CN102445437B - Method and device for measuring turbidity - Google Patents

Abstract

The invention discloses a method and a device for measuring turbidity, related to the turbidity detection technology. The method comprises the steps of irradiating an environment to be detected by using a beam of parallel light, and detecting 90-degree scattered light power in a plurality of positions in the light path of the parallel light, thus obtaining the turbidity value of the environment to be detected by performing mathematic processing on the detected value. The measuring device of the method is packaged in the form of a probe and comprises a housing, a parallel light emitting system, a photoelectric receiving system and a signal processing circuit. The light path structure is capable of satisfying 90-degree scattering detection under any condition and the volume of the device can be reduced. The method and the device provided in the invention eliminate the influence of the unstability of a light source on the measurement, reduce the interference of temperature errors and window pollution to the turbidity measurement, extend the cycle of manual cleaning and maintenance and improve the measurement accuracy. The measuring device is small in volume, low in power consumption, high in sensitivity and good in anti-jamming capability; and the device follows ISO7027 standards, and is convenient for mounting and adjustment and applicable to turbidity measurement and intelligent monitoring of various environments.

Description

A kind of turbidimetry method and device

Technical field

The present invention relates to turbidimetry technical field, be a kind ofly adopt single parallel beam to irradiate environment to be measured and keep multiple positions of equidistance to survey the turbidity detection method of 90 degree scattered light power and the turbidity meter based on the method at optical axis homonymy and with optical axis simultaneously, can be used for the turbidimetry of monitoring water environment, wastewater treatment, chemical industry and food medicine and other fields.

Background technology

Optical sensor refers to the sensor that the core sensitive mechanism of sensor is opticator.Optical sensor has highly sensitive, and electrical insulating property is good, anti-electromagnetic interference (EMI), and the plurality of advantages such as easy microminiaturization, suitable especially applying to surveyed for a long time online.Take monitoring water environment as example, typical application has fluorescence method to measure optical dissolved oxygen and rhodamine, and 90 ° of scattering methods are measured turbidity.

The content of water turbidity reflection silt, clay, the fine suspended material such as organism and inorganics, soluble coloured organic compound and planktonic organism and other microorganism.These suspension mass-energy absorption bacterium and viruses.In general, turbidity is higher, and water body clean-up performance is lower.The measuring method of turbidity comprises transmission beam method and scattering method.Current turbidity meter generally uses scattering method to measure.In the time of low turbidity, can obtain the good data of the linearity.

Nephelometric turbidity probe method is divided into right angle scattering (90 °), three kinds of forward scattering (90 ° of <) and back scattering (90 ° of >) by the angle of received scattered light and incident light is different.The angle of incident light direction and specimen surface can be divided into again vertical incidence and oblique incidence.For on-line measurement, due to effects limit such as volumes, the light path of existing turbidimeter device is generally difficult to guarantee 90 ° of scatterometries.But the light intensity that scattering method is measured is directional light and particle effect to be formed.The diameter of particle can make scattered light intensity change in the distribution in space.Change minimum 90 ° of these angle light intensity amplitudes.Parasitic light can be at utmost avoided in 90 degree scatterings simultaneously, thereby uses strict 90 degree scatterings to have great role for reducing error.

5 pacing itemss of scattered light mensuration in ISO7027 standard, are stipulated.

(1) incident ray wavelength adopts 860nm;

(2) incident ray spectral half width is less than 60nm;

(3) parallel rays of incident does not have emissivity, defocuses and is no more than 1.5 degree;

(4) O=90 ° ± 2.5 ° of the angle measured angular between incident light axis and scattered light optical axis;

(5) aperture angle of instrument is between 20 degree-30 degree.

Water turbidity monitoring device, particularly long-term online sonde-type monitoring device, be difficult for meeting completely ISO7027 standard, and because the pollution of part aging and window is along with the time is in aggravation, turbidimetry is had to considerable influence, easily causes the precision of measurement result to reduce.Thereby the online turbidity sniffer of this class needs manual maintenance more frequently.

Summary of the invention

The object of this invention is to provide a kind of turbidimetry method and device, to overcome existing turbidity meter, particularly online water turbidity probe, generally be difficult to meet completely ISO7027 standard, and detection mode is generally single-point and surveys, easily be subject to the impact of the extraneous factors such as temperature, be difficult to overcome the defects such as error that window pollution, light source drift introduce.

For achieving the above object, technical solution of the present invention is:

A kind of turbidimetry method, it comprises:

A) adopt a branch of directional light to irradiate environment to be measured;

B) also utilize at least two same photodetectors, survey it and propagate 90 degree scattered light power of multiple positions in light path;

C) all sensing points are all positioned at optical axis homonymy, and keep equidistance with optical axis;

D), by the mathematics manipulation to probe value, obtain the turbidity value of environment to be measured.

The turbidity meter that described turbidimetry method is used, it comprises housing, directional light emission coefficient, silicon photoelectric receiving system and signal processing circuit; The sealing of tubular shell one end, the other end are uncovered, in its inner chamber, be provided with signal processing circuit, in housing head end inner chamber, be integrated with directional light emission coefficient and silicon photoelectric receiving system, directional light emission coefficient and silicon photoelectric receiving system are all electrically connected with signal processing circuit, housing tail end middle part is a water seal plug, and water seal plug connection host computer both-way communication, connecting components provide power supply;

Housing opening end and housing head end rear portion are separable affixed;

Housing head end front end is also provided with sampling cover.

Described turbidity meter, described in it, directional light emission coefficient, comprises LED light source, prism and convex lens; In the emergent light light path of LED light source, be sequentially with convex lens, prism;

The light beam planoconvex lens that LED light source sends is adjusted into parallel beam, along the transmitting of device axis direction, then adjusts beam direction through 90 degree reflecting prisms, makes the scattered beam of surveying along light path be always 90 degree scattered lights.

Described turbidity meter, prism described in it, its processing mode is to use prismatic reflection face plated film, or uses prism protection module, prism is embedded in protection module, and has a seal chamber between prismatic reflection face and protection module, is filled with dry gas.

Described turbidity meter, silicon photoelectric receiving system described in it, comprise at least two light activated elements, the end of probe of two light activated elements is positioned at housing head end outside, and in two light activated element end of probe, each order is covered with filter glass, diaphragm, hermetyic window mirror from inside to outside; The scattered light that irradiates determinand enters diaphragm from hermetyic window mirror, then injects light activated element through filter glass; It makes the detection aperture angle of light activated element be less than 20 degree, has reduced emission spectrum half width, and can receive many group scattered light measured values simultaneously.

Described turbidity meter, at least two light activated elements described in it, are the same sides being distributed in directional light emission coefficient emergent light axis, and keep equidistance with optical axis.

Described turbidity meter, described in it, housing opening end and housing head end rear portion are separable affixed, are for being spirally connected, and joint is provided with O-ring seal sealing, can dismantle, and is convenient to opticator and circuit part debugging and safeguards; In housing inner chamber, be also provided with motor drive ic, in housing head end inner chamber, be also provided with stepper motor, the motor shaft of stepper motor is connected with surface cleaning piece, surface cleaning piece is covered on prism or protection module, hermetyic window mirror outside surface, between motor shaft and housing head end, do water-proofing treatment by O-ring seal, stepper motor is electrically connected with motor drive ic, and motor drive ic is electrically connected with signal processing circuit;

After startup, motor shaft has driven insulation blocking and the clean surface cleaning piece wiping housing head end outside surface that maintains effect.

Described turbidity meter, sampling cover described in it, inwall scribbles light absorbent or carries out blackening process, has in the position of the corresponding optical axis of sample cover wall the duct being connected with external environment condition, is convenient to test the turnover of sample; Sampling cover uses thread bush to link with housing head end front end and connects.

Described turbidity meter, surface cleaning piece described in it, is to use elastomeric material to make.

Method of the present invention is measured multiple scattered light performance numbers that water body same plane obtains, and by its ratio reflection turbidity, precision is high, eliminate the instability of light source, reduce the impact on turbidimetry of temperature error and window pollution, extended the artificial cleaning cycle, improved measuring accuracy.Probe light path system all meets 90 degree scatterings under any condition.If the light source 860nm using, surveys and meets ISO7027 standard completely.There is higher precision and antijamming capability, can work under water accurately for a long time.

Accompanying drawing explanation

Fig. 1: the front view of the online turbidity probe tip device of water body of the present invention;

Fig. 2: the online turbidity probe tip device of water body of the present invention upward view (surface cleaning piece closure state);

Fig. 3: the online turbidity probe tip device of water body of the present invention upward view (surface cleaning piece opening);

Fig. 4: the turbidity schematic diagram data that utilizes proving installation of the present invention to obtain;

Fig. 5: the elimination light source drift schematic diagram data that utilizes proving installation of the present invention to obtain.

Number in the figure:

1--housing 2--directional light emission coefficient 3--silicon photoelectric receiving system

4--stepper motor 5--optical filter one 6--optical filter two

7--light activated element one 8--light activated element two 9-LED light sources

10-prism 11-water seal plug 12-signal processing system

13-motor drive ic 14-axle water seal packing ring 15-motor shaft

16-convex lens 17-hermetyic window mirror one 18-diaphragm one

19-hermetyic window mirror 20-diaphragm two 21-surface cleaning pieces

22-housing head end 23-housing body end 24-housing packing ring

25-prism protection module 26-samples cover

Embodiment

With P ₀represent incident intensity, h represents the absorption coefficient of sample, and k represents its scattering coefficient. when after the sample that parallel beam is x by thickness, luminous power should be:

P(x)＝P ₀?exp[-(k+h)x]

To above formula differentiate, available power is the scattering power of the parallel beam of P (x) sample that is dx by thickness.For the liquid (hx levels off to 0) of low absorption, this scattered light power P _sfor

$P_s\left(x\right)=-\frac{\mathrm{dP}\left(x\right)}{\mathrm{dx}}\&ap;k\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">P</figure-callout>}}_0\exp [-(k+h)x]=k\&CenterDot;P\left(x\right)$

For 90 ° of scattered light P that survey in light path _s1, P _s2, above formula integration can be obtained

${\mathrm{<figure-callout\; id="1"\; label="P\; S"\; filenames="HSA00000299777400011.png,HSA00000299777400031.png"\; state="\{\{state\}\}">P</figure-callout>}}_S=\mathrm{\&alpha;}\frac{k}{k+\mathrm{<figure-callout\; id="0"\; label="h\; P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">h</figure-callout>}}{P}_{}{}_0\exp [-(k+h)\&CenterDot;x_1]\&CenterDot;(1-\exp [-(k+h)\&CenterDot;l\left]\right)$

${\mathrm{<figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout>}}_S=\mathrm{\&alpha;}\frac{k}{k+\mathrm{<figure-callout\; id="0"\; label="h\; P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">h</figure-callout>}}{P}_{}{}_0\exp [-(k+h)\&CenterDot;x_2]\&CenterDot;(1-\exp [-(k+h)\&CenterDot;l\left]\right)$

Wherein α is the ratio of total scattering light on 90 °, and l is between the photosensitive area of probe.P _s1and P _s2it is the real power value of two groups of probe measurements.

$\frac{P_{S1}}{{\mathrm{<figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout>}}_S}=\exp \left[(k+h)(x_1-x_2)\right]=\exp [(k+h)\&CenterDot;L]$

Wherein L is the centre distance of two probes.If definition τ=k+h is turbidity coefficient, can obtain

$\mathrm{\&tau;}=L^{-1}\&CenterDot;\ln \frac{P_{S1}}{{\mathrm{<figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout>}}_S}$

Two groups of 90 ° of scattered light measured values are not only distinguished corresponding turbidity, and the logarithm of its ratio is also directly proportional with turbidity.

If the time dependent impact of light source is P ₀(t), the impact of window cleanliness factor is β (t),

P(t)＝P ₀(t)β(t)exp(-τx)

$P_s\left(t\right)=\frac{k}{k+h}P\left(t\right)\mathrm{\&beta;}\left(t\right)(1-\exp (-\mathrm{\&tau;l}))$

Concerning single-point is surveyed, the transmitted light of detection and scattered light are all subject to the impact of light source or light-emitting window cleanliness factor.If use ratioing technigue, in the time that two detection windows approach, can think that window pollution degree is suitable, is all β (t):

${\mathrm{\&tau;}}^{\&prime;}=L^{-1}\left(\mathrm{<figure-callout\; id="1"\; label="ln\; P\; S"\; filenames="HSA00000299777400011.png,HSA00000299777400031.png"\; state="\{\{state\}\}">ln</figure-callout>}\frac{{P_S}^{}}{}\frac{{1_{}}^{\&prime;}}{{{\mathrm{<figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout>}}_S}^{\&prime;}}\right)=L^{-1}\left(\ln \frac{P_{S1}P\left(t\right)\mathrm{\&beta;}\left(t\right)}{P_{S2}P\left(t\right)\mathrm{\&beta;}\left(t\right)}\right)=L^{-1}\left(\ln \frac{P_{S1}}{P_{S2}}\right)=\mathrm{\&tau;}$

For two detection windows near each other, suppose that the pollution level being subject to is identical, the turbidity of the ratio of scattered light performance number reflection can be eliminated light source, the error that temperature and window cleanliness are brought.

Turbidity meter is by housing 1, directional light emission coefficient 2, and the silicon photoelectric receiving system 3 of two probes, power down signal treatment circuit plate 12 forms.Feature is the head end 22 that all optical elements are all integrated in housing.Signal processing circuit is all integrated in the body end 23 of housing.Described directional light emission coefficient 2 and silicon photoelectric receiving system 3 are positioned at same plane, guarantee that 90 degree scattered lights are not subject to the impact of the disturbances such as water refraction rate or temperature.

The light source of directional light emission coefficient is a high-capacity LED 9, and convex lens 16 have guaranteed that the radiative depth of parallelism meets ISO7027 standard-required.The light beam planoconvex lens that LED light source sends is adjusted into parallel beam, along the transmitting of device axis direction, then adjusts beam direction through 90 degree reflecting prisms, makes the scattered beam of surveying along light path be always 90 degree scattered lights.The reflecting surface that is treated to of prism plates mould or is embedded in prism protection module.Directional light emission coefficient 2 is electrically connected with signal processing module 12, is subject to singlechip chip control.

Optical receiver system 3 is by silicon light activated element 7,8, and optical filter 5,6 and diaphragm 18,20 and hermetyic window 17,19 form.Outside scattered light enters diaphragm from hermetyic window mirror, then injects light activated element through optical filter.The centre wavelength of optical filter is corresponding with light source, and has less half band-width.Make instrument aperture angle be down to 20 degree.

Directional light emission coefficient is all connected with processing of circuit system 12 with optical receiver system.Processing of circuit system is amplified processing to the voltage signal of optical receiver system transmission, and after AD conversion and filtering etc. are processed, numerical operation is turbidity value.Processing of circuit system is controlled stepper motor 4 simultaneously, the set of drive surfaces cleaning block and reset.

As shown in Figure 1, the housing of turbidity sniffer is the right cylinder that a duralumin is made, and is of a size of 75mm × 30mm × 30mm.From water seal plug 11 supply powers at housing 1 rear portion, the MSP430 singlechip chip 12 of the low-power consumption of housing body end 22 is controlled motor control chip 13, drives micro-step motor 4 to rotate.Motor shaft 15 drives and covers shape surface cleaning piece 21, exposes light transmitting prism 10 and the optical receiver system 3 of housing head end 23, as shown in Figure 3.Singlechip chip activates directional light emission coefficient 2 simultaneously, wavelength 860nm, and light planoconvex lens 16 and prism 10 that the LED9 of spectral half width 10nm sends are injected water body.

Now in water body, scattered light, by forms 17,19 diaphragms 18,20, enters silicon light activated element 7,8 through the optical filter 5,6 of centre wavelength 860nm spectral half width 30nm.Two silicon light activated elements 7,8 provide scattered light power, obtain turbidity value through numerical operation.Optical filter 5, the 6 centre wavelength 860nm of thickness 5mm, spectral half width 30nm.The amplifying circuit of silicon light activated element 7,8 access signaling modules 12, then carry out data processing.The simulating signal obtaining is amplified through signal, and analog to digital conversion is used RS232 interface output data after singlechip chip data processing.

Use vertical transmission beam method to measure the optical attenuation degree (unit is dB/cm) of a series of turbid liquid samples.Use two probe ratioing technigues to measure the turbidity of identical turbid liquid sample, the data that obtain as shown in Figure 4.The data that two kinds of method of testings obtain are good linear relationship.By the Output optical power of periodically-varied light source, can observe the signal generating period variation thereupon that two probes are measured, but the turbidity that uses two probe mathematics manipulation to characterize only has very little fluctuation, as shown in Figure 5.Show that two probe ratioing technigues can remove the error producing because of factors such as flashing are fixed preferably.

After image data a period of time, signal processing chip 12 is controlled motor 4 drive surfaces cleaning blocks 21 and is set back, as shown in Figure 2.Synchronous signal process chip 12, directional light emission coefficient 2 and optical receiver system 3 enter dormant state.After waiting for the schedule time, again activate.Turbidity sampling number and the cycle of probe all can be set by signal processing chip 12.The data that obtain are electrically connected other terminal device through RS232.

While test, for protection probe keeps measuring accuracy, probing shell front end simultaneously, sampling cover 26 can be installed in advance in rapid current water.Can effectively reduce flow velocity and maintain the accuracy of measurement.

Claims (8)

1. a turbidimetry method, is characterized in that, comprising:

A) adopt a branch of directional light to irradiate environment to be measured;

B) also utilize at least two same light activated elements, survey it and propagate 90 degree scattered light power of multiple positions in light path;

C) all sensing points are all positioned at optical axis homonymy, and keep equidistance with optical axis;

D) pass through probe value according to formula

carry out mathematics manipulation, obtain the turbidity value of environment to be measured, the τ in formula represents turbidity coefficient, i.e. turbidity value, and L is the centre distance of two probes, P _s1and P _s2it is the real power value of two groups of probe measurements.

2. the turbidity meter that turbidimetry method as claimed in claim 1 is used, it is characterized in that, comprise housing (1), directional light emission coefficient (2), silicon photoelectric receiving system (3) and signal processing circuit (12); The sealing of tubular shell (1) one end, the other end are uncovered, in its inner chamber, be provided with signal processing circuit (12), in housing head end (22) inner chamber, be integrated with directional light emission coefficient (2) and silicon photoelectric receiving system (3), directional light emission coefficient (2) and silicon photoelectric receiving system (3) are all electrically connected with signal processing circuit (12), housing tail end (23) middle part is a water seal plug (11), and water seal plug (11) connection host computer both-way communication, connecting components provide power supply;

Housing (1) opening end and housing head end (22) rear portion are separable affixed;

Housing head end (22) front end is also provided with sampling cover (26);

Wherein, described silicon photoelectric receiving system (3), comprise at least two light activated elements (7,8), two light activated elements (7,8) end of probe is positioned at housing head end (22) outside, in two light activated elements (7,8) end of probe, each order is covered with filter glass (5,6), diaphragm (18 from inside to outside, 20), hermetyic window mirror (17,19); The scattered light that irradiates determinand enters diaphragm (18,20) from hermetyic window mirror (17,19), then injects light activated element (7,8) through filter glass (5,6); It makes the detection aperture angle of light activated element (7,8) be less than 20 degree, has reduced emission spectrum half width, and can receive many group scattered light measured values simultaneously.

3. turbidity meter as claimed in claim 2, is characterized in that, described directional light emission coefficient (2) comprises LED light source (9), prism (10) and convex lens (16); In the emergent light light path of LED light source (9), be sequentially with convex lens (16), prism (10);

The light beam planoconvex lens (16) that LED light source (9) sends is adjusted into parallel beam, launch along device axis direction, adjust beam direction through 90 degree reflecting prisms (10) again, make the scattered beam of surveying along light path be always 90 degree scattered lights.

4. turbidity meter as claimed in claim 3; it is characterized in that; described prism (10); its processing mode is to use prismatic reflection face plated film; or use prism protection module (25); prism (10) is embedded in protection module (25), and has a seal chamber between prismatic reflection face and protection module (25), is filled with dry gas.

5. turbidity meter as claimed in claim 2 or claim 3, is characterized in that, described at least two light activated elements (7,8), are the homonymies being distributed in directional light emission coefficient (2) emergent light axis, and keeps equidistance with optical axis.

6. turbidity meter as claimed in claim 2, it is characterized in that, described housing (1) opening end and housing head end (22) rear portion are separable affixed, for being spirally connected, joint is provided with O-ring seal (24) sealing, can dismantle, be convenient to opticator and circuit part debugging and safeguard, in housing (1) inner chamber, be also provided with motor drive ic (13), in housing head end (22) inner chamber, be also provided with stepper motor (4), the motor shaft (15) of stepper motor (4) is connected with surface cleaning piece (21), surface cleaning piece (21) is covered on prism (10) or protection module (25), hermetyic window mirror (17, 19) outside surface, between motor shaft (15) and housing head end (22), do water-proofing treatment by O-ring seal (14), stepper motor (4) is electrically connected with motor drive ic (13), motor drive ic (13) is electrically connected with signal processing circuit (12),

After startup, motor shaft (15) has driven insulation blocking and clean surface cleaning piece (21) wiping housing head end (22) outside surface that maintains effect.

7. turbidity meter as claimed in claim 2, it is characterized in that, described sampling cover (26), inwall scribbles light absorbent or carries out blackening process, position at the corresponding optical axis of sample cover wall has the duct being connected with external environment condition, is convenient to test the turnover of sample; Sampling cover (26) uses thread bush to link with housing head end (22) front end and connects.

8. turbidity meter as claimed in claim 6, is characterized in that, described surface cleaning piece (21) is to use elastomeric material to make.

Images