WO2020217243A1

WO2020217243A1 - Water absorbent tensiometer for determining moisture levels for irrigation

Info

Publication number: WO2020217243A1
Application number: PCT/IL2020/050468
Authority: WO
Inventors: Oleg KOROL
Original assignee: Korol Oleg
Priority date: 2019-04-26
Filing date: 2020-04-23
Publication date: 2020-10-29

Abstract

A tensiometer designed to produce more accurate readings and reduced manual maintenance by means of using Super Absorbent Polymer (SAP) filling inside the tensiometer which absorbs water and expands when the moisture content in the surrounding soil is rising and releases it into the soil when its moisture level decreases. Accordingly by measuring either the pressure produced inside SAP filling or by measuring capacitive change produced by SAP filling or by measuring the electric resistance of SAP filling or by measuring the amount of SAP filling expansion or by measuring SAP filling's weight change; the corresponding level of soil moisture is determined when said measurement is sent to the processor unit. The manual maintenance of this tensiometer is reduced as there is no need to manually remove the accumulating air released from the water or to refill the tensiometer with water.

Description

WATER ABSORBENT TENSIOMETER FOR DETERMINING MOISTURE LEVELS FOR IRRIGATION

Relationship to Prior Applications:

The present patent application is related, pursuant to the concept of unity

of invention, to US provisional patent application 62/839,101 and claims benefit of the filing date of said provisional application.

1. Field of the Invention

This invention relates to devices for measuring moisture levels in the soil for

determination of the irrigation watering requirements and their timing.

2. Description of the Prior Art

There are a number of prior art water-filled tensiometer designs which typically include at least one internal chamber filled with water and comprising either a porous tip or a porous membrane. The US patent 3910300 is a good example of such prior art comprising a water-permeable tip and a diaphragm; which the vacuum produced in the internal chamber will flex thereby moving a linkage connecting said diaphragm with a switch or a valve. The US patent 6772621 features stainless steel casing with the porous stainless steel membrane built into it. It also comprises a pressure sensor for sensing the degree of vacuum produced, which is in fluid hydraulic connection with the internal chamber. These tensiometer designs have evaporation from the surface of water inside the tensiometer, as well as the release from it of air dissolved in the water - thereby making the tensiometer readings less accurate. Heating of the above ground part of tensiometer subjected to diurnal temperature variation of the environment as well as in the soil stratums closer to the surface causes the heat to spread downward, warming up the lower parts of tensiometer body and further increasing said evaporation and release of air. It should also be noted that the air released from the surface of the water will typically require manual labor such as pumping it out using a hand held vacuum pump or filling it with water completely to displace the accumulated air. Thus the existing water-filled tensiometer designs are not only frequently inaccurate, but also their operation is labor intensive. In light of the above we conclude that the prior art and its underlying concepts are clearly inadequate. We intend to propose different solutions containing no body of water inside the tensiometer, but rather a filling comprised of a Super Absorbent Polymers of various chemical compositions or other materials possessing similar qualities such as, for example suitable types of Polysaccharides and Proteins.

3. Objects and Advantages.

One object of the present invention is to provide a tensiometer with no body of water during its regular operation inside its inner chamber for more accurate measurement of the soil moisture level.

Another object is to provide a tensiometer with the reduced manual labor requirement due to elimination of accumulation of air inside of inner chamber of tensiometer.

4. Brief Description of the Drawings

Fig 1 is a tensiometer of first embodiment sideview with partial cutouts.

Fig 2 is a tensiometer of second embodiment partial, cut sideview.

Fig 3 is a tensiometer of third embodiment partial, cut sideview.

Fig 4 is a tensiometer of fourth embodiment partial, cut sideview.

Fig 5 is a tensiometer of fifth embodiment partial, cut sideview.

5. Description of Preferred Embodiments. The first embodiment is as follows; (Fig 1 ) inside the ceramic tip (1 ) of tensiometer’s body (2) up to a predetermined height from its bottom there is a filling comprised of super-absorbent polymer (3) and/or other suitable materials such as highly absorbent polysaccharides and/or proteins.

. Into said filling is placed an elastically compressible tube made of suitable plastic or elastomer (4) filled with suitable liquid such as for example water, glycerin, oil etc and connected to a pressure sensor (5) Said pressure sensor is operatively connected to a computer processor (not shown) interpreting said sensor’s input and producing the soil moisture reading based on said input.

In a second embodiment (Fig 2) inside the ceramic tip (1 ) of tensiometer’s body (2) up to a predetermined height from its bottom there is a filling comprised of super absorbent polymer (3). Under said filling is placed an insulated electrode (4) and above said filling at a predetermined height is placed another such electrode of opposite polarity. Both of them are connected respectively to a (+) and (-) pole tips of a capacitor (6). Said capacitor is operatively connected to a capacitance meter, which is in turn connected to processor. Said processor is receiving a signal corresponding to a change in capacitive charge, interpreting said signal as its input and producing the soil moisture reading based on said input.

Third embodiment is as follows; (Fig 3) inside the ceramic tip (1 ) of tensiometer’s body (2) up to a predetermined height from its bottom there is a filling (3) comprised of super-absorbent polymer. Under said filling is placed an electrode (4) and on top of said filling is placed another such electrode of opposite polarity. Both of them are connected respectively to a (+) and (-) tips of a source of current (not shown) such as a battery, electric cable etc. Into the circuit thus formed is connected a gauge (7) measuring said filling’s (3) electric resistance/conductivity. Said gauge (7) is operatively connected to a processor receiving a signal corresponding to a change in resistance/conductivity and interpreting said signal as its input and producing the soil moisture reading based on said input.

The fourth embodiment is as follows; (Fig 4) inside the ceramic tip (1 ) of

tensiometer’s body (2) up to a predetermined height from its bottom there is a filling comprised of super-absorbent polymer (3). On the upper surface of filling (3) there is a moveable rod (8) of a position sensor and the sensor itself (not shown) is mounted inside the body of tensiometer at a predetermined height from the upper surface of said filling (3). Said position sensor is operatively connected to a processor(not shown) interpreting said sensor’s input and producing the soil moisture reading based on said input. There is a large variety of position sensors available which can be used instead of the sensor just described and mutatis mutandis they are all considered to be within the spirit and scope of this embodiment of this invention.

The fifth embodiment is as follows; (Fig 5) inside the ceramic tip (1 ) of tensiometer’s body (2) there is a perforated cage or a cage made of wire mesh or some other suitable water permeable material (9) slidably inserted into said tip (1 ) and extending vertically up to a predetermined height from its bottom. Inside said cage there is a filling comprised of super-absorbent polymer (3). Said cage (9) is operatively connected to scales (10) located either above said cage or under it. Said scales (10) is also operatively connected to a processor (not shown) interpreting said scales’s input and producing the soil moisture reading based on said input. There is a large variety of suitable scales available which can be used for this embodiment and mutatis mutandis they are all considered to be within the spirit and scope of this embodiment of this invention.

For all of the above described embodiments optionally a water-permeable cartridge, containing anti-microbial metals or their chemical compounds such as for example copper or its various compounds or alternatively silver or its various compounds, is inserted into the tip to prevent biological contamination which could degrade the tensiometer performance.

6. Sketches and Diagrams.

Drawings are provided separately. 7. Operation.

In operation, at the installation into the ground time for all embodiments the tensiometer needs to be filled with water to a predetermined level after it has been inserted into the ground hole and said hole was properly backfilled or alternatively the ground around it needs to be properly irrigated so that water filters into the tensiometer via its ceramic tip. As water surface tension is established via the ceramic walls of tensiometer tip between the water inside tensiometer and water outside of it, water will be pulled into tensiometer when moisture content in surrounding soil is high and water will leave tensiometer when the moisture content of soil is low.

For the first embodiment as the water seeps into the tensiometer through its porous ceramic tip, it is absorbed by the Super Absorbent Polymer (or other suitable material(s) such as Polysaccharide(s) and/or Protein(s)), [hereinafter SAP] filling which expands in volume pressing on the sides of elastic tube (4) causing its compression and

accordingly the rise of hydrostatic pressure of liquid inside said tube (4) which will be measured by the pressure sensor (5) whose output is transmitted to a computer processor that produces a usable reading of moisture level in the soil. If the moisture level in the surrounding soil declines, then the water will seep out of the SAP filling causing its pressure on the tube (4) to lessen and accordingly the pressure of liquid inside the tube (4) also lessens, which results in a reduced moisture level reading produced by the computer processor.

For the second embodiment, as the water seeps inside the tensiometer it is absorbed by SAP filling causing its volume to expand significantly between the electrodes connected to a capacitor, which results in change in the capacitor’s charge.

Capacitance meter Input reflecting said change is sent to the computer processor which produces moisture reading for the soil.

For the third embodiment as the water seeps inside the tensiometer it is absorbed by SAP filling causing its volume to expand significantly between the electrodes connected to an electric resistance gauge causing a change in measured electric resistance of the filling. Output reflecting said change is sent to the computer processor which produces moisture reading for the soil. For the fourth embodiment as the water seeps inside the tensiometer it is absorbed by SAP filling causing its volume to expand significantly which changes the output of the positional sensor. Output reflecting said change is sent to the computer processor which produces moisture reading for the soil.

For the fifth embodiment as the water seeps inside the tensiometer it is absorbed by SAP filling causing its weight to expand significantly, which results in change in the scales output. Output reflecting said change is sent to the computer processor which produces moisture reading for the soil.

Claims

8. Claims. What claimed is:

1 . A soil moisture level measuring tensiometer comprising a highly absorbent filling in the lower part of its body and a device for measuring changes in at least one physical property of said filling due to its water absorption corresponding to soil moisture level whereby said measured change in a given physical property can be used to determine the soil moisture level by soil moisture level determination means.

2. The tensiometer of Claim 1 wherein said highly absorbent filling is at least in part comprised of a highly absorbing material selected from the group consisting of Super Absorbent Polymers, Polysaccharides, and Proteins.

3. The tensiometer of Claim 1 wherein said moisture level determination means is a computer processor accepting output of said device for measuring changes in at least one physical property of said filling.

4. The tensiometer of Claim 1 wherein said one physical property of said filling is a pressure inside of it and said device for measuring changes comprises a pressure sensor.

5. The tensiometer of Claim 1 wherein said one physical property of said filling is its electric resistance level and said device for measuring changes is an electric resistance gauge.

6. The tensiometer of Claim 1 wherein said one physical property of said filling is its capacitive charge level and said device for measuring changes is a capacitance meter. s

7. The tensiometer of Claim 1 wherein said one physical property of said filling is its height and said device for measuring changes is a positional sensor.

8. The tensiometer of Claim 1 wherein said one physical property of said filling is its weight and said device for measuring changes is electric scales.