CN101813618A - Device and method for simultaneously detecting plurality of gases based on optoacoustic effect - Google Patents
Device and method for simultaneously detecting plurality of gases based on optoacoustic effect Download PDFInfo
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- CN101813618A CN101813618A CN201010033961A CN201010033961A CN101813618A CN 101813618 A CN101813618 A CN 101813618A CN 201010033961 A CN201010033961 A CN 201010033961A CN 201010033961 A CN201010033961 A CN 201010033961A CN 101813618 A CN101813618 A CN 101813618A
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Abstract
The invention relates to a device for simultaneously detecting a plurality of gases based on optoacoustic effect, which comprises a first power supply and a second power supply, a first light source and a second light source, a gas chamber, a head amplifier and a computer, wherein input ends of the first light source and the second light source are respectively connected with the first power supply and the second power supply; the gas chamber receives incident light of the first light source and the second light source, and a microphone is placed in the gas chamber; the head amplifier receives a signal of the microphone; and the computer carries out single frequency amplitude extraction on the signal of the head amplifier, wherein the single frequency amplitude is directly related with gas concentration.
Description
Technical field
The present invention relates to the multiple gases pick-up unit, it has solved the length consuming time of measurement in the past, insensitive, the complicated operation of reaction, the loaded down with trivial details problem of plant maintenance, and a kind of multiple gases based on optoacoustic effect pick-up unit and detection method simultaneously particularly are provided.
Background technology
Existing detector kind is a lot, and principle can be divided into: constant potentiometric electrolysis, iodimetric titration, electrical conductivity method.The electrochemical sensor life-span of using in the constant potentiometric electrolysis is generally 2 years, no matter whether use and must change, and this sensor is an external product, costs an arm and a leg.Electrical conductivity method, iodimetric titration must dispose necessary separately electric drain, iodine titer before use, so use inconvenient.
Also did work in the world, be typically the multiple gases pick-up unit of California, USA university making in 2008 based on the multiple gases detection of optoacoustic effect.They use a plurality of light sources, but be when carrying out gas detection successively to single source power supply (that is to say and have only a light source luminescent) at every turn by a power supply, the light beam scioptics converge with chopper and modulate laggard air inlet chamber, the photoacoustic signal that produces is transferred to computer after phase-locked processing, obtain a kind of concentration of gas, make power supply give next light source power supply then, repeat above process, obtain all gases concentration one by one.Though this method has realized the multiple gases detection, the systematic comparison complexity involves great expense, and has the long shortcoming of Measuring Time.And the present invention to be a plurality of light sources power simultaneously, measure simultaneously, one time data processing obtains multiple gases concentration.
Summary of the invention
Fundamental purpose of the present invention is: a kind of multiple gases while pick-up unit and detection method based on optoacoustic effect is provided, its multiple gases that is based on optoacoustic effect is detection method simultaneously, and it has solved, and measurement concentration length consuming time in the past, reaction are insensitive, complicated operation, the loaded down with trivial details problem of plant maintenance.
The invention provides a kind of multiple gases while pick-up unit, comprising based on optoacoustic effect:
One first power supply and a second source;
One first light source and a secondary light source, the input end of this first light source and secondary light source are connected with a second source with first power supply respectively;
One air chamber, this air chamber receives the incident light of first light source and secondary light source, is placed with a microphone in this air chamber;
One prime amplifier, this prime amplifier receives the signal of microphone;
One computing machine, this computing machine carries out the extraction of single-frequency amplitude to the signal of prime amplifier, and the single-frequency amplitude is directly related with gas concentration.
The quantity of wherein said microphone is 1-2.
Wherein microphone is the high sensitivity microphone.
Wherein air chamber comprises: the steel pipe of two cylindrical parallel, these steel pipe two ends are connected by two tubules respectively, have air intake opening and gas outlet in the centre of tubule, have window at an end of the steel pipe of two cylindrical parallel.
Wherein the centre of the steel pipe in the air chamber has circular hole, is used to place microphone.
The present invention also provides a kind of multiple gases while detection method based on optoacoustic effect, and this method is used the described pick-up unit of claim 1, comprises the steps:
Step 1: start first, second power supply, drive first, second light emitted different frequency light modulated simultaneously, this light modulated enters air chamber through the window of air chamber, make gas molecule in the air chamber absorb the light modulated of this wavelength, and energy is discharged by the form of radiationless transition, gas temperature rising air pressure is increased, and light modulated produces periodic air pressure change, and then produces acoustical signal;
Step 2: the acoustical signal that produces in the air chamber is converted into electric signal by the microphone in the air chamber and amplifies afterwards and through prime amplifier;
Step 3: through the electric signal input computing machine that prime amplifier amplifies, computing machine carries out the single-frequency amplitude and extracts;
Wherein when low concentration, the relation of single-frequency amplitude and gas concentration, according to formula:
U＝R
c×R
M×W
0×c×K (1)
Wherein U is the magnitude of voltage of measuring, R
cBe the response of air chamber, R
MBe the sensitivity of microphone, W
0Be the average power of laser instrument, c is a gas concentration to be measured, and K is the absorption coefficient of gas to be measured.
When wherein determining the scale-up factor in the formula (1), make α=R
c* R
M* W
0* K uses normal concentration c
0Gas is measured, and obtains U
0Electric signal, from U
0=α * c
0Obtain the α value, U and concentration c funtcional relationship in direct ratio in measuring afterwards.
The quantity correspondence of wherein said light source and power supply, the quantity of this light source and power supply are that 2-8 is right.
Wherein the pulsed frequency of each power supply generation is inequality.
Description of drawings
In order to further specify structure of the present invention and feature, the present invention is described further below in conjunction with example and accompanying drawing.
Fig. 1 is a pick-up unit synoptic diagram of the present invention;
Fig. 2 is laser spectrum and corresponding gas molecule absorption intensity spectrum thereof;
Fig. 3 is a gas detection master drawing as a result.
Embodiment
See also shown in Figure 1ly, a kind of multiple gases based on optoacoustic effect of the present invention is pick-up unit simultaneously, comprising:
One first power supply 1 and a second source 2, two power supplys all produce the square-wave voltage signal, but frequency is inequality, and the frequency of operation of power supply depends on the resonant frequency of air chamber;
One first light source 3 and a secondary light source 4, the input end of this first light source 3 and secondary light source 4 is connected with second source 2 with first power supply 1 respectively, light source should the selective light spectral limit during narrow and work wave length shift little, in order to avoid other gas also produces photoacoustic signal, make the concentration value of gas to be measured bigger than normal, the angle of divergence of light source should be as far as possible little in addition;
One air chamber 5, this air chamber 5 receives the light modulated of first light source 3 and secondary light source 4, and wherein air chamber 5 comprises: the BaF of two circles
2The steel pipe 52 of 51, two cylindrical parallel of window of material, the centre of steel pipe 52 has circular hole 56, and steel pipe 52 two ends are connected by tubule 53 respectively, have air intake opening 54 and gas outlet 55 in the centre of tubule 53;
Microphone 6, this microphone 6 places circular hole 56 places and the sealing of air chamber 5, the quantity of described microphone 6 is 1-2, wherein microphone 6 is the high sensitivity microphone, selecting microphone is that two parameters are most important: 1. sensitivity, the sensitivity of microphone is high more, same intensity acoustical signal can produce bigger electric signal, the overall sensitivity of sniffer can improve equally, 2. signal to noise ratio (S/N ratio), microphone inevitably can be introduced noise when carrying out the acoustic-electric conversion, and signal to noise ratio (S/N ratio) is high more, it is more little to the interference of useful signal to be equivalent to noise, and the sensitivity of sniffer also can improve;
One prime amplifier 7, this prime amplifier 7 receives the signal of microphone 6, and electric signal is amplified;
One computing machine 8, the sound card in this computing machine 8 plays key effect, and its signal to prime amplifier 7 carries out the single-frequency amplitude and extracts, and the single-frequency amplitude is directly related with gas concentration.
Please shown in Figure 1 in conjunction with consulting, the invention provides a kind of multiple gases while detection method based on optoacoustic effect, this method is used aforesaid pick-up unit, comprises the steps:
Step 1: start first, second power supply 1,2, drive first, second light source 3,4 emission different frequency light modulated simultaneously, this light modulated enters air chamber 5 through the window 51 of air chamber 5, make gas molecule in the air chamber 5 absorb the light modulated of this wavelength, and energy is discharged by the form of radiationless transition, gas temperature rising air pressure is increased, and light modulated produces periodic air pressure change, and then produces acoustical signal; The pulse repetition frequency that each power supply produces is inequality; The quantity correspondence of described light source and power supply, the quantity of this light source and power supply are that 2-8 is to (present embodiment is 2 pairs);
Step 2: the acoustical signal that produces in the air chamber 5 is converted into electric signal by the microphone in the air chamber 56 and amplifies afterwards and through prime amplifier 7;
Step 3: through the electric signal input computing machine 8 that prime amplifier 7 amplifies, computing machine 8 carries out the single-frequency amplitude and extracts;
Wherein when low concentration, the relation of single-frequency amplitude and gas concentration, according to formula:
U＝R
c×R
M×W
0×c×K (1)
Wherein U is the magnitude of voltage of measuring, R
cBe the response of air chamber, R
MBe the sensitivity of microphone, W
0Be the average power of laser instrument, c is a gas concentration to be measured, and K is the absorption coefficient of gas to be measured.
When wherein determining the scale-up factor in the formula (1), make α=R
c* R
M* W
0* K uses normal concentration c
0Gas is measured, and obtains U
0Electric signal, from U
0=α * c
0Obtain α, U and concentration c funtcional relationship in direct ratio in measuring afterwards.
The spectrum that Fig. 2 has provided first light source 3 and secondary light source 4 is respectively 12 and 11 and corresponding SO
2Be respectively 10 and 9 with the absorption spectra of CO gas.
Fig. 3 has provided with SO
2With CO be the experimental measurements of probe gas, 13 is SO
2The peak, 14 be the peak of CO.
Specify measuring process below by embodiment:
According to connection shown in Figure 1, general technician can both finish above operation with each parts.
The laser that first light source 1 and secondary light source 2 send enters air chamber 5 by air chamber window 51, and the corresponding gas molecule in the air chamber 5 absorbs laser and also by the mode of radiationless transition energy discharged the generation sound wave, and the model of high sensitivity microphone 6 is
NT5, prime amplifier 7 is selected the NEOPreAmp low-noise preamplifier of ICON company for use, by microphone acoustical signal is converted to electric signal and is transferred to computing machine 8, carry out analog to digital conversion and simple signal information extraction through computer sound card, comprise its frequency and amplitude, and store and show by 8 pairs of data of computing machine.
The course of work of the present invention is:
Open light source power, prime amplifier power supply and computer power supply;
Gas to be measured enters air chamber;
Parameter by computer settings sound card image data;
Give light source power supply, begin capture program behind the ls clock;
After several seconds, Automatic Program stops, and simultaneous computer is handled data, calculates gas concentration value to be measured and preserves data;
Close each device power supply (DPS), measure and finish.
This detection method is compared with conventional detection has following advantage:
The detection sensitivity height;
Be convenient to safeguard;
Power supply and air chamber are easy to integrated, and be easy to use;
Light source has been selected advanced semiconductor laser for use, and spectrum is narrow, and volume is little, is convenient to integrated and practical;
Measure analysis simultaneously simultaneously for multiple gases, significantly reduced Measuring Time.
Embodiment
Select for use homemade quantum cascade laser as first and second light sources, its wavelength is respectively 7.36 microns and 4.6 microns, compare with other light source, quantum cascade laser has the following advantages: 1. volume is little, does not need complicated apparatus just can realize that multi beam different wave length laser is from same air chamber window incident inlet plenum; 2. spectral range is narrow, is difficult for being produced undesired signal by other gas absorption in the detection time; 3. the choosing wavelength scope is wide, and quantum cascade laser by the adjusting of technological parameter, can cover the middle infrared absorption peak of multiple gases, so have a extensive future in manufacturing process.
It is luminous that the pulse voltage that first power supply 1 produces 220Hz drives first light source 3, and simultaneously, it is luminous that the pulse voltage of second source 2 generation 324Hz drives secondary light source 4, the SO in the air chamber 5
2Absorbing wavelength is the acoustical signal that 7.36 microns light modulated produces 220Hz, CO absorbing wavelength in the air chamber 5 is the acoustical signal that 4.6 microns light produces 324Hz, through a series of processing, computing machine 8 demonstrates the signal amplitude that frequency is 220Hz and 324Hz, two amplitudes respectively with SO
2Relevant with the concentration of CO.
The present invention is based on the detection of optoacoustic effect realization to gas concentration, can not have any impact to gas concentration to be measured in measuring process, does not need liquid in experimental provision, and the reliability of device is improved.As far back as 1880, Bell at first observed the optoacoustic conversion phenomena in solid, and had described relevant experimental results in giving the report of U.S. scientific advance association, claimed that the physical phenomenon of this optoacoustic conversion is an optoacoustic effect.Optoacoustic effect is that the monochromatic light with the adjustable system of a beam intensity shines on the sample that is sealed in the photoacoustic cell, absorption of sample luminous energy, and to discharge the mode de excitation of heat energy, the heat energy that discharges makes sample and surrounding medium periodically heat by the modulating frequency generation of light, thereby cause medium to produce the periodic pressure fluctuation, this pressure surge can detect with sensitive microphone or piezoelectric ceramic microphone, and obtains photoacoustic signal by amplification.Because photoacoustic spectroscopy is the size of absorption of sample luminous energy, thereby reflected light, scattered light etc. are very little to measuring interference.
When probe gas concentration was low, the intensity of optoacoustic effect was determined by following formula:
U＝R
c×R
M×W
0×c×K
Wherein U is the magnitude of voltage of measuring, R
cBe the response of air chamber, R
MBe the sensitivity of microphone, W
0Be the average power of laser instrument, c is a gas concentration to be measured, and K is the absorption coefficient of gas to be measured.
The response of air chamber is the character of air chamber itself, in case chamber structure is fixed, response is exactly a definite value; That yes is high more good more in the sensitivity of microphone, but should consider the cost problem in the practical application; The absorption coefficient of gas changes very little in certain temperature range, can ignore; So what finally accuracy of detection is had the greatest impact is the average power of laser instrument, laser instrument peak power and dutycycle are all linear with average power, so the performance of laser instrument has a direct impact detection sensitivity.So our research emphasis from now on will be placed on the raising of laser performance, further improve detection limit.
In addition, some other method also can further improve the detection sensitivity of optoacoustic effect:
Can improve optoacoustic effect intensity by prolonging the light path of light beam in air chamber, for example the White pond can be increased to light path original tens times, and corresponding acoustic signal intensity also increases tens times on year-on-year basis;
For the big light source of the angle of divergence, can add lens in the light source front and make light beam become directional light to enter air chamber, can improve the utilization factor of luminous energy like this;
Can select the higher microphone of sensitivity for use, same acoustical signal will be bigger when changing into electric signal;
The sound card that common computer carries all is 16, and it is enough utilizing it to carry out data processing; If adopt 24 in addition more seniority sound card or the specialty data collecting card, can increase substantially detection sensitivity certainly; Also can adopt two and above independently lock-in amplifier (perhaps similar device) to gather the signal amplitude of different frequency respectively, but like this, equipment cost will significantly improve with it;
Air chamber has the resonant frequency of self, acoustical signal will produce maximal value when the stimulating frequency of laser instrument is identical with this frequency, big more with the resonant frequency deviation, acoustical signal is weak more, therefore when carrying out the multiple gases detection, the stimulating frequency of a plurality of laser instruments should be under distinguishable prerequisite, is that middle mind-set both sides evenly distribute at the resonant frequency of air chamber.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (9)
1. one kind based on the multiple gases of optoacoustic effect pick-up unit simultaneously, comprising:
One first power supply and a second source;
One first light source and a secondary light source, the input end of this first light source and secondary light source are connected with a second source with first power supply respectively;
One air chamber, this air chamber receives the incident light of first light source and secondary light source, is placed with microphone in this air chamber;
One prime amplifier, this prime amplifier receives the signal of microphone;
One computing machine, this computing machine carries out the extraction of single-frequency amplitude to the signal of prime amplifier, and the single-frequency amplitude is directly related with gas concentration.
2. the multiple gases while pick-up unit based on optoacoustic effect according to claim 1, the quantity of wherein said microphone is 1-2.
3. the multiple gases while pick-up unit based on optoacoustic effect according to claim 1 and 2, wherein microphone is the high sensitivity microphone.
4. the multiple gases while pick-up unit based on optoacoustic effect according to claim 1, wherein air chamber comprises: the steel pipe of two cylindrical parallel, these steel pipe two ends are connected by two tubules respectively, have air intake opening and gas outlet in the centre of tubule, have window at an end of the steel pipe of two cylindrical parallel.
5. according to claim 1 or 4 described multiple gases while pick-up units based on optoacoustic effect, wherein the centre of the steel pipe in the air chamber has circular hole, is used to place microphone.
6. one kind based on the multiple gases of optoacoustic effect detection method simultaneously, and this method is used the described pick-up unit of claim 1, comprises the steps:
Step 1: start first, second power supply, drive first, second light emitted different frequency light modulated simultaneously, this light modulated enters air chamber through the window of air chamber, make gas molecule in the air chamber absorb the light modulated of this wavelength, and energy is discharged by the form of radiationless transition, gas temperature rising air pressure is increased, and light modulated produces periodic air pressure change, and then produces acoustical signal;
Step 2: the acoustical signal that produces in the air chamber is converted into electric signal by the microphone in the air chamber and amplifies afterwards and through prime amplifier;
Step 3: through the electric signal input computing machine that prime amplifier amplifies, computing machine carries out the single-frequency amplitude and extracts;
Wherein when low concentration, the relation of single-frequency amplitude and gas concentration, according to formula:
U＝R
c×R
A4×W
0×c×K (1)
Wherein U is the magnitude of voltage of measuring, R
cBe the response of air chamber, R
MBe the sensitivity of microphone, W
0Be the average power of laser instrument, c is a gas concentration to be measured, and K is the absorption coefficient of gas to be measured.
7. the multiple gases while detection method based on optoacoustic effect according to claim 6 when wherein determining the scale-up factor in the formula (1), makes α=R
c* R
M* W
0* K uses normal concentration c
0Gas is measured, and obtains U
0Electric signal, from U
0=α * c
0Obtain the α value, U and concentration c funtcional relationship in direct ratio in measuring afterwards.
8. the multiple gases while detection method based on optoacoustic effect according to claim 6, the quantity correspondence of wherein said light source and power supply, the quantity of this light source and power supply are that 2-8 is right.
9. according to claim 6 or 8 described multiple gases while detection methods based on optoacoustic effect, wherein the pulsed frequency of each power supply generation is inequality.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102445474A (en) * | 2011-11-22 | 2012-05-09 | 河南汉威电子股份有限公司 | Gas detector, identification method of sensor thereof, and sensor connection detection method |
| CN104251880A (en) * | 2013-06-25 | 2014-12-31 | 德州仪器公司 | Device and system for generating frequency reference and method for generating frequency reference signal |
| CN106124410A (en) * | 2016-06-08 | 2016-11-16 | 中国科学院合肥物质科学研究院 | Single photoacoustic cell measures the new method of aerosol multi-wavelength absorptance simultaneously |
| CN110261379A (en) * | 2013-11-28 | 2019-09-20 | 豪夫迈·罗氏有限公司 | Method and apparatus for determining the concentration of the analyte in body fluid |
| CN110346296A (en) * | 2019-07-20 | 2019-10-18 | 大连理工大学 | A kind of multi-cavity type is partly begun to speak resonance light sound pond and multiple gases measuring system simultaneously |
| CN111337435A (en) * | 2020-04-14 | 2020-06-26 | 聊城大学 | Multi-component trace gas sensor detection system and detection method thereof |
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2010
- 2010-01-07 CN CN201010033961A patent/CN101813618A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102445474A (en) * | 2011-11-22 | 2012-05-09 | 河南汉威电子股份有限公司 | Gas detector, identification method of sensor thereof, and sensor connection detection method |
| CN102445474B (en) * | 2011-11-22 | 2014-07-30 | 河南汉威电子股份有限公司 | Gas detector, identification method of sensor thereof, and sensor connection detection method |
| CN104251880A (en) * | 2013-06-25 | 2014-12-31 | 德州仪器公司 | Device and system for generating frequency reference and method for generating frequency reference signal |
| CN110261379A (en) * | 2013-11-28 | 2019-09-20 | 豪夫迈·罗氏有限公司 | Method and apparatus for determining the concentration of the analyte in body fluid |
| CN110261379B (en) * | 2013-11-28 | 2021-11-12 | 豪夫迈·罗氏有限公司 | Method and device for determining the concentration of an analyte in a body fluid |
| CN106124410A (en) * | 2016-06-08 | 2016-11-16 | 中国科学院合肥物质科学研究院 | Single photoacoustic cell measures the new method of aerosol multi-wavelength absorptance simultaneously |
| CN110346296A (en) * | 2019-07-20 | 2019-10-18 | 大连理工大学 | A kind of multi-cavity type is partly begun to speak resonance light sound pond and multiple gases measuring system simultaneously |
| CN111337435A (en) * | 2020-04-14 | 2020-06-26 | 聊城大学 | Multi-component trace gas sensor detection system and detection method thereof |
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Application publication date: 20100825 |