JPH0720075A - Gas concentration measuring method and device - Google Patents

Abstract

PURPOSE:To accurately measure the concentration of each of a plurality of constituent gases by detecting the concentration of each constituent gas totally using the detection values of all detectors used for detection. CONSTITUTION:A leakage gas monitoring device 1 is provided with detectors A1, A2,..., An provided in a working space using gases X1, X2,..., Xn, converters C1, C2,..., Cn, etc., for converting signals from these converters A1, A2,..., An to specific electrical signals. Signals Y1, Y2,..., Yn from the detectors A1, A2,..., An are input to a microprocessor unit (MPU) 5 which receives digital signals from an A/D converter 4. A coefficient mij which is actually measured by an experiment in advance is stored at a memory 6. Operation data indicated by an expression I are stored in a memory 7. Therefore, the MPU 5 uses the signals Y1, Y2..., YN of the detector A1, A2,..., An, calculates the concentration of the constituent gases X1, X2,..., Xn, and then supplies the result to a monitor 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration measuring method, for example, a gas concentration measuring method and apparatus suitable for use in monitoring leakage of toxic gas in a working space, composition analysis of mixed gas, and the like.

[0002]

2. Description of the Related Art In the field of semiconductor manufacturing, for example, semiconductors are manufactured using various gases in a working space such as a clean room. However, since many of the gases used are toxic to the human body, a detector (gas sensor) for detecting leaked gas is provided in the work space to detect leaks of toxic gas and to ensure worker safety.

As a detector, a hot wire semiconductor type detector for hydrogen detection, a diaphragm electrode type detector for ammonia detection, and a potentiostatic electrolysis type detector for monosilane detection are generally known. In this case, the number of detectors is the same as the number of component gases to be detected, and the component gas is individually detected by a dedicated detector.

[0004]

However, currently used detectors do not have sufficient selectivity with respect to the gas to be detected and may be sensitive to gases other than the gas to be detected (non-detection target gas). For this reason, it is not possible to identify the leaked gas, and even if it is possible to continue operation satisfactorily by closing only the main valve of the pipe through which the gas that is actually leaking flows, all the gas pipes that the detector is sensitive to There was an inconvenience that the main valve was closed and the operation was completely stopped.

The dedicated detector is selected to have high sensitivity to the gas to be detected and low sensitivity to the non-detection target gas. Sensitivity cannot be zero.

For example, Table 1 is an example of a detector using hydrogen chloride as a gas to be detected, and shows indicated values when various component gases are brought into contact with each other at various concentrations.

[0007]

[Table 1]

As is apparent from Table 1, even for hydrogen chloride detection, it is sensitive to various non-detection target gases such as hydrogen, nitric oxide, nitrogen dioxide, and hydrogen sulfide, and especially for hydrogen sulfide, It can be seen that it is more sensitive than the gas to be detected.

As described above, the detector is usually sensitive to various non-detection target gases other than the detection target gas. Therefore, as described above, when the number of component gases increases, only the specific component gas is sensitive. Aligning the detectors becomes extremely difficult.

Therefore, it is an object of the present invention to provide a gas concentration measuring method and apparatus capable of accurately measuring the concentration of a component gas in a mixed gas.

[0011]

In order to achieve the above object, the gas concentration measuring method according to the present invention is a method for measuring the concentration of each component gas by using the same number of detectors as the component gas in the mixed gas. In the above, the component gas (X _j ) (where j
Are detectors (A _i ) (where i is 1 to n, the same applies below) having independent detection characteristics for each of 1 to n, and the same applies below, and each of the component gases (X _j ) is independent. detector (a _i) previously obtained detection value m _ij per unit concentration of the detection at the time of the mixed gas measuring device a ₁ when in the presence,
A _2, A _3, ..., detected value y ₁ of _{A n, y 2, y 3} , ..., each component gas X ₁ from the equation shown below using _{y n, X 2, X 3} ,
,, X _n concentrations α ₁ , α ₂ , α ₃ , ..., α _n are characterized.

Further, the gas concentration measuring device according to the present invention is
A detector (A _i ) having the same number as the number of component gases in the mixed gas and having independent detection characteristics for each component gas (where i is 1 to n, the same applies hereinafter), and each of the component gases ( X _j ) (where j is 1 to n, the same applies hereinafter) is the detection value m per unit concentration of the detector (A _i ).
and coefficient storage means for storing a _ij, detected during the mixed gas measuring device _{A 1, A 2, A 3} , ..., the detection value of A _n y _1, y _2,
y _3, ..., y _n each component from the equation shown below using the gas _{X 1, X 2, X 3} , ..., the concentration of _{X n α 1, α 2,} α 3, ..., α n
It is characterized by comprising a solution storage means for obtaining

[0013]

[Equation 3]

[0014]

In the present invention, the concentration of the component gas in the mixed gas is measured. The mixed gas means air containing the component gas to be detected in the field of leak gas detection, and the gas production In the field of use, it means a base gas containing a component gas to be analyzed.

In the present invention, the concentration of the component gas is measured by the same number of detectors as the number of component gases as in the conventional case.
Each detector used shall have independent detection characteristics for each component gas.

Then, first, the detection value m of the detector A _i per unit concentration when the component gas X _j exists alone.
_ij (hereinafter, referred to as a coefficient) is experimentally obtained in advance.
In this case, when the detection characteristic of the detector is not linear with respect to the concentration of the component gas, the output of the detector is linearized in advance.

By the above processing, the component gases X ₁ , X ₂ ,
X _3, ..., ₁ concentration of X _n is _{α, α 2, α 3,} ..., the detector when the _{α n A 1, A 2,} A 3, ..., the detection value of A _n y _1, y _2,
y ₃ , ..., Y _n are obtained by the following equations.

[0018]

[Equation 4] The above is expressed as follows.

[0019]

[Equation 5] As mentioned above, the detection characteristics of the detector are independent for each component gas, so the vector

[0020] Becomes linearly independent, and the matrix

[0021]

[Equation 6] Is nonsingular, that is, inverse matrix
x), the desired concentrations α ₁ , α ₂ , α ₃ , ..., α
_n is determined by the following equation.

[0022]

[Equation 7] In general, calculation of the inverse matrix is time-consuming, so use Cramer's formula and calculate M

[0023]

[Equation 8] Then, α ₁ , α ₂ , α ₃ , ..., α _n are calculated as follows.

[0024]

[Equation 9] As described above, the present invention calculates the concentration of each component gas using the detection values from all the detectors.

[0025]

【Example】

(Example 1) First, an example in which the present invention is applied to detection of leaked gas will be described. FIG. 1 is a block diagram showing a leakage gas monitoring device according to an embodiment of the present invention. The leakage gas monitoring device 1 is provided in a working space 2 in which gases X ₁ , X ₂ , X ₃ , ..., X _n are used. detector a ₁ provided, a _2, a _3, ..., and a _n, these detectors a _1, a _2, a _3, ..., the signal from a _n (voltage signals, current signals, etc.), respectively Converter C for converting into a predetermined electric signal
₁ , C ₂ , C ₃ , ..., C _n and their converters C ₁ , C ₂ , C
_3, ..., a multiplexer 3 for sequentially one by one output to accept collectively the electrical signals from C _n, the multiplexer 3
AD converter 4 for converting the signal from the AD converter into a predetermined digital signal, and M receiving the digital signal from the AD converter 4.
From a PU (microprocessor unit) 5, memories 6 and 7 electrically connected to the MPU 5, and a monitor 8 that displays predetermined information such as the position, concentration, and alarm of the leaked gas based on a signal from the MPU 5. Composed.

[0026] With the above configuration, the detector via the AD converter 4 in _{MPU5 A 1, A 2, A} 3, ..., the signal from A _n (detection _{value) y 1, y 2, y} 3, ..., y _n is input. In this case, if the detected values y ₁ , y ₂ , y ₃ , ..., Y _n are not proportional to the concentration of the gas X _j , the linearization device (in the converter C _{i after} the detector A _i ( A linearizer) is provided and finally adjusted so that the detection value of the detector A _i is proportional to the concentration of the gas X _j . In the linearization process, the linearization data for each detector A _i may be stored in a separate memory and linearized by the MPU 5.

Next, the coefficient m _ij is stored in the memory 6 (coefficient storage means) in the form of a table as shown in the equation (6).

The coefficient m _ij is intended to advance measured by experiment or the like, for example, detector A ₁ in the _{container, A 2, A 3, ...} , A n
The previously installed, the detector introduces any amount first gas X ₁ into the container _{A 1, A 2, A 3} , ..., the coefficient of _{A n m 11, m 21,} m
_31, ..., m _n1 look, then Similarly coefficient m ₁₂ to introduce any amount of gas X ₂ after completely eliminating gas X _1, m _22,
m ₃₂ , ..., _{M n2} are obtained, and then the gases X ₃ , X ₄ , ... Are sequentially introduced, and finally the gas X _n is used to obtain the coefficients m _1n , m _2n ,
_Find m _3n , ..., _{M nn} .

FIG. 2 shows the detection characteristics of the detector A _i when the gas X _j is independently introduced into the container. As shown in the figure, the coefficient m _ij is the detector A per unit concentration of the gas X _{j. It} indicates the detected value of _i , that is, the slope. If the coefficient m _{jj is set} to 1 when i = j, the subsequent calculation will be easy and convenient.

Next, in the memory 7 (solution storage means), the operation data indicating the solution of the equation shown in the above equation 7, that is, the equation 8 and the equation 9, are stored. Therefore, MPU 5, the detector _{A 1, A 2, A 3} , ..., the detection value of _{A n y 1, y 2,} y 3,
..., the number with y _n 8, calculate each component gas X ₁ performs number 9, X _2, X _3, ..., the concentration of _{X n α 1, α 2,} α 3, ..., α n
Is calculated and the result is supplied to the monitor.

In this way, when an arbitrary component gas leaks into the working space, the concentration of the leaked gas can be calculated based on the data from all the detectors. When the concentration is not a particular problem, the type of leaked gas can be detected by determining the presence or absence of leaked gas.

(Example 2) Next, an example in which the present invention is applied to composition analysis of a mixed gas will be shown. For example, in a gas manufacturing factory, a mixed gas in which a plurality of component gases are contained in a base gas such as nitrogen or helium for calibration of an analyzer is manufactured. In this case, each component gas is precisely filled by the volume method of measuring the volume of the gas to be filled and filling, the gravimetric method of measuring the weight of the gas to be filled, and the like. There is a need to.

In this case, when the kinds of component gases increase,
The analyzer was sensitive to multiple component gases at the same time, making accurate measurement difficult. Although gas chromatography can be used for the analysis of many kinds of component gases, the measurement time becomes long and the productivity decreases.

FIG. 3 shows a gas analyzer according to the method of the present invention capable of eliminating the above-mentioned inconvenience, in which an analyzer is used instead of the detector in FIG. 1 and is connected to a container valve 11 of a mixed gas filling container 10. The analyzer B ₁ connected to the
B ₂ , B ₃ , ..., B _n and their analyzers B ₁ , B ₂ , B ₃ ,
, _Bn, and a processing device 15 for processing the signal output from B _n . The configuration of the processing device 15 conforms to the case of FIG. According to the above configuration, the detector operates the concentration of the component gas in the mixed gas based on the data from all the used analyzers, and the concentration of the leak gas can be calculated.

In the above embodiment, the composition analysis of the mixed gas produced in the gas production factory was carried out, but it can also be used in the gas analysis in the semiconductor factory.

[0036]

As described above, conventionally, the detectors are provided so as to correspond one-to-one to the component gas to be detected, and the component gases are individually detected. This is due to poor selectivity of the detector. Although various inconveniences have occurred, in the present invention, since the concentration of each component gas is detected comprehensively by using the detection values of all the detectors used for the detection, the concentration of each of the plurality of component gases can be changed. Can be measured accurately. Further, since the individual detection was conventionally performed, the sensitivity of the detector corresponding to the component gas to be detected had to be made higher than the other component gases, but in the present invention, the correspondence between the component gas and the detector can be arbitrarily set. Since it can be determined and measured, and there is no limit to the use of the detector, the device configuration becomes simpler than before.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a leaked gas monitoring device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a detection characteristic of a detector A _i when a gas X _j is independently introduced into a container.

FIG. 3 is a block diagram showing a configuration of a gas analyzer according to a second embodiment of the present invention.

[Explanation of symbols]

A ₁ , A ₂ , A ₃ , ..., _An detector 5 MPU (microprocessor unit) 5 6 memory (coefficient storage means) 7 memory (solution storage means) 15 processing device (coefficient storage means; solution storage means)

Claims (2)

[Claims] 1. A method for measuring the concentration of each component gas using the same number of detectors as the number of component gases in the mixed gas, wherein the component gas (X _j ) (where j is 1 to n, and so on). Detectors (A _i ) having detection characteristics independent of each other
(However, i is 1 to n, the same applies hereinafter), and the detector (A _i ) when each of the component gases (X _j ) is present alone
Obtains a detection value m _ij per unit concentration in advance, the detection during the mixed gas measuring device _{A 1, A 2, A 3} , ..., the detection value of A _n y
_{1, y 2, y 3,} ..., y n each component from the equation shown below using the gas _{X 1, X 2, X 3} , ..., the concentration of _{X n α 1, α 2,} α 3,
…, A gas concentration measuring method characterized by obtaining α _n . [Equation 1] 2. A detector (A _i ) having the same number as the number of component gases in the mixed gas and having independent detection characteristics for each component gas (where i is 1 to n, and so on). Coefficient storage means for storing a detection value m _ij per unit concentration of the detector (A _i ) when each of the component gases (X _j ) (where j is 1 to n, the same applies hereinafter) is present alone; detector a _1, a _2, a ₃ when the mixed gas measured, ..., detected value y ₁ of a _{n,
y 2, y 3, ...,} y n each component from the equation shown below using the gas _{X 1, X 2, X 3} , ..., the concentration of _{X n α 1, α 2,} α 3, ...,
A gas concentration measuring device comprising a solution storing means for obtaining α _n . [Equation 2]