JPH11132943A - Gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas analyzer in which the reliability of a measured result can be enhanced. SOLUTION: A gas analyzer 124 is featured so as to be provided with a sample cell 128 into which a sample gas with intermingled<12> CO2 and<13> CO2 is filled and which is arranged in such a way that infrared light L1 and infrared light L2 from a light source 126 are passed through the sample gas, with a changeover means 130 which is arranged in such a way that infrared light L3 and infrared light L4 from the sample cell 128 are passed alternately and with a Golay cell 110 which detects changes in a pressure inside an absorption chamber alternately when a gas, for detection, in which only the<12> CO2 and the<13> CO2 are mixed in a prescribed existence ratio is sealed in an absorption chamber and when the infrared light L3 in a<12> CO2 absorption band is incident on the absorption chamber as well as when the infrared light L4 in a<13> CO2 absorption band is incident on the absorption chamber and in which the changes are output as intensity information of the infrared light L3 and the infrared light L4 which are incident on the absorption chamber are output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas analyzer, and more particularly to an improvement in a detection mechanism thereof.

[0002]

2. Description of the Related Art In general, molecules composed of different atoms (eg, carbon monoxide CO, carbon dioxide CO _2, etc.) have a property of absorbing infrared light having a specific wavelength. A method for selectively measuring the concentration of gas using this characteristic is as follows.
It is a non-dispersive infrared absorption method and is widely used as a continuous concentration analyzer for processes. A gas analyzer using a Golay cell shown in FIG. 1 is known as such a continuous concentration dispersometer. That is, the infrared light L that has passed through the entrance window 12 of the Golay cell 10 is absorbed by the detection gas, and raises the temperature of the absorption chamber 14 in which the detection gas is sealed, thereby changing the pressure of the absorption chamber 14. At this time, the following proportional relationship is established between the temperature change ΔT and the gas pressure change ΔP. ΔP = m ₀ (R _y / v) ΔT (1) where m ₀ is the number of moles of gas, Ry is Ridberg constant,
v is the volume of the absorption chamber.

The change in pressure causes the flexible mirror 16 at the other end of the absorption chamber 14 to bend, and the change is detected by the optical system shown in FIG. That is, in a state where the infrared light L is not incident,
For example, the image of the upper part of the grating 20 illuminated by the visible light source 18 (LED) is formed exactly in the middle of the lower part of the grating 20 and does not reach the photodetector 22 (photodiode). On the other hand, when the infrared light L enters and the flexible mirror 16 is deformed, the position of the flexible mirror 16 is shifted and the intensity of the incident infrared light L can be known by measuring the photoelectromotive force by the photodetector 22. And, conventionally, using breath taken from a person as a sample gas,
When measuring the mixing ratio of ¹² CO ₂ and ¹³ CO ₂ , the measurement was carried out by two independent Golay cells separately enclosing detection gases of ¹² CO ₂ and ¹³ CO ₂ respectively. In this measurement, first, the ratio of absorbance is calibrated with a standard gas whose mixing ratio of ¹² CO ₂ and ¹³ CO ₂ is known, and then the exhaled air collected from a human is measured, and the mixing ratio is measured using a calibration curve. Had been tested.

[0004]

Incidentally, it is desirable that the above-mentioned calibration curve is effective as long as possible. However, in the conventional gas analyzer, the effectiveness of the calibration curve is lost due to several factors. One of them is Goreicel. In particular ¹² CO ₂ and ^{1 3} relative shift of the absorbance sensitivity ratio between CO ₂ for second Golay cell is an important issue.

[0005] Changes in the absorbance sensitivity of the Golay cell may be mainly due to the following causes. 1) Change in the concentration of the detection gas sealed in the Golay cell 2) Misalignment of the Golay cell optical system 3) Deterioration of the flexible mirror of the Golay cell 4) Change in luminance of the visible light source (LED) of the Golay cell optical system

In addition, the sensitivity of the Golay cell has a temperature characteristic, and the measurement of a reference and a sample takes 5 minutes to 1 minute.
Since there is a time difference of 0 minutes, the temperature change of the reference and the sample within the measurement time greatly depends on the absorbance sensitivity of each Golay cell. As described above, various causes have been considered for the relative deviation of the absorbance sensitivity ratio of Golay cells, but there is no appropriate technology that can solve this, and the reliability of the measurement results has not been improved. Was not satisfactory. The present invention has been made in view of the circumstances of the related art, and has as its object to provide a gas analyzer capable of improving the reliability of measurement results obtained by a Golay cell.

[0007]

In order to achieve the above object, a gas analyzer according to the present invention comprises a light source section, a sample cell, a switching means, and a Golay cell. . The light source section includes infrared light having a ¹² CO ₂ absorption band and ¹³
Simultaneously emits infrared light in the CO ₂ absorption band.

The sample cell is filled with a sample gas in which ¹² CO ₂ and ¹³ CO ₂ are mixed, and is arranged so that two infrared lights from the light source unit pass through the sample gas at the same time. . The switching means is arranged so that two infrared lights from the sample cell pass alternately.

In the Golay cell, a detection gas in which only ¹² CO ₂ and ¹³ CO ₂ are mixed at a predetermined abundance ratio is sealed in an absorption chamber, and infrared light from the switching means irradiates the detection gas. The pressure change in the absorption chamber when the infrared light of the ¹² CO ₂ absorption band enters the absorption chamber, and the absorption chamber when the infrared light of the ¹³ CO ₂ absorption band enters the absorption chamber A change in pressure inside the chamber is detected alternately, and this is output as intensity information of infrared light incident on the absorption chamber. Further, the gas analyzer according to the present invention,
A light source unit, a sample cell, and one Golay cell are provided.

[0010] The light source section is provided with infrared light having a ¹² CO ₂ absorption band.
Infrared light in the ¹³ CO ₂ absorption band is emitted alternately. The sample cell is filled with a sample gas in which ¹² CO ₂ and ¹³ CO ₂ are mixed, and is arranged so that infrared light from the light source passes through the sample gas.

In the Golay cell, a detection gas in which only ¹² CO ₂ and ¹³ CO ₂ are mixed at a predetermined abundance ratio is sealed in an absorption chamber, and infrared light from the sample cell irradiates the detection gas. The pressure change in the absorption chamber when the infrared light of the ¹² CO ₂ absorption band enters the absorption chamber, and the absorption chamber when the infrared light of the ¹³ CO ₂ absorption band enters the absorption chamber A change in pressure inside the chamber is detected alternately, and this is output as intensity information of infrared light incident on the absorption chamber.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. First Embodiment FIG. 2 shows a schematic configuration of a gas analyzer according to a first embodiment of the present invention. The portions corresponding to those in FIG. 1 are denoted by reference numeral 100, and description thereof is omitted. The gas analyzer 124 shown in the figure includes a light source unit 126, a sample cell 128, a switching mirror 130 as switching means, a Golay cell 110 as an infrared detector, and a computer 132.
Is provided.

The light source section 126 includes a light source 134 and a filter 136. The light source 134 has at least ¹²
The luminous flux including the CO ₂ absorption band and the ¹³ CO ₂ absorption band is emitted.
The filter 136 includes a ¹² CO ₂ filter unit 138.
And a ¹³ CO ₂ filter section 140. The ¹² CO ₂ filter section 138 outputs the ¹²
It passes only the light flux L1 in the CO ₂ absorption band.

The ¹³ CO ₂ filter section 140 passes only the light flux L ₂ of the ¹³ CO ₂ absorption band out of the light flux from the light source 134. The sample cell 128 is filled with exhaled breath in which ¹² CO ₂ and ¹³ CO ₂ are mixed as a sample gas. The short direction of the sample cell 128 is the short optical path cell unit 1.
Used as 28a.

The short optical path cell section 128a is provided at the entrance window 14
2, includes an exit window 144 (e.g., a flat convex condenser lens), ¹² CO ₂ filter unit 138 ¹² CO ₂ absorption band of the light beam L1 having passed through the, for example, light of only the nitrogen gas is filled The light enters the entrance window 142 through the use cell 146. The light beam that has passed through the entrance window 142 passes in the short direction in the sample cell 128 and exits the exit window 144. The longitudinal direction of the sample cell 128 is used as a long optical path cell section 128b.

The long optical path cell section 128b is connected to the entrance window 14
8 (e.g. planoconvex collecting lens), the exit window 150 comprises a (e.g. planoconvex collecting lens) ¹³ CO light beam L2 of ¹³ CO ₂ absorption band which has passed through the ₂ filter section 140 has a length The light enters the entrance window 148 of the optical path cell unit 128b. Entrance window 1
The light beam L4 that has passed through the reflection mirror 152,
Passing through the longitudinal direction in the sample cell 128 via 154;
Exits the exit window 150.

The switching mirror 130 is provided with ¹² CO ₂ which has passed through the short optical path cell section 128 a which is the short side direction of the sample cell 128.
The infrared light L3 in the absorption band and the infrared light L4 in the ¹³ CO ₂ absorption band that has passed through the long optical path cell portion 128b, which is the longitudinal direction, are arranged so as to alternately irradiate one Golay cell 110. Further, in the optical path between the exit window 144 and the switching mirror 130 of the short optical path cell part 128a, a light component having a specific wavelength (for example ¹² CO ₂ absorption band 2390cm ^-1 ~2290cm ^-1)
The filter 156 is disposed so as to pass only the light component having a specific wavelength (for example, ^{13) in} the optical path between the exit window 150 of the long optical path cell unit 128b and the switching mirror 130.
The filter 158 is arranged so as to pass only the CO ₂ absorption band of 2320 cm ^{−1 to} 2220 cm ⁻¹ ).

The Golay cell 110 is composed of ¹² CO ₂ gas and
Only the ¹³ CO ₂ gas has a predetermined abundance ratio, for example, 50 to 5
The detection gas mixed in 0 or 1: 1 is enclosed in the absorption chamber, and the infrared light L3, L4 from the switching mirror 130 is arranged to irradiate the detection gas.

In the Golay cell 110, the pressure change in the absorption chamber when the infrared light L3 in the ¹² CO ₂ absorption band enters the absorption chamber, and the infrared light L4 in the ¹³ CO ₂ absorption band enters the absorption chamber. The change in the pressure in the absorption chamber at this time is detected alternately, and this is output as intensity information of the infrared light incident on the absorption chamber.

The intensity information of each of the infrared lights L3 and L4 obtained by the Golay cell 110 is input to a computer 132, and the computer 132 uses the information to obtain ¹³ CO ₂ , which will be described later.
The arithmetic processing for obtaining the abundance ratio is performed. The operation of the switching mirror 130 is controlled by operating the computer 132 according to a predetermined procedure.

The gas analyzer 124 according to the present embodiment
The configuration is roughly as described above, and its operation will be described below. In front of the light emitting direction of the light source 134, the filter 13
The filter 136 converts the light beam from the light source 134 into _two light beams, an infrared light L1 having a ¹² CO ₂ absorption band and an infrared light L2 having a ¹³ CO ₂ absorption band.

The infrared light L passing through the filter 136
1 and L2 enter the entrance window 148 of the long optical path cell unit 128b, which is the longitudinal direction of the light guide cell 146 and the sample cell 128, respectively. The infrared light L1 that has passed through the light guiding cell 146 enters the sample cell 128 through the entrance window 142 of the short optical path cell unit 128a, which is the short direction of the sample cell 128 installed in the front, and moves in the short direction. Pass through. Sample cell 1
The light L3 having passed through the short side direction of 28 exits the sample cell 128 through the exit window 144. The infrared light L3 that has exited the short optical path cell unit 128a enters the filter 156, and the filter 156 extracts a light component of a specific wavelength, that is, only the ¹² CO ₂ absorption band. The light L3 that has exited the filter 156 is
Enter 0.

On the other hand, the entrance window 14 of the long optical path cell section 128b
8 passes through the sample cell 128 in the longitudinal direction, but after the optical path is bent by the mirrors 152 and 154 installed in front, the exit window 150 installed in front.
Exits the longer path cell 128b. Long optical path cell unit 128b
The light L4 that has exited the filter 15 enters the filter 158,
By 8, only a light component of a specific wavelength, that is, a ¹³ CO ₂ absorption band is extracted. The light L4 exiting the filter 158 enters the switching mirror 130.

Here, the switching mirror 130 is connected to the short optical path cell unit 1.
One Golay cell 110 is alternately irradiated with infrared light L3 passing through 28a and infrared light L4 passing through long optical path cell section 128b. Then, the Golay cell 110 changes the pressure in the absorption chamber when the infrared light L3 in the ¹² CO ₂ absorption band enters the absorption chamber, and when the infrared light L4 in the ¹³ CO ₂ absorption band enters the absorption chamber. The change in pressure in the absorption chamber is detected alternately, and this is output as intensity information of infrared light incident on the absorption chamber. The electric signal obtained by the Golay cell 110 enters a computer 132, and the computer 132 performs a predetermined calculation process for obtaining a ¹³ CO ₂ abundance ratio described later.

As described above, according to the gas analyzer 124 of this embodiment, the detection gas in which only ¹² CO ₂ and ¹³ CO ₂ are mixed at a predetermined ratio is sealed in the absorption chamber. It was decided that both ¹² CO ₂ and ¹³ CO ₂ were measured by the Golay cell 110. As a result, as described above, the concentration change of the detection gas sealed in the Golay cell 110, the misalignment of the Golay cell optical system, the deterioration of the Golay cell flexible mirror, the deterioration of the luminance of the visible light source of the Golay cell optical system, and the like, as described above. Even so, the influence of ¹² CO ₂ and ¹³ CO _{2 on} the absorbance sensitivity can be the same, and the change in the relative absorbance sensitivity due to these can be offset.

Also, in this embodiment, since one Golay cell 110 can measure both ¹² CO ₂ and ¹³ CO ₂ , the Golay cell for measuring ¹² CO ₂ and the ¹³ C
Compared to a case where Golay cells for measuring O ₂ are separately arranged, cost reduction and downsizing of equipment can be achieved. Further, in the present embodiment, a light source that emits infrared light in the ¹² CO ₂ absorption band and a light source that emits infrared light in the ¹³ CO ₂ absorption band are not separately arranged.
Since the number 4 is used, the value of the measurement error due to the luminance fluctuation of the light source is also equal to that in the case where the two light sources are used as described above, and the measurement error due to the luminance fluctuation of the light source can be canceled.

In the present embodiment, the infrared light L2 in the ¹³ CO ₂ absorption band is made to pass through the sample cell 128 longer than the infrared light L1 in the ¹² CO ₂ absorption band.
¹³ CO ₂ has a very low concentration as compared with ¹² CO ₂ , and even when using a sample gas such as exhaled gas with little absorption, the balance between the signal level of ¹² CO _{2 and} the signal level of ¹³ CO ₂ obtained by the Golay cell 110 can be maintained. Can be planned. Further, in the present embodiment, a plano-convex condensing lens is used for a portion corresponding to the entrance window and the exit window of each cell portion, so that one condensing lens serves as a window material of the cell portion. , And the function of condensing the lens, so that the configuration can be simplified, the price can be reduced, and the like, as compared with the case where the window material and the lens are separately provided.

Further, in the present embodiment, ¹² CO ₂
The light beam L1 that has passed through the filter 138 is guided in the lateral direction of the sample cell 128 via the light guiding cell 146 filled with only nitrogen gas, for example. The measurement error due to the carbon dioxide in the atmosphere can be significantly reduced as compared with the case where the light is guided only through the air.

Second Embodiment FIG. 3 shows a schematic configuration of a gas analyzer according to a second embodiment of the present invention. Note that portions corresponding to those in FIG. 2 are indicated by the reference numeral 100, and description thereof is omitted. The gas analyzer 224 shown in the figure includes a light source 260, one sample cell 262, one Golay cell 210, and a computer 232. The light source unit 260 includes a light source 234.
And switching means 264.

The light source 234 has a ¹² CO ₂ absorption band and a ¹³ C
The infrared light L including the O ₂ absorption band is emitted. The switching means 2
64 represents ¹² CO of infrared light L from the light source 234.
The infrared light L1 and ¹³ CO ₂ absorption band infrared light L2 of the _two absorption bands,
They are arranged to pass alternately.

The Golay cell 210 is composed of ¹² CO ₂ and ¹³
A detection gas in which only CO ₂ is mixed at a predetermined abundance ratio, for example, 50:50 or 1: 1 is sealed in the absorption chamber, and the infrared lights L3, L4 from the sample cell 262 are alternately applied. It is arranged to irradiate a detection gas.
In the Golay cell 210, the change in the pressure in the absorption chamber when the infrared light L3 in the ¹² CO ₂ absorption band enters the absorption chamber, and the infrared light L4 in the ¹³ CO ₂ absorption band enters the absorption chamber. The change in pressure in the absorption chamber at that time is detected alternately, and this is output as intensity information of the infrared light L3, L4 incident on the absorption chamber.

As described above, the second embodiment is characterized in that the switching means 264 shown in FIG. 4 is disposed in the optical path between one light source 234 and one sample cell 262, The infrared light L1 of the ¹² CO ₂ absorption band and the ¹³ CO ₂
That is, the infrared light L2 in the absorption band is alternately incident. That is, as shown in FIG.
The disk 266 includes a filter 268 that allows only the infrared light L1 in the ¹² CO ₂ absorption band of the infrared light L from the light source 234 to pass, and the infrared light L2 in the ¹³ CO ₂ absorption band. And a filter 270 that allows only the light to pass therethrough are arranged concentrically.

Then, the infrared light L from the light source 234 is disposed so as to pass through the filters 268 and 270 of the disk 266, and the disk 266 is rotated by a driving means 272 such as a motor to obtain a ¹² CO ₂ absorption band. Of the infrared light L1
The infrared light L2 in the ¹³ CO ₂ absorption band can be alternately incident on the sample cell 262. Thus, it is possible to enter the one Golay cell 210 infrared light L4 of the infrared light L3 of ¹² CO ₂ absorption band which has passed through the sample cell 262 ¹³ CO ₂ absorption bands alternately.

As described above, according to the gas analyzer 224 according to the second embodiment of the present invention, like the gas analyzer according to the first embodiment, only ¹² CO ₂ and ¹³ CO ₂ have a predetermined ratio. The detection gas mixed in the above is sealed in the absorption chamber, and both of ¹² CO ₂ and ¹³ CO ₂ are measured by one Golay cell, so that the same effect as in the first embodiment can be obtained. Can be.

It should be noted that the gas analyzer of the present invention is not limited to the above-described configurations, and various modifications can be made within the scope of the present invention. That is, in this embodiment, the gas analyzer 124 shown in FIG. 2, has been described a gas analyzer 224 shown in FIG. 3, ¹² CO ₂
When only ¹³ CO ₂ is mixed sensing gas filled in a predetermined ratio, one of the Golay cell, alternately ¹² CO ₂ absorption band infrared light L3 and ¹³ CO ₂ absorption band of infrared light L4 As long as the light can be incident, any other materials such as a light source unit and a sample cell can be used.

In this embodiment, the sample cell 1
By optically polishing the insides of the insides 28 and 262, the infrared lights L1 and L2 can pass through the inside of the cell portion satisfactorily. Further, by the computers 132 and 232
There are various methods for measuring the ¹³ CO ₂ abundance ratio, and the following methods are preferable.

Method 1, that is, FIG. 5 is a block diagram showing a method of measuring the ¹³ CO ₂ abundance ratio by the computers 132 and 142. The method for measuring the ¹³ CO ₂ abundance ratio shown in FIG.
74 and the gas analyzer 124 or 22 according to the present embodiment.
4 and the computers 132 and 23
2 is provided. Preparation Step 374
Is a standard gas with a known ¹³ CO ₂ abundance ratio ( ¹² CO ₂ and ¹³ CO ₂
Are mixed), and a plurality of ¹³ C having different ¹³ CO ₂ abundance ratios are prepared.
A standard gas having a known O ₂ abundance ratio is obtained.

The measuring step 376 is the same as the preparing step 37
The absorption band of ¹² CO ₂ of the standard gas obtained in
The absorbance at 2290 cm ^-1) from 90cm ^{-1 12} C
The O ₂ absorbance and the absorbance in the ¹³ CO ₂ absorption band (for example, 2320 cm ^-1 to 2220 cm ^-1 ) are measured by infrared spectroscopy as ¹³ CO ₂ absorbance, and the ¹³ CO ₂ absorbance is measured by ¹² C
Divide by O ₂ absorbance and absorbance ratio ( ¹³ CO ₂ absorbance / ¹² C
O ₂ absorbance). Also, this measurement step 376
The ¹² CO ₂ absorbance and ¹³ CO ₂ absorbance ¹³ CO ₂ abundance unknown sample gas ⁽¹² CO ₂ and ¹³ CO ₂ are mixed) were measured by infrared spectroscopy and ¹² CO ₂ absorbance the ¹³ CO ₂ absorbance To obtain an absorbance ratio ( ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance). The computer 132 or 234 includes a calibration curve creating unit 380, an approximate straight line determining unit 382, and a ¹³ CO ₂ abundance ratio determining unit 384.

The calibration curve preparing means 380 determines the ¹² CO ₂ absorbance and ¹³ CO _{2 of} the standard gas obtained in the measurement step 376.
From the relationship of absorbance, the ¹³ CO ₂ abundance ratio (for example, -2
4.6δ%, -9.51δ%, 12.62δ%, 33.
A calibration curve is created for 1δ%). However, the value of δ% here is a value when the existing ratio of ¹³ CO ₂ to ¹² CO ₂ in the arrowhead stone is 0δ%.

The approximate straight line determining means 382 checks the ¹² CO ₂ absorbance of the sample gas obtained in the measuring step 376 against the calibration curve obtained by the calibration curve creating means 380,
¹³ CO ₂ abundance in ¹² CO ₂ absorbance and absorbance ratio ⁽¹³ C
A first-order approximation straight line is determined from the relationship of (O ₂ absorbance / ¹² CO ₂ absorbance). The ¹³ CO ₂ abundance ratio determining means 384 calculates the absorbance ratio of the sample gas ( ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) to the primary approximate straight line obtained by the approximate straight line determining means 382.
Are determined, and the ¹³ CO ₂ abundance ratio to ¹² CO ₂ in the sample gas is determined.

Hereinafter, the method for measuring the ¹³ CO ₂ abundance ratio will be described more specifically. First, FIG. 6 shows processing contents from the preparation step 374 to the calibration curve creation step by the calibration curve creation means 380.

1. First, a preparation step 374 is performed. That is, the preparation step 374 includes four 5% standard gases ( ¹³
11. CO ₂ abundance ratio -24.6δ%, -9.51δ%,
62 δ%, 33.1 δ%) are diluted with, for example, N ₂ gas, and the respective ¹³ CO ₂ abundance ratios (−24.6 δ%, −9.5).
1δ%, 12.62δ%, 33.1δ%),
A standard gas of 3.4% is produced (S1).

In the present embodiment, each of the ¹³ CO ₂ abundance ratios (−24.6 δ%, −9.51 δ%, 12.62 δ%,
33.1 δ%), a total of 16, 2, 3, 4 and 5% is used.

2. After the completion of the preparation step s1, a known sample measurement step is performed by the gas analyzer 124 or 224 according to the present embodiment. That is, the measuring step 376 is -2.
Measure 3%, 4% and 5% in order from 2% of 4.6δ%. Thereafter, −9.51 δ%, 12.62 δ%, 33.
Similarly, for 1δ%, 3%, 4%, and 5% are measured in order from 2% (S2).

3. Then, the results of 16 points (4 × 4 points) are plotted with ¹² CO ₂ absorbance on the horizontal axis (x axis) of the graph, and the absorbance ratio ( ¹³ CO ₂ absorbance / ¹² CO ₂ ) is plotted on the vertical axis (y axis) of the graph.
Absorbance) and plotting (S3).

4. After the completion of the plotting, a calibration curve creation step by the calibration curve creation means 380 is performed. That is, calibration curve creating means 380, as shown in FIG. 7, each of the ¹³ CO ₂
For the abundance ratio (δ%), a quadratic approximation formula 386 (y = ax ²
+ Bx + c) (S4).

In this embodiment, when the ¹³ CO ₂ abundance ratio is −24.6δ%, the second approximation formula 386a (y =
0.7389x ² -0.5644x + 0.7086),
^{When the 13} CO ₂ abundance ratio is −9.51 δ%, the second approximation formula 386b (y = 0.7389x ² −0.5644x +
0.7131), and the ¹³ CO ₂ abundance ratio is 12.62 δ%, the second approximation formula 386c (y = 0.7389x ² −
0.5644x + 0.7198), the ¹³ CO ₂ abundance ratio is 3
For 3.1 δ%, the quadratic approximation 386d (y = 0.
7389x ² -0.5644x + 0.7259) was determined. Then, the quadratic approximations 386a to 386d are obtained by
^It is used as a calibration curve of ¹² CO ₂ absorbance and absorbance ratio ( ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance).

[0048] Next, the processing contents from an unknown sample measurement step to the ¹³ CO ₂ present ratio determination steps with ¹³ CO ₂ present ratio determining unit 384 in FIG. 8. 1. After the calibration curve creation step by the calibration curve creation means 380 is completed, an unknown sample measurement step is performed. That is, the ¹² CO ₂ absorbance ¹³ CO ₂ abundance unknown sample gas as shown in FIG. 8 ¹³
The CO ₂ absorbance is measured (S5).

2. Then, measure the ¹³ CO ₂ absorbance of the sample gas.
Divide by ¹² CO ₂ absorbance and absorbance ratio of sample gas ( ¹³ C
O ₂ absorbance / ¹² CO ₂ absorbance).

3. After the end of the unknown sample measuring step, an approximate straight line determining step by the approximate straight line determining means 382 is performed. That is, as shown in FIG. 7, the approximate straight line determining means 382 puts the ¹² CO ₂ absorbance (for example, 0.2) of the sample gas into the second approximation formulas 386a to 386d, and extends the line vertically therefrom (S7). . For example, when the ¹² CO ₂ absorbance of the sample gas is 0.2
If it, as shown in FIG. 7 ^{1 2} CO ₂ absorbance (x)
Draw a straight line of = 0.2.

4. The intersection of the vertically extended straight line (x = 0.2) and the quadratic approximations 386a to 386d is obtained (S8). For example, intersections (P _a , P _b , P _c , P _d ) between the straight line of the ¹² CO ₂ absorbance (x) = 0.2 and the quadratic approximations 386 a to 386 _d are obtained.

5. Taking the ¹³ CO ₂ abundance ratio (δ%) on the horizontal axis (x axis) of the graph, the absorbance ratio at the intersections P _a , P _b , P _c , and P _d ( ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) Is taken on the vertical axis (y-axis) of the graph, and a first-order approximate straight line 388 (y = dx + e) shown in FIG. 9 is drawn (S9). For example, a linear approximation line 388 (y = 0.0003x + 0.6327)
pull.

6. The absorbance ratio of the sample gas ( ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) is compared with the linear approximation line 388,
^{The 13} CO ₂ abundance (δ%) is determined (S10). For example, when the absorbance ratio of sample gas ⁽¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) is 0.63, the presence of ^{1 3} CO ₂ for ¹² CO ₂ in the sample gas than the primary approximate straight line 388 shown in FIG. 9 The ratio (δ%) is obtained as −0.83δ%.

As described above, according to the present embodiment, the abscissa (x-axis) of the graph takes the ¹² CO ₂ absorbance of the standard gas, and the ordinate (y-axis) of the graph similarly expresses the absorbance ratio ( ¹³ ) of the standard gas. C
O ₂ absorbance / ¹² CO ₂ absorbance), so that the second-order approximation formulas 386a to 386d (calibration curves) shown in FIG. 7 are obtained by correlating the ¹² CO ₂ absorbance of the standard gas with the ¹³ CO ₂ absorbance. be able to.

Then,¹³CO_TwoOf unknown sample gas
¹²CO_TwoThe absorbance is compared to the quadratic approximations 386a-d,
Sample gas¹²CO_TwoIn absorbance¹³CO_TwoAbundance ratio and absorbance
Degree ratio ( ¹³CO_TwoAbsorbance /¹²CO_TwoAbsorbance)
A second approximation line 388 is determined, and
Absorbance ratio of sample gas (¹³CO_TwoAbsorbance /¹²CO_TwoAbsorbance)
Match¹³CO_TwoSince we decided to determine the abundance ratio,
¹²CO_TwoAbsorbance and¹³CO_TwoCorrelate the absorbance¹³CO_TwoExistence
The ratio can be determined.

As a result, the absorption band of ¹² CO _{2 and} the absorption band of ¹³ CO ₂ are very close to each other, and these absorption spectra partially overlap, so that ¹² C ₂ in the sample gas in which ¹² CO ₂ and ¹³ CO ₂ coexist.
Only the ¹³ CO ₂ abundance ratio to O ₂ can be accurately measured.

Method 2 For example, in the above method 1, the ¹² CO ₂ absorbance and the absorbance ratio (
^Although the case where the second approximation formulas 386a to 386d (calibration curves) are created from the relationship of ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance has been described, the ¹³ CO ₂ absorbance and the absorbance ratio ( ¹³ CO ₂ absorbance / ¹² C) were described.
It is also possible to create a calibration curve from the relationship (O ₂ absorbance).

Method 3 In the method 1, the ¹² CO ₂ absorbance and the absorbance ratio ( ¹³
The relationship of the CO ₂ absorbance / ¹² CO ₂ absorbance), but the quadratic approximation equation 386 as shown in FIG. 7 has been described a case obtained on a two-dimensional coordinate composed of x-axis and y-axis, further z graphs Take the ¹³ CO ₂ abundance ratio of the standard gas on the axis, for example-
24.6δ%, -9.51δ%, 12.62δ%, 3
It is also possible to plot 3.1δ% and display the relationship between the ¹² CO ₂ absorbance and the absorbance ratio on a three-dimensional coordinate system such as a display (see FIG. 10A). This allows
It is also possible to obtain a visually superior calibration curve 486 by comparing the calibration curve displayed on a display or the like on a two-dimensional coordinate system (second-order approximation formula 386).

Method 4 In addition, the calibration curve creating means 380 uses the ¹² CO ₂ absorbance
Calibration curve based on ¹³ CO ₂ absorbance (quadratic approximation 586)
Can also be created (see FIG. 10B). According to the method 4, ¹² CO ₂ absorbance of the sample gas is taken on the horizontal axis (x axis) of the graph, and the vertical axis (y
Since the ¹³ CO ₂ absorbance of the sample gas is determined on the axis (axis), a second-order approximation equation can be obtained by correlating the ¹² CO ₂ absorbance with the ¹³ CO ₂ absorbance, as in the method 1.

Then, the ¹² CO ₂ absorbance of the sample gas and the ¹³ C
The O ₂ absorbance is measured, and the ¹² CO ₂ absorbance of the sample gas is compared with the calibration curve (second-order approximation formula 586), and the primary CO is determined from the relationship between the ¹³ CO ₂ abundance and the ¹³ CO ₂ absorbance in the ¹² CO ₂ absorbance. An approximate straight line is determined, and the ¹³ C of the sample gas is
O ₂ absorbance matches, ¹³ so it was decided to determine the CO ₂ abundance, the same as the structure, ¹² CO ₂ ¹³ CO ₂ exists for ¹² CO ₂ absorbance and to correlate ¹³ CO ₂ absorbance in the sample gas The ratio can be determined.

As a result, the absorption band of ¹² CO _{2 and} the absorption band of ¹³ CO ₂ are very close to each other, and these absorption spectra partially overlap, so that ¹² C ₂ in the sample gas in which ¹² CO ₂ and ¹³ CO ₂ are mixed is present.
Only the ¹³ CO ₂ abundance ratio to O ₂ can be accurately measured.

[0062] Method 5 In addition, in the method 4, ¹² CO ₂ absorbance of the standard gas and ¹³
Referring to ¹² CO ₂ absorbance of the sample gas to the CO ₂ absorbance quadratic approximate expression 586 has been described for the case of determining the primary approximate line from the relationship of the ¹³ CO ₂ abundance and ¹³ CO ₂ absorbance at the ¹² CO ₂ absorbance Is ¹² CO ₂ absorbance of standard gas and ¹³
CO ₂ refers to the ¹³ CO ₂ absorbance in the absorbance of the sample gas to the quadratic approximation equation 586, it is also possible to determine the primary approximate line from the relationship of the ¹³ CO ₂ abundance and ¹² CO ₂ absorbance at the ¹³ CO ₂ absorbance is there.

Method 6 In the method 5, the case where the quadratic approximation expression 586 is obtained on the two-dimensional coordinates composed of the x-axis and the y-axis as shown in FIG. 10B has been described. The ¹³ CO ₂ abundance ratio of the standard gas is plotted on the z-axis of, for example, −24.6δ.
%, −9.51 δ%, 12.62 δ%, and 33.1 δ%, and the relationship between the ¹² CO ₂ absorbance and the ¹³ CO ₂ absorbance can be displayed on three-dimensional coordinates on a display or the like ( FIG. 10 (c)). This makes it possible to obtain a visually superior calibration curve (second-order approximation equation 686) as compared with a calibration curve displayed on a display or the like on the two-dimensional coordinates (second-order approximation equation 586). .

[0064] In this addition, the respective components has been described for the case where a ¹³ CO ₂ abundance as absorbance ratio was used divided by ¹² CO ₂ absorbance, of course, the ¹² CO ₂ abundances
It is also possible to use a value obtained by dividing by ¹³ CO ₂ absorbance.

[0065] Further, in the respective configurations, for ¹² CO ₂
^Although the case where the value of the ¹³ CO ₂ abundance ratio with respect to ¹² CO ₂ in the arrowhead stone is used as the reference as the ¹³ CO ₂ abundance (δ%) has been described, other arbitrary ones can also be used. Further, in the respective configurations, has been described using the abundance ratio of ¹² CO ₂ for ¹³ CO ₂ in the sample gas as ¹³ CO ₂ abundance, even with the presence ratio of ¹³ CO ₂ to total CO ₂ good.

[0066]

As described above, according to the gas analyzer of the present invention, the detection gas in which only ¹² CO ₂ and ¹³ CO ₂ are mixed at a predetermined ratio is filled in the absorption chamber. Was used to measure both ¹² CO ₂ and ¹³ CO ₂ . As a result, as described above, there are variations in the concentration of the detection gas sealed in the Golay cell, misalignment of the Golay cell optical system, deterioration of the Golay cell flexible mirror, and deterioration of the brightness of the visible light source of the Golay cell optical system. Even
The effect of ¹² CO ₂ and ¹³ CO ₂ on absorbance sensitivity can be the same, and can offset the relative change in absorbance sensitivity. In the present invention,
One Golay cell can measure both ¹² CO ₂ and ¹³ CO ₂ , so a Golay cell that measures ¹² CO ₂
Compared to the case where Golay cells for measuring ¹³ CO ₂ are separately arranged, the cost can be reduced and the size of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a schematic configuration of a general Golay cell.

FIG. 2 is an explanatory diagram of a schematic configuration of a gas analyzer according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a schematic configuration of a gas analyzer according to a second embodiment of the present invention.

FIG. 4 is a front view of the switching unit shown in FIG. 3;

FIG. 5 is a flow chart showing ¹³ CO by the computer shown in FIG. 2;
FIG. ₂ is an explanatory diagram of a method for measuring an abundance ratio.

FIG. 6 is a flowchart showing a part of a processing procedure of a ¹³ CO ₂ abundance ratio measuring method according to an embodiment of the present invention.

FIG. 7 is an example of a calibration curve obtained by the method shown in FIG. 5;

FIG. 8 is a flowchart showing a part of a processing procedure of a ¹³ CO ₂ abundance ratio measuring method according to an embodiment of the present invention.

FIG. 9 is an example of a first-order approximate straight line obtained by the method shown in FIG. 5;

FIG. 10 is an explanatory view of a modified example of the method shown in FIG. 5;

[Explanation of symbols]

 110: Golay cell 124: Gas analyzer 128a: Short optical path cell (sample cell) 128b: Long optical path cell (sample cell) 130: Switching mirror (switching means) 132: Computer 134: Light source (light source) 136: Filter ( Light source)

Claims (2)

[Claims] 1. A light source unit for simultaneously emitting infrared light in a ¹² CO ₂ absorption band and infrared light in a ¹³ CO ₂ absorption band, and a sample gas containing both ¹² CO ₂ and ¹³ CO ₂ filled therein. a sample cell and second infrared light from part are arranged so as to pass through the sample gas at the same time, a switching means and second infrared light from the sample cell is disposed so as to pass alternately ¹² only CO ₂ and ¹³ CO ₂ is detected gas which is mixed at a predetermined abundance ratio is sealed absorption chamber, infrared light from said switching means is arranged to illuminate the該検knowledge gas, ¹²
And changes in pressure in the absorption chamber when CO ₂ absorption band of infrared light is incident on the absorption chamber, the change in pressure in the absorption chamber when infrared light ¹³ CO ₂ absorption band is incident on the absorption chamber And a Golay cell for alternately detecting and detecting the intensity of infrared light incident on the absorption chamber. 2. A light source unit for alternately emitting infrared light in a ¹² CO ₂ absorption band and infrared light in a ¹³ CO ₂ absorption band, and a sample gas containing both ¹² CO ₂ and ¹³ CO ₂ is filled therein. A sample cell arranged so that infrared light from the light source passes through the sample gas, and a detection gas in which only ¹² CO ₂ and ¹³ CO ₂ are mixed at a predetermined abundance are sealed in the absorption chamber, ¹² is arranged so that infrared light from the sample cell irradiates the detection gas,
And changes in pressure in the absorption chamber when CO ₂ absorption band of infrared light is incident on the absorption chamber, the change in pressure in the absorption chamber when infrared light ¹³ CO ₂ absorption band is incident on the absorption chamber And a Golay cell for alternately detecting and detecting the intensity of infrared light incident on the absorption chamber.