Method, device and equipment for measuring soil electrical conductivity

Abstract

This application discloses a method, device, and equipment for measuring soil electrical conductivity, relating to the field of soil testing technology. The method comprises: installing an SFCW-TDR device at a target soil monitoring point while simultaneously collecting the soil dry volume and field water holding capacity of the target soil monitoring point; using the SFCW-TDR device to collect the apparent dielectric constant, soil volume moisture content, and soil conductivity of the target soil monitoring point in real time, with the apparent dielectric constant used to determine the soil conductivity; calculating a relative humidity factor based on the real-time collected soil volume moisture content, soil dry bulk density, and field water holding capacity; and calculating the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the real-time relative humidity factor. This application can achieve rapid on-site measurement of soil electrical conductivity in related technologies, addressing the problem of large errors in the results and improving the accuracy and real-time performance of soil conductivity measurements.

Description

Technical Field

[0001] The present application relates to the technical field of conductivity measurement, and in particular to a method, device and equipment for measuring soil conductivity. Background Art

[0002] Conductivity is a physical quantity that describes a material's ability to conduct electricity. It is the reciprocal of resistivity and is measured in Siemens per meter (S / m). Conductivity typically refers to direct current (DC) conductivity.

[0003] Soil electrical conductivity (SEC) refers to the electrical conductivity of soluble salt ions in a soil solution. It is typically measured by measuring the conductivity of soil leachate or saturated mud. It reflects the salt content in the soil and its impact on plant growth. Measured in millisiemens per meter (mS / m) or microsiemens per centimeter (μS / cm), SEC directly correlates to the degree of soil salinization, nutrient availability, and crop growth potential.

[0004] Bulk electrical conductivity (BEC) refers to the electrical conductivity of the entire soil mass (including solid particles, pore water, and air). It is the result of the interaction of soil solutions, mineral particles, organic matter, and pore structure. Measurement range: Covers the overall conductivity of the soil mass and is significantly affected by soil texture, moisture content, temperature, and structure.

[0005] Measuring soil electrical conductivity is crucial for agricultural production and land management. For example, in irrigated agriculture, soil electrical conductivity can be used to quickly monitor soil nutrient and salt content, helping farmers rationally plan irrigation and fertilization and avoid soil salinization. This is crucial for guiding precision fertilization and water-saving irrigation. Furthermore, soil electrical conductivity can be used to guide crop planting layout, monitor soil pollution, and assess soil health.

[0006] Automated soil conductivity monitoring is a requirement for modernizing and scientifically advancing agriculture. With the rise of precision agriculture and the development of network communication technology, monitoring projects have been launched across China in recent years, which are of great significance to modern agriculture, environmental protection, and sustainable development. However, due to the late start of automated soil conductivity monitoring and the lack of mature technology, many problems currently exist, including the following:

[0007] 1) The standard method for measuring soil electrical conductivity is the laboratory electrode method: add water to an air-dried soil sample at a ratio of 1:5 (m / V), extract by shaking, and use a conductivity meter to measure the DC conductivity of the extract at 25°C. This method has no correlation with the moisture content of the soil and focuses on the conductivity of the soil as a "salt".

[0008] 2) Difficulty in dynamic data monitoring: Soil electrical conductivity, as a key indicator of soil nutrient differences, plays a crucial role in optimizing farmland soil improvement. However, current soil electrical conductivity monitoring technology faces challenges in dynamic data monitoring, which limits its application in precision agriculture.

[0009] 3) The parameter of automatic monitoring is actually soil conductivity: The current automatic soil conductivity monitoring technology is mostly developed from dielectric soil moisture monitoring technology. It measures the conductivity by monitoring the attenuation of electromagnetic wave signals caused by the influence of conductivity during soil propagation. The monitoring results are greatly affected by soil moisture content. The actual monitoring and measurement is of soil conductivity, which does not meet the actual requirements of agricultural production.

[0010] 4) Monitoring results are heavily dependent on formula calibration: Due to technical defects in existing equipment, most of them need to be determined through calibration. That is, the formula or parameters are determined by mathematical statistics based on the monitoring data at the monitoring point and the results of laboratory measurements of soil samples taken. In actual application, the feasibility is low and it is difficult to achieve the actual required measurement accuracy. Summary of the Invention

[0011] The purpose of this application is to provide a method, device and equipment for measuring soil conductivity, which can solve the problem of large errors in measurement results during the automated monitoring of soil conductivity in related technologies and improve the accuracy and real-time performance of soil conductivity measurement.

[0012] To achieve the above objectives, this application provides the following solutions:

[0013] In a first aspect, the present application provides a method for measuring soil electrical conductivity, comprising:

[0014] Installing the SFCW-TDR device at the target soil monitoring point and collecting the soil dry volume and field water holding capacity of the target soil monitoring point;

[0015] The SFCW-TDR device is used to collect the apparent dielectric constant, soil volume moisture content and soil conductivity of the target soil monitoring point in real time; the apparent dielectric constant is used by the SFCW-TDR device to determine the soil conductivity;

[0016] The relative humidity factor is calculated based on the real-time collected soil volumetric moisture content, soil dry bulk density and field capacity;

[0017] The soil electrical conductivity of the target soil monitoring point is calculated in real time according to the soil electrical conductivity and the relative humidity factor obtained in real time.

[0018] Optionally, a relative humidity factor is calculated based on the real-time collected soil volumetric moisture content, soil dry bulk density, and field capacity, specifically including:

[0019] Soil mass moisture content = soil volume moisture content / soil dry bulk density;

[0020] Relative humidity factor = soil mass moisture content / field capacity.

[0021] Optionally, calculating the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the relative humidity factor obtained in real time specifically includes:

[0022] Soil electrical conductivity = soil electrical conductivity / relative humidity factor.

[0023] Optionally, using the SFCW-TDR device to collect the soil conductivity of the target soil monitoring point in real time specifically includes:

[0024] Controlling the SFCW-TDR device to transmit an initial electromagnetic signal to a probe inserted into the target soil monitoring point, wherein the initial electromagnetic signal is transmitted to the probe via a coaxial cable and a first apparent reflection coefficient and a second apparent reflection coefficient are obtained, wherein the first apparent reflection coefficient is the reflection coefficient collected by the SFCW-TDR device of a first reflected signal transmitted back when the initial electromagnetic signal reaches the starting portion of the probe after being transmitted, and the second apparent reflection coefficient is the reflection coefficient collected by the SFCW-TDR device of a second reflected signal transmitted back when the initial electromagnetic signal reaches the terminal portion of the probe after being transmitted;

[0025] calculating an attenuation coefficient according to the first apparent reflection coefficient and the second apparent reflection coefficient, and using the calculated attenuation coefficient as a measured attenuation coefficient;

[0026] The soil conductivity of the target soil monitoring point is calculated based on the measured attenuation coefficient, the apparent dielectric constant and the plane electromagnetic wave equation.

[0027] Optionally, the initial electromagnetic signal is transmitted to the probe via a coaxial cable to obtain a first apparent reflection coefficient and a second apparent reflection coefficient, comprising:

[0028] Obtaining a cable attenuation index according to the model and frequency domain interval of the coaxial cable;

[0029] When the initial electromagnetic signal is transmitted to the starting part of the probe through the coaxial cable, a first reflection point is formed. After reflection occurs at the first reflection point, a first reflection signal is formed. The first reflection signal is collected by the SFCW-TDR device to obtain the first apparent reflection coefficient;

[0030] When the initial electromagnetic signal reaches the starting part of the probe, a portion of the initial electromagnetic signal is reflected, and the remaining portion after reflection is a transmission signal. The transmission signal continues to transmit to the probe terminal, forming a second reflection point, and undergoes total reflection at the second reflection point. Then, it passes through the probe, the first reflection point, and the coaxial cable to form a second reflection signal. The second reflection signal is collected by the SFCW-TDR device to obtain the second apparent reflection coefficient.

[0031] Optionally, calculating an attenuation coefficient according to the first apparent reflectance coefficient and the second apparent reflectance coefficient, and using the calculated attenuation coefficient as the measured attenuation coefficient, specifically includes:

[0032] Calculating a first reflection coefficient based on the first apparent reflection coefficient, where the first reflection coefficient is a reflection coefficient of the initial electromagnetic signal reflected by the first reflection point;

[0033] A measured attenuation coefficient is obtained according to the relationship between the second apparent reflection coefficient and the first reflection coefficient.

[0034] Optionally, calculating the first reflection coefficient according to the first apparent reflection coefficient specifically includes: according to the formula Calculating the First Reflection Coefficient The relationship between the first reflection coefficient of the first reflection point and the first apparent reflection coefficient is expressed as:

[0035] ;

[0036] in, is the first apparent reflection coefficient, is the first reflection coefficient, is the cable attenuation index, is the length of the coaxial cable;

[0037] The relationship between the second apparent reflectance and the first reflectance is expressed as:

[0038] ;

[0039] in, is the second apparent reflectance, To measure the attenuation coefficient, is the length of the probe.

[0040] In a second aspect, the present application provides a device for measuring soil electrical conductivity, comprising:

[0041] Soil dry capacity and field water holding capacity collection module, used to collect soil dry capacity and field water holding capacity of the target soil monitoring point while installing the SFCW-TDR device at the target soil monitoring point;

[0042] A real-time data acquisition module, configured to use the SFCW-TDR device to collect in real time the apparent dielectric constant, soil volume moisture content, and soil conductivity of the target soil monitoring point; the apparent dielectric constant is used by the SFCW-TDR device to determine the soil conductivity;

[0043] Relative humidity factor calculation module, used to calculate relative humidity factor based on real-time collected soil volume moisture content, soil dry bulk density and field water holding capacity;

[0044] The soil conductivity calculation module is used to calculate the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the relative humidity factor obtained in real time.

[0045] Optionally, the device for measuring soil conductivity further includes: a display terminal, which is connected to the soil conductivity calculation module and is used to display the real-time soil conductivity of each target soil monitoring point.

[0046] In a third aspect, the present application provides a computer device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of any one of the above-described methods for measuring soil electrical conductivity.

[0047] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0048] The present application provides a method, device and medium for measuring soil electrical conductivity. The SFCW-TDR device is installed at a target soil monitoring point and simultaneously collects the soil dry volume and field water holding capacity of the target soil monitoring point; the SFCW-TDR device is used to collect the soil volume moisture content and soil electrical conductivity of the target soil monitoring point in real time. Among them, the SFCW-TDR device accurately measures the transmission time of electromagnetic waves through the Stepped-Frequency Continuous Wave (SFCW) system, and applies the Time Domain Reflectometry (TDR) principle to obtain the apparent dielectric constant of the soil, thereby accurately measuring the volumetric moisture content of the soil in arable agricultural land without formula calibration. Then, the relative humidity factor is calculated based on the real-time collected soil volumetric moisture content, soil dry bulk density and field water holding capacity; based on the soil conductivity and the real-time relative humidity factor, the soil conductivity of the target soil monitoring point is calculated in real time. By considering the effects of soil volumetric moisture content and field water holding capacity on soil conductivity, that is, eliminating the influence of moisture content on ion activity, and obtaining the relevant parameters for calculating soil conductivity (soil volumetric moisture content, soil conductivity and field water holding capacity) through synchronous implementation, the problem of large errors in measurement results during the automated monitoring of soil conductivity in related technologies can be solved, and the accuracy and real-time performance of soil conductivity measurements can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0050] Figure 1 A schematic flow chart of a method for measuring soil electrical conductivity provided in one embodiment of the present application.

[0051] Figure 2 A schematic diagram of the soil conductivity calculation process provided for one embodiment of the present application.

[0052] Figure 3 A schematic diagram of a system for measuring soil moisture using a TDR device provided in one embodiment of the present application.

[0053] Figure 4 This is a time domain trace obtained by measuring soil in real time using the SFCW-TDR device provided in one embodiment of the present application.

[0054] Figure 5 Schematic diagram of soil traveling wave analysis measurement using an SFCW-TDR device provided in one embodiment of the present application.

[0055] Figure 6 Schematic diagram of a uniform plane electromagnetic wave.

[0056] Figure 7This is a schematic diagram of the linear relationship fitting between the SFCW-TDR device and the conductivity meter measurement value provided in one embodiment of the present application.

[0057] Figure 8 This is a structural block diagram of a device for measuring soil electrical conductivity provided in an embodiment of the present application.

[0058] Figure 9 A schematic diagram of the SFCW-TDR device structure provided in one embodiment of the present application.

[0059] Figure 10 A schematic diagram of the structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0061] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0062] In an exemplary embodiment, the present application provides a method for measuring soil electrical conductivity, such as Figure 1 As shown, a method for measuring soil electrical conductivity includes steps 101 to 104.

[0063] Step 101: Installing an SFCW-TDR device at a target soil monitoring point while collecting the soil dry volume and field water holding capacity of the target soil monitoring point.

[0064] Step 102: The SFCW-TDR device is used to collect the apparent dielectric constant, soil volume moisture content, and soil conductivity of the target soil monitoring point in real time; the apparent dielectric constant is used by the SFCW-TDR device to determine the soil conductivity.

[0065] Step 103: Calculate the relative humidity factor based on the real-time collected soil volumetric moisture content, soil dry bulk density, and field holding capacity.

[0066] Step 104: Calculate the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the real-time obtained relative humidity factor.

[0067] This application distinguishes between soil bulk conductivity and soil conductivity by considering the effects of soil volumetric moisture content and field water holding capacity on soil conductivity, that is, eliminating the influence of moisture content on ion activity, so that the obtained conductivity is soil conductivity, thereby improving the accuracy of soil conductivity measurement.

[0068] This application installs SFCW-TDR equipment and sensors at target soil monitoring points. The sensors are specifically probes. While installing the SFCW-TDR equipment and sensors, the soil dry capacity and field water holding capacity of the target soil monitoring points are collected.

[0069] The relative humidity factor is calculated based on the real-time collected soil volumetric moisture content, soil dry bulk density and field water holding capacity, specifically including the following formula.

[0070] Soil mass moisture content = soil volume moisture content / soil dry bulk density.

[0071] Relative humidity factor = soil mass moisture content / field capacity.

[0072] Calculating the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the real-time obtained relative humidity factor, specifically including: .

[0073] in, is the soil electrical conductivity, is the soil conductivity, is the relative humidity factor.

[0074] Soil dry bulk density and field water holding capacity are inherent properties of the soil at the monitoring point. They can be collected manually when installing monitoring equipment including SFCW-TDR equipment and then placed into the monitoring equipment as parameters. Soil volumetric moisture content can be obtained through real-time monitoring of the SFCW-TDR equipment, and soil electrical conductivity It will be monitored in real time through SFCW-TDR equipment.

[0075] Field capacity is an indicator that describes the saturated water content of soil. The introduction of reflects the degree of activation of ions in the soil under the action of water molecules, thereby establishing a good connection between soil conductivity and soil bulk conductivity.

[0076] This application provides the relationship between soil electrical conductivity and soil bulk conductivity. The field water holding capacity and dry bulk density of the soil are manually determined, and the volumetric moisture content and soil bulk conductivity of the soil are then measured using an SFCW-TDR device to obtain the soil electrical conductivity of the measured soil. This can achieve rapid on-site measurement of soil electrical conductivity in related technologies, solve the problem of large errors in the results, and improve the accuracy and real-time performance of soil conductivity measurements.

[0077] In an exemplary embodiment, Figure 2 As shown, the SFCW-TDR device is used to collect the soil conductivity of the target soil monitoring point in real time, including the following steps 201 to 203.

[0078] Step 201: Control the SFCW-TDR device to transmit an initial electromagnetic signal to the probe inserted into the target soil monitoring point. The initial electromagnetic signal is transmitted to the probe through a coaxial cable and a first apparent reflection coefficient and a second apparent reflection coefficient are obtained. The first apparent reflection coefficient is the reflection coefficient collected by the SFCW-TDR device of the first reflected signal transmitted back when the initial electromagnetic signal reaches the starting part of the probe after being transmitted. The second apparent reflection coefficient is the reflection coefficient collected by the SFCW-TDR device of the second reflected signal transmitted back when the initial electromagnetic signal reaches the terminal of the probe after being transmitted.

[0079] The probe start and probe end are the two ends of the probe.

[0080] The first apparent reflectance coefficient and the second apparent reflectance coefficient are both collected by the SFCW-TDR device.

[0081] The impedance of the probe's impedance converter matches the impedance of the coaxial cable.

[0082] The cable attenuation index of the coaxial cable used by the measurement probe in the frequency band used during the test is .

[0083] Specifically, Figure 3 This is a schematic diagram of a system that uses TDR equipment to measure soil moisture. and are the times when the electromagnetic signal is collected at one end and the other end of the probe, for and The time interval between The voltage amplitude of the initial electromagnetic signal output by the signal generator in the TDR device is collected by the signal collector at the point where the initial electromagnetic signal is sent (the voltage amplitude here is the superposition of the emitted electromagnetic signal and the reflected electromagnetic signal). The signal collector sends the collected voltage amplitude to the signal processor. The voltage amplitude of the electromagnetic signal received by the signal processor changes with time. Figure 4It is the time domain trace (TDR-Trace) obtained by measuring soil in real time using the stepped frequency domain continuous wave system time domain reflectometry (SFCW-TDR) technology. Its horizontal axis represents the time domain, which can easily obtain the apparent dielectric constant of the soil and realize the measurement of the soil volume moisture content. Its vertical axis represents the reflection coefficient of each point in the time domain along the transmission line during the propagation of electromagnetic signals. Accurate analysis of it can obtain the attenuation condition of the electromagnetic wave in the travel, thereby realizing the measurement of soil conductivity. Figure 4 middle The point coordinates are (15.85, 0.25), The point coordinates are (20.69, 0.18).

[0084] Apparent dielectric constant The expression is: ,in, is the propagation speed of electromagnetic waves in vacuum, is the probe length.

[0085] SFCW-TDR technology has strict requirements for the impedance design of the probe. Its manufacturing process is authorized by the patent number CN207866750U, entitled "A sensor suitable for measuring soil dielectric properties in a frequency domain stepping system". In order to avoid the shielding phenomenon caused by unnecessary reflection, this application uses a probe designed according to the 50 ohm impedance converter. Its traveling wave stroke analysis is as follows: Figure 5 As shown, Figure 5 Schematic diagram of soil traveling wave analysis measured by SFCW-TDR.

[0086] Step 202: Calculate an attenuation coefficient based on the first apparent reflectance coefficient and the second apparent reflectance coefficient, and use the calculated attenuation coefficient as a measured attenuation coefficient.

[0087] Specifically, the first apparent reflectance is , the second apparent reflection coefficient is , the measured attenuation coefficient can be obtained according to the first apparent reflection coefficient and the second apparent reflection coefficient.

[0088] Step 203 : Calculate the soil conductivity of the target soil monitoring point based on the measured attenuation coefficient, the apparent dielectric constant, and the plane electromagnetic wave equation.

[0089] Stepped-Frequency Continuous Wave (SFCW-TDR) is a soil moisture measurement technology. It has developed a series of soil moisture measurement instruments, including portable and handheld instruments suitable for field mobile monitoring, a series of automated online monitoring systems suitable for various fixed monitoring needs, and a series of supporting probes suitable for various measurement requirements. These instruments have been widely used. SFCW-TDR technology utilizes the more advanced and digital stepped-frequency continuous wave (SFCW) system for precise measurement of electromagnetic wave propagation time, the core of TDR technology. This technology provides more digital time- and frequency-domain electromagnetic information about the measured object.

[0090] This application utilizes soil moisture measurement equipment and its advanced, scientific measurement principles to develop an efficient and precise algorithm for accurate soil conductivity measurement. This algorithm is characterized by accuracy, speed, and stability. In particular, leveraging the extensive data accumulated during the application, a technical solution is proposed to simultaneously monitor soil volumetric moisture content and soil conductivity in real time, along with the field water holding capacity of the soil at the monitoring point, as measured during equipment installation, to obtain real-time soil conductivity (DC conductivity) at the monitoring point. This innovative and practical solution has significant practical application.

[0091] In an exemplary embodiment, the initial electromagnetic signal in step 201 is transmitted to the probe via a coaxial cable and a first apparent reflection coefficient and a second apparent reflection coefficient are obtained, including steps 301 to 303.

[0092] Step 301: Obtain a cable attenuation index according to the model and frequency domain interval of the coaxial cable.

[0093] Step 302: When the initial electromagnetic signal is transmitted to the starting part of the probe through the coaxial cable, a first reflection point is formed due to a change in impedance. After reflection occurs at the first reflection point, the first reflected signal is formed. The first reflected signal is collected by the SFCW-TDR device to obtain the first apparent reflection coefficient.

[0094] Step 303: When the initial electromagnetic signal reaches the starting part of the probe, a portion of the initial electromagnetic signal is reflected, and the remaining portion after reflection is a transmission signal. The transmission signal continues to transmit to the probe terminal, forming a second reflection point. Due to the open circuit formed, total reflection occurs at the second reflection point, and then passes through the probe, the first reflection point and the coaxial cable to form the second reflection signal. The second reflection signal is collected by the SFCW-TDR device to obtain the second apparent reflection coefficient.

[0095] Among them, step 303 specifically includes: when the initial electromagnetic signal reaches the starting part of the probe, the initial electromagnetic signal is shielded by the first reflection, and the remaining transmitted signal continues to transmit to the probe terminal, and is shielded and attenuated by the coaxial cable, the first reflection point and the probe itself along the way. The shielding and attenuation amplitude is ,in is the attenuation coefficient of electromagnetic waves propagating along the probe, called the measurement attenuation coefficient, is the length of the probe;

[0096] The open circuit formed by the probe terminal causes total reflection, which is the second reflection coefficient The reflected signal is then transmitted back through the probe, the first reflection point and the coaxial cable, and is received by the SFCW-TDR device to obtain the second apparent reflection coefficient. , with the relationship: .

[0097] Specifically, the receiving device can directly obtain the first and second apparent reflection coefficients. The attenuation index can be derived from the device's own parameters. The attenuation index is related to the cable model and the selected frequency range. The attenuation index is measured and provided by the manufacturer at the time of shipment. The coaxial cable length and probe length can be obtained simply by measurement. The first reflection coefficient can be obtained based on the first apparent reflection coefficient, the attenuation index, and the coaxial cable length. The measured attenuation coefficient is then derived based on the second apparent reflection coefficient, the first reflection coefficient, the attenuation index, the coaxial cable length, and the probe length.

[0098] In an exemplary embodiment, an attenuation coefficient is calculated based on the first apparent reflection coefficient and the second apparent reflection coefficient, and the calculated attenuation coefficient is used as the measured attenuation coefficient, including: calculating a first reflection coefficient based on the first apparent reflection coefficient, the first reflection coefficient being the reflection coefficient of the initial electromagnetic signal reflected by the first reflection point; and obtaining the measured attenuation coefficient based on the relationship between the second apparent reflection coefficient and the first reflection coefficient.

[0099] Calculating the first reflection coefficient according to the first apparent reflection coefficient specifically includes: according to the formula The first reflection coefficient is calculated.

[0100] in, is the first apparent reflection coefficient, is the first reflection coefficient, is the cable attenuation index, is the length of the coaxial cable. It is determined by the selected coaxial cable and the frequency band used for measurement and needs to be determined in advance. is the first reflection coefficient actually obtained.

[0101] The relationship between the second apparent reflectance and the first reflectance is expressed as: .

[0102] in, is the second apparent reflectance, To measure the attenuation coefficient, is the length of the probe.

[0103] In an exemplary embodiment, the measured attenuation coefficient can be derived from the electromagnetic wave plane propagation formula: Soil conductivity and relative dielectric constant The relationship between Substituting the apparent dielectric constant measured in step 102, the measured attenuation coefficient obtained above can be obtained. And the apparent dielectric constant to obtain the soil conductivity.

[0104] Substituting the attenuation coefficient into the plane electromagnetic wave equation, we get the conductivity equation, which is expressed as ,in, is the attenuation coefficient, is the conductivity, is the relative dielectric constant of the soil, and the apparent dielectric constant is substituted into the conductivity equation. , the calculated conductivity is the soil conductivity.

[0105] Specifically, the plane electromagnetic wave equation is related to the attenuation coefficient, so the plane electromagnetic wave equation is derived to obtain the conductivity. From the differential form of Maxwell's equations:

[0106] (1)

[0107] (2)

[0108] (3)

[0109] (4)

[0110] For homogeneous media, we have:

[0111] (5)

[0112] (6)

[0113] (7)

[0114] in, is the electric field strength, is the magnetic induction intensity, is the magnetic field strength, is the electric displacement vector, is the conduction current density, is the dielectric constant, is the magnetic permeability, is the conductivity, t is the time, is the resistivity.

[0115] The surrounding soil where the probe is buried is regarded as a passive space with zero free charge, that is, ρ = 0. Then, from formula (1) to formula (7), we can obtain:

[0116] (8)

[0117] (9)

[0118] (10)

[0119] (11)

[0120] From formula (8) and formula (9), we can get:

[0121]

[0122] Then by: And (10), we get:

[0123] (12)

[0124] Similar results are available:

[0125] (13)

[0126] For uniform plane electromagnetic waves (TEM waves), E is the direction of the electric field and H is the direction of the magnetic field, such as Figure 6 As shown:

[0127] It is only composed of and constitute,

[0128] Therefore, formula (12) and formula (13) can be simplified as:

[0129] (14)

[0130] (15)

[0131] For a sine wave signal, we can set:

[0132]

[0133]

[0134] Substituting into formula (14) and formula (15), we get:

[0135] (16)

[0136] (17)

[0137] in, is the angular frequency, is the electric field propagating along the y direction, is the magnetic field propagating along the z direction, and x represents the x-axis coordinate.

[0138] make:

[0139] (18)

[0140] in, is the intermediate parameter;

[0141] Then from formula (16) and formula (17), we can get:

[0142] (19)

[0143] (20)

[0144] From the definition of γ, we know that it is a complex number, so we can set:

[0145] (twenty one)

[0146] in, Is an imaginary unit.

[0147] Then the instantaneous form of the electric field and magnetic field of the electromagnetic wave propagating forward along the x-axis can be solved as follows:

[0148] (twenty two)

[0149] (twenty three)

[0150] It is easy to see that the amplitudes of the electric field and magnetic field are along the x-axis. Exponential decay, the change of its phase is determined by β, so α is called the decay constant and β is called the phase constant.

[0151] From formula (18) and formula (21), it is easy to solve:

[0152] (twenty four)

[0153] (25)

[0154] when hour, ,

[0155] Then from formula (24), we get:

[0156] (26)

[0157] in is the relative magnetic permeability, for linear homogeneous medium, , is the vacuum permeability, is the dielectric constant of vacuum, is the relative dielectric constant. From this we can obtain:

[0158] (27)

[0159] From the above derivation process, it can be seen that the conclusion formula (27) is derived under the following important premises: 1) The electromagnetic wave considered is a uniform plane electromagnetic wave (TEM wave), which is composed only of the component and composition; 2) The electromagnetic wave signal considered is a sine wave; 3) The test angular frequency , the conductivity of the measured medium and dielectric constant The relationship between .

[0160] In an exemplary embodiment, the relative dielectric constant in the conductivity equation is replaced by the apparent dielectric constant to obtain the conductivity formula ,in, is the conductivity, is the attenuation coefficient, is the apparent dielectric constant.

[0161] Specifically, The apparent dielectric constant is obtained by TDR measurement, and the relative dielectric constant of the soil is replaced by the apparent dielectric constant.

[0162] In an exemplary embodiment, the R-squared value (R²), also known as the coefficient of determination, is a statistic that measures the goodness of fit of a regression model and has a value between 0 and 1. The R-squared value indicates the portion of the variation in the dependent variable that can be explained by the independent variable. Simply put, the closer the R-squared value is to 1, the stronger the explanatory power of the model; the closer it is to 0, the weaker the explanatory power of the model. For example, if a regression model has an R-squared value of 0.8, this means that 80% of the variation in the dependent variable can be explained by the independent variable, while the remaining 20% ​​may be explained by other variables not included in the model or random factors.

[0163] Since the SFCW-TDR technology is to convert a set of acquired complex frequency domain signals into time domain by inverse Fourier transform, we can get:

[0164]

[0165]

[0166] in, is the lower frequency limit, is the upper frequency limit, is the frequency, is the amplitude, is the reflection coefficient, For time, is the phase, is the time point at which the reflection occurs, The time point of collection The emission signal occurs, () represents the inverse Fourier transform, is the inverse Fourier transform result.

[0167] The attenuation coefficient α collected is determined by the frequency arrive The frequencies between the two produce an average value of attenuation, set by the electromagnetic polarization spectrum of water and experimental results. MHz, and GHz, so the conductivity obtained is different from the DC conductivity. This application uses sodium chloride solution and a conductivity meter (such as DDS-307A) for fitting, and the results are shown in Table 1 below.

[0168] Table 1 Fitting results of sodium chloride solution and conductivity meter

[0169]

[0170] in, is the travel time, Ka is the dielectric constant, m1 is the starting reflection coefficient, m2 is the ending reflection coefficient, is the attenuation index, m1' is the reflection coefficient, is the attenuation coefficient, is the soil conductivity value, SFCW-TDR instrument is used to measure the conductivity value. Measure the conductivity value for the conductivity meter.

[0171] Figure 7 The linear relationship between the SFCW-TDR instrument and the conductivity meter is fitted by Figure 7The test results show a very good linear fit, with an R-squared value of up to 0.9999. This shows that the SFCW-TDR electrode method can be used to measure liquid conductivity in the laboratory.

[0172] Table 2 shows the results of measuring fluvo-aquic soil using the SFCW-TDR instrument using this application. The measurement results show that as the volumetric moisture content of the soil increases, the measured value increases continuously, but at the same time, the dry bulk density of the soil also has a certain influence on it. is the calculated soil conductivity, is the calculated soil electrical conductivity. The soil conductivity is obtained by taking air-dried soil samples using laboratory methods, and there are large differences between them. As can be seen from the error, There is good consistency with soil electrical conductivity.

[0173] Table 2 Results of conductivity measurements of fluvo-aquic soil using the SFCW-TDR instrument and the method of this application

[0174]

[0175] The experimental data of red soil electrical conductivity measured by the SFCW-TDR instrument are shown in Table 3.

[0176] Table 3 Experimental data of red soil electrical conductivity measured by SFCW-TDR instrument

[0177]

[0178] The experimental data of sand conductivity measured by SFCW-TDR instrument are shown in Table 4.

[0179] Table 4 Experimental data of sand conductivity measured by SFCW-TDR instrument

[0180]

[0181] Based on the same inventive concept, embodiments of the present application also provide a soil conductivity measuring device for implementing the aforementioned method for measuring soil conductivity. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more of the following embodiments of the soil conductivity measuring device can be found in the aforementioned method for measuring soil conductivity, and will not be further elaborated here.

[0182] In an exemplary embodiment, Figure 8 As shown, the present application provides a device for measuring soil conductivity including the following modules.

[0183] The soil dry capacity and field water holding capacity collection module is used to collect the soil dry capacity and field water holding capacity of the target soil monitoring point while installing the SFCW-TDR device at the target soil monitoring point.

[0184] A real-time data acquisition module is used to use the SFCW-TDR device to collect the apparent dielectric constant, soil volume moisture content and soil conductivity of the target soil monitoring point in real time; the apparent dielectric constant is used by the SFCW-TDR device to determine the soil conductivity.

[0185] The relative humidity factor calculation module is used to calculate the relative humidity factor based on the real-time collected soil volume moisture content, soil dry bulk density and field water holding capacity.

[0186] The soil conductivity calculation module is used to calculate the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the relative humidity factor obtained in real time.

[0187] In an exemplary embodiment, Figure 9 As shown, a device for measuring soil conductivity includes a probe, an analog circuit part and a digital circuit part.

[0188] The analog circuit part includes a signal source module, a signal coupling module, a signal receiver and an analog-to-digital conversion module, and the signal coupling module is connected to the probe.

[0189] The digital circuit part includes the CPU module, and the control circuit module, peripheral module, input module, output module, CPU module, digital signal processing module, communication module, power supply module and storage module connected to the CPU module.

[0190] The control circuit module is connected to the signal source module, the signal receiver and the analog-to-digital conversion module respectively through a digital-analog hybrid control bus, and the analog-to-digital conversion module is connected to the digital signal processing module.

[0191] The signal source module is used to transmit an initial electromagnetic signal to the probe, and the signal coupling module is used to send the initial electromagnetic signal and the signal returned by the probe to the analog-to-digital conversion module through the signal receiver. The signal returned by the probe includes a first reflected signal and a second reflected signal.

[0192] The analog-to-digital conversion module is used to convert the initial electromagnetic signal and the signal returned by the probe into digital signals and send them to the digital signal processing module to obtain three digital signals after digital signal processing. The three digital signals correspond to the initial electromagnetic signal, the first reflected signal and the second reflected signal respectively.

[0193] The digital signal processing module sends the three digital signals to the CPU module for calculation to obtain the soil conductivity.

[0194] The input module is used to input soil dry bulk density and field water capacity data collected manually. The output module is used to output soil electrical conductivity. The storage module is used to store the soil electrical conductivity output at each time point.

[0195] The power module is used to provide power to each module.

[0196] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 10 As shown. The computer device includes a processor, a memory, an input / output interface (I / O) and a communication interface. The processor, memory and input / output interface are connected via a system bus, and the communication interface is connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store data for measuring soil conductivity. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, a method for measuring soil conductivity is implemented.

[0197] Those skilled in the art will understand that Figure 10 The structure shown in the figure is merely a block diagram of a portion of the structure related to the solution of the present application and does not constitute a limitation on the computer device to which the solution of the present application is applied. A specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement. In an exemplary embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps of the above-mentioned method embodiments when executing the computer program.

[0198] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0199] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. In particular, any reference to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0200] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may be, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, data processing logic of programmable logic devices, and the like.

[0201] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0202] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for measuring soil electrical conductivity, characterized in that: The method for measuring soil electrical conductivity comprises: Installing the SFCW-TDR device at the target soil monitoring point and collecting the soil dry volume and field water holding capacity of the target soil monitoring point; The SFCW-TDR device is used to collect the apparent dielectric constant, soil volume moisture content and soil conductivity of the target soil monitoring point in real time; the apparent dielectric constant is used by the SFCW-TDR device to determine the soil conductivity; The relative humidity factor is calculated based on the real-time collected soil volumetric moisture content, soil dry bulk density and field capacity; Calculating the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the real-time obtained relative humidity factor; The relative humidity factor is calculated based on the real-time collected soil volume moisture content, soil dry bulk density and field water holding capacity, including: Soil mass moisture content = soil volume moisture content / soil dry bulk density; Relative humidity factor = soil mass moisture content / field capacity; Calculating the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the real-time obtained relative humidity factor, specifically including: Soil electrical conductivity = soil electrical conductivity / relative humidity factor.

2. The method for measuring soil electrical conductivity according to claim 1, wherein: The SFCW-TDR device is used to collect the soil conductivity of the target soil monitoring point in real time, specifically including: Controlling the SFCW-TDR device to transmit an initial electromagnetic signal to a probe inserted into the target soil monitoring point, wherein the initial electromagnetic signal is transmitted to the probe via a coaxial cable and a first apparent reflection coefficient and a second apparent reflection coefficient are obtained, wherein the first apparent reflection coefficient is the reflection coefficient collected by the SFCW-TDR device of a first reflected signal transmitted back when the initial electromagnetic signal reaches the starting portion of the probe after being transmitted, and the second apparent reflection coefficient is the reflection coefficient collected by the SFCW-TDR device of a second reflected signal transmitted back when the initial electromagnetic signal reaches the terminal portion of the probe after being transmitted; calculating an attenuation coefficient according to the first apparent reflection coefficient and the second apparent reflection coefficient, and using the calculated attenuation coefficient as a measured attenuation coefficient; The soil conductivity of the target soil monitoring point is calculated based on the measured attenuation coefficient, the apparent dielectric constant and the plane electromagnetic wave equation.

3. The method for measuring soil electrical conductivity according to claim 2, wherein: The initial electromagnetic signal is transmitted to the probe via a coaxial cable to obtain a first apparent reflection coefficient and a second apparent reflection coefficient, specifically comprising: Obtaining a cable attenuation index according to the model and frequency domain interval of the coaxial cable; When the initial electromagnetic signal is transmitted to the starting part of the probe through the coaxial cable, a first reflection point is formed. After reflection occurs at the first reflection point, a first reflection signal is formed. The first reflection signal is collected by the SFCW-TDR device to obtain the first apparent reflection coefficient; When the initial electromagnetic signal reaches the starting part of the probe, a portion of the initial electromagnetic signal is reflected, and the remaining portion after reflection is a transmission signal. The transmission signal continues to transmit to the probe terminal, forming a second reflection point, and undergoes total reflection at the second reflection point. Then, it passes through the probe, the first reflection point, and the coaxial cable to form a second reflection signal. The second reflection signal is collected by the SFCW-TDR device to obtain the second apparent reflection coefficient.

4. The method for measuring soil electrical conductivity according to claim 3, wherein: Calculating an attenuation coefficient according to the first apparent reflectance coefficient and the second apparent reflectance coefficient, and using the calculated attenuation coefficient as the measured attenuation coefficient, specifically includes: Calculating a first reflection coefficient based on the first apparent reflection coefficient, where the first reflection coefficient is a reflection coefficient of the initial electromagnetic signal reflected by the first reflection point; A measured attenuation coefficient is obtained according to the relationship between the second apparent reflection coefficient and the first reflection coefficient.

5. The method for measuring soil electrical conductivity according to claim 4, wherein: Calculating the first reflection coefficient according to the first apparent reflection coefficient specifically includes: according to the formula calculating the first reflection coefficient; in, is the first apparent reflection coefficient, is the first reflection coefficient, is the cable attenuation index, is the length of the coaxial cable; The relationship between the second apparent reflectance and the first reflectance is expressed as: ； in, is the second apparent reflectance, is the measured attenuation coefficient, is the length of the probe.

6. A device for measuring soil electrical conductivity, characterized in that: The device for measuring soil electrical conductivity comprises: Soil dry capacity and field water holding capacity collection module, used to collect soil dry capacity and field water holding capacity of the target soil monitoring point while installing the SFCW-TDR device at the target soil monitoring point; A real-time data acquisition module, configured to use the SFCW-TDR device to collect in real time the apparent dielectric constant, soil volume moisture content, and soil conductivity of the target soil monitoring point; the apparent dielectric constant is used by the SFCW-TDR device to determine the soil conductivity; Relative humidity factor calculation module, used to calculate relative humidity factor based on real-time collected soil volume moisture content, soil dry bulk density and field water holding capacity; A soil conductivity calculation module is used to calculate the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the relative humidity factor obtained in real time; The relative humidity factor is calculated based on the real-time collected soil volume moisture content, soil dry bulk density and field water holding capacity, including: Soil mass moisture content = soil volume moisture content / soil dry bulk density; Relative humidity factor = soil mass moisture content / field capacity; Calculating the soil conductivity of the target soil monitoring point in real time based on the soil conductivity and the real-time obtained relative humidity factor, specifically including: Soil electrical conductivity = soil electrical conductivity / relative humidity factor.

7. The device for measuring soil electrical conductivity according to claim 6, characterized in that: The device for measuring soil conductivity further comprises: a display terminal connected to the soil conductivity calculation module, and configured to display the real-time soil conductivity of each target soil monitoring point.

8. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method for measuring soil electrical conductivity according to any one of claims 1 to 5.

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