JP2017020949A - Gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas detector capable of quickly and distinguishably identifying a group of detection target gases comprising a plurality of gas components.SOLUTION: A gas detector X includes: a gas flow channel 10 for a group of detection target gases comprising a plurality of gas components to be detected to flow; a separation column 20 for separating the plurality of gas components; a multi-sensor detection unit 30 having a plurality of gas sensing elements with different gas selectivity; and an identification unit 40 configured to identify the group of detection target gases.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, gas chromatograph devices that perform qualitative and quantitative analysis of components in a gas have been widely used. This involves introducing a gas to be detected together with a carrier gas into a gas separation column filled with a filler, and then detecting the gas to be detected. A plurality of gas components contained therein are separated due to the retention time difference due to the interaction with the packing material in the gas separation column, and the separated gas components are derived from the gas separation column, and a thermal conductivity detector ( A chromatogram is 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 placed in a thermostat and heated and held at a constant temperature, whereby the plurality of gas components in the gas separation column are retained. The retention time is kept constant so that accurate measurement can be performed.

  Patent Document 1 describes a gas chromatograph apparatus that can be configured for detecting components in exhaled breath in the medical field or the like. For example, the presence or absence of bad breath by analysis of methyl mercaptan and hydrogen sulfide in exhaled breath in dentistry, the determination of the amount of acetone in exhaled breath in the treatment of diabetes, the determination of the amount of ammonia and isoprene in the exhaled breath due to liver disease, etc. It can be used for the discovery of diseases and analysis of therapeutic effects by analysis of components in exhaled breath.

  In this gas chromatograph, a gas cylinder filled with an appropriate carrier gas such as hydrogen gas or helium gas corresponding to the sample gas to be detected and the configuration of the detector is connected to the apparatus main body. A flow rate switch, a flow meter, a sample gas supply port, a gas separation column, and a detector are sequentially provided in the apparatus main body 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, there is an increasing need for odor identification in various fields such as food contamination, freshness management of fish meat, and production area identification by odor. In addition, in the semiconductor manufacturing process, there is an increasing need for odor identification in the management of manufacturing environment anomaly detection by measurement of manufacturing environment gas and the influence on the health of gas in the work environment.

  The detection target gas (detected gas group) that is subject to odor identification contains many kinds of gas components, and the gas sensor generally used in the odor identification apparatus has cross sensitivity for each type of gas. If the concentration of a certain component in the sample becomes considerably high, the output of the sensor is governed by changes in the concentration of that component, making it almost impossible to respond to changes in other components, resulting in impossible to identify odors. was there. In addition, if the concentration of the minor component is increased to some extent, there will be a slight difference in the sensor output for similar odor species, which makes it possible to identify similar odor species. It is difficult to maintain the weak differences over time and cannot identify those similar odors over time.

  The apparatus described in Patent Document 1 determines the type of gas component contained in the expiration gas based on the retention time of the peak that appears in the detection output of the detector. However, there is a problem that the type of gas component cannot be determined.

  Accordingly, an object of the present invention is to provide a gas detector capable of quickly identifying a detected gas group including a plurality of gas components.

  In order to achieve the above object, the first characteristic configuration of the gas detector according to the present invention is to separate a gas flow path through which a detected gas group including a plurality of gas components to be detected flows and the plurality of gas components. A 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.

  In general, it is considered that the gas group to be detected contains several tens or more kinds of gas components (odor components), and when a separation column is introduced for odor identification, an attempt is made to separate many types of gas components. Since the retention time of the gas component in the separation column becomes very long, measurement takes time. In addition, since various types of gas components may be diluted by the carrier gas below the detection level of the sensor, the sensor sensitivity required for measurement may not be satisfied. As described above, in identifying the gas group to be detected, it is very difficult and unrealistic to completely separate all the components of the multiple types of gas components.

  A plurality of gas detection elements having different gas selectivity in the multi-sensor detection unit can have different output response waveforms. Therefore, as the output data of the plurality of gas detection elements acquired by the multi-sensor detection unit, data exhibiting various output modes can be acquired according to the number of different gas detection elements. Therefore, even if the separation column does not completely separate many kinds of gas components, if the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes is different, the 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 complex output pattern by the identification unit. Further, even when the timing at which the maximum concentration passes is not clearly different, a difference in gas components can be detected by the multi-sensor detection unit having different gas selectivity. Thereby, it can recognize correctly also in the change (presence / absence) of the minor component in a to-be-detected gas group.

  Therefore, in the gas detector of the present invention, by constructing a system using 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 selectivity, The selectivity with respect to the detected gas group (smell component) including a plurality of gas components can be improved, and the discrimination ability of the detected gas group can be improved compared to the conventional odor identification.

  According to a second characteristic configuration of the gas detector according to the present invention, the identification unit stores in advance a standard output pattern that is an output of a predetermined gas group, an output of the detected gas group, and the standard output pattern. And an analysis means for performing pattern matching by comparing the two.

  According to this configuration, the pattern matching of the output of the detected gas group that 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.

  A third characteristic configuration of the gas detector according to the present invention is that the separation column has a low ability to separate the plurality of gas components.

  According to this configuration, since the separation column only needs to change the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes, there is no need to completely separate many types of gas components, The retention time of the separation column can be shortened. Therefore, in this configuration, the gas group to be detected can be quickly identified. Moreover, since the structure of the separation column can be simplified, the manufacturing cost of the gas detection of the present invention can be reduced.

  A fourth characteristic configuration of the gas detector according to the present invention is that the multi-sensor detection unit includes a plurality of gas detection elements in which at least a semiconductor material in the substrate type semiconductor gas detection element is different.

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

It is the schematic of the gas detector of this invention. It is the schematic of a separation column and its peripheral structure. It is the schematic of a board | substrate type | mold semiconductor type gas detection element. It is the graph which showed that the several gas detection element from which gas selectivity differs has a different output response waveform. It is the figure which plotted the output data with respect to several time. It is an analysis figure 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, the gas detector X of the present invention includes a gas flow path 10 through which a group of gases to be detected including a plurality of gas components to be detected flows, and a separation column 20 that separates the plurality of gas components. And a multi-sensor detection unit 30 having a plurality of gas detection elements 31 having different gas selectivity, and an identification unit 40 for identifying a detected gas group.

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

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

  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. The separation column 20 of the present embodiment can use a so-called packed column. 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 one according to the type of detection target gas or 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, the ability to separate multiple gas components from a known separation column is reduced by changing the normal column driving conditions to the low temperature side, shortening the column length, or changing the composition of the packing material, etc. It can be used as a low resolution separation column. Such a separation column is referred to herein as a non-complete separation column.

  The odor identification can be achieved by identifying each of a plurality of gas components in a detected gas group including a plurality of gas components that are detection target gases. In general, it is considered that the gas group to be detected contains several tens or more kinds of gas components (odor components). In order to identify such many kinds of gas components, an ordinary gas separation column is used. A long retention time is required to completely separate the gas components. If separation takes a long time in this way, the gas group to be detected may be diluted by the carrier gas below the detection level of the sensor and may not be detected by the sensor.

  On the other hand, the separation column 20 (non-complete separation column) used in the present invention only needs to vary the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes. There is no need for complete separation, and the retention time of the separation column can be shortened. 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.

  A specific configuration of the separation column 20 (non-complete separation column) and its peripheral structure are shown in FIG. The separation column 20 is supported by a support cylinder 22 together with the air heating unit 21 and is covered with a heat insulating material 23. The separation column 20 can change the drive temperature by the heater 24, and the drive temperature can be controlled by the control unit 90 by sending a signal measured by the resistance temperature detector to the control unit 90. The driving temperature of the separation column 20 can be about 50 to 60 ° C. (usually about 100 ° C.), and the length when the inner diameter of the separation column 20 is 3 mm is about 40 to 50 cm (usually about 100 cm). However, it is not limited to these. Since the driving temperature of the separation column 20 can be made lower than usual, the driving cost of the gas detector X of the present invention can be reduced. Moreover, although it is good to use salts, Bentone 34 etc. which are organic acid chlorine compounds as a concrete filler, it is not limited to this.

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

The multi-sensor detection unit 30 includes a plurality of gas detection elements 31 having different gas selectivity.
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. For example, a semiconductor type gas detection element such as a hot wire type semiconductor gas detection element or a substrate type semiconductor type gas detection element. An element can be used. The number of gas detection elements 31 is not particularly limited as long as it is plural. In the present 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 in which at least a semiconductor material in the substrate type semiconductor gas detection element is different. The plurality of gas detection elements 31 having different gas selectivity can use different semiconductor materials and catalysts having different gas sensitivity characteristics, so that output response waveforms can be made 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 have different gas selectivity by changing the semiconductor material or by changing the semiconductor material and the catalyst.

  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 mainly composed of tungsten oxide. A sensitive layer 31d is provided by applying a paste and baking at 600 ° C. for 2 hours. 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.

  Instead of a metal oxide semiconductor paste mainly composed of tungsten oxide, a semiconductor material based on titanium oxide / tin oxide core cell structure powder or a semiconductor material based on cerium oxide can be used to improve gas selectivity. Three different substrate type semiconductor gas sensing elements can be produced.

  The identification unit 40 identifies the detected gas group. In other words, the identification unit 40 has a configuration for determining what odor the detected gas group is. Specifically, the identification unit 40 includes a storage unit 41 that 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. 42.

  As long as the memory | storage means 41 is a memory and storage which can memorize | store a standard output pattern, what kind of aspect may be sufficient as it. The standard output pattern is output data of a standard gas (exhaled 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 the 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) that are a plurality of features are determined in advance from the output response waveforms of the respective gas detection elements 31, and the points corresponding to these points are determined. The output is plotted (FIGS. 5 and 6) to pattern the output tendency of the standard gas. Data having a pattern different from the output tendency of the standard gas can be identified as a gas having a different odor 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, the boundary line of the standard gas based on the output data can be objectively defined.

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

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

  When pattern identification is performed by principal component analysis, it may be performed as follows. That is, the data obtained by measuring the standard gas with the gas detector X of the present invention is plotted on a graph as shown in FIG. 6 to determine the plotted region of the standard gas. At this time, the boundary of the region can be determined by the Mahalanobis distance. Next, the data obtained by measuring the gas group to be detected, which is the gas to be detected, by the gas detector X of the present invention is plotted on the same graph as the standard gas, and whether or not it is located within the standard gas region. The gas group to be detected can be identified. That is, in FIG. 6, the plot indicated by the black triangle can be identified as a gas having the same (same type) odor as the standard gas, and the plot indicated by the black square is a gas having an odor different from the standard gas. Can be identified.

  In addition, as described above, instead of determining a plurality of characteristic points such as time (FIG. 4: t1 to t4), waveform frequency components are extracted, and the maximum dispersion is obtained from the patterns formed for each frequency component. A pattern having a pattern may be selected to identify the pattern.

The carrier gas supply unit 50 can be configured by a gas cylinder or the like filled with an appropriate carrier gas such as hydrogen gas or helium gas.
The flow rate 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 of any mode as long as it collects the gas group to be detected, and can be constituted 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 detected gas group from the sampling unit 70.
The control unit 90 includes a microcomputer that can perform temperature control of the separation column 20, carrier gas flow rate control in the flow rate control unit 60, sampling gas group sampling control in the sampling unit 70, and flow path switching unit 80 switching control. 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 detection unit 30 are placed in a carrier gas atmosphere. When the detection target gas is collected, the detection target gas is collected from the sampling unit 70, and then the flow rate control unit 60 is switched so that the detection target gas flows down to the separation column 20. As soon as the 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 concentrations (peaks) of a plurality of gas components of the detected gas group that passes through the multi-sensor detection unit 30 pass is shifted (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 of each gas component passes is offset), which can compensate for the decrease in selectivity due to the cross sensitivity of the sensor, and excellent odor (gas) selectivity is obtained, and the detected gas group High discrimination ability can be secured.

  In general, it is considered that the detected gas group includes several tens or more kinds of gas components (odor components). The plurality of gas detection elements 31 having different gas selectivity in the multi-sensor detection unit 30 can have different output response waveforms. Therefore, as the output data of the plurality of gas detection elements 31 acquired by the multi-sensor detection unit 30, data exhibiting various output modes according to the number of different gas detection elements 31 can be acquired. Therefore, even if the separation column 20 does not completely separate many kinds of gas components, if the timing at which the maximum concentration (peak) of each gas component in a plurality of gas components passes is changed, multiple By using the data acquired by the sensor detection unit 30, the identification unit 40 can recognize the output of the gas group to be detected as a characteristic and complex output pattern. Thereby, it can recognize correctly also in the change (presence / absence) of the minor component in a to-be-detected gas group.

  Therefore, in the gas detector X of the present invention, the selectivity for the detected gas group (odor component) including a plurality of gas components to be detected is improved, and the discrimination ability of the detected gas group is improved compared to the conventional odor identification. Can be improved.

  INDUSTRIAL APPLICABILITY The present invention can be used for a gas detector that identifies a detection target gas (detected gas group) that is an 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 (4)

  Multi-sensor detection unit having a gas flow path through which a group of detected gases including a plurality of gas components to be detected flows, a separation column for separating the plurality of gas components, and a plurality of gas detection elements having different gas selectivity And an identification unit for identifying the detected gas group.   The identification unit includes a storage unit that 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. The gas detector according to claim 1.   The gas detector according to claim 1, wherein the separation column has a low ability to separate the plurality of gas components.   The gas detector according to any one of claims 1 to 3, wherein the multi-sensor detection unit includes a plurality of gas detection elements in which at least a semiconductor material in the substrate type semiconductor gas detection element is different.

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