CN102183492A - 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

Triband integration type 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 big 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 mu m range.In the ordinary course of things, as not being the area that forms thicker aerosol layer by carbon, can think that the scattering process of particulate is much larger than absorption.This shows that aerocolloidal scattering process is very big.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 bigger.Therefore, press for a kind of direct measurement atmospheric aerosol particle scattering coefficient measuring instrument of exploitation.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 continuously observation automatically 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 with Other Instruments, for the research atmospheric aerosol provides new means.

Summary of the invention

The present invention proposes a kind of triband integration type 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, promptly

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

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, scattered light is carried out strict angle weighted integral, solved complicated scattering problem basically according to the knowledge of geometry and illumination; Measured the scattering coefficient of triband correspondence, widened measurement range and can infer the difference that tested particle is formed in view of the above.The present invention adopts and chooses high-power LED light source simultaneously based on the diffused light source of integrating sphere type, and adds constant-flow driver on circuit, has solved the difficulty that needs can obtain by the electric current of accurate each LED of adjusting the cosine characteristic of the surplus light source of diffusion.

Utilize a branch of light 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 has only 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 increases precision and the reliability that scattering coefficient is measured, and triband light-source structure compactness, need not complicated optical system and a plurality of single photon photodetector;

(3) scattering coefficient of measurement triband correspondence can proofread and correct the angle truncation error, and it is extensive to have measurement range, can be applicable to 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 measuring instrument system architecture diagram.

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 synoptic diagram of Fig. 3 light source.

Fig. 5 is a microprocessor count control and treatment synoptic diagram.

Embodiment

Referring to Fig. 1, Fig. 2 and Fig. 3, triband integration type atmospheric aerosol scattering coefficient measuring instrument, comprise the optical measurement chamber and go up configured parts, calibration gas circuit (calibrating gas gas circuit, zero gas air inlet gas circuit) and go up configured parts, measure gas circuit (sample gas air inlet gas circuit, sample gas give vent to anger gas circuit) and on accessory and signal Processing control and display circuit; The control of this signal Processing and display circuit respectively with the optical measurement chamber on configured parts, calibration gas circuit and go up configured parts and the measurement gas circuit and on accessory be electrically connected.Wherein optical measurement chamber and last configured parts 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 and 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 closed that are equipped with of scattering chamber 8 right side light paths, the scattering shutter is made up 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 the 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 big 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 and make scattered light depart 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 to deliver to microprocessor 15 behind the electric signal to count, handle and control with the conversion of signals that receives.

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 fixing side blanking cover 37 and the side plastic lining lid 38 that LED 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 made up 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, it is 99.99% filtrator greater than 0.1 μ m particle and filtration efficiency that fine filtrator 6 is selected removal for use, gas solenoid valve 5 is chosen and inserted voltage is that DC12V and interface are the solenoid valve of 1/8 inch NPT, the inside and outside footpath of calibration tracheae is 4*6mm, links to each other with the calibration tracheae and all adopts quick connector.

The interior external diameter of tracheae employing 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.

Signal Processing control is made up of microprocessor 15 and touch-screen 16 with the critical piece of display circuit.Microprocessor 15 mainly is made up 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; Gather the data of Temperature Humidity Sensor and pressure transducer in real time; The switch of control electromagnetic valve, electromagnet, sampling pump, zero air pump and heating plate; Carry out corresponding work with other parts of touch instruction control that show and accept single-chip microcomputer at last data delivery for single-chip microcomputer.

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

Calibration process:

To after the measurement mechanism energising, set parameter earlier in the calibration menu bar in touch-screen as the mouth mark stability value of the minimum maximum time of calibrating gas type, calibration and calibration; As select for use high-purity CO2 as standard gas, 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 repeatedly scattered 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 with 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 designated as C for measurement count _mWork as light source igniting, when electromagnet was closed, the counting that records was designated as C for measurement count _Sh, when light source extinguishes, no matter electromagnet opens and closes as not, what recorded this moment all is dark counts.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, be equivalent to zero gas, go into 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 by the cleaned air behind the coarse filter 6 from gas air intake opening 2.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 of setting 95%, close zero air pump, zero gas calibration finishes.

At last, draw the measurement ratio and its corresponding respectively scattering coefficient relation curve 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 the slope and the intercept of the calibration curve in the calibration process in the formula.

Claims (7)

1. triband integration type 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 taper light hole (20,21), be separately installed with several diaphragms (19,20,21,22,23,24) in the optical measurement chamber of scattering chamber and arranged on left and right sides, be separately installed with ligh trap (9), single photon photodetector (11) on the left and right sidewall of optical measurement chamber; The diaphragm of right side, scattering chamber light path is equipped with the scattering shutter (10,28,29,30) that can open with closed 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 that goes out the optical measurement chamber by sampling pump (13), sample gas enters the optical measurement chamber from the 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 precision filter (6) simultaneously; The illumination that the integrating sphere light source sends is mapped to the scattered light part that produces on the big aerosol particle in the sample gas in the scattering chamber and arrives ligh trap through taper light hole, the diaphragm in left side, scattering chamber and make scattered light depart from the single photon photodetector, scattered light another part arrives the single photon photodetector through the taper light hole diaphragm on right side, scattering chamber, the single photon photodetector is to deliver to microprocessor (15) behind the electric signal to count, handle and control with the conversion of signals that receives, and the measurements and calculations result is delivered to touch-screen (16) shows.

2. triband integration type 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 made up of rotary magnet 10, the round-meshed pivoted arm 30 of front end, frosted glass 28 and attenuator 29; Optical measurement chamber material is an anodised aluminium.

3. triband integration type 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; Three sides of integrating sphere (S1, S2, S3) are installed red, green, blue triband led light source respectively, and wavelength is elected the ruddiness of 630nm, the green glow of 520nm and the blue light of 450nm respectively as.

4. triband integration type atmospheric aerosol particle scattering coefficient measuring instrument according to claim 1 is characterized in that: the scattering angle of described integrating sphere light source is 10 °-170 °.

5. triband integration type 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 sample gas air inlet gas circuit, the sample gas gas circuit of giving vent to anger respectively, 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.

6. triband integration type atmospheric aerosol particle scattering coefficient measuring instrument according to claim 1, it is characterized in that: described microprocessor mainly is made up of CPLD and C8052 single-chip microcomputer, the CPLD major function is: the photon of ordered pair in a certain period counted during the light source that provides according to single-chip microcomputer, and count results is flowed to single-chip microcomputer; The major function of single-chip microcomputer is: 1) be responsible for the photon number that CPLD provides is calculated in real time; 2) produce the light on and off of PWM clock signal control light source; 3) gather the data of Temperature Humidity Sensor and pressure transducer in real time; 4) switch of control electromagnetic valve, electromagnet, sampling pump, zero air pump and heating plate; 5) thus control other parts with the touch instruction that shows and accept single-chip microcomputer for single-chip microcomputer data delivery and carry out corresponding work.

7. utilize the described measuring instrument of claim 1 to carry out the method that the atmospheric aerosol particle scattering coefficient is measured, it is characterized in that, comprise calibration steps and measuring process:

One, calibration steps is as follows:

(1) gas calibration: allow the calibrating gas of known scattering coefficient enter the optical measurement chamber, measure the measurement count C of the single photon photodetector under scattering shutter opening and closed condition respectively _mWith reference counting C _Sh, the ratio that calculates them obtains the measurement of gas and compares MR _Span=C _m/ C _Sh

(2) zero gas is calibrated: the air after will filtering by membrane pump (zero gas) is pumped into the optical measurement chamber, measures the measurement count C of the single photon photodetector under scattering shutter opening and closed condition respectively _m' and reference counting C _Sh', the ratio that calculates them obtains the measurement of zero gas and compares MR _Zero=C _m'/C ' _Sh

(3) according to the measurement of gas and zero gas their scattering coefficient values separately when, draw measure than and scattering coefficient between the calibration curve that concerns, obtain its slope k and intercept b by calibration curve;

(4) calculate the calibration degree of stability of gas or zero gas: calibration degree of stability computing formula is S=100 * (1-2s/x); X wherein, s are respectively mean value and the standard deviation that calibration gas is measured the ratio sample;

(5) calculating optical is measured the wall signal of chamber: wall calculated signals formula is W=100 * (b/MR _Zero), wherein b is the intercept of calibration curve, MR _ZeroBe the measurement ratio of zero gas;

Two, measuring process is as follows:

(1) sample gas is drawn into the optical measurement chamber, gets rid of from the gas outlet by sampling pump;

(2) the sample gas in the integrating sphere light source irradiation scattering chamber;

(3) gas in the sample gas and big aerosol particle composition cause light scattering;

(4) scattered light allows light enter scattering angle through the diaphragm in the optical measurement chamber to be 10 ° of conical regions between-170 ° (Fig. 4), finally to reach the single photon photodetector that repeatedly scattered light can not enter the single photon photodetector;

(5) electric signal of single photon photodetector generation is proportional with incident intensity, and therefore, the electric signal that the single photon photodetector produces and the scattering coefficient of sample gas are proportional;

(6) measure the measurement count C of the single photon photodetector under scattering shutter opening and closed condition respectively _mWith reference counting C _Sh, obtain measuring and compare MR _Sample=C _m/ C _Sh

(7) calibration curve that obtains according to calibration process calculates aerosol particle thing scattering coefficient:

For arbitrary environmental sample, when measuring ratio, can calculate aerosol particle thing scattering coefficient σ by following formula for MR _Sp, unit is Mm ^-1

${\mathrm{\σ}}_{\mathrm{sp}}={\mathrm{\σ}}_{\mathrm{scat}}-{\mathrm{\σ}}_{\mathrm{scat}}\left(Z\right)=\frac{(\mathrm{MR}-b\×{10}^{-3})}{k\×{10}^{-3}}-{\mathrm{\σ}}_{\mathrm{scat}}\left(Z\right),$

Wherein, b is the intercept of calibration curve, and k is the slope of calibration curve.

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