CN102445437A - 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 the turbidimetry technical field; Be a kind ofly to adopt single parallel beam to shine environment to be measured and keep a plurality of positions of equidistance to survey the turbidity detection method of 90 degree scattered light power simultaneously at the optical axis homonymy and with optical axis and, can be used for the turbidimetry of monitoring water environment, wastewater treatment, chemical industry and food medicine and other fields based on the turbidimetry device of this method.

Background technology

Optical sensor is meant that the core sensitive mechanism of sensor is the sensor of opticator.Optical sensor has highly sensitive, and electrical insulating property is good, anti-electromagnetic interference (EMI), and plurality of advantages such as easy miniaturization, long-term online detection especially suits to apply to.With the monitoring water environment is example, and typical application has fluorescence method to measure optical dissolved oxygen and rhodamine, and 90 ° of scattering methods are measured turbidity.

Water body turbidity reflection silt, clay, fine organism and the content of inorganics, soluble coloured organic compound and suspended materials such as planktonic organism and other microorganism.These suspension mass-energy absorption bacterium and viruses.In general, turbidity is high more, and the water body clean-up performance is low more.The measuring method of turbidity comprises transmission beam method and scattering method.Current turbidimetry device generally uses scattering method to measure.When hanging down turbidity, can obtain linearity data preferably.

The nephelometric turbidity probe method is divided into right angle scattering (90 °), three kinds of forward scattering (＜90 °) and back scattering (＞90 °) by received scattered light is different with the angle of incident light.The angle of incident light direction and specimen surface can be divided into vertical incidence and oblique incidence again.For on-line measurement, because effects limit such as volumes, the light path of existing turbidimeter device generally is 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 spatial distributions.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 for reducing error great role to be arranged.

5 pacing itemss of scattered light mensuration have been stipulated in the ISO7027 standard.

(1) the incident ray wavelength adopts 860nm;

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

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

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

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

Water body turbidity monitoring device, particularly long-term online sonde-type monitoring device is difficult for satisfying fully the ISO7027 standard, and because of the pollution of part aging and window along with the time in aggravation, turbidimetry is had considerable influence, be prone to cause the precision reduction of measurement result.Thereby the online turbidity sniffer of this type needs more frequent manual maintenance.

Summary of the invention

The purpose of this invention is to provide a kind of turbidimetry method and device; To overcome existing turbidimetry device; Particularly online water body turbidity probe tip generally is difficult to satisfy the ISO7027 standard fully, and detection mode is generally the single-point detection; Receive the influence of extraneous factors such as temperature easily, be difficult to overcome the defectives such as error of window pollution, light source drift introducing.

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 shine environment to be measured;

B) also utilize at least two same photodetectors, survey the 90 degree scattered light power that it propagates a plurality of positions in light path;

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

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

The turbidimetry device that a kind of 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; Be provided with signal processing circuit in its inner chamber; Be integrated with directional light emission coefficient and silicon photoelectric receiving system in the housing head end inner chamber; Directional light emission coefficient and silicon photoelectric receiving system all are electrically connected with signal processing circuit, and housing tail end middle part is a water seal plug, and the water seal plug connects host computer and both-way communication, connect each parts provides power supply;

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

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

Described turbidimetry device, its said directional light emission coefficient comprises led light source, prism and convex lens; Be sequentially with convex lens, prism on the emergent light light path of led light source;

The light beam planoconvex lens that led light source sends is adjusted into parallel beam, along the emission of device axis direction, again through 90 degree reflecting prism adjustment beam directions, makes the scattered beam of surveying along light path be always 90 degree scattered lights.

Described turbidimetry device, its said prism, its processing mode is to use prismatic reflection face plated film, or uses the prism protection module, and prism is embedded in the protection module, and between prismatic reflection face and protection module one seal chamber is arranged, and is filled with dry gas.

Described turbidimetry device; Its said silicon photoelectric receiving system; Comprise at least two light activated elements, the end of probe of two light activated elements is positioned at the housing head end outside, and each is covered with filter glass, diaphragm, hermetyic window mirror in proper order from inside to outside on two light activated element end of probe; The scattered light of irradiation determinand gets into diaphragm from the hermetyic window mirror, sees through filter glass again and injects light activated element; It makes the detection aperture angle of light activated element spend less than 20, has reduced the emission spectrum half width, and can receive many group scattered light measured values simultaneously.

Described turbidimetry device, its said at least two light activated elements are the same sides that are distributed in directional light emission coefficient emergent light axis, and keep equidistance with optical axis.

Described turbidimetry device, its said housing opening end and housing head end rear portion are separable affixed, are for being spirally connected, and the joint is provided with the O-ring seal sealing, can dismantle, and is convenient to debugging of opticator and circuit part and maintenance; Also be provided with motor drive ic in the housing inner chamber; Also be provided with stepper motor in the housing head end inner chamber; The motor shaft of stepper motor is connected with the cleaning surfaces piece, and the cleaning surfaces piece is covered on prism or protection module, hermetyic window mirror outside surface, does water-proofing treatment by O-ring seal between motor shaft and the housing head end; Stepper motor is electrically connected with motor drive ic, and motor drive ic is electrically connected with signal processing circuit;

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

Described turbidimetry device, its said sampling cover, inwall scribble light absorbent or the processing of turning black, and have the duct that is connected with external environment condition in the position of the corresponding optical axis of appearance cover wall, are convenient to the turnover of specimen; The sampling cover uses the thread bush buckle with housing head end front end.

Described turbidimetry device, its said cleaning surfaces piece is to use elastomeric material to make.

Method of the present invention is measured a plurality of scattered light performance numbers that the same plane of water body obtains, and by its ratio reflection turbidity, precision is high; Eliminated the instability of light source; Reduced the influence of temperature error and window pollution, prolonged the artificial cleaning cycle, improved measuring accuracy turbidimetry.The probe light path system all satisfies 90 degree scatterings under any condition.If the light source 860nm that uses, detection promptly meets the ISO7027 standard fully.Have higher precision and antijamming capability, can work under water accurately for a long time.

Description of drawings

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 (cleaning surfaces piece closure state);

Fig. 3: the online turbidity probe tip device of water body of the present invention upward view (cleaning surfaces 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.

Label among 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-cleaning surfaces pieces

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

The 25-prism protection module 26-cover of taking a sample

Embodiment

With P ₀The expression incident intensity, h representes the absorption coefficient of sample, and k representes its scattering coefficient. and after parallel beam was the sample of x through thickness, luminous power should be:

P(x)＝P ₀?exp[-(k+h)x]

To the following formula differentiate, available power is that the parallel beam of P (x) is the scattering power of the sample of dx through thickness.For the low liquid (hx levels off to 0) that absorbs, 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 on the light path _S1, P _S2, the following formula integration can be got

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

$P_{S2}=\mathrm{\&alpha;}\frac{k}{k+\mathrm{<figure-callout\; id="0"\; label="h\; P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">h</figure-callout>}}{P}_{}{}_0\exp [-(k+h)\&CenterDot;x_2]\&CenterDot;(1-\exp [-(k+h)\&CenterDot;l\left]\right)$

Wherein α is the ratio of total scattering light on 90 °, between the photosensitive area of l for probe.P _S1And P _S2It is the real power value of two groups of probe measurements.

$\frac{P_{S1}}{P_{S2}}=\exp \left[(k+h)(x_1-x_2)\right]=\exp [(k+h)\&CenterDot;L]$

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

$\mathrm{\&tau;}=L^{-1}\&CenterDot;\ln \frac{P_{S1}}{P_{S2}}$

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

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

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 was surveyed, the transmitted light of detection and scattered light all received the influence of light source or light-emitting window cleanliness factor.If use ratioing technigue, when two detection windows near the time, can think that the window pollution degree is suitable, all be β (t), then:

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

Promptly for two detection windows near each other, suppose that the pollution level that receives is identical, then 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.

The turbidimetry device 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 constitutes.Characteristics are head ends 22 that all optical elements all are integrated in housing.Signal processing circuit all is integrated in the body end 23 of housing.Described directional light emission coefficient 2 is positioned at same plane with silicon photoelectric receiving system 3, guarantees that 90 degree scattered lights do not receive the influence of disturbances such as water body refractive index 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 satisfies the ISO7027 standard-required.The light beam planoconvex lens that led light source sends is adjusted into parallel beam, along the emission of device axis direction, again through 90 degree reflecting prism adjustment beam directions, makes the scattered beam of surveying along light path be always 90 degree scattered lights.The reflecting surface plating mould that is treated to of prism perhaps is embedded in the prism protection module.Directional light emission coefficient 2 is electrically connected with signal processing module 12, controlled by singlechip chip.

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

The directional light emission coefficient all is connected with processing of circuit system 12 with optical receiver system.The processing of circuit system carries out processing and amplifying to the voltage signal of optical receiver system transmission, and after AD conversion and filtering etc. were handled, numerical operation was a turbidity value.The processing of circuit system controls stepper motor 4 simultaneously, the set of drive surfaces cleaning block and resetting.

As shown in Figure 1, the housing of turbidity sniffer is the right cylinder that a duralumin is processed, 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 control motor control chips 13 of the low-power consumption of housing body end 22 drive micro-step motor 4 and rotate.Motor shaft 15 drives and covers shape cleaning surfaces piece 21, exposes the light emission prism 10 and optical receiver system 3 of housing head end 23, and is 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.

Scattered light is through forms 17,19 diaphragms 18,20 in the water body at this moment, and the optical filter 5,6 of process centre wavelength 860nm spectral half width 30nm gets into silicon light activated elements 7,8.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.Silicon light activated element 7,8 inserts the amplifying circuit of signaling module 12, carries out data processing again.The simulating signal that obtains is amplified through signal, and analog to digital conversion is used RS232 interface output data after the singlechip chip data processing.

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

Image data is after a period of time, and signal processing chip 12 control motors 4 drive surfaces cleaning blocks 21 set back, and are as shown in Figure 2.Synchronous signal process chip 12, directional light emission coefficient 2 gets into dormant state with optical receiver system 3.Activate once more after waiting for the schedule time.The turbidity sampling number of probe and cycle all can be set through signal processing chip 12.The data that obtain are electrically connected other terminal device through RS232.

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

Claims (9)

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

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

B) also utilize at least two same light activated elements, survey the 90 degree scattered light power that it propagates a plurality of positions in light path;

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

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

2. the turbidimetry device that turbidimetry method as claimed in claim 1 is used is characterized in that, comprises 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; Be provided with signal processing circuit (12) in its inner chamber; Be integrated with directional light emission coefficient (2) and silicon photoelectric receiving system (3) in housing head end (22) inner chamber; Directional light emission coefficient (2) and silicon photoelectric receiving system (3) all are electrically connected with signal processing circuit (12), and housing tail end (23) middle part is a water seal plug (11), and water seal plug (11) connects host computer and both-way communication, connect each parts provides power supply;

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

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

3. turbidimetry device as claimed in claim 2 is characterized in that, said directional light emission coefficient (2) comprises led light source (9), prism (10) and convex lens (16); Be sequentially with convex lens (16), prism (10) on the emergent light light path of led light source (9);

The light beam planoconvex lens (16) that led light source (9) sends is adjusted into parallel beam, along the emission of device axis direction, again through 90 degree reflecting prism (10) adjustment beam directions, makes the scattered beam of surveying along light path be always 90 degree scattered lights.

4. turbidimetry device as claimed in claim 3; It is characterized in that, said prism (10), its processing mode is to use prismatic reflection face plated film; Or use prism protection module (25); Prism (10) is embedded in the protection module (25), and between prismatic reflection face and protection module (25) seal chamber is arranged, and is filled with dry gas.

5. turbidimetry device as claimed in claim 2 is characterized in that, said 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, and each is covered with filter glass (5 in proper order from inside to outside on two light activated elements (7,8) end of probe; 6), diaphragm (18,20), hermetyic window mirror (17,19); The scattered light of irradiation determinand gets into diaphragm (18,20) from hermetyic window mirror (17,19), sees through filter glass (5,6) again and injects light activated element (7,8); It makes the detection aperture angle of light activated element (7,8) spend less than 20, has reduced the emission spectrum half width, and can receive many group scattered light measured values simultaneously.

6. like claim 3 or 5 described turbidimetry devices, it is characterized in that said at least two light activated elements (7,8) are the homonymies that is distributed in directional light emission coefficient (2) emergent light axis, and keep equidistance with optical axis.

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

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

8. turbidimetry device as claimed in claim 2 is characterized in that, said sampling cover (26), inwall scribble light absorbent or the processing of turning black, and has the duct that is connected with external environment condition in the position of the corresponding optical axis of appearance cover wall, is convenient to the turnover of specimen; Sampling cover (26) uses the thread bush buckle with housing head end (22) front end.

9. turbidimetry device as claimed in claim 7 is characterized in that, said cleaning surfaces piece (21) is to use elastomeric material to make.

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