Electronic soil tensiometer capable of being automatically maintained and maintenance method thereof

Abstract

The invention relates to the technical field of soil moisture monitoring, and discloses an electronic soil tensiometer capable of being automatically maintained and a maintenance method thereof.The electronic soil tensiometer comprises a water storage pipe, a sealing cap, an electric push rod assembly, a pressure sensor and a comprehensive control system; the top of the water storage pipe is provided with a water replenishing port, the bottom of the water storage pipe is connected with the tensiometer, one end of the tensiometer away from the water storage pipe is provided with a porous ceramic head, the inner cavity of the water storage pipe is a water storage cavity, and the bottom of the water storage cavity is provided with a fluid channel to communicate the water storage cavity with the inner cavity of the tensiometer; the sealing cap is used for sealing the fluid channel; the electric push rod assembly is detachably installed at the water supplementing opening of the water storage pipe, and when the output end of the electric push rod assembly acts, the sealing cap can be driven to open or close the fluid channel so as to achieve air exhausting and water supplementing of the tensiometer; the pressure sensor is used for monitoring pressure change of an inner cavity of the tensiometer; the pressure sensor and the electric push rod assembly are both in signal connection with the comprehensive control system so as to control the electric push rod assembly to act according to pressure changes in the tensiometer.

Description

Technical Field

[0001] This invention relates to the field of soil moisture monitoring technology, specifically to an automatically maintainable electronic soil tensiometer and its maintenance method. Background Technology

[0002] Scientific management of soil moisture is a crucial technical aspect of agricultural production. Scientifically controlling soil moisture status can effectively achieve multiple benefits, including water conservation, increased yield, improved agricultural product quality, reduced leaching losses, and control of crop diseases and pests. Real-time soil moisture monitoring is fundamental to scientific soil moisture management. Currently, devices capable of real-time soil moisture monitoring include soil tensiometers, FDRs (Frequency Domain Reflectometers), and TDRs (Time Domain Reflectometers). Among these, soil tensiometers, which monitor the soil matrix potential and directly indicate soil moisture availability, are among the most effective devices for guiding irrigation and are increasingly widely used in agricultural production and scientific research. However, the presence of gas inside a soil tensiometer can significantly impact its response speed due to the greater expansion-contraction ratio of gas compared to water. This gas, with its higher expansion-contraction ratio, buffers pressure changes through volume shifts, resulting in a hysteresis effect and affecting measurement accuracy. Furthermore, most soil tensiometers require frequent manual on-site maintenance, including air removal and water replenishment, increasing labor costs and negatively impacting the enthusiasm of field managers. Existing self-maintaining soil tensiometers are complex in structure, have many sensing elements, are expensive, and have low operational reliability. Summary of the Invention

[0003] The purpose of this invention is to provide an automatically maintainable electronic soil tensiometer to solve the problems of complex structure and low operational reliability of existing automatically maintainable soil tensiometers in the background art.

[0004] Another objective of this invention is to provide a safer maintenance method for electronic soil tensiometers, in order to avoid the problem that existing automatic maintenance methods can cause damage to the pressure sensor by generating shock waves when the sealing cap is opened during maintenance when the soil is relatively dry and the pressure difference between the inside and outside of the tensiometer is too large.

[0005] An automatically maintainable electronic soil tensiometer includes: The water storage pipe has a water inlet at the top along the first direction, and the bottom of the water storage pipe is connected to a tension meter. The end of the tension meter away from the water storage pipe has a porous ceramic head. The inner cavity of the water storage pipe is a water storage chamber, and a fluid channel is opened at the bottom of the water storage chamber to allow the water storage chamber to communicate with the inner cavity of the tension meter. A sealing cap, located inside the water storage cavity, is used to seal the fluid passage; An electric actuator assembly, wherein the axis of the electric actuator assembly extends along a first direction, the electric actuator assembly is detachably installed at the water inlet of the water storage pipe, and the output end of the electric actuator assembly extends into the water storage chamber and is connected to the sealing cap; when the output end of the electric actuator assembly moves along the first direction, it can drive the sealing cap to open or close the fluid channel to realize the exhaust and water replenishment of the tension meter. A pressure sensor is used to monitor pressure changes within the tension gauge cavity; The integrated control system connects both the pressure sensor and the electric actuator assembly to the system to control the actuator assembly's movement based on pressure changes within the tension gauge. This configuration allows for tension gauge venting and water replenishment solely through the electric actuator assembly's movement of the sealing cap. The overall structure is simple and easy to implement. Furthermore, the tension gauge's internal cavity remains under negative pressure during operation, enhancing the sealing effect of the sealing cap and making the overall structure more reliable.

[0006] Furthermore, the electric actuator assembly includes a actuator, a fixed sleeve, a drive mechanism, and a housing; the water inlet is provided with a locking cover, the cover having a through hole along a first direction, the fixed sleeve being installed outside the cover and communicating with the through hole, the housing being disposed inside the fixed sleeve, and the inner cavity of the housing communicating with the through hole, the drive mechanism and the actuator being located inside the housing, the axis of the actuator extending along the first direction, the output end of the drive mechanism being connected to the first end of the actuator, the second end of the actuator extending through the through hole into the water storage chamber, and the second end of the actuator being connected to a sealing cap. The electric actuator assembly has a simple structure; by driving the electric actuator along the first direction through the drive mechanism, the water storage chamber can be sealed or opened.

[0007] Furthermore, it also includes a limiting ring, which is disposed on the outer periphery of the push rod and located inside the water storage cavity. The outer diameter of the limiting ring is larger than the inner diameter of the through hole to limit the upward distance of the push rod along the first direction.

[0008] Furthermore, the distance between the limiting ring and the cover is 5~20mm. By reasonably setting the distance between the limiting ring and the cover, a suitable gap is ensured between the sealing cap and the opening end of the fluid channel after the cap is opened, so that the gas in the tension gauge can be quickly discharged, achieving the purpose of rapid venting and water replenishment.

[0009] Furthermore, it also includes a sealing element, which is a sealing ring disposed at the open end of the fluid channel for engaging with the sealing cap to create a seal. By including the sealing element, the sealing effect between the sealing cap and the fluid channel is further improved.

[0010] Furthermore, the sealing cap is tapered on the side near the tension gauge, and the opening end of the fluid channel is a slope corresponding to the tapered sealing cap, with the seal mounted on the slope. This design improves the compatibility between the sealing cap and the opening end of the fluid channel, and the slope at the opening end of the fluid channel also guides the sealing cap during its descent, preventing it from tilting.

[0011] Furthermore, the cover is also provided with vent holes to make the pressure inside the water storage chamber equal to the atmospheric pressure.

[0012] Furthermore, the integrated control system includes a drive mechanism control module, a data acquisition and storage module, a power supply module, a network and data transmission module, and a data processing and judgment module. The drive mechanism control module, data acquisition and storage module, power supply module, and network and data transmission module are all connected to the data processing and judgment module. The drive mechanism control module is connected to the drive mechanism signal, and the data acquisition and storage module is connected to the pressure sensor signal. By setting the parameters of the integrated control system, it can automatically determine whether water replenishment is needed based on the pressure changes within the tension gauge, achieving intelligent, automatic, and rapid air venting and water replenishment.

[0013] Furthermore, the power supply module includes an energy storage control module and a solar photovoltaic panel, the solar photovoltaic panel being connected to the energy storage control module, and the energy storage control module being connected to the data processing and judgment module.

[0014] A maintenance method for an automatically maintainable electronic soil tensiometer, used for air venting and water replenishment of the aforementioned electronic soil tensiometer: During the process of soil drying after irrigation, the pressure inside the tensiometer gradually decreases. When the pressure inside the tensiometer drops to the irrigation threshold, the irrigation system is activated in the field. If there is rainfall, the soil becomes wet again. After the pressure inside the tensiometer rises rapidly and then fluctuates within a small range, the drive mechanism control module controls the drive mechanism to start an air venting and water replenishment operation.

[0015] The present invention has the following advantages over the prior art: 1. The present invention provides an automatically maintainable electronic soil tensiometer, comprising a water storage pipe, a tensiometer, an electric actuator assembly, a pressure sensor, and an integrated control system. The water storage pipe is connected to the tensiometer, with a water inlet at its top, allowing water to be supplied to both the pipe and the tensiometer. A fluid channel is formed at the bottom of the water storage pipe, connecting the water storage chamber to the inner cavity of the tensiometer. The pressure sensor is mounted on the upper side wall of the tensiometer to monitor pressure changes within the tensiometer and transmit the data to the integrated control system. The electric actuator assembly is mounted on the outer end of the water inlet and drives a sealing cap to close or open the water storage chamber, thereby venting air and supplying water to the tensiometer. During operation, the pressure sensor monitors pressure changes within the tensiometer, and the integrated control system determines whether water supply is needed. When water supply is required, the electric actuator assembly raises the sealing cap, opening the water storage chamber. Water from the storage chamber is supplied to the tensiometer, while gas within the tensiometer is expelled upwards through the water storage chamber. After water supply is complete, the electric actuator assembly closes the fluid channel with the sealing cap, and the tensiometer enters its working state. This invention features a simple overall structure and low manufacturing cost. It eliminates the need for additional liquid level sensors or other devices to determine whether water replenishment is required; instead, it relies solely on the tension gauge's own pressure sensor to monitor pressure changes within the gauge. Furthermore, water replenishment is accomplished simply by the electric actuator assembly moving the sealing cap, resulting in high operational reliability. Additionally, the constant negative pressure within the tension gauge enhances the sealing effect of the sealing cap.

[0016] 2. The maintenance method of the soil tensiometer in this invention refers to the process of venting and replenishing water in the soil tensiometer. The automatic maintenance of the soil tensiometer in this invention is performed after each irrigation or rainfall. During normal monitoring operation, as the soil dries, the pressure value monitored by the tensiometer gradually decreases. When the soil dries to a certain extent, the pressure value reaches the irrigation threshold, and the irrigation system is activated. Alternatively, during rainfall, when irrigation water or rainwater reaches the depth of the porous ceramic head of the tensiometer, water enters the tensiometer through the ceramic head, causing the pressure to rise rapidly. After irrigation stops, the pressure rise ceases and begins a slow decline. This rapid rise and slow decline is a unique data change characteristic of irrigation and its end, and is also an important basis for determining the maintenance timing of the soil tensiometer in this invention. The data processing and judgment module analyzes the characteristics of the most recent six pressure value changes each time a pressure value is read. When a rapid rise followed by a smaller range of change occurs, the tensiometer maintenance action is initiated. This invention stipulates that each maintenance of the soil tensiometer should be carried out after sufficient irrigation to avoid the tensiometer pressure being too low when the soil is dry. If air is released and water is added at this time, the tensiometer will be pressurized instantly, generating a shock wave that will damage the pressure sensor. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the sealing fluid channel of the sealing cap of the automatically maintainable electronic soil tensiometer in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the opening of the fluid channel in the sealing cap of the automatically maintainable electronic soil tensiometer in an embodiment of the present invention; Figure 3 This is a top view of the cover in an embodiment of the present invention; In the diagram: 1. Water storage pipe; 101. Water storage chamber; 102. Fluid channel; 2. Tensiometer; 201. Porous ceramic head; 3. Sealing cap; 4. Pressure sensor; 5. Integrated control system; 501. Drive mechanism control module; 502. Data acquisition and storage module; 503. Networking and data transmission module; 504. Data processing and judgment module; 505. Energy storage control module; 506. Solar photovoltaic panel; 6. Push rod; 7. Fixing sleeve; 8. Drive mechanism; 9. Outer shell; 10. Limiting ring; 11. Sealing element; 12. Cover; 13. Through hole; 14. Vent hole; X, First direction. Detailed Implementation

[0018] 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.

[0019] It should be noted that in the description of this invention, the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] Furthermore, it should be understood that, for ease of description, the dimensions of the various components shown in the accompanying drawings are not drawn to actual scale.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined or described in one figure, it will not need to be further discussed and described in the description of the subsequent figures. Example:

[0022] A soil tensiometer is an instrument installed in the soil to monitor soil matrix potential. Its basic principle is that the water inside the tensiometer chamber establishes a connection with the soil moisture through micropores in the ceramic head. As the soil gradually dries from saturation, the soil water potential decreases, causing the soil to draw water from the tensiometer. The water inside the tensiometer chamber then moves into the soil through the micropores in the ceramic head, causing the pressure inside the tensiometer chamber to decrease. After irrigation, the soil water potential increases, and the soil water is drawn back into the tensiometer chamber due to the negative pressure. The pressure inside the tensiometer chamber is monitored using a pressure gauge or pressure sensor, which represents the soil matrix potential. The magnitude of the soil matrix potential indicates the availability of soil moisture in the field, thus guiding irrigation.

[0023] refer to Figure 1 and Figure 2 An automatically maintainable electronic soil tensiometer includes: a water storage tube 1, a tensiometer 2, a sealing cap 3, an electric push rod assembly, and a pressure sensor 4. The water storage tube 1 has a water inlet at its top along a first direction (X direction in the figure), and its bottom is connected to the tensiometer 2. The end of the tensiometer 21 away from the water storage tube has a porous ceramic head 201. The inner cavity of the water storage tube 1 is a water storage chamber 101, and a fluid channel 102 is opened at the bottom of the water storage chamber 101 to connect the water storage chamber 101 with the inner cavity of the tensiometer. By opening the fluid channel 102, liquid in the water storage chamber 101 can be replenished into the tensiometer. The sealing cap 3 is located inside the water storage chamber 101 and is used to seal the fluid channel 102. The purpose of sealing the fluid channel 102 by the sealing cap 3 is to make the inside of the tensiometer a sealed environment, where pressure changes are caused only by the water exchange between the porous ceramic head 201 and the soil, so that the pressure changes inside the tensiometer can accurately indicate the changes in soil water potential.

[0024] The axis of the electric actuator assembly extends along the first direction. The electric actuator assembly is detachably installed at the water inlet of the water storage pipe 1. The output end of the electric actuator assembly extends into the water storage chamber 101 and is connected to the sealing cap 3. When the output end of the electric actuator assembly moves along the first direction, it can drive the sealing cap 3 to open or close the fluid channel 102 to realize the exhaust and water replenishment of the tension meter. Pressure sensor 4 is used to monitor pressure changes in the inner cavity of the tension gauge; the monitored pressure value is used in conjunction with the integrated control system to determine when maintenance is needed.

[0025] Both the pressure sensor 4 and the electric actuator assembly are connected to the integrated control system 5 to control the electric actuator assembly to move according to the pressure changes in the tension gauge.

[0026] In this embodiment, a cover 12 is fastened to the top of the water inlet. When the cover 12 is opened, the sealing cap 3 moves with the electric push rod assembly and disengages from the fluid channel 102. At this time, water can be manually added to the tension gauge 2 and the water storage pipe 1 through the water inlet. The venting and water replenishment of the tension gauge 2 can be completed simply by the electric push rod assembly driving the sealing cap 3. The overall structure is simple and easy to implement. Water replenishment is determined by monitoring the pressure change inside the tension gauge using the pressure sensor 4. No other sensors are required, resulting in low production costs and high operational reliability. Furthermore, the tension gauge's internal cavity is always under negative pressure during operation, which enhances the sealing effect of the sealing cap and makes the overall structure more reliable.

[0027] Specifically, the electric push rod assembly includes a push rod 6, a fixing sleeve 7, a drive mechanism 8, and a housing 9. The water inlet is provided with a matching cover 12, which has a through hole along a first direction. The fixing sleeve 7 is installed outside the cover 12 and communicates with the through hole. The housing 9 is located inside the fixing sleeve 7, and its inner cavity communicates with the through hole. The fixing sleeve 7 defines the position of the housing 9. The drive mechanism 8 and the push rod 6 are both located inside the housing 9. The axis of the push rod 6 extends along the first direction. The output end of the drive mechanism 8 is connected to the first end of the push rod 6. The second end of the push rod 6 extends through the through hole into the water storage chamber 101, and a sealing cap 3 is connected to the second end of the push rod 6. The drive mechanism is a motor, and a common ball screw assembly is used between the push rod and the motor output end to ensure that the push rod can reciprocate along the first direction.

[0028] In this embodiment, the electric push rod assembly has a simple structure. The push rod is driven by the drive mechanism to move in the first direction, which can seal or open the water storage chamber.

[0029] In this embodiment, no sealing element is provided between the cover 12 and the water inlet, so as to facilitate the discharge of gas in the water storage chamber 101.

[0030] In another embodiment, reference is made to... Figure 3 The cover 12 may also be provided with a vent 14 to ensure that the pressure inside the water storage chamber 101 is equal to the atmospheric pressure. In specific implementations, the diameter of the vent 14 is about 5 mm. Water can also be added to the water storage chamber 101 through the vent 14.

[0031] In this embodiment, a limiting ring 10 is also included. The limiting ring 10 is disposed on the outer periphery of the push rod 6 and located inside the water storage cavity 101. The outer diameter of the limiting ring 10 is larger than the inner diameter of the through hole to limit the upward distance of the push rod 6 in the first direction. The distance between the limiting ring 10 and the cover 12 is 5~20mm. For example, 5mm, 6mm, 8mm, 10mm, 12mm, 15mm, 18mm, 20mm, etc., preferably 15mm. By reasonably setting the distance between the limiting ring 10 and the cover 12, a suitable gap is ensured between the sealing cap 3 and the opening end of the fluid channel after opening, so that the gas in the tension gauge can be quickly discharged, achieving the purpose of rapid air venting and water replenishment.

[0032] In this embodiment, a sealing element 11 is also included. The sealing element 11 is a sealing ring, which is disposed at the open end of the fluid channel and is used to cooperate with the sealing cap 3 for sealing. By providing the sealing element 11, the sealing effect between the sealing cap 3 and the fluid channel 102 is further improved.

[0033] Preferably, the sealing cap 3 is tapered on the side near the tension gauge 2, and the opening end of the fluid channel 102 is an inclined surface corresponding to the tapered sealing cap, with the sealing element 11 mounted on the inclined surface. This design improves the compatibility between the sealing cap 3 and the opening end of the fluid channel, and the inclined surface at the opening end of the fluid channel also guides the sealing cap during its descent, preventing it from tilting. In practice, the drive mechanism has sufficient power, and the negative pressure inside the tension gauge and the water pressure in the water storage chamber will not affect the movement of the sealing cap under the drive mechanism.

[0034] Specifically, the integrated control system 5 includes a drive mechanism control module 501, a data acquisition and storage module 502, a power supply module, a network and data transmission module 503, and a data processing and judgment module 504. The drive mechanism control module 501, data acquisition and storage module 502, power supply module, and network and data transmission module 503 are all connected to the data processing and judgment module 504. The drive mechanism control module 501 is signal-connected to the drive mechanism 8, and the data acquisition and storage module 502 is signal-connected to the pressure sensor 4. By setting the parameters of the integrated control system, it can automatically determine whether water needs to be added based on the pressure changes in the tension gauge 2, achieving intelligent, automatic, and rapid air venting and water replenishment. Specifically, the drive mechanism control module 501 drives the motor according to the instructions of the data processing and judgment module 504; the data acquisition and storage module 502 collects data from the pressure sensor 4 and transmits the pressure value to the data processing and judgment module 504; the network and data transmission module 503 connects the data processing and judgment module 504 to an IoT platform; and the energy storage control module 505 supplies power to the power-consuming modules in the integrated control system 5. The data processing and judgment module 504 has a preset control program, which drives the operation of the integrated control system according to the instructions of the control program.

[0035] The power supply module can be a lithium battery or a solar power supply system, specifically an energy storage control module 505 and a solar photovoltaic panel 506. The solar photovoltaic panel is connected to the energy storage control module, which supplies power to each power-consuming module in the integrated control system. To reduce power consumption and ensure continuous power demand, the power supply to each power-consuming module (including the data processing and judgment module) is automatically controlled by the data processing and judgment module, so that it is in a power-off state or a dormant state during non-working periods.

[0036] In specific implementation: In this embodiment, the drive mechanism 8 is a miniature DC motor equipped with a reducer. When the tension gauge needs maintenance (in this application, maintenance specifically refers to tension gauge venting and water replenishment), the data processing and judgment module 504 sends a command to the drive mechanism control module 501. The drive mechanism control module 501 then drives the miniature DC motor, which, through the reducer, causes the drive push rod 6 to move upward, causing the sealing cap 3 to leave the sealing element 11, thereby opening the fluid channel 102. When the fluid channel 1 is open, there must be a sufficiently large gap between the sealing cap 3 and the opening end of the fluid channel 102 to ensure that the gas in the tension gauge cavity rises smoothly under the action of buoyancy and passes through the gap between the fluid channel 1 and the sealing cap 3. At the same time, the water in the water storage chamber is affected by gravity. The gas is smoothly lowered into the tension gauge chamber, and all gas is completely purged and the tension gauge chamber is fully filled with water within 30 seconds. For this purpose, the sealing cap 3 moves upward by 15mm. The moving distance is controlled by the limit ring 10 installed on the movable push rod. When the push rod 6 rises, the limit ring 10 rises with it and is blocked when it reaches the cover 12. The movement of the push rod 6 is hindered, and the motor operating current will increase significantly. This change is detected by the drive mechanism control module 501 and fed back to the data processing and judgment module 504. The data processing and judgment module 504 immediately makes a judgment and cuts off the power supply to the motor. The motor stops rotating, and the push rod 6 stops moving. One minute later, the data processing and judgment module 504 supplies power to the drive mechanism control module and reverses the power supply polarity. The motor rotates in the opposite direction, driving the push rod 6 downwards. Once the sealing cap 3 contacts the sealing element 11, the push rod 6 experiences resistance, causing a significant increase in the motor's operating current. This change is detected by the drive mechanism control module 501 and fed back to the data processing and judgment module 504. The data processing and judgment module 504 immediately makes a judgment and interrupts the power supply to the motor. The motor stops rotating, and the push rod 6 stops moving. The sealing cap 3 completes the sealing of the tensiometer chamber. As soil moisture decreases, the pressure inside the tensiometer chamber gradually decreases, and the sealing cap 3 strengthens the sealing effect under the pressure difference between the inside and outside of the tensiometer chamber. This completes one maintenance operation (venting and water replenishment).

[0037] This invention also relates to a method for maintaining a tensiometer. Existing methods for automatic maintenance of tensiometers all involve opening a water supply valve to replenish water when the water level inside the tensiometer is below a set level. However, during normal operation of the tensiometer, the soil dries out, the pressure inside the tensiometer decreases, and the gas volume expands, causing the water level to drop. At this time, when performing venting and water replenishment maintenance, because the air pressure outside the tensiometer chamber is much higher than the pressure inside, external air or water rapidly enters the tensiometer the instant the sealing components are opened, generating a shock wave that damages the pressure sensor. Moreover, when maintaining under relatively dry soil conditions, the soil absorbs moisture from the tensiometer through the ceramic head, resulting in significantly higher soil moisture around the ceramic head than the rest of the field. This leads to inaccurate moisture monitoring after tensiometer maintenance for a certain period, and even yield losses due to misjudgments of soil moisture conditions.

[0038] Based on multiple experimental verifications, this application proposes that soil tensiometer maintenance should be carried out after soil irrigation. Therefore, it proposes an automatic maintenance method for the aforementioned electronic soil tensiometer, used for air venting and water replenishment. As the soil dries, the pressure inside the tensiometer gradually decreases. When the pressure inside the tensiometer drops to the irrigation threshold, the field irrigation system is activated or rainfall occurs. After the pressure inside the tensiometer rises rapidly and then fluctuates within a small range, the drive mechanism control module controls the drive mechanism to initiate an air venting and water replenishment operation.

[0039] Specifically, the automatic maintenance of the soil tensiometer of this invention is performed after each irrigation. During normal monitoring operation, as the soil dries, the pressure value monitored by the pressure sensor within the tensiometer gradually decreases. When the soil dries to a certain extent, the monitored pressure value within the tensiometer reaches the irrigation threshold, and irrigation begins in the field (the data processing and judgment module can connect to an automatic irrigation system to automatically start irrigation; or issue a reminder signal to manually start irrigation). Alternatively, if rainfall occurs, and the irrigation water or rainwater reaches the depth of the ceramic head of the tensiometer, water will enter the tensiometer through the ceramic head, causing the pressure value monitored by the pressure sensor to rise rapidly. After irrigation stops, the pressure rise will stop, and a slow decline will begin. This process of rapid rise and slow decline is a special data change characteristic of irrigation and its end, and it is also an important basis for determining the maintenance timing of the soil tensiometer in this invention. The data processing and judgment module analyzes the characteristics of the most recent six pressure value changes each time a pressure value is read. When a rapid rise followed by a small range of change occurs, the tensiometer maintenance action is initiated.

[0040] The rule for judging a rapid pressure increase is as follows: a rapid increase is defined as a pressure value that is 10 kPa higher than the previous 1-2 readings. After a rapid pressure increase is detected, the value monitored is checked to see if the difference from the previous value is within 3 kPa, and whether the current monitored value is higher than -20 kPa. If both conditions are met, tensiometer maintenance is initiated. If only the first condition is met, but the monitored value is still lower than -20 kPa, it is considered that rainfall or irrigation is insufficient, resulting in low pressure within the tensiometer, and maintenance is not performed. When the system prompts for continued irrigation or waiting for the next irrigation, maintenance will begin after sufficient soil moisture.

[0041] Each water replenishment of the tensiometer consumes a certain volume of water from the storage chamber. Therefore, to ensure a sufficient water supply, the storage chamber needs to be replenished periodically. Based on the volume of the storage chamber and the amount of water used for each tensiometer replenishment, the number of times the storage chamber can be replenished can be calculated. The integrated control system uploads the cumulative maintenance count to the IoT platform after each maintenance. The cumulative maintenance count determines whether water replenishment to the storage chamber is necessary. The storage chamber can also be connected to a larger external water source to meet the tensiometer's water needs throughout the crop's growing season.

[0042] The soil tensiometer of this invention has a simple structure and low production cost, with only one moving part, the electric actuator, which greatly improves sealing and operational reliability. After soil irrigation, the tensiometer draws water in through the ceramic head, causing the internal pressure to rise. The seal is only opened when the pressure difference between the inside and outside of the tensiometer cavity reaches its minimum, preventing damage to the pressure sensor due to excessive pressure difference. This application determines the timing of air release and water replenishment based on the pressure change of the soil tensiometer. This is done after the soil tensiometer reading has significantly risen and stabilized following soil irrigation. At this time, the soil moisture content is high, resulting in minimal or no water absorption. Furthermore, the pressure inside the tensiometer cavity rises, and the volume of the gas that expanded due to the pressure drop shrinks again, resulting in a very small amount of water replenishment.

[0043] In existing technology, automatically maintained tensiometers are replenished when the water level drops to a set position. When the soil is relatively dry, the gas volume inside the tensiometer chamber expands due to the pressure drop, requiring a larger amount of water to be added. Moreover, because the soil is relatively dry, the water inside the tensiometer is quickly drawn out through the ceramic head, not only increasing the amount of water to be added, but also causing the soil around the ceramic head to absorb water, resulting in an irrigation effect and increased soil moisture content. After replenishing water, the tensiometer monitors the soil moisture status around the ceramic head, which is significantly higher than the actual soil moisture content in the field at a distance from the ceramic head. This can lead to the tensiometer monitoring result indicating that the soil is not dry, while the actual field needs irrigation, resulting in monitoring failure, untimely irrigation, and in severe cases, economic losses. Furthermore, since the timing of air release and water replenishment is when the soil is relatively dry, and the pressure inside the tensiometer chamber will return to zero (i.e., equal to atmospheric pressure) when the valve is opened during air release and water replenishment, the pressure inside the tensiometer chamber needs to gradually reach equilibrium with the soil water potential through the seepage of water from the chamber before normal monitoring can be performed. This equilibrium process is related to the dryness and wetness of the soil, generally taking 1 to 24 hours, which further affects the real-time performance of the monitoring. The technical solution of this invention determines the timing of air release and water replenishment by observing changes in the soil tensiometer value. This is done after the soil has been irrigated and the soil tensiometer value has significantly rebounded and stabilized. At this time, the soil moisture content is high, the amount of water absorbed is small or even non-existent, and the pressure inside the tensiometer chamber rises, causing the gas volume to shrink due to the pressure drop, resulting in a small amount of water replenishment. After water replenishment, because the soil moisture content is high and the soil water potential is high, the pressure difference with the tensiometer chamber is small, and the tensiometer basically does not require an equilibrium time, resulting in reliable monitoring results and strong real-time performance.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An automatically maintainable electronic soil tensiometer, characterized in that, include: The water storage pipe has a water inlet at the top along the first direction, and the bottom of the water storage pipe is connected to a tension meter. The end of the tension meter away from the water storage pipe has a porous ceramic head. The inner cavity of the water storage pipe is a water storage chamber, and a fluid channel is opened at the bottom of the water storage chamber to allow the water storage chamber to communicate with the inner cavity of the tension meter. A sealing cap, located inside the water storage cavity, is used to seal the fluid passage; An electric actuator assembly, wherein the axis of the electric actuator assembly extends along a first direction, the electric actuator assembly is detachably installed at the water inlet of the water storage pipe, and the output end of the electric actuator assembly extends into the water storage chamber and is connected to the sealing cap; when the output end of the electric actuator assembly moves along the first direction, it can drive the sealing cap to open or close the fluid channel to realize the exhaust and water replenishment of the tension meter. A pressure sensor is used to monitor pressure changes within the tension gauge cavity; The integrated control system includes pressure sensors and electric actuator assemblies that are signal-connected to the integrated control system to control the operation of the electric actuator assemblies based on changes in pressure within the tension gauge.

2. The automatically maintainable electronic soil tensiometer according to claim 1, characterized in that: The electric push rod assembly includes a push rod, a fixed sleeve, a drive mechanism, and a housing; the water inlet is provided with a snap-fit ​​cover, the cover having a through hole along a first direction, the fixed sleeve being installed outside the cover and communicating with the through hole, the housing being disposed inside the fixed sleeve, and the inner cavity of the housing communicating with the through hole, the drive mechanism and the push rod being located inside the housing, the axis of the push rod extending along the first direction, the output end of the drive mechanism being connected to the first end of the push rod, the second end of the push rod extending through the through hole into the water storage cavity, and the second end of the push rod being connected to a sealing cap.

3. The automatically maintainable electronic soil tensiometer according to claim 1, characterized in that: It also includes a limiting ring, which is disposed on the outer periphery of the push rod and located in the water storage cavity. The outer diameter of the limiting ring is larger than the inner diameter of the through hole to limit the upward distance of the push rod along the first direction.

4. The automatically maintainable electronic soil tensiometer according to claim 3, characterized in that: The distance between the limiting ring and the cover is 5~20mm.

5. The automatically maintainable electronic soil tensiometer according to claim 1, characterized in that: It also includes a sealing element, which is a sealing ring disposed at the open end of the fluid channel for use in conjunction with a sealing cap to create a seal.

6. The automatically maintainable electronic soil tensiometer according to claim 5, characterized in that: The sealing cap is tapered on the side near the tension gauge, and the opening end of the fluid channel is an inclined surface corresponding to the tapered sealing cap. The sealing element is installed on the inclined surface.

7. The automatically maintainable electronic soil tensiometer according to claim 2, characterized in that: The cover is also provided with a vent hole to make the pressure inside the water storage chamber equal to the atmospheric pressure.

8. The automatically maintainable electronic soil tensiometer according to claim 1, characterized in that: The integrated control system includes a drive mechanism control module, a data acquisition and storage module, a power supply module, a network and data transmission module, and a data processing and judgment module. The drive mechanism control module, the data acquisition and storage module, the power supply module, and the network and data transmission module are all connected to the data processing and judgment module. The drive mechanism control module is connected to the drive mechanism signal, and the data acquisition and storage module is connected to the pressure sensor signal.

9. The automatically maintainable electronic soil tensiometer according to claim 8, characterized in that: The power supply module includes an energy storage control module and a solar photovoltaic panel. The solar photovoltaic panel is connected to the energy storage control module, and the energy storage control module is connected to the data processing and judgment module.

10. A maintenance method for an automatically maintainable electronic soil tensiometer, characterized in that, Used for venting and water replenishment of the electronic soil tensiometer according to any one of claims 1 to 9: During the process of soil drying after irrigation, the pressure inside the tensiometer gradually decreases. When the pressure inside the tensiometer drops to the irrigation threshold, the irrigation system is activated in the field. If there is rainfall, the soil becomes wet again. After the pressure inside the tensiometer rises rapidly and then fluctuates within a small range, the drive mechanism control module controls the drive mechanism to start an air venting and water replenishment operation.

Images