Device for measuring soil moisture characteristic curve

Abstract

The utility model discloses a soil moisture characteristic curve measuring device which comprises a container, a tensiometer system, a sensing system and a weighing device, the container is of a cylindrical structure and is used for being filled with a soil sample, the tensiometer system comprises a clay head and a scale assembly, one end of the clay head is connected with the container, and the other end of the clay head is connected with the scale assembly. The sensing system is partially arranged in the soil sample, the sensing system is used for acquiring volumetric water content data of the soil sample, the weighing equipment is positioned at the bottom of the container, and a tray is arranged between the weighing equipment and the container. In the application, the tensiometer system, the sensing system and the weighing equipment are combined, so that the measurement error and the data docking difficulty can be reduced, an operator performs a filling and compacting process indoors, the collected soil sample is restored to a state approximate to the original volume weight, the representativeness and reliability of a test result are improved, and the measurement accuracy is improved. And meanwhile, automatic recording and wireless data transmission means are adopted, so that continuous, accurate and long-period observation of data is realized.

Description

Technical Field

[0001] This utility model relates to the field of soil testing technology, and in particular to a device for measuring soil moisture characteristic curves. Background Technology

[0002] The Soil Water Characteristic Curve (SWCC) is a core tool describing the functional relationship between soil matrix potential (water energy state) and soil water content (water quantity). It is fundamental to the study of soil hydrodynamic properties and crucial for accurately understanding soil's water-holding and releasing capacity. This curve is widely used in soil hydrological model parameterization, farmland water use optimization, soil improvement measure evaluation, and eco-hydrological process simulation. Accurately obtaining the SWCC is of great significance for understanding soil water-holding capacity, the dynamic distribution of root-available water, and the prediction of rainfall infiltration and evaporation processes.

[0003] In related technologies, pressure membrane instruments, pressure plate equipment, tension meters and other devices are usually used to measure the data step by step, and the data points are manually matched and fitted in the later stage of the experiment to obtain information on soil matrix potential and water content.

[0004] However, traditional devices are not only cumbersome to use for measurement, but also make it difficult to capture subtle process differences when the matrix potential or water content changes rapidly. This increases experimental uncertainty and error. Furthermore, they cannot accurately reproduce the soil structure and bulk density in the field, thus affecting the accuracy of the test data. Utility Model Content

[0005] To address the problems of cumbersome measurement processes and the difficulty in capturing minute process differences when matrix potential or moisture content changes rapidly, leading to increased experimental uncertainty and error, and the inability to accurately reproduce field soil structure and bulk density, thus affecting the accuracy of test data, this invention provides a device for measuring soil moisture characteristic curves. The technical solution adopted is as follows:

[0006] An apparatus for measuring soil moisture characteristic curves, comprising:

[0007] A container, having a cylindrical structure, is used to fill soil samples;

[0008] A tension meter system is disposed on the side wall of the container. The tension meter system includes a clay head and a scale assembly. One end of the clay head is connected to the container, and the other end is connected to the scale assembly.

[0009] A sensing system, connected to the container, is partially placed inside the soil sample, and is used to acquire volumetric water content data of the soil sample.

[0010] A weighing device is located at the bottom of the container, and a tray is provided between the weighing device and the container.

[0011] In some embodiments, the sidewall of the container is provided with a first through hole and a second through hole, the first through hole and the second through hole being arranged radially symmetrically with respect to the container, and the container communicating with the interior of the clay head through the first through hole.

[0012] In some embodiments, the container is provided with a plurality of holes, and the holes penetrate the bottom of the container in the height direction of the container;

[0013] The bottom of the container is provided with several legs, which are arranged at intervals along the circumference of the container.

[0014] In some embodiments, the tray has a U-shaped cross-section.

[0015] In some embodiments, the sensing system is a time-domain reflectometry sensor, which consists of a sensitive element and a signal conditioning and conversion circuit. The signal conditioning and conversion circuit is electrically connected, and the sensitive element is used to detect the moisture content of the soil sample.

[0016] In the assembled state, the sensitive element is inserted into the soil sample through the second through hole.

[0017] In some embodiments, the time-domain reflectometry sensor is positioned parallel to the radial direction of the container.

[0018] In some embodiments, the container is made of transparent plexiglass.

[0019] In some embodiments, the scale assembly includes a mercury column and a scale, the mercury column being fixed to the scale, and the interior of the mercury column communicating with the interior of the container through the clay head.

[0020] In some embodiments, the apparatus for determining soil moisture characteristic curves further includes a camera device mounted on the side of the container away from the scale assembly.

[0021] The technological advancements achieved by this invention compared to existing technologies are as follows:

[0022] This invention combines a tensiometer system, a sensing system, and a weighing device to reduce measurement errors and data integration difficulties. Operators can perform filling and compaction processes indoors, restoring the collected soil samples to near their original bulk density, thus improving the representativeness and reliability of the test results. At the same time, it adopts automatic recording and wireless data transmission methods to achieve continuous, accurate, and long-term data observation, providing convenience and accuracy for obtaining soil moisture characteristic parameters. Attached Figure Description

[0023] The accompanying drawings are provided to further understand the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation thereof.

[0024] In the attached diagram:

[0025] Figure 1 This is a schematic diagram of the device for measuring soil moisture characteristic curves according to this utility model;

[0026] Figure 2 for Figure 1 Enlarged view of region A in the middle;

[0027] Figure 3 This is a schematic diagram of the structure of the device for measuring soil moisture characteristic curves according to this utility model;

[0028] Figure 4 This is a partial schematic diagram of the device for measuring soil moisture characteristic curves according to this utility model;

[0029] Figure 5 This is a partial structural diagram of the device for measuring soil moisture characteristic curves according to this utility model;

[0030] Figure 6 This is a structural diagram of the device for measuring soil moisture characteristic curves according to this utility model.

[0031] In the diagram: 1. Container; 11. First through hole; 12. Second through hole; 13. Hole; 14. Support leg; 2. Tensiometer system; 21. Clay head; 22. Scale assembly; 220. Mercury column; 221. Scale; 3. Sensing system; 31. Sensing element; 32. Signal conditioning and conversion circuit; 4. Weighing device; 5. Soil sample; 6. Tray; 7. Camera equipment. Detailed Implementation

[0032] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this utility model will be described below with reference to the accompanying drawings.

[0033] like Figures 1 to 6As shown, this utility model discloses a device for determining soil moisture characteristic curves, including a container 1, a tensiometer system 2, a sensing system 3, and a weighing device 4. The container 1 has a cylindrical structure and is used to fill a soil sample 5. The container 1 can be made of glass, plastic, or other materials, adaptable to different needs. The inner wall of the container 1 has a smooth surface, allowing the soil sample 5 to fall smoothly into the container 1, avoiding friction between the soil sample 5 and the inner wall of the container 1, thus ensuring the accuracy of subsequent data. The device also includes a tensiometer system 2, which measures the water tension within the soil sample 5 to calculate the soil moisture characteristic curve. The tensiometer system 2 is located on the side wall of the container 1 and reflects the soil moisture status by measuring the suction force of water in the soil sample 5. The tensiometer system 2 includes a clay head 21 and a scale assembly 22. The soil head 21 is generally made of permeable clay material, which has good stability and uniformity. One end of the clay head 21 is connected to the container 1 and is in direct contact with the soil sample 5 inside the container 1, which can sense the change in soil water tension. The other end is connected to the scale component 22, which reads the value of the tensiometer. The sensing system 3 is connected to the container 1 and part of the sensing system 3 is placed inside the soil sample 5. The sensing system 3 is used to obtain the volumetric water content data of the soil sample 5. The weighing device 4 is located at the bottom of the container 1. The weighing device 4 is used to measure the change in mass of the soil sample 5. As water evaporates or absorbs during the measurement process, the mass of the soil will change. The weighing device 4 can accurately measure the small changes in the mass of the soil. A tray 6 is set between the weighing device 4 and the container 1. The tray 6 is used to support the container 1 and can also contain the water flowing out of the container 1 during the measurement process.

[0034] During the determination of soil moisture characteristics, the operator will air-dry the soil sample 5 collected in the field and then sieve it (e.g., a 2 mm sieve) to remove excessively large particles and impurities such as grass roots. Based on the known bulk density data of the field soil, the treated soil will be layered and placed into container 1, and compacted in an appropriate manner to ensure that the soil sample 5 is evenly distributed and close to its original bulk density and pore structure. After saturating the soil sample 5, it will be left to stand for a period of time to allow the water in the soil sample 5 to seep out. Then, the bottom of container 1 will be wiped clean with a cloth and placed on tray 6. It should be noted that the bottom of container 1 can be equipped with fine holes or a filter paper layer as needed to ensure that the bottom micro-ventilation and evaporation conditions are close to the natural environment. Then, the water tension in the soil will be measured by the tensiometer system 2 and the data will be recorded. At the same time, the sensor system 3 will monitor the volume of soil sample 5 in real time. The system records the water content and feeds the data back to the control system. The weighing device 4 calculates the water loss or absorption in the soil sample 5 by measuring the mass change of the soil sample 5 in real time. As the water content in the soil sample 5 changes, the system continuously records these data. By comparing and analyzing them, the soil moisture characteristic curve can be obtained, thereby deduce parameters such as the soil's water retention capacity and permeability under different environmental conditions. The container 1 containing the soil sample 5, the tensiometer system 2, and the sensing system 3 is placed on the weighing device 4. The weighing device 4 automatically records the total mass of the device at a set time interval (such as every 10 minutes). As the soil evaporates and loses water, the total mass of the container 1 gradually decreases. The change in soil water content can be calculated by the mass difference.

[0035] In this application, by combining a tensiometer system, a sensing system, and a weighing device, measurement errors and data integration difficulties can be reduced. Operators can carry out the filling and compaction process indoors, restoring the collected soil samples to a state close to their original bulk density, thereby improving the representativeness and reliability of the test results. At the same time, the use of automatic recording and wireless data transmission methods enables continuous, accurate, and long-term data observation, providing convenience and accuracy for obtaining soil moisture characteristic parameters.

[0036] In some embodiments, such as Figures 1 to 5 As shown, the side wall of container 1 is provided with a first through hole 11 and a second through hole 12, the first through hole 11 and the second through hole 12 being radially opposite to container 1 (e.g., Figure 1The symmetrical arrangement (as shown in the y-direction) ensures the uniformity and stability of the soil sample 5 inside the container, and also improves the efficiency and measurement accuracy of the entire device. The first through hole 11 and the second through hole 12 are both circular in shape. The first through hole 11 is used to establish a channel between the inside and outside of the container 1, so that the soil sample 5 inside the container 1 can be effectively connected to the tensiometer system 2 outside. In the assembled state, the container 1 is connected to the inside of the clay head 21 in the tensiometer system 2 through the first through hole 11. The water tension signal in the soil sample 5 can be transmitted to the clay head 21 outside, and the relevant value of soil water tension can be displayed through the scale component 22, which is convenient for operators to observe and refer to. The position of the second through hole 12 corresponds to the setting position of the first through hole 11. The sensing system 3 is inserted into the soil sample 5 through the second through hole 12 to effectively measure the relevant data of the soil sample 5.

[0037] In some embodiments, such as Figures 1 to 5 As shown, multiple holes 13 are provided on container 1, along the height direction of container 1 (e.g., ...). Figure 1 In the z-direction shown, the hole 13 penetrates the bottom of the container 1. During the measurement process, the water in the soil sample 5 can seep out through the hole 13 onto the tray 6. The bottom of the container 1 is provided with several legs 14. The legs 14 are arranged at intervals along the circumference of the container 1. The number of legs 14 can be four or six, as long as they can support the container 1. In the assembled state, the legs 14 support the container 1, so that there is a distance between the bottom of the container 1 and the top of the tray 6, so that the water in the soil sample 5 can move freely downward.

[0038] In some embodiments, the tray 6 is used to support the container 1 and contain water. The tray 6 has a U-shaped cross-section. The U-shaped tray 6 can contain the water seeping out of the soil sample 5, which can facilitate subsequent centralized processing. In the assembled state, the container 1 on the tray 6 is placed at the center of the weighing device 4 below to ensure the reliability of the measurement.

[0039] In some embodiments, the sensing system 3 is a time-domain reflectometry (TDRS) sensor, which consists of a sensing element 31 and a signal conditioning and conversion circuit 32. The signal conditioning and conversion circuit 32 is electrically connected. The sensing element 31 is used to detect the moisture content of the soil sample 5. When measuring soil moisture, the sensing element 31 of the sensing system 3 sends an electromagnetic pulse signal to the soil sample 5 and evaluates the moisture content of the soil sample 5 by detecting the reflection of the signal in the soil sample 5. Moisture has a significant impact on the propagation speed of electromagnetic waves, so the moisture content of the soil sample 5 can be accurately calculated. The function of the signal conditioning and conversion circuit 32 is to process the electrical signal from the sensing element 31 and convert the reflected signal into an electrical signal that can be used for data analysis and display. After processing, these signals are transmitted to the calculation module of the control system, thereby displaying the moisture content of the soil sample 5 in real time and ensuring the clarity and stability of the signal.

[0040] In the assembled state, when filling the container 1 with soil sample 5, an iron sheet is used to block it to ensure that the soil sample 5 does not flow out. After compaction, the sensitive element 31 is inserted into the soil sample 5 through the second through hole 12. The sensitive element 31 can directly contact the soil sample 5 and fit tightly with the second through hole 12, thereby effectively acquiring the moisture data of the soil sample 5. The moisture content of the soil sample directly affects the propagation speed of electromagnetic waves. Therefore, the sensitive element 31 of the sensing system 3 is embedded in the soil sample 5 to ensure the accuracy of data acquisition.

[0041] In some embodiments, such as Figure 1 As shown, the orientation of the time-domain reflectometry sensor (e.g.) Figure 1 (as shown in the y-direction) and the radial direction of container 1 (as shown in the image) Figure 1 As shown in the y-direction, the sensing system 3 is parallel to ensure that it can uniformly and accurately detect the soil moisture content throughout the entire volume of the soil sample 5. This effectively eliminates the influence of possible local moisture unevenness, improves the accuracy of the measurement results, and provides reliable data support for the calculation of the soil moisture characteristic curve.

[0042] In some embodiments, such as Figure 1 As shown, container 1 is made of transparent plexiglass. Transparent plexiglass has good light transmittance, durability and impact resistance. During the measurement process, the operator can directly observe the state of the soil sample 5 inside container 1 and can help the operator judge the dryness and wetness changes of the soil sample 5 in a timely manner, which greatly improves the accuracy of subsequent data and the convenience of operation.

[0043] In some embodiments, such as Figure 1 and Figure 2As shown, the scale assembly 22 includes a mercury column 220 and a scale 221. The mercury column 220 is fixed to the scale 221. The interior of the mercury column 220 is connected to the interior of the container 1 through a clay head 21. The scale 221 is a measuring scale connected to the mercury column 220 and is used to display the change in the height of the mercury in the mercury column 220. When the moisture content in the soil sample 5 changes, the water tension is transmitted to the mercury column 220 through the clay head 21. The mercury will change according to the change in moisture content. The height of the mercury is directly proportional to the water tension in the soil sample 5. Specifically, the greater the water tension in the soil, the higher the mercury in the mercury column 220 will rise; conversely, when the soil water tension is low or the soil is moist, the mercury in the mercury column 220 will fall. The operator can display the corresponding value on the scale 221 according to the change in the height of the mercury in the mercury column 220.

[0044] In some embodiments, such as Figures 1 to 6 As shown, the device for measuring soil moisture characteristic curves also includes a camera 7, which is installed on the side of the container 1 away from the scale assembly 22. In one example, the camera 7 is a video camera. The video camera, the sensing system, and the weighing device are all connected to an external data acquisition and recording instrument, enabling continuous recording of measurement data. In the assembled state, the optical axis of the camera is positioned opposite to the scale assembly 22, allowing it to capture changes in the mercury height on the scale assembly 22, thereby acquiring relevant data for subsequent centralized processing and operation.

[0045] The working principle of the device for determining soil moisture characteristic curves in this application is as follows:

[0046] like Figures 1 to 6 As shown, firstly, the operator air-dries the soil sample 5 collected in the field. After air-drying, it is sieved through a 2 mm sieve to make the particle distribution relatively uniform. Based on the measured bulk density of the soil sample 5 in the field (e.g., 1.35 g / cm³), the sieved soil sample 5 is layered and placed into an plexiglass container 1. Each layer is gradually compacted with a fixed amount of soil until the soil in the entire container 1 reaches the required height and density.

[0047] After saturating soil sample 5, let it stand for a period of time to ensure that no more water droplets seep out (i.e., maintain soil sample 5 at a moisture content slightly above field capacity). Then, wipe the bottom of the plexiglass container 1 clean with a cloth and place the container 1 in a tray 6. Next, insert one end of the clay head 21 into the first through hole 11 on the side wall of the container 1 through a watertight head, and connect the other end to the scale assembly 22. At the same time, insert the sensing system 3 horizontally into the second through hole 12 on the side wall and insert the probe of the sensitive element 31 in the sensing system into the soil sample 5.

[0048] Next, place container 1 and the tray on the calibrated weighing device 4 (e.g., a high-precision electronic scale), connect the TDR wireless data module and battery power of the data acquisition and recording instrument, and simultaneously set the shooting interval of the camera device 7 (e.g., once every hour). It should be noted that the operator can set an appropriate time interval according to the different types of soil samples. For example, when using sandy loam, the shooting interval should be five minutes.

[0049] At the start of the experiment, soil sample 5 is usually in a state of high water content. As time goes by, natural evaporation causes the soil to lose water. Weighing device 4 records that the total mass gradually decreases. Sensing system 3 continuously outputs data on the soil volumetric water content that changes over time. Camera device 7 periodically captures the mercury column 220 scale reading of scale component 22 and converts the scale value into the soil matrix potential at each moment. Alternatively, the scale can be identified manually or by image recognition technology and then converted into matrix potential.

[0050] After the experiment, the soil matrix potential obtained at the same time was compared with the water content data estimated from the volumetric water content and mass change to ensure the consistency and accuracy of the data. The matrix potential-water content relationship was fitted using an appropriate mathematical model (such as the van Genuchten model) to finally obtain complete, continuous and high-precision soil moisture characteristic curve parameters.

[0051] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of the claims of this utility model.

Claims

1. A device for measuring soil moisture characteristic curves, characterized in that, include: A container, having a cylindrical structure, is used to fill soil samples; A tension meter system is disposed on the side wall of the container. The tension meter system includes a clay head and a scale assembly. One end of the clay head is connected to the container, and the other end is connected to the scale assembly. A sensing system, connected to the container, is partially placed inside the soil sample, and is used to acquire volumetric water content data of the soil sample. A weighing device is located at the bottom of the container, and a tray is provided between the weighing device and the container.

2. The device for determining soil moisture characteristic curves according to claim 1, characterized in that, The container has a first through hole and a second through hole on its side wall. The first through hole and the second through hole are arranged radially symmetrically with respect to the container. The container communicates with the interior of the clay head through the first through hole.

3. The device for determining soil moisture characteristic curves according to claim 2, characterized in that, The container has multiple holes, and the holes penetrate the bottom of the container along its height. The bottom of the container is provided with several legs, which are arranged at intervals along the circumference of the container.

4. The device for determining soil moisture characteristic curves according to claim 1, characterized in that, The tray has a U-shaped cross-section.

5. The device for determining soil moisture characteristic curves according to claim 3, characterized in that, The sensing system is a time-domain reflectometry sensor, which consists of a sensitive element and a signal conditioning and conversion circuit. The signal conditioning and conversion circuit is electrically connected, and the sensitive element is used to detect the moisture content of the soil sample. In the assembled state, the sensitive element is inserted into the soil sample through the second through hole.

6. The apparatus for determining soil moisture characteristic curves according to claim 5, characterized in that, The time-domain reflectometry sensor is positioned parallel to the radial direction of the container.

7. The device for determining soil moisture characteristic curves according to claim 1, characterized in that, The container is made of transparent plexiglass.

8. The device for determining soil moisture characteristic curves according to claim 1, characterized in that, The scale assembly includes a mercury column and a scale, the mercury column is fixed to the scale, and the interior of the mercury column is connected to the interior of the container through the clay head.

9. The device for determining soil moisture characteristic curves according to claim 1, characterized in that, The device for measuring soil moisture characteristic curves also includes a camera, which is installed on the side of the container away from the scale assembly.

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