CN110579512A - manufacturing and calibration method of filter type soil moisture content sensor - Google Patents
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Abstract
The invention discloses a manufacturing and calibrating method of a filter type soil moisture content sensor, belonging to the technical field of soil moisture content testing tools and tests. The structure of the filter type soil moisture content sensor is formed by filling diatomite in a cylindrical filter, inserting a round rod electrode into the center of the diatomite, respectively welding leads at the top end of the round rod electrode and the upper end of the cylindrical filter, and connecting the leads to a measuring circuit. And then simultaneously measuring by adopting a filter type sensor and an imported main flow TDR sensor, and calibrating the soil sample water content corresponding to the voltage value of the filter type sensor. The filter type soil moisture content sensor manufactured by the invention has the advantages of simple and compact structure, novel principle, stable measurement, low cost and convenient use, and is suitable for agriculture, forestry and green environment plant planting.
Description
Technical Field
The invention belongs to the technical field of soil moisture content testing tools and tests; in particular to a method for manufacturing and calibrating a filter type soil moisture content sensor.
Background
in agricultural production, accurate irrigation requires long-term detection and timely acquisition of soil moisture spatial distribution information in the field, so that a soil moisture testing device needs to be installed in the field.
At present, mature soil moisture content detection methods include a Time Domain Reflectometry (TDR), a Frequency Domain Reflectometry (FDR) and a standing wave rate reflectometry (SWR), wherein the TDR and the FDR are foreign patent technologies and have high measurement accuracy, but the cost is extremely high due to the complexity of a processing circuit, one TDR reaches tens of thousands of dollars, and one FDR reaches thousands of dollars; the three soil moisture sensors cannot be popularized and applied in the field because the average annual income per mu of crops is not high. In the chinese patent 201810191352.8, a cross-sectional soil moisture content monitor for agricultural irrigation, the soil moisture content monitor is formed by sequentially inserting three resistance type water potential probes into a cross-sectional pipe from top to bottom; compact, low-power consumption soil moisture automatic detector based on wireless transmission. The shell of the automatic soil moisture detector is formed by sequentially connecting an embedded support rod, a conversion joint, a main board, a lithium ion battery fixing bin and a detector top cap to form deep-layer water content, and the commodity information of soil with different depths is detected in real time; at 201720067029.0, based on the compact, low-power consumption soil moisture automatic detector of wireless transmission, this soil moisture automatic detector's shell is connected in proper order by burying bracing piece, crossover sub, mainboard and lithium ion battery fixed bin and detector hood and is constituteed, detects different degree of depth soil business situation information in real time. However, in China, water is used for agricultural irrigation or urban greening in a very extensive way, namely, manual irrigation is carried out regularly by experience. The original irrigation mode can not ensure the water quantity required by the normal growth of the plants, and simultaneously, the precious water resource is greatly wasted. The manual flood irrigation method commonly used in landscaping water can cause the water on the surface of soil to flow along the terrain to form water puddles or flow to roads without permeating into the root systems of plants, thus causing waste. In various irrigation systems, because the difference of the deep water content of each of soil top layer and its below, the different degree of depth soil business situation information of real-time detection, according to the water demand of the different growth periods of crop come the appropriate amount to irrigate, this just needs to lay low-cost soil moisture sensor on a large scale, carries out real time monitoring to solve how existing growth that does benefit to the plant does not waste the problem of water resource as far as possible.
Disclosure of Invention
the invention aims to provide a manufacturing and calibration method of a filter type soil moisture content sensor, which is characterized in that the structure of the filter type soil moisture content sensor is that diatomite 1 is filled in a cylindrical filter 2, a round rod electrode 3 is inserted into the center of the diatomite 1, and leads 4 are welded at the top end of the round rod electrode 3 and the upper end of the cylindrical filter 2 and are connected with a measuring circuit 5; wherein, the round bar electrode adopts a stainless steel needle; the filter is made of 1CR18NI9TI stainless steel powder and is pressed and formed according to the aperture of 2 mu m, thus achieving the pottery clay effect, and being corrosion-resistant and strong in plasticity.
the manufacturing process of the filter type soil moisture content sensor comprises the following steps:
1) cleaning the diatomite and the filter to reduce the influence of impurities as much as possible;
2) weighing 6g of diatomite by using an electronic scale, putting the diatomite into a paper cup, and diluting the paper cup to a half cup by using purified water; sealing the lower half part of a stainless steel cylindrical filter by using an O-shaped ring, connecting the lower half part with a vacuum pump, pouring diluted diatomite solution from the upper part of the cylindrical filter, starting the vacuum pump to quickly pump water and air in the diatomite solution, and thus forming diatomite solute with certain density and uniform distribution in the cylindrical filter;
3) Inserting the electrode into the diatomite solute in the cylindrical filter and keeping the electrode coaxial with the filter; a laser welding lead 4 is adopted, one end of one lead is welded with the electrode, the other end of the lead is connected with the measuring circuit 5, one end of the other lead is welded with the upper end of the cylindrical filter shell, and the other end of the other lead is connected with the measuring circuit 5 to form a measuring loop; filling each seal of the filter type soil moisture content sensor with sealant; completing the manufacture of the filter type soil moisture content sensor;
4) the measuring circuit comprises a buck-boost chip tps63030, an AD736 AC/DC conversion chip, an 8038 AC/DC conversion chip, an amplifying circuit OP07, a filter type sensor and a precise sampling resistor which are connected in series; the 3.3V power supply is connected with the buck-boost chip tps63030, and the buck-boost chip tps63030 outputs DC 5V; one path of the DC 5V s is connected with an AD736 AC/DC conversion chip; the other path is connected with a boosting dcdc (0509s) circuit, the output DC 9V is connected with the 8038 alternating current-direct current conversion chip, the output alternating current is 1.5V, and the alternating current 1.5V is connected with an amplifying circuit OP07, a filter type sensor and a precise sampling resistor in series; then the sampling resistor is connected with the AD736 AC/DC conversion chip; the specific test process is that a 3.3V power supply is converted into DC 5V power supply through a buck-boost chip tps63030, and one power supply is used for supplying power to an AD736 alternating current-direct current conversion chip; the other path of the signal is converted into DC 9V through a booster circuit dcdc0509s, and finally converted into an alternating current 1.5V signal through an 8038 alternating current-direct current conversion chip; the following enhancement drive effect of the amplifying circuit OP07 is used for connecting the filter type sensor and the precision sampling resistor in series, and the alternating current voltage signal of the sampling resistor is converted into a direct current voltage signal through the AD736 alternating current-direct current conversion chip for detection. When the filter type soil moisture content sensor is buried in soil, the diatomite 1 of the filter type soil moisture content sensor exchanges with water in the soil through the cylindrical filter 2, the conductivity of the diatomite can be remarkably changed along with the change of the humidity, the conductivity of the diatomite can be remarkably changed corresponding to an alternating current signal on the sampling resistor connected in series, and therefore the change of the soil moisture content can be reflected through detecting the voltage value of the sampling resistor.
In the determination, direct current signals flowing through the filter type soil moisture content sensor and the sampling resistor are detected in the early stage, but when the soil humidity is high, the time for entering a stable state after electrification is long, the power consumption is high, the electrode corrosion is serious, and the measurement accuracy is not high; instead of alternating current measurement, the above problem is solved. However, the ac signal is not conducive to the direct reading of the data card, so the ac signal passing through the sampling resistor is converted into dc by the ac/dc conversion chip and then enters the data card for sampling.
a method for calibrating a filter type soil moisture content sensor is characterized by comprising the following steps:
1) Establishing a testing system, and uniformly filling a soil sample 9 with known water content in a soil tank 10 which is made of organic glass and has the diameter of 200mm and the height of 120mm according to the designed volume weight; burying the filter type soil moisture content sensor 8 into the soil sample 9; inserting an inlet main flow TDR sensor 6; connecting a lead 4 of a filter type soil moisture content sensor 8 with a measuring circuit 5, and respectively connecting a signal output line of the measuring circuit 5 and a signal output line of a TDR sensor 6 with a data acquisition unit 7 to form a test system;
2) placing the system in a water container, wherein the water surface in the container is as close to the upper edge of the soil tank 10 as possible, but the water cannot permeate into the soil tank 10, the soil sample 9 slowly absorbs water through the pores at the bottom end of the soil tank 10, and after standing for 1 day, the soil sample 9 basically reaches a saturated state; then the system is left in the air for evaporation, and simultaneously, the measuring circuit 5 and the data collector 7 connected with the filter type sensor 8 are started to collect signals of the filter type sensor 8 and the main flow TDR sensor 6. When the soil is evaporated to have low water content, saturating the soil sample again and carrying out repeated tests; after a number of iterations, a correspondence of the filter type sensor 8 to the main flow TDR sensor 6 readings is obtained (as shown in fig. 4).
3) the results of multiple tests show that the filter type sensor has good overlap ratio in other processes (processes 2-4) except the system is stable and balanced for the first time (process 1), and has stable performance compared with the test results of an international mainstream TDR probe.
The filter type soil moisture content sensor has the advantages of simple and compact structure, novel principle, stable measurement, low cost and convenient use, and is suitable for agriculture, forestry and green environment plant planting.
drawings
Fig. 1 is a schematic structural view of a filter type soil moisture content sensor.
Fig. 2 is a block diagram of a filter type soil moisture content sensor measuring circuit.
FIG. 3 is a schematic diagram of a calibration system of a filter type soil moisture content sensor.
FIG. 4 is a graph showing the results of repeated tests of the calibration of the filter type soil moisture sensor.
Detailed Description
the invention provides a method for manufacturing and calibrating a filter type soil moisture content sensor, which is described below by combining the accompanying drawings and an embodiment.
Fig. 1 is a schematic structural view of a filter type soil moisture content sensor. In the figure, the structure of the filter type soil moisture content sensor is shown as follows; a cylindrical filter 2 with the outer diameter of 24.6mm, the inner diameter of 19.7mm and the height of 100mm is filled with diatomite 1, a round rod electrode 3 with the diameter of 10mm and the height of 90mm is inserted into the center of the diatomite 1, and leads 4 are welded at the top end of the round rod electrode 3 and the upper end of the cylindrical filter 2 respectively and are connected with a measuring circuit 5; wherein, the round bar electrode adopts a stainless steel needle; the filter is made of 1CR18NI9TI stainless steel powder and is pressed and formed according to the aperture of 2 mu m, thus achieving the pottery clay effect, and being corrosion-resistant and strong in plasticity.
the manufacturing process of the filter type soil moisture content sensor comprises the following steps:
1) Cleaning the diatomite and the filter to reduce the influence of impurities as much as possible;
2) weighing 6g of diatomite by using an electronic scale, putting the diatomite into a paper cup, and diluting the paper cup to a half cup by using purified water; sealing the lower half part of a stainless steel cylindrical filter by using an O-shaped ring, connecting the lower half part with a vacuum pump, pouring diluted diatomite solution from an inlet on the upper part of the cylindrical filter, starting the vacuum pump to quickly pump water and air in the diatomite solution, and thus forming a diatomite solute with certain density and uniform distribution in the cylindrical filter;
3) Inserting the electrode into the diatomite solute in the cylindrical filter and keeping the electrode coaxial with the filter; a laser welding lead 4 is adopted, one end of one lead is welded with the electrode, the other end of the lead is connected with the measuring circuit 5, one end of the other lead is welded with the upper end of the cylindrical filter shell, and the other end of the other lead is connected with the measuring circuit 5 to form a measuring loop; filling each seal of the filter type soil moisture content sensor with sealant; completing the manufacture of the filter type soil moisture content sensor;
4) The measuring circuit comprises a buck-boost chip tps63030, an AD736 AC/DC conversion chip, an 8038 AC/DC conversion chip, an amplifying circuit OP07, a filter type sensor and a precise sampling resistor which are connected in series; the 3.3V power supply is connected with the buck-boost chip tps63030, and the buck-boost chip tps63030 outputs DC 5V; one path of the DC 5V s is connected with an AD736 AC/DC conversion chip; the other path is connected with a boosting dcdc (0509s) circuit, the output DC 9V is connected with the 8038 alternating current-direct current conversion chip, the output alternating current is 1.5V, and the alternating current 1.5V is connected with an amplifying circuit OP07, a filter type sensor and a precise sampling resistor in series; then the sampling resistor is connected with the AD736 AC/DC conversion chip; the specific test process is that a 3.3V power supply is converted into DC 5V power supply through a buck-boost chip tps63030, and one power supply is used for supplying power to an AD736 alternating current-direct current conversion chip; the other path of the signal is converted into DC 9V through a booster circuit dcdc0509s, and finally converted into an alternating current 1.5V signal through an 8038 alternating current-direct current conversion chip; the following enhancement drive effect of the amplifying circuit OP07 is used for connecting the filter type sensor and the precision sampling resistor R in series, and the alternating current voltage signal of the sampling resistor R is converted into a direct current voltage signal through the AD736 alternating current-direct current conversion chip for detection. When the filter type soil moisture content sensor is buried in soil, the diatomite 1 of the filter type soil moisture content sensor exchanges with water in the soil through the cylindrical filter 2, the conductivity of the diatomite can be remarkably changed along with the change of the humidity, the conductivity of the diatomite can be remarkably changed corresponding to an alternating current signal on the sampling resistor connected in series, and therefore the change of the soil moisture content can be reflected through detecting the voltage value of the sampling resistor.
In the determination, direct current signals flowing through the filter type soil moisture content sensor and the sampling resistor are detected in the early stage, but when the soil humidity is high, the time for entering a stable state after electrification is long, the power consumption is high, the electrode corrosion is serious, and the measurement accuracy is not high; instead of alternating current measurement, the above problem is solved. However, the ac signal is not conducive to the direct reading of the data card, so the ac signal passing through the sampling resistor is converted into dc by the ac/dc conversion chip and then enters the data card for sampling.
The water content of the filter type soil moisture content sensor is calibrated,
(1) A schematic diagram of a system for calibrating a filter type soil moisture content sensor is adopted as shown in FIG. 3; a soil tank 10 with the diameter of 200mm and the height of 120mm is filled with soil samples 9 with known water content according to the designed volume weight, and is inserted into a filter type soil moisture content sensor 8, and the depth is a certain depth below the upper surface of the embedded soil samples 9; inserting an inlet main flow TDR sensor 6; connecting a lead 4 of a filter type soil moisture content sensor 8 with a measuring circuit 5, and respectively connecting a signal output line of the measuring circuit 5 and a signal output line of a TDR sensor 6 with a data acquisition unit 7 to form a test system;
(2) The water content calibration process comprises the steps that a soil tank is placed in a water container, the water surface in the container is close to the upper edge of a soil tank 10 as much as possible but cannot penetrate into the soil tank 10, a soil sample 9 slowly absorbs water through a pore at the bottom end of the soil tank 10, and after the soil sample 9 is placed for 1 day, the soil sample 9 basically reaches a saturated state; the system was then left to stand in air for evaporation while the data collector 7 was started for signal acquisition by the filter type sensor 8 and the main flow TDR sensor 6. When the soil is evaporated to have low water content, saturating the soil sample again, and carrying out repeated tests for many times; after four repetitions as shown in fig. 4, a correspondence of the filter type sensor 8 to the readings of the main flow TDR sensor 6 is obtained.
(3) the results of multiple tests show that the filter type sensor has good overlap ratio in other processes (processes 2-4) except the system is stable and balanced for the first time (process 1), and has stable performance compared with the test results of an international mainstream TDR probe.
Claims (5)
1. A filter type soil moisture content sensor is characterized in that a cylindrical filter (2) with an outer diameter is filled with diatomite (1), a round rod electrode (3) is inserted into the center of the diatomite (1), and leads (4) are welded at the top end of the round rod electrode (3) and the upper end of the cylindrical filter (2) and connected with a measuring circuit (5); wherein, the round bar electrode adopts a stainless steel needle; the filter is made of 1CR18NI9TI stainless steel powder and is pressed and formed according to the aperture of 2 mu m, thus achieving the pottery clay effect, and being corrosion-resistant and strong in plasticity.
2. A method for manufacturing a filter type soil moisture sensor according to claim 1, comprising the steps of:
1) Cleaning the diatomite and the filter to reduce the influence of impurities as much as possible;
2) Weighing 6g of diatomite by using an electronic scale, putting the diatomite into a paper cup, and diluting the paper cup to a half cup by using purified water; sealing the lower half part of a stainless steel cylindrical filter by using an O-shaped ring, connecting the stainless steel cylindrical filter with a vacuum pump, and pouring diluted diatomite solution from the upper part of the cylindrical filter; then starting a vacuum pump, and quickly pumping water and air out of the diatomite solution, thereby forming a diatomite solute with certain density and uniform distribution in the cylindrical filter;
3) inserting a round rod electrode (3) into the diatomite solute in the cylindrical filter (2) and keeping the round rod electrode coaxial with the filter; laser welding leads (4) are adopted, one end of one lead is welded with the electrode, the other end of the lead is connected with the measuring circuit (5), one end of the other lead is welded with the upper end of the cylindrical filter shell, and the other end of the other lead is connected with the measuring circuit (5) to form a measuring loop; filling each seal of the filter type soil moisture content sensor with sealant; completing the manufacture of the filter type soil moisture content sensor;
4) The measuring circuit comprises a buck-boost chip tps63030, an AD736 AC/DC conversion chip, an 8038 AC/DC conversion chip, an amplifying circuit OP07, a filter type sensor and a precise sampling resistor which are connected in series; the 3.3V power supply is connected with the buck-boost chip tps63030, and the buck-boost chip tps63030 outputs DC 5V; one path of the DC 5V s is connected with an AD736 AC/DC conversion chip; the other path is connected with a boosting dcdc (0509s) circuit, the output DC 9V is connected with the 8038 alternating current-direct current conversion chip, the output alternating current is 1.5V, and the alternating current 1.5V is connected with an amplifying circuit OP07, a filter type sensor and a precise sampling resistor in series; then the sampling resistor is connected with the AD736 AC/DC conversion chip; the specific test process is that a 3.3V power supply is converted into DC 5V power supply through a buck-boost chip tps63030, and one power supply is used for supplying power to an AD736 alternating current-direct current conversion chip; the other path of the signal is converted into DC 9V through a booster circuit dcdc0509s, and finally converted into an alternating current 1.5V signal through an 8038 alternating current-direct current conversion chip; the following enhanced driving effect of the amplifying circuit OP07 is used for connecting a filter type sensor and a precision sampling resistor in series, and an alternating current voltage signal of the sampling resistor is converted into a direct current voltage signal through an AD736 alternating current-direct current conversion chip for detection; when the filter type soil moisture content sensor is buried in soil, the diatomite (1) exchanges with the moisture in the soil through the cylindrical filter (2), the conductivity of the diatomite can be remarkably changed along with the change of the humidity, the conductivity of the diatomite can be remarkably changed corresponding to an alternating current signal on the sampling resistor connected in series, and therefore the change of the soil moisture content can be reflected by detecting the voltage value of the sampling resistor.
3. the method of claim 2, wherein the filter-type soil moisture sensor detects the dc signal flowing through the filter-type soil moisture sensor and the sampling resistor at an early stage, but when the soil humidity is high, the time required for the filter-type soil moisture sensor to enter a stable state after power-on is long, the power consumption is high, the electrode corrosion is severe, and the measurement accuracy is not high; instead of alternating current measurement, the above problem is solved; however, the ac signal is not conducive to the direct reading of the data card, so the ac signal passing through the sampling resistor is converted into dc by the ac/dc conversion chip and then enters the data card for sampling.
4. The utility model provides a moisture content calibration method of filter type soil moisture content sensor which characterized in that includes:
1) Firstly, establishing a testing system, and uniformly filling a soil sample (9) with known water content in a soil tank (10) made of organic glass according to the designed volume weight; burying all the filter type soil moisture content sensors (8) into a soil sample (9); inserting an inlet main flow TDR sensor (6); connecting a lead (4) of a filter type soil moisture content sensor (8) with a measuring circuit (5), and respectively connecting a signal output line of the measuring circuit (5) and a signal output line of a TDR sensor (6) into a data acquisition unit (7) to form a test system;
2) Placing the testing system in a water container, wherein the water surface in the container is as close to the upper edge of the soil tank (10) as possible but cannot penetrate into the soil tank (10), the soil sample (9) slowly absorbs water through the pores at the bottom end of the soil tank (10), and after standing for 1 day, the soil sample (9) basically reaches a saturated state; then, the system is placed in the air to evaporate, and meanwhile, the measuring circuit (5) and the data collector (7) are started to collect signals of the filter type soil moisture content sensor (8) and the main flow TDR sensor (6); when the soil is evaporated to have low water content, saturating the soil sample again and carrying out repeated tests; obtaining the corresponding relation between the voltage value of the filter type soil moisture content sensor (8) and the measured value of the main flow TDR sensor (6);
3) The filter type sensor needs stable balance except the first test process after multiple test results show; the results obtained in the second process, the third process and the fourth process are good in coincidence degree, and compared with the test result of the international main-flow TDR probe, the performance is stable.
5. A filter type soil moisture sensor is characterized in that a cylindrical filter (2) with the outer diameter of 24.6mm, the inner diameter of 19.7mm and the height of 100mm is filled with diatomite (1), a round rod electrode (3) with the diameter of 10mm and the height of 90mm is inserted into the center of the diatomite (1), and leads (4) are respectively welded at the top end of the round rod electrode (3) and the upper end of the cylindrical filter (2) and are connected with a measuring circuit (5); wherein, the round bar electrode adopts a stainless steel needle; the filter is made of 1CR18NI9TI stainless steel powder and is pressed and formed according to the aperture of 2 mu m, thus achieving the pottery clay effect, and being corrosion-resistant and strong in plasticity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910954922.9A CN110579512B (en) | 2019-10-09 | 2019-10-09 | Manufacturing and calibrating method of filter type soil moisture sensor |
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| CN201910954922.9A CN110579512B (en) | 2019-10-09 | 2019-10-09 | Manufacturing and calibrating method of filter type soil moisture sensor |
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