CN102183492B - Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument and measuring method - Google Patents

Abstract

The invention discloses a three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument and a three-band integrated atmospheric aerosol particle scattering coefficient measuring method. The measuring instrument comprises an optical measurement chamber, a light-emitting-diode (LED)-based integrating sphere light source (7) is arranged at the top of the chamber, a plurality of diaphragms (19, 20, 21, 22, 23 and 24) are arranged in the chamber, and a reflector (9) is arranged at a non-detection end to prevent multiple times of scattered light from entering a detector (11); and a sample gas inlet port (17) and a gas outlet port (18) are formed in the chamber, and the sample gas is extracted through a sampling pump (13) and enters a scattering cavity (8) from the gas inlet port. When the integrating sphere light source (7) is lightened, the light emitted from the light source is irradiated on the sample gas, and the actual measured scattered light intensity is received through a single photon detector (11) and converted into the measured photon number; a frosted glass (28) with stable performance is used for generating scattered light to eliminate errors caused by light intensity fluctuation of a light source and magnification drift of a photoelectric multiplier tube; through the standard gas and the zero gas, the measured scattering coefficient is calibrated and the air Rayleigh scattering background is deducted; and the single photon detector converts the received scattered light signals into electrical signals, then the electrical signals are processed and controlled by a micro processing control circuit, the scattering coefficient is measured in real time, and the data are transmitted to a touch screen (16) and displayed. The measuring instrument has good instantaneity, high measurement precision and stable system, and is easy for maintenance.

Description

Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument and measuring method

Technical field

The present invention relates to a kind of environmental protection, weather monitoring field, specifically a kind of instrument and method of real time on-line monitoring atmospheric aerosol particle scattering coefficient.

Background technology

Atmospheric aerosol is to be the heterogeneous system of liquid state, particulate solid and the gas composition of 0.1～10 μ m by diameter, has very large time and spatial variations.Naturally doing in the clean atmosphere, the mass concentration of atmospheric aerosol is at 1 μ gm ^-3Below, in the municipal pollution atmosphere, aerosol quality and concentration can reach every cubic metre several milligrams.In recent years, atmospheric aerosol has become one of hot issue of current research on global change as one of important driving factor of Global climate change.Successively carried out optical property and the radiation characteristic that atmospheric aerosol is familiar with in a series of research work both at home and abroad.

In visible wavelength range, what atmospheric extinction was had the greatest impact is that diameter is in the particulate in 0.6～1.5 μ m scope.In the ordinary course of things, as not being the area that is formed thicker aerosol layer by carbon, can think that the scattering process of particulate is much larger than absorption.This shows, aerocolloidal scattering process is very large.About the measurement of aerosol scattering character, mainly be by dual mode, a kind of is directly to measure aerocolloidal scattering coefficient, and another kind is by the theoretical Inversion Calculation particle scattering of Mie coefficient according to parameters such as particle spectra distributions.Utilizing the Mie theory to calculate needs hypothesis refractive index, the error that Mie computation process is very complicated and existence is larger.Therefore, in the urgent need to developing a kind of direct measurement atmospheric aerosol particle scattering coefficient measuring instrument.The domestic instrument that yet there are no up to now about direct measurement atmospheric aerosol particle scattering coefficient.

Triband integration type atmospheric aerosol scattering coefficient measuring instrument can carry out continuous automatic Observation to the scattering properties of the atmospheric aerosol under the free position, and its contactless property measurement can not change the character of particulate.It can also further analyze aerocolloidal constituent by being used in conjunction with Other Instruments, for the research atmospheric aerosol provides new means.

Summary of the invention

The present invention proposes a kind of Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument and measuring method.

The technical solution used in the present invention:

Measuring principle

Luminance brightness in the unit solid angle that the single photon photodetector receives is

$L=\frac{1}{\mathrm{\Ω}}{\∫}_{{\mathrm{\θ}}_1}^{{\mathrm{\θ}}_2}\mathrm{dL}=\left(\frac{I_0}{y}\right){\∫}_{{\mathrm{\θ}}_1}^{{\mathrm{\θ}}_2}\mathrm{\β}\left(\mathrm{\θ}\right)\sin \mathrm{\θd\θ}$

Wherein, limit of integration θ ₁, θ ₂Depend on apparatus structure, the limit of integration can comprise 0～π in principle, and then the output L by integral scattering degree meter can directly obtain scattering coefficient σ _Scar, namely

$L=\frac{I_0}{y}{\∫}_0^{\mathrm{\π}}\mathrm{\β}\left(\mathrm{\θ}\right)\sin \mathrm{\θd\θ}=\frac{I_0}{2\mathrm{\πy}}{\mathrm{\σ}}_{\mathrm{scat}}$

But actual instrumentation fails to meet this requirement, and this gives σ _ScatMeasurement bring the angle truncation error, but this error is very little, theoretical analysis shows, to the general atmosphere gasoloid, the σ of measurement _ScatBe not more than ± 10%.

Adopt the integration nephelometry, according to the knowledge of geometry and illumination scattered light is carried out strict angle weighted integral, basically solved complicated scattering problems; Measured scattering coefficient corresponding to triband, widened measurement range and can infer accordingly the molecular difference of tested grain.The present invention adopts and chooses simultaneously high-power LED light source based on the diffused light source of integrating sphere type, and adds constant-flow driver at circuit, has solved the difficulty that needs can obtain by the electric current of each LED of fine adjustment the cosine characteristic in diffusion remaining light source.

Utilize light beam from side direction irradiation scattering chamber, air and aerosol particle in the chamber produce scattering to incident light, between light source and single photon photodetector, intercept direct projection light with diaphragm, like this, the scattered light that only has air in the chamber and aerosol particle to produce can arrive the single photon photodetector.By measuring light-scattering coefficient σ _ScatThen from σ _ScatIn deduct air the Rayleigh scattering item draw the scattering coefficient θ of aerosol particle thing _Sp

Compared with prior art, beneficial effect of the present invention is embodied in:

(1) utilizes the integration nephelometry to measure scattering coefficient, avoided complicated scattering computational problem;

(2) LED-based integrating sphere radiating light source improves light source serviceable life and increase precision and the reliability that scattering coefficient is measured, and the triband light-source structure is compact, need not complicated optical system and a plurality of single photon photodetector;

(3) measure scattering coefficient corresponding to triband, can proofread and correct the angle truncation error, and it is extensive to have measurement range, can be applicable to the monitoring such as visibility, mist, flue gas, flexible car tail gas.

Description of drawings

Below in conjunction with accompanying drawing optimal way of the present invention is described in further detail.

Fig. 1 is described Aerosol scattering coefficient gauge systems structured flowchart.

Fig. 2 is the optical cell structural representation among Fig. 1.

Fig. 3 is the triband radiating light source structural representation based on integrating sphere in the optical cell among Fig. 2.

Fig. 4 is the light-emitting window scattering angle schematic diagram of Fig. 3 light source.

Fig. 5 is that schematic diagram is processed in microprocessor count control.

Embodiment

Referring to Fig. 1, Fig. 2 and Fig. 3, triband integration type atmospheric aerosol scattering coefficient measuring instrument, comprise parts, calibration gas circuit (calibrating gas gas circuit, zero gas air inlet gas circuit) and the upper configuration thereof of optical measurement chamber and upper configuration thereof parts, measure gas circuit (sample gas air inlet gas circuit, sample gas give vent to anger gas circuit) and on accessory and signal processing controls and display circuit; This signal processing controls and display circuit respectively with the optical measurement chamber on the parts, calibration gas circuit and the upper configuration thereof that configure parts and measure gas circuit and on accessory be electrically connected.

Wherein the parts of optical measurement chamber and upper configuration thereof are:

Comprise the optical measurement chamber, the optical measurement chamber inner wall is coated with Berlin black; The centre of optical measurement chamber is scattering chamber 8, and 8 tops, scattering chamber are equipped with LED-based triband cosine radiation integrating sphere light source 7; Scattering chamber 8 left and right sidewalls have the taper light hole, be separately installed with diaphragm 19,20,21,22,23,24 in the optical measurement chamber of scattering chamber 8 arranged on left and right sides, the left end of optical measurement chamber is equipped with ligh trap 9, and right-hand member is connected with single photon photodetector 11 light by O-ring seal 25; The diaphragm 21 outer scattering shutters that to open with closure that are equipped with of scattering chamber 8 right side light paths, the scattering shutter is comprised of rotary magnet 10, the round-meshed pivoted arm 30 of front end, frosted glass 28 and attenuator 29, have calibrating gas and zero gas intake interface 26 and 27 on the end face of optical measurement chamber two ends, there are sample gas air inlet port 17 and the port 18 of giving vent to anger in optical measurement chamber middle part, bleed from the chamber port 18 of giving vent to anger by sampling pump 13, sample gas enters the optical measurement chamber from air inlet port 17; Gas solenoid valve 5 is installed in the calibrating gas gas circuit; Coarse filter 3, zero air pump (membrane pump) 4 are installed in the zero gas air inlet gas circuit successively, and calibrating gas gas circuit, zero gas air inlet gas circuit are linked into described calibrating gas and zero gas intake interface 26 and 27 after importing precision filter 6; The illumination that integrating sphere light source 7 sends be mapped to the scattered light part that produces on the large aerosol particle in the sample gas in the scattering chamber 8 through the taper light hole diaphragm 20,19 in left side, scattering chamber, arrive ligh trap 19 so that scattered light departs from single photon photodetector 11, scattered light another part arrives single photon photodetectors 11 through the taper light hole diaphragm 21,22,23,24 on right side, scattering chamber, and single photon photodetector 11 is converted to the signal that receives and delivers to microprocessor 15 behind the electric signal and count, process and control.

Triband integrating sphere type cosine radiating light source 7 is mainly by red, green, blue three-color LED light source 32,35,34, integrating sphere 36 and be used for side blanking cover 37 and side plastic lining lid 38 that fixed L ED uses and form.There are three baffle plate D1, D2, D3 in integrating sphere 7 inside, and the bottom is equipped with white glass optical window 33.The wavelength of LED three-color light source is elected the ruddiness of 630nm, the green glow of 520nm and the blue light of 450nm as, and power is 3W; Red, green, blue three-color LED light source is installed on respectively in three side S1, S2, the S3 of integrating sphere; The scattering shutter is comprised of rotary magnet 10, the round-meshed pivoted arm 30 of front end, frosted glass 28 and attenuator 29, choosing what be rotated counterclockwise direction and rotation angle is 25 ° rotary magnet, choose transmitance and be 30% frosted glass and transmitance and be 0.3% neutral density filter, thickness is 2mm.Go from the light incident direction, their order is that frosted glass sticks on before the optical filter; Several aperture diaphragms in the zone of a taper, also play beam limit and avoid the interior light by wall reflection and scattering of optical cell to enter the single photon photodetector; Ligh trap 9 is by becoming 25 ° black glass mirror to form with perpendicular, its effect is to allow scattered light be offset to the non-end of probe of optical measurement chamber; Photodetector 11 is chosen H7155 type photon counting head, adopts the betal can encapsulation.Its effect is that faint scattered light signal is converted into electric signal and exports to microprocessor to carry out photon counting and processing with the signal of TTL form.

Coarse filter 3 is chosen high efficiency particulate air filter, it is the membrane pump of 4.2L/min that zero air pump 4 adopts flow, fine filtrator 6 is selected and removed greater than 0.1 μ m particle and filtration efficiency is 99.99% filtrator, it is that DC12V and interface are the solenoid valve of 1/8 inch NPT that gas solenoid valve 5 is chosen access voltage, calibration tracheae internal-and external diameter is 4*6mm, links to each other with the calibration tracheae and all adopts quick connector.

The tracheae employing internal-and external diameter of measuring gas circuit is the conductive silicon sebific duct of 12*14mm, and its flow of sampling pump that is connected in the outlet pipe is 5L/min.

The critical piece of signal processing controls and display circuit is comprised of microprocessor 15 and touch-screen 16.Microprocessor 15 mainly is comprised of CPLD and C8052 single-chip microcomputer, and the photon of ordered pair in a certain period counted during light source that CPLD provides according to single-chip microcomputer, and count results is flowed to single-chip microcomputer; Main being responsible for of single-chip microcomputer calculated the photon number that CPLD provides in real time; Produce the light on and off of PWM clock signal control light source; The data of Real-time Collection Temperature Humidity Sensor and pressure transducer; The switch of control solenoid valve, electromagnet, sampling pump, zero air pump and heating plate; At last data being flowed to single-chip microcomputer controls other parts with the touch instruction that shows and accept single-chip microcomputer and works accordingly.

Referring to Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5, the workflow of the measuring method of Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument was divided into for two steps, i.e. calibration process and in real time measuring process.The concrete operations flow process is as follows:

Calibration process:

To after the measurement mechanism energising, set first parameter in the calibration menu bar in the touch-screen such as the mouth mark stability value of the minimax time of calibrating gas type, calibration and calibration; As select high-purity CO2 as Standard Gases, and the minimum time of calibration is set to 5min, and maximum time is set to 20min, and the target stability value is made as 95%, carries out calibration again.After carrying out calibration, what carry out at the beginning is the gas calibration, open that gas air intake opening 2 that gas solenoid valve 5 allows gas enter calibration gas air inlet gas circuit enters gas solenoid valve 5 successively by the gas tracheae again and fine filtrator 6 enters the optical measurement chamber at last, finally 14 discharge from the gas outlet.

Put bright light source after allowing gas connect 5min, allow calibrating gas in the light source irradiation optical measurement chamber, gas and particulate component in the calibrating gas cause light scattering.Being placed on aperture diaphragm 19,20,21,22,23,24 in the optical measurement chamber, to allow scattered light enter scattering angle be conical region between 10 °-170 °, the final single photon photodetector 11 that arrives, so that Multiple Scattering light can not enter single photon photodetector 11, the luminance brightness in the unit solid angle that single photon photodetector 11 receives is L=σ _Scatl ₀/ 2 π y, the electric signal that the single photon photodetector produces is proportional to luminance brightness L, and the electric signal that the single photon photodetector produces reflects with the photon number, and interior photon number of measuring unit's time what are during actual measurement, be photon counting, unit is Hz.Produce periodic pulse signal control light source and rotary magnet by microprocessor, work as light source igniting, when electromagnet was all opened, the counting that records was that measurement count is designated as C _mWork as light source igniting, when electromagnet was closed, the counting that records was that measurement count is designated as C _Sh, when light source extinguishes, no matter electromagnet opens and closes as is no, and what recorded this moment all is to calculate mentally number.Counting to get gas with measurement count divided by reference measures than being designated as MR _Span, i.e. MR _Span=C _m/ C _ShThen calculate the calibration degree of stability, measure ratio by measuring 50 times, establish x, s is respectively mean value and the standard deviation of measuring ratio.Calibration degree of stability S=100 * (1-2s/x); When the alignment time surpasses minimum alignment time and degree of stability S and surpasses the target degree of stability numerical value of setting, close the gas solenoid valve, the gas calibration finishes.

Open zero air pump 4, allow surrounding air enter from gas air intake opening 2, be equivalent to zero gas by the cleaned air behind the coarse filter 6, enter optics and measure chamber zero gas suction fine filtrator 6 is laggard through the zero passage air pump again, finally also 14 discharge from the gas outlet.Similar with the gas calibration, calculate zero gas and measure than being designated as MR _Zero, then calculate calibration degree of stability S.When the alignment time surpasses minimum alignment time 5min and degree of stability S and surpasses the target degree of stability numerical value 95% of setting, close zero air pump, zero gas calibration finishes.

At last, draw the measurement ratio scattering coefficient relation curve corresponding with its difference that calibration curve is gas and zero gas according to the above results.The wherein scattering coefficient of gas and the zero gas acquisition of can tabling look-up.Obtain slope of a curve k and intercept b by calibration curve.

Measuring process:

Open sampling pump, sample gas is drawn into the measurement chamber from air intake opening 12, by sampling pump 13 14 eliminatings from the gas outlet; Similar with calibration process, calculate sample gas and measure than being designated as MR _Sample, the scattering coefficient σ of sample gas then _Sp=σ _Scat-σ _Scat(Z)=(MR-C * 10 ^-3)/S * 10 ^-3-σ _Scat(Z), k and b are slope and the intercept of the calibration curve in the calibration process in the formula.

Claims (5)

1. Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument, it is characterized in that: comprise the optical measurement chamber, the optical measurement chamber inner wall is coated with Berlin black; The centre of optical measurement chamber is scattering chamber (8), and top, scattering chamber is equipped with LED-based integrating sphere light source (7); The left and right sidewall in scattering chamber has the taper light hole, be separately installed with several diaphragms (19,20,21,22,23,24) in the optical measurement chamber of scattering chamber arranged on left and right sides, ligh trap (9) is installed on the left side wall of optical measurement chamber, single photon photodetector (11) is installed on the right side wall of optical measurement chamber; The outer diaphragm of scattering chamber right side taper light hole is equipped with the scattering shutter (10,28,29,30) that can open with closure outward, two ends, the optical measurement chamber left and right sides (26,27) are provided with calibrating gas and zero gas intake interface, there are sample gas air inlet port (17) and the port of giving vent to anger (18) in optical measurement chamber middle part, bleed from the port of giving vent to anger of optical measurement chamber by sampling pump (13), sample gas enters the optical measurement chamber from sample gas air inlet port; Gas solenoid valve (5) is installed in the calibrating gas gas circuit; Coarse filter (3), zero air pump (4) are installed in the zero gas air inlet gas circuit successively, and calibrating gas gas circuit, zero gas air inlet gas circuit are linked into described calibrating gas and zero gas intake interface after importing simultaneously precision filter (6); The illumination that the integrating sphere light source sends is mapped to the scattered light part that produces on the large aerosol particle in the sample gas in the scattering chamber and arrives ligh trap so that scattered light departs from the single photon photodetector through taper light hole, the diaphragm in left side, scattering chamber, scattered light another part arrives the single photon photodetector through taper light hole, the diaphragm on right side, scattering chamber, the single photon photodetector is converted to the signal that receives and delivers to microprocessor (15) behind the electric signal and count, process and control, and the measurements and calculations result is delivered to touch-screen (16) shows.

2. Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument according to claim 1 is characterized in that: the efficient that described precision filter is removed the above particle of 0.1um is 99.5%; The scattering shutter is comprised of rotary magnet (10), the round-meshed pivoted arm of front end (30), frosted glass (28) and attenuator (29); Optical measurement chamber material is anodised aluminium.

3. Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument according to claim 1 is characterized in that: described integrating sphere light source, satisfy lambertian distribution from the light intensity of integrating sphere light-emitting window (33) outgoing; Red, green, blue triband led light source is installed respectively in three sides of integrating sphere (S1, S2, S3), and wavelength is elected respectively the ruddiness of 630nm, the green glow of 520nm and the blue light of 450nm as.

4. Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument according to claim 1, it is characterized in that: the scattering angle of described integrating sphere light source is 10 °-170 °.

5. Three-band integrated atmospheric aerosol particle scattering coefficient measuring instrument according to claim 1, it is characterized in that: sample gas air inlet port (17) and the port of giving vent to anger (18) are communicated in respectively sample gas air inlet gas circuit, the sample gas gas circuit of giving vent to anger, and the tracheae that sample gas air inlet gas circuit, sample gas are given vent to anger in the gas circuit all adopts the black silicon sebific duct; Sample gas is given vent to anger, and the end of gas outlet is connected with sampling pump in the gas circuit.

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