Gas detector, gas detection method, and gas analysis system

Abstract

The present invention provides a gas detector and the like that can acquire a signal with reduced influence from external disturbances. [Solution] The gas detector 101 comprises a plurality of gas sensor elements 10, each having a sensitive part whose electrical or physical properties change in response to the adsorption of molecules, including a first gas sensor element 10a and a second gas sensor element 10b having a sensitive part with the same configuration as the sensitive part of the first gas sensor element 10a; a first flow path 20a through which a first gas flows and the first gas sensor element 10a is located; a second flow path 20b through which a second gas flows and the second gas sensor element 10b is located; and a measurement circuit 30 that outputs an electrical signal based on the difference between the characteristics of the sensitive part of the first gas sensor element 10a and the characteristics of the sensitive part of the second gas sensor element 10b.

Description

Technical Field

[0001] The present disclosure relates to a gas detector, a gas detection method, and a gas analysis system.

Background Art

[0002] A gas sensor having a sensitive part whose electrical or physical properties change according to the adsorption of molecules is used to detect the molecules contained in a gas. The detection result by such a gas sensor is used for the determination of the quality of the gas, or for the analysis of the gas such as the quantification or identification of the molecules contained in the gas.

[0003] For example, Patent Document 1 discloses a technique for determining the state of the air quality of a sample gas based on a change in the electrical characteristic value of a sensitive part. In the technique disclosed in Patent Document 1, during a predetermined measurement period, the temperature of the sensitive part exposed to the sample gas is controlled to change in a temperature change pattern including a temperature rising period in which the temperature of the sensitive part rises and a temperature falling period in which the temperature of the sensitive part falls.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The electrical or physical properties of the sensitive part of a gas sensor can also change due to various disturbance factors other than the adsorption of molecules to the sensitive part. For example, as in the technique described in Patent Document 1, when the temperature of the sensitive part is changed, the properties of the sensitive part also change. In addition, the sensitive part can change its properties due to various disturbance factors such as the flow rate of the gas and the humidity of the gas, in addition to the temperature.

[0006] Therefore, the present disclosure provides a gas detector or the like that can acquire a signal with reduced influence of disturbance factors. [Means for solving the problem]

[0007] A gas detector according to one aspect of the present disclosure comprises a plurality of gas sensor elements, each having a sensitive portion whose electrical or physical properties change in response to the adsorption of molecules, including a first gas sensor element and a second gas sensor element having a sensitive portion having the same configuration as the sensitive portion of the first gas sensor element; a first flow path through which a first gas flows and the first gas sensor element is located; a second flow path through which a second gas flows and the second gas sensor element is located; and a measurement circuit that outputs an electrical signal based on the difference between the characteristics of the sensitive portion of the first gas sensor element and the characteristics of the sensitive portion of the second gas sensor element.

[0008] A gas detection method according to one aspect of the present disclosure is a gas detection method using the gas detector described above, wherein the first gas and the second gas are simultaneously flowed through the first channel and the second channel, respectively, and the electrical signal output by the measurement circuit is acquired.

[0009] A gas analysis system according to one aspect of this disclosure comprises a gas detector and an analysis unit that analyzes the first gas based on the electrical signal. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a gas detector, etc., that can acquire a signal with reduced influence from disturbance factors. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing the schematic configuration of a gas analysis system according to an embodiment. [Figure 2] Figure 2 is a schematic plan view showing an example of the configuration of a gas detector according to the embodiment. [Figure 3] Figure 3 is a schematic plan view showing an example of the configuration of a gas sensor element according to the embodiment. [Figure 4]FIG. 4 is a diagram showing an example of the circuit configuration of the measurement circuit according to the embodiment. [Figure 5] FIG. 5 is a diagram showing another example of the circuit configuration of the measurement circuit according to the embodiment. [Figure 6] FIG. 6 is a diagram showing the circuit configuration of the measurement circuit according to the comparative example. [Figure 7] FIG. 7 is a diagram showing the time change of Rodor1 used in the simulation. [Figure 8] FIG. 8 is a diagram showing the time change of Rodor2 used in the simulation. [Figure 9] FIG. 9 is a diagram showing the time change of Rtemp used in the simulation. [Figure 10] FIG. 10 is a diagram showing the time change of R1 used in the simulation. [Figure 11] FIG. 11 is a diagram showing the time change of R2 used in the simulation. [Figure 12] FIG. 12 is a diagram showing the time change of a predetermined power supply voltage used in the simulation. [Figure 13] FIG. 13 is a diagram showing the time change of the electrical signal output by the measurement circuit according to the comparative example in the simulation. [Figure 14] FIG. 14 is a diagram showing the time change of the electrical signal output by the measurement circuit according to the present embodiment in the simulation. [Figure 15] FIG. 15 is a diagram showing the time change of the electrical signal output by another measurement circuit according to the present embodiment in the simulation. [Figure 16] FIG. 16 is a flowchart showing an example of the operation of the gas analysis system according to the embodiment. [Figure 17] FIG. 17 is a schematic diagram for explaining examples of the first gas and the second gas. [Figure 18] FIG. 18 is a plan view schematically showing an example of the configuration of the gas detector according to the modified example of the embodiment.

Embodiments of the Invention

[0012] (Summary of the Present Disclosure) Hereinafter, as an overview of the present disclosure, examples of a gas detector, a gas detection method, and a gas analysis system according to the present disclosure will be shown.

[0013] For example, a gas detector according to a first aspect of the present disclosure includes a plurality of gas sensor elements each having a sensitive portion whose electrical or physical characteristics change according to adsorption of molecules, a first gas sensor element, and a second gas sensor element having a sensitive portion having the same configuration as the sensitive portion of the first gas sensor element. The gas detector includes a plurality of gas sensor elements, a first flow path through which a first gas flows and in which the first gas sensor element is disposed, a second flow path through which a second gas flows and in which the second gas sensor element is disposed, and a measurement circuit that outputs an electrical signal based on a difference between the characteristics of the sensitive portion of the first gas sensor element and the characteristics of the sensitive portion of the second gas sensor element.

[0014] Thus, since the sensitive portions of the first gas sensor element and the second gas sensor element have the same configuration, the electrical signal based on the difference between the characteristics of the sensitive portion of the first gas sensor element and the characteristics of the sensitive portion of the second gas sensor element by the measurement circuit is a signal in which disturbance factors, which are factors other than the difference between the first gas and the second gas, cancel each other out. Therefore, in the gas detector according to this aspect, an electrical signal with reduced influence of disturbance factors can be acquired. Further, since the measurement circuit can detect the difference between the characteristics of the sensitive portion of the first gas sensor element and the characteristics of the sensitive portion of the second gas sensor element, compared with the case where electrical signals corresponding to the characteristics of the sensitive portion of the first gas sensor element and electrical signals corresponding to the characteristics of the sensitive portion of the second gas sensor element are acquired and the difference is detected in a subsequent process, the processing in the subsequent stage can be reduced. Further, even when there are a plurality of disturbance factors, the configuration and circuit can be reduced to individually remove the plurality of disturbance factors, and the gas detector can be miniaturized.

[0015] Further, for example, a gas detector according to a second aspect of the present disclosure further includes a temperature control unit that controls the temperature of the plurality of gas sensor elements, and the temperature control unit controls the first gas sensor element and the second gas sensor element to the same temperature.

[0016] This further reduces the influence of temperature-related disturbances on electrical signals.

[0017] Furthermore, for example, a gas detector according to a third aspect of the present disclosure is a gas detector according to the first or second aspect, further comprising a flow path control unit that controls the flow rate of the first gas in the first flow path and the flow rate of the second gas in the second flow path, wherein the flow path control unit controls the flow rate of the first gas in the first flow path and the flow rate of the second gas in the second flow path to the same flow rate.

[0018] This further reduces the influence of disturbances related to gas flow on electrical signals.

[0019] Furthermore, for example, a gas detector according to a fourth aspect of the present disclosure is a gas detector according to any one of the first to third aspects, wherein the characteristic is electrical resistance, and the measurement circuit includes a voltage divider circuit in which the first gas sensor element and the second gas sensor element are connected in series.

[0020] This allows the voltage between the first gas sensor element and the second gas sensor element to be used as an electrical signal output by the measurement circuit.

[0021] Furthermore, for example, a gas detector according to a fifth aspect of the present disclosure is a gas detector according to any one of the first to fourth aspects, wherein the characteristic is electrical resistance, and the measurement circuit includes a bridge circuit that includes the first gas sensor element and the second gas sensor element as resistive elements, and an amplifier circuit that amplifies the output of the bridge circuit.

[0022] This allows for the output of an electrical signal with reduced electrical noise generated in the measurement circuit.

[0023] Furthermore, for example, a gas detection method according to the sixth aspect of this disclosure is a gas detection method using a gas detector according to any one of the first to fifth aspects, wherein the first gas and the second gas are simultaneously flowed through the first flow path and the second flow path, respectively, and the electrical signal output by the measurement circuit is acquired.

[0024] This allows for the acquisition of electrical signals with reduced influence from external disturbances using the gas detector described above.

[0025] Furthermore, for example, the gas detection method according to the seventh aspect of this disclosure is the gas detection method according to the sixth aspect, using the first gas and the second gas having the same humidity.

[0026] This further reduces the influence of gas humidity-related disturbances on electrical signals.

[0027] Furthermore, for example, the gas detection method according to the eighth aspect of this disclosure is a gas detection method according to the sixth or seventh aspect, wherein the first gas is a gas containing odor molecules emitted from the test sample, and the second gas is a gas containing odor molecules emitted from a normal test sample.

[0028] This allows for easy detection of defective products because, if odor molecules different from those of normal products are emitted from the test sample, a change in the electrical signal due to the difference in odor molecules will occur.

[0029] Furthermore, for example, a gas detection method according to the ninth aspect of this disclosure is a gas detection method according to the sixth or seventh aspect, wherein the first gas is a gas containing the target molecule, and the second gas is a gas in which the concentration of the target molecule is lower than that of the first gas.

[0030] As a result, the difference in adsorption of the target molecule to the sensing part of the first gas sensor element and the second gas sensor element is reflected in the electrical signal, making it easy to detect the target molecule.

[0031] Furthermore, for example, a gas analysis system according to the tenth aspect of this disclosure comprises a gas detector according to any one of the first to fifth aspects, and an analysis unit that analyzes the first gas based on the electrical signal.

[0032] This allows for the analysis of the first gas using an electrical signal that is less affected by external disturbances output from the measurement circuit of the gas detector, thereby improving the accuracy of the analysis.

[0033] Furthermore, for example, the gas analysis system according to the 11th aspect of this disclosure is the gas analysis system according to the 10th aspect, wherein the analysis unit identifies molecules contained in the first gas.

[0034] This allows for the identification of molecules contained in the first gas using electrical signals with reduced influence from external disturbances, thereby improving the accuracy of identification.

[0035] The embodiments will be described in detail below, with reference to the drawings as appropriate. The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit the disclosure. Furthermore, any components in the following embodiments that are not described in an independent claim will be described as optional components.

[0036] Furthermore, in this specification, terms indicating relationships between elements such as parallelism, terms indicating the shape of elements, and numerical ranges do not represent only strict meanings, but also include substantially equivalent ranges, such as differences of a few percent.

[0037] Furthermore, the figures are not necessarily strictly accurate. In each figure, substantially identical components are denoted by the same reference numerals, and redundant explanations are omitted or simplified.

[0038] Furthermore, in this specification, ordinal numbers such as "first," "second," etc., do not mean the number or order of components unless otherwise specified, but are used to avoid confusion between similar components and to distinguish them.

[0039] (Embodiment) [Overall structure] First, the overall configuration of the gas analysis system equipped with a gas detector according to the embodiment will be described.

[0040] Figure 1 is a block diagram showing the schematic configuration of the gas analysis system 100 according to this embodiment.

[0041] As shown in Figure 1, the gas analysis system 100 according to this embodiment includes a gas detector 101, a signal processing circuit 70, an analysis unit 80, and a memory 90. The gas detector 101 also includes a plurality of gas sensor elements 10 and a measurement circuit 30. Details of the gas detector 101 will be described later, but the gas detector 101 may also include configurations other than the plurality of gas sensor elements 10 and the measurement circuit 30.

[0042] The gas analysis system 100 analyzes a first gas based on an electrical signal output by the measurement circuit 30 of the gas detector 101 based on the characteristics of the sensing part of the gas sensor element 10. The first gas analyzed by the gas analysis system 100 includes, for example, volatile organic compounds and other molecules that are the target of detection by the gas detector 101. The first gas may include multiple types of molecules to be detected. The molecules to be detected may also be inorganic gas molecules such as ammonia, hydrogen sulfide, and carbon monoxide. The first gas may be, for example, gas collected from food, exhaled breath collected from the human body, air around the human body, or air collected from a room in a building. Note that the gas detector 101 is not limited to being provided in the gas analysis system 100, but may be used in other systems or on its own.

[0043] The gas analysis system 100 may, for example, analyze a first gas to identify the target molecules contained in the first gas. The gas analysis system 100 may, for example, identify which type of molecule is contained in the first gas as the target molecule from among several types of molecules. The gas analysis system 100 may also be used for odor identification. In this case, the target molecules are, for example, odor molecules which are organic compounds that constitute odor components. The gas analysis system 100 may also perform an analysis to determine the concentration of the target molecules contained in the first gas.

[0044] The signal processing circuit 70 acquires the electrical signal output by the measurement circuit 30 and performs signal processing on the acquired electrical signal. The electrical signal output by the measurement circuit 30 is an analog signal, and the signal processing circuit 70, for example, performs AD conversion of the analog signal into a digital signal. The signal processing circuit 70, for example, outputs the waveform data of the AD-converted electrical signal to the analysis unit 80. The signal processing circuit 70 may also be provided in the gas detector 101.

[0045] The analysis unit 80 analyzes the first gas based on the waveform data of the electrical signal output from the signal processing circuit 70. For example, as part of the analysis of the first gas, the analysis unit 80 identifies the target molecules contained in the first gas. For example, the analysis unit 80 extracts one or more feature quantities from the waveform data and analyzes the first gas based on the one or more extracted feature quantities.

[0046] The analysis unit 80 uses, for example, a trained logic model in the analysis of the first gas. The trained logic model takes, for example, one or more of the above-mentioned features as input and outputs the analysis result of the first gas. The analysis result of the first gas is, for example, the identification result of the target molecule to be detected.

[0047] The trained logic model is a logic model for analyzing the first gas. For example, the trained logic model takes one or more of the above-mentioned features as input and outputs the analysis result of the first gas.

[0048] A trained logical model is constructed, for example, by performing machine learning using known analysis results and one or more of the above-mentioned features that result in those analysis results as training data. Examples of logical models used in machine learning include neural networks, random forests, support vector machines, or self-organizing maps.

[0049] The analysis unit 80 displays the analysis results on a display (not shown) provided in the gas analysis system 100, for example. The analysis unit 80 may also output the analysis results to the memory 90 and store the analysis results in the memory 90. Alternatively, the analysis unit 80 may output the analysis results to an external device.

[0050] The analysis unit 80 is implemented by a processing circuit such as a microcontroller or processor that incorporates a program for performing the above and later processing. The analysis unit 80 may also be implemented by a dedicated logic circuit for performing the above and later processing.

[0051] Memory 90 is a storage device that stores the learned logical models used in the analysis unit 80. Memory 90 is implemented, for example, by semiconductor memory or an HDD (Hard Disk Drive).

[0052] [Gas detector configuration] Next, the configuration of the gas detector 101 according to the embodiment will be described.

[0053] Figure 2 is a schematic plan view showing an example of the configuration of the gas detector 101 according to this embodiment. Figure 3 is a schematic plan view showing an example of the configuration of the gas sensor element 10 according to this embodiment.

[0054] As shown in Figure 2, the gas detector 101 comprises a plurality of gas sensor elements 10 including a first gas sensor element 10a and a second gas sensor element 10b, a first flow path 20a, a second flow path 20b, a substrate 15, a measurement circuit 30, a temperature control unit 40, a temperature control element 41, a flow path control unit 50, an intake pump 51, a circuit board 60, and a housing 61. Figure 2 schematically shows the internal configuration of the housing 61. Also in Figure 2, the portions of the first flow path 20a and the second flow path 20b located within the housing 61 are shown by dashed lines. Furthermore, although the first flow path 20a and the second flow path 20b are shown two-dimensionally in Figure 2, the first flow path 20a and the second flow path 20b may have a three-dimensional structure.

[0055] The gas sensor element 10 is, for example, an electrochemical, semiconductor, field-effect transistor, surface acoustic wave, quartz crystal oscillator, resistive switching, or plasmon resonance type gas sensor element. The gas sensor element 10 is not particularly limited as long as it has a sensitive part whose electrical or physical properties change in response to the adsorption of molecules. The gas sensor element 10 is provided, for example, on a substrate 15.

[0056] In the example shown in Figure 3, the gas sensor element 10 has a sensing part 11 and a pair of electrodes 12 electrically connected to the sensing part 11. The pair of electrodes 12 are spaced apart via the sensing part 11. The gas sensor element 10 shown in Figure 3 is an element whose electrical properties change in response to the adsorption of molecules onto the sensing part 11 of the gas sensor element 10. The sensing part 11 is a sensing member whose electrical properties change in response to the adsorption concentration of molecules. Furthermore, if the types of molecules adsorbed onto the sensing part 11 are different, the change in electrical properties will differ even at the same adsorption concentration.

[0057] The sensitive part 11 is a sensitive film whose electrical properties, specifically its electrical resistance, change depending on the adsorption concentration of molecules. The sensitive film is composed of, for example, a resin material, which is an adsorbent that adsorbs the target molecules to be analyzed by the gas analysis system 100, and conductive particles dispersed in the resin material. As the resin material adsorbs molecules, the distance between the conductive particles changes, and as a result, the electrical resistance of the sensitive film between the pair of electrodes 12 changes. Examples of the resin material include polyalkylene glycol resin, polyester resin, and silicone resin. The resin material is, for example, a commercially available material used as the stationary phase of a gas chromatography column. From the viewpoint of durability and molecular adsorption, the resin material may be, for example, a silicone resin having various substituents such as phenyl groups and methyl groups in its side chains, which is commercially available as the stationary phase of a column. Furthermore, the sensitive film is not limited to a composition of resin material and conductive particles, but may be any film whose electrical or physical properties change due to the adsorption of molecules. Furthermore, the following mainly describes an example in which the electrical resistance of the sensing element 11 changes in response to the adsorption of molecules. However, the electrical or physical characteristics of the sensing element 11 that change in response to the adsorption of molecules are not particularly limited as long as they are characteristics that can be converted into an electrical signal.

[0058] The multiple gas sensor elements 10 include a first gas sensor element 10a and a second gas sensor element 10b. In the example shown in Figure 2, the multiple gas sensor elements 10 include a multiple first gas sensor element 10a and a multiple second gas sensor element 10b. In Figure 2, etc., a pattern is applied to the second gas sensor element 10b for clarity. The number of first gas sensor elements 10a and second gas sensor elements 10b included in the multiple gas sensor elements 10 is not particularly limited. The number of first gas sensor elements 10a and second gas sensor elements 10b included in the multiple gas sensor elements 10 may be one or two or more.

[0059] The second gas sensor element 10b has a sensing part 11 with the same configuration as the sensing part 11 of the first gas sensor element 10a. Having the same configuration as the sensing part 11 means that the material composition, structure, and shape of the sensing part 11 are identical. The second gas sensor element 10b is a dummy gas sensor element for measuring the difference in characteristics between it and the first gas sensor element 10a. In the example shown in Figure 2, there is a one-to-one correspondence between the multiple first gas sensor elements 10a and the multiple second gas sensor elements 10b. That is, the multiple gas sensor elements 10 may include multiple pairs of first gas sensor elements 10a and second gas sensor elements 10b that correspond one-to-one. The first gas sensor elements 10a and second gas sensor elements 10b that correspond one-to-one have a sensing part 11 with the same configuration.

[0060] The sensitivity characteristics (changes in electrical or physical properties due to molecular adsorption) of at least two of the multiple first gas sensor elements 10a are different from each other. The sensing parts 11 (specifically, the resin material included in the sensing parts 11) of at least two of the multiple first gas sensor elements 10a are composed of, for example, different types of materials. In the case of resin materials, different types of materials mean, for example, that at least the molecular weight or compositional formula is substantially different. Materials of different types exhibit different adsorption behavior for the same type of molecule. In other words, each of the at least two sensing parts 11 of the first gas sensor elements 10a exhibits different molecular adsorption behavior. The difference in molecular adsorption behavior is particularly large when the materials have different compositional formulas. Furthermore, the types of materials of each sensing part 11 of all of the multiple first gas sensor elements 10a may be different from each other. In this case, when the same type of molecule is adsorbed, different changes in electrical or physical properties will occur in the multiple first gas sensor elements 10a. This allows information corresponding to each of the multiple first gas sensor elements 10a to be obtained, thereby improving the analytical accuracy of the gas analysis system 100.

[0061] In the example shown in Figure 2, the gas detector 101 comprises two substrates 15. The two substrates 15 are, for example, made of the same material and shape. Multiple first gas sensor elements 10a and multiple second gas sensor elements 10b are mounted on different substrates 15. The multiple first gas sensor elements 10a and multiple second gas sensor elements 10b are arranged in an array, for example, in a plan view with respect to the substrate 15. The substrate 15 is, for example, a silicon substrate, but is not particularly limited. The substrate 15 is mounted on a circuit board 60 together with the temperature control element 41.

[0062] Multiple first gas sensor elements 10a are arranged in the first flow path 20a. The first gas flows through the first flow path 20a. In the example shown in Figure 2, the first flow path 20a includes an intake port 21a through which the first gas is drawn in, a sensor housing space 22a through which the first gas drawn in at the intake port 21a passes and through which multiple first gas sensor elements 10a are arranged, and an exhaust port 23a through which the first gas that has passed through the sensor housing space 22a is exhausted.

[0063] Multiple second gas sensor elements 10b are arranged in the second flow path 20b. The second gas flows through the second flow path 20b. In the example shown in Figure 2, the second flow path 20b includes an intake port 21b through which the second gas is drawn in, a sensor housing space 22b through which the second gas drawn in at the intake port 21b passes and through which multiple second gas sensor elements 10b are arranged, and an exhaust port 23b through which the second gas that has passed through the sensor housing space 22b is exhausted.

[0064] The first flow path 20a and the second flow path 20b are isolated within the same housing 61. The sensor housing space 22a and the sensor housing space 22b are, for example, the same shape. The internal atmosphere of the sensor housing space 22a and the sensor housing space 22b is controlled independently. Specifically, the first gas flows through the sensor housing space 22a, but the second gas does not. Also, the second gas flows through the sensor housing space 22b, but the first gas does not. As a result, in the sensor housing space 22a, multiple first gas sensor elements 10a are exposed to the first gas. Also, in the sensor housing space 22b, multiple second gas sensor elements 10b are exposed to the second gas. The sensor housing space 22a and the sensor housing space 22b may be individually formed spaces, or they may be spaces formed by dividing a single space with a partition wall.

[0065] The first gas is the gas to be analyzed. In contrast, the second gas is a comparison gas to the first gas. The second gas is, for example, a gas whose composition does not change during measurement by the gas detector 101.

[0066] The measurement circuit 30 outputs an electrical signal based on the difference between the characteristics of the sensing part 11 of the first gas sensor element 10a and the characteristics of the sensing part 11 of the second gas sensor element 10b. The electrical signal output by the measurement circuit 30 is, for example, an analog voltage signal. If the characteristics of the sensing part 11 are electrical resistance, the measurement circuit 30 may include the first gas sensor element 10a and the second gas sensor element 10b as circuit elements of the measurement circuit 30. In addition, although not shown in the example shown in Figure 2, the measurement circuit 30 may include other circuit elements other than the first gas sensor element 10a and the second gas sensor element 10b. At least some of the other circuit elements are mounted on, for example, a circuit board 60. At least some of the other circuit elements may be formed on a substrate 15.

[0067] Here, the specific circuit configuration of the measurement circuit 30 will be described with reference to Figures 4 and 5. Note that the circuit configuration of the measurement circuit 30 is not limited to the examples shown in Figures 4 and 5.

[0068] Figure 4 shows the circuit configuration of measurement circuit 30A, which is an example of the circuit configuration of measurement circuit 30 according to this embodiment. Figure 5 shows the circuit configuration of measurement circuit 30B, which is another example of the circuit configuration of measurement circuit 30 according to this embodiment. Measurement circuit 30 is, for example, measurement circuit 30A having the circuit configuration shown in Figure 4, or measurement circuit 30B having the circuit configuration shown in Figure 5. Figures 4 and 5 show measurement circuits 30A and 30B that include one pair of first gas sensor elements 10a and second gas sensor elements 10b that correspond one to one. When a plurality of gas sensor elements 10 include a plurality of pairs of first gas sensor elements 10a and second gas sensor elements 10b, the gas detector 101 includes, for example, a plurality of measurement circuits 30A or 30B for each of the pairs. In the gas detector 101, electrical signals are output from each of the plurality of measurement circuits 30A or 30B corresponding to the plurality of pairs.

[0069] The measurement circuit 30A shown in Figure 4 is a voltage divider circuit that includes a first gas sensor element 10a and a second gas sensor element 10b as resistive elements. In the measurement circuit 30A, the first gas sensor element 10a and the second gas sensor element 10b are connected in series. In the example shown in Figure 4, one electrode 12 of the first gas sensor element 10a is connected to node N0, and the other electrode 12 of the first gas sensor element 10a is connected to ground. Also, one electrode 12 of the second gas sensor element 10b is connected to node N0, and the other electrode 12 of the second gas sensor element 10b is connected to a power source supplying a predetermined power supply voltage Vcc. In the measurement circuit 30A, the voltage at node N0 between the first gas sensor element 10a and the second gas sensor element 10b is output as an electrical signal Vout.

[0070] The measurement circuit 30B shown in Figure 5 includes a bridge circuit 31 that includes a first gas sensor element 10a and a second gas sensor element 10b as resistive elements, and an amplifier circuit 32 that amplifies the output of the bridge circuit 31.

[0071] The bridge circuit 31 includes a first gas sensor element 10a, a second gas sensor element 10b, and resistor elements 31a and 31b as fixed reference resistors. One end of resistor elements 31a and 31b is connected to a power source of a predetermined power supply voltage Vcc. The other end of resistor element 31a is connected to one electrode 12 of the first gas sensor element 10a via node N1. The other end of resistor element 31b is connected to one electrode 12 of the second gas sensor element 10b via node N2. The other electrode 12 of the first gas sensor element 10a and the other electrode 12 of the second gas sensor element 10b are connected to common ground, respectively.

[0072] The amplifier circuit 32 amplifies the output of the bridge circuit 31. Specifically, the amplifier circuit 32 amplifies the voltage between (i) node N1 between the resistive element 31a and the first gas sensor element 10a and (ii) node N2 between the resistive element 31b and the second gas sensor element 10b in the bridge circuit 31, and outputs it as an electrical signal Vout. In the example shown in Figure 5, the amplifier circuit 32 uses three operational amplifiers to amplify the voltage between node N1 and node N2, but the circuit configuration of the amplifier circuit 32 can be appropriately changed depending on the desired amplification factor, etc.

[0073] In the above example, the measurement circuit 30 was described when the characteristic of the sensing part 11 that changes in response to molecular adsorption is electrical resistance. However, the characteristic of the sensing part 11 that changes in response to molecular adsorption may be a characteristic other than electrical resistance. For example, if the characteristic is the resonant frequency, the resonance angle of plasmon resonance, or the reflectance, the measurement circuit 30 first converts the information derived from the characteristics of the sensing part 11 of the first gas sensor element 10a and the sensing part 11 of the second gas sensor element 10b into an electrical signal. Then, the measurement circuit 30 outputs an electrical signal Vout based on the difference between the characteristics of the sensing part 11 of the first gas sensor element 10a and the characteristics of the sensing part 11 of the second gas sensor element 10b, as in the example of the measurement circuit 30 above. In this case, the signal processing circuit 70 may convert the output electrical signal Vout into information derived from the characteristics of the sensing part 11. In this case, the gas detector 101 may also include a sensor for measuring the characteristic.

[0074] Referring again to Figure 2, the temperature control unit 40 controls the temperature of the multiple gas sensor elements 10 by controlling the drive of the temperature control element 41. The temperature control unit 40 may, for example, control the temperature of the multiple gas sensor elements 10 with a temperature change pattern that includes a high-temperature period in which the temperature is controlled to a relatively high first temperature, and a low-temperature period in which the temperature is controlled to a second temperature lower than the first temperature. The temperature change pattern may, for example, include at least one high-temperature period and at least one low-temperature period. The temperature control unit 40 may also control the temperature of the multiple gas sensor elements 10 based on the result of measuring the temperature of the gas sensor elements 10 with a temperature sensor (not shown).

[0075] When the temperature of the gas sensor element 10 is changed, the state of molecular adsorption on the sensing part 11 of the gas sensor element 10 changes, and therefore the electrical or physical properties of the sensing part 11 also change in accordance with the adsorption of molecules. Furthermore, the change in the state of molecular adsorption on the sensing part 11 of the gas sensor element 10 due to temperature differs depending on the type of molecule. As a result, by changing the temperature of the gas sensor element 10, the electrical signal output from the measurement circuit 30 changes according to the type and concentration of the target molecule contained in the first gas, and the first gas can be analyzed using the electrical signal.

[0076] Furthermore, the temperature control unit 40 controls, for example, multiple first gas sensor elements 10a and multiple second gas sensor elements 10b to the same temperature. The electrical or physical characteristics of the sensing part 11 can change with temperature. Therefore, by having the first gas sensor elements 10a and the second gas sensor elements 10b at the same temperature, the influence of temperature on the electrical or physical characteristics of the sensing part 11 of the first gas sensor element 10a and the sensing part 11 of the second gas sensor element 10b can be made uniform.

[0077] The temperature control element 41 performs at least one of heating and cooling of the plurality of gas sensor elements 10. The temperature control element 41 is, for example, a thermoelectric element that performs at least one of heating and cooling of the plurality of gas sensor elements 10. The temperature control element 41 may be a heater element that performs only heating, or it may be an element capable of both heating and cooling, such as a Peltier element. In the example shown in Figure 2, a substrate 15 is placed on the temperature control element 41, and the temperature control element 41 performs at least one of heating and cooling of the plurality of gas sensor elements 10 via the substrate 15.

[0078] Furthermore, in the example shown in Figure 2, the gas detector 101 includes two temperature control elements 41. The two temperature control elements 41 are, for example, identical in performance and shape. The multiple first gas sensor elements 10a and the multiple second gas sensor elements 10b are heated and cooled by individual temperature control elements 41. Alternatively, the multiple first gas sensor elements 10a and the multiple second gas sensor elements 10b may be heated and cooled collectively by a single temperature control element 41. In this case, the multiple first gas sensor elements 10a and the multiple second gas sensor elements 10b may be mounted on the same substrate 15.

[0079] The flow path control unit 50 controls the flow of the first gas in the first flow path 20a and the flow of the second gas in the second flow path 20b. The flow path control unit 50 controls, for example, the on / off state of the intake pump 51. The flow path control unit 50 also controls the flow rate of the first gas in the first flow path 20a and the flow rate of the second gas in the second flow path 20b by controlling, for example, the intake pump 51. The flow path control unit 50 may also control the flow rates of the first gas and the second gas based on the results of measuring the flow rates of the first gas and the second gas with a flow meter (not shown). The flow path control unit 50 controls, for example, the flow rate of the first gas in the first flow path 20a and the flow rate of the second gas in the second flow path 20b to be the same flow rate. The electrical or physical characteristics of the sensing unit 11 may change depending on the flow rate of the gas detected by the gas sensor element 10. Therefore, by making the flow rates of the first gas and the second gas the same, the influence of the gas flow rate on the electrical or physical characteristics of the sensing part 11 of the first gas sensor element 10a and the sensing part 11 of the second gas sensor element 10b can be made uniform. Note that the flow rate of the first gas in the first flow path 20a and the flow rate of the second gas in the second flow path 20b are not limited to being controlled by the intake pump 51, but may also be controlled by, for example, a flow rate control valve (not shown).

[0080] In the example shown in Figure 2, the gas detector 101 is equipped with two intake pumps 51. The intake pumps 51 are individually provided corresponding to the first flow path 20a and the second flow path 20b, respectively. When the intake pump 51 located in the middle of the first flow path 20a operates, the first gas is drawn in from the intake port 21a, passes through the sensor housing space 22a, and is exhausted from the exhaust port 23a. Similarly, when the intake pump 51 located in the middle of the second flow path 20b operates, the second gas is drawn in from the intake port 21b, passes through the sensor housing space 22b, and is exhausted from the exhaust port 23b. In the example shown in Figure 2, intake pumps 51 are located between the sensor housing space 22a and the exhaust port 23a in the first flow path 20a, and between the sensor housing space 22b and the exhaust port 23b in the second flow path 20b. Furthermore, the arrangement of the intake pump 51 is not particularly limited, as long as the first gas and the second gas can be flowed through the first flow path 20a and the second flow path 20b, respectively.

[0081] The temperature control unit 40 and the flow path control unit 50 are implemented by a processing circuit such as a microcontroller or processor that incorporates a program to perform the processing described above and later. In this case, the temperature control unit 40 and the flow path control unit 50 may be implemented by separate microcontrollers or processors, or two or more of these functions may be implemented by a single microcontroller or processor. Therefore, although the temperature control unit 40 and the flow path control unit 50 are arranged separately in Figure 2, they can be arranged as a single unit. Furthermore, the temperature control unit 40 and the flow path control unit 50 may each be implemented by a dedicated logic circuit that performs the processing described above and later.

[0082] The circuit board 60 is a substrate on which the components of the gas detector 101 are mounted. In the example shown in Figure 2, the circuit board 60 has a substrate 15 on which a plurality of gas sensor elements 10 are provided, a temperature control unit 40, a temperature control element 41, a flow path control unit 50, and an intake pump 51 mounted on it. Wiring (not shown) is formed on the circuit board 60, and the components of the gas detector 101 are connected to this wiring. In addition, at least one of the above-mentioned signal processing circuit 70 and analysis unit 80 may be mounted on the circuit board 60. The circuit board 60 is, for example, a printed circuit board, but is not particularly limited. The circuit board 60 may also constitute part of the housing 61.

[0083] The housing 61 is a container that houses multiple gas sensor elements 10, a substrate 15, a measurement circuit 30, a temperature control unit 40, a temperature control element 41, a flow path control unit 50, an intake pump 51, and a circuit board 60. The multiple gas sensor elements 10, the substrate 15, the measurement circuit 30, the temperature control unit 40, the temperature control element 41, the flow path control unit 50, the intake pump 51, and the circuit board 60 are arranged, for example, within the same housing 61.

[0084] [Simulation of the measurement circuit output] Next, we will describe the results of a simulation of the electrical signal Vout output by the measurement circuit 30 of the gas detector 101 according to this embodiment. In the simulation, in addition to the measurement circuits 30A and 30B described above, we also simulated the electrical signal Vout output by the measurement circuit 30X according to the comparative example.

[0085] Figure 6 shows the circuit configuration of the measurement circuit 30X according to the comparative example. The measurement circuit 30X according to the comparative example has a configuration in which the second gas sensor element 10b of the measurement circuit 30A is replaced with a resistor element 31x as a fixed reference resistor. Therefore, in the measurement circuit 30X, the voltage at node N0 between the first gas sensor element 10a and the resistor element 31x is output as an electrical signal Vout. The measurement circuit 30X outputs an electrical signal corresponding to the electrical resistance of the sensing part 11 of the first gas sensor element 10a, rather than the difference between the electrical resistance of the sensing part 11 of the first gas sensor element 10a and the electrical resistance of the second gas sensor element 10b.

[0086] In the simulation, let R1 be the electrical resistance of the sensing part 11 of the first gas sensor element 10a, and R2 be the electrical resistance of the sensing part 11 of the second gas sensor element 10b. Also, let R1 = Rodor1 + Rtemp + Rflow + Rhumi and R2 = Rodor2 + Rtemp + Rflow + Rhumi.

[0087] Rodor1 is the resistance component corresponding to the adsorption of molecules onto the sensing portion 11 of the first gas sensor element 10a. Figure 7 shows the time evolution of Rodor1 used in the simulation. Rodor2 is the resistance component corresponding to the adsorption of molecules onto the sensing portion 11 of the second gas sensor element 10b. Figure 8 shows the time evolution of Rodor2 used in the simulation. In Figures 7 and 8, the peaks in Rodor1 and Rodor2 represent the increase in the resistance component caused by the adsorption of molecules onto the sensing portion 11.

[0088] Rtemp is the temperature-dependent resistance component of the sensing element 11. In the simulation, it is assumed that the sensing element 11 of the first gas sensor element 10a and the sensing element 11 of the second gas sensor element 10b have the same configuration, and that the first gas sensor element 10a and the second gas sensor element 10b are controlled at the same temperature. R1 and R2 are set to be the same. Figure 9 shows the time change of Rtemp used in the simulation. In the simulation, Rtemp is set assuming that Rtemp increases as the temperature increases. However, depending on the configuration of the sensing element 11, it is also possible that Rtemp may decrease as the temperature increases.

[0089] Rflow is the resistance component of the sensing element 11, which depends on the gas flow rate. In the simulation, it is assumed that the sensing element 11 of the first gas sensor element 10a and the sensing element 11 of the second gas sensor element 10b have the same configuration, and that the flow rates of the first gas and the second gas are the same. R1 and R2 are set so that Rflow is the same. In the simulation, Rflow is assumed to be constant at 100Ω.

[0090] Rhumi is the resistance component of the humidity-dependent sensing element 11. In the simulation, the sensing element 11 of the first gas sensor element 10a and the sensing element 11 of the second gas sensor element 10b have the same configuration, and it is assumed that the first gas and the second gas have the same humidity. R1 and R2 are set so that Rhumi is the same. In the simulation, Rflow is kept constant at 50Ω.

[0091] As shown in Figures 7 to 9, in the simulation, the resistance component is set assuming that the adsorption of molecules to the sensing part 11 occurs three times due to three repeated temperature changes. Also, as shown in Figure 7, in the simulation, Rodor 1 is set assuming that the sensing part 11 of the first gas sensor element 10a adsorbs molecules generated from normal products in the first and third adsorptions, and molecules generated from abnormal products in the second adsorption. The molecules generated from abnormal products are the molecules to be detected by the gas detector 101. In the second adsorption of the sensing part 11 of the first gas sensor element 10a, a change in Rodor 1 occurs that is different from that of the first and third adsorptions, making it possible for the first gas sensor element 10a to detect molecules generated from abnormal products. On the other hand, as shown in Figure 8, in the simulation, Rodor 2 is set assuming that the sensing part 11 of the second gas sensor element 10b adsorbs molecules generated from normal products in all three adsorptions from the first to the third. In other words, it is assumed that the second gas sensor element 10b is always exposed to a gas with a constant composition. Furthermore, in the simulation, it is assumed that the sensing part 11 of the first gas sensor element 10a and the sensing part 11 of the second gas sensor element 10b have the same configuration, and the change in the resistance component when adsorbing molecules generated from a normal product is the same for Rodor 1 and Rodor 2.

[0092] As a result of setting each resistance component as described above, the time evolution of R1 and R2 is as shown in Figures 10 and 11. Figure 10 shows the time evolution of R1 used in the simulation. Figure 11 shows the time evolution of R2 used in the simulation. As shown in Figures 10 and 11, in R1 and R2, the influence of Rtemp, which is the resistance component of the temperature-dependent sensing part 11, is greater than that of Rodor1 and Rodor2, which are resistance components corresponding to the adsorption of molecules to the sensing part 11.

[0093] Figure 12 shows the time variation of a predetermined power supply voltage Vcc used in the simulation. In the simulation, it is assumed that the power supply voltage Vcc is superimposed with noise as shown in Figure 12. Also, in the simulation, the electrical resistance of the resistors 31x, 31a, and 31b is 100Ω. Also, in the simulation, the amplification factor of the amplifier circuit 32 is 4 times.

[0094] Figures 13 to 15 show the results of simulations performed under the conditions described above. Figure 13 shows the time change of the electrical signal Vout output by the measurement circuit 30X according to the comparative example in the simulation. Figure 14 shows the time change of the electrical signal Vout output by the measurement circuit 30A according to this embodiment in the simulation. Figure 15 shows the time change of the electrical signal Vout output by the measurement circuit 30B according to this embodiment in the simulation.

[0095] As shown in Figure 13, in the comparative example measurement circuit 30X, the difference between the electrical signal Vout corresponding to a normal product and the electrical signal Vout corresponding to an abnormal product is significantly smaller than the fluctuation of the electrical signal Vout due to the influence of Rtemp, which is the resistance component due to the temperature change of the sensing element 11. In other words, in the comparative example measurement circuit 30X, factors other than the adsorption of the target molecule to the sensing element 11 have a large influence on the electrical signal Vout. This is because the electrical resistance of the sensing element 11 of the first gas sensor element 10a is directly reflected in the electrical signal Vout.

[0096] In contrast, as shown in Figure 14, in the measurement circuit 30A according to this embodiment, the electrical signal Vout fluctuates significantly only when the sensing unit 11 adsorbs molecules generated from an abnormal product. Unlike the measurement circuit 30X, the measurement circuit 30A does not have fluctuations in the electrical signal Vout due to the influence of Rtemp, which is the resistance component due to temperature changes in the sensing unit 11. In other words, in the electrical signal Vout output by the measurement circuit 30A, the signal component originating from the adsorption of the target molecule accounts for the majority, and influences other than the adsorption of the target molecule to the sensing unit 11 in the electrical signal Vout are reduced. This is because, in the measurement circuit 30A, the electrical signal Vout is output based on the ratio of R1 and R2 as the difference between R1 and R2, and the influence of Rtemp, which is the resistance component of the sensing unit 11 that depends on a temperature common to R1 and R2, is canceled out. As a result, the range of change in the electrical signal based on the characteristics of the sensing unit 11 is narrowed, which reduces the amount of subsequent processing and improves the accuracy of detection and analysis.

[0097] Furthermore, as shown in Figure 15, in the measurement circuit 30B according to this embodiment, similar to the measurement circuit 30A, the electrical signal Vout fluctuates significantly only when the sensing unit 11 adsorbs molecules generated from the abnormal product. Unlike the measurement circuit 30X, the measurement circuit 30B does not have fluctuations in the electrical signal Vout due to the influence of the resistance component Rtemp caused by temperature changes in the sensing unit 11. In addition, in the measurement circuit 30B, the first gas sensor element 10a and the second gas sensor element 10b are included as resistive elements in the bridge circuit 31, so that an electrical signal Vout is output from which noise from the power supply voltage Vcc, which is an external disturbance factor, has been removed. Therefore, in the electrical signal Vout output by the measurement circuit 30B, influences other than the adsorption of the target molecule to the sensing unit 11 are further reduced. Also, in the measurement circuit 30B, the difference between the voltage drop due to R1 and the voltage drop due to R2 is output from the bridge circuit 31, so the absolute value of the electrical signal Vout can be reduced. Therefore, even if the amplification factor of the amplifier circuit 32 is further increased, the signal is less likely to saturate. Furthermore, when performing AD conversion on an electrical signal Vout, it is also possible to improve the resolution of the AD conversion.

[0098] As described above, in the gas detector 101 according to this embodiment, the measurement circuit 30A or 30B outputs an electrical signal Vout based on the difference between the electrical resistance of the sensing part 11 of the first gas sensor element 10a and the electrical resistance of the sensing part 11 of the second gas sensor element 10b, thereby enabling the acquisition of a signal with reduced influence from disturbance factors.

[0099] [Operation] Next, the operation (processing) of the gas analysis system 100 according to this embodiment will be described. In the operation of the gas analysis system 100 described below, the gas detection method and gas analysis method using the gas detector 101 will be explained.

[0100] Figure 16 is a flowchart showing an example of the operation of the gas analysis system 100 according to this embodiment.

[0101] As shown in Figure 16, first, the flow path control unit 50 simultaneously flows the first gas and the second gas into the first flow path 20a and the second flow path 20b, respectively (step S11). The flow path control unit 50 simultaneously drives, for example, an intake pump 51 located in the middle of the first flow path 20a and an intake pump 51 located in the middle of the second flow path 20b, thereby flowing the first gas into the first flow path 20a and the second gas into the second flow path 20b. As a result, the first gas sensor element 10a is exposed to the first gas and the second gas sensor element 10b is exposed to the second gas.

[0102] In step S11, for example, first and second gases with the same humidity are used. This ensures that the first gas sensor element 10a and the second gas sensor element 10b are affected by humidity in the same way, thus eliminating the effect of humidity from the electrical signal Vout output by the measurement circuit 30.

[0103] Furthermore, in step S11, for example, a gas containing odor molecules emitted from the test sample is used as the first gas, and a gas containing odor molecules emitted from a normal test sample is used as the second gas. As a result, if the test sample is abnormal, a change occurs in the electrical signal Vout, allowing the gas detector 101 to easily detect the abnormal product. The test sample is not particularly limited as long as it is a test sample in which the composition of odor molecules contained in normal and abnormal products is known to be different, but examples include food, pharmaceuticals, cosmetics, industrial gases and fuels.

[0104] Figure 17 is a schematic diagram illustrating examples of the first and second gases. As shown in Figure 17, the second gas is always a gas containing molecules emitted from a normal test sample. On the other hand, the first gas is sequentially supplied with gases containing odor molecules emitted from each of the multiple test samples, from test sample 1 to test sample N (where N is an integer greater than or equal to 2). For example, the multiple test samples are transported by a conveyor belt or the like, and the gases containing odor molecules emitted from test sample 1 to test sample N are sequentially supplied to the gas detector 101 as the first gas.

[0105] In step S11, a gas containing the target molecule may be used as the first gas, and a gas with a lower concentration of the target molecule than the first gas may be used as the second gas. The concentration of the target molecule in the second gas may be zero. For example, by positioning the intake port 21a closer to the source of the target molecule than the intake port 21b, the concentration of the target molecule in the second gas can be made lower than that of the first gas. In this case, a reference gas may be used as the second gas with a lower concentration of the target molecule than the first gas. The reference gas is a gas that does not contain the target molecule and serves as a standard for measurement. Here, "does not contain the target molecule" means that it is substantially absent, and the concentration of the target molecule in the reference gas does not have to be zero as long as it does not affect the analysis. For example, the concentration of the target molecule in the reference gas is below the detection limit of the gas sensor element 10. Also, the composition of the reference gas does not substantially change during measurement. Furthermore, the reference gas is a gas composed of molecules that are less likely to be adsorbed by the sensing part 11 than the target molecule. Furthermore, when using a reference gas as the second gas, the first gas may be a gas in which the target molecule is mixed with the reference gas.

[0106] Referring again to Figure 16, the signal processing circuit 70 then acquires the electrical signal Vout output by the measurement circuit 30 (step S12). The signal processing circuit 70 acquires the electrical signal Vout output by the measurement circuit 30 while the flow path control unit 50 is simultaneously flowing the first gas and the second gas through the first flow path 20a and the second flow path 20b, respectively. The signal processing circuit 70 converts the electrical signal Vout into a digital signal by AD conversion and outputs it to the analysis unit 80 as waveform data of the electrical signal Vout. The signal processing circuit 70 may output the waveform data to an external device instead of the analysis unit 80.

[0107] During the period in which the electrical signal Vout output by the measurement circuit 30 is acquired, the temperature control unit 40 may control the temperatures of the first gas sensor element 10a and the second gas sensor element 10b with the same temperature change pattern. This causes a change in the adsorption state of the target molecule to the sensing part 11 of the first gas sensor element 10a and the second gas sensor element 10b, changing the characteristics of the sensing part 11 of the first gas sensor element 10a and the second gas sensor element 10b, and thus an electrical signal Vout that changes according to the adsorption of the target molecule can be obtained.

[0108] The method for changing the adsorption state of the target molecule to the sensing element 11 is not limited to temperature changes by the temperature control unit 40. For example, the flow path control unit 50 may change the adsorption state of the target molecule to the sensing element 11 by changing the flow rates of the first gas and the second gas by controlling the intake pump 51. Alternatively, the adsorption state of the target molecule to the sensing element 11 may be changed by flowing a reference gas into the sensor housing spaces 22a and 22b from another intake port (not shown). In this case, the gas detector 101 includes, for example, a switching valve (not shown) that switches the gas flowing into the sensor housing space 22a between the reference gas and the first gas, and a switching valve that switches the gas flowing into the sensor housing space 22a between the reference gas and the second gas. These switching valves are controlled, for example, by the flow path control unit 50. When the adsorption state of the target molecule to the sensing element 11 is changed by the flow path control unit 50, the gas detector 101 does not need to be equipped with a temperature control unit 40 and a temperature control element 41.

[0109] Next, the analysis unit 80 analyzes the first gas based on the waveform data of the electrical signal Vout output from the signal processing circuit 70 (step S13). For example, the analysis unit 80 extracts one or more features from the waveform data and outputs the analysis result of the first gas using a trained logic model stored in memory 90, with the extracted one or more features as input. The analysis result of the first gas is, for example, whether or not a specific molecule is contained in the first gas (i.e., whether or not the target molecule to be detected contained in the first gas is a specific molecule), the identification result of the target molecule to be detected contained in the first gas, the concentration of the target molecule to be detected in the first gas, the determination result of whether or not the test sample is normal, or the determination result of the odor of the first gas. The analysis unit 80 may also identify odor molecules as part of the analysis of the first gas. In this case, the analysis result of the first gas is, whether or not the target odor molecule is contained in the first gas, the type of odor molecule contained in the first gas, or the determination result of the odor of the first gas. Note that the analysis by the analysis unit 80 is not limited to the example using a trained logic model. For example, the analysis unit 80 may use a gas containing odor molecules emitted from the test sample as the first gas, and a gas containing odor molecules emitted from a normal test sample as the second gas, and determine whether the electrical signal Vout exceeds a predetermined threshold to analyze whether the test sample is defective.

[0110] As described above, in the gas detection method using the gas detector 101, the first gas and the second gas are simultaneously flowed through the first channel 20a and the second channel 20b, respectively, so that the first gas sensor element 10a and the second gas sensor element 10b are simultaneously exposed to different gases. Furthermore, in the gas detection method using the gas detector 101, an electrical signal Vout is obtained based on the difference between the characteristics of the sensing part 11 of the first gas sensor element 10a and the characteristics of the sensing part 11 of the second gas sensor element 10b, which are output by the measurement circuit 30. Since the first gas sensor element 10a and the second gas sensor element 10b have the same configuration, disturbance factors are canceled out by taking the difference between the characteristics of the sensing part 11 of the first gas sensor element 10a and the characteristics of the sensing part 11 of the second gas sensor element 10b. Therefore, an electrical signal Vout can be obtained in which the influence of disturbance factors other than the difference between the first gas and the second gas is reduced.

[0111] [Differentiation] Next, a modified example of the embodiment will be described. In the following description of the modified example, the differences from the above embodiment will be the main focus, and the similarities will be omitted or simplified.

[0112] Figure 18 is a schematic plan view showing an example of the configuration of the gas detector 101A according to this modified example. The gas analysis system according to this modified example has a configuration in which the gas detector 101 in the gas analysis system 100 is replaced with the gas detector 101A.

[0113] As shown in Figure 18, the gas detector 101A according to this modified example differs from the gas detector 101 according to the embodiment mainly in that it has a first flow path 120a, a second flow path 120b, and a third flow path 20c instead of the first flow path 20a and the second flow path 20b, and that the intake pump 51 is provided in the middle of the third flow path 20c. Furthermore, the gas detector 101A according to this modified example also differs from the gas detector 101 according to the embodiment in that it further includes a plurality of check valves 54a, 55a, 54b, and 55b. In the example shown in Figure 18, the plurality of first gas sensor elements 10a and the plurality of second gas sensor elements 10b are provided on the same substrate 15, and at least one of heating and cooling is performed collectively by a single temperature control element 41. However, as shown in Figure 2, the plurality of first gas sensor elements 10a and the plurality of second gas sensor elements 10b may be provided on different substrates 15, and at least one of heating and cooling may be performed by individual temperature control elements 41.

[0114] Multiple first gas sensor elements 10a are arranged in the first flow path 120a. The first gas flows through the first flow path 120a. In the example shown in Figure 18, the first flow path 120a includes an intake port 21a through which the first gas is drawn in, and a sensor housing space 22a through which the first gas drawn in at the intake port 21a passes and through which multiple first gas sensor elements 10a are arranged. Unlike the first flow path 20a, the first flow path 120a does not include an exhaust port 23a, and the first gas that has passed through the sensor housing space 22a flows into the third flow path 20c. The first flow path 120a is connected to the third flow path 20c via a check valve 55a located downstream of the sensor housing space 22a.

[0115] Multiple second gas sensor elements 10b are arranged in the second flow path 120b. The second gas flows through the second flow path 120b. In the example shown in Figure 18, the second flow path 120b includes an intake port 21b through which the second gas is drawn in, and a sensor housing space 22b through which the second gas drawn in at the intake port 21b passes and through which multiple second gas sensor elements 10b are arranged. Unlike the second flow path 20b, the second flow path 120b does not include an exhaust port 23b, and the second gas that has passed through the sensor housing space 22b flows into the third flow path 20c. The second flow path 120b is connected to the third flow path 20c via a check valve 55b located downstream of the sensor housing space 22b.

[0116] In the example shown in Figure 18, the first channel 120a and the second channel 120b have shapes that are symmetrical to each other.

[0117] The third flow path 20c includes a branch section 24c that branches off to connect to the first flow path 120a and the second flow path 120b, and an exhaust port 23c through which the first gas that has passed through the sensor housing space 22a and the second gas that has passed through the sensor housing space 22b are exhausted.

[0118] The check valve 54a is provided in the first flow path 120a between the intake port 21a and the sensor housing space 22a. The check valve 54a prevents the first gas from flowing from the sensor housing space 22a into the intake port 21a.

[0119] The check valve 54b is installed in the second flow path 120b between the intake port 21b and the sensor housing space 22b. The check valve 54b prevents the second gas from flowing from the sensor housing space 22b into the intake port 21b.

[0120] The check valve 55a is installed between the first flow path 120a and the third flow path 20c. The check valve 55a connects the first flow path 120a and the third flow path 20c, and prevents the inflow of the first gas and the second gas from the third flow path 20c into the first flow path 120a.

[0121] The check valve 55b is installed between the second flow path 120b and the third flow path 20c. The check valve 55b connects the second flow path 120b and the third flow path 20c. The check valve 55b prevents the inflow of the first gas and the second gas from the third flow path 20c into the second flow path 120b.

[0122] Note that the gas detector 101A does not necessarily have to be equipped with check valves 54a and 54b. Also, the gas detector 101 described above may be equipped with check valves 54a and 54b.

[0123] The gas detector 101A is equipped with one intake pump 51. In the gas detector 101A, the intake pump 51 is located in the middle of the third flow path 20c. In the example shown in Figure 18, the intake pump 51 is located between the branch section 24c and the exhaust port 23c. When the intake pump 51 operates, the first gas is drawn in from the intake port 21a, passes through the sensor housing space 22a, and is exhausted from the exhaust port 23c. When the intake pump 51 operates, the second gas is drawn in from the intake port 21b, passes through the sensor housing space 22b, and is exhausted from the exhaust port 23b. When the intake pump 51 operates, the first gas and the second gas flow at the same flow rate through the first flow path 120a and the second flow path 120b, respectively.

[0124] In the gas detector 101A, since both the first and second gases are exhausted from the third flow path 20c, a portion of the flow path for the first gas and the flow path for the second gas can be shared, allowing the gas detector 101A to be miniaturized. Furthermore, since both the first and second gases are drawn in by the same intake pump 51, differences in the flow rates of the first gas and the second gas do not occur due to individual differences in the intake pump 51, making it easy to make the flow rates of the first gas and the second gas the same.

[0125] (Other embodiments) The gas detector, gas detection method, and gas analysis system relating to this disclosure have been described above based on embodiments, but this disclosure is not limited to these embodiments. Without departing from the spirit of this disclosure, various modifications to the embodiments that a person skilled in the art could conceive, as well as other forms constructed by combining some of the components of the embodiments, are also included in the scope of this disclosure.

[0126] Furthermore, for example, the gas analysis system 100 may be implemented with one device or with multiple devices. There are no particular restrictions on how the components of the gas analysis system 100 are distributed among multiple devices. Also, if the gas analysis system 100 is implemented with multiple devices, communication between the devices may be wired or wireless. Furthermore, communication between devices may be conducted via a wide-area communication network such as the Internet.

[0127] Furthermore, in the above embodiment, the processing performed by a specific processing unit may be performed by another processing unit. Also, the order of multiple processing units may be changed, or multiple processing units may be executed in parallel.

[0128] For example, the processing described in the above embodiment may be implemented by centralized processing using a single device (system), or by distributed processing using multiple devices. Furthermore, the processor executing the above program may be single or multiple. That is, centralized processing may be performed, or distributed processing may be performed.

[0129] Furthermore, for example, in the above embodiment, all or part of the components of the gas analysis system according to this disclosure may be made up of dedicated hardware, or they may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as an HDD or semiconductor memory.

[0130] Furthermore, the components of the gas analysis system relating to this disclosure may consist of one or more electronic circuits. Each of these electronic circuits may be a general-purpose circuit or a dedicated circuit.

[0131] One or more electronic circuits may include, for example, semiconductor devices, ICs (Integrated Circuits), or LSIs (Large Scale Integrations). ICs or LSIs may be integrated on a single chip or on multiple chips. While referred to here as ICs or LSIs, the terminology may vary depending on the degree of integration; they might also be called system LSIs, VLSIs (Very Large Scale Integrations), or ULSIs (Ultra Large Scale Integrations). Furthermore, FPGAs (Field Programmable Gate Arrays), which are programmed after the LSI is manufactured, can also be used for the same purpose.

[0132] Furthermore, the general or specific embodiments of this disclosure may be implemented as a system, apparatus, method, integrated circuit, or computer program. Alternatively, they may be implemented as a computer-readable non-temporary recording medium such as an optical disk, HDD, or semiconductor memory on which the computer program is stored. They may also be implemented as any combination of a system, apparatus, method, integrated circuit, computer program, and recording medium.

[0133] For example, this disclosure may be implemented as a gas detection method or gas analysis method executed by a computer, such as in a gas analysis system, or as a program for causing a computer to execute such a gas detection method or gas analysis method. Furthermore, this disclosure may be implemented as a computer-readable non-temporary recording medium on which such a program is recorded, or as a program product containing such a program. [Industrial applicability]

[0134] The gas detector, gas detection method, and gas analysis system relating to this disclosure are useful for systems that detect or analyze molecules contained in gas, and can be used, for example, for the analysis of various odor molecules emitted from food, the human body, or buildings. [Explanation of symbols]

[0135] 10 Gas sensor element 10a First gas sensor element 10b Second gas sensor element 11 Sensing part 12 electrodes 15 circuit boards 20a, 120a First channel 20b, 120b Second channel 20c Third channel 21a, 21b Air intake 22a, 22b Sensor housing space 23a, 23b, 23c Exhaust ports 24c branching point 30, 30A, 30B measurement circuits 31 Bridge Circuit 31a, 31b Resistor elements 32 Amplifier Circuits 40 Temperature control unit 41 Temperature control element 50 Flow channel control unit 51 Intake pump 54a, 54b, 55a, 55b Check valves 60 Circuit boards 61 cabinets 70 Signal Processing Circuits 80 Analysis Department 90 memory 100 Gas Analysis System 101, 101A Gas Detectors Nodes N0, N1, and N2

Claims

1. A plurality of gas sensor elements, each having a sensitive portion whose electrical or physical properties change in response to the adsorption of molecules, comprising: a first gas sensor element and a second gas sensor element having the same configuration as the sensitive portion of the first gas sensor element, A first flow path through which a first gas flows and in which the first gas sensor element is located, A second gas flows through a second channel through which the second gas sensor element is located, The system includes a measurement circuit that outputs an electrical signal based on the difference between the characteristics of the sensing portion of the first gas sensor element and the characteristics of the sensing portion of the second gas sensor element. Gas detector.

2. The system further includes a temperature control unit that controls the temperature of the plurality of gas sensor elements, The temperature control unit controls the first gas sensor element and the second gas sensor element to the same temperature. The gas detector according to claim 1.

3. The system further includes a flow path control unit that controls the flow rate of the first gas in the first flow path and the flow rate of the second gas in the second flow path. The flow path control unit controls the flow rate of the first gas in the first flow path and the flow rate of the second gas in the second flow path to be the same. The gas detector according to claim 1.

4. The aforementioned characteristic is electrical resistance, The measurement circuit includes a voltage divider circuit in which the first gas sensor element and the second gas sensor element are connected in series. The gas detector according to claim 1.

5. The aforementioned characteristic is electrical resistance, The measurement circuit includes a bridge circuit that includes the first gas sensor element and the second gas sensor element as resistive elements, and an amplifier circuit that amplifies the output of the bridge circuit. The gas detector according to claim 1.

6. A gas detection method using a gas detector according to any one of claims 1 to 5, The first gas and the second gas are flowed simultaneously through the first and second flow paths, respectively. The electrical signal output by the measurement circuit is acquired. Gas detection method.

7. Using the first and second gases having the same humidity, The gas detection method according to claim 6.

8. As the first gas, a gas containing odor molecules emitted from the test sample is used. As the second gas, a gas containing odor molecules emitted from a normal sample of the test sample is used. The gas detection method according to claim 6.

9. As the first gas, a gas containing the molecule to be detected is used. As the second gas, a gas is used in which the concentration of the target molecule is lower than that of the first gas. The gas detection method according to claim 6.

10. A gas detector according to any one of claims 1 to 5, The system includes an analysis unit that analyzes the first gas based on the aforementioned electrical signal. Gas analysis system.

11. The analysis unit identifies molecules contained in the first gas. The gas analysis system according to claim 10.

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