CN203299118U - Dust concentration measurement instrument based on light scattering method - Google Patents

Abstract

A dust concentration measurement instrument based on a light scattering method relates to dust concentration measurement instruments and aims at solving the problems of low measurement accuracy and complexity of an existing dust concentration measurement instrument. According to the dust concentration measurement instrument based on the light scattering method, laser signals generated by an infrared laser are emitted into an optical element and are transmitted to a photoelectric converter after being converted by the optical element, and the switching signal input end of a CPU (Central Processing Unit) control unit is connected with a switching signal output end of the photoelectric converter; the power signal output end of a laser power circuit is connected with the power signal input end of the infrared laser; the control signal input end of the laser power circuit is connected with the control signal output end of the CPU control unit; the display signal input end of a display circuit is connected with the display circuit output end of the CPU control unit. The dust concentration measurement instrument based on the light scattering method is applicable to measurement of floating dust concentration in air environments of mines, thermal power plants, enterprises of food processing and the like.

Description

The light scattering method dust concentration tester

Technical field

The utility model relates to a kind of dust concentration tester.

Background technology

Along with the development of society, mechanization production is more and more general, and the colliery industry when having improved coal mining output, has also been brought certain environmental problem.When mine operation, in air, dust content increases, thereby has brought very big harm for operating personnel's health and the safety in production in colliery.Therefore, the dust in air of workplace being prevented and treated and monitored has been the primary task in each mine.The method of at present domestic and international on-line monitoring dust concentration has a variety of, mainly contains capacitance method, optical absorption method, β rays method, friction electrical method etc., technology maturation, but the instrument price is high.And supercritical ultrasonics technology, microwave method also are in the experimental study stage, also fail to form entity products.

The utility model content

The utility model is for the problem that measuring accuracy is low, instrument is complicated that solves existing dust concentration tester, thereby a kind of light scattering method dust concentration tester is provided.

The light scattering method dust concentration tester, it comprises optical unit 1, laser power supply circuit 2, CPU control module 3 and display circuit 4;

Optical unit 1 comprises optical element 11, infrared laser 12 and photoelectric commutator 13; The laser signal that described infrared laser 12 produces is incident to optical element 11, is emitted to photoelectric commutator 13 after optical element 11 conversions, and the switching signal input end of CPU control module 3 is connected with the switching signal output terminal of photoelectric commutator 13; The power supply signal output terminal of described laser power supply circuit 2 is connected with the power supply signal input end of infrared laser 12; The control signal input end of described laser power supply circuit 2 is connected with the control signal output terminal of CPU control module 3; The display input end of display circuit 4 is connected with the display output terminal of CPU control module 3.

It also comprises concentration over-standard warning circuit 5, and the alerting signal input end of described concentration over-standard warning circuit 5 is connected with the alarm signal output ends of CPU control module 3.

Optical element 11 is photoelectric commutators.

The utility model is a kind of apparatus for measuring dust concentration of light scattering theory, and measuring accuracy is high, and of the present utility model simple in structure, and cost is able to decrease.

Description of drawings

Fig. 1 is structural representation of the present utility model;

Fig. 2 is the light absorption schematic diagram of sample in embodiment three;

Fig. 3 is ball-type dust granules Mie scattering schematic diagram in embodiment three.

Embodiment

Embodiment one, in conjunction with Fig. 1, this embodiment is described, the light scattering method dust concentration tester, it comprises optical unit 1, laser power supply circuit 2, CPU control module 3 and display circuit 4;

Optical unit 1 comprises optical element 11, infrared laser 12 and photoelectric commutator 13; The laser signal that described infrared laser 12 produces is incident to optical element 11, is emitted to photoelectric commutator 13 after optical element 11 conversions, and the switching signal input end of CPU control module 3 is connected with the switching signal output terminal of photoelectric commutator 13; The power supply signal output terminal of described laser power supply circuit 2 is connected with the power supply signal input end of infrared laser 12; The control signal input end of described laser power supply circuit 2 is connected with the control signal output terminal of CPU control module 3; The display input end of display circuit 4 is connected with the display output terminal of CPU control module 3.

The difference of embodiment two, this embodiment and the described light scattering method dust concentration tester of embodiment one is, it also comprises concentration over-standard warning circuit 5, and the alerting signal input end of described concentration over-standard warning circuit 5 is connected with the alarm signal output ends of CPU control module 3.

The difference of embodiment three, this embodiment and the described light scattering method dust concentration tester of embodiment one or two is, optical element 11 is photoelectric commutators.

The utility model proposes a kind of effective powder concentration measurement method: application laser loose thoroughly than principle (so-called loose thoroughly refer to than principle be exactly ratio in the light intensity of the light intensity of the transmitted light on the optical transmission direction and the scattered light on perpendicular direction), measuring-signal is measured and analyzed, and set up mathematical model.In this measuring system, opticator is by infrared laser, and optical element and photoelectric commutator three parts form, and when having infrared light to be sent by infrared laser, optical element receives infrared light, then by photoelectric commutator, converts light signal to electric signal.The structure of the system of dust density detector is as shown in Figure 1:

System Working Principle is as follows: after the central control unit power supply, pulse is provided for the laser power supply circuit, laser power supply circuit is controlled infrared laser output, when infrared laser instrument sends infrared laser, by two optical elements (position of two photoelectric commutators: place over against infrared laser for, a vertical infrared laser is placed) receive, by photoelectric commutator, light signal is converted to electric signal, send into the CPU control module and carry out signal analysis after modulate circuit, measure concentration value by the output of MSP430 series monolithic programming Control, when concentration over-standard, by the alarm output alarm signal.In design, the type selecting of sensor and laser instrument is all important.And the design finally to select the effect of infrared laser be the interference of having avoided natural light, directly send infrared light, receive infrared light by infrared receiving device, measuring accuracy is increased.In whole measuring system, applied optics is loose thoroughly than theoretical single light scattering theory and the single light transmission theory of being better than, and has reduced measuring error.

The theoretical analysis of powder concentration measurement and modeling:

1, theoretical analysis

1.1 light scattering principle is measured the feasibility analysis of dust concentration

In ecotopia, when propagating in uniform dielectric, just along the refracted ray direction, propagates light, because the incident light frequency is identical with the frequency of the subwave that dipole in medium sends, incident light and subwave are coherent lights, and all scattered lights of coherent light and other direction except refracted ray are cancelled each other.Only have in material when inhomogeneous structure is arranged, just there will be light scattering phenomenon.

Due to the uneven texture of dust granules, light scattering phenomenon can occur in light when propagating when having irradiation in mine, and this phenomenon is to the coefficient result of light absorption, reflection, refraction, transmission and diffraction due to dust granules., by the research to character such as scattering light intensity, polarization and spectral components, can analyze the information of a lot of detection material such as scatterer size, shape, structure and composition and concentration.And, for the dust granules that the utility model will be measured, be to be suspended in the particle that airborne particle diameter is less than or equal to 100 microns, can be referred to as overall suspended pellet.Dust granules can belong in the biomacromolecule category, and they can make laser that obvious light scattering phenomenon occurs.Its concentration that the scattered light intensity of measurement of species any direction that in theory, can be by detecting particle of the same race just can be surveyed.Known by the Mie scattering theory, it is mainly used in the size section from sub-micron to micron.The particle diameter of dust granules is micron level, so the scattering type that occurs during irradiation belongs to the Mie scattering.This shows, the concentration of using light scattering technique to measure particle swarm is feasible.

1.2 light transmission theoretical analysis

Bill-youth primary (Lambert-Beer) law represents that material is to the power of a certain monochromatic light absorption and the relation between extinction material concentration and thickness, and being applicable to all extinction materials and electromagnetic radiation, the own characteristic of dust granules meets the application requirements of philosophy.

The mathematical description of Beer-Lambert law be when light intensity be the light of I in homogeneous substance by after the l segment distance, in unit distance dl, being counted dI by the light intensity of material absorbing is that sample light absorption schematic diagram is as shown in Figure 2 uniformly.

Its absorption number of degrees A learns expression formula:

$A=\ln \left(\frac{I_1}{I_0}\right)={\mathrm{\α}}_{1}l---\left(1\right)$

In formula: I ₀The expression incident intensity; I ₁The expression output intensity; α ₁Be expressed as the absorption coefficient of light (unit is g/dlmm), l is expressed as the distance of light transmission.Find in the actual conditions of Bill when the research light absorption, light is by thickness of dielectric layers necessarily and uniformly can light absorbing medium the time, in unit distance, weakening to increase C and the incident intensity of concentration of medium of light intensity is directly proportional, and the relation of absorbance log A is shown below:

$A=\ln \left(\frac{I_1}{I_0}\right)=\ln \left(\frac{1}{T}\right)={\mathrm{\α}}_{2}C---\left(2\right)$

In formula: I ₀Be expressed as incident intensity; I ₁Be expressed as output intensity; α ₂Be expressed as absorption coefficient (unit is g/dlmm); C is for detecting the concentration of powder sample.If during the different propagation of same substance variable concentrations width, the Lambert-Beer's law expression formula is:

$A=\ln \left(\frac{I_1}{I_0}\right)=\ln \left(\frac{1}{T}\right)$ (3)

$=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{A}_i\left(\mathrm{\λ}\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\α}}_i\left(\mathrm{\λ}\right)l{C}_i$

Experiment shows, the same substance of variable concentrations has identical absorption coefficient in the same wave strong point.

1.3 light scattering theory analysis

When light beam is propagated in inhomogeneous medium, produce light scattering phenomenon.In the application of light scattering, Mie scattering and Ruili scattering are widely used.The Mie scattering theory is to being in the isotropic single medium ball in uniform dielectric at first, the strict mathematical solution under the Maxwell equation boundary condition under the collimated monochromatic ligth irradiation, and also it can only be applicable to detect spherical particles.Improve afterwards algorithm, calculated out the Mie scattering formula that is suitable for non-spheroid particle, and be applied to study the light scattering aspects such as haemocyte and other particle.

The solution of Mie scattering is to be suitable for the scattering of individual particle ball, also is applicable to the scattering of any a plurality of particle balls.When detected material particle was same sample ingredient and random distribution, particle shape was similar, and size evenly.The analysis of Mie scattering theory draws, and light is the energy of single ball scattering and the product of ball sum in the total scattering luminous energy of test sample.In theory, the sample of particle of the same race, the light intensity of scattered light that can be by measuring any direction obtains its concentration.The Mie scattering theory is mainly used in measuring the size section from sub-micron to micron.The particle diameter of dust granules is micron level, and irradiation is that the scattering type that occurs belongs to the Mie scattering.So when the Ear Mucosa Treated by He Ne Laser Irradiation test sample, the information of dust concentration is mainly reflected in scattered light.

2, the light of setting up powder concentration measurement falls apart thoroughly than theoretical model

By Beer-Lambert law as can be known, during with beam of laser irradiation dusty gas sample, part light can, by dust absorbing in air, can be obtained by conservation of energy principle

I ₀*S ₀＝∑I _siΔS _i+∑I _sjΔS _j+I*S ₀ (4)

In formula: S ₀The cross-sectional area of-incident beam; I _si-light is at dust granules scattering surface Δ S _iOn scattered light intensity; I _sj-light is at dust granules scattering surface Δ S _jOn transmitted light intensity; The pure absorption light intensity of I-dust.

Order:

I _SS _R＝∑I _siΔS _i+∑I _sjΔS _j (5)

In formula: S _R-one imaginary area of spherical surface, this sphere be take light beam irradiates at the test sample center as the centre of sphere, radius is the imaginary sphere of R; I _S-vertical incidence light is at the scattered light intensity of imaginary sphere.

When parallel monochromatic incident light irradiation is on the hypothesis sphere, the light scattering of generation and light absorption phenomenon as shown in Figure 3:

I on the hypothesis sphere _SEquate I everywhere _SSize relevant with the scattering properties of dust granules in air, have:

I ₀＝m ₁I _S+I (6)

In formula: m ₁=S _R/ S ₀

Know again:

$I=e^{d(k_1{\mathrm{\ξ}}_1-c)}=e^{k_1{\mathrm{\ξ}}_{1}d-\mathrm{cd}}---\left(7\right)$

In formula: k ₁For the pure absorption coefficient of dust, c is constant.By formula (2) and formula (3), obtained:

$m_1{Y}_1=e^{{\mathrm{\μ}}_{s1}{\mathrm{\ξ}}_{1}d}-e^{k_1{\mathrm{\ξ}}_{1}d-\mathrm{cd}}-1---\left(8\right)$

Because the sample that detects is dust suspension air under mine, the concentration ξ of dust ₁Value very little, to the right two formula Taylor expansions of formula (8):

$z=l^x=1+x+\frac{x^2}{2!}+\·\·\·\frac{x^n}{n!},$ (| z|＜∞), launch obtains:

$m_1{Y}_1=(d^2{k}_{1}c+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00003428854800011.png"\; state="\{\{state\}\}">d</figure-callout>}}^2{\mathrm{\&mu;}}_{1}c-d{k}_1){\mathrm{\&xi;}}_1$

$-(\frac{1}{2}{k_1}^2+{\mathrm{\&mu;}}_1{k}_1){\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00003428854800011.png"\; state="\{\{state\}\}">d</figure-callout>}}^2{{\mathrm{\&xi;}}_1}^2-(\frac{1}{2}{c}^2{d}^2-\mathrm{cd}+1)---\left(9\right)$

Formula (9) is arranged:

$Y_1=\frac{1}{m_1}[-(\frac{1}{2}{k_1}^2+{\mathrm{\&mu;}}_1{k}_1){\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00003428854800011.png"\; state="\{\{state\}\}">d</figure-callout>}}^2{{\mathrm{\&xi;}}_1}^2+$ (10)

$(d^2{k}_{1}c+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00003428854800011.png"\; state="\{\{state\}\}">d</figure-callout>}}^2{\mathrm{\&mu;}}_{1}c-d{k}_1){\mathrm{\&xi;}}_1-(\frac{1}{2}{c}^2{d}^2-\mathrm{cd}+1)]$

Coefficient to formula (10) carries out the constant setting:

$A=-\frac{1}{m_1}(\frac{1}{2}{k_1}^2+{\mathrm{\&mu;}}_1{k}_1){\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00003428854800011.png"\; state="\{\{state\}\}">d</figure-callout>}}^2;$

$B=\frac{1}{m_1}(d^2{k}_{1}c+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00003428854800011.png"\; state="\{\{state\}\}">d</figure-callout>}}^2{\mathrm{\&mu;}}_{1}c-d{k}_1);$

$C=-\frac{1}{m_1}(\frac{1}{2}{c}^2{d}^2-\mathrm{cd}+1).$

A, B, C is constant. after formula (10) arranges, as follows:

Y ₁＝Aζ ₁ ²+Bζ ₁+C (11)

If second-order equation Y ₁=f (ξ ₁So), the concentration ξ of dust ₁Can pass through Y to the experimental result that detects ₁=f (ξ ₁) inverse function obtain, and loose thoroughly than Y ₁To detect by experiment gained.

At first the utility model is analyzed the feasibility that light scattering theory is applied to detect gaseous impurities, has has then further researched and analysed light scattering and light transmission theory in the applied analysis of measuring on dust concentration.Established on this basis so that laser is loose and thoroughly than theoretical measuring method as basis, detected airborne dust content, and set up the loose saturating ratio method of laser intensity and detected the theoretical model of dust content in gas, carry out laboratory simulation and measure, verified the correct feasibility of theoretical model.

Claims (3)

1. light scattering method dust concentration tester, it is characterized in that: it comprises optical unit (1), laser power supply circuit (2), CPU control module (3) and display circuit (4);

Optical unit (1) comprises optical element (11), infrared laser (12) and photoelectric commutator (13); The laser signal that described infrared laser (12) produces is incident to optical element (11), be emitted to photoelectric commutator (13) after optical element (11) conversion, the switching signal input end of CPU control module (3) is connected with the switching signal output terminal of photoelectric commutator (13); The power supply signal output terminal of described laser power supply circuit (2) is connected with the power supply signal input end of infrared laser (12); The control signal input end of described laser power supply circuit (2) is connected with the control signal output terminal of CPU control module (3); The display input end of display circuit (4) is connected with the display output terminal of CPU control module (3).

2. light scattering method dust concentration tester according to claim 1, it is characterized in that it also comprises concentration over-standard warning circuit (5), the alerting signal input end of described concentration over-standard warning circuit (5) is connected with the alarm signal output ends of CPU control module (3).

3. light scattering method dust concentration tester according to claim 1 and 2, is characterized in that optical element (11) is photoelectric commutator.

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