Gas detection method based on incoherent light source

Abstract

This invention provides a gas detection method based on an incoherent light source, comprising the steps of: (A1) introducing helium gas into a gas cell, the gas cell having reflectors at both ends; measurement light emitted from the incoherent light source entering and exiting the gas cell, and a light receiving unit outputting a helium gas spectrum I. He (A2) Air carrying the sample gas enters the gas cell; the measuring light enters the gas cell and exits, and the light receiving unit outputs the sample gas spectrum I corresponding to the first band. λ And the air spectrum I corresponding to the second band Air The first and second bands do not overlap; (A3) Analysis of the sample gas spectrum using absorption spectroscopy technique I λ The content of the analyte in the sample gas was obtained; based on the helium spectrum I... He and air spectrum I Air Obtain the reflectivity R of the mirror corresponding to the second band; d is the length of the optical cavity inside the gas cell, α He It is the Rayleigh scattering coefficient of helium, α Air It is the Rayleigh scattering coefficient of air; repeat steps (A2)-(A3) to obtain the content of the analyte in the sample gas and the reflectance. This invention has the advantages of high sensitivity.

Description

Technical Field

[0001] This invention relates to gas detection, and more particularly to a gas detection method based on an incoherent light source. Background Technology

[0002] In incoherent light source systems, the reflectivity of the high-reflectivity mirror in the optical cavity has a critical impact on the system's measurement accuracy. Higher reflectivity generally leads to higher gas measurement accuracy, typically requiring a reflectivity of 99.99% or higher. Furthermore, the concentration calculation of the sample gas also requires reflectivity as a parameter. Therefore, reflectivity is particularly important for measurements in incoherent light source systems. However, during the measurement process, the high-reflectivity mirror is highly susceptible to contamination from particulate matter in the ambient gas, leading to measurement errors and poor accuracy.

[0003] Currently, there are two methods for calibrating the reflectivity of incoherent light source systems:

[0004] 1. Introduce O4 of known concentration into the platform and calibrate the reflectivity of the cavity mirror based on the light absorption intensity of O4;

[0005] 2. High-purity nitrogen and helium gas are passed through the optical cavity, and the reflectivity is calibrated by utilizing the difference in Rayleigh scattering extinction of different gas molecules.

[0006] Both of the above methods require a reflectance calibration before the sample gas measurement begins. After calibration, reflectance detection cannot be performed during the sample gas measurement process until the measurement is completed. This introduces some drawbacks, such as:

[0007] 1. During the measurement process, if impurities in the sample gas are not thoroughly cleaned, the high-reflectivity mirror in the optical cavity will become contaminated, affecting the reflectivity and further impacting the measurement accuracy. Since reflectivity cannot be measured in real time, any impact on reflectivity will not be reflected in real time, rendering experimental data under contaminated conditions unusable and wasting experimental time.

[0008] 2. During the measurement of the sample gas, the reflectivity of the reflector drifts due to long-term environmental influences. Traditional measurement methods require the reflectivity to be detected only after the sample gas concentration measurement is complete. Therefore, the change in reflectivity cannot be matched with the real-time calculation of the sample gas concentration, leading to concentration calculation errors. To obtain timely information on reflectivity changes, it is necessary to constantly switch between the sample gas measurement and reflectivity measurement devices. This increases the complexity of the operation, the amount of manpower required, and extends the testing cycle. Summary of the Invention

[0009] To address the shortcomings of the existing technical solutions, this invention provides a gas detection method based on an incoherent light source.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A gas detection method based on an incoherent light source, comprising the following steps:

[0012] (A1) Helium gas is introduced into a gas pool, the gas pool having reflectors at both ends;

[0013] Measurement light emitted from an incoherent light source enters the gas cell, reflects back and forth between two mirrors, passes through the helium gas multiple times, and then exits the gas cell. The light receiving unit outputs the helium gas spectrum I. He and store;

[0014] (A2) Air is used as a carrier gas to carry the sample gas into the gas pool;

[0015] The measurement light emitted by the incoherent light source enters the gas cell, is reflected back and forth between two mirrors, passes through the mixture of air and sample gas multiple times, and then exits from the gas cell. The light receiving unit outputs the sample gas spectrum I corresponding to the first wavelength band. λ And the air spectrum I corresponding to the second band Air The first and second wavebands do not overlap; in the first waveband, air does not absorb, and in the second waveband, the sample gas does not absorb.

[0016] (A3) Based on the helium spectrum I He and air spectrum I Air Obtain the reflectivity R of the mirror corresponding to the second band;

[0017] d is the length of the optical cavity within the gas cell, α He It is the Rayleigh scattering coefficient of helium, α Air It is the Rayleigh scattering coefficient of air;

[0018] Analysis of sample gas spectrum using absorption spectroscopy technique I λ And the reflectance R, to obtain the content of the component to be measured in the sample gas.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. Real-time reflectivity detection;

[0021] Based on the working wavelength of the light source, the first wavelength band for sample gas absorption (air has no absorption) and the second wavelength band for reflectance measurement are selected, so that the reflectance and sample gas are detected simultaneously during the detection process based on the storage of the helium spectrum before detection, thus realizing real-time detection.

[0022] 2. High accuracy in sample gas and reflectivity detection;

[0023] Since the concentration calculation of the sample gas requires reflectance, the real-time measurement of reflectance can correspond to the real-time calculation of the sample gas concentration, thereby improving the accuracy of the sample gas concentration calculation.

[0024] Real-time reflectivity monitoring helps to detect anomalies in the mirrors in the optical cavity in a timely manner, reduces the collection of problematic data under abnormal conditions, and improves the accuracy of sample gas detection.

[0025] Helium is periodically introduced into the gas cell to update the helium spectrum in the reflectance calculation, eliminating the influence of environmental changes on the system reflectance and improving the accuracy of reflectance detection.

[0026] 3. High detection efficiency;

[0027] Air is used as the carrier gas during sample collection. Therefore, calculating reflectance using the difference in scattering coefficients between air and helium helps to use the same gas path when measuring reflectance and sample gas concentration, avoiding gas path switching. At the same time, there are few control components, making operation simple and improving measurement efficiency. Attached Figure Description

[0028] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this invention and are not intended to limit the scope of protection of this invention. In the drawings:

[0029] Figure 1 This is a schematic flowchart of a gas detection method based on an incoherent light source according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram illustrating the measurement of the light output wavelength range according to an embodiment of the present invention. Detailed Implementation

[0031] Figure 1-2 The following description illustrates optional embodiments of the invention to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to explain the technical solutions of the invention. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the following optional embodiments, but is defined only by the claims and their equivalents.

[0032] Example 1:

[0033] Figure 1 A flowchart illustrating a gas detection method based on an incoherent light source according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, the gas detection method based on an incoherent light source includes the following steps:

[0034] (A1) Helium gas is introduced into a gas pool, the two ends of which have high reflectivity mirrors with a reflectivity exceeding 99.9%;

[0035] Measurement light emitted from an incoherent light source enters the gas cell, reflects back and forth between two mirrors, passes through the helium gas multiple times, and then exits the gas cell. The light receiving unit outputs the helium gas spectrum I. He and store;

[0036] (A2) Air is used as a carrier gas to carry the sample gas into the gas pool;

[0037] The measurement light emitted by the incoherent light source enters the gas cell, is reflected back and forth between two mirrors, passes through the mixture of air and sample gas multiple times, and then exits from the gas cell. The light receiving unit outputs the sample gas spectrum I corresponding to the first wavelength band. λ And the air spectrum I corresponding to the second band Air The first and second wavebands do not overlap; in the first waveband, air does not absorb, and in the second waveband, the sample gas does not absorb.

[0038] (A3) Based on the helium spectrum I He and air spectrum I Air Obtain the reflectivity R of the mirror corresponding to the second band;

[0039] d is the length of the optical cavity within the gas cell, α He It is the Rayleigh scattering coefficient of helium, α Air It is the Rayleigh scattering coefficient of air;

[0040] Analysis of sample gas spectrum using absorption spectroscopy technique I λ And reflectance R, to obtain the content of the component to be measured in the sample gas, specifically using Beer-Lambert calculation. The optical path is related to reflectance; the higher the reflectance, the longer the optical path and the higher the detection accuracy.

[0041] Repeat steps (A2)-(A3) to obtain the content of the analyte and the reflectance in the sample gas.

[0042] In order to obtain the light intensity value corresponding to each wavelength, the absorbed measurement light passing through the measurement cell enters the light receiving unit, and after being split, outputs light signals at different wavelengths.

[0043] To further improve detection efficiency, a switching module is used to allow helium and sample gas to selectively enter the gas pool.

[0044] To ensure the accuracy of sample gas detection, the gas detection method based on incoherent light source further includes:

[0045] Determine whether the obtained reflectance R is lower than the threshold;

[0046] If the determination result is yes, stop the detection and maintain the reflector;

[0047] If the result is negative, continue testing.

[0048] To improve the accuracy of reflectance detection, further, in step (A1), multiple helium gas spectra I are obtained. He After averaging, store.

[0049] Example 2:

[0050] An application example of the gas detection method based on an incoherent light source according to Embodiment 1 of the present invention.

[0051] In this application example, such as Figure 1 As shown, the gas detection method based on an incoherent light source includes the following steps:

[0052] (A1) Switching module switching, the inlet of the gas pool is selected as the helium gas path, and helium is introduced into the gas pool. The two ends of the gas pool have high reflectivity mirrors with a reflectivity of more than 99.9%.

[0053] Measurement light emitted from an incoherent light source enters the gas cell, reflects back and forth between two mirrors, passes through the helium gas multiple times, and then exits the gas cell into the spectrometer. After spectral dispersion, it outputs light signals at different wavelengths, thus obtaining the helium gas spectrum I. He For the helium spectrum obtained multiple times I He Calculate the average and store it;

[0054] like Figure 2 As shown, the wavelength range of the measured light is 340-398nm, including the first band 360-380nm and the second band 345-359nm;

[0055] (A2) Switching module switching, the gas pool inlet selects the sample gas path, and air is used as the carrier gas to carry the sample gas into the gas pool;

[0056] The measuring light enters the gas cell, reflects back and forth between two mirrors, passes through the air-sample gas mixture multiple times, and then exits the gas cell. The spectrometer outputs the sample gas spectrum I corresponding to the first wavelength band. λ And the air spectrum I corresponding to the second band Air The first and second wavebands do not overlap; in the first waveband, air does not absorb, and in the second waveband, the sample gas does not absorb.

[0057] (A3) Based on the helium spectrum I He and air spectrum IAir Obtain the reflectivity R of the mirror corresponding to the second band;

[0058] d is the length of the optical cavity within the gas cell, α He It is the Rayleigh scattering coefficient of helium, α Air It is the Rayleigh scattering coefficient of air;

[0059] Analysis of sample gas spectrum using absorption spectroscopy technique I λ And reflectance R, to obtain the content of the component to be measured in the sample gas, specifically using Beer-Lambert calculation. The optical path is related to reflectance; the higher the reflectance, the longer the optical path and the higher the detection accuracy.

[0060] Determine whether the obtained reflectance R is lower than the threshold;

[0061] If the determination result is yes, stop the detection and maintain the reflector;

[0062] If the result is negative, continue testing;

[0063] Repeat steps (A2)-(A3) to obtain the content of the analyte and the reflectance in the sample gas, and periodically proceed to step (A1);

[0064] In this embodiment, the method of obtaining the spectrum is a prior art technique, such as using DOAS technology.

[0065] As can be seen from the above, the detection method of the present invention realizes the simultaneous detection of reflectance and sample gas concentration, and performs real-time sample gas detection along with the detection of reflectance, and takes action on the obtained reflectance, whether to maintain or continue detection, thus ensuring the accuracy of sample gas detection.

Claims

1. A gas detection method based on an incoherent light source, the gas detection method based on an incoherent light source comprising the following steps: (A1) Helium gas is introduced into a gas pool, the gas pool having reflectors at both ends; Measurement light emitted from an incoherent light source enters the gas cell, reflects back and forth between two mirrors, passes through the helium gas multiple times, and then exits the gas cell. The light receiving unit outputs the helium gas spectrum I. He and store; (A2) Air is used as a carrier gas to carry the sample gas into the gas cell; The measurement light emitted by the incoherent light source enters the gas cell, is reflected back and forth between two mirrors, passes through the mixture of air and sample gas multiple times, and then exits from the gas cell. The light receiving unit outputs the sample gas spectrum I corresponding to the first wavelength band. λ And the air spectrum I corresponding to the second band Air The first and second wavebands do not overlap; in the first waveband, air does not absorb, and in the second waveband, the sample gas does not absorb. (A3) Based on the helium spectrum I He and air spectrum I Air Obtain the reflectivity R of the mirror corresponding to the second band; d is the length of the optical cavity within the gas cell, α He It is the Rayleigh scattering coefficient of helium, α Air It is the Rayleigh scattering coefficient of air; Analysis of sample gas spectrum using absorption spectroscopy technique I λ And the reflectance R, to obtain the content of the component to be measured in the sample gas; Repeat steps (A2)-(A3) to obtain the content of the analyte and the reflectance in the sample gas.

2. The gas detection method based on an incoherent light source according to claim 1, characterized in that, The wavelength range of the measurement light is 340-398nm, with the first band being 360-380nm and the second band being 345-359nm.

3. The gas detection method based on an incoherent light source according to claim 2, characterized in that, The absorbed measurement light passes through the gas cell and enters the light receiving unit, where it is split and output as light signals at different wavelengths.

4. The gas detection method based on an incoherent light source according to claim 1, characterized in that, The switching module allows helium and sample gas to selectively enter the gas pool.

5. The gas detection method based on an incoherent light source according to claim 1, characterized in that, The gas detection method based on incoherent light sources also includes: Determine whether the obtained reflectance R is lower than the threshold; If the determination result is yes, stop the detection and maintain the reflector; If the result is negative, continue testing.

6. The gas detection method based on an incoherent light source according to claim 1, characterized in that, In step (A1), multiple helium spectra I are obtained. He After averaging, store.

7. The gas detection method based on an incoherent light source according to claim 1, characterized in that, The light receiving unit is a spectrometer.

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