Gas analyzer

Abstract

To meet a request that one gas analyzer preferably be capable of covering a wide measurement range.SOLUTION: A first reference relationship between the wavelength of light emitted to a reference gas and a reference absorbance of the light by the reference gas is defined in advance. A gas analyzer includes: an acquisition unit that acquires a target relationship between the wavelength of light emitted to a target gas that is of the same type as the reference gas and a target absorbance of the light by the target gas; and a calculation unit that calculates the concentration of the target gas based on the first reference relationship and the target relationship in a wavelength range defined according to the magnitude of the target absorbance acquired by the acquisition unit.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a gas analyzer. [Background technology]

[0002] Patent Document 1 states that "a wide range of ammonia concentrations can be measured with one sample cell" (paragraph 0011). Patent Document 2 states that "the dynamic range of measurable gas concentrations is expanded" (abstract). Non-Patent Document 1 states that "feature quantities related to target components, interfering components, disturbance effects, etc. are extracted from the absorption signal of the sample gas." [Prior art document] [Patent documents] [Patent Document 1] Japanese Patent Application Laid-Open No. 9-61348 [Patent Document 2] JP 2009-276308 A [Non-patent document 1] BUNSEKI KAGAKU Vol. 72, No. 7-8, pp. 265-278 (2023) Summary of the Invention [Problem to be solved by the invention]

[0003] It is preferable that a single gas analyzer be able to cover a wide measurement range. [Means for solving the problem]

[0004] A first aspect of the present invention provides a gas analyzer. When a reference gas is irradiated with light, a first reference relationship between the wavelength of the light and a reference absorbance of the light by the reference gas is predetermined. The gas analyzer includes an acquisition unit that acquires the reference relationship between the wavelength of the light and the target absorbance of the light by the target gas when the light is irradiated on a target gas of the same type as the reference gas, and a calculation unit that calculates the concentration of the target gas based on the first reference relationship and the reference relationship in a wavelength range determined according to the magnitude of the target absorbance acquired by the acquisition unit.

[0005] The wavelength range may be a range of wavelengths in which the target absorbance is equal to or less than a set threshold value.

[0006] In any of the above gas analyzers, the wavelength range may be a wavelength range in which the target absorbance is equal to or less than a threshold value in a wavelength range in which the target absorbance decreases as the wavelength of light increases in an object relationship.

[0007] In any of the above gas analyzers, when the maximum value of the magnitude of the target absorbance is equal to or less than the threshold value, the wavelength range may be equal to or greater than the wavelength corresponding to the maximum value of the magnitude of the target absorbance.

[0008] In any of the above gas analyzers, the acquisition unit may acquire a second reference relationship that is a relationship between the concentration of the reference gas and the reference absorbance, and the threshold value may be a value that is less than a maximum value of the reference absorbance in the second reference relationship.

[0009] In any of the above gas analyzers, the range in which the reference absorbance changes depending on the concentration of the reference gas may have a first range and a second range. The first range may be a range of reference absorbance in which the reference absorbance changes linearly with changes in the concentration of the reference gas. The second range may be a range of reference absorbance in which the reference absorbance changes nonlinearly with changes in the concentration of the reference gas. The threshold may be a value equal to or less than the maximum value of the reference absorbance in the first range.

[0010] In any of the gas analyzers described above, the threshold value may be a maximum value of the reference absorbance in a first range, and the first reference relationship may be a relationship between the wavelength of light and the reference absorbance when a reference gas having a concentration corresponding to the threshold value is irradiated with light.

[0011] In any of the gas analyzers described above, the calculation unit may calculate the concentration of the target gas based on a ratio between the reference absorbance and the target absorbance in the wavelength range.

[0012] Any of the above gas analyzers may further include a storage chamber for storing a target gas, and a light source for generating light to irradiate the target gas stored in the storage chamber.

[0013] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also be inventions. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing an example of the configuration of a gas analyzer 100 according to an embodiment of the present invention. [Figure 2] 10 is a diagram showing an example of the relationship between the wavelength λ of light 72 and the light intensity measured by a spectroscope 90. FIG. [Figure 3] 10 is a diagram showing another example of the relationship between the wavelength λ of the light 72 and the light amount measured by the spectroscope 90. FIG. [Figure 4] FIG. 2 is a block diagram showing an example of a spectrometer 90 according to an embodiment of the present invention. [Figure 5] 10 is a diagram showing an example of the relationship between the wavelength λ of light 72 and the absorbance A of light 72 by a target gas 86 when the light 72 is irradiated onto the target gas 86. FIG. [Figure 6] 10 is a diagram showing an example of the relationship between the wavelength λ of light 72 and the absorbance A of light 72 by a target gas 86 when the light 72 is irradiated onto the target gas 86. FIG. [Figure 7] 10 is a diagram showing an example of the relationship between the wavelength λ of light 72 and the absorbance A of light 72 by a target gas 86 when the light 72 is irradiated onto the target gas 86. FIG. [Figure 8] 10 is a diagram showing an example of the relationship between the concentration C of the reference gas G and the absorbance A of the light 72 by the reference gas G when the reference gas G is irradiated with the light 72. FIG. [Figure 9] FIG. 10 is a diagram illustrating an example of the relationship between wavelength λ and ratio Rc. [Figure 10] 10 is a diagram showing an example of the relationship between the wavelength λ of light 72 and the absorbance A of light 72 by a target gas 86 when the light 72 is irradiated onto the target gas 86. FIG. [Figure 11] 10 is a diagram showing an example of the relationship between wavelength λ and absorbance A of reference gas G when light 72 is irradiated onto reference gas G. FIG. [Figure 12] 12 is a diagram showing an example of the relationship between the reference absorbance Ar in FIG. 11 and the target absorbance At in FIG. 10. FIG. [Figure 13] 10 is a diagram showing the relationship between wavelength λ and absorbance A for reference gas G and target gas 86. FIG. [Figure 14] 10 is a diagram showing an example of the relationship between the concentration D of the target gas 86 calculated by the calculation unit 20 and the actual concentration of the target gas 86. FIG. [Figure 15] 10 is a diagram showing another example of the relationship between the concentration D of the target gas 86 calculated by the calculation unit 20 and the actual concentration of the target gas 86. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0016] FIG. 1 is a diagram showing an example of the configuration of a gas analyzer 100 according to an embodiment of the present invention. The gas analyzer 100 measures the concentration of a target gas 86. Concentration in this specification refers to volumetric concentration unless otherwise specified. The gas analyzer 100 includes a spectrometer 90. The gas analyzer 100 may include a light source 70 and a storage chamber 80. The storage chamber 80 has a gas inlet 82 and a gas outlet 84.

[0017] The storage chamber 80 contains a target gas 86. The light source 70 generates light 72 to irradiate the target gas 86 contained in the storage chamber 80. The light 72 may be infrared light (wavelength of 780 nm or more and 1000 nm or less), visible light (wavelength of 380 nm or more and 780 nm or less), or ultraviolet light (wavelength of 100 nm or more and 380 nm or less). The light 72 irradiated to the target gas 86 and passed through the storage chamber 80 enters the spectroscope 90. The optical path length of the light 72 in the storage chamber 80 is defined as optical path length L.

[0018] When the light 72 passes through the target gas 86, the light 72 is absorbed in a wavelength region specific to the type of target gas 86. The type of target gas 86 is, for example, SO2 (sulfur dioxide), NO2 (nitrogen dioxide), or NH3 (ammonia). The spectrometer 90 measures the spectral characteristics of the intensity (i.e., the amount of light) of the light 72 that has passed through the target gas 86. The gas analyzer 100 measures the spectral characteristics of the absorbance of the target gas 86 by comparing the spectral characteristics of the intensity of the light 72 before it enters the target gas 86 with the spectral characteristics of the intensity of the light 72 after it has passed through the target gas 86. The target gas 86 may be introduced into the storage chamber 80 through the gas inlet 82. The target gas 86 may be discharged to the outside of the storage chamber 80 through the gas outlet 84.

[0019] Fig. 2 is a diagram showing an example of the relationship between the wavelength λ and the light intensity of the light 72 measured by the spectrometer 90. Fig. 2 shows an example of the relationship between the wavelength λ and the light intensity of the light 72 when the target gas 86 is not contained in the containment chamber 80. Fig. 2 shows the spectrum of the light 72 emitted by the light source 70. In Fig. 2, the spectrum of the light 72 is indicated by I0.

[0020] FIG. 3 is a diagram showing another example of the relationship between the wavelength λ and the light intensity of the light 72 measured by the spectroscope 90. FIG. 3 shows an example of the relationship between the wavelength λ and the light intensity of the light 72 when the target gas 86 is contained in the containment chamber 80. FIG. 3 shows the spectrum of the light 72 that has passed through the target gas 86. In FIG. 3, the spectrum of the light 72 is I X2 is indicated by a dashed line. The spectrometer 90 can obtain at least one of the type and amount of gas contained in the target gas 86 by obtaining the change in the amount of light for each wavelength λ.

[0021] 4 is a block diagram showing an example of a spectrometer 90 according to an embodiment of the present invention. The spectrometer 90 includes an acquisition unit 10 and a calculation unit 20. The spectrometer 90 may include an output unit 30, a storage unit 40, and a control unit 50. The control unit 50 may be a CPU (Central Processing Unit). The calculation unit 20 and the control unit 50 may both be a CPU (Central Processing Unit).

[0022] 5 to 7 are diagrams showing an example of the relationship between the wavelength λ of the light 72 and the absorbance A of the light 72 by the target gas 86 when the light 72 is irradiated onto the target gas 86. The calculation unit 20 calculates the light intensity I0 (see FIG. 2) of the light 72 incident on the target gas 86 at each wavelength λ by dividing the light intensity I X (see FIG. 3), the calculation unit 20 may calculate the absorbance A of the light 72 at each wavelength λ due to the target gas 86. The calculation unit 20 may calculate the absorbance A of the light 72 at each wavelength λ due to the target gas 86 using the following formula (1):

number

[0023] The absorbance A of the target gas 86 is referred to as the target absorbance At. In Figures 5 to 7, the relationship between the wavelength λ and the target absorbance At is indicated by a rough dashed line. Figure 5 shows the case where the concentration D of the target gas 86 is D1 (low concentration). Figure 6 shows the case where the concentration D of the target gas 86 is D2 (medium concentration), which is higher than the concentration D1. Figure 7 shows the case where the concentration D of the target gas 86 is D3 (high concentration), which is higher than the concentration D2.

[0024] The relationship between the wavelength λ and the target absorbance At is defined as the target relationship Rt. The acquisition unit 10 (see FIG. 4) acquires the target relationship Rt. The calculation unit 20 may calculate the absorbance A of the target gas 86 at each wavelength λ of the light 72 using the above formula (1). The calculated absorbance A is the target absorbance At. The acquisition unit 10 may acquire the target absorbance At at each wavelength λ calculated by the calculation unit 20 as the target relationship Rt. Data on the spectrum I0 of the light 72 irradiated by the light source 70 may be set in advance in the acquisition unit 10, or may be acquired by measuring the light 72. The wavelength λ at which the absorbance A of the light 72 by the target gas 86 shows the maximum value Am is defined as the wavelength λp.

[0025] 5 to 7 also show an example of the relationship between wavelength λ and absorbance A of reference gas G when light 72 is irradiated onto reference gas G of the same type as target gas 86. Gas types may be distinguished by their chemical formula. A "same type" gas is, for example, a gas with the same chemical formula as target gas 86. When target gas 86 contains multiple types of gases, reference gas G may be a gas with the same chemical formula as the gas most abundant in target gas 86.

[0026] The reference gas G may be a so-called standard gas. The type of gas and the concentration of each type of standard gas are specified in advance. The absorbance A of the reference gas G is defined as the reference absorbance Ar. In FIGS. 5 to 7, the relationship between the wavelength λ and the reference absorbance Ar is shown by a solid line. The relationship between the wavelength λ and the reference absorbance Ar is defined as the first reference relationship Rf1.

[0027] The first reference relationship Rf1 is determined in advance. The first reference relationship Rf1 may be acquired in advance by irradiating the reference gas G contained in the containing chamber 80 with light 72. The acquiring unit 10 (see FIG. 4) may acquire the first reference relationship Rf1. The first reference relationship Rf1 acquired by the acquiring unit 10 may be stored in the memory unit 40 (see FIG. 4).

[0028] The calculation unit 20 calculates the concentration of the target gas 86 based on the first reference relationship Rf1 and the target relationship Rt in the wavelength range R determined according to the magnitude of the target absorbance At acquired by the acquisition unit 10. The calculation unit 20 may set the wavelength range R narrower as the target absorbance At increases (i.e., the concentration of the target gas 86 increases). Through this processing, the calculation unit 20 can appropriately set the wavelength range R for accurately measuring the concentration of the target gas 86 according to the concentration of the target gas 86. The calculation unit 20 can set the wavelength range R suitable for calculating the concentration of the target gas 86 without changing the hardware, as it is only necessary to adjust the range of measurement data used for calculation.

[0029] For example, in a region where the value of the target absorbance At is large, the relationship between the target absorbance At and the concentration of the target gas 86 may be nonlinear. By setting the wavelength range R according to the magnitude of the target absorbance At, the calculation unit 20 can use measurement data from which data that is not suitable for calculating the concentration of the target gas 86 has been excluded. This allows the calculation unit 20 to accurately calculate the concentration of the target gas 86.

[0030] The calculation unit 20 may determine the wavelength range R as a range of wavelengths in which the target absorbance At is equal to or less than a set threshold value Ath. In a region where the target absorbance At is greater than the threshold value Ath, the relationship between the target absorbance At and the concentration of the target gas 86 may be nonlinear. By not including this nonlinear region in the wavelength range R, the calculation unit 20 can use measurement data that excludes the nonlinear region. This allows the calculation unit 20 to accurately calculate the concentration of the target gas 86.

[0031] The wavelength range R may be set to a region equal to or greater than the wavelength λp. In other words, the wavelength range R does not need to include a portion in the region smaller than the wavelength λp where the target absorbance At is equal to or smaller than the threshold Ath.

[0032] On the axis of absorbance A, a range equal to or less than the threshold Ath is defined as a first region Ra1, and a range greater than the threshold Ath is defined as a second region Ra2. The first region Ra1 may be a region in which the relationship between the target absorbance At and the concentration of the target gas 86 is considered to be linear. The second region Ra2 may be a region in which the relationship between the target absorbance At and the concentration of the target gas 86 is nonlinear. By setting the threshold Ath in this manner, the calculation unit 20 can accurately calculate the concentration of the target gas 86 from measurement data in a range in which the relationship between the target absorbance At and the concentration of the target gas 86 is considered to be linear.

[0033] The minimum value of the wavelength λ in the wavelength range R is defined as wavelength λs, and the maximum value is defined as wavelength λe. Figure 5 shows an example where wavelength λs is equal to wavelength λp. Figures 6 and 7 show examples where wavelength λs is greater than wavelength λp.

[0034] The wavelength range R may be a wavelength range (a range of wavelengths equal to or greater than λp and equal to or less than λe) in which the target absorbance At decreases as the wavelength λ increases in the object relationship Rt, and in which the target absorbance At is equal to or less than the threshold value Ath. The wavelength range in which the target absorbance At decreases as the wavelength λ increases refers to the wavelength range in which the absorbance A decreases as the wavelength λ increases in the object relationship Rt in Figures 5 to 7.

[0035] The wavelength range R does not have to include a wavelength range (a range less than wavelength λp) in which the target absorbance At increases with an increase in wavelength λ in the target relationship Rt. In this wavelength range, the target absorbance At tends to increase sharply with an increase in wavelength λ. Therefore, when the concentration of the target gas 86 is calculated based on the first reference relationship Rf1 and the target relationship Rt in a wavelength range in which the target absorbance At increases with an increase in wavelength λ, the calculated concentration of the target gas 86 is likely to include a large error.

[0036] When the maximum value Am is equal to or smaller than the threshold value Ath (as in FIG. 5), the wavelength range R may be a range of wavelengths λ equal to or larger than the wavelength λp. As described above, the wavelength λp is the wavelength λ corresponding to the maximum value Am. When the maximum value Am is greater than the threshold value Ath (as in FIGS. 6 and 7), the wavelength range R may be a range of wavelengths λ greater than the wavelength λp.

[0037] The wavelength range R may be calculated by the calculation unit 20 according to the magnitude of the target absorbance At. The magnitude of the target absorbance At may be the maximum value, the average value, or the median value of the target absorbance At in the wavelength range R of the light 72 in the target relationship Rt.

[0038] When the target gas 86 contains m types of gases (m is an integer of 2 or more), the target absorbance At of each type of gas at a certain wavelength λ is defined as target absorbance At1 to target absorbance Atm. When the reference gas G contains the same m types of gases (m is an integer of 2 or more) as the target gas 86, the reference absorbance Ar of each type of gas is defined as reference absorbance Ar1 to reference absorbance Arm. The target absorbance At of the target gas 86 at a certain wavelength is expressed by the following formula (2). In formula (2), E1 to E m is a coefficient.

number

[0039] When the target gas 86 contains m types of gases (m is an integer of 2 or more), and the absorbance of the target gas 86 is W, the absorbance W is expressed by the following formula (3).

number

[0040] In the equation (3), the case where m is 3 will be explained. Consider the function ψ of the following equation (4).

number

[0041] By partially differentiating the function ψ with respect to the coefficients E1 to E3, the formula (5) is obtained.

number

[0042] If we set the left side of equation (5) to zero, we obtain equation (6).

number

[0043] Equation (6) can be expressed as a matrix as in equation (7).

number

[0044] When the calculation unit 20 calculates the target absorbance At for each of m types of gases, the differences between the gases tend to become unclear in the wavelength region close to the wavelength λe in the waveforms of Figures 5 to 7. For this reason, it may be difficult for the calculation unit 20 to calculate the target absorbance At for each of the m types of gases in this wavelength region. In such a case, the calculation unit 20 may exclude this wavelength region from the wavelength region R (see Figures 5 to 7) and calculate the target absorbance At in the wavelength region R excluding this wavelength region.

[0045] 8 is a diagram showing an example of the relationship between the concentration C of reference gas G and the absorbance A of light 72 by reference gas G when light 72 is irradiated onto the reference gas G. If the optical path length of the light is L (see FIG. 1) and the absorption coefficient is ε, the relationship between the concentration C and the absorbance A generally follows the Beer-Lambert law shown in the following equation (8).

number

[0046] As shown in equation (8), the concentration C is proportional to the absorbance A. However, when the concentration C becomes higher than a certain concentration, the concentration C and the absorbance A are no longer proportional. The certain concentration is the concentration C1 and the concentration C1' shown in FIG.

[0047] The relationship between concentration C and absorbance A shown in FIG. 8 is referred to as the second reference relationship Rf2. The second reference relationship Rf2 may be acquired in advance by measuring the absorbance A at a predetermined wavelength λ while a plurality of reference gases G having different concentrations C are respectively contained in the storage chamber 80. The acquiring unit 10 (see FIG. 4) may acquire the second reference relationship Rf2. The second reference relationship Rf2 acquired by the acquiring unit 10 may be stored in the memory unit 40 (see FIG. 4).

[0048] The range in which the reference absorbance Ar (the absorbance A of light 72 by the reference gas G) changes depending on the concentration C of the reference gas G may have a first range Ra1 and a second range Ra2 of the absorbance A. The first range Ra1 is the range in which the reference absorbance Ar changes linearly with changes in the concentration of the reference gas G. In the example of FIG. 8, the first range Ra1 is the range in which the absorbance A is equal to or greater than zero and equal to or less than a boundary value a. The boundary value a is the maximum value of the absorbance A in the first range Ra1.

[0049] When the target gas 86 and the reference gas G are the same type of gas, the first range Ra1 and the second range Ra2 of the reference absorbance Ar of the reference gas G may be the same as the first range Ra1 and the second range Ra2 of the target absorbance At of the target gas 86, respectively.

[0050] The second range Ra2 is a range of the reference absorbance Ar in which the reference absorbance Ar changes nonlinearly with changes in the concentration of the reference gas G. In the example of FIG. 8, the second range Ra2 is a range in which the absorbance A is greater than the boundary value a and less than or equal to the upper limit value b. The upper limit value b is the maximum value of the reference absorbance Ar in the second reference relationship Rf2. The maximum value of the reference absorbance Ar is the saturation value of the absorbance A. The boundary value a and the upper limit value b are determined depending on the type of gas. The acquisition unit 10 (see FIG. 4) may acquire the upper limit value b.

[0051] In the relationship between concentration C and absorbance A in FIG. 8, the change in absorbance A with respect to the change in concentration C (i.e., the derivative of absorbance A with respect to concentration C) can be defined for any concentration C. The change in absorbance A with respect to the change in concentration C is the slope of the graph showing the relationship between concentration C and absorbance A in FIG. 8. This slope can be maximum at a concentration C close to zero. The boundary value a may be the absorbance A at which the slope of the graph showing the relationship between concentration C and absorbance A is 90%, 95%, or 98% of the maximum slope. When the concentration C is in the range from zero to the boundary value a or less (i.e., the first range Ra1), the relationship between concentration C and absorbance A may be considered linear. The calculation unit 20 (see FIG. 4) may calculate the boundary value a from the second reference relationship Rf2 (the relationship between concentration C and absorbance A) acquired by the acquisition unit 10 (see FIG. 4).

[0052] The threshold value Ath (see FIGS. 5 to 7) may be a value less than the upper limit value b. The threshold value Ath may be a value equal to or less than the boundary value a, or may be the boundary value a. In the examples of FIGS. 5 to 7, the threshold value Ath is the boundary value a. When the threshold value Ath is the boundary value a, the first reference relationship Rf1 may be a relationship between the wavelength λ of the light 72 and the reference absorbance Ar when the light 72 is irradiated onto a reference gas G having a concentration corresponding to the threshold value Ath (= a). The concentration of the reference gas G corresponding to the threshold value Ath (= a) may be concentration C1, or may be a concentration in the range of 90% to 110% of the concentration C1, or may be a concentration in the range of 95% to 105% of the concentration C1. When the first reference relationship Rf1 is the relationship between the wavelength λ and the reference absorbance Ar at the concentration corresponding to the threshold value Ath, the calculation unit 20 (see FIG. 4) can calculate the concentration of the target gas 86 with high accuracy.

[0053] The threshold value Ath may be acquired in advance. The acquired threshold value Ath may be set in advance in the gas analyzer 100. The threshold value Ath may differ depending on the type of the target gas 86.

[0054] When the wavelength λ of light 72 is not λp, the concentration C of reference gas G corresponding to the absorbance A at boundary value a is defined as concentration C1, and the concentration C of reference gas G corresponding to the absorbance A at upper limit value b is defined as concentration C2. When the wavelength λ of light 72 is λp, the concentration C of reference gas G corresponding to the absorbance A at boundary value a is defined as concentration C1', and the concentration C of reference gas G corresponding to the absorbance A at upper limit value b is defined as concentration C2'. In the small range of concentration C, the absorbance A of reference gas G increases according to concentration C. However, as concentration C becomes higher, increasing concentration C does not increase absorbance A and it may become saturated. When the concentration C of reference gas G is increased, the concentrations at which absorbance A first reaches saturated absorbance (upper limit value b) at each wavelength λ are defined as C2 and C2'. Concentration C1' is smaller than concentration C1. Concentration C2' is smaller than concentration C2.

[0055] 8, the relationship between the concentration C and the absorbance A depends on the wavelength λ of the light 72. However, the value of the boundary value a, which is the upper limit of the first range Ra1, is less dependent on the wavelength λ.

[0056] As described above, the calculation unit 20 (see FIG. 4) calculates the concentration of the target gas 86 based on the first reference relationship Rf1 and the target relationship Rt in the wavelength range R (see FIGS. 5 to 7). For example, the calculation unit 20 calculates the concentration of the target gas 86 based on the ratio Rc of the reference absorbance Ar to the target absorbance At in the wavelength range R. The ratio Rc of the reference absorbance Ar to the target absorbance At may be the ratio (At / Ar) of the target absorbance At to the reference absorbance Ar.

[0057] FIG. 9 is a diagram showing an example of the relationship between wavelength λ and ratio Rc. When the wavelength range R is within a range of wavelength λ equal to or less than threshold Ath (e.g., in the cases of FIGS. 5 to 7, or the solid line in FIG. 9), absorbance A may take on values ​​in the first range Ra1 in FIG. 8 as concentration C changes. Therefore, ratio Rc may take on a constant value independent of wavelength λ. This constant value is defined as ratio Rc1. When the wavelength range R includes wavelengths λ greater than threshold Ath (the case of the dashed-dotted line in FIG. 9), absorbance A may take on values ​​in the first range Ra1 and the second range Ra2 in FIG. 8 as concentration C changes. Therefore, when absorbance A takes on values ​​in the second range Ra2, ratio Rc may be smaller than ratio Rc1. In the case of the dashed-dotted line in FIG. 9, the wavelength λ corresponding to threshold Ath is shown as wavelength λs'. The ratio Rc corresponding to wavelength λe is defined as ratio Rc2.

[0058] The acquisition unit 10 (see FIG. 4) may acquire the relationship between the wavelength λ and the ratio Rc over the wavelength range R. In the case of the solid line in FIG. 9, the calculation unit 20 (see FIG. 4) may calculate the ratio Rc1 as the ratio Rc. The calculation unit 20 may calculate the concentration D of the target gas 86 by multiplying the concentration C of the reference gas G by the ratio Rc1. In the case of the dashed-dotted line in FIG. 9, the calculation unit 20 may calculate the average value or median value of the ratio Rc over the wavelength range R. The calculation unit 20 may calculate the concentration D of the target gas 86 by multiplying the concentration C of the reference gas G by the average value or the median value.

[0059] 9 may be obtained for each concentration D of the target gas 86 (see FIGS. 5 to 7). The concentration D of the target gas 86 calculated by the calculation unit 20 may be output by the output unit 30 (see FIG. 4). The output unit 30 is, for example, a display unit of the gas analyzer 100.

[0060] FIG. 10 is a diagram showing an example of the relationship between the wavelength λ of light 72 and the absorbance A of light 72 by target gas 86 when light 72 is irradiated onto target gas 86. FIG. 11 is a diagram showing an example of the relationship between the wavelength λ and the absorbance A of reference gas G when light 72 is irradiated onto reference gas G. FIGS. 10 and 11 are diagrams extracted from the target relationship Rt and the first reference relationship Rf1 in FIG. 6, respectively. The area S1 in FIG. 10 corresponds to the integral value obtained by integrating the target absorbance At over the wavelength range R. The area S2 in FIG. 11 corresponds to the integral value obtained by integrating the reference absorbance Ar over the wavelength range R. The acquisition unit 10 (see FIG. 4) may acquire the areas S1 and S2.

[0061] The ratio Rc may be the ratio of the area S1 to the area S2 (S1 / S2). The calculation unit 20 (see FIG. 4) may calculate the concentration of the target gas 86 by multiplying the concentration C of the reference gas G by the ratio of the area S1 to the area S2. Similarly, in the cases of low concentration (FIG. 5) and high concentration (FIG. 7), the calculation unit 20 may calculate the concentration of the target gas 86 by multiplying the concentration C of the reference gas G by the ratio of the area S1 to the area S2.

[0062] In Fig. 10, the target absorbance At corresponding to the wavelength λs is assumed to be absorbance As1. In the example of Fig. 10, the absorbance As1 is equal to the threshold value Ath. In Fig. 11, the reference absorbance Ar corresponding to the wavelength λs is assumed to be absorbance As2.

[0063] FIG. 12 is a diagram showing an example of the relationship between the reference absorbance Ar in FIG. 11 and the target absorbance At in FIG. 10. One circle in FIG. 12 is drawn at a position corresponding to the target absorbance At at a specific wavelength λ in FIG. 10 and the reference absorbance At at the specific wavelength λ in FIG. 11. For example, at wavelength λs, the reference absorbance Ar is absorbance As2 (see FIG. 11), and the target absorbance At is absorbance As1 (see FIG. 10). Therefore, the circle drawn at coordinates (As2, As1) in FIG. 12 corresponds to wavelength λs. Similar to the coordinates (As2, As1), the reference absorbance Ar and the target absorbance At corresponding to the same wavelength λ may be obtained over the wavelength range R (see FIGS. 10 and 11).

[0064] The calculation unit 20 (see FIG. 4) may calculate the relationship between the reference absorbance Ar and the target absorbance At by regression analysis. The relationship between the reference absorbance Ar and the target absorbance At may be approximated by a linear equation, or may be approximated by a qth order equation (q is an integer of 2 or more). FIG. 12 shows an example of approximation by a linear equation. The calculation unit 20 may approximate the relationship between the reference absorbance Ar and the target absorbance At by the least squares method.

[0065] The calculation unit 20 (see FIG. 4) may calculate the concentration of the target gas 86 based on the relationship between the reference absorbance Ar and the target absorbance At in the wavelength range R, calculated by regression analysis. The calculation unit 20 (see FIG. 4) may calculate the ratio Rc of the reference absorbance Ar to the target absorbance At, based on the relationship between the reference absorbance Ar and the target absorbance At, calculated by regression analysis. The calculation unit 20 may calculate the concentration of the target gas 86 as the value obtained by multiplying the concentration C of the reference gas G by the ratio Rc.

[0066] FIG. 13 is a diagram showing the relationship between wavelength λ and absorbance A for reference gas G and target gas 86. In this example, the concentration of reference gas G is 25 ppm, and the concentration of target gas 86 is 288 ppm. In this example, the relationship between wavelength λ and absorbance A is obtained over the wavelength range of wavelength λ from 200 nm to 240 nm. FIG. 13 also shows the threshold value Ath.

[0067] FIG. 14 is a diagram showing an example of the relationship between the concentration D of the target gas 86 calculated by the calculation unit 20 (see FIG. 4) and the actual concentration of the target gas 86. The concentration D of the target gas 86 in FIG. 14 is calculated using the range F1 in FIG. 13 as the calculation range. In the range F1, the absorbance A of the target gas 86 is greater than the threshold value At. Therefore, the calculated concentration D becomes saturated in a concentration range greater than a specific concentration (approximately 100 ppm in the example of FIG. 14). This results in a large deviation between the calculated concentration D and the actual concentration.

[0068] FIG. 15 is a diagram showing another example of the relationship between the concentration D of the target gas 86 calculated by the calculation unit 20 (see FIG. 4) and the actual concentration of the target gas 86. The concentration D of the target gas 86 in FIG. 15 is calculated using the range F2 in FIG. 13 as the calculation range. In the range F2, the absorbance A of the target gas 86 is smaller than the threshold value At. Therefore, the calculated concentration D is less likely to saturate up to a concentration range of approximately 300 ppm. Therefore, compared to the example in FIG. 14, the deviation between the calculated concentration D and the actual concentration is likely to be smaller. Note that in FIG. 15, when the actual concentration is y and the concentration D is x, the straight line represented by the equation y=x is shown as a solid line.

[0069] As described above, in the gas analyzer 100, the calculation unit 20 (see FIG. 4) calculates the concentration D of the target gas 86 based on the first reference relationship Rf1 and the target relationship Rt in the wavelength range R (see FIGS. 5 to 7). The wavelength range R is determined according to the magnitude of the target absorbance At. Therefore, an optimal wavelength range R can be determined each time according to the concentration D of the target gas 86. This makes it easier to accurately analyze the target gas 86 over a wide range of concentrations D with a single gas analyzer 100.

[0070] When the wavelength range R is selected by hardware (for example, in the case of the technology described in Patent Document 1), variations are likely to occur in the calculated concentration D when the wavelength range R is switched. In the gas analyzer 100, the wavelength range R is not selected by hardware. Therefore, even when the wavelength range R is determined each time, variations are unlikely to occur in the concentration D when the wavelength range R is switched.

[0071] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0072] It should be noted that the execution order of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0073] 10 Acquisition unit, 20 Calculation unit, 30 Output unit, 40 Memory unit, 50 Control unit, 70 Light source, 72 Light, 80 Storage chamber, 82 Gas inlet, 84 Gas outlet, 86 Target gas, 90 Spectrometer, 100 Gas analyzer

Claims

1. a first reference relationship between a wavelength of the light and a reference absorbance of the light by the reference gas when the light is irradiated onto the reference gas is determined in advance; an acquisition unit that acquires a target relationship between a wavelength of the light and a target absorbance of the light by the target gas when the light is irradiated onto the target gas of the same type as the reference gas; a calculation unit that calculates a concentration of the target gas based on the first reference relationship and the target relationship in a wavelength range determined according to the magnitude of the target absorbance acquired by the acquisition unit; A gas analyzer comprising:

2. The gas analyzer according to claim 1 , wherein the wavelength range is a range of wavelengths in which the target absorbance is equal to or less than a set threshold value.

3. 3. The gas analyzer according to claim 2, wherein the wavelength range is a wavelength range in which the target absorbance is equal to or less than the threshold value in a wavelength range in which the target absorbance decreases as the wavelength of the light increases in the target relationship.

4. 3. The gas analyzer according to claim 2, wherein when the maximum value of the magnitude of the target absorbance is equal to or less than the threshold value, the wavelength range is equal to or greater than the wavelength corresponding to the maximum value of the magnitude of the target absorbance.

5. the acquisition unit acquires a second reference relationship which is a relationship between the concentration of the reference gas and the reference absorbance; the threshold value is a value less than the maximum value of the reference absorbance in the second reference relationship.

3. The gas analyzer of claim 2.

6. a range in which the reference absorbance changes depending on the concentration of the reference gas includes a first range and a second range; the first range is a range of the reference absorbance in which the reference absorbance changes linearly with changes in the concentration of the reference gas; the second range is a range of the reference absorbance in which the reference absorbance changes nonlinearly with changes in the concentration of the reference gas; the threshold value is a value equal to or less than the maximum value of the reference absorbance in the first range; 6. The gas analyzer of claim 5.

7. the threshold value is a maximum value of the reference absorbance in the first range, the first reference relationship is a relationship between the wavelength of the light and the reference absorbance when the light is irradiated onto the reference gas at a concentration corresponding to the threshold value; 7. The gas analyzer of claim 6.

8. The gas analyzer according to claim 1 , wherein the calculation unit calculates the concentration of the target gas based on a ratio between the reference absorbance and the target absorbance in the wavelength range.

9. a storage chamber in which the target gas is stored; a light source that generates the light to be irradiated onto the target gas contained in the containing chamber; The gas analyzer of claim 1 , further comprising:

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