CN115060666B - Calibration method of water quality parameter sensor and water quality parameter measuring method and device - Google Patents
Calibration method of water quality parameter sensor and water quality parameter measuring method and device Download PDFInfo
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Abstract
The invention relates to a calibration method of a water quality parameter sensor and a measurement method and a device of a water quality parameter, which are used for solving the problem of poor actual measurement precision of the existing water quality sensor. The calibration method of the water quality parameter sensor comprises the following steps: collecting a water sample; acquiring a chemical test value of a water quality parameter of a certain water sample; acquiring a sensor standard value of the water quality parameter of the water sample; a suitable linear calibration equation is obtained.
Description
Technical Field
The invention relates to the technical field of water quality detection, in particular to a calibration method of a water quality parameter sensor and a water quality parameter measuring method and device.
Background
Because the content of each organic matter in the actual river water is different and different interfering ions exist, the difference between the measured value of the sensor in the actual river water after the calibration of the standard liquid and the measured value of the sensor by the international chemical method is large, and the measurement precision of the sensor is influenced.
Disclosure of Invention
In view of the above analysis, the embodiments of the present invention provide a calibration method for a water quality parameter sensor, and a measurement method and device for a water quality parameter, so as to solve the problem of poor actual measurement accuracy of the existing water quality sensor.
In one aspect, the invention provides a calibration method of a water quality parameter sensor, which comprises the following steps:
taking a water sample;
acquiring a chemical test value of a water quality parameter of the water sample;
acquiring a sensor standard value of the water quality parameter of the water sample;
wherein, the chemical test value is A, and the standard value of the sensor is B;
if A is smaller than a first preset value, obtaining a first linear calibration relation;
if the first preset value is not more than A and not more than a second preset value, acquiring an absolute difference value of A and B; if the absolute difference value is smaller than a third preset value, obtaining a first linear calibration relation; if the absolute difference value is greater than or equal to a third preset value, acquiring the ratio of A to B; if the ratio is within a first threshold, obtaining a second linear calibration relation; if the ratio is outside the first threshold, repeating the steps until a first linear calibration relation or a second linear calibration relation is obtained;
if A is larger than a second preset value, obtaining the ratio of A to B, and if the ratio is within a second threshold value, obtaining a second linear calibration relation; if the ratio is outside the second threshold, repeating the above steps until a first linear calibration relationship or a second linear calibration relationship is obtained.
Further, the first linear calibration relationship is y = x + (a-B);
the second linear calibration relationship is y = (a/B) x;
wherein x is the sensor measurement value and y is the calibrated sensor value.
Further, the step of taking water samples comprises selecting different positions in the same water area to take the water samples.
Further, the method also comprises the steps of obtaining a water quality standard grade;
the water quality standard grade comprises I-type water, II-type water, III-type water, IV-type water and V-type water;
each type of water quality standard grade has a unique corresponding water quality parameter index value;
the first preset value is a water quality parameter index value of the class III water;
the second preset value is a water quality parameter index value of the IV-class water.
Further, the water quality parameters comprise ammonia nitrogen and CODcr;
if the water quality parameter is ammonia nitrogen, the first preset value =1, the second preset value =1.5, the third preset value =0.5, the first threshold value is [0.5,2], and the second threshold value is [0.3,3];
if the water quality parameter is CODcr, the first preset value =20, the second preset value =30, the third preset value =5, the first threshold value is [0.5,2], and the second threshold value is [0.3,3].
Further, the obtaining of the sensor standard value of the water quality parameter of the water sample comprises putting the sensor into the water sample and collecting the sensor measurement value once per minute.
Further, the sensor standard value is one of a last sensor measurement value of the water sample, a weighted average of partial sensor measurement values of the water sample, or a weighted average of all sensor measurement values of the water sample.
Further, the calculation formula of the sensor standard value is as follows: b =0.5 × B1+0.3 × B2+0.2 × B3, where B1, B2, and B3 are sensor measurement values, B1 is a sensor measurement value of the last sensor, an absolute difference between B2 and B1 is smaller than a third preset value, and an absolute difference between B3 and B1 is smaller than the third preset value.
On the other hand, the invention provides a water quality parameter measuring method, which comprises the following steps:
s100: obtaining a first linear calibration relation or a second linear calibration relation by the calibration method;
s200: and collecting a water sample at any point in the water area to obtain a sensor measurement value of the water sample, and obtaining a calibrated sensor value through the first linear calibration relation or the second linear calibration relation obtained in the step S100.
In another aspect, the present invention provides a water quality parameter measuring apparatus, including:
a sensing measurement device comprising a sensor;
the input terminal comprises an input interface and an output interface, wherein the input interface can input a chemical test value of at least one water quality parameter; the output interface can output the calibrated sensor value of at least one water quality parameter;
the processing center is in signal connection with the sensing measurement equipment and the input terminal, and is configured to receive a sensor measurement value of the sensing measurement equipment, receive a chemical test value of the input terminal, run the calibration method and calibrate the sensor value to the input terminal.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
(1) The method combines standard solution calibration and actual water sample calibration, and carries out rapid modeling on the pollution parameters in the actual river water through a little water sample, thereby improving the accuracy of the measurement data of the water quality sensor and reducing the time required by calibration;
(2) After modeling, the test data is closer to the test of a national standard chemical method, so that the measurement error caused by various organic matters and interfering ions in water when the actual water body is measured by an electrode method and a spectrum method is greatly reduced, and the reliability of the measurement data is improved;
(3) The ammonia nitrogen and CODcr rapid calibration uses the vicinity of the III water value as much as possible to carry out the best calibration effect;
(4) The data deviation of different water samples modeled by the method can be less than 30%.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
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The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a histogram of deviations corresponding to Table 2 in the example embodiment;
FIG. 2 is a histogram of deviations corresponding to Table 3 in the example embodiment.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention and not to limit its scope.
After the calibration of the standard liquid is finished, the water quality sensor is directly connected with equipment for testing, the difference between the measured values of an electrode method and a spectroscopy sensor and the chemical method is very small under the condition of testing the standard liquid, but the difference between the actual electrode method and the spectroscopy sensor in river water and the national standard chemical method is large. And because the actual water sample is more complicated by adopting a river water multi-point calibration method, two water samples with different concentrations need to be taken at a far point position, or the concentration of the river water at the same point position needs to be changed for a long time.
The components in the river water on site are more complex than those of the standard liquid in a laboratory, the sensor calibrated by the standard liquid is directly used for testing, data is different from the national standard chemical method to a certain extent, a certain linear relation exists between the sensor and the measured value of the river in the same region by the national standard method, the measured value of the equipment can be optimized through modeling, so that the reading of the equipment is more accurate, namely, the water quality parameter value measured by the sensor is calibrated by obtaining a proper linear equation through modeling, so that the measured value of the sensor is closer to the measured value of the national standard chemical method after being calibrated.
Because the standard detection reagent pack is relatively close to the data of the national standard chemical method, the standard detection reagent pack and the measured value of the sensor are used for modeling treatment during manual calibration.
Aiming at the measurement of two parameters of ammonia nitrogen and CODcr (dichromate index), after the calibration of the standard solution is finished, a manual calibration link is added before the actual river water test, and the rapid modeling is carried out by a little river water. After modeling, the test data is closer to the test of a national standard chemical method, so that the measurement error caused by various organic matters and interfering ions in water when the actual water body is measured by an electrode method and a spectrum method is greatly reduced, and the reliability of the measurement data is improved.
Calibration of the sensor standard solution is recommended to be performed once a week under conditional conditions, and manual calibration is recommended to be performed once a day before each river test.
The invention discloses a calibration method of a water quality parameter sensor, which comprises the following steps:
collecting a water sample;
acquiring a chemical test value of a water quality parameter of a certain water sample;
acquiring a sensor standard value of the water quality parameter of the water sample;
wherein, the chemical test value is A, and the standard value of the sensor is B;
if A is smaller than a first preset value, a first linear calibration relation is obtained;
if the first preset value is not more than A and not more than a second preset value, acquiring an absolute difference value of A and B; if the absolute difference value is smaller than a third preset value, obtaining a first linear calibration relation; if the absolute difference value is larger than or equal to a third preset value, acquiring a ratio of the judgment A to the judgment B; if the ratio is within a first threshold, obtaining a second linear calibration relationship; if the ratio is outside the first threshold, repeating the steps until a first linear calibration relation or a second linear calibration relation is obtained;
if A is larger than a second preset value, obtaining the ratio of A to B, and if the ratio is within a second threshold value, obtaining a second linear calibration relation; if the ratio is outside the second threshold, repeating the above steps until a first linear calibration relationship or a second linear calibration relationship is obtained.
The water sample capable of obtaining the linear calibration relation can be called a modeling water sample, namely the linear calibration relation successful in modeling is obtained through the modeling water sample, the measured value of the sensor of any water sample in the water area is calibrated through the obtained linear calibration relation, the calibrated sensor value is obtained, and then the more accurate statistical record of the water area water quality parameters is obtained, so that the problem that the actual measurement precision of the water quality parameter sensor is poor is solved, the more real water area water quality parameters are obtained, and the method has practical significance for water area planning and management.
The method can be conveniently operated on site by adopting one-point quick calibration, but simultaneously the difficulty is increased by linear modeling, because the absolute difference value of the two methods under low concentration is smaller, but a large ratio can exist, and the absolute difference value of the two methods under high concentration can be larger, but the ratio is smaller, so that the classification grade of the corresponding pollutants of the water sample is referred, and the first preset value and the second preset value of the corresponding pollutants are confirmed.
Specifically, the first linear calibration relationship is y = x + (a-B), and the second linear calibration relationship is y = (a/B) x, where x is a sensor measurement value and y is a calibrated sensor value. Namely, a sensor measurement value x of any water sample in the water area is substituted into y = x + (A-B) or y = (A/B) x, so that a calibrated sensor value y can be obtained, the calibration of the measurement value of the sensor of any water sample in the water area is realized, the calibrated sensor value y is closer to a chemical test value of the water sample relative to the sensor measurement value x, and the calibrated sensor value y is more accurate relative to the sensor measurement value x.
Namely, a calibrated linear relation can be obtained by modeling a water sample, and the formula is a linear equation of a unary with y = ax + b.
If A is less than the first preset value, a =1,b = A-B, i.e. y = x + A-B;
if the first preset value is not more than A and not more than a second preset value, obtaining | A-B |; if | a-B | < the third preset value, then a =1,b = a-B, i.e. y = x + a-B; if the absolute value of A-B is more than or equal to a third preset value, obtaining A/B; if a/B is within the first threshold, then a = a/B, B =0, i.e. y = (a/B) x; if the A/B is beyond the first threshold, repeating the steps, namely, taking the water sample again, and obtaining the chemical test value and the sensor standard value of the new water sample again until a first linear calibration relation (y = x + A-B) or a second linear calibration relation (y = (A/B) x) can be obtained;
if A is larger than a second preset value, obtaining A/B; if a/B is within the second threshold, then a = a/B, B =0, i.e. y = (a/B) x; and if the A/B is beyond the second threshold value, repeating the steps, namely, taking the water sample again, and acquiring the chemical test value and the sensor standard value of the new water sample again until the first linear calibration relation (y = x + A-B) or the second linear calibration relation (y = (A/B) x) can be obtained.
And the water sampling comprises the step of selecting different positions in the same water area to sample the water samples. Preferably, when the water samples need to be collected again, different water samples are taken from different positions in the same water area.
The sensor is placed in a water sample, measurement data (the acquired data are sensor measurement values) is acquired every minute, and the sensor measurement values at each time are recorded and stored. That is, the standard value of the sensor for acquiring the water quality parameters of the water sample comprises the steps of putting the sensor into the water sample and collecting the measured value of the sensor once every minute.
Preferably, the sensor standard value B is one of the last sensor measurement of the water sample, a weighted average of partial sensor measurements of the water sample, or a weighted average of all sensor measurements of the water sample.
In this embodiment, the sensor standard value B is a weighted average of the measured values of the partial sensors, specifically, a calculation formula of the sensor standard value is as follows: b =0.5 × B1+0.3 × B2+0.2 × B3, where B1, B2, and B3 are sensor measurement values, B1 is a sensor measurement value of the sensor last time, an absolute difference between B2 and B1 is smaller than a third preset value, an absolute difference between B3 and B1 is smaller than the third preset value, that is, | B2-B1| < the third preset value, | B3-B1| < the third preset value, that is, B2, and B3 are preferably obtained from measurement values close to B1, and measurement times of the three are closer to each other, so that it is further preferable that, after a measurement value acquired by a sensor inserted into a water sample is stable, a sensor measurement value is obtained, and then a sensor standard value B is obtained from the sensor measurement value.
The chemical test value A of the water quality parameter of the water sample is measured through the standard reagent pack, the method is simple and rapid, and the obtaining speed of the calibration formula is improved.
The first preset value and the second preset value are related to the water quality of the water area, and the method further comprises the step of obtaining a water quality standard grade.
The water area can be divided into I type water, II type water, III type water, IV type water and V type water according to the water quality standard grade, namely the water quality standard grade comprises the I type water, the II type water, the III type water, the IV type water and the V type water.
Each type of water quality standard grade has a unique corresponding water quality parameter index value, the first preset value is the water quality parameter index value of type III water, and the second preset value is the water quality parameter index value of type IV water.
The water quality parameters which are usually measured in the water area comprise ammonia nitrogen and CODcr, and the table 1 shows standard values of the ammonia nitrogen and the CODcr corresponding to the five water quality standard grades.
TABLE 1-Standard value Table of Ammonia nitrogen and CODcr corresponding to five types of water quality standard grade
From the above, if the water quality parameter is ammonia nitrogen, the first preset value =1, and the second preset value =1.5; and if the water quality parameter is CODcr, the first preset value =20, and the second preset value =30.
The third preset value, the first threshold value and the second threshold value are related to the measuring range, the sensitivity and the like of the sensor and are empirical constants or ranges, if the water quality parameter is ammonia nitrogen, the third preset value =0.5, the first threshold value is [0.5,2], and the second threshold value is [0.3,3]; if the water quality parameter is CODcr, the third preset value =5, the first threshold value is [0.5,2], and the second threshold value is [0.3,3].
The calibration method for the ammonia nitrogen sensor in a certain water area comprises the following steps:
collecting a water sample;
obtaining a chemical test value, A, of an ammonia nitrogen parameter of the water sample (Ammonia nitrogen) The ammonia nitrogen reagent kit is a reagent kit produced by the Japan Co-standing physicochemical research institute (KYORITSU CHEMICAL-CHECK lab.. Corp) in the market;
obtaining a sensor standard value, B, of an ammonia nitrogen parameter of the water sample (Ammonia nitrogen) Taking the measured values B1 of three sensors of the ammonia nitrogen sensor (Ammonia nitrogen) 、B2 (Ammonia nitrogen) 、B3 (Ammonia nitrogen) ，B (Ammonia nitrogen) =0.5×B1 (Ammonia nitrogen) +0.3×B2 (Ammonia nitrogen) +0.2×B3 (Ammonia nitrogen) Wherein, B1 (Ammonia nitrogen) Is the latest sensor measurement value, | B2 (Ammonia nitrogen) -B1 (Ammonia nitrogen) |＜0.5，|B3 (Ammonia nitrogen) -B1 (Ammonia nitrogen) |＜0.5。
If A (Ammonia nitrogen) < 1, a first linear calibration relationship is obtained, y = x + a (Ammonia nitrogen) -B (Ammonia nitrogen) ；
If 1 is not more than A (Ammonia nitrogen) When the ratio is less than or equal to 1.5, obtaining A (Ammonia nitrogen) And B (Ammonia nitrogen) If the absolute difference is less than 0.5, then | A (Ammonia nitrogen) -B (Ammonia nitrogen) |<0.5, obtain the first linear calibration offLine, y = x + a (Ammonia nitrogen) -B (Ammonia nitrogen) (ii) a If the absolute difference is greater than or equal to 0.5, | A (Ammonia nitrogen) -B (Ammonia nitrogen) If | ≧ 0.5, then A is obtained (Ammonia nitrogen) And B (Ammonia nitrogen) If said ratio lies in [0.5,2]]Internal, i.e. (A) (Ammonia nitrogen) /B (Ammonia nitrogen) ）∈[0.5，2]Then, the second linear calibration relationship is obtained as y = (A) (Ammonia nitrogen) /B (Ammonia nitrogen) ) x; if the ratio lies in [0.5,2]]Outer, i.e. (A) (Ammonia nitrogen) /B (Ammonia nitrogen) ）∉[0.5，2]Repeating the steps, namely re-taking the water sample, and re-obtaining the chemical test value and the sensor standard value of the new water sample until the first linear calibration relation or the second linear calibration relation is obtained;
if A (Ammonia nitrogen) If > 1.5, then A is obtained (Ammonia nitrogen) And B (Ammonia nitrogen) The ratio of (A) to (B); if the ratio lies in [0.3,3]Internal, i.e. (A) (Ammonia nitrogen) /B (Ammonia nitrogen) ）∈[0.3，3]Then a second linear calibration relationship is obtained, y = (a) (Ammonia nitrogen) /B (Ammonia nitrogen) ) x; if the ratio lies in [0.3,3]Furthermore, (A) (Ammonia nitrogen) /B (Ammonia nitrogen) ）∉[0.3，3]And repeating the steps, namely re-taking the water sample, and re-acquiring the chemical test value and the sensor standard value of the new water sample until the first linear calibration relation or the second linear calibration relation is obtained.
Example 1 Water sample 1,A as in Table 2 (Ammonia nitrogen) =2.9，B (Ammonia nitrogen) =4.17，A (Ammonia nitrogen) ＞1.5，0.3＜A (Ammonia nitrogen) /B (Ammonia nitrogen) =0.7 < 3, so y =0.70x;
when x =2.15, y =0.70 × 2.15=1.51, deviation =100% × |1.7-1.50|/1.70=12%;
when x =3.03, y =0.70 × 3.03=2.12, deviation =100% × |2.3-2.12|/2.3=8%;
when x =2.59, y =0.70 × 2.59=1.81, deviation =100% × |1.9-1.81|/1.9=5%;
when x =1.93, y =0.70 × 1.93=1.35, deviation =100% × |1.5-1.35|/1.5=10%;
when x =1.74, y =0.70 × 1.74=1.22, deviation =100% × |1.2-1.22|/1.2=2%;
when x =1.98, y =0.70 × 1.98=1.39, deviation =100% × 1.55-1.39|/1.55=10%;
when x =2.19, y =0.70 × 2.19=1.53, deviation =100% × |1.4-1.53|/1.4=9%.
TABLE 2 Ammonia nitrogen measurement calibration chart for certain water area
The calibration method of the CODcr sensor aiming at a water area comprises the following steps:
collecting a water sample;
obtaining a chemical test value, A, of a CODcr parameter of the water sample （CODcr） The kit is a kit produced by commercially available Japan Co-vertical physicochemical research institute (KYORITSU CHEMICAL-CHECK lab.
Obtaining a sensor standard value, B, of a CODcr parameter of the water sample （CODcr） Taking three sensor measured values B1 of CODcr sensor （CODcr） 、B2 （CODcr） 、B3 （CODcr） ，B （CODcr） =0.5×B1 （CODcr） +0.3×B2 （CODcr） +0.2×B3 （CODcr） Wherein, B1 （CODcr） Is the latest sensor measurement value, | B2 （CODcr） -B1 （CODcr） |＜5，|B3 （CODcr） -B1 （CODcr） |＜5。
If A （CODcr） If < 20, a first linear calibration relationship is obtained, y = x + A （CODcr） -B （CODcr） ；
If 20 is less than or equal to A （CODcr） If the ratio is less than or equal to 30, obtaining A （CODcr） And B （CODcr） The absolute difference of (a); if the absolute difference is less than 5, i.e. | A （CODcr） -B （CODcr） |<5, then obtain the first linear calibration relation, y = x + a （CODcr） -B （CODcr） (ii) a If said absoluteThe difference is greater than or equal to 5, | A （CODcr） -B （CODcr） If | ≧ 5, obtain A （CODcr） And B （CODcr） If the ratio lies in [0.5,2']Internal, i.e. (A) （CODcr） /B （CODcr） ）∈[0.5，2]Then a second linear calibration relationship is obtained, y = (a) （CODcr） /B （CODcr） ) x; if the ratio lies in [0.5,2]]Outer, i.e. (A) （CODcr） /B （CODcr） ）∉[0.5，2]Repeating the steps, namely re-taking the water sample, and re-obtaining the chemical test value and the sensor standard value of the new water sample until the first linear calibration relation or the second linear calibration relation is obtained;
then A is （CODcr） If > 30, obtaining A （CODcr） And B （CODcr） If the ratio lies in [0.3,3']Inner, i.e. (A) （CODcr） /B （CODcr） ）∈[0.3，3]Then a second linear calibration relationship is obtained, y = (a) （CODcr） /B （CODcr） ) x; if the ratio exceeds [0.3,3]I.e. (A) （CODcr） /B （CODcr） ）∉[0.3，3]And repeating the steps, namely re-taking the water sample, and re-acquiring the chemical test value and the sensor standard value of the new water sample until the first linear calibration relation or the second linear calibration relation is obtained.
Example 2 Water sample 3,A as in Table 3 （CODcr） =26.4，B （CODcr） =15.5，20＜A （CODcr） ＜30，|A （CODcr） -B （CODcr） |=10.9＞5，0.5＜A （CODcr） /B （CODcr） =1.7 < 2, so y =1.7x;
when x =23.2, y =1.7 × 23.2=39.44, deviation =100% × |34.6-39.44|/34.6=14%;
when x =11.3, y =1.7 × 11.3=19.21, deviation =100% × |18.5-19.21|/18.5=4%;
when x =9.7, y =1.7 × 9.7=16.49, deviation =100% × i 16.8-16.49|/16.8=2%;
when x =19.4, y =1.7 × 19.4=32.98, deviation =100% × |28-32.98|/28=18%;
when x =16.7, y =1.7 × 16.7=28.39, deviation =100% × |24.3-28.39|/24.3=17%;
when x =17, y =1.7 × 17=28.9, deviation =100% × |29.3-28.9|/29.3=1%;
when x =25.1, y =1.7 × 25.1=42.67, deviation =100% × l 39.4-42.67|/39.4=8%;
when x =22, y =1.7 × 22=37.4, deviation =100% × |36.4-37.4|/36.4=3%;
TABLE 3 CODcr MEASUREMENT CALIBRATION TABLE FOR WATER-AREA
The deviation histograms corresponding to the table 2 and the table 3 are respectively shown as a figure 1 and a figure 2, and it can be seen from the figure 1 and the figure 2 that the ammonia nitrogen and the CODcr are calibrated by using water samples at different points of the river according to the calibration method, the deviation of the results is far smaller than that of the original data, and the deviation of the results is below 30%.
The result deviation is the deviation of the calibrated sensor value from the chemical test value, and the result deviation =100% × | calibrated sensor value-chemical test value |/chemical test value.
The raw data deviation is the deviation of the sensor measurement value from the chemical test value, and the raw data deviation =100% × | sensor measurement value-chemical test value |/chemical test value.
The calibrated sensor value in the result deviation formula is obtained by substituting the sensor measurement value in the raw data deviation formula into the corresponding first linear calibration relation or second linear calibration relation.
Different water quality parameters use different standard detection reagent packages and sensors.
The invention discloses a water quality parameter measuring method, which is used for measuring a certain water quality parameter of a certain water area and comprises the following steps:
s100: obtaining a first linear calibration relation or a second linear calibration relation by the calibration method: y = ax + b;
s200: and collecting a water sample at any point in the water area to obtain a sensor measurement value x of the water sample, and obtaining a calibrated sensor value y through the first linear calibration relation or the second linear calibration relation obtained in the step S100.
Specifically, step S100 includes the steps of:
s101: taking a water sample;
s102: respectively detecting S101 water samples by using a standard detection reagent bag and a sensor, acquiring a chemical test value A and a sensor measurement value of the water quality parameter of the water samples, and acquiring a sensor standard value B of the water quality parameter of the water samples according to the sensor measurement value;
s103: if A is less than the first preset value, a =1,b = A-B, i.e. y = x + A-B;
if the first preset value is not more than A and not more than a second preset value, obtaining | A-B |; if | a-B | < a third preset value, then a =1,b = a-B, i.e. y = x + a-B; if the absolute value of A-B is more than or equal to a third preset value, obtaining A/B; if a/B is within the first threshold, then a = a/B, B =0, i.e. y = (a/B) x; if the A/B is out of the first threshold value, repeating the steps, namely, taking the water sample again, and obtaining the chemical test value and the sensor standard value of the new water sample again until a first linear calibration relation (y = x + A-B) or a second linear calibration relation (y = (A/B) x) can be obtained;
if A is larger than a second preset value, obtaining A/B; if a/B is within the second threshold, then a = a/B, B =0, i.e. y = (a/B) x; and if the A/B is beyond the second threshold value, repeating the steps, namely, taking the water sample again, and acquiring the chemical test value and the sensor standard value of the new water sample again until the first linear calibration relation (y = x + A-B) or the second linear calibration relation (y = (A/B) x) can be obtained.
And preferably, all the water samples are sampled from the middle part of the water area to be detected, and the supernatant is taken after the water samples are stood for a certain time to obtain the required water sample. For example, a water taking bucket is used for sampling about 500mL from the middle part of a water area to be detected, and after standing for 5min, supernatant is taken for testing.
It should be noted that a water sample near the sewage draining exit does not need to be collected, so that the test result is not accurate enough.
In step S100, approximately 3/4 of the sampled water is used for chemical measurement by the standard detection kit, resulting in a chemical test value A.
In step S102, the sensor is calibrated with the sensor standard solution before the water sample is measured, the calibration of the sensor standard solution is preferably performed at least once a week, and the calibration of the calibration formula in step S100 is preferably performed at least once before the actual test (which refers to the test of any point in the water in step S200) in each water area every day.
In step S102, the sensor standard value B is one of the latest sensor measurement value of the water sample, a weighted average of partial sensor measurement values of the water sample, or a weighted average of all sensor measurement values of the water sample. In this embodiment, the sensor standard value B is a weighted average of the measured values of the partial sensors, specifically, a calculation formula of the sensor standard value is as follows: b =0.5 × B1+0.3 × B2+0.2 × B3, where B1, B2, and B3 are sensor measurement values, B1 is a sensor measurement value of the sensor last time, an absolute difference between B2 and B1 is smaller than a third preset value, an absolute difference between B3 and B1 is smaller than the third preset value, that is, | B2-B1| < the third preset value, | B3-B1| < the third preset value, that is, B2, and B3 are preferably obtained from measurement values close to B1, and measurement times of the three are closer to each other, so that it is further preferable that, after a measurement value acquired by a sensor inserted into a water sample is stable, a sensor measurement value is obtained, and then a sensor standard value B is obtained from the sensor measurement value.
When using the sensor to test the water sample, need to guarantee that the water sample can not cross the probe of sensor.
One specific embodiment of the present invention also discloses a water quality parameter measuring device, comprising:
the sensing measurement equipment comprises a sensor, wherein the sensor is provided with a probe and is used for detecting water quality parameters of a water sample to obtain a sensor measurement value;
the input terminal comprises an input interface and an output interface, wherein the input interface can input a chemical test value A of at least one water quality parameter; the output interface can output a calibrated sensor value y of at least one water quality parameter; the input terminal can be a mobile phone, a tablet, a computer notebook and the like, and a movable input terminal such as a mobile phone and the like is preferred;
and the processing center is in signal connection with the sensing measurement equipment and the input terminal, and is configured to receive a sensor measurement value of the sensing measurement equipment, receive a chemical test value of the input terminal, run the calibration method and output a calibrated sensor value y to the input terminal.
The method comprises the steps of firstly obtaining a sensor measurement value and a chemical test value A of a water quality parameter of a certain water sample by using a sensor and a standard detection reagent bag, uploading the two values to a processing center through sensing measurement equipment and a mobile phone APP, receiving the sensor measurement value and the chemical test value A by the processing center, firstly processing the received sensor measurement value to obtain a chemical standard value B, then operating the calibration method to obtain a calibration formula or reminding a user to resample, determining a final calibration formula (a first linear calibration relation or a second linear calibration relation) of a certain water area, and storing the calibration formula in the processing center. And then, carrying out a normal test process of the water area through the sensing measurement equipment, namely, after the sensing measurement equipment acquires the sensor measurement value x of any water sample in the water area, synchronously uploading the sensor measurement value x to a processing center, carrying the sensor measurement value x into the calibration formula by the processing center to calculate to obtain a calibrated sensor value y, and displaying the calibrated sensor value y on the mobile phone APP.
The output interface of the input terminal can simultaneously output a plurality of groups of corresponding sensor measured values x and calibrated sensor values y, so that a user can know the condition of the water quality parameters of a certain water area and the calibration result of the sensor.
The processing center is configured to process a plurality of sets of corresponding sensor measurement values x and calibrated sensor values y at the same time to form a more intuitive visual chart, and output the visual chart to the input terminal. So that the user can more intuitively and clearly know the water quality parameter of a certain water area and the calibration result of the sensor.
Those skilled in the art will appreciate that all or part of the processes for implementing the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, for instructing the relevant hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.
While the invention has been described with reference to specific preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
Claims (9)
1. A calibration method of a water quality parameter sensor is characterized by comprising the following steps:
collecting a water sample;
acquiring a chemical test value of a water quality parameter of the water sample;
acquiring a sensor standard value of the water quality parameter of the water sample;
wherein, the chemical test value is A, and the standard value of the sensor is B;
if A is smaller than a first preset value, a first linear calibration relation is obtained;
if the first preset value is less than or equal to the second preset value, acquiring an absolute difference value of A and B; if the absolute difference value is smaller than a third preset value, obtaining a first linear calibration relation; if the absolute difference value is greater than or equal to a third preset value, acquiring the ratio of A to B; if the ratio is within a first threshold, obtaining a second linear calibration relationship; if the ratio is outside the first threshold value, re-taking the water sample, and re-obtaining the chemical test value and the sensor standard value of the new water sample until a first linear calibration relation or a second linear calibration relation is obtained;
if A is larger than a second preset value, obtaining the ratio of A to B, and if the ratio is within a second threshold value, obtaining a second linear calibration relation; if the ratio is outside the second threshold value, re-taking the water sample, and re-obtaining the chemical test value and the sensor standard value of the new water sample until a first linear calibration relation or a second linear calibration relation is obtained;
the water quality parameters comprise ammonia nitrogen and CODcr, if the water quality parameters are ammonia nitrogen, the first preset value =1, the second preset value =1.5, the third preset value =0.5, the first threshold value is [0.5,2], and the second threshold value is [0.3,3]; if the water quality parameter is CODcr, the first preset value =20, the second preset value =30, the third preset value =5, the first threshold value is [0.5,2], and the second threshold value is [0.3,3].
2. The calibration method according to claim 1, wherein the first linear calibration relationship is y = x + (a-B);
the second linear calibration relationship is y = (a/B) x;
wherein x is the sensor measurement value and y is the calibrated sensor value.
3. The calibration method of claim 1, wherein said sampling water comprises selecting to sample water at different locations in the same body of water.
4. The calibration method according to claim 1, wherein the method further comprises obtaining a water quality standard grade;
the water quality standard grade comprises I-type water, II-type water, III-type water, IV-type water and V-type water;
each type of water quality standard grade has a unique corresponding water quality parameter index value;
the first preset value is a water quality parameter index value of the III-class water;
the second preset value is a water quality parameter index value of the IV-class water.
5. The calibration method according to claim 1, wherein the obtaining of the sensor standard value of the water quality parameter of the water sample comprises placing a sensor in the water sample and collecting the sensor measurement value once per minute.
6. The calibration method according to claim 5, wherein the sensor standard value is one of the last sensor measurement of the water sample, a weighted average of partial sensor measurements of the water sample, or a weighted average of all sensor measurements of the water sample.
7. Calibration method according to claim 6, characterized in that the calculation formula of the sensor standard values is: b =0.5 × B1+0.3 × B2+0.2 × B3, where B1, B2, and B3 are sensor measurement values, B1 is a sensor measurement value of the last sensor, an absolute difference between B2 and B1 is smaller than a third preset value, and an absolute difference between B3 and B1 is smaller than the third preset value.
8. A method for measuring water quality parameters is characterized by comprising the following steps:
s100: obtaining a first linear calibration relationship or a second linear calibration relationship by a calibration method according to any one of claims 1 to 7;
s200: and collecting a water sample at any point in the water area to obtain a sensor measurement value of the water sample, and obtaining a calibrated sensor value through the first linear calibration relation or the second linear calibration relation obtained in the step S100.
9. A water quality parameter measuring device is characterized by comprising:
a sensing measurement device comprising a sensor;
the input terminal comprises an input interface and an output interface, wherein the input interface can input a chemical test value A of at least one water quality parameter; the output interface can output a calibrated sensor value y of at least one water quality parameter;
a processing center in signal connection with the sensing and measuring device and the input terminal, wherein the processing center is configured to receive the sensor measurement value of the sensing and measuring device, receive the chemical test value of the input terminal, operate the calibration method according to any one of claims 1 to 7, and output the calibrated sensor value to the input terminal.
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