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WO1997001090A1 - Procede de mesure de la teneur en eau de supports de cultures - Google Patents

Procede de mesure de la teneur en eau de supports de cultures Download PDF

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Publication number
WO1997001090A1
WO1997001090A1 PCT/NL1996/000251 NL9600251W WO9701090A1 WO 1997001090 A1 WO1997001090 A1 WO 1997001090A1 NL 9600251 W NL9600251 W NL 9600251W WO 9701090 A1 WO9701090 A1 WO 9701090A1
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WO
WIPO (PCT)
Prior art keywords
mhz
permittivity
water content
real part
frequencies
Prior art date
Application number
PCT/NL1996/000251
Other languages
English (en)
Inventor
Maximus Andreas Hilhorst
Original Assignee
Instituut Voor Milieu- En Agritechniek
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 Instituut Voor Milieu- En Agritechniek filed Critical Instituut Voor Milieu- En Agritechniek
Priority to AU61396/96A priority Critical patent/AU6139696A/en
Publication of WO1997001090A1 publication Critical patent/WO1997001090A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/12—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electromagnetic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G01N22/04—Investigating moisture content
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity

Definitions

  • the invention relates to a method for measuring the water content of growing substrates. It is known from WO 86/05278 that the * impedance of the soil can be measured by a probe being positioned therein 5 which has two or more electric contacts. From this impedance the electric i permittivity of the soil can be determined.
  • the electric permittivity, or the dielectric constant is largely determined by the water content of the soil. For most minerals the dielectric constant is in the order of 4- 6, whereas for water it has an order of magnitude of 80. It is noted, in
  • the dielectric constant of a soil type and comparison with a number of calibration curves, the composition of the soil and the water content.
  • the dispersion of the dielectric constant the difference between the maximum and minimum value of the dielectric constant within a specific frequency range
  • 35 permittivity at a reference frequency within a second frequency band, at least most of which is situated above the first frequency band, c) comparing the values determined at b) with values which, depending on the moisture content, hold good at the reference frequency for a reference material, and determining therefrom the moisture content of the soil sample in question.
  • the invention is based on the insight that for many types of soil, in particular for growing substrates such as, for example, rock wool, glass wool, granular clay, compressed organic material or potting soil, the real part e* of the complex electric permittivity varies with the frequency.
  • the real part e' of the electric permittivity of these growing substrates depends on the water content, ⁇ , in the same manner as the permittivity e' of sand, or granular materials having a similar dielectric behaviour as sand.
  • the real part of the electric permittivity does not, up to a frequency of 17 GHz, vary with the frequency.
  • the dielectric behaviour of a material such as a growing substrate can be described by the complex dielectric constant, sometimes known as the complex electric permittivity.
  • the real part of the permittivity, e ' is a measure for the polarizability of different material components, including the water which may or may not be bound.
  • the imaginary part of the permittivity, e" is a measure for the absorption of energy.
  • the ionic conductivity contributes to e".
  • the two components e ' and e" of the permittivity can be measured as the capacitance, C (in farad) and the conductivity G (in Sm "1 ), respectively, of a capacitor with the growing ⁇ ubstrate as the dielectric between the electrodes.
  • Two electrodes with the growing substrate in between them as a dielectric can be represented, in electronic network theory, by the complex impedance Z which is formed by a connection in parallel of a capacitor having a capacitance in F and a resistor having a conductivity G in S/m.
  • the extrapolation of the real part e ' of the electric permittivity to e'( ⁇ 0 ) is carried out at ⁇ 0 between 100 and 200 MHz on the basis of measurement at frequencies of approximately 10 MHz, approximately 20 MHz and approximately 30 MHz. Measuring at these relatively low frequencies results in considerable simplification of the measuring apparatus.
  • the behaviour of the electric permittivity of a growing substrate can further be described as a relationship with three unknowns, which can be solved by determining the three values for e'.
  • e* can be expressed, for a growing substrate, as:
  • ⁇ is the difference between the electric permittivity of the growing substrate and that of pure sand at a predetermined angular frequency ⁇ .
  • ⁇ is a constant, and e m is the permittivity at an infinitely high frequency.
  • An apparatus for implementing the method comprises:
  • the alternating-current source comprises three stable oscillators working at frequencies which have a mutually integer ratio.
  • three frequencies are u ⁇ ed in a ratio of 1:2:3, for example 10, 20 and 30 MHz.
  • Such oscillators are relatively simple and inexpensive and take up little space.
  • Figure 1 shows the behaviour of the real part e ' of the complex electric permittivity for a mixture of sand and clay and for pure sand having the ⁇ ame water content
  • FIG. 1 schematically shows the circuit for carrying out dielectric measurements according to the invention.
  • Figure 3 shows an apparatus for measuring the impedance of a growing substrate, where the electrodes are located in the growing substrate, and
  • Figure 4 shows an apparatus for measuring the impedance of a growing substrate, where four electrodes are situated at a distance from the growing substrate.
  • curve I shows the behaviour of the real part e * of the electric permittivity for sand.
  • e' for sand is virtually constant up to a frequency of 17 GHz.
  • Sand generally refers to granular particles without cohesion.
  • the electric permittivity e varies with frequency according to curve II in Figure 1.
  • curve II intersects with curve I, and the permittivity of the sand-clay mixture having a particular water content ⁇ is equal to the permittivity of pure sand having the same water content ⁇ .
  • ⁇ is a constant which is found from the three measured permittivity value ⁇ e1, e2 and e3 via the relationship
  • Figure 2 schematically shows the measurement set-up for determining the real part e'(t) and the imaginary part e"(t) of the complex permittivity e of a growing substrate.
  • the electrode configuration with in between, as the dielectric, the hardenable material is repre ⁇ ented a ⁇ a complex impedance Z*.
  • Via a feeder line 1 an alternating current i ⁇ fed, via a switch 3, to an input terminal 5 of the impedance Z * .
  • the alternating-current source 7 i ⁇ formed by three cry ⁇ tal oscillators which generate a sinusoidal current with an o ⁇ cillator frequency of, for example, 10 MHz, 20 MHz and 30 MHz.
  • the output signal of the oscillator 7 is fed to a switch 11.
  • the switch 11 can be selectively connected to a phase-shifting element such as a capacitor 13 or a constant-pha ⁇ e element ⁇ uch a ⁇ a resistor 15.
  • the input terminal 5 of the electrode configuration and the input terminal of the capacitor 13 or the resistor 15 are connected to a multiplier 17, the voltages formed over the electrode configuration Z * and the element 13 or 15, u 2 and u shift , re ⁇ pectively, being multiplied with one another.
  • the product u 2 *u shift is fed to a low-pass filter 19.
  • the signal of the output of the low-pass filter 19 is converted in an analog-digital converter 21 whose output is connected to the input of an arithmetic unit 23.
  • the arithmetic unit 23 the real part e*(t) of the complex permittivity is determined. Then, in the arithmetic unit 23, the permittivity e'( ⁇ 0 ) at 200 MHz is calculated in the above-specified manner, and from e'( ⁇ 0 ) the water content ⁇ is determined.
  • the switches 3, 11, the analog-digital converter 21 and the arithmetic unit 23 can be triggered to take a measurement at predetermined time intervals, for example every hour.
  • the time control unit 25, the switches 3, 11 and the phase-shifting element 13 could be omitted.
  • the manner shown here of measuring the impedance Z * of the electrode configuration is based on synchronous detection.
  • the sinusoidal voltage frequencies ⁇ which may be chosen between 1 MHz and 100 MHz, are fed to the multiplier 17.
  • the phase of the current fed to the multiplier 17 via the shunt line 9, can be phase-shifted by 0° or 90° by positioning the switch 11.
  • the output voltage of the multiplier u u-,u shift ha ⁇ a frequency component with frequency 2 ⁇ and a d.c. voltage component.
  • the low-pass filter 19 removes the a.c. voltage component having frequency 2 ⁇ .
  • the switch 11 is connected to the resistor 9, no phase shift takes place, and the d.c. voltage is a measure for the capacitance of the impedance Z * .
  • the switch 11 is connected to the capacitor 13, the voltage on the output terminal thereof has been shifted by 90°. This voltage is a measure for the conductivity G of the impedor Z*. As it is the ca ⁇ e that
  • the circuit in Figure 2 is constructed as an integrated circuit in the form of an ASIC.
  • Figure 3 schematically shows an electrode configuration where two electrode ⁇ 30,31 are di ⁇ posed in a growing substrate 33.
  • the electrodes are connected to an alternating-current source 35.
  • the current paths between the electrodes 30, 31 are schematically indicated by 37.
  • the voltage across the input terminals of these electrodes, which is generated by the current flowing between the electrodes 30, 31, is mea ⁇ ured with the aid of a voltmeter 39.
  • the output ⁇ ignal of the voltmeter 39 is fed to a signal processing unit 40 which comprises, for example, a multiplier 17, a low-pas ⁇ filter 19, an analog-digital converter 21, an arithmetic unit 23 and a time control unit 25, as shotm in Figure 3.
  • Figure 4 shows an alternative set-up, where four electrodes 41,

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  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
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  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • General Health & Medical Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
  • Analytical Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geophysics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

La présente invention concerne un procédé de mesure de la teneur en eau de supports de cultures tels que le sable, l'argile, la terre, la laine de verre ou la laine minérale. Dans ce but, on mesure l'impédance du support de culture et on détermine la partie réelle ε' de la permittivité complexe ε' - jε' pour au moins deux fréquences. A partir de ces deux permittivités, la partie réelle ε' de la permittivité complexe est extrapolée pour une fréquence comprise entre 100 et 200 MHz. Dans ces conditions, on a constaté que la permittivité du support de culture est égale à celle du sable ayant une teneur en eau similaire. A partir de la variation de la permittivité du sable ou d'un matériau granulaire analogue ayant la même teneur en eau, il est possible de déterminer celle du support de culture sans qu'il soit nécessaire de procéder au préalable à des mesures de calibrage.
PCT/NL1996/000251 1995-06-20 1996-06-20 Procede de mesure de la teneur en eau de supports de cultures WO1997001090A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU61396/96A AU6139696A (en) 1995-06-20 1996-06-20 Method for measuring the water content of growing substrates

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL1000613 1995-06-20
NL1000613 1995-06-20

Publications (1)

Publication Number Publication Date
WO1997001090A1 true WO1997001090A1 (fr) 1997-01-09

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WO (1) WO1997001090A1 (fr)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999017124A1 (fr) * 1997-09-27 1999-04-08 The University Of Wales, Aberystwyth Mesure de la capacite d'un milieu dielectrique
WO2000033071A3 (fr) * 1998-12-03 2000-08-24 Fairfield Control Systems Ltd Technique de controle du degre d'humidite d'un sol, dispositif et systeme correspondants
US7042234B2 (en) 2002-12-16 2006-05-09 Sentek Pty Ltd Soil matric potential and salinity measurement apparatus and method of use
WO2008006973A1 (fr) * 2006-07-12 2008-01-17 Universite Paris Diderot - Paris 7 Dispositif de mesure de propriétés électriques d'un milieu comportant de l'eau
RU2428718C2 (ru) * 2005-09-12 2011-09-10 Шлюмбергер Текнолоджи Б.В. Способ для определения свойств земных формаций, использующий измерения диэлектрической проницаемости
CN103048339A (zh) * 2011-12-01 2013-04-17 中国科学院对地观测与数字地球科学中心 土壤水分检测方法及设备
RU2484453C1 (ru) * 2011-12-13 2013-06-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Башкирский государственный университет" Способ определения водонасыщенности керна
CN103308589A (zh) * 2013-06-26 2013-09-18 哈尔滨理工大学 湿型粘土砂极化性能的测试方法
RU2585169C1 (ru) * 2014-12-03 2016-05-27 федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Омский государственный педагогический университет" Радиофизический способ определения состава почвы
CN108709908A (zh) * 2018-06-11 2018-10-26 中国科学院地理科学与资源研究所 水盐一体速测仪以及土壤含盐量检测方法、装置
US20230228698A1 (en) * 2022-01-04 2023-07-20 Prophecy Sensorlytics, Llc Systems and methods for determining the moisture level in plastics and other materials

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2347694A1 (fr) * 1976-04-08 1977-11-04 Schlumberger Prospection Procede et dispositif pour determiner la quantite de fluide adsorbe dans les formations souterraines
EP0159270A2 (fr) * 1984-04-13 1985-10-23 Schlumberger Limited Procédé pour la détermination des propriétés des formations souterraines
WO1986005278A1 (fr) * 1985-03-08 1986-09-12 Regents Of The University Of California Procedes et appareils dielectriques pour classification in situ du sol
US4727311A (en) * 1986-03-06 1988-02-23 Walker Charles W E Microwave moisture measurement using two microwave signals of different frequency and phase shift determination

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2347694A1 (fr) * 1976-04-08 1977-11-04 Schlumberger Prospection Procede et dispositif pour determiner la quantite de fluide adsorbe dans les formations souterraines
EP0159270A2 (fr) * 1984-04-13 1985-10-23 Schlumberger Limited Procédé pour la détermination des propriétés des formations souterraines
WO1986005278A1 (fr) * 1985-03-08 1986-09-12 Regents Of The University Of California Procedes et appareils dielectriques pour classification in situ du sol
US4727311A (en) * 1986-03-06 1988-02-23 Walker Charles W E Microwave moisture measurement using two microwave signals of different frequency and phase shift determination

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999017124A1 (fr) * 1997-09-27 1999-04-08 The University Of Wales, Aberystwyth Mesure de la capacite d'un milieu dielectrique
US6496020B1 (en) 1997-09-27 2002-12-17 University Of Wales Aberystwyth Method and apparatus for capacitance measurement of a dielectric medium utilizing the ratio of capacitance measurement made at different frequencies
WO2000033071A3 (fr) * 1998-12-03 2000-08-24 Fairfield Control Systems Ltd Technique de controle du degre d'humidite d'un sol, dispositif et systeme correspondants
US7042234B2 (en) 2002-12-16 2006-05-09 Sentek Pty Ltd Soil matric potential and salinity measurement apparatus and method of use
RU2428718C2 (ru) * 2005-09-12 2011-09-10 Шлюмбергер Текнолоджи Б.В. Способ для определения свойств земных формаций, использующий измерения диэлектрической проницаемости
FR2903776A1 (fr) * 2006-07-12 2008-01-18 Univ Paris 7 Denis Diderot Dispositif de mesure de proprietes electriques d'un milieu comportant de l'eau.
WO2008006973A1 (fr) * 2006-07-12 2008-01-17 Universite Paris Diderot - Paris 7 Dispositif de mesure de propriétés électriques d'un milieu comportant de l'eau
CN103048339A (zh) * 2011-12-01 2013-04-17 中国科学院对地观测与数字地球科学中心 土壤水分检测方法及设备
RU2484453C1 (ru) * 2011-12-13 2013-06-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Башкирский государственный университет" Способ определения водонасыщенности керна
CN103308589A (zh) * 2013-06-26 2013-09-18 哈尔滨理工大学 湿型粘土砂极化性能的测试方法
RU2585169C1 (ru) * 2014-12-03 2016-05-27 федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Омский государственный педагогический университет" Радиофизический способ определения состава почвы
CN108709908A (zh) * 2018-06-11 2018-10-26 中国科学院地理科学与资源研究所 水盐一体速测仪以及土壤含盐量检测方法、装置
CN108709908B (zh) * 2018-06-11 2024-04-26 中国科学院地理科学与资源研究所 水盐一体速测仪以及土壤含盐量检测方法、装置
US20230228698A1 (en) * 2022-01-04 2023-07-20 Prophecy Sensorlytics, Llc Systems and methods for determining the moisture level in plastics and other materials

Also Published As

Publication number Publication date
AU6139696A (en) 1997-01-22

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