Measuring device with ultra-wide gas detection range and measuring method thereof

Abstract

The application relates to a measuring device with an ultra-wide gas detection range and a measuring method thereof, and the measuring device comprises a laser, an isolator, a light splitting module, an acousto-optic modulator, a double-light-path absorber, a first detector and a second detector; the double-light-path absorber comprises a cylindrical shell, a first reflector and a second reflector; the first reflector and the second reflector are located in the shell and oppositely arranged to form a double-light-path absorption cavity; the double-light-path absorption cavity is formed by a central ring-down cavity and a multiple-reflection pool. By designing the double-light-path absorber, the TDLAS and CRDS two spectral detection technologies can be synchronously and independently operated on the same cavity, the gas ultra-wide range detection of seven orders of magnitude can be realized, and the detection range of the measuring device is expanded; compared with a simple combined scheme in which different spectral detection technologies still independently work, the measuring method of the application has the advantages of lower required gas amount, faster response speed and better synchronism during detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spectral detection technology, and particularly relates to a measuring device with super-wide gas detection range and a measuring method thereof. BACKGROUND

[0002] There are several common spectral detection technologies, each of which has corresponding advantages and disadvantages.

[0003] Tunable diode laser absorption spectroscopy (TDLAS) is a spectral detection technology with high sensitivity, which can realize gas detection with concentration in ppm (10 -6 ) order of magnitude, and its measurement range is generally about 3 orders of magnitude (10 3 ). In order to improve the detection capability of TDLAS, a Herriott multi-pass cell can be combined, and the absorption path thereof can be increased from cm order of magnitude to m order of magnitude, thereby enhancing the detection capability of TDLAS.

[0004] Cavity ring-down spectroscopy (CRDS) is a spectral detection technology with extremely high sensitivity, which can realize ultra-low content gas detection with concentration in ppb (10 -9 ) order of magnitude or even ppt (10 -12 ) order of magnitude, and its measurement range is generally about 4 orders of magnitude (10 4 ).

[0005] It is difficult for a single spectral detection technology to meet the measurement requirements of wide range and high precision. In the prior art, several spectral detection technologies are simply combined to solve this problem. However, in this simple combination scheme, each spectral detection technology still works independently, the required gas content is almost unchanged compared with the case of using multiple independent detection methods, and the response speed is also not significantly improved, and the synchronization is weak.

[0006] Therefore, it is urgent to design a measuring device with super-wide gas detection range and a measuring method thereof to solve the above problems in the prior art. SUMMARY

[0007] Therefore, the present application provides a measuring device with super-wide gas detection range and a measuring method thereof, which aims to make TDLAS and CRDS two spectral detection technologies work synchronously and independently on the same cavity by designing a double-light-path absorber with a specific structure, so as to realize gas detection in a super-wide range.

[0008] To achieve the above purpose, the present application adopts the following technical solutions:

[0009] A kind of measuring device of ultra-wide gas detection range, the measuring device includes laser, isolator, light splitting module, acoustooptic modulator, double optical path absorber, first detector and second detector;

[0010] The laser emits laser;Laser is connected with the input end of isolator;The isolator is used to isolate protection for laser, prevent laser from returning to laser;

[0011] The output end of the isolator is connected with the input end of light splitting module;The light splitting module is used to divide the laser into two lasers, first path laser and second path laser;

[0012] The light path output end of first path laser of light splitting module is first connected with the input end of acoustooptic modulator, and the acoustooptic modulator is used to make first path laser generate frequency offset;The output end of acoustooptic modulator is connected with the first input end of double optical path absorber;The first output end of double optical path absorber is connected with first detector;

[0013] The light path output end of second path laser of light splitting module is connected with the second input end of double optical path absorber;The second output end of double optical path absorber is connected with second detector.

[0014] Further, the double optical path absorber includes cylindrical shell, first mirror and second mirror;First mirror and second mirror are located in the shell, and are oppositely arranged to form double optical path absorption cavity;The double optical path absorption cavity is composed of central decaying cavity and multiple reflection pool.

[0015] Further, the first mirror is circular, and the mirror surface is divided into two regions with different reflectivities, the central circular region has a reflectivity of 99.999%, and the outer circular ring region has a reflectivity of 98%;An optical hole is further arranged in the outer circular ring region, and the optical hole is used for allowing laser of the multiple reflection pool to pass through;The second mirror has the same structure as the first mirror.

[0016] Further, the central decaying cavity is a cylindrical space composed of two central circular regions of the first mirror and the second mirror as end faces;The multiple reflection pool is a hollow cylindrical space composed of two outer circular ring regions of the first mirror and the second mirror as end faces.

[0017] Further, the shell is provided with a circular input end face and a circular output end face at two ends respectively, a first input end is arranged at the center of the circular input end face, a second input end is arranged at the non-center of the circular input end face, the first input end and the second input end are both fiber joints, and a collimator is arranged in the fiber joint;A first output end is arranged at the center of the circular output end face, the first output end is a fiber joint, a second output end is arranged at the non-center of the circular output end face, and the second output end is an electrical signal joint.

[0018] Further, the first laser passes through the first input end into the center ring-down cavity in the double optical path absorber to form a center ring-down cavity optical path; and the second laser passes through the second input end into the multi-reflection cell of the double optical path absorber to form an outer ring multi-reflection optical path.

[0019] Further, the shell is provided with an air inlet and an air outlet for the to-be-measured gas to enter and exit the double optical path absorber.

[0020] The application further provides a measurement method based on the above-mentioned ultra-wide gas detection range measurement device, and the measurement method comprises the following steps:

[0021] S1. The to-be-measured gas enters the double optical path absorber through the air inlet;

[0022] S2. The laser emits laser, which enters the light splitting module after passing through the isolator;

[0023] S3. The light splitting module splits the laser into first laser and second laser with different powers;

[0024] S4. The first laser and the second laser are detected by different detection technologies respectively;

[0025] S4-a. The first laser enters the center ring-down cavity of the double optical path absorber through the first input end after being modulated by the acousto-optic modulator to form a center ring-down cavity optical path; then the first laser enters the first detector through the first output end to realize single-frequency ring-down signal detection; then the frequency of the modulated laser is scanned to scan the complete absorption spectral line profile, and the spectral line is analyzed and processed, so that the measurement of the gas can be realized;

[0026] S4-b. The second laser enters the multi-reflection cell of the double optical path absorber through the second input end to form an outer ring multi-reflection optical path; then the second laser enters the second detector through the second output end to realize single-frequency absorption signal detection; then the frequency of the modulated laser is scanned to scan the complete absorption spectral line profile, and the spectral line is analyzed and processed, so that the measurement of the gas can be realized;

[0027] S5. The two measurement results are compared, the detection technology with a more optimal measurement accuracy range is selected according to the measurement results, the selected detection technology is observed intensively, and the other detection technology is observed weakly or stopped.

[0028] Further, the to-be-measured gas entering the double optical path absorber through the air inlet in the step S1 is specifically divided into two cases:

[0029] S1-a. Static detection: after the to-be-measured gas enters the double optical path absorber through the air inlet, the air inlet and the air outlet are closed;

[0030] S1-b. Dynamic detection: the to-be-detected gas continuously passes through the gas inlet into the double-light-path absorber and flows out through the gas outlet;

[0031] According to the measurement requirements, the static detection or the dynamic detection is reasonably selected.

[0032] Further, when the dynamic detection is selected in step S1, the step S5 further comprises:

[0033] The selected detection technology is subjected to intensive observation, and the other detection technology is subjected to weakened observation; and the measurement results of the two are compared in real time, and when the measurement results change, the objects of the intensive observation and the weakened observation are switched according to the real-time measurement results.

[0034] The application realizes the synchronous independent work of the TDLAS and the CRDS two kinds of spectral detection technologies on the same cavity, can realize the gas ultra-wide range detection of 7 orders of magnitude (10 7 ) and expands the detection range of the measurement device. Compared with the simple combination scheme in which different spectral detection technologies still work independently, the measurement method of the application has lower gas consumption, faster response speed, better synchronization during detection, and the structure design of the double-light-path absorber in the application makes the measurement device miniaturized and improves the integration of the measurement device. The measurement method in the application compares the measurement results of the two in real time, selects the detection technology with a more optimal measurement precision range according to the measurement results, improves the detection efficiency, ensures the high precision of the detection results, and especially in dynamic detection, the measurement method of the application can make dynamic adjustment according to the change of the gas, further improves the measurement accuracy and applicability.

[0035] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the structure indicated in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without any creative labor.

[0037] Figure 1 The structure schematic diagram of the measurement device of the ultra-wide gas detection range of the embodiment of the present application is shown;

[0038] Figure 2The first angle three-dimensional structure schematic diagram of the double light path absorber of the measuring device of the super wide gas detection range of the embodiment of the application is shown.

[0039] Figure 3 The second angle three-dimensional structure schematic diagram of the double light path absorber of the measuring device of the super wide gas detection range of the embodiment of the application is shown.

[0040] Figure 4 The cross-sectional view of the double light path absorber of the measuring device of the super wide gas detection range of the embodiment of the application is shown.

[0041] Figure 5 The center ring multi-reflection light path schematic diagram of the double light path absorber of the measuring device of the super wide gas detection range of the embodiment of the application is shown.

[0042] Figure 6 The outer ring multi-reflection light path schematic diagram of the double light path absorber of the measuring device of the super wide gas detection range of the embodiment of the application is shown.

[0043] Figure 7 The mirror structure schematic diagram of the double light path absorber of the measuring device of the super wide gas detection range of the embodiment of the application is shown.

[0044] In the figure: 1, laser; 2, isolator; 3, light splitting module; 4, acousto-optic modulator; 5, double light path absorber; 6, first detector; 7, second detector;

[0045] 5-1, shell; 5-2, first mirror; 5-3, second mirror; 5-4, air inlet; 5-5, air outlet; 5-6, circular input end face; 5-7, circular output end face; 5-8, first input end; 5-9, second input end; 5-10, first output end; 5-11, second output end;

[0046] 5-2-1, center circle area; 5-2-2, outer circle area; 5-2-3, light transmission hole. DETAILED DESCRIPTION

[0047] To make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are some embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0048] The embodiment of the application proposes a measuring device of a super wide gas detection range, as shown in the accompanying drawings Figures 1-7As shown, the measuring device comprises a laser 1, an isolator 2, a light splitting module 3, an acousto-optic modulator 4, a double optical path absorber 5, a first detector 7 and a second detector 6;

[0049] The laser 1 emits laser light; the laser 1 is connected to the input end of the isolator 2; the isolator 2 is used for isolating and protecting the laser 1 from returning laser light to the laser 1.

[0050] The output end of the isolator 2 is connected to the input end of the light splitting module 3; the light splitting module 3 is used for splitting the laser light into two beams of laser light, i.e. a first path of laser light and a second path of laser light.

[0051] The light path output end of the first path of laser light of the light splitting module 3 is first connected to the input end of the acousto-optic modulator 4, which is used for causing the first path of laser light to produce frequency shift and play a role of turning off the laser light; the output end of the acousto-optic modulator 4 is connected to the first input end of the double optical path absorber 5; the first output end of the double optical path absorber 5 is connected to the first detector 7.

[0052] The light path output end of the second path of laser light of the light splitting module 3 is connected to the second input end of the double optical path absorber 5; the second output end of the double optical path absorber 5 is connected to the second detector 6.

[0053] Preferably, the power ratio of the first path of laser light and the second path of laser light is 9:1.

[0054] The double optical path absorber 5 comprises a cylindrical shell 5-1, a first mirror 5-2 and a second mirror 5-3; the first mirror 5-2 and the second mirror 5-3 are located in the shell and oppositely arranged to form a double optical path absorption cavity; the double optical path absorption cavity is composed of a central decaying cavity and a multiple reflection pool.

[0055] The first mirror 5-2 is circular, and its mirror surface is divided into two regions with different reflectivities, i.e. a central circular region 5-2-1 with a reflectivity of 99.999% and an outer circular ring region 5-2-2 with a reflectivity of 98%; a light transmission hole 5-2-3 is further arranged in the outer circular ring region 5-2-2, which is used for allowing the laser light of the multiple reflection pool to pass through; the second mirror 5-3 has the same structure as the first mirror 5-2.

[0056] The central decaying cavity is a cylindrical space with the two central circular regions of the first mirror 5-2 and the second mirror 5-3 as end faces; the multiple reflection pool is a hollow cylindrical space with the two outer circular ring regions of the first mirror 5-2 and the second mirror 5-3 as end faces.

[0057] The shell 5-1 is provided with a circular input end face 5-6 and a circular output end face 5-7 at two ends, respectively, a first input end 5-8 is arranged at the center of the circular input end face 5-6, a second input end 5-9 is arranged at a non-center position of the circular input end face 5-6, the first input end 5-8 and the second input end 5-9 are both optical fiber joints, and a collimator is arranged in each of the optical fiber joints; a first output end 5-10 is arranged at the center of the circular output end face 5-7, the first output end 5-10 is an optical fiber joint, and a second output end 5-11 is arranged at a non-center position of the circular output end face 5-7, the second output end 5-11 is an electrical signal joint.

[0058] The first laser passes through the first input end 5-8 into the center ring-down cavity of the double optical path absorber 5 to form a center ring-down cavity optical path, and the second laser passes through the second input end 5-9 into the multi-reflection cell of the double optical path absorber 5 to form an outer ring multi-reflection optical path.

[0059] An air inlet 5-4 and an air outlet 5-5 are arranged on the shell for the inflow and outflow of the gas to be measured into and out of the double optical path absorber 5.

[0060] The inner wall of the cavity of the double optical path absorber 5 is coated with a silicon dioxide protective film to reduce the influence of the adsorption and chemical reaction of the gas to be measured.

[0061] The application also provides a measurement method of the measurement device based on the super-wide gas detection range, and the measurement method comprises the following steps:

[0062] S1. The gas to be measured enters the double optical path absorber 5 through the air inlet 5-4.

[0063] S2. The laser 1 emits laser, which enters the light splitting module 3 after passing through the isolator 2.

[0064] S3. The light splitting module 3 splits the laser into first laser and second laser with different powers.

[0065] S4. The first laser and the second laser are detected by different detection technologies, respectively.

[0066] S4-a. The first laser enters the center ring-down cavity of the double optical path absorber 5 through the first input end 5-8 after being modulated by the acousto-optic modulator 4 to form a center ring-down cavity optical path, then enters the first detector 7 through the first output end 5-10 to realize single-frequency ring-down signal detection, then the frequency of the modulation laser is scanned to complete the absorption spectrum line profile, and the spectrum line is analyzed and processed, so that the measurement of the gas can be realized; this step is the CRDS spectrum detection technology.

[0067] S4-b. The second path laser enters the multiple reflection cell of the dual optical path absorber 5 through the second input end 5-9, forming an outer ring multiple reflection optical path; then enters the second detector 6 through the second output end 5-11, realizing single frequency absorption signal detection, then modulating the frequency of the laser, scanning the complete absorption spectrum line profile, analyzing and processing the spectrum line, that is, realizing the measurement of the gas; this step is the TDLAS spectrum detection technology;

[0068] S5. Comparing the two measurement results, selecting the detection technology with better measurement accuracy range according to the measurement results; and strengthening the observation of the selected detection technology, such as through adaptive adjustment of the laser control algorithm, to achieve higher performance indicators; and weakening the observation or stopping the observation of the other detection technology.

[0069] The step S1 is divided into two cases:

[0070] S1-a. Static detection: after the to-be-measured gas enters the dual optical path absorber 5 through the gas inlet 5-4, the gas inlet 5-4 and the gas outlet 5-5 are closed;

[0071] S1-b. Dynamic detection: the to-be-measured gas continuously enters the dual optical path absorber 5 through the gas inlet 5-4 and flows out through the gas outlet 5-5;

[0072] According to the measurement requirements, the static detection or the dynamic detection is reasonably selected.

[0073] When the dynamic detection is selected in the step S1, the step S5 further includes:

[0074] The selected detection technology is strengthened for observation, and the other detection technology is weakened for observation; and the two measurement results are compared in real time, and when the measurement result changes, the objects of the strengthened observation and the weakened observation are switched according to the real-time measurement result.

[0075] The present application realizes the synchronous independent work of the TDLAS and the CRDS spectrum detection technologies on the same cavity by designing the dual optical path absorber, and can realize the measurement of 7 orders of magnitude (10 7The gas ultra-wide range detection of the application expands the detection range of the measuring device. Compared with the simple combination of different spectral detection technologies which still work independently, the measuring method of the application has lower gas consumption, faster response speed, better synchronization during detection, and the structure design of the double-light-path absorber in the application makes the measuring device miniaturized and improves the integration of the measuring device. The measuring method in the application compares the two measurement results in real time, selects the detection technology with better measurement accuracy range according to the measurement results, improves the detection efficiency, and ensures the high precision of the detection results. Especially in dynamic detection, the measuring method of the application can make dynamic adjustment according to the change of the gas, further improving the accuracy and applicability of the measurement.

[0076] Although the application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application.

Claims

1. A measuring device of an ultra-wide gas detection range, characterized by, The measuring device comprises a laser (1), an isolator (2), a light splitting module (3), an acousto-optic modulator (4), a double optical path absorber (5), a first detector (7) and a second detector (6); The laser (1) emits laser light; the laser (1) is connected to the input end of the isolator (2); the isolator (2) is used for isolating and protecting the laser (1) to prevent the laser light from returning to the laser (1); The output end of the isolator (2) is connected to the input end of the light splitting module (3); the light splitting module (3) is used for splitting the laser light into two beams, i.e. a first path laser light and a second path laser light; The light path output end of the first path laser light of the light splitting module (3) is first connected to the input end of the acousto-optic modulator (4), which is used for causing the first path laser light to generate frequency shift; the output end of the acousto-optic modulator (4) is connected to the first input end of the double optical path absorber (5); the first output end of the double optical path absorber (5) is connected to the first detector (7); The light path output end of the second path laser light of the light splitting module (3) is connected to the second input end of the double optical path absorber (5); the second output end of the double optical path absorber (5) is connected to the second detector (6); The double optical path absorber (5) comprises a cylindrical shell (5-1), a first reflector (5-2) and a second reflector (5-3); the first reflector (5-2) and the second reflector (5-3) are located in the shell and oppositely arranged to form a double optical path absorption cavity; the double optical path absorption cavity is composed of a central decaying cavity and a multiple reflection pool; The first reflector (5-2) is circular, and the mirror surface thereof is divided into two regions with different reflectivities, i.e. a central circular region (5-2-1) with a reflectivity of 99.999% and an outer circular ring region (5-2-2) with a reflectivity of 98%; a light transmission hole (5-2-3) is further arranged in the outer circular ring region (5-2-2), and the light transmission hole (5-2-3) is used for allowing the laser light of the multiple reflection pool to pass through; the second reflector (5-3) has the same structure as the first reflector (5-2); The central decaying cavity is a cylindrical space with the two central circular regions of the first reflector (5-2) and the second reflector (5-3) as end faces; and the multiple reflection pool is a hollow cylindrical space with the two outer circular ring regions of the first reflector (5-2) and the second reflector (5-3) as end faces; The first path laser light enters the central decaying cavity in the double optical path absorber (5) through the first input end (5-8) to form a central decaying cavity light path; and the second path laser light enters the multiple reflection pool of the double optical path absorber (5) through the second input end (5-9) to form an outer ring multiple reflection light path. The shell (5-1) is provided with a circular input end face (5-6) and a circular output end face (5-7) at two ends respectively, the center of the circular input end face (5-6) is provided with a first input end (5-8), and the non-center of the circular input end face (5-6) is provided with a second input end (5-9); the center of the circular output end face (5-7) is provided with a first output end (5-10); and the non-center of the circular output end face (5-7) is provided with a second output end (5-11).

2. The measurement device of an ultra-wide gas detection range according to claim 1, wherein, The first input end (5-8) and the second input end (5-9) are both optical fiber joints, and a collimator is arranged in the optical fiber joint; the first output end (5-10) is an optical fiber joint, and the second output end (5-11) is an electrical signal joint.

3. The measurement device of an ultra-wide gas detection range according to claim 1, wherein, An air inlet (5-4) and an air outlet (5-5) are arranged on the shell, for the inflow and outflow of the gas to be measured into the double-light-path absorber (5).

4. A measurement method based on the measurement apparatus of any one of claims 1 to 3, characterized by, The measurement method comprises: S1. The gas to be measured enters the double-light-path absorber (5) through the air inlet (5-4), which is specifically divided into two cases: S1-a. Static detection: after the gas to be measured enters the double-light-path absorber (5) through the air inlet (5-4), the air inlet (5-4) and the air outlet (5-5) are closed; S1-b. Dynamic detection: the gas to be measured continuously enters the double-light-path absorber (5) through the air inlet (5-4) and flows out through the air outlet (5-5); According to the measurement requirements, the static detection or the dynamic detection is reasonably selected; S2. The laser (1) emits laser, which enters the light splitting module (3) after passing through the isolator (2); S3. The light splitting module (3) splits the laser into first laser and second laser with different powers; S4. The first laser and the second laser are detected by different detection technologies respectively; S4-a. The first laser enters the center ring-down cavity of the double-light-path absorber (5) through the first input end (5-8) after being modulated by the acousto-optic modulator (4), forming a center ring-down cavity light path; then it enters the first detector (7) through the first output end (5-10), realizing single-frequency ring-down signal detection, then the frequency of the modulated laser is scanned to complete the absorption spectrum line profile, and the spectrum line is analyzed and processed, so that the measurement of the gas can be realized; S4-b. The second laser enters the multiple reflection cell of the double-light-path absorber (5) through the second input end (5-9), forming an outer ring multiple reflection light path; then it enters the second detector (6) through the second output end (5-11), realizing single-frequency absorption signal detection, then the frequency of the modulated laser is scanned to complete the absorption spectrum line profile, and the spectrum line is analyzed and processed, so that the measurement of the gas can be realized; S5. Compare the two measurement results, select the detection technology with better measurement accuracy range according to the measurement results, and strengthen the observation of the selected detection technology; the other detection technology is selected to be weakened or stopped.

5. The measurement method of the ultra-wide gas detection range measurement apparatus according to claim 4, wherein When the dynamic detection is selected in step S1, the step S5 further comprises: The selected detection technology is strengthened in observation, and another detection technology is selected to weaken the observation; and the two measurement results are compared in real time, and when the measurement result changes, the object of the strengthened observation and the weakened observation is switched according to the real-time measurement result.

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