CN107014774A - A kind of double air chamber trace gas analysis systems and gas concentration in parallel calculate method - Google Patents
A kind of double air chamber trace gas analysis systems and gas concentration in parallel calculate method Download PDFInfo
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- CN107014774A CN107014774A CN201710435871.XA CN201710435871A CN107014774A CN 107014774 A CN107014774 A CN 107014774A CN 201710435871 A CN201710435871 A CN 201710435871A CN 107014774 A CN107014774 A CN 107014774A
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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
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
Abstract
The present invention proposes a kind of double air chamber trace gas analysis systems in parallel, it is characterised in that comprising circuit module, optical module and gas path module, and laser drive circuit and digital temperature control module are connected to laser；Laser is divided into the laser light incident interface that two beams are connected to standard air chamber and sample gas air chamber by optical fiber respectively by beam splitter；Optical fiber is connected to standard air chamber and the laser emitting interface of sample gas air chamber is respectively connecting to the second collimation plus lens and the 3rd collimation plus lens by optical fiber；First photodiode detector is connected to the first pre-amplification circuit, and the second photodiode detector is connected to the second pre-amplification circuit.This invention removes the influence of the destabilizing factor to gas analysis result such as laser wavelength drift in TDLAS technologies and temperature, pressure change, serious forgiveness of the system to laser performance and the adaptive faculty to environment are improved.
Description
Technical field
Method is calculated the present invention relates to a kind of double air chamber trace gas analysis systems and gas concentration in parallel.
Background technology
Tunable diode laser absorption spectroscopy method (TDLAS, Tunable Diode Laser Absorption
Spectroscopy it is) a kind of technology for being widely used in trace gas concentration detection, is widely used in petrochemical industry, environment
The fields such as detection, biological medicine, Aero-Space, having the advantages that selectivity, good, precision is high, real-time noncontact.TDLAS technology bases
In molecular absorption spectrum principle, because the vibration mode of gas with various molecule causes molecule to absorb the laser of specific wavelength, than
Erlang wins (Beer-Lambert) law, i.e., when the laser of a branch of specific wavelength contains the absorption of object gas by certain length
Chi Hou, the decay intensity of its output intensity relation proportional to the concentration of gas.In actual applications, the driving current of laser
Increase high frequency sinusoidal modulates electric current to reduce the interference of low-frequency noise, improve measurement accuracy, can be proved by mathematical computations,
Under the conditions of certain environment, the signal height of the second harmonic signal of spectral signal and the concentration of under test gas and absorption cell light path into
Direct ratio.
Often only one of which analyzes air chamber to existing TDLAS systems, and under test gas is irradiated shape in the air chamber by laser
Into corresponding spectral signal, but property due to gas in itself is influenceed by temperature and pressure, and the gas of same concentrations is not
Absorption spectrum broadening and height under synthermal is all different, therefore generally needs to carry out constant temperature heat tracing processing to air chamber, adds suction
Receive spectral line positioning and temperature adjustmemt scheduling algorithm reduces the influence of destabilizing factor, and the tunable semiconductor that system is used
(DFB) laser, all has higher requirements to laser breadth of spectrum line, side mode suppression ratio and stability, this laser price compared with
For costliness.To sum up, the application of constant temperature system, precision components and correction algorithm can greatly improve the cost of equipment, increase equipment
Volume, it is often more important that the determination of various corrected parameters needs a large amount of nominal data accumulation, can not be completely secured on long terms
Measure the accuracy of concentration.
The content of the invention
The present invention proposes a kind of double air chamber trace gas analysis systems and computational methods method in parallel, eliminates TDLAS skills
The influence of the destabilizing factor to gas analysis result such as laser wavelength drift and temperature, pressure change in art, improves system to swashing
The serious forgiveness and the adaptive faculty to environment of light device performance.
What the present invention was realized particular by following technical scheme：
A kind of double air chamber trace gas analysis systems in parallel, comprising circuit module, optical module and gas path module,
The circuit module is divided into control circuit, signal processing circuit and data processing unit, and the control circuit includes
Modulation waveform generator, laser drive circuit and digital temperature control module, the modulation waveform generator and laser drive circuit phase
Even；The signal processing circuit includes the first process circuit and second processing circuit, and first process circuit includes connecting successively
The first pre-amplification circuit, the first filter circuit, the first lock-in amplifier connect；The second processing circuit is included successively respectively
The second pre-amplification circuit, the second filter circuit, the second lock-in amplifier of connection；First filter circuit, the first lock phase
Amplifier, the second filter circuit, the second lock-in amplifier are connected to data processing unit；The modulation waveform generator difference
It is connected to the first lock-in amplifier, the second lock-in amplifier；
The optical module include laser, first collimation plus lens, beam splitter, the first photodiode detector,
Second photodiode detector, the second collimation plus lens and the 3rd collimation plus lens, the laser, the first collimation converge
Poly- lens, beam splitter coordinate installation successively；First photodiode detector and the second collimation plus lens, which coordinate, to be installed；
Second photodiode detector and the 3rd collimation plus lens, which coordinate, to be installed；
The gas path module includes the standard air chamber and sample gas air chamber being set up in parallel, standard air chamber and sample the gas air chamber
One end is respectively equipped with laser light incident interface and laser emitting interface, and the other end is provided with speculum, and what laser light incident interface was accessed swashs
Light is projected after speculum from laser emitting interface；
The laser drive circuit and digital temperature control module are connected to laser；Laser is divided into two beams by the beam splitter
The laser light incident interface of standard air chamber and sample gas air chamber is connected to by optical fiber respectively；The optical fiber is connected to standard air chamber and sample
The laser emitting interface of gas air chamber is respectively connecting to the second collimation plus lens and the 3rd collimation plus lens by optical fiber；It is described
First photodiode detector is connected to the first pre-amplification circuit, and second photodiode detector is connected to second
Pre-amplification circuit.
A kind of gas concentration of double air chamber trace gas analysis systems in parallel calculates method, comprises the following steps：
S1：Standard air chamber encapsulates the calibrating gas of concentration known, and sample gas air chamber is passed through under test gas；
S2：Adjust modulation waveform generator, it is tuned after laser transmitting laser intensity be I0(v) it is, accurate by first
It is divided into laser intensity by beam splitter for I after straight plus lens collimation convergence1And I (v)2(v) two-way, wherein laser intensity are I1
(v) it is L that laser enters light path by the laser light incident interface of standard air chamber1Standard air chamber, with the concentration encapsulated in air chamber
For C1Calibrating gas act on and be reflected by a reflector, projected from the laser emitting interface of standard air chamber, the spectral signal of formation
Introduced the first photodiode detector by optical fiber and the second collimation plus lens and received；Laser intensity is I2(v) laser leads to
The laser light incident interface for crossing sample gas air chamber enters light path for L2Sample gas air chamber, with concentration in air chamber be C2Under test gas effect
And be reflected by a reflector, projected from the laser emitting interface of sample gas air chamber, the spectral signal of formation is converged by optical fiber and the 3rd collimation
Poly- lens introduce the second photodiode detector and received；
S3：The optical signal of above-mentioned first photodiode detector is respectively through the first pre-amplification circuit, the first filtering
Circuit, the first lock-in amplifier obtain second harmonic, are used as reference signal；The optical signal of above-mentioned second photodiode detector
Second harmonic is obtained respectively through the second pre-amplification circuit, the second filter circuit, the second lock-in amplifier, letter to be measured is used as
Number；
S4：The reference signal and measured signal of the second harmonic relatively obtained by data processing unit, calculate and treat
Survey the concentration of gas.
Computational methods in above-mentioned steps S4 are：
S4.1：Calculate the actual current i (t) that laser drive circuit provides for laser：
I (t)=ic+imcosωt (I)
In public formula (I), icRepresent the central current of laser drive circuit, imRepresent the current-modulation of modulation waveform generator
Amplitude, ω represents modulating frequency, and t represents the time；
Calculate the actual frequency v (t) that laser sends laser：
V (t)=vc+vmcosωt (II)
In public formula (II), vcRepresent laser emitting light center frequency, vmRepresent frequency modulation(PFM) amplitude；
S4.2：The second harmonic waveform of nondimensionalization is set up, mathematical computations can be obtained：The ripple of the second harmonic extracted
Shape A0(v) it can be written as：
Wherein, I0(v) incident intensity that frequency is v is represented；C represents the concentration of tested component, and L represents light beam in gas
The light path passed by, α (v) represents the absorption cross-section of gas at frequency v, relevant with temperature T and pressure P, secondary after nondimensionalization
Harmonic amplitude, i.e. peak height are directly proportional to concentration of component to be measured；
S4.3：It is according to the second harmonic waveform that public formula (III) can obtain reference signal：
The second harmonic waveform of measured signal is：
It can be obtained with reference to public formula (IV) and (V)：
S4.4：Only need to extract the central light strength I that the amplitude A and detector of second harmonic are detected in practical application, i.e.,
For：
Wherein I1To enter the laser intensity of standard air chamber, I2To enter the laser intensity of sample gas air chamber, A1To obtain
Second harmonic reference signal value, A2For the measured signal value of obtained second harmonic,
Above-mentioned formula (VII) is the concentration calculation formula of under test gas.
What the present invention was produced has the beneficial effect that：Because the beam splitting laser entered in two air chambers comes from same light source, wavelength
Drift there is uniformity, therefore the influence to reference signal and measured signal is synchronous；In addition, at double air chamber structures in parallel
Under same environment temperature, gas intensity of variation relative with the curve of spectrum of sample gas is consistent.To sum up, even if laser ripple
Long drift or environment temperature change, and have reference signal all the time to assess the influence of these destabilizing factors in real time, so as to realize
To the exact inversion of gas concentration to be measured.
Brief description of the drawings
In order to illustrate more clearly about the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing
There is the accompanying drawing used required in technology description to be briefly described, it should be apparent that, drawings in the following description are only this
Some embodiments of invention, for those of ordinary skill in the art, on the premise of not paying creative work, can be with
Other accompanying drawings are obtained according to these accompanying drawings.
Fig. 1 is the structure principle chart of the analysis system of the present invention.
Fig. 2 is the second harmonic oscillogram of nondimensionalization.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete
Site preparation is described, it is clear that described embodiment is only a part of embodiment of the invention, rather than whole embodiments.It is based on
Embodiment in the present invention, it is every other that those of ordinary skill in the art are obtained under the premise of creative work is not made
Embodiment, belongs to the scope of protection of the invention.
A kind of double air chamber trace gas analysis systems in parallel, include circuit module 1, optical module 2 and gas circuit as shown in Figure 1
Module 3,
1 point of the circuit module is control circuit 1.1, signal processing circuit 1.2 and data processing unit 1.3, the control
Circuit 1.1 processed includes modulation waveform generator 1.1.1, laser drive circuit 1.1.2 and digital temperature control module 1.1.3, the tune
Waveform generator 1.1.1 processed is connected with laser drive circuit 1.1.2；The signal processing circuit 1.2 includes the first process circuit
1.2.1 with second processing circuit 1.2.2, the first process circuit 1.2.1 includes the first pre-amplification circuit being sequentially connected
1.2.1.1, the first filter circuit 1.2.1.2, the first lock-in amplifier 1.2.1.3；The second processing circuit 1.2.2 is wrapped respectively
Include the second pre-amplification circuit 1.2.2.1 being sequentially connected, the second filter circuit 1.2.2.2, the second lock-in amplifier
1.2.2.3；The first filter circuit 1.2.1.2, the first lock-in amplifier 1.2.1.3, the second filter circuit 1.2.2.2,
Two lock-in amplifier 1.2.2.3 are connected to data processing unit 1.3；The modulation waveform generator 1.1.1 is respectively connecting to
First lock-in amplifier 1.2.1.3, the second lock-in amplifier 1.2.2.3；
The optical module 2 includes the collimation of laser 2.1, first plus lens 2.2, beam splitter 2.3, the pole of the first photoelectricity two
Pipe detector 2.5, the second photodiode detector 2.6, second collimation collimation plus lens 2.8 of plus lens 2.7 and the 3rd,
The collimation of laser 2.1, first plus lens 2.2, beam splitter 2.3 coordinate installation successively；First photodiode is visited
Survey the collimation plus lens 2.7 of device 2.5 and second and coordinate installation；The collimation of second photodiode detector 2.6 and the 3rd converges
Poly- lens 2.8, which coordinate, to be installed；
The gas path module 3 includes the standard air chamber 3.1 and sample gas air chamber 3.2 being set up in parallel, the He of standard air chamber 3.1
One end of sample gas air chamber 3.2 is respectively equipped with laser light incident interface and laser emitting interface, and the other end is provided with speculum 3.3, laser
The laser of incident interface access is projected after speculum 3.3 from laser emitting interface；
The laser drive circuit 1.1.2 and numeral temperature control module 1.1.3 are connected to laser 2.1；The beam splitter
Laser is divided into the laser light incident interface that two beams are connected to standard air chamber 3.1 and sample gas air chamber 3.2 by optical fiber respectively by 2.3；Institute
State that optical fiber is connected to standard air chamber 3.1 and the laser emitting interface of sample gas air chamber 3.2 is respectively connecting to the second collimation by optical fiber
Plus lens 2.7 and the 3rd collimates plus lens 2.8；First photodiode detector 2.5 is put before being connected to first
Big circuit 1.2.1.1, second photodiode detector 2.6 is connected to the second pre-amplification circuit 1.2.2.1.
A kind of gas concentration of double air chamber trace gas analysis systems in parallel calculates method, comprises the following steps：
S1：Standard air chamber 3.1 encapsulates the calibrating gas of concentration known, and sample gas air chamber 3.2 is passed through under test gas；
S2：Adjust modulation waveform generator 1.1.1, it is tuned after the laser intensity launched of laser 2.1 be I0(v),
By first collimation plus lens 2.2 collimate convergence after by beam splitter 2.3 points be that laser intensity is I1And I (v)2(v) two-way, its
Middle laser intensity is I1(v) it is L that laser enters light path by the laser light incident interface of standard air chamber 3.11Standard air chamber 3.1,
It is C with the concentration that is encapsulated in air chamber1Calibrating gas act on and be reflected by a reflector, connect from the laser emitting of standard air chamber 3.1
Mouth is projected, and the spectral signal of formation is introduced the first photodiode detector 2.5 and connect by optical fiber and the second collimation plus lens 2.7
Receive；Laser intensity is I2(v) it is L that laser enters light path by the laser light incident interface of sample gas air chamber 3.22Sample gas air chamber
Concentration is C in 3.2, with air chamber2Under test gas act on and be reflected by a reflector, from the laser emitting interface of sample gas air chamber 3.2
Project, the spectral signal of formation is introduced the second photodiode detector 2.6 and connect by optical fiber and the 3rd collimation plus lens 2.8
Receive；
S3：The optical signal of above-mentioned first photodiode detector 2.5 is respectively through the first pre-amplification circuit
1.2.1.1, the first filter circuit 1.2.1.2, the first lock-in amplifier 1.2.1.3 obtain second harmonic, are used as reference signal；On
The optical signal of the second photodiode detector 2.6 is stated respectively through the second pre-amplification circuit 1.2.2.1, the second filter circuit
1.2.2.2, the second lock-in amplifier 1.2.2.3 obtains second harmonic, is used as measured signal；
S4：Compare the reference signal and measured signal of obtained second harmonic by data processing unit 1.3, calculate
The concentration of under test gas.
Computational methods in above-mentioned steps S4 are：
S4.1：It is the actual current i (t) that laser 2.1 is provided to calculate laser drive circuit 1.1.2：
I (t)=ic+imcosωt (I)
In public formula (I), icRepresent the central current of laser drive circuit, imRepresent the current-modulation of modulation waveform generator
Amplitude, ω represents modulating frequency, and t represents the time；
Calculate the actual frequency v (t) that laser 2.1 sends laser：
V (t)=vc+vmcosωt (II)
In public formula (II), vcRepresent laser emitting light center frequency, vmRepresent frequency modulation(PFM) amplitude；
S4.2：The second harmonic waveform of nondimensionalization is as shown in Fig. 2 mathematical computations can be obtained：That extracts is secondary humorous
The waveform A of ripple0(v) it can be written as：
Wherein, I0(v) incident intensity that frequency is v is represented；C represents the concentration of tested component, and L represents light beam in gas
The light path passed by, α (v) represents the absorption cross-section of gas at frequency v, relevant with temperature T and pressure P, secondary after nondimensionalization
Harmonic amplitude, i.e. peak height are directly proportional to concentration of component to be measured；
S4.3：It is according to the second harmonic waveform that public formula (III) can obtain reference signal：
The second harmonic waveform of measured signal is：
It can be obtained with reference to public formula (IV) and (V)：
S4.4：Only need to extract the central light strength I that the amplitude A and detector of second harmonic are detected in practical application, i.e.,
For：
Wherein I1To enter the laser intensity of standard air chamber, I2To enter the laser intensity of sample gas air chamber, A1To obtain
Second harmonic reference signal value, A2For the measured signal value of obtained second harmonic,
Above-mentioned formula (VII) is the concentration calculation formula of under test gas.
Factor alpha not related to environmental condition in public formula (VII), also eliminates the ν related to laser performance, remaining
Item is known terms and can survey item.Therefore use after this double air chamber structures in parallel, can be straight in inverting under test gas concentration
Connect and carry out ratio calculating using reference signal, eliminate the shadow of the destabilizing factor such as laser wavelength drift and temperature, pressure change
Ring, improve serious forgiveness of the system to laser performance and the adaptive faculty to environment.
Laser drive circuit provides tuning and high frequency modulated electric current for laser in the present invention, and the control of digital temperature control module swashs
The temperature of light device and detector.Laser drive circuit control laser sends the laser of certain frequency, and laser is saturating by the first collimation
Enter beam splitter after mirror convergence, then be introduced between by optical fiber in double air chamber structures in parallel；One of air chamber is used as reference gas
Room, for encapsulating certain density calibrating gas, another air chamber is passed through under test gas as sample gas air chamber with certain flow；
The same laser of two bundle natures is reflected by a reflector light echo in different air chambers after calibrating gas and under test gas are acted on
Fibre, is received after convergence by respective photodiode detector；The optical signal that two detectors are received passes through respective letter
After the amplification of number process circuit, filtering and lock phase processor, reference signal and measured signal are respectively obtained；Eventually pass analysis system fortune
Calculate the concentration information that inverting obtains under test gas.The system simplifies system and calculated without temperature correction coefficient and peak value tracking function
Method and demarcation flow, it is to avoid the inaccurate interference to measurement result of correction factor.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all essences in the present invention
God is with principle, and any modification, equivalent substitution and improvements made etc. should be included in the scope of the protection.
Claims (3)
1. a kind of in parallel double air chamber trace gas analysis systems, it is characterised in that comprising circuit module (1), optical module (2) and
Gas path module (3),
The circuit module (1) is divided into control circuit (1.1), signal processing circuit (1.2) and data processing unit (1.3), institute
Stating control circuit (1.1) includes modulation waveform generator (1.1.1), laser drive circuit (1.1.2) and digital temperature control module
(1.1.3), the modulation waveform generator (1.1.1) is connected with laser drive circuit (1.1.2)；The signal processing circuit
(1.2) the first process circuit (1.2.1) and second processing circuit (1.2.2) are included, first process circuit (1.2.1) includes
The first pre-amplification circuit (1.2.1.1), the first filter circuit (1.2.1.2), the first lock-in amplifier being sequentially connected
(1.2.1.3)；The second processing circuit (1.2.2) respectively include be sequentially connected the second pre-amplification circuit (1.2.2.1),
Second filter circuit (1.2.2.2), the second lock-in amplifier (1.2.2.3)；First filter circuit (1.2.1.2), first
Lock-in amplifier (1.2.1.3), the second filter circuit (1.2.2.2), the second lock-in amplifier (1.2.2.3) are connected to data
Processing unit (1.3)；The modulation waveform generator (1.1.1) is respectively connecting to the first lock-in amplifier (1.2.1.3), second
Lock-in amplifier (1.2.2.3)；
The optical module (2) includes laser (2.1), the first collimation plus lens (2.2), beam splitter (2.3), the first photoelectricity
Diode detector (2.5), the second photodiode detector (2.6), the second collimation plus lens (2.7) and the 3rd collimation converge
Poly- lens (2.8), the laser (2.1), the first collimation plus lens (2.2), beam splitter (2.3) coordinate installation successively；Institute
State the first photodiode detector (2.5) and the second collimation plus lens (2.7) coordinates installation；Second photodiode
Detector (2.6) and the 3rd collimation plus lens (2.8), which coordinate, to be installed；
The gas path module (3) includes the standard air chamber (3.1) and sample gas air chamber (3.2) being set up in parallel, the standard air chamber
(3.1) and one end of sample gas air chamber (3.2) is respectively equipped with laser light incident interface and laser emitting interface, the other end is provided with speculum
(3.3), the laser of laser light incident interface access is projected after speculum (3.3) from laser emitting interface；
The laser drive circuit (1.1.2) and digital temperature control module (1.1.3) are connected to laser (2.1)；The beam splitting
Laser is divided into the laser light incident that two beams are connected to standard air chamber (3.1) and sample gas air chamber (3.2) by optical fiber respectively by device (2.3)
Interface；The optical fiber is connected to standard air chamber (3.1) and the laser emitting interface of sample gas air chamber (3.2) is connected respectively by optical fiber
To the second collimation plus lens (2.7) and the 3rd collimation plus lens (2.8)；First photodiode detector (2.5)
The first pre-amplification circuit (1.2.1.1) is connected to, second photodiode detector (2.6) is put before being connected to second
Big circuit (1.2.2.1).
2. a kind of gas concentration of the double air chamber trace gas analysis systems of the parallel connection of utilization claim 1 calculates method, its feature
It is, comprises the following steps：
S1：Standard air chamber (3.1) encapsulates the calibrating gas of concentration known, and sample gas air chamber (3.2) is passed through under test gas；
S2：Adjust modulation waveform generator (1.1.1), it is tuned after laser (2.1) transmitting laser intensity be I0(v), quilt
It is divided into laser intensity by beam splitter (2.3) for I after first collimation plus lens (2.2) collimation convergence1And I (v)2(v) two-way,
Wherein laser intensity is I1(v) it is L that laser enters light path by the laser light incident interface of standard air chamber (3.1)1Standard air chamber
(3.1) it is, C with the concentration that is encapsulated in air chamber1Calibrating gas act on and be reflected by a reflector, from standard air chamber (3.1) swash
Light outgoing interface is projected, and the spectral signal of formation introduces the first photodiode by optical fiber and the second collimation plus lens (2.7)
Detector (2.5) is received；Laser intensity is I2(v) laser enters light path by the laser light incident interface of sample gas air chamber (3.2)
For L2Sample gas air chamber (3.2), with concentration in air chamber be C2Under test gas act on and be reflected by a reflector, from sample gas air chamber
(3.2) laser emitting interface is projected, and the spectral signal of formation introduces the second light by optical fiber and the 3rd collimation plus lens (2.8)
Electric diode detector (2.6) is received；
S3：The optical signal of above-mentioned first photodiode detector (2.5) is respectively through the first pre-amplification circuit
(1.2.1.1), the first filter circuit (1.2.1.2), the first lock-in amplifier (1.2.1.3) obtain second harmonic, are used as reference
Signal；The optical signal of above-mentioned second photodiode detector (2.6) respectively through the second pre-amplification circuit (1.2.2.1),
Second filter circuit (1.2.2.2), the second lock-in amplifier (1.2.2.3) obtain second harmonic, are used as measured signal；
S4：Compare the reference signal and measured signal of obtained second harmonic by data processing unit (1.3), calculate and treat
Survey the concentration of gas.
3. a kind of gas concentration of double air chamber trace gas analysis systems in parallel as claimed in claim 2 calculates method, it is special
Levy and be, the computational methods in above-mentioned steps S4 are：
S4.1：It is the actual current i (t) that laser (2.1) is provided to calculate laser drive circuit (1.1.2)：
I (t)=ic+imcosωt (I)
In public formula (I), icRepresent the central current of laser drive circuit, imThe current-modulation amplitude of modulation waveform generator is represented,
ω represents modulating frequency, and t represents the time；
Calculate the actual frequency v (t) that laser (2.1) sends laser：
V (t)=vc+vmcosωt (II)
In public formula (II), vcRepresent laser emitting light center frequency, vmRepresent frequency modulation(PFM) amplitude；
S4.2：The second harmonic waveform of nondimensionalization is set up, mathematical computations can be obtained：The waveform A of the second harmonic extracted0
(v) it can be written as：
Wherein, I0(v) incident intensity that frequency is v is represented；C represents the concentration of tested component, and L represents that light beam is passed by gas
Light path, α (v) represents the absorption cross-section of gas at frequency v, second harmonic nondimensionalization after relevant with temperature T and pressure P
Amplitude, i.e. peak height are directly proportional to concentration of component to be measured；
S4.3：It is according to the second harmonic waveform that public formula (III) can obtain reference signal：
The second harmonic waveform of measured signal is：
It can be obtained with reference to public formula (IV) and (V)：
S4.4：Only need to extract the central light strength I that the amplitude A and detector of second harmonic are detected in practical application, be：
Wherein I1To enter the laser intensity of standard air chamber, I2To enter the laser intensity of sample gas air chamber, A1For obtain two
The reference signal value of subharmonic, A2For the measured signal value of obtained second harmonic,
Above-mentioned formula (VII) is the concentration calculation formula of under test gas.
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Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108426813A (en) * | 2018-04-08 | 2018-08-21 | 山东省科学院激光研究所 | Mixed gas concentration detecting system, method and device |
| CN108507976A (en) * | 2018-04-17 | 2018-09-07 | 广东电网有限责任公司 | A kind of CO analyzers based on TDLAS technologies |
| CN108507975A (en) * | 2018-04-17 | 2018-09-07 | 广东电网有限责任公司 | A kind of acetylene analyzer based on TDLAS technologies |
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| CN110057779A (en) * | 2019-04-28 | 2019-07-26 | 西北核技术研究所 | Method and apparatus based on temperature self-compensation TDLAS technology measurement gas concentration |
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| CN110470622A (en) * | 2019-08-28 | 2019-11-19 | 中国科学院长春光学精密机械与物理研究所 | Gas concentration detection method, apparatus and system |
| CN110553987A (en) * | 2019-08-28 | 2019-12-10 | 华中科技大学 | gas detection method and system |
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| CN111781164A (en) * | 2019-04-04 | 2020-10-16 | 深圳米字科技发展有限公司 | Laser detection method for simultaneously analyzing content of acidic components in natural gas |
| CN113029956A (en) * | 2021-03-31 | 2021-06-25 | 中国科学院长春光学精密机械与物理研究所 | Gas concentration detection device and method |
| CN113092410A (en) * | 2021-04-07 | 2021-07-09 | 清华大学 | Multilayer multi-optical-path cavity and electrical insulation equipment running state monitoring system |
| CN113390825A (en) * | 2021-05-17 | 2021-09-14 | 西安理工大学 | TDLAS-based time-frequency domain combined gas concentration inversion method and device |
| CN113406021A (en) * | 2020-03-17 | 2021-09-17 | 山东大学 | Optical frequency comb gas detection system and method based on neural network |
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| CN108426813A (en) * | 2018-04-08 | 2018-08-21 | 山东省科学院激光研究所 | Mixed gas concentration detecting system, method and device |
| CN108507976A (en) * | 2018-04-17 | 2018-09-07 | 广东电网有限责任公司 | A kind of CO analyzers based on TDLAS technologies |
| CN108507975A (en) * | 2018-04-17 | 2018-09-07 | 广东电网有限责任公司 | A kind of acetylene analyzer based on TDLAS technologies |
| CN108535215A (en) * | 2018-04-17 | 2018-09-14 | 广东电网有限责任公司 | A kind of inorganic gas analyzer based on TDLAS technologies |
| CN111781164B (en) * | 2019-04-04 | 2023-04-25 | 武汉米字能源科技有限公司 | Laser detection method for simultaneously analyzing content of acidic components in natural gas |
| CN111781164A (en) * | 2019-04-04 | 2020-10-16 | 深圳米字科技发展有限公司 | Laser detection method for simultaneously analyzing content of acidic components in natural gas |
| CN110231313A (en) * | 2019-04-25 | 2019-09-13 | 光力科技股份有限公司 | A kind of online zero point correction method and device of laser gas analyzer |
| CN110057779A (en) * | 2019-04-28 | 2019-07-26 | 西北核技术研究所 | Method and apparatus based on temperature self-compensation TDLAS technology measurement gas concentration |
| CN110160990A (en) * | 2019-05-30 | 2019-08-23 | 深圳华领气体技术有限公司 | Trace gas and its isotope real time on-line detection device |
| CN110470622B (en) * | 2019-08-28 | 2020-09-08 | 中国科学院长春光学精密机械与物理研究所 | Gas concentration detection method, device and system |
| CN110553987A (en) * | 2019-08-28 | 2019-12-10 | 华中科技大学 | gas detection method and system |
| CN110470622A (en) * | 2019-08-28 | 2019-11-19 | 中国科学院长春光学精密机械与物理研究所 | Gas concentration detection method, apparatus and system |
| CN110470623A (en) * | 2019-08-28 | 2019-11-19 | 中国科学院长春光学精密机械与物理研究所 | Gas concentration detection system |
| CN113406021A (en) * | 2020-03-17 | 2021-09-17 | 山东大学 | Optical frequency comb gas detection system and method based on neural network |
| CN111707634A (en) * | 2020-06-30 | 2020-09-25 | 华南理工大学 | Multi-channel gas concentration detection system and method based on mid-infrared absorption spectrum |
| CN111707634B (en) * | 2020-06-30 | 2024-04-19 | 华南理工大学 | Multichannel gas concentration detection system and method based on mid-infrared absorption spectrum |
| CN113029956A (en) * | 2021-03-31 | 2021-06-25 | 中国科学院长春光学精密机械与物理研究所 | Gas concentration detection device and method |
| CN113092410A (en) * | 2021-04-07 | 2021-07-09 | 清华大学 | Multilayer multi-optical-path cavity and electrical insulation equipment running state monitoring system |
| CN113390825A (en) * | 2021-05-17 | 2021-09-14 | 西安理工大学 | TDLAS-based time-frequency domain combined gas concentration inversion method and device |
| CN114235655A (en) * | 2021-12-17 | 2022-03-25 | 数量级(上海)信息技术有限公司 | Novel laser PM sensor and method for monitoring PM in field to be measured |
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