JP3122480B2 - Gas concentration analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration analyzer.

[0002]

2. Description of the Related Art A conventional gas concentration analyzer is shown in FIGS.
This will be described with reference to FIG.

[0005] In FIG. 5, reference numeral 1 denotes a cryostat for accommodating and supporting a laser 3 such as a wavelength-variable semiconductor laser via a mount 2, and 4 denotes a compressor used for cooling the inside of the cryostat 1 with helium gas.

A mirror 5 reflects a laser beam emitted from the laser 3 to form an optical path 6 for the laser beam.
Is a chopper which is placed in the middle of the optical path and has a slit 9 in the radial direction formed in a rotating disk 8 as shown in FIG. It is a placed spectroscope.

[0005] Numerals 11 and 12 are disposed after the spectroscope 10 in the optical path 6 to split a laser beam by transmitting a part of the laser beam and reflecting a portion thereof, and 13 is a beam splitter by the beam splitter 11. The split optical path, the transmitted optical path 14 transmitted through the beam splitter 11,
Reference numeral 15 denotes a branched optical path branched by the beam splitter 12, 1
Reference numeral 6 denotes a transmitted light path transmitted through the beam splitter 12.

Reference numeral 17 denotes a corner cube mirror for forming the forward path 18 and the return path 19 by folding the transmitted light path 13 in parallel, and reference numeral 20 denotes a gas to be inspected arranged so as to block the forward path 18 and the return path 19 of the transmitted light path 13. g gas passage 21 is a transmission window provided in the gas passage 20 for transmitting laser light.

Reference numeral 22 is provided in the middle of the branching optical path 15. For example, two parallel mirrors (not shown) are placed inside, and the laser light is reflected by the two parallel mirrors a plurality of times and then extracted. The intensity of the emitted laser light is periodically changed, and by changing the wavelength of the incident laser light, a waveform is generated in which the intensity of the laser light periodically changes in accordance with the wavelength. A conventionally well-known etalon in which the interval between the peaks of the waveform is used as a ruler for examining the wavelength;
This is a reference cell provided in the middle of 6 and the inside of which is evacuated.

Reference numerals 24, 25, and 26 denote branch optical paths 13,
15, a light intensity detector provided at the end of the transmitted light path 16,
27, 28, and 29 are preamplifiers that amplify detection signals 30, 31, and 32 from the respective light intensity detectors 24, 25, and 26;
33, 34 and 35 are lock-in amplifiers for amplifying while removing noise from amplified signals 36, 37 and 38 from the preamplifiers 27, 28 and 29, and 39 is a lock-in amplifier 33,
This is an arithmetic and control unit that calculates the concentration of the gas to be inspected g flowing through the gas passage 20 based on the intensity signals 40, 41 and 42 from 34 and 35.

Reference numeral 43 denotes a chopper control device; 44, a control current transmitted from the chopper control device 43 to the chopper 7;
Reference numeral 5 designates each lock-in amplifier 3 from the chopper control device 43.
3, 34, 35 are tuning signals to be sent.

Reference numeral 46 denotes a temperature controller for the entire cryostat 1; 47, a control command sent from the arithmetic and control unit 39 to the temperature controller 46; and 48, a control current sent from the temperature controller 46 to the heater of the cryostat 1 (not shown).

Reference numeral 51 denotes a power cord 4 wound around the mount 2 inside the cryostat 1 in a coil shape as shown in FIG.
The temperature around mount 2 is changed by adjusting the control current 50 applied to laser 3 via
A laser current control device capable of changing the wavelength of the control signal transmitted from the arithmetic control device 39 to the laser current control device 51; a feedback signal 53 transmitted from the laser current control device 51 to the arithmetic control device 39;
Reference numeral 54 denotes a laser wavelength signal sent from the laser current control device 51 to each of the lock-in amplifiers 33, 34, 35.

A control command 52 is sent from the arithmetic and control unit 39 to the laser current control unit 51, and the laser current control unit 5
The control current 50 is supplied from 1 to the laser 3 to cause the laser 3 to emit laser light in the infrared region. At this time, the control current 5
By changing the size of 0 within a small range, the power cord 49 wound in a coil shape around the mount 2 inside the cryostat 1 generates heat, the temperature around the mount 2 changes, and the wavelength of the laser 3 changes. You.

When the laser beam emitted from the laser 3 exits the cryostat 1, it travels along the optical path 6 while being reflected by the mirror 5, and is interrupted by the chopper 7 on the way.
The light is split by the spectroscope 10.

Then, the laser light is transmitted to the beam splitter 1.
At 1, the laser light branched into the branch light path 13 and the transmission light path 14 and traveling to the branch light path 13 is turned into a corner cube mirror 17.
Turns back in parallel, passes through the outbound route 18 and the inbound route 19,
The laser light passes through the gas passage 20 provided so as to block the outward path 18 and the return path 19, and is weakened by being absorbed by the gas to be inspected g flowing through the gas passage 20, and the intensity of the weakened laser light is reduced. The light intensity is detected by the light intensity detector 24.

On the other hand, the laser light that has advanced to the transmission optical path 14 is further split by the beam splitter 12 into a split optical path 15 and a transmission optical path 16, and the laser light that has advanced to the split optical path 16 enters the etalon 22 and enters the etalon 22. Is reflected multiple times between two parallel mirrors (not shown) provided in the light source, and is extracted as a waveform whose intensity changes periodically according to the wavelength, and the intensity of the laser light that changes with the periodic waveform is the light intensity. It is detected by the detector 25.

Finally, the laser beam that has proceeded to the branching optical path 16 enters the reference cell 23 having a vacuum inside, and is taken out at the original intensity without being absorbed, and the intensity of the original laser beam is reduced to the light intensity. Detected by detector 26.

A detection signal indicating the intensity of the laser light detected by the light intensity detectors 24, 25, 26
The amplified signals are amplified by 28 and 29 to obtain amplified signals 36, 37 and 38, and the amplified signals 36, 37 and 38 are amplified by the lock-in amplifiers 33, 34 and 35 while noise is removed, and the amplified signals are intensity signals 40, 41 and 42, respectively. And the intensity signals 40, 41,
The concentration of the gas to be inspected g is obtained by the arithmetic and control unit 39 on the basis of 42 as follows.

FIG. 8 is a graph showing the relationship between the intensity and the wavelength of a laser beam.
And an intensity signal 41 from the etalon 22 and an intensity signal 42 from the reference cell 23 are shown.

According to FIG. 8, the intensity signal 40 from the gas passage 20 is a curve indicating that the gas g to be inspected absorbs a laser beam near a certain wavelength and the intensity of the laser beam is weakened near that wavelength. And etalon 22
The intensity signal 41 from the reference cell 23 has a periodic waveform curve as described above.
No. 2 is a straight line of intensity I ₀ as it was when the laser light was emitted since no absorption is performed.

In FIG. 8, an intensity signal 40 and an intensity signal 42 are shown.
The area of the hatched portion surrounded by the two curves indicates the intensity of the laser beam absorbed by the gas g to be inspected.

On the other hand, between the intensity I ₀ of the incident light to the cell filled with the gas to be inspected g and the intensity I of the transmitted light, the absorption coefficient of the gas to be inspected α is α, and the gas to be inspected in the cell is α. When the concentration of g c, the passing distance of the light in the cell is L, since Seiritsu' the law of Ranbatobe Lumpur, such as equation 1,

(Equation 1) From the intensity I of the transmitted light by the intensity signal 40 in FIG. 8 and the intensity I ₀ of the incident light by the intensity signal 42 in FIG. The absorption coefficient α of g and the light transmission distance L in the cell are specified if the type of the gas g to be inspected and the size of the cell are determined).

Here, as shown in FIG. 8, the absorption of the laser beam is a certain wavelength width (a-β to a + β, where a is the wavelength of the absorption peak and β is the absorption centered on the wavelength a of the absorption peak). One side of the range, hereinafter simply referred to as an absorption range, and the wavelength a of the absorption peak and the absorption range β are shifted depending on operating conditions such as the temperature of the cryostat 1, so the intensity signal 41 from the etalon 22 is corrected as a rule). The Lambertian curve over the entire wavelength range where absorption occurs.
It is necessary to consider as law Lumpur is applied.

Therefore, the natural logarithm of Equation 1 is taken and transformed into Equation 2 (the vertical axis represents the intensity of incident light I ₀ and the intensity of transmitted light I _0).
, Taking the natural logarithm of the ratio and taking the wavelength on the horizontal axis to represent the relationship of FIG. 8) (see FIG. 9),

(Equation 2) The left side of Equation 2 is represented by Equation 3,

(Equation 3) Integrating in the range of absorption from a-β to a + β,
FIG. 1 shows the area indicated by oblique lines in FIG. 9, that is, the so-called area strength, and FIG.
The concentration of the gas to be inspected g is obtained from the relationship between the area intensity such as 0 and the concentration of the gas to be inspected g.

[0024]

SUMMARY OF THE INVENTION However, the conventional
The gas concentration analyzer has the following problems.

That is, since the reference cell 23 is provided for obtaining the intensity I _{0 of the} incident light and the etalon 22 is provided for obtaining a + β from the integration interval a-β, the branch optical path 15 provided with the reference cell 23 is provided. In addition, expensive light intensity detectors 25 and 26, preamplifiers 28 and 29, and lock-in amplifiers 34 and 35 are required in the transmission optical path 16 provided with the etalon 22 and the etalon 22.

The present invention has been made in view of the above circumstances, and has as its object to provide a gas concentration analyzer capable of reducing the required number of expensive light intensity detectors and the like.

[0027]

According to the first aspect of the present invention, a test object
A light source that irradiates the inspection gas with light, a light intensity detector that detects the intensity of light transmitted through the gas to be inspected, a detection signal from the light intensity detector, an absorption peak setting value from the absorption peak setting device, and an absorption range. An arithmetic and control unit for obtaining the concentration of the gas to be inspected based on the set value of the absorption range from the setting device ;
Form a single optical path without splitting light from the etalon or at least one of the reference cells.
It is provided movably inside and outside the road, and the absorption peak set value and
And a light source for irradiating the gas to be inspected with light.
And a light intensity detector that detects the intensity of light transmitted through the gas to be inspected , a detection signal from the light intensity detector, an absorption peak setting value from the absorption peak setting device, and an absorption range setting value from the absorption range setting device. and an arithmetic control unit for determining the concentration of the test gas based on, I to branch light from the light source
Ku to form a single optical path, the single etalon and reference cells
It is provided movably inside and outside one optical path, and the absorption peak setting
The configuration is such that the fixed value and the absorption range setting value can be corrected .

[0028]

In the present invention, the arithmetic and control unit determines the concentration of the gas to be inspected based on the detection signal from the light intensity detector, the absorption peak setting value from the absorption peak setting device, and the absorption range setting value from the absorption range setting device. with obtaining, by moving the etalon and the reference cell in the transmission optical path, from the light source
Since may determine the concentration of the test gas in a single optical path without branching the light, it is possible to reduce the required number of such high-value light intensity detector. Also, by moving one of the etalon or the reference cell into the transmitted light path, the intensity signal of the light of the gas to be inspected transmitted through the etalon or the reference cell can be obtained.
The absorption peak set value and the absorption range set value can be corrected.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 4 show an embodiment of the present invention.

In the figure, the basic configuration itself of the gas concentration analyzer is the same as that shown in FIGS. 5 to 10. Therefore, the same components are denoted by the same reference numerals and description thereof will be omitted. Hereinafter, only the configuration specific to the present invention will be described.

In the figure, 55 is an absorption peak setting unit for inputting the wavelength a of the absorption peak to the arithmetic and control unit 39, and 56 is an absorption range setting unit for inputting the absorption range β to the arithmetic and control unit 39.

Reference numeral 57 denotes an etalon provided on the outward path 18 so as to be movable in and out, and reference numeral 58 denotes a reference cell provided on the outward path 18 so as to be movable in and out.

Reference numeral 59 in FIGS. 2 and 3 denotes a moving device for the etalon 57 and the reference cell 58 as an example, and a cylinder 6 is provided between a fixed base 60 and a slide 61 slidably fitted to each other.
2 is provided.

Next, the operation will be described.

The route up to the input of the intensity signal 40 from the gas passage 20 to the computing device 39 and the computing method for determining the concentration of the gas g to be inspected are the same as those shown in FIGS.

In the present invention, however, the wavelength a of the absorption peak, which is set in the absorption peak setting unit 55 and the absorption range setting unit 56 and already known from past experimental data and the like, is used in the calculation.
And an absorption range β, and a straight line connecting the value of the point a−β and the value of the point a + β of the curve based on the intensity signal 40 from the gas passage 20 as the intensity I ₀ of the incident light.

By doing so, the etalon 57 and the reference cell 58 can be eliminated without changing the intensity so much, and the required number of expensive light intensity detectors can be reduced to one third.

Also, the etalon 57 and the reference cell 58 are connected
8 so that the flow of the gas to be inspected in the gas passage 20 is stopped, and one of the etalon 57 and the reference cell 58 is moved into the outward path 18 so that the etalon 57 or the reference cell is moved. Since the intensity signals of the laser light transmitted through the light source 58 can be obtained, the absorption peak a and the absorption range β which are set in advance can be corrected based on the intensity signals, and a conventional calculation method can be performed.

It should be noted that the present invention is not limited only to the above-described embodiment, and it is needless to say that various changes can be made without departing from the scope of the present invention.

[0041]

As described above, according to the gas concentration analyzer of the present invention, the arithmetic and control unit includes the detection signal from the light intensity detector, the absorption peak setting value from the absorption peak setting unit, and the absorption range setting unit. The concentration of the gas to be inspected is determined based on the set value of the absorption range, and the light from the light source is moved by moving the etalon and the reference cell into the transmission light path.
Since may determine the concentration of the test gas in a single optical path without branching, it is possible to reduce the required number of such high-value light intensity detector. In addition, by moving one of the etalon or the reference cell into the transmitted light path, the intensity signal of the light of the gas to be inspected transmitted through the etalon or the reference cell can be obtained, so that the absorption peak set value and the absorption range set value are corrected. It is possible to achieve an excellent effect of being able to do so.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a front view of the moving device of FIG.

FIG. 3 is a view taken in the direction of arrows III-III in FIG. 2;

FIG. 4 is a diagram showing the relationship between the intensity and wavelength of laser light according to the present invention.

FIG. 5 is a configuration diagram of a conventional example.

FIG. 6 is a schematic view of a cryostat.

FIG. 7 is a front view of the chopper.

FIG. 8 is a diagram showing the relationship between the intensity and wavelength of laser light according to a conventional example.

9 is a diagram showing the relationship of FIG. 8 with the natural logarithm of the ratio of the intensity I ₀ of the incident light and the intensity I of the transmitted light on the vertical axis and the wavelength on the horizontal axis.

FIG. 10 is a diagram showing a relationship between area intensity and gas concentration.

[Explanation of symbols]

6 Optical path of laser beam as light 13 Transmitted optical path (optical path) 24 Light intensity detector 30 Detection signal 39 Arithmetic controller 55 Absorption peak setting unit 56 Absorption range setting unit 57 Etalon 58 Reference cell α Absorption peak setting value β Absorption range setting Value g Inspection gas

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koji Ito 3-3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka Inside Kansai Electric Power Company (72) Inventor Fumihiko Yamaguchi 3-2-1, Toyosu, Koto-ku, Tokyo No.Ishikawa Shima-Harima Heavy Industries, Ltd.Toyosu Sogo Office (72) Inventor Yoshio Kusaba 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawa Shima-Harima Heavy Industries, Ltd.In the Toji Technical Center (72) Inventor Takao Kurata Tokyo 3-11-15 Toyosu, Koto-ku Ishikawa Shima-Harima Heavy Industries Co., Ltd.In the Toji Technical Center (72) Inventor Takeichi Kondo 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawa Shima-Harima Heavy Industries, Ltd. Inventor Hiroaki Nishikawa 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawajima-Harima Heavy Industries, Ltd. References JP-A-63-47637 (JP, A) JP-A-63-113346 (JP, A) JP-A-63-9844 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name ) G01N 21/00-21/61 G01J 3/00-3/52

Claims (2)

(57) [Claims] A light source for irradiating the gas to be inspected with light; a light intensity detector for detecting the intensity of light transmitted through the gas to be inspected;
And a detection signal and the absorption peak set value from the absorption peak setter and based on the absorption range setting value from the absorption range setting device to determine the concentration of the test gas arithmetic and control unit from the optical intensity detector from the light source Single without splitting light
Forming an optical path, at least one of an etalon or a reference cell movably provided inside and outside the single optical path,
To be able to correct the absorption peak set value and absorption range set value
Gas concentration analysis apparatus characterized by being configured to. A light source for irradiating the gas to be inspected with light; a light intensity detector for detecting the intensity of light transmitted through the gas to be inspected;
And a detection signal and the absorption peak set value from the absorption peak setter and based on the absorption range setting value from the absorption range setting device to determine the concentration of the test gas arithmetic and control unit from the optical intensity detector from the light source Single without splitting light
Form an optical path and connect the etalon and reference cell to the single optical path
Movably provided inside and outside of the, the absorption peak set value and
A gas concentration analyzer configured to correct an absorption range set value .