CN205879783U - Infrared micro - water of high resolution evaporates gas detection and surveys system based on wavelength modulation spectrum - Google Patents
Infrared micro - water of high resolution evaporates gas detection and surveys system based on wavelength modulation spectrum Download PDFInfo
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- CN205879783U CN205879783U CN201620788170.5U CN201620788170U CN205879783U CN 205879783 U CN205879783 U CN 205879783U CN 201620788170 U CN201620788170 U CN 201620788170U CN 205879783 U CN205879783 U CN 205879783U
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- water vapor
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Abstract
The utility model discloses an infrared micro - water of high resolution evaporates gas detection and surveys system based on wavelength modulation spectrum, gaseous air chamber awaits measuring including being used for keeping in, the air chamber is connected laser and is taken place subassembly and laser receiving subassembly, subassembly output laser takes place and gets into the air chamber for laser, laser get into in the air chamber with the gas reaction that awaits measuring after the laser signal received by the laser receiving subassembly, the subassembly takes place and sends secondary demodulation reference signal to the laser receiving subassembly for laser, laser receiving subassembly nationality by secondary reference signal in to a plurality of laser signals of receiving in the air chamber demodulation obtain the second harmonic signal, the signal acquisition module is connected to the laser receiving subassembly, and with second harmonic signal transmission to signal acquisition module, signal acquisition pair of module second harmonic signal detection and the output of average back. The utility model discloses according to the second harmonic method, utilize secondary signal demodulation modulating signal once, successfully avoid the DC bias's that first harmonic brought influence, improve the SNR greatly.
Description
Technical field
This utility model relates to Fibre Optical Sensor Detection Techniques art, particularly to a kind of based on Wavelength modulation spectroscopy
High-resolution infrared micro water vapor detecting system.
Background technology
Water is the important substance that we depend on for existence, and detection water vapor concentration is the most significant in a lot of fields.Such as
Extra-high voltage electric transmission and transformation system equipment medium gas SF6In containing moisture time, toxicity and the strongest chemicals of corrosivity can be generated
Matter, etching insulative equipment, even explodes.Water content in food-processing industry, packaging bag exceeds standard, and can directly affect food
Quality.In transformer oil, water content is the most, and oil itself is aging, apparatus insulated aging and metal parts corrosion rate is the fastest；
In natural gas, the existence of water can cause pipeline water blocking, corroded pipeline, instrument and equipment, affects the accuracy of gas metering, gives
Safety in production and the use of natural gas cause high risks.The method of the detection minimum gas nowadays used has dew point method, electricity
Solution, capacitance-resistance method etc..And these detection methods exist response speed slowly, degree of accuracy is low, and the life-span is short and cost is the highest.Therefore,
Problems is solved in the urgent need to a kind of the most accurate new method.
Utility model content
Because the drawbacks described above of prior art, this utility model provides a kind of high-resolution based on Wavelength modulation spectroscopy
Infrared micro water vapor detecting system, it is achieved one of purpose be the modulated signal utilizing secondary singal demodulation once, successfully advise
Keep away the impact of the direct current biasing that first harmonic brings, be greatly improved signal to noise ratio so that circuit reduction, reduce that circuit is lengthy and jumbled to be brought
Unwanted noise.
For achieving the above object, this utility model provides a kind of infrared trace of high-resolution based on Wavelength modulation spectroscopy
Steam detecting system, including the air chamber for keeping in gas to be measured, described air chamber connects laser generating assembly and laser pick-off
Assembly, described laser generating assembly Output of laser enters described air chamber, with described gas to be measured in the described laser described air chamber of entrance
The reacted laser signal of steam in body is received by described laser pick-off assembly, and described laser generating assembly swashs to described
Light-receiving assembly send secondary demodulation reference signal, described laser pick-off assembly nationality by described secondary reference signal at described gas
In the some described laser signal of indoor reception, demodulation obtains second harmonic signal, and described laser pick-off assembly connects signals collecting
Module, and described second harmonic signal is transferred to described signal acquisition module, described signal acquisition module is humorous to described secondary
Ripple signal detection average rear output.
Aforementioned structure, according to the method for quadratic harmonics, utilizes secondary singal demodulation modulated signal once, successfully evades the most humorous
The impact of the direct current biasing that wavestrip is come, is greatly improved signal to noise ratio.
Preferably, described laser pick-off assembly includes photodetector, current/voltage modular converter and demodulation of phase locking module；
Described photodetector receives described laser to be believed with the reacted laser of steam in described gas to be measured in described air chamber
Number, described laser signal includes that described photodetector is by institute through water vapor absorption Feng Chu with without the multi-wavelength at absorption
Stating laser signal and be converted to photoelectric current, described photoelectric current is sent to current/voltage modular converter；Described current/voltage modular converter
Described photoelectric current is converted to voltage signal, and described voltage signal is sent to described demodulation of phase locking module；Described demodulation of phase locking mould
Block nationality is chosen described second harmonic signal by described secondary demodulation reference signal from some described voltage signals.
By utilizing phase lock amplifying technology, efficiently and precisely measure micro water vapor concentration, by the phase-locked electricity of single channel
Road, utilizes secondary singal demodulation modulated signal once, successfully evades the impact of the direct current biasing that first harmonic brings, significantly carry
High s/n ratio so that circuit reduction, reduces the lengthy and jumbled unwanted noise brought of circuit.
In some preferred embodiment, described current/voltage modular converter connects light intensity automatic control module, described light
The described optical signal light intensity shakiness that strong automatic control module receives at described photodetector causes described voltage signal magnitude to float
The described voltage signal of described current/voltage modular converter output is stablized during shifting.
Described light intensity automatic control module outfan connects described demodulation of phase locking module, carries out phase-locked to output signal, institute
State demodulation of phase locking module nationality to be demodulated by secondary reference signal, obtain humorous with the secondary of described low-frequency sweep signal same frequency
Ripple signal.Adopt to obtain secondary harmonic amplitude information by signal acquisition module, according to water vapor concentration and magnitude relation, calculate
Water vapor concentration information.
Preferably, the frequency of described secondary demodulation reference signal is the twice of frequency of described voltage signal.
Preferably, described laser generating assembly includes waveform generating module, Laser Drive module and Distributed Feedback Laser, institute
State waveform generating module and send described primary modulation signal to described Laser Drive module, simultaneously to described laser pick-off assembly
Send described secondary demodulation reference signal.
Preferably, described secondary demodulation reference signal is produced low-frequency sweep Signal averaging in institute by described waveform generating module
Stating and formed on primary modulation signal, the frequency of described secondary demodulation reference signal is the two of the frequency of described primary modulation signal
Times.
Described waveform generating module produces high-frequency modulation signal and is transported to Laser Drive module as primary modulation signal
For modulating laser instrument, the most described waveform generating module produces low-frequency sweep Signal averaging in described high-frequency modulation signal simultaneously
Upper formation described secondary demodulation reference signal, described low-frequency sweep Signal averaging is used for expanding wavelength in described high-frequency modulation signal
Sweep limits, more can suppress noise further.
Preferably, described Distributed Feedback Laser connecting laser temperature control module, described laser instrument temperature control module controls described DFB
The temperature of laser instrument, and provide the wavelength at water vapor absorption peak and the direct current without the wavelength at absorption to described Distributed Feedback Laser
Offset signal, for the selection of described Distributed Feedback Laser output center wavelength.
In certain embodiments, the wavelength at described water vapor absorption peak is 1368.597nm, the ripple at described place without absorption
A length of 1368.41nm.
Preferably, described Distributed Feedback Laser nationality is connected with described air chamber by 3:7 bonder.
The beneficial effects of the utility model:
1, this utility model is theoretical based on spectral absorption, utilizes modulated spectrum technology and phase lock amplifying technology, effective and smart
Really measure micro water vapor concentration.
2, this utility model combines the method for quadratic harmonics, by single channel phase lock circuitry, utilizes secondary singal demodulation tune once
Signal processed, successfully evades the impact of the direct current biasing that first harmonic brings, is greatly improved signal to noise ratio so that circuit reduction, reduces
The lengthy and jumbled unwanted noise brought of circuit.
2, this utility model is also added with light intensity automatic control module, is used for eliminating light intensity and changes the measurement error brought, increases
Strong system stability, is greatly improved detection accuracy, improves resolution.
Below with reference to accompanying drawing, the technique effect of design of the present utility model, concrete structure and generation is made furtherly
Bright, to be fully understood from the purpose of this utility model, feature and effect.
Accompanying drawing explanation
Fig. 1 is illustrated that system structure schematic diagram of the present utility model.
Fig. 2 is illustrated that the spectrogram wavelength of this utility model water vapor absorption selects schematic diagram.
Fig. 3 is illustrated that the laser drive signal oscillogram that this utility model uses.
Fig. 4 is illustrated that the second harmonic signal oscillogram that this utility model detects.
Detailed description of the invention
Embodiment 1
As it is shown in figure 1, a kind of infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy, including using
In the air chamber 5 of temporary gas to be measured, air chamber 5 connects laser generating assembly and laser pick-off assembly, and the output of laser generating assembly swashs
Light enters air chamber 5, and the reacted laser signal of steam in laser enters air chamber 5 and in gas to be measured is by laser pick-off assembly
Receiving, laser generating assembly sends secondary demodulation reference signal 13 to laser pick-off assembly, and laser pick-off assembly nationality is joined by secondary
Examining demodulation in the signal 13 some laser signals to receiving in air chamber 5 and obtain second harmonic signal, laser pick-off assembly connects
Signal acquisition module 11, and second harmonic signal is transferred to signal acquisition module 11, signal acquisition module 11 is to second harmonic
The averagely rear output display of signal detection.
In certain embodiments, laser pick-off assembly includes photodetector 6, current/voltage modular converter 8 and phase-locked solution
Mode transfer block 10；Photodetector 6 receives the laser reacted laser signal of steam in air chamber 5 and in gas to be measured, swashs
Optical signal includes that laser signal is converted to by photodetector 6 through water vapor absorption Feng Chu with without the some wavelength at absorption
Photoelectric current, photoelectric current is sent to current/voltage modular converter 8；Photoelectric current is converted to voltage signal by current/voltage modular converter 8,
Voltage signal is sent to demodulation of phase locking module 10；Demodulation of phase locking module 10 nationality is believed from some voltages by secondary demodulation reference signal 13
Second harmonic signal is chosen in number.
Foregoing design features is have employed, by the application of demodulation of phase locking module 10, according to ripple just because of this utility model
Long modulated spectrum and Harmonic Detected Theory, on the basis of frequency modulated signal model, use frequency-intensity-modulated signal, depend on
According to each harmonic signal and the relation of wavelength-modulated coefficient of Gaussian lineshape and lorentzian curve, determine the ripple that each harmonic is optimal
The long index of modulation.Based on the ultimate principle of lock-in amplifier, lock-in amplifier is utilized to extract the amplitude signal of second harmonic,
Effectively suppression phase shift regulation error and the analog device drift impact on harmonic amplitude measurement accuracy, improve the detection essence of system
Degree.
Specifically, Cleaning Principle such as Harbin Engineering University Zhang Keke the write paper " spectrum that this utility model uses
Absorb optical fiber gas detecting theory and technical research ", at one atm, the absorption of steam linearly can be by lorentzian curve
Representing, at infrared band, the absorptance of steam is less, and the output intensity of standard atmosphere pressure is represented by:
I (v)=I0(v)[1-α(v)CL] 1)
In formula α (ν) be gas at the absorptance that light frequency is at ν, L is the light path that light passes through gas to be measured, and C is to be measured
The volumetric concentration of gas.The temperature of regulation laser instrument and direct driving current, making optical maser wavelength is to be scheduled on a certain suction of steam
Receive at peak.Then, superposition appropriate frequency and the sinusoidal signal of amplitude, the ripple to laser instrument in the driving current signal of laser instrument
Length is modulated so that it is by sinusoidal rule change at absworption peak, laser instrument instantaneous output is:
V (t)=vc+Δv cosωt 2)
In formula, Δ ν is modulation amplitude, and ω is modulation angular frequency, νcFor filters center frequency.Laser wavelength is stable
At absorbent core, i.e. there is νc=ν0, normalized frequency skew x may utilize line half-width γ and instantaneous frequency ν represents:
In formula: x0=(νc-ν0)/γ；M=Δ ν/γ is wavelength-modulated coefficient.After GAS ABSORPTION, detect is defeated
Going out signal is:
S (x)=I (x)=I (x0+mcosωt) 4)
To 4) carry out Fourier expansion, available direct current and the expression formula of 1,2,3 subharmonic, for warbled long-range navigation
Hereby for line style, the even harmonics signal amplitude at the mid frequency of Absorption Line contains the concentration information of gas to be measured,
Can be used for measuring gas concentration.But the maximum amplitude of each even harmonics signal reduces with the increase of overtone order, the most occasionally
Subharmonic and second harmonic signal are the strongest in each harmonic, and second harmonic expression formula is as follows:
In formula: X=1-x2+m2；
As shown in Figure 4, utilizing the signal of other frequencies of target signal filter of Phase Lock Technique locking second harmonic frequency, secondary is humorous
The amplitude of ripple will determine the concentration of steam, and nationality can be drawn the dense of steam by the amplitude detecting second harmonic frequency signal
Degree.
In some preferred implementation, current/voltage modular converter 8 can be connected light intensity automatic control module 9, light
Strong automatic control module 9 is stable electricity when the optical signal light intensity shakiness that photodetector 6 receives causes voltage signal magnitude to drift about
The voltage signal of stream voltage transformation module 8 output.
In some preferred implementation, the frequency of secondary demodulation reference signal 13 is the twice of voltage signal.
In certain embodiments, laser generating assembly includes waveform generating module 1, Laser Drive module 2 and DFB laser
Device 3, waveform generating module 1 sends primary modulation signal 12 to Laser Drive module 2, sends two to laser pick-off assembly simultaneously
Secondary demodulated reference signal 13.
In some preferred embodiments, secondary demodulation reference signal 13 is produced low-frequency sweep letter by waveform generating module 1
Number being superimposed on primary modulation signal 12 formation, the frequency of secondary demodulation reference signal 13 is the twice of primary modulation signal 12.
In some preferred embodiments, Distributed Feedback Laser 3 connecting laser temperature control module 7, laser instrument temperature control module 7 is controlled
The temperature of Distributed Feedback Laser 3 processed, and provide the wavelength at water vapor absorption peak and straight without the wavelength at absorption to Distributed Feedback Laser
Stream offset signal, for the selection of Distributed Feedback Laser output center wavelength.
As in figure 2 it is shown, at A be the wavelength at water vapor absorption peak be 1368.597nm, at B be without absorption at ripple
A length of 1368.41nm.
Distributed Feedback Laser 3 nationality is connected with air chamber 5 by 3:7 bonder 4.
Using method of the present utility model below described:
Trapezoidal wave is scanning signal as shown in Figure 3, and thickened portion is to carry high frequency sinusoidal modulated signal, makes actual
In with, waveform generating module 1 produces high frequency primary modulation signal 12 for modulating Distributed Feedback Laser 3, produces low frequency the most simultaneously and sweeps
Retouching Signal averaging to be formed on primary modulation signal 12, the frequency of secondary demodulation reference signal 13 is the two of primary modulation letter 12
Times, it is used for expanding wavelength scanning range, more can suppress noise further.
Distributed Feedback Laser 3 Output of laser is to the air chamber 5 of full gas to be measured, then is received by photodetector 6, afterwards by electricity
Stream voltage transformation module 8 is changed.
Current/voltage modular converter 8 outfan connects light intensity automatic control module 9, and nationality is by the electricity making output from gain circuitry
Pressure value keeps stable.
The voltage signal stable through light intensity automatic control module 9 enters demodulation of phase locking module 10, locks the signal of telecommunication
Phase, nationality is demodulated by secondary reference signal 13, obtains and the second harmonic signal of primary modulation signal 12 same frequency.Pass through
Signal acquisition module adopts to obtain secondary harmonic amplitude information, according to water vapor concentration and magnitude relation, calculates water vapor concentration
Information.
Preferred embodiment of the present utility model described in detail above.Should be appreciated that the ordinary skill people of this area
Member just can make many modifications and variations according to design of the present utility model without creative work.Therefore, all technology neck
In territory, technical staff passes through logical analysis, reasoning or limited reality on the basis of existing technology according to design of the present utility model
Test available technical scheme, all should be in the protection domain being defined in the patent claims.
Claims (8)
1. the infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy, including for keeping in gas to be measured
The air chamber (5) of body；It is characterized in that, described air chamber (5) connects laser generating assembly and laser pick-off assembly, and described laser occurs
Assembly Output of laser enters described air chamber (5), swashing in described laser enters described air chamber (5) and after described gas reaction to be measured
Optical signal is received by described laser pick-off assembly, and described laser generating assembly sends secondary demodulation ginseng to described laser pick-off assembly
Examine signal (13), described laser pick-off assembly nationality by described secondary reference signal (13) at described air chamber (5) if in receive
In dry described laser signal, demodulation obtains second harmonic signal, and described laser pick-off assembly connects signal acquisition module (11), and
Described second harmonic signal is transferred to described signal acquisition module (11), and described signal acquisition module (11) is humorous to described secondary
Ripple signal detection average rear output.
The infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy the most according to claim 1, its
Being characterised by, described laser pick-off assembly includes photodetector (6), current/voltage modular converter (8) and demodulation of phase locking module
(10)；Described photodetector (6) receives described laser and reacts with the steam in described gas to be measured in described air chamber (5)
After laser signal, described laser signal includes through water vapor absorption Feng Chu with without the some wavelength at absorption, described photoelectricity
Described laser signal is converted to photoelectric current by detector (6), and described photoelectric current is sent to current/voltage modular converter (8)；Described
Described photoelectric current is converted to voltage signal by current/voltage modular converter (8), and described voltage signal is sent to described demodulation of phase locking
Module (10)；Described demodulation of phase locking module (10) nationality by described secondary demodulation reference signal (13) from some described voltage signals
Choose described second harmonic signal.
The infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy the most according to claim 2, its
Being characterised by, described current/voltage modular converter (8) connects light intensity automatic control module (9), described light intensity automatic control module
(9) the described optical signal light intensity shakiness received at described photodetector (6) is stablized when causing described voltage signal magnitude to drift about
The described voltage signal that described current/voltage modular converter (8) exports.
The infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy the most according to claim 2, its
Being characterised by, the frequency of described secondary demodulation reference signal (13) is the twice of the frequency of described voltage signal.
The infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy the most according to claim 1, its
Being characterised by, described laser generating assembly includes waveform generating module (1), Laser Drive module (2) and Distributed Feedback Laser (3),
Described waveform generating module (1) sends primary modulation signal (12) to described Laser Drive module (2), simultaneously to described laser
Receiving unit sends described secondary demodulation reference signal (13).
The infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy the most according to claim 5, its
Be characterised by, described secondary demodulation reference signal (13) by described waveform generating module (1) produce low-frequency sweep Signal averaging in
Described primary modulation signal (12) is upper to be formed, and the frequency of described secondary demodulation reference signal (13) is described primary modulation signal
(12) twice of frequency.
The infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy the most according to claim 5, its
Being characterised by, described Distributed Feedback Laser (3) connecting laser temperature control module (7), described laser instrument temperature control module (7) controls described
The temperature of Distributed Feedback Laser (3), and provide the wavelength at water vapor absorption peak and without the wavelength at absorption to described Distributed Feedback Laser
DC bias signal.
The infrared micro water vapor detecting system of high-resolution based on Wavelength modulation spectroscopy the most according to claim 5, its
Being characterised by, described Distributed Feedback Laser (3) nationality is connected with described air chamber (5) by 3:7 bonder (4).
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| Application Number | Priority Date | Filing Date | Title |
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| CN201620788170.5U CN205879783U (en) | 2016-07-26 | 2016-07-26 | Infrared micro - water of high resolution evaporates gas detection and surveys system based on wavelength modulation spectrum |
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| CN201620788170.5U CN205879783U (en) | 2016-07-26 | 2016-07-26 | Infrared micro - water of high resolution evaporates gas detection and surveys system based on wavelength modulation spectrum |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106990071A (en) * | 2017-05-15 | 2017-07-28 | 东南大学 | A kind of full digital gas detecting instrument |
| CN110320178A (en) * | 2019-07-17 | 2019-10-11 | 电子科技大学 | A kind of gas detecting system and its detection method based on wavelength modulation spectrum technology |
| CN113624407A (en) * | 2021-08-17 | 2021-11-09 | 安图实验仪器(郑州)有限公司 | TDLAS-based method for detecting air tightness of to-be-detected transparent closed container |
-
2016
- 2016-07-26 CN CN201620788170.5U patent/CN205879783U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106990071A (en) * | 2017-05-15 | 2017-07-28 | 东南大学 | A kind of full digital gas detecting instrument |
| CN110320178A (en) * | 2019-07-17 | 2019-10-11 | 电子科技大学 | A kind of gas detecting system and its detection method based on wavelength modulation spectrum technology |
| CN113624407A (en) * | 2021-08-17 | 2021-11-09 | 安图实验仪器(郑州)有限公司 | TDLAS-based method for detecting air tightness of to-be-detected transparent closed container |
| CN113624407B (en) * | 2021-08-17 | 2023-11-21 | 安图实验仪器(郑州)有限公司 | TDLAS-based method for detecting air tightness of transparent closed container to be detected |
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Granted publication date: 20170111 Termination date: 20200726 |