EP1889051A1 - Device for using with a sensor for improving accuracy, and sensor with an improved accuracy - Google Patents

Device for using with a sensor for improving accuracy, and sensor with an improved accuracy

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Publication number
EP1889051A1
EP1889051A1 EP06741616A EP06741616A EP1889051A1 EP 1889051 A1 EP1889051 A1 EP 1889051A1 EP 06741616 A EP06741616 A EP 06741616A EP 06741616 A EP06741616 A EP 06741616A EP 1889051 A1 EP1889051 A1 EP 1889051A1
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EP
European Patent Office
Prior art keywords
sensor
interface
moisture
surrounding
solid medium
Prior art date
Legal status (The legal status 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 status listed.)
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Application number
EP06741616A
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German (de)
French (fr)
Inventor
Walter Schmidt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PlantCare AG
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PlantCare AG
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Filing date
Publication date
Application filed by PlantCare AG filed Critical PlantCare AG
Publication of EP1889051A1 publication Critical patent/EP1889051A1/en
Withdrawn legal-status Critical Current

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Classifications

    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
    • A01G25/00—Watering gardens, fields, sports grounds or the like
    • A01G25/16—Control of watering
    • A01G25/167—Control by humidity of the soil itself or of devices simulating soil or of the atmosphere; Soil humidity sensors
    • 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

  • the invention is in the field of improving sensor accuracy and reliability, and more particularly relates to a device for use with a sensor to improve its accuracy, and to an apparatus for measuring the moisture content in solid materials with improved accuracy.
  • tensiometers are used to measure soil moisture. These gauges consist of a hermetically sealable tube with a porous ceramic cap at the bottom. At the upper end a conventional or electronic manometer is connected. If the tube is filled with water, this flows through the porous ceramic cap to the outside. If the tube is inserted into a medium which can absorb water, this creates a vacuum in the tube which can be measured.
  • this measurement principle has a number of serious disadvantages:
  • the accuracy of the measurement depends strongly on the type of medium surrounding the ceramic cap. In sandy or with stones or gravel staggered substrates, it is very common that the contact surface between ceramic and surrounding earth is not defined; This means that air gaps form, which strongly influence the measurement.
  • the porous ceramic can calcify by calcareous water and microorganisms can colonize the ceramic. This leads to a drift of the measurement result over time.
  • the suction stress of Kunststofferde on the grain size of, for example, quartz sand is adjusted.
  • the Kunststofferde but also has a high heat capacity and thermal conductivity, so that the moisture measurement, especially those by thermal processes, determined by the properties of Kunststofferde.
  • the Kunststofferde In order for the still little defined interface earth / Kunststofferde, which consists of a, the Kunststofferde enclosing, network, does not come to fruition, the Kunststofferde must also have a certain volume.
  • the object of the invention is thus to increase the measurement accuracy of sensors, in particular by improving the interaction between the sensor and the surrounding medium.
  • the invention is based on the idea by the use of a standardized interface between the sensor and the surrounding medium to compensate for differences in the surface morphology and thereby increase the accuracy of the sensors, in particular of soil moisture sensors, such as. Tensiometers.
  • Such interfaces should have as little influence on humidity as possible due to their material properties and design.
  • Such an interface allows a moisture balance between Sensoroberfiumblee and surrounding medium as possible without affecting the measurement, in particular due to thermal properties.
  • the interface is mechanically deformable so that it can adapt to a not clearly defined surface of a Feststoffstoffrnediums or solid mixture and z. B. impressions of stones or interstices, the inhomogeneous surface of a granular medium, such as bulk material, etc., are compensated. Also by a certain change in volume of the surrounding medium, eg. By drying or swelling, taken into account.
  • the interface should additionally also have a very low heat capacity for hydrophilic "soft and configuration.
  • the little-defined contact area between sensor and environment is optimized and the negative, because undefined influence on a measurement eliminated or at least greatly reduced.
  • a low thermal conductivity and thermal capacity of the interface is advantageous, especially in thermal measuring methods, for example, with soil moisture sensors with heating element. This guarantees that a temperature change in the measuring sensor takes place due to the moisture of the surrounding medium and not due to the heat capacity of the interface.
  • the interface preferably also has a thermal decoupling effect. This is in contrast to ceramics, or even Kunststofferden, which themselves have a high thermal conductivity and in the case of ceramics do not allow complete displacement of the air in the pores by moisture. A measurement is thus falsified by 'ceramic properties'.
  • the interface, or the materials from which it is made still further desired properties
  • the interface is interchangeable and designed as a sensor or sensor head, in the case of a tensiometer, on the ceramic cap, turntable material.
  • This may also be a cap-shaped interface, for.
  • a fingerstall be, or, depending on the shape of the sensor also be composed of individual layers with openings for sensors, etc. interface.
  • the interface can also be firmly attached to a sensor / sensor head.
  • the material of the interface should absorb moisture from the surrounding medium and release it again so that there is no moisture difference between the interface and the surrounding medium. Therefore, hydrophilic, open-pored material is suitable, which in particular also has substantially the same pore size as that of the surrounding medium.
  • the interface should also be as corrosion-resistant and protected against rotting as possible. This is preferably accomplished by using suitable synthetic material, such as plastic, for example in the form of processed plastic fiber, as the article material. If the interface is or is attached to a sensor which is inserted into the ground, the interface material also has a certain mechanical stability, so that it does not break or break easily when pressed into the ground. Depending on the type of sensor, z. With sensor, If necessary, the interface surrounding the sensor may be surrounded by a stable but very open mechanical support. If possible, this support has no influence on a measurement and preferably makes a small area proportion of the sensor resp. an effective measuring range.
  • the support may be stable, preferably made of a solid material, such that a sensor or interface is protected by the tip of the support upon insertion of the sensor into a more solid mass of solid matter, such as compact earth.
  • An interface may also include a sensor or sensor head, e.g. As an existing ceramic, protect against external influences such as calcification and infestation of microorganisms, but also from mechanical influences. At very low cost, material and time, an interchangeable interface can be replaced, for. B. due to wear and aging of the interface or when using the sensor in another medium.
  • a sensor or sensor head e.g. As an existing ceramic, protect against external influences such as calcification and infestation of microorganisms, but also from mechanical influences.
  • an interchangeable interface can be replaced, for. B. due to wear and aging of the interface or when using the sensor in another medium.
  • the ratio of pores or cavities or passages in the material to the amount and distribution of the material itself should be optimized as much as possible so that the material as little as possible impairs a moisture exchange of the solid-state / interface. This is the case in particular for interfaces which are made of fibers, for example of felt, gauze, fleece, knitted fabric or fabric.
  • an interface is that conventional sensors can be provided with it and thus its accuracy and in particular reliability is substantially increased. In addition, such interfaces can be made very cheap. Via the interface, the contact surface between the sensor and the surrounding medium is optimized or enlarged or as in the case of volume reduction of the surrounding medium, for example, by shrinkage of soil by dehydration, a contact only made or guaranteed.
  • Fig. 1 is a tensiometer
  • Fig. 2 shows a detail of a sensor tip
  • FIG. 1 shows a tensiometer.
  • a water-filled pipe 1 is closed at its lower end by a cap of porous ceramic 2. The lower end is located at a certain depth below the bottom surface 5.
  • At the upper end of the tensiometer is the Wasserein Schollöfmung airtight seal by means of a closure 3.
  • In the upper part of the manometer 4 is attached, on which the pressure prevailing in the tube can be read.
  • water is now forced out of the tensiometer into the soil through the ceramic cap 2.
  • An imbalance of moisture always causes a pressure change in the tube, which is readable on the manometer.
  • the interaction of the moisture is only guaranteed with an optimal contact between the ceramic cap 2 and the surrounding earth.
  • Figure 2 shows a section through an inventive embodiment of the foremost part of the sensor tip of a tensiometer as shown in Figure 1. It can be seen the hollow and filled with water 6, porous ceramic cap 2, the felt with 7th is covered.
  • the felt may be in the form of a felt cap which can be slipped over the ceramic cap and which is exchangeable or also fixedly attached to the sensor. With the appropriate choice of felt, this easily absorbs moisture and releases it again so that there is no moisture difference between the felt and the surrounding medium.
  • felts made of synthetic fibers can be used which are largely resistant to fungi and do not rot. As soon as a felt no longer meets the requirements due to the aging phenomena, it can be replaced and replaced with little effort and expense.
  • the felt or other suitable materials such as open celled polyurethane foam, gauze, knit fabrics, woven fabric, nonwoven webs, and especially nonwoven webs made and wound from plastic fibers, have a thickness in a range of 1 to 10 mm, typically 3 to 7 mm, e.g. B. 5mm. Depending on the type of sensor and the surrounding mixture of solids, the thickness can be adjusted accordingly.
  • the softness or mechanical compliance of the interface allows adaptation to the undefined, non-uniform, grainy surface of soil or other solid media such as grain. Also, a certain reduction in volume of the surrounding earth due to dehydration is compensated for by the flexibility of the interface and, in particular, the size of the contact surface is defined or kept essentially the same.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • General Health & Medical Sciences (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Food Science & Technology (AREA)
  • Medicinal Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • Remote Sensing (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Soil Sciences (AREA)
  • Water Supply & Treatment (AREA)
  • Environmental Sciences (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

The invention relates to a sensor for measuring the water or moisture content in a solid substance medium, particularly a soil moisture sensor, and to a device for use with a sensor for improving the accuracy thereof. The sensor or at least the area of the sensor designed for measuring is surrounded by an interface, which is designed for taking up and releasing moisture and is mechanically flexible whereby enabling the interface to adapt to an inconstant or unclearly defined surface of the solid substance medium, e.g. the soil, surrounding the sensor. As a result, the contact surface between the sensor and medium is optimized, and air gaps, indentations by stones, etc. are compensated for or bypassed. The interface is preferably comprised of a felt made of synthetic fibers and can be removeably placed over a sensor or sensor head.

Description

VORRICHTUNG ZUR VERWENDUNG MIT EINEM SENSOR DEVICE FOR USE WITH A SENSOR
ZUR VERBESSERUNG DER GENAUIGKEIT, SOWIE SENSORFOR IMPROVING ACCURACY AND SENSOR
MIT VERBESSERTER GENAUIGKEITWITH IMPROVED ACCURACY
Die Erfindung liegt auf dem Gebiet der Verbesserung der Sensorgenauigkeit und Zuverlässigkeit, und betrifft insbesondere eine Vorrichtung zur Verwendung mit einem Sensor zu dessen Genauigkeitsverbesserung, sowie einen Vorrichtung zum Messen des Wasser- bzw. Feuchtigkeitsgehalts in Feststoffinedien mit verbesserter Genauigkeit.The invention is in the field of improving sensor accuracy and reliability, and more particularly relates to a device for use with a sensor to improve its accuracy, and to an apparatus for measuring the moisture content in solid materials with improved accuracy.
Heute werden zur Messung von Bodenfeuchte primär sogenannte Tensiometer verwendet. Diese Messgeräte bestehen aus einer luftdicht verschliessbaren Röhre, die am unteren Ende eine Kappe aus poröser Keramik aufweist. Am oberen Ende ist ein konventionelles oder elektronisches Manometer angeschlossen. Wird die Röhre mit Wasser gefüllt, so fliesst dieses durch die poröse Keramikkappe nach aussen. Wird die Röhre in ein Medium gesteckt, welches Wasser aufnehmen kann, so erzeugt dies in der Röhre einen Unterdruck der gemessen werden kann. Dieses Messprinzip weist aber eine Reihe von gravierenden Nachteilen auf:Today, primarily so-called tensiometers are used to measure soil moisture. These gauges consist of a hermetically sealable tube with a porous ceramic cap at the bottom. At the upper end a conventional or electronic manometer is connected. If the tube is filled with water, this flows through the porous ceramic cap to the outside. If the tube is inserted into a medium which can absorb water, this creates a vacuum in the tube which can be measured. However, this measurement principle has a number of serious disadvantages:
- Die Genauigkeit der Messung hängt stark von der Art des die Keramikkappe umgebenden Mediums ab. Bei sandigen oder mit Steinen oder Schotter versetzten Substraten kommt es sehr häufig vor, dass die Berührungsfläche zwischen Keramik und umgebender Erde nicht definiert ist; D.h. es kommt zur Bildung von Luftspalten, die die Messung stark beeinflussen.The accuracy of the measurement depends strongly on the type of medium surrounding the ceramic cap. In sandy or with stones or gravel staggered substrates, it is very common that the contact surface between ceramic and surrounding earth is not defined; This means that air gaps form, which strongly influence the measurement.
Trocknet die umgebende Erde aus, so bilden sich Spalten zwischen Keramik und Erde, die zu Falschmessungen fuhren.If the surrounding earth dries up, gaps between ceramic and earth form, leading to false measurements.
Die poröse Keramik kann durch kalkhaltiges Wasser verkalken und Mikroorganismen können die Keramik besiedeln. Dadurch kommt es zu einer Drift des Messergebnisses über die Zeit.The porous ceramic can calcify by calcareous water and microorganisms can colonize the ceramic. This leads to a drift of the measurement result over time.
Bei einer Änderung der Temperatur oder auch des barometrischen Luftdruckes ändert sich das Messergebnis.If the temperature or the barometric air pressure changes, the measurement result changes.
- Da aus der Keramikkappe Wasser austritt, muss der Wasserpegel im Rohr immer wieder kontrolliert und allenfalls Wasser nachgefüllt werden.- Since water leaks out of the ceramic cap, the water level in the tube has to be checked again and again and if necessary water has to be added.
Bei einer Verkleinerung der Keramikkappe verkleinert sich auch die Kontaktfläche zwischen Keramik und Umgebung und demnach sinkt auch die Genauigkeit und die Sensitivität.With a reduction of the ceramic cap also reduces the contact area between the ceramic and the environment and therefore also decreases the accuracy and sensitivity.
Der grösste und wichtigste Faktor, der zur Ungenauigkeit der Messergebnisse führt ist die prinzipiell unbestimmte Grenzfläche zwischen Keramik und Umgebungsmedium. Das gleiche gilt natürlich auch für Bodenfeuchtesensoren, die auf thermischen Messverfahren beruhen. Die Problematik der mechanisch-thermischen Ankopplung eines Bodenfeuchtesensors wurde bereits in der Schrift DE 2536777 erkannt. Zur Umgehung des Problems einer unbestimmten Grenzfläche wird vorgeschlagen, die Messung nicht in der Erde, sondern in einer den eigentlichen Messfühler, einen Heizstift, umgebenden definierten Kunsterde durchzuführen. Die Kunsterde weist dieselbe Saugspannung auf, wie die eigentlich zu messende Erde. Die Kunsterde muss den Eigenschaften derThe biggest and most important factor that leads to the inaccuracy of the measurement results is the fundamentally indeterminate interface between ceramic and surrounding medium. Of course, the same applies to soil moisture sensors based on thermal measurement methods. The problem of the mechanical-thermal coupling of a soil moisture sensor has already been recognized in the document DE 2536777. To circumvent the problem of an indeterminate interface, it is proposed to perform the measurement not in the earth, but in a defined Kunsterde surrounding the actual sensor, a heating pin. The artificial earth has the same suction tension as the earth actually to be measured. The Kunsterde must the characteristics of the
Erde möglichst genau nachempfunden sein, wobei die Saugspannung der Kunsterde über die Körnung von bspw. Quarzsand eingestellt wird. Die Kunsterde weist aber ebenfalls eine hohe Wärmekapazität und Wärmeleitfähigkeit auf, so dass die Feuchtemessung, insbesondere solche mittels thermischem Verfahren, durch die Eigenschaften der Kunsterde bestimmt ist. Damit die weiterhin wenig definierte Grenzfläche Erde/Kunsterde, welche aus einem, die Kunsterde umhüllenden, Netz besteht, nicht zum tragen kommt, muss die Kunsterde zudem ein gewisses Volumen aufweisen.Earth be modeled as accurately as possible, the suction stress of Kunsterde on the grain size of, for example, quartz sand is adjusted. The Kunsterde but also has a high heat capacity and thermal conductivity, so that the moisture measurement, especially those by thermal processes, determined by the properties of Kunsterde. In order for the still little defined interface earth / Kunsterde, which consists of a, the Kunsterde enclosing, network, does not come to fruition, the Kunsterde must also have a certain volume.
Aufgabe der Erfindung ist es somit, die Messgenauigkeit von Sensoren zu erhöhen, insbesondere durch Verbesserung der Wechselwirkung zwischen Sensor und umgebendem Medium.The object of the invention is thus to increase the measurement accuracy of sensors, in particular by improving the interaction between the sensor and the surrounding medium.
Die Aufgabe wird durch die Vorrichtung, den Sensor und die Verwendung der Vorrichtung gelöst, wie sie in den Patentansprüchen definiert sind.The object is achieved by the device, the sensor and the use of the device, as defined in the patent claims.
Der Erfindung liegt die Idee zugrunde durch den Einsatz eines standardisierten Interfaces zwischen Sensor und Umgebungsmedium, Unterschiede in der Oberflächenmorphologie auszugleichen und dadurch die Genauigkeit der Sensoren, insbesondere von Bodenfeuchtesensoren,' wie bspw. Tensiometern, zu erhöhen. Solche Interfaces sollen eine Feuchteinessimg durch ihre Materialeigenschaften und Gestaltung, möglichst wenig beeinflussen. Ein solche Interface erlaubt einen Feuchteausgleich zwischen Sensoroberfiäche und umgebendem Medium möglichst ohne Beeinflussung der Messung, insbesondere aufgrund thermischer Eigenschaften.The invention is based on the idea by the use of a standardized interface between the sensor and the surrounding medium to compensate for differences in the surface morphology and thereby increase the accuracy of the sensors, in particular of soil moisture sensors, such as. Tensiometers. Such interfaces should have as little influence on humidity as possible due to their material properties and design. Such an interface allows a moisture balance between Sensoroberfiäche and surrounding medium as possible without affecting the measurement, in particular due to thermal properties.
Als Interface kommen Materialien in Frage, die möglichst eng am Sensor oder zumindest an den für die Messung relevanten Bereichen des Sensors anliegen und die Feuchtigkeit vom Umgebungsmedium, beispielsweise Erde, aufsaugen und auch wieder an dieses abzugeben vermögen. Zudem ist das Interface mechanisch deformierbar, so dass es sich an eine nicht klar definierte Oberfläche eines Feststoffrnediums oder Feststoffgemenge anpassen kann und z. B. Eindrücke von Steinen oder Zwischenräume, die inhomogene Oberfläche eines körnigen Mediums, wie Schüttgut etc., ausgeglichen werden. Auch wird dadurch eine gewisse Volumenveränderung des umgebenden Mediums, bspw. durch Austrocken oder Aufquellen, berücksichtigt. Bei Sensoren mit thermischen Messverfahren, sollte das Interface zusätzlich zur hydrophilen " und weichen Ausgestaltung zudem eine möglichst niedrige Wärmekapazität aufweisen.As an interface materials come into question, as close as possible to the sensor or at least abut the relevant for the measurement areas of the sensor and absorb the moisture from the surrounding medium, such as earth, and also able to give it back to this. In addition, the interface is mechanically deformable so that it can adapt to a not clearly defined surface of a Feststoffstoffrnediums or solid mixture and z. B. impressions of stones or interstices, the inhomogeneous surface of a granular medium, such as bulk material, etc., are compensated. Also by a certain change in volume of the surrounding medium, eg. By drying or swelling, taken into account. For sensors with a thermal measurement method, the interface should additionally also have a very low heat capacity for hydrophilic "soft and configuration.
Durch ein Interface wird die wenig definierte Kontaktfläche zwischen Sensor und Umgebung optimiert und der negative, weil Undefinierte Einfluss auf eine Messung eliminiert oder zumindest stark verringert.Through an interface, the little-defined contact area between sensor and environment is optimized and the negative, because undefined influence on a measurement eliminated or at least greatly reduced.
Eine geringe Wärmeleitfähigkeit und Wärmekapazität des Interface ist vorteilhaft, insbesondere bei thermischen Messverfahren, beispielsweise mit Bodenfeuchtesensoren mit Heizelement. Damit wird garantiert, dass eine Temperaturänderung beim Messsensor aufgrund der Feuchtigkeit des umgebenden Mediums und nicht aufgrund der Wärmekapazität des Interfaces stattfindet. Das Interface hat vorzugsweise auch einen thermischen Entkoppeleffekt auf. Dies steht im Gegensatz zu Keramiken, oder auch Kunsterden, welche selber eine hohe Wärmeleitfähigkeit aufweisen und im Falle von Keramiken keine gänzliche Verdrängung der Luft in den Poren durch Feuchtigkeit ermöglichen. Eine Messung wird so durch ,Keramikeigenschaften' verfälscht. Je nach Sensor und umgebendem Medium weist das Interface, bzw. die Materialien aus denen es hergestellt ist, noch weitere gewünschte Eigenschaften aufA low thermal conductivity and thermal capacity of the interface is advantageous, especially in thermal measuring methods, for example, with soil moisture sensors with heating element. This guarantees that a temperature change in the measuring sensor takes place due to the moisture of the surrounding medium and not due to the heat capacity of the interface. The interface preferably also has a thermal decoupling effect. This is in contrast to ceramics, or even Kunsterden, which themselves have a high thermal conductivity and in the case of ceramics do not allow complete displacement of the air in the pores by moisture. A measurement is thus falsified by 'ceramic properties'. Depending on the sensor and surrounding medium, the interface, or the materials from which it is made, still further desired properties
In einer bevorzugten Ausfuhrungsform ist das Interface auswechselbar und als über einen Sensor oder Sensorkopf, im Falle eines Tensiometers, über die Keramikkappe, stülpbares Material, gestaltet. Dies kann ein ebenfalls als Kappe geformtes Interface, z. B. ein Fingerling, sein, oder je nach Form des Sensors auch ein aus einzelnen Schichten mit Öffnungen für Messfühler etc. zusammengesetztes Interface sein. Das Interface kann auch fest an einem Sensor/Sensorkopf angebracht sein.In a preferred embodiment, the interface is interchangeable and designed as a sensor or sensor head, in the case of a tensiometer, on the ceramic cap, turntable material. This may also be a cap-shaped interface, for. As a fingerstall be, or, depending on the shape of the sensor also be composed of individual layers with openings for sensors, etc. interface. The interface can also be firmly attached to a sensor / sensor head.
Das Material des Interfaces sollte Feuchtigkeit des umgebenden Mediums leicht aufnehmen und sie auch wieder so abgeben, dass keine Feuchtigkeitsdifferenz zwischen Interface und umgebendem Medium auftritt. Daher eignet sich hydrophiles, offenporiges Material, welches im speziellen auch im wesentlichen die gleiche Porengrösse wie die des umgebenden Mediums aufweist.The material of the interface should absorb moisture from the surrounding medium and release it again so that there is no moisture difference between the interface and the surrounding medium. Therefore, hydrophilic, open-pored material is suitable, which in particular also has substantially the same pore size as that of the surrounding medium.
Da Sensoren oft einer korrosiven Umgebung ausgesetzt sind, sollte auch das Interface möglichst korrosionsbeständig und gegenüber Verrottung geschützt sein. Dies wird bevorzugt dadurch erreicht, indem geeignetes synthetisches Material, wie Kunststoff, beispielsweise in der Form von verarbeiteten Kunststoffasera, als Ihterfacematerial verwendet wird. Ist oder wird das Interface an einem Sensor befestigt, welcher in die Erde eingesteckt wird, so weist das Interfacematerial auch eine gewisse mechanische Stabilität auf, um beim Einpressen in die Erde nicht zu leicht zu zerreissen oder zerbrechen. Je nach Art eines Sensors, z. B. mit Messfühler, kann das den Messfühler umgebende Interface gegebenenfalls noch durch eine stabile, aber sehr offene, mechanische Stütze umgeben sein. Diese Stütze nimmt möglichst keinen Einfluss auf eine Messung und macht vorzugsweise einen geringen Flächenanteil des Sensor resp. eines effektiven Messbereichs aus. Die Stütze kann stabil, vorzugsweise aus einem festen Material gestaltet sein, so dass ein Sensor oder ein Interface beim Einstecken des Sensors in ein festeres Feststoffgemenge, wie kompakte Erde, durch die Spitze der Stütze geschützt ist.Since sensors are often exposed to a corrosive environment, the interface should also be as corrosion-resistant and protected against rotting as possible. This is preferably accomplished by using suitable synthetic material, such as plastic, for example in the form of processed plastic fiber, as the article material. If the interface is or is attached to a sensor which is inserted into the ground, the interface material also has a certain mechanical stability, so that it does not break or break easily when pressed into the ground. Depending on the type of sensor, z. With sensor, If necessary, the interface surrounding the sensor may be surrounded by a stable but very open mechanical support. If possible, this support has no influence on a measurement and preferably makes a small area proportion of the sensor resp. an effective measuring range. The support may be stable, preferably made of a solid material, such that a sensor or interface is protected by the tip of the support upon insertion of the sensor into a more solid mass of solid matter, such as compact earth.
Ein Interface kann auch einen Sensor oder Sensorkopf, z. B. eine vorhandene Keramik, vor äusseren Einflüssen wie Verkalkung und Befall von Mikroorganismen, aber auch vor mechanischen Einflüssen schützen. Unter sehr geringem Kosten-, Material- und Zeitaufwand kann ein auswechselbares Interface ersetzt werden, z. B. aufgrund Abnutzung und Alterung des Interfaces oder bei Verwendung des Sensors in einem anderen Medium.An interface may also include a sensor or sensor head, e.g. As an existing ceramic, protect against external influences such as calcification and infestation of microorganisms, but also from mechanical influences. At very low cost, material and time, an interchangeable interface can be replaced, for. B. due to wear and aging of the interface or when using the sensor in another medium.
Das Verhältnis Poren bzw. Hohlräume oder Durchgänge im Material zur Menge und Verteilung des Materials selber, sollte möglichst derart optimiert sein, dass das Material einen Feuchtigkeitsaustausch Feststoffinedium/Interface möglichst wenig beeinfiusst. Dies ist insbesondere bei Interfaces der Fall, welche aus Fasern hergestellt sind, bspw. aus Filz, Gaze, Vlies, Gestrick oder Gewebe.The ratio of pores or cavities or passages in the material to the amount and distribution of the material itself should be optimized as much as possible so that the material as little as possible impairs a moisture exchange of the solid-state / interface. This is the case in particular for interfaces which are made of fibers, for example of felt, gauze, fleece, knitted fabric or fabric.
Ein weiterer Vorteil eines Interface ist, dass herkömmliche Sensoren damit versehen werden können und damit deren Genauigkeit und insbesondere Zuverlässigkeit wesentlich erhöht wird. Zudem können solche Interfaces sehr günstig hergestellt werden. Über das Interface wird die Kontaktoberfläche zwischen Sensor und Umgebungsmedium optimiert bzw. vergrössert oder wie im Falle von Volumenverkleinerung des umgebenden Mediums, beispielsweise durch Schrumpfung von Erde durch Austrocknung, ein Kontakt erst hergestellt bzw. garantiert.Another advantage of an interface is that conventional sensors can be provided with it and thus its accuracy and in particular reliability is substantially increased. In addition, such interfaces can be made very cheap. Via the interface, the contact surface between the sensor and the surrounding medium is optimized or enlarged or as in the case of volume reduction of the surrounding medium, for example, by shrinkage of soil by dehydration, a contact only made or guaranteed.
Im Folgenden ist die Erfindung anhand beispielhafter Figuren dargestellt. Dabei zeigtThe invention is illustrated below with reference to exemplary figures. It shows
Fig. 1 ein TensiometerFig. 1 is a tensiometer
Fig. 2 einen Ausschnitt aus einer SensorspitzeFig. 2 shows a detail of a sensor tip
Figur 1 zeigt ein Tensiometer. Ein mit Wasser gefülltes Rohr 1 ist an seinem unteren Ende durch eine Kappe aus poröser Keramik 2 abgeschlossen. Das untere Ende befindet sich in einer bestimmten Tiefe unter der Bodenoberfläche 5. Am oberen Ende des Tensiometers befindet sich die Wassereinfüllöfmung die mittels eines Verschlusses 3 luftdicht abschliessbar ist. Im oberen Bereich ist auch das Manometer 4 angebracht, an dem der im Rohr herrschende Druck abgelesen werden kann. Je nach Feuchtigkeit im Boden wird nun Wasser durch die Keramikkappe 2 aus dem Tensiometer in den Boden gedrückt. Ein Ungleichgewicht an Feuchtigkeit bewirkt immer eine Druckänderung im Rohr, welche am Manometer ablesbar ist. Die Wechselwirkung der Feuchtigkeit ist jedoch nur gewährleistet bei einem optimalen Kontakt zwischen Keramikkappe 2 und umgebender Erde.FIG. 1 shows a tensiometer. A water-filled pipe 1 is closed at its lower end by a cap of porous ceramic 2. The lower end is located at a certain depth below the bottom surface 5. At the upper end of the tensiometer is the Wassereinfüllöfmung airtight seal by means of a closure 3. In the upper part of the manometer 4 is attached, on which the pressure prevailing in the tube can be read. Depending on the moisture in the soil, water is now forced out of the tensiometer into the soil through the ceramic cap 2. An imbalance of moisture always causes a pressure change in the tube, which is readable on the manometer. However, the interaction of the moisture is only guaranteed with an optimal contact between the ceramic cap 2 and the surrounding earth.
Figur 2 zeigt einen Schnitt durch eine erfindungsgemässe Ausführung des vordersten Teils der Sensorspitze eines Tensiometers wie aus Figur 1. Man erkennt die hohle und mit Wasser 6 gefüllte, poröse Keramikkappe 2, die mit Filz 7 überzogen ist. Der Filz kann in der Form einer über die Keramikkappe stülpbaren Filzkappe ausgeführt sein, welche auswechselbar oder auch fest am Sensor angebracht ist. Bei entsprechender Wahl des Filzes, nimmt dieser die Feuchtigkeit leicht auf und gibt sie auch wieder so ab, dass keine Feuchtigkeitsdifferenz zwischen Filz und umgebendem Medium auftritt. Zudem können Filze aus Kunststoffasern verwendet werden, die weitgehend resistent gegenüber Pilzen sind und nicht verrotten. Sobald ein Filz aufgrund der Alterungserscheinungen nicht mehr den Anforderungen entspricht kann er unter geringem Aufwand und Kosten ersetzt und ausgetauscht werden. Der Filz oder andere geeignete Materialien, wie beispielsweise offenporiger Polyurethanschaum, Gaze, Gestricke, Gewebe, Vlies, insbesondere aus Kunststoffasern hergestellte und gewickelte Vliese, weisen eine Dicke in einem Bereich von 1 bis 10 mm, typischerweise 3 -7mm, z. B. 5mm auf. Je nach Art des Sensors und umgebenden Feststoffgemenges kann die Dicke entsprechend angepasst werden. Die Weichheit bzw. mechanische Nachgiebigkeit des Interfaces erlaubt ein Anpassen an die Undefinierte, ungleichmässige, körnige Oberfläche von Erde oder anderen Feststoffmedien wie bspw. Getreide. Auch eine gewisse Volumenverkleinerung der umgebenden Erde aufgrund von Austrocknen wird mit der Flexibilität des Interfaces ausgeglichen und dadurch insbesondere die Grosse der Kontaktfläche definiert bzw. diese im wesentlichen immer gleich gross gehalten. Figure 2 shows a section through an inventive embodiment of the foremost part of the sensor tip of a tensiometer as shown in Figure 1. It can be seen the hollow and filled with water 6, porous ceramic cap 2, the felt with 7th is covered. The felt may be in the form of a felt cap which can be slipped over the ceramic cap and which is exchangeable or also fixedly attached to the sensor. With the appropriate choice of felt, this easily absorbs moisture and releases it again so that there is no moisture difference between the felt and the surrounding medium. In addition, felts made of synthetic fibers can be used which are largely resistant to fungi and do not rot. As soon as a felt no longer meets the requirements due to the aging phenomena, it can be replaced and replaced with little effort and expense. The felt or other suitable materials, such as open celled polyurethane foam, gauze, knit fabrics, woven fabric, nonwoven webs, and especially nonwoven webs made and wound from plastic fibers, have a thickness in a range of 1 to 10 mm, typically 3 to 7 mm, e.g. B. 5mm. Depending on the type of sensor and the surrounding mixture of solids, the thickness can be adjusted accordingly. The softness or mechanical compliance of the interface allows adaptation to the undefined, non-uniform, grainy surface of soil or other solid media such as grain. Also, a certain reduction in volume of the surrounding earth due to dehydration is compensated for by the flexibility of the interface and, in particular, the size of the contact surface is defined or kept essentially the same.

Claims

PATENTANSPRÜCHE
1. Vorrichtung zur Verwendung mit einem Sensor zur Messung von Wasser bzw. Feuchtigkeit eines Feststof&nediums, dadurch gekennzeichnet, dass die Vorrichtung offenporig, Feuchtigkeit aufnehmend und abgebend, mechanisch nachgiebig, sowie an einem Sensor anbringbar ist, derart dass sie bündig an diesen anschliesst und ein Interface zwischen Sensor oder Teilen davon und umgebendem Feststoffmedium bildet und dabei an eine nicht konstante bzw. nicht klar definierte Oberfläche eines den Sensor zumindest teilweise umgebenden Feststofrmediums anpassbar gestaltet ist, um eine optimierte Kontaktfläche zwischen Sensor und Feststoffinedium zu bilden.An apparatus for use with a sensor for measuring water or moisture of a solid, characterized in that the apparatus is open-pored, moisture absorbing and dispensing, mechanically compliant, and attachable to a sensor such that it is flush with and adjoins it Formed interface between the sensor or parts thereof and surrounding solid medium and thereby adapted to a non-constant or not clearly defined surface of the sensor at least partially surrounding Feststofrmediums customizable to form an optimized contact surface between the sensor and the solid medium.
2. Vorrichtung nach Anspruch 1, ■ aufweisend eine, geringe . Wärmekapazität und Wärmeleitfähigkeit in Bezug auf ein umgebendes Feststoffmedium.2. Apparatus according to claim 1, ■ having a, low. Heat capacity and thermal conductivity relative to a surrounding solid medium.
3. Vorrichtung nach Anspruch 1 oder 2, hergestellt aus Fasern, wie bspw. FiIz5 Gaze, Vlies, Gestrick oder Gewebe.3. Apparatus according to claim 1 or 2, made of fibers, such as, for example, 5 gauze, nonwoven, knitted or woven fabric.
4. Vorrichtung nach einem der Ansprüche 1 bis 3, wobei sie aus synthetischem Material ist.4. Device according to one of claims 1 to 3, wherein it is made of synthetic material.
5. Vorrichtung nach einem der vorangehenden Ansprüche, wobei sie eine Dicke zwischen 1 und 10 mm aufweist.5. Device according to one of the preceding claims, wherein it has a thickness between 1 and 10 mm.
6. Verwendung einer Vorrichtung nach einem der Ansprüche 1-5, zum bündigen Überziehen zumindest von Teilen eines Sensors, als Interface zwischen einer Sensoroberfläche und einer Oberfläche eines den Sensor umgebenden Feststoffinediums .6. Use of a device according to any one of claims 1-5, for flush coating at least parts of a sensor, as an interface between a Sensor surface and a surface of a surrounding the sensor solid state.
7. Sensor zur Messung des Wasser- bzw. Feuchtigkeitgehalts eines, die Vorrichtung zumindest teilweise umgebenden, im wesentlichen keine konstante und klar definierte Oberfläche aufweisenden Feststofrmediums, dadurch gekennzeichnet, dass der zur Messung ausgelegte Bereich des Sensors mit einem Interface umgeben ist, welches Interface Feuchtigkeit aufnehmend und abgebend, sowie mechanisch nachgiebig gestaltet ist, derart dass das Interface an eine nicht konstante bzw. nicht klar definierte Oberfläclie eines den Sensor zumindest teilweise umgebenden Feststoffmediums anpassbar ist und dadurch eine Kontaktfläche zwischen Sensor und Feststoffmedium optimierbar ist.7. Sensor for measuring the water or moisture content of a, the device at least partially surrounding, substantially no constant and clearly defined surface having Feststofrmediums, characterized in that the designed for measurement area of the sensor is surrounded with an interface, which interface moisture receiving and dispensing, as well as designed mechanically resilient, so that the interface to a non-constant or not clearly defined Oberfläclie the sensor at least partially surrounding solid medium is customizable and thereby a contact surface between the sensor and solid medium can be optimized.
8. Sensor nach Anspruch 7, wobei das Interface auswechselbar am Sensor angebracht ist.8. Sensor according to claim 7, wherein the interface is removably mounted on the sensor.
9. Sensor nach Anspruch 7 oder 8, wobei das Feststoffmedium Erde und die Vorrichtung ein Bodenfeuchtesensor ist.9. Sensor according to claim 7 or 8, wherein the solid medium is earth and the device is a soil moisture sensor.
10. Sensor nach Anspruch 9, wobei eine Messung der Bodenfeuchte durch Messung der Saugkraft des Bodens geschieht und eine zur Messung benötigte poröse Keramik (2) mit dem Interface überzogen ist.10. Sensor according to claim 9, wherein a measurement of the soil moisture is done by measuring the suction of the soil and a required for the measurement porous ceramic (2) is coated with the interface.
11. Sensor nach einem der Ansprüche 7 - 10, wobei das Interface offenporig ist und im wesentlichen die gleiche Porengrösse wie die des umgebenden Feststoffmediums aufweist. 11. Sensor according to any one of claims 7 - 10, wherein the interface is open-pored and has substantially the same pore size as that of the surrounding solid medium.
EP06741616A 2005-06-07 2006-06-01 Device for using with a sensor for improving accuracy, and sensor with an improved accuracy Withdrawn EP1889051A1 (en)

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CA2611196A1 (en) 2006-12-14

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