Gas analysis method and gas analysis system

Abstract

This gas analysis method is for analyzing a sample gas containing an analyte molecule by using a gas sensor having an electrical characteristic value that changes in response to adsorption of a molecule, the gas sensor being arranged within an accommodation unit. The gas analysis method comprises: an acquisition step (S12) for acquiring a signal indicating the electrical characteristic value outputted by the gas sensor in a predetermined measurement period at least a part of which includes a period during which the sample gas flows inside the accommodation unit; a correction step (S13) for correcting information pertaining to the signal acquired in the acquisition step on the basis of the flow rate of the sample gas flowing through the accommodation unit measured by a flow meter in the predetermined measurement period; and an analysis step (S14) for analyzing the sample gas on the basis of the information that was corrected in the correction step.

Description

Gas analysis method and gas analysis system

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

[0002] Gas sensors whose electrical characteristics change in response to molecular adsorption are used in gas analysis, such as gas odor analysis, by exposing the gas sensor to a sample gas containing target molecules.

[0003] For example, Patent Document 1 discloses an odor measuring device that introduces a gas to be measured into an odor sensor using a pump that is connected to a measurement cell and keeps the gas flow rate constant.

[0004] Patent No. 3131958

[0005] The present disclosure provides a gas analysis method and a gas analysis system that can suppress a decrease in analysis accuracy.

[0006] A gas analysis method according to one aspect of the present disclosure is a gas analysis method for analyzing a sample gas containing target molecules using a gas sensor whose electrical characteristic value changes in response to molecular adsorption and which is arranged in a storage unit, and includes an acquisition step of acquiring a signal indicating the electrical characteristic value output by the gas sensor during a predetermined measurement period that includes at least a portion of the period during which the sample gas flows through the storage unit, a correction step of correcting information about the signal acquired in the acquisition step based on the flow rate of the sample gas flowing through the storage unit measured by a flow meter during the predetermined measurement period, and an analysis step of analyzing the sample gas based on the information corrected in the correction step.

[0007] A gas analysis system according to one aspect of the present disclosure includes a gas sensor whose electrical characteristic value changes in response to molecular adsorption, a storage unit in which the gas sensor is disposed, a pump that flows sample gas into the storage unit, a flow meter that measures the flow rate of the sample gas flowing through the storage unit, an acquisition unit that acquires a signal indicating the electrical characteristic value output by the gas sensor during a predetermined measurement period that includes at least a portion of the period during which the sample gas flows through the storage unit, a correction unit that corrects information about the signal acquired by the acquisition unit based on the flow rate of the sample gas flowing through the storage unit measured by the flow meter during the predetermined measurement period, and an analysis unit that analyzes the sample gas based on the information corrected by the correction unit.

[0008] These comprehensive or specific aspects may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM (Compact Disc-Read Only Memory), or may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0009] According to the present disclosure, it is possible to suppress a decrease in the analytical accuracy of gas analysis.

[0010] FIG. 1 is a block diagram showing a schematic configuration of a gas analysis system according to an embodiment. FIG. 2 is a top view showing an example of a gas sensor according to an embodiment. FIG. 3 is a schematic diagram showing an example of a configuration of an exposure unit according to an embodiment. FIG. 4 is a diagram showing an example of a signal output from a gas sensor. FIG. 5 is a diagram showing another example of a signal output from a gas sensor. FIG. 6 is a diagram showing a relationship between a flow rate of a sample gas and a feature amount. FIG. 7 is a diagram showing a relationship between feature 1 and feature 2 before correction of the feature amount. FIG. 8 is a diagram showing a relationship between feature 1 and feature 2 after correction of the feature amount. FIG. 9 is a flowchart showing an example of operation of the gas analysis system according to an embodiment. FIG. 10 is a timing chart showing an example of operation of an intake pump and a temperature controller during a measurement period. FIG. 11 is a block diagram showing a schematic configuration of a gas analysis system according to a modified embodiment. FIG. 12 is a schematic diagram showing an example of a configuration of an exposure unit according to a modified embodiment. FIG. 13 is a timing chart showing an example of operation of an intake pump and a three-way solenoid valve during a measurement period.

[0011] (How an Aspect of the Present Disclosure Was Achieved) Before describing specific embodiments of the present disclosure, how an aspect of the present disclosure was achieved will be described. The present inventors have discovered that the following problems arise in gas analysis using a gas sensor.

[0012] As described above, a gas sensor whose electrical characteristic value changes in response to molecular adsorption outputs a signal indicating the electrical characteristic value. When such a gas sensor is used for gas analysis, for example, a signal output from the gas sensor exposed to a sample gas containing target molecules is acquired, and the sample gas is analyzed using feature quantities extracted from the acquired signal. In this case, for example, the gas sensor is exposed to the sample gas by flowing the sample gas into a housing that houses the gas sensor. The technology described in Patent Document 1 claims that odor measurement can be performed without being affected by fluctuations in the gas flow rate by using a pump to maintain a constant gas flow rate.

[0013] However, even when using a pump to flow gas into the storage unit, as in the technology described in Patent Document 1, the gas flow rate can vary due to individual differences in the pump, a decrease in pump output, and changes in the flow path condition, such as blockages. While a method of controlling the gas flow rate using a pump through feedback control using the flow rate of the gas flowing through the storage unit when the gas flow rate changes is conceivable, this requires the introduction of a flow rate adjustment mechanism into the pump and an additional control circuit for feedback control, resulting in increased cost and size. Furthermore, it may not be possible to control the gas flow rate to the desired value, for example, if the pump itself deteriorates or if the flow rate needs to be adjusted beyond the capacity of the pump's flow rate adjustment mechanism. Changes in the flow rate of the sample gas flowing through the storage unit also change the output from the gas sensor, leading to a decrease in the accuracy of gas analysis. In particular, when performing analyses such as identifying odor molecules, it is necessary to detect slight differences in the gas sensor output due to differences in molecular species, and changes in the gas sensor output due to gas flow rate can significantly reduce the identification accuracy.

[0014] Therefore, the present disclosure provides a gas analysis method and a gas analysis system that can suppress a decrease in analysis accuracy even when the flow rate of gas flowing inside a housing that houses a gas sensor changes.

[0015] (Summary of the Present Disclosure) As an overview of the present disclosure, examples of a gas analysis system and a gas analysis method according to the present disclosure will be described below.

[0016] For example, a gas analysis method according to a first aspect of the present disclosure is a gas analysis method for analyzing a sample gas containing target molecules using a gas sensor whose electrical characteristic value changes in response to molecular adsorption and which is arranged in a storage unit, and includes: an acquisition step for acquiring a signal indicating the electrical characteristic value output by the gas sensor during a predetermined measurement period that includes at least a portion of a period during which the sample gas flows through the storage unit; a correction step for correcting information about the signal acquired in the acquisition step based on the flow rate of the sample gas flowing through the storage unit measured by a flow meter during the predetermined measurement period; and an analysis step for analyzing the sample gas based on the information corrected in the correction step.

[0017] As a result, in the correction step, information about the signal acquired in the acquisition step is corrected based on the flow rate of the sample gas. Therefore, even if the flow rate of the sample gas flowing through the container during a predetermined measurement period differs from the expected flow rate, the influence of the flow rate on the analysis results can be reduced by performing analysis using the corrected information. Therefore, according to the gas analysis method of this embodiment, a decrease in analysis accuracy can be suppressed. Furthermore, since there is no need to use a mechanism for accurately controlling the flow rate of the sample gas, the configuration of the analysis device can be simplified.

[0018] Furthermore, for example, a gas analysis method according to a second aspect of the present disclosure is the gas analysis method according to the first aspect, wherein during the predetermined measurement period, at least one of heating and cooling of the gas sensor exposed to the sample gas flowing within the container is performed.

[0019] This allows the sample gas to be analyzed by utilizing the difference in molecular adsorption to the gas sensor depending on the temperature.

[0020] Furthermore, for example, a gas analysis method according to a third aspect of the present disclosure is the gas analysis method according to the first or second aspect, wherein the predetermined measurement period includes a period during which the sample gas flows through the storage unit and a period during which a reference gas that does not contain the target molecules flows through the storage unit.

[0021] This allows the output from a gas sensor exposed to a reference gas that does not contain target molecules to be used in analysis, for example, as a reference for extracting feature quantities.

[0022] Furthermore, for example, a gas analysis method according to a fourth aspect of the present disclosure is a gas analysis method according to any one of the first to third aspects, wherein in the correction step, a feature extracted from the signal acquired in the acquisition step is corrected as the information.

[0023] This allows the feature amount extracted from the signal to be corrected, thereby reducing the amount of information to be corrected and the correction process.

[0024] Furthermore, for example, a gas analysis method according to a fifth aspect of the present disclosure is a gas analysis method according to any one of the first to fourth aspects, wherein in the acquisition step, the signal is acquired from the gas sensor arranged in the same housing as the flow meter and a pump that flows the sample gas into the storage section.

[0025] This makes the gas sensor, flow meter, and pump less susceptible to the influence of the external environment, improving analytical accuracy.

[0026] Also, for example, a gas analysis method according to a sixth aspect of the present disclosure is a gas analysis method according to any one of the first to fifth aspects, wherein the acquisition step acquires the signal from the gas sensor via a network.

[0027] This makes it possible to easily acquire a signal from a gas sensor even if the gas sensor is located at a remote location.

[0028] Also, for example, a gas analysis method according to a seventh aspect of the present disclosure is a gas analysis method according to any one of the first to sixth aspects, wherein in the analysis step, the sample gas is analyzed by identifying the target molecules contained in the sample gas.

[0029] This allows the identification of the analyte molecules to be performed using a method that can suppress a decrease in analytical accuracy, that is, it is possible to suppress a decrease in the accuracy of identification of the analyte molecules.

[0030] Furthermore, for example, a gas analysis system according to an eighth aspect of the present disclosure includes a gas sensor whose electrical characteristic value changes in response to molecular adsorption, a storage unit in which the gas sensor is disposed, a pump that flows sample gas into the storage unit, a flow meter that measures the flow rate of the sample gas flowing through the storage unit, an acquisition unit that acquires a signal indicating the electrical characteristic value output by the gas sensor during a predetermined measurement period that includes at least a portion of the period during which the sample gas flows through the storage unit, a correction unit that corrects information related to the signal acquired by the acquisition unit based on the flow rate of the sample gas flowing through the storage unit measured by the flow meter during the predetermined measurement period, and an analysis unit that analyzes the sample gas based on the information corrected by the correction unit.

[0031] This makes it possible to suppress a decrease in analytical accuracy, similar to the gas analysis method according to the first aspect.

[0032] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection forms, steps, step order, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims will be described as optional components.

[0033] Furthermore, in this specification, terms indicating relationships between elements such as parallelism, terms indicating the shapes of elements, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0034] In addition, the drawings are not necessarily strict illustrations, and the same reference numerals are used to designate substantially the same components in the drawings, and redundant explanations are omitted or simplified.

[0035] (Embodiment) [Configuration] First, the configuration of a gas analysis system according to an embodiment will be described.

[0036] FIG. 1 is a block diagram showing a schematic configuration of a gas analysis system 100 according to this embodiment.

[0037] 1 , a gas analysis system 100 according to this embodiment includes a detection device 101 and an analysis device 102. The detection device 101 includes a gas sensor 10, a temperature regulator 20, a flow meter 30, an exposure unit 40, and a control unit 50. The analysis device 102 includes an acquisition unit 60, a correction unit 70, an analysis unit 80, and a memory 90.

[0038] The gas analysis system 100 analyzes the sample gas based on the output of the gas sensor 10 exposed to the sample gas. The sample gas contains analyte molecules to be analyzed, such as volatilized organic compounds. The sample gas may contain multiple types of analyte molecules. The analyte molecules may be inorganic gas molecules such as ammonia, hydrogen sulfide, and carbon monoxide. The sample gas may be, for example, gas collected from food, exhaled breath collected from a human body, air surrounding a human body, or air collected from a room in a building.

[0039] The gas analysis system 100, for example, analyzes a sample gas by identifying target molecules contained in the sample gas. The gas analysis system 100 identifies, for example, which types of molecules are included in the sample gas as target molecules from among multiple types of molecules. The gas analysis system 100 may also be used to identify odors. In this case, the target molecules are, for example, odor molecules, which are organic compounds that become odor components. The gas analysis system 100 may also perform an analysis to identify the concentration of the target molecules contained in the sample gas.

[0040] The gas sensor 10 is a gas sensor whose electrical characteristic value changes in response to the adsorption of molecules to the gas sensor 10 (specifically, a sensitive part 11, which will be described later), and outputs a signal indicating the electrical characteristic value. For example, the gas sensor 10 outputs a signal that changes in response to the concentration of adsorbed molecules. The gas sensor 10 may be, for example, an electrochemical type, a semiconductor type, a field-effect transistor type, a surface acoustic wave type, a quartz oscillator type, or a resistance change type gas sensor.

[0041] Fig. 2 is a top view showing an example of a gas sensor 10 according to the present embodiment. As shown in Fig. 2, the gas sensor 10 includes, for example, a sensitive portion 11 and a pair of electrodes 12 and 13 electrically connected to the sensitive portion 11. In the example shown in Fig. 2, the gas sensor 10 is provided on a substrate 15.

[0042] The sensitive part 11 is, for example, a sensitive film whose electrical resistance, as an electrical characteristic value, changes in response to the adsorption of molecules. A signal indicating the electrical resistance of the sensitive part 11 of the gas sensor 10 is output, for example, as a voltage signal or a current signal via a pair of electrodes 12 and 13. The electrical resistance of the sensitive part 11 between the pair of electrodes 12 and 13 is converted into a voltage signal or a current signal, for example, by a detection circuit (not shown). The electrical resistance of the sensitive part 11 is converted into a voltage using, for example, a bridge circuit, and the voltage is amplified as necessary and output as a signal indicating the electrical resistance of the sensitive part 11. The gas sensor 10 outputs a signal that changes depending on the concentration of molecules adsorbed to the sensitive part 11. The ease of adsorption to the sensitive part 11 varies depending on the type of molecule. Furthermore, if different types of molecules adsorb to the sensitive part 11, the signal output from the gas sensor 10 may differ even for the same adsorption concentration.

[0043] The sensitive part 11 is composed of, for example, a resin material, which is an adsorbent that adsorbs analyte molecules to be analyzed by the gas analysis system 100, and conductive particles dispersed in the resin material. Examples of the resin material include polyalkylene glycol resin, polyester resin, and silicone resin. The resin material is, for example, a material commercially available as a stationary phase for gas chromatography columns. From the standpoint 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, on its side chain. When the resin material adsorbs molecules, the resin material expands, reducing the connections between the dispersed conductive particles and increasing the electrical resistance of the sensitive part 11.

[0044] Furthermore, the sensitive part 11 is not limited to being made of a resin material and conductive particles, but may be any material whose electrical resistance changes upon adsorption of molecules to be analyzed. The sensitive part 11 may be made of, for example, an inorganic material such as a metal oxide, or may be made of porous ceramics.

[0045] The gas analysis system 100 may include multiple gas sensors 10. In this case, the sensitivity characteristics of at least two of the multiple gas sensors 10 are different from each other. The sensitive portions 11 of at least two of the multiple gas sensors 10 are, for example, composed of different types of materials. For example, the types of organic compositions contained in the sensitive portions 11 are different. When the organic compositions are resin materials, different types of materials mean, for example, that at least one of the molecular weight and the composition formula is substantially different. Different types of materials exhibit different adsorption behaviors with respect to the same type of molecule. In other words, at least two of the multiple gas sensors 10 exhibit different molecular adsorption behaviors. In particular, when the materials have different composition formulas, the difference in molecular adsorption behavior is significant. Furthermore, the sensitive portions 11 of all of the multiple gas sensors 10 may be made of different materials. In this case, the multiple gas sensors 10 output different signals when adsorbing the same type of molecule. This allows different features to be extracted from the outputs of the multiple gas sensors 10, thereby improving the identification accuracy when using the gas analysis system 100 to identify molecules.

[0046] 1 , the temperature regulator 20 performs at least one of heating and cooling of the gas sensor 10 (specifically, the sensitive portion 11 of the gas sensor 10). The temperature regulator 20 operates under the control of the control unit 50. The temperature regulator 20 heats or cools the gas sensor 10 with a predetermined output, for example. The temperature regulator 20 may also have a temperature control function for adjusting the temperature of the gas sensor 10 to a predetermined temperature or a predetermined temperature pattern.

[0047] The temperature regulator 20 is, for example, a thermoelectric element that heats and / or cools the gas sensor 10. The temperature regulator 20 may be a heater that only heats, or an element that can heat and cool, such as a Peltier element. The temperature regulator 20 may also be a combination of multiple elements or devices. For example, the temperature regulator 20 may include a heater and a cooling fan to heat and cool the gas sensor 10. The temperature regulator 20 may also be a device that heats the gas sensor 10 via a medium such as a liquid.

[0048] When the temperature of the gas sensor 10 is changed, the state of adsorption of molecules to the sensitive part 11 of the gas sensor 10 changes, and therefore the signal output from the gas sensor 10 also changes. Furthermore, the temperature-dependent change in the state of adsorption of molecules to the sensitive part 11 of the gas sensor 10 differs depending on the type of molecule. For these reasons, by changing the temperature of the gas sensor 10, a signal corresponding to the type and concentration of target molecules contained in the sample gas is output from the gas sensor 10, and the sample gas can be analyzed using this signal.

[0049] The flow meter 30 measures the flow rate of a gas, such as a sample gas, to which the gas sensor 10 is exposed. The flow meter 30 is not particularly limited, and various known flow meters can be used, such as a thermal mass flow meter, an electromagnetic flow meter, an ultrasonic flow meter, an impeller flow meter, and a turbine flow meter. The flow meter 30 outputs information indicating the measured flow rate of the gas to the correction unit 70.

[0050] The exposure unit 40 is an exposure mechanism that exposes the gas sensor 10 to gas under the control of the control unit 50. Fig. 3 is a schematic diagram showing an example of the configuration of the exposure unit 40 according to the present embodiment. As shown in Fig. 3, the exposure unit 40 includes, for example, a housing unit 41, a plurality of pipes 42 and 43, and an intake pump 31. The intake pump 31 is an example of a pump.

[0051] The accommodation unit 41 is a box-shaped container that accommodates the gas sensor 10 and the temperature regulator 20. In the example shown in Fig. 3, a plurality of gas sensors 10 are arranged in the accommodation unit 41. The plurality of gas sensors 10 are arranged, for example, in an array on the substrate 15. In the example shown in Fig. 3, the temperature regulator 20 is arranged so that the plurality of gas sensors 10 can be heated or cooled collectively. Note that the accommodation unit 41 is not particularly limited as long as it can accommodate the gas sensor 10 and the temperature regulator 20. The accommodation unit 41 may be, for example, a part of a pipe through which a gas flows.

[0052] One end of each of the pipes 42 and 43 is connected to the storage unit 41. When the intake pump 31 is operated, gas flows from one end of the pipe 42 to one end of the pipe 43. In other words, the intake pump 31 causes gas such as sample gas to flow into the storage unit 41. The plurality of gas sensors 10 are arranged in the flow path of the gas flowed by the intake pump 31.

[0053] The pipe 42 is a pipe for drawing in gas such as a sample gas containing molecules to be analyzed from outside the exposure unit 40. For example, by operating the intake pump 31, the sample gas is drawn in through the pipe 42, and the drawn sample gas is introduced into the storage unit 41 and flows inside the storage unit 41. As a result, the gas sensor 10 is exposed to the sample gas flowing inside the storage unit 41. The pipe 42 may be provided with an automatic valve or a valve for blocking the inflow of gas from outside the exposure unit 40 to the storage unit 41.

[0054] 3, the flow meter 30 is provided midway through the pipe 42. The flow meter 30 measures the flow rate of the gas flowing through the pipe 42, thereby measuring the flow rate of the gas flowing within the storage unit 41. There are no particular limitations on the location at which the flow meter 30 is provided, as long as the flow meter 30 can measure the flow rate of the gas flowing within the storage unit 41. For example, the flow meter 30 may be provided at the end of the pipe 42 or midway through or at the end of the pipe 43. Depending on the shape of the storage unit 41, the flow meter 30 may be provided in the storage unit 41.

[0055] The pipe 43 is a pipe for discharging the gas inside the accommodation unit 41. For example, when the intake pump 31 is operated, the sample gas introduced into the accommodation unit 41 is discharged to the outside of the exposure unit 40.

[0056] The intake pump 31 is a pump for introducing gas into the storage unit 41 from the pipe 42 and discharging the introduced gas from the pipe 43. The intake pump 31 is provided midway through the pipe 43. The operation of the intake pump 31 is controlled by the control unit 50. The intake pump 31 may be provided at the end of the pipe 42 or midway through or at the end of the pipe 42.

[0057] The configuration of the exposure unit 40 is not limited to the configuration shown in FIG. 3 , and is not particularly limited as long as it can expose the gas sensor 10 to the sample gas. For example, the exposure unit 40 may be configured to constantly flow a carrier gas into the storage unit 41, mixing the sample gas into the carrier gas. The exposure unit 40 may further include various removal filters for removing moisture or particles from the sample gas, as well as check valves for preventing backflow in the piping. For example, if the exposure unit 40 includes a filter, the flow rate of the sample gas flowing through the storage unit 41 is likely to change due to clogging of the filter, etc. However, in the gas analysis system 100, a correction process described below can be used to suppress a decrease in analysis accuracy due to changes in the flow rate of the sample gas.

[0058] The control unit 50 controls the operation of the temperature regulator 20 and the exposure unit 40. For example, the control unit 50 controls the on / off of the intake pump 31 and the on / off of the heating or cooling of the temperature regulator 20. The control unit 50 may also output information indicating the timing of the operation of the temperature regulator 20 and the exposure unit 40 to the acquisition unit 60 and the correction unit 70.

[0059] As shown in FIG. 3 , the detection device 101 further includes a housing 49 in which the gas sensor 10, the flow meter 30, and the intake pump 31 are disposed. That is, the gas sensor 10 is disposed in the same housing 49 as the flow meter 30 and the intake pump 31. This reduces the influence of the external environment on the gas sensor 10, the flow meter 30, and the intake pump 31, thereby improving analysis accuracy. For example, the exposure unit 40 is disposed in the housing 49 so that only the vicinity of the other end of the pipe 42 and the vicinity of the other end of the pipe 43 of the exposure unit 40 are exposed to the outside of the housing 49. In the example shown in FIG. 3 , the control unit 50 is also disposed in the housing 49. Note that at least one of the gas sensor 10, the flow meter 30, the intake pump 31, and the control unit 50 may be disposed outside the housing 49. Alternatively, the detection device 101 may not include the housing 49, and the exposure unit 40, the flow meter 30, and the control unit 50 may be disposed on a substrate, for example.

[0060] Referring back to FIG. 1 , the acquisition unit 60 acquires a signal output from the gas sensor 10, which indicates an electrical characteristic value of the sensitive part 11 of the gas sensor 10. For example, the acquisition unit 60 acquires the signal output from the gas sensor 10 during a predetermined measurement period that includes at least a portion of a period during which the sample gas flows through the accommodation unit 41. The signal output from the gas sensor 10 during the predetermined measurement period is a signal for analyzing the sample gas. The acquisition unit 60 may extract a feature value from the acquired signal. Examples of the feature value include the magnitude (i.e., signal value) of the acquired signal at a certain point in time, the amount and rate of change of the signal over a certain period, and the waveform slope. The extraction of the feature value may be performed by the correction unit 70 or the analysis unit 80. Furthermore, multiple feature values ​​may be extracted from the signal.

[0061] The correction unit 70 corrects the information about the signal acquired by the acquisition unit 60 based on the flow rate of the sample gas flowing through the accommodation unit 41 measured by the flowmeter 30 during a predetermined measurement period. The information about the signal acquired by the acquisition unit 60 is, for example, a feature extracted from the signal acquired by the acquisition unit 60. The information about the signal acquired by the acquisition unit 60 may be waveform data of the signal. The waveform data of the signal is data indicating the signal value of the signal over time. The correction unit 70 performs the correction using, for example, a correction parameter indicating the relationship between the temperature of the gas sensor 10 and the information about the signal acquired by the acquisition unit 60. Furthermore, when there are multiple gas sensors 10, the correction unit 70 applies individual correction parameters, etc. to each of the multiple gas sensors 10 to correct the information about the signal acquired by the acquisition unit 60.

[0062] The analysis unit 80 analyzes the sample gas based on the information corrected by the correction unit 70. For example, the analysis unit 80 identifies target molecules contained in the sample gas as part of its analysis of the sample gas. For example, if the information corrected by the correction unit 70 is a feature, the analysis unit 80 analyzes the sample gas based on the corrected feature. Furthermore, for example, if the information corrected by the correction unit 70 is waveform data, the analysis unit 80 extracts a feature from the corrected waveform data and analyzes the sample gas based on the extracted feature.

[0063] The analysis unit 80 uses, for example, a trained logical model in analyzing the sample gas. The trained logical model receives, for example, the above-mentioned feature values ​​(the above-mentioned corrected feature values ​​or feature values ​​extracted from the above-mentioned corrected waveform data) corresponding to each gas sensor 10 as input, and outputs the analysis results of the sample gas. The analysis results of the sample gas are, for example, the identification results of the molecules to be analyzed.

[0064] The trained logical model is a logical model for analyzing a sample gas, and the trained logical model receives, for example, the above-described feature quantities as input and outputs the analysis results of the sample gas.

[0065] The trained logical model is constructed by performing machine learning using, for example, a known analysis result and the above-mentioned feature quantities (the above-mentioned corrected feature quantities or feature quantities extracted from the above-mentioned corrected waveform data) when the sample gas that results from the analysis is used as training data. Instead of the above-mentioned feature quantities, feature quantities extracted from the signal output by the gas sensor 10 when the sample gas flows through the storage portion 41 at a predetermined flow rate may be used as training data. For example, a neural network, a random forest, a support vector machine, or a self-organizing map may be used as the logical model in machine learning.

[0066] The analysis unit 80 displays the analysis results on, for example, a display (not shown) provided in the gas analysis system 100. The analysis unit 80 may output the analysis results to the memory 90 and store the analysis results in the memory 90. The analysis unit 80 may also output the analysis results to an external device.

[0067] The memory 90 is a storage device that stores the correction parameters used by the correction unit 70 and the trained logical model used by the analysis unit 80. The memory 90 is realized by, for example, a semiconductor memory.

[0068] The control unit 50, the acquisition unit 60, the correction unit 70, and the analysis unit 80 are realized by a microcomputer or a processor or the like that has built-in programs that perform the above-mentioned and later-described processes. In this case, the control unit 50, the acquisition unit 60, the correction unit 70, and the analysis unit 80 may each be realized by an individual microcomputer or processor or the like, or two or more of these functions may be realized by a single microcomputer or processor or the like. Therefore, the detection device 101 and the analysis device 102 may share one or more microcomputers or processors. Furthermore, the control unit 50, the acquisition unit 60, the correction unit 70, and the analysis unit 80 may each be realized by a dedicated logic circuit that performs the above-mentioned and later-described processes.

[0069] [Experiment to verify the effect of correction] In the gas analysis system 100 according to this embodiment, the correction unit 70 corrects information about the signal acquired by the acquisition unit 60 (e.g., features extracted from the signal) based on the flow rate of the sample gas flowing through the storage unit 41, thereby preventing a decrease in analytical accuracy.

[0070] In this regard, the inventors conducted an experiment in which signals output from a plurality of gas sensors 10 were actually acquired, and verified the effect of correcting information relating to the acquired signals.

[0071] First, in this experiment, two gas sensors 10 with different materials for the sensitive part 11 (specifically, the resin material of the sensitive film) were prepared. These two gas sensors 10 were placed in the housing 41 so that they could be heated by a heater. A sample gas was then flowed into the housing 41, exposing the two gas sensors 10 to the sample gas. Signals output from each of the two gas sensors 10 were acquired during a predetermined measurement period while the sample gas was flowing through the housing 41. The length of the predetermined measurement period was 5 seconds. The heater was turned on for 1 second from the start of the measurement period and for 1 second until the end of the measurement period, and turned off from 1 second to 4 seconds after the start of the measurement period. The flow rate of the sample gas flowing through the housing 41 was controlled, and signals were acquired from the gas sensors 10 at three sample gas flow rates: 100 ml / min, 150 ml / min, and 200 ml / min. In this experiment, the flow rate of the sample gas flowing in the storage unit 41 was controlled, but in the gas analysis system 100, it is not necessary to control the flow rate of the sample gas flowing in the storage unit 41, and for example, the intake pump 31 flows the sample gas into the storage unit 41 with a constant power. Furthermore, the unit for expressing the flow rate is not limited to ml / min, and is not particularly limited as long as it is a unit that expresses the amount of gas moving per unit time.

[0072] The following two types of gas were used as sample gases: Gas off-08: 2,4,6-trichloroanisole (mold odor molecules) + air Gas off-10: 2,6-dichlorophenol (disinfectant odor, chlorine odor molecules) + air

[0073] In this experiment, the operation of acquiring a signal from the gas sensor 10 during the measurement period was performed three times for each level of sample gas flow rate. Therefore, signals were acquired from each of the two gas sensors 10 three times x three levels of sample gas flow rate under the condition of exposure to each sample gas.

[0074] FIG. 4 is a diagram showing an example of a signal output from the gas sensor 10. FIG. 5 is a diagram showing another example of a signal output from the gas sensor 10. FIG. 4 shows a signal output from one of two gas sensors 10 exposed to GAS OFF-08 under three sample gas flow rate conditions. FIG. 5 shows a signal output from one of two gas sensors 10 exposed to GAS OFF-08 and GAS OFF-10 under a sample gas flow rate of 150 ml / min. In FIGS. 4 and 5, the vertical axis represents the sensor value, which is the signal value of the signal output from the gas sensor 10, and the horizontal axis represents the time from the start of the measurement period.

[0075] As shown in Figure 4, the sensor value of the gas sensor 10 changes as the temperature of the gas sensor 10 changes due to turning the heater on and off. This change in sensor value is thought to be due to changes in the state of adsorption of molecules to the sensitive part 11 of the gas sensor 10 and changes in the electrical resistance of the sensitive part 11 due to temperature changes that are not dependent on the state of adsorption of molecules. Also, as shown in Figure 4, when the flow rate of the sample gas is different, the sensor value of the gas sensor 10 also differs. This difference in sensor value is thought to be due to differences in the state of adsorption of molecules to the sensitive part 11 and differences in the temperature of the sensitive part 11 caused by differences in the flow rate of the sample gas.

[0076] 5, the sensor value of the gas sensor 10 also varies depending on the type of odor molecules contained in the sample gas. However, compared to the difference in sensor value due to the flow rate of the sample gas, the difference in sensor value due to the difference in the type of odor molecules contained in the sample gas is small. Therefore, if the sensor value of the gas sensor 10 changes due to a change in the flow rate of the sample gas, it becomes difficult to distinguish the difference in sensor value due to the type of odor molecules contained in the sample gas.

[0077] Next, feature quantities were extracted from the signals acquired in this experiment. The feature quantity used was the value calculated as b-(a+c) / 2, where a is the sensor value at 1 second after the start of the measurement period, b is the sensor value at 2 seconds, and c is the sensor value at 5 seconds (see Figure 4). An approximate formula was then derived for the extracted feature quantity as a function of the sample gas flow rate. Figure 6 shows the relationship between the sample gas flow rate and the feature quantity. Figure 6 shows the average value of the feature quantity for each sample gas flow rate level, without distinguishing between different types of sample gas. In other words, the average value is the average value of the feature quantities extracted from the signals of two types of sample gas × three times. Note that averaging the feature quantities is not required in deriving the approximate formula; the approximate formula may be derived without averaging the feature quantities.

[0078] As shown in Figure 6, there is a correlation between the flow rate of the sample gas and the feature quantity, so if an approximation formula is used in which the feature quantity is a function of the flow rate of the sample gas, it is possible to correct the effect of the flow rate of the sample gas on the feature quantity. In the example shown in Figure 6, the approximation is made with a linear equation of y = αx + β. Since y is the feature quantity and x is the flow rate of the sample gas, the feature quantity can be corrected by the flow rate by using the coefficient α of x as a correction parameter.

[0079] In this experiment, such an approximate formula was derived for each of the two gas sensors 10. That is, a correction parameter (coefficient α) corresponding to each of the two gas sensors 10 was determined.

[0080] Next, the effect of correction using the coefficient α determined as described above will be described. The feature amount was corrected using the following formula.

[0081] Corrected feature quantity = Uncorrected feature quantity + (Reference sample gas flow rate - Sample gas flow rate) × α

[0082] In this experiment, the reference sample gas flow rate was 150 ml / min. That is, when the sample gas flow rate was 150 ml / min, the pre-correction feature amount was used as the post-correction feature amount. When the sample gas flow rate was 100 ml / min, 50α was added to the pre-correction feature amount to obtain the post-correction feature amount. When the sample gas flow rate was 200 ml / min, 50α was subtracted from the pre-correction feature amount to obtain the post-correction feature amount.

[0083] In verifying the effect of the correction, first, the feature quantity extracted from the sensor value of one of the two gas sensors 10 was designated as feature 1, and the feature quantity extracted from the sensor value of the other of the two gas sensors 10 was designated as feature 2. Then, the correlation between feature 1 and feature 2 before and after feature correction was confirmed. FIG. 7 is a diagram showing the relationship between feature 1 and feature 2 before feature correction. FIG. 8 is a diagram showing the relationship between feature 1 and feature 2 after feature correction.

[0084] As shown in FIG. 7 , before the feature correction, there is a large variation in the plotted points corresponding to each sample gas, and the correlation between feature 1 and feature 2 is low. This is because the feature includes features extracted from sensor values ​​obtained when the flow rates of the sample gases flowing through the storage section 41 are different. Furthermore, the range in which the plots for the case in which the gas sensor 10 is exposed to GAS OFF-08 overlaps with the range in which the plots for the case in which the gas sensor 10 is exposed to GAS OFF-10 exist. Therefore, when attempting to distinguish between GAS OFF-08 and GAS OFF-10, using the feature before correction for analysis is likely to result in erroneous identification due to the difference in the flow rates of the sample gases.

[0085] In contrast, as shown in FIG. 8 , after the feature correction, the plotted points corresponding to each sample gas are closer together than before the correction, and the correlation between feature 1 and feature 2 is high. Furthermore, the range in which the plots exist when the gas sensor 10 is exposed to Gas Off-08 does not overlap with the range in which the plots exist when the gas sensor 10 is exposed to Gas Off-10. Therefore, even when trying to distinguish between Gas Off-08 and Gas Off-10, accurate distinction can be achieved by using the corrected feature in analysis. In other words, it can be seen that by correcting the feature based on the flow rate of the sample gas, degradation of analytical accuracy can be suppressed even when the flow rate of the sample gas differs from the expected flow rate.

[0086] [Operation] Next, the operation (processing) of the gas analysis system 100 according to this embodiment, that is, the gas analysis method, will be described.

[0087] 9 is a flowchart showing an example of the operation of the gas analysis system 100 according to this embodiment. In the following description, step S12 is an example of an acquisition step, step S13 is an example of a correction step, and step S14 is an example of an analysis step.

[0088] 9 , first, the intake pump 31, under the control of the control unit 50, causes a gas to flow into the housing unit 41 in which the gas sensor 10 is disposed (step S11). For example, the intake pump 31 operates under the control of the control unit 50 to cause the sample gas to flow into the housing unit 41. This exposes the gas sensor 10 to the sample gas. For example, the intake pump 31 is driven with a constant power to introduce the sample gas into the housing unit 41 via the piping 42.

[0089] Next, the acquisition unit 60 acquires a signal output from the gas sensor 10 during a predetermined measurement period (step S12). During the measurement period, sample gas flows into the housing 41. During the measurement period, the temperature regulator 20 at least heats and cools the gas sensor 10. As a result, during the measurement period, the gas sensor 10 exposed to the sample gas undergoes at least one of a temperature increase and a temperature decrease. In this case, one of the temperature increases and decreases may be a temperature change resulting from the gas sensor 10 attempting to return to the ambient temperature because no temperature adjustment is performed on the gas sensor 10. The acquisition unit 60 then acquires the signal output from the gas sensor 10 during the measurement period. After acquiring the signal output from the gas sensor 10, the acquisition unit 60 may extract feature quantities from the acquired signal.

[0090] 10 is a timing chart showing an example of the operation of the intake pump 31 and the temperature controller 20 during the measurement period. In FIG. 10, "H" indicates a high level, and "L" indicates a low level.

[0091] "Pump control" in Figure 10 shows a pump control signal used by the control unit 50 to control the operation of the intake pump 31. In the example shown in Figure 10, when the pump control signal is at a high level, the intake pump 31 is turned on, and when the pump control signal is at a low level, the intake pump 31 is turned off. In other words, when the pump control signal is at a high level, the intake pump 31 causes gas to flow into the storage unit 41, and when the pump control signal is at a low level, the intake pump 31 does not cause gas to flow into the storage unit 41. Note that the control for causing gas to flow into the storage unit 41 is not limited to this example, and is not particularly limited.

[0092] Furthermore, "Temperature Control" in FIG. 10 shows a temperature control signal used by the control unit 50 to control the operation of the temperature regulator 20. In the example shown in FIG. 10 , when the temperature control signal is at a high level, the temperature regulator 20 is turned on, and when the temperature control signal is at a low level, the temperature regulator 20 is turned off. For example, if the temperature regulator 20 is a heater, the heater heats the gas sensor 10 to increase the temperature of the gas sensor 10 while the temperature control signal is at a high level, and when the temperature control signal is at a low level, the gas sensor 10 is cooled to decrease the temperature. Note that the control of the temperature regulator 20 is not limited to this example, and is not particularly limited. For example, the temperature regulator 20 may heat the gas sensor 10 when the temperature control signal is at a high level, and the temperature regulator 20 may cool the gas sensor 10 when the temperature control signal is at a low level.

[0093] In the example shown in FIG. 10 , the measurement period Tm begins after the intake pump 31 is turned on. Also, in the example shown in FIG. 10 , the measurement period Tm includes a temperature rise period Th during which the temperature of the gas sensor 10 is raised and a temperature fall period Tc during which the temperature of the gas sensor 10 is lowered. Specifically, the temperature regulator 20 is turned on simultaneously with the start of the measurement period Tm, starting the temperature rise period Th. After a certain time, the temperature regulator 20 is turned off and the temperature falls to the temperature fall period Tc. Then, the temperature regulator 20 is turned on again and the temperature rise period Th continues until the end of the measurement period Tm. Note that the operation of the intake pump 31 and the temperature regulator 20 is not limited to the example shown in FIG. 10 , and is not particularly limited as long as the measurement period Tm includes at least a portion of a period during which the sample gas flows through the storage portion 41. For example, the intake pump 31 may be turned on simultaneously with or after the start of the measurement period Tm. 10 , the number of temperature rise periods Th and temperature fall periods Tc included in the measurement period Tm may be different, and the measurement period Tm may include only one of the temperature rise periods Th and the temperature fall periods Tc. The order of the temperature rise periods Th and the temperature fall periods Tc in the measurement period Tm is not particularly limited. A predetermined period from the start of the measurement period Tm may be a period during which the temperature of the gas sensor 10 remains constant at the ambient temperature.

[0094] 9 , the correction unit 70 then corrects the information about the signal acquired in step S12 based on the flow rate of the sample gas flowing through the storage unit 41 measured by the flowmeter 30 during the measurement period Tm (step S13). The correction unit 70 corrects, for example, feature quantities extracted from the signal as information about the signal acquired in step S12. This reduces the amount of information to be corrected, thereby easing the correction process.

[0095] The feature amount includes, for example, at least one of the amount of change in the signal waveform, the rate of change, the slope, the signal value at a certain point in time, and the calculation results of the signal values ​​at two or more points in time. Furthermore, when multiple feature amounts are extracted, all of the multiple feature amounts may be corrected, or only some of the feature amounts may be corrected.

[0096] Furthermore, the correction unit 70 acquires the flow rate of the sample gas flowing in the storage unit 41 from the flow meter 30 during the measurement period Tm, for example, and corrects the extracted feature amount based on the acquired flow rate of the sample gas flowing in the storage unit 41. The flow rate of the sample gas flowing in the storage unit 41 may be the flow rate at a certain point in time during the measurement period Tm, or may be the average flow rate for at least a portion of the measurement period Tm.

[0097] The correction unit 70 corrects the extracted feature quantities using, for example, correction parameters stored in the memory 90. The correction parameters are parameters that indicate the relationship between the flow rate of the sample gas flowing in the storage unit 41 and information about the signal acquired by the acquisition unit 60. The correction parameters are, for example, coefficients of a function that indicates the relationship between the flow rate of the sample gas flowing in the storage unit 41 and information about the signal acquired by the acquisition unit 60. A specific example of the correction parameters is the coefficient α of a linear expression that indicates the relationship between the flow rate of the sample gas flowing in the storage unit 41 and the feature quantities, which is predetermined by deriving an approximation equation through experiments such as the above-mentioned verification experiment. The correction unit 70 corrects the feature quantities using, for example, the same method as described in the above-mentioned verification experiment. The function for deriving the correction parameters is not limited to linear expressions, but may be a polynomial expression of quadratic or higher order, or may be an exponential, logarithmic, or power expression. Instead of the correction parameters, a correction table for correction may be stored in the memory 90.

[0098] The correction parameters are determined, for example, by conducting a preliminary experiment or the like, based on information such as feature quantities extracted from the signal to be corrected and the target molecules to be analyzed contained in the sample gas. For example, an experiment similar to the above verification experiment is conducted using a sample gas containing the molecules to be identified. Note that the preliminary experiment is not limited to the example of the above verification experiment. For example, in the above verification experiment, the correction parameters were determined based on the feature quantities and the flow rate of the sample gas, but the correction parameters may also be determined based on the sensor value of the gas sensor 10 at a certain point in time and the flow rate of the sample gas.

[0099] The correction unit 70 can also correct waveform data of the signal as information related to the signal acquired in step S12. For example, to correct the waveform data of the signal, the correction may be performed using a correction parameter that indicates the correlation between the flow rate of the sample gas flowing in the accommodation unit 41 and the signal value of the signal output by the gas sensor 10. In this case, the correction may be performed using a common correction parameter throughout the entire measurement period Tm, or the measurement period Tm may be divided into several periods and different correction parameters may be used for each of the divided periods.

[0100] Next, the analysis unit 80 analyzes the sample gas based on the information corrected in step S13 (step S14). The analysis unit 80 uses, for example, the trained logical model stored in memory 90, inputs the feature quantities corrected in step S13, and outputs the analysis results of the sample gas. The analysis results of the sample gas include, for example, whether or not the sample gas contains a specific molecule (i.e., whether or not the analyte molecules contained in the sample gas are specific molecules), the identification results of the analyte molecules contained in the sample gas, the concentration of the analyte molecules in the sample gas, or the odor determination results of the sample gas. The analysis unit 80 may also identify odor molecules as part of the analysis of the sample gas. In this case, the analysis results of the sample gas include whether or not the sample gas contains a target odor molecule, the type of odor molecule contained in the sample gas, or the odor determination results of the sample gas.

[0101] In the operation of the gas analysis system 100 described above, if there are multiple gas sensors 10, for example, the multiple gas sensors 10 are collectively exposed to the sample gas and / or heated and cooled, and in steps S12 and S13, the above operations are performed for each individual gas sensor 10. Then, in step S14, the sample gas is analyzed based on the information corrected in step S13 corresponding to each of the multiple gas sensors 10.

[0102] As described above, the gas analysis method according to this embodiment is a gas analysis method for analyzing a sample gas containing analyte molecules using the gas sensor 10 disposed in the storage unit 41. The gas analysis method includes an acquisition step (step S12), a correction step (step S13), and an analysis step (step S14). In the acquisition step, a signal indicating an electrical characteristic value output by the gas sensor 10 is acquired during a predetermined measurement period that includes at least a portion of a period during which the sample gas flows through the storage unit 41. In the correction step, information about the signal acquired in the acquisition step is corrected based on the flow rate of the sample gas flowing through the storage unit 41 measured by the flow meter 30 during the predetermined measurement period. In the analysis step, the sample gas is analyzed based on the information corrected in the correction step.

[0103] As a result, in the correction step, information about the signal acquired in the acquisition step is corrected based on the flow rate of the sample gas. Therefore, even if the flow rate of the sample gas flowing through the storage unit 41 during a predetermined measurement period differs from the expected flow rate due to individual differences in the intake pump 31, a decrease in the output of the intake pump 31, or changes in the state of the flow path such as clogging, the influence of the flow rate on the analysis results can be reduced by performing analysis using the corrected information. Therefore, the gas analysis method according to this embodiment can suppress a decrease in analytical accuracy. Furthermore, since there is no need to use a mechanism for accurately controlling the flow rate of the sample gas, the configuration of the analysis device can be simplified.

[0104] [Modifications] Next, modifications of the embodiment will be described. In the following description of the modifications, differences from the above embodiment will be mainly described, and descriptions of commonalities will be omitted or simplified.

[0105] Fig. 11 is a block diagram showing a schematic configuration of a gas analysis system 100a according to this modification. Fig. 12 is a schematic diagram showing an example of the configuration of an exposure section 40a according to this modification.

[0106] 11 , a gas analysis system 100a according to this modification has a configuration in which the detection device 101 in the gas analysis system 100 according to the embodiment is replaced with a detection device 101a. The detection device 101a differs from the detection device 101 mainly in that it includes an exposure unit 40a instead of the exposure unit 40 and does not include the temperature regulator 20. Note that the detection device 101a may also include the temperature regulator 20.

[0107] The exposure unit 40a is an exposure mechanism that exposes the gas sensor 10 to a gas under the control of the control unit 50. The control unit 50 controls the exposure of the gas sensor 10 to a gas in an exposure pattern that includes a period during which the gas sensor 10 is exposed to a sample gas and a period during which the gas sensor 10 is exposed to a reference gas, by controlling the exposure unit 40a.

[0108] The reference gas has a different composition from the sample gas and serves as a reference for measurement. The reference gas is a gas that does not contain analyte molecules. Note that "not containing analyte molecules" means that the analyte molecules are substantially absent, and the concentration of the analyte molecules in the reference gas does not have to be zero as long as it is within a range that does not affect the analysis. For example, the concentration of the analyte molecules in the reference gas is below the lower detection limit of the gas sensor 10. Furthermore, the composition of the reference gas does not substantially change with each measurement. Furthermore, the reference gas is, for example, a gas composed of molecules that are less likely to be adsorbed by the sensitive part 11 than the analyte molecules.

[0109] Specific examples of reference gases include industrial or analytical air, inert gases such as nitrogen or rare gases that are substantially free of water molecules and organic compounds, and gases obtained by removing target molecules from sample gas using a filter, etc. By exposing the gas sensor 10 to the reference gas, the signal output from the gas sensor 10 becomes stable for each measurement, and the output from the gas sensor 10 exposed to the reference gas can be used as a reference for extracting feature quantities, for example.

[0110] As shown in FIG. 12, the exposure section 40a includes, for example, a storage section 41a, a three-way electromagnetic valve 22, an intake pump 31, and a plurality of pipes 42a, 43a, 44a, and 45a.

[0111] One end of the pipe 42a is provided with an intake port 46a for introducing a sample gas. The intake port 46a is provided, for example, in a space filled with the sample gas. One end of the pipe 43a is provided with an intake port 46b for introducing a reference gas. The intake port 46b is provided, for example, in a space filled with the reference gas. One end of the pipe 45a is provided with an exhaust port 46e for discharging the introduced sample gas and reference gas.

[0112] The accommodation unit 41a is a box-shaped container that accommodates a plurality of gas sensors 10. The number of gas sensors 10 accommodated in the accommodation unit 41a may be one. For example, the plurality of gas sensors 10 are arranged in an array on the substrate 15 inside the accommodation unit 41a. One end of a pipe 44a and the other end of a pipe 45a are connected to the accommodation unit 41a. When the intake pump 31 operates, gas flows from one end of the pipe 44a to the other end of the pipe 45a. The plurality of gas sensors 10 are arranged in a flow path through which gas flows.

[0113] The sample gas introduced through the intake port 46a by operating the intake pump 31 is introduced into the interior of the storage section 41a via the piping 42a, the three-way solenoid valve 22, and the piping 44a. The reference gas introduced through the intake port 46b by operating the intake pump 31 is introduced into the interior of the storage section 41a via the piping 43a, the three-way solenoid valve 22, and the piping 44a. The sample gas and reference gas introduced into the interior of the storage section 41a are exhausted from the exhaust port 46e via the piping 45a.

[0114] In the example shown in Fig. 12, the flow meter 30 is provided midway through the pipe 44a. The flow meter 30 measures the flow rate of the gas flowing through the pipe 44a, thereby measuring the flow rate of the gas flowing within the accommodation unit 41a. The location at which the flow meter 30 is provided is not particularly limited as long as the flow meter 30 can measure the flow rate of the gas flowing within the accommodation unit 41a. For example, the flow meter 30 may be provided at the end of the pipe 44a or midway through or at the end of the pipe 45a. Furthermore, depending on the shape of the accommodation unit 41a, the flow meter 30 may be provided in the accommodation unit 41a.

[0115] The three-way solenoid valve 22 is a solenoid valve for switching the gas introduced into the storage section 41a. The three-way solenoid valve 22 has an input port P1 connected to the other end of the pipe 42a, an input port P2 connected to the other end of the pipe 43a, and an output port P3 connected to the other end of the pipe 44a. The three-way solenoid valve 22 has each port controlled to open and close under the control of the control unit 50. The three-way solenoid valve 22 switches between a first state in which the input port P1 and the output port P3 are electrically connected and a second state in which the input port P2 and the output port P3 are electrically connected under the control of the control unit 50. In the first state, the input port P1 and the output port P3 are open, and the input port P2 is closed. In the second state, the input port P2 and the output port P3 are open, and the input port P1 is closed. Note that other switching valves may be used instead of the three-way solenoid valve 22 as long as they can switch the gas introduced into the storage section 41a under the control of the control unit 50.

[0116] The intake pump 31 introduces the sample gas and the reference gas into the storage section 41a and discharges the introduced sample gas and reference gas from the exhaust port 46e. In other words, the intake pump 31 causes the sample gas and the reference gas to flow into the storage section 41a. The intake pump 31 is provided midway through the piping 45a. The operation of the intake pump 31 is controlled by the control section 50.

[0117] With this configuration, when the intake pump 31 is operating and the three-way solenoid valve 22 is in the first state, the sample gas flows through the storage section 41a. As a result, the gas sensor 10 is exposed to the sample gas flowing through the storage section 41a. When the intake pump 31 is operating and the three-way solenoid valve 22 is in the second state, the reference gas flows through the storage section 41a. As a result, the gas sensor 10 is exposed to the reference gas flowing through the storage section 41a. By controlling the three-way solenoid valve 22 in this way, the type of gas flowing through the storage section 41a is switched exclusively.

[0118] In the example shown in FIG. 12, the exposed portion 40a is disposed inside the housing 49 so that only the vicinity of the intake ports 46a, 46b and the vicinity of the exhaust port 46e of the exposed portion 40a are exposed to the outside of the housing 49.

[0119] The configuration of the exposure unit 40a is not limited to the configuration shown in FIG. 12 , and is not particularly limited as long as it can expose the gas sensor 10 to the sample gas and reference gas flowing inside the accommodation unit 41a. For example, the exposure unit 40a may be configured such that the sample gas and reference gas are introduced into the accommodation unit 41a through separate pipes without passing through the three-way solenoid valve 22. The exposure unit 40a may also be configured without the intake pump 31, in which the sample gas is constantly flowing into the accommodation unit 41a as a carrier gas, and the sample gas is mixed into the carrier gas. The exposure unit 40a may further include various removal filters for removing moisture or particles from the sample gas and reference gas, check valves for preventing backflow in the pipes, etc.

[0120] In the gas analysis system 100a, the control unit 50 controls the operation of the exposure unit 40a by controlling the on / off of the intake pump 31 and the opening and closing of each port of the three-way electromagnetic valve 22.

[0121] In the gas analysis system 100a, the operation is the same as that of the gas analysis system 100 described above with reference to FIG. 9, except that the type of gas flowing in the container 41a during a predetermined measurement period is controlled.

[0122] 13 is a timing chart showing an example of the operation of the intake pump 31 and the three-way electromagnetic valve 22 during the measurement period. In FIG. 13, "H" indicates a high level, and "L" indicates a low level.

[0123] In the "Pump Control" section of FIG. 13, similar to FIG. 10, a pump control signal for the control unit 50 to control the operation of the intake pump 31 is shown.

[0124] Furthermore, "Fluid Control" in Figure 13 shows a fluid control signal that the control unit 50 uses to control the type of gas that flows into the storage unit 41a. In the example shown in Figure 13, when the fluid control signal is at a high level, the three-way solenoid valve 22 is in the first state, and the sample gas flows into the storage unit 41a. When the fluid control signal is at a low level, the three-way solenoid valve 22 is in the second state, and the reference gas flows into the storage unit 41a. Note that control of the type of gas that flows into the storage unit 41a is not limited to this example, and is not particularly limited.

[0125] In the example shown in FIG. 13 , the measurement period Tma begins after the intake pump 31 is turned on. Also in the example shown in FIG. 13 , the measurement period Tma includes a sample period Ts during which the sample gas flows through the storage section 41a and a reference period Tr during which the reference gas flows through the storage section 41a. Specifically, at the start of the measurement period Tma, the three-way solenoid valve 22 is in the second state, the reference gas flows through the storage section 41a, and a certain period from the start of the measurement period Tma is the reference period Tr. Then, a certain time after the start of the measurement period Tma, the three-way solenoid valve 22 switches to the first state, and the period switches to the sample period Ts during which the sample gas flows through the storage section 41a. Then, the three-way solenoid valve 22 switches back to the second state, and the period switches to the reference period Tr during which the reference gas flows through the storage section 41a, and this period continues until the end of the measurement period Tma. The operation of the intake pump 31 and the type of gas flowing through the accommodation portion 41a (the operation of the three-way solenoid valve 22) are not limited to the example shown in FIG. 13 , and are not particularly limited as long as the measurement period Tma includes a sample period Ts and a reference period Tr. For example, the intake pump 31 may be turned on simultaneously with or after the start of the measurement period Tma. Furthermore, the number of sample periods Ts and reference periods Tr included in the measurement period Tma may be different from that shown in FIG. 13 . Furthermore, the order of the sample periods Ts and reference periods Tr in the measurement period Tma is not particularly limited. Furthermore, if the detection device 101a includes a temperature regulator 20, the gas sensor 10 may be heated or cooled during at least one of the sample period Ts and the reference period Tr.

[0126] Furthermore, in the gas analysis system 100a, the flow rate of the reference gas flowing in the storage unit 41a during the reference period Tr may be used for the correction in step S13. For example, when correcting waveform data of a signal as information related to the signal acquired in step S12, the flow rate of the reference gas flowing in the storage unit 41a may be used for correcting the signal value during the reference period Tr, and the flow rate of the sample gas flowing in the storage unit 41a may be used for correcting the signal value during the sample period Ts.

[0127] While the gas analysis method and gas analysis system according to the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the gist of the present disclosure, various modifications that a person skilled in the art can conceive of to the embodiments and other forms constructed by combining some of the components of the embodiments are also included in the scope of the present disclosure.

[0128] In each of the above embodiments, the acquisition unit 60 directly acquires the signal output from the gas sensor 10, but this is not limited thereto. For example, in step S12, the acquisition unit 60 may acquire the signal output from the gas sensor 10 via a network. Similarly, in step S13, the correction unit 70 may acquire the flow rate of the sample gas from the flowmeter 30 via a network. In this case, for example, the detection device 101 or 101a and the analysis device 102 each include a communication circuit and communicate with each other via the network. This communication may be wireless or wired. Furthermore, the communication method (communication standard) for this communication is not particularly limited. Furthermore, this communication may be communication via a wide area communication network such as the Internet.

[0129] Furthermore, in the above-described embodiments, a process executed by a specific processing unit may be executed by another processing unit. Furthermore, the order of multiple processes may be changed, or multiple processes may be executed in parallel. Furthermore, the allocation of components included in the gas analysis systems 100 and 100a to multiple devices is an example. Components included in one device may be included in another device. For example, components included in one of the detection device 101 or 101a and the analysis device 102 may be included in the other of the detection device 101 or 101a and the analysis device 102. Furthermore, for example, the gas analysis systems 100 and 100a may be realized by one device, or by three or more devices.

[0130] For example, the processing described in the above embodiments may be realized by centralized processing using a single device (system), or may be realized by distributed processing using multiple devices. Furthermore, the processor that executes the program may be a single processor or multiple processors. That is, centralized processing or distributed processing may be performed.

[0131] Furthermore, for example, in the above-described embodiments, all or some of the components of the gas analysis system according to the present disclosure may be configured with dedicated hardware, or 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 a HDD or semiconductor memory.

[0132] Furthermore, the components of the gas analysis system according to the present disclosure may be configured with one or more electronic circuits, each of which may be a general-purpose circuit or a dedicated circuit.

[0133] The one or more electronic circuits may include, for example, a semiconductor device, an integrated circuit (IC), or a large-scale integration (LSI). The IC or LSI may be integrated on a single chip or on multiple chips. Although the IC or LSI is referred to here as an IC or LSI, the name may vary depending on the degree of integration, and may be called a system LSI, a very large-scale integration (VLSI), or an ultra-large-scale integration (ULSI). A field programmable gate array (FPGA), which is programmed after the LSI is manufactured, can also be used for the same purpose.

[0134] Furthermore, the general or specific aspects of the present disclosure may be realized as a system, an apparatus, a method, an integrated circuit, or a computer program. Alternatively, the general or specific aspects may be realized as a computer-readable non-transitory recording medium such as an optical disk, a HDD, or a semiconductor memory on which the computer program is stored. Alternatively, the general or specific aspects of the present disclosure may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0135] For example, the present disclosure may be realized as a gas analysis method executed by a computer included in a gas analysis system, or as a program for causing a computer to execute such a gas analysis method. Furthermore, the present disclosure may be realized as a computer-readable non-transitory recording medium on which such a program is recorded.

[0136] The gas analysis method and gas analysis system according to the present disclosure are useful for analyzing gases, such as determining air quality or odors and identifying molecules in gases.

[0137] REFERENCE SIGNS LIST 10 Gas sensor 11 Sensing part 12, 13 Electrode 15 Substrate 20 Temperature regulator 22 Three-way solenoid valve 30 Flow meter 31 Intake pump 40, 40a Exposure part 41, 41a Storage part 42, 42a, 43, 43a, 44a, 45a Piping 46a, 46b Intake port 46e Exhaust port 49 Housing 50 Control part 60 Acquisition part 70 Correction part 80 Analysis part 90 Memory 100, 100a Gas analysis system 101, 101a Detection device 102 Analysis device

Claims

1. A gas analysis method for analyzing a sample gas containing an analyte molecule using a gas sensor disposed in a housing, the gas sensor being such that its electrical characteristic value changes according to adsorption of molecules, the method including: an acquisition step of acquiring a signal indicating the electrical characteristic value output by the gas sensor in a predetermined measurement period including at least a part of a period during which the sample gas flows through the housing; a correction step of correcting information regarding the signal acquired in the acquisition step based on the flow rate of the sample gas flowing through the housing measured by a flow meter in the predetermined measurement period; and an analysis step of analyzing the sample gas based on the information corrected in the correction step.

2. The gas analysis method according to claim 1, wherein in the predetermined measurement period, at least one of temperature increase and temperature decrease of the gas sensor exposed to the sample gas flowing through the housing is performed.

3. The gas analysis method according to claim 1, wherein the predetermined measurement period includes a period during which the sample gas flows through the housing and a period during which a reference gas not containing the analyte molecule flows through the housing.

4. The gas analysis method according to any one of claims 1 to 3, wherein in the correction step, as the information, a feature amount extracted from the signal acquired in the acquisition step is corrected.

5. The gas analysis method according to any one of claims 1 to 3, wherein in the acquisition step, the signal is acquired from the gas sensor disposed in the same housing as the flow meter and a pump for flowing the sample gas through the housing.

6. The gas analysis method according to any one of claims 1 to 3, wherein in the acquisition step, the signal is acquired from the gas sensor via a network.

7. The gas analysis method according to any one of claims 1 to 3, wherein in the analysis step, as the analysis of the sample gas, the analyte molecule contained in the sample gas is identified.

8. A gas sensor whose electrical characteristic value changes according to the adsorption of molecules, a housing portion in which the gas sensor is disposed inside, a pump for flowing a sample gas in the housing portion, a flow meter for measuring the flow rate of the sample gas flowing in the housing portion, an acquisition unit for acquiring a signal indicating the electrical characteristic value output by the gas sensor in a predetermined measurement period including at least a part of a period during which the sample gas flows in the housing portion, a correction unit for correcting information regarding the signal acquired by the acquisition unit based on the flow rate of the sample gas flowing in the housing portion measured by the flow meter in the predetermined measurement period, and an analysis unit for analyzing the sample gas based on the information corrected by the correction unit. A gas analysis system.

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