JP6624826B2 - Gas detector - Google Patents

Description

  The present invention relates to a gas detector for identifying a detection target gas (a group of detected gases) to be subjected to odor identification.

  Conventionally, a gas chromatograph device that performs qualitative and quantitative analysis of components in a gas has been widely used. In this method, a gas to be detected is introduced together with a carrier gas into a gas separation column filled with a packing material, and the gas to be detected is introduced. A plurality of gas components contained therein are separated by a retention time difference due to an interaction with the packing material in the gas separation column, and the separated plurality of gas components are derived from the gas separation column, and the heat conductivity detector ( A chromatogram can be obtained by detecting with a detector such as TCD) or a flame ionization detector (FID).

  Since the retention time of a plurality of gas components in the gas separation column depends on the temperature, for example, the gas separation column is disposed in a constant temperature bath and is heated and held at a constant temperature. The retention time is kept constant so that accurate measurements can be made.

  Patent Literature 1 describes a gas chromatograph device that can be configured for detecting components in breath in the medical field and the like. For example, determination of the presence or absence of bad breath by analysis of methyl mercaptan and hydrogen sulfide in breath in dental care, quantification of the amount of acetone in breath in the treatment of diabetes, quantification of the amount of ammonia and isoprene in breath caused by liver disease, It can be used for finding diseases and confirming the therapeutic effect by analyzing the components in the breath.

  In this gas chromatograph, a gas cylinder filled with an appropriate carrier gas such as a hydrogen gas, a helium gas, or the like according to a sample gas to be detected, a configuration of a detector, or the like is connected to the main body of the apparatus. A flow switch, a flow meter, a sample gas supply port, a gas separation column, and a detector are sequentially provided in the main body of the apparatus from the upstream side to the downstream side of the gas flow path through which the carrier gas supplied from the gas cylinder flows. is there.

JP 2003-057222 A

  In recent years, for example, in product quality control, the need for odor identification has been increasing in various fields such as contamination of food, freshness control of fish and meat, and identification of a production area by odor. Further, in the semiconductor manufacturing process, there is an increasing need for identification of odors in detecting abnormalities in the manufacturing environment by measuring a manufacturing environment gas and managing the effects of gas in the working environment on health.

  The detection target gas (detected gas group) to be subjected to odor identification contains various types of gas components, and the gas sensor generally used in the odor identification device has a cross sensitivity for each type of gas. If the concentration of a certain component in the sample becomes too high, the output of the sensor will be dominated by changes in the concentration of that component and will be almost insensitive to changes in other components, resulting in the inability to identify odors. was there. Also, if the concentration of the minor component is high to some extent, a slight difference occurs in the sensor output for similar odorous species, and the difference enables the identification of similar odorous species. It is difficult to maintain weak differences over time, and it is not possible to identify those similar odors over time.

  The device described in Patent Document 1 determines the type of gas component contained in the exhaled gas based on the retention time of the peak that appears in the detection output of the detector. In such a case, the type of gas component cannot be determined.

  Therefore, an object of the present invention is to provide a gas detector that can quickly identify a gas group to be detected including a plurality of gas components.

In order to achieve the above object, a first characteristic configuration of the gas detector according to the present invention includes a gas flow path in which a gas group to be detected including a plurality of gas components to be detected flows down, and the plurality of gas components are separated. Separation column, a multi-sensor detection unit having a plurality of gas detection elements having different gas selectivity, and an identification unit for identifying the detected gas group, the separation column, the maximum concentration of each gas component, Storage means for storing in advance a standard output pattern which is an output of a predetermined gas group; an output of the detected gas group and the standard; Analysis means for performing pattern matching by comparing output patterns, wherein the standard output pattern plots outputs of a plurality of time points of each gas detection element. Lies in is obtained by patterning the output tendency of standard gas Te.

  In general, it is considered that the detected gas group contains tens or more types of gas components (odor components). When a separation column is used for odor discrimination, it is necessary to separate many types of gas components. Measurement time is required because the retention time of gas components in the separation column is very long. In addition, since many types of gas components may be diluted to below the detection level of the sensor by the carrier gas, the sensor sensitivity required for measurement may not be satisfied. As described above, it is extremely difficult and impractical to completely separate all of the various types of gas components in identifying the detected gas group.

  A plurality of gas detecting elements having different gas selectivities in the multi-sensor detecting section can have different output response waveforms. Therefore, as the output data of the plurality of gas detection elements obtained by the multi-sensor detection unit, data exhibiting various output modes can be obtained according to the number of different gas detection elements. Therefore, even in a state where many kinds of gas components are not completely separated by the separation column, if the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes is made different, a multi-sensor By using the data acquired by the detection unit, the output of the detected gas group can be recognized as a characteristic and complicated output pattern by the identification unit. Further, even when the timing at which the maximum concentration passes is not clearly different, the difference in gas components can be detected by the multi-sensor detectors having different gas selectivities. Thus, the change (presence / absence) of the minor component in the detected gas group can be accurately recognized.

Therefore, in the gas detector of the present invention, a separation column that separates a plurality of gas components and a multi-sensor detection unit having a plurality of gas detection elements having different gas selectivities are used to construct a system, so that a detection target can be used. It is possible to improve the selectivity to a detected gas group (odor component) containing a plurality of gas components, and to improve the discrimination ability of the detected gas group as compared with the conventional odor identification.
Further, according to this configuration, the separation column is a non-complete separation column that can vary the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes, so that various types of gas components are used. There is no need for complete separation, and the retention time of the separation column can be reduced. Therefore, in this configuration, the detected gas group can be quickly identified. Further, since the configuration of the separation column can be simplified, the manufacturing cost of the gas detector of the present invention can be reduced.

In the present invention , the identification unit stores in advance a standard output pattern that is an output of a predetermined gas group, and an analysis unit that performs pattern matching by comparing the output of the detected gas group and the standard output pattern. When, wherein the standard output pattern are patterned output tendency standard gas by plotting the output for a plurality of time points in each of the gas sensing element.

According to this configuration, pattern matching of the output of the detected gas group, which is the detection target gas, is performed using the standard output pattern of the predetermined gas group (standard gas) acquired in advance. Identification can be performed accurately and objectively. In addition, the standard output pattern is obtained by plotting the output of each gas detection element with respect to a plurality of time points and patterning the output tendency of the standard gas, so that the boundary line of the standard gas based on the output data is obtained. Can be objectively defined.

A second characteristic configuration of the gas detector according to the present invention resides in that the multi-sensor detection unit includes a plurality of gas detection elements of different semiconductor materials in the substrate-type semiconductor gas detection element.

  According to this configuration, the output response waveform of the gas detection element can be easily changed by using a semiconductor material or a catalyst having different gas-sensitive characteristics in the substrate-type semiconductor gas detection element.

It is the schematic of the gas detector of this invention. It is a schematic diagram of a separation column and its peripheral structure. It is a schematic diagram of a substrate type semiconductor type gas sensing element. 5 is a graph showing that a plurality of gas sensing elements having different gas selectivities have different output response waveforms. It is the figure which plotted the output data with respect to several time. FIG. 9 is an analysis diagram obtained when pattern identification is performed by principal component analysis.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a gas detector X of the present invention includes a gas flow path 10 through which a gas group to be detected including a plurality of gas components to be detected flows, and a separation column 20 for separating a plurality of gas components. And a multi-sensor detection unit 30 having a plurality of gas detection elements 31 having different gas selectivities, and an identification unit 40 for identifying a gas group to be detected.

  The gas detector X of the present embodiment further includes a carrier gas supply unit 50 that supplies a carrier gas, a flow control unit 60 that controls a gas flow rate in the gas flow path 10, and a sampling unit that samples a group of detected gases. 70, a flow switching unit 80 for switching the gas flow path 10, and a control unit 90 for controlling the separation column 20, the flow control unit 60, the sampling unit 70, and the flow switching unit 80. Such a gas detector X may be of a stationary type or a small and portable type.

  The gas detector X of the present invention identifies a gas group to be detected including a plurality of gas components that are detection target gases. Examples of such a gas to be detected include, but are not limited to, breath in the medical field and the like and gas containing food odor.

  The separation column 20 is formed in a hollow cylindrical shape using a corrosion-resistant metal such as stainless steel, and is filled with a filler serving as a stationary phase. As the separation column 20 of the present embodiment, a so-called packed column can be used. As the filler, for example, a carrier impregnated and coated with a stationary phase, an adsorbent, or the like can be used, and an appropriate material according to the type of the detection target gas or the carrier gas is used.

  The separation column 20 of the present invention may be a column that can vary the timing at which the maximum concentration of each gas component in a plurality of gas components in the detected gas group passes. For example, by changing the ordinary column driving conditions to a lower temperature side, shortening the column length, or changing the composition of the packing material, the ability to separate a plurality of gas components from a known separation column is low. It can be used as a low-resolution separation column. Such a separation column is referred to herein as a non-complete separation column.

  It is considered that the identification of odor can be achieved by identifying each of a plurality of gas components in a detected gas group including a plurality of gas components which are detection target gases. Generally, it is considered that the detected gas group contains several dozen or more types of gas components (odor components). To identify such various types of gas components, a normal gas separation column is used. In order to completely separate the respective gas components, a long retention time is required. If a long time is required for the separation, the detected gas group may be diluted by the carrier gas below the detection level of the sensor, and the detection may not be performed by the sensor.

  On the other hand, the separation column 20 (incomplete separation column) used in the present invention only needs to change the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes, so that various types of gas components can be used. There is no need for complete separation, and the retention time of the separation column can be reduced. For example, in order to completely separate each gas component using a normal gas separation column, a retention time of about 30 minutes is required. However, the separation column 20 used in the present invention may have a retention time of about 10 minutes.

  FIG. 2 shows a specific configuration of the separation column 20 (incomplete separation column) and its peripheral structure. The separation column 20 is supported by a support cylinder 22 together with an air heating unit 21, and is covered with a heat insulating material 23. The drive temperature of the separation column 20 can be changed by the heater 24, and the drive temperature can be controlled by the control unit 90 by sending a signal measured by the temperature measuring resistor to the control unit 90. The driving temperature of the separation column 20 can be about 50 to 60 ° C. (normally about 100 ° C.), and the length when the inner diameter of the separation column 20 is 3 mm is about 40 to 50 cm (normally about 100 cm). However, the present invention is not limited to these. Since the driving temperature of the separation column 20 can be lower than usual, the driving cost of the gas detector X of the present invention can be reduced. As a specific filler, it is preferable to use salts, organic acid chlorine compound Bentone 34 or the like, but it is not limited thereto.

  As described above, the low-resolution separation column 20 (incomplete separation column) used in the present invention can be made smaller than a normal separation column because the column length can be reduced. Therefore, the gas detector X of the present invention can be a small and portable mode.

The multi-sensor detection unit 30 has a plurality of gas detection elements 31 having different gas selectivities.
The gas detection element 31 is not particularly limited as long as it is a known gas detection element capable of detecting a gas to be detected, and is, for example, a semiconductor gas detection element such as a hot-wire type semiconductor gas detection element or a substrate type semiconductor type gas detection element. Devices can be used. The number of gas detection elements 31 is not particularly limited as long as it is plural. In this embodiment, a case where three substrate type semiconductor gas detection elements are used will be described. That is, the multi-sensor detection unit 30 includes a plurality of gas detection elements 31 having different semiconductor materials at least in the substrate-type semiconductor gas detection element. The plurality of gas detection elements 31 having different gas selectivities can use semiconductor materials and catalysts having different gas-sensitive characteristics to make output response waveforms different in each gas detection element 31.

  A known catalyst may be used as the catalyst. That is, the plurality of gas detection elements 31 in the multi-sensor detection unit 30 may be configured to use different semiconductor materials or different semiconductor materials and catalysts so as to have different gas selectivities.

  As shown in FIG. 3, the substrate type semiconductor gas detection element 31 is provided by depositing platinum comb electrodes 31b and 31c on the surface of an alumina substrate 31a, and a metal oxide semiconductor containing tungsten oxide as a main component thereon. The paste is applied and baked at 600 ° C. for 2 hours to provide a sensitive layer 31d. Further, a platinum thin film heater 31e is provided on the back surface of the alumina substrate 31a, and is used to maintain the operating temperature of the gas detection element.

  By using a semiconductor material based on a titanium oxide / tin oxide core cell structure powder or a cerium oxide based semiconductor material instead of a metal oxide semiconductor paste containing tungsten oxide as a main component, gas selectivity is improved. Three different substrate-type semiconductor gas detection elements can be manufactured.

  The identification unit 40 identifies a detected gas group. That is, the identification unit 40 has a configuration to determine what kind of odor the detected gas group has. Specifically, the identification unit 40 includes a storage unit 41 that previously stores a standard output pattern that is an output of a predetermined gas group, and an analysis unit that performs pattern matching by comparing the output of the detected gas group and the standard output pattern. 42.

  The storage means 41 may take any form as long as it is a memory or storage capable of storing a standard output pattern. The standard output pattern is output data of a standard gas (exhaled gas in the medical field, gas containing food odor, etc.) acquired in advance. That is, the standard gas is sampled by the gas detector X of the present invention, and the output data of the plurality of gas detection elements 31 acquired by the multi-sensor detection unit 30 can be used as a standard output pattern. At this time, in the standard output pattern, a plurality of points such as a plurality of times (FIG. 4: t1 to t4), which are a plurality of features, are determined in advance from output response waveforms of the respective gas detection elements 31, and these points are determined. The output is plotted (FIGS. 5 and 6) and the output tendency of the standard gas is patterned. Data having a pattern different from the output tendency of the standard gas can be identified as a gas having a different smell from the standard gas (different gas). FIG. 6 shows an example of pattern identification by principal component analysis. By patterning the output tendency in this way, it is possible to objectively define the boundary line of the standard gas based on the output data.

  The analyzing means 42 may be constituted by a microcomputer or the like that compares the output of the detected gas group that is the detection target gas and the standard output pattern and performs pattern matching.

  When the pattern identification in the identification unit 40 is performed by the principal component analysis, it can be configured to be visualized by a PC and to automate the identification.

  When the pattern identification is performed by the principal component analysis, it may be performed as follows. That is, data obtained by measuring the standard gas by the gas detector X of the present invention is plotted on a graph as shown in FIG. 6, and the plotted region of the standard gas is determined. At this time, the boundary of the area can be determined by the Mahalanobis distance. Next, data obtained by measuring a gas group to be detected, which is a gas to be detected, with the gas detector X of the present invention is plotted on the same graph as the standard gas. , The group of detected gases can be identified. That is, in FIG. 6, a plot indicated by a black triangle can be identified as a gas having the same (same type) odor as the standard gas, and a plot indicated by a black square indicates a gas having an odor different from the standard gas. Can be identified.

  Also, as described above, instead of determining a plurality of characteristic points such as time (FIG. 4: t1 to t4), a waveform frequency component is extracted and a maximum variance is calculated from a pattern formed for each frequency component. May be selected to identify the pattern.

The carrier gas supply unit 50 can be configured by a gas cylinder filled with an appropriate carrier gas such as a hydrogen gas and a helium gas.
The flow control unit 60 can be configured by a mass flow controller or the like, and can adjust the flow rate of the carrier gas.
The sampling unit 70 may be in any mode as long as it is a mode in which a group of detected gases is sampled, and may be configured by, for example, a nozzle-shaped member.
The flow path switching unit 80 can be configured by a control valve that can switch and control the carrier gas from the carrier gas supply unit 50 or the group of detected gases from the sampling unit 70.
The control unit 90 is configured by a microcomputer or the like capable of controlling the temperature of the separation column 20, the flow rate control of the carrier gas in the flow rate control unit 60, the sampling control of the group of detected gases in the sampling unit 70, and the switching control of the flow path switching unit 80. can do.

  In the gas detector X of the present invention, the carrier gas flows at a constant flow rate (normal mode) except when the detection target gas is collected, and the separation column 20 and the multi-sensor detector 30 are placed in a carrier gas atmosphere. When the gas to be detected is collected, the gas to be detected is sampled from the sampling unit 70, and then the flow rate control unit 60 is switched so that the sampled gas to be detected flows down to the separation column 20. As soon as sampling of the detection target gas is completed, the flow path is switched to the normal mode, and the detection target gas sampled by the carrier gas flows down the separation column 20, reaches the multi-sensor detection unit 30, and is measured.

  At this time, the timing at which the maximum concentration (peak) of the plurality of gas components of the detected gas group passing through the multi-sensor detection unit 30 passes is shifted (the timing overlaps with the timing at which each gas component passes through the multi-sensor detection unit 30). Even if there is a portion, the timing at which the maximum concentration passes for each gas component is deviated), which can compensate for the decrease in selectivity due to the cross sensitivity of the sensor, and achieves excellent odor (gas) selectivity, and the detected gas group High discrimination ability can be secured.

  Generally, it is considered that several tens or more types of gas components (odor components) are contained in the detected gas group. A plurality of gas detecting elements 31 having different gas selectivities in the multi-sensor detecting section 30 can have different output response waveforms. Therefore, as the output data of the plurality of gas detection elements 31 obtained by the multi-sensor detection unit 30, data exhibiting various output modes according to the number of different gas detection elements 31 can be obtained. Therefore, even in a state where many types of gas components are not completely separated by the separation column 20, if the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes is made different, multi-components can be obtained. By using the data acquired by the sensor detection unit 30, the identification unit 40 can recognize the output of the detected gas group as a characteristic and complicated output pattern. Thus, the change (presence / absence) of the minor component in the detected gas group can be accurately recognized.

  Therefore, in the gas detector X of the present invention, the selectivity with respect to the detected gas group (smell component) containing a plurality of gas components to be detected is improved, and the detection capability of the detected gas group is improved as compared with the conventional odor identification. Can be improved.

  INDUSTRIAL APPLICATION This invention can be utilized for the gas detector which identifies the detection target gas (detected gas group) used as the object of odor identification.

X gas detector 10 gas flow path 20 separation column 30 multi-sensor detection unit 40 identification unit 41 storage unit 42 analysis unit

Claims (2)

A gas passage through which a gas group to be detected including a plurality of gas components to be detected flows down, a separation column for separating the plurality of gas components, and a multi-sensor detection unit having a plurality of gas detection elements having different gas selectivities And an identification unit for identifying the detected gas group,
The separation column, Ri Thea and imperfect separation column maximum density can be varied timing of the passage of the gas components,
The identification unit includes a storage unit that previously stores a standard output pattern that is an output of a predetermined gas group, and an analysis unit that performs pattern matching by comparing the output of the detected gas group and the standard output pattern. ,
The standard output pattern is a gas detector in which the output of each gas detection element at a plurality of time points is plotted to pattern the standard gas output tendency . 2. The gas detector according to claim 1 , wherein the multi-sensor detection unit includes a plurality of gas detection elements having different semiconductor materials in the substrate-type semiconductor gas detection element. 3.

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