CN108827894A - A kind of chamber based on software phlase locking subtracts phase shift spectroscopic gas detection method and device - Google Patents
A kind of chamber based on software phlase locking subtracts phase shift spectroscopic gas detection method and device Download PDFInfo
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Abstract
The invention discloses a kind of chambers based on software phlase locking to subtract phase shift spectroscopic gas detection method and device.Apparatus of the present invention include LED, temperature control module, optical component, gas path component, circuit block；Circuit block includes photodetector, LED driver, data collecting card, computer；Optical component includes plano-convex lens, optical resonator, high reflective mirror, interferometric filter；Gas path component includes three-way air valve, mass flowmenter, pneumatic filter and sampling pump.Detection method includes：Generate driving signal；LED light source is modulated；Modulation light is projected by optical resonator, is converted to obtain voltage signal for optical signal through photodetector, is acquired by capture card and be input in computer；Amplify and be filtered by software phlase locking, demodulates the concentration of under test gas.The present invention can accelerate arithmetic speed, reduce system noise；Improve detection accuracy, sensitivity and stability；And can continuous sampling, it is easy to carry.
Description
Technical field
The invention belongs to Atmospheric components detection technique fields, are related to the detection of chamber attenuating phase-shift spectroscopic gas more particularly to one
Chamber of the kind based on software phlase locking subtracts phase shift spectroscopic gas detection method and device.
Background technique
There are many type of atmosphere pollution at present, and it is gentle molten to may be summarized to be gaseous pollutant for state according to existing for it
Gluey state pollutant.The type of gaseous pollutant is more, is broadly divided into 5 aspects：With SO2Based on sulfur-containing compound, with NO and
NO2Based on nitrogenous compound, hydrocarbon, the oxide of carbon and halogen compounds etc..Atmosphere pollution has human health
High risks, human body Long Term Contact low concentration pollutant can cause bronchitis, lung cancer etc., will cause acute poisoning under high concentration
It is even dead.Atmosphere pollution is also very big to the harm of plant, and plant can generate acute lesion, blade surface under high density pollution
Stomata be damaged, there is necrotic spot in surface, and photosynthesis and secretion are impacted.It is therefore desirable to real-time and accurately examine
Survey the concentration of toxic and harmful gas in ambient air.
Chamber attenuating phase-shift spectral technique (CAPS) is will to couple through the Wideband Incoherent light-emitting diode (LED) of ovennodulation
Into the optical resonator formed by two high reflective mirrors, light multiple reflections back and forth in resonant cavity, from the light of intracavitary injection through light
Electric explorer detection, photodetector converts light signals into electric signal and is input in lock-in amplifier, it is intracavitary if it exists with LED
Light source corresponds to the gas of absorbing wavelength, then can cause the phase shift variations of modulated signal, and phase shift size is directly proportional to gas concentration,
It is possible thereby to extrapolate the concentration value of under test gas.CAPS method is used primarily for measurement specular reflectivity, is used subsequently to survey NO2With
Aerosol Extinction.It is both at home and abroad at present total by arbitrary waveform generator and lock-in amplifier for the realization of CAPS technology
It is completed with building modulating lock phase system, but existing defect has：Lock-in amplifier and arbitrary waveform generator are bulky, make
It is inconvenient to carry to obtain a whole set of instrument.And lock-in amplifier purchase need to be limited larger from overseas import by relevant policies.
Summary of the invention
In order to overcome the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a kind of chambers based on software phlase locking to subtract phase
Spectroscopic gas detection method and device are moved, can be improved system detection limit, arithmetic speed is fast.
The technical scheme is that：
A kind of chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking, it is characterised in that：Software phlase locking uses
One universal data collection card (hereinafter referred to as " capture card ") is equipped with software phlase locking amplification filtering algorithm, realizes arbitrary waveform generator
It with the function of lock-in amplifier, is exported using the output of the simulation output port of capture card as signal generator, is amplified in locking phase
On the basis of use Savitzky-Golay convolution smothing filtering algorithm (S-G filtering), further increase system detection limit, operation
Speed is fast；Chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking includes the following steps：
Step 1: generating driving signal driving capture card by computer generates voltage signal, voltage signal is loaded into LED light
The driver in source, driving LED light source emit the light through ovennodulation：
Driving signal is generated in computer using software program development environment, acquires (data as the data built in capture card
Acquisition, DAQ) DAQ drive module driving capture card simulation output port generate voltage signal, the voltage signal
It is loaded on the driver of LED light source, to drive the LED light source to emit the light through ovennodulation；
Step 2: gas absorbs and detection；
Light through ovennodulation is over-filled the optical resonator of under test gas, and a part of light is absorbed by under test gas；It is remaining
Another part light carries under test gas concentration information, projects from optical resonator, will carry gas through photodetector
The optical signal of concentration information is converted to the voltage signal of different absorption coefficients, then collects electricity by the simulation input port of capture card
In brain；
Step 3: software phlase locking and demodulation；
The electric signal being input in computer (uses Savitzky-Golay convolution by software phlase locking amplification filtering algorithm
Smothing filtering algorithm S-G), demodulate the intracavitary gas concentration information of optical resonance at this time.
Further, the present invention is based on the chamber attenuating phase-shift spectroscopic gas detection methods of software phlase locking, wherein：
Include in step 1：Modulation of the generation and driving signal of driving signal to LED light source, capture card walk herein
Has the function of signal generator in rapid, as signal generator；
Incident intensity I after modulated0(t) it is expressed as formula 1：
I0(t)=I0(1+ β sin (2 π ft)) (formula 1)
In formula 1, I0It is non-modulated light intensity, β is modulation depth, and f is modulating frequency；T is the time.
LED light source driver is modulated using virtual instrument technology, can be realized with sine wave, square wave, triangular wave etc., with just
For string wave, the driving voltage V (t) being loaded into LED light source driver is expressed as formula 2：
V (t)=V0(1+ β sin (2 π ft)) (formula 2)
Wherein, V0For voltage DC component, β is modulation depth, and f is modulating frequency；T is the time.Driving voltage function by
Software Create is simultaneously exported by data collecting card simulation output port.
In step 2, modulated LED light is absorbed by various concentration gas through optical resonator or is transmitted by cavity
After resonant cavity, the voltage that the optical signal for carrying gas concentration information is converted to different absorption coefficients is believed through photodetector
Number, it is specific as follows：
For light after without the cavity for absorbing gas, transmitted light intensity I (t) is expressed as formula 3：
Wherein,The phase difference of incoming signal and outgoing signal, τ when being cavity0It is cavity time constant；k0For static spirit
Sensitivity is amplitude correlative；I0It is non-modulated light intensity；β is modulation depth；F is modulating frequency；T is the time.
When existing in optical resonator, when absorbing gas, transmitted light intensity I (t) is expressed as formula 4：
It is the phase difference that there is incoming signal and outgoing signal when absorbing gas in resonant cavity, τ is time constant.
Optimum modulation frequency is selected when cavity, so that(n is integer), so that the present apparatus has most preferably
Sensitivity, gas concentration withIt is in a linear relationship, therefore willMeasurement as gas concentration.
In step 3, software phlase locking amplification filtering algorithm is using LED modulated signal as the first reference signal, by the first ginseng
It examines signal phase shift pi/2 and obtains the second reference signal, capture card collects the voltage signal in computer as detection signal, utilizes ginseng
It is related to detection signal frequency to examine signal (including the first reference signal and second reference signal) frequency, and with noise frequency not phase
The feature of pass carries the signal of under test gas concentration information to extract useful signal from noise.This method is letter to be measured
The signal synchronous with reference signal amplification in number, that is, AC compounent is amplified and becomes corresponding direct current signal, by software
Locking phase amplifies filtering algorithm output, as the data for calculating under test gas concentration.
Further, the actual measuring signal of system is expressed as formula 5：
Vs(t)=x (t)+n (t) (formula 5)
Wherein, x (t) is the sample signal for needing detected, and n (t) indicates ambient noise；
X (t) is expressed as formula 6：
In formula 6, A V0k0；
With x (t) with the first reference signal V of frequencyr(t) formula 7, the phase of the second reference signal and the first reference signal are expressed as
Phase difference pi/2, the second reference signal V 'r(t) it is expressed as formula 8：
Vr(t)=V0(1+ β sin (2 π ft)) (formula 7)
It is discrete-time signal by the signal that capture card collects, the cross-correlation function value with the first reference signal
Rsr(0), with the cross-correlation function value R ' of the second reference signalsr(0) and auto-correlation function value Rrr(0) it is expressed as：
Wherein, N indicates sampling number；I indicates ith sample point.Vs(i) the collected discrete time letter of capture card is indicated
Number, Vr(i) the first reference signal of corresponding sampled point, V ' are indicatedr(t) the second reference signal of corresponding sampled point is indicated.
It can be with filtering appts noise, but due to having using above-mentioned phase locked algorithm (step 1~step 3, formula 5- formula 11)
The presence of many occasional noises, it is single to be not enough to filter out occasional noise using phase locked algorithm denoising, therefore also need to filter using S-G,
S-G filtering algorithm is filtered compared to Butterworth and Chebyshev, and mean square deviation is smaller, and will not generate phase shift, will not be to survey
Amount result has interference, so that measurement result can improve the detection accuracy of system closer to actual concentration value.
Sample signal x (t) and the first reference signal Vr(t) phase differenceIt is represented by：
Demarcate calibrating gas (including the N for determining concentration2, i.e., concentration be 0 calibrating gas) measure phase differenceWorking curve is made, working curve is once linear curve, and software is fitted to obtain slope a and intercept b, can table
It is shown as formula 13.The phase difference of under test gas is measured againIt will by computerIt brings formula 13 into, calculates the concentration of under test gas
Value c.
Wherein,Indicate that under test gas sample signal and cavity (are full of N2) signal phase difference；C indicates that under test gas is dense
Degree；The slope of a expression working curve；The intercept of b expression working curve.
A kind of chamber attenuating phase-shift spectroscopic gas detection device based on software phlase locking, it is characterised in that：It is LED including LED
With the temperature control module of photodetector temperature control, optical component, gas path component, circuit block；The optical component includes that plano-convex is saturating
Mirror, optical resonator, high reflective mirror, interferometric filter；The gas path component includes three-way air valve, two mass flowmenters, gases
Filter and sampling pump；The circuit block includes photodetector, LED driver, data collecting card, computer.
The LED and optical component are mounted in same optical axis, and optical component is disposed as perpendicular to optical axis.Plano-convex lens
It is mounted between LED and resonant cavity, so that hot spot focuses among resonant cavity, another piece of plano-convex lens are mounted on resonant cavity end
Between interferometric filter, photodetector is mounted on after interferometric filter.Plano-convex lens, interferometric filter and photodetection
Device need to be installed in stringent shading environment, so that only the luminous energy from resonant cavity is entered by plano-convex lens and interferometric filter
Photodetector.
One of mass flowmenter is connect with the purging port on resonant cavity both ends top, for introducing N2Purging is high
Anti- mirror.The three-way air valve is connect with standard gas mouth, resonant cavity air inlet and pneumatic filter respectively, pneumatic filter access sampling
Atmosphere.Mass flowmenter, three-way air valve and computer connect.
Another mass flowmenter is connect with resonant cavity gas outlet and sampling pump, and mass flowmenter is connect with computer.
The capture card is connect with computer, and capture card simulation output port is connect with LED driver, capture card simulation input
Port is connect with photodetector.
The LED is connect with LED driver.The temperature control module includes temperature sensor, temperature control module pedestal, temperature control
Instrument, cooling fin, semiconductor chilling plate, radiator fan.The LED and photodetector are placed in temperature control module pedestal, and temperature passes
Temperature is measured in sensor insertion temperature control module pedestal, and is connect with temperature controller, is provided with semiconductor system below temperature control module pedestal
Cold, semiconductor chilling plate lower section is provided with cooling fin, is provided with radiator fan below the cooling fin.Cooling piece and temperature controller
Connection, temperature controller are connect with computer.Radiator fan connects power supply.
The invention adopts the above technical scheme, which has the following advantages：
1, the present invention realizes data due to the lock-in amplifier and waveform generator huge using capture card substituted volume
Function occurs for acquisition, phase shift calculating, drive waveforms, and simplied system structure is realized instrument miniaturization, portability, not only reduced
System cost is also easier to realize the system integration, and gas on-site detection is facilitated to use.Phase locked algorithm improves the essence of system detection
Degree, sensitivity and stability.
2, the present invention is due to controlling N using mass flowmenter2High reflective mirror is purged, high reflective mirror service life is extended, is improved
Whole system uses the time.
3, the present invention is removed into the particulate matter of resonant cavity, extends the use of high reflective mirror due to using pneumatic filter
Service life guarantees the high reflectance of high reflective mirror.
4, the present invention is due to using temperature control module to LED and photodetector temperature control, so that LED is maintained at stable temperature
Degree, improves the service life of LED, so that light stability, reduces system so that electric signal is stablized to photodetector temperature control
Noise improves detection accuracy, sensitivity and stability.
5, the present invention is due to using capture card, required without that can be purchased at home from external import lock-in amplifier
All accessories.
6, the present invention can use the optical component of different wave length for different detection gas, realize multiple gases detection.
7, the present invention is small and exquisite portable, is moved easily detection.
8, the present invention can continuous sampling, it is easy to carry, it can be achieved that effectively quickly on-line automatic analysis.
Detailed description of the invention
Fig. 1 is the structural representation of the chamber attenuating phase-shift spectroscopic gas detection device provided by the invention based on software phlase locking
Figure；
Wherein, 11-LED；20-be the temperature control module of LED and photodetector temperature control；Optical component includes：12-is flat
Convex lens, 133-resonant cavities, 131-high reflective mirrors, 132-another high reflective mirrors, 14-plano-convex lens, 15-interferometric filters；Gas
Circuit unit includes：31-mass flowmenters (for controlling purge gas flow), 321-purging air inlets, 322-another purgings
Air inlet, 33-three-way air valves, 34-pneumatic filters, 37-mass flowmenters (for controlling sample introduction gas flow), 38-
Sampling pump；Circuit block includes：41-photodetectors, 42-data collecting cards, 43-LED drivers, 44-computers.
Fig. 2 is the flow diagram for the software phlase locking algorithm that the present invention uses；
Wherein, 421 LED drive signal to be generated in computer, as the first reference signal；422 be the second reference information；
423 and 424 indicate to carry out cross-correlation calculation to the acquired obtained discrete-time signal that blocks；425 indicate S-G filtering algorithm；426
For data processing module；427 be that optical signal is converted to the sample measuring signal that electric signal obtains through photodetector.
Fig. 3 is the structural schematic diagram of the temperature control module component of apparatus of the present invention；
Wherein, 21-temperature controller；The temperature sensor of 221-LED temperature control modules；The temperature control mould of 231-LED temperature control modules
Block pedestal；The semiconductor chilling plate of 241-LED temperature control modules；The cooling fin of 251-LED temperature control modules；261-LED temperature control moulds
The radiator fan of block；The temperature sensor of 222-photodetector temperature control modules；The temperature of 232-photodetector temperature control modules
Control modular substrate；The semiconductor chilling plate of 242-photodetector temperature control modules；252-photodetector temperature control modules dissipate
Backing；The radiator fan of 262-photodetector temperature control modules.
Specific embodiment
The present invention is described in detail with reference to the accompanying drawings and examples.
As shown in Figure 1, in the embodiment of the present invention, the chamber attenuating phase-shift spectroscopic gas detection device based on software phlase locking includes
LED 11, is the temperature control module 20 of LED and photodetector temperature control, and optical component of the present invention includes a plano-convex lens 12, resonance
Chamber 133, a high reflective mirror 131, another high reflective mirror 132, a plano-convex lens 14, an interferometric filter 15；Gas path component packet of the present invention
Include a mass flowmenter 31, one purging air inlet 321, another purging air inlet 322, a three-way air valve 33, a pneumatic filter
34, a mass flowmenter 37, a sampling pump 38；Circuit block of the present invention include a photodetector 41, a data collecting card 42,
One LED driver 43, a computer 44.
As shown in figure 3, temperature control module 20 of the invention includes a temperature controller 21, a LED temperature control module and a photodetection
Device temperature control module, LED temperature control module include a temperature sensor 221, a temperature control module pedestal 231, a temperature controller 21, one heat dissipation
Piece 251, semiconductor cooling piece 241, a radiator fan 261.Temperature sensor 221 is inserted into temperature control module pedestal 231, temperature
Sensor 221 is connect with temperature controller 21, and 231 bottom of temperature control module pedestal is provided with semiconductor cooling piece 241, semiconductor refrigerating
The hot face of piece 241 is provided with a cooling fin 251, and 251 other end of cooling fin is provided with a radiator fan 261.Cooling piece 241 and temperature control
Instrument 21 connects, and temperature controller 21 is connect with computer 44, and setting PID adjusts the temperature of control LED 11, and radiator fan 261 is with power supply electricity
Source.Photodetector temperature control module includes a temperature sensor 222, a temperature control module pedestal 232, a temperature controller 21, one heat dissipation
Piece 252, semiconductor cooling piece 242, a radiator fan 262, temperature sensor 222 are inserted into temperature control module pedestal 232, temperature
Sensor 222 is connect with temperature controller 21, and 232 bottom of temperature control module pedestal is provided with semiconductor cooling piece 242, semiconductor refrigerating
The hot face of piece 242 is provided with a cooling fin 252, and 252 other end of cooling fin is provided with a radiator fan 262.Cooling piece 242 and temperature control
Instrument 21 connects, and temperature controller 21 is connect with computer 44, and setting PID adjusts the temperature of control photodetector 41, and radiator fan 262 is matched
Power supply.Temperature control module pedestal 231, semiconductor chilling plate 241, cooling fin 251 and radiator fan 261 are successively fixed with screw
Constitute LED temperature control module.Temperature control module pedestal 232, semiconductor chilling plate 242, cooling fin 252 and radiator fan 262 use screw
It is successively fixed to constitute photodetector temperature control module.
In the temperature control module of the present embodiment, semiconductor chilling plate 241 and 242 is that temperature control module pedestal 231 and 232 provides
Low temperature, cooling fin 251 and 252 and radiator fan 261 and 262 enable the heat of cooling piece 241 and 242 to distribute, to guarantee to make
It works normally for cold 241 and 242.
As shown in Figure 1, LED 11, plano-convex lens 12, high reflective mirror 131, high reflective mirror 132, plano-convex lens 14, interferometric filter
15 are sequentially arranged in same optical axis, plano-convex lens 12, high reflective mirror 131, high reflective mirror 132, plano-convex lens 14, interferometric filter 15
It is disposed as perpendicular to optical axis.Relative distance between LED 11, plano-convex lens 12 and high reflective mirror 131 is arranged so that hot spot is poly-
Coke is among resonant cavity 133.Plano-convex lens 14, interferometric filter 15 and photodetector 41 are set in stringent shading environment,
So that only the luminous energy from resonant cavity 133 passes through plano-convex lens 14 and interferometric filter 15 enters photodetector 41.
High reflective mirror 131 and high reflective mirror 132 is respectively set in 133 both ends of resonant cavity of the present invention, and purge gass are arranged at 133 top of resonant cavity
Entrance 321 and purge gass entrance 322, flow is arranged by computer 44 in mass flowmenter 31, so that the N of certain flow2Purge gass are logical
The surface for crossing 321 and 322 purging high reflective mirrors 131 and 132, protects high reflective mirror.Three-way air valve 33 is cut by the control of computer 44
Dehorn gas and atmosphere, standard gas or atmosphere enter resonant cavity, gas outlet 36 and mass flowmenter 37 and sampling pump by air inlet 35
38 connections, computer 44 control the charge flow rate of mass flowmenter 37.Atmosphere into resonant cavity 133 passes through 34 mistake of pneumatic filter
Particulate matter is filtered, high reflective mirror 131 and 132 is protected, in order to avoid influence device precision.
Invention software phase locked algorithm flow diagram as shown in Fig. 2, generate driving signal 421 in computer 44 by software,
Driving signal 421 generates voltage letter by the simulation output port of the DAQ drive module driving capture card 42 built in capture card 42
Number, voltage signal sends LED driver 43 to, and voltage signal is converted to current signal and sends LED 11 to by LED driver 43,
Modulated LED light passes through resonant cavity, and the optical signal under test gas concentration information is converted to telecommunications through photodetector 41
Number, then collected in computer 44 by the simulation input port of capture card 42, it is realized by the software phlase locking amplification filtering algorithm of computer
Phase shift calculates, and demodulates gas concentration information.
Further, the driving voltage 421 being loaded into LED light source driver 43 is expressed as：
Vr(t)=V0(1+ β sin (2 π ft)) (formula 7)
Driving voltage function is exported by Software Create and by 42 simulation output port of data collecting card.
LED drive signal 421 obtains reference signal 2, i.e., to 421 phase shift pi/2 of LED drive signal as reference signal 1
422, it is expressed as：
Optical signal is converted to voltage signal through photodetector 41 and obtains the actual measuring signal 427 of system, is expressed as：
Vs(t)=x (t)+n (t) (formula 5)
Wherein,
It is the sample signal for needing detected, n (t) indicates ambient noise.
The signal obtained after data collecting card 42 is discrete-time signal, and 423 He of cross-correlation calculation is carried out to it
424, cross-correlation function value can be expressed as：
It can be with filtering appts noise, but due to there is depositing for many occasional noises using above-mentioned phase locked algorithm (formula 5- formula 9)
, it is single to be not enough to filter out occasional noise using phase locked algorithm denoising, therefore also need using S-G filtering algorithm 425, S-G filtering is calculated
Method 425 is filtered compared to Butterworth and Chebyshev, and mean square deviation is smaller, and will not generate phase shift, will not be to measurement result
There is interference, so that measurement result can improve the detection sensitivity of system closer to actual concentration value.
The phase difference of sample signal 427 and reference signal 421It is represented by：
It calculates the phase difference of sample signal 427 Yu reference signal 421, demarcates calibrating gas (including the N for determining concentration2,
I.e. concentration be 0 calibrating gas) measure phase differenceWorking curve is made, working curve is once linear curve,
Software is fitted to obtain slope a and intercept b, is represented by formula 13.The phase difference of under test gas is measured againIt will by computerIt brings formula 13 into, calculates the concentration value c of under test gas.
Wherein,Indicate that under test gas sample signal and cavity (are full of N2) signal phase difference；C indicates that under test gas is dense
Degree；The slope of a expression working curve；The intercept of b expression working curve.
The operating procedure of the method for the present invention is as follows：
1, it demarcates
Sampling pump 38 is opened, mass flowmenter 37 is set, three-way air valve 33 is switched to standard gas mouth and is passed through N2, clean resonance
(this place refers to except N other remaining gases in chamber 1332Except gas), so that resonant cavity 133 in be full of N2, open mass flow
Meter 31 is passed through N2Purging protection is carried out to high reflective mirror 131 and 132.LED 11 and optical section are selected according to surveyed gas absorption wavelength
The wavelength of part.Acquired 42 driving of card of LED 11 shines, after stable luminescence, the light quilt that is transmitted by 133 cavity of resonant cavity
Photodetector 41 receives, and phase difference when cavity is demodulated by software phlase locking amplification filtering algorithm.The gas that standard gas mouth is passed through
Body is changed to the gas of known concentration, and the phase of known concentration gas is demodulated by the software phlase locking amplification filtering algorithm of computer
Difference obtains working curve according to concentration and phase difference.
2, it detects
Sampling pump 38 is opened, mass flowmenter 37 is set, mass flowmenter 31 is opened and is passed through N2To high reflective mirror 131 and 132
Purging protection is carried out, three-way air valve 33 is switched to atmospheric air port and is passed through atmosphere to be measured, atmosphere to be measured is removed by pneumatic filter 34
Enter resonant cavity 133 after falling particulate matter.Acquired 42 driving of card of LED 11 shines, and after stable luminescence, transmits by resonant cavity 133
Light out is received by photodetector 41, and the phase difference of under test gas, computer are demodulated by software phlase locking amplification filtering algorithm
44 extrapolate under test gas concentration according under test gas phase difference and working curve, and real-time display simultaneously records.
In addition to normal debugging maintenance, device provided by the invention can continuous non-stop run.
The present invention is not limited to above-mentioned preferred forms, anyone can show that other are various under the inspiration of the present invention
The product of form, however, make any variation in its shape or structure, it is all that there is skill identical or similar to the present application
Art scheme, all falls within the scope of protection of the patent of the present invention.
Claims (10)
1. a kind of chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking, it is characterised in that：Software phlase locking passes through number
According to capture card and amplification filtering algorithm, the function of arbitrary waveform generator and lock-in amplifier is realized；With the mould of data collecting card
The output of quasi- output port is exported as signal generator, carries out locking phase amplification, then be filtered, and further increases system detection
Limit accelerates arithmetic speed；Include the following steps：
Step 1: generating driving signal by computer using data collecting card as signal generator；Driving signal is to LED light source
It is modulated, including：Driving signal drives capture card to generate voltage signal, and voltage signal is loaded into the driver of LED light source, adopts
LED light source driver is modulated with virtual instrument technology；LED light source is driven to emit the light through ovennodulation；Enter after modulated
Penetrate light intensity I0(t) it is expressed as formula 1：
I0(t)=I0(1+ β sin (2 π ft)) (formula 1)
In formula 1, I0It is non-modulated light intensity, β is modulation depth, and f is modulating frequency；T is the time；
Step 2: gas absorbs and detection：Light through ovennodulation is over-filled the optical resonator of under test gas, a part of light quilt
Under test gas absorbs；Remaining another part light carries under test gas concentration information, projects from optical resonator, visits through photoelectricity
It surveys device to convert optical signal to obtain voltage signal, is acquired by the simulation input port of capture card and be input in computer；
The light for transmiting optical resonator include the light for carrying under test gas concentration information that is absorbed by various concentration gas and
The light transmitted by cavity；Wherein：
Light is by being expressed as formula 3 without the transmitted light intensity I (t) after the cavity for absorbing gas：
Wherein,The phase difference of incoming signal and outgoing signal, τ when be optical resonator being cavity0It is cavity time constant；k0
It is amplitude correlative for static sensitivity；I0It is non-modulated light intensity；β is modulation depth；F is modulating frequency；T is the time；
Formula 4 is expressed as when there is the transmitted light intensity I (t) when absorbing gas in optical resonator：
It is the phase difference that there is incoming signal and outgoing signal when absorbing gas in resonant cavity, τ is time constant；
Step 3: software phlase locking and demodulation：The electric signal being input in computer amplifies and is filtered by software phlase locking, solves
Recall the concentration information of under test gas；Software phlase locking amplification filtering algorithm specifically performs the following operations：
31) using LED modulated signal as reference signal, including the first reference signal and the second reference signal；Capture card collects
Signal in computer is as measured signal；By signal amplification synchronous with reference signal in measured signal, i.e., AC compounent
Amplify and becomes corresponding direct current signal；
32) using reference signal frequency with detect signal frequency it is related and with the incoherent feature of noise frequency, mentioned from noise
Obtain the signal for carrying under test gas concentration information；
33) by phase locked algorithm filtering appts noise, practical measurement signals are obtained；Practical measurement signals are expressed as formula 5：
Vs(t)=x (t)+n (t) (formula 5)
Wherein, x (t) is the sample signal for needing detected, and n (t) indicates ambient noise；
X (t) is expressed as formula 6：
In formula 6, A V0k0；V0For voltage DC component；
With x (t) with the first reference signal V of frequencyr(t) formula 7, the phase phase of the second reference signal and the first reference signal are expressed as
Poor pi/2, the second reference signal V 'r(t) it is expressed as formula 8：
Vr(t)=V0(1+ β sin (2 π ft)) (formula 7)
It is discrete-time signal by the signal that capture card collects, the cross-correlation function value R with the first reference signalsr
(0), with the cross-correlation function value R ' of the second reference signalsr(0) and auto-correlation function value Rrr(0) it is expressed as：
Wherein, N indicates sampling number；I indicates ith sample point.Vs(i) the collected discrete-time signal of capture card, V are indicatedr
(i) the first reference signal of corresponding sampled point, V ' are indicatedr(t) the second reference signal of corresponding sampled point is indicated；
34) occasional noise is filtered out using filtering algorithm, so that measurement result improves detection accuracy closer to actual concentration value；It holds
The following operation of row：
By sample signal x (t) and the first reference signal Vr(t) phase differenceIt is expressed as formula 12：
The phase difference of sample signal and reference signal is calculated, demarcates and determines that the calibrating gas of concentration measures phase difference and obtains work
Curve, working curve are once linear curve, are expressed as formula 13：
Wherein,Indicate the phase difference of under test gas sample signal and cavity signal；C indicates under test gas concentration；A indicates work
Make slope of a curve；The intercept of b expression working curve；
It brings the phase difference of under test gas into working curve, that is, extrapolates the concentration value of under test gas.
2. the chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking as described in claim 1, characterized in that step 1
In, LED light source driver is modulated using virtual instrument technology, the implementation method including sine wave, square wave, triangular wave.
3. the chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking as claimed in claim 2, characterized in that using just
The realization of string wave is modulated LED light source driver, and the driving voltage V (t) being loaded into LED light source driver is expressed as formula 2：
V (t)=V0(1+ β sin (2 π ft)) (formula 2)
Wherein, V0For voltage DC component, β is modulation depth, and f is modulating frequency；T is the time；The driving voltage of generation is by adopting
The simulation output port of truck exports.
4. the chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking as described in claim 1, characterized in that step 2
In, optimum modulation frequency is selected when optical resonator is cavity, so thatN is integer, so that sensitivity
Most preferably；Gas concentration withIt is in a linear relationship, it willFor measuring gas concentration.
5. the chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking as described in claim 1, characterized in that step
34) in, filtering algorithm uses S-G convolution smothing filtering algorithm.
6. the chamber attenuating phase-shift spectroscopic gas detection method based on software phlase locking as described in claim 1, characterized in that step 1
In, voltage signal is specifically generated as the simulation output port of the data acquisition DAQ drive module driving capture card built in capture card.
7. a kind of chamber attenuating phase-shift spectroscopic gas detection device based on software phlase locking, including LED, for being visited for LED and photoelectricity
Survey temperature control module, optical component, gas path component, the circuit block of device control temperature；
The optical component includes the first plano-convex lens, the second plano-convex lens, optical resonator, high reflective mirror, interferometric filter；
The gas path component includes three-way air valve, the first mass flowmenter, the second mass flowmenter, pneumatic filter and sampling
Pump；
The circuit block includes photodetector, LED driver, data collecting card, computer；
The LED and optical component are mounted in same optical axis, and optical component is disposed as perpendicular to optical axis；
First plano-convex lens are mounted between LED and optical resonator, so that hot spot focuses on the centre of optical resonator；
Second plano-convex lens are mounted between resonant cavity end and interferometric filter；Photodetector be mounted on interferometric filter it
Afterwards；
Plano-convex lens, interferometric filter and photodetector are mounted in stringent shading environment, so that only coming from resonant cavity
Luminous energy enter photodetector by plano-convex lens and interferometric filter；
First mass flowmenter is connect with the purging port on resonant cavity both ends top, for introducing N2Purge high reflective mirror；
Three-way air valve is connect with standard gas mouth, resonant cavity air inlet and pneumatic filter respectively；Pneumatic filter access sampling atmosphere；
First mass flowmenter, three-way air valve are connect with computer；
Second mass flowmenter is connect with resonant cavity gas outlet and sampling pump；Second mass flowmenter is connected to a computer；
Data collecting card is connected to a computer, and data collecting card simulation output port is connect with LED driver, data collecting card
Simulation input port is connect with photodetector；
LED is connect with LED driver.
8. the chamber attenuating phase-shift spectroscopic gas detection device based on software phlase locking as claimed in claim 7, characterized in that the temperature
Controlling module includes temperature sensor, temperature control module pedestal, temperature controller, cooling fin, semiconductor chilling plate, radiator fan；
LED and photodetector are placed in temperature control module pedestal；Temperature sensor is inserted into temperature control module pedestal, and and temperature controller
Connection, for measuring temperature；Semiconductor chilling plate is set below temperature control module pedestal；Setting heat dissipation below semiconductor chilling plate
Piece；Radiator fan is set below cooling fin；Cooling piece is connect with temperature controller, and temperature controller is connect with computer.
9. the chamber attenuating phase-shift spectroscopic gas detection device based on software phlase locking as claimed in claim 8, characterized in that radiation air
Fan connects power supply.
10. the chamber attenuating phase-shift spectroscopic gas detection device based on software phlase locking as claimed in claim 7, characterized in that described
When detection device works, including calibration process and detection process；
Calibration process performs the following operations：
Open sampling pump；
Second mass flowmenter is set, three-way air valve is switched to standard gas mouth and is passed through N2, clean remaining gas in resonant cavity；
The first mass flowmenter is opened, N is passed through2Purging protection is carried out to high reflective mirror；
The wavelength of LED and optical component are selected according to the absorbing wavelength of under test gas；LED drives through data collecting card and shines；
It after stable luminescence, is received by a photoelectric detector by the light that the cavity of resonant cavity transmits, software is passed through by computer
Locking phase amplification filtering algorithm demodulates phase difference when cavity；
The gas that standard gas mouth is passed through is changed to the gas of known concentration, filtering algorithm demodulation is amplified by software phlase locking by computer
The phase difference of known concentration gas out obtains working curve according to concentration and phase difference；
Detection process performs the following operations：
Open sampling pump；Second mass flowmenter is set；
The first mass flowmenter is opened, N is passed through2Purging protection is carried out to high reflective mirror 131 and 132；
Three-way air valve is switched to atmospheric air port and is passed through atmosphere to be measured, atmosphere to be measured removes particulate matter by pneumatic filter；Then
Into resonant cavity；
The acquired card driving of LED shines；
It after stable luminescence, is received by a photoelectric detector by the light that resonant cavity transmits, is put by computer using software phlase locking
Big filtering algorithm demodulates the phase difference of under test gas, is extrapolating under test gas according under test gas phase difference and working curve
Concentration；
Real-time display simultaneously records；
It is achieved in the detection of the chamber attenuating phase-shift spectroscopic gas based on software phlase locking.
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