CN107655854A - A kind of trace N2O gas detecting systems - Google Patents
A kind of trace N2O gas detecting systems Download PDFInfo
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- CN107655854A CN107655854A CN201610583306.3A CN201610583306A CN107655854A CN 107655854 A CN107655854 A CN 107655854A CN 201610583306 A CN201610583306 A CN 201610583306A CN 107655854 A CN107655854 A CN 107655854A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
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Abstract
A kind of trace N2O gas detecting systems, using modulation of source, the mutually technology such as amplification is locked, realizes the parsing of gas concentration weak signal under strong clutter background；System can be in 0~1% effective detection N20 gas concentration, Monitoring lower-cut are 5.0 × 10‑5, it is 0.11% with respect to detection error, testing result linear equation is y=192.69909x 1, the linearity 0.99807.Repeated detection experiment shows that system relative standard deviation is 0.137%, C02、O2, the common gas such as vapor on testing result without influence.Change the centre wavelength of laser, this method also can be used for CO2, CH4Etc. the detection of other greenhouse gases.
Description
Art
The present invention relates to a kind of detecting system, more particularly to a kind of trace N2O gas detecting systems.
Background technology
N2O gases are one of main greenhouse gases, although its content in an atmosphere is seldom, concentration is 0.3~0.4 μ
L/L, but N2O warming effect is extremely obvious, about CO2150~200 times, and N2O is extremely stable in an atmosphere, and it is flat
The equal life-span was up to 120 years.In recent years, because agricultural and industrial develop rapidly, the N in air is caused2O concentration is with annual
0.3% speed increase, so monitor N2O concentration is significant.
At present, it is used to detect N both at home and abroad2O method is mainly gas chromatography, and it has accuracy of detection height, reliability
The advantages that strong, but it is clearly disadvantageous there is also some：Detecting instrument cost is high, detection time length；Further, since O2, H2O,
CO2Interference can cause measurement N2Chromatogram Baseline rapid lifting mouth during O], gas chromatography is influenceed to N2The standard of O gasmetries
Exactness.
The content of the invention
The invention aims to quickly and accurately measure N20 gas concentration, devise a kind of trace N2O gases detect
System.
The technical solution adopted for the present invention to solve the technical problems is：
Trace N2O gas detecting systems include power and the adjustable Distributed Feedback Laser of wavelength, the temperature and current-modulation of laser
System, light path system, spectral absorption system, photodetector, lock-in amplifier and the embedded data acquisition of gas and place
Reason system, the performance of signal detection can be improved by adjusting the amplitude of sinusoidal modulation signal, improve measurement accuracy and detection spirit
Sensitivity.
Described Distributed Feedback Laser employs the commercial Distributed Feedback Laser that wavelength is 1522nm, power is 5mW, and it is by changing
The Injection Current for becoming laser changes the active region temperature of laser, realizes the tunable of laser output intensity and wavelength.
The operating temperature of laser is 25 DEG C, central current 60mA, and experiment is made by the tuning of 50Hz low frequency sawtooth sweep currents
Optical maser wavelength is inswept N2O gaseous absorption line 1522.45nm, the length scanning after laser tuning is 1520~1524nm.
Described photodetector have selected PIN-type InGaAs photodiodes.
Described lock-in amplifier uses the SR830 of Harvard University.
The gas absorption cell length of described experiment is 50cm.
Described system is provided with multipath reflection cavity configuration, and reflective cavity is mainly made up of 4 pieces of level crossings, by multiple anti-
Structure is penetrated, effective absorption distance of gas is increased into 5.5m on the basis of gas absorption cell length L is not changed, improves inspection
The sensitivity of examining system.
The beneficial effects of the invention are as follows：
Trace N2O gas detecting systems have preferably repeatability, relative standard deviation 0.137%.The system is to CO2、O2、
The common gas such as vapor have stronger antijamming capability, can be applied to trace N2The quick detection of O gas concentrations.Meanwhile
By changing the centre wavelength of laser, this method can also be applied to CO2、CH4Deng the detection of other greenhouse gases.
Brief description of the drawings
The present invention is further described with reference to the accompanying drawings and examples.
Fig. 1 is check system structure.
Fig. 2 is multipath reflection formula gas absorption cell internal structure.
Wherein, [1], [2], [3], [4] are all level crossings.
Embodiment
As shown in figure 1, trace N2O gas detecting systems include power and the adjustable Distributed Feedback Laser of wavelength, laser
Temperature and current modulating system, spectral absorption system, photodetector, lock-in amplifier and the insertion of light path system, gas
Formula data Collection ＆ Processing System.According to HIT-RAN databases, N2O gaseous absorption lines center wave number is 6568.34243cm-1,
Absorption line intensity is 2.2 × 10-23cm/mol·cm-2, so in the measuring system designed herein, employing wavelength is
1522nm, the commercial Distributed Feedback Laser that power is 5mW, it is to change swashing for laser by changing the Injection Current of laser
Area's temperature living, realize the tunable of laser output intensity and wavelength.The operating temperature of laser is 25 DEG C, and central current is
60mA, experiment make the inswept N of optical maser wavelength by the tuning of 50Hz low frequency sawtooth sweep currents2O gaseous absorption lines
1522.45nm, the length scanning after laser tuning is 1520~1524nm.While in order to realize second harmonic I2f, detection,
Superposition modulated frequency is that 4 kHz high_frequency sine wave realizes the tuning of laser output frequency on sawtooth waveforms, is passed through in experiment
The amplitude of sinusoidal modulation signal is adjusted to improve the performance of signal detection, improves measurement accuracy and detection sensitivity.In experiment, light
Electric explorer have selected PIN-type InGaAs photodiodes, and lock-in amplifier uses the SR830 of Harvard University.It is secondary in progress
Harmonic wave I2f, during detection, modulation circuit produces sawtooch sweep signal and sinewave modulation signal simultaneously, by controlling laser
Electric current realizes the modulation to optical maser wavelength, the laser I after modulationin.By gas absorption cell, because the spectral absorption of gas is made
With decaying to I in receiving terminal laser signalOUTGas absorption cell both ends set graded index (GRIN) condenser lens, ensure that
The parallel people of laser is injected into gas absorption cell, and the light come out from absorption cell all converges to the photosurface of photodetector
On.Electric signal V after detector opto-electronic conversionIN.By being linked into lock-in amplifier after the pretreatment of pre-amplification circuit
Input, and the reference signal of lock-in amplifier termination modulated signal VREF.According to cross-correlation test principle, can with one with
Measured signal frequency identical reference signal extracts information measured, reference signal V among this experimental systemREFWith input signal
VINIn active ingredient frequency f it is completely the same, can reach from strong clutter background extract small-signal purpose.Lock mutually amplifies
The output signal of device enters embedded system after A/D is converted, and the system mainly completes collection to gas concentration signal, place
Reason and display, realize N2The automation and visualization of O gases detection.
As shown in Fig. 2 the gas absorption cell length of experiment is 50 cm, and gas absorption cell length L is longer, and its light intensity becomes
Change amount is bigger.In order to obtain higher sensitivity, it is necessary to increase the light-absorbing length L of gas, but can not ad infinitum increase
The length of absorption cell.This experimental design has made multipath reflection cavity configuration, as shown in Fig. 2 reflective cavity is mainly by 4 pieces of planes
Microscope group is into input level crossing [1] and rz] the angle of the crossing and output end level crossing r-3] and E4] the angle of the crossing be 175., and
And level crossing [1] and [3], E2] parallel respectively with [4].By multipath reflection structure, do not changing gas absorption cell length L's
On the basis of effective absorption distance of gas increased into 5.5 m, improve the sensitivity of detecting system.
Claims (6)
- A kind of 1. trace N2O gas detecting systems include power and the adjustable Distributed Feedback Laser of wavelength, the temperature and electricity of laser Stream modulating system, light path system, spectral absorption system, photodetector, lock-in amplifier and the embedded data of gas are adopted Collection and processing system, the performance of signal detection can be improved by adjusting the amplitude of sinusoidal modulation signal, improve measurement accuracy and Detection sensitivity.
- 2. trace N according to claim 12O gas detecting systems, it is characterized in that described Distributed Feedback Laser employs wavelength The commercial Distributed Feedback Laser for being 5mW for 1522nm, power, it is to change laser by changing the Injection Current of laser Active region temperature, realize the tunable of laser output intensity and wavelength；The operating temperature of laser is 25 DEG C, and central current is 60mA, experiment make the inswept N of optical maser wavelength by the tuning of 50Hz low frequency sawtooth sweep currents2O gaseous absorption lines 1522.45nm, the length scanning after laser tuning is 1520~1524nm.
- 3. trace N according to claim 12O gas detecting systems, it is characterized in that described photodetector have selected PIN Type InGaAs photodiodes.
- 4. trace N according to claim 12O gas detecting systems, it is characterized in that described lock-in amplifier uses Harvard The SR830 of university.
- 5. trace N according to claim 12O gas detecting systems, it is characterized in that the gas absorption cell length of described experiment Spend for 50cm.
- 6. trace N according to claim 12O gas detecting systems, it is characterized in that described system is provided with multipath reflection chamber Structure, reflective cavity are mainly made up of 4 pieces of level crossings, by multipath reflection structure, are not changing gas absorption cell length L's On the basis of effective absorption distance of gas increased into 5.5m, improve the sensitivity of detecting system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201610583306.3A CN107655854A (en) | 2016-07-24 | 2016-07-24 | A kind of trace N2O gas detecting systems |
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| CN201610583306.3A CN107655854A (en) | 2016-07-24 | 2016-07-24 | A kind of trace N2O gas detecting systems |
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| CN107655854A true CN107655854A (en) | 2018-02-02 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109490226A (en) * | 2018-09-19 | 2019-03-19 | 北京农业智能装备技术研究中心 | Nitrous oxide measuring device and its measurement method in a kind of soil crack |
| CN109530917A (en) * | 2018-12-24 | 2019-03-29 | 大族激光科技产业集团股份有限公司 | Laser welding system and method |
| CN115855871A (en) * | 2022-12-09 | 2023-03-28 | 重庆大学 | Nitrous oxide monitoring devices based on solid raman laser |
-
2016
- 2016-07-24 CN CN201610583306.3A patent/CN107655854A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109490226A (en) * | 2018-09-19 | 2019-03-19 | 北京农业智能装备技术研究中心 | Nitrous oxide measuring device and its measurement method in a kind of soil crack |
| CN109530917A (en) * | 2018-12-24 | 2019-03-29 | 大族激光科技产业集团股份有限公司 | Laser welding system and method |
| CN115855871A (en) * | 2022-12-09 | 2023-03-28 | 重庆大学 | Nitrous oxide monitoring devices based on solid raman laser |
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Application publication date: 20180202 |