Devices and methods for in-situ soil analysis

Abstract

Sensor device (1) for in-situ soil analysis, comprising: a sensor assembly comprising one or more sensors that are individually or cumulatively configured for the simultaneous in-situ measurement of an absorption spectrum in a spectral range NIR-VIS-UV extending from NIR to UV and of at least one of the following soil properties of a soil to be analyzed (11) and for the provision of corresponding respective measurement data: (a) Impedance spectrum (b) temperature (c) acidic or basic character; wherein the distance defined between any two sensors of the sensor assembly with respect to their respective measuring quantity sensors does not exceed a value of 10 cm, wherein the sensor assembly for in-situ acquisition of an absorption spectrum of the soil to be analyzed (11) includes an absorption spectrometer assembly (5) which has: at least two MEMS absorption spectrometers (26a, 26b) whose spectral coverage differs at least for partial regions of the electromagnetic spectrum, so that cumulatively an absorption spectrum of the soil (11) to be analyzed can be acquired by the entirety of the MEMS absorption spectrometers (26a, 26b), which has components in the NIR, VIS and UV regions, wherein the absorption spectrometer assembly (5) further comprises a movable shutter device (28) configured to temporarily retract an aperture into a spatial region defined between the absorption spectrometers and the measurement surface, wherein a calibration reference (29) for calibrating at least one of the absorption spectrometers is arranged on the side of the aperture facing the absorption spectrometers.

Description

[0001] The present invention relates to the field of soil analysis, in particular – but not limited thereto – the technical analysis of soils used in agriculture or horticulture. In particular, the invention relates to a sensor device for in-situ soil analysis, a method for in-situ soil analysis, and a device configured for carrying out the soil analysis method, wherein this device, together with and in conjunction with one or more of the aforementioned sensor devices, constitutes a system for in-situ soil analysis.

[0002] In the field of soil analysis, laboratory-based analytical methods are currently the predominant approach. These methods involve taking one or more soil samples, transporting them to a suitable laboratory, and processing and analyzing them there. A corresponding analysis report is then generated and sent to the recipient or client. From sampling to receiving the analysis results, this process typically takes at least several days, but usually weeks, especially during peak demand periods such as spring (in Central Europe). In a typical standard soil analysis laboratory, water content, micro- and macronutrient content, electrical conductivity, soil type, pH value, as well as available and total amounts or concentrations of nitrogen, phosphorus, and carbon can be determined using standardized laboratory-based analytical methods.A typical soil sample for a farmer includes parameters such as soil type, nitrogen, phosphorus, potassium, magnesium, boron, copper, zinc, manganese, and iron content, as well as the soil's pH value and possibly an indication of its lime requirement. While the methods used in such laboratory analyses are very accurate, they are not "in-situ"—that is, they cannot be used without prior sampling and on-site in the soil being analyzed, such as on agricultural or horticultural land—because either the necessary technical equipment is not portable, or because standardized environmental conditions are required for the analysis, which can only be achieved in a laboratory.

[0003] As an alternative to laboratory soil analysis, several methods for in-situ or semi-in-situ soil analysis are already available. However, the analytical scope is limited to determining the water content, pH value, electrical conductivity, and soil type from the soil sample. Other parameters, particularly those highly relevant to farmers and horticulturalists, such as potassium, magnesium, copper, manganese, zinc, bromine, iron, available phosphorus, humus, total nitrogen, and total carbon content, cannot currently be analyzed in situ. Furthermore, none of the currently known in-situ analysis methods inherently provide legally compliant documentation of the measurement or analysis results, which may be required in many countries for the verification of legal regulations, such as statutory fertilizer ordinances.

[0004] From US Patent 5,621,669 A, a sensor probe for moisture and other properties of bulk materials is known, which includes selection, input, excitation, and isolation functions to obtain signals from a group of sensors, convert the signals into digital information, correlate parts of the information, and transmit the information to one or more external actuators, remote receivers, and controllers.

[0005] From US Patent 2015 / 0216442A1, a spatial impedance mapping system is known which includes a multilayer coaxial probe for spatial impedance mapping. The multilayer coaxial probe comprises an elongated core with a distal end and a proximal end; a first coating layer wound around the core; and a set of alternating conductive and insulating coating layers on the first coating layer, wherein an N-th coating layer is shorter than an N-1-th coating layer below it. The elongated core includes a needle or other suitable elongated element.

[0006] From CN 1 06 950 183 A, a portable soil nutrient detection device is known, based on a spectral technique, comprising a measuring probe, a panel computer (the microprocessor of which is arranged in a housing), a spectral collection unit, a driver element, and a power supply. The measuring probe comprises a probe body arranged on a light source within the probe body.

[0007] From EP 1 203 955 A1, a model for determining soil type, soil water content, and soil properties, as well as a soil measurement data storage unit for storing measurement data required for the model's execution and correlated with specific measurement conditions, is known. The water content is measured by a water content measurement section based on measurement data supplied by a soil sensor. The soil type is determined by a feature extraction section and a soil type determination section, and the determined soil type is sent to a determination section. The determination section determines appropriate conditions and a model according to the soil type and water content of the received measurement point and places them in a predetermined processing section.The soil sensor feeds measurement data that meets the measurement conditions into a measurement information processing unit, and the processing unit determines the soil properties according to the determined model.

[0008] The present invention aims to provide improved devices and methods for in-situ soil analysis. In particular, it is an object of the invention to provide devices and methods for in-situ soil analysis that, compared to previously known solutions, make it possible to analyze additional soil properties and / or achieve improved quality of the analysis results.

[0009] The solution to this problem is achieved according to the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the dependent claims.

[0010] A first aspect of the invention relates to a sensor device for in-situ soil analysis. The sensor device comprises a sensor assembly with one or more sensors, which are configured individually or cumulatively for the simultaneous in-situ measurement of an absorption spectrum in a spectral range extending from NIR (near-infrared) to UV (ultraviolet), NIR-VIS-UV, and of at least one, preferably at least two or all, of the following soil properties of a soil to be analyzed, and for providing corresponding respective measurement data: (a) impedance spectrum, (b) temperature, and (c) acidity or alkalinity, in particular pH value. The defined distance between any two sensors of the sensor assembly, with respect to their respective measuring elements, does not exceed 10 cm, preferably 5 cm, and particularly preferably 3 cm.

[0011] An "in-situ soil analysis" within the meaning of the invention is understood to be an analysis of soil, in particular soil on agriculturally or horticulturally used land, in which desired soil properties are measured on-site on the soil itself, without the need for taking a soil sample. In particular, an in-situ soil analysis can be carried out by arranging a suitable sensor device on or above the soil to be analyzed, or by inserting it, at least partially, so that the sensor device can measure the relevant soil property, with the soil remaining, at least substantially, unchanged in place. An evaluation of the measurement data generated by one or more in-situ measurements for the purpose of further soil analysis beyond mere data acquisition can also be carried out "in-situ," i.e., directly on the soil surface.The measurements can be taken at the site of the measurement, although this is not mandatory. In contrast, soil analyses that are based on first taking a sample from the soil to be analyzed, which is then subjected to measurement and, if necessary, further analysis at the same or a different location, are not in-situ soil analyses within the meaning of the invention.

[0012] A "simultaneous" in-situ measurement of multiple soil properties is understood to mean an "in-situ" measurement process in which the measurement periods for at least two of the soil properties to be measured overlap at least partially. In particular, measurements of multiple soil properties that actually take place exactly simultaneously are considered simultaneous measurements within the meaning of the invention, as are measurements in which, for example, a first measurement period for a first soil property does not coincide exactly with a second measurement period for a second soil property, but there is at least a time interval within which both properties are measured simultaneously. A measurement period for a soil property is defined as a period in which a corresponding sensor is active in order to perform a measurement of the soil property itself or of a quantity used for its indirect determination.

[0013] An "impedance spectrum" within the meaning of the invention is understood to be a spectrum that represents the alternating current resistance (impedance Z) of a material, here a soil section to be measured, as a function of the frequency (ω) of an alternating voltage applied to the soil section, for example by means of electrodes, which can be achieved in particular by means of a mathematical function Z(ω). The alternating current resistance of a two-terminal network element (here the soil section) is defined as the ratio of electrical voltage to current.

[0014] An absorption spectrum, as defined in the invention, is an electromagnetic spectrum containing "dark" spectral lines, i.e., dips in the spectral profile, which arise when broadband electromagnetic radiation irradiates or passes through matter and radiation quanta (photons) of specific wavelengths or wavelength ranges are absorbed by the matter. One or more different absorption mechanisms, usually wavelength-dependent, can occur. In particular, electronic transitions between different energy levels of atoms, molecules, crystals, or other solids (for example, in the context of luminescence), as well as excitations of other degrees of freedom, especially rotational or vibrational degrees of freedom of molecules and solids, are possible.By comparing obtained absorption spectra, especially reflection spectra, with corresponding reference spectra, qualitative and / or quantitative conclusions can be drawn about the material composition of the measured matter.

[0015] In the context of the invention, a "measuring quantity transducer" or simply "transducer" is understood to be the part of a measuring device, i.e., a sensor, that responds directly to a measured quantity. The transducer is thus the first element in a measuring chain. In particular, the transducer can be implemented—but is not limited to—in the form of one or more electrodes, an optical receiver, or a temperature sensor. The distance between two transducers is understood to be the shortest distance between them.

[0016] The sensor device according to the first aspect of the invention is characterized by the fact that it can detect at least two different soil properties sensorially and, at least essentially, non-destructively. These properties are furthermore selected such that a clear correlation exists between them, enabling data fusion of the measurement data to achieve increased measurement accuracy and thus improved soil analysis quality compared to individual measurements. In addition, the sensor's measuring elements are concentrated in a very small area (e.g., on an area ≤ 100 cm²). 2 , preferably ≤ 25 cm 2 , especially preferred ≤ 9 cm 2), so that the measured soil section can be assumed to be homogeneous to a good approximation, which is used to further improve the measurement accuracy, especially with regard to the fact that the correlation between the individual measurement results is strongly distance-dependent and regularly only allows a significant improvement in soil analysis quality by means of data fusion at small distances.

[0017] Furthermore, the measurements are performed simultaneously, thus minimizing time-dependent measurement errors. Such an error could otherwise occur, for example, if an impedance measurement led to local heating of the soil, which would then result in distorted temperature readings in a subsequent temperature measurement taken at a later time. Moreover, the combination of the aforementioned measurement methods makes it possible to obtain soil properties that go beyond previous in-situ measurement methods by combining the measurement data from the individual measurements. Simultaneous measurement also reduces the overall time required for the measurement process compared to purely sequential individual measurements.

[0018] Since the taking of soil samples is no longer necessary, nor is their transport to an ex-situ laboratory, the soil analysis results can be provided in a very short time, especially on site immediately during the measurement, so that no significant delay is required before the analysis results are available.

[0019] The absorption spectrometer assembly further comprises a movable shutter device. This device is configured to temporarily retract an aperture into a defined area between the absorption spectrometers and the measurement surface. On the side of the aperture facing the absorption spectrometers, a calibration reference, such as Spectralon, is arranged for calibrating at least one, preferably all, of the absorption spectrometers. This allows the sensor device to automatically self-calibrate, for example, after a certain predetermined number of measurements (e.g., using dark current and reference calibration), particularly during in-situ soil analysis.

[0020] Preferred embodiments of the sensor device are described below, which, unless expressly excluded or technically impossible, can be combined with each other and with the other described aspects of the invention as desired.

[0021] In some embodiments, the sensor assembly for in-situ acquisition of an impedance spectrum of the soil to be analyzed includes an impedance sensor. This sensor comprises (i) a first support element; (ii) two conductor tracks arranged on the first support element but electrically insulated from it and from each other, at least one of which contains an electrically conductive, corrosion-resistant polymer or composite material; (iii) and a control device.The control device is configured to apply an alternating voltage between the two conductor tracks, varying the frequency over a predetermined frequency range. During operation, when the sensor device is inserted into the soil to be analyzed in such a way that the conductor tracks are in electrical contact with it, the device acquires an impedance spectrum of the soil in response to the alternating voltage applied via the conductor tracks and provides this information as corresponding measurement data. In this way, the sensor device is able to record an impedance spectrum of the soil being analyzed, which can be used to determine various soil types, soil textures, conductivities, water content, ion concentrations, and ion types.

[0022] The special design of the conductor tracks on the carrier element, as well as their special choice of material, enable both a particularly good electrical contact with the surrounding ground, as well as high resistance, especially abrasion and corrosion resistance, to the ground and thus a long service life of the sensor device.

[0023] The conductor tracks can be wound onto the first support element, preferably such that the two conductor tracks run parallel to each other, which represents a particularly precise and space-optimized solution. "Electrical conductivity" is understood to be a physical quantity that indicates how strongly a material conducts electric current. Therefore, "electrically conductive" within the meaning of the invention refers to an electrical conductivity that is at least 10⁶ S / m (at 25 °C), thus corresponding at least to the conductivity of metals.

[0024] In some further embodiments, the first support element is electrically conductive, particularly metallic, at least in an area covered by the conductor tracks, and the control device is further configured to connect the electrical potential of at least one area to a ground potential during the acquisition of the impedance spectrum of the soil to be analyzed. In this way, signal distortion of the recorded impedance spectrum by external electromagnetic coupling can be reduced or even avoided. The ground potential can, in particular, be the ground potential (zero potential) of a power supply for the sensor device, for example, a battery used for this purpose.

[0025] In some further embodiments, the predetermined frequency range includes the range from 100 Hz to 1 MHz, which allows a spectrum to be determined that, due to its width and position in the electromagnetic spectrum, is particularly good at providing conclusions about a variety of different soil properties.

[0026] In some further embodiments, the first support element is designed as a mandrel that is at least partially hollow, for insertion, at least partially, into the soil to be analyzed. Furthermore, an insulating layer is applied to the surface of the mandrel, on which the two conductor tracks are arranged, in particular wound. The control device is located inside a hollow section of the first support element. The mandrel-like design of the first support element serves to be inserted (pierced) at least partially into the soil to be analyzed, thereby bringing the conductor tracks, which serve as sensors for the impedance sensor, into contact with the soil. The insulation electrically decouples the conductor tracks from each other and from the mandrel, which—as described above—can be connected to ground potential.Furthermore, the control device inside the hollow section of the first support element is protected from unwanted influences, in particular from the ground or other environment, especially from dust, moisture and corrosive substances.

[0027] In some further embodiments, the sensor assembly for detecting the temperature of the soil being analyzed includes a temperature sensor, which, together with the impedance sensor, is designed as an integrated impedance / temperature sensor assembly. This assembly is configured to simultaneously and in-situ acquire both an impedance spectrum and a temperature of the soil being analyzed and provide each as corresponding measurement data. In this way, not only are at least two different measured quantities determined, which, as explained above, enable a broader range of determinable soil properties and higher analysis quality, but a particularly high integration density is also achieved, allowing for a particularly compact sensor device.

[0028] The temperature sensor, or parts thereof, can be arranged inside a high section of the first support element, just like the control device, in order to be protected there from unwanted external influences.

[0029] The first support element and / or at least one of the conductor tracks can, in particular, simultaneously serve as a temperature measuring probe (i.e., a sensor) and be thermally connected to the temperature sensor for this purpose. Preferably, the first support element or the at least one conductor track is therefore made of a highly thermally conductive material, in particular a metal such as aluminum or a highly thermally conductive polymer or composite material.

[0030] In some embodiments, the temperature sensor is integrated into the control device, for example on a common PCB or a common integrated circuit, which in turn is advantageous in terms of a high and therefore space-saving integration of the sensor device, especially also with regard to achieving an arrangement of the measuring quantity sensors of the various sensors of the sensor device that is optimized as much as possible in terms of their density.

[0031] In some embodiments, the temperature sensor is arranged inside an electrically conductive section of the first support element, resulting in at least partial shielding of the temperature sensor from any electromagnetic interactions generated by the conductor tracks when the alternating voltage is applied to it, thereby increasing the measurement accuracy and counteracting unwanted interference effects.

[0032] In some embodiments, the sensor assembly for in-situ acquisition of an absorption spectrum of the soil to be analyzed includes an absorption spectrometer assembly. This assembly comprises at least two MEMS absorption spectrometers (i.e., absorption spectrometers that are at least partially manufactured using MEMS technology, and in particular contain MEMS components), which are based on a Fabry-Perot interferometer and whose spectral coverage differs at least for sub-regions of the electromagnetic spectrum. Cumulatively, the entirety of the MEMS absorption spectrometers enables the acquisition of an absorption spectrum of the soil to be analyzed, which includes components in the NIR, VIS, and UV ranges.The spectral coverage can extend continuously from the NIR range to the UV range and, in particular, include the range from 350nm to 1700nm in order to enable a particularly highly differentiated measurement in a spectral range that is regularly particularly relevant for soil analysis.

[0033] In some embodiments, the absorption spectrometer assembly further comprises a movable, in particular rotatable and / or translationally displaceable, support on which the absorption spectrometers are arranged such that, when the support moves relative to a virtual measurement surface (where the soil to be analyzed lies during the measurement operation of the sensor device), they can spectrometrically measure a region of the soil to be scanned by the absorption spectrometers in order to acquire an absorption spectrum integrated over the scanned region. In this way, statistically more usable and accurate results can be obtained, whereby the largest possible soil area can be scanned, ideally at the shortest possible distance.In the case of a rotatable support, the measured absorption spectrum can be integrated or averaged, in particular over the angle of rotation of the support, and in the case of translational movement, in particular over the path length of this translational movement. In this way, non-specific characteristics of the ground, such as small stones, twigs, etc., have, on average, only a reduced, and in particular a negligible, influence on the measurement results obtained, which can also be largely eliminated, in particular by means of targeted filtering, for example by means of threshold values.

[0034] In some embodiments, at least one source of electromagnetic radiation is arranged on the movable carrier. This source is configured to electromagnetically irradiate the area of ​​the ground being scanned by the absorption spectrometers during measurement operation while the carrier is moving relative to the measurement surface, in order to generate the absorption spectrum to be measured. This makes it possible, on the one hand, to scan a larger ground area due to the movement, while on the other hand, to keep the relative position of the radiation source to the absorption spectrometers unchanged. This can result in increased measurement accuracy and help reduce or eliminate the need for adjustments.

[0035] In some embodiments, the absorption spectrometer assembly further comprises optics that are, at least substantially, transparent in a wavelength range corresponding to the absorption spectrum to be recorded. These optics are arranged in the space between the absorption spectrometers and the measurement surface to spatially separate them. The optics are provided on their side facing the measurement surface with a hydrophilic nanocoating, which may also exhibit increased scratch resistance compared to the optical material itself. To achieve the highest possible scratch resistance, the optics may also be made of sapphire glass. This spatial separation serves, in particular, to protect the absorption spectrometers and, if applicable, the shutter device from undesirable external influences (especially dust, moisture, and mechanical stress), such as those from the soil being analyzed.

[0036] In some embodiments, the sensor assembly for in-situ detection of the acidity or alkalinity, in particular the pH value, of the soil to be analyzed includes a potential measurement assembly. This assembly comprises: (i) a second support element; (ii) an electrolyte / metal reference electrode arranged in or on the second support element; (iii) a metal oxide electrode arranged on a surface of the second support element provided for contact with the soil to be analyzed during measurement operation; (iv) an ion diaphragm arranged on the second support element between the metal oxide electrode and the electrolyte / metal reference electrode and in contact with the electrolyte / metal reference electrode; (v) a corrosion-resistant calibration electrode arranged on the surface of the second support element provided for contact with the soil to be analyzed and electrically insulated from the metal oxide electrode; and (vi) a measuring device.The measuring device is configured: (a) to determine the current state of the metal oxide electrode by measuring an electrical resistance and / or an electrical capacitance occurring between the calibration electrode and the metal oxide electrode when these two electrodes are each in contact with the soil to be analyzed; and (b) to determine the acidic or basic character, in particular the pH value, of the soil to be analyzed by measuring an electrical potential difference occurring between the reference electrode and the metal oxide electrode, taking into account a measurement calibration previously established on the basis of the determined current state of the metal oxide electrode when these two electrodes are each in contact with the soil to be analyzed.

[0037] The measurement of the soil's acidity or alkalinity by the potential measurement unit can be carried out in operation by measuring the electrical potential difference occurring between the reference electrode and the metal oxide electrode, as described in sub-feature (b) above. This potential difference depends on the acidity or alkalinity of the soil, which is in contact with the two electrodes during the measurement process, and can therefore be used to measure it. The measured potential corresponds to, or at least is equivalent to, the redox potential between the two electrodes, with the corresponding chemical redox equation being as follows: RedOx xMe+yH2O↔MexOy+y2H++y2e−

[0038] The abbreviation "Me" stands for a metal. The potential difference is thus based on the special electrochemical properties of metal oxide / metal-based sensors, particularly pH sensors, where the metal oxide / metal system can be, in particular, Sb₂O₃ / Sb, IrO₂ / IR, TiO₂ / Ti, or RuO₂ / Ru. These materials exhibit a direct oxidation or reduction dependence while simultaneously possessing good electrical conductivity relative to the surrounding hydrogen ion concentration (pH value) in the soil. Their redox potential can therefore be correlated with the reference electrode, and the acidic or basic character or pH value of the soil can be determined from this. Furthermore, the material of the metal oxide electrode is preferably selected to have good abrasion and impact resistance (to the soil), which is the case with the aforementioned material systems.

[0039] The redox potential difference is determined by measuring the ion currents flowing between the two electrodes through the ion diaphragm. Preferably, an impedance converter or amplifier is also provided to convert or amplify the potentially very weak currents before measurement, thus improving measurability and accuracy. The size of the ion diaphragm is also preferably chosen to be as large as possible relative to the size of the (second) support element in order to provide the largest possible cross-sectional area for the ion current flow through the ion diaphragm.

[0040] However, metal oxides are generally only limitedly resistant to corrosion from acids and bases, so metal oxide electrodes used for soil analysis often degrade over time. This can lead, in particular, to a reduction in the electrode layer thickness, resulting in a change in electrical resistance, and thus in the current and consequently in the measurement results. Therefore, the measuring device, according to sub-feature (a), is further configured to determine the current state, in particular the electrode layer thickness, of the metal oxide electrode by measuring the electrical resistance (or conductivity) and / or capacitance occurring between the calibration electrode and the metal oxide electrode while both are in contact with the soil being analyzed, which then electrically connects both electrodes. The measurement can be performed cyclically.The conductivity and / or capacitance of the soil can be determined, in particular, if not already known a priori, using the aforementioned impedance sensor of the sensor device. This allows the conductivity, electrical resistance, or capacitance of the metal oxide layer to be determined by the measuring device using the aforementioned measurement method. The conductivity or capacitance of the metal oxide electrode correlates directly with its metal oxide layer thickness. Therefore, the measurement using the measuring device can be recalibrated as needed, particularly preventively and cyclically, based on the measurement of the metal oxide electrode's condition, to ensure measurement accuracy even over long periods despite the degradation of the metal oxide.

[0041] In some embodiments, the calibration electrode is made of a material containing an electrically conductive and corrosion-resistant polymer and / or composite material. These materials offer particular advantages such as low weight, high corrosion resistance, and long durability and stability as a calibration reference.

[0042] In some embodiments, the second support element is designed as a mandrel for at least partial insertion into the soil to be analyzed. An insulating layer is applied to the surface of the mandrel, on which the metal oxide electrode, the ion diaphragm, and / or the calibration electrode are arranged. This allows for a particularly compact implementation. Furthermore, the electrolyte / metal reference electrode can advantageously be arranged within the (second) support element, i.e., the mandrel, and thus protected against unwanted external influences.

[0043] In some embodiments, the sensor device further includes a communication device for transmitting acquired measurement data to an external counterpart for evaluation. This counterpart can be, in particular, a separate evaluation device, a remote computing platform (e.g., in a cloud environment), a backend server, or a distributed computer network. This allows the further processing of the measurement data to determine the final soil analysis results to be outsourced from the sensor device. This can be particularly advantageous when complex, resource-intensive calculations are required that can be performed faster or more efficiently on centralized or specialized computing systems than locally on the sensor device itself.

[0044] However, in other embodiments it is equally possible to integrate the equipment required for evaluating the measurement results into the sensor device itself. Even in this case, however, it may be advantageous to integrate the aforementioned communication device into the sensor device, at least to enable remote updates of software used for evaluating and / or controlling the sensor device.

[0045] In some embodiments, the communication device is configured to transmit measurement data wirelessly using communication based on LoRa radio technology and / or NarrowBand Internet of Things (NB-IoT) radio technology. These technologies are particularly advantageous when the sensor device is to be used in locations where other wireless data coverage, such as conventional mobile networks, is lacking or insufficient. The aforementioned radio technologies allow wireless data transmission over distances of up to 30 km, which is approximately twice the maximum range (device - base station) of conventional mobile communication technologies. Furthermore, energy consumption is typically very low, making these technologies particularly suitable for use in mobile, battery-powered devices.Furthermore, the use of LoRa technology is license-free in many countries, which has a correspondingly positive effect on operating costs.

[0046] The communication device can also be configured to receive data, in particular external soil analysis result data, so that corresponding information can be made available to the user in situ at the sensor device itself via a suitable human-machine interface, for example a display device or an optical or acoustic output device.

[0047] In some embodiments, the sensor device further comprises a secure storage device for the secure storage, protected against unauthorized access, of a unique device identification of the sensor device and / or at least a cryptographic key for encrypting measurement and / or metadata transmitted via the communication device. The metadata can, in particular—but is not limited to—represent the location, time, and / or measurement mode of an in-situ measurement performed with the sensor device, as well as the device identification or a user identification. In this way, it is possible, in particular, to implement communication via the communication device that is protected against "man-in-the-middle" attacks, as well as a device identity that is protected against unauthorized modification.

[0048] In some embodiments, the communication device is further configured to write the transmitted measurement and / or metadata to a blockchain acting as an external counterpart, or to induce another external counterpart to write the measurement and / or metadata transmitted to it to a blockchain. These embodiments are particularly advantageous with regard to legally compliant documentation of the measurement results. Moreover, these embodiments also allow for the protection of communication, especially with regard to protection against subsequent falsification of the obtained measurement results or soil analysis results.

[0049] In some embodiments, the sensor device is configured to authenticate a user of the sensor device and to only allow the transmission of measurement and / or metadata to an external party if the authentication is successful. This measure also protects the communication and documentation of the measurement results against attacks, particularly with regard to the falsification of the measurement data. One or more of the aforementioned protective measures thus fulfill the requirements for achieving legally compliant documentation of the measurement results, which may be legally mandated.

[0050] In some embodiments, the sensor device further includes a position determination device for determining its current position and providing corresponding position-identifying metadata. This allows, in particular, the provision of measurement location along with the measurement data via corresponding metadata. Furthermore, spatial monitoring of the sensor device can be implemented, which also provides additional protection against misuse, especially misuse by unauthorized persons.

[0051] In some embodiments, the sensor device is designed as a portable unit. This means, in particular, that the dimensions and weight of the device allow it to be easily carried by a human user, for example, to a measuring point in a field. Ideally, therefore, the dimensions of the sensor device in every direction are at most a few decimeters (e.g., < 50 cm), and the weight is preferably less than 25 kg, ideally less than 10 kg. Thus, the sensor device can be used with particular flexibility and without the need for vehicles or other maneuvering devices.

[0052] A second aspect of the invention relates to a method for soil analysis, comprising: (i) Receiving measurement data relating to an absorption spectrum in a spectral range NIR-VIS-UV extending from NIR to UV and of at least one further, preferably at least two or all, of the following soil properties of a soil to be analyzed: (a) impedance spectrum, (b) temperature and (c) acidity or basicity, in particular pH value; and (ii) determining at least one of the soil properties or at least one derived soil property based on a combination of the received measurement data by means of data fusion to obtain a respective measurement result for the at least one soil property to be determined.This method makes it possible to link the measurement results regarding the aforementioned soil properties through data fusion. It should be noted that the soil properties in question were selected such that, at least in some combinations, a correlation exists between them, which can be used within the data fusion process to obtain more precise or additional soil analysis results. The data fusion can be implemented, in particular, using fuzzy logic and / or one or more artificial neural networks.

[0053] In some embodiments, the measurement data is acquired by a sensor device according to the first aspect of the invention, in particular according to one or more of the described embodiments thereof. The method then follows the actual in-situ measurement for acquiring the measurement data, wherein the sensor device can, in particular as described above, transmit the measurement data and optionally additional metadata thereto by means of its communication device via a suitable communication link to a central or spatially distributed device executing the method.

[0054] In some embodiments, the method is carried out in at least one central node of a network, in particular a cloud environment or a distributed computer network, which is configured to receive the respective measurement data and to be in communication with a plurality of sensor devices, in particular according to the first aspect of the invention, for acquiring the respective measurement data. This allows, in particular, efficient and variable resource utilization for carrying out the method. Furthermore, changes, especially updates, to the software used to carry out the method can thus be implemented centrally without having to be distributed to the respective sensor devices, so that the overall system can be easily developed and updated.

[0055] A third aspect of the invention relates to a computer program configured to execute the method according to the second aspect of the invention, particularly according to one or more of the described embodiments thereof, when running on a processor platform. The processor platform can contain a single or a plurality of processors and can be implemented locally, for example in a single computer, or across a decentralized, distributed computer network. In particular, the processor platform and the corresponding computer program can also be located within the sensor device itself to enable it to execute the method.

[0056] The computer program can be stored, in particular, on a non-volatile data carrier. Preferably, this is a data carrier in the form of an optical data carrier or a flash memory module. This can be advantageous if the computer program itself is to be handled independently of a processor platform on which the one or more programs are to be executed. In another implementation, the computer program can exist as a file on a data processing unit, in particular on a server, and be downloadable via a data connection, for example, the Internet or a dedicated data connection, such as a proprietary or local network. Furthermore, the computer program can comprise a plurality of interacting individual program modules.

[0057] A fourth aspect of the invention relates to a device for soil analysis, wherein the device is configured to carry out the method according to the second aspect of the invention, in particular according to one or more of the described embodiments thereof. The device may, in particular, include the aforementioned processor platform and thus, in particular, comprise a single data processing unit, such as a computer, or a decentralized, distributed computer network.

[0058] In particular, in some embodiments, the device for acquiring the measurement data can itself comprise a sensor device according to the first aspect of the invention, especially according to one or more of the described embodiments thereof. This is particularly advantageous when the analysis of the measurement data for obtaining further soil analysis results is to be carried out in situ, i.e., on-site at the sensor device itself, which in particular also allows offline operation and the determination of such results independent of the quality of a communication connection to an external processor platform.

[0059] The features and advantages explained in relation to the second aspect of the invention also apply accordingly to the third and fourth aspects of the invention.

[0060] Further advantages, features and applications of the present invention will become apparent from the following detailed description in conjunction with the figures.

[0061] This shows Fig. 1 schematically a sensor device according to an embodiment of the invention; Fig. 2 schematically a modularly constructed sensor device according to a further embodiment of the invention, in which, in addition to a measuring module, an operating / radio module is also provided; Fig. 3A schematically an integrated impedance / temperature sensor assembly for a sensor device according to an embodiment of the invention and Fig. 3B a simplified equivalent circuit diagram for this; Fig. 4 schematically a potential measurement assembly, in particular a pH sensor assembly, for a sensor device according to an embodiment of the invention; Fig. 5 schematically an absorption spectrometer assembly for a sensor device according to an embodiment of the invention; Fig. 6 a schematic overview of a complete system for soil analysis, according to an embodiment of the invention; and Fig. 7 an exemplary overview of various relationships between individual sensors of the sensor device according to Fig. 1 or 2 detectable measurement variables, by means of which various soil properties can be determined within the framework of a data fusion according to the inventive method.

[0062] The same reference numerals are used throughout the figures for the same or corresponding elements of the invention.

[0063] The in Fig. The sensor device 1 shown in Figure 1, according to an embodiment of the invention, is designed as a module comprising several subassemblies, in particular sensor subassemblies, in a common housing 2. A first of these subassemblies is a combined impedance / temperature sensor subassembly 3, which is at least partially formed in a rod- or pin-like first support element and is configured for insertion into soil to be analyzed. A further subassembly is a potential measurement subassembly 4, in particular a pH sensor subassembly, which is formed by means of a second support element, which, like the first support element, has a rod- or pin-like shape and is likewise designed for insertion into the soil to be analyzed.Between these two subassemblies 3 and 4, and in their immediate vicinity, an absorption spectrometer subassembly 5 is arranged as a further subassembly. This subassembly has a measuring window positioned so that when the first and second support elements are inserted into the soil to be analyzed simultaneously, it lies on or above the soil. Thus, the three sensor subassemblies are located in a small space, preferably on a total area of ​​less than 100 cm². 2The sensor device 1 is designed to be concentrated so that the influence of heterogeneities in the soil being analyzed on the measurement results can be kept low and, in particular, reduced to a minimum. The sensor device 1 is designed as a mobile, in particular portable, unit, preferably weighing less than 25 kg and having a maximum extension of less than 1 m, preferably a maximum of 0.5 m. Furthermore, the sensor device 1 includes a power supply device (not shown), which may be in the form of a rechargeable electrochemical energy storage device, such as a lithium-ion battery.

[0064] The individual assemblies, in particular sensor assemblies 2, 3 and 4 of the sensor device 1, can also each be designed as an individually removable or replaceable module, which makes it possible in particular to create different sensor configurations in a simple and dynamic way, as well as to maintain or replace the individual sensor assemblies individually depending on their aging or functional state.

[0065] The sensor device 1 thus allows up to four different sensor types to be used per measurement and their various measurement principles to be exploited in order to obtain corresponding measurement data. Based on this data, correlation and data fusion enable the determination of soil properties in situ with sufficiently high accuracy for many applications, going beyond the direct measurement of soil properties. In particular, the impedance of the soil being measured, the soil temperature, its absorption spectrum across the entire UV-VIS-IR spectral range, and its pH value can be measured simultaneously and in close proximity.It is precisely this close proximity of the measuring sensors of the various sensor assemblies 2, 3, and 4 that makes it possible to successfully correlate the measurement data for determining soil properties with the accuracy required for typical applications, particularly in agricultural engineering. Furthermore, the dense arrangement of the measuring sensors also allows for the creation of ultra-high-resolution soil maps, i.e., soil maps with a grid spacing of less than 100 cm. 2 Grid cell area. The simultaneous acquisition of the various quantities to be measured also enables the representation of dynamic and true dependencies between the individual measured values. In particular, measurement artifacts can thus be detected and removed in-situ using appropriate evaluation software, for example based on artificial intelligence, in order to further improve the quality of the original measurement results.

[0066] Fig. Figure 2 shows a modularly constructed sensor device 1 according to a further embodiment of the invention, which, in addition to a sensor module 6a, also has an operating / radio module 6b that can be coupled to it by means of a detachable connection. The two modules 6a and 6b are in Fig. 2 is shown on the one hand as separate modules (lower left), and on the other hand in the connected state (top right). The housings of the two modules 6a and 6b are preferably shaped such that, when the two modules are connected, a carrying or handling handle 10 is formed at the connection point that is easy for the human hand to grasp, in particular to grip, and is particularly suitable for removing a sensor device 1 that has been inserted into the ground for analysis. The handle can, in particular, be shaped as shown in Fig. Figure 2 shows that the sensor device 1 is designed as a narrowing of the cross-section at the connection point between the two modules 6a and 6b. The operating / radio module 6b has a position determination device 7, with the aid of which, for example in conjunction with a satellite-based position detection system such as GPS, GALILEO or GLONASS, or with the aid of mobile network-based position determination, the position of the sensor device 1 can be determined, particularly during a measurement process, and corresponding position data can be generated as metadata belonging to the measurement.

[0067] Furthermore, the operating / radio module 6b has a communication device 8, which may in particular be configured to carry out data communication with an external counterpart using mobile communication technology (e.g. 3G, LTE, 5G), or another radio technology, such as LoRa and / or NBloT, in particular to send measurement data obtained by means of the sensor device 1 to an external data processing center for further evaluation, and to receive soil analysis results resulting from such evaluation, if applicable, in order to output them on the sensor device 1 itself at a human-machine interface 9.Such a human-machine interface 9 can be provided, in particular, in the form of a display device on the sensor device 1, preferably as an operating display with a view to a space-saving solution, which enables both user input and output of information, as is the case, for example, with a touch-sensitive screen.

[0068] Fig. Figure 3A shows an integrated impedance / temperature sensor assembly 3 inserted into a soil 11 to be analyzed for a sensor device according to an embodiment of the invention, which is particularly in a sensor device 1 according to Fig. 1 or Fig. 2 may be provided. Fig. Figure 3B shows a simplified equivalent circuit diagram for the impedance measurement branch of the impedance / temperature sensor assembly 3.

[0069] The sensor assembly 3 from Fig. 3A comprises a first support element 12 in the form of a mandrel, which may be made of metal, preferably a corrosion-resistant metal. The mandrel may, in particular, have a substantially cylindrical shape and be pointed at its end face intended for insertion into the ground to facilitate insertion. A passivation layer 13, which may, in particular, contain one or more polymer materials and act as an electrical insulator, is applied to the first support element 12 on a surface area that typically comes into contact with the surrounding ground when inserted. Two conductive tracks 14 are wound around the first support element 12 on the passivation layer 13, parallel to each other and without touching each other. The two conductive tracks 14 are thus electrically insulated from the support element 12 by means of the passivation layer 13.On its end face opposite the point that can be inserted into the ground, the impedance / temperature sensor assembly 3 has a printed circuit board (PCB) 15 arranged inside the carrier element 12 and protected by a metal cap 16 (metal housing). This PCB incorporates a control device 15a, a signal preamplifier 15b, and a temperature sensor 15c, respectively, in the form of an integrated circuit or a semiconductor sensor component. The metal cap 16 serves not only as mechanical protection but also as electromagnetic shielding for the temperature sensor 15c, the control device 15a, and the signal preamplifier 15b located within it. In addition to controlling the sensor assembly 3, the control device 15a also measures the impedance and provides corresponding measurement data. It is electrically connected to the two conductor tracks 14 via the signal preamplifier 15b.The temperature sensor 15c can also be connected to the conductor tracks 14, in which case they serve as measurement quantity sensors in addition to or as an alternative to the first support element 12 for the temperature sensor 15c, while in any case they serve as measuring electrodes for impedance measurement.

[0070] The impedance / temperature sensor assembly 3 can therefore, with regard to its impedance measurement branch, be used by means of the in Fig. The simplified equivalent circuit diagram described in 3B is used to describe the impedance measurement process. During the impedance measurement, the control device 15a applies a defined AC measuring voltage between a first conductor 14a and the corresponding second conductor 14b of the two conductors 14. Since, during the measurement process, the first support element 11 with the conductors 14 located on it is inserted into the substrate 11 to be analyzed, the two conductors 14a, 14b are in electrical contact with the substrate 11 surrounding them, so that the substrate exhibits an electrical resistance R between the two conductors 14a, 14b. el connects. The two conductor tracks 14a, 14b each have an electrical resistance R in the equivalent circuit diagram. CT1 or R CT1 , as well as a parallel (parasitic) capacitance C DL1 or C DL2 up. By means of the in Fig. The relationship given in Figure 3B allows an impedance spectrum Z(ω) to be determined as a function of the frequency ω of the applied AC measurement voltage. The frequency range used to obtain the impedance spectrum Z(ω) can be selected according to the application and typically includes the frequency range from 100 Hz to 1 MHz. Ideally, the first carrier element 12 is connected to a ground potential during the impedance measurement process, for example, by being electrically connected to the neutral terminal of the power supply of the sensor device 1. This counteracts signal distortion of Z(ω) due to external electromagnetic coupling.

[0071] Based on this obtained impedance spectrum Z(ω), further analysis allows for differentiation with regard to soil type, soil texture, electrical conductivity, water content, ion concentration, and ion type, particularly using dielectric mixed models (for example, the Bruggeman model, the Maxwell-Garnett model). Quantitative analyses are also possible in this way. Simultaneously with the impedance measurement, a temperature measurement can also be performed using the temperature sensor, whereby, as already mentioned, the two conductor tracks 14 and / or the first support element 12 can serve as the sensor. In some embodiments, the impedance / temperature sensor assembly 3 can represent the entirety of the sensors of the sensor device 1 or even the device itself.

[0072] Fig. Figure 4 shows a potential measurement assembly 4 inserted into a soil 11 to be analyzed, according to an embodiment of the invention, in particular a pH sensor assembly, which is in particular in a sensor device 1 according to Fig. 1 or Fig. 2. The potential measurement assembly 4 has a second support element 17 in the form of a mandrel, the shape of which can essentially correspond to that of the first support element 12 of the impedance / temperature sensor assembly 3. A passivation layer 18, in particular a polymer passivation (e.g., made of HDPE), is provided on a surface section of the second support element 17, which is intended to come into contact with the soil 11 to be analyzed when inserted.

[0073] On this passivation layer 18, a metal oxide electrode 21 and a calibration electrode 22 are arranged in the form of ring-shaped conductive tracks. With the aid of these electrodes, and given knowledge of the electrical resistance of the soil 11, which can be determined in particular by means of the impedance / temperature sensor assembly 3, the condition, in particular the layer thickness, of the metal oxide electrode 21 can be determined by measuring the resistance or conductivity between the two electrodes 21 and 22, which are electrically coupled through the soil 11. The layer thickness can then serve as a calibration parameter for the actual measurement of the acidity or alkalinity, in particular the pH value, of the soil 11. The measurement can be performed in particular before each pH measurement or cyclically at predetermined time intervals. Thus, the potential measurement assembly is capable of performing an independent (in-situ) autocalibration.

[0074] The metal oxide electrode 21 and the calibration electrode 22 are each electrically insulated from the second support element 17, which may be made of metal, and from each other by the passivation layer 18. The calibration electrode 22 may, in particular, contain a conductive polymer material and / or a conductive composite material, or be made entirely of such material. The metal oxide electrode 21 and the calibration electrode 22 each have electrical connections 21a and 22a, respectively, which may, in particular, be made of the same material as the associated electrode 21 and 22.

[0075] For measuring the acidity or alkalinity of the soil by means of potential measurement, the potential measurement assembly 4 further comprises an electrolyte / metal reference electrode 19 (for example, an AgCl / Ag electrode), which, as components arranged in a metal housing 23 (metal cap) designed as part of or supplementing the second support element 17, contains an electrolyte vessel 19b for holding a liquid or pasty electrolyte 19a as an electrolyte reference electrode, and a metal reference electrode 19c, which is in electrically conductive contact with the electrolyte vessel 19b and the electrolyte 19a contained therein. The metal housing 23 provides, in particular, robust mechanical protection for the reference electrode 19.

[0076] The combination of the metal oxide electrode 21, the electrolyte / metal reference electrode 19, and an ion diaphragm 20 arranged between them on the surface of the second support element 17, which is in ion-conducting connection with the electrolyte / metal reference electrode 19 and which can also be brought into ion-conducting connection with the metal oxide electrode via the surrounding soil 11 during the measurement process, constitutes a measuring device for measuring the acidic or basic character of the soil 11 based on the chemical redox reaction already mentioned above: xMe + yH2O ↔ Me x O y + y2H + + y2e - their reaction equilibrium is significantly influenced by the concentration of hydrogen ions (H) present in the soil. +) is also determined, so that the H is determined by means of the ion currents occurring during the measurement or the potential difference occurring between the metal oxide electrode 21 and the electrolyte / metal reference electrode 19, taking into account a calibration based on the described measurement of the state of the metal oxide electrode 21. + -Ion concentration in the soil and thus its pH value can be determined.

[0077] Fig. Figure 5 schematically shows an absorption spectrometer assembly 5 for a sensor device according to the invention, which in particular includes the sensor device 1 according to Fig. 1 or Fig. 2. Accordingly, reference is made below to the sensor device 1. The absorption spectrometer assembly 5 has a substantially disc-shaped support 24, rotatable about an axis A, fitted into the housing 2 of the sensor device 1 between the two sensor assemblies 3 and 4. One disc surface of the support 24 faces an opening in the housing 2, which serves as the measuring aperture or measuring window of the absorption spectrometer assembly 5. The virtual surface of this opening, located at its outer geometric boundary, can also be referred to as the measuring surface M, which, during measurement operation, typically lies, at least substantially, parallel to or coincides with the surface of the soil 11 to be analyzed. Fig. Figure 5 is shown as a dashed line. The support 24 is positioned relative to this measuring surface M such that it lies above the ground surface during measurement operation, with a minimum distance defined by the shape of the housing 2. On the side of the support 24 facing the measuring surface, two (or more) individual MEMS absorption spectrometers 26a, 26b are arranged, each covering at least partially different spectral ranges, and cumulatively covering a UV-VIS-NIR spectral range that includes, in particular, the spectral range from 350 nm to 1700 nm. The use of MEMS technology for the production of the absorption spectrometers enables the manufacture of particularly small and thus space-efficient designs.

[0078] Furthermore, a source 25 for electromagnetic radiation, for example a halogen lamp, whose radiation covers this spectral range UV-VIS-NIR, is provided on the same side of the carrier 24. The source 25 and the absorption spectrometers 26a, 26b are arranged relative to each other, or optically separated from each other by an aperture formed on the carrier 24, such that the radiation from the source 25 can only reach the absorption spectrometers 26a, 26b indirectly in the form of reflected radiation.

[0079] Additionally, the absorption spectrometer assembly 5 includes a protective optic 27, which can be designed, in particular, as a disk made of scratch-resistant material that is at least largely transparent in the specified spectral range, for example, a sapphire glass disk, with a hydrophilic nanocoating that improves scratch resistance. The nanocoating facilitates keeping the optic clean and its cleaning, and increases its mechanical robustness. The protective optic 27 is positioned between the support 24 with the optical components 25, 26a, 26b located thereon and the measurement surface (at a distance of, for example, approximately 3 cm). The protective optic 27 protects the optical components against harmful external influences, especially from the soil 11 being analyzed, such as dust, moisture, and mechanical damage.

[0080] Furthermore, the absorption spectrometer assembly 5 includes a closing or shutter device 28, which is essentially a disc-shaped aperture that can be inserted (and removed) into the spatial area defined between the carrier 24 with the optical components 25, 26a, 26b and the protective optics 27, preferably parallel to the protective optics 27. On its side facing the optical components 25, 26a, 26b, this aperture is coated with a calibration coating 29, for example, Spectralon. Spectralon is a sintered PTFE material that exhibits an extremely high and uniform reflectance in the ultraviolet (UV), visible (VIS), and near-infrared (NIR) regions of the electromagnetic spectrum. It exhibits Lambertian reflection behavior, meaning it reflects very diffusely or mattely.The calibration coating 29 serves as a calibration reference, which can be used to calibrate the absorption spectrometers 26a, 26b in situ when the aperture is retracted into the space between the absorption spectrometers 26a, 26b and the protective optics 27. During the soil analysis measurement process, however, the aperture is extended so as not to disturb the beam path between the optical components 25, 26a, 26b and the soil 11.

[0081] The absorption spectrometer assembly 5 is also configured such that during measurement operation, when the soil surface of the soil 11 to be analyzed coincides, at least substantially, with the measurement surface, the support 24 is rotated about the axis of rotation A, which is then substantially perpendicular to the measurement surface, while the source 25 and the two absorption spectrometers 26a, 26b are active in order to record an absorption spectrum in the specified spectral range on the basis of the radiation from the source 25 reflected at the soil surface.

[0082] Fig. Figure 6 shows a schematic overview of a (complete) system 30 for soil analysis, according to an embodiment of the invention. The system 30 comprises one or typically several sensor devices, in particular sensor devices 1 according to the Fig. 1 or Fig. 2 (of which only one is shown here) which serve on-site, i.e., in-situ, to obtain measurement data characterizing the properties of a soil to be analyzed. 11 These measurement data can then be transmitted from the respective sensor device 1, via the communication device 8, to an external counterpart 33, which can be implemented in particular as one or more network nodes (for example, servers) in a computer network or a cloud environment.

[0083] In the example shown, the transmission occurs in several stages. The measurement data, and any associated metadata, are first transmitted via a wireless communication link, which can be implemented using LoRa or NB-IoT radio technologies, to a gateway 32. This gateway 32 might be located, for example, on the farm of a farmer using system 30. From this gateway 32, the measurement data and metadata can be further transmitted to the counterpart 33 for evaluation, for example, via a conventional wireless or wired internet connection. A blockchain transfer is also preferably used, so that all communication between the sensor device 1 and the counterpart 33 is implemented using blockchain technology.This communication path is bidirectional, meaning it can also be used in the reverse direction, in particular for transmitting analysis data obtained by the other party 33 based on the measurement data and metadata transmitted to it to the respective sensor device 1. Depending on the design, the metadata recorded by the respective sensor device 1 can contain, in particular, information on the time and location of a ground measurement, as well as a unique device identification and / or user identification.

[0084] Additionally or alternatively, a further communication link 35 can be provided between the counterpart 33 and one or more user terminals 34, which can be designed as remote access, for example via a web portal, and can again be advantageously implemented using blockchain technology. All communication links in the system are preferably encrypted for the purpose of maintaining data security and protecting against manipulation, for example using known asymmetric or symmetric encryption methods. The communication link 35 provides a further means of accessing the acquired analysis data.For example, the farmer or gardener can in this way access the analysis data via a suitable terminal device 34 even at a greater time interval from the measurement being carried out, for example from his farm or while on the go, without having to have the sensor device 1 with him.

[0085] Fig. 7 provides an exemplary overview of various relationships between individual sensors of the sensor device according to Fig.The diagram shows the measurable quantities of 1 or 2, which can be determined using data fusion (or, synonymously, sensor fusion) according to the inventive method. The relationships are indicated by corresponding labeled arrows, the labels indicating the physical or chemical quantities that can be used in the data fusion process, in particular to form links between the various direct measurands supplied by sensor assemblies 3 to 5. This allows for the determination of additional derived soil properties and / or increases the accuracy of the achievable results.In particular, a number of important parameters for agriculture and horticulture can be determined in this way, including the total nitrogen content, the total humus content, the ratio of nitrogen to organic matter, the available phosphate, the available potassium, the available magnesium, the electrical conductivity, soil moisture and the pH value of the soil.

[0086] While at least one exemplary embodiment has been described above, it should be noted that a large number of variations exist. It should also be noted that the described exemplary embodiments are merely non-limiting examples, and it is not intended to restrict the scope, applicability, or configuration of the devices and methods described herein. Rather, the preceding description will provide the person skilled in the art with guidance for implementing at least one exemplary embodiment. It is understood that various modifications to the function and arrangement of the elements described in an exemplary embodiment can be made without derogating from the subject matter defined in the appended claims and their legal equivalents.

Claims

[1] Sensor device (1) for in-situ soil analysis, comprising: a sensor assembly comprising one or more sensors that are individually or cumulatively configured for the simultaneous in-situ measurement of an absorption spectrum in a spectral range NIR-VIS-UV extending from NIR to UV and of at least one of the following soil properties of a soil to be analyzed (11) and for the provision of corresponding respective measurement data: (a) Impedance spectrum (b) temperature (c) acidic or basic character; wherein the distance defined between any two sensors of the sensor assembly with respect to their respective measuring quantity sensors does not exceed a value of 10 cm, wherein the sensor assembly for in-situ acquisition of an absorption spectrum of the soil to be analyzed (11) includes an absorption spectrometer assembly (5) which has: at least two MEMS absorption spectrometers (26a, 26b) whose spectral coverage differs at least for partial regions of the electromagnetic spectrum, so that cumulatively an absorption spectrum of the soil (11) to be analyzed can be acquired by the entirety of the MEMS absorption spectrometers (26a, 26b), which has components in the NIR, VIS and UV regions, wherein the absorption spectrometer assembly (5) further comprises a movable shutter device (28) configured to temporarily retract an aperture into a spatial region defined between the absorption spectrometers and the measurement surface, wherein a calibration reference (29) for calibrating at least one of the absorption spectrometers is arranged on the side of the aperture facing the absorption spectrometers. [2] Sensor device (1) according to claim 1, wherein the sensor assembly for in-situ detection of an impedance spectrum of the soil (11) to be analyzed includes an impedance sensor comprising: a first support element (12); two conductor tracks (14) arranged on the first support element (12) but electrically insulated from it and from each other, at least one of which contains an electrically conductive corrosion-resistant polymer or composite material; a control device (15a) configured to apply an alternating voltage between the two conductor tracks (14), the frequency of which is varied over a predetermined frequency range, and in the operation of the sensor device (1), when it is inserted into the soil (11) to be analyzed in such a way that the conductor tracks (14) are in electrical contact with it, to detect an impedance spectrum of the soil (11) to be analyzed in response to the alternating voltage applied to it via the conductor tracks (14) and to provide it in the form of corresponding measurement data. [3] Sensor device (1) according to claim 2, wherein the first carrier element (12) is electrically conductive at least in one area covered by the conductor tracks (14) and the control device (15a) is further configured to place the electrical potential of at least one area to a ground potential during the detection of the impedance spectrum of the soil (11) to be analyzed. [4] Sensor device (1) according to claim 2 or 3, wherein the predetermined frequency range includes the range from 100 Hz to 1 MHz. [5] Sensor device (1) according to any one of claims 2 to 4, wherein: the first support element (12) is designed as a thorn that is at least partially hollow for insertion at least partially into the soil (11) to be analyzed, wherein an insulating layer is applied to the surface of the mandrel, and on which the two conductive tracks (14) are arranged; and the control device (15a) is arranged inside a hollow section of the first support element (12). [6] Sensor device (1) according to one of claims 2 to 5, wherein the sensor assembly for detecting a temperature of the soil (11) to be analyzed includes a temperature sensor (15c), wherein this together with the impedance sensor is designed as an integrated impedance / temperature sensor assembly (3) which is configured to simultaneously and in-situ detect both an impedance spectrum and a temperature of the soil (11) to be analyzed and to provide each in the form of corresponding measurement data. [7] Sensor device (1) according to claim 1, wherein the absorption spectrometer assembly (5) further comprises a movable carrier (24) on which the absorption spectrometers are arranged such that, when the carrier (24) is moved relative to a virtual measuring surface on which the soil (11) to be analyzed is located during the measuring operation of the sensor device (1), they can spectrometrically measure an area of ​​the soil (11) to be scanned by the absorption spectrometers in order to acquire an absorption spectrum integrated over the area to be scanned. [8] Sensor device (1) according to claim 1 or 7, wherein the absorption spectrometer assembly (5) further comprises an optics (27) which is at least substantially optically transparent in a wavelength range corresponding to the absorption spectrum to be recorded, and which is arranged in the spatial region between the absorption spectrometers and the measuring surface in order to spatially separate them from each other; wherein the optics (27) is provided on its side facing the measuring surface with a hydrophilic nanocoating that improves scratch resistance. [9] Sensor device (1) according to one of the preceding claims, wherein the sensor assembly for in-situ detection of an acidic or basic character of the soil to be analyzed (11) comprises a potential measurement assembly (4) which has: a second support element (17); an electrolyte / metal reference electrode (19) arranged in or on the second support element (17); a metal oxide electrode (21) arranged on a surface of the second support element (17) provided for contacting the soil (11) to be analyzed during measurement operation; an ion diaphragm (20) arranged on the second support element (17) between the metal oxide electrode (21) and the electrolyte / metal reference electrode (19) and in contact with the electrolyte / metal reference electrode (19); a corrosion-resistant calibration electrode (22) arranged on the surface of the second support element (17) provided for contacting the soil (11) to be analyzed and electrically insulated from the metal oxide electrode (21); and a measuring device that is configured: to determine the current state of the metal oxide electrode (21) by measuring an electrical resistance and / or an electrical capacitance occurring between the calibration electrode (22) and the metal oxide electrode (21) when these two electrodes are each in contact with the soil (11) to be analyzed; and To determine whether the soil (11) to be analyzed is acidic or basic, an electrical potential difference occurring between the reference electrode and the metal oxide electrode (21) is measured, taking into account a measurement calibration previously determined on the basis of the current state of the metal oxide electrode (21), when these two electrodes are each in contact with the soil (11) to be analyzed. [10] Sensor device (1) according to claim 9, wherein the calibration electrode (22) is made of a material that contains an electrically conductive and corrosion-resistant polymer or composite material. [11] Sensor device (1) according to claim 9 or 10, wherein the second support element (17) is designed as a mandrel for at least partial insertion into the soil (11) to be analyzed, wherein an insulating layer is applied to the surface of the mandrel on which the metal oxide electrode (21), the ion diaphragm (20), and / or the calibration electrode (22) are arranged. [12] Sensor device (1) according to one of the preceding claims, further comprising a communication device (8) for transmitting recorded measurement data to an external counterpart with respect to the sensor device (1) for evaluation. [13] Sensor device (1) according to claim 12, wherein the communication device (8) is configured to transmit the measurement data wirelessly by means of communication based on LoRa radio technology and / or NarrowBand Internet of Things, NB-IoT, radio technology. [14] Sensor device (1) according to claim 12 or 13, further comprising a secure storage device for storing a unique device identification of the sensor device (1) and / or at least one cryptographic key for encrypting measurement and / or metadata transmitted by means of the communication device (8) in a manner protected against unauthorized access. [15] Sensor device (1) according to one of claims 12 to 14, wherein the communication device (8) is further configured to write measurement and / or metadata to be transmitted into a blockchain acting as an external counterpart or to cause another external counterpart to write the measurement and / or metadata transmitted to it into a blockchain. [16] Sensor device (1) according to claim 15, wherein the sensor device (1) is configured to authenticate a user of the sensor device (1) and to allow the transmission of the measurement and / or metadata to an external counterpart only if the authentication has been successful. [17] Sensor device (1) according to one of the preceding claims, further comprising a position determination device (7) for determining a current position of the sensor device (1) and for providing corresponding metadata characterizing the position. [18] Methods for soil analysis, comprising: Receiving measurement data relating to an absorption spectrum in a spectral range NIR-VIS-UV extending from NIR to UV and of at least one further of the following soil properties of a soil to be analyzed (11): (a) Impedance spectrum (b) temperature (c) acidic or basic character; Determining at least one of the soil properties or at least one derived soil property based on a combination of the received measurement data by means of data fusion to obtain a respective measurement result for the at least one soil property to be determined, wherein the measurement data are acquired by a sensor device (1) according to one of claims 1 to 17. [19] Method according to claim 18, wherein the method is carried out in at least one central node (33) of a network which is configured to receive the respective measurement data and to be in communication connection (31) with a plurality of sensor devices (1) for acquiring the respective measurement data. [20] Computer program configured to execute the method according to one of claims 18 or 19 when running on a processor platform. [21] Device (33) for soil analysis, wherein the device is configured to perform the method according to one of claims 18 or 19. [22] Device (1, 33) according to claim 21, comprising a sensor device (1) according to any one of claims 1 to 17 for recording the measurement data.

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