A non-invasive time domain reflection probe calibration method and system

Abstract

The invention discloses a non-invasive time domain reflection probe calibration method and system, which utilizes ethanol and deionized water mixed solutions of different volume ratios to calibrate the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe; utilizes NaCl solutions of different concentrations to calibrate the waveguide geometric dimension parameters of the non-invasive time domain reflection probe; prepares compacted soil samples with known different moisture contents and densities, and calibrates the correlation parameters of the dielectric constant and conductivity of the soil tested by the non-invasive time domain reflection probe with the moisture content and density. The method of the invention not only determines the test target medium sensitivity of the non-invasive time domain reflection probe, but also can obtain the waveguide length and geometric dimension parameters of the probe, and realizes the accurate test of the moisture content and density of the soil. The calibration method of the invention has clear theory, accurate calibration results, wide application range, reliable technology, convenient operation, strong practicality, and is a new means in the field of geotechnical engineering measurement instrument calibration technology.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering measurement instrument calibration, and in particular relates to a non-invasive time domain reflection probe calibration method and system. Background Art

[0002] As a technology that can simultaneously measure the moisture content and density of soil, time domain reflection technology is widely used in geotechnical engineering, soil science and other disciplines. With the promotion of engineering applications, time domain reflection probes, as an important component of time domain reflection technology, have developed rapidly. According to the test method, time domain reflection probes can be divided into invasive and non-invasive types. For invasive probes, they can be divided into fixed-point and penetration types according to the design form and test purpose. Fixed-point probes (such as coaxial, two-needle, two-plate and three-needle, etc.) can only be buried in the surface of the soil to test the moisture content and density of the soil at fixed points; penetration probes can continuously test the moisture content and density of soil at different depths. During the test process, the invasive probe needs to be inserted into the soil, causing the extrusion of the tested soil ("soil squeezing effect"), which in turn produces test errors. For non-invasive probes (such as circuit board type), since they do not need to be inserted into the soil during the test process, the "soil squeezing effect" problem of invasive probes is overcome. However, for non-intrusive time domain reflectometry probes, a pre-test calibration procedure is a prerequisite for ensuring the reliability of soil moisture and density test results.

[0003] At present, the calibration procedure of the known time domain reflection technology for testing soil moisture content and density is mainly for invasive probes. Its calibration procedure mainly includes: calibration of the waveguide length and geometric dimension parameters of the probe, and calibration of the correlation parameters of the soil dielectric constant and conductivity with moisture content and density. For the calibration of the invasive probe for testing soil moisture content and density, deionized water is first used to calibrate the waveguide length of the probe; then different concentrations of NaCl solution are used to calibrate the waveguide geometric dimension parameters of the probe; finally, compacted soil samples with known different moisture contents and densities are used to calibrate the correlation parameters of the soil dielectric constant and conductivity with moisture content and density. Although this calibration procedure is simple and mature, it is not suitable for non-invasive time domain reflection probes. This is mainly because the non-invasive time domain reflection probe attaches the waveguide to the circuit board substrate. The above design method prevents the probe from being inserted into the soil during the test, and also causes the probe's effective test range to include both the target soil and the circuit board substrate. Therefore, in order to accurately test the moisture content and density of the soil, a scientific calibration procedure needs to be designed to eliminate the influence of the circuit board substrate on the test results in the non-intrusive time domain reflection probe.

[0004] In summary, the existing calibration procedures for testing soil moisture content and density using invasive time domain reflection probes are relatively mature, but are not suitable for non-invasive time domain reflection probes. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a non-invasive time domain reflection probe calibration method and system in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that the non-invasive time domain reflection probe cannot accurately test the moisture content and density of the soil.

[0006] The present invention adopts the following technical solutions:

[0007] A non-invasive time domain reflection probe calibration method is disclosed. The method comprises the following steps: using a mixed solution of ethanol and deionized water in different volume ratios to calculate a test target medium weight coefficient and a waveguide length of the non-invasive time domain reflection probe; based on the test target medium weight coefficient, using NaCl solutions of different concentrations to calibrate the waveguide geometric dimension parameters of the non-invasive time domain reflection probe; preparing compacted soil samples with different known moisture contents and densities, and calibrating the correlation parameters of the dielectric constant and conductivity of the compacted soil samples with the moisture content and density based on the waveguide length and waveguide geometric dimension parameters of the non-invasive time domain reflection probe.

[0008] Specifically, step S1 is as follows:

[0009] S101, mixing ethanol and deionized water into at least 4 groups of mixed solutions with different concentrations, then using an invasive time domain reflection probe and a non-invasive time domain reflection probe to test the time domain reflection waveforms of the mixed solutions with different concentrations, and finally calculating the dielectric constant of the mixed solution according to the time domain reflection waveform tested by the invasive time domain reflection probe, and obtaining the propagation time Δt of the electromagnetic wave along the waveguide from the time domain reflection waveform tested by the non-invasive time domain reflection probe e ;

[0010] S102. According to the dielectric mixing model, regression analysis is performed on the effective dielectric constant tested by the non-invasive time domain reflection probe, the dielectric constant of the mixed solution tested by the invasive time domain reflection probe, and the dielectric constant of the circuit board substrate medium, and the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe are calculated.

[0011] Further, in step S102, the test target medium weight coefficient m and the waveguide length L of the non-intrusive time domain reflection probe are e They are:

[0012]

[0013]

[0014] Among them, K m is the dielectric constant of the circuit board substrate medium, and a and b are the fitting parameters of the dielectric hybrid model regression analysis calculation formula.

[0015] Specifically, step S2 is as follows:

[0016] S201. Considering a reasonable conductivity gradient, four or more NaCl solutions of different concentrations are prepared. Then, the time domain reflection waveform of the NaCl solution is tested at a constant temperature using an invasive time domain reflection probe and a non-invasive time domain reflection probe. The conductivity of the NaCl solution is calculated based on the time domain reflection waveform tested by the invasive time domain reflection probe, and the initial voltage V of the electromagnetic pulse is obtained from the time domain reflection waveform tested by the non-invasive time domain reflection probe. e0 And the stable voltage V after multiple reflections e∞ ;

[0017] S202. According to the conductivity hybrid model, a regression analysis is performed on the effective conductivity tested by the non-invasive time domain reflection probe, the conductivity tested by the invasive time domain reflection probe, and the conductivity of the substrate medium of the circuit board to calculate the waveguide geometric dimension parameter C of the non-invasive time domain reflection probe. e .

[0018] Further, in step S201, the conductivity EC of the NaCl solution tested by the invasive time domain reflectometry probe is s for:

[0019]

[0020] Where C is the waveguide geometric dimension parameter of the invasive time domain reflection probe, V0 is the initial voltage of the electromagnetic pulse tested by the invasive time domain reflection probe, V ∞ Test the stable voltage of electromagnetic pulse after multiple reflections for invasive time domain reflection probe.

[0021] Further, in step S202, the waveguide geometric dimension parameter C of the non-invasive time domain reflectometry probe e for:

[0022]

[0023] Among them, EC s The conductivity of NaCl solution tested by invasive time domain reflectometer.

[0024] Specifically, step S3 is as follows:

[0025] S301. The dried and sieved soil is configured as compacted soil samples covering the test moisture content range, and the number of compacted soil samples is greater than or equal to 4 groups. Then, in combination with the waveguide length and geometric size parameters of the non-invasive time domain reflection probe, the time domain reflection waveform of the compacted soil sample is tested using the non-invasive time domain reflection probe under constant temperature conditions, and the dielectric constant K of the compacted soil sample is calculated using the dielectric and conductivity hybrid model. s and electrical conductivity EC s ;

[0026] S302, using the calculation formula to calculate the soil dielectric constant K obtained by the dielectric and conductivity mixed model s and electrical conductivity EC s Regression analysis was performed with moisture content and density to obtain calibration parameters a1, b1, c1, and d1.

[0027] Furthermore, in step S301, the dielectric constant K of the compacted soil sample s and electrical conductivity EC s They are:

[0028]

[0029]

[0030] Among them, K e is the effective dielectric constant tested by the non-invasive time domain reflection probe, m is the test target medium weight coefficient of the non-invasive time domain reflection probe, K m is the dielectric constant of the circuit board substrate medium, V e0 The initial voltage of the electromagnetic pulse tested by the non-intrusive time domain reflection probe, V e∞ The stable voltage after multiple reflections of electromagnetic pulses is tested by non-invasive time domain reflection probe, C e are the waveguide geometric dimension parameters of the non-intrusive time domain reflection probe.

[0031] Furthermore, in step S302, the volume moisture content θ and soil density ρ of the compacted soil sample c The calculation is as follows:

[0032]

[0033]

[0034] In a second aspect, an embodiment of the present invention provides a non-invasive time domain reflectometry probe calibration system, comprising:

[0035] A calculation module, used for calculating a test target medium weight coefficient and a waveguide length of a non-invasive time domain reflection probe by using mixed solutions of ethanol and deionized water in different volume ratios;

[0036] A regression module is used to calibrate the waveguide geometric dimension parameters of the non-intrusive time domain reflection probe using the test target medium weight coefficient obtained by the calculation module and NaCl solutions of different concentrations;

[0037] The calibration module is used to prepare compacted soil samples with different known moisture contents and densities. Based on the waveguide length of the non-invasive time domain reflection probe obtained by the calculation module and the geometric size parameters calibrated by the regression module, the dielectric constant and conductivity of the compacted soil samples are calibrated with the associated parameters of moisture content and density.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] The invention discloses a non-invasive time domain reflection probe calibration method. The method comprises the following steps: using a mixed solution of ethanol and deionized water in different volume ratios to calibrate a test target medium weight coefficient and a waveguide length of the non-invasive time domain reflection probe; based on the test target medium weight coefficient, using NaCl solutions of different concentrations to calibrate the waveguide geometric dimension parameters of the non-invasive time domain reflection probe; finally, preparing compacted soil samples with different known moisture contents and densities, calibrating the associated parameters of the dielectric constant and conductivity of the compacted soil samples with the moisture content and density based on the waveguide length and the waveguide geometric dimension parameters of the non-invasive time domain reflection probe, utilizing the difference in dielectric properties of different media and adopting a dielectric / conductivity hybrid model, realizing the accurate calibration of the sensitivity and parameters of the non-invasive time domain reflection probe, and establishing the relationship between the dielectric constant and conductivity of the compacted soil sample and the moisture content and density based on the dielectric constant and conductivity of the compacted soil body tested by the non-invasive time domain reflection probe, thereby providing an effective path for indoor tests and field engineering applications of the non-invasive time domain reflection probe in the field of geotechnical engineering.

[0040] Furthermore, the use of mixed solutions of ethanol and deionized water in different volume ratios can not only make the dielectric constant of the solution used in the test have a certain interval, but also ensure the uniformity of the solution. Setting a reasonable concentration gradient and configuring more than or equal to 4 groups of solutions can ensure that the dielectric constant range of the mixed solution can include the dielectric constant of the soil to be tested, and ensure the representativeness of the regression analysis parameters. The time domain reflection technology is used to test the dielectric constant of the mixed solution of ethanol and deionized water and the propagation time of electromagnetic waves along the waveguide. The test is accurate, the principle is clear, the technology is mature, and the operation is simple. Combining the effective dielectric constant tested by the non-invasive time domain reflection probe, the dielectric constant of the mixed solution tested by the invasive time domain reflection probe, and the dielectric constant of the circuit board substrate medium, the dielectric mixed model regression analysis is used to calculate and obtain the test target medium weight coefficient m and waveguide length L of the non-invasive time domain reflection probe. e According to the characteristics of uneven distribution of electric potential field energy around the waveguide of non-invasive time domain reflection probe, the weight distribution theory is used to quantitatively solve the electric potential field energy weight coefficients in different areas around the waveguide, and the test target medium weight coefficient m and waveguide length L are obtained. e .

[0041] Furthermore, obtaining the test target medium weight coefficient m of the non-invasive time domain reflection probe can determine and exclude the influence of the circuit board substrate medium when the non-invasive time domain reflection probe tests the soil dielectric constant / conductivity; obtaining the waveguide length L of the non-invasive time domain reflection probe e The influence of manufacturing errors on the waveguide length can be eliminated to ensure the accuracy of the test results.

[0042] Furthermore, considering a reasonable conductivity gradient and configuring more than or equal to 4 groups of NaCl solutions with different concentrations can ensure that the conductivity range of the mixed solution can include the conductivity of the soil to be tested, ensuring the representativeness of the regression analysis parameters. The conductivity of the NaCl solution and the initial voltage V of the electromagnetic pulse are tested using time domain reflectometry. e0 And the stable voltage V after multiple reflections e∞ The test is accurate, the principle is clear, the technology is mature, and the operation is simple. Combining the effective conductivity tested by the non-invasive time domain reflection probe, the conductivity of the mixed solution tested by the invasive time domain reflection probe, and the conductivity of the circuit board substrate medium, the waveguide geometric size parameter C of the non-invasive time domain reflection probe is obtained by using the conductivity mixed model regression analysis. e According to the characteristics of uneven distribution of electric potential field energy around the waveguide of non-invasive time domain reflection probe, the weight distribution theory is used to quantitatively solve the electric potential field energy weight coefficients in different areas around the waveguide, and the waveguide geometric size parameter C is obtained. e .

[0043] Furthermore, the conductivity EC of NaCl solution was tested using an invasive time domain reflectometer. s The test is accurate, the principle is clear, the technology is mature, and the operation is simple. It can provide accurate conductivity values ​​of NaCl solutions with different concentrations and provide parameters for the regression analysis of the conductivity mixing model.

[0044] Furthermore, the waveguide geometric dimension parameters C of the non-intrusive time domain reflectometry probe are determined. e The comprehensive influence of the transmission line geometry and physical properties and the waveguide arrangement of the non-invasive time domain reflection probe on the conductivity calculation of the target medium can be determined, thereby improving the accuracy of the conductivity test results of the non-invasive time domain reflection probe.

[0045] Furthermore, the dried and sieved soil samples were configured as compacted soil samples covering the test moisture content range and greater than or equal to 4 groups. This process not only standardized the preparation steps of the compacted samples, but also provided support for the representativeness of the subsequent dielectric constant and conductivity calibration parameters. Using the non-invasive time domain reflection probe parameters calculated by calibration, the dielectric constant K of the compacted soil samples was tested and calculated under constant temperature conditions. s and electrical conductivity EC s The technology is mature and the theory is reliable. The influence of probe parameters and temperature on the dielectric constant and conductivity of the test soil sample is considered at the same time, which improves the accuracy and repeatability of the test results. The dielectric constant and conductivity are calibrated using the calculation formula, and the relationship between the dielectric constant and conductivity and the soil density and volume moisture content is established, providing representative calibration values ​​of parameters a1, b1, c1, and d1 for the indoor calibration test of the non-invasive time domain reflection probe.

[0046] Furthermore, the dielectric constant and conductivity of the compacted soil samples were tested and calculated using a non-invasive time domain reflection probe. The theoretical model was used to eliminate the influence of the dielectric properties of the circuit board substrate medium and the parameter errors of the probe / transmission line itself on the dielectric properties of the target medium to be tested, thereby achieving accurate calculation of the dielectric constant and conductivity of the compacted soil samples, providing a theoretical basis for the non-invasive time domain reflection probe to accurately test the dielectric properties of compacted soil samples.

[0047] Furthermore, by combining the dielectric constant and conductivity of compacted soil tested by the non-invasive time domain reflection probe with the calibrated parameters a1, b1, c1, and d1 to calculate the moisture content and density of the soil sample, the relationship between the dielectric constant and conductivity of compacted soil and the density and moisture content was established, providing theoretical support for indoor experiments and engineering applications of non-invasive time domain reflection probes in the field of geotechnical engineering.

[0048] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0049] In summary, the present invention can determine the test target medium sensitivity of the non-invasive time domain reflection probe, realize the accurate calibration of the probe parameters, and establish the relationship between the dielectric constant and conductivity of compacted soil tested by the non-invasive time domain reflection probe and the water content and density. The method and system have clear theory, accurate calibration results, wide application range, reliable technology, convenient operation, and strong practicality.

[0050] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 : is a diagram of the non-invasive time domain reflection device of the present invention, wherein (a) is a calibration diagram of the non-invasive time domain reflection device; (b) is an outline diagram of the non-invasive time domain reflection probe; (c) is a plan layout diagram of the non-invasive time domain reflection probe;

[0052] Figure 2 This is a graph showing the analysis results of the test target medium weight coefficient of the present invention;

[0053] Figure 3 is the waveguide geometric dimension parameter C of the present invention e Analysis result graph;

[0054] Figure 4 The present invention provides a non-invasive time domain reflection probe calibration method for soil dielectric constant and conductivity and water content and density correlation parameter calibration results, wherein: (a) water content; (b) density.

[0055] Among them, 1. Computer; 2. Data cable; 3. Time domain signal processor; 4. Coaxial cable; 5. Non-invasive time domain reflection probe; 6. Acrylic bucket; 7. Target test medium; 8. Epoxy resin; 9. Circuit board; 10. Waveguide. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0058] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0059] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects are in an "or" relationship.

[0060] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0061] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0062] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0063] The present invention provides a non-invasive time domain reflection probe calibration method, which uses a mixed solution of ethanol and deionized water in different volume ratios to calibrate the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe; uses NaCl solutions of different concentrations to calibrate the waveguide geometric size parameters of the non-invasive time domain reflection probe; prepares compacted soil samples with known different moisture contents and densities, and calibrates the associated parameters of the dielectric constant and conductivity of the soil tested by the non-invasive time domain reflection probe with the moisture content and density. The method of the present invention can not only determine the test target medium sensitivity of the non-invasive time domain reflection probe, but also obtain the waveguide length and geometric size parameters of the probe, and realize the accurate test of the moisture content and density of the soil. The steps are clear in theory, the calibration results are accurate, the application range is wide, the technology is reliable, the operation is convenient, and the practicability is strong. It can become a new means in the field of geotechnical engineering measurement instrument calibration technology.

[0064] See also Figure 1 The non-invasive time domain reflection device includes a computer 1, a data line 2, a time domain signal processor 3, a coaxial cable 4, a non-invasive time domain reflection probe 5, an acrylic barrel 6 and a target test medium 7; the non-invasive time domain reflection probe 5 includes an epoxy resin 8, a circuit board 9 and a waveguide 10.

[0065] The portable computer 1 is connected to the time domain signal processor 3 via a data transmission line 2, and then the time domain signal processor 3 is connected to the waveguide 10 of the non-invasive time domain reflection probe via a coaxial cable 4. Finally, the waveguide 10 is attached to the circuit board 9 and fits tightly to the target test medium 7.

[0066] In addition, epoxy resin 8 is provided at the end of the coaxial cable 4, and the waveguide 10 is a three-plate type, using a gold guide plate with a width of 1.5 mm and a thickness of 0.03 mm. The center distance between the two gold guide plates is 4 mm.

[0067] The present invention provides a non-invasive time domain reflection probe calibration method, comprising the following steps:

[0068] S1. Using an invasive time domain reflection probe and a non-invasive time domain reflection probe to test the time domain reflection waveforms of mixed solutions of ethanol and deionized water in different volume ratios (greater than or equal to 4 groups), then calculating the dielectric constant of the mixed solution according to the time domain reflection waveform, and finally using a dielectric mixing model to perform regression analysis on the dielectric constant / effective dielectric constant tested by the invasive / non-invasive time domain reflection probe and the dielectric constant of the substrate medium of the circuit board, and calculating the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe;

[0069] The time domain reflection waveforms of mixed solutions of ethanol and deionized water with different volume ratios (greater than or equal to 4 groups) were tested by invasive time domain reflection probe and non-invasive time domain reflection probe respectively. Then the dielectric constant of the mixed solution was calculated according to the time domain reflection waveform. Finally, the dielectric mixture model was used to perform regression analysis on the dielectric constant / effective dielectric constant tested by the invasive / non-invasive time domain reflection probe and the dielectric constant of the circuit board substrate medium. The test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe were calculated, which are as follows:

[0070] S101. Using mixed solutions of ethanol and deionized water in different volume ratios, setting a reasonable concentration gradient and configuring 4 or more mixed solutions, then using invasive and non-invasive time domain reflection probes to test the time domain reflection waveforms of the mixed solutions of ethanol and deionized water in different volume ratios, respectively, and finally calculating the dielectric constant of the mixed solution based on the time domain reflection waveform tested by the invasive time domain reflection probe, and obtaining the propagation time Δt of the electromagnetic wave along the waveguide from the time domain reflection waveform tested by the non-invasive time domain reflection probe. e ;

[0071] The calculation formula for the dielectric constant of the mixed solution tested by the invasive time domain reflection probe is as follows:

[0072]

[0073] Among them, K s is the dielectric constant of the mixed solution tested by the invasive time domain reflection probe, and c is the propagation speed of electromagnetic waves in vacuum (3×10 8 m / s), Δt is the propagation time of the electromagnetic wave along the waveguide tested by the intrusive time domain reflection probe, and L is the waveguide length of the intrusive time domain reflection probe.

[0074] S102. According to the dielectric mixing model, a regression analysis is performed on the effective dielectric constant expression of the non-invasive time domain reflection probe test, the dielectric constant of the mixed solution tested by the invasive time domain reflection probe, and the dielectric constant of the circuit board substrate medium, and the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe are calculated.

[0075] The waveguide length calculation formula for the dielectric hybrid model and non-intrusive time domain reflectometry probe is as follows:

[0076] K e n =mK s n +(1–m)K m n (2)

[0077]

[0078] Among them, K e The effective dielectric constant, K, is measured by the non-invasive time domain reflection probe. m is the dielectric constant of the substrate medium of the circuit board, m is the test target medium weight coefficient of the non-invasive time domain reflection probe, L e is the waveguide length of the non-invasive time domain reflection probe, a and b are the fitting parameters of the dielectric hybrid model regression analysis calculation formula, and n is the shape parameter of the target medium relative to the external electric field (-1≤n≤1). When the target medium and the capacitor are combined in parallel, n=1, and when the target medium and the capacitor are combined vertically, n=-1. The present invention adopts a parallel combination of the target medium and the capacitor, that is, n=1.

[0079] The dielectric mixed model regression analysis calculation formula and the test target medium weight coefficient m are calculated as follows:

[0080] y=aK s +b (4)

[0081]

[0082] The variables and constants in the dielectric hybrid model regression analysis calculation formula are calculated as follows:

[0083] y=(cΔt e ) 2 (6)

[0084] a=4mL e 2 (7)

[0085] b=4(1–m)L e 2 K m (8)

[0086] Among them, Δt e The non-intrusive time domain reflectometry probe measures the propagation time of electromagnetic waves along a waveguide.

[0087] S2. Use an invasive time domain reflection probe and a non-invasive time domain reflection probe to test the time domain reflection waveforms of NaCl solutions of different concentrations (greater than or equal to 4 groups), then calculate the conductivity of the NaCl solution according to the time domain reflection waveforms, and finally use a conductivity hybrid model to perform regression analysis on the conductivity / effective conductivity tested by the invasive / non-invasive time domain reflection probe and the conductivity of the circuit board substrate medium, and calculate the waveguide geometric size parameters of the probe;

[0088] The time domain reflection waveforms of NaCl solutions with different concentrations (greater than or equal to 4 groups) were tested by invasive and non-invasive time domain reflection probes respectively. The conductivity of the NaCl solution was then calculated based on the time domain reflection waveforms. Finally, the dielectric hybrid model was used to perform regression analysis on the conductivity / effective conductivity tested by the invasive / non-invasive time domain reflection probes and the dielectric conductivity of the circuit board substrate. The waveguide geometric size parameters of the probe were calculated, which are as follows:

[0089] S201. Considering a reasonable conductivity gradient, prepare NaCl solutions of different concentrations (greater than or equal to 4 groups), then use invasive and non-invasive time domain reflection probes to test the time domain reflection waveform of the NaCl solution at a constant temperature, and finally calculate the conductivity of the NaCl solution according to the time domain reflection waveform tested by the invasive time domain reflection probe, and obtain the initial voltage V of the electromagnetic pulse from the time domain reflection waveform tested by the non-invasive time domain reflection probe. e0 And the stable voltage V after multiple reflections e∞ ;

[0090] The conductivity calculation of the intrusive time domain reflection probe test is as follows:

[0091]

[0092] Among them, EC s is the conductivity tested by the invasive time domain reflection probe, C is the waveguide geometric dimension parameter of the invasive time domain reflection probe, V0 is the initial voltage of the electromagnetic pulse tested by the invasive time domain reflection probe, V ∞ Test the stable voltage of electromagnetic pulse after multiple reflections for invasive time domain reflection probe.

[0093] S202. According to the conductivity hybrid model, a regression analysis is performed on the effective conductivity expression of the non-invasive time domain reflection probe test, the conductivity of the invasive time domain reflection probe test, and the conductivity of the circuit board substrate medium, and the waveguide geometric dimension parameter C of the non-invasive time domain reflection probe is calculated. e .

[0094] Conductivity hybrid model and waveguide geometry parameters C of non-intrusive time domain reflectometry probe e The calculation is as follows:

[0095] EC e n =mEC s n +(1-m)EC m n (10)

[0096]

[0097] Among them, EC e Effective conductivity measured by non-invasive time domain reflectometry probe, EC m is the conductivity of the circuit board substrate medium, C e is the waveguide geometrical dimension parameter of the non-intrusive time domain reflectometry probe, V e0 The initial voltage of the electromagnetic pulse tested by the non-intrusive time domain reflection probe, V e∞ The non-intrusive time domain reflection probe is used to test the stable voltage of electromagnetic pulses after multiple reflections.

[0098] The conductivity mixed model regression analysis calculation is as follows:

[0099] y=cEC s (12)

[0100] Where c is the fitting parameter of the conductivity mixed model regression analysis calculation formula.

[0101] The variables and constants in the conductivity mixed model regression analysis calculation formula are as follows:

[0102]

[0103] c=C e (14)

[0104] S3. Use a non-invasive time domain reflection probe to test the time domain reflection waveform of compacted soil samples with different known moisture contents and densities (greater than or equal to 4 groups), and calculate the soil dielectric constant and conductivity in combination with the waveguide length and geometric size parameters of the non-invasive time domain reflection probe. Then use the relevant model to perform regression analysis on the soil dielectric constant and conductivity with moisture content and density to obtain the correlation parameters between the soil dielectric constant and conductivity with moisture content and density.

[0105] Combined with the waveguide length and geometric size parameters of the non-invasive time domain reflection probe, the non-invasive time domain reflection probe was used to test the time domain reflection waveform of compacted soil samples (greater than or equal to 4 groups) at different moisture contents, and the dielectric mixed model was used to calculate the dielectric constant and conductivity of the soil. Then, the relevant model was used to regress the dielectric constant and conductivity of the soil with the moisture content and density to obtain the associated parameters, which are as follows:

[0106] S301. By keeping the soil dry density constant and changing the moisture content, the dried and sieved soil is configured into compacted soil samples (greater than or equal to 4 groups) covering the test moisture content range. Then, in combination with the waveguide length and geometric size parameters of the non-invasive time domain reflection probe, the non-invasive time domain reflection probe is used to test the time domain reflection waveform of the compacted soil sample under constant temperature conditions, and the dielectric constant (K) of the compacted soil sample is calculated using the dielectric and conductivity hybrid model. s ) and electrical conductivity (EC s );

[0107] The dielectric constant and conductivity of the compacted soil sample were calculated as follows:

[0108]

[0109]

[0110] S302, using the calculation formula to calculate the soil dielectric constant K obtained by the dielectric and conductivity mixed model s and electrical conductivity EC s Regression analysis was performed with moisture content and density to obtain calibration parameters a1, b1, c1, and d1.

[0111] The calibration calculations for moisture content and density of compacted soil samples are as follows:

[0112]

[0113]

[0114] Among them, θ is the volume water content, a1, b1, c1, d1 are calibration parameters, ρ c is the soil sample density.

[0115] In addition, the effective dielectric constant for non-intrusive time domain reflectometry testing is calculated as:

[0116]

[0117] In another embodiment of the present invention, a non-invasive time domain reflection probe calibration system is provided, which can be used to implement the above-mentioned non-invasive time domain reflection probe calibration method. Specifically, the non-invasive time domain reflection probe calibration system includes a calculation module, a regression module and a calibration module.

[0118] The calculation module is used to calculate the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe using mixed solutions of ethanol and deionized water in different volume ratios;

[0119] A regression module is used to calibrate the waveguide geometric dimension parameters of the non-intrusive time domain reflection probe using the test target medium weight coefficient obtained by the calculation module and NaCl solutions of different concentrations;

[0120] The calibration module is used to prepare compacted soil samples with different known moisture contents and densities. Based on the waveguide length of the non-invasive time domain reflection probe obtained by the calculation module and the geometric size parameters calibrated by the regression module, the dielectric constant and conductivity of the compacted soil samples are calibrated with the associated parameters of moisture content and density.

[0121] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0122] Example

[0123] Non-intrusive time domain reflection probe: The waveguide of the non-intrusive time domain reflection probe calibrated this time is a three-plate type and uses a gold guide plate with a width of 1.5mm and a thickness of 0.03mm. The average length of the three metal plates is 173mm, and the center distance between the two gold guide plates is 4mm. In addition, the circuit board substrate medium of the probe is epoxy resin, with a conductivity of 0S / m and a dielectric constant of 3.1.

[0124] S1. Prepare a mixed solution of ethanol and deionized water according to a gradient of 0%, 20%, 40%, 60%, 80%, and 100% by volume. Then, use invasive and non-invasive time domain reflection probes to test the time domain reflection waveforms of the mixed solutions of ethanol and deionized water with different volume ratios under constant temperature conditions. Finally, calculate the dielectric constant of the mixed solution according to the time domain reflection waveform tested by the invasive time domain reflection probe according to formula (1), and obtain the propagation time Δt of the electromagnetic wave along the waveguide from the time domain reflection waveform tested by the non-invasive time domain reflection probe. eFurthermore, the dielectric hybrid model (2) is used in combination with the effective dielectric constant expression of the non-invasive time domain reflection probe test, the dielectric constant of the invasive time domain reflection probe test, and the dielectric constant of the circuit board substrate medium. The calculation formula (4) is regressed according to the dielectric hybrid model, and finally the test target medium weight coefficient m and waveguide length L of the non-invasive time domain reflection probe are calculated. e They are 0.47 and 175mm respectively.

[0125] Specifically, the test target medium weight coefficient analysis results of the non-invasive time domain reflection probe are as follows: Figure 2 shown.

[0126] S2. According to the electrical characteristics of the target medium, NaCl solutions with concentrations of 0.003, 0.005, 0.007, 0.009, 0.011, 0.013, 0.015, 0.017, and 0.019 mol / L are prepared. Then, the time domain reflection waveform of the NaCl solution is tested at a constant temperature using an invasive and non-invasive time domain reflection probe. Finally, according to the time domain reflection waveform tested by the invasive time domain reflection probe, the conductivity of the solution is calculated according to formula (9) and the initial voltage V of the electromagnetic pulse is obtained from the time domain reflection waveform tested by the non-invasive time domain reflection probe. e0 And the stable voltage V after multiple reflections e∞ Furthermore, the conductivity hybrid model (10) is used in combination with the effective conductivity expression of the non-invasive time domain reflection probe test, the conductivity of the invasive time domain reflection probe test, and the conductivity of the circuit board substrate medium. According to the conductivity hybrid model, the calculation formula (12) is regressed and analyzed, and finally the waveguide geometric size parameter C of the non-invasive time domain reflection probe is obtained. e is 0.0127. Specifically, the waveguide geometric dimension parameter C of the non-invasive time domain reflectometer is e The analysis results are as follows Figure 3 shown.

[0127] Example 1 Sandy soil:

[0128] Fujian standard sand, its maximum dry density is 1.638g / cm 3 , the minimum dry density is 1.349g / cm 3 , specific gravity is 2.67, D 10 0.11mm, D 50 0.16mm, D 60 It is 0.175mm.

[0129] S3, by keeping the soil dry density constant and changing the moisture content, the dried and sieved soil is configured into compacted soil samples with a volume moisture content of 5%, 10%, 15%, 20%, 25%, 30%, and 35%, and then combined with the waveguide length L of the non-intrusive time domain reflection probe e and geometrical dimension parameters C e , under constant temperature conditions, a non-invasive time domain reflection probe was used to test the time domain reflection waveform of the compacted soil sample and the soil dielectric constant and conductivity were calculated according to formulas (15) and (16). Further, the soil dielectric constant and conductivity calculated by formulas (15) and (16) were regressed with the moisture content and density using formulas (17) and (18), and the values ​​of the calibration parameters a1, b1, c1, and d1 were obtained as follows: 0.0976, –0.0879, 0.3005, and 0.2399, respectively. Specifically, the analysis results of the parameters associated with the dielectric constant and conductivity of sand and the moisture content and density using a non-invasive time domain reflection probe are as follows: Figure 4 As shown in (a) and (b).

[0130] Example 2 Clay:

[0131] Kaolin has clay, silt and sand contents of 59.96%, 40.51% and 0% respectively, and a specific gravity of 2.65; in addition, the liquid limit and plastic limit of the clay are 65.35% and 40.04% respectively.

[0132] S4. By keeping the soil dry density constant and changing the moisture content, the dried and sieved soil is configured into compacted soil samples with a volume moisture content of 5%, 10%, 15%, 20%, 25%, 30%, and 35%. Then, the waveguide length L of the non-intrusive time domain reflectometer is combined with the e and geometrical dimension parameter C e , under constant temperature conditions, a non-invasive time domain reflection probe is used to test the time domain reflection waveform of the compacted soil sample and the dielectric constant and conductivity of the soil are calculated according to equations (15) and (16).

[0133] Furthermore, the soil dielectric constant and conductivity calculated by equations (15) and (16) were regressed with the water content and density using equations (17) and (18), and the values ​​of the calibration parameters a1, b1, c1, and d1 were obtained as 0.0939, –0.0172, 0.4483, and 2.2868, respectively.

[0134] Specifically, the analysis results of the parameters related to clay dielectric constant and conductivity, water content and density using the non-invasive time domain reflectometry probe are as follows: Figure 4 (a) and Figure 4 (b) as shown.

[0135] In summary, the non-invasive time domain reflection probe calibration method and system of the present invention have the following characteristics:

[0136] (1) It has the advantages of clear theory, accurate calibration results, wide application range, reliable technology, convenient operation and strong practicality;

[0137] (2) Taking advantage of the differences in dielectric properties of different media, the dielectric hybrid model is used to determine the test target medium sensitivity of the non-intrusive time domain reflectometry probe. This indicator has a clear physical meaning and determines the test accuracy of the probe;

[0138] (3) Using the dielectric / conductivity hybrid model, the non-invasive time domain reflection probe waveguide length and geometric dimension parameters are accurately calibrated, which improves the accuracy of the non-invasive time domain reflection probe in testing the dielectric constant and conductivity of the target medium;

[0139] (4) The relationship between the dielectric constant and conductivity of compacted soil tested by a non-invasive time-domain reflectometry probe and the soil density and volumetric moisture content was established, providing theoretical support for indoor testing and engineering applications of the probe in geotechnical engineering.

[0140] (5) The calibration method of the existing time domain reflection probe has been expanded, which has strong applicability in indoor tests and field engineering, and can become a new means in the field of calibration technology of geotechnical engineering measurement instruments.

[0141] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0142] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0143] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0144] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0145] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A non-invasive time domain reflectometry probe calibration method, characterized in that: The following steps are involved: S1. Calculate the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe using mixed solutions of ethanol and deionized water in different volume ratios; The test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe are calculated using mixed solutions of ethanol and deionized water in different volume ratios as follows: S101, mixing ethanol and deionized water into at least 4 groups of mixed solutions with different concentrations, then using an invasive time domain reflection probe and a non-invasive time domain reflection probe to test the time domain reflection waveforms of the mixed solutions with different concentrations, and finally calculating the dielectric constant of the mixed solution according to the time domain reflection waveform tested by the invasive time domain reflection probe, and obtaining the propagation time Δt of the electromagnetic wave along the waveguide from the time domain reflection waveform tested by the non-invasive time domain reflection probe e ; S102. According to the dielectric mixing model, a regression analysis is performed on the effective dielectric constant tested by the non-invasive time domain reflection probe, the dielectric constant of the mixed solution tested by the invasive time domain reflection probe, and the dielectric constant of the substrate medium of the circuit board, and the test target medium weight coefficient and waveguide length of the non-invasive time domain reflection probe are calculated. and waveguide length They are: in, is the dielectric constant of the circuit board substrate medium, , Fitting parameters for dielectric hybrid model regression analysis calculation formula; S2. Based on the test target medium weight coefficient, the waveguide geometric dimension parameters of the non-intrusive time domain reflectometer are calibrated using NaCl solutions of different concentrations; specifically: S201. Considering a reasonable conductivity gradient, four or more NaCl solutions of different concentrations are configured. Then, the time domain reflection waveform of the NaCl solution is tested at a constant temperature using an invasive time domain reflection probe and a non-invasive time domain reflection probe. The conductivity of the NaCl solution is calculated based on the time domain reflection waveform tested by the invasive time domain reflection probe, and the initial voltage of the electromagnetic pulse is obtained from the time domain reflection waveform tested by the non-invasive time domain reflection probe. And the stable voltage after multiple reflections ; Conductivity of NaCl solution tested by invasive time domain reflectometry probe for: in, is the waveguide geometric dimension parameter of the invasive time domain reflectometer, Test the initial voltage of electromagnetic pulse for invasive time domain reflection probe, Test the stable voltage of electromagnetic pulse after multiple reflections for invasive time domain reflection probe; S202. According to the conductivity hybrid model, a regression analysis is performed on the effective conductivity tested by the non-invasive time domain reflection probe, the conductivity tested by the invasive time domain reflection probe, and the conductivity of the substrate medium of the circuit board to calculate the waveguide geometric dimension parameters of the non-invasive time domain reflection probe. ; Waveguide geometry parameters of non-intrusive time domain reflectometry probe for: in, The conductivity of NaCl solution tested by invasive time domain reflectometry probe; S3, preparing compacted soil samples with different known moisture contents and densities, and calibrating the associated parameters of the dielectric constant and conductivity of the compacted soil samples with the moisture content and density based on the waveguide length and waveguide geometric dimension parameters of the non-invasive time domain reflectometry probe; step S3 is specifically as follows: S301, configuring the dried and sieved soil into compacted soil samples covering the test moisture content range, the number of compacted soil samples is greater than or equal to 4 groups, and then combining the waveguide length and geometric size parameters of the non-invasive time domain reflection probe, using the non-invasive time domain reflection probe to test the time domain reflection waveform of the compacted soil sample under constant temperature conditions, and using the dielectric and conductivity hybrid model to calculate the dielectric constant of the compacted soil sample and conductivity ; Dielectric constant of compacted soil sample and conductivity They are: in, The effective dielectric constant measured by the non-invasive time domain reflection probe, is the test target medium weight coefficient of the non-intrusive time domain reflection probe, is the dielectric constant of the circuit board substrate medium, Testing the initial voltage of electromagnetic pulse for non-intrusive time domain reflection probe, It is a non-invasive time domain reflection probe that tests the stable voltage of electromagnetic pulses after multiple reflections. The waveguide geometrical dimension parameters of the non-intrusive time domain reflectometry probe; S302, using the calculation formula to calculate the soil dielectric constant obtained by the dielectric and conductivity mixed model and conductivity Regression analysis was performed with moisture content and density to obtain calibration parameters , , , ; Volumetric moisture content of compacted soil samples and soil density The calculation is as follows: 。 2. A non-invasive time domain reflectometry probe calibration system, characterized in that: The non-intrusive time domain reflection probe calibration system is applicable to the non-intrusive time domain reflection probe calibration method according to claim 1, comprising: A calculation module, used for calculating a test target medium weight coefficient and a waveguide length of a non-invasive time domain reflection probe by using mixed solutions of ethanol and deionized water in different volume ratios; A regression module is used to calibrate the waveguide geometric dimension parameters of the non-intrusive time domain reflection probe using the test target medium weight coefficient obtained by the calculation module and NaCl solutions of different concentrations; The calibration module is used to prepare compacted soil samples with different known moisture contents and densities. Based on the waveguide length of the non-invasive time domain reflection probe obtained by the calculation module and the geometric size parameters calibrated by the regression module, the dielectric constant and conductivity of the compacted soil samples are calibrated with the associated parameters of moisture content and density.

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