JP2015232532A - Gas measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas measuring device capable of determining a plurality of kinds of gases and detecting its concentration by the same detector paper.SOLUTION: A gas measuring device comprises: means for detecting the optical concentration by wavelengths of different reaction marks of detector paper carrying silver salt which generates the reaction mark of silver colloid in reaction to at least a plurality of kinds of measured gases; gas determination means for specifying the kind of gases based on a ratio of the optical concentration of respective wavelengths of the same reaction mark; and concentration computing means for calculating the gas concentration based on the chemical concentration.

Description

  The present invention relates to a gas measuring apparatus for performing a color reaction of a plurality of types of gases contained in an atmosphere to determine the type of gas and measure its concentration.

For example, semiconductor manufacturing plants store a plurality of types of hydrogen compound gases, and their concentrations in the environment are monitored.
Although detection paper such as found in Patent Documents 1 and 2 is used for detection of such gas, it is necessary to select the type of detection paper corresponding to the type of gas.

JP2004-163371

JP2008-20285

    The present invention has been made in view of such problems, and an object of the present invention is to provide a gas measuring device capable of detecting a plurality of types of gases and detecting their concentrations using the same detection paper. It is.

  In order to solve such a problem, in the present invention, the optical density due to the different wavelengths of the reaction traces of the detection paper carrying a reagent that generates reaction traces that change the optical density in response to at least a plurality of kinds of gases to be measured. Detecting means, gas type determining means for specifying the type of gas based on the optical density ratio of each wavelength of the same reaction trace, concentration calculating means for calculating the gas concentration based on the optical density, Consists of.

  One type of detection paper can measure the types and concentrations of multiple gases.

It is a block diagram which shows one Example of this invention. It is a diagram which shows the ratio of the optical density in the some wavelength for every kind of gas and density | concentration.

Therefore, details of the present invention will be described below based on the illustrated embodiment.
FIG. 1 shows an embodiment of the present invention, in which a detection paper 2 contained in a cassette 1 or the like reacts with at least one of silver salts such as silver nitrate, silver perchlorate and silver paratoluenesulfonate. As a reagent, a humectant such as glycerin and a buffer drug are supported on a breathable carrier as required. Further, a measurement head 4 and a suction head 5 are arranged in the area of the window 3 so as to sandwich the front and back of the detection paper 2.

  The measuring head 4 is configured as a light-shielding container having a gas inlet 6 for detection gas, and emits light that selectively emits a plurality of emission spectra, for example, a first wavelength of 555 nm and a second wavelength of 475 nm. The means 7, for example, a diode, and the light receiving means 8, for example, a photodiode capable of detecting the plurality of emission spectra, are configured to be accommodated so as to have an incident / reflection relationship through reaction marks formed on the detection paper 2. The inlet 6 is communicated with the environment to be measured by a pipe 9.

  The suction head 5 is provided with an outlet 10 so as to face the inlet 6 and receives a negative pressure of a suction pump (not shown) via a pipe 11.

  Reference numeral 12 in the figure is a signal processing device, which selects one wavelength of the light emitting means 7 or wavelength selecting means 13 for selecting one of the light receiving wavelengths of the light receiving means 8, and indicates the optical density of the reaction mark at each selected wavelength. Optical density detection means 14 to detect, gas type determination means 15 for determining the type of gas by calculating the optical density ratio at each wavelength of the same reaction trace, and the optical density of the reaction trace at any wavelength Concentration calculation means 16 for calculating the concentration of gas based on this is constituted.

  In addition, when the intensity | strength for each wavelength of the light emission means 7 and the sensitivity for each wavelength of a light-receiving means differ for every wavelength, it correct | amends with an appropriate means and normalizes the optical density of the reaction trace in each wavelength. Is possible.

  In this embodiment, when the detection paper 2 in the area exposed from the window 3 of the cassette 1 is sandwiched between the measurement head 4 and the suction head 5 and measurement is started, a suction pump (not shown) is activated.

  The test gas is sucked into the measurement head 4 through the pipe 9 and is made of a silver salt impregnated in the detection paper 2 in the process of passing from the measurement head 4 through the detection paper 2 to the suction head 5. Reaction traces are generated on the surface of the gas with an optical density corresponding to the product of the concentration of the gas to be detected and time.

  This reaction mark is caused by the precipitation of silver colloid due to the reaction between the hydride to be detected and the silver salt. The particle size of the silver colloid depends on the reaction intensity with the gas to be detected. The particle size of the colloid affects the absorbance at each wavelength.

  In this process, the light of the first wavelength emitted from the light emitting means 7 is absorbed and reflected according to the optical density of the reaction mark formed on the surface of the detection paper 2 and is incident on the light receiving means 8. It is converted into an electrical signal. The optical density detector 13 calculates the optical density at the first wavelength based on the signal from the light receiver 8.

Subsequently, light of the second wavelength is emitted from the light emitting means 7 to measure the optical density of the same reaction trace on the detection paper 2.
The gas type determination unit 16 determines the type of gas from the ratio of the optical densities at these two wavelengths, and the gas concentration calculation unit 17 calculates the gas concentration based on the optical density at any wavelength.
When the measurement operation is completed in this way, the detection paper is fed by one frame to prepare for the next measurement.

  That is, using a test gas such as monosilane (SiH4 code (1)), hydrogen selenide (H2Se code (2)), phosphine (PH3 code (3)), arsine (AsH3 code (4)) The exposure time was kept constant, the gas concentration was changed to generate reaction traces, and the reflectance of the green light emitting diode and the blue light emitting diode was plotted as shown in FIG.

  That is, at least for arsine (AsH3), phosphine (PH3), hydrogen selenide (H2Se), and monosilane (SiH4), the reflectance ratio of blue and green light emitting diodes is constant depending on the type of gas regardless of the concentration. And the ratio of reflectivity is different between gases.

  Therefore, the optical density (reflectance) of the same reaction trace is measured by light emitting means having different emission spectra and easily available, for example, green light emitting diode and blue light emitting diode, and the gas type and optical density itself are determined from the ratio. From this, the gas concentration can be calculated.

In the above-described embodiment, the wavelength of light emitted from the light emitting means 7 is switched. However, the light emitting means 7 simultaneously emits light of the first and second wavelengths, and the light receiving means 8 changes the wavelength of the first wavelength. Obviously, the same effect can be obtained even if the light and the light of the second wavelength are selectively received separately.
In the above-described embodiments, the case where a silver salt that reacts with a gas to be measured to produce a reaction trace of silver colloid is used as a reagent has been described. However, it is clear that the same effect is achieved.

2 Detecting paper 4 Measuring head 5 Suction head 7 Light emitting means 8 Light receiving means

Claims (4)

Means for detecting an optical density at a different wavelength of the reaction trace of a detection paper carrying a reagent that generates a reaction trace in which the optical density changes in response to at least a plurality of types of gases to be measured, and each wavelength of the same reaction trace A gas measuring device comprising: a gas type determining unit that specifies a gas type based on an optical density ratio; and a concentration calculating unit that calculates a gas concentration based on the optical density. The gas measuring apparatus according to claim 1, wherein the reagent is a silver salt that reacts with a gas to be measured to generate reaction traces of silver colloid. The gas measuring apparatus according to claim 1, wherein the means for detecting the optical density includes light emitting means for selectively irradiating light having different wavelengths. The gas measuring device according to claim 1, wherein the means for detecting the optical density has a light receiving means for selectively detecting light having different wavelengths.

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