JPH0533952Y2 - - Google Patents

Description

[Detailed Description of the Invention] {Industrial Field of Application} The present invention relates to an infrared gas analyzer that analyzes gases contained in various types of exhaust gas, the atmosphere, and the like.

{Prior art} Infrared gas analyzers analyze gases contained in various types of exhaust gas, the atmosphere, and other substances by utilizing the fact that gases absorb infrared rays in specific wavelength ranges. .

However, when measuring CO, for example, when the measurement gas also contains CO ₂ , the infrared absorption wavelength range of the measurement component gas and the infrared absorption wavelength range of the interference component gas may partially overlap. If the measurement gas contains an interference component gas, the interference component gas absorbs infrared rays, which reduces measurement accuracy. Therefore, it is necessary to reduce the influence of interference component light.

For example, the one shown in FIG. 9 is known as a gas analyzer that reduces the influence of interference component light.

In this gas analyzer, a measurement cell 21 to which a measurement gas is supplied and a comparison cell 21 filled with a comparison gas are arranged in parallel, and the measurement cell 21 has a measurement gas supply port 21a and a discharge port 21b. It is provided. Infrared light sources 23a and 23b are arranged on one side of the cells 21 and 22, and detectors 24a and 24b such as condenser microphones are arranged on the other side.
Interference filters 25a and 25b are arranged between them. The interference filters 25a and 25b transmit infrared rays in the absorption wavelength range of the measurement component gas (hereinafter referred to as measurement component light) and reflect infrared rays in the absorption wavelength range of the interference component gas (hereinafter referred to as interference component light). It is.

Reflection mirror 26a of the light sources 23a and 23b,
26b is a curved spherical light source 2.
The infrared rays emitted from 3a and 23b are transmitted to each cell 2.
It is reflected in the direction of 1 and 22. 27 is a chopper, 28a and 28b are preamplifiers, and 29 is an amplifier.

Gas analysis by this gas analyzer is performed using the light source 23.
The infrared rays of a and 23b are made into intermittent light by a chopper 27 and are incident on the cells 21 and 22. Then, it passes through the interference filters 25a and 25b to the detector 24.
The measurement gas is analyzed based on the difference in the amount of infrared rays entering a and 24b, and interference component light is reflected by interference filters 25a and 25b, and it is detected that it enters detectors 24a and 24b. This prevents deterioration in analysis accuracy due to interference component light.

{Problem to be solved by the invention} In the conventional gas analyzer, the interference component light is reflected by the interference filters 25a, 25b to prevent the interference component light from entering the detectors 24a, 24b. , the reflectance of infrared rays in the reflection wavelength range of the interference filters 25a and 25b is not 100% but 0.1~
A trace amount of about 0.001% will pass through.

The interference component light reflected by the interference filters 25a, 25b is reflected by the inner surfaces of the cells 21, 22, reaches the reflection mirrors 26a, 26b of the light sources 23a, 23b, and is reflected. Reflection mirror 2
The interference component lights reflected by 6a and 26b reach the interference filters 25a and 25b again and are repeatedly reflected.

In this way, the interference component light passes through the interference filter 25.
a, 25b and reflection mirrors 26a, 26b are repeated. On the other hand, since the interference filters 25a and 25b transmit a minute amount of interference component light as described above, the interference filters 25a and 25b
If the reflection of the interference component light by b is repeated many times, the total amount of the interference component light that passes through the interference filters 25a, 25b and enters the detectors 24a, 24b increases, resulting in a problem of deterioration of analysis accuracy.

The present invention solves the above-mentioned problems, and eliminates the repeated reflection of interference component light, thereby creating an infrared gas analyzer that does not reduce accuracy due to repeated reflection of interference component light. The purpose is to obtain the following.

{Means for solving the problem} The infrared gas analyzer according to the present invention has a detector disposed at the infrared ray emission port of the measurement cell, and a light source that enters the infrared rays into the detector through the filter and the measurement cell. In an infrared gas analyzer, the infrared receiving surface of the filter is arranged at an angle to face both the light source emission aperture and the infrared infrared incident aperture of the measurement cell, such that the light source receives the infrared light from the light source emission aperture. Of the infrared rays emitted toward the light receiving surface, infrared rays in the absorption wavelength range of the measurement component gas are reflected by the infrared light receiving surface and made to enter the measurement cell,
and is characterized in that the infrared rays in the absorption wavelength range of the interference component gas are transmitted through a non-infrared ray receiving surface located on the opposite side from the infrared ray receiving surface and are not incident on the measuring cell. .

The filter can have any configuration such as a flat plate, a concave mirror shape, or a polygon mirror shape, and reflects the measurement component light in the infrared rays from the light source and makes it enter the measurement cell, so that the interference component light enters the measurement cell. It is only necessary to place the light so that it can be transmitted so as to prevent it from entering. Well, the number of filters provided for one measurement cell is also arbitrary.

{Function} In this infrared gas analyzer, infrared rays emitted from its light source are first incident on a filter, where the components to be measured are reflected and incident on a detector via a measurement cell. On the other hand, the interference component light passes through the filter and is removed, and does not enter the measurement cell.

When the minute amount of interference component light reflected by the filter is incident on the filter again, it is transmitted through the filter and removed, thereby preventing a decrease in analysis accuracy caused by repeated reflection of interference component light by the filter, etc. It is something.

{Example} An example of the infrared gas analyzer of the present invention will be described with reference to FIG.

In FIG. 1, a reference gas and a measurement gas are alternately supplied to the reference gas 1. This is a measurement cell using a so-called sample modulation method, and is provided with a gas supply port 1a and a gas discharge port 1b. And the infrared incidence port D of cell 1
A filter 3 is arranged on the side so that the infrared receiving surface B is inclined at 45 degrees with respect to the axis of the cell 1.
This filter 3 reflects the measurement component light and transmits the interference component light.

Reference numeral 4 denotes a light source that emits infrared rays toward the filter 3. The infrared rays emitted by this light source 4 and passed through the light source emission port C are the measurement component light, which is reflected by the infrared receiving surface B of the filter 3 and enters the measurement cell 1. is incident on
The interference component light passes through the infrared ray non-receiving surface E side of the filter 3 and is removed, and does not enter the measurement cell 1.

5 is a detector such as a condenser microphone into which the infrared rays that have passed through the measurement cell 1 and passed through the infrared emission port A are incident; 6 is an auxiliary interference filter placed between the measurement cell 1 and the detector 5; It transmits the measurement component light and reflects the interference component light. 8 is a preamplifier.

In this infrared gas analyzer, a comparison gas and a measurement gas are alternately supplied to a measurement cell 1 through a supply port 1a and a discharge port 1b. Then, the infrared rays emitted from the light source 4 are incident on the filter 3. In the infrared rays incident on the filter 3, interference component light b is transmitted through the infrared ray non-receiving surface E side of the filter 3 and removed, and is not incident on the measurement cell 1.

On the other hand, the measurement component light a is reflected by the infrared receiving surface B of the filter 3, passes through the infrared entrance D, and enters the measurement cell 1. A part of the measurement component light a that enters the measurement cell 1 is absorbed by the component to be measured in the measurement cell 1, and passes through the auxiliary interference filter 6.
passes through and enters the detector 5.

Note that a small amount of reflected interference component light that is reflected and enters the measurement cell 1 without passing through the filter 3
b ₁ is reflected by the auxiliary interference filter 6, passes through the measurement cell 1, and enters the filter 3 again, but this interference component light b ₁ also passes through the infrared non-receiving surface E of the filter 3.
It passes through to the side and is removed.

As in this embodiment, if an auxiliary interference filter 6 is arranged between the measurement cell 1 and the detector 5 to reflect a minute amount of interference component light _b1 , the minute amount of reflected interference component light b reflected by the filter 3 can be ₁ is incident on the measurement cell 1, this reflected interference component light b ₁ can be reflected by the auxiliary interference filter 6 and transmitted through the filter 3 to be removed, making it possible to more reliably eliminate the influence of the interference component light b ₁ . can be lost.

For example, the transmittance of the interference component light b of the filter 3 is set to 99%, and the transmittance of the interference component light b of the auxiliary interference filter 6 is set to 99%.
If the reflectance of b ₁ is 99.9%, then 0.01×0.001=1×10 ^-5 =1×10 ^-3 %≒0, and the interference component light b and the reflected interference component light b ₁ are incident on the detector 5. It is clear that it is possible to eliminate this problem and greatly improve the analytical accuracy.

The auxiliary interference filter 6 can also be changed to a gas filter that absorbs the interference component light b and transmits the measurement component light a.

However, even without providing the auxiliary interference filter 6,
The interference component light b ₁ reflected by the filter 3 is very small, and when this reflected interference component light b ₁ is reflected by the measurement cell 1 or the window of the detector 5 and enters the filter 3 again, it is transmitted through the filter 3. It can be removed. In other words, the reflected interference component light b ₁ repeats reflection, and the reflected interference component light b1 enters the detector 5.
By eliminating the increase in the total amount of b ₁ using a filter, it is possible to reduce the influence of reflected interference component light on analysis accuracy. Therefore, the provision of the auxiliary interference filter 6 is optional.

FIG. 2 shows another embodiment of the mounting structure for the filter 3.

In FIG. 2, 11 indicates one end of the filter 3;
A pin that supports swingably in the thickness direction, 1
A support plate 2 is fixed to the other end of the filter 3, and fixing members 13a and 13b are arranged on both sides of the support plate. A spring 14 is inserted into a screw hole (not shown) of the fixing member 13a, and its tip urges the support plate 12 toward the adjustment screw 14.
The other configurations are the same as those of the embodiment shown in FIG. 1, and are designated by the same reference numerals.

In this embodiment, when the adjustment screw 14 is advanced or retracted, the spring 15 is compressed or expanded in response to the adjustment screw 14, and the filter 3 can be caused to swing through the support plate 12. Therefore,
By adjusting the angle of the filter 3, the direction of the measurement component light a reflected thereby can be adjusted, and the direction of incidence of the measurement component light a onto the measurement cell 1 can be easily set.

FIG. 3 shows another embodiment in which the arrangement of the filters is different.

In this embodiment, a filter 3a is arranged in front of an infrared light source 4 at an angle of 45 degrees with respect to the traveling direction of the infrared rays, and a filter 3b is arranged at an angle of 90 degrees with respect to the filter 3a. , the infrared receiving surface B ₁ of this filter 3a and the filter 3
Measurement component light a reflected by infrared receiving surface B ₂ of b
is configured so that the infrared rays are incident on the infrared ray entrance D of the measurement cell 1. Since the other configurations are the same as those of the embodiment shown in FIG. 1, detailed explanation will be omitted and the same reference numerals will be used.

This infrared gas analyzer filters measurement component light a in infrared rays emitted from a light source through a filter 3a,
The infrared rays are sequentially reflected by the infrared receiving surfaces B ₁ and B ₂ of 3b and are incident on the measurement cell 1. Then, the interference component light b is transmitted to the infrared non-receiving surface E ₁ of the filter 3a and removed, and a small amount of reflected interference component light b ₁ reflected by the infrared receiving surface B ₁ of the filter 3a is
It is transmitted to the infrared non-receiving surface _E2 side of the filter 3b and removed.

Therefore, it is possible to further reduce the amount of interference component light reflected by the infrared receiving surfaces B ₁ and B ₂ of the filters 3a and 3b and incident on the measurement cell 1.
Gas can be analyzed with high precision.

Note that in this embodiment as well, the measurement cell 1 and the detector 5
It is also possible to provide an auxiliary interference filter that reflects the interference component light between the two.

FIG. 4 shows another embodiment.

In FIG. 4, reference numeral 1 denotes a measurement cell to which a measurement gas is supplied, and is provided with a measurement gas supply port 1a and a discharge port 1b. Reference numeral 2 denotes a comparison cell arranged parallel to the measurement cell 1, and filled with a comparison gas.
3a and 3b are respectively slightly curved concave mirror-like filters, which are used for measurement cell 1 and comparison cell 2.
are placed on one side at a slight angle to their axes. In the infrared rays emitted from the light source 4 disposed between the filters 3a and 3b, the measurement component light is reflected by the infrared receiving surfaces B and B of the filters 3a and 3b, and the measurement cell 1 and comparison cell 2 are separated. Inject the infrared rays into the infrared entrance ports D and D, respectively,
The interference component light is configured to be transmitted to the infrared non-receiving surfaces E and E sides of the filters 3a and 3b and removed.

5a and 5b are detectors, 6a and 6b are auxiliary interference filters arranged between the measurement cell 1 and comparison cell 2 and filters 3a and 3b, respectively, 7 is a chopper, 8a and 8b are preamplifiers, and 9 is an amplifier. , 10
is a reflection mirror of the light source 4.

Note that it is also possible to arrange light sources separately for each of the filters 3a and 3b.

In this infrared gas analyzer, a measurement gas is supplied to a measurement cell 1. In the infrared rays emitted from the light source 4, the measurement component light a is passed through the filter 3a,
3b, and transmitted through the auxiliary interference filters 6a, 6b to the measurement cell 1, the comparison cell 2, and the infrared emission ports A, A.
The light passes through and enters the detectors 5a and 5b.

The interference component light b is transmitted to the infrared non-receiving surface E side of the filters 3a and 3b and is removed, but a small amount of reflected interference component light b ₁ is reflected by the infrared receiving surfaces B and B of the filters 3a and 3b. is reflected by the auxiliary interference filters 6a, 6b, transmitted to the infrared non-receiving surfaces E, E sides of the filters 3a, 3b, and removed.
Therefore, there is no risk that the reflected interference component light b ₁ will be repeatedly reflected by the reflection mirror 10 of the light source 4 and will be incident on the detector 5, thereby reducing the accuracy of analysis.

FIG. 5 is another embodiment, and shows a multi-component type infrared gas analyzer.

In this infrared gas analyzer, a filter 3 is arranged on one side of a measurement cell 1, which is provided with a supply port 1a and a discharge port 1b for supplying measurement gas, and is inclined at 45 degrees with respect to its axis. Katsuko filter 3
A light source 4 is provided that emits infrared rays toward. 5a and 5b are non-selective detectors, 6a and 6b are auxiliary interference filters, 7 is a chopper provided in the measuring cell 1, and 7a is a motor of the chopper 7.

The filters 3, 3a, 3b and the auxiliary filters 6, 6a, 6b in each of the above embodiments use known filters. For example, in an infrared gas analyzer for measuring CO, as shown in FIG. Si substrate 1
One side of the filter 6 is coated with a minus filter 17 having a transmission center wavelength λc=4.7 μm, and the other side is coated with an anti-reflection coat 18. Figure 7 shows the spectral spectrum of the AR-coated minus filter.

In addition, a Ge-SiO multilayer film that transmits short wavelengths, whose spectroscopic spectrum is shown in FIG. There are also filters whose other side is coated with a transparent Ge-SiO multilayer film.

{Effect of the invention} As described above, the infrared gas analyzer of the invention makes the infrared rays emitted from the light source enter the filter before entering the measurement cell, and the measurement component light is absorbed by the infrared receiving surface of the filter. The interference component light was reflected and made to enter the measurement cell, but the interference component light was transmitted through the infrared non-receiving surface side of the filter and removed, so that it did not enter the measurement cell.

Therefore, it is possible to solve the problem that a large amount of interference component light is incident on the measurement cell and a part of it enters the detector, reducing analysis accuracy.

Even if a small amount of interference component light is reflected by the infrared receiving surface of the filter and enters the measurement cell, if it is reflected from the window of the measurement cell and enters the filter again, the interference component light will be absorbed into the filter. It can be removed by transmitting the infrared rays to the non-receiving surface side. Therefore, it is possible to solve the problem that the interference component light reflected by the filter repeats further reflection, thereby increasing the total amount of interference component light incident on the detector, which affects the analysis accuracy. can.

[Brief explanation of the drawing]

1 to 8 show embodiments of the present invention, FIG. 1 is a sectional view, FIG. 2 is a sectional view of another embodiment of the filter installation, and FIGS. 3, 4, and 5 are different examples. 6 is an enlarged front view of the filter, FIG. 7 is a spectral diagram of the minus filter of the filter shown in FIG. 6, and FIG. 8 is the spectral spectrum of one side of each of the other filters. 9 are sectional views of the conventional example. 1...Measurement cell, 2...Comparison cell, 3...Filter, 4...Light source, 5, 5a, 5b...Detector.

Claims (1)

[Scope of utility model registration request] In an infrared analyzer in which a detector 5 is disposed at an infrared emission port A of a measurement cell 1, and a light source 4 is provided for injecting infrared rays into the detector 5 through a filter 3 and a measurement cell 1, the infrared light receiving surface of the filter 3 B
is arranged at an angle to face both the light source emission opening C and the infrared entrance D of the measurement cell 1, so that the light source 4 emits from the light source emission opening C toward the infrared receiving surface B. Of the infrared rays, infrared rays in the absorption wavelength range of the measurement component gas are reflected by the infrared receiving surface B and made to enter the measurement cell 1, and infrared rays in the absorption wavelength range of the interference component gas are reflected by the infrared ray receiving surface B. An infrared gas analyzer characterized in that the infrared gas analyzer is configured so that the infrared rays are transmitted to the side of the non-receiving surface E located on the side and do not enter the measurement cell 1.