Double-column soil moisture content testing method

Abstract

The invention discloses a double-column soil moisture content testing method, belongs to the technical field of soil moisture content testing, and solves the problem that geological disasters cannot be accurately warned early due to the fact that only resistance serves as an index in an existing soil moisture content measuring method. Impedance spectrum measurement and resistance measurement are carried out on the monitored soil layer through the multiple electrodes, the impedance spectrum and the resistance are obtained, the impedance spectrum comprises an impedance modulus and a phase, richer information can be provided, meanwhile, the two soil testing columns are arranged in a bilateral symmetry mode, the distance between the two soil testing columns provides a larger transverse span, and the measurement accuracy is improved. Therefore, the data measured by the across electrode pair can better represent the average condition of the whole monitoring area. The comprehensive correlation coefficient is obtained through comprehensive calculation of the resistance correlation coefficient, the impedance modulus correlation coefficient and the phase correlation coefficient, and the calibrated soil moisture content distribution soil layer closest to the monitored soil layer can be judged.

Description

Technical Field

[0001] The invention relates to the technical field of soil moisture content testing, and in particular to a double-column soil moisture content testing method. Background Art

[0002] Soil moisture content refers to the amount of water contained in the soil per unit volume or weight. It is one of the key factors affecting plant growth, soil physical properties and ecological processes. Accurately measuring soil moisture content is of great significance for agricultural irrigation management, water resource protection, environmental protection and geological disaster early warning.

[0003] In the prior art, soil moisture measurement methods often rely on resistance measurement. The principle is that the increase in water content increases the conductivity of the soil and reduces the resistance. For example, the invention patent with publication number CN111257374B discloses a soil moisture and nitrogen content monitoring method, device, equipment and storage medium, which includes the steps of: inputting the voltage value, resistance value and capacitance value into the soil moisture and nitrogen content prediction model, and outputting the moisture content and nitrogen content corresponding to the soil to be tested; wherein the voltage value, resistance value and capacitance value of the monitored soil sample are used as training samples, and the moisture content and nitrogen content corresponding to the soil sample are used as training labels for training.

[0004] Although the invention obtains soil moisture content through resistance value, there is an inaccuracy problem. Soil is a multiphase system, including solid, liquid and gas. Resistance can only reflect the overall resistance encountered by the current, and cannot distinguish different forms of water, which limits its accuracy. Specifically, first, the relationship between soil resistivity and moisture content is nonlinear and affected by soil type. For example, in sandy soil, changes in moisture content have little effect on resistance; while in clay, slight changes in moisture content may cause significant fluctuations in resistivity. Temperature also affects resistance measurement results because it changes the rate of ion migration. Secondly, soil is composed of minerals, air, water, organic matter, etc., all of which affect electrical properties. Therefore, resistance changes may be the result of the combined action of multiple factors, not just changes in moisture content, so using resistance as an indicator alone is not enough to accurately reflect soil moisture content, and thus cannot accurately warn of geological disasters. Summary of the invention

[0005] In view of the above problems in the prior art, the present invention provides a double-column soil moisture testing method, which solves the problem that the existing soil moisture measurement method cannot accurately warn of geological disasters because it only uses resistance as an indicator.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A double-column soil moisture content testing method is provided, characterized in that it comprises the steps of: S1. Fix two soil test columns symmetrically in the monitored soil layer; wherein, a plurality of soil electrodes connected to the soil moisture measurement circuit through a wire selection circuit are arranged on two adjacent sides of the two soil test columns, and the soil moisture measurement circuit is remotely communicated with the host computer.

[0007] S2. Pair all soil electrodes into electrode pairs, number all electrode pairs and the measurement frequency points of the impedance spectrum measurement circuit in the soil moisture measurement, and use the host computer to make the soil moisture measurement circuit turn on one of the electrode pairs through the wire selection circuit.

[0008] S3. The impedance spectrum and phase between the selected conductive electrode pairs are measured respectively by the impedance spectrum measurement circuit and the bridge measurement circuit in the soil moisture measurement circuit, wherein the impedance spectrum includes an impedance modulus and a phase.

[0009] S4, repeat steps S2 to S3 until all electrode pairs are measured and obtain , and ,in, For the number The resistance between the electrode pairs, and They are numbered The electrode pairs and the frequency points are numbered The impedance magnitude and phase of

[0010] S5. According to , and Calculate the correlation coefficient with the calibration data.

[0011] Calibration data includes , and ,in, For the The soil moisture content distribution in the calibrated soil layer is numbered as The resistance between the electrode pairs, and Respectively The soil moisture content distribution in the calibrated soil layer is numbered as The electrode pairs and the frequency points are numbered The impedance magnitude and phase of

[0012] The correlation coefficients include , , and ; 、 and They are and The resistance correlation coefficient between and The impedance modulus correlation coefficient between and The phase correlation coefficient between pass , and Calculated to monitor soil layer and The comprehensive correlation coefficient of the calibrated soil moisture distribution soil layers.

[0013] S6. Acquisition The maximum value of , will be The corresponding calibrated soil moisture distribution layer is used as the actual soil moisture distribution layer of the monitoring soil layer.

[0014] S7. Based on the actual soil moisture content, soil layer distribution and geological structure of the monitored soil layer, the geological disaster warning level of the monitored soil layer is given by expert evaluation.

[0015] In this scheme, the impedance spectrum and resistance are obtained by making the two soil test columns symmetrical and selecting two soil electrodes on the two soil test columns for impedance spectrum measurement and resistance measurement. The impedance spectrum includes impedance mode and phase, which can provide richer information. At the same time, since the two soil test columns are symmetrically set, the distance between them provides a larger horizontal span, so that the data measured by the cross-electrode pairs between them can better represent the average conditions of the entire monitoring area. And the comprehensive correlation coefficient of this scheme is obtained by comprehensive calculation with the resistance correlation coefficient, the impedance mode correlation coefficient and the phase correlation coefficient, which is more convenient to determine the calibration soil moisture distribution layer closest to the monitored soil layer. The calibration soil moisture distribution layer is the benchmark value set for the calibration experiment. Considering the complex and changeable conditions of the actual monitored soil layer, the calibration experiment soil layer has stronger robustness. Even when the environmental conditions change, the strategy can be quickly adjusted by comparing the calibration data to ensure the continuity and stability of the monitoring work, which is convenient for experts to assess the accurate geological disaster warning level.

[0016] Furthermore, each soil test column includes a cylindrical shell, the bottom of the shell is a conical structure, a top cover is arranged on the top of the shell, a filling layer is arranged inside the shell, an electrode sandwich is arranged between the inner wall of the shell and the outer wall of the filling layer, a plurality of soil electrodes are fixed on one side of the electrode sandwich, one end of the plurality of soil electrodes respectively passes through a plurality of measuring holes on the outer wall of one side of the shell to contact the soil, and the other ends of the plurality of soil electrodes are connected to the soil moisture measurement circuit through electrode connecting wires. The soil test column is easy to install and maintain, and ensures the stability and repeatability of the measurement results.

[0017] Furthermore, a plurality of guide grooves are provided on the inner wall of each shell in the height direction, and a flange is provided on the outer wall of the filling layer to slide with the plurality of guide grooves. The design of the guide grooves and the flange enables the filling layer to slide up and down in the shell without rotating, thereby ensuring the consistency of the position of the soil electrode, improving the measurement accuracy, helping to reduce the error caused by the movement of the device, and enhancing the reliability of the test results.

[0018] Furthermore, a plurality of fixing holes for the lock buckles to pass through are provided on the outer wall of the conical structure at the bottom of each shell, and a plurality of guide holes are vertically provided inside the filling column. The bottoms of the plurality of guide holes are bent and connected to the plurality of fixing holes respectively, and the tips of the plurality of lock buckles enter the plurality of guide holes respectively and drill out from the plurality of fixing holes into the soil. The design of the fixing holes on the outer wall of the conical structure and the internal guide holes and lock buckles enables the entire device to be firmly embedded in the soil and remain stable even under soft or slippery surface conditions. For long-term monitoring, the lock buckle can prevent data deviation caused by equipment displacement.

[0019] Furthermore, the multiple measuring holes on the two adjacent sides of the two shells are evenly spaced and distributed in the height direction. The measuring holes are evenly distributed in the height direction to ensure the consistency of the soil contact area of ​​each electrode, thereby improving the comparability between the soil moisture content measurement values ​​at different depths.

[0020] Furthermore, a fixing plate for fixing the soil moisture measurement circuit with bolts is arranged on the top of the filling layer, and a connecting wire through-hole for passing a plurality of electrode connecting wires is opened in the middle of the fixing plate.

[0021] Furthermore, the soil moisture measurement circuit includes three wire gating circuits, and the three wire gating circuits include a first wire gating circuit, a second wire gating circuit, and a third wire gating circuit, all of which are connected to the microprocessor; the second wire gating circuit and the third wire gating circuit are respectively connected to the bridge measurement circuit and the impedance spectrum measurement circuit, and the bridge measurement circuit and the impedance spectrum measurement circuit are both connected to the first wire gating circuit; wherein the first wire gating circuit is used to select and conduct a plurality of soil electrodes located on the left soil test column; the second wire gating circuit and the third wire gating circuit are both used to select and conduct a plurality of soil electrodes located on the right soil test column. The setting of the three wire gating circuits allows for selective conduction of soil electrodes of different combinations, and is used in conjunction with the bridge measurement circuit and the impedance spectrum measurement circuit to achieve accurate measurement of soil moisture content between selected electrodes, enhance system flexibility and adaptability, and meet diverse measurement needs.

[0022] Further, The calculation method is:

[0023]

[0024]

[0025] in, The average resistance measured by all electrode pairs in the monitoring soil layer; for The product of is the total number of soil electrodes in a soil test column; For the The average resistance value of all electrode pairs in a calibrated soil moisture distribution layer.

[0026] Further, The calculation method is:

[0027]

[0028]

[0029] in, It is the average value of the impedance modulus measured by all electrode pairs in the monitoring soil layer; for The product of is the total number of soil electrodes in a soil test column; is the total number of frequency points in the impedance spectrum measurement circuit; For the The average impedance modulus measured by all electrode pairs in a calibrated soil moisture distribution layer.

[0030] Further, The calculation method is:

[0031]

[0032]

[0033] in, The average phase value measured by all electrode pairs in the monitored soil layer; for The product of is the total number of soil electrodes in a soil test column; is the total number of frequency points in the impedance spectrum measurement circuit; For the The average phase value measured by all electrode pairs in a calibrated soil moisture distribution layer.

[0034] The invention discloses a double-column soil moisture content testing method, which has the following beneficial effects: The present invention obtains impedance spectrum and resistance by making two soil test columns symmetrical and selecting two soil electrodes on the two soil test columns to measure impedance spectrum and resistance respectively. The impedance spectrum includes impedance mode and phase, which can provide richer information. At the same time, since the two soil test columns are symmetrically arranged, the distance between the two provides a larger lateral span, so that the data measured by the cross-electrode pairs between them can better represent the average condition of the entire monitoring area. The comprehensive correlation coefficient is obtained by comprehensive calculation with the resistance correlation coefficient, the impedance mode correlation coefficient and the phase correlation coefficient, and can better judge the calibrated soil moisture distribution soil layer closest to the monitored soil layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the process of the double-column soil moisture content test method; Figure 2 It is a schematic diagram of the structure of two soil test columns; Figure 3 This is a schematic diagram of the internal structure of the soil test column; Figure 4 is a schematic diagram of the structure of the shell; Figure 5 is a cross-sectional view of the housing; Figure 6 Schematic diagram of the structure of the electrode sandwich; Figure 7 It is the structural schematic diagram of soil electrode; Figure 8 It is a top view of the filling layer; Fig. 9 is the internal schematic diagram of the filling layer; Fig.10 is a structural schematic diagram of a fixed plate; Fig.11 The circuit diagram of the soil moisture measurement circuit is shown below; Fig.12 A circuit diagram of a wire gating circuit; Fig.13 is a circuit diagram of an impedance spectrum measurement circuit; Fig.14 This is the circuit diagram of the bridge measurement circuit; Wherein: 1. Shell; 5. Electrode interlayer; 7. Soil electrode; 8. Electrode connecting wire; 9. Conductor; 12. Impedance spectrum measurement circuit; 13. Bridge measurement circuit; 14. Microprocessor; 15. Communication interface; 16. Power supply circuit; 30. Filling layer; 40. Fixing plate; 50. Top cover. DETAILED DESCRIPTION

[0036] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0037] Example 1 This embodiment provides a double-column soil moisture testing method, the purpose of which is to solve the problem that the existing soil moisture measurement method cannot accurately reflect the soil moisture content because it only uses resistance as an indicator. It will be demonstrated in detail below.

[0038] A double column soil moisture test method, reference Figure 1 , including the steps of: S1. Reference Figure 2 , two soil test columns are fixed symmetrically in the monitored soil layer; wherein, a plurality of soil electrodes 7 connected to the soil moisture measurement circuit through a wire selection circuit are arranged on two adjacent sides of the two soil test columns, and the soil moisture measurement circuit is remotely communicated with the host computer.

[0039] S2. Pair all soil electrodes 7 into electrode pairs, number all electrode pairs and the measurement frequency points of the impedance spectrum measurement circuit 12 in soil moisture measurement, and use the host computer to make the soil moisture measurement circuit conduct one of the electrode pairs through the wire selection circuit.

[0040] In this implementation, since the two soil test columns are symmetrically arranged, the distance between them provides a larger horizontal span, so that the data measured by the electrode pair across the columns can better represent the average conditions of the entire monitoring area. The double-column measurement across the columns expands the current path, reduces the impact of local anomalies on the overall measurement results, and improves the accuracy and stability of the data.

[0041] S3. The impedance spectrum measurement circuit 12 and the bridge measurement circuit 13 in the soil moisture measurement circuit respectively measure the impedance spectrum and phase between the selected conductive electrode pairs, where the impedance spectrum includes an impedance modulus and a phase.

[0042] S4, repeat steps S2 to S3 until all electrode pairs are measured and obtain , and ,in, For the number The resistance between the electrode pairs, and They are numbered The electrode pairs and the frequency points are numbered The impedance magnitude and phase of

[0043] S5. According to , and Calculate the correlation coefficient with the calibration data.

[0044] Calibration data includes , and ,in, For the The soil moisture content distribution in the calibrated soil layer is numbered as The resistance between the electrode pairs, and Respectively The soil moisture content distribution in the calibrated soil layer is numbered as The electrode pairs and the frequency points are numbered The impedance magnitude and phase of

[0045] The correlation coefficients include , , and ; 、 and They are and The resistance correlation coefficient between and The impedance modulus correlation coefficient between and The phase correlation coefficient between pass , and Calculated to monitor soil layer and The comprehensive correlation coefficient of the calibrated soil moisture distribution soil layers.

[0046] S6. Acquisition The maximum value of , will be The corresponding calibrated soil moisture distribution layer is used as the actual soil moisture distribution layer of the monitoring soil layer.

[0047] S7. Based on the actual soil moisture content, soil layer distribution and geological structure of the monitored soil layer, the geological disaster warning level of the monitored soil layer is given by expert evaluation.

[0048] As a further solution of this embodiment, The calculation method is:

[0049]

[0050]

[0051] in, The average resistance measured by all electrode pairs in the monitoring soil layer; for The product of is the total number of soil electrodes in a soil test column; For the The average resistance value of all electrode pairs in a calibrated soil moisture distribution layer.

[0052] The calculation method is:

[0053]

[0054]

[0055] in, It is the average value of the impedance modulus measured by all electrode pairs in the monitoring soil layer; is the total number of frequency points in the impedance spectrum measurement circuit; For the The average impedance modulus measured by all electrode pairs in a calibrated soil moisture distribution layer.

[0056] The calculation method is:

[0057]

[0058]

[0059] in, The average phase value measured by all electrode pairs in the monitored soil layer; For the The average phase value measured by all electrode pairs in a calibrated soil moisture distribution layer.

[0060] The calculation method is: .

[0061] The comprehensive correlation coefficient is obtained by comprehensive calculation with the resistance correlation coefficient, impedance module correlation coefficient and phase correlation coefficient. It is more convenient to determine the calibration soil moisture distribution layer that is closest to the monitored soil layer. The calibration soil moisture distribution layer is the benchmark value set for the calibration experiment. Considering the complex and changeable conditions of the actual monitored soil layer, the calibration experimental soil layer has stronger robustness. Even when the environmental conditions change, the strategy can be quickly adjusted by comparing the calibration data to ensure the continuity and stability of the monitoring work, which is convenient for experts to assess the accurate geological disaster warning level.

[0062] Specifically, refer to Figure 3 As the specific structure of the soil test column, each soil test column includes an outer shell 1, an electrode interlayer 5, a plurality of soil electrodes 7, a filling layer 30, a fixing plate 40 and a top cover 50.

[0063] Housing 1, reference Figure 4 . The outer shell 1 is a cylindrical structure with a hollow interior, and the bottom of the outer shell 1 is a conical structure. The outer shell 1 is made of a material with good stress resistance. In this embodiment, steel is used and manufactured by a casting process. A plurality of circular measuring holes are provided on the outer wall surface of the cylindrical structure. The plurality of measuring holes on the outer shell 1 are evenly spaced along the height direction, and the plurality of measuring holes on the two soil test columns are symmetrically arranged. The measuring holes are evenly distributed in the height direction, which ensures the consistency of the soil contact area of ​​the soil electrode 7 in each measuring hole, thereby improving the comparability between the measured values ​​of soil moisture content at different depths. Reference Figure 4 ,in Figure 4 2-1, 2-2, 2-3 and 2-N are all measuring holes.

[0064] The outer wall of the conical structure at the bottom of the housing 1 is provided with a plurality of fixing holes for the lock to pass through. In this embodiment, three fixing holes are arranged in a circular pattern. The plane formed by the three fixing holes is perpendicular to the axis of the housing 1, and the distance between adjacent measuring holes is 120°. Figure 4 ,in Figure 4 3-1 and 3-2 are both fixing holes.

[0065] Electrode sandwich 5, reference Figure 6 The electrode sandwich 5 is a cylindrical structure, made of insulating material, and polytetrafluoroethylene is used in this embodiment; the outer diameter of the electrode sandwich 5 is smaller than the inner diameter of the upper half of the shell 1, so that the electrode sandwich 5 can be inserted into the shell 1 and fit closely to the shell 1. The height of the electrode sandwich 5 is slightly higher than the height of the uppermost and lowermost measuring holes, and an electrode mounting hole is opened at the measuring hole position corresponding to the shell 1. Figure 6 , where 6-1, 6-2, 6-3 and 6-N in the figure are electrode mounting holes.

[0066] The electrode mounting hole opening may be circular, and its radius is less than 0.8 times the radius of the measuring hole of the housing 1. The electrode interlayer 5 is fixed with a plurality of soil electrodes 7 through the electrode mounting hole, one end of the plurality of soil electrodes 7 respectively passes through the plurality of measuring holes on the housing 1 to contact the soil, and the other ends of the plurality of soil electrodes 7 are electrically connected to the soil moisture measurement circuit through the electrode connecting wire 8.

[0067] Soil electrode 7, reference Figure 7 The soil electrode 7 is circular, smaller than the electrode mounting hole, and is glued to the electrode mounting hole by glue; one end of the soil electrode 7 is connected to the electrode connecting wire 8, which is a connecting wire with a conductor 9 in the middle and an insulating layer on the outside. The insulating layers are peeled off at both ends, one end is welded to the inside of the electrode, and the other end is fixed to the electrode connector with a screw; the electrode connecting wire 8 is led out from the top, passes through the connecting wire hole from the top, and is fixed to the electrode connector, and the electrode connector is electrically connected to the wire selection circuit through a connecting cable.

[0068] Filling layer 30, reference Fig. 9 The filling layer 30 is made of engineering plastics and has the same shape as the inner part of the outer shell 1. It is installed in the outer shell 1 and is used to fix the electrode interlayer 5 in the outer shell 1. The inner part of the filling layer 30 is vertically provided with multiple guide holes. The bottoms of the multiple guide holes are bent and connected to the multiple fixing holes respectively. The tips of the multiple lock buckles enter the multiple guide holes respectively and drill out from the multiple fixing holes into the soil. The lock buckle is a strip-shaped cylinder with a pointed end; it is made of a material with good stress resistance and a certain deformation ability. The lock buckle is used to pass through the guide hole and embed into the soil. Reference Fig. 9 , Fig. 9 31-1 is the guide hole. The fixing holes on the outer wall of the conical structure and the design of the internal guide hole and the lock enable the entire device to be firmly embedded in the soil and remain stable even in soft or slippery surface conditions. For long-term monitoring, the lock can prevent data deviation caused by equipment displacement. In order to facilitate the filling layer 30 to be loaded into the housing 1, refer to 5 and Figure 8 In this embodiment, a plurality of guide grooves are provided on the inner wall of the housing 1 along the height direction, and a flange that is slidably matched with the plurality of guide grooves is provided on the outer wall of the filling layer 30 . Figure 8 32-1, 32-2, 32-3 and 32-4 are flanges. Figure 5 4-1, 4-2, 4-3 and 4-4 are all guide grooves. The design of the guide groove and the flange allows the filling layer 30 to slide up and down in the housing 1 without rotating, ensuring the consistency of the position of the soil electrode 7, improving the measurement accuracy, helping to reduce the error caused by the movement of the device, and enhancing the reliability of the test results. In this embodiment, there are three guide holes, and they are arranged in a circle at intervals of °.

[0069] Fixing plate 40, reference Fig.10 The fixing plate 40 is located on the top of the filling layer 30 and is used to fix the fixing plate 40 of the measurement circuit with bolts. A connection wire through-hole for multiple electrode connection wires 8 to pass through is opened in the middle of the fixing plate 40. The fixing plate 40 is a disc structure with an outer thread on the outside, and the outer thread matches the inner thread on the top of the outer shell 1; the fixing plate 40 is fixed to the top of the outer shell 1 by the outer thread on the outside engaging with the inner thread on the top of the outer shell 1. The fixing plate 40 has four circuit board fixing holes for installing the circuit board of the soil moisture measurement circuit. Reference Fig.10 , Fig.10 42-1, 42-2, 42-3 and 42-4 are all holes for fixing the circuit board.

[0070] Top cover 50, ref. Figure 3 The top cover 50 matches the external thread on the top of the housing 1 and is used to be installed on the top of the housing 1 and seal the housing 1 . This embodiment provides a method for installing two soil test columns, comprising the steps of: Step 1: Put the electrode sandwich 5 on the filling layer 30 and put it into the shell 1; when putting it in, the soil electrode 7 corresponds to the measuring hole of the shell 1 and is concentric with the soil electrode 7, and the soil electrode 7 does not contact the shell 1; Step 2: Use a hammer to knock the housing 1 into the monitored soil layer; Step 3: With the pointed ends of the three lock buckles facing downward, use hammers to knock them through the three guide holes - and through the fixing holes of the outer shell 1 - into the soil layer, so that the lock buckle parts are in the soil, locking the outer shell 1; the tops of the lock buckles are knocked into the inner layer.

[0071] Step 4: After passing the connecting wire 9 through the connecting wire hole, install it to the electrode connector; and install the fixing plate 40 on the housing 1.

[0072] Step 5: Connect the electrode connector to the circuit board; Step 6: Mount the circuit board of the measuring circuit on the fixing plate 40; Step 7: Install the top cover 50 onto the housing 1; Step 8: Repeat steps 1 to 8 to fix the two soil test columns symmetrically in the monitoring soil.

[0073] Specifically, as a specific circuit of the soil moisture measurement circuit of this embodiment, refer to Fig.12 The soil moisture measurement circuit includes three wire gating circuits, and the three wire gating circuits include a first wire gating circuit, a second wire gating circuit, and a third wire gating circuit, each of which is connected to the microprocessor 14. The microprocessor 14 is electrically connected to the power supply circuit 16.

[0074] The second wire gating circuit and the third wire gating circuit are connected to the bridge measurement circuit 13 and the impedance spectrum measurement circuit 12 respectively, and the bridge measurement circuit 13 and the impedance spectrum measurement circuit 12 are both connected to the first wire gating circuit. Among them, the first wire gating circuit is used to select and conduct multiple soil electrodes 7 located on the left soil test column; the second wire gating circuit and the third wire gating circuit are both used to select and conduct multiple soil electrodes 7 located on the right soil test column. The setting of the three wire gating circuits allows the soil electrodes 7 of different combinations to be selectively conducted, and is used in conjunction with the bridge measurement circuit 13 and the impedance spectrum measurement circuit 12 to achieve accurate measurement of the soil moisture content between the selected electrodes, enhance the flexibility and adaptability of the system, and meet diverse measurement needs.

[0075] refer to Fig.11 , Fig.12 11-1, 11-2 and 11-3 are respectively the first wire gating circuit, the second wire gating circuit and the third wire gating circuit, and the microprocessor 14 is respectively connected to the first wire gating circuit, the second wire gating circuit and the third wire gating circuit through a control cable. Fig.11 17-1, 17-2 and 17-3 are all control cables.

[0076] Preferably, the first wire gating circuit is used to select the left soil electrode, and the second wire gating circuit and the third wire gating circuit are used to select the right soil electrode. Figure 2 2-L1, 2-L2, 2-L3 and 2-LN are left soil electrodes, 2-R1, 2-R2, 2-R3 and 2-RN are right soil electrodes, that is, the value of N in this embodiment is 4.

[0077] In this embodiment, the communication interface 15 adopts the M905R-433 wireless transparent transmission module of Zhengzhou Yiling Electronic Technology Co., Ltd.; the microprocessor 14 chip adopts the microprocessor 14 of Atmel company model AR91RM9200. The impedance spectrum measurement circuit can refer to the impedance spectrum measurement circuit in the invention patent with publication number CN103105418B, a concrete monitoring detector with steel bars as electrodes and its monitoring and detection method.

[0078] refer to Fig.12The first wire gating circuit, the second wire gating circuit, and the third wire gating circuit are all composed of 7 chips MM74HC4051 of National Semiconductor Corporation, U1~U7; and 1 chip MM74HC4052 of National Semiconductor Corporation, U8. A1, B1, C1, A2, B2, C2, A3, B3, C3, A4, B4, C4, A5, B5, C5, A6, B6, C6, A7, B7 of 12 in the figure are connected to the microcontroller to control the input address code; 54-a, 54-b are short-circuited to 55-a, 55-b of the bridge measurement circuit 13, or short-circuited to POLE1, POLE2 of the impedance spectrum measurement circuit 12.

[0079] Impedance spectrum measurement circuit 12 reference Fig.13 The chip of the impedance spectrum measurement circuit 12 is the chip AD5933 of Analog Devices, Inc. of the United States. Fig.13 In the embodiment, POLE1, POLE2 and both ends of 54-a, 54-b are short-circuited. SCL, SDA are connected to the impedance measurement control interface of the measurement control microprocessor 14.

[0080] Bridge measurement circuit 13 reference Fig.14 , Fig.14 55-a, 55-b in the gate circuit are respectively short-circuited to 54-A, 54-A in the gate circuit; 57 interface is short-circuited to the microprocessor 14, wherein Fig.14 The two clock signals CLK-1 and CLK-2 are provided by the microprocessor 14.

[0081] Example 2 This embodiment is further limited on the basis of Embodiment 1. The specific improvement lies in proposing a method for making a soil layer for calibrating soil moisture content distribution. For other parts not mentioned, refer to Embodiment 1 or the prior art.

[0082] This embodiment provides a method for calibrating soil moisture distribution soil layers, including the following steps: (1) Extract soil samples from the test points of the monitoring soil layer; (2) Dry the soil sample and grind it with a grinder; (3) Take dried soil and water and mix them with a mixer; (4) Place soil samples in multiple test chambers according to the uniform humidity and stratified humidity methods, and install humidity sensors. Use the humidity sensors to calibrate the soil moisture content distribution of two types of soil layers: uniform humidity and stratified humidity.

[0083] The length, width and height of the test chamber are all 1 meter. Uniform humidity means that all soil has the same humidity. Layered humidity means that the humidity increases in layers from bottom to top.

[0084] In this embodiment, ten kinds of calibrated soil moisture distribution soil layers with uniform humidity of 5%, 10%, 15%, ..., 50% were prepared respectively; there were seven kinds of calibrated soil moisture distribution soil layers with stratified humidity, all of which were set in 20 cm thick layers. The stratified humidity is shown in Table 1: Table 1 Layered humidity of soil layers for seven calibrated soil moisture content distributions

[0085] Therefore, this embodiment has a total of 17 calibrated soil moisture distribution soil layers, namely .

[0086] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. Double-column soil moisture test method, characterized in that: Includes steps: S1. Two soil test columns are fixed symmetrically in the monitored soil layer; wherein, two adjacent sides of the two soil test columns are provided with a plurality of soil electrodes connected to a soil moisture measurement circuit through a wire gating circuit, and the soil moisture measurement circuit is remotely communicated with a host computer; S2, pairing all soil electrodes into electrode pairs, numbering all electrode pairs and the measurement frequency points of the impedance spectrum measurement circuit in the soil moisture measurement, and making the soil moisture measurement circuit conduct one of the electrode pairs through the wire gating circuit through the host computer; S3, respectively measuring the impedance spectrum and phase between the selected conductive electrode pairs through the impedance spectrum measurement circuit and the bridge measurement circuit in the soil moisture measurement circuit, wherein the impedance spectrum includes an impedance modulus and a phase; S4, repeat steps S2 to S3 until all electrode pairs are measured and obtain , and ,in, For the number The resistance between the electrode pairs, and They are numbered The electrode pairs and the frequency points are numbered Impedance modulus and phase; S5. According to , and Calculate the correlation coefficient with the calibration data; Calibration data includes , and ,in, For the The soil moisture content distribution in the calibrated soil layer is numbered as The resistance between the electrode pairs, and Respectively The soil moisture content distribution in the calibrated soil layer is numbered as The electrode pairs and the frequency points are numbered Impedance modulus and phase; The correlation coefficients include , , and ; 、 and They are and The resistance correlation coefficient between and The impedance modulus correlation coefficient between and The phase correlation coefficient between pass , and Calculated to monitor soil layer and Comprehensive correlation coefficient of the calibrated soil moisture distribution layer; S6. Acquisition The maximum value of , will be The corresponding calibrated soil moisture distribution soil layer is used as the actual soil moisture distribution soil layer of the monitoring soil layer; S7. Based on the actual soil moisture content, soil layer distribution and geological structure of the monitored soil layer, the geological disaster warning level of the monitored soil layer is given by expert evaluation.

2. The double-column soil moisture content testing method according to claim 1, characterized in that: Each soil test column includes a cylindrical shell, the bottom of the shell is a conical structure, a top cover is arranged on the top of the shell, a filling layer is arranged inside the shell, an electrode sandwich is arranged between the inner wall of the shell and the outer wall of the filling layer, a plurality of soil electrodes are fixed on one side of the electrode sandwich, one end of the plurality of soil electrodes respectively passes through a plurality of measuring holes on the outer wall of one side of the shell to contact the soil, and the other ends of the plurality of soil electrodes are connected to the soil moisture measurement circuit through electrode connecting wires.

3. The double-column soil moisture content testing method according to claim 2 is characterized in that: A plurality of guide grooves are provided on the inner wall of each shell along the height direction, and a flange which is slidably matched with the plurality of guide grooves is provided on the outer wall of the filling layer.

4. The double-column soil moisture content testing method according to claim 2 is characterized in that: A plurality of fixing holes for locking buckles to pass through are provided on the outer wall of the conical structure at the bottom of each shell, a plurality of guide holes are vertically arranged inside the filling column, the bottoms of the plurality of guide holes are bent and respectively connected with the plurality of fixing holes, and the tips of the plurality of locking buckles respectively enter the plurality of guide holes and drill out from the plurality of fixing holes into the soil.

5. The double-column soil moisture content testing method according to claim 2, characterized in that: A plurality of measuring holes on two adjacent side surfaces of the two shells are evenly spaced and distributed along the height direction.

6. The double-column soil moisture content testing method according to claim 2 is characterized in that: A fixing plate for fixing a soil moisture measurement circuit with bolts is arranged on the top of the filling layer, and a connecting wire through-hole for passing a plurality of electrode connecting wires is opened in the middle of the fixing plate.

7. The double-column soil moisture content testing method according to claim 2, characterized in that: The soil moisture measurement circuit includes three wire gating circuits, and the three wire gating circuits include a first wire gating circuit, a second wire gating circuit, and a third wire gating circuit, all of which are connected to the microprocessor; The second wire gating circuit and the third wire gating circuit are connected to the bridge measurement circuit and the impedance spectrum measurement circuit respectively, and the bridge measurement circuit and the impedance spectrum measurement circuit are both connected to the first wire gating circuit; Among them, the first wire gating circuit is used to select and conduct multiple soil electrodes located on the left soil test column; the second wire gating circuit and the third wire gating circuit are both used to select and conduct multiple soil electrodes located on the right soil test column.

8. The double-column soil moisture content testing method according to claim 1, characterized in that: The calculation method is: in, The average resistance measured by all electrode pairs in the monitoring soil layer; for The product of is the total number of soil electrodes in a soil test column; For the The average resistance value of all electrode pairs in a calibrated soil moisture distribution layer.

9. The double-column soil moisture content testing method according to claim 1, characterized in that: The calculation method is: in, It is the average value of the impedance modulus measured by all electrode pairs in the monitoring soil layer; for The product of is the total number of soil electrodes in a soil test column; is the total number of frequency points in the impedance spectrum measurement circuit; For the The average impedance modulus measured by all electrode pairs in a calibrated soil moisture distribution layer.

10. The double-column soil moisture content testing method according to claim 1, characterized in that: The calculation method is: in, The average phase value measured by all electrode pairs in the monitored soil layer; for The product of is the total number of soil electrodes in a soil test column; is the total number of frequency points in the impedance spectrum measurement circuit; For the The average phase value measured by all electrode pairs in a calibrated soil moisture distribution layer.

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