CN101067598A - Double-light path photoelectric detector and method for detecting light decrement thereof - Google Patents

Abstract

The invention discloses a double ray paths photo detector and the method of testing the light attenuation quantity, the gas monitor room exterior joint has the positioning electro-magnet, the top-mounted of the gas monitor room is furnished with the multi- wave lengths photo source array as examining the photo source, the gas monitor room associates the enter airport, the gas monitor room base is the glass ledger wall, the ventilation window installs on the glass ledger wall; the quartz filter paper tape underneath the gas monitor room; there are refer and survey two photo detectors installs underneath the quartz filter paper belt, a group used as the reference, another group used as the examination. The optics attenuation method which is used has well timeliness, high precision, low cost, enhanced the automaticity, time-saving reduced effort, all-weather automatic continuous working merit, guaranteed the atmospheric pellet carbon black aerosol continuously, the real-time on-line monitor.

Description

The method of double-light path photoelectric detector and detection light decrement thereof

Technical field

The invention belongs to environmental pollution and monitor the field automatically, specifically is the instrument that double-light path photoelectric detector detects light decrement.

Background technology

Carbon black aerosol has crucial influence to zone and even global climate and the change of circumstances, and its particle diameter is generally less than 2.5 microns, and the harm of health more is far more than PM10, therefore becomes the detected object of various countries meteorological department and environmental protection organization gradually.The optical attenuator method is measured carbon black aerosol, this method utilizes carbon black aerosol to seeing the strong extinction characteristic in the infrared band scope, with constant flow velocity sample gas is drawn into the monitoring chamber, on the uniform quartz fibre filter paper of printing opacity, again with the light source irradiation of fixed wave length it, detect its damping capacity by two photo-detectors.The mass incremental of absorption carbon black aerosol is linear on the difference of damping capacity and the filter paper, by calculating the mass concentration that can obtain carbon black aerosol in this monitoring period atmosphere.

Summary of the invention

The purpose of this invention is to provide the instrument that a kind of double-light path photoelectric detector detects carbon black aerosol quality and concentration, improve real-time and robotization that atmosphere particle concentration is measured.

Technical scheme of the present invention is as follows:

Double-light path photoelectric detector, the outside that it is characterized in that the gas-monitoring chamber is connected with positioning electromagnet, the top of gas-monitoring chamber is equipped with the multi wave length illuminating source array as detection light source, gas-monitoring chamber UNICOM air intake, the bottom of gas-monitoring chamber is a glass film plates, place on the pedestal, ventilative window is arranged on the glass film plates; Described glass film plates below is the glass partition that is installed on the pedestal, the glass partition below is equipped with the reference light electric explorer, and the air intake opening of the discharge chamber on ventilative window and the pedestal coincide, and there is gas vent the discharge chamber side, the discharge chamber bottom is a glass, and its below is equipped with the measuring light electric explorer; Be pressed with the quartz filter paper band that can cover ventilative window between gas-monitoring chamber and the pedestal; Described gas vent is through mass flow controller, three-way solenoid valve and air pump UNICOM, and another interface of three-way solenoid valve is by filtrator and atmosphere UNICOM.

Described double-light path photoelectric detector detects the method for light decrement, it is characterized in that may further comprise the steps: the gas-monitoring chamber is set, the top of gas is equipped with the led light source array, the gas-monitoring chamber is linked with the gas access, the bottom of gas-monitoring chamber is a glass film plates, and ventilative window is arranged on the glass film plates; The quartzy paper tape that filters is arranged at the bottom of gas-monitoring chamber; Air intake opening on the discharge chamber of ventilative window and its below coincide, and quartz filter paper is pressed in middle; Bleed by air pump, and measure air volume simultaneously, atmosphere to be measured is entered from the gas access of gas-monitoring chamber, extract out from the gas outlet of discharge chamber, atmosphere can deposit Atmospheric particulates through quartzy filter paper filtration on quartzy filter paper; Utilize the reference light electric explorer to see through the light signal of glass film plates and quartz filter paper, utilize the measuring light electric explorer to receive the light signal that sees through ventilative beneath window quartz filter paper.

Inventive principle

When light source shone the testing sample on the quartz filter paper, because the influence of various factors (as environment temperature, power-supply fluctuation, light emitted angle, circuit noise etc.), detected value existed than multiple error.The present invention utilizes multiple spot light source and two silicon photodetectors to constitute double-light path photoelectric detector, determines the light decrement of determinand by detecting two ways of optical signals.For improving accuracy and stability, designed the measurement and the zero point of reference beam and detected.When the light intensity output of light source had subtle change, the reading of reference light detector just can be used for revising the variation of light source.Detect zero point then be meant each measuring period at first, close light source earlier, under no optical condition, read the output of one group of photo-detector earlier, determined the zero shift amount of two detectors.

Define in a certain measuring period S _B, S _ZBe respectively and detect the output of photo-detector when the light source opening and closing; R _B, R _ZBe respectively the output of reference beam detector when the light source opening and closing, light decrement ATN that then should measuring period is:

$\mathrm{ATN}\left(t\right)=-\ln \frac{S_B-S_Z}{R_B-R_Z}---\left(1\right)$

Equally, the light decay depreciation of following one-period is ATN (t+ Δ t), can obtain light decay depreciation increment Delta ATN by calculating:

ΔATN＝ATN(t+Δt)-ATN(t)＝σ*Δm (2)

Δ m value is for being adsorbed on the mass incremental of determinand on the filter paper, and σ then is the optical quality absorption cross section of determinand.

Use the uniform quartz filter paper of printing opacity to gather the carbon black aerosol sample, measure the damping capacity (ATN) that is produced when light sees through filter paper again.Along with the increase of amount of carbon blacks, also will be reduced by the detected light intensity of photodetector, its corresponding light decrement then increases.In effective range, the carbon black gross mass m that deposits on light decrement ATN and the unit area quartz filter paper _BCLinear relationship is arranged:

ATN＝ln(I ₀/I)＝σ _(1/λ)*m _BC (3)

In the formula (3), I ₀For by original filter paper being the light intensity of blank filter paper part; I is the light intensity by sample filter paper; m _BCBe the carbon black gross mass that deposits on the unit area quartz filter paper, unit is gm ^-2σ _{(1/ λ)}Then being the quality absorption cross section of carbon black aerosol, is most important parameters in the BC measurement of concetration, and it is inversely proportional to detecting light wavelength lambda in actual applications, and unit is m ²G ^-1

m _BCIncrement Delta m _BCWith carbon black aerosol quality and concentration ρ _BCLinear relationship is arranged:

${\mathrm{\Δm}}_{\mathrm{BC}}=\frac{{\mathrm{\ρ}}_{\mathrm{BC}}*F*\mathrm{\Δt}}{S}---\left(4\right)$

In the formula (4), F is a sampling flow, and Δ t is a sampling time interval, and S is the area of aerosol deposition on quartz filter paper.Bring (3) formula into mass concentration ρ that (4) formula can obtain carbon black aerosol in this sampling period _BC:

${\mathrm{\ρ}}_{\mathrm{BC}}=\frac{\mathrm{ATN}\·S}{\mathrm{\Δ}\·F\·\mathrm{\Δt}}---\left(5\right)$

The multi wave length illuminating source array

Seven kinds of light sources are arranged in the described led light source array, when measuring, can open one of them light source and measure; Perhaps open various light sources successively, measure, and will under various Different Light irradiations, measurement result compare.

Seven kinds of light sources are arranged in the described led light source array, purple light-350nm, blue light-450nm, green glow-571nm, gold-tinted-590nm, ruddiness-660nm, infrared 1-880nm, infrared 2-950nm, every kind of light source adopts the light emitting diode of pair of series.

For come source distribution and physicochemical property to carbon black aerosol are made further analysis, designed the multi wave length illuminating source array, make that other waveband channels also can detect the atypical material that adsorbs in the carbon black aerosol in real time when detecting carbon black aerosol with the 880nm standard channel.The multi wave length illuminating source array technique has been formed in the timesharing break-make of the type selecting of this array light source, location and multi wave length illuminating source and the selection of transmission eyeglass and photodetector jointly.

The invention effect

Adopt the optical attenuator method, real-time is good, the precision height, cost is low, has improved automaticity, and is time saving and energy saving, can round-the-clock automatic continuous working, guarantee the Atmospheric particulates carbon black aerosol continuously, real time on-line monitoring.

Description of drawings

Fig. 1 is a structural representation of the present invention.

Fig. 2 is a principle of work block diagram of the present invention.

Embodiment

Atmospheric particulates of the present invention---carbon black aerosol quality and concentration, mainly by multi wave length illuminating source array 11, gas-monitoring chamber 4, reference light electric explorer 13, measuring light electric explorer 14, paper feed gear train, three-way solenoid valve 8, mass flow controller 7, air pump 1, gas filter 6 are formed; In the above-mentioned gas-monitoring chamber 4, the top is a led light source array 11, and 4 bottoms, gas-monitoring chamber are transparent glass partitions 12 of sealing, and behind the light transmission glass partition 12 of led array 11, energy distribution is even; Has only a ventilative window on the glass partition 12; The bottom of gas-monitoring chamber is pressed on the uniform quartz filter paper band of printing opacity, is mounted in the optical glass dividing plate on the pedestal below the paper tape, is reference light electric explorer 13 under the dividing plate; Printing opacity quartz filter paper band 10 upper surfaces in ventilative beneath window, the deposition that carbon black aerosol particle in the gas is arranged, the paper tape below is the air intake opening of discharge chamber 2, discharge chamber 2 bottoms are optical glass dividing plates, be measuring light electric explorer 14 under the optical glass dividing plate, convert the light signal that receives to electric signal; 4 sides, whole gas-monitoring chamber have outside the gas outlet, other part sealings.

On the described gas-monitoring chamber 4 air intake opening is arranged, atmosphere enters thus when bleeding, and discharge chamber is connected to mass flow controller 7 by silicone tube, arrives air pump 1 through three-way solenoid valve 8 main road gas circuits again; Gas filter 6 external atmosphere by silicone tube, arrive air pump 1 through three-way solenoid valve 8 bypass gas circuits.

The gear train that is used for the quartz filter paper paper feed is by paper tape supplies trays 3, and paper feed motor 5 changes paper motor 9, changes paper disc 10 and travel switch and forms.

4 upper ends, gas-monitoring chamber are connected with the electromagnet 15 of suspension, and when electromagnet 15 adhesives moved up, gas-monitoring chamber 4 also moved up in the lump; Otherwise, when electromagnet 15 is in normal condition, be pressed in 4 tops, gas-monitoring chamber, make quartz filter paper be adjacent to 4 bottoms, gas-monitoring chamber.

Gas to be measured sampling period and detection period the gas circuit of process be different: during sampling, the main road gas circuit is open-minded, and the bypass gas circuit is closed; During detection, the main road gas circuit is closed, and the bypass gas circuit is open-minded; This gas circuit design has guaranteed the stability of flow, the harmful effect that has caused when having avoided air pump 1 switch.

Arranging of multi wave length illuminating source array 11 is comparatively concentrated, each independent hot spot covers the surveyed area of double-photoelectric detector as far as possible equably, the transmittance wavelength coverage will include visible light near infrared wide territory in the light path, and guarantee light source intensity in the valid analysing range of back level analog-to-digital conversion circuit, so that the effective attenuation signal of output multi wave length illuminating source.When the determinand on being adsorbed on quartz filter paper surpasses sensing range, move on the electromagnet, filter paper is measured background after upgrading once more.

Claims (2)

1, double-light path photoelectric detector, the outside that it is characterized in that the gas-monitoring chamber is connected with positioning electromagnet, the top of gas-monitoring chamber is equipped with the multi wave length illuminating source array as detection light source, gas-monitoring chamber UNICOM air intake, the bottom of gas-monitoring chamber is a glass film plates, place on the pedestal, ventilative window is arranged on the glass film plates; Described glass film plates below is the glass partition that is installed on the pedestal, the glass partition below is equipped with the reference light electric explorer, and the air intake opening of the discharge chamber on ventilative window and the pedestal coincide, and there is gas vent the discharge chamber side, the discharge chamber bottom is a glass, and its below is equipped with the measuring light electric explorer; Be pressed with the quartz filter paper band that can cover ventilative window between gas-monitoring chamber and the pedestal; Described gas vent is through mass flow controller, three-way solenoid valve and air pump UNICOM, and another interface of three-way solenoid valve is by filtrator and atmosphere UNICOM.

2, utilize the described double-light path photoelectric detector of claim 1 to detect the method for light decrement, it is characterized in that may further comprise the steps: the gas-monitoring chamber is set, the top of gas is equipped with the led light source array, the gas-monitoring chamber is linked with the gas access, the bottom of gas-monitoring chamber is a glass film plates, and ventilative window is arranged on the glass film plates; The quartzy paper tape that filters is arranged at the bottom of gas-monitoring chamber; Air intake opening on the discharge chamber of ventilative window and its below coincide, and quartz filter paper is pressed in middle; Bleed by air pump, and measure air volume simultaneously, atmosphere to be measured is entered from the gas access of gas-monitoring chamber, extract out from the gas outlet of discharge chamber, atmosphere can deposit Atmospheric particulates through quartzy filter paper filtration on quartzy filter paper; Utilize the reference light electric explorer to see through the light signal of glass film plates and quartz filter paper, utilize the measuring light electric explorer to receive the light signal that sees through ventilative beneath window quartz filter paper.

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