Reflection signal reception part 250 AD conversion part 255 Calculation part 260 Input / output part 280 Communication line 282 Power supply line 290 Temperature sensor 292 Inclination sensor 300 Shaft part 400 Stress detection device 480 Communication line 500 Operation handle 600 Control device 644 Input device 645 Display device 646 Height sensor 647 Power supply 660 Judgment part 662 S-parameter acquisition part 664 Physical property conversion part 664 Physical property conversion section 664A Y-parameter calculation part 664B Reference proportional constant and reference floating capacitance calculation part 664C Electrical conductivity calculation part 666 Hardness acquisition part 668 Data display part 669 Frequency selection part D Signal transmission path J1 Front engagement structure J2 Rear engagement structure J3 Base engagement structure J4-axis engagement structure K1 to K4 annular regions

Claims

1. A method for measuring physical properties of soil underground, comprising: a step of inserting a measurement probe into water and air, which are reference objects with known dielectric constants, applying a frequency signal, calculating two reference values from the respective reflected signals, and storing the two reference values in a memory; an entry step of entering a measurement probe into the ground; a measurement step of applying a frequency signal to the probe within the ground and detecting a reflected signal from the probe; a calculation step of calculating the relative dielectric constant and the electrical conductivity of the soil based on the reflected signal detected in the actual measurement step and the two reference values, Methods for measuring soil physical properties.

2. In the actual measurement step, the frequency signal of a specific frequency selected from a plurality of frequencies is applied. The method for measuring soil physical properties according to claim 1.

3. a response detection device positioned underground that applies electricity to the probe and detects the reflected signal from the soil; The method for measuring soil physical properties according to claim 1.

4. The probe is a first electrode surface in contact with the soil; a second electrode surface in contact with the soil; an isolation surface isolating the first electrode surface and the second electrode surface by an insulator; a first wiring electrically connected to the first electrode surface; a second wiring electrically connected to the second electrode surface; characterized in that it comprises The method for measuring soil physical properties according to claim 1.

5. a frequency of the subharmonic signal applied to the probe in the measurement step is 30 MHz to 0.3 GHz or 0.3 GHz or more; The method for measuring soil physical properties according to claim 1.

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