WO2021070705A1 - Gas concentration measurement device - Google Patents

Gas concentration measurement device Download PDF

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Publication number
WO2021070705A1
WO2021070705A1 PCT/JP2020/037167 JP2020037167W WO2021070705A1 WO 2021070705 A1 WO2021070705 A1 WO 2021070705A1 JP 2020037167 W JP2020037167 W JP 2020037167W WO 2021070705 A1 WO2021070705 A1 WO 2021070705A1
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WO
WIPO (PCT)
Prior art keywords
detection unit
concentration
gas
resistance value
amount
Prior art date
Application number
PCT/JP2020/037167
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French (fr)
Japanese (ja)
Inventor
蛇口　広行
義幸 古山
Original Assignee
アルプスアルパイン株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by アルプスアルパイン株式会社 filed Critical アルプスアルパイン株式会社
Priority to JP2021551377A priority Critical patent/JP7198940B2/en
Priority to CN202080071168.5A priority patent/CN114514423A/en
Publication of WO2021070705A1 publication Critical patent/WO2021070705A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid

Definitions

  • the present invention relates to a gas concentration measuring device.
  • Gas concentration measuring devices equipped with gas sensors that detect specific gases (chemical substances) contained in the gas to be detected (gas to be inspected) are used for various purposes in buildings, vehicles, and the like.
  • Volatile Organic Compounds such as ethanol (C 2 H 5 OH), formaldehyde (HCHO), acetone (C 3 H 6 O), chloroform (CHCl 3 ) and the like can be detected by the gas sensor. ); Combustible gas such as methane (CH 4 ), propane (C 3 H 8 ), butane (C 4 H 10 ); toxic gas such as carbon monoxide (CO), nitrogen oxide (NOx); sulfur compound ( Examples include malodorous gas such as SOx).
  • VOCs contain highly toxic chemical substances, are air pollutants that cause health hazards such as headache, dizziness and nausea, and are also causative substances of sick house syndrome.
  • formaldehyde which is a kind of aldehydes, is known to be generated from housing and daily necessities, and is considered to be a substance that is a main cause of sick house syndrome, and is considered to be a carcinogenic substance.
  • semiconductor type sensor As one of the gas sensors that detect the above gas.
  • Semiconductor-type sensors can react to various types of gases with high sensitivity, and are less costly than other sensors such as electrochemical sensors. Therefore, it is being studied to use a semiconductor sensor for VOC analysis and the like. At that time, since the semiconductor sensor reacts with high sensitivity to various types of VOCs, it easily reacts with alcohols such as ethanol in addition to formaldehyde. Therefore, in order to measure formaldehyde separately from other VOCs such as alcohol, a gas concentration detecting device having a plurality of gas sensors and detecting a plurality of gases has been proposed.
  • a gas concentration measuring device for example, a first gas sensor that detects a gas such as formaldehyde in the room, a second gas sensor that detects the alcohol concentration in the room, a first gas sensor, and a second gas sensor.
  • a gas concentration measuring device including a control unit that converts a concentration signal into an electric signal and calculates a gas concentration in a room has been proposed (see, for example, Patent Document 1).
  • the control unit measures the formaldehyde concentration based on the output difference between the concentration signal from the first gas sensor and the concentration signal from the second gas sensor.
  • the gas type depends on the case of only formaldehyde, the case of only ethanol, and the case of a mixed state of formaldehyde and ethanol. It is necessary to correct the concentration signal of the gas sensor of 1 and perform arithmetic processing. Therefore, the concentration of aldehydes such as formaldehyde cannot be easily measured.
  • An object of the gas concentration measuring device according to the present invention is to provide a gas concentration measuring device capable of easily and accurately measuring aldehydes.
  • One aspect of the gas concentration measuring device is a gas concentration measuring device that measures the concentration of the aldehydes in the gas to be inspected containing aldehydes and alcohol, and detects as the concentration of the alcohol increases.
  • a first detection unit having a first alcohol-derived change amount in which the resistance value to be increased increases at a predetermined rate, and the detected resistance value does not increase even when the concentration of the aldehydes increases, and the alcohol.
  • the resistance value detected as the concentration increases has a second alcohol-derived change amount that decreases at the same rate as the first alcohol-derived change amount, and the resistance detected as the concentration of the aldehydes increases.
  • One aspect of the gas concentration measuring device according to the present invention can easily measure aldehydes with high accuracy.
  • VOCs are aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butanal, pentanal, hexanal, heptanal, octanal, nonanal and glutalaldehyde; alcohols such as ethanol, methanol and n-butanol; acetone, toluene, xylene and acetic acid.
  • ethyl, chloroform, paradichlorobenzene, etc. are included, for example, in chemicals, paints, printing inks, adhesives, solvents, combustion and the like.
  • the case where the VOC measured by the gas concentration measuring device is formaldehyde and ethanol will be described.
  • FIG. 1 is a diagram showing an example of the configuration of the gas concentration measuring device according to the embodiment.
  • the gas concentration measuring device 1 includes a device main body 10, a first detecting unit 20, a second detecting unit 30, a power supply unit 40, a resistance measuring unit 50, and a control device 60.
  • the gas concentration measuring device 1 is provided in the same space S1 such as a building or a vehicle.
  • the first detection unit 20, the second detection unit 30, and the power supply unit 40 are connected in series via an energization line L.
  • the air in the space S1 contains formaldehyde and ethanol, which are VOCs, as the gas to be inspected.
  • the device main body 10 can be formed in a rectangular parallelepiped shape or the like and has a space inside.
  • the device body 10 can be formed of, for example, a synthetic resin or the like.
  • the apparatus main body 10 has a first detection unit 20 and a second detection unit 30 arranged on the surface thereof so as to be in contact with the space S1.
  • the device main body 10 includes a power supply unit 40 and a resistance measuring unit 50 inside, and a control device 60 outside.
  • the first detection unit 20 measures the concentration of ethanol (ethanol concentration) as the gas concentration in the gas to be inspected, and functions as an ethanol concentration sensor. As shown in FIG. 2, the first detection unit 20 increases the detected resistance value from the resistance value R0 to the resistance value R11 at a predetermined rate as the ethanol concentration increases from the concentration zero to the concentration C1. It has a change amount derived from (first alcohol-derived change amount) ⁇ R11. In the first detection unit 20, when the ethanol concentration exceeds the concentration C1, the detected resistance value decreases. In the first detection unit 20, the resistance value detected by the first detection unit 20 changes by changing the amount of oxygen around the first detection unit 20 according to the ethanol concentration. The details of the resistance value changing in the first detection unit 20 will be described later.
  • the resistance value detected by the first detection unit 20, that is, the resistance value R11 detected when the ethanol concentration is the concentration C1, can be maximized, for example, when the ethanol concentration is 0.1 ppm to 1.2 ppm. Good.
  • the first detection unit 20 does not increase the resistance value derived from formaldehyde detected even if the formaldehyde concentration (formaldehyde concentration) increases from zero to the concentrations C1 and C2 as the gas concentration. .. That is, in the first detection unit 20, the amount of change in the detected formaldehyde-derived resistance may be constant from zero to zero, regardless of the formaldehyde concentration, and is preferably zero.
  • the resistance value detected by the first detection unit 20 decreases at a predetermined rate from the resistance value R0 to the resistance value R12 as the formaldehyde concentration increases from zero concentration to concentration C1.
  • Formaldehyde-derived change amount (first aldehyde-derived change amount) ⁇ R12 may be provided.
  • the resistance value detected when the formaldehyde concentration is higher than the concentration C1 (for example, the concentration C2) decreases at a rate of the change amount ⁇ R12 derived from the first aldehydes from the resistance value R12. May be.
  • the first detection unit 20 can use a semiconductor sensor including a gas sensor element as the semiconductor element.
  • FIG. 4 is a conceptual cross-sectional view showing an example of the configuration of the first detection unit 20.
  • the first detection unit 20 includes a case body 21, a sensor base 22, a gas sensor element 23, a metal mesh 24, and a terminal 25.
  • the first detection unit 20 detects the inspection target gas G flowing into the case body 21 from the space S1.
  • the arrow in FIG. 4 indicates the direction of the flow of the inspection target gas G.
  • the configuration of the first detection unit 20 shown in FIG. 4 shows an example, and the configuration of the first detection unit 20 is not limited to this. Each configuration of the first detection unit 20 will be described.
  • the case body 21 is a substantially cylindrical body, and has an inflow port 211 having a diameter smaller than the diameter of the case body 21 at one end thereof.
  • the diameter of the inflow port 211 is not limited to a specific size, and may be, for example, about several mm.
  • the sensor base 22 is formed in a disk shape and has a step on the end face.
  • the sensor base 22 has an insertion portion 221 whose outer diameter is substantially the same as the inner diameter of the case body 21, and a fixing portion 222 whose outer diameter is larger than the outer diameter of the case body 21.
  • the insertion portion 221 is fitted into the other end of the case body 21.
  • the fixing portion 222 is fixed to the other end of the case body 21 by welding, an adhesive or the like.
  • the detection space S2 is formed inside the case body 21 by fitting the insertion portion 221 of the sensor base 22 into the case body 21.
  • the gas sensor element 23 is arranged in the detection space S2 and is fixed to the upper surface (upward direction in FIG. 4) of the sensor base 22.
  • the gas sensor element 23 is a thin film type semiconductor element.
  • FIG. 5 is a conceptual cross-sectional view showing an example of the configuration of the gas sensor element 23. As shown in FIG. 5, the gas sensor element 23 includes a substrate 231, a heat insulating support layer 232, a heater layer 233, an insulating layer 234, and a gas detection unit 235.
  • the substrate 231 is a silicon substrate (Si substrate), and instead of the Si substrate, an alumina substrate, a sapphire substrate, a mica substrate, or the like may be used.
  • the substrate 231 has a through hole 231a at a position where the gas detection unit 235 is formed in a plan view.
  • the heat insulating support layer 232 is provided on the upper surface of the substrate 231 (upward in FIG. 5), and is formed in the through hole 231a like a diaphragm.
  • the thermal insulating support layer 232, a first SiO 2 layer 232a is composed of a three-layer structure the Si 3 N 4 layer 232b and the second SiO 2 layer 232c.
  • the first SiO 2 layer 232a can be formed by thermal oxidation at a thermal oxidation temperature of 800 ° C. to 1100 ° C.
  • the first SiO 2 layer 232a functions as a heat insulating layer, and has a function of reducing the heat capacity by preventing heat transfer generated in the heater layer 233 to the Si substrate 11 side. Further, the first SiO 2 layer 232a exhibits high resistance to plasma etching, and can facilitate the formation of through holes in the substrate 231 by plasma etching.
  • the Si 3 N 4 layer 232b is formed on the upper surface (upward direction in FIG. 5) of the first SiO 2 layer 232a by using a chemical vapor deposition (CVD) method.
  • CVD chemical vapor deposition
  • the second SiO 2 layer 232c can be formed by a CVD method, and can improve the adhesion with the heater layer 233 and secure the insulating property. Since the second SiO 2 layer formed by the CVD method has a small internal stress, it is possible to reduce the occurrence of distortion in the heat insulating support layer 232.
  • the heater layer 233 is provided substantially in the center of the upper surface (upward direction in FIG. 5) of the heat insulating support layer 232.
  • the heater layer 233 is a thin film, and can be formed of, for example, a Pt—W film containing Pt and W.
  • the heater layer 233 is connected to the terminal 25 (see FIG. 4), and is electrically connected to the power supply unit 40 via the terminal 25 (see FIG. 4) to supply power.
  • the insulating layer 234 is provided so as to cover the heat insulating support layer 232 and the heater layer 233.
  • the insulating layer 234 can be formed of, for example, two SiO layers.
  • the insulating layer 234 can secure electrical insulation between the heater layer 233 and the sensing layer electrode 235b and improve the adhesion to the gas sensing layer 235c.
  • the gas detection unit 235 includes a pair of bonding layers 235a, a pair of sensing layer electrodes 235b, a gas sensing layer 235c, and an adsorption layer 235d.
  • the bonding layer 235a can be formed of, for example, a tantalum film (Ta film) or a titanium film (Ti film), and is provided on the insulating layer 234.
  • the bonding layer 235a can increase the bonding strength between the sensing layer electrode 235b and the insulating layer 234.
  • the sensing layer electrode 235b can be formed of, for example, a platinum film (Pt film) or a gold film (Au film).
  • the sensing layer electrode 235b is provided on the pair of bonding layers 235a and serves as a sensing electrode for the gas sensing layer 235c.
  • the gas sensing layer 235c is formed on the insulating layer 234 so as to connect the pair of sensing layer electrodes 235b.
  • the gas sensing layer 235c has a first alcohol-derived change amount ⁇ R11 in which the detected resistance value increases as the ethanol concentration increases, formaldehyde is hardly detected, and aldehydes are used. It can be formed by using a material in which the detected resistance value does not increase even if the concentration increases. As shown in FIG. 2, the material forming the gas sensing layer 235c has a constant change in resistance derived from formaldehyde, or as shown in FIG. 3, a resistance value detected as the formaldehyde concentration increases. It can be formed by using a material having a first aldehyde-derived change amount ⁇ R12 in which the amount is reduced. As a material for forming the gas sensing layer 235c, for example, a metal oxide semiconductor containing SnO 2 and a subcomponent can be used.
  • the gas sensing layer 235c may contain a metal oxide such as In 2 O 3 , WO 3 , ZnO or TiO 2 as a main component in addition to SnO 2.
  • Fe, Al, Si, Ag, etc. can be used as the sub-ingredient. These may be used alone or in combination of two or more. Among these, Fe, Al and Si are preferable, and Fe is more preferable, from the viewpoint of easy adjustment of the magnitude of the first alcohol-derived change amount ⁇ R11.
  • the content of the sub-component can be appropriately designed with the magnitude of the first alcohol-derived change amount ⁇ R11, but the gas sensing layer 235c contains 1.0 mol% to 10.0 mol% of the sub-component with respect to SnO 2. It is more preferable, and it is more preferable to contain 2.0 mol% to 8.0 mol%, and further preferably 4.0 mol% to 6.0 mol%.
  • the gas sensing layer 235c may have a porous structure or a columnar structure. As a result, the specific surface area of the gas sensing layer 235c can be increased, so that the contact area with the gas to be inspected can be increased and the sensitivity can be increased.
  • the adsorption layer 235d is provided so as to cover the surfaces of the insulating layer 234, the pair of bonding layers 235a, the pair of sensing layer electrodes 235b, and the gas sensing layer 235c.
  • a sintered body supported on a carrier having a porous structure can be used using at least one of noble metal elements such as palladium (Pd) and platinum (Pt) as a catalyst.
  • the carrier for example, alumina (Al 2 O 3 ), chromium oxide (Cr 2 O 3 ), iron oxide (Fe 2 O 3 ), nickel oxide (Ni 2 O 3 ), zirconium oxide (ZrO 2 ), silica ( Metal oxides such as SiO 2 ) and zeolite can be used. These may be used alone or in combination of two or more.
  • the carrier such as alumina has a porous structure, the area where the gas to be inspected passing through the pores comes into contact with the catalyst can be increased. Further, when the atmosphere contains a reducing gas having a stronger oxidizing activity than the inspection target gas in addition to the inspection target gas, the combustion reaction of the reducing gas can be promoted and the selectivity of the inspection target gas can be enhanced. .. As a result, the gas concentration of the gas to be inspected reaching the gas sensing layer 235c increases, and the sensitivity of the gas sensor element 23 can be further increased.
  • the gas sensor element 23 has a diaphragm structure with high heat insulation and low heat capacity.
  • the gas sensor element 23 does not have to have a diaphragm structure.
  • the metal mesh 24 is provided at the inflow port 211.
  • the outer diameter of the metal mesh 24 has a disk-like shape having substantially the same diameter as the diameter of the inflow port 211.
  • the metal mesh 24 is a stainless steel net, the opening of the metal mesh 24 is about several mm, and the aperture ratio may be such that the gas to be inspected can flow in and out of the detection space S2.
  • the terminal 25 is an electrode provided so as to project from the sensor base 22, and the energization line L (see FIG. 1) is connected to the second detection unit 30 (see FIG. 1) and the power supply unit 40 (see FIG. 1). See).
  • the first detection unit 20 includes a plurality of (four in FIG. 4) terminals 25a, 25b, 25c and 25d.
  • the terminals 25a and 25b are electrodes for connecting the power supply unit 40 (see FIG. 1) and the second detection unit 30 (see FIG. 1).
  • the terminals 25c and 25d are electrodes for driving the heater layer 233 (see FIG. 5) constituting the gas sensor element 23.
  • the terminals 25a, 25c and 25d are connected to the power supply unit 40 (see FIG. 1) via the energization line L (see FIG. 1), and the terminal 25b is connected to the second detection unit 30 (see FIG. 1) via the energization line L (see FIG. 1). It is connected via (see FIG. 1).
  • the first detection unit 20 has a gas sensor element 23 in the case body 21, and the first detection unit 20 has a gas sensor element according to the amount of oxygen around the gas sensor element 23.
  • the resistance value of 23 changes.
  • the gas sensor element 23 has a gas sensing layer 235c, and when oxygen adsorbed on the surface of the gas sensing layer 235c reacts with ethanol (surface reaction), oxygen is released, but Ethanol deprives the gas sensing layer 235c of free electrons and adheres in the form of ions (C 2 H 5 O ⁇ ).
  • the number of free electrons existing on the surface of the gas sensing layer 235c is relatively reduced, and the resistance value of the gas sensor element 23 is increased (see FIG.
  • the ethanol concentration in the air can be calculated from the amount of increase in the resistance value. However, it can be said that the volume of ethanol is larger than that of oxygen and tends to be easily released. Therefore, when ethanol is adsorbed to a certain concentration in the state of ions, the ethanol ions (C 2 H 5 O ⁇ ) are desorbed from the gas sensing layer 235c and donate electrons to the surface of the gas sensing layer 235c. Therefore, the resistance value of the gas sensor element 23 decreases due to the relative increase of free electrons existing on the surface of the gas sensing layer 235c (see FIG. 2).
  • the second detection unit 30 measures the formaldehyde concentration and the ethanol concentration in the air, respectively, and functions as a formaldehyde concentration sensor and an ethanol concentration sensor. As shown in FIG. 6, the second detection unit 30 has an ethanol-derived change amount (second) in which the detected resistance value decreases at a predetermined rate as the ethanol concentration increases from zero concentration to concentration C1. Alcohol-derived change amount) ⁇ R21. The second alcohol-derived change amount ⁇ R21 decreases at the same rate as the first alcohol-derived change amount ⁇ R11 (see FIG. 2). Further, in the second detection unit 30, the resistance value detected when the ethanol concentration is higher than the concentration C1 (for example, the concentration C2) decreases at a rate of the change amount ⁇ R21 derived from the second alcohol from the resistance value R21. You may.
  • the second detection unit 30 has a formaldehyde-derived change amount (second aldehyde-derived change amount) ⁇ R22 in which the detected resistance value decreases at a predetermined rate as the formaldehyde concentration increases from zero concentration to concentration C1.
  • the resistance value detected when the formaldehyde concentration is higher than the concentration C1 decreases at a rate of the change amount ⁇ R22 derived from the second aldehydes from the resistance value R22. May be.
  • the second detection unit 30 can use a semiconductor sensor including a gas sensor element as the semiconductor element.
  • the second detection unit 30 is the same as the first detection unit 20 except that the material of the gas sensing layer 235c (see FIG. 5) constituting the gas sensor element 23 of the first detection unit 20 shown in FIG. 4 is changed. Has the configuration of. Therefore, only the gas sensing layer 235c constituting the second detection unit 30 will be described with reference to FIGS. 4 and 5.
  • the second detection unit 30 has a gas sensor element 23 in the case body 21 as shown in FIG. 4, and the gas sensor element 23 has gas sensing as shown in FIG. It has layer 235c.
  • the detected resistance value decreases as the ethanol concentration and the formaldehyde concentration increase from zero to the concentration C2 as the gas concentration. It can be formed by using a material having an alcohol-derived change amount ⁇ R21 and a second aldehyde-derived change amount ⁇ R22.
  • a material for forming the gas sensing layer 235c of the second detection unit 30 for example, a metal oxide semiconductor containing SnO 2 can be used.
  • the second detection unit 30 has a gas sensor element 23 in the case body 21, and the second detection unit 30 has a gas sensor element according to the amount of oxygen around the gas sensor element 23.
  • the resistance value of 23 changes.
  • the gas sensor element 23 has a gas sensing layer 235c, and oxygen adsorbed on the surface of the gas sensing layer 235c reacts with formaldehyde or ethanol (surface reaction), and oxygen is released. ..
  • the oxygen ions (O 2- ) adhering to the gas sensing layer 235c are desorbed from the gas sensing layer 235c, free electrons are given to the gas sensing layer 235c.
  • the amount of oxygen adsorbed on the surface of the gas sensing layer 235c is relatively small, and the amount of free electrons given to the gas sensing layer 235c is increased, so that the resistance value of the gas sensor element 23 is reduced.
  • the concentration of formaldehyde and ethanol in the air is calculated from the amount of change in the resistance value.
  • the terminal 25a (see FIG. 4) of the second detection unit 30 is connected to the terminal 25b (see FIG. 4) of the first detection unit 20 via the energization line L (see FIG. 1), and the second detection unit 30 Terminals 25b, 25c and 25d (see FIG. 4) are connected to the power supply unit 40 (see FIG. 1) via an energization line L (see FIG. 1).
  • the first detection unit 20 and the second detection unit 30 are connected in series in the apparatus main body 10 via an energization line L. That is, the terminal 25a (see FIG. 4) of the first detection unit 20 is connected to the power supply unit 40 via the energizing line L, and the terminal 25b (see FIG. 4) of the first detection unit 20 is the second detection unit.
  • the terminal 25a (see FIG. 4) of the 30 is connected via the energizing line L, and the terminal 25b (see FIG. 4) of the second detection unit 30 is connected to the power supply unit 40 (see FIG. 4) via the energizing line L. Will be done.
  • the power supply unit 40 is provided in the device main body 10 and supplies electric power to the first detection unit 20 and the second detection unit 30.
  • One electrode of the power supply unit 40 is connected to the first detection unit 20, the other electrode is connected to the second detection unit 30, and the power supply unit 40 has the first detection unit 20 and the second detection unit 20.
  • the detection units 30 of the above are connected in series.
  • the resistance measuring unit 50 includes a first resistance measuring unit 50A for calculating the resistance value of the first detecting unit 20, and a second resistance for calculating the resistance value of the second detecting unit 30. It has a measuring unit 50B.
  • the first resistance measuring unit 50A connects the pair of resistance parts 50a to the energizing line L so as to sandwich the first detection unit 20, and the second resistance measuring unit 50B connects the pair of resistance parts 50a to the second. It is connected to the energizing line L so as to sandwich the detection unit 30. That is, the resistance measuring unit 50 is measured by the resistance value of the gas sensing layer 235c (see FIG.
  • the total resistance value is calculated by adding the resistance values of the gas sensing layer 235c (see FIG. 5) of the second detection unit 30.
  • the resistance measuring unit 50 is electrically connected to the control unit 61 (see FIG. 7) described later of the control device 60, and the resistance value of the first detecting unit 20 measured by the first resistance measuring unit 50A and the resistance value of the first detecting unit 20.
  • the resistance value of the second detection unit 30 measured by the second resistance measurement unit 50B can be read out by the control unit 61 (see FIG. 7).
  • the gas concentration measuring device 1 may include a resistance measuring device such as an amplifier circuit and an analog-to-digital (AD) converter in addition to the power supply unit 40 and the resistance measuring unit 50 in the device main body 10. At this time, the resistance measuring device may be installed so as to be connected in series with the first detection unit 20, the second detection unit 30, and the power supply unit 40.
  • a resistance measuring device such as an amplifier circuit and an analog-to-digital (AD) converter in addition to the power supply unit 40 and the resistance measuring unit 50 in the device main body 10.
  • AD analog-to-digital
  • the control device 60 includes a control unit 61, an operation unit 62 connected to the control unit 61, and a display unit 63.
  • the control unit 61 is connected to the power supply unit 40 and the display unit 63 in a controllable manner.
  • the control unit 61 has a storage means for storing a control program and various storage information, and a calculation means for operating based on the control program.
  • the storage means includes RAM, ROM, storage, and the like.
  • the calculation means includes a CPU and the like.
  • the control unit 61 is realized by the arithmetic means reading and executing a control program or the like stored in the storage means.
  • the storage means possessed by the control unit 61 is the relationship between the ethanol concentration and the change amount of the resistance value and the resistance value (first alcohol-derived change amount ⁇ R11 and second alcohol-derived change amount ⁇ R21), the formaldehyde concentration and the resistance value, and the change amount. It is preferable that information indicating the relationship with the amount of change in the resistance value (the amount of change ⁇ R12 derived from the first aldehydes and the amount of change ⁇ R22 derived from the second aldehydes) is stored.
  • the control unit 61 can determine the formaldehyde concentration or the ethanol concentration by comparing the stored value stored in the storage means with the measured value measured by the resistance measuring unit 50.
  • the control unit 61 receives the measurement results of the resistance measurement unit 50 (first resistance measurement unit 50A and second resistance measurement unit 50B). In the present embodiment, the control unit 61 receives the signal of the measurement result of the ethanol concentration measured by the first resistance measurement unit 50A and the formaldehyde concentration and the ethanol concentration measured by the second resistance measurement unit 50B. .. The control unit 61 determines the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30 based on the signals received from the first resistance measurement unit 50A and the second resistance measurement unit 50B. Calculated, the amount of change in the resistance value of the first detection unit 20 detected by the first resistance measurement unit 50A and the amount of change in the resistance value of the second detection unit 30 detected by the second resistance measurement unit 50B.
  • control unit 61 adds up the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30, and sets the amount of change in the resistance value detected by the first detection unit 20 and the first.
  • the combined change amount is calculated by adding up the change amount of the resistance value detected by the detection unit 30 of 2.
  • the control unit 61 can determine the obtained synthetic change amount as the change amount of the resistance derived from formaldehyde and calculate the formaldehyde concentration.
  • each of the resistance values is derived from ethanol measured by the first detection unit 20 and the second detection unit 30. Find the combined resistance of the resistance to be produced and the combined resistance of the resistance derived from formaldehyde.
  • the total resistance of the resistance derived from ethanol measured by the first detection unit 20 and the second detection unit 30 will be described.
  • the first alcohol-derived change amount ⁇ R11 and the second alcohol-derived change amount ⁇ R21 of the resistance value derived from ethanol are added together, the change in resistance derived from ethanol up to the ethanol concentration concentration C1.
  • the amount is almost zero. That is, as shown in FIG. 9, when the ethanol concentration is C1 or less, the ethanol when the resistance value detected by the first detection unit 20 and the resistance value detected by the second detection unit 30 are added up.
  • the combined resistance R1 total derived from is almost constant.
  • the combined resistance of the formaldehyde-derived resistor measured by the first detection unit 20 and the second detection unit 30 will be described.
  • the resistance value derived from formaldehyde in the first detection unit 20 is constant, the amount of change in the resistance value is zero, and the resistance value derived from formaldehyde in the second detection unit 30
  • the amount of change ⁇ R22 derived from the second aldehydes decreases at a predetermined rate.
  • the combined resistance R2 total derived from formaldehyde when the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30 are added is the concentration from zero to the concentration.
  • the amount of change ⁇ R12 derived from the first aldehydes in the resistance value derived from formaldehyde in the first detection unit 20 decreases at a predetermined rate, and is derived from formaldehyde in the second detection unit 30.
  • the amount of change ⁇ R22 derived from the second aldehydes in the resistance value to be changed decreases at a predetermined rate.
  • the combined resistance R2 total derived from formaldehyde when the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30 are added is the concentration from zero to the concentration.
  • the synthetic change amount when the synthetic change amount is calculated, the change amount of the resistance derived from ethanol, which is calculated by adding the first alcohol-derived change amount ⁇ R11 and the second alcohol-derived change amount ⁇ R21, becomes almost zero. Therefore, the synthetic change amount shows only the change amount of the resistance derived from formaldehyde.
  • the control unit 61 has a relationship between the ethanol concentration and the resistance value and the change amount of the resistance value (first alcohol-derived change amount ⁇ R11 and second alcohol-derived change amount ⁇ R21) stored in the storage means in advance.
  • a relationship diagram showing the relationship between the formaldehyde concentration and the resistance value and the amount of change in the resistance value (first aldehyde-derived change amount ⁇ R12 and second aldehyde-derived change amount ⁇ R22) may be used.
  • the control unit 61 can obtain the formaldehyde concentration corresponding to the amount of synthetic change by comparing the measured value with the recorded value.
  • the control unit 61 sets the resistance value derived from ethanol or formaldehyde stored in the storage means as the resistance value obtained when the ethanol concentration and the formaldehyde concentration are 0 ppm, respectively, as shown in the following formulas (1) and (2).
  • the value divided by R01 and R02 may be stored as ethanol sensitivity and formaldehyde sensitivity.
  • the control unit 61 responds to the amount of synthetic change by comparing the measured value with the recorded value by using the relationship diagram showing the relationship between the ethanol concentration and the ethanol sensitivity and the relationship diagram showing the relationship between the formaldehyde concentration and the formaldehyde sensitivity.
  • the ethanol concentration and formaldehyde concentration are required.
  • Ethanol sensitivity (change in resistance value) resistance value derived from ethanol / resistance value R01 ...
  • Formaldehyde sensitivity (change in resistance value) resistance value derived from formaldehyde / resistance value R02 ... (2)
  • the operation unit 62 is electrically connected to the control unit 61 and controls the control unit 61.
  • the display unit 63 displays the calculated formaldehyde concentration and the like.
  • a liquid crystal display or the like can be used as the display unit 63.
  • the gas concentration measuring device 1 includes a first detection unit 20 and a second detection unit 30.
  • the combined change amount is calculated by adding up the change amount of the resistance value of the first detection unit 20 and the change amount of the resistance value of the second detection unit 30, and the first detection unit 20
  • the first alcohol-derived change amount ⁇ R11 and the second alcohol-derived change amount ⁇ R21 of the second detection unit 30 are added together.
  • the amount of change in resistance derived from ethanol, which is calculated by adding up these, can be made almost zero.
  • the synthetic change amount shows only the change amount of the resistance derived from formaldehyde. ..
  • the gas concentration measuring device 1 stably obtains only the amount of change in resistance derived from formaldehyde from the amount of synthetic change by using a relationship diagram or the like showing the relationship between the formaldehyde concentration and the amount of synthetic change obtained in advance. be able to. Therefore, the control device 60 can calculate only the formaldehyde concentration from the amount of synthetic change.
  • the gas concentration measuring device 1 can reduce the influence of ethanol even if the gas to be inspected contains ethanol or the like, so that the formaldehyde concentration can be easily measured with higher accuracy.
  • the gas concentration measuring device 1 Since the gas concentration measuring device 1 has the above-mentioned characteristics, it can be effectively used for VOC analysis. Therefore, when analyzing VOCs, even if the atmosphere contains ethanol or the like in addition to formaldehyde, the gas concentration measuring device 1 can easily measure the concentration of formaldehyde alone, so that VOC analysis in an indoor environment and humans can be performed. It can be effectively used for analysis of VOC contained in the exhaled breath of formaldehyde. Therefore, since the gas concentration measuring device 1 can be effectively used for VOC analysis and the like, it can be suitably used for preventing sick house syndrome and managing physical condition.
  • the gas concentration measuring device 1 includes the control device 60, and the control device 60 synthesizes the amount of change in the resistance value of the first detection unit 20 and the amount of change in the resistance value of the second detection unit 30.
  • the amount of change can be calculated. Since the amount of change in resistance derived from ethanol, which is calculated by adding the amount of change ⁇ R11 derived from the first alcohol and the amount of change ⁇ R21 derived from the second alcohol, can be set to zero, the amount of synthetic change can be changed to formaldehyde. Only the amount of change in the resulting resistance can be calculated.
  • control device 60 can obtain the amount of change in resistance derived from formaldehyde from the amount of synthetic change by using a relationship diagram or the like showing the relationship between the formaldehyde concentration and the amount of synthetic change obtained in advance.
  • Formaldehyde concentration can be calculated from the amount of change.
  • the first detection unit 20 can set the amount of change in resistance due to the concentration of aldehydes to zero. As a result, the gas concentration measuring device 1 calculates the combined change amount by adding up the change amount of the resistance value of the first detection unit 20 and the change amount of the resistance value of the second detection unit 30. Since only the amount of change ⁇ R22 derived from aldehydes can be detected, only the amount of change in resistance derived from formaldehyde can be reliably calculated from the amount of synthetic change. Therefore, the gas concentration measuring device 1 can more reliably calculate only the formaldehyde concentration from the synthetic change amount.
  • the gas concentration measuring device 1 can maximize the resistance value detected by the first detection unit 20 when the ethanol concentration is 0.1 ppm to 1.2 ppm. As a result, the formaldehyde concentration can be stably measured even if ethanol is contained in the atmosphere in a low concentration range such as 0.1 ppm to 1.2 ppm.
  • the gas concentration measuring device 1 can be arranged in the device main body 10 in a state where the first detection unit 20 and the second detection unit 30 are connected in series via the energization line L. As a result, for example, it is sufficient to install only one AD converter or the like that converts the detection signals measured by the first detection unit 20 and the second detection unit 30 into resistance values in the apparatus main body 10. , The manufacturing cost can be reduced while simplifying the configuration of the gas concentration measuring device 1.
  • the gas concentration measuring device 1 forms the first detection unit 20 with a gas sensing layer 235c containing SnO 2 and one or more subcomponents of Fe, Al, Si and Ag, and the second detection.
  • the portion 30 can be formed by the gas sensing layer 235c containing SnO 2.
  • the gas concentration measuring device 1 can use the gas sensing layer 235c containing 1.0 mol% to 10.0 mol% of an auxiliary component with respect to SnO 2 as the first detection unit 20.
  • the first detection unit 20 can adjust the amount of change ⁇ R11 derived from the first alcohol derived from ethanol detected by the first detection unit 20 to an arbitrary size, so that the second detection unit 30 can adjust the amount of change ⁇ R11. It is adjusted to the magnitude of the second alcohol-derived change amount ⁇ R21 derived from the detected ethanol. Therefore, the difference between the first alcohol-derived change amount ⁇ R11 detected by the first detection unit 20 and the second alcohol-derived change amount ⁇ R21 detected by the second detection unit 30 is easily set to zero. Can be adjusted.
  • the gas concentration measuring device 1 has a change in resistance derived from formaldehyde from a synthetic change in which the change in resistance of the first detection unit 20 and the change in resistance in the second detection unit 30 are added up. Since only can be calculated with high accuracy, the concentration of formaldehyde contained in the atmosphere can be measured more reliably.
  • the gas concentration measuring device 1 measures only the formaldehyde concentration in the atmosphere in the space S of the building has been described, but the gas concentration measuring device 1 has only the formaldehyde concentration in the atmosphere as described above. Can be easily measured. Therefore, the gas concentration measuring device 1 is installed not only in the interior of a building but also in a vehicle, a train, an airplane, etc., and is effectively used for measuring the formaldehyde concentration in the air in those spaces. be able to.
  • the gas concentration measuring device 1 can measure aldehydes such as acetaldehyde other than formaldehyde and alcohols such as methanol other than ethanol as the gas to be inspected, and is effectively used for analysis of VOCs other than aldehydes and alcohols. be able to.
  • the gas to be inspected includes flammable gases such as methane (CH 4 ), propane (C 3 H 8 ) and butane (C 4 H 10 ), and carbon monoxide (CO). ), Toxic gas such as nitrogen oxide (NOx), malodorous gas such as sulfur compound (SOx), etc. can also be effectively used.
  • the gas concentration measuring device 1 can be used, for example, for detecting gas leakage or incomplete combustion.
  • the resistance value of the second aldehyde-derived change amount ⁇ R22 detected by the second detection unit 30 may increase at a predetermined rate as the formaldehyde concentration increases. ..
  • the first detection unit 20 and the second detection unit 30 may be connected in parallel with the power supply unit 40 via the energization line L.
  • the first detection unit 20 and the second detection unit 30 are installed in the device main body 10, but even if only one of them is installed in the device main body 10 and the other is provided in the space S1. Good.
  • the pair of resistance portions 50a of the resistance measuring unit 50 may be provided so as to be connected to the energizing line L so as to straddle the first detection unit 20 and the second detection unit 30.
  • the gas concentration measuring device 1 for example, as shown in FIG. 14, the first detecting unit 20 and the second detecting unit 30 are connected in series, and the pair of resistance units 50a of the first resistance measuring unit 50A are connected. Can be connected to the energizing line L so as to straddle the first detection unit 20 and the second detection unit 30.
  • the gas concentration measuring device 1 can measure the change amount of the combined resistance of the first detection unit 20 and the second detection unit 30 as the change amount of the resistance derived from the formaldehyde concentration by the control device 60. Only the concentration of formaldehyde can be calculated stably.
  • control device 60 may be provided in the device main body 10, or at least one of the control unit 61, the operation unit 62, and the display unit 63 of the control device 60 is provided in the device main body 10. You may.
  • Example 1 [Manufacturing of semiconductor sensor] A semiconductor type gas sensor element formed of a thin film of tin oxide (SnO 2) was prepared.
  • ethanol gas is supplied into the container using the gas sensor element as the detection target gas, and the resistance values when the ethanol gas concentrations are about 0.01 ppm, about 0.04 ppm, about 0.1 ppm, and about 1.0 ppm are set. Each was measured, and the resistance value R1 (unit: ⁇ ) was measured.
  • the resistance values R1 and R2 were divided by the resistance value R0 obtained when the concentrations of ethanol gas and formaldehyde gas were 0 ppm, and the amount of change in each resistance value was determined as ethanol sensitivity and formaldehyde sensitivity.
  • FIG. 15 shows the relationship between the ethanol concentration and the amount of change in the resistance value of the gas sensor element formed of SnO 2
  • FIG. 16 shows the relationship between the formaldehyde concentration and the amount of change in the resistance value.
  • the magnitude of the change in resistance value means the magnitude of gas sensitivity, the larger the change in resistance value, the higher the gas sensitivity, and the smaller the change in resistance value, the lower the gas sensitivity. This means that gas is not detected when there is no change in resistance value.
  • Ethanol sensitivity (change in resistance value) resistance value R1 / resistance value R0
  • Formaldehyde sensitivity (change in resistance value) resistance value R2 / resistance value R0
  • Example 2 tin oxide (Fe: 1 mol%) to which iron (Fe) was added, tin oxide (Fe addition amount: 2 mol%) to which iron (Fe) was added, and aluminum (Al) were used as materials for forming the gas sensor element.
  • the relationship between the ethanol concentration and the amount of change in the resistance value of the gas sensor element is shown in FIG. 15, and the relationship between the formaldehyde concentration and the amount of change in the resistance value is shown in FIG.
  • the gas concentration measuring device can measure only the formaldehyde concentration with high accuracy even if the ethanol concentration is as low as about 0.1 ppm or less with a simple configuration.
  • Gas concentration measuring device 10 Device main body 20 First detection unit 235 Gas detection unit 235c Gas sensing layer 30 Second detection unit 40 Power supply unit 50 Resistance measurement unit 50A First resistance measurement unit 50B Second resistance measurement unit 60 Control device 61 Control unit G Inspection target gas S1 Space S2 Detection space ⁇ R11 First alcohol-derived change amount ⁇ R12 First aldehyde-derived change amount ⁇ R21 Second alcohol-derived change amount ⁇ R22 Second aldehyde-derived change amount

Abstract

A gas concentration measurement device according to the present invention can measure the concentration of an aldehyde in a gas of interest that contains the aldehyde and an alcohol, the device being equipped with: a first detection section which has such a first alcohol-related change amount that a detected resistance value increases at a specific rate with the increase in the concentration of the alcohol and in which the detected resistance value does not increase even when the concentration of the aldehyde increases; and a second detection section which has such a second alcohol-related change amount that a detected resistance value decreases at the same rate as that for the first alcohol-related change amount with the increase in the concentration of the alcohol and also has such an aldehyde-related change amount that the detected resistance value decreases at a specific rate with the increase in the concentration of the aldehyde.

Description

ガス濃度測定装置Gas concentration measuring device
　本発明は、ガス濃度測定装置に関する。 The present invention relates to a gas concentration measuring device.
　検知対象となるガス（検査対象ガス）中に含まれる特定のガス（化学物質）を検出するガスセンサを備えたガス濃度測定装置は、建物や車両等において様々な用途に用いられている。 Gas concentration measuring devices equipped with gas sensors that detect specific gases (chemical substances) contained in the gas to be detected (gas to be inspected) are used for various purposes in buildings, vehicles, and the like.
　ガスセンサにより検出されるガスとして、例えば、エタノール（Ｃ2Ｈ5ＯＨ）、ホルムアルデヒド（ＨＣＨＯ）、アセトン（Ｃ3Ｈ6Ｏ）、クロロホルム（ＣＨＣl3）等の揮発性有機化合物（Volatile Organic Compounds：ＶＯＣ）；メタン(ＣＨ4)、プロパン(Ｃ3Ｈ8)、ブタン(Ｃ4Ｈ10)等の可燃性ガス；一酸化炭素(ＣＯ)、窒素酸化物(ＮＯｘ)等の有毒ガス；硫黄化合物（ＳＯｘ）等の悪臭ガスが挙げられる。上記ガスの中でも、ＶＯＣは、毒性の高い化学物質を含み、頭痛、めまい又は吐き気等の健康被害の原因となる大気汚染物質であると共に、シックハウス症候群の原因物質でもある。特に、アルデヒド類の一種であるホルムアルデヒドは、住宅や生活用品から発生することが知られており、シックハウス症候群の主要因の物質であると考えられ、発がん性のある物質とされている。 Volatile Organic Compounds (VOC) such as ethanol (C 2 H 5 OH), formaldehyde (HCHO), acetone (C 3 H 6 O), chloroform (CHCl 3 ) and the like can be detected by the gas sensor. ); Combustible gas such as methane (CH 4 ), propane (C 3 H 8 ), butane (C 4 H 10 ); toxic gas such as carbon monoxide (CO), nitrogen oxide (NOx); sulfur compound ( Examples include malodorous gas such as SOx). Among the above gases, VOCs contain highly toxic chemical substances, are air pollutants that cause health hazards such as headache, dizziness and nausea, and are also causative substances of sick house syndrome. In particular, formaldehyde, which is a kind of aldehydes, is known to be generated from housing and daily necessities, and is considered to be a substance that is a main cause of sick house syndrome, and is considered to be a carcinogenic substance.
　上記ガスを検出するガスセンサの一つに半導体式センサがある。半導体式センサは、様々な種類のガスに対して高感度に反応でき、電気化学式センサ等の他のセンサに比べて低コストである。そのため、半導体式センサをＶＯＣの分析等に用いることが検討されている。その際、半導体式センサは、様々な種類のＶＯＣに対して高感度に反応するため、ホルムアルデヒドの他に、エタノール等のアルコールにも反応し易い。そこで、ホルムアルデヒドをアルコール等の他のＶＯＣと区別して測定するため、複数のガスセンサを備えて、複数のガスを検出するガス濃度検出装置が提案されている。 There is a semiconductor type sensor as one of the gas sensors that detect the above gas. Semiconductor-type sensors can react to various types of gases with high sensitivity, and are less costly than other sensors such as electrochemical sensors. Therefore, it is being studied to use a semiconductor sensor for VOC analysis and the like. At that time, since the semiconductor sensor reacts with high sensitivity to various types of VOCs, it easily reacts with alcohols such as ethanol in addition to formaldehyde. Therefore, in order to measure formaldehyde separately from other VOCs such as alcohol, a gas concentration detecting device having a plurality of gas sensors and detecting a plurality of gases has been proposed.
　このようなガス濃度測定装置として、例えば、室内のホルムアルデヒド等のガスを検知する第１のガスセンサと、室内のアルコール濃度を検出する第２のガスセンサと、第１のガスセンサと第２のガスセンサとの濃度信号を電気信号に変換して室内のガス濃度を演算する制御部とを備えたガス濃度測定装置が提案されている（例えば、特許文献１参照）。このガス濃度測定装置では、制御部が第１のガスセンサからの濃度信号と第２のガスセンサからの濃度信号の出力差に基づいてホルムアルデヒドの濃度を測定している。 As such a gas concentration measuring device, for example, a first gas sensor that detects a gas such as formaldehyde in the room, a second gas sensor that detects the alcohol concentration in the room, a first gas sensor, and a second gas sensor. A gas concentration measuring device including a control unit that converts a concentration signal into an electric signal and calculates a gas concentration in a room has been proposed (see, for example, Patent Document 1). In this gas concentration measuring device, the control unit measures the formaldehyde concentration based on the output difference between the concentration signal from the first gas sensor and the concentration signal from the second gas sensor.
日本国特開２０１８－１３６２９１号公報Japanese Patent Application Laid-Open No. 2018-136291
　しかしながら、特許文献１のガス濃度測定装置では、ホルムアルデヒドの濃度を算出する際、ガスの種類がホルムアルデヒドのみの場合と、エタノールのみの場合と、ホルムアルデヒドとエタノールの混合状態の場合とに応じて、第１のガスセンサの濃度信号を補正して演算処理する必要がある。そのため、ホルムアルデヒド等のアルデヒド類の濃度を簡易に測定できない。 However, in the gas concentration measuring device of Patent Document 1, when calculating the concentration of formaldehyde, the gas type depends on the case of only formaldehyde, the case of only ethanol, and the case of a mixed state of formaldehyde and ethanol. It is necessary to correct the concentration signal of the gas sensor of 1 and perform arithmetic processing. Therefore, the concentration of aldehydes such as formaldehyde cannot be easily measured.
　本発明に係るガス濃度測定装置は、簡易にアルデヒド類を高精度に測定できるガス濃度測定装置を提供することを目的とする。 An object of the gas concentration measuring device according to the present invention is to provide a gas concentration measuring device capable of easily and accurately measuring aldehydes.
　本発明に係るガス濃度測定装置の一態様は、アルデヒド類とアルコールとを含む検査対象ガスの前記アルデヒド類の濃度を測定するガス濃度測定装置であって、前記アルコールの濃度が高くなるにしたがって検出される抵抗値が所定の割合で上昇する第１のアルコール由来変化量を有し、前記アルデヒド類の濃度が高くなっても検出される抵抗値が上昇しない第１の検出部と、前記アルコールの濃度が高くなるにしたがって検出される抵抗値が第１のアルコール由来変化量と同じ割合で低下する第２のアルコール由来変化量を有し、前記アルデヒド類の濃度が高くなるにしたがって検出される抵抗値が所定の割合で低下する、アルデヒド類由来の変化量を有する第２の検出部と、を備える。 One aspect of the gas concentration measuring device according to the present invention is a gas concentration measuring device that measures the concentration of the aldehydes in the gas to be inspected containing aldehydes and alcohol, and detects as the concentration of the alcohol increases. A first detection unit having a first alcohol-derived change amount in which the resistance value to be increased increases at a predetermined rate, and the detected resistance value does not increase even when the concentration of the aldehydes increases, and the alcohol. The resistance value detected as the concentration increases has a second alcohol-derived change amount that decreases at the same rate as the first alcohol-derived change amount, and the resistance detected as the concentration of the aldehydes increases. A second detection unit having a change amount derived from aldehydes, the value of which decreases at a predetermined rate, is provided.
　本発明に係るガス濃度測定装置の一態様は、簡易にアルデヒド類を高精度に測定できる。 One aspect of the gas concentration measuring device according to the present invention can easily measure aldehydes with high accuracy.
一実施形態に係るガス濃度測定装置の構成の一例を示す図である。It is a figure which shows an example of the structure of the gas concentration measuring apparatus which concerns on one Embodiment. 第１の検出部のガス濃度と抵抗値との関係の一例を示す図である。It is a figure which shows an example of the relationship between a gas concentration of a 1st detection part, and a resistance value. 第１の検出部のガス濃度と抵抗値との関係の他の一例を示す図である。It is a figure which shows another example of the relationship between a gas concentration of a 1st detection part, and a resistance value. ガスセンサの構成の一例を示す概念断面図である。It is a conceptual cross-sectional view which shows an example of the structure of a gas sensor. ガスセンサを構成する、ガスセンサ素子の構成の一例を示す概念断面図である。It is a conceptual cross-sectional view which shows an example of the structure of the gas sensor element which constitutes a gas sensor. 第２の検出部のガス濃度と抵抗値との関係の一例を示す図である。It is a figure which shows an example of the relationship between a gas concentration of a 2nd detection part, and a resistance value. 制御装置の一例を説明する図である。It is a figure explaining an example of a control device. エタノールの合成抵抗値の算出の一例を示す説明図である。It is explanatory drawing which shows an example of the calculation of the synthesis resistance value of ethanol. エタノールの合成抵抗値の算出の一例を示す説明図である。It is explanatory drawing which shows an example of the calculation of the synthesis resistance value of ethanol. ホルムアルデヒドの合成抵抗値の算出の一例を示す説明図である。It is explanatory drawing which shows an example of the calculation of the synthetic resistance value of formaldehyde. ホルムアルデヒドの合成抵抗値の算出の一例を示す説明図である。It is explanatory drawing which shows an example of the calculation of the synthetic resistance value of formaldehyde. ホルムアルデヒドの合成抵抗値の算出の他の一例を示す説明図である。It is explanatory drawing which shows another example of the calculation of the synthetic resistance value of formaldehyde. ホルムアルデヒドの合成抵抗値の算出の他の一例を示す説明図である。It is explanatory drawing which shows another example of the calculation of the synthetic resistance value of formaldehyde. ガス濃度測定装置の他の構成の一例を示す図である。It is a figure which shows an example of another configuration of a gas concentration measuring apparatus. 例１～例５のガスセンサ素子の、エタノール濃度と抵抗値の変化量との関係を示す図である。It is a figure which shows the relationship between the ethanol concentration and the change amount of the resistance value of the gas sensor element of Examples 1 to 5. 例１～例５のガスセンサ素子の、ホルムアルデヒド濃度と抵抗値の変化量との関係を示す図である。It is a figure which shows the relationship between the formaldehyde concentration and the change amount of the resistance value of the gas sensor element of Examples 1 to 5.
　以下、本発明の実施の形態について、詳細に説明する。なお、説明の理解を容易にするため、各図面において同一の構成要素に対しては同一の符号を付して、重複する説明は省略する。また、図面における各部材の縮尺は実際とは異なる場合がある。本明細書において数値範囲を示すチルダ「～」は、別段の断わりがない限り、その前後に記載された数値を下限値及び上限値として含むことを意味する。 Hereinafter, embodiments of the present invention will be described in detail. In addition, in order to facilitate understanding of the description, the same components are designated by the same reference numerals in each drawing, and duplicate description will be omitted. In addition, the scale of each member in the drawing may differ from the actual scale. Unless otherwise specified, the tilde "-" indicating a numerical range in the present specification means that the numerical values described before and after the tilde are included as the lower limit value and the upper limit value.
＜ガス濃度測定装置＞
　一実施形態に係るガス濃度測定装置について説明する。本実施形態では、一例として、建物の室内空間（空間）の空気中に含まれるＶＯＣを測定する場合について説明する。なお、ＶＯＣとは、ホルムアルデヒド、アセトアルデヒド、プロピオンアルデヒド、ブタナール、ペンタナール、ヘキサナール、ヘプタナール、オクタナール、ノナナール、グルタルアルデヒド等のアルデヒド類；エタノール、メタノール、ｎ－ブタノール等のアルコール；アセトン、トルエン、キシレン、酢酸エチル、クロロホルム、パラジクロロベンゼン等をいう。これらは、例えば、化学品、塗料、印刷インキ、接着剤、溶剤及び燃焼等に含まれる。本実施形態では、ガス濃度測定装置で測定するＶＯＣがホルムアルデヒド及びエタノールである場合について説明する。 <Gas concentration measuring device>
A gas concentration measuring device according to an embodiment will be described. In the present embodiment, as an example, a case where VOC contained in the air of the indoor space (space) of the building is measured will be described. VOCs are aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butanal, pentanal, hexanal, heptanal, octanal, nonanal and glutalaldehyde; alcohols such as ethanol, methanol and n-butanol; acetone, toluene, xylene and acetic acid. Refers to ethyl, chloroform, paradichlorobenzene, etc. These are included, for example, in chemicals, paints, printing inks, adhesives, solvents, combustion and the like. In this embodiment, the case where the VOC measured by the gas concentration measuring device is formaldehyde and ethanol will be described.
　図１は、一実施形態に係るガス濃度測定装置の構成の一例を示す図である。図１に示すように、ガス濃度測定装置１は、装置本体１０、第１の検出部２０、第２の検出部３０、電源部４０、抵抗測定部５０及び制御装置６０を有する。ガス濃度測定装置１は、建物や車両等の同一の空間Ｓ１内に設けられる。第１の検出部２０、第２の検出部３０及び電源部４０は、通電ラインＬを介して直列に接続されている。空間Ｓ１内の空気中には、検査対象ガスとしてＶＯＣであるホルムアルデヒド及びエタノールを含む。 FIG. 1 is a diagram showing an example of the configuration of the gas concentration measuring device according to the embodiment. As shown in FIG. 1, the gas concentration measuring device 1 includes a device main body 10, a first detecting unit 20, a second detecting unit 30, a power supply unit 40, a resistance measuring unit 50, and a control device 60. The gas concentration measuring device 1 is provided in the same space S1 such as a building or a vehicle. The first detection unit 20, the second detection unit 30, and the power supply unit 40 are connected in series via an energization line L. The air in the space S1 contains formaldehyde and ethanol, which are VOCs, as the gas to be inspected.
　装置本体１０は、直方体状等に形成され、内部に空間を有するものを用いることができる。装置本体１０は、例えば合成樹脂等で形成できる。装置本体１０は、図１に示すように、その表面に第１の検出部２０及び第２の検出部３０を空間Ｓ１と接触可能となるように配置している。装置本体１０は、その内部に電源部４０及び抵抗測定部５０を備え、外部に制御装置６０を備える。 The device main body 10 can be formed in a rectangular parallelepiped shape or the like and has a space inside. The device body 10 can be formed of, for example, a synthetic resin or the like. As shown in FIG. 1, the apparatus main body 10 has a first detection unit 20 and a second detection unit 30 arranged on the surface thereof so as to be in contact with the space S1. The device main body 10 includes a power supply unit 40 and a resistance measuring unit 50 inside, and a control device 60 outside.
　第１の検出部２０は、検査対象ガス中のガス濃度としてエタノールの濃度（エタノール濃度）を測定するものであり、エタノール濃度センサとして機能する。第１の検出部２０は、図２に示すように、エタノール濃度が濃度ゼロから濃度Ｃ１にかけて高くなるにしたがって検出される抵抗値が抵抗値Ｒ０から抵抗値Ｒ１１にかけて所定の割合で上昇する、エタノール由来の変化量（第１のアルコール由来変化量）ΔＲ１１を有する。なお、第１の検出部２０では、エタノール濃度が濃度Ｃ１を超えると、検出される抵抗値は低下する。第１の検出部２０では、エタノール濃度に応じて第１の検出部２０の周囲の酸素量が変化することで、第１の検出部２０で検出される抵抗値が変化する。第１の検出部２０で抵抗値が変化する詳細については、後述する。 The first detection unit 20 measures the concentration of ethanol (ethanol concentration) as the gas concentration in the gas to be inspected, and functions as an ethanol concentration sensor. As shown in FIG. 2, the first detection unit 20 increases the detected resistance value from the resistance value R0 to the resistance value R11 at a predetermined rate as the ethanol concentration increases from the concentration zero to the concentration C1. It has a change amount derived from (first alcohol-derived change amount) ΔR11. In the first detection unit 20, when the ethanol concentration exceeds the concentration C1, the detected resistance value decreases. In the first detection unit 20, the resistance value detected by the first detection unit 20 changes by changing the amount of oxygen around the first detection unit 20 according to the ethanol concentration. The details of the resistance value changing in the first detection unit 20 will be described later.
　第１の検出部２０で検出される抵抗値、すなわちエタノール濃度が濃度Ｃ１である時に検出される抵抗値Ｒ１１は、例えば、エタノール濃度が０．１ｐｐｍ～１．２ｐｐｍで最大となるようにしてもよい。 The resistance value detected by the first detection unit 20, that is, the resistance value R11 detected when the ethanol concentration is the concentration C1, can be maximized, for example, when the ethanol concentration is 0.1 ppm to 1.2 ppm. Good.
　第１の検出部２０は、図２に示すように、ガス濃度としてホルムアルデヒドの濃度（ホルムアルデヒド濃度）が濃度ゼロから濃度Ｃ１及びＣ２にかけて高くなっても検出されるホルムアルデヒドに由来する抵抗値が上昇しない。すなわち、第１の検出部２０は、ホルムアルデヒド濃度が濃度ゼロから濃度Ｃ２にかけて、ホルムアルデヒド濃度に関わらず、検出されるホルムアルデヒドに由来する抵抗の変化量は一定でもよく、ゼロであることが好ましい。 As shown in FIG. 2, the first detection unit 20 does not increase the resistance value derived from formaldehyde detected even if the formaldehyde concentration (formaldehyde concentration) increases from zero to the concentrations C1 and C2 as the gas concentration. .. That is, in the first detection unit 20, the amount of change in the detected formaldehyde-derived resistance may be constant from zero to zero, regardless of the formaldehyde concentration, and is preferably zero.
　また、第１の検出部２０は、図３に示すように、ホルムアルデヒド濃度が濃度ゼロから濃度Ｃ１にかけて高くなるにしたがって検出される抵抗値が抵抗値Ｒ０から抵抗値Ｒ１２にかけて所定の割合で低下する、ホルムアルデヒド由来の変化量（第１のアルデヒド類由来変化量）ΔＲ１２を有してもよい。また、第１の検出部２０は、ホルムアルデヒド濃度が濃度Ｃ１よりも高い濃度（例えば、濃度Ｃ２）にかけて検出される抵抗値が抵抗値Ｒ１２から第１のアルデヒド類由来変化量ΔＲ１２の割合で低下していてもよい。 Further, as shown in FIG. 3, the resistance value detected by the first detection unit 20 decreases at a predetermined rate from the resistance value R0 to the resistance value R12 as the formaldehyde concentration increases from zero concentration to concentration C1. , Formaldehyde-derived change amount (first aldehyde-derived change amount) ΔR12 may be provided. Further, in the first detection unit 20, the resistance value detected when the formaldehyde concentration is higher than the concentration C1 (for example, the concentration C2) decreases at a rate of the change amount ΔR12 derived from the first aldehydes from the resistance value R12. May be.
　第１の検出部２０は、半導体素子としてガスセンサ素子を備える半導体式センサを用いることができる。第１の検出部２０の構成の一例について説明する。図４は、第１の検出部２０の構成の一例を示す概念断面図である。図４に示すように、第１の検出部２０は、ケース体２１、センサベース２２、ガスセンサ素子２３、金属メッシュ２４及び端子２５を備える。第１の検出部２０は、空間Ｓ１からケース体２１に流入する検査対象ガスＧを検出する。なお、図４中の矢印は検査対象ガスＧの流れの向きを示す。また、図４に示す第１の検出部２０の構成は、一例を示すものであって第１の検出部２０の構成はこれに限定されない。第１の検出部２０の各構成について説明する。 The first detection unit 20 can use a semiconductor sensor including a gas sensor element as the semiconductor element. An example of the configuration of the first detection unit 20 will be described. FIG. 4 is a conceptual cross-sectional view showing an example of the configuration of the first detection unit 20. As shown in FIG. 4, the first detection unit 20 includes a case body 21, a sensor base 22, a gas sensor element 23, a metal mesh 24, and a terminal 25. The first detection unit 20 detects the inspection target gas G flowing into the case body 21 from the space S1. The arrow in FIG. 4 indicates the direction of the flow of the inspection target gas G. Further, the configuration of the first detection unit 20 shown in FIG. 4 shows an example, and the configuration of the first detection unit 20 is not limited to this. Each configuration of the first detection unit 20 will be described.
　ケース体２１は、略円筒体であり、その一端にケース体２１の直径よりも小さい口径の流入口２１１を有する。流入口２１１の口径は、特定の大きさに限定されず、例えば数ｍｍ程度でよい。 The case body 21 is a substantially cylindrical body, and has an inflow port 211 having a diameter smaller than the diameter of the case body 21 at one end thereof. The diameter of the inflow port 211 is not limited to a specific size, and may be, for example, about several mm.
　センサベース２２は、円板状に形成され、端面に段差を有する。センサベース２２は、その外径がケース体２１の内径と略同じ径を有する挿入部２２１と、外径がケース体２１の外径よりも大きい径を有する固定部２２２とを有する。挿入部２２１は、ケース体２１の他端に嵌め込まれる。固定部２２２は、ケース体２１の他端に溶接又は接着剤等により固定される。 The sensor base 22 is formed in a disk shape and has a step on the end face. The sensor base 22 has an insertion portion 221 whose outer diameter is substantially the same as the inner diameter of the case body 21, and a fixing portion 222 whose outer diameter is larger than the outer diameter of the case body 21. The insertion portion 221 is fitted into the other end of the case body 21. The fixing portion 222 is fixed to the other end of the case body 21 by welding, an adhesive or the like.
　ケース体２１にセンサベース２２の挿入部２２１が嵌め込まれることで、ケース体２１の内部に検出空間Ｓ２が形成される。 The detection space S2 is formed inside the case body 21 by fitting the insertion portion 221 of the sensor base 22 into the case body 21.
　ガスセンサ素子２３は、検出空間Ｓ２内に配置され、センサベース２２の上面（図４中の上方向）に固定されている。ガスセンサ素子２３は、薄膜型の半導体素子である。図５は、ガスセンサ素子２３の構成の一例を示す概念断面図である。図５に示すように、ガスセンサ素子２３は、基板２３１、熱絶縁支持層２３２、ヒーター層２３３、絶縁層２３４及びガス検知部２３５を備える。 The gas sensor element 23 is arranged in the detection space S2 and is fixed to the upper surface (upward direction in FIG. 4) of the sensor base 22. The gas sensor element 23 is a thin film type semiconductor element. FIG. 5 is a conceptual cross-sectional view showing an example of the configuration of the gas sensor element 23. As shown in FIG. 5, the gas sensor element 23 includes a substrate 231, a heat insulating support layer 232, a heater layer 233, an insulating layer 234, and a gas detection unit 235.
　基板２３１は、シリコン基板（Ｓｉ基板）であり、Ｓｉ基板の代わりに、アルミナ基板、サファイア基板及びマイカ基板等を用いてもよい。基板２３１は、平面視においてガス検知部２３５が形成された位置に貫通孔２３１ａを有する。 The substrate 231 is a silicon substrate (Si substrate), and instead of the Si substrate, an alumina substrate, a sapphire substrate, a mica substrate, or the like may be used. The substrate 231 has a through hole 231a at a position where the gas detection unit 235 is formed in a plan view.
　熱絶縁支持層２３２は、基板２３１の上面（図５中の上方向）に設けられ、貫通孔２３１ａにダイアフラム様に形成されている。本実施形態では、熱絶縁支持層２３２は、第１のＳｉＯ２層２３２ａ、Ｓｉ3Ｎ4層２３２ｂ及び第２のＳｉＯ2層２３２ｃの三層構造で構成されている。 The heat insulating support layer 232 is provided on the upper surface of the substrate 231 (upward in FIG. 5), and is formed in the through hole 231a like a diaphragm. In the present embodiment, the thermal insulating support layer 232, a first SiO 2 layer 232a, is composed of a three-layer structure the Si 3 N 4 layer 232b and the second SiO 2 layer 232c.
　第１のＳｉＯ2層２３２ａは、熱酸化温度８００℃～１１００℃で熱酸化により形成できる。第１のＳｉＯ2層２３２ａは、断熱層として機能し、ヒーター層２３３で発生する熱をＳｉ基板１１側へ伝熱しないようにして熱容量を小さくする機能を有する。また、第１のＳｉＯ２層２３２ａは、プラズマエッチングに対して高い抵抗力を示し、プラズマエッチングによる基板２３１への貫通孔の形成を容易にすることができる。 The first SiO 2 layer 232a can be formed by thermal oxidation at a thermal oxidation temperature of 800 ° C. to 1100 ° C. The first SiO 2 layer 232a functions as a heat insulating layer, and has a function of reducing the heat capacity by preventing heat transfer generated in the heater layer 233 to the Si substrate 11 side. Further, the first SiO 2 layer 232a exhibits high resistance to plasma etching, and can facilitate the formation of through holes in the substrate 231 by plasma etching.
　Ｓｉ３Ｎ４層２３２ｂは、第１のＳｉＯ２層２３２ａの上面（図５中の上方向）に、化学気相成長法（ＣＶＤ）法を用いて形成される。 The Si 3 N 4 layer 232b is formed on the upper surface (upward direction in FIG. 5) of the first SiO 2 layer 232a by using a chemical vapor deposition (CVD) method.
　第２のＳｉＯ２層２３２ｃは、ＣＶＤ法により形成でき、ヒーター層２３３との密着性を向上させると共に絶縁性を確保することができる。ＣＶＤ法により形成される第２のＳｉＯ２層は内部応力が小さいため、熱絶縁支持層２３２に歪みが生じるのを軽減できる。 The second SiO 2 layer 232c can be formed by a CVD method, and can improve the adhesion with the heater layer 233 and secure the insulating property. Since the second SiO 2 layer formed by the CVD method has a small internal stress, it is possible to reduce the occurrence of distortion in the heat insulating support layer 232.
　ヒーター層２３３は、熱絶縁支持層２３２の上面（図５中の上方向）の略中央に設けられる。ヒーター層２３３は、薄膜であり、例えば、ＰｔとＷとを含むＰｔ－Ｗ膜等で形成できる。ヒーター層２３３は、端子２５（図４参照）に接続され、端子２５（図４参照）を介して電源部４０と電気的に接続され、給電される。 The heater layer 233 is provided substantially in the center of the upper surface (upward direction in FIG. 5) of the heat insulating support layer 232. The heater layer 233 is a thin film, and can be formed of, for example, a Pt—W film containing Pt and W. The heater layer 233 is connected to the terminal 25 (see FIG. 4), and is electrically connected to the power supply unit 40 via the terminal 25 (see FIG. 4) to supply power.
　絶縁層２３４は、熱絶縁支持層２３２及びヒーター層２３３を覆うように設けられる。絶縁層２３４は、例えばＳｉＯ２層等で形成できる。絶縁層２３４は、ヒーター層２３３と感知層電極２３５ｂとの間に電気的な絶縁を確保することができると共に、ガス感知層２３５ｃとの密着性を向上させる。 The insulating layer 234 is provided so as to cover the heat insulating support layer 232 and the heater layer 233. The insulating layer 234 can be formed of, for example, two SiO layers. The insulating layer 234 can secure electrical insulation between the heater layer 233 and the sensing layer electrode 235b and improve the adhesion to the gas sensing layer 235c.
　ガス検知部２３５は、一対の接合層２３５ａ、一対の感知層電極２３５ｂ、ガス感知層２３５ｃ及び吸着層２３５ｄを備える。 The gas detection unit 235 includes a pair of bonding layers 235a, a pair of sensing layer electrodes 235b, a gas sensing layer 235c, and an adsorption layer 235d.
　接合層２３５ａは、例えば、タンタル膜（Ｔａ膜）又はチタン膜（Ｔｉ膜）等で形成でき、絶縁層２３４の上に設けられる。接合層２３５ａは、感知層電極２３５ｂと絶縁層２３４との接合強度を高めることができる。 The bonding layer 235a can be formed of, for example, a tantalum film (Ta film) or a titanium film (Ti film), and is provided on the insulating layer 234. The bonding layer 235a can increase the bonding strength between the sensing layer electrode 235b and the insulating layer 234.
　感知層電極２３５ｂは、例えば、白金膜（Ｐｔ膜）又は金膜（Ａｕ膜）等で形成できる。感知層電極２３５ｂは、一対の接合層２３５ａの上に設けられ、ガス感知層２３５ｃの感知電極となる。 The sensing layer electrode 235b can be formed of, for example, a platinum film (Pt film) or a gold film (Au film). The sensing layer electrode 235b is provided on the pair of bonding layers 235a and serves as a sensing electrode for the gas sensing layer 235c.
　ガス感知層２３５ｃは、一対の感知層電極２３５ｂを連結するように絶縁層２３４の上に形成される。 The gas sensing layer 235c is formed on the insulating layer 234 so as to connect the pair of sensing layer electrodes 235b.
　ガス感知層２３５ｃは、図２に示すように、エタノール濃度が高くなるにしたがって検出される抵抗値が上昇する第１のアルコール由来変化量ΔＲ１１を有し、ホルムアルデヒドは殆ど検出せず、アルデヒド類の濃度が高くなっても検出される抵抗値が上昇しない材料を用いて形成することができる。ガス感知層２３５ｃを形成する材料は、図２に示すように、ホルムアルデヒドに由来する抵抗の変化量が一定であるか、図３に示すように、ホルムアルデヒド濃度が高くなるにしたがって検出される抵抗値が低下する第１のアルデヒド類由来変化量ΔＲ１２を有する材料を用いて形成することができる。ガス感知層２３５ｃを形成する材料としては、例えば、ＳｎＯ２と副成分とを含む金属酸化物半導体を用いることができる。 As shown in FIG. 2, the gas sensing layer 235c has a first alcohol-derived change amount ΔR11 in which the detected resistance value increases as the ethanol concentration increases, formaldehyde is hardly detected, and aldehydes are used. It can be formed by using a material in which the detected resistance value does not increase even if the concentration increases. As shown in FIG. 2, the material forming the gas sensing layer 235c has a constant change in resistance derived from formaldehyde, or as shown in FIG. 3, a resistance value detected as the formaldehyde concentration increases. It can be formed by using a material having a first aldehyde-derived change amount ΔR12 in which the amount is reduced. As a material for forming the gas sensing layer 235c, for example, a metal oxide semiconductor containing SnO 2 and a subcomponent can be used.
　ガス感知層２３５ｃは、主成分として、ＳｎＯ２以外に、Ｉｎ2Ｏ3、ＷＯ3、ＺｎＯ又はＴｉＯ2等の金属酸化物を含んでもよい。 The gas sensing layer 235c may contain a metal oxide such as In 2 O 3 , WO 3 , ZnO or TiO 2 as a main component in addition to SnO 2.
　副成分としては、Ｆｅ、Ａｌ、Ｓｉ、Ａｇ等を用いることができる。これらは一種単独で用いてよいし、二種以上を併用してもよい。これらの中でも、第１のアルコール由来変化量ΔＲ１１の大きさの調整のし易さ等の点から、Ｆｅ、Ａｌ及びＳｉが好ましく、Ｆｅがより好ましい。 Fe, Al, Si, Ag, etc. can be used as the sub-ingredient. These may be used alone or in combination of two or more. Among these, Fe, Al and Si are preferable, and Fe is more preferable, from the viewpoint of easy adjustment of the magnitude of the first alcohol-derived change amount ΔR11.
　副成分の含有量は、第１のアルコール由来変化量ΔＲ１１の大きさや適宜設計可能であるが、ガス感知層２３５ｃは、ＳｎＯ2に対して、副成分を１．０ｍｏｌ％～１０．０ｍｏｌ％含むことが好ましく、２．０ｍｏｌ％～８．０ｍｏｌ％含むことがより好ましく、４．０ｍｏｌ％～６．０ｍｏｌ％含むことがさらに好ましい。 The content of the sub-component can be appropriately designed with the magnitude of the first alcohol-derived change amount ΔR11, but the gas sensing layer 235c contains 1.0 mol% to 10.0 mol% of the sub-component with respect to SnO 2. It is more preferable, and it is more preferable to contain 2.0 mol% to 8.0 mol%, and further preferably 4.0 mol% to 6.0 mol%.
　ガス感知層２３５ｃは、多孔質構造や柱状構造としてもよい。これにより、ガス感知層２３５ｃの比表面積を増大させることができるので、検査対象ガスとの接触面積を増加させ、感度を高められる。 The gas sensing layer 235c may have a porous structure or a columnar structure. As a result, the specific surface area of the gas sensing layer 235c can be increased, so that the contact area with the gas to be inspected can be increased and the sensitivity can be increased.
　吸着層２３５ｄは、絶縁層２３４、一対の接合層２３５ａ、一対の感知層電極２３５ｂ及びガス感知層２３５ｃの表面を覆うように設けられる。 The adsorption layer 235d is provided so as to cover the surfaces of the insulating layer 234, the pair of bonding layers 235a, the pair of sensing layer electrodes 235b, and the gas sensing layer 235c.
　吸着層２３５ｄは、パラジウム（Ｐｄ）、白金（Ｐｔ）等の貴金属元素の少なくとも一種を触媒として、多孔質構造を有する担持体に担持した焼結体を用いることができる。担持体として、例えば、アルミナ（Ａｌ2Ｏ3）、酸化クロム（Ｃｒ2Ｏ3）、酸化鉄（Ｆｅ2Ｏ3）、酸化ニッケル（Ｎｉ2Ｏ3）、酸化ジルコニウム（ＺｒＯ2）、シリカ（ＳｉＯ2）、ゼオライト等の金属酸化物を用いることができる。これらは一種単独で用いてもよいし、二種以上を併用してもよい。アルミナ等の担持体は多孔質構造を有するため、孔を通過する検査対象ガスが触媒に接触する面積を増加させることができる。また、大気中に、検査対象ガス以外に、検査対象ガスよりも酸化活性の強い還元性ガスが含まれる場合、還元性ガスの燃焼反応を促進し、検査対象ガスの選択性を高めることができる。これにより、ガス感知層２３５ｃへ達する検査対象ガスのガス濃度が高まり、ガスセンサ素子２３はより感度を高めることができる。 As the adsorption layer 235d, a sintered body supported on a carrier having a porous structure can be used using at least one of noble metal elements such as palladium (Pd) and platinum (Pt) as a catalyst. As the carrier, for example, alumina (Al 2 O 3 ), chromium oxide (Cr 2 O 3 ), iron oxide (Fe 2 O 3 ), nickel oxide (Ni 2 O 3 ), zirconium oxide (ZrO 2 ), silica ( Metal oxides such as SiO 2 ) and zeolite can be used. These may be used alone or in combination of two or more. Since the carrier such as alumina has a porous structure, the area where the gas to be inspected passing through the pores comes into contact with the catalyst can be increased. Further, when the atmosphere contains a reducing gas having a stronger oxidizing activity than the inspection target gas in addition to the inspection target gas, the combustion reaction of the reducing gas can be promoted and the selectivity of the inspection target gas can be enhanced. .. As a result, the gas concentration of the gas to be inspected reaching the gas sensing layer 235c increases, and the sensitivity of the gas sensor element 23 can be further increased.
　ガスセンサ素子２３は、ダイアフラム構造として、高断熱及び低熱容量としている。なお、ガスセンサ素子２３は、ダイアフラム構造でなくてもよい。 The gas sensor element 23 has a diaphragm structure with high heat insulation and low heat capacity. The gas sensor element 23 does not have to have a diaphragm structure.
　図４に示すように、金属メッシュ２４は、流入口２１１に設けられる。金属メッシュ２４の外径は流入口２１１の口径と略同じ径を有する円板状の形状を有する。金属メッシュ２４は、ステンレス製のネットであり、金属メッシュ２４の目開きは数ｍｍ程度であり、開口率は、検査対象ガスが検出空間Ｓ２内に流出入できる大きさであればよい。 As shown in FIG. 4, the metal mesh 24 is provided at the inflow port 211. The outer diameter of the metal mesh 24 has a disk-like shape having substantially the same diameter as the diameter of the inflow port 211. The metal mesh 24 is a stainless steel net, the opening of the metal mesh 24 is about several mm, and the aperture ratio may be such that the gas to be inspected can flow in and out of the detection space S2.
　図４に示すように、端子２５は、センサベース２２から突出して設けられる電極であり、第２の検出部３０（図１参照）及び電源部４０（図１参照）に通電ラインＬ（図１参照）を介して接続されている。図４に示すように、第１の検出部２０は、複数（図４では、４つ）の端子２５ａ、２５ｂ、２５ｃ及び２５ｄを備える。端子２５ａ及び２５ｂは、電源部４０（図１参照）及び第２の検出部３０（図１参照）を接続するための電極である。端子２５ｃ及び２５ｄは、ガスセンサ素子２３を構成するヒーター層２３３（図５参照）を駆動するための電極である。 As shown in FIG. 4, the terminal 25 is an electrode provided so as to project from the sensor base 22, and the energization line L (see FIG. 1) is connected to the second detection unit 30 (see FIG. 1) and the power supply unit 40 (see FIG. 1). See). As shown in FIG. 4, the first detection unit 20 includes a plurality of (four in FIG. 4) terminals 25a, 25b, 25c and 25d. The terminals 25a and 25b are electrodes for connecting the power supply unit 40 (see FIG. 1) and the second detection unit 30 (see FIG. 1). The terminals 25c and 25d are electrodes for driving the heater layer 233 (see FIG. 5) constituting the gas sensor element 23.
　端子２５ａ、２５ｃ及び２５ｄは、電源部４０（図１参照）に通電ラインＬ（図１参照）を介して接続され、端子２５ｂは第２の検出部３０（図１参照）に通電ラインＬ（図１参照）を介して接続される。 The terminals 25a, 25c and 25d are connected to the power supply unit 40 (see FIG. 1) via the energization line L (see FIG. 1), and the terminal 25b is connected to the second detection unit 30 (see FIG. 1) via the energization line L (see FIG. 1). It is connected via (see FIG. 1).
　図４に示すように、第１の検出部２０は、ケース体２１内にガスセンサ素子２３を有しており、第１の検出部２０では、ガスセンサ素子２３の周囲の酸素量に応じてガスセンサ素子２３の抵抗値が変化する。図５に示すように、ガスセンサ素子２３は、ガス感知層２３５ｃを有しており、ガス感知層２３５ｃの表面に吸着している酸素がエタノールと反応（表面反応）すると、酸素が離脱するが、エタノールがガス感知層２３５ｃから自由電子を奪ってイオン（Ｃ2Ｈ5Ｏ－）の状態で付着する。これにより、相対的にガス感知層２３５ｃの表面に存在する自由電子が減少して、ガスセンサ素子２３の抵抗値が増大する（図２参照）。この抵抗値の増加量から、空気中のエタノール濃度を算出できる。ただし、エタノールの体積は酸素よりも大きく、離脱し易い傾向にあるといえる。そのため、エタノールがイオンの状態である程度の濃度まで吸着すると、エタノールのイオン（Ｃ2Ｈ5Ｏ－）はガス感知層２３５ｃから脱離して、ガス感知層２３５ｃの表面に電子を与える。そのため、相対的にガス感知層２３５ｃの表面に存在する自由電子が増大することで、ガスセンサ素子２３の抵抗値が低下する（図２参照）。 As shown in FIG. 4, the first detection unit 20 has a gas sensor element 23 in the case body 21, and the first detection unit 20 has a gas sensor element according to the amount of oxygen around the gas sensor element 23. The resistance value of 23 changes. As shown in FIG. 5, the gas sensor element 23 has a gas sensing layer 235c, and when oxygen adsorbed on the surface of the gas sensing layer 235c reacts with ethanol (surface reaction), oxygen is released, but Ethanol deprives the gas sensing layer 235c of free electrons and adheres in the form of ions (C 2 H 5 O −). As a result, the number of free electrons existing on the surface of the gas sensing layer 235c is relatively reduced, and the resistance value of the gas sensor element 23 is increased (see FIG. 2). The ethanol concentration in the air can be calculated from the amount of increase in the resistance value. However, it can be said that the volume of ethanol is larger than that of oxygen and tends to be easily released. Therefore, when ethanol is adsorbed to a certain concentration in the state of ions, the ethanol ions (C 2 H 5 O − ) are desorbed from the gas sensing layer 235c and donate electrons to the surface of the gas sensing layer 235c. Therefore, the resistance value of the gas sensor element 23 decreases due to the relative increase of free electrons existing on the surface of the gas sensing layer 235c (see FIG. 2).
　第２の検出部３０は、空気中のホルムアルデヒド濃度及びエタノール濃度をそれぞれ測定するものであり、ホルムアルデヒド濃度センサ及びエタノール濃度センサとして機能する。第２の検出部３０は、図６に示すように、エタノール濃度が濃度ゼロから濃度Ｃ１にかけて高くなるにしたがって検出される抵抗値が所定の割合で低下する、エタノール由来の変化量（第２のアルコール由来変化量）ΔＲ２１を有する。第２のアルコール由来変化量ΔＲ２１は、第１のアルコール由来変化量ΔＲ１１（図２参照）と同じ割合で低下する。また、第２の検出部３０は、エタノール濃度が濃度Ｃ１よりも高い濃度（例えば、濃度Ｃ２）にかけて検出される抵抗値が抵抗値Ｒ２１から第２のアルコール由来変化量ΔＲ２１の割合で低下していてもよい。 The second detection unit 30 measures the formaldehyde concentration and the ethanol concentration in the air, respectively, and functions as a formaldehyde concentration sensor and an ethanol concentration sensor. As shown in FIG. 6, the second detection unit 30 has an ethanol-derived change amount (second) in which the detected resistance value decreases at a predetermined rate as the ethanol concentration increases from zero concentration to concentration C1. Alcohol-derived change amount) ΔR21. The second alcohol-derived change amount ΔR21 decreases at the same rate as the first alcohol-derived change amount ΔR11 (see FIG. 2). Further, in the second detection unit 30, the resistance value detected when the ethanol concentration is higher than the concentration C1 (for example, the concentration C2) decreases at a rate of the change amount ΔR21 derived from the second alcohol from the resistance value R21. You may.
　第２の検出部３０は、ホルムアルデヒド濃度が濃度ゼロから濃度Ｃ１にかけて高くなるにしたがって検出される抵抗値が所定の割合で低下する、ホルムアルデヒド由来の変化量（第２のアルデヒド類由来変化量）ΔＲ２２を有する。また、第２の検出部３０は、ホルムアルデヒド濃度が濃度Ｃ１よりも高い濃度（例えば、濃度Ｃ２）にかけて検出される抵抗値が抵抗値Ｒ２２から第２のアルデヒド類由来変化量ΔＲ２２の割合で低下していてもよい。 The second detection unit 30 has a formaldehyde-derived change amount (second aldehyde-derived change amount) ΔR22 in which the detected resistance value decreases at a predetermined rate as the formaldehyde concentration increases from zero concentration to concentration C1. Has. Further, in the second detection unit 30, the resistance value detected when the formaldehyde concentration is higher than the concentration C1 (for example, the concentration C2) decreases at a rate of the change amount ΔR22 derived from the second aldehydes from the resistance value R22. May be.
　第２の検出部３０は、半導体素子としてガスセンサ素子を備える半導体式センサを用いることができる。第２の検出部３０は、図４に示す第１の検出部２０のガスセンサ素子２３を構成するガス感知層２３５ｃ（図５参照）の材料を変更したこと以外は第１の検出部２０と同様の構成を有する。そのため、図４及び図５を用いて、第２の検出部３０を構成するガス感知層２３５ｃについてのみ説明する。 The second detection unit 30 can use a semiconductor sensor including a gas sensor element as the semiconductor element. The second detection unit 30 is the same as the first detection unit 20 except that the material of the gas sensing layer 235c (see FIG. 5) constituting the gas sensor element 23 of the first detection unit 20 shown in FIG. 4 is changed. Has the configuration of. Therefore, only the gas sensing layer 235c constituting the second detection unit 30 will be described with reference to FIGS. 4 and 5.
　第２の検出部３０は、第１の検出部２０と同様、図４に示すように、ケース体２１内にガスセンサ素子２３を有し、ガスセンサ素子２３は、図５に示すように、ガス感知層２３５ｃを有している。 Like the first detection unit 20, the second detection unit 30 has a gas sensor element 23 in the case body 21 as shown in FIG. 4, and the gas sensor element 23 has gas sensing as shown in FIG. It has layer 235c.
　第２の検出部３０のガス感知層２３５ｃは、図６に示すように、ガス濃度としてエタノール濃度及びホルムアルデヒド濃度が濃度ゼロから濃度Ｃ２にかけて高くなるにしたがって検出される抵抗値が低下する第２のアルコール由来変化量ΔＲ２１及び第２のアルデヒド類由来変化量ΔＲ２２を有する材料を用いて形成することができる。第２の検出部３０のガス感知層２３５ｃを形成する材料としては、例えば、ＳｎＯ2を含む金属酸化物半導体を用いることができる。 As shown in FIG. 6, in the gas sensing layer 235c of the second detection unit 30, the detected resistance value decreases as the ethanol concentration and the formaldehyde concentration increase from zero to the concentration C2 as the gas concentration. It can be formed by using a material having an alcohol-derived change amount ΔR21 and a second aldehyde-derived change amount ΔR22. As a material for forming the gas sensing layer 235c of the second detection unit 30, for example, a metal oxide semiconductor containing SnO 2 can be used.
　第２の検出部３０は、図４に示すように、ケース体２１内にガスセンサ素子２３を有しており、第２の検出部３０では、ガスセンサ素子２３の周囲の酸素量に応じてガスセンサ素子２３の抵抗値が変化する。ガスセンサ素子２３は、図５に示すように、ガス感知層２３５ｃを有しており、ガス感知層２３５ｃの表面に吸着している酸素がホルムアルデヒド又はエタノールと反応（表面反応）し、酸素が離脱する。これにより、ガス感知層２３５ｃに付着していた酸素イオン（Ｏ2-）がガス感知層２３５ｃから脱離する際にガス感知層２３５ｃに自由電子を与える。そのため、相対的にガス感知層２３５ｃの表面に吸着している酸素量が少なくなり、ガス感知層２３５ｃに与えられる自由電子の量が増えることで、ガスセンサ素子２３の抵抗値が減少する。この抵抗値の変化量から、空気中のホルムアルデヒド及びエタノールの濃度が算出される。 As shown in FIG. 4, the second detection unit 30 has a gas sensor element 23 in the case body 21, and the second detection unit 30 has a gas sensor element according to the amount of oxygen around the gas sensor element 23. The resistance value of 23 changes. As shown in FIG. 5, the gas sensor element 23 has a gas sensing layer 235c, and oxygen adsorbed on the surface of the gas sensing layer 235c reacts with formaldehyde or ethanol (surface reaction), and oxygen is released. .. As a result, when the oxygen ions (O 2- ) adhering to the gas sensing layer 235c are desorbed from the gas sensing layer 235c, free electrons are given to the gas sensing layer 235c. Therefore, the amount of oxygen adsorbed on the surface of the gas sensing layer 235c is relatively small, and the amount of free electrons given to the gas sensing layer 235c is increased, so that the resistance value of the gas sensor element 23 is reduced. The concentration of formaldehyde and ethanol in the air is calculated from the amount of change in the resistance value.
　第２の検出部３０の端子２５ａ（図４参照）は第１の検出部２０の端子２５ｂ（図４参照）に通電ラインＬ（図１参照）を介して接続され、第２の検出部３０の端子２５ｂ、２５ｃ及び２５ｄ（図４参照）は電源部４０（図１参照）に通電ラインＬ（図１参照）を介して接続されている。 The terminal 25a (see FIG. 4) of the second detection unit 30 is connected to the terminal 25b (see FIG. 4) of the first detection unit 20 via the energization line L (see FIG. 1), and the second detection unit 30 Terminals 25b, 25c and 25d (see FIG. 4) are connected to the power supply unit 40 (see FIG. 1) via an energization line L (see FIG. 1).
　図１に示すように、第１の検出部２０及び第２の検出部３０は、装置本体１０内に、通電ラインＬを介して直列に接続されている。すなわち、第１の検出部２０の端子２５ａ（図４参照）が電源部４０に通電ラインＬを介して接続され、第１の検出部２０の端子２５ｂ（図４参照）が第２の検出部３０の端子２５ａ（図４参照）に通電ラインＬを介して接続され、第２の検出部３０の端子２５ｂ（図４参照）が電源部４０（図４参照）に通電ラインＬを介して接続される。 As shown in FIG. 1, the first detection unit 20 and the second detection unit 30 are connected in series in the apparatus main body 10 via an energization line L. That is, the terminal 25a (see FIG. 4) of the first detection unit 20 is connected to the power supply unit 40 via the energizing line L, and the terminal 25b (see FIG. 4) of the first detection unit 20 is the second detection unit. The terminal 25a (see FIG. 4) of the 30 is connected via the energizing line L, and the terminal 25b (see FIG. 4) of the second detection unit 30 is connected to the power supply unit 40 (see FIG. 4) via the energizing line L. Will be done.
　電源部４０は、図１に示すように、装置本体１０内に設けられており、第１の検出部２０及び第２の検出部３０に電力を供給する。電源部４０は、その一方の電極が第１の検出部２０に接続され、他方の電極が第２の検出部３０に接続されており、電源部４０は、第１の検出部２０及び第２の検出部３０が直列となるように接続されている。 As shown in FIG. 1, the power supply unit 40 is provided in the device main body 10 and supplies electric power to the first detection unit 20 and the second detection unit 30. One electrode of the power supply unit 40 is connected to the first detection unit 20, the other electrode is connected to the second detection unit 30, and the power supply unit 40 has the first detection unit 20 and the second detection unit 20. The detection units 30 of the above are connected in series.
　抵抗測定部５０は、図１に示すように、第１の検出部２０の抵抗値を算出する第１の抵抗測定部５０Ａと、第２の検出部３０の抵抗値を算出する第２の抵抗測定部５０Ｂとを有する。第１の抵抗測定部５０Ａは、一対の抵抗部５０ａを第１の検出部２０を挟み込むように通電ラインＬに接続し、第２の抵抗測定部５０Ｂは、一対の抵抗部５０ａを第２の検出部３０を挟み込むように通電ラインＬに接続する。すなわち、抵抗測定部５０は、第１の抵抗測定部５０Ａで測定された第１の検出部２０のガス感知層２３５ｃ（図５参照）の抵抗値と、第２の抵抗測定部５０Ｂで測定された第２の検出部３０のガス感知層２３５ｃ（図５参照）の抵抗値とを合算した合算抵抗値を算出する。 As shown in FIG. 1, the resistance measuring unit 50 includes a first resistance measuring unit 50A for calculating the resistance value of the first detecting unit 20, and a second resistance for calculating the resistance value of the second detecting unit 30. It has a measuring unit 50B. The first resistance measuring unit 50A connects the pair of resistance parts 50a to the energizing line L so as to sandwich the first detection unit 20, and the second resistance measuring unit 50B connects the pair of resistance parts 50a to the second. It is connected to the energizing line L so as to sandwich the detection unit 30. That is, the resistance measuring unit 50 is measured by the resistance value of the gas sensing layer 235c (see FIG. 5) of the first detecting unit 20 measured by the first resistance measuring unit 50A and the resistance value of the second resistance measuring unit 50B. The total resistance value is calculated by adding the resistance values of the gas sensing layer 235c (see FIG. 5) of the second detection unit 30.
　抵抗測定部５０は、制御装置６０の、後述する制御部６１（図７参照）と電気的に接続され、第１の抵抗測定部５０Ａで測定された第１の検出部２０の抵抗値と、第２の抵抗測定部５０Ｂで測定された第２の検出部３０の抵抗値は制御部６１（図７参照）で読み出すことができる。 The resistance measuring unit 50 is electrically connected to the control unit 61 (see FIG. 7) described later of the control device 60, and the resistance value of the first detecting unit 20 measured by the first resistance measuring unit 50A and the resistance value of the first detecting unit 20. The resistance value of the second detection unit 30 measured by the second resistance measurement unit 50B can be read out by the control unit 61 (see FIG. 7).
　ガス濃度測定装置１は、装置本体１０内に、電源部４０及び抵抗測定部５０の他に、増幅回路、アナログ－デジタル（Ａ－Ｄ）変換器等の抵抗測定装置を備えていてもよい。このとき、抵抗測定装置は、第１の検出部２０、第２の検出部３０及び電源部４０と直列に接続されるように設置してもよい。 The gas concentration measuring device 1 may include a resistance measuring device such as an amplifier circuit and an analog-to-digital (AD) converter in addition to the power supply unit 40 and the resistance measuring unit 50 in the device main body 10. At this time, the resistance measuring device may be installed so as to be connected in series with the first detection unit 20, the second detection unit 30, and the power supply unit 40.
　制御装置６０は、図７に示すように、制御部６１、制御部６１に接続される操作部６２及び表示部６３を有する。 As shown in FIG. 7, the control device 60 includes a control unit 61, an operation unit 62 connected to the control unit 61, and a display unit 63.
　制御部６１は、電源部４０及び表示部６３を制御可能にこれらと接続されている。 The control unit 61 is connected to the power supply unit 40 and the display unit 63 in a controllable manner.
　制御部６１は、制御プログラムや各種記憶情報を格納する記憶手段と、制御プログラムに基づいて動作する演算手段とを有する。記憶手段には、ＲＡＭ、ＲＯＭ及びストレージ等がある。演算手段には、ＣＰＵ等がある。制御部６１は、演算手段が記憶手段に格納されている制御プログラム等を読み出して実行することで実現される。 The control unit 61 has a storage means for storing a control program and various storage information, and a calculation means for operating based on the control program. The storage means includes RAM, ROM, storage, and the like. The calculation means includes a CPU and the like. The control unit 61 is realized by the arithmetic means reading and executing a control program or the like stored in the storage means.
　制御部６１の有する記憶手段は、エタノール濃度と抵抗値及び抵抗値の変化量（第１のアルコール由来変化量ΔＲ１１及び第２のアルコール由来変化量ΔＲ２１）との関係と、ホルムアルデヒド濃度と抵抗値及び抵抗値の変化量（第１のアルデヒド類由来変化量ΔＲ１２及び第２のアルデヒド類由来変化量ΔＲ２２）との関係とを示す情報が格納されていることが好ましい。制御部６１は、記憶手段に記憶されている記憶値と、抵抗測定部５０で測定された測定値とを比較することで、ホルムアルデヒド濃度又はエタノール濃度を判断できる。 The storage means possessed by the control unit 61 is the relationship between the ethanol concentration and the change amount of the resistance value and the resistance value (first alcohol-derived change amount ΔR11 and second alcohol-derived change amount ΔR21), the formaldehyde concentration and the resistance value, and the change amount. It is preferable that information indicating the relationship with the amount of change in the resistance value (the amount of change ΔR12 derived from the first aldehydes and the amount of change ΔR22 derived from the second aldehydes) is stored. The control unit 61 can determine the formaldehyde concentration or the ethanol concentration by comparing the stored value stored in the storage means with the measured value measured by the resistance measuring unit 50.
　制御部６１は、抵抗測定部５０（第１の抵抗測定部５０Ａ及び第２の抵抗測定部５０Ｂ）の測定結果を受信する。本実施形態では、制御部６１は、第１の抵抗測定部５０Ａで測定されたエタノール濃度と、第２の抵抗測定部５０Ｂで測定されたホルムアルデヒド濃度及びエタノール濃度との測定結果の信号を受信する。制御部６１は、第１の抵抗測定部５０Ａ及び第２の抵抗測定部５０Ｂから受信した信号に基づいて、第１の検出部２０の抵抗値と、第２の検出部３０の抵抗値とを算出し、第１の抵抗測定部５０Ａで検出された第１の検出部２０の抵抗値の変化量と第２の抵抗測定部５０Ｂで検出された第２の検出部３０の抵抗値の変化量とを算出する。そして、制御部６１は、第１の検出部２０の抵抗値と、第２の検出部３０の抵抗値とを合算して、第１の検出部２０で検出された抵抗値の変化量と第２の検出部３０で検出された抵抗値の変化量とを合算した合成変化量を算出する。制御部６１は、得られた合成変化量を、ホルムアルデヒドに由来する抵抗の変化量と判断し、ホルムアルデヒド濃度を算出することができる。 The control unit 61 receives the measurement results of the resistance measurement unit 50 (first resistance measurement unit 50A and second resistance measurement unit 50B). In the present embodiment, the control unit 61 receives the signal of the measurement result of the ethanol concentration measured by the first resistance measurement unit 50A and the formaldehyde concentration and the ethanol concentration measured by the second resistance measurement unit 50B. .. The control unit 61 determines the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30 based on the signals received from the first resistance measurement unit 50A and the second resistance measurement unit 50B. Calculated, the amount of change in the resistance value of the first detection unit 20 detected by the first resistance measurement unit 50A and the amount of change in the resistance value of the second detection unit 30 detected by the second resistance measurement unit 50B. And are calculated. Then, the control unit 61 adds up the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30, and sets the amount of change in the resistance value detected by the first detection unit 20 and the first. The combined change amount is calculated by adding up the change amount of the resistance value detected by the detection unit 30 of 2. The control unit 61 can determine the obtained synthetic change amount as the change amount of the resistance derived from formaldehyde and calculate the formaldehyde concentration.
　合成変化量からホルムアルデヒド濃度を算出する方法について具体的に説明する。合成変化量を算出するとき、第１の検出部２０及び第２の検出部３０のそれぞれの抵抗値のうち、第１の検出部２０及び第２の検出部３０で測定される、エタノールに由来する抵抗の合算抵抗と、ホルムアルデヒドに由来する抵抗の合成抵抗を求める。 The method of calculating the formaldehyde concentration from the amount of synthetic change will be explained concretely. When calculating the synthetic change amount, among the resistance values of the first detection unit 20 and the second detection unit 30, each of the resistance values is derived from ethanol measured by the first detection unit 20 and the second detection unit 30. Find the combined resistance of the resistance to be produced and the combined resistance of the resistance derived from formaldehyde.
　第１の検出部２０及び第２の検出部３０で測定される、エタノールに由来する抵抗の合算抵抗について説明する。図８に示すように、エタノールに由来する抵抗値の第１のアルコール由来変化量ΔＲ１１と第２のアルコール由来変化量ΔＲ２１とを合算すると、エタノール濃度が濃度Ｃ１まではエタノールに由来する抵抗の変化量はほぼゼロとなる。すなわち、図９に示すように、エタノール濃度が濃度Ｃ１以下では、第１の検出部２０で検出される抵抗値と、第２の検出部３０で検出された抵抗値とを合算したときのエタノールに由来する合成抵抗Ｒ１totalがほぼ一定となる。 The total resistance of the resistance derived from ethanol measured by the first detection unit 20 and the second detection unit 30 will be described. As shown in FIG. 8, when the first alcohol-derived change amount ΔR11 and the second alcohol-derived change amount ΔR21 of the resistance value derived from ethanol are added together, the change in resistance derived from ethanol up to the ethanol concentration concentration C1. The amount is almost zero. That is, as shown in FIG. 9, when the ethanol concentration is C1 or less, the ethanol when the resistance value detected by the first detection unit 20 and the resistance value detected by the second detection unit 30 are added up. The combined resistance R1 total derived from is almost constant.
　第１の検出部２０及び第２の検出部３０で測定される、ホルムアルデヒドに由来する抵抗の合成抵抗について説明する。図１０に示すように、第１の検出部２０におけるホルムアルデヒドに由来する抵抗値は一定であって、抵抗値の変化量はゼロであり、第２の検出部３０におけるホルムアルデヒドに由来する抵抗値の第２のアルデヒド類由来変化量ΔＲ２２は、所定の割合で低下する。この場合、図１１に示すように、第１の検出部２０の抵抗値と、第２の検出部３０の抵抗値とを合算したときのホルムアルデヒドに由来する合成抵抗Ｒ２totalは、濃度ゼロから濃度Ｃ１まで第２のアルデヒド類由来変化量ΔＲ２２の割合で低下することになる。また、合成抵抗Ｒ２totalは、濃度Ｃ１から濃度Ｃ２までにおいても、同様に、第２のアルデヒド類由来変化量ΔＲ２２の割合で低下する。 The combined resistance of the formaldehyde-derived resistor measured by the first detection unit 20 and the second detection unit 30 will be described. As shown in FIG. 10, the resistance value derived from formaldehyde in the first detection unit 20 is constant, the amount of change in the resistance value is zero, and the resistance value derived from formaldehyde in the second detection unit 30 The amount of change ΔR22 derived from the second aldehydes decreases at a predetermined rate. In this case, as shown in FIG. 11, the combined resistance R2 total derived from formaldehyde when the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30 are added is the concentration from zero to the concentration. It will decrease to C1 at the rate of the second aldehyde-derived change amount ΔR22. Further, the synthesis resistance R2 total also decreases at a rate of the second aldehyde-derived change amount ΔR22 from the concentration C1 to the concentration C2.
　また、図１２に示すように、第１の検出部２０におけるホルムアルデヒドに由来する抵抗値の第１のアルデヒド類由来変化量ΔＲ１２が所定の割合で低下し、第２の検出部３０におけるホルムアルデヒドに由来する抵抗値の第２のアルデヒド類由来変化量ΔＲ２２が所定の割合で低下する。この場合、図１３に示すように、第１の検出部２０の抵抗値と、第２の検出部３０の抵抗値とを合算したときのホルムアルデヒドに由来する合成抵抗Ｒ２totalは、濃度ゼロから濃度Ｃ１まで第２のアルデヒド類由来変化量ΔＲ１２及びΔＲ２２を合算した割合で低下することになる。また、合成抵抗Ｒ２totalは、濃度Ｃ１から濃度Ｃ２までにおいても、同様に、第２のアルデヒド類由来変化量ΔＲ１２及びΔＲ２２を合算した割合ΔＲ２２の割合で低下する。 Further, as shown in FIG. 12, the amount of change ΔR12 derived from the first aldehydes in the resistance value derived from formaldehyde in the first detection unit 20 decreases at a predetermined rate, and is derived from formaldehyde in the second detection unit 30. The amount of change ΔR22 derived from the second aldehydes in the resistance value to be changed decreases at a predetermined rate. In this case, as shown in FIG. 13, the combined resistance R2 total derived from formaldehyde when the resistance value of the first detection unit 20 and the resistance value of the second detection unit 30 are added is the concentration from zero to the concentration. The amount of change derived from the second aldehydes, ΔR12 and ΔR22, decreases up to C1 at the total ratio. Further, the combined resistance R2 total also decreases from the concentration C1 to the concentration C2 at a ratio of ΔR22, which is the sum of the amounts of change ΔR12 and ΔR22 derived from the second aldehydes.
　よって、合成変化量を算出した際、第１のアルコール由来変化量ΔＲ１１と第２のアルコール由来変化量ΔＲ２１とを合算することにより算出される、エタノールに由来する抵抗の変化量はほぼゼロとなるため、合成変化量はホルムアルデヒドに由来する抵抗の変化量のみを示すことになる。 Therefore, when the synthetic change amount is calculated, the change amount of the resistance derived from ethanol, which is calculated by adding the first alcohol-derived change amount ΔR11 and the second alcohol-derived change amount ΔR21, becomes almost zero. Therefore, the synthetic change amount shows only the change amount of the resistance derived from formaldehyde.
　制御部６１は、予め記憶手段に記憶しておいた、エタノール濃度と抵抗値及び抵抗値の変化量（第１のアルコール由来変化量ΔＲ１１及び第２のアルコール由来変化量ΔＲ２１）との関係と、ホルムアルデヒド濃度と抵抗値及び抵抗値の変化量（第１のアルデヒド類由来変化量ΔＲ１２及び第２のアルデヒド類由来変化量ΔＲ２２）との関係とを示す関係図を用いてもよい。制御部６１は、測定値を記録値と比較することで、合成変化量に対応したホルムアルデヒド濃度を求めることができる。 The control unit 61 has a relationship between the ethanol concentration and the resistance value and the change amount of the resistance value (first alcohol-derived change amount ΔR11 and second alcohol-derived change amount ΔR21) stored in the storage means in advance. A relationship diagram showing the relationship between the formaldehyde concentration and the resistance value and the amount of change in the resistance value (first aldehyde-derived change amount ΔR12 and second aldehyde-derived change amount ΔR22) may be used. The control unit 61 can obtain the formaldehyde concentration corresponding to the amount of synthetic change by comparing the measured value with the recorded value.
　制御部６１は、記憶手段に記憶される、エタノール又はホルムアルデヒドに由来する抵抗値を、下記式（１）及び（２）のように、エタノール濃度とホルムアルデヒド濃度がそれぞれ０ｐｐｍの時に得られた抵抗値Ｒ０１及びＲ０２で除した値を、エタノール感度及びホルムアルデヒド感度として記憶させてもよい。制御部６１は、エタノール濃度とエタノール感度との関係を示す関係図と、ホルムアルデヒド濃度とホルムアルデヒド感度との関係を示す関係図を用い、測定値を記録値と比較することで、合成変化量に対応した、エタノール濃度及びホルムアルデヒド濃度が求められる。
エタノール感度（抵抗値の変化量）＝エタノールに由来する抵抗値／抵抗値Ｒ０１　・・・（１）
ホルムアルデヒド感度（抵抗値の変化量）＝ホルムアルデヒドに由来する抵抗値／抵抗値Ｒ０２　・・・（２） The control unit 61 sets the resistance value derived from ethanol or formaldehyde stored in the storage means as the resistance value obtained when the ethanol concentration and the formaldehyde concentration are 0 ppm, respectively, as shown in the following formulas (1) and (2). The value divided by R01 and R02 may be stored as ethanol sensitivity and formaldehyde sensitivity. The control unit 61 responds to the amount of synthetic change by comparing the measured value with the recorded value by using the relationship diagram showing the relationship between the ethanol concentration and the ethanol sensitivity and the relationship diagram showing the relationship between the formaldehyde concentration and the formaldehyde sensitivity. The ethanol concentration and formaldehyde concentration are required.
Ethanol sensitivity (change in resistance value) = resistance value derived from ethanol / resistance value R01 ... (1)
Formaldehyde sensitivity (change in resistance value) = resistance value derived from formaldehyde / resistance value R02 ... (2)
　操作部６２は、図７に示すように、制御部６１と電気的に接続されており、制御部６１を制御する。 As shown in FIG. 7, the operation unit 62 is electrically connected to the control unit 61 and controls the control unit 61.
　表示部６３は、算出されたホルムアルデヒド濃度等を表示する。表示部６３としては、液晶表示等を用いることができる。 The display unit 63 displays the calculated formaldehyde concentration and the like. As the display unit 63, a liquid crystal display or the like can be used.
　このように、ガス濃度測定装置１は、第１の検出部２０及び第２の検出部３０を備える。ガス濃度測定装置１では、第１の検出部２０の抵抗値の変化量と第２の検出部３０の抵抗値の変化量とを合算して合成変化量を算出すると、第１の検出部２０の第１のアルコール由来変化量ΔＲ１１と第２の検出部３０の第２のアルコール由来変化量ΔＲ２１とを合算することになる。これらを合算することにより算出される、エタノールに由来する抵抗の変化量はほぼゼロとすることができる。ガス濃度測定装置１では、第２の検出部３０の第２のアルデヒド類由来変化量ΔＲ２２が検出されることになるため、合成変化量はホルムアルデヒドに由来する抵抗の変化量のみを示すことになる。そのため、ガス濃度測定装置１は、予め求めた、ホルムアルデヒド濃度と合成変化量との関係を示す関係図等を用いることで、合成変化量からホルムアルデヒドに由来する抵抗の変化量のみを安定して求めることができる。よって、制御装置６０は、合成変化量からホルムアルデヒド濃度のみを算出することができる。 As described above, the gas concentration measuring device 1 includes a first detection unit 20 and a second detection unit 30. In the gas concentration measuring device 1, the combined change amount is calculated by adding up the change amount of the resistance value of the first detection unit 20 and the change amount of the resistance value of the second detection unit 30, and the first detection unit 20 The first alcohol-derived change amount ΔR11 and the second alcohol-derived change amount ΔR21 of the second detection unit 30 are added together. The amount of change in resistance derived from ethanol, which is calculated by adding up these, can be made almost zero. In the gas concentration measuring device 1, since the second aldehyde-derived change amount ΔR22 of the second detection unit 30 is detected, the synthetic change amount shows only the change amount of the resistance derived from formaldehyde. .. Therefore, the gas concentration measuring device 1 stably obtains only the amount of change in resistance derived from formaldehyde from the amount of synthetic change by using a relationship diagram or the like showing the relationship between the formaldehyde concentration and the amount of synthetic change obtained in advance. be able to. Therefore, the control device 60 can calculate only the formaldehyde concentration from the amount of synthetic change.
　したがって、ガス濃度測定装置１は、検査対象ガス中にエタノール等が含まれていても、エタノールの影響を低減できるので、簡易にホルムアルデヒド濃度をより高精度に測定することができる。 Therefore, the gas concentration measuring device 1 can reduce the influence of ethanol even if the gas to be inspected contains ethanol or the like, so that the formaldehyde concentration can be easily measured with higher accuracy.
　ガス濃度測定装置１は、上記のような特性を有することから、ＶＯＣの分析に有効に用いることができる。そのため、ＶＯＣを分析する際、大気中にホルムアルデヒド以外にエタノール等が含まれていても、ガス濃度測定装置１は、ホルムアルデヒドのみの濃度を簡易に測定できるので、室内環境におけるＶＯＣの分析や、人の呼気に含まれるＶＯＣの分析等に有効に用いることができる。よって、ガス濃度測定装置１は、ＶＯＣの分析等に有効に用いることができるため、シックハウス症候群の防止や体調管理等を行うのに好適に用いることができる。 Since the gas concentration measuring device 1 has the above-mentioned characteristics, it can be effectively used for VOC analysis. Therefore, when analyzing VOCs, even if the atmosphere contains ethanol or the like in addition to formaldehyde, the gas concentration measuring device 1 can easily measure the concentration of formaldehyde alone, so that VOC analysis in an indoor environment and humans can be performed. It can be effectively used for analysis of VOC contained in the exhaled breath of formaldehyde. Therefore, since the gas concentration measuring device 1 can be effectively used for VOC analysis and the like, it can be suitably used for preventing sick house syndrome and managing physical condition.
　ガス濃度測定装置１は、制御装置６０を備えることで、制御装置６０で第１の検出部２０の抵抗値の変化量と第２の検出部３０の抵抗値の変化量とを合算して合成変化量を算出することができる。第１のアルコール由来変化量ΔＲ１１と第２のアルコール由来変化量ΔＲ２１とを合算することにより算出される、エタノールに由来する抵抗の変化量をゼロとすることができるため、合成変化量はホルムアルデヒドに由来する抵抗の変化量のみを算出できる。そのため、制御装置６０は、予め求めた、ホルムアルデヒド濃度と合成変化量との関係を示す関係図等を用いることで、合成変化量からホルムアルデヒドに由来する抵抗の変化量を求めることができるため、合成変化量からホルムアルデヒド濃度を算出できる。 The gas concentration measuring device 1 includes the control device 60, and the control device 60 synthesizes the amount of change in the resistance value of the first detection unit 20 and the amount of change in the resistance value of the second detection unit 30. The amount of change can be calculated. Since the amount of change in resistance derived from ethanol, which is calculated by adding the amount of change ΔR11 derived from the first alcohol and the amount of change ΔR21 derived from the second alcohol, can be set to zero, the amount of synthetic change can be changed to formaldehyde. Only the amount of change in the resulting resistance can be calculated. Therefore, the control device 60 can obtain the amount of change in resistance derived from formaldehyde from the amount of synthetic change by using a relationship diagram or the like showing the relationship between the formaldehyde concentration and the amount of synthetic change obtained in advance. Formaldehyde concentration can be calculated from the amount of change.
　ガス濃度測定装置１では、第１の検出部２０は、アルデヒド類の濃度に由来する抵抗の変化量をゼロとすることができる。これにより、ガス濃度測定装置１は、第１の検出部２０の抵抗値の変化量と第２の検出部３０の抵抗値の変化量とを合算して合成変化量を算出した際、第２のアルデヒド類由来変化量ΔＲ２２のみを検出することができるため、合成変化量からホルムアルデヒドに由来する抵抗の変化量のみを確実に算出できる。よって、ガス濃度測定装置１は、合成変化量からホルムアルデヒド濃度のみをより確実に算出することができる。 In the gas concentration measuring device 1, the first detection unit 20 can set the amount of change in resistance due to the concentration of aldehydes to zero. As a result, the gas concentration measuring device 1 calculates the combined change amount by adding up the change amount of the resistance value of the first detection unit 20 and the change amount of the resistance value of the second detection unit 30. Since only the amount of change ΔR22 derived from aldehydes can be detected, only the amount of change in resistance derived from formaldehyde can be reliably calculated from the amount of synthetic change. Therefore, the gas concentration measuring device 1 can more reliably calculate only the formaldehyde concentration from the synthetic change amount.
　ガス濃度測定装置１は、第１の検出部２０で検出される抵抗値を、エタノール濃度が０．１ｐｐｍ～１．２ｐｐｍで最大となるようにすることができる。これにより、エタノールが０．１ｐｐｍ～１．２ｐｐｍのような低濃度の範囲で大気中に含まれていても、ホルムアルデヒド濃度を安定して測定できる。 The gas concentration measuring device 1 can maximize the resistance value detected by the first detection unit 20 when the ethanol concentration is 0.1 ppm to 1.2 ppm. As a result, the formaldehyde concentration can be stably measured even if ethanol is contained in the atmosphere in a low concentration range such as 0.1 ppm to 1.2 ppm.
　ガス濃度測定装置１は、第１の検出部２０及び第２の検出部３０を通電ラインＬを介して直列に接続した状態で装置本体１０内に配置することができる。これにより、例えば、第１の検出部２０及び第２の検出部３０で測定された検出信号を抵抗値に変換するＡ－Ｄ変換器等を装置本体１０内に１つだけ設置すれば足りるので、ガス濃度測定装置１の構成を簡易としつつ製造コストの低減を図れる。 The gas concentration measuring device 1 can be arranged in the device main body 10 in a state where the first detection unit 20 and the second detection unit 30 are connected in series via the energization line L. As a result, for example, it is sufficient to install only one AD converter or the like that converts the detection signals measured by the first detection unit 20 and the second detection unit 30 into resistance values in the apparatus main body 10. , The manufacturing cost can be reduced while simplifying the configuration of the gas concentration measuring device 1.
　ガス濃度測定装置１は、第１の検出部２０を、ＳｎＯ2と、Ｆｅ、Ａｌ、Ｓｉ及びＡｇの何れか１つ以上の副成分とを含むガス感知層２３５ｃで形成し、第２の検出部３０を、ＳｎＯ2を含むガス感知層２３５ｃで形成することができる。これにより、第１の検出部２０でエタノールのみの濃度を測定でき、第２の検出部３０でホルムアルデヒド及びエタノールの濃度を測定できるので、大気中に含まれるホルムアルデヒド濃度をより確実に測定できる。 The gas concentration measuring device 1 forms the first detection unit 20 with a gas sensing layer 235c containing SnO 2 and one or more subcomponents of Fe, Al, Si and Ag, and the second detection. The portion 30 can be formed by the gas sensing layer 235c containing SnO 2. As a result, the concentration of only ethanol can be measured by the first detection unit 20, and the concentration of formaldehyde and ethanol can be measured by the second detection unit 30, so that the concentration of formaldehyde contained in the atmosphere can be measured more reliably.
　ガス濃度測定装置１は、第１の検出部２０を、ＳｎＯ2に対して副成分を１．０ｍｏｌ％～１０．０ｍｏｌ％含むガス感知層２３５ｃを用いることができる。これにより、第１の検出部２０は、第１の検出部２０で検出されるエタノールに由来する第１のアルコール由来変化量ΔＲ１１を任意の大きさに調整できるため、第２の検出部３０で検出されるエタノールに由来する第２のアルコール由来変化量ΔＲ２１の大きさに合わせられる。そのため、第１の検出部２０で検出される第１のアルコール由来変化量ΔＲ１１を第２の検出部３０で検出される第２のアルコール由来変化量ΔＲ２１との差がゼロとなるように容易に調整できる。よって、ガス濃度測定装置１は、第１の検出部２０の抵抗値の変化量と第２の検出部３０の抵抗値の変化量とを合算した合成変化量からホルムアルデヒドに由来する抵抗の変化量のみを高精度に算出できるので、大気中に含まれるホルムアルデヒド濃度をより確実に測定できる。 The gas concentration measuring device 1 can use the gas sensing layer 235c containing 1.0 mol% to 10.0 mol% of an auxiliary component with respect to SnO 2 as the first detection unit 20. As a result, the first detection unit 20 can adjust the amount of change ΔR11 derived from the first alcohol derived from ethanol detected by the first detection unit 20 to an arbitrary size, so that the second detection unit 30 can adjust the amount of change ΔR11. It is adjusted to the magnitude of the second alcohol-derived change amount ΔR21 derived from the detected ethanol. Therefore, the difference between the first alcohol-derived change amount ΔR11 detected by the first detection unit 20 and the second alcohol-derived change amount ΔR21 detected by the second detection unit 30 is easily set to zero. Can be adjusted. Therefore, the gas concentration measuring device 1 has a change in resistance derived from formaldehyde from a synthetic change in which the change in resistance of the first detection unit 20 and the change in resistance in the second detection unit 30 are added up. Since only can be calculated with high accuracy, the concentration of formaldehyde contained in the atmosphere can be measured more reliably.
　以上のように、ガス濃度測定装置１は、建物の空間Ｓ内の大気中のホルムアルデヒド濃度のみを測定する場合について説明したが、ガス濃度測定装置１は、上述の通り、大気中のホルムアルデヒド濃度のみを簡易に測定できる。そのため、ガス濃度測定装置１は、建物の室内以外に、例えば、車両の車内、電車の車内、飛行機の機内等に設置して、それらの空間内の空気中のホルムアルデヒド濃度の測定に有効に用いることができる。 As described above, the case where the gas concentration measuring device 1 measures only the formaldehyde concentration in the atmosphere in the space S of the building has been described, but the gas concentration measuring device 1 has only the formaldehyde concentration in the atmosphere as described above. Can be easily measured. Therefore, the gas concentration measuring device 1 is installed not only in the interior of a building but also in a vehicle, a train, an airplane, etc., and is effectively used for measuring the formaldehyde concentration in the air in those spaces. be able to.
　また、ガス濃度測定装置１は、検査対象ガスとして、ホルムアルデヒド以外のアセトアルデヒド等のアルデヒド類や、エタノール以外のメタノール等のアルコール等も測定でき、アルデヒド類やアルコール以外のＶＯＣの分析にも有効に用いることができる。 Further, the gas concentration measuring device 1 can measure aldehydes such as acetaldehyde other than formaldehyde and alcohols such as methanol other than ethanol as the gas to be inspected, and is effectively used for analysis of VOCs other than aldehydes and alcohols. be able to.
　さらに、ガス濃度測定装置１は、検査対象ガスとしてはＶＯＣ以外に、メタン(ＣＨ4)、プロパン(Ｃ3Ｈ8)及びブタン(Ｃ4Ｈ10)等の可燃性ガス、一酸化炭素(ＣＯ)や窒素酸化物(ＮＯｘ)等の有毒ガス、硫黄化合物（ＳＯｘ）等の悪臭ガス等の分析にも有効に用いることができる。この場合、ガス濃度測定装置１は、例えば、ガス漏れや不完全燃焼の検出等に用いることができる。 Further, in the gas concentration measuring device 1, in addition to VOC, the gas to be inspected includes flammable gases such as methane (CH 4 ), propane (C 3 H 8 ) and butane (C 4 H 10 ), and carbon monoxide (CO). ), Toxic gas such as nitrogen oxide (NOx), malodorous gas such as sulfur compound (SOx), etc. can also be effectively used. In this case, the gas concentration measuring device 1 can be used, for example, for detecting gas leakage or incomplete combustion.
（変形例）
　なお、本実施形態では、第２の検出部３０で検出される第２のアルデヒド類由来変化量ΔＲ２２は、ホルムアルデヒド濃度が高くなるにしたがって検出される抵抗値が所定の割合で上昇してもよい。 (Modification example)
In the present embodiment, the resistance value of the second aldehyde-derived change amount ΔR22 detected by the second detection unit 30 may increase at a predetermined rate as the formaldehyde concentration increases. ..
　本実施形態では、第１の検出部２０及び第２の検出部３０は通電ラインＬを介して電源部４０と並列に接続されていてもよい。 In the present embodiment, the first detection unit 20 and the second detection unit 30 may be connected in parallel with the power supply unit 40 via the energization line L.
　本実施形態では、第１の検出部２０及び第２の検出部３０が装置本体１０に設置されているが、何れか一方のみを装置本体１０に設置し、他方を空間Ｓ１内に設けてもよい。 In the present embodiment, the first detection unit 20 and the second detection unit 30 are installed in the device main body 10, but even if only one of them is installed in the device main body 10 and the other is provided in the space S1. Good.
　本実施形態では、抵抗測定部５０の一対の抵抗部５０ａを、第１の検出部２０及び第２の検出部３０を跨ぐように通電ラインＬと接続するように設けてもよい。ガス濃度測定装置１は、例えば、図１４に示すように、第１の検出部２０と第２の検出部３０とを直列に接続して、第１の抵抗測定部５０Ａの一対の抵抗部５０ａを、第１の検出部２０及び第２の検出部３０を跨ぐように通電ラインＬと接続させることができる。これにより、ガス濃度測定装置１は、制御装置６０で、第１の検出部２０と第２の検出部３０の合成抵抗の変化量をホルムアルデヒドの濃度に由来する抵抗の変化量として測定できるので、ホルムアルデヒドの濃度のみを安定して算出することができる。 In the present embodiment, the pair of resistance portions 50a of the resistance measuring unit 50 may be provided so as to be connected to the energizing line L so as to straddle the first detection unit 20 and the second detection unit 30. In the gas concentration measuring device 1, for example, as shown in FIG. 14, the first detecting unit 20 and the second detecting unit 30 are connected in series, and the pair of resistance units 50a of the first resistance measuring unit 50A are connected. Can be connected to the energizing line L so as to straddle the first detection unit 20 and the second detection unit 30. As a result, the gas concentration measuring device 1 can measure the change amount of the combined resistance of the first detection unit 20 and the second detection unit 30 as the change amount of the resistance derived from the formaldehyde concentration by the control device 60. Only the concentration of formaldehyde can be calculated stably.
　本実施形態では、制御装置６０は、装置本体１０内に設けてもよいし、制御装置６０の制御部６１、操作部６２及び表示部６３の少なくとも何れか１つだけを装置本体１０内に設けてもよい。 In the present embodiment, the control device 60 may be provided in the device main body 10, or at least one of the control unit 61, the operation unit 62, and the display unit 63 of the control device 60 is provided in the device main body 10. You may.
　以下、例を示して実施形態を更に具体的に説明するが、実施形態はこれらの例により限定されるものではない。 Hereinafter, embodiments will be described in more detail with reference to examples, but the embodiments are not limited to these examples.
＜例１＞
［半導体式センサの作製］
　酸化スズ（ＳｎＯ2）の薄膜で形成された、半導体式のガスセンサ素子を準備した。 <Example 1>
[Manufacturing of semiconductor sensor]
A semiconductor type gas sensor element formed of a thin film of tin oxide (SnO 2) was prepared.
［エタノール濃度及びホルムアルデヒド濃度の測定］
　ガスセンサ素子を内部に空間をする容器内に設置し、大気（エタノールガス及びホルムアルデヒドガスの濃度が０ｐｐｍ）中に設置した時の抵抗値Ｒ０（単位：Ω）を求めた。 [Measurement of ethanol concentration and formaldehyde concentration]
The resistance value R0 (unit: Ω) when the gas sensor element was installed in a container having a space inside and installed in the atmosphere (concentration of ethanol gas and formaldehyde gas was 0 ppm) was determined.
　次に、ガスセンサ素子を検出対象ガスとしてエタノールガスを容器内に供給して、エタノールガスの濃度が約０．０１ｐｐｍ、約０．０４ｐｐｍ、約０．１ｐｐｍ及び約１．０ｐｐｍの時の抵抗値をそれぞれ測定し、抵抗値Ｒ１（単位：Ω）を測定した。 Next, ethanol gas is supplied into the container using the gas sensor element as the detection target gas, and the resistance values when the ethanol gas concentrations are about 0.01 ppm, about 0.04 ppm, about 0.1 ppm, and about 1.0 ppm are set. Each was measured, and the resistance value R1 (unit: Ω) was measured.
　次に、容器内に検出対象ガスとしてホルムアルデヒドガスを供給して、ガスセンサ素子で容器内のホルムアルデヒド濃度が０．０４ｐｐｍ、０．１ｐｐｍ及び１．０ｐｐｍの時の抵抗値を測定し、抵抗値Ｒ２（単位：Ω）を測定した。 Next, formaldehyde gas is supplied into the container as a gas to be detected, and the resistance values when the formaldehyde concentrations in the container are 0.04 ppm, 0.1 ppm, and 1.0 ppm are measured by the gas sensor element, and the resistance value R2 ( Unit: Ω) was measured.
　抵抗値Ｒ１及びＲ２を、エタノールガスとホルムアルデヒドガスの濃度が０ｐｐｍの時に得られた抵抗値Ｒ０で除し、それぞれの抵抗値の変化量をエタノール感度及びホルムアルデヒド感度として求めた。ＳｎＯ2で形成されたガスセンサ素子の、エタノール濃度と抵抗値の変化量との関係を図１５に示し、ホルムアルデヒド濃度と抵抗値の変化量との関係を図１６に示す。抵抗値の変化量の大きさは、ガス感度の大きさを意味し、抵抗値の変化量が大きいほどガス感度は高いことを意味し、抵抗値の変化量が小さいほどガス感度は低ことを意味し、抵抗値の変化量が無い場合にはガスを検知していないことを意味する。
エタノール感度（抵抗値の変化量）＝抵抗値Ｒ１／抵抗値Ｒ０
ホルムアルデヒド感度（抵抗値の変化量）＝抵抗値Ｒ２／抵抗値Ｒ０ The resistance values R1 and R2 were divided by the resistance value R0 obtained when the concentrations of ethanol gas and formaldehyde gas were 0 ppm, and the amount of change in each resistance value was determined as ethanol sensitivity and formaldehyde sensitivity. FIG. 15 shows the relationship between the ethanol concentration and the amount of change in the resistance value of the gas sensor element formed of SnO 2, and FIG. 16 shows the relationship between the formaldehyde concentration and the amount of change in the resistance value. The magnitude of the change in resistance value means the magnitude of gas sensitivity, the larger the change in resistance value, the higher the gas sensitivity, and the smaller the change in resistance value, the lower the gas sensitivity. This means that gas is not detected when there is no change in resistance value.
Ethanol sensitivity (change in resistance value) = resistance value R1 / resistance value R0
Formaldehyde sensitivity (change in resistance value) = resistance value R2 / resistance value R0
＜例２～６＞
　例１において、ガスセンサ素子を形成する材料として、鉄（Ｆｅ）を添加した酸化スズ（Ｆｅ：１ｍｏｌ％）、鉄（Ｆｅ）を添加した酸化スズ（Ｆｅ添加量：２ｍｏｌ％）、アルミニウム（Ａｌ）を添加した酸化スズ（Ａｌ添加量：２ｍｏｌ％）、シリカ（Ｓｉ）を添加した酸化スズ（Ｓｉ添加量：４ｍｏｌ％）及びシリカ（Ｓｉ）を添加した酸化スズ（Ｓｉ添加量：８ｍｏｌ％）を用いたこと以外は、それぞれ例１と同様にして行った。ガスセンサ素子の、エタノール濃度と抵抗値の変化量との関係を図１５に示し、ホルムアルデヒド濃度と抵抗値の変化量との関係を図１６に示す。 <Examples 2 to 6>
In Example 1, tin oxide (Fe: 1 mol%) to which iron (Fe) was added, tin oxide (Fe addition amount: 2 mol%) to which iron (Fe) was added, and aluminum (Al) were used as materials for forming the gas sensor element. Tin oxide (Al addition amount: 2 mol%), tin oxide (Si addition amount: 4 mol%) to which silica (Si) was added, and tin oxide (Si addition amount: 8 mol%) to which silica (Si) was added. Except for the fact that they were used, each was carried out in the same manner as in Example 1. The relationship between the ethanol concentration and the amount of change in the resistance value of the gas sensor element is shown in FIG. 15, and the relationship between the formaldehyde concentration and the amount of change in the resistance value is shown in FIG.
　例１、例５及び例６は、図１５に示すように、エタノール濃度が増加するのに伴い、抵抗値は低下する傾向を示した。また、図１６に示すように、ホルムアルデヒド濃度が０．０４ｐｐｍまではホルムアルデヒド濃度は殆ど変化せず、ホルムアルデヒド濃度が０．０４ｐｐｍを超えると、ホルムアルデヒド濃度は低下する傾向を示したことが確認された。 In Examples 1, 5 and 6, as shown in FIG. 15, the resistance value tended to decrease as the ethanol concentration increased. Further, as shown in FIG. 16, it was confirmed that the formaldehyde concentration hardly changed up to the formaldehyde concentration of 0.04 ppm, and the formaldehyde concentration tended to decrease when the formaldehyde concentration exceeded 0.04 ppm.
　例２～例４は、図１５に示すように、エタノール濃度が０．１ｐｐｍまではエタノール濃度が増加するのに伴い、抵抗値の変化量が増加した。また、図１６に示すように、ホルムアルデヒド濃度が０．１ｐｐｍまではホルムアルデヒド濃度は変化しないか殆ど変化せず、抵抗値が略一定であったことが確認された。 In Examples 2 to 4, as shown in FIG. 15, the amount of change in the resistance value increased as the ethanol concentration increased up to 0.1 ppm. Further, as shown in FIG. 16, it was confirmed that the formaldehyde concentration did not change or hardly changed until the formaldehyde concentration was 0.1 ppm, and the resistance value was substantially constant.
　例１、例５及び例６から分かるように、Ｓｉの添加量を調節することで、エタノールの感度を調整することができることが確認された。よって、エタノールの感度を調整したものと、例２～例４のいずれかとを第１の検知部又は第２の検知部として用いれば、第１の検出部２０及び第２の検出部３０で得られるエタノール濃度の変化量を略ゼロにすることができるので、ホルムアルデヒドのみを測定できるといえる。 As can be seen from Examples 1, 5 and 6, it was confirmed that the sensitivity of ethanol can be adjusted by adjusting the amount of Si added. Therefore, if one of the adjusted ethanol sensitivities and any of Examples 2 to 4 is used as the first detection unit or the second detection unit, the first detection unit 20 and the second detection unit 30 can obtain the results. Since the amount of change in ethanol concentration can be made almost zero, it can be said that only formaldehyde can be measured.
　よって、一実施形態に係るガス濃度測定装置は、簡易な構成で、エタノール濃度が約０．１ｐｐｍ以下の低濃度であっても、ホルムアルデヒド濃度のみを高精度に測定できるといえる。 Therefore, it can be said that the gas concentration measuring device according to the embodiment can measure only the formaldehyde concentration with high accuracy even if the ethanol concentration is as low as about 0.1 ppm or less with a simple configuration.
　以上の通り、実施形態を説明したが、上記実施形態は、例として提示したものであり、上記実施形態により本発明が限定されるものではない。上記実施形態は、その他の様々な形態で実施されることが可能であり、発明の要旨を逸脱しない範囲で、種々の組み合わせ、省略、置き換え、変更等を行うことが可能である。これら実施形態やその変形は、発明の範囲や要旨に含まれると共に、特許請求の範囲に記載された発明とその均等の範囲に含まれる。 As described above, the embodiments have been described, but the above embodiments are presented as examples, and the present invention is not limited to the above embodiments. The above-described embodiment can be implemented in various other forms, and various combinations, omissions, replacements, changes, etc. can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.
　本出願は、２０１９年１０月１１日に日本国特許庁に出願した特願２０１９－１８８１２３号に基づく優先権を主張するものであり、特願２０１９－１８８１２３号の全内容を本出願に援用する。 This application claims priority based on Japanese Patent Application No. 2019-188123 filed with the Japan Patent Office on October 11, 2019, and the entire contents of Japanese Patent Application No. 2019-188123 are incorporated in this application. ..
　１　ガス濃度測定装置
　１０　装置本体
　２０　第１の検出部
　２３５　ガス検知部
　２３５ｃ　ガス感知層
　３０　第２の検出部
　４０　電源部
　５０　抵抗測定部
　５０Ａ　第１の抵抗測定部
　５０Ｂ　第２の抵抗測定部
　６０　制御装置
　６１　制御部
　Ｇ　検査対象ガス
　Ｓ１　空間
　Ｓ２　検出空間
　ΔＲ１１　第１のアルコール由来変化量
　ΔＲ１２　第１のアルデヒド類由来変化量
　ΔＲ２１　第２のアルコール由来変化量
　ΔＲ２２　第２のアルデヒド類由来変化量 1 Gas concentration measuring device 10 Device main body 20 First detection unit 235 Gas detection unit 235c Gas sensing layer 30 Second detection unit 40 Power supply unit 50 Resistance measurement unit 50A First resistance measurement unit 50B Second resistance measurement unit 60 Control device 61 Control unit G Inspection target gas S1 Space S2 Detection space ΔR11 First alcohol-derived change amount ΔR12 First aldehyde-derived change amount ΔR21 Second alcohol-derived change amount ΔR22 Second aldehyde-derived change amount

Claims (8)

  1. 　アルデヒド類とアルコールとを含む検査対象ガスの前記アルデヒド類の濃度を測定するガス濃度測定装置であって、
    　前記アルコールの濃度が高くなるにしたがって検出される抵抗値が所定の割合で上昇する第１のアルコール由来変化量を有し、前記アルデヒド類の濃度が高くなっても検出される抵抗値が上昇しない第１の検出部と、
    　前記アルコールの濃度が高くなるにしたがって検出される抵抗値が第１のアルコール由来変化量と同じ割合で低下する第２のアルコール由来変化量を有し、前記アルデヒド類の濃度が高くなるにしたがって検出される抵抗値が所定の割合で低下する、アルデヒド類由来の変化量を有する第２の検出部と、
    を備えるガス濃度測定装置。     A gas concentration measuring device for measuring the concentration of the aldehydes in the gas to be inspected containing aldehydes and alcohol.
    It has a first alcohol-derived change amount in which the detected resistance value increases at a predetermined rate as the concentration of the alcohol increases, and the detected resistance value does not increase even if the concentration of the aldehydes increases. The first detector and
    The resistance value detected as the concentration of the alcohol increases has a second alcohol-derived change amount that decreases at the same rate as the first alcohol-derived change amount, and is detected as the concentration of the aldehydes increases. A second detector having a change amount derived from aldehydes, which reduces the resistance value to be obtained at a predetermined rate,
    A gas concentration measuring device including.
  2. 　前記第１の検出部で検出される抵抗値の変化量と前記第２の検出部で検出される抵抗値の変化量とを合算して得られた合成変化量を前記アルデヒド類に由来する抵抗の変化量と判断し、前記合成変化量から前記アルデヒド類の濃度を算出する制御部を有する請求項１に記載のガス濃度測定装置。 The amount of synthetic change obtained by adding the amount of change in the resistance value detected by the first detection unit and the amount of change in the resistance value detected by the second detection unit is the resistance derived from the aldehydes. The gas concentration measuring apparatus according to claim 1, further comprising a control unit for calculating the concentration of the aldehydes from the synthetic change amount.
  3. 　前記第１の検出部と前記第２の検出部が直列に接続され、
    　前記第１の検出部と前記第２の検出部の合成抵抗の変化量を前記アルデヒド類の濃度に由来する抵抗の変化量として前記アルデヒド類の濃度を算出する制御部を有する請求項１に記載のガス濃度測定装置。     The first detection unit and the second detection unit are connected in series, and the first detection unit and the second detection unit are connected in series.
    The first aspect of claim 1 has a control unit that calculates the concentration of the aldehydes by using the amount of change in the combined resistance of the first detection unit and the second detection unit as the amount of change in the resistance derived from the concentration of the aldehydes. Gas concentration measuring device.
  4. 　前記第１の検出部は、前記アルデヒド類の濃度に由来する抵抗の変化量がゼロである請求項１～３の何れか一項に記載のガス濃度測定装置。 The gas concentration measuring device according to any one of claims 1 to 3, wherein the first detecting unit is a gas concentration measuring device according to any one of claims 1 to 3, wherein the amount of change in resistance derived from the concentration of the aldehydes is zero.
  5. 　前記第１の検出部で検出される抵抗値は、アルコール濃度が０．１ｐｐｍ～１．２ｐｐｍで最大となる請求項１～４の何れか一項に記載のガス濃度測定装置。 The gas concentration measuring device according to any one of claims 1 to 4, wherein the resistance value detected by the first detection unit is the maximum when the alcohol concentration is 0.1 ppm to 1.2 ppm.
  6. 　前記第１の検出部及び前記第２の検出部は、並列又は直列に接続される請求項１～５の何れか一項に記載のガス濃度測定装置。 The gas concentration measuring device according to any one of claims 1 to 5, wherein the first detection unit and the second detection unit are connected in parallel or in series.
  7. 　前記第１の検出部は、ＳｎＯ2と、Ｆｅ、Ａｌ、Ｓｉ及びＡｇの何れか１つ以上の副成分とを含み、
    　前記第２の検出部は、ＳｎＯ2を含む請求項１～６の何れか一項に記載のガス濃度測定装置。     The first detection unit contains SnO 2 and one or more subcomponents of Fe, Al, Si and Ag.
    The gas concentration measuring device according to any one of claims 1 to 6, wherein the second detection unit includes SnO 2.
  8. 　前記第１の検出部は、ＳｎＯ2に対して副成分を１．０ｍｏｌ％～１０．０ｍｏｌ％含む請求項７に記載のガス濃度測定装置。 The gas concentration measuring device according to claim 7, wherein the first detection unit contains 1.0 mol% to 10.0 mol% of a sub-component with respect to SnO 2.
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