Sensor assembly for determining a concentration of a target gas, and method therefor

Abstract

The invention relates to a sensor assembly (1) for determining a concentration of a target gas, wherein the sensor assembly (1) includes a measurement sensor (2) comprising a metal oxide material for gas detection. In order to achieve a high degree of usability, according to the invention the sensor assembly (1) comprises a reference sensor (3), which comprises a metal oxide material for gas detection, which metal oxide material has substantially the same composition as the metal oxide material of the measurement sensor (2), wherein the metal oxide material of the measurement sensor (2) is functionalised with nanoparticles (5) such that the measurement sensor (2) has a modified sensitivity with respect to the target gas in order to compensate for drift behaviour of the measurement sensor (2) at least in part by measuring the difference between the measurement sensor (2) and the reference sensor (3). The invention also relates to a method for determining a concentration of a target gas using a sensor assembly (1).

Description

[0001] Sensor arrangement for determining the concentration of a target gas and method for doing so

[0002] The invention relates to a sensor arrangement for determining the concentration of a target gas, wherein the sensor arrangement comprises a measuring sensor comprising a metal oxide material for gas detection.

[0003] The invention further relates to a method for determining the concentration of a target gas using a sensor arrangement.

[0004] It is known to use a multi-gas sensor, comprising several individual measuring sensors, to characterize a gas mixture. Different measuring sensors are designed to detect different target gases within the mixture. For gas detection, each measuring sensor can incorporate a metal oxide material. The composition of this metal oxide is typically chosen such that, when exposed to the target gas, its electrical resistance changes, allowing the target gas to be detected by measuring this electrical resistance. The metal oxide material is usually implemented as a porous layer to generate a large interaction surface for contact with the target gas.

[0005] The measuring sensors typically exhibit drift behavior caused by changes in the ambient atmosphere, such as humidity, and structural changes in the metal oxide materials, such as alterations in their crystalline structure. As a result, each sensor usually displays a changing electrical resistance over time, impairing measurement reliability and accuracy, especially under varying environmental conditions and / or over extended periods. This is particularly true for multi-gas sensors, which combine several such sensors, leading to an accumulation of measurement uncertainties and ultimately affecting the multi-gas sensor's overall measurement capability.To mitigate drift, calibration curves, measured under defined laboratory conditions, are typically used to mathematically align the measurement signals obtained from the sensors with these curves, for example, using a microprocessor unit of the multi-gas sensor. The multi-gas sensor usually incorporates a humidity sensor to correlate the calibration curves with the measurement signals. This often reduces drift to a manageable level, at least in limited applications. However, multi-gas sensors generally exhibit significant measurement uncertainty, particularly during long-term operation.

[0006] This is where the invention comes in. The object of the invention is to provide a sensor arrangement of the type mentioned above, which exhibits high operational capability, particularly under changing environmental conditions.

[0007] Furthermore, it is an objective of the invention to provide a method of the type mentioned above which has a high degree of usability, especially under changing environmental conditions.

[0008] The object of the invention is achieved in that, in a sensor arrangement of the type mentioned at the outset, the sensor arrangement comprises a reference sensor comprising a metal oxide material for gas detection which has a substantially the same composition as the metal oxide material of the measuring sensor, wherein the metal oxide material of the measuring sensor is functionalized with nanoparticles, so that the measuring sensor has a modified sensitivity to the target gas in order to at least partially compensate for a drift behavior of the measuring sensor by differential measurement of the measuring sensor and the reference sensor.

[0009] The background of the invention is the realization that, in the specific case of implementing a gas detection sensor with a metal oxide material functionalized with nanoparticles, where the nanoparticles are typically applied to a surface of the metal oxide material, the metal oxide material and the nanoparticles can be considered separate contributing factors with regard to the sensor's drift behavior. This is because, generally, the contribution of the nanoparticles can be neglected due to their very low mass compared to that of the metal oxide material. Based on this realization, the idea arose to design a measurement setup in such a way that the sensitivity to a target gas caused by the nanoparticles is separated from the drift behavior, which is essentially determined by the metal oxide material.This can be achieved by combining two gas detection sensors made of metal oxide materials, where the metal oxide materials of both sensors have the same composition. In one of the sensors, the metal oxide is functionalized with nanoparticles to modify its sensitivity to a target gas compared to the other sensor. Furthermore, if the two sensors are coupled in a differential measurement system, i.e., by subtracting the sensor signals, the resulting differential signal is free of drift factors caused by the metal oxide materials. These drift factors are identical for both sensors due to the same composition. In this way, drift can be largely, and in some cases almost completely, compensated.The sensor whose metal oxide is functionalized with nanoparticles, so that it has a changed sensitivity to the target gas compared to the other sensor, can be appropriately referred to as the measuring sensor and the other sensor as the reference sensor.

[0010] Since the metal oxide material of the measuring sensor and the metal oxide material of the reference sensor have essentially the same composition, the measuring sensor and the reference sensor generally exhibit the same drift behavior caused by the metal oxide material, particularly under the same environmental conditions. This drift behavior can be at least partially, and preferably essentially completely, compensated for by differential measurement between the measuring sensor and the reference sensor. Differential measurement is typically implemented by calculating the difference between a measurement signal from the measuring sensor and a measurement signal from the reference sensor. The measuring sensor and the reference sensor can be coupled to each other to perform the differential measurement. The measuring sensor and the reference sensor can also be components of a differential measurement system within the sensor arrangement to perform the differential measurement.The measurement signal of the measuring sensor and the measurement signal of the reference sensor typically correspond to simultaneous measurements of the measuring sensor and the reference sensor. For measurement, in particular determination of the concentration of the target gas, the measuring sensor and the reference sensor are usually exposed to the same gas, especially a gas mixture. The target gas can be the gas itself or a component of the gas mixture. The measuring sensor can have a detection element formed from the metal oxide material and nanoparticles of the measuring sensor. The reference sensor can also have a detection element formed from the metal oxide material of the reference sensor. Due to the functionalization of the measuring sensor with the nanoparticles, the measuring sensor, and in particular its detection element, typically exhibits a different sensitivity to the target gas compared to the reference sensor, and in particular its detection element.The sensitivity can be increased or decreased. The measurement signal of the measuring sensor typically represents an electrical resistance of the measuring sensor, in particular its detection element. The measurement signal of the reference sensor typically represents an electrical resistance of the reference sensor, in particular its detection element. The drift behavior of the measuring sensor is typically a drift behavior of the measurement signal, in particular the electrical resistance, of the measuring sensor. This usually applies analogously to the reference sensor. The drift behavior can relate to a dependence of the measuring sensor's signal on environmental conditions, in particular humidity, and on the operating time of the measuring sensor, usually with the same gas composition, in particular the same concentration of the target gas.

[0011] It is advantageous if the metal oxide material of the measuring sensor and / or the metal oxide material of the reference sensor is each a metal oxide layer and / or is formed with nanofibers. The metal oxide layer is typically a thin film. The metal oxide material can be a closed metal oxide layer, with typically one surface of the metal oxide layer being closed. The metal oxide material can form a substantially non-porous structure. It is advantageous if the metal oxide material of the measuring sensor and the metal oxide material of the reference sensor have substantially the same size and / or shape. In this way, a high efficiency in compensating for drift behavior can be achieved. An average thickness of the metal oxide layer can be less than 10 pm, particularly less than 5 pm, preferably less than 1 pm, and most preferably less than 0.5 pm.It is advantageous if the nanoparticles are arranged in a surface area, particularly on a surface, of the metal oxide material, especially the metal oxide layer, of the measuring sensor, in order to functionalize the metal oxide material of the measuring sensor, in particular to sensitize it. This allows for high accuracy in concentration determination while simultaneously enabling efficient drift compensation. Functionalizing, in particular sensitizing, the metal oxide material with the nanoparticles can modify, in particular increase or decrease, the sensitivity of the metal oxide material to the target gas. Specifically, the sensitivity can be modified, in particular increase or decrease, with respect to, or relative to, the sensitivity of the reference sensor, in particular its detection element and / or its metal oxide material.The surface region of the metal oxide material is usually understood as distinct from a bulk region of the metal oxide, the bulk region typically comprising more than 90%, and in particular more than 95%, of the mass of the metal oxide. The bulk region is typically enclosed by the surface region. As a rule, the vast majority by mass, in particular more than 75%, preferably more than 90%, and especially preferably more than 99%, of the nanoparticles of the measuring sensor is located in the surface region, and in particular on the surface, of the metal oxide. This applies in particular to those nanoparticles that effect the functionalization or the modification of the sensitivity to the target gas. The aforementioned proportions of the nanoparticles refer in particular to mass percent (m%) of the nanoparticles.The nanoparticles can be applied using a coating process, in particular chemical gas deposition, and / or a printing process by printing the nanoparticles onto the metal oxide material of the measuring sensor.

[0012] For high gas detection efficiency, it is advantageous if the metal oxide material of the measuring sensor and / or the metal oxide material of the reference sensor is composed at least partially, in particular predominantly, preferably essentially, of tin oxide, especially SnO₂, or copper oxide, especially CuO, or zinc oxide, especially ZnO. The metal oxide material can be composed at least partially, in particular predominantly, preferably essentially, of the tin oxide and the zinc oxide, and in particular of the copper oxide. The metal oxide material can be doped. For example, the tin oxide and / or zinc oxide can be n-doped. For example, the zinc oxide can be p-doped.The respective detection element, in particular the respective metal oxide material, of the measuring sensor and the reference sensor are usually gas-sensitive, so that an electrical resistance of the detection element, in particular the metal oxide material, changes depending on a gas composition and / or gas concentration of a gas, in particular a gas mixture, acting on the detection element, in particular the metal oxide.

[0013] To efficiently compensate for drift, it is advantageous for the measuring sensor and the reference sensor to be arranged such that they are exposed to as similar environmental conditions as possible during operation. The measuring sensor and the reference sensor can be arranged side by side, usually spaced apart. It is advantageous if the average distance between the measuring sensor and the reference sensor is less than five times, and particularly less than three times, the average longitudinal diameter of the measuring sensor, especially of its metal oxide material. Preferably, the average distance is less than the average longitudinal diameter of the measuring sensor, especially of its metal oxide material. The distance can refer to an intermediate region of the sensor arrangement between the measuring sensor and the reference sensor, and in particular, can be formed by this intermediate region.In particular, the spaced arrangement applies to the metal oxide material of the measuring sensor and the metal oxide material of the reference sensor. The measuring sensor and the reference sensor can be arranged side by side in contact with each other, with the detection elements of the measuring sensor and the reference sensor typically being electrically isolated from each other, for example by an insulating element of the sensor assembly. The measuring sensor and the reference sensor can be arranged as part of an integrated circuit of the sensor assembly, in particular on a common base of the integrated circuit.

[0014] It is advantageous if the sensor arrangement includes a temperature control device, in particular a micro-temperature control plate, to control the temperature of the measuring sensor and the reference sensor, especially by heating and / or cooling them. This makes it possible to set a controlled ambient temperature for the measuring sensor and the reference sensor in order to perform drift compensation with high accuracy. The temperature control device can be implemented with a heating element for heating and / or with a cooling element for cooling the measuring sensor and the reference sensor. The temperature control device can be configured to bring the measuring sensor and the reference sensor to a predetermined temperature and / or to simultaneously temperature-control them according to the same, in particular predefined, temperature control program, especially by heating and / or cooling them.It is advantageous if the measuring sensor and the reference sensor are arranged on a micro-temperature control plate, in particular a micro-heating plate, of the sensor assembly in order to temperature-control the measuring sensor and the reference sensor with the micro-temperature control plate, in particular to heat and / or cool them. The temperature control device can include the micro-temperature control plate, in particular a micro-heating plate. It is preferred if the measuring sensor and the reference sensor are arranged on a common or the same micro-temperature control plate, in particular a common micro-heating plate, of the sensor assembly. The measuring sensor and the reference sensor can be arranged side by side on the micro-temperature control plate, in particular along its length. The measuring sensor and the reference sensor are usually arranged in a central region of the micro-temperature control plate.It is advantageous if, in a top view of the micro-temperature plate, one area of ​​the micro-temperature plate is at least twice, and preferably three times, the sum of the areas of the metal oxide materials of the measuring sensor and reference sensor. "Top view" usually refers to a view orthogonal to the micro-temperature plate, particularly its longitudinal and lateral dimensions. Typically, the length and width of the micro-temperature plate are each greater than its height. The micro-temperature plate may incorporate resistance heating and / or Peltier heating for heating. It may also incorporate Peltier cooling for cooling. The arrangement and / or temperature control of the measuring sensor and the reference sensor applies specifically to their respective metal oxide materials.

[0015] For practical implementation, the sensor arrangement typically includes a resistance measuring device for measuring the electrical resistance of the measuring sensor, particularly its detection element, and the electrical resistance of the reference sensor, particularly its detection element, in order to generate the measurement signals of the measuring sensor and the reference sensor from the measured electrical resistances. The resistance measuring device can be implemented with a first resistance detection device for measuring the electrical resistance of the measuring sensor and a second resistance detection device for measuring the electrical resistance of the reference sensor. The first resistance detection device can be part of the measuring sensor. The second resistance detection device can be part of the reference sensor. The resistance measuring device can be part of the differential measurement system.

[0016] To perform efficient drift compensation, it is advantageous for the differential measurement sensor arrangement to include a differential generation device to calculate the difference between the measurement signals of the measuring sensor and the measurement signals of the reference sensor. This difference is typically a differential signal. The differential signal usually corresponds to a concentration of the target gas measured by the sensor arrangement. The differential generation device can be an electrical differential circuit and / or a microprocessor, either implemented using the electrical circuit and / or a computer-implemented microprocessor. The differential generation device can be part of the differential measurement system.

[0017] The measuring sensor and the reference sensor typically each have electrical control lines to control them, in particular to measure their respective electrical resistances or to transmit, and especially to read, their respective measurement signals. The sensor arrangement may include a control unit, particularly an electronic one, to control the sensor arrangement, especially its operation. The control unit may be connected to the measuring sensor and the reference sensor via signal conductors, in particular via the control lines, to control them, in particular to transmit measurement signals from the measuring sensor and the reference sensor to the control unit via the control lines. The control unit may include a microprocessor for performing the control. The control unit may include the differential generator and / or resistance measuring device.The control unit can be configured to control, in particular regulate, the temperature control devices, resistance measuring devices, and / or differential generation devices of the sensor arrangements. For this purpose, the control unit can be connected to these devices via signal conductors, particularly electrical control lines. The resistance measuring device and / or the differential generation device can be part of the control unit. The measuring sensor and the reference sensor are typically each a metal oxide semiconductor gas sensor. The control unit can be part of the differential measuring system.

[0018] For high accuracy in concentration determination, it has proven advantageous if the nanoparticles are formed with, in particular predominantly, preferably essentially with, platinum or nickel-platinum or palladium or gold or silver or copper.

[0019] It is advantageous to implement a multi-gas sensor, particularly an electronic nose, wherein the multi-gas sensor comprises several sensor arrangements for determining the concentrations of different target gases in a gas mixture, each sensor arrangement being configured as described in this document. Each sensor arrangement is typically configured to determine, and in particular measure, the concentration of one of the target gases. Typically, different sensor arrangements are used to determine, and in particular measure, the concentrations of different target gases. Preferably, each sensor arrangement is uniquely, and in particular bijectively, assigned to the respective target gas. The measuring sensors of different sensor arrangements can comprise different metal oxide materials and / or metal oxide materials functionalized with different nanoparticles.In this way, the measuring sensors can be configured to measure the concentrations of different target gases. Typically, each sensor arrangement consists of its own measuring sensor and a corresponding reference sensor. This allows for at least partial, and often substantial, compensation of the drift behavior of the measuring sensors, particularly their dependence on environmental parameters, especially humidity, and / or time, or in determining the concentrations of the target gases. This ensures high operational reliability of the multi-gas sensor, especially under changing environmental conditions and / or during long-term use. The sensor arrangements can be configured in one or more rows.For efficient control, it is advantageous if the sensor arrays are spaced at regular intervals. It is beneficial if each measuring sensor is assigned its own reference sensor to form the basis of that sensor array. In this way, the drift behavior can be tailored to each individual sensor array, resulting in high accuracy in characterizing the gas mixture through efficient drift compensation. Typically, the average distance between the measuring sensor and the reference sensor of a given sensor array is smaller than the average distance between the measuring sensors within that array.In particular, the average distance between the measuring sensor and the reference sensor of the respective sensor arrangement is smaller than the average distance between the measuring sensor and the nearest measuring sensor of the other sensor arrangements. This distance can refer, in particular, to an intermediate range between any two sensors, especially the measuring sensors and reference sensors. The foregoing applies especially to the metal oxide materials of the sensors, particularly the measuring sensors and reference sensors.

[0020] It is advantageous if each sensor assembly has its own temperature control device, in particular a dedicated micro-temperature control plate, to regulate the temperature of the measuring sensor and the reference sensor of the sensor assembly. In this way, an ambient temperature can be precisely controlled and preset for each individual sensor assembly to achieve high accuracy in drift compensation. It is particularly advantageous if the measuring sensor and the reference sensor of each sensor assembly are arranged on their own dedicated micro-temperature control plate. The temperature control device, in particular the micro-temperature control plate, and / or the arrangement of the measuring sensor and reference sensor of the respective sensor assembly on the micro-temperature control plate can be implemented as described in this document, particularly above. The micro-temperature control plates of the sensor assemblies are typically spaced apart from one another.This minimizes mutual interference. It is advantageous if the temperature control devices, especially micro-temperature control plates, of the sensor arrangements can be controlled separately, in order to temperature-control the measuring and reference sensors of different sensor arrangements according to different, especially predefined, temperature programs. This can be achieved with a control unit for each sensor arrangement. The control units can also be implemented with a common control unit.

[0021] The multi-gas sensor can include a control device, particularly an electronic one, to control the sensor arrangements, and in particular their operation. The control device can include a microprocessor for performing the control function. The control device can form the control unit of the respective sensor arrangement. The control device can be configured to control, and in particular regulate, the temperature control devices, resistance measuring devices, and / or differential generator devices of the sensor arrangements. The sensor arrangements can include a common resistance measuring device and / or a common differential generator device. The resistance measuring device and / or the differential generator device can be part of the control device.

[0022] For optimal usability, it is advantageous for the multi-gas sensor to have an electronic data processing unit configured for the computer implementation of a machine learning procedure. This unit receives measurement data from the sensor arrays as input data for the machine learning procedure, which then characterizes the gas mixture. Typically, the measurement data is generated from, or consists of, the differential signals from the sensor arrays. The data processing unit can be configured to execute the machine learning procedure on a computer. The machine learning procedure can be a neural network, specifically a feed-forward neural network or a recurrent neural network.

[0023] The sensor arrangement and / or the multi-gas sensor can be implemented in the form of a sensor microstructure, in particular a sensor microchip, and / or a semiconductor device, in particular a CMOS semiconductor device.

[0024] The object of the invention is achieved by a method of the type mentioned at the outset for determining a concentration of a target gas with a sensor arrangement, if the sensor arrangement is designed as described in this document, wherein the measuring sensor and the reference sensor are exposed to the target gas, in particular a gas mixture containing the target gas, after which a difference between a measuring signal of the measuring sensor and a measuring signal of the reference sensor, in particular in the form of a difference signal of the sensor arrangement, is formed in order to at least partially compensate for a drift behavior of the measuring sensor.

[0025] The method for determining the concentration of a target gas using a sensor arrangement can be designed according to the characteristics and effects described in this document, particularly in relation to the sensor arrangement described above. The same applies to the sensor arrangement with regard to the method. This allows the drift behavior, especially the dependence on environmental parameters, particularly humidity, and / or time, of the measurement signal from the sensor to be at least partially, and in particular essentially completely, compensated. This enables high operational reliability of the sensor arrangement and / or the method, especially under changing environmental conditions and / or during long-term use. The target gas is typically a gas or part of a gas mixture with which the gas or...The sensor assembly, in particular the measuring sensor and the reference sensor, is exposed to a gas mixture during operation. The measuring sensor and / or the reference sensor typically incorporate the respective metal oxide material for gas detection. Generally, for gas detection, the respective metal oxide material is exposed to the target gas, and the electrical resistance of the measuring sensor and / or the reference sensor is measured.

[0026] Advantageously, a method for determining the concentrations of different target gases in a gas mixture can be implemented using a multi-gas sensor, wherein the multi-gas sensor is configured as described in this document, the sensor arrangements of the multi-gas sensor are exposed to the gas mixture, and the concentration of each of the different target gases is determined using the sensor arrangements according to the method for determining the concentration of a target gas with a sensor arrangement. In particular, a difference is calculated between the measurement signal of the measuring sensor and the measurement signal of the reference sensor of the respective sensor arrangement in order to at least partially compensate for any drift behavior of the measuring sensor of the respective sensor arrangement. In this way, the drift behavior, in particular an environmental parameter dependence, especially humidity dependence, and / or time dependence, of the measurement signals of the measuring sensors can be minimized.Drift in the determination of target gas concentrations is at least partially, and in particular essentially completely, compensated. This enables a high degree of usability of the multi-gas sensor and / or the method, especially under changing environmental conditions and / or during long-term use.

[0027] The method for determining the concentration of a target gas using a multi-gas sensor can be designed according to the characteristics and effects described in this document, particularly in relation to a sensor arrangement and / or a multi-gas sensor. The same applies to the sensor arrangement or the multi-gas sensor with regard to the method.

[0028] It is advantageous to combine a sensor arrangement or a multi-gas sensor, or a method for determining the concentration of a target gas, with a sensor arrangement or a method for determining the concentrations of different target gases in a gas mixture, using a multi-gas sensor to determine the concentration of, in particular, gaseous CO, CO2, acetone, formaldehyde, or toluene, each of which can be the target gas. In this way, the respective concentration can be determined with high accuracy, especially under changing environmental conditions and / or during long-term use. This ensures high operational reliability. Other conversions of the target gas known to those skilled in the art may be used, particularly as an alternative. However, the specified conversions of the target gas are preferred.The sensor arrangement, the multi-gas sensor, the method for determining the concentration of a target gas with a sensor arrangement, and the method for determining the concentrations of different target gases in a gas mixture with a multi-gas sensor can each be implemented as described in this document. Further features, advantages, and effects of the invention will become apparent from the following description of an exemplary embodiment. The drawings referred to therein show:

[0029] Fig. 1 shows a schematic representation of a section of a sensor arrangement, comprising a measuring sensor and a reference sensor, which are arranged on a micro-heating plate;

[0030] Fig. 2 shows a microscopic image of a sensor arrangement comprising a measuring sensor and a reference sensor, which are arranged on a micro-heating plate;

[0031] Fig. 3 shows a schematic representation of a multi-gas sensor, comprising several sensor arrangements;

[0032] Fig. 4 shows a microscopic image of a multi-gas sensor, comprising several sensor arrangements;

[0033] Fig. 5 Graphs showing, by way of example, a measurement signal from a measuring sensor, a measurement signal from a reference sensor and a difference signal of the measurement signals at different relative humidity.

[0034] Figure 1 shows a schematic representation of a section of a sensor arrangement 1 for determining the concentration of a target gas. The sensor arrangement 1 comprises a measuring sensor 2 and a reference sensor 3. Both the measuring sensor 2 and the reference sensor 3 have a metal oxide layer 4 for gas detection, the metal oxide layers 4 of the measuring sensor 2 and the reference sensor 3 having substantially the same composition. The metal oxide layer 4 of the measuring sensor 2 is functionalized with nanoparticles 5, such that the measuring sensor 2 exhibits a modified sensitivity to the target gas, particularly compared to the reference sensor 3. The nanoparticles 5 are applied to a surface of the metal oxide layer 4 of the measuring sensor 2.The measuring sensor 2 and the reference sensor 3 are arranged on a micro-heating plate 6 as a temperature control device, preferably in a central region of the micro-heating plate 6, typically side by side along a heating surface of the micro-heating plate 6, in order to temperature-control the measuring sensor 2 and the reference sensor 3. This ensures that the measuring sensor 2 and the reference sensor 3 are subjected to essentially identical environmental conditions. In this way, the measuring sensor 2 and the reference sensor 3 typically exhibit essentially identical drift behavior. By differential measurement of the measuring sensor 2 and the reference sensor 3, typically by subtracting a measurement signal of the measuring sensor 2 from a measurement signal of the reference sensor 3, the drift behavior of the measuring sensor 2, in particular of the measurement signal of the measuring sensor 2, can be at least partially, and preferably essentially completely, compensated.For this purpose, measuring sensor 2 and reference sensor 3 are typically coupled in the form of a differential measurement system. The result of the subtraction is usually a differential signal, which corresponds to the concentration of the target gas.

[0035] The measuring sensor 2 and the reference sensor 3 are typically connected via electrical control lines 7 of the sensor arrangement 1 to a control unit, in particular an electronic one, to control, and in particular regulate, the measuring sensor 2 and the reference sensor 3 for determining the concentration of the target gas. The control unit can be part of the sensor arrangement 1. The control unit can be configured to measure an electrical resistance of the measuring sensor 2 to generate the measurement signal of the measuring sensor 2 and an electrical resistance of the reference sensor 3 to generate the measurement signal of the reference sensor 3. This can be done with a resistance measuring device of the control unit. The control unit can be configured to perform the differential measurement, in particular with a differential generation device of the control unit.For example, the metal oxide layer 4 of the measuring sensor 2 and the metal oxide layer 4 of the reference sensor 3 can be formed with, in particular, SnO2. The metal oxide layer 4 of the measuring sensor 2 can be functionalized with platinum nanoparticles 5. Figure 2 shows a microscopic image of a sensor arrangement 1 comprising a measuring sensor 2 and a reference sensor 3, which are arranged on a micro-heating plate 6. The sensor arrangement 1 can be configured as described in Figure 1.

[0036] Figure 5 shows six graphs illustrating the measurement signal MS of the measuring sensor 2, the measurement signal RS of the reference sensor 3, and the difference signal DS (the difference between the measurement signal MS of the measuring sensor 2 and the measurement signal RS of the reference sensor 3) for a sensor arrangement 1 at three different relative humidity levels rH in the environment of the sensor arrangement 1. The sensor arrangement can be implemented as described in Figures 1 and / or 2. The top two graphs show the measurement signals MS, RS, and DS at a relative humidity rH of 25%, the middle two graphs show the measurement signals MS, RS, and DS at a relative humidity rH of 50%, and the bottom two graphs show the measurement signals MS, RS, and DS at a relative humidity rH of 75%. The measurement signals MS, RS, and DS are represented as electrical resistances R over a measurement time t.The differential signal DS corresponds to a concentration c of a target gas, which is converted to CO. The respective graphs show the measurement signals against three different CO concentrations: 5 ppm, 10 ppm, and 20 ppm, which are represented as vertical rectangular bars in the graphs. Both the measuring sensor 2 and the reference sensor 3 have a metal oxide layer 4 formed from SnÜ2, with the metal oxide layer 4 of measuring sensor 2 being functionalized by platinum nanoparticles 5. The measurement signal MS of measuring sensor 2 and the measurement signal RS of reference sensor 3 exhibit drift behavior dependent on the relative humidity rH. The differential signal DS, which is generated by calculating the difference between the measurement signal MS of measuring sensor 2 and the measurement signal RS of reference sensor 3, exhibits essentially eliminated drift behavior.The difference signal DS thus corresponds essentially to the concentration c of the target gas, independent of the relative humidity rH.

[0037] Figure 3 shows a schematic representation of a multi-gas sensor 8 comprising several, in particular eight, sensor assemblies 1. The multi-gas sensor 8 has several sensor assemblies 1 for determining the concentrations of different target gases in a gas mixture. The respective sensor assemblies 1 can be implemented as described for Figure 1 and / or Figure 2. Each sensor assemblies 1 is configured to measure the concentration of one of the target gases, which differs from that of the other sensor assemblies 1. The measuring sensors 2 of different sensor assemblies 1 have different compositions of their metal oxide materials and / or nanoparticles 5. The sensor assemblies 1 are spaced apart from one another, in particular forming one or more rows of sensor assemblies 1.Each sensor arrangement 1 has a micro-heating plate 6, wherein the measuring sensor 2 and the reference sensor 3 of the respective sensor arrangement 1 are arranged on the micro-heating plate 6. The multi-gas sensor 8 can have a control device 9 for controlling the sensor arrangements 1, in particular the respective measuring sensor 2 and reference sensor 3. The micro-heating plates 6 can preferably be controlled separately from one another by the control device 9. The control device 9 can form the control elements of the sensor arrangements 1.

[0038] The multi-gas sensor 8 can have more than 5 sensor assemblies 1, for example 8 sensor assemblies 1, in particular more than 10, preferably more than 50, sensor assemblies 1. In this way, a gas mixture with a correspondingly large number of different target gases can be characterized with the multi-gas sensor 8. Figure 4 shows a microscopic image of a multi-gas sensor 8 having 8 sensor assemblies 1. The multi-gas sensor 8 can be configured as described in Figure 3 or as shown in Figure 3.

[0039] For example, the sensor arrangements 1 of the multi-gas sensor 8 can comprise a first sensor arrangement 1 (SA 1), a second sensor arrangement 1 (SA 2), a third sensor arrangement 1 (SA 3), and a fourth sensor arrangement 1 (SA 4). The respective measuring sensor 2 and the respective reference sensor 3 can have a metal oxide layer 4, which may optionally be functionalized with nanoparticles 5, as specified in the following table.

[0040] A multi-gas sensor 8, as described above, can be used in a freely scalable manner with respect to a number of sensor arrangements 1. The multi-gas sensor 8 can represent a so-called electronic nose. With such a multi-gas sensor 8, it is possible to characterize multi-component gas mixtures with high accuracy, whereby the cumulative measurement uncertainty caused by the drift behavior of each of the sensor arrangements 1 is greatly reduced, in particular to a negligible degree, due to drift compensation. This enables high operational reliability, especially under changing environmental conditions and / or in the long-term use of the multi-gas sensor 8.

Claims

Patent claims 1. Sensor arrangement (1) for determining the concentration of a target gas, wherein the sensor arrangement (1) comprises a measuring sensor (2) comprising a metal oxide material for gas detection, characterized in that the sensor arrangement (1) comprises a reference sensor (3) comprising a metal oxide material for gas detection, which has a substantially the same composition as the metal oxide material of the measuring sensor (2), wherein the metal oxide material of the measuring sensor (2) is functionalized with nanoparticles (5) such that the measuring sensor (2) has a modified sensitivity to the target gas in order to at least partially compensate for a drift behavior of the measuring sensor (2) by differential measurement of the measuring sensor (2) and the reference sensor (3).

2. Sensor arrangement (1) according to claim 1, characterized in that the metal oxide material of the measuring sensor (2) and / or the metal oxide material of the reference sensor (3) is each a, in particular closed, metal oxide layer (4) and / or is formed with nanofibers.

3. Sensor arrangement (1) according to claim 1 or 2, characterized in that the nanoparticles (5) are arranged in a surface area, in particular on a surface, of the metal oxide material of the measuring sensor (2) in order to functionalize the metal oxide material of the measuring sensor (2).

4. Sensor arrangement (1) according to one of claims 1 to 3, characterized in that the metal oxide material of the measuring sensor (2) and / or the metal oxide material of the reference sensor (3) is formed at least partially, in particular substantially, from tin oxide, in particular SnÜ2, or copper oxide or zinc oxide.

5. Sensor arrangement (1) according to one of claims 1 to 4, characterized in that the sensor arrangement (1) has a temperature control device, in particular a micro-temperature control plate, to control the temperature of the measuring sensor (2) and the reference sensor (3) with the temperature control device, in particular to heat and / or cool.

6. Sensor arrangement (1) according to one of claims 1 to 5, characterized in that the sensor arrangement (1) has a resistance measuring device for measuring an electrical resistance of the measuring sensor (2) and an electrical resistance of the reference sensor (3).

7. Sensor arrangement (1) according to one of claims 1 to 6, characterized in that the sensor arrangement (1) for differential measurement has a differential generation device to form a difference between measurement signals of the measuring sensor (2) and measurement signals of the reference sensor (3).

8. Sensor arrangement (1) according to one of claims 1 to 7, characterized in that the nanoparticles (5) are formed with platinum or nickel-platinum or palladium or gold or silver or copper.

9. Multi-gas sensor (8), in particular electronic nose, comprising several sensor arrangements (1) for determining concentrations of different target gases of a gas mixture, characterized in that the sensor arrangements (1) are each configured according to one of claims 1 to 8, wherein the measuring sensors (2) of different sensor arrangements (1) comprise metal oxide materials different from one another and / or metal oxide materials functionalized with nanoparticles (5) different from one another.

10. Multi-gas sensor (8) according to claim 9, characterized in that each measuring sensor (2) is assigned its own reference sensor (3) to form the respective sensor arrangement (1), wherein preferably an average distance between the measuring sensor (2) and the reference sensor (3) of the respective sensor arrangement (1) is smaller than an average distance between the measuring sensors (2) of the sensor arrangements (1) among each other.

11. Multi-gas sensor (8) according to claim 9, characterized in that the respective sensor arrangement (1) has its own temperature control device, in particular a micro-temperature control plate, to temperature control the measuring sensor (2) and the reference sensor (3) of the sensor arrangement (1).

12. Multi-gas sensor (8) according to one of claims 9 to 11, characterized in that the multi-gas sensor (8) has an electronic data processing unit which is set up for the computer implementation of a machine learning procedure in order to supply measurement data from the sensor arrangements (1) transmitted to the data processing unit as input data to the machine learning procedure in order to implement a characterization of the gas mixture with the machine learning procedure.

13. Method for determining the concentration of a target gas using a sensor arrangement (1), wherein the sensor arrangement (1) is configured according to any one of claims 1 to 8, wherein the measuring sensor (2) and the reference sensor (3) are exposed to the target gas, in particular a gas mixture containing the target gas, after which a difference between a measuring signal of the measuring sensor (2) and a measuring signal of the reference sensor (3) is calculated in order to at least partially compensate for a drift behavior of the measuring sensor (2).

14. Method for determining concentrations of different target gases of a gas mixture with a multi-gas sensor (8), wherein the multi-gas sensor (8) is configured according to one of claims 9 to 12, wherein the sensor arrangements (1) of the multi-gas sensor (8) are exposed to the gas mixture, wherein a concentration of one of the different target gases is determined with the sensor arrangements (1) according to a method according to claim 13.

15. Use of a sensor arrangement (1) according to any one of claims 1 to 8 or of a multi-gas sensor (8) according to any one of claims 9 to 12 or of a method according to any one of claims 13 or 14 for determining a concentration of CO, CO2, acetone, formaldehyde or toluene.

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