Nitrate nitrogen water quality detection equipment based on composite packaging light source

Abstract

The utility model discloses nitrate nitrogen water quality detection equipment based on a composite packaging light source, which comprises the composite packaging light source, a semi-transparent and semi-reflecting mirror, a sampling area, a reference photodiode, a detection photodiode, a first band-pass optical filter and a second band-pass optical filter, the composite packaging light source comprises two deep ultraviolet LED chips which are packaged on the same substrate and have different wavelengths, and the composite packaging light source, the semi-transparent and semi-reflecting mirror, the sampling area, the first band-pass optical filter and the detection photodiode are sequentially arranged along a light path to form a detection light path. The composite packaging light source, the semi-transparent and semi-reflecting mirror, the second band-pass optical filter and the reference photodiode are sequentially arranged along the light path to form a reference light path. According to the utility model, the LED chips with different wave bands are packaged on the same substrate, so that the concentration level of nitrate nitrogen in a water body can be measured; the nitrate nitrogen water quality detection equipment adopts a double-light-path structure, and a reference signal is used as a reference to eliminate the influence of light source attenuation and light path transmission loss on a measurement result, so that errors are reduced.

Description

Technical Field

[0001] The utility model belongs to the field of online water quality monitoring in the field of environmental protection, and particularly relates to a nitric nitrogen water quality detection device based on a composite encapsulated light source. Background Art

[0002] Online water quality monitoring technology plays an important role in preventing and controlling water pollution and ensuring drinking water safety. At present, online water quality monitoring mainly relies on traditional chemical analysis methods, but this method has unstable reagents, complex equipment structure, and long detection cycle. Spectroscopy has attracted widespread attention as a new type of online monitoring technology that is fast and reagent-free. However, existing spectral monitoring equipment has the problems of large size, high power consumption, and high cost, making it difficult to achieve widespread deployment.

[0003] Affected by sewage discharge and the large-scale application of chemical fertilizers in agriculture, eutrophication has become one of the main problems of water pollution. Nitrogen and phosphorus are important nutrients that cause eutrophication of water bodies. In natural water bodies, nitrate is the final product of the oxidation and decomposition of nitrogen-containing organic matter, and nitrate nitrogen (NO3-N) is the main form of nitrogen in natural water bodies. The testing methods for nitrate nitrogen include phenol disulfonic acid photometry, ultraviolet spectrophotometry, ion chromatography, etc. Although there are online monitoring equipment for phenol disulfonic acid photometry, the instability of phenol disulfonic acid reagents requires regular replacement, which also limits their widespread application. The principle of ultraviolet spectrophotometry is to use the fact that nitrate ions have ultraviolet absorption at 220nm and no ultraviolet absorption at 275nm. The relationship between the absorbance of dissolved organic matter in natural water bodies at 220nm and 275nm is approximately Abs. 220 =2*Abs 275 , by calculating Abs 220 -2*Abs 275 To eliminate the interference of dissolved organic matter on nitrate determination.

[0004] As a new type of light source, light-emitting diodes have the advantages of small size, high efficiency and low cost, but single-wavelength LED light sources cannot detect nitrate nitrogen and organic matter at the same time, and cannot overcome the interference of the complex matrix of natural water bodies.

[0005] The U.S. invention patent US20170254752A1 discloses a water quality monitoring probe that uses a 229nm LED as a light source and is used to detect the nitrate concentration in water based on the ultraviolet absorbance of nitrate at 229nm. However, there are a large number of natural organic matter in natural water bodies, and natural organic matter also has significant absorption at 229nm, which seriously interferes with the detection of nitrate in actual water samples.

[0006] Chinese invention patent CN201410502662.9 discloses a UV fluorescence dual-signal water quality monitoring device with LED as light source and its application method. Chinese invention patent CN201510738667.6 discloses a UV fluorescence three-signal water quality sensor with a single UV-LED as light source and its application. Both of the above applications use a single UV LED as a light source and simultaneously measure the UV absorbance value and protein or humus fluorescence signals to monitor the concentration of dissolved organic matter in water.

[0007] The above technical solution is mainly suitable for monitoring dissolved organic matter in low turbidity water such as drinking water or recycled water in municipal water plants. However, when applied to online water quality monitoring in the field, there are still the following problems to be overcome: (1) Turbidity in water will interfere with the test of dissolved organic matter, and turbidity needs to be used for numerical correction and auxiliary judgment; (2) Nitrate or nitrate nitrogen concentration is one of the important indicators for online water quality monitoring, but the existing water quality monitoring devices cannot effectively achieve this; (3) The intensity of the LED light source decays over time, affecting the accuracy of the spectral signal. Utility Model Content

[0008] In view of this, the technical problem solved by the utility model is to provide a nitric nitrogen water quality detection device based on a composite packaged LED light source to achieve online monitoring of nitric nitrogen in water quality.

[0009] In order to achieve the above purpose, the utility model proposes a nitric nitrogen water quality detection device based on a composite packaged light source, which adopts the following technical solutions:

[0010] A nitrate-nitrogen water quality detection device based on a composite packaged light source comprises: a composite packaged light source, a semi-transparent and semi-reflective mirror, a sampling area, a reference photodiode, a detection photodiode, a first bandpass filter and a second bandpass filter, wherein the composite packaged light source comprises two deep ultraviolet LED chips of different wavelengths packaged on the same substrate, the composite packaged light source, the semi-transparent and semi-reflective mirror, the sampling area, the first bandpass filter and the detection photodiode are arranged in sequence along an optical path to form a detection optical path, and the composite packaged light source, the semi-transparent and semi-reflective mirror, the second bandpass filter and the reference photodiode are arranged in sequence along the optical path to form a reference optical path.

[0011] Furthermore, the deep ultraviolet LED chip includes a 220±10nm deep ultraviolet LED chip and a 275±10nm deep ultraviolet LED chip.

[0012] Furthermore, the two deep ultraviolet LED chips in the composite packaged light source adopt a packaging structure with a common anode and an independent cathode to lead out wiring pins, which are respectively connected to respective driving circuits.

[0013] Furthermore, the detection optical path is provided with an optical fiber between the sampling area and the first bandpass filter.

[0014] Furthermore, the semi-transparent and semi-reflective mirror is used to split a single beam of light into two beams of light, wherein one beam of light is detected by a detection photodiode after passing through a sampling region, and the other beam of light is detected by a reference photodiode.

[0015] Furthermore, a first condensing lens is arranged between the composite packaged light source and the semi-transparent and semi-reflective mirror; a second condensing lens is arranged between the semi-transparent and semi-reflective mirror and the sampling area; and a third condensing lens is arranged between the sampling area and the first bandpass filter.

[0016] Furthermore, the sampling area includes two glass sheets arranged opposite to each other, and a cleaning brush is arranged between the two glass sheets.

[0017] Furthermore, the nitric nitrogen water quality detection equipment is arranged in a shell composed of an outer shell and an end cover.

[0018] The beneficial effects of the utility model are as follows:

[0019] The utility model integrates a multi-band LED chip, which can realize online monitoring of nitrate nitrogen in water quality by quickly switching to excite light of different wavelengths and detecting spectral signals with different photodiodes. It can also effectively avoid interference from soluble organic matter in natural water bodies through correction compensation at a wavelength of 275nm. It has the advantages of simple structure and small size, and can promote the development of water quality detection technology towards miniaturization and intelligence. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the optical path principle diagram of the utility model;

[0021] Figure 2 It is a structural schematic diagram of the utility model.

[0022] Markings in the figure: 1-composite package light source; 2-reference photodiode; 3-sampling area; 4-optical fiber; 5-detection photodiode; 6-semi-transparent and semi-reflective mirror; 71-first bandpass filter; 72-second bandpass filter; 81-first focusing lens; 82-second focusing lens; 83-third focusing lens; 91-first circuit board; 92-second circuit board; 101-first probe base; 102-second probe base; 103-end cover; 111-first housing; 112-second housing; 12-receiving light support; 13-cleaning brush; 14-motor; 15-glass sheet; 16-wiring tube. DETAILED DESCRIPTION

[0023] The specific implementation of the utility model is further described below in conjunction with the accompanying drawings.

[0024] The implementation principle of the nitrate-nitrogen water quality detection device based on the composite packaged light source in this embodiment is as follows: Figure 1 The specific structure is as shown in Figure 2 The nitrate-nitrogen water quality detection equipment mainly includes a composite package light source 1, a semi-transparent and semi-reflective mirror 6, a sampling area 3, a reference photodiode 2, a detection photodiode 5, a first bandpass filter 71 and a second bandpass filter 72. A first condensing lens 81 is arranged between the composite package light source 1 and the semi-transparent and semi-reflective mirror 6, a second condensing lens 82 is arranged between the semi-transparent and semi-reflective mirror 6 and the sampling area 3, and a third condensing lens 83 is arranged between the sampling area 3 and the first bandpass filter 71.

[0025] This embodiment adopts a dual optical path design to improve the stability of the spectral signal: the composite packaged light source 1, the semi-transparent and semi-reflective mirror 6, the sampling area 3, the first bandpass filter 71, and the detection photodiode 5 are arranged in sequence along the optical path to form a detection optical path; the composite packaged light source 1, the semi-transparent and semi-reflective mirror 6, the second bandpass filter 72, and the reference photodiode 2 are arranged in sequence along the optical path to form a reference optical path. By measuring the output voltage of the photodiode and the reference signal, the absorption amount can be calculated, and the concentration of nitrate can be further calculated. The use of dual optical paths improves measurement accuracy, and the reference signal is used as a benchmark to eliminate the influence of light source intensity and optical path transmission loss on the measurement results, thereby reducing errors. This device based on dual optical path calibration technology has lower electrical noise and more flexible arrangement.

[0026] in:

[0027] The composite packaged light source 1 is connected to the second circuit board 92, and is used to illuminate the water body confined in the specified area, and includes two deep ultraviolet LED chips with different wavelengths. The deep ultraviolet LED chips preferably include a 220±10nm deep ultraviolet LED chip and a 275±10nm deep ultraviolet LED chip. The two deep ultraviolet LED chips in the composite packaged light source are preferably packaged on the same substrate, and the wiring pins are led out using a packaging structure with a shared anode and an independent cathode, and are respectively connected to their respective drive circuits to achieve independent switch control.

[0028] The semi-transparent and semi-reflective mirror 6 splits the monochromatic light emitted by the monochromator into two beams of light, one beam of light is the sample light source and is detected by the UV-visible absorption detection photodiode after passing through the optical path of the water sample to be tested, and the other beam of light is the reference light source and is directly detected by the reference light path photodiode.

[0029] One or more optical fibers 4 may be further provided in the detection optical path between the sampling region and the first bandpass filter to guide light into or out of the sampling chamber.

[0030] The reference photodiode 2 is used to monitor and correct the intensity change of the attenuation of the excitation light source within a fixed distance to generate a reference signal.

[0031] The detection photodiode 5 is connected to the first circuit board 91, and is used to detect the intensity of light passing through the restricted water volume in the presence of deep ultraviolet absorbing substances represented by nitric nitrogen, convert it into photocurrent, and then convert it into voltage through a transimpedance amplifier.

[0032] The bandpass filters (including the first bandpass filter 71 and the second bandpass filter 72 ) are used to selectively detect the light intensity in a specific wavelength band.

[0033] The sampling area 3 includes two glass sheets 15 arranged opposite to each other.

[0034] The nitrate nitrogen water quality detection equipment is arranged in a shell composed of a shell (including a first shell 111 and a second shell 112) and an end cover 103, a wiring tube 16 is arranged in the shell, and a base is arranged on the opposite side of the first shell 111 and the second shell 112. Specifically, a first probe base 101 is arranged at the right end of the first shell 111, and a second probe base 102 is arranged at the left end of the second shell 112. A light receiving support 12 is installed on the first probe base 101, and a motor 14 is installed on the second probe base 102, and a cleaning brush 13 is connected to the output end of the motor 14.

[0035] When working, the composite package light source sequentially emits excitation light with wavelengths of 220nm and 275nm. After proportional light splitting, a part of the light is directly incident on the reference photodiode as the reference light, and the change of the excitation light intensity is detected and corrected in real time to ensure the detection accuracy. The other part of the light is irradiated to the water sample in the quartz water sample pool through the optical fiber. The light that is not absorbed and scattered passes through the water sample and is transmitted through the optical fiber to the detection photodiode. By measuring the ultraviolet absorbance of the photodiode at wavelengths of 220nm and 275nm, the concentration of nitrate and dissolved organic matter can be obtained.

[0036] To perform this measurement, a UV LED with a central wavelength of 220nm is positioned to illuminate a confined body of water within a designated area of ​​the sensor body. Light passing through the confined body of water is attenuated when absorbing substances are present. The attenuated light is projected onto a photodiode, generating a photocurrent, which is then converted to a voltage via a transimpedance amplifier. This signal is designated as the measured value (M) or measured signal. Prior to the sample interaction, a portion of the UV light is sampled by a reference photodiode, where the photocurrent is converted to a voltage without interacting with the water. This signal is designated as the reference value (R) or reference signal.

[0037] The absorption can be calculated as follows:

[0038] Absorption = -log(optical transmittance) = -log(M / a*R)

[0039] where a is a proportionality constant that can be adjusted for electrical gain normalization.

[0040] In this embodiment, ultraviolet light can be emitted to the water body along a preset path. At this time, the light emitted by the LED will not be interfered by other optical components, and the light passes through the gap and directly illuminates the photodiode after 220nm filtering; the ultraviolet light can be transmitted to the water body by selecting a suitable optical waveguide material (such as sapphire or UV-grade fused silica), so that the LED does not have to be close to the measurement point, and separating the LED from the light detector helps to reduce electrical noise through physical isolation; the light transmitted along the customized optical path will hit the photodiode, and the photon intensity is converted into current intensity. The light can be directly coupled to the photodiode without other optical components, or it can be collected by a suitable optical waveguide material (such as sapphire or UV-grade fused silica) and then guided to a photodiode separated from the measurement point.

[0041] The nitrate nitrogen water quality detection device of the utility model can realize the online monitoring of nitrate nitrogen in water. The device integrates multiple LED chips of different bands, which can simultaneously emit characteristic bands corresponding to nitrate nitrogen and organic matter, can detect different spectral signals and effectively eliminate background interference, and improve detection accuracy. The device has the following advantages:

[0042] 1. Dual-wavelength light source reduces the interference of dissolved organic matter: Through the absorbance ratio of the two wavelengths of 220nm and 275nm, the interference of dissolved organic matter can be effectively eliminated, and the accuracy of nitrate nitrogen detection can be improved.

[0043] 2. Dual optical path design improves spectral signal stability: The intensity of LED light source decays over time, affecting the accuracy of spectral signal. By introducing dual optical path design, the error caused by LED light source attenuation can be eliminated by real-time comparison of the spectral characteristics of the detection optical path and the reference optical path, thereby improving the accuracy of spectral signal.

[0044] 3. Compact structure and small size: The device adopts a composite package light source, which makes the light source part have a compact structure and small size, which is convenient for designing a miniature water quality probe.

[0045] 4. Reagent-free and fast response: Compared with traditional chemical analysis methods, this equipment does not require the use of reagents, realizes reagent-free detection, can perform long-term environmental water quality monitoring, and has the characteristics of fast response.

[0046] During operation, the LED chips in the composite packaged LED light source emit light of different wavelengths alternately. These lights are irradiated onto the water body to be detected, and the water body absorbs and scatters part of the light. The light that is not absorbed and scattered will irradiate the detection photodiode. The utility model packages LED chips of different wavelengths on the same substrate, which can determine the concentration level of nitrate nitrogen in the water body. In addition, the nitrate nitrogen water quality detection equipment adopts a dual optical path structure, in which the reference signal is used as a benchmark to eliminate the influence of light source attenuation and optical path transmission loss on the measurement results, thereby reducing errors.

[0047] In summary, the utility model provides a nitrate nitrogen water quality detection device based on a composite packaged light source. The light source integrates multiple LED chips of different bands and can simultaneously emit characteristic bands corresponding to nitrate nitrogen and organic matter. In conjunction with the photoelectric detection circuit, different spectral signals can be detected. Through the multivariate data analysis algorithm, the background interference can be effectively eliminated and the detection accuracy can be improved. The light source has a compact structure and small size, which can realize the design of a water quality micro-probe. The nitrate nitrogen water quality monitoring equipment has a simple structure, no reagents, and fast response, and can realize online and in-situ detection of nitrate nitrogen in water bodies. This technology improves the shortcomings of existing water quality monitoring equipment such as large size, long detection cycle, and poor anti-interference ability. Its miniature, simple and efficient characteristics can promote the development of water quality monitoring towards a distributed layout.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nitric nitrogen water quality detection device based on a composite encapsulated light source, characterized in that: include: A composite packaged light source, a semi-transparent and semi-reflective mirror, a sampling area, a reference photodiode, a detection photodiode, a first bandpass filter and a second bandpass filter. The composite packaged light source includes two deep ultraviolet LED chips of different wavelengths packaged on the same substrate. The composite packaged light source, the semi-transparent and semi-reflective mirror, the sampling area, the first bandpass filter and the detection photodiode are arranged in sequence along the optical path to form a detection optical path. The composite packaged light source, the semi-transparent and semi-reflective mirror, the second bandpass filter and the reference photodiode are arranged in sequence along the optical path to form a reference optical path.

2. The nitric nitrogen water quality detection equipment based on a composite encapsulated light source according to claim 1 is characterized in that: The deep ultraviolet LED chips include a 220±10nm deep ultraviolet LED chip and a 275±10nm deep ultraviolet LED chip.

3. A nitric nitrogen water quality detection device based on a composite encapsulated light source according to claim 1 or 2, characterized in that: The two deep ultraviolet LED chips in the composite packaged light source adopt a package structure with a common anode and an independent cathode to lead out wiring pins, which are respectively connected to respective driving circuits.

4. The nitric nitrogen water quality detection equipment based on a composite packaged light source according to claim 1 is characterized in that: The detection optical path is provided with an optical fiber between the sampling area and the first bandpass filter.

5. The nitric nitrogen water quality detection equipment based on composite packaged light source according to claim 1 is characterized in that: The semi-transparent and semi-reflective mirror is used to split a single beam of light into two beams of light, one of which is detected by a detection photodiode after passing through a sampling area, and the other is detected by a reference photodiode.

6. The nitric nitrogen water quality detection equipment based on composite packaged light source according to claim 1 is characterized in that: A first condensing lens is arranged between the composite package light source and the semi-transparent and semi-reflective mirror; a second condensing lens is arranged between the semi-transparent and semi-reflective mirror and the sampling area; and a third condensing lens is arranged between the sampling area and the first band-pass filter.

7. The nitric nitrogen water quality detection equipment based on composite packaged light source according to claim 1 is characterized in that: The sampling area comprises two glass sheets arranged opposite to each other, and a cleaning brush is arranged between the two glass sheets.

8. The nitric nitrogen water quality detection equipment based on composite packaged light source according to claim 1 is characterized in that: The nitric nitrogen water quality detection device is arranged in a shell composed of an outer shell and an end cover.

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