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WO1990013812A1 - Evaluation de l'humidite du sol par capacite thermique - Google Patents

Evaluation de l'humidite du sol par capacite thermique Download PDF

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Publication number
WO1990013812A1
WO1990013812A1 PCT/AU1990/000179 AU9000179W WO9013812A1 WO 1990013812 A1 WO1990013812 A1 WO 1990013812A1 AU 9000179 W AU9000179 W AU 9000179W WO 9013812 A1 WO9013812 A1 WO 9013812A1
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WO
WIPO (PCT)
Prior art keywords
soil
probe
temperature
soil moisture
tube
Prior art date
Application number
PCT/AU1990/000179
Other languages
English (en)
Inventor
Allan Kenneth Wallace
James Dunstone Townsend
Original Assignee
Allan Kenneth Wallace
James Dunstone Townsend
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Allan Kenneth Wallace, James Dunstone Townsend filed Critical Allan Kenneth Wallace
Publication of WO1990013812A1 publication Critical patent/WO1990013812A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/005—Investigating or analyzing materials by the use of thermal means by investigating specific heat
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/24—Earth materials
    • G01N33/246—Earth materials for water content

Definitions

  • This invention relates to a method and means pertaining to assessment of soil moisture.
  • the problem to which this invention is directed relates to difficulties in establishing soil moisture which can be reliably used with respect to a variety of different soils and with water that can be sometimes more saline than other waters, and which can establish such moisture content at a selected depth within the soil and all of these by means which are both economic and which can be operated remotely.
  • This invention is directed specifically to techniques of moisture content using means to assess thermal properties of the soil.
  • a method of assessing an extent of moisture content within soil which includes subjecting a part of the soil or an equivalent material in terms of water take up potential to be assessed to a selected heating, and detecting any resultant temperature differentials such that a magnitude which is substantially proportional to a thermal capacitance of the sample is obtained.
  • Such a technique differs from previous techniques in which the assessment has depended to a very large extent upon thermal conductivity of the soil.
  • a body providing some insulating in a thermal sense of heat source from a remainder part of the soil with in which the detector is buried, and temperature sensing means within the vicinity of the heat source means are adapted especially to detect a peak temperature reached subsequent to a pulse and then if required, a drop off against time of such temperature of the soil.
  • a sample of this soil is contained within a cylindrically shaped aperture open at both ends which is adapted to be inserted within the soil and to have a soil or its equivalent of the type being detected inserted and as appropriate in fact slightly tamped into the aperture space.
  • the cylindrical shape is preferably of constant cross sectional shape and size along its length and within a centre of the cylindrical shape, a surrounding surface is comprised of a metal of high conductivity such as stainless steel and at a first side there is a heating means comprising an electrical resistor which can be remotely pulsed with an energy level which resistor is in contact with the stainless steel surface so that would be caused to raise its temperature and by transmitting the temperature quickly through the stainless steel surface subject with relatively constant conduction and radiant heating effects, the central portion of the soil within the aperture.
  • a heating means comprising an electrical resistor which can be remotely pulsed with an energy level which resistor is in contact with the stainless steel surface so that would be caused to raise its temperature and by transmitting the temperature quickly through the stainless steel surface subject with relatively constant conduction and radiant heating effects, the central portion of the soil within the aperture.
  • temperature detection means also coupled to the stainless steel conductor and such that the temperature can be remotely determined and in accord with the method, the peak temperature of the soil subsequent to the heating pulse is detected.
  • thermal capacity can be achieved then by containment in some thermally insulating way of a soil sample or its equivalent which is however kept in appropriate communication with a remainder of the soil but such that loss of heat by thermal conductances is substantially reduced and soil subject to the temperature rise together with means for providing communication from a heating source to the soil, are generally insulated in a thermal sense from a remainder of the soil material.
  • the concept then differs from a probe in which a metal rod is inserted into soil to be tested and in which there is a heat source and a temperature detector but such that the heat source will heat surrounding soil which is everything but contained and any temperature detection is sufficiently remote from such temperature source such that any detection will be found to be substantially correlated with thermal conductance rather than thermal capacity of the surrounding soil.
  • the body is comprised of a cylindrical member constituted by being formed of a plastics material of thermally insulating character but having therein and defining within a cylindrically shaped central core which is coaxial with the cylindrical shape of the plastics material forming the body.
  • the method according to the invention can variously reside in the broader concept expressed previously or in the further method of effecting assessment of soil moisture comprising the steps of locating a body which has an open cavity therein for holding and capturing soil, within the soil to be tested, holding some of the soil or its equivalent in such a cavity and such that such holding means allow for a diffusion of moisture from the surrounding soil into any sample thus contained, effecting a selected heating of the soil within the cavity and detecting any resulting peak temperature reached subsequent to such heating.
  • such further detection of resulting temperatures comprises detecting the maximum temperature differential achieved by reason of a select given temperature pulse.
  • the invention can be said to reside in a soil moisture probe comprising means for detection of temperature, means to generate heat, a body adapted to substantially encompass a sample of the soil or an equivalent material in terms of water take up potential but allowing communication with the soil external to the body, and means for detecting any resultant temperature differentials such that a magnitude which is substantially proportional to a thermal capacitance of the sample is obtained.
  • the soil moisture probe in preferance can be further characterised by the means to generate heat provides singularly or repeatedly a pulse of heat of known characteristics of magnitude, change in magnitude with regard to time and duration for an interval of time.
  • the soil moisture probe in preference can be further characterised by the body providing some insulation in a thermal sense of heat generated by the means to generate heat for the sample from the soil within which the probe is buried but external to the body, and the means for detecting being adapted for the detection of temperature within the vicinity of the means to generate heat especially adapted to detect a peak temperature reached subsequent to a pulse and then if required, a drop of temperature against time of such temperature of the soil.
  • the soil moisture probe can, in preference, be further characterised as being a probe in which the body is comprised of a cylindrical member constituted by being formed of a plastics material of thermally insulating character but having therein and defining within a cylindrically shaped central core which is coaxial with the cylindrical shape of the plastics material forming the body.
  • the soil moisture probe can, in preference, be further characterised as being a probe in which the body is a cylindrically shaped aperture open at both ends which is adapted to be inserted within the soil and to have the sample inserted therein.
  • the soil moisture probe can, in preference, be further characterised as being a probe in which the sample is slightly tamped into the aperture space.
  • the soil moisture probe can, in preference, be further characterised as being a probe in which the sample is soil of the type or the equivalent material in terms of water take up potential is an equivalent of soil in which the probe is buried.
  • the soil moisture probe can, in preference, be further characterised as being a probe in which the means to generate heat is of an electrical resistance heater type.
  • the soil moisture probe can, in preference, be further characterised as being a probe in which the means for detection of temperature is adapted to assess the thermal capacity of the sample substantially from the peak detected temperature and the thermal conductance substantially from the decay over time of the detected temperature.
  • the invention can be said to reside in a soil moisture probe comprising a body having a partly enclosed space, an electrical resistor with the body appropriate to effect a heating of any material within the partly enclosed space, and temperature detection means adapted to detect the temperature of any material within the partly enclosed space subsequent to any heating from the electrical resistor.
  • the invention can in preference be characterised by including means to provide an electrical current into the electrical resistor for a selected duration.
  • the invention can in preference be a soil moisture probe wherein the partly enclosed space is a cylindrically shaped chamber open at both ends of the cylindrical shape.
  • the invention can be further characterised as a soil moisture probe wherein there are means to detect and store a peak temperature of any material within the partly enclosed space.
  • the invention can be further characterised as a soil moisture probe in which the body is comprised of a thermally conducting material having included therein an electrical resistor, a partly enclosed space within the body adapted to be heated by the electrical resistor, temperature detection means adapted to measure the temperature of any material within the partly enclosed space, and the body of the probe being a substantially cylindrical tube, herein refered to as the first tube, made of a material which is a thermal insulator except for a second cylindrical tube made of metal, the first tube encasing the second tube except for the inner surface of the second tube, and the length to diameter ratio of the first tube being chosen such that the magnitude of the area defined by the apertures of the first tube is small compared with the magnitude of surface area of the inner surface of the tube.
  • the invention can be said to reside in a method of effecting assessment of soil moisture comprising the steps of locating a body which has a enclosed space therein for holding soil within the soil to be tested, holding a sample of some of the soil or an equivalent material in terms of water take up potential in such a space such as to allow for a diffusion of moisture from the surrounding soil into any sample thus contained, effecting a selected heating of the soil within the space and detecting any resulting peak temperature reached subsequent to such heating.
  • the method of effecting assessment of soil moisture may be further characterised as one where the step of effecting selected heating comprises applying a pulse of electrical current to an electrical heater for a selected interval of time to heat the sample.
  • the method of effecting assessment of soil moisture may be further characterised as one where the step of effecting selected heating comprises applying singularly or repeatedly a pulse of heat for an interval of time to the sample.
  • the method of effecting assessment of soil moisture may be further characterised as one in which the step of detecting of temperature provides an intelligible result for the thermal capacity of the sample substantially from the peak detected temperature and the thermal conductance substantially from the decay overtime of the detected temperature.
  • the invention can be described as an apparatus for the control of an irrigation means by the determination of soil moisture content
  • an electrical power supply at least one probe adapted to be buried in the soil, incorporating an electrical resistive heater and at least one thermal couple, the probe being connected to the distal power supply by means of at least one wire
  • the body of the probe being a substantially cylindrical tube, herein refered to as the first tube, made of a material which is a thermal insulator except for a second cylindrical tube made of metal, the first tube encasing the second tube except for the inner surface of the second tube, and the length to diameter ratio of the first tube being chosen such that the magnitude of the area defined by the apertures of the first tube is small compared with the magnitude of surface area of the inner surface of the tube; a controller incorporating: a microprocessor, a memory means for microprocessor program and data, means to interface the microprocessor with the thermal couple or couples and the power supply; means for setting a setpoint; wire or wires connecting the controller to the power supply and to
  • Figure 1 is graph of calibration curve for a conventional thermal probe in sand.
  • the X-axis is the percentage moisture content, and the Y-axis is Tend, the temperature reading of the probe.
  • Figure 2 is graph of a typical temperature pulse resultant from a heater being on (8) for a limited period of time.
  • the X-axis is the time in seconds
  • the Y-axis is the temperature in degrees C.
  • the X-axis is the time, and the Y-axis is the temperature.
  • the X-axis is the time, and the Y-axis is the temperature.
  • Figure 5 is a normalised version of Figure 3 also showing the time when the heater is on (8).
  • Figure 6 is a normalised version of Figure 4 also showing the time when the heater is on (8).
  • Figure 7 is a graph of calorimetric probe output in sand and ⁇ n loam. Sand is indicated by the concentric circles, loam by the single circle. The X-axis is the percentage water, and the Y-axis is the temperature rise in degrees C.
  • Figure 8 is a graph of the response of the probe disclosed herein for sand, the upper curve being a dry sand sample, the lower curve being a sand sample which contains 15% water.
  • the X-axis is the time in seconds, and the Y-axis is the temperature rise in degrees C.
  • Figure 9 is a graph of the response of the probe disclosed herein for loam, the upper curve being a dry loam sample, the lower curve being a loam sample which contains 15% water.
  • the X-axis is the time in seconds, and the Y-axis is the temperature rise in degrees C.
  • Figure 10 is a normalised version of Figure 8.
  • Figure 11 is a normalised version of Figure 9.
  • Figure 12 is a graph of the time response of a calorimetric probe in sand.
  • the X-axis is the time in hours, and the Y-axis is the temperature rise in degrees C.
  • Figure 13 is the drying out response with expansive loam.
  • the X-axis is the time in hours, and the Y-axis is the temperature rise in degrees C.
  • Figure 14 is a cross-sectional diagram of a probe exhibiting the invention disclose herein in one prefered embodiment.
  • Figure 15 is a sketch of a probe.
  • Figure 16 is a schematic diagram in cross-section of the probe illustrated in Figure 15 in the ground.
  • Figure 17 is a schematic diagram in cross-section of the probe illustrated in Figure 15 in the ground further illustrating source of heat (9) and the temperature peak detector (7).
  • Figure 18 is a schematic diagram of a moisture probe controller and soil moisture detection system in block diagram form.
  • FIG 19 is a block diagram of a moisture probe controller logic flow. This illustrates the steps involved in utilising the invention in one form.
  • the probe studied was a solid cylinder of stainless steel 16mm dia. by 40mm long, incorporating a heater and temperature probe.
  • the measurement basis was that of a thermal pulse, i.e. a precise energy (65 Joules) over a precise time (10 seconds) was "pumped in", and the temperature acquired throughout the resulting pulse (typically for 20 minutes).
  • Figure 2 is an example of the form of output.
  • the objective was to model the probe so that a response could be predicted for various values of the input parameters of k and C, to see if the probe tested was actually measuring primarily k or C or a combination of both.
  • the probe is merely measuring the air gap. This was able to be confirmed to a small degree by re-compressing the soil around a probe as it dried.
  • the aim is to measure soil thermal capacity with minimal influence of conductivity.
  • Figures 14, 15, 16 and 17 illustrate an embodiment of the invention in which Figure 14 is a cross sectional view of a body adapted to be inserted within the soil the moisture of which is to be detected,
  • Figure 15 is an external perspective view of the body as shown in Figure 14,
  • Figure 16 illustrates the same cross sectional view as in Figure 14 encompassed by and having inserted there through, soil the moisture content of which is to be assessed, and finally
  • Figure 17 is a schematic view including the view of Figure 16 illustrating the respective inputs and outputs that will be expected for moisture assessment purposes.
  • the body 1 is shaped so as to have an external cylindrical surface and an internal cylindrical surface shown at 2 these surfaces and the body generally being defined by a hollow co-annular shape formed from plastics material to provide thermal insulation.
  • Assisting to define the inner cylindrical core 2 is a cylindrical metallic part 3 which includes at one part an electrical resistance member 4 to provide a heating effect.
  • a temperature detector 5 detects through the medium of the metallic member particularly a non-corrosive conductor and is adapted to detect the temperature reached of soil within the cylindrical area 2, both the electrical resistance 4 and the temperature detector 5 being coupled to be connected through electrical conduits shown collectively at 6.
  • such a level can be correlated against an expected moisture level of the soil.
  • the cylindrical aperture within the body 1 is filled with soil of the same type for which the moisture is to be assessed and is then inserted at an appropriate depth in the soil.
  • a burst of energy perhaps typically 75 joules of energy over ten seconds is supplied through the electrical connections and the resulting temperature observed through the peak temperature detection means 7 within which there are means to store the detected such peak temperature and to provide as an output in this here indicating then the temperature differential achieved from an existing temperature to the peak temperature.
  • the sample should be matched to the surrounding soil, so that the calorimetric potentials equate.
  • the heat flow is radially inward in contrast to the dissipative form of the device described previously.
  • the heat enters the sample through a large contact area relative to the thermal volume, and the dimensions are such that the sample reaches thermal equilibrium with the metal ring in a short time relative to the time it takes for conduction to the outside soil to occur.
  • the metal ring is insulated on all external surfaces, to minimise losses.
  • controllers which have no way of knowing if (a) there has been sufficient natural precipitation to cover the needs of the vegetation or if (b) the irrigation program is applying excessive water for the current atmospheric conditions affecting evaporative and transpiration loss of soil moisture. It should be noted that such controllers would normally be programmed to deliver adequate water for the driest conditions. Thus on average more water than required is being applied.
  • V/F voltage to frequency
  • A/D analogue to digital
  • the software comprises a single main loop which periodically makes a determination of the soil moisture.
  • the loop When a determination is not being made, the loop merely compares the soil moisture with the set point, and operates the irrigation cutout relay accordingly.
  • Some modes of operating may incorporate an algorithm to low pass filter determinations and/or delay the relay actuation to allow a controller to complete a watering cycle, for example.
  • the set point can be adjusted by pressing the button and turning the potentiometer.
  • the display displays the value of the set point.
  • step 30 the controller proceeds form step 30 to step 36 where it resets the main timer, reads the temperature as determined temperature detector 27, turns the heater 26 on for a period of time, reads the peak temperature detected, and then determines the moisture content of the soil.
  • step 31 which is to display the moisture content.
  • the next step in the logic flow is to determine if the soil moisture content is greater than the set point. If yes, then by step 33 irrigation is inhibited, if not, then irrigation is allowed by perfoming step 37.
  • step 33 or 37 the controller returns to step 33
  • the disclosed herein moisture probe can provide a moisture probe which is substantially responsive to the moisture content of the soil without being overly subjected to other soil characteristics, easy to produce and maintain. It is therefore an object of the present invention to provide a moisture probe which will obviate of minimize any one of the foregoing disadvantages in a simple yet effective manner or at least provide the public with a useful choice.

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  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Pathology (AREA)
  • Immunology (AREA)
  • General Physics & Mathematics (AREA)
  • General Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Geology (AREA)
  • Medicinal Chemistry (AREA)
  • Food Science & Technology (AREA)
  • Remote Sensing (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)

Abstract

Sont décrits un procédé et un appareil pour déterminer la teneur hygrométrique du sol. L'appareil comporte une sonde, un détecteur de température de crête (7) et une source d'impulsion thermique (9). La sonde est principalement sensible à la capacité thermique d'un échantillon, et comprend un corps (1) enserrant sensiblement l'échantillon (2), lequel peut être de la terre, de manière à minimiser l'effet de la conductibilité thermique de l'échantillon. Une impulsion thermique est appliquée à l'échantillon et l'augmentation de température de crête qui en résulte est détectée. Cette augmentation permet d'évaluer la teneur hygrométrique.
PCT/AU1990/000179 1989-05-04 1990-05-04 Evaluation de l'humidite du sol par capacite thermique WO1990013812A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPJ402289 1989-05-04
AUPJ4022 1989-05-04

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009084971A1 (fr) * 2007-12-27 2009-07-09 Utad-Universidade De Tras-Os-Montes E Alto Douro Système de mesure de propriétés du sol
US8001990B2 (en) 2005-02-02 2011-08-23 Plantcare Ag Device for measuring thermal properties in a medium and method for determining the moisture content in the medium
CN103389322A (zh) * 2012-05-08 2013-11-13 中国科学院沈阳应用生态研究所 一种壤中凝结水形成过程的模拟测定方法
WO2019064018A1 (fr) * 2017-09-29 2019-04-04 Oxford University Innovation Limited Procédé et appareil de sonde pour tester des produits pharmaceutiques

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2536777A1 (de) * 1975-08-19 1977-03-03 Issel Wolfgang Messfuehler zur bestimmung der wasserspannung im boden nach dem waermepulsprinzip
US4142403A (en) * 1977-10-17 1979-03-06 Iowa State University Research Foundation, Inc. Method and means for testing soils
SU911282A1 (ru) * 1979-08-09 1982-03-07 Агрофизический научно-исследовательский институт Тепловой преобразователь потенциала влаги почвы
SU916650A1 (ru) * 1980-05-23 1982-03-30 Uralsky Politekhn Inst Устройство процессов для моделирования промерзания грунта 1
SU1122953A1 (ru) * 1983-06-03 1984-11-07 МГУ им.М.В.Ломоносова Устройство дл определени теплофизических параметров веществ
SU1408327A1 (ru) * 1985-09-23 1988-07-07 Специализированная Проектно-Конструкторская Технологическая Организация "Росавтоматстром" Способ измерени влажности
EP0280229A2 (fr) * 1987-02-27 1988-08-31 LUCAS INDUSTRIES public limited company Processus pour l'obtention de la teneur en eau d'un fluide hydraulique
DD262917A1 (de) * 1987-08-10 1988-12-14 Univ Dresden Tech Schaltungsanordnung und verfahren fuer ein thermophysikalisches stoffdatenmessgeraet

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2536777A1 (de) * 1975-08-19 1977-03-03 Issel Wolfgang Messfuehler zur bestimmung der wasserspannung im boden nach dem waermepulsprinzip
US4142403A (en) * 1977-10-17 1979-03-06 Iowa State University Research Foundation, Inc. Method and means for testing soils
SU911282A1 (ru) * 1979-08-09 1982-03-07 Агрофизический научно-исследовательский институт Тепловой преобразователь потенциала влаги почвы
SU916650A1 (ru) * 1980-05-23 1982-03-30 Uralsky Politekhn Inst Устройство процессов для моделирования промерзания грунта 1
SU1122953A1 (ru) * 1983-06-03 1984-11-07 МГУ им.М.В.Ломоносова Устройство дл определени теплофизических параметров веществ
SU1408327A1 (ru) * 1985-09-23 1988-07-07 Специализированная Проектно-Конструкторская Технологическая Организация "Росавтоматстром" Способ измерени влажности
EP0280229A2 (fr) * 1987-02-27 1988-08-31 LUCAS INDUSTRIES public limited company Processus pour l'obtention de la teneur en eau d'un fluide hydraulique
DD262917A1 (de) * 1987-08-10 1988-12-14 Univ Dresden Tech Schaltungsanordnung und verfahren fuer ein thermophysikalisches stoffdatenmessgeraet

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
DERWENT ABSTRACT; Accession No. 127361/21, Class S03; & SU,A,1122953 (MOSCOW LOMONOSOV UNIV.), 7 November 1984, (see abstract). *
DERWENT ABSTRACT; Accession No. 89-022148/03, Class S03; & SU,A,1408327 (ROSAVTOMATSTROM DES), 7 July 1988. *
DERWENT ABSTRACT; Accession No. A2898K/01, Class S03; & SU,A,911282 (AGROPHYS RES INST), 7 March 1982, (see abstract). *
DERWENT ABSTRACT; Accession No. B3304K/04, Class S03; & SU,A,916650 (URALS KIROV POLY), 30 March 1982. *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8001990B2 (en) 2005-02-02 2011-08-23 Plantcare Ag Device for measuring thermal properties in a medium and method for determining the moisture content in the medium
WO2009084971A1 (fr) * 2007-12-27 2009-07-09 Utad-Universidade De Tras-Os-Montes E Alto Douro Système de mesure de propriétés du sol
CN103389322A (zh) * 2012-05-08 2013-11-13 中国科学院沈阳应用生态研究所 一种壤中凝结水形成过程的模拟测定方法
WO2019064018A1 (fr) * 2017-09-29 2019-04-04 Oxford University Innovation Limited Procédé et appareil de sonde pour tester des produits pharmaceutiques
US11307189B2 (en) 2017-09-29 2022-04-19 Oxford University Innovation Limited Method and probe apparatus for testing pharmaceutical products

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