CN102445437B - Method and device for measuring turbidity - Google Patents

Abstract

The invention discloses a turbidity measurement method and device, which relate to turbidity detection technology. The method uses a beam of parallel light to irradiate the environment to be measured, and detects the 90-degree scattered light power at multiple positions in the optical path. Mathematical processing of the detection value to obtain the turbidity value of the environment to be measured. The measuring device of the method is packaged in the form of a probe, and includes a casing, a parallel light emitting system, a photoelectric receiving system, and a signal processing circuit. Its light path structure meets 90-degree scattering detection under any conditions, and can reduce the volume of the device. The invention eliminates the influence of the instability of the light source on the measurement, reduces the interference of the temperature error and the window pollution on the turbidity measurement, prolongs the period of manual cleaning and maintenance, and improves the measurement accuracy. The measuring device is small in size, low in power consumption, high in sensitivity and strong in anti-interference ability. It complies with ISO7027 standard and is easy to install and debug. It can be applied to turbidity measurement and intelligent monitoring in various environments.

Description

Method and device for measuring turbidity

technical field

The invention relates to the technical field of turbidity measurement, and relates to a turbidity detection method that uses a single parallel light beam to irradiate the environment to be measured and simultaneously detects 90-degree scattered light power at multiple positions on the same side of the optical axis and at an equal distance from the optical axis. The turbidity measurement device based on the method can be used for turbidity measurement in the fields of water environment monitoring, sewage treatment, chemical industry, food medicine and the like.

Background technique

Optical sensor refers to the sensor whose core sensitive mechanism is the optical part. Optical sensors have many advantages such as high sensitivity, good electrical insulation, anti-electromagnetic interference, and easy miniaturization, and are especially suitable for long-term online detection. Taking water environment monitoring as an example, typical applications include the measurement of optical dissolved oxygen and rhodamine by fluorescence method, and the measurement of turbidity by 90° scattering method.

Water turbidity reflects the content of sediment, clay, fine organic and inorganic matter, soluble colored organic compounds, and suspended matter such as plankton and other microorganisms. These suspended substances can attract bacteria and viruses. In general, the higher the turbidity, the less clean the water. The measurement methods of turbidity include transmission method and scattering method. Current turbidity measurement devices generally use scattering methods for measurement. Data with better linearity can be obtained at low turbidity.

According to the angle between the received scattered light and the incident light, the scattering nephelometric detection method is divided into three types: right-angle scattering (90°), forward scattering (<90°) and backward scattering (>90°). The angle between the incident light direction and the sample surface can be divided into vertical incidence and oblique incidence. For online measurement, due to limitations of volume and other factors, the optical path of existing turbidimeter devices is generally difficult to guarantee 90° scattering measurement. However, the light intensity measured by the scattering method is formed by the interaction between parallel light and particles. The diameter of the particles can change the spatial distribution of the scattered light intensity. At the angle of 90°, the amplitude of light intensity changes the least. At the same time, 90-degree scattering can avoid stray light to the greatest extent, so the use of strict 90-degree scattering has a great effect on reducing errors.

The ISO7027 standard stipulates five basic conditions for the scattered light measurement method.

(1) The incident light wavelength is 860nm;

(2) The half-width of the incident light spectrum is less than 60nm;

(3) The incident parallel rays are not emissive, and the defocus does not exceed 1.5 degrees;

(4) The angle measurement angle O=90°±2.5° between the incident light axis and the scattered light axis;

(5) The aperture angle of the instrument is between 20°-30°.

Water turbidity monitoring devices, especially long-term online probe-type monitoring devices, are not easy to fully meet the ISO7027 standard, and the aging of components and the pollution of the window increase with time, which has a greater impact on turbidity measurement and easily leads to the accuracy of measurement results reduce. Therefore, this type of online turbidity detection device requires more frequent manual maintenance.

Contents of the invention

The purpose of the present invention is to provide a turbidity measurement method and device to overcome the existing turbidity measurement device, especially the online water body turbidity probe, it is generally difficult to fully meet the ISO7027 standard, and the detection method is generally single-point detection, which is easy Affected by external factors such as temperature, it is difficult to overcome defects such as window pollution and errors introduced by light source drift.

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

A method for measuring turbidity, comprising:

a) Use a beam of parallel light to irradiate the environment to be tested;

b) and use at least two identical photodetectors to detect the 90-degree scattered optical power at multiple positions in its propagation optical path;

c) All detection points are located on the same side of the optical axis and keep an equal distance from the optical axis;

d) Obtain the turbidity value of the environment to be measured through mathematical processing on the detection value.

A turbidity measurement device used in the turbidity measurement method, which includes a housing, a parallel light emitting system, a silicon photoelectric receiving system and a signal processing circuit; one end of the cylindrical housing is closed, the other end is open, and the inside There is a signal processing circuit in the cavity, and a parallel light emitting system and a silicon photoelectric receiving system are integrated in the inner cavity of the head end of the shell. Both the parallel light emitting system and the silicon photoelectric receiving system are electrically connected to the signal processing circuit. A water seal plug, the water seal plug is connected to the host computer and communicates bidirectionally, and connects various components to provide power;

The open end of the shell is detachably fixed to the rear part of the head end of the shell;

The front end of the head end of the shell is also provided with a sampling cover.

Described turbidity measurement device, its described parallel light emitting system, comprises LED light source, prism and convex lens; The outgoing light optical path of LED light source is provided with convex lens, prism sequentially;

The beam emitted by the LED light source is adjusted to a parallel beam by a convex lens, emitted along the axis of the device, and then adjusted by a 90-degree reflective prism, so that the scattered light detected along the optical path is always 90-degree scattered light.

In the turbidity measurement device, the prism is processed by coating the reflective surface of the prism, or using a prism protection module, the prism is embedded in the protection module, and there is a sealed cavity between the reflective surface of the prism and the protection module, filled with There is dry gas.

The said turbidity measurement device, said silicon photoelectric receiving system, includes at least two photosensitive elements, the detection ends of the two photosensitive elements are located outside the head end of the housing, and the detection ends of the two photosensitive elements are sequentially covered from inside to outside. There are filter lenses, apertures, and sealed windows; the scattered light irradiating the object to be measured enters the aperture from the sealed window, and then enters the photosensitive element through the filter lens; it makes the detection aperture angle of the photosensitive element less than 20 degrees, reducing The half-width of the emission spectrum is achieved, and multiple sets of scattered light measurement values can be received at the same time.

In the turbidity measurement device, the at least two photosensitive elements are distributed on the same side of the outgoing optical axis of the parallel light emitting system, and keep an equal distance from the optical axis.

In the turbidity measuring device, the open end of the housing is detachably connected to the rear part of the head end of the housing, which is a screw connection, and a sealing ring is provided at the junction, which can be disassembled and is convenient for the optical part. Debugging and maintenance of the circuit part; there is also a motor drive chip in the inner cavity of the housing, and a stepping motor is also installed in the inner cavity of the head end of the housing. The motor shaft of the stepping motor is fixed with a surface cleaning block, and the surface cleaning block is pasted The outer surface of the prism or protection module, the sealed window mirror, the sealing ring between the motor shaft and the head end of the housing is treated with waterproofing, the stepping motor is electrically connected to the motor drive chip, and the motor drive chip is electrically connected to the signal processing circuit;

After starting, the motor shaft drives the surface cleaning block, which plays the role of isolation protection and cleanliness maintenance, to wipe the outer surface of the head end of the housing.

In the turbidity measuring device, the inner wall of the sampling cover is coated with light-absorbing material or blackened, and the position corresponding to the optical axis of the sample cover wall has a hole connected to the external environment to facilitate the entry and exit of test samples; The cover is connected with the front end of the head end of the housing using a threaded buckle.

In the turbidity measuring device, the surface cleaning block is made of rubber material.

The method of the present invention measures multiple scattered light power values obtained on the same plane of the water body, and the turbidity is reflected by its ratio, which has high precision, eliminates the instability of the light source, reduces the influence of temperature errors and window pollution on turbidity measurement, and prolongs the turbidity measurement. The manual cleaning and maintenance cycle is shortened, and the measurement accuracy is improved. The optical system of the probe meets 90-degree scattering under any conditions. If the light source used is 860nm, the detection is in full compliance with the ISO7027 standard. With high precision and anti-interference ability, it can work accurately underwater for a long time.

Description of drawings

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

Fig. 2: bottom view of the water body online turbidity probe device of the present invention (surface cleaning block closed state);

Fig. 3: bottom view of the water body online turbidity probe device of the present invention (surface cleaning block open state);

Fig. 4: Utilize the schematic diagram of the turbidity data that the test device of the present invention obtains;

Fig. 5: Schematic diagram of light source drift elimination data obtained by using the test device of the present invention.

Labels in the figure:

1--Shell 2--Parallel light emitting system 3--Silicon photoelectric receiving system

4--stepper motor 5--filter 1 6--filter 2

7--photosensitive element 1 8--photosensitive element 2 9-LED light source

10-Prism 11-Water seal plug 12-Signal processing system

13-Motor drive chip 14-Shaft water seal washer 15-Motor shaft

16-convex lens 17-sealed window mirror 1 18-diaphragm 1

19-Sealed window mirror 20-Aperture 2 21-Surface cleaning block

22-shell head end 23-shell body end 24-shell gasket

25-prism protection module 26-sampling cover

Detailed ways

Let P ₀ represent the incident light intensity, h represent the absorption coefficient of the sample, and k represent its scattering coefficient. When the parallel beam passes through the sample with a thickness of x, the optical power should be:

P(x)=P ₀ exp[-(k+h)x]

Deriving the above formula, the scattered power of a parallel beam of power P(x) passing through a sample with a thickness of dx can be obtained. For a liquid with low absorption (h·x approaches 0), the scattered light power P _S is

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

For the 90° scattered light P _S1 and P _S2 detected on the optical path, the above formula can be integrated to get

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="P\; S"\; filenames="HSA00000299777400011.png,HSA00000299777400031.png"\; state="\{\{state\}\}">P</figure-callout></span><figure-callout\; id="1"\; label="P\; S"\; filenames="HSA00000299777400011.png,HSA00000299777400031.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="h\; P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">h</figure-callout></span><figure-callout\; id="0"\; label="h\; P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">\; </figure-callout>}}{\mathrm{<span\; class="notranslate">\; </span>}}_{}{\mathrm{<span\; class="notranslate">P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout></span><figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="h\; P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">h</figure-callout></span><figure-callout\; id="0"\; label="h\; P"\; filenames="HSA00000299777400031.png,HSA00000299777400041.png"\; state="\{\{state\}\}">\; </figure-callout>}}{\mathrm{<span\; class="notranslate">\; </span>}}_{}{\mathrm{<span\; class="notranslate">P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>$

Where α is the ratio of the total scattered light at 90°, and l is the photosensitive interval of the probe. P _S1 and P _S2 are the actual power values measured by the two sets of probes.

$\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout></span><figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; ]</span>$

Where L is the center distance between the two probes. If τ=k+h is defined as the turbidity coefficient, it can be obtained

$\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; L</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout></span><figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}$

That is to say, the two sets of 90° scattered light measurement values not only correspond to the turbidity respectively, but also the logarithm of the ratio is directly proportional to the turbidity.

Assuming that the influence of the light source changing with time is P ₀ (t), and the influence of window cleanliness is β(t), then

P(t)＝P ₀ (t)β(t)exp(-τx)

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;l</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$

For single-point detection, both the detected transmitted light and scattered light are affected by the cleanliness of the light source or the light exit window. If the ratio method is used, when the two detection windows are close to each other, it can be considered that the pollution degree of the windows is equal, both are β(t), then:

${\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; L</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="ln\; P\; S"\; filenames="HSA00000299777400011.png,HSA00000299777400031.png"\; state="\{\{state\}\}">ln</figure-callout></span><figure-callout\; id="1"\; label="ln\; P\; S"\; filenames="HSA00000299777400011.png,HSA00000299777400031.png"\; state="\{\{state\}\}">\; </figure-callout>}\frac{{{\mathrm{<span\; class="notranslate">\; P</span>}}_{}}^{}}{}\frac{{{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}_{}}^{<span\; class="notranslate">\; \&prime;</span>}}{{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">P</figure-callout></span><figure-callout\; id="2"\; label="P\; S"\; filenames="HSA00000299777400011.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; L</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; L</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}$

That is to say, for two detection windows that are close to each other, assuming the degree of pollution is the same, the turbidity reflected by the ratio of scattered light power values can eliminate the errors caused by light source, temperature and window cleanliness.

The turbidity measurement device is composed of a housing 1 , a parallel light emitting system 2 , a silicon photoelectric receiving system 3 with two probes, and a low-power signal processing circuit board 12 . The characteristic is that all optical components are integrated at the head end 22 of the housing. The signal processing circuits are all integrated in the body end 23 of the casing. The parallel light emitting system 2 and the silicon photoelectric receiving system 3 are located on the same plane to ensure that the 90-degree scattered light is not affected by disturbances such as water body refractive index or temperature.

The light source of the parallel light emitting system is a high-power LED9, and the convex lens 16 ensures that the parallelism of the emitted light meets the requirements of the ISO7027 standard. The beam emitted by the LED light source is adjusted to a parallel beam by a convex lens, emitted along the axis of the device, and then adjusted by a 90-degree reflective prism, so that the scattered light detected along the optical path is always 90-degree scattered light. The processing of the prism is to plate the reflective surface or embedded in the prism protection module. The parallel light emitting system 2 is electrically connected to the signal processing module 12 and controlled by a single-chip microcomputer chip.

The light receiving system 3 is composed of silicon photosensitive elements 7,8, optical filters 5,6, apertures 18,20 and sealing windows 17,19. External scattered light enters the diaphragm from the sealed window, and then enters the photosensitive element through the filter. The center wavelength of the filter corresponds to the light source and has a small half-wave width. This reduces the instrument aperture angle to 20 degrees.

Both the parallel light emitting system and the light receiving system are connected with the circuit processing system 12 . The circuit processing system amplifies the voltage signal transmitted by the light receiving system, and after AD conversion and filtering, the numerical calculation is the turbidity value. The circuit processing system simultaneously controls the stepping motor 4 to drive the setting and resetting of the surface cleaning block.

As shown in Figure 1, the housing of the turbidity detection device is a cylinder made of duralumin, with a size of 75mm×30mm×30mm. Power is supplied from the water-sealed plug 11 at the rear of the housing 1, and the MSP430 single-chip microcomputer chip 12 with low power consumption at the body end 22 of the housing controls the motor control chip 13 to drive the micro stepping motor 4 to rotate. The motor shaft 15 drives the cover-shaped surface cleaning block 21 to expose the light-emitting prism 10 and the light-receiving system 3 at the head end 23 of the housing, as shown in FIG. 3 . The single-chip microcomputer chip activates the parallel light emission system 2 at the same time, and the light emitted by the LED9 with a wavelength of 860nm and a spectral half-width of 10nm is injected into the water body through the convex lens 16 and the prism 10 .

At this time, the scattered light in the water body passes through the windows 17, 19 and the diaphragms 18, 20, and enters the silicon photosensitive elements 7, 8 through the optical filters 5, 6 with a central wavelength of 860 nm and a spectral half-width of 30 nm. The two silicon photosensitive elements 7 and 8 provide scattered light power, and the turbidity value is obtained through numerical calculation. The optical filters 5 and 6 with a thickness of 5mm have a center wavelength of 860nm and a spectral half width of 30nm. The silicon photosensitive elements 7 and 8 are connected to the amplifying circuit of the signal module 12, and then data processing is performed. The obtained analog signal is amplified, converted from analog to digital, and processed by the single-chip microcomputer chip to output data through the RS232 interface.

The light attenuation (in dB/cm) of a series of turbid liquid samples was determined using the vertical transmission method. The turbidity of the same turbid liquid sample was measured using the dual-probe ratio method, and the obtained data are shown in Figure 4. The data obtained by the two test methods showed a good linear relationship. By periodically changing the output optical power of the light source, it can be observed that the signal measured by the dual probes changes periodically, but the turbidity characterized by the mathematical processing of the dual probes has only small fluctuations, as shown in Figure 5. It shows that the double-probe ratio method can better remove the errors caused by the unstable light source and other factors.

After collecting data for a period of time, the signal processing chip 12 controls the motor 4 to drive the surface cleaning block 21 to return to its original position, as shown in FIG. 2 . At the same time, the signal processing chip 12, the parallel light emitting system 2 and the light receiving system 3 enter a dormant state. Activate again after waiting for a predetermined time. Both the number of turbidity sampling points and the period of the probe can be set through the signal processing chip 12 . The obtained data is electrically connected to other terminal equipment via RS232.

When testing in turbulent flowing water, in order to protect the probe while maintaining measurement accuracy, the front end of the probe housing can be pre-installed with a sampling cover 26 . It can effectively reduce the flow rate and maintain the accuracy of the 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.

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