Full-spectrum water quality analysis equipment with variable optical path and detection method

Abstract

The invention provides an optical path variable full-spectrum water quality analysis method, and relates to the technical field of water quality detection, and the method comprises the following steps: S1, equipment enters a water sample to be detected, so that an open groove type flow cell is filled with the water sample to be detected to form a measurement light path and a reference light path; s2, starting a micro spectrometer, collecting a dark field spectrum, and then starting a xenon lamp light source; performing water sample testing; s3, a first stepping motor drives a baffle plate to move, selection of a reference light path and a measurement light path is achieved, and meanwhile a micro spectrograph collects spectral data of the two light paths to a control panel; and S4, transmitting the collected spectrum data and temperature data to an upper computer by the equipment through a waterproof cable, and finally outputting measurement parameters and measurement values by the upper computer. The accuracy, stability and applicability of multi-index synchronous detection in a complex water body environment are improved, low operation and maintenance cost and high environmental adaptability are considered, and the multi-scene monitoring requirement from a pollution source to a drinking water pipe network is met.

Description

Technical Field

[0001] This invention relates to the field of water quality testing technology, and in particular to a variable optical path full-spectrum water quality analysis device and testing method. Background Technology

[0002] With the rapid development of industrialization and urbanization in my country, water pollution problems are becoming increasingly complex, and the demand for water quality monitoring is expanding from conventional physicochemical indicators to more diverse and trace characteristic pollutants. Traditional chemical analysis methods, such as spectrophotometry and titration, are still used in national standard methods (such as GB 7488-87 and GB 11893-89), but their analysis cycles are long, reagent consumption is large, and they are prone to secondary pollution, making it difficult to meet the needs of modern online water quality monitoring and rapid emergency response.

[0003] Absorption spectroscopy, a widely used technique in environmental monitoring, can simultaneously retrieve multiple indicators through full-spectrum spectral information and chemometric models. Currently, several full-spectrum water quality analysis devices are available on the market, primarily dominated by European and American companies. However, significant technical bottlenecks still exist in practical applications.

[0004] Firstly, some commercial instruments only support single-wavelength (such as UV254) or limited discrete wavelength measurements. Although they are simple in structure, they are difficult to deal with water bodies with complex compositions.

[0005] Secondly, although some devices are equipped with full-spectrum scanning capabilities, the optical path design lacks a real-time reference correction mechanism. Experimental data shows that the light intensity of a xenon lamp light source decays after operating for a period of time. If only a single optical path is used for measurement, it will directly lead to a drift in the absorbance value. Furthermore, the irradiance varies at different angles, and both of these factors will affect the accuracy of the model inversion.

[0006] Third, existing high-end spectral analysis equipment is mostly cabinet-style, integrating complex flow paths and temperature control systems. It is bulky and energy-intensive, making it difficult to miniaturize and deploy in the field, which restricts its application in portable monitoring, pipeline-based in-situ deployment, and other fields.

[0007] Fourth, the optical properties of natural water bodies and discharged sewage differ significantly. However, most commercial instruments on the market are fixed optical path systems, which are difficult to adapt to the measurement needs of a wide range under different water quality conditions, thus limiting their applicability in actual water body monitoring.

[0008] Therefore, there is an urgent need to develop a water quality analysis technology and instrument that features full-spectrum detection, real-time dual-optical-path correction, compact structure, and applicability to in-situ measurements in different water bodies. This would solve one or more of the aforementioned problems, improve the accuracy, stability, and applicability of simultaneous multi-indicator detection in complex water environments, while also ensuring low operation and maintenance costs and high environmental adaptability, and meeting the monitoring needs of multiple scenarios from pollution sources to drinking water pipe networks. Summary of the Invention

[0009] To address the aforementioned issues, this invention provides a variable optical path full-spectrum water quality analysis device and detection method. This invention improves the accuracy, stability, and applicability of simultaneous detection of multiple indicators in complex water environments, while also taking into account low operation and maintenance costs and high environmental adaptability, meeting the monitoring needs of multiple scenarios from pollution sources to drinking water pipelines.

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A variable optical path full-spectrum water quality analysis method includes the following steps: S1, inserting the device into the water sample to be tested, so that the open groove-type flow cell is filled with the water sample to be tested, forming a measurement optical path and a reference optical path; S2, turning on the miniature spectrometer to collect dark-field spectra, and then turning on the xenon lamp light source; conducting water sample testing; S3, a stepper motor drives a baffle plate to move, realizing the selection of the reference optical path and the measurement optical path, while the miniature spectrometer collects spectral data of the two optical paths to the control board; S4, the device transmits the collected spectral data and temperature data to the host computer through a waterproof cable, and finally the host computer outputs the measurement parameters and measurement values.

[0012] Preferably, before testing, the measuring optical path and the reference optical path are filled with pure water, and the two optical paths are measured separately by controlling the shielding plate. The measured spectral intensity is optimized by the algorithm on the main control board, and the intensity of the two optical paths is corrected to ensure that the full spectrum intensity of the two light paths is consistent.

[0013] Preferably, calibration is performed using the following formula: Among them, E i，A To measure the intensity of the pure water optical path at wavelength i, E i，B To encapsulate the intensity of the pure water optical path at wavelength i, K i This is the proportionality coefficient.

[0014] Preferably, after acquiring the spectral data, temperature compensation is first performed on the spectral data.

[0015] Preferably, the temperature compensation of the spectral data is performed using the following formula: In the formula: For actual wavelength, The change in temperature The coefficient of thermal expansion is... Thermo-optic coefficient, This is the original wavelength position.

[0016] Preferably, during a single measurement, the miniature spectrometer collects the spectra of the dark field, the reference optical path, and the measurement optical path; by calculating the above spectral data, the absorbance at different wavelengths can be obtained, and the concentration of water quality parameters can be determined by the absorbance.

[0017] Preferably, the concentration of water quality parameters is determined by measuring absorbance using the following formula; In the formula: wavelength absorbance at that point wavelength Reference optical path signal value at that location, wavelength The measured optical path signal value at that location, wavelength The dark field signal value at that location, These represent the maximum and minimum values ​​of the measured wavelength, respectively.

[0018] Preferably, absorbance A λ With each concentration of C i The relationship is: In the formula: wavelength absorbance at K i,λ Is the i-th substance at wavelength The molar absorptivity at C i Where is the concentration of the substance; L is the optical path length. Through algorithmic analysis and inversion of the full-spectrum data, accurate measurement of various water quality parameters can be achieved.

[0019] Preferably, after the device is turned on, the host computer self-tests the communication connection of each part of the probe and whether the temperature is within the stable operating range of the device. If there is a problem, the host computer will alarm and provide a solution. After the problem is solved, the host computer will perform a self-test again. After the self-test is normal, the optical path will be set on the host computer.

[0020] The beneficial effects of this invention are as follows:

[0021] Compared with existing technologies, this invention improves the accuracy, stability and applicability of simultaneous detection of multiple indicators in complex water environments, while taking into account low operation and maintenance costs and high environmental adaptability, meeting the monitoring needs of multiple scenarios from pollution sources to drinking water pipe networks. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a full-spectrum water quality analysis device with variable optical path according to the present invention.

[0023] Figure 2 This is a flowchart of the method of the present invention. Figure 3 This is a schematic diagram showing the relationship between absorbance and wavelength. Figure 4 This is a schematic diagram showing the relationship between absorbance and concentration.

[0024] In the diagram: 1. Outer shell; 2. Light source; 3. Air gap double-cemented collimating lens; 4. Optical window; 5. Reference water sample; 6. Shielding plate; 7. Stepper motor one; 8. Miniature spectrometer; 9. Temperature sensor; 10. Main control board; 11. Optical path control board; 12. Stepper motor two; 13. Aspherical converging lens; 14. Sealed joint; 15. Waterproof cable. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] See attached document Figure 1 This invention discloses a variable optical path full-spectrum water quality analysis device, which can be used for in-situ online determination of absorption spectra in water. The device mainly comprises a housing, within which are a light source module, an optical detection module, a miniature spectrometer module, a temperature sensor, and a controller. Along the light propagation direction, the components are arranged in sequence: light source, collimating lens, optical window, reference optical path and measurement optical path, a stepper motor-controlled shielding plate and optical path control board, converging lens, miniature spectrometer, main control board, sealed connector, and waterproof cable. This invention can be widely applied to environmental water quality monitoring and industrial process monitoring.

[0027] A variable optical path full-spectrum water quality analysis device includes a housing 1 and an optical measurement module inside the housing. Except for the open flow cell, all other components are sealed within the housing. The optical measurement module generates two parallel beams of light through a light source 2 and an air-gap double-cemented collimating lens 3. One beam passes through an optical window 4 into an open-groove flow cell for measuring the water sample, while the other beam passes through a sealed reference water sample 5. Both beams are then converged by an aspherical converging lens 13 to a miniature spectrometer 8. The spectral data is stored and transmitted by a main control board 10. Simultaneously, the main control board 10 can control a shielding plate 6, perpendicular to the two optical paths and controlled by a stepper motor 7, for optical path selection. It can also control an optical path control plate located on one side of the open groove, controlled by a stepper motor 2, to adjust the optical path of the water sample being measured. This device enables in-situ measurement of water quality parameters.

[0028] In summary, compared with the existing technology that uses a combination of optical fibers and lenses, this invention uses spatial light to achieve light transmission, and uses air gap double bonding and a detached reflector to eliminate chromatic aberration. (In the existing technology, there is a lens at the very front, which is then coupled into the optical fiber and then splits the light.) The existing technology has a complex optical system and suffers from energy loss. This invention innovatively omits the relevant structures, resulting in less energy loss.

[0029] The device also includes a sealed connector 14 for connecting the waterproof cable 15 to the main control board 10 inside the device housing, achieving an IP68 waterproof rating.

[0030] The device also includes a temperature sensor 9 on one side of the miniature spectrometer 8. The temperature sensor 9 is used for temperature compensation algorithms and is directly connected to the waterproof cable 15, which can avoid the influence of temperature fluctuations on the measurement results and ensure the accuracy of the measurement data.

[0031] Powered by the main control board 10 and command sent, the optical path control board controlled by the stepper motor 2 adjusts the optical path of the water sample to be tested. The optical path is continuously adjustable and combined with the algorithm to perform two-channel spectral correction, which can realize the measurement of various water samples and has a wide range of applications.

[0032] The shield 6, controlled by stepper motor 7, can be used to select the received light for the reference optical path and the measurement optical path. The edge of the shield 6 is in contact with the inner wall of the equipment housing 1 through a peripheral seal. The dual optical path system reduces the impact of light source aging on the accuracy of measurement results.

[0033] The device contains optical windows 4. An open flow cell for measuring water samples is located between the two optical windows in the open groove (upper part of the diagram). One of the optical windows is located on a baffle plate 6, and the two optical windows are coaxial. Inside the outer casing (lower part of the diagram) is a sealed reference water sample 5.

[0034] The edge of the baffle plate 6 is ring-shaped through the peripheral seal, tightly fitting against the inner wall of the equipment casing. Fixed blocks are designed before and after the seal to prevent deformation of the sealing ring during long-term use, ensuring the equipment's lifespan and reducing maintenance costs.

[0035] The miniature spectrometer 8 collects the spectra of the dark field, the reference optical path, and the measurement optical path, while the temperature sensor 9 collects the temperature near the miniature spectrometer. By processing the above data, the concentration of the sample to be tested is calculated.

[0036] In the dark field, the light from the reference light path and the measurement light path will all converge to the miniature spectrometer 8. Using only a single spectrometer can eliminate the influence caused by different detectors; the device is cylindrical.

[0037] The air gap double-cemented collimating lens 3 and the aspherical converging lens 13 can eliminate the influence of optical path chromatic aberration and ensure the intensity of wavelengths across the entire spectrum.

[0038] To facilitate the use of novel water quality analysis equipment, this invention also provides a method for measuring multiple parameters of water quality, specifically including the following steps:

[0039] Step 1: Fill the measuring optical path and the reference optical path with pure water. Control the measurement of the two optical paths separately through the shielding plate 6. The measured spectral intensity is optimized by the algorithm on the main control board 10. The intensity of the two optical paths is corrected to ensure that the full spectrum light intensity of the two optical paths is consistent, thus ensuring the accuracy of the test and reducing the maintenance cost of the xenon lamp.

[0040]

[0041] Among them, E i，A To measure the intensity of the pure water optical path at wavelength i, E i，B To encapsulate the intensity of the pure water optical path at wavelength i, K i This is the proportionality coefficient.

[0042] By correcting the full-spectrum light intensity, this method can eliminate differences in light intensity caused by variations in the irradiance of the xenon lamp at different angles and the cuvette in the reference optical path. Simultaneously, when the temperature changes, the entire spectrometer drifts, and the measured wavelength of the reference light will change.

[0043] Step Two: After acquiring the spectral data, temperature compensation is first applied to ensure the accuracy of the spectral data and the precision of the measured values, thus broadening the application scenarios of the equipment. Among these steps... It is related to the amount of temperature change, the coefficient of thermal expansion, and the thermo-optical coefficient:

[0044]

[0045] In the formula: For actual wavelength, The change in temperature The coefficient of thermal expansion is... Thermo-optic coefficient, This is the original wavelength position.

[0046] Step 3: During a measurement, the miniature spectrometer 8 collects spectra from the dark field, the reference optical path, and the measurement optical path. By calculating the absorbance at different wavelengths, the concentration of water quality parameters can be determined using absorbance data. Subtracting the dark field data makes the test results more accurate. Among these, wavelength... The absorbance A in the dark field is correlated with the dark field signal value D, the reference optical path signal value R, and the measurement optical path signal value D.

[0047]

[0048] In the formula: wavelength absorbance at that point wavelength Reference optical path signal value at that location, wavelength The measured optical path signal value at that location, wavelength The dark field signal value at that location, These represent the maximum and minimum values ​​of the measured wavelength, respectively.

[0049] Step 4: In actual water quality testing, the measured spectrum includes various water quality parameters such as the absorption characteristics of different chemical substances, which are distributed across different wavelength bands. This means that at any wavelength, the measured absorbance is the result of the combined contribution of all substances.

[0050] Based on the additive assumption of the Lambert-Beer law, which states that there is no interaction between substances, the total absorbance is equal to the linear superposition of the absorbances of each substance. Let there be n water quality parameters to be measured, with concentrations C1, C2, C3, ..., C... i L is the optical path length constant, determined by the experimental setup, and K... i,λ Is the i-th substance at wavelength The molar absorptivity at each wavelength Where λ is in the measurement range Within, absorbance A λ With each concentration of C i The relationship is:

[0051]

[0052] In the formula: wavelength absorbance at K i,λ Is the i-th substance at wavelength The molar absorptivity at C i Where is the concentration of the substance; L is the optical path length. Through algorithmic analysis and inversion of the full-spectrum data, multiple water quality parameters can be measured simultaneously, and the testing method is simple.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] The technical solution adopted in this invention is: a full-spectrum water quality analysis device with variable optical path, the device including a shell 1 and an optical measurement module inside the shell. The optical measurement module includes a light source 2, an air gap double-cemented collimating lens 3, an optical window 4, a sealed reference water sample 5 for comparison, an open groove-type measurement water sample flow cell, a shielding plate 6 controlled by stepper motor 7, an optical path control board 11 controlled by stepper motor 12, an aspherical converging lens 13, a miniature spectrometer 8, and a main control board 10.

[0055] Preferably, except for the open flow cell, all other components of the device are sealed within the housing. Preferably, the optical path control board 11 can control the optical path of the measurement optical path. The distance L between the optical windows 4 of the measurement optical path can be adjusted according to the object being measured and its concentration.

[0056] Preferably, the device also includes a sealing connector 14 and a waterproof cable 15. The sealing connector 14 is located at one end of the device and is connected to the waterproof cable 15. The waterproof cable 15 enables communication between the inside and outside of the device. The device also includes a temperature sensor 9 for temperature compensation of the device.

[0057] Preferably, the air gap double-cemented collimating lens 3, the aspherical converging lens 13, and the optical window 4 contained in the device are made of fused silica or sapphire material.

[0058] Preferably, the light source 2 used in the device is a flashing xenon lamp light source, which has a longer service life.

[0059] Preferably, the outer casing 1 of the device can be made of stainless steel, aluminum alloy or titanium alloy, which can be suitable for different water quality environments.

[0060] Preferably, the edge of the equipment shield 6 is annular through a peripheral seal, tightly adhering to the inner wall of the equipment housing. Furthermore, fixing blocks are designed before and after the seal to prevent deformation of the sealing ring during long-term use.

[0061] A method for measuring multiple parameters of water quality includes the following steps:

[0062] Step 1: Fill both the measurement and reference optical paths with pure water. Measurements are then performed on both paths using a shielding plate 6. Since the xenon lamp's irradiance varies at different angles, the host computer performs algorithmic optimization on the measured spectral intensity to eliminate differences in light intensity caused by angle variations and the window. Simultaneously, when the temperature changes, the spectrometer drifts, causing changes in the measured wavelength of the reference light.

[0063] Step Two: It is related to the amount of temperature change, the coefficient of thermal expansion, and the thermo-optical coefficient:

[0064]

[0065] For actual wavelength, This represents the change in temperature. The coefficient of thermal expansion is... Thermo-optic coefficient, This is the original wavelength position.

[0066] Step 3: During a measurement, the miniature spectrometer 8 will collect the spectra of the dark field, the reference optical path, and the measurement optical path. Wavelength The absorbance A in the dark field is correlated with the dark field signal value D, the reference optical path signal value R, and the measurement optical path signal value D.

[0067]

[0068] wavelength absorbance at that point wavelength Reference optical path signal value at that location, wavelength The measured optical path signal value at that location, wavelength The dark field signal value at that location, These represent the maximum and minimum values ​​of the measured wavelength, respectively.

[0069] Step Four: In actual water quality testing, the measured spectrum includes various water quality parameters such as the absorption characteristics of different chemical substances. These characteristics are distributed across different wavelength bands. This means that at any wavelength, the measured absorbance is the result of the combined contribution of all substances. Based on the additive assumption of Lambert-Beer's law, which assumes no interaction between substances, the total absorbance is equal to the linear superposition of the absorbances of each substance. Suppose there are n water quality parameters to be measured, with concentrations C1, C2, C3, ..., C i L is the optical path length constant, determined by the experimental setup, and K... i,λ Is the i-th substance at wavelength The molar absorptivity at each wavelength Where λ is in the measurement range Within, absorbance A λ With each concentration of C i The relationship is:

[0070]

[0071] wavelength absorbance at K i,λ Is the i-th substance at wavelength The molar absorptivity at C i This represents the concentration of the substance.

[0072] Example 1:

[0073] Figure 1 The diagram illustrates a variable optical path full-spectrum water quality analysis device, comprising an analytical device housing 1, and internal light source module, measurement module, and spectral receiving module. Along the beam propagation direction, the components are arranged in sequence: light source 2, air-gap doublet collimating lens 3, optical window 4, sealed reference water sample 5, open groove-type measurement water sample flow cell, shielding plate 6 controlled by stepper motor 7, optical path control board 11 controlled by stepper motor 12, aspherical converging lens 13, and miniature spectrometer 8. The light emitted by light source 2 diverges and is transformed into parallel light by the air-gap doublet collimating lens 3. One path of this light passes through the open groove-type measurement water sample flow cell, serving as the measurement optical path; the other path passes through the sealed reference water sample, serving as the reference optical path.

[0074] Before measurement, a suitable optical path is set via the optical path control board 11, and pure water with the same optical path is encapsulated in the reference optical path. During measurement, when the light source 2 is off, the miniature spectrometer 8 acquires spectral data of the dark field. Subsequently, the light source 2 is turned on, and after flashing a few times, the light intensity output stabilizes. The miniature spectrometer then acquires spectral data of the reference optical path. Finally, the stepper motor 7 controls the movement of the shielding plate 6, and the miniature spectrometer 8 acquires spectral data of the measurement optical path, thus completing the measurement. Simultaneously, the temperature sensor 9 measures the temperature of the miniature spectrometer 8, and the main control board 10 of the analysis equipment receives the above data and transmits it to the host computer via the waterproof cable 15.

[0075] A multi-parameter water quality measurement method includes the following steps:

[0076] It is related to the amount of temperature change, the coefficient of thermal expansion, and the thermo-optical coefficient:

[0077]

[0078] For actual wavelength, This represents the change in temperature. The coefficient of thermal expansion is... Thermo-optic coefficient, This is the original wavelength position.

[0079] During a measurement, the miniature spectrometer 8 collects spectra from the dark field, the reference optical path, and the measurement optical path. Wavelength The absorbance A in the dark field is correlated with the dark field signal value D, the reference optical path signal value R, and the measurement optical path signal value D.

[0080]

[0081] wavelength absorbance at that point wavelength Reference optical path signal value at that location, wavelength The measured optical path signal value at that location, wavelength The dark field signal value at that location, These represent the maximum and minimum values ​​of the measured wavelength, respectively.

[0082] In actual water quality testing, the measured spectrum includes the absorption characteristics of various water quality parameters, such as different chemical substances, which are distributed across different wavelength bands. This means that at any wavelength, the measured absorbance is the result of the combined contribution of all substances. Based on the additive assumption of Lambert-Beer's law, which states that there is no interaction between substances, the total absorbance is equal to the linear superposition of the absorbances of each substance. Let there be n water quality parameters to be measured, with concentrations C1, C2, C3, ..., C... i L is the optical path length constant, determined by the experimental setup, and K... i,λ Is the i-th substance at wavelength The molar absorptivity at each wavelength Where λ is in the measurement range Within, absorbance A λ With each concentration of C i The relationship is:

[0083]

[0084] wavelength absorbance at K i,λ Is the i-th substance at wavelength The molar absorptivity at C i This represents the concentration of the substance.

[0085] By using standard solutions to determine the proportion coefficients of each analyte, the measurement results of multiple parameters in water quality can be obtained.

[0086] The outer casing 1, optical window 4, optical path control board 11, and sealing joint 14 constitute the outer casing mechanism of the device, sealing the internal components and enabling the device to be completely immersed in the liquid to be tested, thus achieving in-situ underwater detection. The device can also be used for in-situ detection of water samples.

[0087] The air gap double-cemented collimating lens 3, aspherical converging lens 13, and optical window 4 contained in the equipment are made of fused silica or sapphire material.

[0088] The light source 2 used in the device is a scintillation xenon lamp, which has a longer lifespan and a wavelength range of 180 nm-2000 nm. The miniature spectrometer 8 used in the device can receive wavelengths of 200 nm-800 nm, covering the required bands, with a wavelength resolution of ≤5 nm, meeting the water quality detection requirements of the device.

[0089] The outer casing of the device can be made of stainless steel, aluminum alloy or titanium alloy, making it suitable for different water quality environments.

[0090] The optical path control board 11 can control the optical path of the measurement optical path. The distance L between the optical windows 4 of the measurement optical path can be adjusted according to the object being measured and its concentration.

[0091] Example 2:

[0092] The difference between Example 1 and Example 2 is that Example 1 mainly describes the principles of each part of the system and the implementation method, while Example 2 describes the workflow of the entire instrument.

[0093] A detection process method for a variable optical path full-spectrum water quality analysis device, as follows: Figure 2 As shown. The detection method flow is as follows:

[0094] Step 1: Insert the device into the water sample to be tested, so that the open groove-type flow cell is filled with the water sample to be tested;

[0095] Step 2: Turn on the device. The host computer will self-test the communication connections of each part of the probe, including the xenon lamp light source 2, the miniature spectrometer 8, the temperature sensor 9, and the two stepper motors 7 and 12. It will self-test whether the temperature is within the stable operating range of the device. If there is a problem, the host computer will alarm and provide a solution. After the problem is solved, it will self-test again. If there is no problem, continue to the next step.

[0096] Step 3: After the self-test shows no abnormalities, set the optical path on the host computer;

[0097] Step 4: The equipment executes the water sample test command;

[0098] Step 5: Turn on the miniature spectrometer 8 to collect dark-field spectra;

[0099] Step Six: The miniature spectrometer 8 drives the xenon lamp light source 2 to turn on and conduct water sample testing;

[0100] Step 7: Stepper motor 7 drives the shield 6 to move, realizing the selection of the reference optical path and the measurement optical path. At the same time, the miniature spectrometer 8 collects the spectral data of the two optical paths and sends them to the control board 10.

[0101] Step 8: The device transmits the collected spectral data to the host computer via waterproof cable 15;

[0102] Step 9: Simultaneously, the temperature sensor 9 transmits the collected temperature data to the host computer via the waterproof cable 15;

[0103] Step 10: The host computer outputs the measurement parameters and values.

[0104] Example 3:

[0105] The difference between Example 3 and Example 1 and Example 2 is that Example 3 is a case of a single application.

[0106] Using analytical grade potassium nitrate reagent, 722.14 mg was accurately weighed and diluted to 1000 mL of ultrapure water to prepare a potassium nitrate stock solution with a mass concentration of 722.14 mg / L, which translates to a nitrogen element mass concentration of 100.00 mg / L. Using this potassium nitrate stock solution, nitrogen element mass concentrations of 0.5 mg / L, 1 mg / L, 2 mg / L, 3 mg / L, and 4 mg / L were prepared. The absorption spectra of the prepared solutions at different concentrations were measured using the detection method of this equipment. The test results are as follows: Figure 3 As shown, the horizontal axis represents wavelength, with the micro spectrometer 8 used in the actual implementation case having a wavelength range of 187 nm to 821 nm; the vertical axis represents absorbance values. The absorption characteristics of nitrate at 200-250 nm can be clearly attributed to nitrate ions.

[0107] like Figure 4 As shown, the absorbance increases with increasing concentration, and within a specific concentration range, the absorbance at a specific wavelength of 220 nm exhibits a good linear response with the solution concentration, conforming to the Lambert-Beer law. The linearity R was measured. 2 >0.999. Therefore, this linear relationship can be used to achieve precise quantification of nitrate nitrogen concentration.

[0108] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A full-spectrum water quality analysis method with variable optical path, characterized in that, Includes the following steps: S1. Insert the device into the water sample to be tested, so that the open groove-type flow cell is filled with the water sample to be tested to form the measurement optical path and the reference optical path; S2. Turn on the miniature spectrometer (8) to collect dark field spectra, and then turn on the xenon lamp light source (2); conduct water sample testing; S3. Stepper motor (7) drives the shield (6) to move, thereby enabling the selection of the reference optical path and the measurement optical path. At the same time, the micro spectrometer (8) collects the spectral data of the two optical paths to the control board (10). S4. The device transmits the collected spectral and temperature data to the host computer via a waterproof cable (15), and the host computer outputs the measurement parameters and values.

2. The variable optical path full-spectrum water quality analysis method according to claim 1, characterized in that, Before testing, the measurement optical path and the reference optical path are filled with pure water. The two optical paths are measured by controlling the shield (6). The measured spectral intensity is optimized by the algorithm on the main control board (10) and the intensity of the two optical paths is corrected to ensure that the full spectrum intensity of the two optical paths is consistent.

3. The variable optical path full-spectrum water quality analysis method according to claim 2, characterized in that, Use the following formula for calibration: ； Among them, E i，A To measure the intensity of the pure water optical path at wavelength i, E i，B To encapsulate the intensity of the pure water optical path at wavelength i, K i This is the proportionality coefficient.

4. The method for full-spectrum water quality analysis with variable optical path as described in claim 1, characterized in that, After acquiring the spectral data, temperature compensation is first performed on the spectral data.

5. The variable optical path full-spectrum water quality analysis method according to claim 4, characterized in that, The spectral data is temperature compensated using the following formula: ； In the formula: For actual wavelength, The change in temperature The coefficient of thermal expansion is... Thermo-optic coefficient, This is the original wavelength position.

6. The method for full-spectrum water quality analysis with variable optical path according to claim 1, characterized in that, During a measurement, the micro spectrometer (8) collects the spectra of the dark field, the reference optical path, and the measurement optical path; by calculating the above spectral data, the absorbance at different wavelengths can be obtained, and the concentration of water quality parameters can be determined by the absorbance.

7. The method for full-spectrum water quality analysis with variable optical path as described in claim 6, characterized in that, The concentration of water quality parameters can be determined by measuring absorbance using the following formula; ； In the formula: wavelength absorbance at that point wavelength Reference optical path signal value at that location, wavelength The measured optical path signal value at that location, wavelength The dark field signal value at that location, These represent the maximum and minimum values ​​of the measured wavelength, respectively.

8. The variable optical path full-spectrum water quality analysis method according to claim 7, characterized in that, Absorbance A λ With each concentration of C i The relationship is: ； In the formula: wavelength absorbance at K i,λ Is the i-th substance at wavelength The molar absorptivity at C i Where is the concentration of the substance; L is the optical path length. Through algorithmic analysis and inversion of the full-spectrum data, accurate measurement of various water quality parameters can be achieved.

9. The variable optical path full-spectrum water quality analysis method according to claim 1, characterized in that, After the device is turned on, the host computer will self-test the communication connection of each part of the probe and check whether the temperature is within the stable operating range of the device. If there is a problem, the host computer will alarm and provide a solution. After the problem is solved, the host computer will self-test again. After the self-test is normal, the optical path will be set on the host computer.

Images