CN109540842B - Double-fluorescence signal and water quality monitoring probe based on LED light source and use method - Google Patents

Abstract

The invention discloses a dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source and a method of using it, and belongs to the technical field of online water quality monitoring. It includes a housing, an internal support, optical components and an electronic circuit system. The housing is provided with an internal support, optical components and an electronic circuit system. The optical component provides a light source and converts fluorescence or fluorescence and scattered light signals into electrical signals. The electronic circuit system processes the electrical signal and then outputs it. The probe of the present invention simultaneously excites and detects protein fluorescence and humus fluorescence through deep ultraviolet LED and calculates the ratio between the two signals to reflect the composition type and concentration changes of dissolved organic matter in the water body. It can also use the scattered light of blue LED to detect Reflects the turbidity of the water body and assists in judging the pollution of the water body.

Description

Dual fluorescence signal and water quality monitoring probe based on LED light source and method of use

Technical field

The invention relates to online water quality monitoring technology in the field of environmental protection, and specifically relates to a water quality monitoring probe that detects dissolved organic matter based on the fluorescence method of an LED light source and uses scattered light to detect turbidity.

Background technique

Dissolved organic matter (DOM) existing in natural water bodies mainly includes macromolecular proteins, medium molecular weight humic acid, fulvic acid and other small molecular substances. In the drinking water treatment process, DOM can generate carcinogenic disinfection by-products in the chlorination disinfection process; in the terminal pipe network, DOM can provide a carbon source for the growth of microorganisms in the pipes and form biofilms; in the natural water environment Among them, DOM is the main contributor to the Chemical Oxygen Demand (COD) indicator and affects the migration and transformation of other pollutants.

Methods for analyzing and detecting DOM concentration levels mainly include chemical methods and spectroscopic methods. The chemical method mainly includes chemical oxygen demand test and total organic carbon test, while the spectroscopic method mainly includes ultraviolet-visible absorbance method and fluorescence spectrometry. Although the chemical method is widely used in national or industry standards, its online monitoring equipment has a complex structure, large volume, high price, long test cycle, requires chemical reagents, secondary chemical pollution, and high operation and maintenance and waste liquid treatment costs; The spectroscopic method has the advantages of rapid sensitivity and no need for chemical reagents. UV absorbance method mainly detects benzene rings and other aromatic structures and their derivatives in water. Macromolecular proteins, humic acid, fulvic acid and some small molecular compounds containing benzene rings in water can all be detected by UV absorbance method; Dissolution The fluorescence of organic matter mainly includes protein fluorescence, humus fluorescence and chlorophyll and other pigment fluorescence. The emission wavelength range of protein fluorescence is 310-370nm; the emission wavelength range of humus fluorescence is 400-500nm; the intracellular substances released by the death of cyanobacteria include protein fluorescence, humus fluorescence and chlorophyll fluorescence. The peak wavelength of chlorophyll fluorescence is Around 685nm. Protein fluorescence signals are mainly used to detect substances containing phenol or aniline structures in water, including macromolecular proteins, humic substances, fulvic acid, tryptophan, tyrosine and some small molecule compounds containing phenol or aniline structures; humus fluorescence signals It mainly detects humic acid, fulvic acid, naphthol, naphthylamine, quinine, pterin and other substances containing polycyclic aromatic structures in water. To a certain extent, ultraviolet absorbance UV254, protein fluorescence and humus fluorescence can reflect the types and concentration levels of dissolved organic matter in water. With the rapid development of smart water services in recent years, the water environment monitoring industry is in urgent need of small, low-cost and easy-to-maintain water quality sensors or monitoring equipment to enable widespread deployment of monitoring points. Against this background, online monitoring of DOM concentration levels using spectroscopic methods has gradually been recognized by the water quality industry and has been widely used in a series of "river chief system" water quality monitoring projects.

Currently, commercially available spectroscopic equipment that reflects DOM concentration levels is mainly based on UV absorbance or UV-visible absorption spectrometry. For example, a low-pressure mercury lamp is used as a light source, and the ultraviolet absorbance (UV254) at a wavelength of 254nm is tested as an alternative indicator of chemical oxygen demand; a pulsed xenon lamp source is used, and the ultraviolet-visible absorption luminosity in the 200-750nm band is tested to achieve Analysis and detection of indicators such as nitrate concentration, DOM concentration and turbidity. However, these spectroscopic water quality monitoring equipment or probes based on low-pressure mercury lamps or pulsed xenon lamp sources still have problems of large size and high power consumption.

Chinese invention patent 201410502662.9, published on December 10, 2014. The application discloses a UV fluorescence dual-signal water quality monitoring device using LED light-emitting diodes as the light source and its application method. Chinese patent application number 201510738667.6, published on 2015 The application filed on December 23, 2019 disclosed a UV fluorescence three-signal water quality sensor and its application using a single UV-LED as the light source. Both of the above two applications used UV LED as the light source and used photoelectric sensors at opposite positions in the optical path. The diode detects the UV absorbance value, and uses a bandpass filter and a photodiode positioned perpendicular to the UV LED light path to detect two fluorescent signals, protein or humic. However, the above invention still has the following problems that need to be overcome: 1) Natural light interferes with fluorescence signal detection. If a light shield is added to the probe, it will affect the flow of water. The electronic circuit design needs to be further optimized to eliminate natural light interference and improve the signal-to-noise ratio; 2) U-shaped probe or flow cell design, it is difficult to clean the quartz light window after being contaminated by biofilm; 3) Some natural water bodies receive humic acid washed down from the surrounding mountain soil and show higher UV absorbance or chemical Oxygen demand value, but the bioavailability of organic matter in this type of water body is low, and it is not a black and smelly water body or a polluted water body; 4) Under the influence of rainfall events, soil particles and humus substances in the soil are washed into the river medium, resulting in increased turbidity and higher chemical oxygen demand. Since humus has low bioavailability and is harmless to the water environment, it is impossible to increase the absolute value of ultraviolet absorbance or humus-type fluorescence signals caused by rainfall events. Highly classified as a water pollution event, it is necessary to detect turbidity while detecting fluorescence signals. Studies have shown that in water bodies affected by urban sewage discharge, due to the abundance of microorganisms, the ratio of protein fluorescence to humus fluorescence signals is significantly higher than that in unpolluted water bodies; in addition, the tyrosine and tryptophan that make up the protein are The key fluorescent structures are derivatives of phenol and aniline. Some chemical pollution incidents often contain phenol or aniline and their derivatives, which will cause protein fluorescence signals to be high.

Chinese patent application number 201521042180.6, published on June 1, 2016, discloses an immersed oil-in-water monitoring probe. The application discloses a shell that includes a closed structure and an ultraviolet light source and fluorescence placed inside the shell. Optical filter, photodetector, main board and drive circuit board, the front end of the casing is open and a glass window is embedded in the opening; a photodetector and an ultraviolet light source are correspondingly provided on the inside of the glass window, and the photodetector and ultraviolet light source are provided Connected to the drive circuit board, the drive circuit board is connected to the main board; a waterproof connector is provided on the housing. Its advantages are (1) using a high-frequency modulated light source, which has stronger resistance to ambient light interference; (2) using a large aperture The optical path design has greater light flux and stronger resistance to interference from suspended solids in water samples; (3) the optical path is simpler and the cost is lower, making it suitable for widespread application and promotion. However, this invention is characterized by using multiple LED light sources distributed in a ring around a photodiode, and one probe can only measure fluorescence signals in one wavelength range. According to the principle of fluorescence, for a fluorescent substance, its fluorescence emission wavelength is fixed and depends on the energy difference between its first excited state and the ground state. That is, no matter what wavelength excites the light source, the electrons transition to the first excited state or Higher excited states, electrons in higher excited states fall back to the first excited state through the molecular relaxation process. This process does not produce fluorescence, only the process of falling back from the first excited state to the ground state emits fluorescence. Therefore, it is not necessary to use UV light sources of multiple wavelengths to excite fluorescence; the probe is designed to only have one fluorescence signal, and cannot simultaneously measure two fluorescence signals, protein fluorescence and humus fluorescence, and thus cannot obtain two fluorescence signals. ratio. In addition, the probe described in this invention cannot analyze the turbidity in the water, and therefore cannot determine whether the changes in the fluorescence signal in the water are affected by the turbidity.

Chinese patent application number 201510166525.7, published on June 24, 2015, discloses an integrated probe-type photoelectric water quality multi-parameter online measurement system. The application discloses that it includes a control and data acquisition unit and an optical system unit; The control and data acquisition unit includes a host computer, a control and data acquisition unit, and an acquisition device; the optical system unit includes a light source and a light path, and the light source includes a left light source and a right light source, and the left light source is a set of multiple LED light sources of different wavelengths. It consists of an LED array; the ultraviolet LED light source and the near-infrared LED light source form the right light source; the host computer controls the light source through the control and data acquisition unit to emit the required light of different wavelengths to illuminate the water body to be measured, and stimulate the water body material to be measured to emit fluorescence and scattered light signals. ; The advantages of the present invention are: it does not require any chemical reagents for direct measurement, the detection data is fast, and tedious steps are avoided; and it simultaneously completes the classification and concentration detection of various algae in water quality, and the online detection of hydrocarbon content and turbidity; It can carry out independent and accurate detection to meet the needs of different environmental monitoring. However, this invention mainly distinguishes the types of algae in the water and reflects the concentration of algae by testing the form of chlorophyll or other pigments. The light source used is a visible light LED combination light source above 370nm. However, the visible light above 370nm cannot be used due to its low energy. To excite protein substances and humus substances in water to produce fluorescence, it should be noted that the filter B502 described in the embodiment of the invention can be a 360nm filter for hydrocarbon testing, which is against the principle of fluorescence. Due to the energy loss during the electronic transition process, the emission wavelength of fluorescence must be greater than its excitation wavelength. Usually the emission wavelength is greater than the excitation wavelength by more than 30 nm.

To sum up, it is necessary to design a water quality monitoring probe that can simultaneously monitor protein fluorescence, humus fluorescence and turbidity signals.

Contents of the invention

1.Problems to be solved

In response to the technical needs of the water environment monitoring industry to quickly and sensitively monitor the concentration of dissolved organic matter in water and accurately reflect the pollution status of water bodies, the present invention aims to provide a dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source and a method of use. The probe simultaneously excites and detects protein fluorescence and humus fluorescence through deep ultraviolet LED, and calculates the ratio between the two signals to reflect the composition and concentration changes of dissolved organic matter in the water body. It can also reflect the water turbidity through the scattered light of the blue LED. degree to assist in determining water pollution.

2.Technical solutions

In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

A dual fluorescence signal and turbidity water quality monitoring probe based on LED light source, consisting of a shell, an internal support, optical components and an electronic circuit system. The shell includes a front cover with a waterproof and light-transmitting function, accommodating and supporting optoelectronic devices The barrel and the tail cover with cables are provided with a quartz plate light outlet at one end of the casing. The casing is provided with internal supports, optical components and electronic circuit systems; the internal supports are used to carry optical components and electronic circuit systems. , and the position and angle are fixed, wherein the optical components include an LED light source and two sets of detection components. The detection components convert two kinds of fluorescence or two kinds of fluorescence + blue light scattering light signals into electrical signals; the described electronic circuit system The received electrical signal is processed and output.

Furthermore, a dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source uses deep ultraviolet light to excite dissolved organic matter in the water to detect protein fluorescence signals and humus fluorescence signals, and is supplemented by blue light to illuminate particulate matter in the water to produce impurities. Astigmatism to detect turbidity.

As a further elaboration of the present invention, the front cover includes an annular base, a sealing ring, and a quartz plate. The side of the annular base has internal threads and the bottom has a groove for inserting the sealing ring; the barrel includes Sealing ring, front-end external thread, annular support and rear-end internal thread; the tail cover includes a sealing ring, an annular tail cover body, a sealing gasket, a hollow screw and a cable; the annular base and the front end of the cylinder are sealed by threads and sealing rings The connection causes the quartz piece to squeeze the sealing ring on the groove of the annular base to achieve a waterproof and light-transmitting seal.

Furthermore, the LED light source is formed by composite packaging of a deep ultraviolet LED chip with a central wavelength of 280±10nm and a blue LED chip with a central wavelength of 465±10nm on the same base, and a quartz lens is packaged above the chip base. Concentrate light so that the luminous angle of the LED light source is less than 30°. The deep ultraviolet LED chip and the blue LED chip use independent pins or a common anode or a common cathode pin to connect to their respective drive circuits to achieve independent switch control. And adopt time-division multiplexing method to control the LED light source to output blue light or deep ultraviolet light.

Furthermore, the LED light source uses a deep ultraviolet LED chip with a central wavelength of 280±10nm, and a quartz lens is packaged above the LED chip to condense the light, so that the luminous angle of the LED light source is less than 30°.

Furthermore, the two sets of detection components are detection component one and detection component two. Among them, detection component one is composed of bandpass filter A and photodiode A package, and detection component two is composed of bandpass filter B and photodiode A. Photodiode B package consists of.

Furthermore, the wavelength range of the band-pass filter A is 330-370 nm, and the wavelength range of the band-pass filter B is 400-500 nm. The band-pass filter A and the band-pass filter B has a cut-off rate of more than 99.9% for light intensity outside the bandpass wavelength range. The photodiode A and photodiode B are silicon photodiodes with a high linear response to ultraviolet-visible light in the range of 300 to 500nm to achieve For the detection of fluorescence light intensity or scattered light intensity, the bandpass filter is fixed above the photodiode.

Furthermore, the positions of the LED light source and the two sets of detection components are fixed through internal supports. The two sets of detection components are located on both sides of the LED light source. The angle α between the respective axes of the two sets of detection components and the axis of the LED light source is α. is 45±15°, and the axis of the LED light source and the axes of the two sets of detection components intersect at the outside of the quartz sheet.

Furthermore, the positions of the LED light source and the two sets of detection components are fixed through internal supports. The LED light source and the two sets of detection components are located at the three vertices A, B and C at the bottom of the tetrahedron, and the axes of the three intersect at the tetrahedron. The upper vertex D, that is, the angle between any two of the three ridges AD, BD and CD is between 45 and 135°, and the vertex D is located outside the quartz sheet.

Furthermore, the electronic circuit system includes a single-chip microcomputer, a power module, a photoelectric signal amplifier circuit, an AD analog-to-digital conversion module and a communication module; the photoelectric signal amplifier circuit preferably adopts lock-in amplification technology. Phase amplification further includes a photoelectric signal operational amplifier module, a band-pass filter module, a phase-sensitive detection module and a low-pass filter module.

The power module supplies power to various components of the electronic circuit system. The microcontroller controls the drive circuit. The drive circuit controls the LED light source to switch on and off at a frequency of 10Hz to 10kHz. The organic matter in the water body is irradiated to produce fluorescence or scattered light signals of the same frequency. The deep ultraviolet light excites the dissolved organic matter in the water to produce proteins of the same frequency. Fluorescence or humus-like fluorescence, blue light irradiates particles in the water to produce weak stray light of the same frequency. The photodiode receives the light that passes through the bandpass filter and converts it into an electrical signal for output. The photoelectric signal operational amplifier module processes the electrical signal output by the photodiode. Going one step further, the photoelectric signal operational amplifier module uses zero power to process the photodiode. In the photovoltaic mode of bias voltage, the operational amplifier adopts a transimpedance amplification design. The electrical signal output by the photoelectric signal operational amplifier module is processed by the bandpass filter module and then input to the phase-sensitive detection module, and is combined with the signal of the same frequency as the LED light source switch emitted by the microcontroller. The reference signal is used for frequency comparison; the phase-sensitive detection module then inputs the electrical signal to the low-pass filter module, and the obtained signal is converted into a digital signal by the AD analog-to-digital conversion module and input into the microcontroller, which then communicates with the host computer.

Furthermore, the blue light scattered light for detecting turbidity and the fluorescent signal for detecting humus are used in a time-division multiplexing manner using the same signal amplification and processing circuit; only the fluorescence signal or scattered light signal of a specific frequency is processed by the phase-sensitive detection module. DC can pass through the low-pass filter module, while the signal generated by natural light is still an AC signal after passing through the phase-sensitive detection module and is eliminated by the low-pass filter module; the obtained signal is converted into a digital signal by the AD analog-to-digital conversion module and input into the microcontroller , the microcontroller uses MODBUS-RTU communication protocol to transmit data with the host computer.

Furthermore, the LED light source is a light source composed of a composite package of a deep ultraviolet LED chip with a central wavelength of 280±10nm and a blue LED chip with a central wavelength of 465±10nm. The LED light source is controlled by a time-sharing multiplexing method to alternately output blue light or For deep ultraviolet light, the frequency of the LED light source switch is set from 10Hz to 10kHz.

A method of using a dual fluorescence signal and turbidity water quality monitoring probe based on LED light source, the steps are:

(1) Immerse the probe into the water sample to be measured;

(2) Turn on the power module, the microcontroller controls the drive circuit, and the drive circuit controls the LED light source to switch at a frequency of 10Hz to 10kHz. When the LED light source is a deep ultraviolet LED chip with a central wavelength of 280±10nm and a central wavelength of 465±10nm, When the light source is composed of a blue LED chip composite package, a time-division multiplexing method is used to control the LED light source to alternately output blue light or deep ultraviolet light;

(3) When the LED light source outputs deep ultraviolet light with a central wavelength of 280±10nm, the deep ultraviolet light irradiates the dissolved organic matter in the water sample through the quartz plate, and generates protein fluorescence and/or humus fluorescence signals. The fluorescence signal is transmitted to photodiode A through bandpass filter A, and the humic substance fluorescence signal is transmitted to photodiode B through bandpass filter B;

(4) When the LED light source outputs blue light, the blue light shines through the quartz plate onto the particles in the water sample to form a scattered light signal, and the blue scattered light signal is transmitted to the photodiode B through the bandpass filter B;

(5) Photodiode A and/or photodiode B convert the optical signal into an electrical signal and output it;

(6) The photoelectric signal operational amplifier module processes the electrical signal output by photodiode A and/or photodiode B, amplifies the electrical signal, and transmits it to the bandpass filter module; after processing by the bandpass filter module, the electrical signal is input to the phase-sensitive detector module, and then transmit it to the low-pass filter module, and then convert the electrical signal into a digital signal through the AD analog-to-digital conversion module;

(7) The microcontroller collects digital signals and communicates with the host computer to obtain online monitoring data of protein fluorescence, humus fluorescence and scattered light intensity signals, and calculate the ratio of protein fluorescence signal to humus fluorescence signal.

3. Beneficial effects

Compared with the existing technology, the beneficial effects of the present invention are:

(1) A dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source according to the present invention has the advantage of using the same deep ultraviolet LED to excite and using two sets of photodiodes and bandpass filters to detect proteins simultaneously. Compared with the existing online spectrum monitoring equipment of xenon lamp or mercury lamp source, the fluorescence-like signal and humus-like fluorescence signal have the advantages of small size, low power consumption, low cost and simple structure.

(2) A dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source according to the present invention has the advantage of utilizing the characteristics of the LED chip that can be switched on and off quickly and frequently to work at a set frequency to stimulate the generation of fluorescence signals of a specific frequency. , thus lock-in amplification technology can be used to demodulate the weak fluorescence signal of a specific frequency from the stronger natural light interference signal, which has the advantage of strong anti-interference ability.

(3) A dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source according to the present invention has the advantage that while detecting the fluorescence signal, it also detects the turbidity signal, that is, when the blue LED chip is working, humic substances Fluorescence signal detection devices and circuits can be used to detect blue stray light caused by particulate matter in water and realize time-division multiplexing of optical paths.

(4) A dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source according to the present invention has the advantage that the front cover of the probe only uses a quartz plate as the common light window for the LED light source and two sets of photodiodes to achieve waterproofing The functions of sealing and light transmission make cleaning and maintenance easier.

(5) The dual fluorescence signal and turbidity water quality monitoring probe based on LED light source of the present invention has the advantage that compared with the ultraviolet spectroscopy water quality monitoring probe, it can simultaneously monitor protein fluorescence, humus fluorescence and turbidity signals. The relative ratio between protein fluorescence and humus fluorescence signals can be used to determine whether it is contaminated by domestic sewage or phenolic compounds. The turbidity signal can assist in determining whether the increase in fluorescence signal in the water comes from events such as rainfall.

Description of drawings

Figure 1 is an exploded structural view of a dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source according to the present invention;

Figure 2 is a cross-sectional view of a dual fluorescence signal and turbidity water quality monitoring probe based on LED light sources according to the present invention;

Figure 3 is a first spatial layout design scheme for the optical components at the front end of the probe of the present invention;

Figure 4 shows the first design solution of the internal support of the probe of the present invention (a) top view, (b) bottom view and (c) side view;

Figure 5 is a structural diagram of the electronic circuit system of the present invention;

Figure 6 is a schematic diagram of the fluorescence and turbidity detection principles of the present invention: (a) a schematic diagram of protein fluorescence and humic substance fluorescence excited by deep ultraviolet light, (b) a schematic diagram of scattered light detection of turbidity;

Figure 7 is a linear regression curve between the fluorescence and scattered light signals of the probe of the present invention and the standard solution: (a) the linear regression curve between the protein fluorescence signal and tryptophan concentration, (b) the humic substance fluorescence signal and quinine sulfate Linear regression curve for concentration and (c) linear regression curve between scattered light signal and turbidity;

Figure 8 is a second spatial layout design scheme for the optical components of the probe of the present invention: (a) top view of the front end, (b) schematic diagram of the spatial vertical relationship between the LED light source and the two photodiodes;

Figure 9 is the continuous monitoring data of protein fluorescence, humus fluorescence and blue light scattered light intensity after the river water sample in a certain city of the present invention was processed through a 0.45 μm filter membrane and a 4 NTU unit of hydrazine sulfate turbidity reagent was added;

Figure 10 is the continuous monitoring data of protein fluorescence, humic substance fluorescence and blue light scattered light intensity after the effluent from the secondary sedimentation tank of the domestic sewage treatment plant of the present invention is treated with a 0.45 μm filter membrane and a 4 NTU unit of hydrazine sulfate turbidity reagent is added.

In the picture:

1. Front cover; 101. Annular base; 102. Seal ring one; 103. Quartz chip; 2. Cylinder; 201. Seal ring two; 202. Front external thread; 203. Ring support; 204. Rear end internal thread; 3. Tail cap; 301. Seal ring three; 302. Ring-shaped tail cap body; 303. Sealing gasket; 304. Hollow screw; 305. Cable; 4. Internal support; 401. Center hole; 402. Side hole; 5. Detection component one; 501. Bandpass filter A; 502. Photodiode A; 6. Detection component two; 601. Bandpass filter B; 602. Photodiode B; 7. LED light source; 8. Electronic circuit system ; 801. Microcontroller; 802. Power supply module; 803. Optoelectronic signal operational amplifier module; 804. Bandpass filter module; 805. Phase-sensitive detection module; 806. Low-pass filter module; 807. AD analog-to-digital conversion module; 808. Communication Module; 809, temperature sensor; 810, drive circuit.

Detailed ways

The present invention will be further described below with reference to specific embodiments.

Example 1

As shown in Figure 1, a dual fluorescence signal and turbidity water quality monitoring probe based on an LED light source in this embodiment includes a housing, an internal support 4, optical components and an electronic circuit system 8.

The housing includes a front cover 1 with a waterproof and light-transmitting function, a cylinder 2 that accommodates and supports the optoelectronic device, and a tail cover 3 with a cable 305. The optical component includes two detection components and a central wavelength of The deep ultraviolet LED chip of 280±10nm and the blue LED chip with a central wavelength of 465±10nm are compositely packaged in the LED light source 7 on the same base. The internal support 4 provides support for the optical components and fixes the position and angle; The electronic circuit system 8 controls the switch of the composite packaged LED light source 7, the amplification and data communication of the photodiode A502 and photodiode B602 signals; the probe simultaneously detects protein fluorescence signals and Humic substance fluorescent signal detects turbidity by illuminating particles in water with blue light to produce stray light.

As shown in Figures 1 and 2, the front cover 1 includes an annular base 101, a sealing ring 102 and a quartz plate 103. The annular base 101 has internal threads on its side and a recess at the bottom for inserting the sealing ring. groove; the barrel 2 includes sealing ring two 201, front-end external thread 202, annular support 203 and rear-end internal thread 204; the tail cap 3 includes sealing ring three 301, annular tail cap body 302, sealing gasket 303 , hollow screws 304 and cables 305; the annular base 101 and the front end of the cylinder 2 are sealed and connected through threads and sealing rings 102, so that the quartz piece 103 squeezes the sealing ring 102 on the groove of the annular base 101 to achieve waterproof and light-transmitting sealing. . The main bodies of the front cover 1, cylinder 2 and tail cover 3 are made of stainless steel and processed by CNC lathes.

The two circular bandpass filters A501 and B601 respectively adopt (i) the bandpass filter A501 with a wavelength in the range of 330-370nm, used for the detection of protein fluorescence signals, (ii) Bandpass filter B601 with a wavelength range of 400 to 500nm, used for detection of humic substance fluorescence signals. The cutoff rate of the two bandpass filters for light outside the bandpass wavelength range is more than 99.9%. The diameter is 8mm and the thickness is 2.2mm.

The two photodiodes are purple-blue light-enhanced high-precision linear response silicon photodiodes. Their packaging form is TO-18 metal packaging, with a photosensitive area of 3.7mm×3.7mm, as shown in Figure 2, and a bandpass filter. A501 and bandpass filter B601 are fixed above photodiode A502 and photodiode B602 respectively.

The deep ultraviolet + blue light composite packaged LED light source 7 is characterized in that the deep ultraviolet LED chip with a central wavelength of 280±10nm and the blue LED chip with a central wavelength of 465±10nm are compositely packaged in a TO39 metal package, and the ultraviolet LED chip and The blue LED chip uses independent positive and negative pins, which are connected to the drive circuit 810 respectively. The microcontroller 801 controls the opening and closing of the LED drive circuit 810 by outputting high and low levels to achieve independent switching control of the two LED chips. The TO39 package is quartz The luminous angle of the condenser lens has been measured to be approximately 7°.

The positional relationship between the deep ultraviolet + blue light composite LED light source 7 and the two sets of detection components is fixed through the internal support 4. As shown in Figure 3, the LED light source 7 is located in the middle, and the detection component one 5 and the detection component two 6 are located on both sides. The angle α between the axis of the side detection component one 5 and the detection component two 6 and the axis of the LED light source 7 is 45°, and ensure that the axis of the LED light source 7 and the axes of the two sets of detection components intersect on the outside of the quartz plate 103; with the first The structure of the internal support 4 corresponding to this design is shown in Figure 4. The central hole 401 is used to fix the LED light source 7, and the two side holes 402 are used to fix the bandpass filter and photodiode.

The components in the electronic circuit system 8 are all welded on a printed circuit board, as shown in Figure 5, including a single-chip microcomputer 801, a power module 802, a photoelectric signal operational amplifier module 803, a band-pass filter module 804, and a phase-sensitive detector. Module 805, low-pass filtering module 806, AD analog-to-digital conversion module 807, communication module 808 and temperature sensor 809.

The power module 802 supplies power to each component of the electronic circuit system 8; the single-chip microcomputer 801 outputs a digital signal to control the drive circuit 810, and the drive circuit 810 controls the deep ultraviolet LED chip and the blue LED chip in the LED light source 7 for time-sharing multiplexing, with 1s as the test Period, within 0-499ms, the deep ultraviolet LED chip switches with a frequency of 1kHz and emits 1kHz of deep ultraviolet light. Within 500-999ms, the blue LED chip switches with a frequency of 1kHz and emits 1kHz of blue light; where deep ultraviolet light excites The dissolved organic matter in the water produces protein fluorescence with a frequency of 1kHz, which can be detected by the photodiode A502 through the bandpass filter A501. The generated humus fluorescence can be detected by the photodiode B602 through the bandpass filter B601. Blue light The weak blue stray light with a frequency of 1 kHz generated by irradiation on the particles in the water can be detected by the photodiode B602 through the bandpass filter B601. The principle is shown in Figure 6; the photoelectric signal operational amplifier module 803 adopts a photodiode In the photovoltaic mode with zero bias voltage, the operational amplifier uses TI's OPA129 chip for transimpedance amplification design. The channel used to measure protein fluorescence signals uses a 500MΩ resistor, and the channel used to measure humic substance fluorescence signals and turbidity signals uses a 100MΩ resistor. resistor, and its output signal is processed by the bandpass filter module 804 and then input to the phase-sensitive detection module 805, and is compared in frequency and phase with the 1kHz reference signal sent by the microcontroller 801; the stray light for detecting turbidity and the fluorescent signal for detecting humus are passed through the analyzer. The time multiplexing method uses the same signal amplification and processing circuit; only the 1kHz fluorescence signal or stray light signal is processed by the phase-sensitive detection module 805 and becomes DC, which can pass through the low-pass filter module 806, while the signal generated by natural light is AC The signal is eliminated by the low-pass filter module 806; the obtained signal is converted into a digital signal by the AD analog-to-digital conversion module 807 and input into the microcontroller 801; the band-pass filter module 804 and the low-pass filter module 806 both use TI's NE5532 The chip, the phase-sensitive detection module 805 uses TI's AD630 chip, and the single-chip computer 801 uses the STM32F103C8T6 chip; the single-chip computer 801 separately analyzes the values of protein fluorescence signals and humus fluorescence signals within 0-499ms, and turbidity signals within 500-999ms. For average processing, the communication module 808 performs bidirectional signal conversion between TTL and RS485, and uses the MODBUS-RTU communication protocol to realize signal transmission between the microcontroller 801 and the host computer. The microcontroller 801 monitors the temperature of the circuit board through the chip temperature sensor 809, and performs temperature compensation calibration on the obtained signal.

For example, a series of concentrations of tryptophan aqueous solution, quinine sulfate aqueous solution and hydrazine sulfate turbidity reagent are used as calibration reagents to test the protein fluorescence signal, humic substance fluorescence signal and turbidity signal of the probe, and obtain a linear regression curve as follows: As shown in Figure 7, ^R2 is greater than 0.99, indicating good accuracy.

Example 2

This embodiment is basically the same as Embodiment 1, except that:

The front cover 1, cylinder 2 and tail cover 3 of the shell structure are made of POM plastic and processed by CNC lathes.

The characteristics of the design of the internal support 4 are as shown in Figure 8. The fluorescence detection device composed of the LED light source 7, the detection component 5 and the detection component 2 6 are respectively located at the three vertices A and B at the bottom of the rectangular tetrahedron. and C, the axes of the three intersect at the upper vertex D of the rectangular tetrahedron, that is, any two lines AD, BD and CD are perpendicular to each other. The tail cover 3 with the cable 305 can be made of M12 nylon material with bending resistance to fix the waterproof cable joint. It only needs to open a round hole with a diameter of 12mm in the center of the annular tail cover body 302, and the sealing gasket can be omitted. 303 and hollow screw 304.

The pre-operational amplifier of the photoelectric signal operational amplifier module 803 in the electronic circuit system 8 adopts the LMP7721 chip of TI Company, and the band-pass filter module 804 and the low-pass filter module 806 both adopt the OPA227 chip of TI Company.

A city's river water sample and the effluent from the secondary sedimentation tank of the domestic sewage plant were treated with a 0.45 μm filter membrane and then a 4 NTU unit of hydrazine sulfate turbidity standard reagent was added. The dual fluorescence signal and turbidity based on the composite LED light source in this example were used. The water quality monitoring probe is used for detection and online monitoring data from 0 to 1000 seconds is obtained, as shown in Figure 9. Among them, the protein fluorescence, humus fluorescence and scattered light intensity signals of the river water sample were 39, 90 and 261 AU respectively, and the ratio of the protein fluorescence signal to the humus fluorescence signal was ~0.43; the secondary sedimentation water sample of the domestic sewage plant The protein fluorescence, humus fluorescence and scattered light intensity signals were 99, 235 and 265 AU respectively, and the ratio of protein fluorescence signal to humus fluorescence signal was ~0.42. The ratio of protein fluorescence signal/humus fluorescence signal in river water samples and domestic sewage secondary sedimentation tank effluent is similar, indicating that there is more biodegradable organic carbon in the river and a large number of microbial metabolism to produce proteinaceous extracellular polymers, which is consistent with the river. consistent with a state of eutrophication.

Example 3

This embodiment is basically the same as Embodiment 1, except that:

The LED light source 7 is a TO39 metal-encapsulated deep ultraviolet LED light source with a central wavelength of 280±10nm. The single-chip microcomputer 801 outputs a digital signal to control the drive circuit 810. The drive circuit 810 controls the LED light source 7 to switch on and off at a frequency of 1 kHz to emit deep ultraviolet light. Light, deep ultraviolet light excites dissolved organic matter in the water to produce protein-based fluorescence or humus-based fluorescence with a frequency of 1 kHz. The detection component 1 5 and the detection component 2 6 respectively realize the detection of protein-based fluorescence and humus-based fluorescence signals. In this embodiment, scattered light of blue light is not used to detect turbidity, which is a simple design of Embodiment 1.

A city's river water sample and the effluent from the secondary sedimentation tank of the domestic sewage plant were treated with a 0.45 μm filter membrane and then a 4 NTU unit of hydrazine sulfate turbidity standard reagent was added. The dual fluorescence signal and turbidity based on the composite LED light source in this example were used. Water quality monitoring probes are used to detect and obtain online monitoring data from 0 to 1000 seconds. Among them, the protein fluorescence and humus fluorescence signals of the river water sample are 38 and 91 AU respectively, and the ratio of the protein fluorescence signal to the humus fluorescence signal is ~0.42; the protein fluorescence and humus fluorescence signals of the secondary sedimentation water sample of the domestic sewage plant The fluorescence signals were 98 and 233 AU respectively, and the ratio of protein-based fluorescence signal to humic substance-based fluorescence signal was ~0.42. The ratio of protein fluorescence signal/humus fluorescence signal in river water samples and domestic sewage secondary sedimentation tank effluent is similar, indicating that there is more biodegradable organic carbon in the river and a large number of microbial metabolism to produce proteinaceous extracellular polymers, which is consistent with the river. consistent with a state of eutrophication.

Claims (9)

1. The utility model provides a two fluorescence signal and turbidity water quality monitoring probe based on LED light source, comprises shell, interior support (4), optical component and electronic circuit system (8), its characterized in that: the LED fluorescent lamp is characterized in that a quartz plate (103) is arranged at one end of the shell and used as a light outlet, an inner support (4), an optical component and an electronic circuit system (8) are arranged in the shell, the inner support (4) is used for bearing the optical component and the electronic circuit system (8), the optical component comprises an LED light source (7) and two groups of detection components, the light emitting angle of the LED light source (7) is smaller than 30 degrees, the positions of the LED light source (7) and the two groups of detection components are fixed through the inner support (4), the two groups of detection components are respectively positioned at two sides of the LED light source (7), an included angle alpha between the axes of the two groups of detection components and the axis of the LED light source (7) is 45+/-15 degrees, the axes of the LED light source (7) and the axes of the two groups of detection components are intersected at the outer side of the quartz plate (103), and the detection components convert two fluorescent or two fluorescent and blue light scattering light signals into electric signals; the electronic circuit system (8) processes the received electric signals and outputs the processed electric signals.

2. The dual fluorescent signal and turbidity water quality monitoring probe based on an LED light source of claim 1, wherein: the LED light source (7) is formed by compositely packaging a deep ultraviolet LED chip with the center wavelength of 280+/-10 nm and a blue LED chip with the center wavelength of 465+/-10 nm on the same base, a quartz lens is packaged above the chip base, the deep ultraviolet LED chip and the blue LED chip are respectively connected with respective driving circuits (810) by adopting respective independent pins or shared anodes or shared cathode pins, independent switching control is realized, and the LED light source (7) is controlled to output blue light or deep ultraviolet light in a time-sharing multiplexing mode.

3. The dual fluorescent signal and turbidity water quality monitoring probe based on an LED light source of claim 1, wherein: the LED light source (7) adopts a deep ultraviolet LED chip with the central wavelength of 280+/-10 nm, and a quartz lens is packaged above the LED chip.

4. The dual fluorescent signal and turbidity water quality monitoring probe based on an LED light source of claim 1, wherein: the two groups of detection components are a first detection component (5) and a second detection component (6), wherein the first detection component (5) is formed by packaging a band-pass filter A (501) and a photodiode A (502), and the second detection component (6) is formed by packaging a band-pass filter B (601) and a photodiode B (602).

5. The dual fluorescent signal and turbidity water quality monitoring probe based on an LED light source of claim 4, wherein: the wavelength range of the band-pass filter A (501) is 330-370nm, the wavelength range of the band-pass filter B (601) is 400-500nm, the cut-off rate of the band-pass filter A (501) and the band-pass filter B (601) to the light intensity outside the band-pass wavelength range is more than 99.9%, and the photodiode A (502) and the photodiode B (602) are silicon photodiodes with higher linear response to ultraviolet-visible light in the range of 300-500 nm.

6. The dual fluorescent signal and turbidity water quality monitoring probe based on an LED light source of claim 1, wherein: the positions of the LED light source (7) and the two groups of detection components are fixed through the internal support (4), the LED light source (7) and the two groups of detection components are respectively located at three vertexes A, B and C at the bottom of the tetrahedron, the axes of the three vertexes are intersected at an upper vertex D of the tetrahedron, namely the included angle of any two of the three edge lines AD, BD and CD is between 45 and 135 degrees, and the vertex D is located outside the quartz plate (103).

7. The dual fluorescent signal and turbidity water quality monitoring probe based on an LED light source of claim 1, wherein: the electronic circuit system (8) comprises a singlechip (801), a power supply module (802), an optoelectronic signal amplifying circuit, an AD analog-to-digital conversion module (807) and a communication module (808).

8. The dual fluorescent signal and turbidity water quality monitoring probe based on an LED light source of claim 7, wherein: the photoelectric signal amplifying circuit adopts a phase-locked amplifying technology and comprises a photoelectric signal operational amplifier module (803), a band-pass filtering module (804), a phase-sensitive detection module (805) and a low-pass filtering module (806); the power module (802) supplies power for all components of the electronic circuit system (8); the singlechip (801) controls the driving circuit (810), the driving circuit (810) controls the LED light source (7) to switch according to the frequency of 10 Hz-10 kHz, the organic matters in the water body are irradiated to generate fluorescence or scattered light signals with the same frequency, the photodiode receives light transmitted through the band-pass filter and converts the light into electric signals to be output, the photoelectric signal operational amplifier module (803) processes the electric signals output by the photodiode, the electric signals output by the photoelectric signal operational amplifier module (803) are processed by the band-pass filter module (804) and then are input into the phase-sensitive detection module (805), and the electric signals are compared with reference signals which are sent by the singlechip (801) and have the same frequency as the switching of the LED light source (7); the phase-sensitive detection module (805) inputs the electric signal into the low-pass filtering module (806), the obtained signal is converted into a digital signal by the AD analog-to-digital conversion module (807) and is input into the singlechip (801), and the singlechip (801) is communicated with the upper computer.

9. A method for using the dual fluorescent signal and turbidity water quality monitoring probe based on the LED light source according to any one of claims 1 to 8, characterized in that: the method comprises the following steps:

(1) Immersing the probe into a water sample to be detected;

(2) The power supply module (802) is turned on, the singlechip (801) controls the driving circuit (810), the driving circuit (810) controls the LED light source (7) to switch according to the frequency of 10Hz to 10kHz, and when the LED light source (7) is a light source formed by compositely packaging a deep ultraviolet LED chip with the center wavelength of 280+/-10 nm and a blue LED chip with the center wavelength of 465+/-10 nm, the LED light source (7) is controlled to alternately output blue light or deep ultraviolet light in a time-sharing multiplexing mode;

(3) When the LED light source (7) outputs deep ultraviolet light with the center wavelength of 280+/-10 nm, the deep ultraviolet light irradiates soluble organic matters in a water sample through the quartz plate (103) and generates protein fluorescence and/or humus fluorescence signals, the protein fluorescence signals are transmitted to the photodiode A (502) through the band-pass filter A (501), and the humus fluorescence signals are transmitted to the photodiode B (602) through the band-pass filter B (601);

(4) When the LED light source (7) outputs blue light, the blue light irradiates particles in a water sample through the quartz plate (103) to form scattered light signals, and the scattered light signals are transmitted into the photodiode B (602) through the band-pass filter B (601);

(5) Photodiode a (502) and/or photodiode B (602) convert the optical signal to an electrical signal output;

(6) The photoelectric signal operational amplifier module (803) processes the electric signals output by the photoelectric diode A (502) and/or the photoelectric diode B (602), amplifies the electric signals and transmits the amplified electric signals to the band-pass filter module (804); the band-pass filtering module (804) inputs the electric signal to the phase-sensitive detection module (805), then transmits the electric signal to the low-pass filtering module (806), and then converts the electric signal into a digital signal through the AD analog-to-digital conversion module (807);

(7) The singlechip (801) is used for collecting the digital signals and communicating with the upper computer to obtain on-line monitoring data of protein fluorescence, humus fluorescence and scattered light intensity signals, and calculating the ratio of the protein fluorescence signals to the humus fluorescence signals.