A linear multi-location compensated wide-range turbidity measurement sensor and its application

Abstract

This invention provides a linearly multi-position compensated, wide-range turbidity measurement sensor, including a solution carrier disk, an LED light source, and a linear photodiode array corresponding to the solution carrier disk. A collimating lens is positioned between the LED light source and the solution carrier disk. Light from the LED light source, incident through the collimating lens, is scattered in the solution to be measured and exits through the aperture of an aperture stop. The scattered light at each angle is captured by the linear photodiode array, and the light intensity information is linearly compensated by the linear photodiode array. Both the LED light source and the linear photodiode array are electrically connected to a control system. This invention, based on the linear array compensation of scattered light at each angle, greatly increases the applicable range of turbidity measurement, achieving comprehensiveness and integration of turbidity measurement. It also solves the problems of increased measurement error and reduced resolution under high turbidity conditions, significantly improving the turbidity measurement range and measurement accuracy under high turbidity, and can be widely applied in the field of water turbidity measurement.

Description

Technical Field

[0001] This invention belongs to the field of measurement technology for large-scale turbidity water bodies, and in particular relates to a linear multi-location compensated large-scale turbidity measurement sensor and its application. Background Technology

[0002] Turbidity, as a key indicator of water quality, is of great significance for assessing the health of the aquatic environment and ensuring drinking water safety. Currently, online turbidity measurement technologies are mainly based on optical principles, such as the 90° scattering method, which is widely used due to its simplicity and cost-effectiveness. However, traditional optical measurement methods are usually only suitable for single-level turbidity measurements. At high turbidity levels, measurement errors and reduced resolution have become bottlenecks for technological development. Furthermore, the measurement results are also poor at low turbidity levels. Summary of the Invention

[0003] In view of this, the present invention aims to overcome the defects in the prior art and proposes a linear multi-position compensation large-range turbidity measurement sensor and its application, which solves the problems of the current turbidity measurement range being limited and the error increasing under high turbidity. By using a linear photodiode array for linear multi-position compensation, it can measure a large range of turbidity and significantly improves the measurement accuracy. Therefore, the present invention provides a new technical path for the large-range and accurate measurement of water turbidity, and can be applied to application scenarios under both high and low turbidity conditions.

[0004] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0005] A linear multi-position compensated wide-range turbidity measurement sensor includes a solution carrier disk, an LED light source and a linear photodiode array corresponding to the solution carrier disk, and a collimating lens between the LED light source and the solution carrier disk; the LED light source enters the solution carrier disk through the collimating lens, and the light is scattered in the solution to be measured in the solution carrier disk and exits through the light transmission hole of the aperture stop.

[0006] When light is scattered in the solution being tested, the intensity of the scattered light from a single scattering particle is:

[0007] I′=I(θ,l,λ,d,m1,m2,…mx);

[0008] In the above formula: θ is the scattering angle; l is the scattering optical path length; λ is the incident light wavelength; d is the particle size of the solution; m1, m2, ... m n This indicates other factors that can affect light intensity;

[0009] The scattered light from each angle emitted through the aperture stop is captured by a linear photodiode array. After linear compensation by the linear photodiode array, the overall light intensity information for the current turbidity is:

[0010]

[0011] In the above formula: I″ represents the combined light intensity after linear compensation; C(I1,I2,...,I...) n ) represents the photocurrent I captured by the i-th diode. i The linear compensation function,

[0012] Furthermore, both the LED light source and the linear photodiode array are electrically connected to the control system.

[0013] Furthermore, the solution carrier disk is a circular disk with a radius of 5 cm.

[0014] Furthermore, the LED light source uses 10kHz sinusoidal modulated light.

[0015] Furthermore, the linear photodiode array uses a Hamamatsu S11865-256 chip.

[0016] Furthermore, the diameter of the light-transmitting aperture of the aperture stop is 15mm.

[0017] Furthermore, the control system adopts MC9S08AW16CFGE.

[0018] A method for measuring turbidity using the aforementioned linear multi-location compensation wide-range turbidity measurement sensor includes the following steps:

[0019] The photocurrent I generated by a photodiode when it receives scattered light i Then, the signal is amplified by a transimpedance amplifier and converted into a voltage value to obtain usable turbidity information linearly acquired at each location, followed by further signal compensation.

[0020] The curves of unknown turbidity solutions are collected by sensors, and then fitted to various standard curves to obtain the fitting coefficients and determine the linear compensation coefficients.

[0021] After determining the linear compensation coefficient, the turbidity measurement result is converted and output based on the obtained comprehensive light intensity information, and then transmitted to the PC by the control system.

[0022] Furthermore, the methods for obtaining the standard curves S1, S2, and S3 are as follows:

[0023] Three standard turbidity solutions, L1 (low turbidity), L2 (medium turbidity), and L3 (high turbidity), were used for calibration; the three sets of turbidity information are as follows:

[0024]

[0025] In the formula, L1, L2, and L3 represent the light intensity information received by the linear photodiode array under low-turbidity, medium-turbidity, and high-turbidity solutions, respectively; A11, A12, ..., A1 256 Available turbidity information linearly collected at various locations under low turbidity conditions; A21, A22...A2 256 Available turbidity information linearly collected at various locations under intermediate turbidity; A31, A32...A3 256 This provides usable turbidity information obtained linearly from various locations under high turbidity conditions.

[0026] Based on L1, L2, and L3, curves S1, S2, and S3 of the received light intensity versus diode position under low, medium, and high turbidity conditions were plotted respectively, and three sets of turbidity coefficients were determined for each set of data vectors based on the turbidity of its predetermined standard solution.

[0027]

[0028] In the formula, C1, C2, and C3 are the standard coefficients for low-turbidity, medium-turbidity, and high-turbidity solutions, respectively, thus obtaining the standard curve sets S1, S2, and S3 and the standard coefficient sets C1, C2, and C3 for low-turbidity, medium-turbidity, and high-turbidity calibration solutions.

[0029] Compared with existing technologies, the present invention has the following advantages:

[0030] This invention proposes a linear multi-position compensation method to achieve turbidity measurement of solutions, freeing it from being limited to a fixed turbidity range and enabling turbidity measurement over a wide range. Based on the linear array compensation of scattered light at various angles, the applicable range of turbidity measurement is greatly increased, realizing the comprehensiveness and integration of turbidity measurement. At the same time, it solves the problems of increased measurement error and reduced resolution under high turbidity, greatly improving the turbidity measurement range and measurement accuracy under high turbidity, and can be widely used in the field of water turbidity measurement. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 A schematic diagram illustrating the turbidity measurement sensor created for this invention;

[0033] Figure 2 This is a schematic diagram of the turbidity measurement process;

[0034] Figure 3 This is a schematic diagram of the linear compensation process.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1-Solution carrier disk; 2-LED light source; 3-Linear photodiode array; 4-Collimating lens; 5-Incident light ray; 6-Aperture stop. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0038] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] A linear, multi-location compensated, wide-range turbidity measurement sensor, such as Figure 1 As shown, the system includes a solution carrier plate 1 for holding the water sample to be tested. Corresponding to the solution carrier plate are an LED light source 2 and a linear photodiode array 3, both of which are electrically connected to a control system, which is in turn electrically connected to a PC. A collimating lens 4 is positioned between the LED light source and the solution carrier plate to ensure the parallelism of the light rays.

[0042] The light from the LED light source is incident on the solution under test through the collimating lens 5 and is scattered. The light then exits through the aperture stop 6, which is used to limit the light transmission area. The scattered light at each angle is captured by the linear photodiode array. The light intensity information is linearly compensated by the linear photodiode array and then converted into the turbidity measurement result. The turbidity measurement result is then transmitted to the PC by the control system.

[0043] The LED light source selected is model L9437. The LED is fixed to the base platform and generates near-infrared light with a wavelength of 870nm. A collimating lens is added at the front end to ensure the parallelism of the light beam. To reduce interference from stray light in the environment, a 10kHz sinusoidal modulated light source is used for measurement. The solution tray is a circular disk with a radius of 5cm, used to place and fix the solution sample. The measurement container is made of high-transmittance optical glass. During measurement, the solution to be measured is added to the container until it covers the LED and photodiode.

[0044] The linear photodiode array uses the Hamamatsu S11865-256 chip, with an effective photosensitive area length of 51.2 mm and 256 diodes. The photodiodes are fixed to the base, and two vertical aperture stops with a diameter of 15 mm are installed at the front of the photodiode array to limit the light path. The control system uses an MC9S08AW16CFGE as the main control MCU, capable of controlling the acquisition and signal processing sections, and communicating with the PC.

[0045] A method for turbidity measurement using the aforementioned linear multi-location compensated wide-range turbidity measurement sensor, such as... Figure 2 As shown, it includes the following steps:

[0046] The photocurrent I generated by the photodiode upon receiving scattered light i Then, it is amplified by the transimpedance amplifier AD8641 and converted into a voltage value, so that the output voltage is amplified to the range of the MCU acquisition.

[0047] The photocurrent, after being amplified to a voltage by transimpedance, is linearly related to the received light intensity, denoted as:

[0048] U i =aI i

[0049] In the formula, a is the linear coefficient.

[0050] The signal is then demodulated by a dual-channel lock-in amplifier, denoted as:

[0051] A i =g(U i )

[0052] In the formula, g() represents the demodulation process; Ai This is the demodulation result, i.e., the usable turbidity information. It involves obtaining the usable turbidity information A1, A2, ... A from linearly acquired data at each location. n Then, further signal compensation is performed;

[0053] When using a solution of unknown turbidity for turbidity measurement, the sensor first acquires the change curve S of the unknown turbidity solution. O , will S O Curve fitting was performed with the standard curve sets S1, S2, and S3 respectively, and the fitting coefficients m1, m2, and m3 were obtained. The standard coefficient C corresponding to MAX(m1, m2, m3) was then taken. i (i = 1, 2 or 3) are used as the linear compensation coefficients assigned to this measurement;

[0054] After determining the linear compensation coefficient, the turbidity measurement result is converted and output based on the obtained comprehensive light intensity information, and then transmitted to the PC by the control system.

[0055] like Figure 3 As shown, the standard curves S1, S2, and S3 are obtained as follows:

[0056] Three standard turbidity solutions, L1 (low turbidity), L2 (medium turbidity), and L3 (high turbidity), were used for calibration. The three sets of turbidity information are as follows:

[0057]

[0058] In the formula, L1, L2, and L3 represent the light intensity information received by the linear photodiode array under low-turbidity, medium-turbidity, and high-turbidity solutions, respectively.

[0059] Based on L1, L2, and L3, curves S1, S2, and S3 of the received light intensity versus diode position under low, medium, and high turbidity conditions were plotted respectively, and three sets of turbidity coefficients were determined for each set of data vectors based on the turbidity of its predetermined standard solution.

[0060]

[0061] In the formula, C1, C2, and C3 are the standard coefficients for low-turbidity, medium-turbidity, and high-turbidity solutions, respectively, thus obtaining the standard curve sets S1, S2, and S3 and the standard coefficient sets C1, C2, and C3 for low-turbidity, medium-turbidity, and high-turbidity calibration solutions.

[0062] The LED light source is collimated by a lens to ensure the parallelism of the incident light. The light is scattered in the solution being tested, and the intensity of the scattered light from a single scattering particle can be expressed as:

[0063] I′=I(θ,l,λ,d,m1,m2,…m n )

[0064] In the formula: the contents in parentheses are the quantities that affect the intensity of scattered light; θ is the scattering angle; l is the scattering optical path; λ is the incident light wavelength; d is the particle size of the solution; m1 and m2, etc., represent other factors that affect the light intensity.

[0065] The intensity of light reflected by a liquid varies depending on its turbidity. Generally, the greater the turbidity, the larger the required scattering angle.

[0066] Subsequently, an aperture stop was added in front of the photodiode array to define the light-transmitting area, ensuring that the photodiodes at different positions receive light primarily from different directions. For each diode element in the photodiode array, assume its incident scattered photocurrent is I. i ′, where i represents the diode at the i-th position.

[0067] Because the photodiode array is linearly arranged, each diode at each position captures scattered light from each angle and undergoes linear compensation. The result of linear compensation of the light intensity information captured by N linear sensors is the comprehensive light intensity information reflecting the current turbidity, i.e.:

[0068]

[0069] In the formula: I″ is the combined light intensity after linear compensation, used for outputting turbidity information after subsequent processing; C(I1, I2, ..., I n ) represents the photocurrent I captured by the i-th diode. i The linear compensation function and the overall light intensity received at each position are used to determine the current I. i compensation coefficient C i F(I) is the comprehensive processing function after multi-position linear compensation.

[0070] Generally, at medium turbidity, the light intensity information in the middle angle has a greater weight, while the weights on the outer edges decrease. Therefore, it is necessary to appropriately increase the compensation coefficient C of the diode in the middle section. i The compensation coefficients at both ends are reduced; at high turbidity, the light intensity information at large angles has high turbidity, so the weight coefficients of the middle and low positions are reduced. Since the light intensity measured at different positions is different, after comprehensively comparing and arranging the light intensity received at each position, the coefficients of each part are reasonably allocated to perform linear compensation, thereby outputting the linearly compensated comprehensive light intensity I″.

[0071] Finally, the comprehensive light intensity information obtained from the compensation process is further converted into the final turbidity information and output to the PC by the control system.

[0072] This invention proposes a linear multi-position compensation method to achieve turbidity measurement of solutions, freeing it from being limited to a fixed turbidity range and enabling turbidity measurement over a wide range. Based on the linear array compensation of scattered light at various angles, the applicable range of turbidity measurement is greatly increased, realizing the comprehensiveness and integration of turbidity measurement. At the same time, it solves the problems of increased measurement error and reduced resolution under high turbidity, greatly improving the turbidity measurement range and measurement accuracy under high turbidity, and can be widely used in the field of water turbidity measurement.

[0073] The above description is merely a preferred embodiment of the present invention and is 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 linear multi-position compensated wide-range turbidity measurement sensor, characterized in that: It includes a solution carrier disk, with an LED light source and a linear photodiode array corresponding to the solution carrier disk. A collimating lens is provided between the LED light source and the solution carrier disk. The LED light source enters the solution carrier disk through the collimating lens, and the light is scattered in the solution to be tested in the solution carrier disk and exits through the light transmission hole of an aperture stop. Two vertical aperture stops are installed in front of the linear photodiode array to define the light transmission area, so that photodiodes at different positions receive scattered light at different scattering angles. When light is scattered in the solution being tested, the intensity of the scattered light from a single scattering particle is: ； In the above formula: The scattering angle; For the scattering optical path; The wavelength of the incident light; The particle sizes of the solution particles are: m1, m2, ... m n This indicates other factors that can affect light intensity; The scattered light from each angle emitted through the aperture stop is captured by a linear photodiode array. After linear compensation by the linear photodiode array, the overall light intensity information for the current turbidity is: ； In the above formula: The combined light intensity after linear compensation; Capture photocurrent for the i-th diode The linear compensation function, This is the comprehensive processing function after multi-position linear compensation; The linear compensation function is determined by combining the light intensity received at each position and the overall light intensity, and is used to determine the compensation coefficient of the photocurrent at each position. In moderate turbidity, the light intensity information at the middle angle has a greater weight, so the compensation coefficient of the diodes in the middle section is appropriately increased while the compensation coefficients at the outer positions are decreased. In high turbidity, the light intensity information at large angles has a greater weight, so the compensation coefficients at the middle and low positions are decreased. Since the light intensity measured at different positions is different, the coefficients of each part are reasonably allocated after comprehensively comparing and arranging the light intensity received at each position for linear compensation, thereby outputting the linearly compensated overall light intensity. Furthermore, both the LED light source and the linear photodiode array are electrically connected to the control system.

2. The linear multi-position compensated large-range turbidity measurement sensor according to claim 1, characterized in that: The solution carrier is a circular disk with a radius of 5 cm.

3. The linear multi-position compensated wide-range turbidity measurement sensor according to claim 1, characterized in that: The LED light source uses 10kHz sinusoidal modulated light.

4. A linear multi-position compensated wide-range turbidity measurement sensor according to claim 1, characterized in that: The linear photodiode array uses a Hamamatsu S11865-256 chip.

5. A linear multi-position compensated wide-range turbidity measurement sensor according to claim 1, characterized in that: The aperture stop has a light-transmitting hole diameter of 15mm.

6. A linear multi-position compensated wide-range turbidity measurement sensor according to claim 1, characterized in that: The control system uses MC9S08AW16CFGE.

7. A method for measuring turbidity using a large-range turbidity measurement sensor with linear multi-position compensation as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The photocurrent generated by a photodiode when it receives scattered light Then, the signal is amplified by a transimpedance amplifier and converted into a voltage value to obtain usable turbidity information linearly acquired at each location, followed by further signal compensation. The curves of unknown turbidity solutions are collected by sensors, and then fitted to various standard curves to obtain the fitting coefficients and determine the linear compensation coefficients. After determining the linear compensation coefficient, the turbidity measurement result is converted and output based on the obtained comprehensive light intensity information, and then transmitted to the PC by the control system.

8. The method according to claim 7, characterized in that, The standard curves S1, S2, and S3 are obtained as follows: Take low turbidity solutions separately Medium turbidity High turbidity Three standard turbidity solutions were used for calibration; three sets of turbidity information were obtained. In the formula, L1, L2, and L3 represent the light intensity information received by the linear photodiode array under low-turbidity, medium-turbidity, and high-turbidity solutions, respectively; A11, A12, ..., A1 256 Available turbidity information linearly collected at various locations under low turbidity conditions; A21, A22...A2 256 Available turbidity information linearly collected at various locations under intermediate turbidity; A31, A32...A3 256 This provides usable turbidity information obtained linearly from various locations under high turbidity conditions. Based on L1, L2, and L3, standard curves S1, S2, and S3 of the received light intensity versus diode position under low turbidity, medium turbidity, and high turbidity conditions were plotted respectively, and three sets of turbidity coefficients were determined for each set of data vectors based on the turbidity of its given standard solution. In the formula, C1, C2, and C3 are the standard coefficients for low-turbidity, medium-turbidity, and high-turbidity solutions, respectively, thus obtaining the standard curve sets S1, S2, and S3 and the standard coefficient sets C1, C2, and C3 for low-turbidity, medium-turbidity, and high-turbidity calibration solutions.

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