CN107462521B - Device for measuring optimal frequency harmonic signals of target gas and application method - Google Patents
Device for measuring optimal frequency harmonic signals of target gas and application method Download PDFInfo
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- CN107462521B CN107462521B CN201710695197.9A CN201710695197A CN107462521B CN 107462521 B CN107462521 B CN 107462521B CN 201710695197 A CN201710695197 A CN 201710695197A CN 107462521 B CN107462521 B CN 107462521B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
Abstract
The invention relates to a target gas optimal harmonic signal measuring device and an application method, which are based on a brand new structural design, accurately realize the measurement of the target gas optimal harmonic signal under various different temperatures and pressures by adopting a laser technology, are particularly suitable for the measurement of the target gas optimal harmonic signal under extreme environments, and can greatly improve the measurement working efficiency.
Description
Technical Field
The invention relates to a device for measuring an optimal harmonic signal of target gas and an application method thereof, and belongs to the technical field of gas detection.
Background
When the combustion diagnosis is carried out in a high-pressure environment, the modulation amplitude under the optimal modulation coefficient in the wavelength modulation technology is increased due to the increase of the linewidth, and at the moment, the background signal caused by the optical element is very serious and continuously changed from nonlinear intensity modulation, an etalon effect and the like, so that the extraction of the target spectrum signal is difficult. The analog signal and the measurement signal at high temperature and high pressure have larger difference, wherein the difference is related to the selection of the analog line type on the one hand, but is mainly due to the accuracy of spectral line parameters at high temperature and high pressure on the other hand, because the data in the Hitemp database commonly used at present are mostly obtained through theoretical calculation according to normal temperature data, the accurate measurement of the spectral line parameters is an indispensable precondition in the establishment of a temperature and concentration inversion model, and meanwhile, the spectral line parameters at high temperature and high pressure can also play a role in supplementing and correcting the database.
Disclosure of Invention
The invention aims to solve the technical problem of providing the device for measuring the optimal harmonic signals of the target gas, which adopts a brand new structural design and can accurately measure and acquire the optimal harmonic signals of the target gas under various temperature and pressure environments.
The invention adopts the following technical scheme for solving the technical problems: the invention designs a target gas optimal harmonic signal measuring device which comprises a function signal generator, an adder, a laser controller, a laser, a collimating lens, a sample cell pipeline, a heating device, a temperature measuring device, a signal detector and a data processing control terminal, wherein the adder is connected with the function signal generator; the data processing control terminal is connected with the function signal generator to perform signal interaction; the output end of the function signal generator is connected with the input end of the adder; the output end of the adder is connected with the input end of the laser controller, the output end of the laser controller is connected with the control end of the laser, and the laser controller controls the laser according to the received data; the output end of the laser points to one end of the collimating lens; the two ends of the sample cell pipeline are respectively provided with a laser incident end and a laser emitting end, the laser incident end and the laser emitting end of the sample cell pipeline are respectively opened and communicated with each other, and the central line of a communication area between the laser incident end and the laser emitting end in the sample cell pipeline is a straight line; the laser incidence end and the laser emission end of the sample cell pipeline are respectively provided with a high-reflectivity lens in a sealing way, and the main optical axes of the two high-reflectivity lenses are collinear with each other; the other end of the collimating lens points to a high-reflectivity lens on the laser incident end of the sample cell pipeline, the high-reflectivity lens on the laser emitting end of the sample cell pipeline points to a signal receiving end of a signal detector, and the output end of the signal detector is connected with the input end of the data processing control terminal; the outer surface of the sample cell pipeline is of a sealing structure, a target gas input pipeline and a target gas output pipeline are arranged on the surface of the sample cell pipeline, the inner space and the outer space of the sample cell pipeline are communicated, and valves are respectively arranged on the target gas input pipeline and the target gas output pipeline; the surface of the sample cell pipeline is also provided with an air pressure control pipeline which is communicated with the inner space and the outer space of the sample cell pipeline, a valve is arranged on the air pressure control pipeline, and the air pressure change in the sample cell pipeline is regulated by inputting and outputting protective gas which is not fused with laser through the air pressure control pipeline; the heating device is positioned outside the sample cell pipeline and is used for heating the sample cell pipeline; the temperature measuring device is located outside the sample cell pipeline, and the measuring end of the temperature measuring device penetrates through the surface of the sample cell pipeline and is located inside the sample cell pipeline and used for detecting the temperature inside the sample cell pipeline.
As a preferred technical scheme of the invention: the device comprises a sample cell pipeline, a collimating lens, a laser emitting end, a high-reflectivity lens, a protective gas and a purifying device, wherein the laser emitting end of the collimating lens is in butt joint with the laser emitting end of the purifying device, the other end of the collimating lens, which faces the laser relatively, is in butt joint with the laser emitting end of the purifying device, the high-reflectivity lens of the laser emitting end of the purifying device is in butt joint with the sample cell pipeline, the central line of the laser emitting end of the purifying device and the central line of the laser emitting end of the purifying device are collinear, and the purifying device is filled with the protective gas which is not fused with laser.
As a preferred technical scheme of the invention: the protective gas which is not fused with the laser is high-purity N 2 。
As a preferred technical scheme of the invention: the temperature measuring device is a thermocouple.
As a preferred technical scheme of the invention: the laser is a DFB semiconductor laser.
Compared with the prior art, the device for measuring the optimal harmonic signals of the target gas has the following technical effects: the device for measuring the optimal harmonic signals of the target gas, which is designed by the invention, adopts a brand new structural design, introduces a laser technology, and can accurately realize the measurement of the optimal harmonic signals of the target gas at various different temperatures and pressures.
Based on the designed device for measuring the optimal harmonic signals of the target gas, the invention also aims to provide an application method of the device for measuring the optimal harmonic signals of the target gas, which can accurately measure and acquire the optimal harmonic signals of the target gas under various temperature and pressure environments.
The invention adopts the following technical scheme for solving the technical problems: the invention designs an application method of a target gas optimal harmonic signal measuring device, which is used for obtaining optimal harmonic signals of target gas under different temperature and air pressure environments; for laser light passing through the cuvette channel, the measurement is performed as follows:
step A, taking room temperature as the current temperature in a sample cell pipeline, and entering the step B;
step B, vacuumizing the sample pool pipeline, measuring background signals of the vacuum sample pool pipeline corresponding to the subharmonic signals respectively at the current temperature, and then entering the step C; wherein, each subharmonic signal is each subharmonic signal from 1 subharmonic signal to M subharmonic signal, M is the preset maximum subharmonic signal;
step C, injecting target gas and shielding gas which is not fused with laser into the sample cell pipeline, controlling the air pressure in the sample cell pipeline to be a preset initial air pressure value by adjusting the injection amount of the shielding gas which is not fused with the laser, taking the air pressure as the current air pressure in the sample cell pipeline, initializing the parameter n=2, and then entering the step D;
step D, measuring the complete waveform of the 1 st harmonic signal under the current temperature and the air pressure, and obtaining the 1 st harmonic signal under the current temperature and the air pressure through a phase-locked amplifier and data processing; measuring the complete waveform of the n-order harmonic signal at the current temperature and the air pressure, and obtaining the n-order harmonic signal at the current temperature and the air pressure through a phase-locked amplifier and data processing; then enter step E;
e, obtaining the vector difference between the 1 st harmonic signal at the current temperature and the air pressure and the background signal of the 1 st harmonic signal at the current temperature, and using the vector difference as an absorption related signal corresponding to the 1 st harmonic signal at the current temperature and the air pressure; meanwhile, obtaining the vector difference between the n-order harmonic signal at the current temperature and the air pressure and the background signal of the n-order harmonic signal at the current temperature, and taking the vector difference as an absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure, and then entering the step F;
step F, adopting absorption related signals corresponding to the 1 st harmonic signals under the current temperature and the air pressure, carrying out normalization operation on the absorption related signals corresponding to the n th harmonic signals under the current temperature and the air pressure, and updating the absorption related signals corresponding to the n th harmonic signals under the current temperature and the air pressure; meanwhile, the background signal of the 1 st harmonic signal at the current temperature is adopted, normalization operation is carried out on the background signal of the n th harmonic signal at the current temperature, and the background signal of the n th harmonic signal at the current temperature is updated; then enter step G;
step G, obtaining the peak value ratio between the absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure and the background signal of the n-order harmonic signal at the current temperature, taking the peak value ratio as the signal-to-background ratio SBR of the n-order harmonic signal at the current temperature and the air pressure, and then entering the step H;
step H, judging whether n is equal to M, if so, entering the step I; otherwise, adopting the sum of the value corresponding to n and 1, updating n, and returning to the step D;
step I, obtaining the signal-to-back ratio SBR of each subharmonic signal from the 2 subharmonic signals to the M subharmonic signals at the current temperature and the current air pressure; then selecting a harmonic signal corresponding to the SBR with the maximum signal-to-back ratio as the optimal harmonic signal of the target gas at the current temperature and the air pressure; then enter step J;
step J, judging whether the air pressure in the sample pool pipeline is equal to a preset air pressure upper limit threshold value, if so, entering a step K; otherwise, controlling the air pressure in the sample cell pipeline by adjusting the injection amount of the protective gas which is not fused with the laser, increasing the preset air pressure increment value based on the current air pressure, updating the current air pressure in the sample cell pipeline, setting the parameter n=2, and returning to the step D;
step K, judging whether the temperature in the sample pool pipeline is equal to a preset upper temperature limit threshold value, and if so, obtaining optimal harmonic signals of target gas under different temperatures and air pressure environments; otherwise, controlling the temperature in the sample cell pipeline by heating the sample cell pipeline, increasing the preset temperature increment value based on the current temperature, updating the current temperature in the sample cell pipeline, and returning to the step B.
As a preferred technical scheme of the invention: the laser is first purged with a shielding gas that does not fuse with the laser before passing through the cell conduit, and then through the cell conduit.
As a preferred technical scheme of the invention: and D, measuring the complete waveforms of the subharmonic signals under the condition of carrying out optimal modulation amplitude on the injection current of the laser based on a sine wave with preset frequency.
As a preferred technical scheme of the invention: in the step D, the center temperature of the laser is continuously changed by adopting a GPIB card, so that the center wavelength of the laser is continuously changed, and the complete waveform of each subharmonic signal is obtained.
As a preferred technical scheme of the invention: in the step C, the target gas and the shielding gas which is not fused with the laser are injected into the sample cell pipeline, and the concentration of the target gas is recorded and used as the actual concentration of the target gas;
in the step F, after updating the absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure, obtaining the target gas measured concentration of the absorption related signal peak value inversion, which is used as the target gas measured concentration corresponding to the n-order harmonic signal at the current temperature and the air pressure, and obtaining the absolute value of the difference between the target gas measured concentration and the actual target gas concentration, which is used as the target gas concentration detection error corresponding to the n-order harmonic signal at the current temperature and the air pressure;
in the step I, sequencing the signal-to-back ratio SBR of each harmonic signal in the 2 nd harmonic signals to the M th harmonic signals under the current temperature and the air pressure according to the sequence from big to small, and starting from the first signal-to-back ratio SBR, sequentially selecting [ (M-1) G ] signal-to-back ratios SBR as each signal-to-back ratio SBR to be selected; then selecting harmonic signals corresponding to the minimum target gas concentration detection errors as the optimal harmonic signals of the target gas at the current temperature and the current gas pressure according to harmonic signals corresponding to the signal-to-back ratio SBR respectively, and then entering a step J, wherein G is a preset percentage value, and 0 < G < 50%.
Compared with the prior art, the application method of the target gas optimal harmonic signal measuring device has the following technical effects: the application method of the target gas optimal harmonic signal measuring device designed by the invention is based on the target gas optimal harmonic signal measuring device designed by a brand new structure, adopts a laser technology, accurately realizes the measurement of the target gas optimal harmonic signal under various different temperatures and pressures, and greatly improves the measurement work efficiency.
Drawings
FIG. 1 is a schematic diagram of a device for measuring the optimal harmonic signals of a target gas according to the present invention.
The system comprises a function signal generator (1), an adder (2), a laser controller (3), a laser (4), a collimating lens (6), a sample cell pipeline (7), a heating device (8), a temperature measuring device (10), a signal detector (11), a data processing control terminal (15) and a purifying device.
Detailed Description
The following describes the embodiments of the present invention in further detail with reference to the drawings.
As shown in FIG. 1, the invention designs a target gas optimal harmonic signal measuring device, which specifically comprises a function signal generator 1, an adder 2, a laser controller 3, a DFB semiconductor laser, a collimating lens 6, a sample cell pipeline 7, a heating device 8, a thermocouple, a signal detector 11, a data processing control terminal 15 and a purifying device 16 in practical application; wherein, the data processing control terminal 15 is connected with the function signal generator 1 for signal interaction; the output end of the function signal generator 1 is connected with the input end of the adder 2; the output end of the adder 2 is connected with the input end of the laser controller 3, the output end of the laser controller 3 is connected with the control end of the DFB semiconductor laser, and the laser controller 3 controls the DFB semiconductor laser according to the received data; the output end of the DFB semiconductor laser points to one end of the collimating lens 6; the two ends of the sample cell pipeline 7 are respectively provided with a laser incidence end and a laser emission end, the laser incidence end and the laser emission end of the sample cell pipeline 7 are respectively opened and communicated with each other, and the central line of a communication area between the laser incidence end and the laser emission end in the sample cell pipeline 7 is a straight line; the laser incidence end and the laser emission end of the sample cell pipeline 7 are respectively provided with high-reflectivity lenses in a sealing way, and the main optical axes of the two high-reflectivity lenses are collinear with each other; the other end of the collimating lens 6 facing the DFB semiconductor laser is butted with the laser incident end of the purifying device 16, the laser emitting end of the purifying device 16 is butted with the high-reflectivity lens of the laser incident end of the sample cell pipeline 7, the center line of the laser incident end of the purifying device 16 and the center line of the laser emitting end are collinear with each other, and the purifying device 16 is filled with protective gas which is not fused with laser; the high-reflectivity lens on the laser emission end of the sample cell pipeline 7 points to the signal receiving end of the signal detector 11, and the output end of the signal detector 11 is connected with the input end of the data processing control terminal 15; the outer surface of the sample cell pipeline 7 is of a sealing structure, and a target gas input pipeline and a target gas output pipeline are arranged on the surface of the sample cell pipeline 7 and are connected with each otherThe inner space and the outer space of the sample cell pipeline 7 are communicated, and valves are respectively arranged on the target gas input pipeline and the target gas output pipeline; the surface of the sample cell pipeline 7 is also provided with an air pressure control pipeline which is communicated with the internal space and the external space of the sample cell pipeline 7, and a valve is arranged on the air pressure control pipeline, and the air pressure change in the sample cell pipeline 7 is regulated by inputting and outputting protective gas which is not fused with laser through the air pressure control pipeline; the heating device 8 is positioned outside the sample cell pipeline 7 and is used for heating the sample cell pipeline 7; the thermocouple is located outside the sample cell tube 7, and the measuring end of the thermocouple passes through the surface of the sample cell tube 7, is located inside the sample cell tube 7, and is used for detecting the temperature inside the sample cell tube 7. In practical application, the protective gas which is not fused with the laser is specifically designed as high-purity N 2 。
Based on the designed optimal harmonic signal measuring device of the target gas, the invention specifically designs an application method of the optimal harmonic signal measuring device of the target gas, which is used for obtaining the optimal harmonic signals of the target gas under different temperature and air pressure environments; the laser is first purged by a shielding gas that does not merge with the laser and then passes through the cell tube 7, wherein the laser passing through the cell tube 7 is measured as follows:
step a. Taking room temperature as the current temperature in the sample cell tube 7 and entering step B.
Step B, carrying out vacuumizing treatment on the sample pool pipeline 7, measuring background signals of the vacuum sample pool pipeline 7 corresponding to each subharmonic signal at the current temperature, and then entering the step C; wherein, each subharmonic signal is each subharmonic signal from 1 subharmonic signal to M subharmonic signal, M is the preset maximum subharmonic signal.
And C, injecting target gas and shielding gas which is not fused with laser into the sample cell pipeline 7, recording the concentration of the target gas as the actual concentration of the target gas, controlling the air pressure in the sample cell pipeline 7 to be a preset initial air pressure value by adjusting the injection amount of the shielding gas which is not fused with the laser, taking the air pressure as the current air pressure in the sample cell pipeline 7, initializing the parameter n=2, and then entering the step D.
Step D, under the condition of carrying out optimal modulation amplitude on the injection current of the laser based on a sine wave with preset frequency, continuously changing the central temperature of the laser by adopting a GPIB (general purpose interface bus) card, so that the central wavelength of the laser is continuously changed, measuring the complete waveform of a 1 st harmonic signal under the current temperature and the air pressure, and obtaining the 1 st harmonic signal under the current temperature and the air pressure through a phase-locked amplifier and data processing; measuring the complete waveform of the n-order harmonic signal at the current temperature and the air pressure, and obtaining the n-order harmonic signal at the current temperature and the air pressure through a phase-locked amplifier and data processing; step E is then entered.
In the step D, the center temperature of the laser is continuously changed by adopting the GPIB card, so that the center wavelength of the laser is continuously changed, and the complete waveform of each subharmonic signal is obtained.
E, obtaining the vector difference between the 1 st harmonic signal at the current temperature and the air pressure and the background signal of the 1 st harmonic signal at the current temperature, and using the vector difference as an absorption related signal corresponding to the 1 st harmonic signal at the current temperature and the air pressure; and meanwhile, obtaining the vector difference between the n-order harmonic signal at the current temperature and the air pressure and the background signal of the n-order harmonic signal at the current temperature, taking the vector difference as an absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure, and then entering the step F.
Step F, adopting absorption related signals corresponding to 1-order harmonic signals under the current temperature and the air pressure, carrying out normalization operation on the absorption related signals corresponding to n-order harmonic signals under the current temperature and the air pressure, updating the absorption related signals corresponding to the n-order harmonic signals under the current temperature and the air pressure, then obtaining the target gas measured concentration of the peak value inversion of the absorption related signals, serving as the target gas measured concentration corresponding to the n-order harmonic signals under the current temperature and the air pressure, and obtaining the absolute value of the difference value between the target gas measured concentration and the actual concentration of the target gas, and serving as the target gas concentration detection error corresponding to the n-order harmonic signals under the current temperature and the air pressure; meanwhile, the background signal of the 1 st harmonic signal at the current temperature is adopted, normalization operation is carried out on the background signal of the n th harmonic signal at the current temperature, and the background signal of the n th harmonic signal at the current temperature is updated; step G is then entered.
And G, obtaining the peak value ratio between the absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure and the background signal of the n-order harmonic signal at the current temperature, taking the peak value ratio as the signal-to-background ratio SBR of the n-order harmonic signal at the current temperature and the air pressure, and then entering the step H.
Step H, judging whether n is equal to M, if so, entering the step I; otherwise, adopting the sum of the value corresponding to n and 1, updating n, and returning to the step D.
Step I, obtaining the signal-to-back ratio SBR of each subharmonic signal from the 2 subharmonic signals to the M subharmonic signals at the current temperature and the current air pressure; sequencing the signal-to-back ratios SBR of each harmonic signal in the 2 nd harmonic signals to the M th harmonic signals of the obtained current temperature and air pressure according to the sequence from big to small, and starting from the first signal-to-back ratio SBR, sequentially selecting [ (M-1) G ] signal-to-back ratios SBR as each signal-to-back ratio SBR to be selected; then selecting harmonic signals corresponding to the minimum target gas concentration detection errors as the optimal harmonic signals of the target gas at the current temperature and the current gas pressure according to harmonic signals corresponding to the signal-to-back ratio SBR respectively, and then entering a step J, wherein G is a preset percentage value, and 0 < G < 50%.
Step J, judging whether the air pressure in the sample pool pipeline 7 is equal to a preset air pressure upper limit threshold value, if so, entering a step K; otherwise, the injection amount of the protective gas which is not fused with the laser is adjusted to be injected into the sample cell pipeline 7, the air pressure in the sample cell pipeline 7 is controlled, the preset air pressure increment value is increased based on the current air pressure, the current air pressure in the sample cell pipeline 7 is updated, the parameter n=2 is set, and then the step D is returned. In practical application, specific design adopts 1atm for preset air pressure increment value.
Step K, judging whether the temperature in the sample pool pipeline 7 is equal to a preset upper temperature limit threshold value, if so, obtaining optimal harmonic signals of target gas under different temperatures and air pressure environments; otherwise, the temperature in the sample cell pipeline 7 is controlled by heating the sample cell pipeline 7, the preset temperature increment value is increased based on the current temperature, the current temperature in the sample cell pipeline 7 is updated, and the step B is returned. In practical application, specific design adopts 100 ℃ aiming at a preset temperature increment value.
Based on the designed target gas optimal harmonic signal measuring device and the application method, the target gas optimal harmonic signal measuring device based on the brand new structural design adopts a laser technology, so that the measurement of the target gas optimal harmonic signal under various different temperatures and pressures is accurately realized, and the measurement working efficiency is greatly improved.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Claims (7)
1. The utility model provides a target gas best order harmonic signal measuring device which characterized in that: the device comprises a function signal generator (1), an adder (2), a laser controller (3), a laser (4), a collimating lens (6), a sample cell pipeline (7), a heating device (8), a temperature measuring device (10), a signal detector (11) and a data processing control terminal (15); the data processing control terminal (15) is connected with the function signal generator (1) for signal interaction; the output end of the function signal generator (1) is connected with the input end of the adder (2); the output end of the adder (2) is connected with the input end of the laser controller (3), the output end of the laser controller (3) is connected with the control end of the laser (4), and the laser controller (3) controls the laser (4) according to the received data; the output end of the laser (4) points to one end of the collimating lens (6); the two ends of the sample cell pipeline (7) are respectively provided with a laser incident end and a laser emitting end, the laser incident end and the laser emitting end of the sample cell pipeline (7) are respectively opened and communicated with each other, and the central line of a communication area between the laser incident end and the laser emitting end in the sample cell pipeline (7) is a straight line; the laser incidence end and the laser emission end of the sample cell pipeline (7) are respectively provided with high-reflectivity lenses in a sealing way, and the main optical axes of the two high-reflectivity lenses are collinear with each other; the other end of the collimating lens (6) points to a high-reflectivity lens on the laser incident end of the sample cell pipeline (7), the high-reflectivity lens on the laser emitting end of the sample cell pipeline (7) points to the signal receiving end of the signal detector (11), and the output end of the signal detector (11) is connected with the input end of the data processing control terminal (15); the outer surface of the sample cell pipeline (7) is of a sealing structure, a target gas input pipeline and a target gas output pipeline are arranged on the surface of the sample cell pipeline (7), the inner space and the outer space of the sample cell pipeline (7) are communicated, and valves are respectively arranged on the target gas input pipeline and the target gas output pipeline; the surface of the sample cell pipeline (7) is also provided with an air pressure control pipeline which is communicated with the inner space and the outer space of the sample cell pipeline (7), and a valve is arranged on the air pressure control pipeline, and the air pressure change in the sample cell pipeline (7) is regulated by inputting and outputting protective gas which is not fused with laser through the air pressure control pipeline; the heating device (8) is positioned outside the sample cell pipeline (7) and is used for heating the sample cell pipeline (7); the temperature measuring device (10) is positioned outside the sample cell pipeline (7), and a measuring end of the temperature measuring device (10) penetrates through the surface of the sample cell pipeline (7) and is positioned inside the sample cell pipeline (7) to detect the temperature inside the sample cell pipeline (7);
the device also comprises a purification device (16), the other end of the collimating lens (6) facing the laser (4) is butted with the laser incident end of the purification device (16), the laser emitting end of the purification device (16) is butted with the high-reflectivity lens of the laser incident end of the sample cell pipeline (7), the central line of the laser incident end of the purification device (16) and the central line of the laser emitting end are collinear, and the purification device (16) is filled with protective gas which is not fused with laser;
the temperature measuring device (10) is a thermocouple, and the laser (4) is a DFB semiconductor laser.
2. The apparatus for measuring an optimum harmonic signal of a target gas according to claim 1, wherein: the protective gas which is not fused with the laser is high-purity N 2 。
3. An application method of the device for measuring the optimal harmonic signals of the target gas based on the method of claim 1, wherein the device is used for obtaining the optimal harmonic signals of the target gas under different temperature and air pressure environments; characterized in that the measurement is performed for the laser passing through the cuvette channel (7) according to the following steps:
step A, taking room temperature as the current temperature in a sample cell pipeline (7), and entering the step B;
step B, carrying out vacuumizing treatment on the sample pool pipeline (7), measuring background signals of the vacuum sample pool pipeline (7) corresponding to each subharmonic signal at the current temperature, and then entering the step C; wherein, each subharmonic signal is each subharmonic signal from 1 subharmonic signal to M subharmonic signal, M is the preset maximum subharmonic signal;
step C, injecting target gas and shielding gas which is not fused with laser into the sample cell pipeline (7), controlling the air pressure in the sample cell pipeline (7) to be a preset initial air pressure value by adjusting the injection amount of the shielding gas which is not fused with the laser, taking the air pressure as the current air pressure in the sample cell pipeline (7), initializing the parameter n=2, and then entering the step D;
step D, measuring the complete waveform of the 1 st harmonic signal under the current temperature and the air pressure, and obtaining the 1 st harmonic signal under the current temperature and the air pressure through a phase-locked amplifier and data processing; measuring the complete waveform of the n-order harmonic signal at the current temperature and the air pressure, and obtaining the n-order harmonic signal at the current temperature and the air pressure through a phase-locked amplifier and data processing; then enter step E;
e, obtaining the vector difference between the 1 st harmonic signal at the current temperature and the air pressure and the background signal of the 1 st harmonic signal at the current temperature, and using the vector difference as an absorption related signal corresponding to the 1 st harmonic signal at the current temperature and the air pressure; meanwhile, obtaining the vector difference between the n-order harmonic signal at the current temperature and the air pressure and the background signal of the n-order harmonic signal at the current temperature, and taking the vector difference as an absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure, and then entering the step F;
step F, adopting absorption related signals corresponding to the 1 st harmonic signals under the current temperature and the air pressure, carrying out normalization operation on the absorption related signals corresponding to the n th harmonic signals under the current temperature and the air pressure, and updating the absorption related signals corresponding to the n th harmonic signals under the current temperature and the air pressure; meanwhile, the background signal of the 1 st harmonic signal at the current temperature is adopted, normalization operation is carried out on the background signal of the n th harmonic signal at the current temperature, and the background signal of the n th harmonic signal at the current temperature is updated; then enter step G;
step G, obtaining the peak value ratio between the absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure and the background signal of the n-order harmonic signal at the current temperature, taking the peak value ratio as the signal-to-background ratio SBR of the n-order harmonic signal at the current temperature and the air pressure, and then entering the step H;
step H, judging whether n is equal to M, if so, entering the step I; otherwise, adopting the sum of the value corresponding to n and 1, updating n, and returning to the step D;
step I, obtaining the signal-to-back ratio SBR of each subharmonic signal from the 2 subharmonic signals to the M subharmonic signals at the current temperature and the current air pressure; then selecting a harmonic signal corresponding to the SBR with the maximum signal-to-back ratio as the optimal harmonic signal of the target gas at the current temperature and the air pressure; then enter step J;
step J, judging whether the air pressure in the sample pool pipeline (7) is equal to a preset air pressure upper limit threshold value, and if so, entering the step K; otherwise, controlling the air pressure in the sample cell pipeline (7) by adjusting the injection amount of the protective gas which is not fused with the laser, increasing the preset air pressure increment value based on the current air pressure, updating the current air pressure in the sample cell pipeline (7), setting the parameter n=2, and returning to the step D;
step K, judging whether the temperature in the sample pool pipeline (7) is equal to a preset upper temperature limit threshold value, if so, obtaining optimal harmonic signals of target gas under different temperatures and air pressure environments; otherwise, the temperature in the sample cell pipeline (7) is controlled by heating the sample cell pipeline (7), the preset temperature increment value is increased based on the current temperature, the current temperature in the sample cell pipeline (7) is updated, and the step B is returned.
4. A method of using a harmonic signal measurement apparatus based on an optimal order of a target gas according to claim 3, wherein: the laser is first purged with a shielding gas that does not fuse with the laser before passing through the cell tube (7), and then through the cell tube (7).
5. A method of using a harmonic signal measurement apparatus based on an optimal order of a target gas according to claim 3, wherein: and D, measuring the complete waveforms of the subharmonic signals under the condition of carrying out optimal modulation amplitude on the injection current of the laser based on a sine wave with preset frequency.
6. A method of using a harmonic signal measurement apparatus based on an optimal order of a target gas according to claim 3, wherein: in the step D, the center temperature of the laser is continuously changed by adopting a GPIB card, so that the center wavelength of the laser is continuously changed, and the complete waveform of each subharmonic signal is obtained.
7. A method of using a harmonic signal measurement apparatus based on an optimal order of a target gas according to claim 3, wherein: in the step C, the target gas and the shielding gas which is not fused with the laser are injected into the sample cell pipeline (7), and the target gas concentration is recorded as the actual concentration of the target gas;
in the step F, after updating the absorption related signal corresponding to the n-order harmonic signal at the current temperature and the air pressure, obtaining the target gas measured concentration of the absorption related signal peak value inversion, which is used as the target gas measured concentration corresponding to the n-order harmonic signal at the current temperature and the air pressure, and obtaining the absolute value of the difference between the target gas measured concentration and the actual target gas concentration, which is used as the target gas concentration detection error corresponding to the n-order harmonic signal at the current temperature and the air pressure;
in the step I, sequencing the signal-to-back ratio SBR of each harmonic signal in the 2 nd harmonic signals to the M th harmonic signals under the current temperature and the air pressure according to the sequence from big to small, and starting from the first signal-to-back ratio SBR, sequentially selecting [ (M-1) G ] signal-to-back ratios SBR as each signal-to-back ratio SBR to be selected; then selecting harmonic signals corresponding to the minimum target gas concentration detection errors as the optimal harmonic signals of the target gas at the current temperature and the current gas pressure according to harmonic signals corresponding to the signal-to-back ratio SBR respectively, and then entering a step J, wherein G is a preset percentage value, and 0 < G < 50%.
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| CN101915737A (en) * | 2010-08-03 | 2010-12-15 | 武汉科技大学 | Detection instrument for detecting concentration of CO gas |
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| CN101915737A (en) * | 2010-08-03 | 2010-12-15 | 武汉科技大学 | Detection instrument for detecting concentration of CO gas |
| CN103323115A (en) * | 2013-06-24 | 2013-09-25 | 清华大学 | Method for measuring gas absorption spectrum line width and line-type coefficient based on wavelength modulation |
| CN103868885A (en) * | 2014-03-27 | 2014-06-18 | 清华大学 | Composite multi-harmonic-based online gas concentration measurement method |
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| CN207280930U (en) * | 2017-08-15 | 2018-04-27 | 江苏师范大学 | A kind of optimal times harmonic signal measurement apparatus of object gas |
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