JPH0529060B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is characterized in that both ends of a cell in the longitudinal direction are closed with cell windows, a light source is provided outside one of the cell windows for illuminating the inside of the cell, and This invention relates to a gas analyzer in which a detector is provided outside the cell window.

[Conventional technology]

For example, when measuring multiple components in a sample gas using a single cell in an infrared gas analyzer, it is necessary to be aware that the absorption coefficients of each component gas are different. For example, the absorption coefficient of CO ₂ (carbon dioxide gas) is much larger than that of CO (carbon monoxide), so in order to measure these component gases with a single cell, conventional methods as shown in Figure 3 were used. It was configured like this.

In the figure, reference numeral 10 denotes a cell made of, for example, an aluminum block, to which sample gas SG is supplied, and its inner circumferential wall is formed to be easily reflective. Reference numerals 11 and 12 indicate a sample gas inlet and an outlet, respectively, and 13 and 14 indicate cell windows that close both ends of the cell 10. Reference numeral 20 designates a light source that emits infrared rays provided outside one of the cell windows 13, and 30 designates a chopper as a modulation means interposed between the cell window 13 and the light source 20.

Detectors 41, 42, and 43 are semiconductor sensors, pyrosensors, or the like arranged in parallel to each other outside the other cell window 14. Detector 41 is CO
It is equipped with a solid type bandpass filter 41F that passes only infrared rays in the absorption wavelength band of , and mainly detects CO in the sample gas SG. The detector 42 is equipped with a solid type bandpass filter 42F that passes only infrared rays in the CO ₂ absorption wavelength band.
Mainly detects CO ₂ . Further, the detector 43 includes a filter 43F that passes infrared rays in a specific absorption wavelength band different from the absorption wavelength bands of the bandpass filters 41F and 42F, and functions as a comparison detector.

51, 52, 53 are amplifiers that amplify the output signals of the detectors 41, 42, 43, respectively; 61, 62;
is a subtracter, 70 is a linearizer provided on the output side of the subtracter 62, and 81 and 82 are output terminals.

In the gas analyzer configured in this manner, the concentration of CO in the sample gas SG is output to the output terminal 81 as the difference between the output of the detector 41 and the output of the detector 43. Further, the concentration of CO ₂ in the sample gas SG is outputted to the output terminal 82 as the difference between the output of the detector 42 and the output of the detector 43. Here, since a linearizer 70 is provided in the calculation system on the detector 42 side corresponding to CO ₂ having a large absorption coefficient, the output signal is linearized, and a predetermined detection output proportional to the CO ₂ concentration is sent to the output terminal. 82.

[Problem that the invention seeks to solve]

However, the gas analyzer having the above configuration has the disadvantage that the configuration is complicated because it includes the linearizer 70, and that this kind of linearizer 70 is expensive, increasing the cost of the analyzer as a whole.

On the other hand, as shown in Japanese Patent Application Laid-Open No. 51-40192, a plurality of reflecting mirrors are used to form a plurality of optical paths having the optimum optical path length for each component gas, and a detector is placed in each of the optical paths. Some attempts have been made to measure each component gas under optimal conditions, but this method has the disadvantage of complicating the cell configuration.

The present invention has been made with the above-mentioned considerations in mind, and an object thereof is to provide a gas analyzer that can accurately measure component gases at low cost with a simple configuration.

[Means for solving problems]

In order to achieve the above object, in the present invention, both ends of the cell in the longitudinal direction are closed with cell windows,
In a gas analyzer in which a light source that illuminates the inside of the cell is provided outside one cell window, and a detector is provided outside the other cell window, the cell window is formed on a side surface perpendicular to the longitudinal direction of the cell, A detector corresponding to a component having an absorption coefficient larger than the absorption coefficient of the component detected by the detector is provided outside the cell window and at a position shorter than the effective cell length of the detector.

[Effect]

Since the amount of light incident on the detector corresponding to a component gas with a large absorption coefficient is reduced and the effective cell length for the component gas is shortened, component gases with a large absorption coefficient can also be measured under optimal conditions. .

〔Example〕

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

FIG. 1 shows an embodiment of the present invention, in particular, a plurality of component gases (in the illustrated example, CO,
Two component gases of CO ₂ (hereinafter simply referred to as components)
An example of the configuration of a gas analyzer that can independently measure the concentrations of

In this figure, the same reference numerals as those shown in FIG. 3 indicate the same or equivalent parts, and the explanation thereof will be omitted.
The main difference between the gas analyzer shown in FIG. 1 and the one shown in FIG. 3 is that the side surface 10S of the cell 10 is
A cell window 15 having the same configuration as the cell windows 13 and 14 is provided, and a detector 42 corresponding to a component with a large absorption coefficient (CO ₂ in this example) is installed outside of this cell window 15 using a bandpass sensor. This is provided together with the filter 42F.

That is, the position is perpendicular to the axis (hereinafter referred to as optical axis) L of light that travels linearly from the light source 20 toward the detectors 41 and 43, and the detector 4
Detector 4 is located at a position shorter than the effective cell length of 1 and 43.
2 was established.

With this configuration, both direct light and reflected light that travel straight along the optical axis L among the light emitted from the light source 20 enter the detectors 41 and 43 provided on the optical axis L. However, since only the reflected light enters the detector 42 provided on the side surface 10S of the cell 10, the amount of light incident on the detector 42 corresponding to the component with a large absorption coefficient is smaller than that of the other detectors 41, 43.
It is considerably smaller than that of the detector 42.
Since the effective cell length of the detector 42 is shorter than that of the other detectors 41 and 43, the output signal of the detector 42 does not saturate and lose linearity as in the conventional case, and the signal output characteristic itself approaches a straight line. Therefore, a signal that accurately represents the concentration of CO ₂ , which is the component to be measured, is output. As a result, there is no need to provide an expensive linearizer on the output side of the detector 42, which simplifies the configuration of this type of analyzer and reduces the cost of the analyzer. It goes without saying that with the above configuration, it is possible to accurately measure the concentration of CO, which has a smaller absorption coefficient than CO ₂ .

FIG. 2 shows another embodiment of the present invention, in particular, interference components contained in the sample gas (in the illustrated example,
An example of the configuration of a gas analyzer that can measure the concentration of a specific component to be measured (in the illustrated example, CO) while removing the influence of CO ₂ is shown.

In FIG. 2, a detector 41 corresponding to the component to be measured CO is provided on the optical axis L together with a bandpass filter 41F, and a detector 42 corresponding to the interference component CO ₂ having a larger absorption coefficient than CO is provided on the other hand. A band pass filter 42F is provided outside the cell window 15 formed on the side surface 10S of the cell 10, and further,
A subtracter 63 is provided after the amplifiers 51 and 52 that amplify the outputs of the detectors 41 and 42, respectively, and this subtracter 63 subtracts the concentration of the interference component CO ₂ to obtain the concentration of the measurement target component CO. A signal representing this is outputted to the output terminal 83.

It should be noted that the present invention is not limited to the above two embodiments; for example, an analyzer that measures three or more components simultaneously and independently, or a specific analyzer that removes the influence of two or more interfering components. It can be applied to an analyzer that measures the concentration of a component to be measured. Further, the present invention can also be applied to a so-called fluid modulation type analyzer in which a comparison gas and a sample gas are alternately supplied to a cell.

〔Effect of the invention〕

As explained above, in the present invention, both ends of the cell in the longitudinal direction are closed with cell windows, a light source is provided outside one cell window for illuminating the inside of the cell, and a light source is provided outside the other cell window. In a gas analyzer equipped with a detector, a cell window is formed on a side surface perpendicular to the longitudinal direction of the cell, and a cell window is formed outside the cell window and at a position shorter than the effective cell length of the detector, and the detector detects the cell window. Since a detector corresponding to a component having an absorption coefficient larger than that of the component to be detected is provided, the output characteristic of the detector for a component having a large absorption coefficient is improved to be close to a straight line.

Therefore, only a plurality of components or a desired component can be measured with high precision without using an expensive linearizer as in the conventional method. According to the present invention, there is no need to use a plurality of reflecting mirrors to form the optimal optical path length for each component, as is the case in the past, and this simplifies the overall configuration of the cell and gas analyzer. Various types of gas analyzers can be obtained at low cost.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a block diagram showing another embodiment of the present invention, and FIG. 3 is a block diagram for explaining the prior art. 10... Cell, 10S... Side, 13, 14,
15... Cell window, 20... Light source, 41, 42, 4
3...Detector.

[Claims]

1 pneumatic-to-electrical conversion having gas-filled detector chambers arranged coaxially one after the other, provided with infrared-transparent end faces, which detector chambers are pressure- or flow-sensitive; In pneumatic detectors for non-dispersive infrared gas analyzers which are connected to each other via conduits containing chambers, after the second chamber 6 there is a second chamber 6 which has an infrared transparent end face 11 and which is filled with gas. 3 chambers 9 are arranged coaxially, the third chamber 9 is connected to the second chamber 6 so that gas can be conducted thereto, and the second chamber 6 and the third chamber 9 are A pneumatic detector for a non-dispersive infrared gas analyzer, characterized in that a displaceable infrared absorbing aperture 12 is arranged in between. 2. A pneumatic detector according to claim 1, characterized in that the sum of the heights of the second and third chambers 6, 9 is greater than the height of the first chamber 5. 3. The pneumatic detector according to claim 1, wherein the aperture 12 has an infrared absorbing surface.