CN107084946A - The method that phase difference eliminates second harmonic residual amplitude modulation is locked based on two-way - Google Patents
The method that phase difference eliminates second harmonic residual amplitude modulation is locked based on two-way Download PDFInfo
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- CN107084946A CN107084946A CN201710327064.6A CN201710327064A CN107084946A CN 107084946 A CN107084946 A CN 107084946A CN 201710327064 A CN201710327064 A CN 201710327064A CN 107084946 A CN107084946 A CN 107084946A
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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
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
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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
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
- H03L7/093—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using special filtering or amplification characteristics in the loop
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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
- G01N2021/3196—Correlating located peaks in spectrum with reference data, e.g. fingerprint data
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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
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
- G01N2021/391—Intracavity sample
Abstract
The method that phase difference eliminates second harmonic residual amplitude modulation is locked based on two-way, belong to optical fiber gas sensing technology for detection field, the system includes Distributed Feedback Laser, air chamber, coupler, photodetector, operational amplifier, signal generator, lock-in amplifier, subtracter, oscillograph etc..Distributed Feedback Laser is used as light source, the light that it sends is after air chamber absorbs, it is divided into two by coupler, respectively enter two photodetectors, signal is input to lock-in amplifier with phase for η reference signal all the way is used for the demodulation to gas concentration, and another road signal is input to lock-in amplifier with phase for φ reference signal is used for the measurement of residual amplitude modulation, then by subtracter, the second harmonic signal without residual amplitude modulation is obtained, and is shown on oscillograph.The method can be effectively eliminated in the case where ensureing that signal amplitude is constant to residual amplitude modulation, it is ensured that signal to noise ratio is not reduced.
Description
Technical field
The present invention relates to a kind of signal processing technology, specifically be a kind of second harmonic to be eliminated based on two-way lock phase difference
The method of residual amplitude modulation.Belong to optical fiber gas sensing detection technique field.
Background technology
The detection of trace gas, now in multi-field extensive use, includes metallurgy, oil, chemical industry, electronics, electric power, spinning
Knit, medicine, food, timber, papermaking, building, air-conditioning, even nuclear energy and aerospace industry.And at present to Trace gas detection
Most efficient method is wavelength modulation spectrum technology, and wavelength modulation spectrum technology is to carry out second harmonic by phase lock amplifying technology
Extraction carry out gas concentration detection, there is higher sensitivity compared to other detection methods, higher signal to noise ratio, and
Absorption line baseline is 0, but when laser wavelength is modulated, often along with intensity modulated, causes luminous power
Rise and fall, and then cause second harmonic to distort, this phenomenon is referred to as residual amplitude modulation.Residual amplitude modulation can influence secondary humorous
The baseline of ripple, causes the component of second harmonic impure, shows on second harmonic waveform to be exactly asymmetry, influence measurement
Accuracy.Therefore problem above is solved in the urgent need to a kind of method.
Zhu Cunguang in paper " TDLAS line distortions mechanism of production is studied with alignment technique ", (discuss by Shandong University's doctorate
2015 P101-115 of text) in propose it is a kind of based on electrooptic modulator build a kind of invariable power continuous wavelength modulated light source enter
Row Wavelength modulation spectroscopy is detected to eliminate residual amplitude modulation, can effectively canceled out by the external modulation of electrooptic modulator
The useless optical power modulation produced is modulated with semiconductor laser wavelength, and then eliminates residual amplitude modulation.But it is above-mentioned
Method is that residual amplitude modulation is eliminated with victim signal amplitude, and signal to noise ratio is substantially reduced, and is unfavorable for the detection of signal.
In order to improve the degree of accuracy of measurement, it is ensured that signal to noise ratio does not reduce, it is badly in need of one kind and effectively eliminates residual amplitude modulation
Method.
The content of the invention
In order to overcome the defect and deficiency of prior art, the present invention proposes a kind of secondary based on two-way lock phase difference elimination
The method of harmonic wave residual amplitude modulation, this method can eliminate residual amplitude modulation on the premise of ensureing not reducing signal to noise ratio.
The technical scheme is that realize in the following manner：
It is a kind of that the method that phase difference eliminates second harmonic residual amplitude modulation is locked based on two-way, realized by following system,
The system include single-chip microcomputer a, single-chip microcomputer b, adder, temperature control module, Distributed Feedback Laser, air chamber, coupler, photodetector a,
Photodetector b, operational amplifier, signal generator, lock-in amplifier a, lock-in amplifier b, subtracter, oscillograph, monolithic
Machine a and single-chip microcomputer b are connected respectively to two inputs of adder, the primary modulation Signal averaging single-chip microcomputer b that single-chip microcomputer a is produced
The low-frequency sweep signal of generation is added by adder as drive signal, is used as drive signal；Adder output and DFB
Laser is connected, and its output current is used as the driving current for controlling Distributed Feedback Laser；Temperature control module be connected to Distributed Feedback Laser with
The temperature of Distributed Feedback Laser is controlled, the output end of Distributed Feedback Laser is connected by optical fiber with air chamber, and air chamber is connected to by optical fiber
Coupler, two output ends of coupler are connected respectively to photodetector a and photodetector b, photodetector a through optical fiber
Output end is connected with a lock-in amplifier a input, photodetector b output end and the one of operational amplifier it is defeated
Enter end to be connected, signal generator is connected respectively to another input of lock-in amplifier a and operational amplifier, operation amplifier
The output end of device is connected to lock-in amplifier b input, and lock-in amplifier a and lock-in amplifier b output end are connected respectively
To two inputs of subtracter, the output end of subtracter is connected with oscillograph, as follows the step of this method：
1) said system is connected, circuit and oscillograph power supply is opened, under test gas is injected in air chamber；
2) single-chip microcomputer a is made to produce high-frequency modulation signal；Single-chip microcomputer b produces low-frequency sweep signal, high-frequency modulation signal and low
Frequency scanning signal after adder is added as drive signal to control the driving current of laser, temperature control module control temperature
Degree, adjustment signal generator sends the signal that phase is η and φ respectively so that this signal frequency is the height produced by single-chip microcomputer a
Two times of frequency signal, to be used as lock-in amplifier a and lock-in amplifier b reference signal；
3) light that laser is sent is divided into two-way after air chamber absorbs by coupler, by photodetector a and
Optical signal is respectively converted into two path signal by photodetector b, and being directly entered lock with phase for η reference signals all the way mutually amplifies
Device a, for being demodulated to signal, the amplitude of the second harmonic signal of output represents the size of gas concentration, and another road is with phase
φ reference signal first passes through operational amplifier adjustment, enters back into lock-in amplifier b, the signal magnitude of output is represent by once
The size of residual amplitude modulation caused by harmonic wave and triple-frequency harmonics, is consecutively connected to lock-in amplifier a by oscillograph and is mutually put with lock
Whether there is second harmonic signal and the residual amplitude modulation signal in odd symmetry on big device b output end, observation oscilloscope, if
It is to carry out next step, if not then inputting two paths of signals to check that two locks are mutually put with lock-in amplifier b to lock-in amplifier a
The phase-locked function of big device, adjusts lock-in amplifier a and lock-in amplifier b parameter setting, until occur second harmonic signal and
In the residual amplitude modulation signal of odd symmetry, next step is then carried out；
4) subtracted each other by lock-in amplifier a and the b two paths of signals exported into subtracter, oscillograph is connected to subtracter
Output end, the then display output signal on oscillograph, by adjusting operational amplifier, changes the times magnification of operational amplifier
Number changes the size of second road signal, and output signal is observed on oscillograph, until two sides of output signal observed
The lower peak value on side is equal in magnitude, now obtains the second harmonic signal without residual amplitude modulation；
5) signal transacting is finished, and closes power supply.
The principle that the present invention is used is as follows：
Absorption of the under test gas that the light that laser is sent passes through in air chamber, air chamber to light follows Beer-lambert and determined
Rule：
I (ν)=I0(ν)·exp[-α(ν)·C·L] (1)
Wherein α (ν) is absorption coefficient, and ν is light frequency, and C is under test gas concentration, and L is to absorb light path, I0(ν) is incident
Light intensity, I (ν) is transmitted light intensity.
By splitting ratio 1:After 11 × 2 coupler light splitting, the light intensity of two-way light is respectively I1(ν),I2(ν)：
Wherein α is the cavity loss of air chamber, and β is the transmitance of coupler.
In wavelength modulation spectrum technology, we are generally believed with a low frequency ramp sweep signal and high_frequency sine wave modulation
Number superposition is driven semiconductor laser, and the frequency and amplitude of the light of laser output can be written as：
ν=νs+δν·cos(ωt-ψ) (3)
I0(ν)=Is(ν)+ΔI·cos(ωt) (4)
νs, Is(ν) is the frequency and intensity of the corresponding light of low frequency ramp sweep signal, and δ ν and Δ I are high_frequency sine wave modulation
The frequency and intensity of the corresponding light of signal, Ψ is the phase difference of intensity modulated and wavelength modulation.
As α (ν) CL<<When 1, formula (2) can be expressed as：
Absorption coefficient (ν) can be expressed as：
α0(α0=S/ π γ) and ν0It is the absorption coefficient and light frequency of Absorption Line center, S is absorption line intensity, and γ is to inhale
The high half width of take-up half, modulation factor m=δ ν/γ, makes x (ν)=(νs-ν0)/γ, θ=ω t- Ψ, by absorption coefficient (ν) Fu
In leaf expand into：
Wherein a0And anThe coefficient of Fourier expansion formula is represented, formula (7) is substituted into formula (5) obtains：
It is used for gas concentration measurement to extract second harmonic, frequency need to be added to lock-in amplifier and is believed for 2 ω t reference
Number, there are the two-way reference signal that signal generator is sent different phases to be respectively η and φ, two after lock-in amplifier
Road signal is respectively：
Q1 is second harmonic signal, and q2 is the residual amplitude modulation signal terms as caused by once with triple-frequency harmonics.Adjust η,
Make
Ψ=0 of η+2, signal V1The q1 items of (ν) obtain maximum；φ is adjusted, makes the Ψ of φ+2=pi/2, signal V2The q1 of (ν)
Item is 0.Operational amplifier is adjusted, changes the size of second road signal by changing the multiplication factor of operational amplifier, is adjusted
The factor is ε.Two paths of signals signal after subtracter is：
By adjusting amplifier, change Dynamic gene ε so that two paths of signals residual amplitude modulation signal terms are equal, pass through
After subtracter, the signal that subtracter comes out does not have the influence of residual amplitude modulation signal terms, and signal amplitude is unaffected.
The under test gas of the present invention includes vapor, carbon monoxide, sulfur dioxide, the gas such as methane.
The method that the present invention is used, with simple to operate, the advantages of with low cost.Residual amplitude modulation pair can be completely eliminated
The influence of second harmonic, and the size of signal amplitude is not influenceed, it is ensured that signal to noise ratio is constant.
Brief description of the drawings
Fig. 1 is the system construction drawing of the present invention.
Wherein：1st, single-chip microcomputer a, 2, single-chip microcomputer b, 3, adder, 4, temperature control module, 5, Distributed Feedback Laser, 6, air chamber, 7, coupling
Clutch, 8, photodetector a, 9, photodetector b, 10, signal generator, 11, operational amplifier, 12, lock-in amplifier a,
13rd, lock-in amplifier b, 14, subtracter, 15, oscillograph.
Fig. 2 is the gas concentration signal of lock-in amplifier a outputs, hence it is evident that found out in second harmonic signal containing remaining amplitude
Modulation.
Fig. 3 be lock-in amplifier b output be the residual amplitude modulation as caused by first harmonic and triple-frequency harmonics signal.
Fig. 4 is the second harmonic signal without residual amplitude modulation exported by subtracter, hence it is evident that find out that two paths of signals is passed through
Cross after lock phase difference processing, residual amplitude modulation is completely eliminated.
Embodiment
The invention will be further described with reference to the accompanying drawings and examples, but not limited to this.
Embodiment：
It is a kind of that the method that phase difference eliminates second harmonic residual amplitude modulation is locked based on two-way, realized by following system,
As shown in figure 1, the system includes single-chip microcomputer a 1, single-chip microcomputer b 2, adder 3, temperature control module 4, Distributed Feedback Laser 5, air chamber 6, coupling
Clutch 7, photodetector a 8, photodetector b 9, operational amplifier 10, signal generator 11, lock-in amplifier a 12, lock
Phase amplifier b 13, subtracter 14, oscillograph 15, single-chip microcomputer a and single-chip microcomputer b are connected respectively to two inputs of adder 3,
The low-frequency sweep signal that the primary modulation Signal averaging single-chip microcomputer b that single-chip microcomputer a is produced is produced is as drive signal, by adder
3 are added, and are used as drive signal；The output end of adder 3 is connected with Distributed Feedback Laser 5, and its output current is used as control DFB laser
The driving current of device 5；Temperature control module 4 is connected to Distributed Feedback Laser 5 to control the temperature of Distributed Feedback Laser 5, Distributed Feedback Laser 5 it is defeated
Go out end by optical fiber with air chamber 6 to be connected, air chamber 6 is connected to coupler 7 by optical fiber, and two output ends of coupler 7 are through light
Fibre is connected respectively to photodetector a and photodetector b, photodetector a output ends and lock-in amplifier a an input
End is connected, and photodetector b output end is connected with an input of operational amplifier 10, and signal generator 11 is distinguished
Another input of lock-in amplifier a and operational amplifier 10 is connected to, the output end of operational amplifier 10 is connected to lock phase
Amplifier b input, lock-in amplifier a and lock-in amplifier b output end are connected respectively to two inputs of subtracter 14
End, the output end of subtracter 14 is connected with oscillograph 15, as follows the step of this method：
1) said system is connected, circuit and oscillograph power supply is opened, under test gas is injected in air chamber；
2) single-chip microcomputer a is made to produce high-frequency modulation signal；Single-chip microcomputer b produces low-frequency sweep signal, high-frequency modulation signal and low
Frequency scanning signal after adder is added as drive signal to control the driving current of laser, temperature control module control temperature
Degree, adjustment signal generator sends the signal that phase is η and φ respectively so that this signal frequency is the height produced by single-chip microcomputer a
Two times of frequency signal, to be used as lock-in amplifier a and lock-in amplifier b reference signal；
3) light that laser is sent is divided into two-way after air chamber absorbs by coupler, respectively through photodetection
Device a and photodetector b convert optical signals to two path signal, and being directly entered lock with phase for η reference signals all the way mutually puts
Big device a, for being demodulated to signal, the amplitude of the second harmonic signal of output represents the size of gas concentration, another road and phase
Operational amplifier adjustment is first passed through for φ reference signal, lock-in amplifier b is entered back into, the signal magnitude of output is represent by one
The size of residual amplitude modulation caused by subharmonic and triple-frequency harmonics, lock-in amplifier a and lock phase are consecutively connected to by oscillograph
Whether second harmonic signal and residual amplitude modulation signal in odd symmetry are occurred on amplifier b output end, observation oscilloscope,
If then carrying out next step, if not then checking two lock phases to lock-in amplifier a and lock-in amplifier b input two paths of signals
The phase-locked function of amplifier, adjusts lock-in amplifier a and lock-in amplifier b parameter setting, until there is second harmonic signal
Residual amplitude modulation signal with odd symmetry, then carries out next step, as shown in Figures 2 and 3, hence it is evident that it can be seen that by changing
The multiplication factor of operational amplifier, changes the size of Fig. 3 residual amplitude modulation signals, can eliminate second harmonic in Fig. 2
Residual amplitude modulation；
4) subtracted each other by lock-in amplifier a and the b two paths of signals exported into subtracter, oscillograph is connected to subtracter
Output end, the then display output signal on oscillograph, by adjusting operational amplifier, changes the times magnification of operational amplifier
Number changes the size of second road signal, the observation signal on oscillograph, until two sides of output signal for observing
Lower peak value is equal in magnitude, now obtains the second harmonic signal without residual amplitude modulation；As shown in Figure 4, it can be seen that two
There is no the influence of residual amplitude modulation in rd harmonic signal, and signal amplitude is basically unchanged；
5) signal transacting is finished, and closes power supply.
Claims (1)
1. a kind of lock the method that phase difference eliminates second harmonic residual amplitude modulation based on two-way, realized by following system, should
System includes single-chip microcomputer a, single-chip microcomputer b, adder, temperature control module, Distributed Feedback Laser, air chamber, coupler, photodetector a, light
Electric explorer b, operational amplifier, signal generator, lock-in amplifier a, lock-in amplifier b, subtracter, oscillograph, single-chip microcomputer a
Two inputs of adder are connected respectively to single-chip microcomputer b, the primary modulation Signal averaging single-chip microcomputer b productions that single-chip microcomputer a is produced
Raw low-frequency sweep signal is added by adder as drive signal, is used as drive signal；Adder output and DFB swash
Light device is connected, and its output current is used as the driving current for controlling Distributed Feedback Laser；Temperature control module is connected to Distributed Feedback Laser to control
The temperature of Distributed Feedback Laser processed, the output end of Distributed Feedback Laser is connected by optical fiber with air chamber, and air chamber is connected to coupling by optical fiber
Clutch, two output ends of coupler are connected respectively to photodetector a and photodetector b through optical fiber, and photodetector a is defeated
Go out end with a lock-in amplifier a input to be connected, photodetector b output end and operational amplifier input
End is connected, and signal generator is connected respectively to another input of lock-in amplifier a and operational amplifier, operational amplifier
Output end be connected to lock-in amplifier b input, lock-in amplifier a and lock-in amplifier b output end are connected respectively to
Two inputs of subtracter, the output end of subtracter is connected with oscillograph, as follows the step of this method：
1) said system is connected, circuit and oscillograph power supply is opened, under test gas is injected in air chamber；
2) single-chip microcomputer a is made to produce high-frequency modulation signal；Single-chip microcomputer b produces low-frequency sweep signal, and high-frequency modulation signal and low frequency are swept
Retouch signal after adder is added as drive signal to control the driving current of laser, temperature control module control temperature is adjusted
Entire signal generator sends the signal that phase is η and φ respectively so that this signal frequency is the high-frequency signal produced by single-chip microcomputer a
Two times, to be used as lock-in amplifier a and lock-in amplifier b reference signal；
3) light that laser is sent is divided into two-way after air chamber absorbs by coupler, is visited by photodetector a and photoelectricity
Survey device b and optical signal is respectively converted into two path signal, be all the way that η reference signals are directly entered lock-in amplifier a with phase, use
Demodulated in signal, the amplitude of the second harmonic signal of output represents the size of gas concentration, another road and the ginseng that phase is φ
Examine signal and first pass through operational amplifier adjustment, enter back into lock-in amplifier b, the signal magnitude of output represent by first harmonic and
The size of residual amplitude modulation caused by triple-frequency harmonics, is consecutively connected to lock-in amplifier a's and lock-in amplifier b by oscillograph
Whether second harmonic signal and residual amplitude modulation signal in odd symmetry are occurred on output end, observation oscilloscope, if then entering
Row next step, if not then checking two lock-in amplifiers to lock-in amplifier a and lock-in amplifier b input two paths of signals
The phase-locked function, adjusts lock-in amplifier a and lock-in amplifier b parameter setting, until there is second harmonic signal and in strange right
The residual amplitude modulation signal of title, then carries out next step；
4) subtracted each other by lock-in amplifier a and the b two paths of signals exported into subtracter, oscillograph is connected to the defeated of subtracter
Go out end, then the display output signal on oscillograph, by adjusting operational amplifier, the multiplication factor for changing operational amplifier is come
Change the size of second road signal, output signal is observed on oscillograph, until two sides of output signal for observing
Lower peak value is equal in magnitude, now obtains the second harmonic signal without residual amplitude modulation；
5) signal transacting is finished, and closes power supply.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108279218A (en) * | 2018-02-06 | 2018-07-13 | 山东大学 | The long light path gas-detecting device of light intensity is compensated using erbium-doped fiber amplifier |
| CN108896487A (en) * | 2018-07-05 | 2018-11-27 | 山东大学 | The device and method for correcting optoacoustic secondary system harmonic wave forms and promoting precision |
| CN110987869A (en) * | 2019-12-12 | 2020-04-10 | 华中科技大学 | Integrated optical fiber gas detection system and method |
| CN112666124A (en) * | 2020-12-03 | 2021-04-16 | 山东大学 | Absorption spectrum full-width half-maximum integral gas detection method for complex environment |
| CN109696418B (en) * | 2019-02-27 | 2021-08-10 | 南京科远智慧科技集团股份有限公司 | Heterodyne balance detection system and detection method applied to TDLAS direct absorption method under low signal-to-noise ratio |
| CN115963081A (en) * | 2023-03-16 | 2023-04-14 | 杭州泽天春来科技有限公司 | Gas analyzer |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108279218A (en) * | 2018-02-06 | 2018-07-13 | 山东大学 | The long light path gas-detecting device of light intensity is compensated using erbium-doped fiber amplifier |
| CN108896487A (en) * | 2018-07-05 | 2018-11-27 | 山东大学 | The device and method for correcting optoacoustic secondary system harmonic wave forms and promoting precision |
| CN109696418B (en) * | 2019-02-27 | 2021-08-10 | 南京科远智慧科技集团股份有限公司 | Heterodyne balance detection system and detection method applied to TDLAS direct absorption method under low signal-to-noise ratio |
| CN110987869A (en) * | 2019-12-12 | 2020-04-10 | 华中科技大学 | Integrated optical fiber gas detection system and method |
| CN112666124A (en) * | 2020-12-03 | 2021-04-16 | 山东大学 | Absorption spectrum full-width half-maximum integral gas detection method for complex environment |
| CN115963081A (en) * | 2023-03-16 | 2023-04-14 | 杭州泽天春来科技有限公司 | Gas analyzer |
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| CN107084946B (en) | 2019-08-06 |
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