CN116448704A - TDLAS-based gas detection self-calibration system and method - Google Patents

TDLAS-based gas detection self-calibration system and method Download PDF

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Publication number
CN116448704A
CN116448704A CN202310370437.3A CN202310370437A CN116448704A CN 116448704 A CN116448704 A CN 116448704A CN 202310370437 A CN202310370437 A CN 202310370437A CN 116448704 A CN116448704 A CN 116448704A
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tdlas
laser
gas
gas detection
calibration
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何奇
杨帆
刘伟
甄玉龙
韩一梁
马玉林
汪左成
陈涛
童瀚瑶
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Beijing Institute of Radio Metrology and Measurement
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Beijing Institute of Radio Metrology and Measurement
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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
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/12—Circuits of general importance; Signal processing
    • G01N2201/121—Correction signals
    • G01N2201/1211—Correction signals for temperature
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/12—Circuits of general importance; Signal processing
    • G01N2201/127—Calibration; base line adjustment; drift compensation
    • G01N2201/12723—Self check capacity; automatic, periodic step of checking
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

The invention discloses a TDLAS-based gas detection self-calibration system and a method thereof, wherein the gas detection self-calibration system consists of a spectroscope, a standard gas chamber, a first converging mirror and a light intensity detector, wherein the spectroscope is used for receiving a measuring light beam generated by a laser after passing through the collimating mirror; the standard gas cell is used for absorbing the measuring beam; the first converging mirror is used for converging the measuring light beam absorbed by the standard air chamber; the light intensity detector is used for generating photoelectric signals according to the converged measuring light beams and transmitting the photoelectric signals to the detection control system, and the detection control system modulates the measuring light beams according to the photoelectric signals, wherein the detection control system is electrically connected with the laser and the light intensity detector respectively; the invention uses the data characteristics of the received signals obtained by the detector in the calibration light path, and the temperature of the laser is controlled in a feedback way, so that the laser wavelength can be always strictly aligned with the central position of the gas absorption peak under different working conditions, thereby realizing the calibration of the central wavelength of the laser in a complex environment.

Description

TDLAS-based gas detection self-calibration system and method
Technical Field
The invention relates to the technical field of infrared absorption spectroscopy, in particular to a TDLAS-based gas detection self-calibration system and method.
Background
The wavelength modulation method mainly comprises a peak-determining method and a peak-sweeping method, wherein the peak-sweeping method is to modulate laser output by a laser by overlapping a high-frequency sine wave with a low-frequency sawtooth wave or a triangular wave. The peak-setting method is to superimpose a high-frequency sine wave driving signal to modulate the laser output when the output wavelength of the laser is coincident with the gas absorption peak position. The peak-determining method can obtain a large amount of gas concentration data from the absorption waveform, and can realize higher signal-to-noise ratio by a method of averaging measurement results in a scene with higher laser temperature control precision or small environmental change.
When the peak-fixing method is used for measuring the gas concentration, the wavelength of the laser corresponding to the zero crossing point of the sinusoidal signal is aligned with the central wavelength of the absorption peak of the measured object, but in different use environments, the peak position of the gas absorption peak and the central wavelength of the laser are possibly deviated due to the influence of the drifting of the environmental air pressure, the temperature, the humidity and the electrical parameters of the system, so that the problems that the measurement distance is shortened, the sensitivity is lowered, the target gas cannot be measured even when the measurement is serious and the like are solved.
In summary, how to realize automatic calibration of a system under a complex environment in the TDLAS technology is a difficulty of current research, so a self-calibration method for TDLAS is needed to realize strict alignment of a center wavelength and a gas absorption peak position, and provide a new solution for measurement calibration of a wavelength modulation technology.
Disclosure of Invention
The invention aims to solve the problem of realizing automatic calibration of laser wavelength in a complex environment, and provides a TDLAS-based gas detection self-calibration system and a TDLAS-based gas detection self-calibration method, which are used for realizing calibration of laser center wavelength in the complex environment.
In order to achieve the above technical object, the present invention provides a TDLAS-based gas detection self-calibration system, comprising:
a spectroscope for receiving the measuring beam generated by the laser after passing through the collimating mirror;
a standard gas cell for absorbing the measuring beam;
a first converging mirror for converging the measuring beam absorbed by the standard gas cell;
the light intensity detector is used for generating photoelectric signals according to the converged measuring light beams and transmitting the photoelectric signals to the detection control system, and the detection control system modulates the measuring light beams according to the photoelectric signals, wherein the detection control system is electrically connected with the laser and the light intensity detector respectively.
Preferably, the detection control system is configured to modulate the measuring beam using a sawtooth signal and a sinusoidal signal superimposed with a fixed dc bias as the drive signals.
Preferably, the detection control system is further used for performing phase-locking amplification on the photoelectric signal according to Beer-Lambert law to obtain a second harmonic of the photoelectric signal;
the method comprises the steps of adjusting the temperature parameter value of a laser, changing the peak position of a curve of a second harmonic wave, enabling the output wavelength of the laser to be aligned with the gas absorption peak position, and calibrating a TDLAS gas detection system, wherein the TDLAS gas detection system comprises the laser, a collimating mirror, a reflecting surface, a detection control system, a photoelectric detector and a second converging mirror which are sequentially arranged, measuring light beams penetrate through detected gas, are reflected to the second converging mirror through the reflecting surface to be converged, are collected by the photoelectric detector, and are transmitted to the detection control system for detecting gas types and gas concentrations in the detected gas.
The invention also provides a TDLAS-based gas detection self-calibration method, which is applied to a gas detection self-calibration system and comprises the following steps:
acquiring a first moment corresponding to a first period starting phase of a driving signal generated by a detection control system and a second moment corresponding to a second period starting phase of the driving signal;
acquiring a third moment corresponding to a curve peak value of a second harmonic of a photoelectric signal generated by a measuring beam generated by a laser after passing through a collimating mirror, wherein the third moment is acquired by a detection control system;
based on the first moment and the second moment, judging whether the output waveform of the laser generates offset according to the third moment, if so, adjusting the output wavelength of the laser to align with the gas absorption peak position according to the first difference value of the second moment and the third moment by adjusting the temperature parameter value of the laser, and calibrating the TDLAS gas detection system, otherwise, not calibrating the TDLAS gas detection system.
Preferably, in the process of obtaining the second harmonic, the photoelectric signal is subjected to phase-locked amplification based on Beer-Lambert law to obtain the second harmonic of the photoelectric signal.
Preferably, in the process of judging whether the output waveform generates the offset, judging whether the output waveform generates the offset according to a second difference value between the first moment and the second moment, and judging that the output waveform does not generate the offset when the second difference value is constant, otherwise, judging that the output waveform generates the offset.
Preferably, in the process of modulating the output wavelength, the alignment of the modulated output wavelength and the gas absorption peak position is realized by adjusting the temperature parameter value to enable the first difference value to be 0, so as to calibrate the TDLAS gas detection system.
Preferably, after calibrating the TDLAS gas detection system, the driving signal of the laser is changed to a sine wave signal superimposed with a fixed dc bias, and the gas concentration measurement of the measured gas is calibrated according to the relation between the second harmonic and the fundamental wave component extracted from the light intensity response signal generated by the sine wave signal according to Beer-Lambert law.
Preferably, in the process of changing the dynamic signal into the sine wave signal, after controlling the current value corresponding to the sine wave signal and the third moment to be equal, the concentration calibration is performed according to the relationship between the second harmonic and the fundamental component extracted by the light intensity response signal.
Preferably, after the concentration calibration is performed, the gas detection self-calibration system is separated from the TDLAS gas detection system, and the TDLAS gas detection system is controlled to detect the detected gas.
The invention discloses the following technical effects:
the invention uses the data characteristics of the received signals obtained by the detector in the calibration light path, and the temperature of the laser is controlled in a feedback way, so that the laser wavelength can be always strictly aligned with the central position of the gas absorption peak under different working conditions, thereby realizing the calibration of the central wavelength of the laser in a complex environment.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a calibration system according to the present invention;
FIG. 2 is a plot of the driving signal versus the second harmonic according to the present invention;
FIG. 3 is a schematic diagram of a telemetry optical path according to the present invention;
fig. 4 is a schematic diagram of a calibration optical path according to the present invention, wherein 1 is a laser, 2 is a collimating mirror, 3 is a spectroscope, 4 is a reflecting surface, 5 is a standard air chamber, 6 is a first converging mirror, 7 is a light intensity detector, 8 is a detection control system, 9 is a photodetector, 10 is a second converging mirror, and 11 is a calibration system.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to be within the scope of the present application.
As shown in fig. 1-4, the present invention provides a TDLAS-based gas detection self-calibration system, comprising:
a beam splitter 3 for receiving the measuring beam generated by the laser 1 through the collimator lens 2;
a standard gas cell 5 for absorbing the measuring beam;
a first converging mirror 6 for converging the measuring beam absorbed by the standard gas cell 5;
the light intensity detector 7 is configured to generate a photoelectric signal according to the converged measuring beam, and transmit the photoelectric signal to the detection control system 8, where the detection control system 8 modulates the measuring beam according to the photoelectric signal, and the detection control system 8 is electrically connected with the laser 1 and the light intensity detector 7 respectively.
Still preferably, the present invention provides a detection control system 8 for modulating the measuring beam using a sawtooth signal and a sinusoidal signal superimposed with a fixed dc offset as driving signals.
Still preferably, the detection control system 8 provided by the present invention is further configured to perform phase-locked amplification on the photoelectric signal according to Beer-Lambert law, so as to obtain a second harmonic of the photoelectric signal;
the temperature parameter value of the laser 1 is adjusted, the peak position of the curve of the second harmonic is changed, the output wavelength of the laser 1 is aligned with the gas absorption peak position, and the TDLAS gas detection system is calibrated, wherein the TDLAS gas detection system comprises the laser 1, a collimating mirror 2, a reflecting surface 4, a detection control system 8, a photoelectric detector 9 and a second converging mirror 10 which are sequentially arranged, and after measuring beams pass through the measured gas, the measuring beams are reflected to the second converging mirror 10 through the reflecting surface 4 and are converged and then are collected by the photoelectric detector 9, and the measuring beams are transmitted to the detection control system 8 for detecting the gas types and the gas concentration in the measured gas.
The invention provides a TDLAS-based gas detection self-calibration method, which is applied to a gas detection self-calibration system and comprises the following steps:
acquiring a first moment corresponding to a first period starting phase of a driving signal generated by the detection control system 8 and a second moment corresponding to a second period starting phase of the driving signal;
acquiring a third moment corresponding to a curve peak value of a second harmonic of a photoelectric signal generated by a measuring beam generated by the laser 1 after passing through the collimating mirror 2, wherein the third moment is acquired by the detection control system 8;
based on the first moment and the second moment, judging whether the output waveform of the laser 1 is deviated according to the third moment, if so, adjusting the temperature parameter value of the laser 1 to align the output wavelength of the laser 1 with the gas absorption peak position according to the first difference value of the second moment and the third moment, and calibrating the TDLAS gas detection system, otherwise, not calibrating the TDLAS gas detection system.
Further preferably, in the process of obtaining the second harmonic, the invention performs phase-locked amplification on the photoelectric signal based on Beer-Lambert law to obtain the second harmonic of the photoelectric signal.
Further preferably, in the process of judging whether the output waveform generates the offset, the invention judges whether the output waveform generates the offset according to the second difference value between the first moment and the second moment, when the second difference value is constant, the output waveform is judged not to generate the offset, otherwise, the output waveform is judged to generate the offset.
Further preferably, in the process of modulating the output wavelength, the method realizes the alignment of the modulated output wavelength and the gas absorption peak position by adjusting the temperature parameter value to enable the first difference value to be 0, and is used for calibrating the TDLAS gas detection system.
Further preferably, after calibrating the TDLAS gas detection system, the present invention changes the driving signal of the laser 1 into a sine wave signal superimposed with a fixed dc bias, and calibrates the gas concentration measurement of the measured gas according to the relation between the second harmonic and the fundamental component extracted from the light intensity response signal generated by the sine wave signal according to the Beer-Lambert law.
Further preferably, in the process of changing the dynamic signal into the sine wave signal, the concentration calibration is performed according to the relationship between the second harmonic and the fundamental component extracted from the light intensity response signal after the current value corresponding to the third moment of the sine wave signal is controlled to be equal.
Further preferably, after the concentration calibration is performed, the gas detection self-calibration system is separated from the TDLAS gas detection system, and the TDLAS gas detection system is controlled to detect the detected gas.
The gas detection self-calibration method is realized through the following technical scheme.
The laser 1 is turned on, the emitted light passes through the collimating mirror 2 to generate a measuring beam, the measuring beam passes through a standard air chamber with known gas concentration and is collected by the first collecting mirror 6 receiving lens, then the measuring beam is collected by the light intensity detector 7, the detection control system 8 is turned on, the measuring beam is modulated by using a sawtooth wave signal and a sine signal overlapped with a fixed direct current bias as driving signals, the driving signals are shown as (a) of fig. 2, wherein t is as follows 2 The output wavelength of the laser 1 corresponding to the moment is the wavelength corresponding to the absorption peak of the measured gas. At the start of each cycle, a synchronous pulse width signal is synchronously generated to mark the 0-phase point of the drive signal, as shown in fig. 2 (b).
After the photoelectric signal collected by the light intensity detector 7 is transmitted to the detection control system 8, the signal is further phase-locked amplified according to Beer-Lambert law, and the second harmonic of the photoelectric signal can be obtained, as shown in (c) of fig. 2, t 0 And t 3 For the moment t corresponding to the initial phase of two periods of the driving signal 2 The peak position t of the second harmonic curve is the corresponding point of the peak of the second harmonic curve 2 And the starting time t 0 Distance t 2 -t 0 ＝Δt 1 When the center wavelength of the laser 1 is aligned with the gas absorption peak level, Δt 1 Constant and unchanged; when the wavelength of the laser 1 is shifted or when the gas absorption peak position is shifted due to environmental influence, the peak position of the second harmonic curve is also changed, as shown in fig. 2 (d), t 1 And the starting time t 0 Distance t 1 -t 0 ＝Δt 3 。
The wavelength of the laser 1 can be modulated by changing the driving current and the temperature parameter, but changing the laser wavelength by changing the driving current affects the output power of the laser and further affects the gas measurement distance, so that the alignment of the output wavelength of the laser 1 and the gas absorption peak can be achieved on the premise that the output power of the laser 1 is not affected by changing the temperature parameter to realize the wavelength change. By adjusting the temperature parameter value of the laser 1, the peak position of the second harmonic curve can be changed, i.e. Δt in (d) of fig. 2 3 Is a width of (c). In the wavelength calibration mode, the temperature parameter value is adjusted in real time, and when deltat is calculated 3 When the peak position is equal to 0, the second harmonic peak position stably appears at t 0 And t 3 At the middle position of the moment, the wavelength of the laser 1 is aligned with the gas absorption peak position, so that the automatic calibration of a TDLAS-based gas detection system is realized.
As shown in the conventional telemetry optical path schematic diagram 3, in combination with the wavelength modulation spectrum calibration method proposed herein, when calibrating the telemetry system shown in fig. 3, the calibration system 11 is coupled into the optical path system shown in fig. 3 by controlling a mechanical switching device or a guide rail, wherein the calibration system 11 is composed of a spectroscope 3, a standard gas chamber 5, a converging lens 6 and an optical intensity detector 7, and the overall optical path during calibration is shown in fig. 4.
By using the optical path system shown in fig. 4 and the method proposed herein, the automatic calibration of the gas detection system can be realized, after each driving parameter of the laser 1 is determined, the driving signal of the laser 1 is changed into a sine wave signal overlapped with a fixed direct current bias, the laser signal is absorbed by the gas in the standard gas chamber, and the relationship between the second harmonic and the fundamental wave component extracted from the photoelectric signal can further realize the calibration of gas measurement according to the Beer-Lambert law.
With the optical path system shown in fig. 4 and the method presented herein, an automatic calibration of the wavelength of the measuring beam of the gas detection system can be achieved.
After determining the driving parameters of the laser 1, the driving signal of the laser 1 is changed to a sine wave signal superimposed with a fixed dc bias, wherein the dc bias signal is identical to t in fig. 2 (a) 2 The current values corresponding to the moments are equal. At this time, the measuring beam emitted from the laser 1 passes through the standard gas chamber 5 and is partially absorbed, and the concentration calibration of gas detection can be further realized by using the relationship between the second harmonic and the fundamental component extracted from the light intensity response signal according to Beer-Lambert law.
After calibration, the calibration system 11 can be disconnected from the optical path by controlling the mechanical switching device or the guide rail, and the measurement system can be restored to the optical path state shown in fig. 3, so that the device enters a conventional gas measurement mode.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third, etc. do not denote any order. These words may be interpreted as names.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims (10)

1. A TDLAS based gas detection self-calibration system, comprising:
a spectroscope (3) for receiving the measuring beam generated by the laser (1) through the collimating mirror (2);
-a standard gas cell (5) for absorbing said measuring beam;
a first converging mirror (6) for converging the measuring beam absorbed by the standard gas cell (5);
the light intensity detector (7) is used for generating photoelectric signals according to the converged measuring light beams and transmitting the photoelectric signals to the detection control system (8), and the detection control system (8) modulates the measuring light beams according to the photoelectric signals, wherein the detection control system (8) is electrically connected with the laser (1) and the light intensity detector (7) respectively.
2. The TDLAS based gas detection self-calibration system of claim 1, wherein:
the detection control system (8) is configured to modulate the measuring beam using a sawtooth signal and a sinusoidal signal superimposed with a fixed dc offset as drive signals.
3. The TDLAS based gas detection self-calibration system of claim 2, wherein:
the detection control system (8) is also used for carrying out phase-locking amplification on the photoelectric signal according to Beer-Lambert law to obtain the second harmonic of the photoelectric signal;
the method comprises the steps of adjusting temperature parameter values of a laser (1), changing peak positions of curves of second harmonic waves, enabling output wavelengths of the laser (1) to be aligned with gas absorption peak positions, and calibrating a TDLAS gas detection system, wherein the TDLAS gas detection system comprises the laser (1), a collimating mirror (2), a reflecting surface (4), a detection control system (8), a photoelectric detector (9) and a second converging mirror (10) which are sequentially arranged, and measuring light beams penetrate through measured gas, are reflected to the second converging mirror (10) through the reflecting surface (4) and are collected by the photoelectric detector (9) and then are transmitted to the detection control system (8) for detecting gas types and gas concentrations in the measured gas.
4. A TDLAS-based gas detection self-calibration method applied to the gas detection self-calibration system according to any one of claims 1-3, comprising the steps of:
acquiring a first moment corresponding to a driving signal generated by a detection control system (8) at a first period starting phase and a second moment corresponding to a driving signal at a second period starting phase;
acquiring a third moment corresponding to a curve peak value of a second harmonic of a photoelectric signal generated by a measuring beam generated by a laser (1) after passing through a collimating mirror (2) and acquired by the detection control system (8);
and judging whether the output waveform of the laser (1) deviates or not according to the third moment based on the first moment and the second moment, and if so, adjusting the output wavelength of the laser (1) to align with the gas absorption peak position by adjusting the temperature parameter value of the laser (1) according to the first difference value of the second moment and the third moment so as to calibrate a TDLAS gas detection system, otherwise, not calibrating the TDLAS gas detection system.
5. The TDLAS based gas detection self-calibration method of claim 4, wherein:
and in the process of acquiring the second harmonic, carrying out phase-locked amplification on the photoelectric signal based on Beer-Lambert law to acquire the second harmonic of the photoelectric signal.
6. The TDLAS based gas detection self-calibration method of claim 5, wherein:
in the process of judging whether the output waveform generates offset, judging whether the output waveform generates offset according to a second difference value between the first moment and the second moment, if the second difference value is constant, judging that the output waveform does not generate offset, otherwise, judging that the output waveform generates offset.
7. The TDLAS based gas detection self-calibration method of claim 6, wherein:
in the process of modulating the output wavelength, the first difference value is 0 by adjusting the temperature parameter value, so that the output wavelength and the gas absorption peak position are modulated to be aligned, and the TDLAS gas detection system is calibrated.
8. The TDLAS based gas detection self-calibration method of claim 7, wherein:
after the TDLAS gas detection system is calibrated, the driving signal of the laser (1) is changed into a sine wave signal overlapped with a fixed direct current bias, and the gas concentration measurement of the detected gas is calibrated according to the relation between a second harmonic wave and a fundamental wave component extracted from a light intensity response signal generated by the sine wave signal according to the Beer-Lambert law.
9. The TDLAS based gas detection self-calibration method of claim 6, wherein:
and in the process of changing the dynamic signal into the sine wave signal, controlling the sine wave signal to be equal to the current value corresponding to the third moment, and then carrying out concentration calibration according to the relationship between the second harmonic and the fundamental wave component extracted by the light intensity response signal.
10. The TDLAS based gas detection self-calibration method of claim 9, wherein:
and after the concentration calibration is carried out, separating the gas detection self-calibration system from the TDLAS gas detection system, and controlling the TDLAS gas detection system to detect the detected gas.
CN202310370437.3A 2023-04-07 2023-04-07 TDLAS-based gas detection self-calibration system and method Pending CN116448704A (en)

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CN202310370437.3A CN116448704A (en) 2023-04-07 2023-04-07 TDLAS-based gas detection self-calibration system and method

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