CN103389270A - Apparatus for measuring concentration of trace gas, and method thereof - Google Patents
Apparatus for measuring concentration of trace gas, and method thereof Download PDFInfo
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- CN103389270A CN103389270A CN2012101451771A CN201210145177A CN103389270A CN 103389270 A CN103389270 A CN 103389270A CN 2012101451771 A CN2012101451771 A CN 2012101451771A CN 201210145177 A CN201210145177 A CN 201210145177A CN 103389270 A CN103389270 A CN 103389270A
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Abstract
The invention discloses an apparatus for measuring the concentration of a trace gas, and a method thereof, and relates to the photoelectric field to solve the problems of low resolution, bad measuring precision, and unsatisfying of the practical demands of present technologies for measuring the concentration of the trace gas. The apparatus comprises a laser of an optical assembly portion, and a spatial light beam filter and a sample cell which are sequentially arranged in the direction of an optical path emitted by the laser; the spatial light beam filter comprises two focusing lenses and a pin hole positioned between the two focusing lenses; the sample cell comprises a quartz crystal oscillator and two micro-resonant cavities symmetrically arranged at two sides of the quartz crystal oscillator; an electric signal control measuring portion is electrically connected with the laser and the quartz crystal oscillator respectively; the quartz crystal oscillator is calibrated in a calibration mode before measurement; and when measurement is carried out, the calibration mode is switched to a measurement mode, and the concentration of the trace gas is measured through an electric signal obtained through converting an acoustical signal by the quartz crystal oscillator. The method comprises the steps of quartz crystal oscillator calibration, mode switching and trace gas concentration measurement.
Description
Technical field
The present invention relates to photoelectric field, particularly relate to a kind of device and method of measuring trace gas concentration.
Background technology
Trace gas detection has important application in a plurality of fields such as contamination monitoring, petroleum prospecting, industrial process control, space industry and medical diagnosiss.But the resolution of existing measurement trace gas concentration technology is lower, measuring accuracy is poor, can not practical requirement.
Summary of the invention
The invention provides a kind of device and method of measuring trace gas concentration, in order to solve, the existing resolution of measuring trace gas concentration technology is lower, measuring accuracy is poor, so problem that can not practical requirement.
The inventive system comprises: optical module part and electric signal control survey part; Wherein, described optical module partly comprises: laser instrument, and the spatial beam wave filter and the sample cell that on the optical path direction penetrated at laser instrument, set gradually are injected with trace gas in described sample cell; Described spatial beam wave filter comprises two condenser lenses, and the pin hole between described two condenser lenses, and light path is passed through in described two condenser lenses and pin hole; Described sample cell comprises quartz crystal oscillator, and two micro-resonant cavities that are symmetricly set on described quartz crystal oscillator both sides, the axle center of described quartz crystal oscillator and two micro-resonant cavities and light path coaxial, described quartz crystal oscillator plane and light path are perpendicular, light path in described two micro-resonant cavities and quartz crystal oscillator two pass through between raising one's arm; Wherein, described electric signal control survey part is electrically connected to laser instrument and quartz crystal oscillator respectively; Before measuring described trace gas concentration, the electric signal control survey partly adopts calibration mode to be calibrated quartz crystal oscillator; When measuring described trace gas concentration, the electric signal control survey partly is switched to measurement pattern, and acoustical signal is transformed to the electric signal obtained according to described quartz crystal oscillator, measures the concentration of described trace gas.
Further, pin hole plane and the light path of spatial beam wave filter are non-perpendicular.The pin hole of spatial beam wave filter and the condenser lens focus between laser instrument are positioned at described pin hole center; The pin hole of described spatial beam wave filter and the condenser lens imaging point between sample cell are positioned at quartz crystal oscillator Liang Bei center.The pinhole diameter of spatial beam wave filter is 50 μ m to 300 μ m.
Further, the length of each micro-resonant cavity is less than 1/2nd wave length of sounds for being greater than 1/4th wave length of sounds.The micro-resonant cavity internal diameter is 0.6mm to 1mm, and the gap of each micro-resonant cavity and quartz crystal oscillator is 30 μ m to 50 μ m.
Further, also be equipped with incidence window and outgoing window on the optical path direction of sample cell, and non-perpendicular with light path.
Further, also be equipped with air intake opening and gas outlet on sample cell, for injecting and the discharge trace gas.
Further, the electric signal control survey partly comprises: handover module is electrically connected to described quartz crystal oscillator, for switching calibration mode and measurement pattern; Signal generating module, be electrically connected to described handover module and laser instrument, for signal occurs; Lock-in amplifier, be electrically connected to described handover module and signal generating module, for the Harmonic Detection pattern is set, and the signal of surveying carried out to demodulation, and draw response curve; Data collecting card, be electrically connected to lock-in amplifier, the response curve drawn for gathering lock-in amplifier; Computing machine, be electrically connected to signal generating module and data collecting card, for control signal generation module, sends signal, and analyze the data that data collecting card gathers.Handover module comprises: the electronic switch be electrically connected to described quartz crystal oscillator input end; Control end and a coupling capacitance that input end is electrically connected to described electronic switch; The integrated transporting discharging be electrically connected to described quartz crystal oscillator output terminal and amplification resistance, and the output terminal of described integrated transporting discharging is electrically connected to lock-in amplifier.Perhaps, handover module comprises: the relay be electrically connected to described quartz crystal oscillator input end; The coupling capacitance be electrically connected to normally opened contact and the first signal generator output end of described relay; The triode be electrically connected to relay coil; The integrated transporting discharging be electrically connected to described quartz crystal oscillator output terminal and amplification resistance, and the output terminal of described integrated transporting discharging is electrically connected to lock-in amplifier.Signal generating module comprises: the first signal generator that output terminal is electrically connected to described handover module; Trigger the secondary signal generator that input end is electrically connected to the triggering output terminal of described first signal generator; With the electronics totalizer that the Laser Modulation input end of described laser instrument is electrically connected to, described electronics totalizer also is electrically connected to the triggering output terminal of secondary signal generator; The 3rd signal generator be electrically connected to an input end of described electronics totalizer.
Further, laser instrument is middle INFRARED QUANTUM CASCADE LASERS, launches mid-infrared laser.
Method of the present invention comprises: the step of quartz crystal oscillator calibration: under calibration mode, the vibration of electricity consumption signal excitation quartz crystal oscillator, with the first harmonic detection mode, the electric signal by the quartz crystal oscillator generation of vibration is surveyed, drawn the resonant frequency of described quartz crystal oscillator through the demodulation post analysis; The step of switch mode: be switched to measurement pattern, and, according to described quartz crystal oscillator resonant frequency, the first harmonic detection mode be switched to the second harmonic detection pattern; Measure the step of trace gas concentration: the frequency of infrared light beam is adjusted to 1/2nd of described quartz crystal oscillator resonant frequency, and is surveyed by quartz crystal oscillator, acoustical signal being transformed to the electric signal obtained with the second harmonic detection pattern; Wherein, the step of quartz crystal oscillator calibration, the step of switch mode and the step of measuring trace gas concentration, adopt the device of measurement trace gas concentration of the present invention to implement.
Further, adopt the step of electronic switch to the quartz crystal oscillator calibration, specifically comprise: signal by sine wave and DC level stack of computer control first signal generator output, wherein DC level is controlled electronic switch closes, connect band coupling capacitance end, the sinusoidal wave input pin that is directed to quartz crystal oscillator by coupling capacitance; The first signal generator, to the described sinusoidal wave frequency of high frequency direction scanning output, is exported synchronizing signal to lock-in amplifier simultaneously; Integrated transporting discharging and amplification resistance are amplified the output signal of quartz crystal oscillator; Lock-in amplifier is arranged on the first harmonic detection mode, and the signal of surveying is carried out to demodulation, obtains corresponding curve, via after the data collecting card collection, sending computing machine to, is drawn the resonant frequency of quartz crystal oscillator by computing machine analysis.
Further, adopt electronic switch to complete the step of switch mode and the step of measurement trace gas concentration, specifically comprise: computer control first signal generator output no-voltage, the synchronizing signal of synchronous end output 1/2nd described quartz crystal oscillator resonant frequencies is to lock-in amplifier and secondary signal amplifier simultaneously; The secondary signal generator is triggered and produces with sine wave signal frequently, with the triangular signal of the 3rd signal generator output, together is imported into the electronics totalizer, and the signal after stack is admitted to the laser instrument input port and carries out frequency modulation (PFM) and scanning; The no-voltage of first signal generator output is connected the input pin of the signal ground of electronic switch and quartz crystal oscillator, make quartz crystal oscillator be switched to measurement pattern, the acoustical signal produced is converted into electric signal by quartz crystal oscillator, send into integrated transporting discharging and amplify resistance and amplified, lock-in amplifier is switched to the second harmonic detection pattern, synchronizing signal according to described 1/2nd quartz crystal oscillator resonant frequencies, the electric signal that conversion is obtained carries out demodulation, draw corresponding curve, via after the data collecting card collection, sending computing machine to, by computing machine, carry out record.
Further, adopt the step of relay to the quartz crystal oscillator calibration, specifically comprise: signal by sine wave and DC level stack of computer control first signal generator output, wherein DC level is controlled the triode conducting, the coil of relay obtains electric, the contact of closure state is normally opened contact, connects band coupling capacitance end, the sinusoidal wave input pin that is directed to quartz crystal oscillator by coupling capacitance.
Further, adopt relay to complete the step of switch mode and the step of measurement trace gas concentration, specifically comprise: the no-voltage of first signal generator output is ended triode, do not have electric current to pass through from relay coil, the contact of closure state is normally closed contact, and the input pin of signal ground and quartz crystal oscillator is connected, and makes quartz crystal oscillator be switched to measurement pattern, the acoustical signal produced is converted into electric signal by quartz crystal oscillator, sends into integrated transporting discharging and amplifies resistance and amplified; Lock-in amplifier is according to the synchronizing signal of described 1/2nd quartz crystal oscillator resonant frequencies, be switched to the second harmonic detection pattern, the electric signal that conversion is obtained carries out demodulation, draws corresponding curve, via after the data collecting card collection, sending computing machine to, by computing machine, carry out record.
Further, infrared light beam is mid-infrared laser.
Beneficial effect of the present invention is as follows:
Opticator of the present invention comprises laser instrument, and the spatial beam wave filter and the sample cell that on the optical path direction penetrated at laser instrument, set gradually; Further, the spatial beam wave filter comprises two condenser lenses and therebetween pin hole, two micro-resonant cavities that sample cell comprises quartz crystal oscillator and is symmetricly set on the quartz crystal oscillator both sides.The inventor has also considered that the resonant frequency of quartz crystal oscillator is affected by environment and has changed, and before measuring trace gas concentration, quartz crystal oscillator is calibrated and automatically switch calibration mode and measurement pattern.By above-mentioned each device is set, set the relative position between each device, and partly complete calibration, switching and measure operation by the electric signal control survey, thereby make the device and method of measurement trace gas concentration of the present invention there is higher resolution and measuring accuracy with respect to prior art, but practical requirement.
The accompanying drawing explanation
The structural representation that Fig. 1 is the embodiment of the present invention one;
The structural representation that Fig. 2 is the embodiment of the present invention two;
The structural representation that Fig. 3 is the embodiment of the present invention three;
The quartz crystal oscillator that Fig. 4 is the embodiment of the present invention three and micro-resonant cavity position relationship schematic diagram;
The quartz crystal oscillator that Fig. 5 is the embodiment of the present invention three and micro-resonant cavity internal pressure distribution plan;
The structural representation that Fig. 6 is the embodiment of the present invention four;
The structural representation that Fig. 7 is the embodiment of the present invention five;
The signal intensity amplitude comparison diagram that Fig. 8 is the embodiment of the present invention five, embodiment mono-and prior art;
Fig. 9 be the embodiment of the present invention six repeat circuits and with the connection diagram of its associative cell;
The process flow diagram that Figure 10 is the embodiment of the present invention seven.
Embodiment
In order to improve resolution and the measuring accuracy of trace gas measurement of concetration technology, to meet practical application request, the invention provides a kind of device and method of measuring trace gas concentration, below by some embodiment, further illustrate.
A kind of device of measuring trace gas concentration is provided in embodiment mono-, the present embodiment, shown in Figure 1, comprising: optical module part 11 and electric signal control survey part 12.
Wherein, optical module part 11 comprises: laser instrument 111, and the spatial beam wave filter 112 and the sample cell 113 that on the optical path direction penetrated at laser instrument 111, set gradually wherein are injected with trace gas in sample cell 113.The light beam that laser instrument 111 sends can be the light beam of each infrared band.Spatial beam wave filter 112 comprises two condenser lenses 1121 and 1122, and the pin hole 1123 between two condenser lenses 1121 and 1122, light path from two condenser lenses 1121 and 1122 and pin hole 1123 in pass through.Sample cell 113 comprises quartz crystal oscillator 1131, and two micro-resonant cavities 1132 and 1133 that are symmetricly set on quartz crystal oscillator 1131 both sides, quartz crystal oscillator 1131 and two micro-resonant cavities 1132 and 1133 axle center and light path coaxial, quartz crystal oscillator 1131 planes and light path are perpendicular, light path from two micro-resonant cavities 1132 and 1133 and 1131 liang of quartz crystal oscillators pass through between raising one's arm.Electric signal control survey part 12 is electrically connected to laser instrument 111 and quartz crystal oscillator 1131 respectively; Before measuring described trace gas concentration, electric signal control survey part 12 adopts calibration mode to be calibrated quartz crystal oscillator 1131; When measuring described trace gas concentration, electric signal control survey part 12 is switched to measurement pattern, and acoustical signal is transformed to the electric signal obtained according to quartz crystal oscillator 1131, measures trace gas concentration.
Visible, in the present embodiment, opticator comprises laser instrument, and the spatial beam wave filter and the sample cell that on the optical path direction penetrated at laser instrument, set gradually; Further, the spatial beam wave filter comprises two condenser lenses and therebetween pin hole, two micro-resonant cavities that sample cell comprises quartz crystal oscillator and is symmetricly set on the quartz crystal oscillator both sides.The inventor has also considered that the resonant frequency of quartz crystal oscillator is affected by environment and has changed, and before measuring trace gas concentration, quartz crystal oscillator is calibrated and automatically switch calibration mode and measurement pattern.By above-mentioned each device is set, set the relative position between each device, and partly complete calibration, switching and measure operation by the electric signal control survey, thereby make the measurement trace gas concentration device of the present embodiment there is higher resolution and measuring accuracy with respect to prior art, but practical requirement.
Study discovery through the inventor, the molecular based frequency vibration that is arranged in mid infrared region absorbs the strongest in the infrared active vibration, the detection sensitivity of mid infrared region can reach the ppbV magnitude, than the ppmV level of near infrared region, exceeds several orders of magnitude, is best infrared-gas detecting band.The fast development of middle INFRARED QUANTUM CASCADE LASERS in recent years, make the detection Absorption Line used in the trace gas measurement of concetration shift from traditional near infrared region (0.78-2.5 μ m) to mid infrared region (2.5-25 μ m).Yet lag behind at present the development of LASER Light Source in the development of this band detection device.On the other hand, its ultimate principle of optoacoustic spectroscopy is when a branch of light with surveying the Absorption Line same frequency passes through from tested gas, the object gas molecule is arrived high-energy state by laser excitation, because the collision de excitation is sent out process, come back to ground state, the generation of simultaneous sound wave, sound wave is detected device and surveys and change into the electric signal be directly proportional to tested gas concentration.The inventor also finds, optoacoustic spectroscopy does not have dependence to wavelength, can be used in theory from ultraviolet to infrared all wave bands, if can be combined mid-infrared laser with optoacoustic spectroscopy, the series of problems that in solving surely, the infrared eye development lags behind and brings.Below provide some preferred embodiments that mid-infrared laser is combined with optoacoustic spectroscopy.
A kind of device of measuring trace gas concentration is provided in embodiment bis-, the present embodiment, shown in Figure 2, comprising: optical module part 21 and electric signal control survey part 22.
Wherein, spatial beam wave filter 212 comprises two condenser lenses 2121 and 2122, can be the germainium lens of plating anti-reflection film, also comprises the pin hole 2123 between two condenser lenses 2121 and 2122.Light path from two condenser lenses 2121 and 2122 and pin hole 2123 in pass through, the focus of condenser lens 2121 is positioned at pin hole 2123 centers, the imaging point of condenser lens 2122 is positioned at quartz crystal oscillator 2131 Liang Bei centers.The diameter of pin hole 2123 is 50 μ m to 300 μ m, and plane and the light path of pin hole 2123 are non-perpendicular, and the angulation scope is for being more than or equal to 40 degree and being less than or equal to 80 degree.
Wherein, sample cell 213 comprises quartz crystal oscillator 2131, its resonant frequency includes but not limited to 32.768kHz, also comprise two micro-resonant cavities 2132 and 2133 that are symmetricly set on quartz crystal oscillator 2131 both sides, quartz crystal oscillator 2131 and two micro-resonant cavities 2132 and 2133 axle center and light path coaxial, quartz crystal oscillator 2131 planes and light path are perpendicular, light path from two micro-resonant cavities 2132 and 2133 and 2131 liang of quartz crystal oscillators pass through between raising one's arm.Also be equipped with incidence window 2134 and outgoing window 2135 on the optical path direction of sample cell 213, the materials such as zinc selenide that can be infrared in transmission, germanium, magnesium fluoride, calcium fluoride are made, be coated with anti-reflection film, and non-perpendicular with light path, the angulation scope is for being more than or equal to 60 degree and being less than or equal to 90 degree.
Electric signal control survey part 22 is electrically connected to laser instrument 211 and quartz crystal oscillator 2131 respectively; Before measuring described trace gas, electric signal control survey part 22 adopts calibration mode to be calibrated quartz crystal oscillator 2131; When measuring described trace gas concentration, electric signal control survey part 22 is switched to measurement pattern, and acoustical signal is transformed to the electric signal obtained according to quartz crystal oscillator 2131, measures trace gas concentration.
Visible, device in the present embodiment has advantages of embodiment mono-, and the inventor considers that the mid-infrared laser source is responsive especially to feedback light, even be reflected back from lens, air chamber window, micro-resonant cavity the pattern fluctuation that extremely faint light also can cause laser, may cause the deviation of measuring.So, the pin hole plane of installing in the present embodiment and the angled design of light path, and sample cell window and the angled design of light path avoided the reflection of light beam effectively, make quantum cascade laser in whole scanning process without Mode-hopping Phenomena.
A kind of device of measuring trace gas concentration is provided in embodiment tri-, the present embodiment, shown in Figure 3, comprising: optical module part 31 and electric signal control survey part 32.
Wherein, spatial beam wave filter 312 comprises two condenser lenses 3121 and 3122, and the pin hole 3123 between two condenser lenses 3121 and 3122, light path from two condenser lenses 31121 and 3122 and pin hole 3123 in pass through.
Wherein, sample cell 313 comprises quartz crystal oscillator 3131, its resonant frequency includes but not limited to 32.768Hz, also comprise two micro-resonant cavities 3132 and 3133 that are symmetricly set on quartz crystal oscillator 3131 both sides, quartz crystal oscillator 3131 and two micro-resonant cavities 3132 and 3133 axle center and light path coaxial, quartz crystal oscillator 3131 planes and light path are perpendicular, light path from two micro-resonant cavities 3132 and 3133 and 3131 liang of quartz crystal oscillators pass through between raising one's arm. Micro-resonant cavity 3132 and 3133 can adopt stainless steel needle tubing or glass tube, and length is for being more than or equal to 1/4th wave length of sounds and being less than or equal to 1/2nd wave length of sounds, and internal diameter is 0.6mm to 1mm, and external diameter is 0.8 to 1.4mm; The gap of each micro-resonant cavity and quartz crystal oscillator 3131 is 30 μ m to 50 μ m; Concrete quartz crystal oscillator and micro-resonant cavity position relationship can be shown in Figure 4.
Electric signal control survey part 32 is electrically connected to laser instrument 311 and quartz crystal oscillator 3131 respectively; Before measuring described trace gas concentration, electric signal control survey part 32 adopts calibration mode to be calibrated quartz crystal oscillator 3131; When measuring described trace gas concentration, the electric signal control survey partly is switched to measurement pattern, and acoustical signal is transformed to the electric signal obtained according to quartz crystal oscillator 3131, measures trace gas concentration.
Visible, device in the present embodiment has advantages of embodiment mono-, and the inventor considers that half-wave standing wave resonance situation is for confined space, if insertion quartz crystal oscillator, interference due to quartz crystal oscillator, and have gap between micro-resonant cavity and quartz crystal oscillator, and can destroy resonant condition, resonance effects is had a greatly reduced quality; The inventor also considers that typical mid-infrared laser beam diameter is 3mm, if the internal diameter of micro-resonant cavity is too small, can cause contacting of laser beam and micro-resonant cavity and quartz crystal oscillator, and then the ground unrest of generation non-zero, this noise exceeds several times to tens times than thermonoise level originally usually, has seriously reduced the detection sensitivity of sensing device.Therefore, in the present embodiment, the length of single micro-resonant cavity adopts and is more than or equal to 1/4th wave length of sounds and is less than or equal to 1/2nd wave length of sounds, this makes the frequency of micro-resonant cavity and the frequency overlap of quartz crystal oscillator, resonance effect strengthens greatly, at this moment micro-resonant cavity is in the opening part air-flow velocity maximum of quartz crystal oscillator direction, and cause acoustic pressure to produce local maximum in the quartz crystal oscillator center from the back draught impact of two micro-resonant cavities, thereby the resonance that has improved greatly output strengthens signal, concrete quartz crystal oscillator and micro-resonant cavity internal pressure distribution plan can be shown in Figure 5, employing is more than or equal to 1/4th wave length of sounds and is less than or equal to the micro-resonant cavity of 1/2nd wave length of sounds, allow the micro-resonant cavity interior diameter further to increase to 0.6mm to 1mm and do not lose resonance enhancing signal, insert spatial filter between laser instrument and sample cell, further filtering the high-order transverse mode of quanta cascade light beam, be beneficial to and focus on 3mm mid-infrared light bundle touchless ground by micro-resonant cavity and quartz crystal oscillator, through repeatedly test, the energy percent of pass is up to 98%.
A kind of device of measuring trace gas concentration is provided in embodiment tetra-, the present embodiment, shown in Figure 6, comprising: optical module part 41 and electric signal control survey part 42.
Wherein, optical module part 41 comprises: laser instrument 411, and the spatial beam wave filter 412 and the sample cell 413 that on the optical path direction penetrated at laser instrument 411, set gradually are injected with trace gas in sample cell 413.Laser instrument 411 is middle INFRARED QUANTUM CASCADE LASERS, launches mid-infrared laser.Spatial beam wave filter 412 comprises two condenser lenses 4121 and 4122, and the pin hole 4123 between two condenser lenses 4121 and 4122, light path from two condenser lenses 4121 and 4122 and pin hole 4123 in pass through.Sample cell 413 comprises quartz crystal oscillator 4131, and two micro-resonant cavities 4132 and 4133 that are symmetricly set on quartz crystal oscillator 4131 both sides, quartz crystal oscillator 4131 and two micro-resonant cavities 4132 and 4133 axle center and light path coaxial, quartz crystal oscillator 4131 planes and light path are perpendicular, light path from two micro-resonant cavities 4132 and 4133 and 4131 liang of quartz crystal oscillators pass through between raising one's arm.
Wherein, electric signal control survey part 42 is electrically connected to laser instrument 411 and quartz crystal oscillator 4131 respectively.Before measuring described trace gas, electric signal control survey part 42 adopts calibration mode to be calibrated quartz crystal oscillator 4131, when measuring trace gas concentration, electric signal control survey part 42 is switched to measurement pattern, and according to quartz crystal oscillator 4131, acoustical signal is transformed to the electric signal obtained, measure trace gas concentration.Specifically, electric signal control survey part 42 comprises: handover module 421 is electrically connected to quartz crystal oscillator 4131, for switching calibration mode and measurement pattern; Signal generating module 422, be electrically connected to handover module 421 and laser instrument 411, for signal occurs; Lock-in amplifier 423, be electrically connected to handover module 421 and signal generating module 422, for the Harmonic Detection pattern is set, and the signal of surveying carried out to demodulation, and draw response curve; Data collecting card 424, be electrically connected to the response curve drawn for gathering lock-in amplifier 423 with lock-in amplifier 423; Computing machine 425, be electrically connected to signal generating module 422 and data collecting card 424, for control signal generation module, sends signal, and analyze the data that data collecting card gathers.
Visible, the device in the present embodiment has advantages of embodiment mono-, and the electric signal control survey of the present embodiment part carried out refinement to the function of switching calibration mode and measurement pattern, to meet the actual demand that first calibration is measured again.
A kind of device of measuring trace gas concentration is provided in embodiment five, the present embodiment, shown in Figure 7, comprising: optical module part 51 and electric signal control survey part 52.
Optical module part 51 comprises: laser instrument 511, and the spatial beam wave filter 512 and the sample cell 513 that on the optical path direction penetrated at laser instrument 511, set gradually are injected with trace gas in sample cell 513.Laser instrument 511 is middle INFRARED QUANTUM CASCADE LASERS, launches mid-infrared laser.
Wherein, spatial beam wave filter 512 comprises two condenser lenses 5121 and 5122, can be the germainium lens of plating anti-reflection film, also comprises the pin hole 5123 between two condenser lenses 5121 and 5122.Light path from two condenser lenses 5121 and 5122 and pin hole 5123 in pass through, the focus of condenser lens 5121 is positioned at pin hole 5123 centers, condenser lens 5122 imaging points are positioned at quartz crystal oscillator 5131 Liang Bei centers.The diameter of pin hole 5123 is 50 μ m to 300 μ m, and pin hole 5123 planes and light path are non-perpendicular, and the angulation scope is for being more than or equal to 40 degree and being less than or equal to 80 degree.
Wherein, sample cell 513 comprises quartz crystal oscillator 5131, its resonant frequency includes but not limited to 32.768kHz, also comprise two micro-resonant cavities 5132 and 5133 that are symmetricly set on quartz crystal oscillator 5131 both sides, quartz crystal oscillator 5131 and two micro-resonant cavities 5132 and 5133 axle center and light path coaxial, quartz crystal oscillator 5131 planes and light path are perpendicular, light path from two micro-resonant cavities 5132 and 5133 and 5131 liang of quartz crystal oscillators pass through between raising one's arm.Micro-resonant cavity 5132 and 5133 can adopt stainless steel needle tubing or glass tube, and length is for being more than or equal to 1/4th wave length of sounds and being less than or equal to 1/2nd wave length of sounds, and internal diameter is 0.6mm to 1mm, and external diameter is 0.8mm to 1.4mm; The gap of each micro-resonant cavity and quartz crystal oscillator 5131 is 30 μ m to 50 μ m.Also be equipped with incidence window 5134 and outgoing window 5135 on the optical path direction of sample cell 513, the materials such as zinc selenide that can be infrared in transmission, germanium, magnesium fluoride, calcium fluoride are made, be coated with anti-reflection film, and non-perpendicular with light path, the angulation scope is for being more than or equal to 60 degree and being less than or equal to 90 degree.Also be equipped with air intake opening 5136 and gas outlet 5137 on sample cell 513, for injecting and the discharge trace gas.
Electric signal control survey part 52 comprises: the input end of laser instrument 511 is electrically connected to the output terminal of electronics totalizer 521, an input end of electronics totalizer 521 is electrically connected to the 3rd signal generator 522 output terminals, another input end is electrically connected to the output terminal of secondary signal generator 523, the trigger end of the trigger end of secondary signal generator 523 and lock-in amplifier 524 is electrically connected to the synchronous output end of first signal generator 525, the signal output part of first signal generator 525 is electrically connected to coupling capacitance 5261 ends of electronic switch 526, another input end of electronic switch 526 is electrically connected to signal ground, the output terminal of electronic switch 526 is electrically connected to the input end of quartz crystal oscillator 5131, the output terminal of quartz crystal oscillator 5131 is electrically connected to the negative input end of integrated transporting discharging 527, the positive input terminal of integrated transporting discharging 527 is electrically connected to signal ground, the negative input end of integrated transporting discharging 527 and output terminal having amplifies resistance R 1 (can value 5M to 10M ohm), the input end of the output terminal of integrated transporting discharging 527 and lock-in amplifier 524 is electrically connected to.In addition for realizing the function of automatic calibration quartz crystal oscillator before test, also be provided with data collecting card 528 and computing machine 529, the input end of the output terminal of lock-in amplifier 524 and data collecting card 528 is electrically connected to, the input end of the output terminal of data collecting card 528 and computing machine 529 is electrically connected to, and the control end of the control end of computing machine 529 and first signal generator 525 is electrically connected to.
Visible, device in the present embodiment has all advantages of embodiment mono-to four, and preferably be connected in series electronic switch between quartz crystal oscillator and signal generator, coordinate data collecting card, computing machine and first signal generator, realized the quick switching of calibration and measuring process and be electrically connected to without changing any equipment.Further can be shown in Figure 8, wherein horizontal ordinate is air pressure, ordinate is the signal intensity amplitude, the result that curve A 1 (shown in the solid square form point) records for the measurement mechanism that uses the present embodiment, the result of curve A 3 (shown in black circle) for using the described measurement mechanism of embodiment mono-to record, the result of curve A 2 (shown in black triangle) for using existing apparatus to record.Visible, using signal amplitude that the measurement mechanism of the present embodiment obtains is 30 times of the signal amplitude that uses existing apparatus to obtain; The signal amplitude that uses the described measurement mechanism of embodiment mono-to obtain is 5 times of the signal amplitude that uses existing apparatus to obtain.
Embodiment six, provide a kind of device of measuring trace gas concentration, having comprised: optical module part and electric signal control survey part.Adopt the electronic switch 526 in relay alternative embodiment five in the present embodiment, therefore, the present embodiment only describes relay and the unit associated with it, and other parts can be referring to the associated description in embodiment five.
In the step of quartz crystal oscillator calibration: signal by sine wave and DC level stack of computer control first signal generator 625 output, wherein DC level is controlled triode 6262 conductings, the coil of relay 626 obtains electric, the contact of closure state is normally opened contact, connect band coupling capacitance end 6261, the sinusoidal wave input pin that is directed to quartz crystal oscillator 6131 by coupling capacitance 6261.
In switch mode: the no-voltage of first signal generator 625 outputs is by triode 6262 cut-offs, do not have electric current to pass through from relay coil, the contact of closure state is normally closed contact, the input pin of signal ground and quartz crystal oscillator 6131 is connected, make quartz crystal oscillator 6131 be switched to measurement pattern, the acoustical signal produced is converted into electric signal by quartz crystal oscillator 6131, sends into integrated transporting discharging and amplifies resistance and amplified.
A kind of method of measuring trace gas concentration is provided in embodiment seven, the present embodiment, has realized through but not limited to the arbitrary device described in embodiment mono-to six.Shown in Figure 10, comprise the following steps:
S71, under calibration mode, electricity consumption signal excitation quartz crystal oscillator vibration, surveyed the electric signal by the quartz crystal oscillator generation of vibration with the first harmonic detection mode, draws the resonant frequency of described quartz crystal oscillator through the demodulation post analysis.
S72, be switched to measurement pattern, and, according to described quartz crystal oscillator resonant frequency, the first harmonic detection mode be switched to the second harmonic detection pattern.
S73, the frequency of infrared light beam is adjusted to 1/2nd of quartz crystal oscillator resonant frequency, and is surveyed by quartz crystal oscillator, acoustical signal being transformed to the electric signal obtained with the second harmonic detection pattern.
In the present embodiment, the inventor has considered that the resonant frequency of quartz crystal oscillator is affected by environment and has changed, and before measuring trace gas concentration, comprises the step that quartz crystal oscillator is calibrated, automatically switch to the step of measurement pattern after calibration, carry out again afterwards the measurement of trace gas.Therefore the method for the measurement trace gas concentration of the present embodiment has higher resolution and measuring accuracy with respect to prior art, but practical requirement.
A kind of method of measuring trace gas concentration is provided in embodiment eight, the present embodiment, has realized through but not limited to the device described in embodiment five.Specifically comprise:
In quartz crystal oscillator automatic calibration process, computing machine 529 is controlled the voltage signal of a stack of first signal generator 525 outputs, this voltage signal is formed by stacking by the sine wave of 30kHz and the DC level of a 5V, DC level is wherein controlled the closed band coupling capacitance end of connecting of electronic switch 526, the sinusoidal wave input pin that is directed to quartz crystal oscillator 5131 by coupling capacitance 5261, then first signal generator 525 is controlled by computing machine 529, sine wave freuqency to high frequency direction scanning output, export synchronizing signal to lock-in amplifier 524 simultaneously, lock-in amplifier 524 is arranged on the first harmonic detection mode, integrated transporting discharging 527, 1 pair of signal of the amplification resistance R of value 5M to 10M ohm is amplified, the output signal of 524 pairs of quartz crystal oscillators 5131 of lock-in amplifier is carried out demodulation, after the response curve obtained is gathered by data collecting card 528, send computing machine 529 to, computing machine 529 is analyzed the resonant frequency f that draws quartz crystal oscillator 5131
0.
In measuring process, computing machine 529 is controlled first signal generator 525 output no-voltages, and the synchronous end output frequency of first signal generator 525 is f simultaneously
0/ 2 synchronizing signal is to lock-in amplifier 524 and secondary signal generator 523, and lock-in amplifier 524 is arranged on the second harmonic detection pattern, and secondary signal generator 523 is triggered and produces with f frequently
0/ 2, amplitude is the 6mV sine wave signal, the amplitude of exporting with the 3rd signal generator 522 is that the 20mV triangular signal together is imported into electronics totalizer 521, signal after stack is admitted to laser instrument 511 input ports quantum cascade laser is carried out to frequency modulation (PFM) and scanning, the no-voltage of first signal generator 525 outputs makes electronic switch 526 connect the input pin of signal ground and quartz crystal oscillator 5131, make quartz crystal oscillator 5131 in measurement pattern, the weak acoustic signal produced is converted into electric signal by quartz crystal oscillator 5131, deliver to integrated transporting discharging 527 and amplify resistance R 1 and amplified, lock-in amplifier 524 is to its demodulation, data collecting card 528 is gathered and is transferred to computing machine 529 and carried out record.
Obviously, those skilled in the art can carry out various changes and modification and not break away from the spirit and scope of the present invention the present invention.Like this, if within of the present invention these are revised and modification belongs to the scope of the claims in the present invention and equivalent technologies thereof, the present invention also is intended to comprise these changes and modification interior.
Claims (19)
1. a device of measuring trace gas concentration, is characterized in that, comprising: optical module part and electric signal control survey part;
Wherein, described optical module partly comprises: laser instrument, and the spatial beam wave filter and the sample cell that on the optical path direction penetrated at laser instrument, set gradually are injected with trace gas in described sample cell; Described spatial beam wave filter comprises two condenser lenses, and the pin hole between described two condenser lenses, and light path is passed through in described two condenser lenses and pin hole; Described sample cell comprises quartz crystal oscillator, and two micro-resonant cavities that are symmetricly set on described quartz crystal oscillator both sides, the axle center of described quartz crystal oscillator and two micro-resonant cavities and light path coaxial, described quartz crystal oscillator plane and light path are perpendicular, light path in described two micro-resonant cavities and quartz crystal oscillator two pass through between raising one's arm;
Wherein, described electric signal control survey part is electrically connected to laser instrument and quartz crystal oscillator respectively; Before measuring described trace gas concentration, the electric signal control survey partly adopts calibration mode to be calibrated quartz crystal oscillator; When measuring described trace gas concentration, the electric signal control survey partly is switched to measurement pattern, and acoustical signal is transformed to the electric signal obtained according to described quartz crystal oscillator, measures described trace gas concentration.
2. device as claimed in claim 1, is characterized in that, pin hole plane and the light path of described spatial beam wave filter are non-perpendicular.
3. device as claimed in claim 1, is characterized in that, the pin hole of described spatial beam wave filter and the condenser lens focus between laser instrument are positioned at described pin hole center; The pin hole of described spatial beam wave filter and the condenser lens imaging point between sample cell are positioned at quartz crystal oscillator Liang Bei center.
4. device as claimed in claim 1, is characterized in that, the pinhole diameter of described spatial beam wave filter is 50 μ m to 300 μ m.
5. device as claimed in claim 1, it is characterized in that, the length of described each micro-resonant cavity is less than 1/2nd wave length of sounds for being greater than 1/4th wave length of sounds, described wave length of sound refers in trace gas, the length that acoustic vibration minimum period propagates, numerical value equals the resonant frequency of the velocity of sound divided by quartz crystal oscillator.
6. device as claimed in claim 5, is characterized in that, described micro-resonant cavity internal diameter is 0.6mm to 1mm, and the gap of each micro-resonant cavity and quartz crystal oscillator is 30 μ m to 50 μ m.
7. device as claimed in claim 1, is characterized in that, also is equipped with incidence window and outgoing window on the optical path direction of described sample cell, and non-perpendicular with light path.
8. device as claimed in claim 1, is characterized in that, also is equipped with air intake opening and gas outlet on described sample cell, for injecting and the discharge trace gas.
9. device as claimed in claim 1, is characterized in that, described electric signal control survey partly comprises:
Handover module, be electrically connected to described quartz crystal oscillator, for switching calibration mode and measurement pattern;
Signal generating module, be electrically connected to described handover module and laser instrument, for signal occurs;
Lock-in amplifier, be electrically connected to described handover module and signal generating module, for the Harmonic Detection pattern is set, and the signal of surveying carried out to demodulation, and draw response curve;
Data collecting card, be electrically connected to lock-in amplifier, the response curve drawn for gathering lock-in amplifier;
Computing machine, be electrically connected to signal generating module and data collecting card, for control signal generation module, sends signal, and analyze the data that data collecting card gathers.
10. device as claimed in claim 9, is characterized in that, described handover module comprises: the electronic switch be electrically connected to described quartz crystal oscillator input end; Control end and a coupling capacitance that input end is electrically connected to described electronic switch; The integrated transporting discharging be electrically connected to described quartz crystal oscillator output terminal and amplification resistance, and the output terminal of described integrated transporting discharging is electrically connected to lock-in amplifier.
11. device as claimed in claim 9, is characterized in that, described handover module comprises: the relay be electrically connected to described quartz crystal oscillator input end; The coupling capacitance be electrically connected to normally opened contact and the first signal generator output end of described relay; The triode be electrically connected to relay coil; The integrated transporting discharging be electrically connected to described quartz crystal oscillator output terminal and amplification resistance, and the output terminal of described integrated transporting discharging is electrically connected to lock-in amplifier.
12. device as claimed in claim 9, is characterized in that, described signal generating module comprises: the first signal generator that output terminal is electrically connected to described handover module; Trigger the secondary signal generator that input end is electrically connected to the triggering output terminal of described first signal generator; With the electronics totalizer that the Laser Modulation input end of described laser instrument is electrically connected to, described electronics totalizer also is electrically connected to the triggering output terminal of secondary signal generator; The 3rd signal generator be electrically connected to an input end of described electronics totalizer.
13. device as described as claim 1 to 12 any one is characterized in that described laser instrument is middle INFRARED QUANTUM CASCADE LASERS, launches mid-infrared laser.
14. a method of measuring trace gas concentration, is characterized in that, comprises the following steps:
The step of quartz crystal oscillator calibration: under calibration mode, the vibration of electricity consumption signal excitation quartz crystal oscillator, surveyed the electric signal by the quartz crystal oscillator generation of vibration with the first harmonic detection mode, draws the resonant frequency of described quartz crystal oscillator through the demodulation post analysis;
The step of switch mode: be switched to measurement pattern, and, according to described quartz crystal oscillator resonant frequency, the first harmonic detection mode be switched to the second harmonic detection pattern;
Measure the step of trace gas concentration: the frequency of infrared light beam is adjusted to 1/2nd of described quartz crystal oscillator resonant frequency, and is surveyed by quartz crystal oscillator, acoustical signal being transformed to the electric signal obtained with the second harmonic detection pattern;
Wherein, the step of described quartz crystal oscillator calibration, the step of switch mode and the step of measuring trace gas concentration, adopt the device of the described measurement trace gas of claim 1 to 12 any one concentration to implement.
15. method as claimed in claim 14, it is characterized in that, the step of described quartz crystal oscillator calibration, specifically comprise: signal by sine wave and DC level stack of computer control first signal generator output, wherein DC level is controlled electronic switch closes, connect band coupling capacitance end, the sinusoidal wave input pin that is directed to quartz crystal oscillator by coupling capacitance; The first signal generator, to the described sinusoidal wave frequency of high frequency direction scanning output, is exported synchronizing signal to lock-in amplifier simultaneously; Integrated transporting discharging and amplification resistance are amplified the output signal of quartz crystal oscillator; Lock-in amplifier is arranged on the first harmonic detection mode, and the signal of surveying is carried out to demodulation, obtains corresponding curve, via after the data collecting card collection, sending computing machine to, is drawn the resonant frequency of quartz crystal oscillator by computing machine analysis.
16. method as claimed in claim 14, is characterized in that, the step of the step of described switch mode and measurement trace gas concentration specifically comprises:
Computer control first signal generator output no-voltage, the synchronizing signal of synchronous end output 1/2nd described quartz crystal oscillator resonant frequencies is to lock-in amplifier and secondary signal amplifier simultaneously; The secondary signal generator is triggered and produces with sine wave signal frequently, with the triangular signal of the 3rd signal generator output, together is imported into the electronics totalizer, and the signal after stack is admitted to the laser instrument input port and carries out frequency modulation (PFM) and scanning; The no-voltage of first signal generator output is connected the input pin of the signal ground of electronic switch and quartz crystal oscillator, makes quartz crystal oscillator be switched to measurement pattern, and the acoustical signal of generation is converted into electric signal by quartz crystal oscillator, sends into integrated transporting discharging and amplifies resistance and amplified;
Lock-in amplifier is according to the synchronizing signal of described 1/2nd quartz crystal oscillator resonant frequencies, be switched to the second harmonic detection pattern, the electric signal that conversion is obtained carries out demodulation, draws corresponding curve, via after the data collecting card collection, sending computing machine to, by computing machine, carry out record.
17. method as claimed in claim 14, it is characterized in that, the step of described quartz crystal oscillator calibration, specifically comprise: signal by sine wave and DC level stack of computer control first signal generator output, wherein DC level is controlled the triode conducting, and the coil of relay obtains electric, and the contact of closure state is normally opened contact, connect band coupling capacitance end, the sinusoidal wave input pin that is directed to quartz crystal oscillator by coupling capacitance.
18. method as claimed in claim 14, is characterized in that, the step of the step of described switch mode and measurement trace gas concentration specifically comprises:
The no-voltage of first signal generator output is ended triode, do not have electric current to pass through from relay coil, the contact of closure state is normally closed contact, the input pin of signal ground and quartz crystal oscillator is connected, make quartz crystal oscillator be switched to measurement pattern, the acoustical signal produced is converted into electric signal by quartz crystal oscillator, sends into integrated transporting discharging and amplifies resistance and amplified;
Lock-in amplifier is according to the synchronizing signal of described 1/2nd quartz crystal oscillator resonant frequencies, be switched to the second harmonic detection pattern, the electric signal that conversion is obtained carries out demodulation, draws corresponding curve, via after the data collecting card collection, sending computing machine to, by computing machine, carry out record.
19. method as described as claim 14 to 18 any one, is characterized in that, described infrared light beam is mid-infrared laser.
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Application publication date: 20131113 |