JPS6348443A - Gas analyzer - Google Patents

Abstract

PURPOSE:To approximate the output characteristic of a detector for a component having a large coefft. of absorption to linearity and to enhance the accuracy of measurement by providing the detector for the component having the large coefft. of absorption among the plural detectors corresponding to the plural components to the side face of a cell. CONSTITUTION:Both of the direct light which is emitted from a light source 20 and advances rectilinearly along an optical axis L and the reflected light enters the detectors 41, 43 provided on the optical axis L, but only the reflected light enters the detector 42 provided to the side face 10s of the cell 10; therefore, the quantity of the incident light on the detector 42 corresponding to the component having the large coefft. of absorption is sizably smaller than the quantity of the incident light on the other detectors 41, 43 and since the effective cell length of the detector 42 is shorter than the effective cell length of the other detectors 41, 43 the output of the detector 42 is not saturated to be broken of the linearily, unlike with the conventional analyzer, and the signal output characteristic itself approximates to the linearily; therefore, the signal correctly indicating the concn. of CO2 which is the component to be measured is outputted. As a result, the need for providing a costly linearizer on the output side of the detector 42 is eliminated and the constitution of this kind of the analyzer is simplified; in addition, the cost of the analyzer is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a gas analyzer that is provided with detectors for each of a plurality of components.

[Conventional technology]

When measuring multiple components in a sample gas using a single cell in an infrared analyzer, it is necessary to be careful that the absorption coefficients of each component gas are different. For example, Co
Since the absorption coefficient of w (carbon dioxide gas) is considerably larger than that of C0 (-carbon oxide), the conventional configuration for measuring these component gases with a single cell was as shown in Figure 3. Ta.

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 easily reflect light. 11.12
13.14 are the sample gas inlet and outlet, respectively.
are cell windows that close both ends of the cell 10. 20 is a light source that emits infrared rays and is provided outside one cell window 13;
30 is a chopper interposed between the cell window 13 and the light source 20 as a modulation means.

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

51, 52, and 53 are amplifiers that amplify the output signals of the detectors 41, 42, and 43, respectively, 61.62 is a subtracter, and 70
is a linearizer 81 provided on the output side of the subtracter 62;
82 is an output terminal.

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 Cot 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 COl having a large absorption coefficient, the output signal is linearized, and a predetermined detection output proportional to the CO□ concentration is output to the output terminal 82. is output to.

[Problems to be Solved by the Invention] However, in the gas analyzer having the above configuration, the configuration is complicated because the linearizer 70 is provided.
Since this type of linearizer 70 is expensive, it has the disadvantage of 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 optical paths having the optimum optical path length for each component gas are formed using a plurality of reflecting mirrors, 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 analysis needle that has a simple configuration, can inexpensively and accurately measure component gases.

[Means for solving problems]

In order to achieve the above object, the gas analyzer according to the present invention is provided with a detector corresponding to a component having a large absorption coefficient on the side of the cell.

[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 components (in the illustrated example, co, co, etc.) in a sample gas.

An example of the configuration of a gas analyzer that can independently measure the concentrations of two components) is shown below.

In this figure, the same reference numerals as those shown in FIG. 3 indicate the same or equivalent parts, and their explanation will be omitted.

The gas analyzer shown in FIG. 1 is largely different from the one shown in FIG.
A cell window 15 having the same configuration as in 3.14 is provided, and a detector 42 corresponding to a component with a large absorption coefficient (in this example, C(h)) is installed outside the cell window 15 together with a bandpass filter 42F. This is the point I made.

That is, it is a position perpendicular to the axis (hereinafter referred to as optical axis) L of light that travels linearly from the light source 20 toward the detector 41.43, and furthermore, the position is longer than the effective cell length of the detector 41.43. The detector 42 was provided at a short position.

With this configuration, both the direct light that travels straight along the optical axis and the reflected light out of the light emitted from the light source 20 enter the detectors 41 and 43 provided on the optical axis. However, the detector 4 provided on the side surface 10S of the cell IO
Since only the reflected light is incident on the detector 42, the amount of light incident on the detector 42 corresponding to the component with a large absorption coefficient is smaller than that on the other detector 41.
．． The number of detectors 42 is considerably smaller than that of 43, and the number of detectors 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, but the signal output characteristic itself becomes linear. Therefore, a signal that correctly represents the concentration of COI, which is the component to be measured, is output. As a result, there is no need to provide an expensive nearer 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.

FIG. 2 shows another embodiment of the present invention, in particular, removes the influence of interference components (in the illustrated example, CO'ton) contained in the rubble gas and selects a specific measurement target component (in the illustrated example, CO'ton).
) shows an example of the configuration of a gas analyzer that can measure the concentration of

In FIG. 2, a detector 41 corresponding to the component to be measured CO is provided on the optical axis together with a bandpass filter 41F, and an interference component Cot having a larger absorption coefficient than CO is arranged on the optical axis.
A detector 42 corresponding to the detector 42 is provided outside the cell window 15 formed on the side surface 10S of the cell 10 together with a bandpass filter 42F, and further, an amplifier 51.52 is provided at the rear stage of the amplifier 51.52 to amplify the output of each detector 41.42. A subtracter 63 is provided in the subtracter 63, and the interference component CO! Subtract the concentration of
A signal representing the concentration of the measurement target component CO 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. Furthermore, 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, the gas analyzer according to the present invention has a detector corresponding to a component with a large absorption coefficient on the side of the cell, so the output characteristic of the detector for a component with a large absorption coefficient is close to a straight line. Therefore, multiple components can be measured with high accuracy without using an expensive linearizer. Furthermore, the structure of the analyzer becomes simple and can be constructed at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 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, 41, 42.43
···Detector.

Claims (1)

[Claims] What is claimed is: 1. A gas analyzer comprising detectors for each of a plurality of components, characterized in that a detector corresponding to a component with a large absorption coefficient is provided on the side of a cell.