Gas component detection device and gas component measurement system

Abstract

Provided is a gas component inspection device capable of measuring the concentration of a gas component contained in an air flow with higher accuracy. A gas component detection device for detecting a prescribed gas component contained in a gas includes: a gas introduction port for introducing a gas into a container; and a plurality of gas detection elements arranged in the container and exposed to the gas discharged from the gas introduction port, wherein the plurality of gas detection elements are arranged at intervals at positions where distances from the gas introduction port are made different from each other. The concentration of the gas component in the gas is determined by arithmetic processing on the basis of output signals from the plurality of gas detection elements.

Description

Gas component detection device and gas component measurement system

[0001] The present invention relates to a gas component detection device and a gas component measurement system for measuring the concentration of a predetermined gas component contained in a gas.

[0002] In the field of gas component testing devices and gas component measurement systems, one of the most common devices is an alcohol measuring device for measuring the alcohol concentration in breath. In conventional alcohol measuring devices, a sensor unit for detecting alcohol is attached to the end of a pipe that introduces breath, and the subject blows breath into the breath inlet at the other end of the pipe.

[0003] The breath alcohol measuring device shown in Patent Document 1 is a device that has a mouthpiece into which breath is blown, a flow sensor that measures the amount of gas blown into the mouthpiece, and a suction pump that draws gas into an alcohol sensor that measures the alcohol concentration.A portion of the breath blown into the mouthpiece is sucked in by the suction pump and directed to the gas sensor.

[0004] Patent Document 2 discloses a method for an exhaled breath component testing device in which the speaker sound is adjusted in accordance with the detection result of a pressure sensor to inform the subject so that the subject can blow a constant flow rate of exhaled breath.

[0005] Furthermore, Patent Document 3 discloses the configuration of an exhaled breath measurement system in which a flow rate sensor for measuring the amount of exhaled breath is attached inside an exhaust pipe in order to measure accurate gas concentrations.

[0006] JP 2012-159482 A JP 2021-110642 A JP 2022-26622 A

[0007] As in the configurations disclosed in the above-mentioned patent documents, in the prior art, in order to avoid the influence of fluctuations in the exhaled breath flow rate on the gas sensor response, accurate measurement of gas components requires supplying a constant flow rate of gas to the gas sensor that detects the gas. In other words, because the sensor response tends to saturate at a value corresponding to the gas concentration above a certain flow rate, it is necessary to blow exhaled breath at a relatively high flow rate, which makes it difficult to accurately measure gas components contained in a weak airflow, such as the exhaled breath exhaled during natural breathing, or an airflow whose flow rate fluctuates.

[0008] Furthermore, in order to confirm that a constant flow rate of gas is being supplied, gas component testing devices such as breathalyzers are equipped with additional devices such as suction pumps and other sensors other than gas sensors for gas detection, such as pressure sensors and flow sensors. As a result, there are limits to how small the gas component testing device can be made, and it is difficult to make the size of the gas component testing device smaller than the palm of a hand, making it impossible to install the gas component testing device in small, portable information terminals such as smartphones and smartwatches.

[0009] As described above, when measuring gas components in exhaled breath, the strength of the subject's exhalation (flow rate) has a significant effect on the measurement. Furthermore, methods that eliminate the effect of exhalation strength by combining a pressure sensor or flow rate sensor have the problem of increasing the size of the gas component testing device.

[0010] Therefore, the present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a gas component testing device and a gas component measurement system equipped with the same that can measure with high accuracy the concentrations of gas components contained in an airflow, even if the airflow is weak and has a fluctuating flow rate, such as exhaled breath or a gentle breeze. Another object of the present invention is to provide a gas component testing device and a gas component measurement system equipped with the same that can be miniaturized to a size that can be incorporated into a small information terminal such as a smart watch.

[0011] In order to achieve the above-mentioned object, the gas component testing device of the present invention is a gas component detection device that detects a specified gas component contained in a gas, and is characterized in that it comprises a gas inlet for introducing the gas into a container, and a plurality of gas detection elements that are arranged in the container and exposed to the gas released from the gas inlet, and the plurality of gas detection elements are arranged at intervals at positions that are different distances from the gas inlet.

[0012] The gas component measurement system of the present invention is characterized by comprising the gas component inspection device of the present invention described above, and an analysis device that determines the concentration of the gas component in the gas by calculation based on output signals from the plurality of gas detection elements.

[0013] Further features of the present invention will become apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0014] According to the gas component inspection device and gas component measurement system of the present invention, by arranging a plurality of gas detection elements at intervals at positions with different distances from the gas inlet and analyzing and processing the output signals of the plurality of gas detection elements, it is possible to accurately measure the concentration of gas components contained in the gas, regardless of the gas flow rate, even in the case of a particularly weak airflow with a small flow rate or an airflow with a fluctuating flow rate.

[0015] Furthermore, the gas component inspection device and gas component measurement system of the present invention can measure the gas component concentration regardless of the flow rate of the introduced gas, eliminating the need for components for controlling the gas flow rate, such as flow sensors and suction pumps, and making it possible to miniaturize the device.

[0016] 1 is a diagram showing an example of the configuration of a gas component inspection device according to an embodiment of the present invention. FIG. 1 is a diagram showing an example of an arrangement of a plurality of gas detection elements 14. FIG. 2 is a diagram showing the relative arrangement of a gas inlet 12 and a plurality of gas detection elements 14. FIG. 3 is a diagram showing an example of a measurement of the time change in the output signal (sensor response) of a plurality of gas detection elements 14 in the arrangement of FIG. 3. FIG. 4 is a diagram showing an example (map) of the arrangement positions of a plurality of gas detection elements 14 and the distribution of the output signal with respect to elapsed time. FIG. 5 is a diagram showing the output signal (sensor response) of the gas detection element 14 according to the gas flow rate. FIG. 6 is a diagram showing a neural network model of deep learning processing. FIG. 7 is a graph showing the relationship between the output gas flow rate and estimated values ​​of gas component concentration and their respective setting values ​​in a test pattern. FIG. 7 is a diagram showing an example of the configuration of a gas component measurement system according to the present embodiment. FIG. 8 is a diagram showing another example of the configuration of a gas component detection device. FIG. 9 is a diagram showing the results of a fluid simulation.

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments. The embodiments of the present invention will be described with reference to specific drawings.

[0018] 1 is a diagram showing an example of the configuration of a gas component detection device according to an embodiment of the present invention. Gas component detection device 1 is configured to include gas inlet 12 for introducing a gas to be measured, such as exhaled breath, into container 10, and a plurality of gas detection elements (sensors) 14 disposed within container 10.

[0019] In this embodiment, as described in detail below, a plurality of gas detection elements 14 are arranged at different distances from the gas inlet 12, and the concentration of a predetermined gas component in the gas is measured based on the relationship between the arrangement positions of the plurality of gas detection elements 14 and their respective output signals, without being affected by the flow rate of the gas released from the gas inlet 12.

[0020] 1 , gas inlet 12 is an opening for introducing gas into container 10. In a configuration in which an elongated hollow tube 13, through which the gas to be measured flows from the upstream side, communicates with container 10, downstream end opening 13 a of elongated hollow tube 13 serves as gas inlet 12. As shown in FIG. 1 , elongated hollow tube 13 may be configured, for example, such that a portion of its length is inserted into container 10, with downstream end opening 13 a, which serves as gas inlet 12, inserted into container 10. Alternatively, downstream end opening 13 a of elongated hollow tube 13 may be formed as a peripheral hole in container 10 to communicate with container 10, or a peripheral hole drilled in container 10 may serve as the gas inlet without elongated hollow tube 13. Container 10 is provided with gas outlet 17 for discharging the introduced gas. Gas outlet 17 is preferably located along the gas flow path, downstream of the arrangement direction of the multiple gas detection elements 14. Furthermore, there is no problem if multiple gas outlets are provided.

[0021] The gas detection elements 14 are sensor elements that detect specific gas components contained in gas. A plurality of gas detection elements 14 are arranged on a surface of a substrate 15 disposed within the container 10, facing the gas inlet 12, so as to be exposed to the gas released from the gas inlet 12. The gas inlet 12 is oriented so that its central axis is perpendicular to the surface of the substrate 15. A heater 18 is provided when heating is required to drive the gas detection elements 14. The distance (height) H between the gas inlet 12 and the substrate 15 is preferably equal to or less than the opening diameter of the gas inlet 12. Specifically, the arrangement of the plurality of gas detection elements 14 is such that the plurality of gas detection elements 14 are arranged in a row at intervals from each other at positions that are different distances from the gas inlet 12.

[0022] By arranging the multiple gas detection elements 14 at different distances from the gas inlet 12, the flow or diffusion of the gas released from the gas inlet 12 causes the flow rate and timing of the gas reaching and exposing each gas detection element 14 to be different. Specifically, the gas released from the gas inlet 12 is exposed to the gas detection element 14 closest to the gas inlet 12 earliest and at the highest flow rate, and the gas diffuses to reach and expose the gas detection elements 14 in order of closest to the gas inlet 12. The present invention accurately measures the concentrations of gas components by utilizing the differences in the output signals of multiple gas detection elements 14 located at different distances from the gas inlet 12.

[0023] The arranged multiple gas detection elements 14 include individual gas detection elements 14#0, 14#1, 14#2, ..., and in the following description, the set of individual gas detection elements 14#0, 14#01, 14#02, ... will be referred to as multiple gas detection elements 14, and the individual gas detection elements 14#0, 14#01, 14#02, ... may also be referred to as gas detection element 14 when referring to a single gas detection element without distinguishing between them.

[0024] Gas detection element 14#0 at one end of the arranged plurality of gas detection elements 14 is disposed directly below the central axis of gas inlet 12 and closest to gas inlet 12, while adjacent gas detection element 14#1 is disposed at a distance from gas detection element 14#0 and offset from the central axis of gas inlet 12, further away from gas inlet 12 than gas detection element 14#0, and gas detection element 14#2 is disposed adjacent to gas detection element 14#1 and further away from gas inlet 12 than gas detection element 14#1. In this manner, the plurality of gas detection elements 14 are disposed in the same row at predetermined intervals, preferably at equal intervals, so that the distances (lengths) from gas inlet 12 increase in order. Note that gas detection element 14#0 does not have to be directly below the central axis of gas inlet 12, but is disposed at the position closest to gas inlet 12 among the plurality of gas detection elements 14.

[0025] 2 is a diagram showing an example of the arrangement of multiple gas detection elements 14. Fig. 2 schematically shows an example of the arrangement of multiple gas detection elements 14 from the upper surface side of the gas inlet 12, with the individual gas detection elements 14#0, 14#1, 14#2, ... arranged in a line (in the same row) at a predetermined interval L in order of decreasing distance from the gas inlet 12. Each gas detection element 14 is a sensor element that reacts with a predetermined gas component and whose electrical characteristics change depending on its concentration, and is composed of an element body 14a that reacts with the predetermined gas component and electrodes 14b formed on both ends of the element body 14a.

[0026] The gas detection element 14 can be selected from a variety of gas detection elements with various detection methods and materials depending on the gas to be detected, such as a so-called semiconductor sensor that detects reducing gases such as carbon monoxide gas by utilizing the adsorption of oxygen on the surface of a metal oxide such as tin oxide, a so-called catalytic combustion sensor that electrically detects the temperature increase due to contact with a combustible gas, a so-called electrochemical sensor that detects the gas concentration based on the current generated by the oxidation-reduction reaction of the target gas on an electrode, and even a gas sensor using carbon nanotubes or graphene.

[0027] In this embodiment, as an example, a measurement example will be described using an ultrathin sheet-like gas detection element 14 called an Au nanosheet, which has a gold (Au) thin film formed on a substrate to detect hydrogen sulfide (HS) gas.

[0028] The gas detection element 14, an Au nanosheet (Au NS), is a gas sensor that utilizes the phenomenon of resistance change caused by modifying the surface of an Au thin film with a thiol-based self-assembled monolayer. The output signal is a relative change in resistance from the value before gas introduction, depending on the concentration of the gas component. The Au nanosheet is a thin film sheet that can be fabricated on a silicon substrate using an electron beam deposition system. The element body 14a is configured, for example, as a 16 nm gold (Au) single-layer nanosheet with a width of 0.3 mm and a length of 1.5 mm. The electrodes 14b electrically connected to both ends of the element body 14a are gold (Au) electrodes (100 nm thick) with a 5 nm chromium adhesion layer.

[0029] Details of Au nanosheets are described, for example, in the following technical publications written by the present inventors: Kato, T., Tanaka, T., Yajima, T. & Uchida, K. Temperature dependence of resistivity increases induced by thiols adsorption in gold nanosheets. Japanese Journal of Applied Physics 60, SBBH13 (2021) and Kato, T., Tanaka, T. & Uchida, Detection of PPB-Level H2S Concentrations in Exhaled Breath Using Au Nanosheet Sensors with Small Variability, High Selectivity, and Long-Term Stability,” ACS Sensors, 2024. doi: 10.1021 / acssensors.3c01944.

[0030] 2, the multiple gas detection elements 14 are arranged in a row, preferably at equal intervals, in the order of gas detection elements 14#0, 14#1, 14#2, ... (denoted as #0, #1, #2, ... in the drawings, and similarly in other drawings), with intervals L between them, preferably at equal intervals, so that the distance (length) from the gas inlet 12 increases. Because the multiple gas detection elements 14 are arranged in order away from the gas inlet 12, the gas detection element 14#0 closest to the gas inlet 12 is exposed to the gas released from the gas inlet 12 first, followed by the elements closest to the gas inlet 12, with a time lag between them. Note that the intervals L do not have to be equal as long as the relative positions of the multiple gas detection elements 14 are defined. Furthermore, if the intervals L are equal, it is desirable that the intervals L be the same as the distance (height) H (see FIG. 1) between the gas inlet 12 and the surface of the gas detection element 14. If the intervals L are not equal, it is desirable that the farthest (longest) interval L among the different intervals L is the same as the distance (height) H between the gas inlet 12 and the surface of the gas detection element 14 (see Figure 1).

[0031] If the gas ejected from the gas inlet 12 becomes turbulent near the gas detection element 14, it may become difficult to accurately predict the difference in concentration due to differences in the position of the gas detection element 14. The gas ejected from the gas inlet 12 entrains surrounding gas, forming a turbulent layer around it. When the diameter of the gas inlet 12 (diameter if circular, or the length of the short side if rectangular) is W, laminar flow can be maintained up to a distance of approximately five times W from the gas inlet 12. Therefore, the height distance H (see FIG. 1 ) between the gas inlet 12 and the surface of the gas detection element 14 is preferably five times W or less (H≦5W), where W is the diameter (diameter if circular, or the length of the short side if rectangular) of the narrowest part of the gas inlet 12. Furthermore, it is even more desirable for this height H to be one time W or less, since this tends to significantly affect response time depending on the position of the gas detection element 14.

[0032] Consider a situation in which gas is introduced at a maximum flow rate of 1.5 m / s, which is the maximum flow rate of exhaled air. Figure 11(a) shows the fluid simulation results for the gas inlet 12 with a diameter of 1 mm and a height of 3 mm (H = 2W), Figure 11(b) shows the fluid simulation results for the gas inlet 12 with a diameter of 1 mm and a height of 5 mm (H = 5W), and Figure 11(c) shows the fluid simulation results for the gas inlet 12 with a diameter of 1 mm and a height of 6 mm. The contour lines in each figure in Figure 11 indicate the concentration of the introduced gas, and the difference from 1 indicates the concentration of the surrounding gas. As shown in Figure 11(a), the concentration is 1 directly below the gas inlet, allowing accurate measurement of the gas concentration. However, in Figure 11(c), there is almost no area on the substrate where the concentration is 1, even directly below the gas inlet, making it impossible to accurately measure the concentration of the introduced gas. From the above simulation results, it can be seen that, as a result of being able to maintain laminar flow, if H≦5W, the gas detection element located directly below the gas inlet 12 can measure the gas concentration in the airflow with high accuracy.

[0033] Furthermore, the distance Lmax between the gas detection element 14 (sensor #0 in FIG. 2) closest to the gas inlet 12 and the gas detection element 14 (sensor #n in FIG. 2) farthest from the gas inlet 12 is preferably no more than five times the diameter (diameter in the case of a circle, or the length of the short side in the case of a rectangle) of the narrowest part of the gas inlet 12. If the gas detection element 14 is positioned too far from the gas inlet 12, the response of the farther gas detection element 14 will be slow and weak, requiring longer detection times and making measurement more difficult.

[0034] Human breath consists of one cycle of inhalation and exhalation, approximately three seconds apart. Therefore, if the measurement takes approximately three seconds, the measured breath cycle will be offset depending on the position of the gas detection element 14. To avoid this, the measurement cycle of the gas detection element 14 (i.e., the time it takes for the farthest gas detection element 14 to measure) must be sufficiently shorter than the breathing cycle (e.g., approximately 0.1 seconds, an order of magnitude shorter). Gas introduced through the gas inlet 12 and hitting the substrate flows laterally across the substrate. When the diameter W of the gas inlet 12 (the diameter if circular, or the length of the short side if rectangular) and the height H between the gas inlet 12 and the surface of the gas detection element 14 are H≦5W, as described above, the flow velocity Uin of the gas (e.g., breath) flowing into the gas inlet and the flow velocity U0 flowing laterally near the edge of the gas inlet are approximately equal (see, for example, Toshihiko Shakouchi, "Jet Engineering: Fundamentals and Applications," Morikita Publishing, 2004).

[0035] Furthermore, the inventors have calculated that when H>W, the distance that the gas on the substrate directly below the gas inlet reaches after t seconds is 1.45×(Uin×t×W) ０．５ In addition, when H<W, the distance the gas travels after t seconds is at most 2.22 × (Uin × t × W) ０．５ Specifically, when the maximum speed of natural breathing of a person is 1.5 m / s and the measurement time interval is 0.1 seconds, 21 × W ０．５ mm, 27 x W ０．５where W is the unit of millimeters. Therefore, for example, if the diameter of the gas inlet 12 is 4 mm, the distance between the gas detection element 14 closest to the gas inlet 12 (sensor #0 in FIG. 2) and the gas detection element 14 farthest from the gas inlet 12 (sensor #n in FIG. 2) should be 42 mm when H > W, and 54 mm when H < W, in order to be able to measure the gas flow rate and concentration simultaneously.

[0036] As mentioned above, human exhaled breath pulsates in a cycle of about three seconds, so it is desirable to take in gas for a period equivalent to one cycle of this pulsation. For example, one cycle of exhaled breath can be taken in by opening the gas valve 19 shown in Fig. 10(b) described below for only three seconds. Furthermore, even if the gas valve 19 is not provided, if the gas detection element 14 is a resistor, the driving device 2 shown in Fig. 9 described below can increase the voltage applied to the resistor, and the Joule heat generated by the resistor will cause the target gas and the gas detection element 14 to respond to each other, thereby achieving the same effect as opening and closing the gas valve 19.

[0037] Of the multiple gas detection elements 14, at least the element body 14a of gas detection element 14#0 closest to the gas inlet 12 is arranged so as to fit within the projected surface of the gas inlet 12, and at least one of gas detection elements 14#1, 14#2, ... which are lined up in sequence at a predetermined interval L between them are arranged at a position outside the projected surface of the gas inlet 12. Figure 2 shows an example in which gas detection element 14#1 is arranged at a position outside the projected surface of the gas inlet 12. The predetermined interval L is set to a level that causes differences in the timing of exposure to gas and the output signal levels among the multiple gas detection elements 14.

[0038] The multiple gas detection elements 14 are aligned in a direction perpendicular to the direction connecting the electrodes 14b of each element 14. This alignment allows the gas released from the gas inlet 12 to flow smoothly in the aligned direction of the multiple gas detection elements 14. For example, if the height of the electrodes 14b is relatively high compared to the height of the thin-film element body 14a, there is a possibility that the gas will hit the electrodes 14b and disrupt the airflow. Therefore, it is preferable to orient the gas detection elements 14 so that the electrodes 14b are not positioned between the element bodies 14a of adjacent gas detection elements 14.

[0039] Furthermore, the element body 14a of the gas detection element 14 is sized smaller than the opening diameter of the gas inlet 12. This size configuration allows the entire element body 14a of the gas detection element 14 to be exposed to the gas released from the gas inlet 12, thereby increasing the response sensitivity of the gas detection element 14.

[0040] Figures 3, 4, 5 and 6 show examples of measurements using a gas detection device that uses an Au nanosheet as the gas detection element 14. Figure 3 shows the relative positioning of the gas inlet 12 and multiple gas detection elements 14. Figure 4 shows an example of a measurement of the time change in the output signal (sensor response) of multiple gas detection elements 14 in the arrangement of Figure 3. Figure 5 shows an example (map) of the distribution of output signals over time and the arrangement positions of multiple gas detection elements 14. Figure 6 shows the output signal (response) of the gas detection element 14 according to the gas flow rate (particularly, a flow rate within the range where the sensor response does not saturate).

[0041] As shown in Figure 3, eleven gas detection elements 14#0, 14#1, ..., 14#10 were arranged in a row, with gas detection element 14#0, which was closest to gas inlet 12, positioned directly below the central axis of gas inlet 12, and gas detection elements 14#1, ..., 14#10 being equally spaced at a predetermined interval L of 1 mm in the direction moving away from gas inlet 12, starting from 14#0. Gas containing hydrogen sulfide (HS) gas was released from gas inlet 12, and the output signal (response) of each gas detection element 14 was measured.

[0042] 4(a) shows a measurement example with a gas flow rate of 200 sccm and a gas component concentration of 1 ppm, and FIG. 4(b) shows a measurement example with a gas flow rate of 500 sccm and a gas component concentration of 0.3 ppm. As shown in FIG. 4, the gas detection element 14#0 closest to the gas inlet 12 has the fastest response time and the highest output level. The response time becomes slower and the output level becomes lower as the element becomes farther from the gas inlet 12.

[0043] 5(a) is a measurement example with a gas flow rate of 200 sccm and a gas component concentration of 0.3 ppm, FIG. 5(b) is a measurement example with a gas flow rate of 300 sccm and a gas component concentration of 0.3 ppm, FIG. 5(c) is a measurement example with a gas flow rate of 400 sccm and a gas component concentration of 0.3 ppm, and FIG. 5(d) is a measurement example with a gas flow rate of 500 sccm and a gas component concentration of 0.3 ppm. As shown in FIG. 5, as the flow rate of gas containing hydrogen sulfide (HS) gas of the same concentration (0.3 ppm) increases, the distribution of high-level output signals from the gas detection element 14 expands to gas detection elements 14 that are further away from the gas inlet 12, and furthermore, there is a clear tendency for the response delay of the gas detection elements 14 that are further away to become shorter.

[0044] 6 shows the magnitude of the output signal (sensor response) versus gas flow rate when the gas detection element 14 alone is exposed to a gas with a hydrogen sulfide (HS) gas concentration of 4 ppm, and as shown in Fig. 6, the output signal from the gas detection element 14 increases as the gas flow rate increases. As described above in the problem to be solved by the invention, the sensor response (output signal) saturates at a value corresponding to the gas concentration when the flow rate is above a certain level, but in the case of a weak airflow that does not reach a certain level, the response of the gas detection element 14 increases as the gas flow rate increases.

[0045] In this way, the gas flow rate and the concentration of a predetermined gas component contained therein are determined by utilizing the differences in the output signals of the multiple gas detection elements 14 located at different positions and performing data analysis processing on the output signals of the multiple gas detection elements 14. Specifically, deep learning processing is used to calculate estimated values ​​of the gas flow rate and gas component concentration.

[0046] 7 is a diagram showing a neural network model for deep learning processing. In this embodiment, the machine learning library PyTorch was used to construct the neural network for deep learning processing. Measurements were performed using six test patterns combining two set flow rates (200 sccm and 500 sccm) and three hydrogen sulfide concentrations (0.6 ppm, 1.3 ppm, and 5.0 ppm). For each test pattern, output signals from each of the multiple gas detection elements 14 were acquired eight times. The acquired output signals included 14 time-series output values ​​from 11 gas detection elements 14#0 to 14#10, sampled every nine seconds.

[0047] In this measurement, the neural network was composed of an input layer consisting of 154 variables, two hidden layers each consisting of 231 neurons, and an output layer with two nodes, and 75% of all measurement data obtained as output signals from multiple gas detection elements 14 was used as training data and 25% as analysis data. The output layer output normalized gas flow rate and estimated gas component concentrations.

[0048] 8A and 8B are graphs showing the relationship between the output estimated values ​​of gas flow rate and gas component concentration and the respective set values ​​in the test pattern, with Fig. 8A showing the correlation between the estimated value of gas flow rate and the set value, and Fig. 8B showing the correlation between the estimated value of gas component concentration and the set value. As shown in Fig. 8, both the gas flow rate and the gas component concentration show a very high correlation, with the estimated values ​​and the set values ​​almost agreeing. In this embodiment, the gas flow rate and gas component concentration can be accurately measured, and even when the flow rate of the introduced gas is different, particularly when the flow rate is so small that it results in a weak airflow, the gas flow rate and the gas component concentration can be accurately measured without being affected by the gas flow rate.

[0049] Furthermore, since the gas component detection device in this embodiment can measure the gas component concentration regardless of the flow rate of the introduced gas, it can be configured in a relatively small size that only exposes a weak airflow to the gas detection element, and since it does not require components for controlling the gas flow rate, such as a flow sensor or suction pump, the device can be made small enough to be incorporated into a small information terminal such as a smart watch.

[0050] 9 is a diagram showing an example of the configuration of a gas component measurement system according to this embodiment. Gas component measurement system 100 includes gas component detection device 1 described above, a drive device 2 that drives multiple gas detection elements 14 of gas component detection device 1, and a data analysis device 3 that acquires and analyzes the output signals from multiple gas detection elements 14 of gas component detection device 1.

[0051] The driver 2 is a power source that applies a voltage to the multiple gas detection elements 14 of the gas component detection device 1, and is used when voltage-driving the gas detection elements 14. When heating the gas detection elements 14 during measurement, the voltage is varied, and a voltage larger than the drive voltage is applied to the gas detection elements at a heating timing before the measurement timing, causing a current to flow, thereby generating Joule heat and instantaneously raising the temperature of the gas detection elements 14. The driver 2 applies voltage to the multiple gas detection elements 14 at the same timing or sequentially at high speed, driving them in parallel or serially at high speed. As described above, the driver 2 can generate Joule heat by applying a large voltage to the gas detection elements to cause a current to flow, or it can apply a voltage to the heater 18 to heat the gas detection elements.

[0052] The data analyzer 3 is a computer that reads output signals from the multiple gas detection elements 14, performs arithmetic processing using the deep learning process described above, and calculates estimated values ​​for the gas flow rate and gas component concentrations. The computer is a processing device such as a general-purpose personal computer or a server device on a communication network. The data analyzer 3 acquires output signals that are read out in parallel from the multiple gas detection elements 14 at the same time or serially at high speed. Instead of the deep learning process, arithmetic processing using a separate analysis program or arithmetic circuit may be performed.

[0053] Furthermore, the data analyzer 3 is preferably required to analyze the cycle of the taken-in gas with sufficient accuracy. To achieve this, it is necessary to measure and analyze the response data at a time interval Δt that is sufficiently shorter than the time difference between the output timing of the output signal of the gas detection element 14 closest to the gas inlet 12 and the output timing of the output signal of the gas detection element 14 farthest from the gas inlet 12. Furthermore, the time interval Δt is determined by setting the opening area of ​​the gas inlet 12 as A (when the gas inlet 12 is circular, A=π(W / 2) in FIG. 2). 2 , the height distance from the gas inlet 12 to the nearest gas detection element 14 is H (see FIG. 1), and the maximum gas flow velocity is v, the relationship in the following equation (1) must be established: Δt<A·H / v (more preferably Δt<<A·H / v) (1) In other words, it is desirable that the data analyzer 3, which measures and analyzes the response (output) of the gas detection element 14, has a reading speed sufficient to measure the output 1 / Δt times per second.

[0054] 10A and 10B are diagrams showing another example configuration of the gas component detection device 1. In the example configuration shown in FIG. 10A, a central gas detection element 14#3 of a plurality (e.g., seven) of gas detection elements 14 arranged in a row is positioned closest to the gas inlet 12, and the multiple gas detection elements 14 are arranged on both sides of the central gas detection element 14#3, increasing in distance from the gas inlet 12. Because gas released from the gas inlet 12 diffuses in all directions, by arranging the gas detection elements 14 on both sides of the gas inlet 12 at the center, the detection capability and detection accuracy of the diffused gas are improved. Furthermore, in the example configuration shown in FIG. 10A, gas outlets 17 may be provided on both sides of the arrangement of the gas detection elements 14.

[0055] 10(b), a gas valve 19 is provided in the hollow thin tube 13 to control the timing of gas release from the gas inlet 12, i.e., to open and close the gas inlet 12. By providing the gas valve 19, gas can be released intermittently, allowing the gas detection element 14 to be exposed to the target gas at regular time intervals. When the driver 2 that drives the gas detection element 14 drives the gas detection element 14 intermittently, the gas valve 19 turns the timing of gas release on and off in synchronization with the intermittent driving, and may be ON / OFF controlled by the driver 2, for example, to synchronize with the timing of voltage application by the driver 2.

[0056] 1 , in which the central axis of hollow, elongated tube 13 having gas inlet 12 is arranged perpendicular to the surfaces of gas detection element 14 and substrate 15, the central axis is arranged at an angle to the surface of substrate 15, and among the plurality of gas detection elements 14, gas detection element 14#0, which is arranged at one end closest to gas inlet 12, is preferably arranged at a position where a line extending from the axis of hollow, elongated tube 13 including gas inlet 12 intersects with substrate 15, and the plurality of gas detection elements 14 are arranged on the substrate in order in a direction away from gas inlet 12. This allows for a flexible arrangement of the positional relationship between gas inlet 12 and gas detection element 14, even in the limited installation space of gas component detection device 1.

[0057] It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that the present invention also includes design changes that do not deviate from the gist of the present invention, including various modifications and alterations that can be conceived by a person having ordinary knowledge in the field of the present invention.

[0058] 1: Gas component inspection device, 2: Driving device, 3: Data analysis device, 10: Container, 12: Gas inlet, 13: Hollow thin tube, 13a: Downstream end opening, 14: Gas detection element, 14a: Element body, 14b: Electrode, 15: Substrate, 17: Gas outlet, 18: Heater, 19: Gas valve, 100: Gas component measurement system

Claims

1. A gas component detection device that detects a specific gas component contained in a gas, comprising: a gas inlet for introducing the gas into a container; and a plurality of gas detection elements that are disposed within the container and exposed to the gas released from the gas inlet, wherein the plurality of gas detection elements are disposed at intervals at positions that vary in distance from the gas inlet.

2. The gas component detection device according to claim 1, wherein the plurality of gas detection elements include a first gas detection element and a second gas detection element, the first gas detection element is positioned closer to the gas inlet than the second gas detection element, and the first gas detection element is exposed to the gas released from the gas inlet earlier than the second gas detection element.

3. A gas component detection device as described in claim 2, characterized in that the first gas detection element is arranged opposite the gas inlet at a position on the central axis of the gas inlet, and the second gas detection element is arranged opposite the gas inlet at a position off the central axis of the gas inlet.

4. The gas component detection device described in claim 2, characterized in that the first gas detection element is the gas detection element among the plurality of gas detection elements that is positioned closest to the gas inlet, and the distance from the first gas detection element to the gas inlet is 5 times or less the diameter of the gas inlet.

5. The first gas detection element is the gas detection element that is located closest to the gas inlet among the plurality of gas detection elements, the second gas detection element is the gas detection element that is located farthest from the gas inlet among the plurality of gas detection elements, and the distance between the first gas detection element and the second gas detection element is the value of the following formula: 2.22 × (Uin × Δt × W) ０．５ 3. The gas component detection device according to claim 2, wherein W is the diameter of the gas inlet, Uin is the flow rate of the gas introduced into the gas inlet, and Δt is the measurement time interval of the measurement device.

6. The gas component detection device according to claim 1, wherein the plurality of gas detection elements are arranged in a line.

7. A gas component detection device as described in claim 1, characterized in that each of the plurality of gas detection elements comprises an element body that reacts with a predetermined gas component and electrodes formed on both ends of the element body.

8. A gas component detection device according to claim 7, wherein the size of said element body is smaller than the diameter of said gas inlet.

9. A gas component detection device according to claim 7, wherein the element body is a thin film body formed in a thin film state.

10. A gas component detection device according to claim 7, wherein the plurality of gas detection elements are arranged in a row in a direction perpendicular to the direction connecting the electrodes.

11. The gas component detection device according to claim 1, wherein the plurality of gas detection elements are arranged on a surface of the substrate facing the gas inlet.

12. The gas component detection device according to claim 1, further comprising a gas valve that can be opened and closed to expose the gas to the plurality of gas detection elements at regular time intervals.

13. The gas component detection device according to claim 11, wherein the gas inlet is disposed with its central axis perpendicular to the surface of the substrate.

14. The gas component detection device according to claim 11, wherein the gas inlet is disposed with its central axis inclined relative to the surface of the substrate.

15. A gas component measurement system comprising: a gas component detection device according to any one of claims 1 to 14; and an analysis device that determines the concentration of the gas component in the gas by calculation based on output signals from the plurality of gas detection elements.

16. The gas component measuring system according to claim 15, wherein the analyzer calculates the gas flow rate as well as the concentration of the gas component based on the output signals from the plurality of gas detection elements.

17. A gas component measuring system according to claim 15, further comprising a driving device for instantaneously applying a voltage sufficient to generate Joule heat to said plurality of gas detection elements.

18. The gas component measurement system described in claim 15, wherein the analyzer reads the output signals of the plurality of gas detection elements at a time interval Δt that is shorter than the time difference between the output timing of an output signal from the gas detection element closest to the gas inlet among the plurality of gas detection elements and the output timing of an output signal from the gas detection element farthest from the gas inlet, and further wherein the time interval Δt satisfies the following relationship: Δt < A H / v, where A is the opening area of ​​the gas inlet, H is the height distance from the gas inlet to the nearest gas detection element, and v is the maximum flow velocity of the gas.

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