Method for detecting chromaticity of water body

Abstract

The invention relates to a water body chromaticity detection method which comprises the following steps: splitting light of a light source to obtain reflected light and transmitted light; acquiring the light intensity of the transmission light after penetrating through a plurality of standard solutions with known chromaticity and the light intensity of the reflected light at the corresponding moment, and analyzing to obtain a relation curve of the chromaticity of the water body and the light absorbance; the method comprises the following steps: detecting a water sample to be detected, collecting a set number of real-time transmission light intensities and real-time reflection light intensities, and further calculating to obtain a set number of light absorbance detection values of the water sample to be detected; determining a light absorbance reference value, updating the relation curve according to a comparison relation between the light absorbance detection value of each to-be-detected water sample and the light absorbance reference value, substituting the light absorbance detection value into the updated relation curve, and calculating to obtain the water body chroma of the to-be-detected water sample. According to the invention, low-range high-precision real-time automatic water body chromaticity detection can be realized, the precision is high, and detection consumables are not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of water body chromaticity detection, and in particular to a water body chromaticity detection method. Background Art

[0002] The newly released GB5749-2022 "Sanitary Standards for Drinking Water" has stricter color detection indicators in the centralized water supply sector, requiring no more than 15 degrees; the color value of treated drinking water is required to be less than or equal to 5 degrees. The existing national color detection standards mainly use visual colorimetry to visually compare the water sample to be tested with platinum-cobalt standard solutions of different chromaticities. This method has low accuracy and cannot be distinguished by the naked eye below the low range of 30 degrees.

[0003] At present, online colorimetric detection equipment using optical principles is mostly used in high-concentration application scenarios such as sewage, and the detection accuracy is generally greater than ±5% FS. If it is applied to low-range scenarios such as drinking water, it will have low accuracy and poor stability. The imported laboratory desktop equipment that can meet high-precision detection is generally capable of 1% FS, but the price is very expensive.

[0004] The main reasons that affect stability and accuracy are that the light source is affected by the ambient temperature and the irregular attenuation over time. In addition, the system will also have irregular signal drift over time. Therefore, a detection method is needed to solve the above problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a water body chromaticity detection method, which can realize low-range and high-precision real-time automatic water body chromaticity detection with high accuracy and without the need for detection consumables.

[0006] The technical solution adopted by the present invention to solve the technical problem is: to provide a water body chromaticity detection method, comprising the following steps:

[0007] Splitting the light source to obtain reflected light and transmitted light;

[0008] Obtaining the intensity of the transmitted light after passing through a plurality of standard solutions of known chromaticity, and the intensity of the reflected light at a corresponding moment, and analyzing to obtain a relationship curve between the chromaticity of the water body and the light absorbance;

[0009] Collect the real-time transmitted light intensity and real-time reflected light intensity of several water samples to be tested, wherein the real-time transmitted light intensity is the light intensity after the transmitted light passes through the water sample to be tested, and the real-time reflected light intensity is the light intensity of the reflected light at the corresponding moment, and calculate the light absorbance detection value;

[0010] Based on the comparison relationship between the current light absorbance detection value and the set light absorbance reference value, determine whether the change in the water chromaticity of the water sample to be tested is caused by the system parameter drift. If it is not caused by the system parameter drift, select one of the light absorbance detection values ​​to substitute into the relationship curve to calculate the water chromaticity of the water sample to be tested. Otherwise, update the relationship curve, and select one of the light absorbance detection values ​​to substitute into the updated relationship curve to calculate the water chromaticity of the water sample to be tested.

[0011] Furthermore, obtaining the intensity of the transmitted light after passing through a plurality of standard solutions of known chromaticity, and the intensity of the corresponding reflected light, comprises:

[0012] Detecting the zero-point mark liquid to obtain a first transmitted light intensity and a first reflected light intensity, wherein the first transmitted light intensity is the light intensity of the transmitted light after passing through the zero-point mark liquid, and the first reflected light intensity is the light intensity of the reflected light at a corresponding moment;

[0013] A plurality of standard solutions of different chromaticities are detected to obtain a plurality of second transmitted light intensities and a plurality of second reflected light intensities, wherein the second transmitted light intensity is the light intensity converted into the transmitted light after passing through the standard solutions of different chromaticities, and the second reflected light intensity is the light intensity of the reflected light at the corresponding moment.

[0014] Furthermore, the analysis obtains a relationship curve between water body chromaticity and light absorbance, including:

[0015] Calculating the attenuation ratio of any second reflected light intensity relative to the first reflected light intensity, and then estimating the intensity of the transmitted light before passing through the standard solution of corresponding chromaticity as the third transmitted light intensity;

[0016] Calculating a difference between the second transmitted light intensity and the third transmitted light intensity as a transmitted light detection difference;

[0017] The transmitted light detection difference corresponding to all the standard solutions of different chromaticities is obtained, and a relationship curve between the chromaticity of the water body and the light absorbance is obtained by fitting.

[0018] Furthermore, the transmitted light detection difference is calculated by the following formula:

[0019]

[0020] Furthermore, the light absorbance detection value is calculated by the following formula:

[0021]

[0022] Furthermore, the relationship curve between the chromaticity of the water body and the light absorbance is a piecewise linear function based on different chromaticity intervals.

[0023] Furthermore, the method of determining whether the change in water body chromaticity is caused by system parameter drift according to the comparison relationship between the light absorbance detection value of the water sample to be tested and the set light absorbance reference value includes:

[0024] The difference between the current light absorbance detection value of the water sample to be tested and the set light absorbance reference value is calculated. If the obtained difference is not greater than the set threshold, it is considered that the change in water body chromaticity is caused by system parameter drift.

[0025] Further, the step of selecting one of the light absorbance detection values ​​and substituting it into the relationship curve to calculate the water chromaticity of the water sample to be tested includes:

[0026] Determine whether the current value is the Nth light absorbance detection value, and if so, substitute the N / 2th light absorbance detection value into the relationship curve to calculate the water chromaticity of the water sample to be tested, where N is not greater than M;

[0027] Return to the step of collecting the real-time transmitted light intensity and the real-time reflected light intensity of a plurality of water samples to be tested.

[0028] Further, the updating of the relationship curve and the selection of one of the light absorbance detection values ​​to substitute into the updated relationship curve to calculate the water chromaticity of the water sample to be tested include:

[0029] Determine whether the current value is the Mth light absorbance detection value, and if so, calculate the difference between the M / 2th light absorbance detection value and the set light absorbance reference value, and move the relationship curve along the light absorbance dimension by the difference;

[0030] Substituting the M / 2th light absorbance detection value into the relationship curve, and calculating the water chromaticity of the water sample to be tested;

[0031] Setting the light absorbance reference value as the Mth light absorbance detection value;

[0032] Return to the step of collecting the real-time transmitted light intensity and the real-time reflected light intensity of a plurality of water samples to be tested.

[0033] Furthermore, the first reflected light intensity, the first transmitted light intensity, the second reflected light intensity, the second transmitted light intensity, the real-time reflected light intensity and the real-time transmitted light intensity are all light intensities converted into electrical signals.

[0034] Furthermore, the detection of the standard solution and the water sample to be detected is obtained after the detection probe is placed in the liquid and stabilized.

[0035] Beneficial Effects

[0036] Due to the adoption of the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention divides the light source into two paths, reflected light and transmitted light, by using a spectroscope, and calculates the attenuation ratio of the light source using the light intensity information of the reflected light, and then calculates the light absorbance of the water sample, and at the same time designs a compensation algorithm for online automatic calibration compensation, infers the cause of the change in water body chromaticity based on the real-time detected data, and adopts different compensation strategies for different causes, thereby solving the problem of irregular attenuation changes of the detection light source and the system, and making the system output more stable and more accurate in detection of low-range water samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of light intensity voltage signal acquisition according to an embodiment of the present invention;

[0038] Figure 2 It is a flow chart of the automatic calibration compensation calculation method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0040] The embodiment of the present invention relates to a method for detecting the chromaticity of a water body, comprising the following steps:

[0041] S0 Figure 1 As shown, the 365nm wavelength LED detection light source is passed through the spectroscope, and the 90° direction light is directly received by the photocell as compensation for the original light source. After the 180° transmitted light passes through the glass window into the circulating water sample, the detection light signal is received by the photocell behind the detection glass window.

[0042] S1 analysis obtains the relationship curve between water chromaticity and light absorbance. The specific method is as follows:

[0043] Assume that the reflected light from the light source through the spectroscope is received by the photodiode and the output real-time voltage signal is V 反保 , the real-time voltage signal output by the photodiode after the water sample is transmitted is V 透保 ;

[0044] After the detection probe is placed in different color standard liquids [CI0, CI1, CI2, CI3] and stabilized, the current real-time reflected light voltage signal is saved as [V 反0 ,V 反1 ,V 反2 ,V 反3] and the real-time transmitted light voltage signal is [V 透0 ,V 透1 ,V 透2 ,V 透3 ];

[0045] Calculate the attenuation ratio of the light source output K = [K0, K1, K2, K3],

[0046] in

[0047] K0=V 反0 / V 反保

[0048] K1=V 反1 / V 反保

[0049] K2=V 反2 / V 反保

[0050] K3=V 反3 / V 反保 ;

[0051] Fit the calculated transmission voltage signal [Y0, Y1, Y2, Y3] of the light source, where

[0052] Y0=K0*V 透保

[0053] Y1=K1*V 透保

[0054] Y2=K2*V 透保

[0055] Y3=K3*V 透保 ;

[0056] Calculate the signal change S = [S0, S1, S2, S3] after the light source is absorbed by the water sample, where

[0057] S0=Y0-V 透0

[0058] S1=Y1-V 透1

[0059] S2=Y2-V 透2

[0060] S3=Y3-V 透3 ;

[0061] Four points [(S0,CI0), (S1,CI1), (S2,CI2), (S3,CI3)] are obtained, among which CI0 and CI3 can cover the detection range, and the relationship curve between chromaticity and absorbance is fitted:

[0062] f(x)=k(x+c)+b

[0063] x∈[S0,S1)k=k1,b=b1

[0064] x∈[S1,S2)k=k2,b=b2

[0065] x∈[S2,S3]k=k3,b=b3

[0066] The default value is c=0.

[0067] S2 performs online real-time detection on the water sample to be tested, and then uses the relationship curve obtained in the previous step to output the chromaticity value in real time. The specific method is as follows:

[0068] When the system starts detection, save the current stable calculated voltage signal S 保 , the default c=0, and the chromaticity reference CI is obtained;

[0069] Get a data S every time t i , i=[0,n];

[0070] According to the sample test, a minimum voltage signal value △ is set, and the number of consecutive times z that meet the calculation conditions is set;

[0071] If |S i -S 保 |≤△, i=[0,z], then it is judged that the detection signal is affected by the environment and changes slowly. The small change in chromaticity is caused by system drift. i Select the median in the data Then the chromaticity reference line becomes CI', that is Use S i The value replaces the initial saved value S 保 Restart the judgment cycle;

[0072] If |S i -S 保 |>△, i=[0,z], it is considered that the chromaticity of the water sample does change, and S i Substitute directly into the formula, keep c unchanged, and directly output the calculated chromaticity value.

[0073] The calculation process in this embodiment is further described below with reference to specific data.

[0074] First, the relationship curve between water chromaticity and light absorbance is obtained by analysis:

[0075] Assuming that the detection probe is placed in the zero-point standard solution and stabilized, the reflected light from the light source through the spectroscope is received by the photodiode and outputs a real-time voltage signal. The voltage V saved after stabilization 反保=706.7mV, the real-time voltage signal output by the photodiode after the water sample is transmitted is V 透保 =1785.866mV;

[0076] After the detection probe is placed in different color standard liquids [CI0, CI1, CI2, CI3] = [0, 5, 16, 36] and stabilized, the current real-time reflected voltage is recorded as [V 反0 ,V 反1 ,V 反2 ,V 反3 ]=[706.1,704.9,702.5,701.9] and the real-time V is [V 透0 ,V 透1 ,V 透2 ,V 透3 ] = [1784.06, 1699.83, 1516.72, 1242.68];

[0077] Calculate the real-time change ratio of the light source output [K0, K1, K2, K3] = [0.999, 0.997, 0.994, 0.993];

[0078] Fit the stable output of the light source [Y0, Y1, Y2, Y3] = [1784.35, 1781.318, 1775.253, 1773.736];

[0079] Calculate the signal change after the light source is absorbed by the water sample S = [S0, S1, S2, S3] = [0.289, 82.318, 259.253, 531.736];

[0080] We get four points [(0.289,0), (82.318,5), (259.253,16), 531.736,36)], and then get the relationship curve between the fitted chromaticity and absorbance:

[0081] f(x)=k(x+c)+b

[0082] x∈[0.289,82.318)k=0.061, b=-0.0176

[0083] x∈[82.318,259.253)k=0.0622, b=-0.1177

[0084] x∈[259.253,531.736]k=0.0734, b=-3.0289

[0085] Wherein, c is a constant and defaults to c=0;

[0086] First, if Figure 2The automatic calibration compensation calculation method shown is:

[0087] After many tests, it was found that after the above light source compensation, in the water sample with stable chromaticity, the signal S showed a trend of slowly rising or falling to varying degrees for a long time as the environment changed, while the electrical signal in a stable environment was stable and fluctuating. Therefore, in the actual operating environment, the stable calculated voltage signal S when the system started to detect was saved. 保 , default c=0, take a data S every time t=5 i , i = [0, 24];

[0088] According to the sample test, a minimum voltage signal value of 30mV is set, and the judgment conditions include:

[0089] If |S i -S 保 |≤△, it is judged that the detection signal is affected by the environment and changes slowly. The small change of chromaticity is caused by system drift, which meets the calculation conditions of long-term drift. Set the number of consecutive times to 24, that is, i=[0,24], set the interval time to 2 hours, and the data collection is 5min / time. i Select the median S in the data 12 , that is, f(x)=k(x+c)+b, where c=S 12 -S 保 , S 24 The value replaces the initial saved value S 保 Restart the judgment cycle;

[0090] If |S i -S 保 |>△, it is considered that the chromaticity in the water sample detected does change in a short period of time, which meets the calculation conditions of large-scale real changes in a short period of time. Set the number of consecutive times to 12, that is, i=[0,12], set the interval time to 1 hour, and collect data for 5 minutes / time. Substitute S6 directly into the formula, keep c unchanged, and directly output the chromaticity value.

[0091] All changes within the formula are adjusted according to the specific test results, and different test results will be obtained.

Claims

1. A method for detecting water chromaticity, characterized in that: The following steps are involved: Splitting the light source to obtain reflected light and transmitted light; Obtaining the intensity of the transmitted light after passing through a plurality of standard solutions of known chromaticity, and the intensity of the reflected light at a corresponding moment, The relationship curve between water chromaticity and light absorbance is obtained by analysis; Collect the real-time transmitted light intensity and real-time reflected light intensity of several water samples to be tested, wherein the real-time transmitted light intensity is the light intensity after the transmitted light passes through the water sample to be tested, and the real-time reflected light intensity is the light intensity of the reflected light at the corresponding moment, and calculate the light absorbance detection value; Based on the comparison relationship between the current light absorbance detection value and the set light absorbance reference value, determine whether the change in the water chromaticity of the water sample to be tested is caused by the system parameter drift. If it is not caused by the system parameter drift, select one of the light absorbance detection values ​​to substitute into the relationship curve to calculate the water chromaticity of the water sample to be tested. Otherwise, update the relationship curve, and select one of the light absorbance detection values ​​to substitute into the updated relationship curve to calculate the water chromaticity of the water sample to be tested.

2. The method according to claim 1, characterized in that The step of obtaining the intensity of the transmitted light after passing through a plurality of standard solutions of known chromaticity, and the intensity of the corresponding reflected light, comprises: The zero-point standard liquid is detected to obtain a first transmitted light intensity and a first reflected light intensity, wherein the first transmitted light intensity is the light intensity of the transmitted light after passing through the zero-point standard liquid, and the first reflected light intensity is the light intensity of the reflected light at the corresponding moment; multiple standard liquids of different chromaticities are detected to obtain multiple second transmitted light intensities and multiple second reflected light intensities, wherein the second transmitted light intensity is the light intensity converted into the transmitted light after passing through the standard liquids of different chromaticities, and the second reflected light intensity is the light intensity of the reflected light at the corresponding moment.

3. The method according to claim 2, characterized in that The analysis obtains a relationship curve between water body chromaticity and light absorbance, including: Calculating the attenuation ratio of any second reflected light intensity relative to the first reflected light intensity, and then estimating the intensity of the transmitted light before passing through the standard solution of corresponding chromaticity as the third transmitted light intensity; Calculating a difference between the second transmitted light intensity and the third transmitted light intensity as a transmitted light detection difference; The transmitted light detection difference corresponding to all the standard solutions of different chromaticities is obtained, and a relationship curve between the chromaticity of the water body and the light absorbance is obtained by fitting.

4. The method according to claim 3, characterized in that The transmitted light detection difference is calculated by the following formula:

5. The method according to claim 4, characterized in that The light absorbance detection value is calculated by the following formula:

6. The method according to claim 1, characterized in that The relationship curve between the water body chromaticity and light absorbance is a piecewise linear function based on different chromaticity intervals.

7. The method according to claim 1, characterized in that The method of determining whether the change in water body chromaticity is caused by system parameter drift according to the comparison relationship between the light absorbance detection value of the water sample to be detected and the set light absorbance reference value comprises: The difference between the current light absorbance detection value of the water sample to be tested and the set light absorbance reference value is calculated. If the obtained difference is not greater than the set threshold, it is considered that the change in water body chromaticity is caused by system parameter drift.

8. The method according to claim 7, characterized in that The step of selecting a light absorbance detection value and substituting it into the relationship curve to calculate the water chromaticity of the water sample to be tested comprises: Determine whether the current value is the Nth light absorbance detection value, and if so, substitute the N / 2th light absorbance detection value into the relationship curve to calculate the water chromaticity of the water sample to be tested, where N is not greater than M; Return to the step of collecting the real-time transmitted light intensity and the real-time reflected light intensity of a plurality of water samples to be tested.

9. The method according to claim 7, characterized in that: The updating of the relationship curve, and selecting one of the light absorbance detection values ​​to substitute into the updated relationship curve to calculate the water chromaticity of the water sample to be tested, comprises: Determine whether the current value is the Mth light absorbance detection value, and if so, calculate the difference between the M / 2th light absorbance detection value and the set light absorbance reference value, and move the relationship curve along the light absorbance dimension by the difference; Substituting the M / 2th light absorbance detection value into the relationship curve, and calculating the water chromaticity of the water sample to be tested; Setting the light absorbance reference value as the Mth light absorbance detection value; Return to the step of collecting the real-time transmitted light intensity and the real-time reflected light intensity of a plurality of water samples to be tested.

10. The method according to claim 2, characterized in that The first reflected light intensity, the first transmitted light intensity, the second reflected light intensity, the second transmitted light intensity, the real-time reflected light intensity and the real-time transmitted light intensity are all light intensities converted into electrical signals.

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