Gas detection method and system based on multi-channel integrating sphere optical gas chamber

Abstract

The gas detection method and system based on the multi-channel integrating sphere optical gas chamber of the present invention uses a multi-channel integrating sphere optical gas chamber, wherein the integrating sphere is provided with 5 through holes along the equatorial axis direction, each through hole is equipped with a filter, through holes are respectively provided on both sides of the horizontal axis of the integrating sphere, one through hole is used as a light inlet, the opening direction of the light inlet is perpendicular to the opening direction of the through hole for installing the filter, and the other through hole is provided with a connector, the connector is driven to rotate the integrating sphere, and an air inlet and an air outlet are also provided on the integrating sphere; infrared light enters the optical gas chamber through the light inlet, and the mixed gas to be measured enters the optical gas chamber through the air inlet, the connector is driven to rotate the integrating sphere, and the light passes through different filters, and the optical signal of each channel is converted into an electrical signal through a photoelectric detector to obtain the electrical signal value of each gas. The present invention utilizes the rotation characteristics of the sphere of the integrating sphere and the setting of multiple filters to efficiently and accurately detect multiple gases synchronously.

Description

Technical Field

[0001] The invention belongs to the field of optical gas detection, and in particular relates to a gas detection method and system based on a multi-channel integrating sphere optical gas chamber. Background Art

[0002] With the acceleration of industrialization and the continuous advancement of urbanization, gas pollution is becoming increasingly serious, posing a great threat to the environment and human health. Non-dispersive infrared gas detection NDIR technology has become a key means in environmental monitoring and industrial process control due to its high sensitivity, high selectivity and stability.

[0003] Miniaturized NDIR gas detectors not only have the advantages of traditional NDIR technology, but also have the characteristics of small size, light weight, and low power consumption, which enable them to be widely used in portable devices and wearable devices. In environmental monitoring, miniaturized NDIR gas detectors can be easily deployed on drones or mobile monitoring stations for large-scale, real-time air quality monitoring; in industrial processes, they can be installed in small spaces for accurate gas leak detection. In addition, the application of multi-gas detection capabilities in complex environments is particularly important. In industrial production processes, multiple harmful gases can be monitored simultaneously to provide comprehensive safety protection; in environmental monitoring, the concentration distribution of multiple pollutants can be understood in real time to help formulate more effective pollution prevention and control measures.

[0004] The existing solution to multi-gas detection is to replace the light source and detector to achieve multi-channel, each detector corresponds to a gas, or replace a filter and a light source of the corresponding wavelength for each gas to detect multiple gases. However, it cannot test multiple gases at the same time, and the filter and the light source of the corresponding wavelength need to be replaced to measure different gases, which increases the cost. This also makes the structure more complicated, usually large in size and poor in flexibility, and it is difficult to meet the needs of modern applications for convenience and versatility. If the gas chamber is made very small, the optical path will be greatly reduced, reducing the sensitivity.

[0005] In the prior art, Chinese invention patent CN114279563A discloses a portable radiation standard source and a radiation calibration method for an imaging spectrometer. The standard source includes an integrating sphere, a laser diode, a polychromatic light source, an electric substitution absolute radiometer assembly, a photodetector assembly and a filter wheel assembly, all of which are installed on the integrating sphere; the laser diode is a multi-channel structure; the polychromatic light source adjusts the incident radiation flux through an adjustable aperture; the integrating sphere forms a surface light source with uniform radiance, and the integrating sphere has an absolute observation port, a secondary observation port and an exit light port; the electric substitution absolute radiometer assembly installed at the absolute observation port includes an electric substitution absolute radiometer; the photodetector assembly is installed at the secondary observation port; the filter wheel assembly has filters with the same number of channels, so that light with the same wavelength as the channel in the integrating sphere enters the photodetector assembly; the electric substitution absolute radiometer assembly and the photodetector assembly respectively detect the radiance of the integrating sphere. It integrates all components with the main body of the integrating sphere structure, and realizes the high simplification and miniaturization of the calibration radiation standard source under the premise of ensuring the high precision and traceability of the radiation calibration, so that it can realize the high-precision, high-frequency, and portable radiation calibration of the imaging spectrometer at different radiation levels in the visible and near-infrared bands in different scenes and environments. However, it can only detect one gas by rotating the turntable of the filter wheel set, one filter at a time, and cannot detect multiple gases at the same time. Secondly, the motor device generates vibration and noise when working. These factors will affect the stability of the experiment. In high-precision measurements, vibration may introduce additional errors. For gases with spectral line cross-interference, different data points cannot be obtained at the same time, which will cause errors when performing concentration inversion. Summary of the invention

[0006] The first object of the present invention is to provide a gas detection method based on a multi-channel integrating sphere optical gas cell in order to solve the problems in the prior art.

[0007] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] The non-dispersive infrared gas detection method based on a multi-channel integrating sphere optical gas chamber is characterized by:

[0009] A multi-channel integrating sphere optical chamber is used, and the integrating sphere is provided with 5 through holes along the equatorial axis, and each through hole is equipped with a filter.

[0010] Through holes are respectively arranged on both sides of the horizontal axis of the integrating sphere, one through hole is used as a light inlet, the opening direction of the light inlet is perpendicular to the opening direction of the through hole for installing the filter, and a connecting piece is installed in the through hole on the other side, and the connecting piece is driven to rotate the integrating sphere, and an air inlet and an air outlet are also arranged on the integrating sphere;

[0011] Infrared light enters the optical chamber through the light inlet, and the mixed gas to be measured enters the optical chamber through the air inlet. The connecting part is driven to rotate the integrating sphere, and the light passes through different filters. The optical signal of each channel is converted into an electrical signal through the photoelectric detector to obtain the electrical signal value of each gas.

[0012] For gases with similar spectral characteristics, nonlinear surface fitting is performed using MATLAB software through the collected electrical signal values ​​and the corresponding gas concentration data. The surface equation is obtained through fitting, and the differences between the theoretical electrical signal values ​​z1 and z2 of gases with similar spectral characteristics and the actual electrical signals are calculated, Δz1 = |z1 – z1-actual value| and Δz2 = |z2– z2-actual value|, where z1-actual value and z2-actual value are the actual electrical signal values ​​of gases with similar spectral characteristics, respectively. The accuracy of concentration reconstruction is judged by the standard deviation Δz of Δz1 and Δz2. If Δz approaches zero, it means that the reconstructed concentration is consistent with the actual concentration. According to the minimum error principle, the gas concentration with similar spectral characteristics when Δz approaches zero is selected to determine the concentration of gases with similar spectral characteristics in the gas to be measured.

[0013] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0014] As a preferred technical solution of the present invention: the connecting piece is a bearing and a bearing handle fixed on the integrating sphere, and the bearing handle is driven to rotate the integrating sphere.

[0015] As a preferred technical solution of the present invention: the diameter of the air chamber in the integrating sphere is 10 cm, the diameter of the light inlet is 8 mm, and the light inlet is equipped with a sapphire window to seal the air.

[0016] As a preferred technical solution of the present invention: a black body light source with a spectral wavelength in the range of 450nm-5500nm is used, and a gas with a central wavelength of the corresponding absorption spectrum in the mid-infrared band enters the integrating sphere optical gas chamber through the air inlet.

[0017] As a preferred technical solution of the present invention: gases whose central wavelength of absorption spectrum is in the mid-infrared band include C2H2, CH4, CO2, N2O and CO.

[0018] As a preferred technical solution of the present invention: the filter has a diameter of 13 mm and a thickness of 0.6 mm, and each filter is detachably sealed and connected to the sphere of the integrating sphere via a sealing ring.

[0019] As a preferred technical solution of the present invention: the gases with similar spectral characteristics are CO and N2O. The surface equation obtained by fitting is used to calculate the difference between the theoretical electrical signal values ​​z1 and z2 and the actual electrical signal of the test point in the CO channel and the N2O channel, respectively. Δz1 = |z1 – z1-actual value| and Δz2 = |z2 – z2-actual value|, where z1-actual value and z2-actual value are the actual electrical signal values ​​of the test sample in the CO channel and the N2O channel, respectively. The accuracy of the concentration reconstruction is determined by the standard deviation Δz of Δz1 and Δz2. If Δz approaches zero, it means that the reconstructed concentration is consistent with the actual concentration. According to the minimum error principle, the concentrations of CO and N2O are selected when Δz approaches zero to determine the concentrations of CO and N2O in the test sample.

[0020] The second object of the present invention is to provide a gas detection system based on a multi-channel integrating sphere optical gas chamber in response to the problems in the prior art.

[0021] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0022] A non-dispersive infrared gas detection system based on a multi-channel integrating sphere optical gas chamber is characterized by including

[0023] An infrared light source disposed outside the light inlet;

[0024] Multi-channel integrating sphere optical gas chamber detects different gas detection channels. The infrared light interacts with the target gas in the integrating sphere gas chamber, and the light comes out from the light outlet of the filter.

[0025] Each photodetector set at the light outlet of each filter focuses the light transmitted from the light outlet of the filter through a lens and detects it for the InAsSb photodetector, converting the optical signal into an electrical signal, and then synchronously extracting the electrical signal of each channel through a preamplifier and a phase-locked amplifier, and transmitting the final electrical signal to a computer to invert the concentration of the corresponding gas.

[0026] Compared with the prior art, the gas detection method and system based on the multi-channel integrating sphere optical gas chamber of the present invention have the following beneficial effects: utilizing the rotation characteristics of the integrating sphere and the setting of multiple filters, when the light source light enters the integrating sphere and undergoes multiple reflections, the detectors behind each filter will synchronously collect the spectral information of the corresponding band, and can efficiently and accurately synchronously detect multiple gases, greatly improving the detection efficiency, expanding the application scenarios, and realizing real-time monitoring of more trace gases in multiple environments; when a single detector is required to test a mixed gas, a plurality of different gases can be detected in sequence by rotating the handle; and when synchronous testing is required, multiple detectors can be used to realize simultaneous, synchronous and effective gas detection to ensure that the concentrations of all gases can be monitored in real time and accurately, improving the response speed and reliability of the system, realizing single-detector multi-gas detection and multi-detector multi-gas synchronous detection on the same device, and is suitable for scenarios that do not require completely synchronous detection, and can also be used in situations where synchronous detection of multiple gases is required, and can be flexibly used in a variety of environments with great application prospects.

[0027] In the present invention, when detecting mixed gases, there is no need to change filters, and the mixed gases are introduced synchronously. While ensuring that the variables remain unchanged, all conditions are consistent, and the measured gas concentration is more accurate. At the same time, through gas concentration reconstruction, for gases with overlapping absorption spectra, data collection is performed simultaneously by selecting different channels without changing filters, ensuring that all collection conditions remain unchanged, and then performing concentration reconstruction. In this way, the errors introduced by cross-interference can be effectively eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of a multi-channel integrating sphere optical gas cell;

[0029] Figure 2 The fitting curve for CO2 follows Beer-Lambert law;

[0030] Figure 3 This is the relationship between the detection limit of CO2 and the integration time;

[0031] Figure 4 Absorption spectra of five gases;

[0032] Figure 5 Reconstruct the fitted surface of the CO channel for concentration;

[0033] Figure 6 Reconstruct the fitted surface of the N2O channel for concentration;

[0034] Figure 7 Process diagram reconstructed for concentration;

[0035] Figure 8 The result map reconstructed for concentration;

[0036] In the attached drawing, there are an integrating sphere 1, a light inlet 2, a sapphire window 3, an air inlet 4, a light inlet 5 of a photodetector, a filter 6, a bearing handle 7, and an air outlet 8. DETAILED DESCRIPTION

[0037] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0038] The present invention provides a gas detection method based on a multi-channel integrating sphere optical gas chamber.

[0039] A multi-channel integrating sphere optical air chamber is used, wherein the integrating sphere 1 is provided with 5 through holes along the equatorial axis, and each through hole is equipped with a filter 6.

[0040] Through holes are respectively provided on both sides of the horizontal axis of the integrating sphere, one through hole is used as a light inlet 2, the opening direction of the light inlet 2 is perpendicular to the opening direction of the through hole for installing the filter 6, and a connector is installed in the other through hole to drive the connector to rotate the integrating sphere, and an air inlet 4 and an air outlet 8 are also provided on the integrating sphere;

[0041] Infrared light enters the optical chamber through the light inlet 2, and the mixed gas to be measured enters the optical chamber through the air inlet. The connecting part is driven to rotate the integrating sphere, and the light passes through different filters 6. The optical signal of each channel is converted into an electrical signal through the photoelectric detector to obtain the electrical signal value of each gas.

[0042] For gases with similar spectral characteristics, nonlinear surface fitting is performed using MATLAB software through the collected electrical signal values ​​and the corresponding gas concentration data. The surface equation is obtained through fitting, and the differences between the theoretical electrical signal values ​​z1 and z2 of gases with similar spectral characteristics and the actual electrical signals are calculated, Δz1 = |z1 – z1-actual value| and Δz2 = |z2– z2-actual value|, where z1-actual value and z2-actual value are the actual electrical signal values ​​of gases with similar spectral characteristics, respectively. The accuracy of concentration reconstruction is judged by the standard deviation Δz of Δz1 and Δz2. If Δz approaches zero, it means that the reconstructed concentration is consistent with the actual concentration. According to the minimum error principle, the gas concentration with similar spectral characteristics when Δz approaches zero is selected to determine the concentration of gases with similar spectral characteristics in the gas to be measured.

[0043] The connecting piece is a bearing and a bearing handle 7 fixed on the integrating sphere, and the bearing handle is driven to rotate the integrating sphere.

[0044] The diameter of the air chamber in the integrating sphere is 10 cm, the diameter of the light inlet is 8 mm, and the light inlet is equipped with a sapphire window 3 for air sealing.

[0045] A black body light source with a spectral wavelength in the range of 450nm-5500nm is used, and the gas with a corresponding absorption spectrum having a central wavelength in the mid-infrared band enters the integrating sphere optical gas chamber through the air inlet 4.

[0046] Gases whose absorption spectra have center wavelengths in the mid-infrared band include C2H2, CH4, CO2, N2O and CO.

[0047] The filter has a diameter of 13 mm and a thickness of 0.6 mm. Each filter is detachably sealed and connected to the sphere of the integrating sphere via a sealing ring.

[0048] The gases with similar spectral characteristics are CO and N2O. The surface equation obtained by fitting is used to calculate the difference between the theoretical electrical signal values ​​z1 and z2 and the actual electrical signal of the test point in the CO channel and N2O channel, respectively. Δz1 = |z1 – z1-actual value| and Δz2 = |z2 – z2-actual value|, where z1-actual value and z2-actual value are the actual electrical signal values ​​of the test sample in the CO channel and N2O channel, respectively.

[0049] The accuracy of the concentration reconstruction is determined by the standard deviation Δz of Δz1 and Δz2. If Δz approaches zero, it means that the reconstructed concentration is consistent with the actual concentration. According to the minimum error principle, the concentrations of CO and N2O when Δz approaches zero are selected to determine the concentrations of CO and N2O in the test sample.

[0050] The gas detection system based on the multi-channel integrating sphere optical gas cell includes:

[0051] An infrared light source disposed outside the light inlet;

[0052] Multi-channel integrating sphere optical gas chamber detects different gas detection channels. The infrared light interacts with the target gas in the integrating sphere gas chamber, and the light comes out from the light outlet of the filter.

[0053] Each photodetector is arranged at the light outlet of each filter, and the light outlet of each filter is the light inlet 5 of the photodetector. The light transmitted from the light outlet of the filter is focused by a lens and detected by the InAsSb photodetector, and the optical signal is converted into an electrical signal. The electrical signal of each channel is then synchronously extracted through a preamplifier and a phase-locked amplifier, and the final electrical signal is transmitted to a computer to invert the concentration of the corresponding gas.

[0054] Example 1

[0055] Mixed gas detection usually requires multiple gas channels, and each gas channel requires a corresponding filter to limit the infrared light to the wavelength range where the gas absorption peak is located. The present invention utilizes the characteristics of sphere rotation to integrate the filter on the surface of the integrating sphere. Each rotation corresponds to a filter, that is, a gas channel. When synchronous testing is required, the present invention can use multiple detectors to synchronously test the gas.

[0056] like Figure 1 As shown, the diameter of the integrating sphere air chamber used in the present invention is 10 cm, which can achieve an optical path of 78.07 cm while ensuring miniaturization. Five filter ports are dug on the surface of the integrating sphere 1 along the equatorial axis, with a diameter of 9 mm. The diameter of the filter is 13 mm, which can completely cover the light outlet and also achieve the purpose of sealing the air to prevent gas from entering the air chamber and leaking. Secondly, two holes are dug on both sides of the horizontal axis, one is to add the bearing handle 7 and the bearing to allow the integrating sphere to rotate, and the other hole is the light inlet 2, with a diameter of 8 mm. Then, a sapphire window with a diameter of 13 mm is used to seal the air. The wavelength of light transmitted by sapphire is between 1500 nm and 5500 nm, which just covers the wavelengths corresponding to the absorption spectra of several common gases in the atmosphere; two holes with a diameter of 3 mm are dug on both sides of the light inlet, one is the air inlet and the other is the air outlet.

[0057] With the above-mentioned air chamber structure, the present invention uses a blackbody light source with a spectral wavelength in the range of 450nm-5500nm, which is a wide-spectrum light source that includes wavelengths corresponding to absorption peaks of common gases in the atmosphere. Infrared light enters the air chamber through a chopper, and gas enters the air chamber through an air inlet. A mixed gas can be introduced at one time, and each rotation corresponds to a gas channel. The infrared light interacts with the target gas in the air chamber of the integrating sphere. The light comes out from the filter port, is focused by a lens, and is collected by an InAsSb photodetector, which converts the optical signal into an electrical signal. The final electrical signal is then extracted through a preamplifier and a phase-locked amplifier, and the final electrical signal is transmitted to a computer to invert the concentration of the corresponding gas.

[0058] Bearings are added on both sides of the integrating sphere and bearing handles are added on the outside. Each rotation corresponds to a gas channel. Mixed gas detection was experimented with. Multiple photoelectric detectors can also be set up as needed to simultaneously realize the detection of multiple gases.

[0059] Compared with the traditional solutions, this solution reduces a lot of costs. At the same time, it can utilize the diffuse reflection characteristics of the integrating sphere to greatly increase the optical path. In a small volume, it can realize the simultaneous testing of multiple gases and has the properties of long optical path, high sensitivity, and miniaturization.

[0060] In the present invention, five filters are respectively arranged on the integrating sphere, each filter passes a spectrum of a specific band and cuts off light of other bands, and each filter is respectively equipped with a photodetector, so that the detection of five gases is realized synchronously on the integrating sphere; in the present invention, the diffuse reflection characteristics of the integrating sphere are utilized, and the infrared light enters the gas chamber, and after multiple reflections, the light intensity at each point on the surface of the integrating sphere is evenly distributed, and the multiple reflections effectively increase the optical path, thereby improving the sensitivity. Through this design, the present invention realizes mixed gas detection in a small volume gas chamber by rotating the integrating sphere, and at the same time increases the optical path to further improve the sensitivity.

[0061] (2) Structural effect

[0062] The present invention uses this system to test four gases, CO2, CH4, C2H2, and CO. Four gases are introduced at the same time. For each gas tested, the handle is rotated once to the corresponding filter port. Four detectors can also be used to test the four gases synchronously. Through experimental testing, the present invention can obtain an image of the relationship between concentration and electrical signal, extract each group of points and fit them into a curve that follows Beer-Lambert's law, such as Figure 2 The figure shows the fitting curve for CO2. Then the present invention uses Allan variance to calculate the detection limits of the four gases, as shown in FIG. Figure 3 Shown is the detection limit of CO2, which is 27.3 ppb, and the detection limits of CO, C2H2 and CH4 are 85.96 ppm, 102.19 ppb and 38.76 ppm, respectively.

[0063] like Figure 4As shown, in order to synchronously test the mixed gas, these gases are five common gas components in the atmosphere, and the central wavelength of the corresponding absorption spectrum is in the mid-infrared band, among which C2H2 is 3050nm, CH4 is 3300, CO2 is 4260nm, N2O is 4510nm, and CO is 4600nm. In order to synchronously detect the concentration of these gases, the multi-channel integrating sphere optical air chamber of the present invention has five holes dug in the equatorial direction of the integrating sphere, and each hole is installed with a specific filter. In order to ensure that the gas can be sealed, the size of the filter should be larger than the hole dug in the integrating sphere. The customized filter with a diameter of 13mm and a thickness of 0.6mm here is to reduce the light intensity as little as possible, and this thickness will not be fractured by air pressure under standard atmospheric pressure. At the same time, a sealing ring is added on each filter to prevent air leakage. In order to facilitate integration and miniaturization, the filter is integrated on the sphere by utilizing the characteristics of the rotation of the sphere. The detector can be further integrated on the housing to achieve miniaturization. In order to ensure that the light source port is fixed for each test, so that the light intensity emitted for each test is constant, the light source port is placed on the horizontal axis, and the five filters are on the equatorial axis. Secondly, there are air inlets and air outlets. In order to prevent the tubes from getting tangled when the air inlets and air outlets rotate, the air inlets and air outlets should be set at both ends of the axis. If they are placed opposite to the light source, the light source and the gas will be in direct contact, which will increase the error. Therefore, the present invention places the air inlet and air outlet on both sides of the light source. At the same time as the light source port is introduced, two small holes are dug at both ends of the light source port, one for air inlet and one for air outlet. This can ensure that the tubes are not tangled when rotating.

[0064] The advantage of this design is that when testing mixed gases, there is no need to change the filter. The mixed gases can be introduced synchronously. Under the condition that the variables are kept constant, all conditions are consistent, and the measured gas concentration is more accurate. At the same time, the concentration can be reconstructed. The absorption spectra of the two gases overlap each other. This detection system can introduce the two gases into the gas chamber at the same time, ensuring that all conditions are unchanged, rotating to obtain different channels, testing the corresponding concentration, and then performing concentration inversion.

[0065] from Figure 4It can be seen from the gas absorption spectrum shown that sometimes when measuring mixed gases, the absorption spectra of two or more gases overlap with each other, which leads to obvious cross-interference problems, thereby reducing the measurement accuracy and may even cause misjudgment. For gases with overlapping spectral lines, the traditional method is to minimize the spectral bandwidth of the system and select a narrower bandwidth filter to filter out the overlapping spectral components, thereby overcoming the cross-interference problem. However, this method usually increases the complexity and cost of the process, and for gases with severe spectral overlap, even narrow bandwidth filters cannot completely separate the overlapping parts, resulting in large errors in concentration reconstruction. Here, the gas detection system designed in this article can effectively invert the concentration of the target gas from two gases with overlapping absorption spectral lines. First, the present invention constructs a concentration reconstruction model, such as Figure 5 As shown, the integrating sphere is first rotated to the CO window, and mixed gases of CO and N2O of different concentrations are measured to obtain different electrical signal values, forming the training set data of the CO channel. In the same way, the integrating sphere is rotated to the N2O window, and mixed gases of CO and N2O of different concentrations are measured to obtain the training set data of the N2O channel as shown in FIG. Figure 6 As shown. Then the present invention performs surface fitting according to Beer-Lambert's law, and obtains the fitting formula z=z0+BEXP(-X / CY / D) in the two-dimensional case, where z0 represents the electrical signal value of weak absorption or no absorption under a wide spectrum, and B represents the corresponding optical bandwidth when the absorption coefficient is K. X and y represent the CO concentration and N2O concentration respectively. Figure 7 The figure shows the concentration reconstruction process. The present invention first fits two two-dimensional curves according to the training data sets of the CO channel and the N2O channel respectively. Then, the present invention randomly selects a point as the test point to reconstruct the concentration. The present invention defines Δz1 = |z1 – z1-measured|, Δz2 = |z2 – z2-measured|, where z1-measured represents the electrical signal value corresponding to the test point in the CO channel, and z2-measured represents the electrical signal corresponding to the test point in the N2O channel. Therefore, Δz1 and Δz2 represent the absolute difference between the electrical signal of the calculated value and the actual test value in the two channels respectively. The standard deviation Δz of Δz1 and Δz2 is further defined as the error between the calculated value and the actual value. When the error is zero, the CO and N2O concentrations that are the same as the electrical signal of the test point can be calculated. By comparing with the actual value, it can be found that this reconstruction method can effectively realize the reconstruction of the concentrations of two gases containing spectral cross-interference. As shown in FIG. Figure 8 The figure shows the result of reconstruction. It can be seen from the figure that the theoretical calculation value and the experimental detection value are both in the red area, and the two values ​​are close to each other, indicating that the error between the reconstruction result and the experimental value is small, and the concentration reconstruction effect performed by this system and this method is better.

[0066] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A gas detection method based on a multi-channel integrating sphere optical gas chamber, characterized in that: A multi-channel integrating sphere optical chamber is used, and the integrating sphere is provided with 5 through holes along the equatorial axis, and each through hole is equipped with a filter. Through holes are respectively arranged on both sides of the horizontal axis of the integrating sphere, one through hole is used as a light inlet, the opening direction of the light inlet is perpendicular to the opening direction of the through hole for installing the filter, and a connecting piece is installed in the through hole on the other side, and the connecting piece is driven to rotate the integrating sphere, and an air inlet and an air outlet are also arranged on the integrating sphere; Infrared light enters the optical chamber through the light inlet, and the mixed gas to be tested enters the optical chamber through the air inlet. The connecting piece is driven to rotate the integrating sphere, and the light passes through different filters. Multiple photoelectric detectors are used to synchronously test the gas. The optical signal of each channel is converted into an electrical signal through the photoelectric detector to obtain the electrical signal value of each gas. For gases with similar spectral characteristics, nonlinear surface fitting is performed using MATLAB software through the collected electrical signal values ​​and the corresponding gas concentration data. The surface equation is obtained through fitting, and the differences between the theoretical electrical signal values ​​z1 and z2 of gases with similar spectral characteristics and the actual electrical signals are calculated, Δz1 = |z1 – z1-actual value| and Δz2 = |z2 – z2-actual value|, where z1-actual value and z2-actual value are the actual electrical signal values ​​of gases with similar spectral characteristics, respectively. The accuracy of concentration reconstruction is judged by the standard deviation Δz of Δz1 and Δz2. If Δz approaches zero, it means that the reconstructed concentration is consistent with the actual concentration. According to the minimum error principle, the gas concentration with similar spectral characteristics when Δz approaches zero is selected to determine the concentration of gases with similar spectral characteristics in the gas to be measured.

2. The gas detection method based on a multi-channel integrating sphere optical gas cell according to claim 1 is characterized in that: The connecting piece is a bearing and a bearing handle fixed on the integrating sphere, and the bearing handle is driven to rotate the integrating sphere.

3. The gas detection method based on a multi-channel integrating sphere optical gas cell according to claim 1, characterized in that: The diameter of the air chamber in the integrating sphere is 10 cm, the diameter of the light inlet is 8 mm, and the light inlet is equipped with a sapphire window to seal the air.

4. The gas detection method based on a multi-channel integrating sphere optical gas cell according to claim 1, characterized in that: A black body light source with a spectral wavelength in the range of 450nm-5500nm is used, and a gas with a corresponding absorption spectrum with a central wavelength in the mid-infrared band enters the integrating sphere optical gas chamber through the air inlet.

5. The gas detection method based on a multi-channel integrating sphere optical gas cell according to claim 4, characterized in that: Gases whose absorption spectra have center wavelengths in the mid-infrared band include C2H2, CH4, CO2, N2O and CO.

6. The gas detection method based on a multi-channel integrating sphere optical gas cell according to claim 1, characterized in that: The filter has a diameter of 13 mm and a thickness of 0.6 mm. Each filter is detachably sealed and connected to the sphere of the integrating sphere via a sealing ring.

7. The gas detection method based on a multi-channel integrating sphere optical gas cell according to claim 1, characterized in that: The gases with similar spectral characteristics are CO and N2O. The surface equation obtained by fitting is used to calculate the difference between the theoretical electrical signal values ​​z1 and z2 and the actual electrical signal of the test point in the CO channel and N2O channel, respectively. Δz1 = |z1 – z1-actual value| and Δz2 = |z2– z2-actual value|, where z1-actual value and z2-actual value are the actual electrical signal values ​​of the test sample in the CO channel and N2O channel, respectively. The accuracy of concentration reconstruction is judged by the standard deviation Δz of Δz1 and Δz2. If Δz approaches zero, it means that the reconstructed concentration is consistent with the actual concentration. According to the minimum error principle, the concentrations of CO and N2O when Δz approaches zero are selected to determine the concentrations of CO and N2O in the test sample.

8. A gas detection system based on a multi-channel integrating sphere optical gas cell used in any one of the methods of claims 1 to 7, characterized in that: include An infrared light source disposed outside the light inlet; Multi-channel integrating sphere optical gas chamber detects different gas detection channels. The infrared light interacts with the target gas in the integrating sphere gas chamber, and the light comes out from the light outlet of the filter. Each photodetector set at the light outlet of each filter focuses the light transmitted from the light outlet of the filter through a lens and detects it for the InAsSb photodetector, converting the optical signal into an electrical signal, and then synchronously extracting the electrical signal of each channel through a preamplifier and a phase-locked amplifier, and transmitting the final electrical signal to a computer to invert the concentration of the corresponding gas.

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