CN104458634B - Pulsed multi-channel photoacoustic spectrometry device for gas detection - Google Patents
Pulsed multi-channel photoacoustic spectrometry device for gas detection Download PDFInfo
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- CN104458634B CN104458634B CN201410697178.6A CN201410697178A CN104458634B CN 104458634 B CN104458634 B CN 104458634B CN 201410697178 A CN201410697178 A CN 201410697178A CN 104458634 B CN104458634 B CN 104458634B
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Abstract
A pulsed multi-channel photoacoustic spectrometry device for gas detection mainly comprises a light source module, an optoacoustic signal generating module and a controlling and signal processing module, wherein under modulation of electric pulses generated by the controlling and signal processing module, an infrared source in a light source module emits pulsed beams which are reflected by a parabolic reflector to form parallel beams, and the parallel beams are sent to the optoacoustic signal generating module. The optoacoustic signal generating module comprises a plurality of cylindrical optoacoustic cavities, and the axes of the optoacoustic cavities are in circumferential array distribution around the optical axis of the light source module, so that the light intensities of the beams sent into the optoacoustic cavities are the same. An optical filter is mounted at the light-in hole of each optoacoustic cavity, and a light deflector is mounted at each light-out hole. Optoacoustic sensors corresponding to the optoacoustic cavities are mounted in the middles of the optoacoustic cavities, generated optoacoustic signals are transmitted to the controlling and signal processing module through signal cables, and the concentration values of all gases are calculated.
Description
Technical field
The present invention relates to a kind of gas-detecting device, detect dress particularly to a kind of pulse controlled multichannel optoacoustic spectroscopy
Put.
Background technology
Gas detection technology has in industrialized production and daily life and is extremely widely applied, such as oil and gas pipes
Gases Dissolved in Transformer Oil detection in Leak Detection, power system, the discharge wasted nickel catalyst of chemical enterprise and in the air
Trace contamination gas detecting etc..At present, the relatively conventional method for gas detecting mainly includes：Gas sensor
Method, infrared absorption spectroscopy, chromatography, photocaustic spectroscopy etc..The precision of wherein gas sensor method detection is relatively low, and to mixing
Gas is also easy to produce cross interference, and the gas sample amount that infrared absorption spectroscopy needs is big, and precision is low；Chromatography needs carrier gas increased
Maintenance, less applicable for on-line monitoring.
The optoacoustic effect based on gas for the optoacoustic spectroscopy detection method, its mechanism is the luminous energy of gas molecules sorb specific wavelength
Afterwards, de excitation in the way of radiationless transition immediately, the heat energy discharging makes gas produce pressure wave, pressure in the chamber of closing
The intensity of ripple relation proportional to the concentration of gas molecule, then be changed enter photoacoustic cell in light wavelength it is possible to
The concentration value of detection gas with various component, is a kind of high-precision detection method.
But optoacoustic spectroscopy gas-detecting device at this stage there is also resolution element many shortcomings of, such as exist mechanical
Chopper, revolving optical filter disk, are unfavorable for onsite application；As patent CN101213438A " photo-acoustic spectrometer apparatus " adopts
The mechanical chopper modulated light source of rotation, optical filter exchanged by the mechanical type optical filter disk using rotation；In addition current equipment
There is a PA cell, need in the detection to select different optical filters that the heterogeneity in mixed gas to be measured is detected one by one, institute
Take time longer, be difficult to detect simultaneously for the gas componant being unable to stable existence.Additionally, current optoacoustic spectroscopy gas detecting
Device due to the restriction of light source, chopper, optical filter disk etc., also have the shortcomings that bulky it is impossible to as sensor with many
MEMS (MEMS) combination application of passage.
Content of the invention
The purpose of the present invention is to overcome the deficiencies in the prior art, provides a kind of pulse controlled gas multichannel optoacoustic spectroscopy
Detection means.Present configuration is simply compact, mechanical rotating part, good stability, can be used for multiple gases component is carried out
Concentration value detects.
Optoacoustic spectroscopy is based on optoacoustic effect.Optoacoustic effect is produced, gas molecule by gas molecules sorb electromagnetic wave
To excited state after the electromagnetic wave of absorption specific wavelength, de excitation in the way of discharging heat energy immediately, the heat energy discharging is in gas
Produce pressure wave, the intensity of pressure wave is proportional to the concentration of gas molecule, pressure different wave length being absorbed by detection and producing
The intensity of Reeb, can get the concentration of gas with various component.
The present invention is used for the pulsed multichannel optoacoustic spectroscopy device of gas detecting, mainly includes light source module, optoacoustic letter
Number generation module and control and signal processing module.
So that the penetrating of beam orthogonal that produce of light source module after described photoacoustic signal generation module is arranged on light source module
Enter photoacoustic signal generation module, the centrage of light beam is coaxial with the centrage of photoacoustic signal generation module；Described control and signal
Processing module is electrically connected with photoacoustic signal generation module, light source module, for controlling light signal generation module and light source die
Block.
Described light source module includes infrared thermal source and parabolic reflector.Infrared thermal source is located at parabolic reflector
Focal point, infrared thermal source produce light through parabolic reflector reflection after formed collimated light beam, be then incident on optoacoustic letter
In the PA cell of photoacoustic cell in number generation module.It is coated with layer of metal film, to increase infrared band on described parabolic reflector
Light radiation reflectance.Because light beam is radiated at, the signal to noise ratio of background noise reduction system can be increased on optoacoustic cavity wall, and light beam
The angle of divergence directly affect the irradiance being radiated at optoacoustic cavity wall glazing, according to the exhibition luminosity principle of optics, compression light beam
The angle of divergence, needs to increase the diameter of light beam, this requires that the diameter of parabolic reflector increases；And gas in another aspect PA cell
The pressure wave that body produces after absorbing luminous energy increases with optoacoustic cavity volume and reduces, and the increase of optoacoustic cavity volume also increases further
Add the volume of testing sample.Therefore, the present invention adopts heavy-caliber paraboloid illuminator to increase beam diameter, adopts many simultaneously
Passage PA cell is to reduce optoacoustic cavity volume.Described infrared thermal source carries out light modulation using electric pulse, at control and signal
Pulsed light beam is launched, electric pulse transmits the lock to control and signal processing module simultaneously under the modulation that reason module produces
Phase amplifier is as reference signal.
Photoacoustic signal generation module includes photoacoustic cell and mike.Described photoacoustic cell is by two or more cylinder optoacoustics
The optical filter composition installed on chamber, and each PA cell.The axle center of described PA cell around the central optical axis of light source module is in
Circumference array is distributed.The quantity of PA cell to be determined by gaseous species to be detected.Each PA cell symmetrically divides relative to optical axis
Cloth is so that the light intensity receiving is equal, and light beam and PA cell axis parallel.The axial two ends of described PA cell have circle
Through hole, respectively light inlet and light-emitting window.Optical filter is installed at described light inlet, described light-emitting window is provided with light-emitting window
Parabolic reflector.On each PA cell light inlet, the optical filter of installing can be by the light beam of different wave length, i.e. each optoacoustic
Chamber is respectively used to detect different gases.The medium position of each PA cell described is equiped with mike.Described microphonic
The axis perpendicular of receiving plane is in the side wall of PA cell.The focus of described light-emitting window parabolic reflector is in the geometric center of PA cell
Place, makes the parallel infrared light reflection light echo operatic tunes being projected by light hole, and converges at the geometric center of PA cell.Described go out light
The diameter with diameter greater than PA cell of mouth parabolic reflector, spuious anti-to light beam to reduce parabolic reflective minute surface boundary
Penetrate.
Particularly because gas to be detected has cross influence in gas sample, according to traditional detection mode, measure and complete one
After the photoacoustic signal of kind of absorption bandses, then change the wavelength of light and detected, two signals are solved presence and hand over by algorithm
The concentration value of every kind of gas of fork interference.And gas componant during actually described detection twice is possible to have occurred and that change,
This solution has obvious error；The present invention utilizes multiple PA cell, and the arrival end of each PA cell utilizes optical filter to make
For window, multi-wave signal is detected simultaneously, error can be reduced.
Each described PA cell axial direction two ends has air inlet and gas outlet, is located normal to each PA cell axially
Side wall on, can set the air inlet of adjacent PA cell and gas outlet is respectively connected with so that whole photoacoustic signal generation module
Total air inlet and total gas outlet to outside only one of which；Can also be air inlet and the gas outlet phase of certain or certain several PA cell
Connect, and the air inlet of remaining several PA cell is connected with gas outlet, to detect different gases respectively；As part PA cell can use
In background detection, background carrier gas can be passed through, such as other background gas such as air, nitrogen or SF6, the photoacoustic signal of its output is permissible
In order to detect the stability of detector and the change of ambient temperature etc., another part PA cell is used for detection sample gas
Constituent content.
Described control and signal processing module include lock-in amplifier and DSP panel, wherein lock-in amplifier have many
Individual signal input channel, each signal input channel is connected to mike by signal cable.The photoacoustic signal producing enters through DSP
Row is processed, and is calculated the concentration value of each gas.The present invention can detect to the various ingredients in gas sample to be detected simultaneously,
And the process such as background difference, alternate analyses can be carried out, effectively shorten detection time, improve accuracy of detection.Mechanical rotates
Device, improves life-span and stability.
Described microphonic frequency response range is 0.1Hz～30kHz, and sensitivity is more than 20mV/Pa.Described lock mutually amplifies
The frequency range of device is 1mHz～102.4kHz, and sensitivity is 2nV～1V, and gain accuracy is ± 1%, dynamic memory>
100dB, has two kinds of interfaces of GPIB and RS232.
The mechanical chopper that the present invention compares the use of traditional infrared light source has frequency stable, reference signal no phase frequency shift
The advantages of, without the need for optical filter disk, less rotation-control members, and decrease the use of mechanical component, have
Beneficial to the life-span improving package unit.In addition the present invention utilizes multiple PA cell, and the arrival end of each PA cell utilizes optical filter
As window, multi-wave signal is detected with have significantly excellent when measurement has cross interference multicomponent gases simultaneously
Gesture.The present invention can realize multiple gases component with less volume and measures simultaneously simultaneously, be beneficial to the knot with technology such as MEMS
Close application.
Brief description
Fig. 1 is pulsed multichannel optoacoustic spectroscopy structure of the detecting device schematic diagram of the present invention；
Fig. 2 a, Fig. 2 b, Fig. 2 c are optoacoustic spectroscopy detection means photoacoustic cell structural representation of the present invention.
Specific embodiment
Further illustrate the present invention below in conjunction with the drawings and specific embodiments.
Fig. 1 is pulsed multichannel optoacoustic spectroscopy structure of the detecting device schematic diagram of the present invention.As shown in figure 1, present invention dress
Put main inclusion light source module 1, photoacoustic signal generation module 2 and control and signal processing module 3.Light source module 1 is by infrared light
Source 1-1 and parabolic reflector 1-2 is constituted.Photoacoustic signal generation module 2 includes photoacoustic cell 2-1 and mike 2-4.Described infrared
The light that light source 1-1 sends launches pulsed light beam under the modulation that control and signal processing module 3 produce, via parabolic
Form collimated light beam after face illuminator 1-2 reflection, be then incident in the PA cell 2-2 in photoacoustic signal generation module 2.Optoacoustic
Mike 2-4 installed in the 2-2 of chamber absorbs photoacoustic signal produced by infrared light under test gas and is converted to the signal of telecommunication, then defeated
Go out and carry out signal processing to control and signal processing module 3, calculate the concentration value of each component under test gas.Described mike
2-4 is arranged on the side wall of PA cell 2-2, and the axis perpendicular of mike 2-4 receiving plane is in PA cell 2-2 side wall, and is located at
PA cell 2-2 center；The light acoustoelectric signal that mike 2-4 produces, through DSP process, is calculated the concentration of each gas
Value.
Described infrared light supply 1-1 is fixedly installed in the focal point of parabolic reflector 1-2.Parabolic reflector face is coated with
Layer of metal film, to increase the light radiation reflectance of infrared band.DSP panel in control and signal processing module 3 produces
Impulse modulation after DC voltage reach the port of infrared light supply 1-1 by cable 3-2, so that infrared light supply 1-1 is produced
Pulse collimated light beam.
Fig. 2 is optoacoustic spectroscopy detection means photoacoustic cell structural representation of the present invention.Represent respectively as shown in Fig. 2 a, 2b, 2c
The quantity of PA cell is 2,4,6 when sectional view.The making material of the photoacoustic cell 2-1 in described photoacoustic signal generation module 2
Expect for pyrite or rustless steel.The embodiment of the present invention contains the PA cell 2-2 of two or more cylinder, PA cell
Quantity by gas to be detected species determine.The axle center of PA cell 2-2 is around optical axis circumferentially array etc. of light source module 1
Angular distribution.The axial two ends of PA cell 2-2 have manhole, respectively light inlet and light-emitting window.It is provided with light inlet
Optical filter 2-5, is provided with light-emitting window parabolic reflector 2-6 at light-emitting window.Optical filter is fixed by trim ring, and using close
Sealing is sealed.The focus of light hole parabolic reflector 2-6, at the geometric center of PA cell, makes to be projected by light hole
The parallel infrared light reflection light echo operatic tunes, and converge at the geometric center of PA cell.Described light-emitting window parabolic reflector 2-6's
Diameter with diameter greater than PA cell.Have air inlet 2-3 on the PA cell two side wall of each PA cell axial direction and go out
QI KOU, the adjacent air inlet of PA cell can be respectively connected with gas outlet, and whole photoacoustic signal generation module only has to outside
One air inlet and gas outlet.
Claims (3)
1. a kind of pulsed multichannel optoacoustic spectroscopy device for gas detecting is it is characterised in that described optoacoustic spectroscopy fills
Put including light source module (1), photoacoustic signal generation module (2) and control and signal processing module (3)；Described photoacoustic signal produces
Module (2) is arranged on after light source module (1) so that the photoacoustic signal of injecting of beam orthogonal that light source module (1) produces produces
Module (2), the centrage of light beam is coaxial with the centrage of photoacoustic signal generation module (2)；Described control and signal processing module
(3) electrically connect with photoacoustic signal generation module (2), light source module (1), for controlling photoacoustic signal generation module (2) and light
Source module (1)；Described light source module (1) includes infrared light supply (1-1) and parabolic reflector (1-2)；Described infrared light
Source (1-1) is fixedly installed in the focal point of parabolic reflector (1-2), by the electric arteries and veins controlling and signal processing module (3) produces
Rush in the modulation of row light radiation intensity, form pulsed light beam；Pulsed light beam is parallel via being formed after parabolic reflector (1-2) reflection
Light beam, is then incident in the PA cell (2-2) of photoacoustic signal generation module (2) photoacoustic cell；Described parabolic reflector (1-2)
Minute surface is coated with the highly reflecting films of one layer of infrared band；Parabolic reflector (1-2) parabola diameter is slightly larger than the diameter of photoacoustic cell；
Described photoacoustic cell is by two or more cylindrical PA cell (2-2), and the upper optical filtering installed with each PA cell (2-2)
Piece forms；The axle center of described PA cell (2-2) is around the central optical axis circumferentially array distribution of light source module (1)；PA cell (2-
2) quantity is determined by gaseous species to be detected, and each PA cell is respectively used to detect different gases；Each PA cell phase
The optical axis of light source module (1) is symmetric so that the light intensity receiving is equal, and the axis of light beam and PA cell (2-2)
Line is parallel；The axial two ends of described PA cell (2-2) have manhole, respectively light inlet and light-emitting window；Described enters light
Mouth is provided with optical filter (2-5), and described light-emitting window is provided with light-emitting window parabolic reflector (2-6)；Each PA cell enters light
On mouth, the optical filter of installing can be by the light beam of different wave length；Install on the side wall of the medium position of each PA cell (2-2)
There is mike (2-4)；The axis perpendicular of microphonic receiving plane is in the side wall of PA cell, described light-emitting window parabolic reflector
(2-6) focus, at the geometric center of PA cell (2-2), makes the parallel infrared light reflection light echo operatic tunes being projected by light hole,
And converge at the geometric center of PA cell (2-2)；Described light-emitting window parabolic reflector (2-6) with diameter greater than PA cell
(2-2) diameter, to reduce the spurious reflections to light beam for the parabolic reflective minute surface boundary；In each described PA cell (2-2)
Air inlet (2-3) and gas outlet are had on two side walls of its axial direction；The adjacent air inlet of described PA cell with go out
QI KOU is respectively connected with, and whole photoacoustic signal generation module is to outside only one of which air inlet and gas outlet.
2. optoacoustic spectroscopy detection means according to claim 1 is it is characterised in that micro- in described PA cell (2-2)
Sound device (2-4) absorbs photoacoustic signal produced by infrared light under test gas and is converted to the signal of telecommunication, then exports to control and believes
Number processing module (3) carries out signal processing, calculates the concentration value of each component under test gas；The arrival end profit of each PA cell
With optical filter as window, multi-wave signal is detected, measurement has the multicomponent gases of cross interference simultaneously.
3. optoacoustic spectroscopy detection means according to claim 1 is it is characterised in that described control and signal processing module
(3) lock-in amplifier and DSP panel are included；DC voltage after the impulse modulation that described DSP panel produces passes through electricity
Cable (3-2) connects to infrared light supply (1-1)；Described lock-in amplifier includes multiple signal input channels, each signal
Input channel is connected to mike (2-4) by signal cable.
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