High-precision method for measuring soil moisture in different soil profiles

Abstract

The application provides a high-precision soil moisture determination method for different soil profiles, which comprises the following steps: horizontally placing a combined bending probe into different soil profiles; generating stable high-frequency electromagnetic waves by a high-frequency electromagnetic field generator; transmitting the high-frequency electromagnetic waves along the combined bending probe to the probe end and returning; receiving the returned high-frequency electromagnetic waves by a signal transmission module and a signal acquisition and analysis device; analyzing the high-frequency electromagnetic waveforms by the signal acquisition and analysis device; and obtaining the returning time of the high-frequency electromagnetic waves after penetrating through the different soil profiles ， The dielectric constant of the different soil profiles is calculated, the relationship between the soil dielectric constant and the soil volume water content is established, and thus the soil volume water content is obtained. The combined bending probe is horizontally placed, does not disturb the soil, and detects the soil water content at different soil depths. The effective length of the combined bending probe is expanded to 1.5 times of that of the original straight probe, the dielectric constant measurement precision is greatly improved, and the accuracy of the soil water content measurement of the soil layers with uneven soil moisture distribution is improved.

Description

Technical Field

[0001] This invention relates to the field of soil moisture measurement technology, and in particular to a high-precision method for measuring soil moisture in different soil profiles without disturbing the soil body, for measuring soil moisture in soils with uneven soil composition and moisture content distribution. Background Technology

[0002] Currently, soil moisture detection commonly employs the time-domain reflectometry (TDRS) probe method, primarily using traditional linear probes suitable for detecting soil moisture content at different depths. In smart agriculture, multiple soil moisture probes are needed at different soil profiles (e.g., 20-30cm in the topsoil layer, and 60cm, 90cm, 120cm in other layers). However, conventional TDRS probes are often inserted vertically, reflecting the overall soil moisture value within the probe's length. This fails to reflect soil moisture values ​​at different soil profiles and is inefficient for measuring moisture in soil profiles with uneven soil composition and moisture content distribution. The insertion of traditional linear TDRS probes into the soil damages the soil structure, and the limited electromagnetic field distribution area makes the soil dielectric system measured by the TDRS inaccurate, thus affecting the accuracy of soil moisture measurement. Therefore, it is necessary to develop a new method for measuring moisture in soil profiles with uneven soil moisture content distribution. Summary of the Invention

[0003] To address the technical problems of traditional time-domain reflectometry (TDRS) linear probes damaging soil structure and having limited electromagnetic field distribution areas that affect the accuracy of moisture measurements across different soil profiles, this invention proposes a high-precision method for measuring soil moisture across different soil profiles. This method can be used for accurate moisture measurement in soil profiles with uneven soil composition and moisture content distribution. It overcomes the limitations of existing TRS methods in terms of the spatial distribution of electromagnetic fields transmitted along the probe, which leads to large errors in measuring moisture data for unevenly distributed soils.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A method for high-precision measurement of soil moisture in different soil profiles includes: placing identical combined curved probes horizontally into different soil profiles; a high-frequency electromagnetic field generator generating stable high-frequency electromagnetic waves under the action of a power supply unit; the high-frequency electromagnetic waves being transmitted along the combined curved probes to the probe ends and then returning; the returning high-frequency electromagnetic waves being received by a signal acquisition and analysis unit through a signal transmission module; the signal acquisition and analysis unit analyzing the waveform of the received high-frequency electromagnetic waves to obtain the return time of the high-frequency electromagnetic waves after passing through different soil profiles; calculating the dielectric constant of different soil profiles; and then establishing the relationship between the soil dielectric constant and the soil volumetric water content to obtain the soil volumetric water content.

[0005] Preferably, any combination of curved probes includes probe A and probe B, both of which are bent into a J-shape, with the ends of probe A and probe B positioned opposite each other; the probes of probe A and probe B are completely embedded in the soil.

[0006] Preferably, probe A and probe B are both connected to a high-frequency electromagnetic field generator via a coaxial cable. The high-frequency electromagnetic field generator is connected to a power supply unit and a signal transmission module, respectively. The signal transmission module is connected to a signal acquisition and analysis unit.

[0007] Preferably, both probe A and probe B are connected to a coaxial cable via a connector.

[0008] Preferably, the combined bending probes of different soil profiles are all connected to a high-frequency electromagnetic field generator, and the high-frequency signal generator is connected to a signal acquisition and analysis unit through a signal transmission module.

[0009] Preferably, the high-frequency electromagnetic field generator emits high-frequency electromagnetic waves to the inner conductor of the coaxial cable, and transmits them to different soil profile combination bending probes through the connector. After passing through the soil along the different soil profile combination bending probes, the high-frequency electromagnetic waves are received and analyzed by the signal acquisition and analysis unit.

[0010] Preferably, the return time is ,in, L To combine the effective length of the bending probe, ε The dielectric constant of the soil, c It is the speed of light.

[0011] Preferably, after calibrating the system parameters using a numerical optimization algorithm for non-uniform transmission lines, the spectrum of high-frequency electromagnetic waves is fitted to inversely determine the dielectric constant of the soil sample.

[0012] Preferably, the soil dielectric constant is calculated based on the waveform of the high-frequency electromagnetic wave, and the relationship between the soil dielectric constant and the volumetric water content is plotted. The least squares method is used to fit the data to obtain the soil volumetric water content.

[0013] The beneficial effects of this invention are as follows: Compared with traditional time-domain reflectometry probes, the probe of this invention changes the traditional method of vertical insertion. The combined curved probe is placed horizontally, without disturbing the soil, allowing for the detection of soil moisture content in different soil profiles. Because the effective length of the combined curved probe is increased to 1.5 times that of the original probe, this invention improves the accuracy of soil dielectric constant measurement. Simultaneously, the high-frequency electromagnetic wave distribution area is wider, improving the accuracy of moisture content measurement in soil profiles with uneven moisture distribution. Although the bending at the end of the combined curved probe causes a slight loss of electromagnetic field, compared with a straight probe of the same equivalent length, the increased effective probe length correspondingly prolongs the high-frequency electromagnetic wave propagation time along the probe, thus improving the accuracy of calculating the high-frequency electromagnetic wave propagation time. Furthermore, the bending of the combined curved probe results in a wider electromagnetic field distribution than a straight probe, thus greatly improving the accuracy of soil moisture measurement for soils with uneven soil composition and moisture content distribution. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a structural diagram of the overall measurement system of the present invention.

[0016] Figure 2 The signal acquisition and analysis device of the present invention receives the response spectrum of high-frequency electromagnetic waves, wherein a) is the traditional time-domain reflection method and b) is the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1As shown, a method for high-precision measurement of soil moisture in different soil profiles includes: horizontally and undisturbedly placing a combined curved probe into different soil profiles; a high-frequency electromagnetic field generator generating stable high-frequency electromagnetic waves under the action of a power supply unit; the high-frequency electromagnetic waves being transmitted along the combined curved probe to the probe tip and then returning; the returning high-frequency electromagnetic waves being received by a signal acquisition and analysis unit through a signal transmission module; and the signal acquisition and analysis unit analyzing the spectrum of the received high-frequency electromagnetic waves to obtain the return time of the high-frequency electromagnetic waves after passing through the soil. t The soil dielectric constant is calculated, and then the relationship between the soil dielectric constant and soil volumetric water content is established to obtain the soil volumetric water content. The signal transmission module modulates the electromagnetic waves generated by the high-frequency electromagnetic field generator with the high-frequency electromagnetic waves returned from the combined bending probe, ensuring that the high-frequency electromagnetic waves are transmitted without distortion. The signal acquisition and analysis unit analyzes the spectrum of the returned high-frequency electromagnetic waves to calculate the soil dielectric constant, and finally calculates the soil water content.

[0019] During operation, the combined bending probe is inserted undisturbed into different soil profiles at varying depths, ensuring that the entire probe is submerged. The power supply unit is activated, triggering the high-frequency electromagnetic field generator, which initiates the operation of the combined bending probe. The collected time-domain reflected wave spectrum signal is then transmitted back to the signal acquisition and analysis unit, which transmits the information to the computer. Based on the high-frequency electromagnetic wave spectrum, the soil dielectric constant is retrieved, and the time return value is calculated. ,in, L The effective length of the probe. ε The dielectric constant of the soil, c The speed of light is used. Then, the soil dielectric constant and soil moisture content are fitted using the least squares method to obtain the soil volumetric water content.

[0020] Furthermore, any combination of curved probes includes probe A and probe B, both of which are curved in a J-shape. Probe A and probe B are symmetrically distributed, with their ends facing each other. Probe A and probe B are completely buried in the soil. The combined curved probes of this invention are buried parallel to each other in the soil, and the probes are completely submerged, greatly increasing the effective length of the probes and overcoming the problem of inaccurate soil moisture measurement caused by soil agitation, thus achieving accurate detection of soil moisture content in different soil layers. The distance between probe A and probe B can be set according to the size of the electromagnetic field sensitive area, typically 5-10 cm. The length of the curved portion is half the length of the straight section, increasing the electromagnetic radiation area of ​​the two fixed probes A and B, averaging the dielectric coefficient of soil with uneven moisture content in the soil profile, and improving the accuracy of soil moisture measurement.

[0021] The response spectrum of the signal acquisition and analysis unit receiving high-frequency electromagnetic waves is as follows: Figure 2As shown, it is obvious that the transmission time along probe A and probe B in the high-precision soil moisture measurement method for different soil profiles in this invention is longer than that of the traditional straight probe. The high-precision soil moisture measurement method and structure composed of symmetrically distributed embedded probes A and B in this invention changes the traditional method of vertically inserting probes. The combined curved probes are horizontally inserted into the soil without disturbing the soil, thus improving the measurement of soil moisture in soils with uneven moisture content distribution.

[0022] In any combination of bending probes, probes A and B are connected to a high-frequency electromagnetic field generator via a coaxial cable. The high-frequency electromagnetic field generator is connected to both the power supply unit and the signal transmission module. The signal transmission module is connected to the signal acquisition and analysis unit. The power supply unit provides power to the high-frequency electromagnetic field generator, the signal transmission module, and the signal acquisition and analysis unit.

[0023] The coaxial cable, from the outside in, mainly consists of an outer insulating sheath, an outer conductor, an inner insulating sheath, and an inner conductor. The coaxial cable is connected to a high-frequency electromagnetic field generator and, through a signal transmission module, to a signal acquisition and analysis unit. Probes A and B of the combined bent probe are completely buried in the soil. The high-frequency electromagnetic field generator emits high-frequency electromagnetic waves into the coaxial cable to detect the soil dielectric constant. After propagating through the soil, the high-frequency electromagnetic waves are received and analyzed by the signal acquisition and analysis unit via the signal transmission module. Due to the bent probe, the electromagnetic field distribution is wider than with a straight probe, making this method suitable for measuring soil moisture in soils with uneven composition and moisture content distribution. Since the effective length of the probe is increased to 1.5 times that of the original probe, the propagation time of the high-frequency electromagnetic wave along the probe is correspondingly extended, thus improving the accuracy of the calculation of the high-frequency electromagnetic wave propagation time along the probe.

[0024] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for high-precision determination of soil moisture in different soil profiles, characterized in that, include: The same combination of curved probes is horizontally placed into different soil profiles. The high-frequency electromagnetic field generator generates stable high-frequency electromagnetic waves under the action of the power supply unit. The high-frequency electromagnetic waves are transmitted along the combination of curved probes to the end of the probes and then return. The returned high-frequency electromagnetic waves are received by the signal acquisition and analysis unit through the signal transmission module. The signal acquisition and analysis unit analyzes the waveform of the received high-frequency electromagnetic waves, obtains the return time of the high-frequency electromagnetic waves after passing through different soil profiles, calculates the dielectric constant of different soil profiles, and then establishes the relationship between the soil dielectric constant and the soil volumetric water content, thereby obtaining the soil volumetric water content. Any combination of curved probes includes probe A and probe B, both of which are bent into a J-shape, with the ends of probe A and probe B positioned opposite each other; the probes of probe A and probe B are completely embedded in the soil; the length of the curved portion is half the length of the straight portion. After calibrating the system parameters using a numerical optimization algorithm for non-uniform transmission lines, the spectrum of high-frequency electromagnetic waves was fitted to deduce the dielectric constant of the soil sample.

2. The method for high-precision determination of soil moisture in different soil profiles according to claim 1, characterized in that, Both probe A and probe B are connected to a high-frequency electromagnetic field generator via coaxial cables. The high-frequency electromagnetic field generator is connected to a power supply unit and a signal transmission module, respectively. The signal transmission module is connected to a signal acquisition and analysis unit.

3. The method for high-precision determination of soil moisture in different soil profiles according to claim 2, characterized in that, Both probe A and probe B are connected to a coaxial cable via connectors.

4. The method for high-precision determination of soil moisture in different soil profiles according to claim 3, characterized in that, The combined bending probes for different soil profiles are all connected to a high-frequency electromagnetic field generator, and the high-frequency signal generator is connected to a signal acquisition and analysis unit through a signal transmission module.

5. The method for high-precision determination of soil moisture in different soil profiles according to claim 3 or 4, characterized in that, The high-frequency electromagnetic field generator emits high-frequency electromagnetic waves to the inner conductor of the coaxial cable, and transmits them to the combined bending probes of different soil profiles through the connector. After passing through the soil, the high-frequency electromagnetic waves are received and analyzed by the signal acquisition and analysis unit.

6. The method for high-precision determination of soil moisture in different soil profiles according to claim 5, characterized in that, The return time is Where L is the effective length of the combined bending probe, ε is the soil dielectric constant, and c is the speed of light.

7. The method for high-precision determination of soil moisture in different soil profiles according to claim 6, characterized in that, The soil dielectric constant is calculated based on the waveform of high-frequency electromagnetic waves, and the relationship between the soil dielectric constant and volumetric water content is plotted. The least squares method is used to fit the data to obtain the soil volumetric water content.

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