CN2814404Y - Capacitance type soil moisture sensor - Google Patents
Capacitance type soil moisture sensor Download PDFInfo
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- CN2814404Y CN2814404Y CN 200520074027 CN200520074027U CN2814404Y CN 2814404 Y CN2814404 Y CN 2814404Y CN 200520074027 CN200520074027 CN 200520074027 CN 200520074027 U CN200520074027 U CN 200520074027U CN 2814404 Y CN2814404 Y CN 2814404Y
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- polyacrylamide
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Abstract
The utility model relates to a capacitance type soil moisture sensor which is provided with two poles of a capacitor, wherein conducting wires of the two poles are connected with a signaling conversion circuit. The utility model is characterized in that a stainless steel bar with a helical groove port is wound with an enamelled wire, the stainless steel bar is used as one pole and the enamelled wire is used as the other pole. A clay pipe chamber is arranged outside a core of the stainless steel sensor, and the clay pipe chamber is loaded with light loam which is treated by artificial structure modifying agents. In a prioritization proposal, the artificial structure modifying agents adopt polyacrylamide which takes 0.1 % of the weight of the loam. The light loam which is treated by the artificial structure modifying agents has the components: 8 to 10% of clay particles which are smaller than 0.001 mm, 70 to 72% of powder particles which are between 0.001 mm and 0.05 mm, and 19 to 21% of fine sand particles which are larger than 0.05 mm, and the particles are fixed by high molecular polymers. The utility model makes the sensor kept favorable hydraulic connection with outside soil, rating work between the capacitance content of the sensor and the moisture content of the soil is simplified and the utility model solves a difficult problem in the traditional technology.
Description
Technical field
The utility model relates to a kind of soil monitoring instrument, is specifically related to a kind of capacity type soil humidity sensor.
Background technology
Capacity type soil humidity sensor is a kind of soil monitoring instrument of monitoring farmland moisture condition.Conventional condenser soil moisture sensor structure is: form capacitor plate by copper cone and copper ring, connect cable on two pole plates, draw in the middle of sensor.Copper ring and cone are twisted and are connected on the PVC plastic tube.For further preventing to leak electricity between two pole plates, on copper ring, scribble 502 glue of insulation.After its inserts soil, can measure that soil moisture changes and the electric capacitance change that causes.Because the structured testing narrow range of traditional capacitive transducer, and be subject to disturb, so general and often use.
In actual use, the elasticity of soil has a significant effect to condenser type soil moisture sensor measurement result.Therefore the condenser type moisture transducer often is more suitable for the determination of moisture in composition single (as cereal, sugar, sand, chemical fertilizer etc.) object.And the soil constituent complexity, degree of tightness differs, and this makes troubles to sensor application.Table 1 data is: when water cut is 11.3% light loam, and under different unit weights, the soil capacitance that records with capacity type soil humidity sensor probe (stainless steel bar is around last enameled wire).Visible influences is bigger.Therefore, directly with this type of naked stainless steel bar (around last enameled wire) capacitor as holard sensor, must carry out the relation curve calibration of soil moisture content and electric capacity at the scene.This is with very time-consuming and consumption power, and the laboratory calibration work of big quantity sensor can't be carried out.Even demarcate because you carry out correlation curve with undisturbed soil in the laboratory, but elasticity of its contact soil will take place greater than the test error more than 10% with to test soil consistent can not guarantee that sensor inserts field soil the time.This will make the application of sensor be restricted.
The soil weight is to capacitive effect during the identical water cut of table 1
| Soil weight g/cm 3 | Electric capacity (picofarad PF) |
| 1.15 1.26 1.38 | 1230 1440 1760 |
Summary of the invention
In order to overcome the above-mentioned difficult problem that the conventional condenser soil humidity sensor in use runs into, the purpose of this utility model is to make improvements, and a kind of capacity type soil humidity sensor of new construction is provided.New departure will make the good hydraulic connection of maintenance between sensor and extraneous soil, make soil texture, elasticity around the capacitor constant, make calibration work simplification between the electric capacity of sensor and the soil moisture content.
The technical scheme of finishing the foregoing invention task is, capacity type soil humidity sensor, be provided with two utmost points of capacitor, the lead of drawing two utmost points is connected with signaling conversion circuit, the signaling conversion circuit outgoing cable, output data, it is characterized in that, on the stainless steel bar that has the spiral notch, be wound with enameled wire, with stainless steel bar is a utmost point, is another utmost point with the enameled wire that twines its notch, is provided with the vitrified-clay pipe chamber in stainless steel sensor core outside, this pottery only is filled with the soil of handling with artificial texture modifier in the tube chamber chamber, and this soil adopts light loam.
Above-described artificial structure's modifying agent can be selected from following high molecular polymer: the high molecular polymer of the soil particles of reuniting such as polyacrylamide (PAM), polyvinyl alcohol (PVA) or polyacrylonitrile.Wherein the polyvinyl alcohol (PVA) consumption is wanted big (account for dry ground and weigh 0.2%); And agglomeration can not last till that polyacrylonitrile (account for dry ground and weigh 0.15%) function was the same with PAM 3 years, but the monomer whose severe toxicity is noted gas defence when handling soil.Account for native 0.05～0.2% the polyacrylamide (PAM) that weighs so the application recommends to adopt, its optimal values is 0.1%.
The pulsing circuit method is adopted in capacitance measurement during use.Through circuit conversion, electric capacity is converted to frequency signal.
Above scheme can further be improved, its prioritization scheme is: the light loam that the artificial texture modifier of described usefulness was handled, and its composition is: contain＜0.001mm clay 8～10% 0.05～0.001mm powder 70～72%,＞0.05mm fine sand 19～21%, and fix by high molecular polymer.
The high molecular polymer of described fixedly usefulness can still adopt high molecular polymers such as polyacrylamide (PAM), polyvinyl alcohol (PVA) or polyacrylonitrile, and wherein, the polyacrylamide addition is that soil is heavy by 0.09～0.11%; Polyacrylonitrile dry powder addition is that soil is heavy by 0.14～0.16%, and the polyvinyl alcohol (PVA) addition be native heavy by 0.19～0.21%.
In other words, feature of the present invention is: stainless steel sensor core is placed a kind of specific light loam, and this light loam contains＜0.001mm clay 9%, 0.05～0.001mm powder 71%,＞0.05mm fine sand 20%.The high molecular polymer that is used as artificial structure's modifying agent is handled soil, makes it reunionization, by certain unit weight vitrified-clay pipe chamber of packing into, and injects high molecular polymer again, makes its structure firm.This class soil should have preferable soil texture hole characteristic, each suction section soil to release water-based more well-balanced.So that keep good hydraulic connection between sensor and extraneous soil.Make capacitor soil texture, elasticity on every side constant like this.Make calibration work simplification between the electric capacity of sensor and the soil moisture content.
Because the soil of stainless steel sensor core outside has preferable soil texture hole characteristic, each suction section soil to release water-based more well-balanced.So that keep good hydraulic connection between sensor and extraneous soil, make capacitor soil texture, elasticity on every side constant.Make calibration work simplification between the electric capacity of sensor and the soil moisture content, solved the long-standing problem of traditional structure.
Principle: the electric capacity size of capacitor, relevant with medium character between pole plate and quantity.The potpourri that soil is made up of moisture, air, solid phase particles, the specific inductive capacity of soil moisture can reach 81, and the soil air specific inductive capacity is about 1, and the solid phase of soil material is owing to composition in the different soils is different, and their specific inductive capacity change is between 2～10.When soil becomes condenser dielectric, because three-phase of soil content of material (the especially amount of water and air growth and decline each other) often is among the upset condition, make the electric capacity of capacitor often be among the variation, because the specific inductive capacity of water is significantly greater than solid phase of soil particle and air, therefore, as dielectric capacitor, its DIELECTRIC CONSTANT value depends on the content of soil moisture with soil.
The DIELECTRIC CONSTANT of usual hybridization can be tried to achieve by following formula:
Vi is the volume of each composition of potpourri, and ε i is the specific inductive capacity of i phase, and this formula shows that the ε value of soil mixture depends primarily on the content of soil moisture.Because the density of soil and with condenser armature interpolar geometric influence the ε value, following formula can not directly be calculated the variation of soil electricity intermediate value (ε).But because the specific inductive capacity of water is the major event that influences soil dielectric constant.Therefore, what of soil moisture quantity are the mensuration electric capacitance change just can know.Though the two is not linear.
The utility model makes the good hydraulic connection of maintenance between sensor and extraneous soil, makes soil texture, elasticity around the capacitor constant, makes calibration work simplification between the electric capacity of sensor and the soil moisture content.
Description of drawings
Fig. 1 is a condenser type soil moisture sensor synoptic diagram;
Fig. 2 is threaded stainless steel bar synoptic diagram;
Fig. 3 represents capacitance type sensor electric capacity and output frequency relation;
Fig. 4 represents sensor output frequency and soil water content relation (sandy loam, Fengqiu, Henan);
Fig. 5 represents sensor capacitance variation and soil water content relation (sandy loam, Fengqiu, Henan).
Embodiment
Sensor construction
Condenser type soil moisture sensor structure as shown in Figure 1.By the diameter 12mm of band asperities, long 75mm stainless steel bar 2 and the φ 1.04mm that is around on the rod justify two pole plates of enameled wire 1 as capacitor.Be placed on diameter 33mm, long 100mm is in the pot clay end 3 of wall thickness 5mm.Be full of the light loamy texture soil of handling through polyacrylamide (PAM) 4 therebetween.
Pot clay end chamber roof epoxy resin and silastic mixture 5 sealing, and draw capacitor two pole plate leads.Signaling conversion circuit plate 6 place the PVC that joins with pot clay end mould the pipe 7 in, glue 8 sealing are also used at its top, and from the circular hole of top outgoing cable 9.
Capacitor as shown in Figure 2.With stainless steel bar 2 is a utmost point, is another utmost point with the enameled wire 1 that twines its notch, has formed the capacitor of testing soil electric capacity.After its inserts soil, can measure that soil moisture changes and the electric capacitance change that causes.Stainless steel bar winding slot length overall 63mm, 32 circles can wind the line.Wide 2mm between its screw thread, groove depth 1mm.The stainless steel bar of this physical dimension, wide more little between screw thread, electric capacity is big (as table 2).For convenience that winds the line and the embedded quantity that increases soil, we have selected the size of present application for use.
Wide and electric capacity relation between table 2 screw thread
| Wide between the stainless steel bar screw thread (mm) | Electric capacity during water saturation (picofarad) |
| 1.5 2 3 | 3800 3650 2740 |
There is the hole of a φ 2mm on the left side of rod, is used for fixing enameled wire one end.The pore that can twist bolt is arranged at the right-hand member top of rod.So that connection lead.
The pulsing circuit method is adopted in capacitance measurement.Through circuit conversion, electric capacity is converted to frequency signal.Mensuration shows, from 0.758 microfarad to 5.43 microfarad, is equivalent to 6.1～0.883 kilo hertzs of frequency signals after circuit conversion, and the relationship of the two as shown in Figure 3.Change electric capacity into frequency signal, it has two aspect superiority, and the frequency signal antijamming capability is stronger on the one hand, has improved the precision of signal transmission.It can directly be accepted by computing machine on the other hand, reduces change and send link and save cost.
The manufacture craft of sensor
New soil moisture transducer manufacture craft is roughly divided following step.
(1) device is prepared:
1. the stainless steel core of car system (as Fig. 1) after batch is big, can adopt the pressed film method manufacturing.Make individual difference littler.
2. φ 1.04mm justifies enameled wire.Skin is coated with polyurethane paint, chemical corrosion abilities such as tool is antiacid, alkali.
3. wiring board is made and the device welding.
4. air-dry, the levigate 2mm of mistake of soil sample sieves.Adding accounts for the heavy per mille polyacrylamide of soil, makes soil particle aggregation, and air-dry again, the levigate 2mm of mistake sieves standby.Polyacrylamide dry powder dissolves in earlier in the hot distilled water that constantly boils with 1% concentration.When handling soil, more above-mentioned 1%PAM stoste is added certain water yield, make soil moisture content after the processing, and soil is sucked account for soil and weigh 1 ‰ PAM near field capacity.
The light loam that the artificial texture modifier of above-mentioned usefulness was handled, its composition is: contain＜0.001mm clay 9%, 0.05～0.001mm powder 71%＞0.05mm fine sand 20%.
(2) sensor production:
1. coiling capacitor core
Enameled wire one end puts about 15mm soft plastic pipe, and inserts in stainless steel left end (Fig. 2) circular hole, is coated with that (epoxy resin: sealing silicon rubber=8: 2) prevents that the conducting phenomenon takes place between copper cash and stainless steel into insulating resin.Then, enameled wire is taken up on stainless steel bar, and fix with nylon wire at right-hand member along screw thread.On stainless steel core right-hand member double-screw bolt, draw a lead.
Resistance should be more than 20 megaohms between measurement enameled wire and the stainless steel core.Otherwise recoil.This test should be immersed stainless steel bar after the coiling in the tap water and be carried out.
2. take by weighing the soil that 21 grams are handled well, the stainless steel capacitor that winds line is put into pot clay end, it is placed on the axis, around add soil, and by beaing the first-class way of potter's clay that grogs is arranged is fine and close, and splash into the PAM solution of 0.25% concentration, further strengthen cementing power between grogs.
3. after treating the grogs drying, with epoxy resin and silicon rubber epoxy glue sealing pot clay end upper end (about 20mm height).
4. the enameled wire of the pot clay end upper end that will stretch out is cut short into 20～25mm length with the lead that draws from stainless steel upper end bolt.And connect wiring board.On three connection terminals of the other end of wiring board, connect three open traverses respectively.They are respectively power supply (9 volts) positive and negative electrode (shared with the signal negative pole), and another lead then is an output line.
5. at the glued place of pot clay end and pvc pipe, be coated with lateral surface and top in the envelope total interface (making in the future sensor imbed in the soil the unlikely chamber that enters electric appliance circuits of moisture afterwards) with epoxy resin.Connect PVC then and mould pipe.On moulding pipe, fill in perforated foams.10～25mm place is packed into epoxy resin and silicon rubber epoxy glue at distance pvc pipe top.This glue not only has certain intensity, and certain elasticity is arranged, and prevents that inwall from entering moisture owing to coming unstuck, and then corrodes electric appliance circuits.Therefore, three lines that pass epoxy glue part all should be bare wires (not wrap insulate material) in case steam infiltrates.
6. the sensor of having made, treat the aging scleroma of glue after, 2/3 pot clay end was vertically steeped in the entry two days, it is fully absorbed water.Take out then and dry.(record frequency values more than 2.2 kilo hertzs the time, show that pot clay end and inner soil are dry).Soaked again, dry three times repeatedly.Make inner soil structure behind alternation of wetting and drying repeatedly further stable.
The performance of sensor and use
Fig. 4 is the rating curve of condenser type soil moisture sensor in sand loam.Fig. 5 is the response curve that sensor capacitance and soil moisture content change.Can see that from the figure upper curve water cut and electric capacity are not linear.The match formula of the relationship of the two is a trinomial, R
2Be 0.9963.Data shows, and is still very good even soil moisture content is in the response of dry its rating curve of scope (2.5%～10%).Therefore this sensor is much better than tensiometer at the power of test of antecedent soil moisture section.The scope of testing soil moisture has had remarkable expansion.Be applicable to the fixed point supervision of arid area soil moisture.This sensor is also unlike tensiometer, and the latter need add water when the supervision of location.After it imbeds in the soil, need not to do other management again, easy to use.
The rating method of transmitter:
Because the various places soil property has nothing in common with each other, during the identical water cut of different soils, the measured frequency signal of moisture probe is not quite similar.Therefore, before using this sensor to carry out mensuration work, must carry out the calibration work that concerns between soil moisture content and the output frequency signal.
The method of calibration is as follows: obtain original-state soil, place wooden case or iron case, with the earth boring auger punching, imbed moisture probe (moisture probe should soak more than 6 hours earlier) in water.Sensor is connected the power supply of 9VDC power supply.
Soil adds water in case, makes it water saturation.
In the soil evaporation dehydration process, constantly test the output frequency of transmitter, with soil moisture content.Until the soil bone dry.Thereby obtained soil moisture content and transmitter output frequency calibration relation.And it is standby that it is fitted to formula.
Soil moisture content can be with weighing method or is used little earth boring auger soil sampling at every turn, uses oven method measuring.
Can adopt ways such as order solarization, wind for accelerating evaporation process.
In the arid area, also can directly demarcate between water cut and the transmitter output frequency and concern in the field.The using method of transmitter:
Sensor behind calibration can be used in the field.Before in imbedding soil, pot clay end 3/4ths should be immersed in a night in the water.Make it fully moistening.
With the earth boring auger punching, the degree of depth is decided by the monitoring depth of soil.In boring, pour about 30ML mud into, on pot clay end, also coat mud, sensor is headed in the hole with wooden stick.Mud can make between pot clay end and the soil and contact closely.
Moistening soil is after half a day, and dry soil can be tested after one day.
The available frequency signal that ammeter (or several) determination sensor output once a day of frequency test shelves is arranged.With the frequency data that record by the fitting formula of rating curve calculate soil moisture content.
Claims (5)
1, a kind of capacity type soil humidity sensor, be provided with two utmost points of capacitor, the lead of drawing two utmost points is connected with signaling conversion circuit, the signaling conversion circuit outgoing cable, output data, it is characterized in that, on the stainless steel bar that has the spiral notch, be wound with enameled wire, with stainless steel bar is a utmost point, with the enameled wire that twines its notch is another utmost point, be provided with the vitrified-clay pipe chamber in stainless steel sensor core outside, be filled with the soil of handling with artificial texture modifier in this vitrified-clay pipe chamber, this soil adopts light loam.
2, according to the described capacity type soil humidity sensor of claim 1, it is characterized in that described artificial structure's modifying agent is selected from following high molecular polymer: account for soil and weigh 0.05～0.2% polyacrylamide, account for soil and weigh 0.18～0.25% polyvinyl alcohol (PVA) or account for soil and weigh 0.12～0.2% polyacrylonitrile.
According to the described capacity type soil humidity sensor of claim 2, it is characterized in that 3, the high molecular polymer of described artificial structure's modifying agent adopts and accounts for native 0.1% the polyacrylamide that weighs.
4, according to claim 1 or 2 or 3 described capacity type soil humidity sensors, it is characterized in that, the light loam that the artificial texture modifier of described usefulness was handled, its composition is: contain＜0.001mm clay 8～10%, 0.05～0.001mm powder 70～72%,＞0.05mm fine sand 19～21%, and fix by high molecular polymer;
The high molecular polymer of described fixedly usefulness is selected from polyacrylamide, polyvinyl alcohol (PVA) or polyacrylonitrile, and wherein, the polyacrylamide addition is that soil is heavy by 0.09～0.11%; Polyacrylonitrile dry powder addition is that soil is heavy by 0.14～0.16%, and the polyvinyl alcohol (PVA) addition be native heavy by 0.19～0.21%.
According to the described capacity type soil humidity sensor of claim 4, it is characterized in that 5, the high molecular polymer of described fixedly usefulness adopts 0.10% heavy polyacrylamide of soil.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200520074027 CN2814404Y (en) | 2005-07-29 | 2005-07-29 | Capacitance type soil moisture sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200520074027 CN2814404Y (en) | 2005-07-29 | 2005-07-29 | Capacitance type soil moisture sensor |
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| CN2814404Y true CN2814404Y (en) | 2006-09-06 |
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| CN 200520074027 Expired - Lifetime CN2814404Y (en) | 2005-07-29 | 2005-07-29 | Capacitance type soil moisture sensor |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100368797C (en) * | 2005-07-29 | 2008-02-13 | 中国科学院南京土壤研究所 | Capacity type soil humidity sensor and its manufacturing method |
| CN104508472A (en) * | 2012-07-27 | 2015-04-08 | 阿尔弗雷德·凯驰两合公司 | Capacitive device for measuring the moisture content of soil and having a porous access element |
| US9303458B2 (en) | 2010-12-03 | 2016-04-05 | Shell Oil Company | Method and system for radially expanding a tubular element |
| CN105486729A (en) * | 2016-01-18 | 2016-04-13 | 北京至感传感器技术研究院有限公司 | Humidity sensor |
| CN107384422A (en) * | 2017-07-25 | 2017-11-24 | 安徽天知蓝农林科技有限公司 | A kind of fruit tree planting soil modifying agent |
| CN112042506A (en) * | 2020-05-27 | 2020-12-08 | 宁波大叶园林工业股份有限公司 | Soil humidity alarm with soil standard wetting box |
-
2005
- 2005-07-29 CN CN 200520074027 patent/CN2814404Y/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100368797C (en) * | 2005-07-29 | 2008-02-13 | 中国科学院南京土壤研究所 | Capacity type soil humidity sensor and its manufacturing method |
| US9303458B2 (en) | 2010-12-03 | 2016-04-05 | Shell Oil Company | Method and system for radially expanding a tubular element |
| CN104508472A (en) * | 2012-07-27 | 2015-04-08 | 阿尔弗雷德·凯驰两合公司 | Capacitive device for measuring the moisture content of soil and having a porous access element |
| CN105486729A (en) * | 2016-01-18 | 2016-04-13 | 北京至感传感器技术研究院有限公司 | Humidity sensor |
| CN107384422A (en) * | 2017-07-25 | 2017-11-24 | 安徽天知蓝农林科技有限公司 | A kind of fruit tree planting soil modifying agent |
| CN112042506A (en) * | 2020-05-27 | 2020-12-08 | 宁波大叶园林工业股份有限公司 | Soil humidity alarm with soil standard wetting box |
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| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned |
Effective date of abandoning: 20080213 |
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| AV01 | Patent right actively abandoned |
Effective date of abandoning: 20080213 |
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| C25 | Abandonment of patent right or utility model to avoid double patenting |