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WO2024116167A1 - Jauge de précipitation capacitive - Google Patents

Jauge de précipitation capacitive Download PDF

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WO2024116167A1
WO2024116167A1 PCT/IL2023/050765 IL2023050765W WO2024116167A1 WO 2024116167 A1 WO2024116167 A1 WO 2024116167A1 IL 2023050765 W IL2023050765 W IL 2023050765W WO 2024116167 A1 WO2024116167 A1 WO 2024116167A1
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electrode
electrically conductive
water
grounded
capacitor
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Igal ZLOCHIN
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
    • G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01W—METEOROLOGY
    • G01W1/00—Meteorology
    • G01W1/14—Rainfall or precipitation gauges

Definitions

  • TECHNICAL FIELD This invention relates to capacitive transducers, and more particularly to variable capacitance transducers for determining amount and intensity of water precipitations in agriculture, as well as for measuring the level of electrically conductive fluent materials within a container.
  • BACKGROUND OF THE INVENTION 1. Applications 70% of fresh water is used in agriculture. Over half of the average home's water use goes to residential landscaping.
  • Irrigation control systems known in the art typically employ a time clock and controller coupled to one or more electrically actuated or activated valves. Considerable inefficiency and poor performance can result when using pre-programmed watering controls as described above. For example, such watering systems typically irrigate during rainstorms, thus resulting in wasted water.
  • Overwatering is not only costly but may promote shallow roots, which in turn increase the plants susceptibility to disease.
  • about 12.5 million hectares were allegedly disturbed by plant diseases, mostly in Asia and Europe. Keeping track of rainfall amounts is a great way to cut costs and conserve water while retain a beautiful, lush healthy landscape.
  • crops in grape vineyards, apple and pear orchards, cotton and potato fields, etc. are prone to diseases, developing from freestanding water on the leaves.
  • Golf courses, (and other sports fields) are among the highest per-hectare users of fungicide treatment. Their high expenditure will make the precipitation gauge, having a leaf wetness sensor, an immediate cost saving device in utilizing the disease prevention models.
  • fungicides When the farmer knows that his field has had a certain number of hours of surface wetness at a certain temperature, he can use fungicides to reduce or prevent the disease. Such precision use of fungicides can reduce spraying costs by 50% and give far better disease control.
  • prevention of condensation on crops which usually takes place at night and causes fungal crop diseases, requires either heating or ventilation or both. To save on operating expenses of dehumidification devices, they should only be activated when necessary. A more reliable indication of the onset of condensation might be obtained by using a leaf wetness sensor (artificial leaf,) over which it is easy to detect the initial stages of dew formation. Once detected, a signal may be transmitted to the control system (heating, ventilating and/or dehumidification).
  • a dew sensor This sensor in fact mimics the condensation of humidity on a natural surface such as on leaves, without control of the temperature of the sensor, and thus in fact is very reliable since it directly mimics the natural process of condensation.
  • Various measurements have shown a good correlation between the temperature of the leaf and the temperature of the dew sensor at night.
  • a sensor is suitable for use in detecting condensation of water on various surfaces, such as leaves in greenhouses, giving a warning when a humidity of the air is too high, a situation which occurs for example at night, which is a cause of many plant diseases. Such a warning may operate various drying mechanisms to lower again greenhouse humidity.
  • the dew sensor is more suitable for use than humidity meter in greenhouses, since it indeed reflects the true and natural situation of condensation on surfaces, which is a better predictor to the state of the leaves than humidity content detected by humidity meters.
  • the most popular method for wetness detection nowadays is based on measuring the electrical impedance between two electrodes, which are shorted by water.
  • Conventional dew sensors such as those used in greenhouses typically employ a pair of spaced electrical wires, the resistance between which drops from approximately 19 megohms to 3 megohms when dew bridges the two wires. But such devices are electrically noisy and have changeable sensitivity that depends on salts precipitation and pollution on the sensor.
  • Example of another technology is PHYTOS 31 LWS Dielectric Leaf Wetness Sensor of METER Group, Inc. USA. It measures both the onset and duration of wetness on a simulated leaf, which in turn predicts when the onset of certain diseases or infections may occur. It uses capacitance technology, so it can sense sub-milligram levels of water condensing on the surface, including frost and ice formation. That way you can establish a threshold that not only indicates when the sensor is wet, but also senses how much water there is.
  • the LWS measures the dielectric constant of a zone approximately 1 cm from the upper surface of the sensor.
  • the surface coating is hydrophobic — similar to a leaf with a hydrophobic cuticle.
  • the sensor matches the wetness state of these types of leaves but may not match the wetness duration of pubescent leaves or leaves with less waxy cuticles.
  • the accumulation of dust and debris will cause the dry output to increase and change the Boolean threshold. It needs cleaning the sensing surface with a moist cloth periodically or when elevated dry output is detected. If using the LWS in areas with unusually high radiation loads, Campbell Scientific recommends applying Revivex UV Protectant every 45 days [3].
  • U.S Patent 4,626,774 is directed to a dew-point measuring instrument which has a capacitive dew-point sensor which is cooled by a cooling device to the dew-point temperature measured by a temperature sensor.
  • a phase measuring circuit measures the phase angle of the impedance of the capacitive dew-point sensor. The measured phase angle is used as a gauge for the contamination of the dew-point sensor.
  • U.S Patent 4,948,263 is directed to a dew point sensor for a dew-point measuring device for measuring the water vapor dew point in gases comprising a sensor surface which is exposed to the gas to be measured and on which, upon cooling, the dew-point temperature water vapor condenses.
  • two electrode structures which comprise electrode portions which are arranged a uniform interval parallel to each other and which are covered with a moisture-insensitive insulating layer.
  • the reaching of the dew-point temperature is determined by measuring the impedance or capacitance between the two electrode structures.
  • the distance between the electrode portions, arranged parallel to each other, of the two electrode structures is of the order of magnitude of the diameter of the largest condensation droplet forming on reaching the dew-point temperature, or smaller than said diameter, and the thickness of the insulating layer is small compared with the distance between the electrode portions.
  • U.S Patent 5,402,075 is directed to a capacitive moisture sensor includes insulator means; capacitance means including a sensing capacitor having a plurality of spaced capacitive sensor conductors mounted with the insulator means for exposure to the atmosphere; and first and second electrodes mounted with the insulator means remote from the spaced capacitive sensor conductors; means for applying a periodic input current across the first and second electrodes; and means for detecting a change in capacitance between the first and second electrodes indicative of moisture bridging at least two of the capacitive sensor conductors.
  • U.S. Patent No.6,926,439 to Zlochin concerns dew point hygrometers based on condensation of dew on ends of optical fibers, or on surfaces of an optical prism.
  • U.S. Patent No.6,575,621 to Zlochin describes a capacitive dew sensor comprising: a first electrode separated from the ambient environment by a coating which does not allow penetration of humidity and electrolyte there through; an insulator mounted on said first electrode, a second electrode formed on the exposed outer surface of the insulator when water containing electrolytes condenses or precipitates on said exposed outer surface of the insulator to form a continuous layer; electric wires connecting the two electrode structures to a measuring circuit for applying a current to said first and second electrode structures, so as to detect a change in capacitance between said first and second electrode structures when water layer is present.
  • An absorbent material can be mounted on the exposed outer surface of the insulator, thereby speeding the dew condensation onset and to increase the sensitivity of the sensor. But absorbent material slowing water evaporation from the sensor in the drying cycle of greenhouse or cooling room humidity control.
  • wetness control apparatuses which provide improved surface wetness measurement despite contamination and application of fertilizers, pesticides, herbicides and other chemical treatments which may be routinely applied to the plants and soil.
  • a liquid level sensor can also be used for the detection of liquid level in a tank for the purpose of controlling process pumps or inventory control, toilet monitoring and intelligent control, controlling the level of a liquid in a boiler and a coffee machine,
  • the amount of liquid medium accumulated in a storage or process vessel is an important process variable. Knowledge of the liquid inventory therein present allows better operation of the process.
  • Liquid level information may be a process parameter necessary for the actuation of pumps, heaters, and other common process equipment. The ability to monitor liquid levels accurately allows the efficient operation of a process and contributes to the quality of typical industrial products.
  • One traditional liquid level sensor determines the liquid level using image identification technology, as shown in U.S. Pat. No.7,982,201.
  • U.S. Patent No. 5,005005 to Brossia, et al. (1991) includes a fiber optic probe system for automatic and real time detection of the presence or absence of a substance in an environment by monitoring variations in light energy transmitted through an optical fiber having a specially processed sensitive probe area.
  • the sensitive probe area is positioned on, about or within the environment where a substance is to be detected. Because of differences in optical indices of refraction and energy absorption characteristics of different substances, the presence of different substances at the processed sensitive area will cause different proportional and characteristic attenuation of the light energy passing through the optical fiber.
  • Prior art liquid level sensors such as fuel sensors for motor vehicles, usually include a float that rides on an upper surface of the fuel in a fuel tank. The float is typically connected to one end of a pivot arm while the other end of the pivot arm typically includes a wiper mechanism that brushes against a resistor strip when the arm is rotated due to a change in fuel level in the tank. Such sensors are prone to wear, mechanical and/or electrical breakdown or inaccurate liquid level detection. Variable capacitance probes have been developed to overcome these drawbacks.
  • Contemporary capacitive liquid level sensors used for dielectric media, typically employ a parallel plate capacitor configured to be immersed or embedded in the medium so that a portion of the medium becomes embedded between the parallel plates and functions as a dielectric between the plates.
  • the capacitance provided by such a capacitor is used as part of an RC oscillator circuit having an oscillation frequency which varies with changes in the dielectric property of the small portion of the medium between the plates.
  • the frequency of the oscillator circuit is used as an indicator of the moisture content of the medium.
  • Another traditional capacitive liquid level sensors are used for electrically conductive liquids. They are two type [4]: • Dielectric Type (D-Type) - capacitive proximity sensors are configured with two sensing electrodes integrated in the oscillator.
  • the sensing field projects away from the sensor face and entrance of any object into the sensing field will increase the capacitance, resulting in oscillation.
  • Such sensors will detect all materials, insulative or conductive. These sensors are often called “shielded” and they may be flush mounted.
  • Conductive Type (L-Type) - capacitive proximity sensors are configured with only one sensing electrode integrated with the oscillator. Entrance of a conductive material into the field provides the second coupling electrode which then causes oscillation.
  • Such sensors are excellent for “looking through” an insulative material such as rubber, glass or paper in order to detect a conductive material such as water, or metal. These sensors are often called “unshielded” and they may not be flush mounted.
  • Conductive media typically has an electrical conductivity > 20 ⁇ S/cm. Conductive material can easily be detected by all sensor types whether they have a GND electrode or not. In conductive media the dielectric constant is irrelevant for the sensing distance. The sensing distance is influenced by the size of the object and its grounding. Non- conductive media typically has an electrical conductivity ⁇ 20 ⁇ S/cm. In general sensors with a GND electrode are recommended for non-conductive media. If a non-conductive object is moved into the sensor field, the field increases depending on the dielectric constant and the size of the material to be detected, increasing the capacity of the measuring field [5]. There are some patents on this subject, describing probable solutions and problems. A capacitive moisture sensors is proposed in U.S. Pat.
  • No.5,103,368 to Hart describes a capacitive fluid level sensor which senses level by charging a plurality of capacitors in sequence.
  • the capacitors are formed by two concentric tubes which are vertically oriented in a tank. The vertical orientation allows the fluid to be the dielectric between the plates. As the fluid level falls, a greater area of the plates is exposed to air as the dielectric, which changes the capacitance of the capacitor.
  • the capacitors are arranged in a non-linear manner. After each capacitor is charged for a fixed time interval, the resultant voltage is compared with a known voltage to obtain an output signal representing liquid depth.
  • No.6,766,728 to Fogagnolo et al.
  • the device in which the boiler is connected with an external cylindrical container made of dielectric material, comprises a capacitive sensor, coupled externally of cylindrical container, and means for detecting the changes in the capacitance of the capacitive sensor, thereby generating an electric signal representative of the liquid level in the boiler, and for controlling the liquid flow into the boiler.
  • a capacitive sensor coupled externally of cylindrical container, and means for detecting the changes in the capacitance of the capacitive sensor, thereby generating an electric signal representative of the liquid level in the boiler, and for controlling the liquid flow into the boiler.
  • a capacitive transducer for detecting the level of liquids and other materials has one or more antenna probes connected to an integrated chip normally associated with touch-screen displays. Each antenna probe operates independently and senses the level condition of wet or dry flowable materials such as water, oil, fuel, grain, and so on.
  • the antenna probes may be formed as insulated conductive wires or conductive traces between layers of a stiff or flexible substrate, such as a PCB, with the substrate material serving as the insulating layers.
  • Each antenna probe has a different length representing different depths of the material being measured to provide dynamic calibration of the level condition independent of the material type and ambient conditions.
  • Transducers for determining liquid level are often used in vehicles, industrial equipment and other systems and components.
  • the probe section is adapted for mounting inside or outside a tank, vessel or other container for measuring a level.
  • the probe section in accordance with an exemplary embodiment of the invention preferably includes a primary antenna probe and a plurality of secondary antenna probes formed as elongate electrically conductive electrodes or traces on an elongate electrically insulating substrate.
  • the primary probe is preferably constantly immersed in the material being measured while the secondary probes are used to dynamically calibrate the primary probe during measurement.
  • U.S. Patent No.9,983,042 to Huang apparatus for detecting liquid level is disclosed.
  • An embodiment of the invention provides a liquid-level sensor to detect liquid-level information of a liquid to be tested in a container.
  • the sensor includes an electrode, a sensing circuit, an amplifier and a controller.
  • the electrode is disposed on the outer surface of the container, comprising a first electrode and a second electrode.
  • the sensing circuit is coupled to a first electrode and a second electrode and receives a clock signal to generate a first voltage signal and a second voltage signal.
  • the amplifier receives the first voltage signal and the second voltage signal to output an output voltage.
  • the controller acquires liquid-level information of the liquid to be tested according to the output voltage and a voltage-volume table.
  • a toilet monitor uses a toilet tank water level sensor producing a toilet tank water level measurement signal.
  • a processor detects rate of change of the measurement signal and conditionally produce a responsive actuation signal in response to the detected rate of change.
  • a transducer connected to receive the actuation signal and transmit information, provide a humanly-perceptible indication, generate a data log and/or control an electronic water supply valve.
  • the sensor includes an uninsulated conductor and an insulated conductor.
  • the uninsulated conductor when immersed in the water of a toilet tank, provides direct electrical current conduction path into the water. The amount of conduction depends on several factors including the mineral content of the water.
  • the other conductor is insulated and is thus not electrically connected to the surrounding water in the toilet tank.
  • This other conductor acts as a second plate of the two-plate capacitor.
  • the equivalent circuit is thus a 2-plate variable capacitor--with the capacitance between the two plates varying based on the level or height of the water into which the conductors are immersed as well as the mineral content, temperature and other characteristics of that water, and the length of at least the insulated conductor. Due to the very high impedance of RC oscillator the sensor exhibits no substantial variation in accuracy over a wide range of liquid or water impurities, conductivity, temperature, depth of submersion, or variation of metals that might be used to construct uninsulated conductor.
  • the processor logs the rate of change for later retrieval and water usage tracking.
  • the sensor is configured to be disposed inside the tank and has a length that is less than the extent of the water level change within the tank, and the processor uses the measurement signal to extrapolate the measurements based on the extent of the water level change within the tank.
  • the processor is configured to sleep and to wake up at time intervals to sample the rate of change.
  • the toilet tank monitor is battery powered and has no on/off switch.
  • isolated capacitive liquid level probe is disclosed.
  • the device includes a first insulated electrode along with a second insulated electrode in the rod that is immersed in an electrically conductive liquid the depth of which is to be measured, contained in a tank.
  • the device is so constructed that any signal generated in the coil of the first transformer that is connected to the measurement circuit caused by a change in any external magnetic field relative to the measurement circuit is in anti-phase with the corresponding signal generated in the coil of the second transformer that is connected to the measurement circuit.
  • a problem is encountered with such a construction in the presence of stray external electromagnetic radiation, for example, in that the resulting changes in the external electromagnetic field may adversely interfere with the measurement which is made.
  • the readings obtained from prior art capacitive-type sensors are subject to variation and inaccuracies based on several variables. For example, a change in the dielectric constant of either the liquid being measured or the gas above the liquid can significantly affect sensor readings.
  • It is an object of the present invention is to provide a cheap precipitation gauge, with improved watering control, based on the actual watering needs of the irrigated zone or zones, while reducing or eliminating wasted water and preventing frequent manual adjustment of the controller due to daily, episode or seasonal fluctuations in weather conditions. It must provide reliable operation based on moisture content despite application of fertilizers, pesticides, herbicides and other chemical treatments which may be routinely applied to the soil being irrigated. Another object of the invention is to provide a precipitation gauge, which is versatile, rugged, low maintenance and low in cost, as well as to be capable measuring extremes high and low of precipitation and moisture events.
  • It is a further object of the present invention is to provide a precipitation, condensation and moisture sensors that can be used in various applications including, for example, but not limited to: greenhouses and cooling rooms humidity control, as well as conductive liquid level monitoring in tanks. Accordingly, several objects and advantages of the invention are: (a) to ensure reliable operation over a long period of time, (b) to reduce cost of the device, (c) to reduce the power consumption of the device by using low power capacitance SUMMARY OF THE INVENTION These and other objects are provided by a reliable and cheap Capacitive Precipitation Gauge (CPG), monitoring amount and intensity of water precipitation in agriculture and meteorology at unstable environmental conditions, as well as at salt/dirt deposition and water vapor condensation on the sensitive elements.
  • CPG Capacitive Precipitation Gauge
  • the Rain Gauge can accurately track both rainfall and sprinklers’ output, providing essential data for irrigation management and timing. It delivers accurate measured values for both amount and intensity of rainwater precipitation at both light and heavy rain.
  • the Rain Gaige is based on the change in capacitance of the electronic capacitor as a result of the change in the water level.
  • the Wetness Sensor intends for measuring small amount of rainfall and can be used as additional reference for RG self-calibration. It is based on continuous measurements of electronic capacitance change caused by wetness change of a water absorbent sheet. Moreover, the Wetness Sensor accurately tracks moisture on surfaces like plant leaves in open field, providing, together with the temperature meter, essential data for timing and reducing plants’ spray treatments. It measures both the onset and duration of wetness on a simulated leaf, which in turn predicts when the onset of certain diseases or infections may occur. In addition, it can be used for dew condensation control in greenhouses and cooling rooms.
  • a water layer as a one of the capacitor’s electrodes. It includes two electrode structures, connecting each of the electrodes to a measuring circuit.
  • the first electrode structure is formed when a water (including some electrolytes which are naturally present in the atmosphere) condenses or precipitates on the exposed outer surface of the absorbent sheet.
  • the second electrode structure is an electrically insulated conductive structure, isolated from the ambient atmosphere.
  • a measuring circuit is connected through wires to apply a current to both first and second electrode structures to detect a change in capacitance between them.
  • the Capacitive Precipitation Gauge is provided in certain example embodiments.
  • the present invention concerns a precipitation gauge, intended for measuring amount and intensity of rainfall and other water precipitations at unstable environment conditions of agriculture and meteorology, consists of: a rainfall collector of electrically conductive water, a primary capacitor including: • at least one first electrode in form of a vertical elongate tube, made of insulated electrically conductive material, located within the rainfall collector • at least one second electrode, including an assembly, surrounding the first electrode, formed by a grounded electrically conductive cup, having top horizontal surface, and the conductive water that is in physical contact with the first electrode outer surface and in electrical contact with the grounded electrically conductive cup • a floating body, sliding along the first electrode inside the electrically conductive cup as result of the level changes of the water, intended for prevention salt and dirt accumulation, as well as water vapor condensation on the first electrode outer surface and damping the water level instability • wherein the contacted area of the conductive water with the first electrode is changed due to the water level changes, that, in turn, causes the capacitance changes of the primary capacitor, correlated with the water level changes
  • the wetness sensor is used for measuring dew condensation and wetness duration on plant leaves and determining water condensation on agricultural products in cooling rooms.
  • the water level measurement device of the precipitation gauge can be used for measuring the water level in all types of tanks in industry, meteorology and automatic home installations. It has advantages in the areas of measuring the amount of rain, the coolant level of engines in unstable conditions such as a car radiator, managing fertilization systems of crops in greenhouses and in open areas, controlling residential water supply systems, etc.
  • This embodiment concerns a fluid level meter of conductive liquid in a vessel, based on electrical capacitors, immersed into said liquid, including: • at least one first electrode in form of a vertical elongate tube, made of insulated electrically conductive material • at least one second electrode, including an assembly formed by the conductive liquid with a grounded electrically conductive tube, surrounding said first electrode; the conductive liquid is in physical contact with the first electrode outer surface and in electrical contact with the grounded electrically conductive tube • the first and second electrodes form a primary capacitor • a floating body, sliding along the first electrode inside the grounded electrically conductive tube during the liquid level changes, intended for prevention salt and dirt accumulation on the first electrode outer surface and damping the liquid level instability • a measuring circuit, providing an output signal, indicating changes in capacitance between the first and second electrodes during the liquid level changes • electric leads connecting the two electrodes tothe measuring circuit for applying an electrical field to them • a central processing unit connected to the measuring circuit, programmed to compute the liquid level changes every given time • a wireless data transmitter to transmit
  • FIG.1 illustrates a principal scheme of the capacitive precipitation gauge with a central siphon.
  • FIG.2 illustrates a principal scheme of additional embodiment of the capacitive liquid level meter.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereafter with reference to the accompany drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
  • FIG.1 shows a principal scheme of a preferable embodiment of the present invention, illustrating a capacitive precipitation gauge with a central siphon. It includes a rainfall collector 1, having a funnel 2.
  • a primary capacitor which measures rain and other water precipitations, includes a first electrode, forming by an insulated conductive tube 3, electrically isolated from a surrounding rainwater 4.
  • the second electrode of the capacitor is formed by surface of the rainwater 4 that is in physical contact with the insulated conductive tube 3 and in electrical contact, via a conductive grounded capped tube 5, with a measuring circuit 6, which placed under the rainfall collector 1.
  • the rainwater is conductive since it contains naturally appearing salts present in the atmosphere.
  • An assembly of the insulated conductive tube 3 and the conductive grounded capped tube 5, together with the floating disk 7, serves as mechanical damper in case of water level instability caused by rainfall and wind. Moreover, the conductive grounded capped tube 5, around the insulated conductive tube 3, prevents the gauge from the environmental electromagnetic interference, which decrease the water level measurement accuracy.
  • a siphon tube 8 is mounted inside the insulated conductive tube 3. When rainwater level is reached to the upper point of the siphon tube 8, the rainwater begins running out via the siphon from the rainfall collector 1 and it is self-emptied. Further, a capacitive wetness sensor 9, including a second capacitor, is mounted at the top end of the rainfall collector. It is used for measurement of small amount of rainfall.
  • a first electrode of the wetness sensor is formed by a conductive grounded tube 10, a water absorbent fabric sheet 11, attached to the upper end of the conductive grounded tube 10 by a conductive fixing cover 12.
  • the second electrode of the wetness is formed by a grid 13, made of an insulated electrical wire, mounted closely to the fabric sheet bottom surface. When the fabric sheet 11 is wet, the capacitance between it and the grid 13 increased.
  • the capacitance value depends, also, on amount of water between upper surface of the fabric sheet and the grid 13 surface. In this way, small amount of rainfall can be measured.
  • the fabric sheet is served as artificial leaf for measurement of wetness present and duration on plant’s leaves. Water condensation or precipitation on the artificial leaf causes increasing conductive area of the wetness sensor first electrode that, in turn, increases tits capacitor capacitance.
  • the condensed water is conductive because it contains naturally appearing salts present in the air.
  • the electrodes are connected to a measuring circuit 6.
  • a grounded conductive tube 14 together with the insulated conductive tube 3 form a third reference capacitor, that used as the reference of the lower point of the primary capacitor measuring range for compensations of environmental temperature changes and primary capacitor electrodes contamination.
  • a temperature meter 15 is placed under the rainwater collector 1.
  • the precipitation gauge is further equipped with a wireless communications device 16 to wirelessly communicate with a monitoring network, LAN or the like via Wi-Fi, WAN, Bluetooth or any other convenient wireless technology.
  • the reliability and accuracy of the measurements are high at high intensities of wind and rain, as result of its the water damping features • Thanks for this design, the problems of ambient temperature changes, environmental electromagnetic disturbances, and salt/dirt deposition are, also reduced •
  • the innovative Wetness Sensor design allows, also, reducing the effect of salt, dirt and chemical agents on the accuracy and reliability of the measurement of the small amount of the water precipitation at dew and light rain •
  • Combination the Rain Gauge and Wetness Sensor, both based on the same capacitive principle, in one instrument allows regular self-calibration both the devices in the field to prevent temperature and contamination influence on the measurements •
  • the problem of solid contaminants (salts, dust etc.) deposited on the measuring surfaces of the gauge significantly reduced by using a water layer as a one of the capacitor’s electrodes •
  • the instrument is simple, without any movable or elastic components, so its reliability is extremely high.
  • FIG.2 shows a principal scheme of a further embodiment of the present invention, illustrating a capacitive liquid level meter.
  • the sensor mounting inside a tank 21, includes a first electrode of a primary capacitor that is an insulated conductive rod 22 electrically isolated from the surrounding environment.
  • the second electrode structure of the capacitor is formed by conductive liquid surface 23 and conductive grounded tube 24, which provides direct electrical current conduction path into the liquid 23 from a measuring circuit 25.
  • the bottom end of the insulated conductive rod 22 measures low level of the liquid in the bottom of the tank 21.
  • the surface of the second electrode, contacted with the first electrode is changed and, as a result, the capacitance changes somewhat from 20 to 500 picofarads and said change in the capacitance can be measured.
  • the assembly of the conductive rod 22 and conductive grounded tube 24, together with the floating disk 26 serves as mechanical damper in case of the liquid level instability. It intends, also, to reduce or resist the effects of dirt and vibrations.
  • This capacitor intends for compensations of mineral content, temperature, and other variable characteristics of the conductive liquid, as well as contaminations of the primary capacitor. When it is immersed in the liquid being measured, it is used as the reference of the higher point of the primary capacitor measuring range.
  • a temperature meter 29 are mounted inside the mechanical body of the measuring circuit 25. It intends for compensations of temperature changes of the measured liquid.
  • the meter is further equipped with a wireless communications device 30 to wirelessly communicate with a monitoring network, LAN or the like via Wi-Fi, WAN, Bluetooth or any other convenient wireless technology.
  • United State Patent No.5,088,324 Nemeth, February 18, 1992, 73/291.
  • United State Patent No.5,391,891, Wiegleb et al., February 21, 1995, 250/574.
  • United State Patent No.5,402,075, Lu et al., March 28, 1995, 324/664.
  • United State Patent No.7,982,201 B2 Bryant et al., Jul.19, 2011, GOIF 23/00.
  • United State Patent No.8,022,842 B2 Levine, September 20, 2011, 340/962.

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  • Measuring Fluid Pressure (AREA)

Abstract

Une jauge de précipitation capacitive fiable et bon marché, basée sur la mesure de niveau de liquide électroconducteur, tel que des liquides à base d'eau, vise à surveiller la précipitation de l'eau dans l'agriculture et la météorologie à des conditions environnementales instables, ainsi qu'un dépôt de sel/saleté et une condensation de vapeur d'eau sur les éléments sensibles. Elle comprend une jauge de pluie capacitive, un capteur d'humidité capacitif et un dispositif de mesure de température d'air. La jauge de pluie peut suivre avec précision à la fois la quantité/l'intensité de la pluie et la sortie des gicleurs, fournissant ainsi des données essentielles pour la gestion et la synchronisation d'irrigation. Le capteur d'humidité suit avec précision la petite quantité de pluie et l'humidité sur des surfaces telles que des feuilles de plante, fournissant ainsi, conjointement avec le dispositif de mesure de température, des données essentielles pour la synchronisation et réduisant ainsi les traitements de pulvérisation de plantes. De plus, il peut être utilisé pour une commande de condensation de rosée dans des serres et des salles de refroidissement.
PCT/IL2023/050765 2022-11-28 2023-07-23 Jauge de précipitation capacitive Ceased WO2024116167A1 (fr)

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