System for measuring the moisture content of a granular medium

Abstract

System for measuring the moisture content of a granular medium. This description relates to a system (1) for measuring the moisture content of a granular medium (2) comprising a collection element (3) intended to be placed in the granular medium (2) in contact with the granular medium (2), and configured to collect water present in the granular medium (2), a reservoir (14) for receiving the collected water, moisture sensors (16) in regions at least partially distinct from the granular medium (2), at least one temperature sensor (24), at least one conductivity sensor (26) configured to measure the conductivity of the water received in the reservoir (14), and transport means (18, 21) configured to transport water from the reservoir (14) to the conductivity sensor (26). Figure for the abstract: Fig. 1

Description

Title of the invention: System for measuring the moisture content of a granular medium. Technical field

[0001] The present description relates in general to a system for measuring the moisture of a granular medium, for example soil. Previous technique

[0002] For certain applications, it is desirable to be able to measure the moisture content of a granular medium. One example of such an application is the cultivation of plants in soil, where it is desirable to be able to determine the amount of water present between the soil grains available to the plants in order to determine the soil's irrigation requirements.

[0003] The use of moisture measurement systems on a farm requires that these measurement systems be low-cost. However, the signals provided by existing low-cost moisture measurement systems, for example capacitive sensors, do indeed vary according to soil moisture, but generally also according to other parameters such as temperature or soil conductivity. It can therefore be difficult to directly use the signals provided by such moisture measurement systems. Summary of the invention

[0004] One embodiment overcomes all or part of the drawbacks of known humidity measurement systems.

[0005] One embodiment provides a system for measuring the moisture of a granular medium comprising a collection element intended to be placed in the granular medium in contact with the granular medium, and configured to collect water present in the granular medium, a reservoir for receiving the collected water, moisture sensors of regions at least partly distinct from the granular medium, at least one temperature sensor, at least one conductivity sensor configured to measure the conductivity of the water received in the reservoir and transport means configured to transport water from the reservoir to the conductivity sensor.

[0006] According to one embodiment, the transport means comprise a pipe connecting the reservoir to the conductivity sensor, the collection element surrounding the pipe.

[0007] According to one embodiment, the system further includes a sensor for the concentration of a first ion contained in the water received in the reservoir.

[0008] According to one embodiment, the system further includes a sensor for the concentration of a second ion contained in the water received in the reservoir.

[0009] According to one embodiment, the collection element is permeable to water present in the granular medium.

[0010] According to one embodiment, the collection element comprises a first enclosure elongated in one direction, the reservoir and the humidity sensors being contained in the first enclosure.

[0011] According to one embodiment, the system comprises a second enclosure, contained within the first enclosure, the humidity sensors being located in the second enclosure.

[0012] According to one embodiment, the first enclosure comprises an external face including a channel for collecting water in the granular medium by gravity and a passage connecting the channel to the reservoir.

[0013] According to one embodiment, the system comprises collection elements and tubes, the humidity sensors being contained in the tubes, the collection elements and the tubes being arranged alternately in a direction.

[0014] According to one embodiment, the means of transport include a suction pump.

[0015] According to one embodiment, the system further comprises a distilled water container, the transport means being further configured to transport distilled water from the container to the conductivity sensor.

[0016] According to one embodiment, the transport means are further configured to transport distilled water from the container to the first ion concentration sensor.

[0017] According to one embodiment, the system includes wireless communication means.

[0018] According to one embodiment, the system includes a battery of electric accumulators and means for recharging the battery.

[0019] One embodiment also provides for the use of the humidity measurement system as defined above, comprising the following steps: - acquisition of humidity measurements by the humidity sensors and acquisition of at least one temperature measurement by said at least one temperature sensor; - determination of the presence of water in the tank; - transport of water from the reservoir to the conductivity sensor; - measurement of the conductivity of the water transported to the conductivity sensor; and - correction of the humidity measurements from the conductivity measurement and said at least one temperature measurement.

[0020] According to one embodiment, the use further includes transporting water from the reservoir to the first ion concentration sensor and measuring the concentration of the first ion in the water transported to the first ion concentration sensor.

[0021] According to one embodiment, the use includes, between two measurements of the conductivity of the water in the reservoir, bringing the conductivity sensor into contact with distilled water.

[0022] According to one embodiment, the use further includes, between two measurements of the concentration of the first ion in the water of the reservoir, bringing the sensor of the concentration of the first ion into contact with distilled water.

[0023] According to one embodiment, the use includes the system being used for measuring the moisture content of a soil.

[0024] According to one embodiment, the use includes determining the presence of water in the tank is carried out from the humidity measurement of the humidity sensor closest to the tank.

[0025] According to one embodiment, the transport of water from the reservoir to the conductivity sensor is carried out only if the state of charge of the electric accumulator battery is greater than a state of charge threshold. Brief description of the drawings

[0026] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0027] [Fig.1] is a partial and schematic side-sectional view of an embodiment of a soil moisture measurement system;

[0028] [Fig.2] is a cross-sectional view of [Fig.1] along the section plane II-II;

[0029] [Fig.3] is an electrical diagram of an embodiment of a Colpitts oscillator;

[0030] [Fig.4] represents a diagram of an ISFET sensor;

[0031] [Fig.5] is a block diagram illustrating one embodiment of a method of operation of the measurement system of [Fig.1];

[0032] [Fig.6] is a diagram illustrating steps in the implementation of the operating process illustrated in [Fig.5];

[0033] [Fig.7] and [Fig.8] are respectively a partial side view and a partial and schematic lateral sectional view of another embodiment of a soil moisture measurement system;

[0034] [Fig. 9] is a partial, schematic, side-sectional view of another embodiment of a soil moisture measurement system; and

[0035] [Fig. 10] is a partial and schematic side-sectional view of another embodiment of a soil moisture measurement system. Description of the implementation methods

[0036] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0037] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0038] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements coupled together, this means that these two elements can be connected or linked through one or more other elements.

[0039] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to a humidity measurement system in a normal operating position or to the orientation of the figures.

[0040] Unless otherwise specified, the expressions "approximately", "roughly", "about", and "on the order of" mean to the nearest 10% or 10°, preferably to the nearest 5% or 5°. Furthermore, the terms "insulator" and "conductor" are taken to mean "electrically insulating" and "electrically conductive", respectively.

[0041] Embodiments of a moisture measurement system will be described for measuring the moisture content of soil. However, these embodiments of the moisture measurement system can be used for measuring the moisture content of any granular medium, particularly powdery or fibrous media, for example cotton, cereals, coal dust, or concrete.

[0042] [Fig.1] is a partial and schematic lateral cross-sectional view of an embodiment of a system 1 for measuring the moisture of a soil 2 and [Fig.2] is a cross-sectional view of [Fig.1] along the cross-sectional plane II-II.

[0043] System 1 comprises: - an elongated external enclosure 3, extending along an axis D, and embedded in the ground 2, the external enclosure 3 comprising an external lateral face 4 in contact with the ground 2 when the external enclosure 3 is embedded in the ground 2 and a lateral face internal 5, opposite the external lateral face 4, a closed lower end 6 and an open upper end 7; - an elongated inner enclosure 8, extending along axis D, contained within the inner enclosure 3, the inner enclosure 8 comprising an external lateral face 9 and an internal lateral face 10, opposite the external lateral face 9, a lower end traversed by an opening 11 and an open upper end 12, the external lateral face 9 of the inner enclosure 8 being separated from the internal lateral face 5 of the external enclosure 3 by a gap 13; - a reservoir 14 located between the base of the inner enclosure 8 and the base of the outer enclosure 3 and capable of collecting water 15 present in the soil 2; - at least one humidity sensor 16, three humidity sensors 16 being shown as an example in [Fig.1]; - a pipe 18 extending into the internal enclosure 8 along the axis D, the pipe 18 having a first end 19 and a second end 20, the first end 19 being located in the tank 14; - a suction pump 21 arranged on the pipe 18; - a box 22 located outside the ground 2 and connected to the external enclosure 3 and the internal enclosure 8, the conduit 18 further extending into the box 22 and the second end 20 of the conduit 18 being located outside the box 22; - at least one temperature sensor 24, four temperature sensors 24 being shown as an example in [Fig.1]; - at least one sensor 26 for measuring the concentration of solutes present in the water contained in the pipe 18 and / or properties of the water contained in the pipe 18, five sensors 26 being represented as an example in [Fig.1]; - a processing circuit 28 located in the housing 22 and comprising a control circuit 30 for the suction pump 21 and an interface circuit 32 with the sensors 16, 24, 26; - a battery of electric accumulators 34 for the power supply of all the elements of the humidity measurement system 1 and located in the housing 22; - means of recharging 36 of the electric accumulator battery 34; and - means for transmitting data 38, for example an antenna for transmitting and receiving electromagnetic waves, the processing circuit 28 further comprising a communication circuit 40 located in the housing 22 and connected to the antenna 38 and configured to control the antenna 38.

[0044] The dimensions of the humidity measurement system 1 depend on the intended applications. According to one embodiment, the length of the external enclosure 3, measured along axis D, is between 30 cm and 1.20 m, preferably between 30 cm and 80 cm, and is, for example, approximately 60 cm. In one embodiment, the outer enclosure 3 has a cylindrical tubular shape with axis D and a circular base. In one embodiment, the diameter of the outer lateral face 4 of the outer enclosure 3 is between 2 cm and 10 cm. In one embodiment, the inner enclosure 4 has a cylindrical tubular shape with axis D and a circular base. In one embodiment, the diameter of the outer lateral face 9 of the inner enclosure 8 is between 2 cm and 10 cm. In one embodiment, the outer diameter of the pipe 18 is between 2 mm and 20 mm. In one embodiment, the water storage capacity in the humidity measurement system 1 is between 1 ml and 100 ml.

[0045] In one embodiment, the outer enclosure 3 is made of an electrically insulating material. In one embodiment, the outer enclosure 3 is permeable to water present in the soil 2, optionally except around the reservoir 14. In one embodiment, the outer enclosure 3 includes perforations allowing the passage of water present in the soil 2. When water is present in the soil 2, it passes through the outer enclosure 3 and falls into the reservoir 14 under the action of gravity. In one embodiment, the outer enclosure 3 is made of concrete, terracotta, ceramic, lime, or gypsum. In one embodiment, the inner enclosure 8 is made of an electrically insulating material.

[0046] According to one embodiment, the humidity measurement system 1 comprises at least two humidity sensors 16 distributed in the inner enclosure 8 along the axis D, the humidity sensors 16 thus being located at different depths in the soil 2 when the outer enclosure 3 is driven into the soil 2.

[0047] According to one embodiment, the humidity measurement system 1 comprises at least two temperature sensors 24. According to one embodiment, the humidity measurement system 1 comprises at least two temperature sensors 24 distributed in the inner enclosure 8 along the axis D, the temperature sensors 24 thus being located at different depths in the soil 2 when the outer enclosure 3 is embedded in the soil 2. According to one embodiment, the humidity measurement system 1 comprises at least one temperature sensor 24 located in the housing 22. By way of example, each temperature sensor 24 corresponds to the LM335 analog integrated circuit.

[0048] According to one embodiment, each humidity sensor 16 includes an oscillator and is configured to measure the variation in the oscillator's oscillation frequency. According to one embodiment, the oscillator includes a capacitor whose capacitance varies according to the humidity and salinity of the soil 2 in the vicinity of the capacitor, such that the oscillator's oscillation frequency varies according to the humidity and salinity of the soil 2 in the vicinity of the capacitor.

[0049] In one embodiment, each humidity sensor 16 comprises a capacitor Ci including a first plate 41 and a second plate 42. In one embodiment, the inner chamber 8 has a cylindrical tubular shape with axis D. In one embodiment, each plate 41, 42 corresponds to a segment of cylindrical tube pressed against the inner face 10 of the inner chamber 8, the outer radius R of which is between 1 cm and 5 cm. The plates 41, 42 are arranged diametrically opposite each other with respect to the axis D. In one embodiment, each plate 41, 42 has a height H, measured along the axis D, and is inscribed in an arc of a circle with angle α in the plane of section [Fig. 2]. In one embodiment, the height H is between 1 cm and 15 cm. In one embodiment, the angle α is between 30° and 160°. According to one embodiment, the armatures 41, 42 are made of metal, for example copper.

[0050] According to one embodiment, the oscillator corresponds to a Colpitts oscillator.

[0051] Fig. 3 is an electrical diagram of an embodiment of a Colpitts oscillator.

[0052] The OSC oscillator comprises capacitor Ci and capacitor C2. A first plate of capacitor Ci and a first plate of capacitor C2 are connected, preferably connected, to a source with a low reference potential, for example, the ground (GND) of the humidity measurement system 1. The second plate of capacitor Ci is connected, preferably connected, to a first terminal of an inductor L. The second plate of capacitor C2 is connected, preferably connected, to the second terminal of the inductor L. The second plate of capacitor Ci is further connected, preferably connected, to the input of a logic inverter circuit INV, and the second plate of capacitor C2 is connected, preferably connected, to the output of the logic inverter circuit INV. The OSC oscillator provides, at the output of the logic inverter circuit INV, a voltage Vout oscillating at an oscillation frequency F given by the following relation:

[0053] [Math.l]

[0054] where the capacity C is given by the following relation:

[0055] [Math.2]

[0056] According to one embodiment, the inductance L is between 10 pH and 1000 pH. According to one embodiment, the oscillation frequency F is between 0.1 MHz and 5 MHz. Preferably, the oscillation frequency F is approximately 1 MHz. This advantageously minimizes the influence of absorbed water. by the soil grains 2, which are unusable by plants. This also allows for a good compromise with the effect of conductivity. Generally, the shape of the capacitor plates Ci and the oscillation frequency F determine the volume of the soil region 2 that influences the capacitance of capacitor Cl, and must therefore be adjusted to obtain the desired volume of influence. For example, the volume of influence is contained within a sphere containing plates 41, 42, and extending beyond the plates over a radial distance ranging from 2 cm to 20 cm, for example, approximately 5 cm.

[0057] As an alternative, the oscillator may be different from a Colpitts oscillator, and correspond to any type of oscillator implementing the capacitor Cl, for example a Hartley oscillator.

[0058] According to one embodiment, each sensor 26 is an optical sensor or an electrochemical sensor. The sensor 26 or sensors 26 are chosen from the group comprising a sensor for the conductivity of the water contained in the pipe 18, a sensor for the pH of the water contained in the pipe 18, a sensor for the nitrogen concentration of the water contained in the pipe 18, a sensor for the phosphorus concentration of the water contained in the pipe 18, a sensor for the potassium concentration of the water contained in the pipe 18, and a sensor for the dioxygen concentration of the water contained in the pipe 18.

[0059] An example of an optical sensor includes a photodetector. An example of an electrochemical sensor includes an ion-sensitive field-effect transistor (ISFET) and is hereafter referred to as an ISFET sensor. Another example of an electrochemical sensor is a sensor comprising diamond-like carbon elements, or a DLC (Diamond-Like Carbon) sensor.

[0060] Fig. 4 represents a schematic of an ISFET 26 sensor.

[0061] The ISFET sensor 26 comprises a semiconductor substrate 44 including a face 45, and a drain region 46 and a source region 47 formed in the substrate 44. The ISFET sensor 26 further comprises a conductive pad 48 in contact with the drain region 46 and a conductive pad 49 in contact with the source region 47. The face 45 is covered with an insulating layer 50 forming part of the gate insulator of the ISFET transistor. The insulating layer 50 is in contact with the water 15 to be analyzed. The conductive pads 48 and 49 are covered with an insulating encapsulation layer 51. The conductive pad 48 is connected, preferably connected, to a first terminal of a voltage source Vds, and the conductive pad 49 is connected, preferably connected, to the second terminal of the voltage source Vds. The substrate 44 is further connected, preferably connected, to the second terminal of the voltage source Vds.The ISFET 26 sensor further includes a reference electrode 52 in contact with water 15 and . connected, preferably connected, to the first terminal of a voltage source Vg. The conductive contact 49 is connected, preferably connected, to the second terminal of the voltage source Vg. The current flowing through the transistor channel varies according to the ion concentration of water 15.

[0062] The charging means 36 allow the electric storage battery 34 to be recharged. In one example, the charging means 36 include, for example, a photovoltaic panel connected to the battery 34. In another example, the charging means 36 include, for example, a microturbine. This advantageously ensures the operating autonomy of the humidity measurement system 1. In another example, the humidity measurement system includes a power supply terminal accessible from outside the humidity measurement system 1 and connected to the battery 34, thus allowing the temporary connection of an external power supply system to the humidity measurement system 1 for recharging the battery 34.

[0063] The data transmission means 38 advantageously enable wireless communication with the humidity measurement system 1, for example according to the LoRa communication protocol. Alternatively, the data transmission means 38 include a connection terminal accessible from outside the humidity measurement system 1 and connected to the communication circuit 40, thus enabling the temporary connection of an external communication system to the humidity measurement system 1 for data exchange with the processing circuit 28 via a wired connection, for example according to the RS485 or BTLE (Bluetooth Low Energy) communication protocol.

[0064] [Fig.5] is a block diagram illustrating one embodiment of a method of operation of the humidity measurement system 1 of [Fig.1].

[0065] In step 60, the processing circuit 28 controls each humidity sensor 16 to perform a humidity measurement and controls each temperature sensor 24 to perform a temperature measurement. In particular, the humidity can vary depending on the depth in the soil 2. The process continues in step 62.

[0066] In step 62, the processing circuit 28 determines whether water 15 is present in the tank 14 based on measurements provided by the humidity sensors 16. According to one embodiment, the presence of water 15 is detected in the tank 14 when the humidity measurement provided by the humidity sensor 16 closest to the tank 14 exceeds a threshold or reaches a saturation level. If there is water 15 in the tank 14, the processing circuit 28 can further determine whether the state of charge of the battery 34 exceeds a state of charge threshold corresponding to the energy required to pump the water 15 present in the tank 14. If there is water 15 in the tank 14, and if the state of charge of the battery 34 is above the state of charge threshold of If there is no water in tank 14, the process continues at step 64. If there is no water in tank 14, the process continues at step 60.

[0067] In step 64, the treatment circuit 28 controls the suction pump 21 to draw water from the reservoir 14 to the sensors 26 via the pipe 18. A vacuum of, for example, 0.33 atmospheres (33437.25 Pa) can be applied to extract the water from the soil. Operating the suction pump 21 only when it is determined that water 15 is present in the reservoir 14 advantageously reduces the electrical consumption of the suction pump 21 and increases the service life of the sensors 26. In one embodiment, the moisture measurement system 1 includes means for creating a vacuum in the pipe 18 to initiate the suction of water into the pipe 18, for example, by using the pump 41. The process continues in step 66.

[0068] In step 66, the treatment circuit 28 controls the sensors 26 to perform measurements of the concentration of solutes present in the water contained in the pipe 18 and / or of the properties of the water contained in the pipe 18. In particular, in step 66, a measurement of the conductivity of the water contained in the pipe 18 is performed. In one embodiment, the measurement method may include performing electrochemical impedance spectroscopy and / or optical spectroscopy. In one embodiment, a correction is applied to the conductivity measurement based on the temperature measurement provided by the temperature sensor 24 closest to the sensors 26. In one embodiment, a 2% correction is applied to the conductivity value for each degree outside 25 °C. When the measurements by the sensors 26 are completed, the water is evacuated from the pipe through the end 20 (arrow A in [Fig.1]) until reservoir 14 is empty. The process continues at step 68.

[0069] In step 68, the processing circuit 28 applies corrections to the measurement provided by each humidity sensor 16. In one embodiment, a correction is applied to the measurement provided by each humidity sensor 16 based on the temperature measurement provided by the temperature sensor 24 closest to the humidity sensor 16. In one embodiment, when the oscillation frequency of the humidity sensor 16 is substantially equal to 1 MHz, the variation of the measurement provided by the humidity sensor 16 as a function of temperature is approximately -0.3 kHz / °C for each degree outside 25°C. In another embodiment, a correction is applied to the humidity measurement provided by each humidity sensor 16 based on the conductivity measurement determined in step 66.According to one embodiment, the correction factor applied to the moisture measurement to account for conductivity depends on the oscillation frequency and the nature of the soil. The process continues at step 70.

[0070] In step 70, an action is performed by the processing circuit 28. This action may correspond to the remote transmission of data by the processing circuit 28 via the antenna 38. The data may include measurements taken and corrected if necessary, in particular corrected humidity measurements, temperature measurements, corrected conductivity measurements, ion concentration measurements (N, P, K, pH, redox), and possibly dissolved O2 and CO2 concentrations. The data may further include the rate of change of humidity (e.g., over a day), the rate of change of temperature (e.g., over a day), the moisture gradient in soil 2 as a function of depth, and the temperature gradient in soil 2 as a function of depth.In one embodiment, the data provided by the processing circuit 28 may take into account meteorological data, including atmospheric pressure, sunlight, and wind, possibly with the concept of evapotranspiration. The data may include an indicator for the user of the moisture measurement system 1, specifically regarding the need for watering, the expected watering duration, the concentration of fertilizers to be added to the soil 2, etc. When the moisture measurement system 1 is connected to a soil irrigation system 2, the action may include the activation of the irrigation system by the moisture measurement system 1. The process continues in step 60. In particular, when the soil 2 is saturated with water, soil moisture measurement is no longer necessary, since no watering is required.A delay can then be implemented, for example from 1 to 3 days, before the process continues to step 60 to order new humidity measurements. This advantageously reduces the electrical consumption of the humidity measurement system 1.

[0071] When an analysis of the water in tank 14 has been performed, a delay can be introduced before the treatment circuit determines, in step 60, whether water is present in the tank. Indeed, the analysis of pore water is not necessary daily since its evolution is slow. One measurement per week or only after a watering or fertilization sequence is sufficient. This advantageously increases the autonomy of the moisture measurement system.

[0072] Advantageously, since the moisture sensors 16 and the sensors 26 are not in direct contact with the soil 2, the measurements provided by the moisture measurement system 1 are less sensitive to the presence of irregularities in the soil 2 coming into contact with the external enclosure 2, for example cracks, clumps, or organic matter, in particular mycelium, algae, earthworms, or roots.

[0073] Fig. 6 is a diagram illustrating a more detailed embodiment of steps 60, 68 and 70.

[0074] The method includes, in step 60, collecting by the treatment circuit 28 a number N of uncorrected measurements Si to SN, including humidity measurements provided by the humidity sensors 16, temperature values ​​provided by the temperature sensors 24, and measurements of solute concentrations present in the water contained in the pipe 18 and / or properties of the water contained in the pipe 18 provided by the sensors 26. The method includes, in a phase 68_1 of step 68, correcting at least some of the measurements, for example, the humidity measurements and the measurements of solute concentrations present in the water contained in the pipe 18 and / or properties of the water contained in the pipe 18 provided by the sensors 26. The method may include, in phase 68_1 of step 68, correcting the humidity measurements to take into account the temperature values ​​provided by the temperature sensors. 24.Furthermore, the process may include, in phase 68_1 of step 68, correcting the conductivity measurement to take into account the temperature values ​​provided by the temperature sensors 24. Furthermore, the process may include, in phase 68_1 of step 68, correcting the measurements of solute concentrations present in the water contained in the pipe 18 and / or of the properties of the water contained in the pipe 18 provided by the sensors 26 to take into account interferences related to the non-selectivity of the sensors 26. Furthermore, the process may include, in phase 68_1 of step 68, correcting the measurements of solute concentrations present in the water contained in the pipe 18 and / or of the properties of the water contained in the pipe 18 provided by the sensors 26 to take into account the temperature values ​​provided by the temperature sensors 24.The method includes, in a phase 68_2 of step 68, the calibration of at least some of the measurements, for example, moisture measurements and measurements of solute concentrations present in the water contained in pipe 18 and / or properties of the water contained in pipe 18 corrected from measurements Mi to MN carried out on reference samples. The method includes, in phase 68_2 of step 68, the calibration of moisture measurements from REF measurements carried out on reference samples. This advantageously allows for a calibration of the moisture measurements provided by the moisture sensors that takes into account the nature of the soil 2. The method includes, in step 70, the determination of data Di to DM to be provided to the user, in particular concerning the required irrigation time, the concentration of fertilizers to be added to the soil 2, etc.

[0075] Fig. 7 and Fig. 8 are respectively a side view and a lateral cross-sectional view of another embodiment of a soil moisture measurement system 80.

[0076] The humidity measurement system 80 shown in Figures 7 and 8 comprises all the elements of the humidity measurement system 1 shown in [Fig. 1], except that the outer wall 4 of the outer enclosure 3 includes at least one peripheral channel 82, open to the ground 2, and configured to collect water seeping by gravity into the ground 2, and at least one passage 84, visible in [Fig. 8], connecting the channel 52 to the reservoir 14. In one embodiment, the channel 82 extends in a helix around the axis D. Water falling into the channel 82 flows by gravity along the channel 82 until it reaches the passage 84 and then flows into the reservoir 14. In the present embodiment, the outer enclosure 3 can then be made of a material that is not permeable to water.

[0077] Figure 9 is a partial, schematic, side-sectional view of another embodiment of a soil moisture measurement system 90. The moisture measurement system 90 shown in Figure 9 comprises all the elements of the moisture measurement system 1 shown in Figure 1 and, in addition, includes a container 92 filled with distilled water 94. The distilled water container 92 communicates with the pipe 18 via a three-way valve 96. The valve 96 can operate in first and second configurations. In the first configuration, the distilled water container 92 does not communicate with the pipe 18 and the water 15 can flow in the pipe 18 from the tank 14 to the end 20. In the second configuration, the distilled water container 92 communicates with the pipe 18, and the flow of water through the end 20 is blocked.According to one embodiment, the point of measurement of the water contained in the pipe 18 by the sensor 26 is located between the reservoir 14 and the point of communication of the distilled water container 92 with the pipe 18.

[0078] In this embodiment, the suction pump 21 is a bidirectional pump that can be controlled to circulate water in the conduit 18 in either of two opposite directions. To perform measurements on the water 15 contained in the tank 14, the valve 96 is in the first configuration, and the pump 21 can be actuated to circulate water 15 from the tank 14 to the sensors 26, as described previously, and then to the end 20. One embodiment of a method for cleaning the sensors 26 includes controlling the valve 96 to connect the distilled water container 92 to the conduit 18 and activating the suction pump 21 to circulate distilled water 94 from the container 92 to the sensors 26 in order to clean the sensors 26.Cleaning the electrodes of sensors 26 advantageously reduces sensor drift and increases their lifespan. In one embodiment, between two measurements by sensors 26, distilled water 94 is supplied from container 92 to the sensors 26 to maintain contact with the distilled water. In addition to cleaning, this also provides storage of the sensors. The electrodes of the sensors 26 are immersed in distilled water between two measurements, which advantageously increases the lifespan of the sensors 26 and reduces the drift of the sensors 26. This also allows for calibration of the sensors 26 between measurements, with distilled water serving as a reference, thus enabling the offset of each sensor 26 to be determined and the drift to be quantified.

[0079] Figure 10 is a partial, schematic, side-sectional view of another embodiment of a soil moisture measurement system 100. The moisture measurement system 100 shown in Figure 10 comprises all the elements of the moisture measurement system 1 shown in Figure 1, except that the outer enclosure 3 is replaced by cylindrical elements 101 with axis D and an end element 102, three cylindrical elements 101 being shown as an example in Figure 10, and the inner enclosure 8 is replaced by tubes 110 with axis D, three tubes 110 being shown as an example in Figure 10. Each cylindrical element 101 comprises an external lateral face 103 in contact with the ground 2 and a cylindrical through opening 104. Each tube 110 comprises an external lateral face 111 in contact with the ground 2 and an internal lateral face 112 opposite the external lateral face 111.The conduit 18 extends into the cylindrical through openings 104 of the cylindrical elements 101 and extends into the tubes 110. The cylindrical elements 101 and the tubes 110 are alternated along the axis D.

[0080] The reservoir 14 is contained within the end element 102. A humidity sensor 16 and a temperature sensor 24 are located in each tube 110. Each cylindrical element 101 and the end element 102 are made of an electrically insulating material. In one embodiment, each cylindrical element 101 is permeable to water present in the soil 2 and allows the water present in the soil 2 to reach the pipe 18. In another embodiment, each tube 110 is watertight to ensure good insulation of the armatures of the humidity sensor 16 contained within the tube 110 from water. Partitions or joints, not shown, may be provided between the tubes 110 and the cylindrical elements 101 to prevent water present in the cylindrical elements 101 from entering the tubes 110.

[0081] According to one embodiment, the pipe 18 includes through holes 105, for example extending radially with respect to the axis D, in each area of ​​the pipe 18 that come into contact with one of the cylindrical elements 101. The pipe 18 includes an external thread 106 at the end 19. The end element 102 includes a threaded opening 107 cooperating with the external thread 106 of the pipe 18. The assembly of the humidity measurement system 100 includes threading the tubes 110 and the cylindrical elements 101, alternately, onto the pipe 18, and then screwing the end element 102 onto the pipe 18, the tubes 110 and the cylindrical elements 101 then being sandwiched between the end element 102 and the housing 22.

[0082] In operation, when water is present in the soil 2, it passes through the cylindrical elements 101 and flows into the pipe 18 to the reservoir 14 under the action of gravity.

[0083] The moisture measurement system 100 illustrated in [Fig. 10] advantageously offers improved moisture sensitivity due to the greater proximity of the moisture sensors 26 to the soil 2 and a reduced risk of interference. Furthermore, the moisture measurement system 100 illustrated in [Fig. 10] advantageously offers a smaller footprint since the external diameter of the tubes 110 and cylindrical elements 101 can be smaller than the diameter of the external enclosure 3 of the moisture measurement systems 1, 80, 90 described previously. This facilitates the insertion of the moisture measurement system 100 into the soil 2. In addition, the manufacturing cost of the moisture measurement system 100 is reduced.

[0084] As an alternative, the cleaning of the sensors 26 can be carried out by a method other than soaking the electrodes of the sensors 26 in distilled water. For example, the electrodes of the sensors 26 can be cleaned by ultrasound. For example, the electrodes of the sensors 26 can be cleaned by heating.

[0085] Various embodiments and variations have been described. A person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

[0086] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. System (1; 80; 90; 100) for measuring the moisture of a granular medium (2) comprising a collection element (3; 101) intended to be placed in the granular medium (2) in contact with the granular medium (2), and configured to collect water present in the granular medium (2), a reservoir (14) for receiving the collected water, moisture sensors (16) of regions at least partly distinct from the granular medium (2), at least one temperature sensor (24), at least one conductivity sensor (26) configured to measure the conductivity of the water received in the reservoir (14) and transport means (18, 21) configured to transport water from the reservoir (14) to the conductivity sensor (26).

2. System according to claim 1, wherein the transport means (18, 21) comprise a conduit (18) connecting the reservoir (14) to the conductivity sensor (26), the collection element (3; 101) surrounding the conduit (18).

3. System according to claim 1 or 2, further comprising a sensor (26) of the concentration of a first ion contained in the water received in the reservoir (14).

4. System according to claim 3, further comprising a sensor (26) of the concentration of a second ion contained in the water received in the reservoir (14).

5. System according to any one of claims 1 to 4, wherein the collecting element (3; 101) is permeable to water present in the granular medium (2).

6. System according to any one of claims 1 to 5, wherein the collection element (3; 101) comprises a first enclosure (3) elongated along a direction (D), the reservoir (14) and the humidity sensors (16) being contained in the first enclosure (3).

7. System according to claim 6, comprising a second enclosure (8), contained within the first enclosure (3), the humidity sensors (16) being located in the second enclosure (8).

8. System according to claim 6 or 7, wherein the first enclosure (2) comprises an external face (3) comprising a channel (80) for collecting water in the granular medium (2) by gravity and a passage (84) connecting the channel (80) to the reservoir (14).

9. System according to any one of claims 1 to 5, comprising collection elements (3; 101) and tubes (110), the humidity sensors (16) being contained in the tubes (110), the collection elements (3; 101) and the tubes (110) being arranged alternately in a direction (D).

10. System according to any one of claims 1 to 8, wherein the means of transport (21) comprise a suction pump.

11. System according to any one of claims 1 to 9, further comprising a container (92) of distilled water (94), in which the transport means (21) are further configured to transport distilled water from the container (92) to the conductivity sensor (26).

12. System according to claim 11 in its dependence on claim 3, wherein the transport means (21) are further configured to transport distilled water from the container (92) to the sensor (26) of the concentration of the first ion.

13. System according to any one of claims 1 to 12, comprising wireless communication means (38).

14. System according to any one of claims 1 to 13, comprising a battery of electric accumulators (34) and means (36) for recharging the battery.

15. Use of the humidity measurement system (1; 80; 90) according to any one of claims 1 to 14, comprising the following steps: - acquisition of humidity measurements by the humidity sensors (26) and acquisition of at least one temperature measurement by said at least one temperature sensor (24); - determination of the presence of water in the tank (14); - transport of water from the tank (14) to the conductivity sensor (26); - measurement of the conductivity of the water transported to the conductivity sensor (26); and - correction of the humidity measurements from the conductivity measurement and said at least one temperature measurement.

16. Use according to claim 15, wherein the humidity measurement system (1; 80; 90) is according to claim 3, further comprising the transport of water from the reservoir (14) to the first ion concentration sensor (26) and the measurement of the concentration of the first ion in the water transported to the first ion concentration sensor.

17. Use according to claim 15 or 16, wherein the humidity measurement system (1; 80; 90) is according to claim 11, comprising, between two measurements of the conductivity of the water in the reservoir (14), bringing the conductivity sensor (26) into contact with distilled water.

18. Use according to claim 16, further comprising, between two measurements of the concentration of the first ion in the water of the reservoir (14), bringing the sensor (26) of the concentration of the first ion into contact with distilled water.

19. Use according to any one of claims 15 to 18, for measuring the moisture content of a soil (2).

20. Use according to any one of claims 15 to 19, wherein the determination of the presence of water in the tank (14) is carried out from the humidity measurement of the humidity sensor (26) closest to the tank (14).

21. Use according to any one of claims 15 to 20, wherein the humidity measurement system (1; 80; 90) is according to claim 13, and wherein the transport of water from the reservoir (14) to the conductivity sensor (26) is carried out only if the state of charge of the electric storage battery (34) is above a state of charge threshold.

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