On-site online calibration system for soil moisture sensor

Abstract

The utility model discloses an on-site online calibration system for a soil moisture sensor. The on-site online calibration system comprises an outer barrel, an inner barrel, a weighing platform, an edge measurement and control terminal, a to-be-calibrated soil moisture sensor, a power supply system, a drainage system and a water replenishing system, the soil moisture in the inner barrel is actively regulated and controlled through the edge control terminal, weighing data and data of the to-be-calibrated soil moisture sensor are synchronously recorded, the actual soil moisture is calculated and compared with the soil moisture measured by the to-be-calibrated soil moisture sensor, and automatic calibration of the to-be-calibrated soil moisture sensor is achieved. The calibration process of the soil moisture sensor is fully automatic, and the original state of soil is kept.

Description

Technical Field

[0001] This utility model relates to the field of soil moisture monitoring technology, and in particular to a field online calibration system for soil moisture sensors. Background Technology

[0002] Soil moisture directly impacts crop growth. Monitoring soil moisture not only helps optimize irrigation decisions and reduce water waste, but also provides early warnings of drought, offering a scientific basis for agricultural production. Against the backdrop of climate change, accurate soil moisture monitoring plays an irreplaceable role in ensuring food security and responding to extreme weather events.

[0003] Because soil has a low dielectric constant while water has a high dielectric constant, the moisture content in a soil-water mixture can be indirectly measured using the dielectric constant. This is the basic principle behind most current soil moisture sensors. Since the physical and chemical properties of soil directly affect sensor readings, and the dielectric properties vary across different regions and soil types, calibration is necessary to establish an accurate relationship between sensor readings and actual soil moisture content. Currently, the commonly used calibration method involves using standard soil samples with known moisture content or determining the soil moisture content using an oven-drying method, then comparing and analyzing the results with the sensor readings to establish a calibration formula. However, this method often requires altering the original physical properties of the soil. For example, it is difficult to restore the bulk density of natural soil during the preparation of soil samples with known moisture content. This is a key conversion factor between the volumetric moisture content measured by the sensor and the mass moisture content measured by the oven-drying method, and the uncontrollability of this factor greatly affects the sensor calibration results. Therefore, there is an urgent need to develop a device capable of in-situ calibration of soil moisture sensors. Summary of the Invention

[0004] Purpose of the invention: The purpose of this utility model is to provide a device that can calibrate soil moisture sensors in situ on site.

[0005] Technical Solution: This utility model discloses an online calibration system for a soil moisture sensor, comprising an outer barrel, an inner barrel, a weighing platform, an edge monitoring and control terminal, a soil moisture sensor to be calibrated, and a power supply system. The weighing platform is installed inside the outer barrel and contains a built-in weighing sensor, which is electrically connected to the edge monitoring and control terminal. The inner barrel is placed on the weighing platform, and its inner wall and bottom are covered with a permeable material. A drain pipe is provided at the bottom of the inner barrel, and a drain pump is provided at the outlet end of the drain pipe, which is electrically connected to the edge monitoring and control terminal. The outlet end of the drain pump is connected to a water outlet pipe, which extends upward along the outer wall of the inner barrel, with the outlet located outside the outer barrel. The soil moisture sensor to be calibrated is installed inside the inner barrel and electrically connected to the edge monitoring and control terminal. The power supply system is electrically connected to and supplies power to the weighing platform, the edge monitoring and control terminal, the drain pump, and the soil moisture sensor to be calibrated.

[0006] When in use, the outer bucket is buried at the measurement site with its top above the ground, and the inner bucket contains soil from the measurement site.

[0007] Furthermore, it also includes an adjustable temperature heating resistor installed at the bottom of the inner barrel, which is electrically connected to the edge monitoring and control terminal.

[0008] Furthermore, a rangefinder for the soil surface of the inner barrel is installed above the inner barrel, and the rangefinder is electrically connected to the edge monitoring and control terminal.

[0009] Furthermore, it also includes a rain collector and a water storage tank, wherein the rain collector collects rainwater and stores it in the water storage tank.

[0010] Furthermore, the outlet of the drain pipe is located inside the water storage tank.

[0011] Furthermore, the water storage tank includes a water replenishment pump, which is electrically connected to the edge monitoring and control terminal. The outlet end of the water replenishment pump is connected to a water replenishment pipe, and a nozzle is provided at the outlet of the water replenishment pipe. The nozzle is located directly above the inner tank and sprays water downwards evenly.

[0012] Furthermore, the inner barrel includes a liquid level monitoring cylinder, which consists of a porous rigid pipe wrapped with permeable geotextile and a liquid level gauge, and the liquid level gauge is electrically connected to the edge monitoring and control terminal.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) The present invention can realize the in-situ on-site measurement of soil moisture by the soil moisture sensor, avoid various interference factors in the process of preparing soil samples with determined moisture content for calibration, and the equipment described in the present invention can be automatically operated without human input after installation; (2) The present invention can quickly realize the change from saturated soil to relatively dry soil by scheduling the equipped water replenishment, drainage and heating devices, and can form continuous monitoring and calibration of the whole process from wet to dry, avoiding the problem of limited sample quantity for preparing soil samples with determined moisture content for calibration; (3) The present invention can also combine weighing data and sensor data at different burial depths to realize the study of soil evaporation process, soil capillary water rise during rainfall, soil infiltration and other processes. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of this utility model. Detailed Implementation

[0015] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0016] This utility model discloses an online calibration system for a soil moisture sensor, such as... Figure 1 As shown, the system includes an outer bucket 1, an inner bucket 2, a weighing platform 3, an edge monitoring and control terminal 4, a soil moisture sensor 5 to be calibrated, and a power supply system. The outer bucket 1 is buried at the measurement site with its top higher than the ground. The weighing platform 3 is horizontally installed inside the outer bucket 1, and the weighing platform 3 has a built-in weighing sensor that is electrically connected to the edge monitoring and control terminal 4. The inner bucket 2 is placed on the weighing platform 3, and the inner wall and bottom of the inner bucket 2 are covered with a permeable material 6. Soil from the measurement site is placed inside the inner bucket. A drain pipe 7 is provided at the bottom of the inner bucket, and a drain pump 8 is provided at the outlet end of the drain pipe. The drain pump 8 is electrically connected to the edge monitoring and control terminal 4. The outlet end of the drain pump 8 is connected to a water outlet pipe 9, which extends upward along the outer wall of the inner bucket, with the outlet located outside the outer bucket 1. The soil moisture sensor 5 to be calibrated is installed in the soil of the inner bucket 2 and is electrically connected to the edge monitoring and control terminal 4. The power supply system is electrically connected to and supplies power to the edge monitoring and control terminal 4, the weighing platform 3, the drain pump 8, and the soil moisture sensor 5 to be calibrated.

[0017] In order to shorten the cycle of soil moisture changing from high to low, an adjustable temperature heating resistor 17 is located at the bottom of the inner barrel. The heating resistor 17 is electrically connected to the edge monitoring and control terminal 4, which accelerates soil moisture evaporation by heating the soil.

[0018] Since soil volume is affected by settlement and expansion and contraction caused by changes in soil moisture, a rangefinder 10 is installed above the inner measuring bucket 2 to measure the soil surface of the inner bucket. The rangefinder 10 is electrically connected to the edge monitoring and control terminal 4 to monitor the soil surface height and then calculate the soil volume.

[0019] To simulate the process of soil changing from dry to wet, a rain collector and a water storage tank 11 are included. The rain collector collects rainwater and stores it in the water storage tank 11 as a water source for actively humidifying the soil. The outlet of the drain pipe 9 is located inside the water storage tank 11, and the water actively discharged from the inner tank is collected in the water storage tank for reuse. In order to evenly spray the water in the water storage tank onto the soil in the inner tank for humidification and water replenishment, a water replenishment pump 12 is installed in the water storage tank. The water replenishment pump 12 is electrically connected to the edge monitoring and control terminal 4. The outlet end of the water replenishment pump 12 is connected to the water replenishment pipe 13. A nozzle 14 is installed at the outlet of the water replenishment pipe 13, and the nozzle 14 is located directly above the inner tank 2 to spray water evenly downwards.

[0020] In order to distinguish between saturated and unsaturated soil layers, a liquid level monitoring cylinder is installed in the inner barrel 2. The liquid level monitoring cylinder 15 consists of a porous rigid pipe wrapped with permeable geotextile and a liquid level gauge 16. The liquid level gauge 16 is electrically connected to the edge monitoring and control terminal 4.

[0021] The specific calibration calculation process is as follows:

[0022] S1: Fill the inner bucket 2 with dry soil of known weight w1, and keep it consistent with the bulk density of the external natural soil.

[0023] S2: The soil in the inner bucket 2 is moistened by water replenishment pump 12 or natural rainfall. The water level gauge 16 is used to determine whether there is a saturated layer in the soil. If there is a saturated layer, the drainage pump 8 is turned on to drain the gravity water in the soil.

[0024] S3: The weight of the moist soil in the inner bucket without a saturation layer is recorded as w2. The distance measuring instrument 10 above the measuring bucket measures the soil depth h in the inner bucket 2. The bottom area of ​​the inner bucket 2 is recorded as s, and the density of water is recorded as ρ. w The real-time volumetric water content of the soil is then...

[0025] S4: Compare and calibrate the soil volumetric moisture content calculated in S3 with the moisture content measured by the soil moisture sensor 5 to be calibrated;

[0026] S5: In addition to calibrating the soil moisture sensor under natural wet conditions, the soil moisture status can be quickly adjusted by the water supply pump 12, drainage pump 8, and heating resistor 17, thereby forming a continuous monitoring and calibration process from wet to dry.

Claims

1. A soil moisture sensor on-site online calibration system, characterized in that, The system includes an outer bucket (1), an inner bucket (2), a weighing platform (3), an edge monitoring and control terminal (4), a soil moisture sensor to be calibrated (5), and a power supply system. The weighing platform (3) is installed inside the outer bucket (1). The weighing platform (3) has a built-in weighing sensor, which is electrically connected to the edge monitoring and control terminal (4). The inner bucket (2) is placed on the weighing platform (3). The inner wall and bottom of the inner bucket (2) are covered with a permeable material (6). The bottom of the inner bucket (2) is provided with a drain pipe (7), which passes through the inner bucket (2) and exits at the outlet. A drainage pump (8) is provided at the end. The drainage pump (8) is electrically connected to the edge monitoring and control terminal (4). The outlet end of the drainage pump (8) is connected to the outlet pipe (9). The outlet pipe (9) extends upward along the outer wall of the inner bucket (2) and the outlet is located outside the outer bucket (1). The soil moisture sensor (5) to be calibrated is installed inside the inner bucket (2) and electrically connected to the edge monitoring and control terminal (4). The power supply system is electrically connected to and supplies power to the weighing platform (3), the edge monitoring and control terminal (4), the drainage pump (8), and the soil moisture sensor (5) to be calibrated.

2. The soil moisture sensor on-site online calibration system according to claim 1, characterized in that, It also includes an adjustable temperature heating resistor (17) installed at the bottom of the inner barrel, which is electrically connected to the edge monitoring and control terminal (4).

3. The soil moisture sensor on-site online calibration system according to claim 1, characterized in that, A rangefinder (10) for the soil surface of the inner bucket (2) is installed above the inner bucket, and the rangefinder (10) is electrically connected to the edge monitoring and control terminal (4).

4. The soil moisture sensor on-site online calibration system according to claim 1, characterized in that, It also includes a rain collector and a water storage tank (11), wherein the rain collector collects rainwater and stores it in the water storage tank (11).

5. The soil moisture sensor on-site online calibration system according to claim 4, characterized in that, The outlet of the water outlet pipe (9) is located inside the water storage tank (11).

6. The soil moisture sensor on-site online calibration system according to claim 4 or 5, characterized in that, The water storage tank (11) contains a water replenishment pump (12), which is electrically connected to the edge monitoring and control terminal (4). The outlet end of the water replenishment pump (12) is connected to a water replenishment pipe (13), and a nozzle (14) is provided at the outlet of the water replenishment pipe (13). The nozzle (14) is located directly above the inner tank (2) and sprays water downwards evenly.

7. The soil moisture sensor on-site online calibration system according to claim 1, characterized in that, The inner barrel (2) contains a liquid level monitoring cylinder (15), which is composed of a porous rigid pipe wrapped with permeable geotextile and a liquid level gauge (16). The liquid level gauge (16) is electrically connected to the edge monitoring and control terminal (4).

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