CN108181243A - An error reduction method for an automatic calibration device of an online water quality analyzer - Google Patents

Abstract

The invention discloses an error reduction method of an automatic calibration device of a water quality on-line analyzer, which prepares a concentration c through the automatic calibration device of the water quality on-line analyzer₀Measuring the absorbance A of the solution at a certain wavelength₀Preparing the solution at different distribution ratios by using a calibration device, and calculating the theoretical absorbance A of the solution by using the distribution ratios_s1‑A_siThe actual absorbance A was measured under the same conditions_X1‑A_XiAccording to the theoretical absorbance A_s1‑A_siAnd the actual absorbance A_X1‑A_XiObtaining the correction factor K under different distribution ratios₁‑K_iWhen the solution is prepared, the correction factor plays a role in reducing system errors.

Description

An error reduction method for an automatic calibration device of an online water quality analyzer

technical field

The invention relates to a method for reducing errors, in particular to a method for reducing errors in a calibration device for a water quality analyzer.

Background technique

In the environmental water body monitoring system, the online water quality analyzer is generally used to detect the water body parameters. Whether the detection accuracy of the online water quality analyzer meets the requirements of the national verification regulations, the measurement performance of the online water quality analyzer is generally calibrated manually, and the manual detection The time period of the online analyzer is long (typically 36 hours). However, the automatic calibration device of the water quality online analyzer itself has certain inherent errors, and how to reduce the inherent errors is a major research direction that affects the preparation of the calibration device solution.

Contents of the invention

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides an error reduction method for an automatic calibration device of an online water quality analyzer that can reduce the inherent error of the system.

Technical scheme: in order to achieve the above object, the technical scheme adopted in the present invention is:

A method for reducing errors of an automatic calibration device for an online water quality analyzer, comprising the following steps: preparing a mother liquor of a potassium dichromate solution with a concentration of C ₀ , measuring the absorbance A ₀ of the solution at a certain wavelength, and using a calibration device to prepare the solution at different distribution ratios , use the distribution ratio to calculate the theoretical absorbance A _s1 -A _si of the solution, and measure the actual absorbance A _X1 -A _Xi under the same conditions, according to the theoretical absorbance A _s1 -A _si and the actual absorbance A _X1 -A _Xi to get Correction factor K ₁ -K _i , which can reduce system error by taking this correction factor into account when mixing solutions.

The calculation formula of the system correction factor K _i is:

K _i =A _xi /A _si

Wherein, according to the volume x of the mother solution drawn by the first syringe pump (4): the volume y of the diluent drawn by the second syringe pump (5) obtains the theoretical dilution ratio i _n (x: y); the dilution ratio i _n =x/(x +y), theoretical absorbance A _si = A ₀ *i _n , theoretical concentration of diluted solution c _si = c ₀ *i _n , actual preparation concentration c _xi =K _i *c _si , actual dilution ratio l _n =K _i i _n .

Preferably: when the concentration of the mother liquor is fixed and a specific target solution concentration c _i is selected, the theoretical distribution ratio _in is first calculated, and then corrected by K _i , and the dilution ratio _In is corrected; the first control signal and the second control signal are generated on the host computer Add the dilution ratio In during the second control signal, change the stepping motor steps of the quantitative syringe pump to change the dv value, _In =(x+dv)/(x+dv+y-dv), the prepared after correction at this _time The solution concentration error reduces the systematic error portion.

Compared with the prior art, the present invention has the following beneficial effects:

Through the error feedback, the present invention reduces the inherent error part of the system in the concentration error of the prepared solution after correction, and improves the configuration accuracy of the solution.

Description of drawings

Fig. 1 is a schematic diagram of the principle of the present invention;

Fig. 2 is a schematic diagram of the workflow of the present invention;

Fig. 3 is a structural representation of the present invention;

Fig. 4 is the structural representation of solution mixing tank;

Fig. 5 is the three-dimensional schematic view of solution mixing pool;

Fig. 6 is a structural schematic diagram of an electromagnetic fixing seat;

Fig. 7 is a schematic diagram of the structure of the tank cover;

Fig. 8 is a structural schematic diagram of the tee.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, further illustrate the present invention, should be understood that these examples are only for illustrating the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various aspects of the present invention All modifications of the valence form fall within the scope defined by the appended claims of the present application.

A method for reducing the error of an automatic calibration device for an online water quality analyzer. The liquid is prepared by the calibration device, and the absorbance of the potassium dichromate solution is tested. The error of the solution preparation is less than ± 2%, and there is a systematic deviation in the entire system. When the upper computer generates the first control signal and the second control signal, the system correction factor K is introduced to reduce the error of the mechanical liquid distribution system, so that the overall error is better than ±1%. The specific optimization scheme is:

Prepare the mother liquor of potassium dichromate solution with a concentration of c ₀ , measure the absorbance A ₀ of the solution at 440nm, use a calibration device to prepare the solution at different distribution ratios, and use the distribution ratio to calculate the theoretical absorbance A _s1 -A _si of the solution, under the same conditions Measure the actual absorbance A _X1 -A _Xi , calculate the correction factors K ₁ -K _i under different distribution ratios, and consider this correction factor when mixing solutions to reduce system errors. The correction factor K is stable within x months. After the calibration device has been running for a long time, the absorbance time can be re-adjusted to adjust the correction factor.

Theoretical dilution ratio _in (x:y) refers to the volume x of the mother solution drawn by the first syringe pump (4) and the volume y of the diluent drawn by the second syringe pump (5).

Dilution ratio i _n =x/(x+y)

Theoretical absorbance A _si =A ₀ *i _n , the theoretical concentration of the diluted solution c _si =c ₀ i _n ,

System correction factor K _i =A _xi /A _si

Actual preparation concentration c _xi =K _i *c _si

Actual dilution ratio l _n = K _i i _n

K _i is calculated separately based on the repeatability data of multiple experiments. When the concentration of the mother solution is fixed and a specific target solution concentration c _i is selected, the theoretical distribution ratio _in is first calculated, and then corrected using K _i . After the correction, the dilution ratio I _n . When the upper computer generates the first control signal and the second control signal, the dilution ratio _In is added, and the stepping motor steps of the quantitative syringe pump are changed to change the dv value, _In = (x+dv)/(x+dv+y -dv), at this time, the concentration error of the prepared solution after correction reduces the part of the system error.

As shown in Figures 1-8, the automatic calibration device of the online water quality analyzer with reduced error of the present invention, the automatic calibration device of the online water quality analyzer includes a host computer, a first control module A, a second control module B, and a third control module C. Circuit control board, solution mixing tank (1), mixing tank inlet pipe (2), Y-shaped tee (3), first syringe pump (4), second syringe pump (5), peristaltic pump (6 ), electromagnetic stirrer (7), detection liquid pipe (8), wherein:

The Y-shaped tee (3) is a pipe fitting with two inlets and one outlet, which are respectively the first inlet pipe, the second inlet pipe and the first outlet pipe. One end of the liquid inlet pipe (2) of the mixing tank is connected with the first outlet pipe, and the other end is connected with the mixing tank. One end of the first liquid outlet pipe (42), the first liquid outlet one-way valve (44) and the first inlet pipe are connected in sequence, and the other end of the first liquid outlet pipe (42) is connected with the standard mother liquor bottle. Outlet connection. One end of the second liquid outlet pipe (52), the second liquid outlet one-way valve (54) and the second inlet pipe are connected in sequence, and the other end of the second liquid outlet pipe (52) is connected to the diluent bottle. Outlet connection.

The first liquid outlet check valve (44) has two purposes. The first one is to prevent the liquid from flowing back from the Y-shaped tee (3). When the distance L to the outlet of the first inlet pipe is less than 4 times the pipe diameter r at the outlet end of the first liquid outlet check valve (44), the first liquid outlet check valve (44) and the outlet of the first inlet pipe form a turbulent flow structure, when When the first liquid stops flowing into the liquid inlet pipe (2) of the mixing pool, there is the first liquid between the closing port of the first liquid outlet check valve (44) and the outlet of the first inlet pipe. When the second liquid continues to pass through the Y Type tee (3) flows into the liquid inlet pipe (2) of the mixing tank. Due to the angle between the first inlet pipe and the second inlet pipe, the second liquid flowing out from the second inlet pipe rushes to the first inlet pipe The outlet collides with the outlet of the first inlet pipe, and the second liquid after the collision forms a turbulent flow, agitating the solution in and around the outlet of the first inlet pipe and in the first liquid outlet check valve (44), and then enters the first outlet In the liquid one-way valve (44), when the turbulent flow reaches the closing port of the first liquid outlet one-way valve (44), due to the blocking of the closing port, the turbulent flow returns, and the return of the turbulent flow will cause the first liquid outlet one-way valve (44) to The solution is taken out, and then the exchange of the solution in the first liquid outlet check valve (44) is realized, that is, the first liquid that exists between the closed port of the first liquid outlet check valve (44) and the outlet of the first inlet pipe Through the action of turbulent flow, it is gradually diluted and brought out to avoid the influence of the residual liquid on the solution preparation, thereby improving the preparation accuracy of the solution. In the same way, the setting purpose of the second liquid outlet check valve (54) can be known.

The distance L from the closed port of the first liquid outlet check valve (44) to the outlet of the first inlet pipe is less than 4 times the pipe diameter r at the outlet end of the first liquid outlet check valve (44), and the second liquid outlet check valve (44) is The distance L from the closing port of the valve (54) to the outlet of the second inlet pipe is less than 4 times the pipe diameter r at the outlet end of the second liquid outlet check valve (54). The shorter the distance L from the closed mouth of the first liquid outlet check valve (44) to the outlet of the first inlet pipe, the better. The shorter the distance, the greater the turbulence effect, which can better resist the second liquid outlet check valve ( 54) Solution at the closure port.

The Y-shaped tee (3) only needs to ensure that there is an angle between the first inlet pipe and the second inlet pipe. The best angle is 45°. It is made of PTEF material. The Y-shaped tee with a specific angle makes the calibration device The connecting lines should be as short as possible with as little dead volume as possible.

The mixed solution pool (1) comprises an open main tank body (11), a tank cover (12), and the tank cover (12) is used to cover the opening of the main tank body (11) to close the main tank body (11). Tank body (11). A star handle nut (121) is arranged on the slot cover (12). A sealing ring is provided at the place where the tank cover (12) is in contact with the opening of the main tank body (11). The shape of the inner cavity of the main tank body (11) is funnel-shaped. The bottom of the main tank body (11) is provided with a liquid inlet channel (111), a detection liquid outflow channel (112) and a liquid discharge channel (113). The liquid inlet of the liquid discharge channel (113) is located at the bottom of the inner cavity of the main tank body (11), and the liquid inlet of the liquid inlet channel (111) is higher than the liquid inlet of the detection liquid outflow channel (112) , while the liquid inlet of the liquid discharge channel (113) is lower than the liquid inlet of the test liquid outflow channel (112), and the test liquid outflow channel (112) is used for connecting sampling inspection equipment.

Described electromagnetic stirrer (7) comprises electromagnet holder (71), electromagnet (72), stirrer (73), and described electromagnet holder (71) is used for electromagnet (72) is fixed on main groove The bottom of the body (11), and the stirring bar (73) is arranged in the inner cavity of the main tank body (11).

The electromagnet fixing seat (71) is provided with a fixing seat through hole (711). The drain pipe passes through the through hole (711) of the fixing seat to communicate with the drain channel (113), and the drain pipe is provided with a peristaltic pump (6).

The first outlet pipe communicates with the liquid inlet channel (11) of the mixed solution pool (1) through the liquid inlet pipe (2) of the mixing pool. The mixed solution pool (1) comprises an open main tank body (11), a tank cover (12), and the tank cover (12) is used to cover the opening of the main tank body (11) to close the main tank body (11). The tank body (11), the tank cover (12) is provided with a star-shaped handle nut (121), and the tank cover (12) is provided with a sealing ring at a place in contact with the opening. The shape of the hollow tank of the main tank body (11) is funnel-shaped, and the main tank body (11) is provided with a liquid inlet channel (111), a detection liquid outflow channel (112) and a liquid discharge channel (113), The liquid inlet of the liquid discharge channel (113) is located at the bottom of the hollow groove, and the liquid inlet of the liquid inlet channel (111) is higher than the liquid inlet of the detection liquid outflow channel (112), while the liquid discharge The liquid inlet of the channel (113) is lower than the liquid inlet of the detection liquid outflow channel (112), and the detection liquid outflow channel (112) is used to communicate with the liquid inlet of the water quality analyzer through the detection liquid pipe (8).

The present invention adopts the liquid inlet channel (111) to be arranged on the bottom of the hollow tank, so that the diluent and the standard mother liquor enter the mixed solution pool (1) from the bottom of the mixed solution pool (1), so that when the stirring bar 73 is prevented from rotating, the diluent and the standard mother liquor will be mixed. The standard mother liquor flies on the inner wall of the mixed solution pool (1), affecting the mixing accuracy of the solution. In addition, when there is a solution in the mixing solution pool (1), the stirring bar starts to work to mix the test solution and speed up the mixing speed. The invention adopts the solution to mix the pool from the bottom of the pool, and at the same time, the top is covered, and this structure can reduce the influence of the evaporation of the solution and the phenomenon of solution hanging on the wall of the mixing pool on the preparation accuracy.

The detection liquid outflow channel (112) of the present invention is also arranged at the bottom of the hollow tank, and the pipeline is sealed and connected by a pressure ring, and this structure can improve the solution utilization rate and the stability of the pipeline. In addition, this structure can take samples from the mixed solution pool (1) when the stirrer 73 is still working, avoiding the phenomenon of deposition of the mixed solution when the stirrer 73 stops working, which affects the analysis of the water quality analyzer. In addition, when sampling from the detection liquid outflow channel (112), the waste sample in the first half should be removed to prevent the residual dead volume in the detection liquid outflow channel (112) and the detection liquid pipe (8) from affecting the analysis of the water quality analyzer.

The liquid inlet of the liquid discharge channel (113) is arranged at the bottom of the hollow tank, which can ensure sufficient discharge of waste liquid.

Described electromagnetic stirrer (7) comprises electromagnet holder (71), electromagnet (72), stirrer (73), and described electromagnet holder (71) is used for electromagnet (72) is fixed on main groove The bottom of the body (11), and the stirring bar (73) is arranged in the hollow groove.

The present invention adopts the electromagnetic stirrer (7), which has two purposes, one is to speed up the mixing of the solution, and the other is to speed up the drying of the main tank body (11). When the solutions are mixed, since the stirring bar (73) rotates under the action of the electromagnet (72), the solutions are mixed more uniformly through the rotation of the stirring bar (73). When drying, wind is generated by the rotation of the stirrer (73), and the generated wind rotates in the hollow groove in the main tank body (11) to accelerate the evaporation of the solution on the inner wall of the main tank body (11), and then through the peristaltic pump (6) The suction action of the wet air is extracted from the main tank body (11), so the drying of the main tank body (11) is accelerated, and the residual liquid is prevented from affecting the configuration accuracy of the next solution.

The first control module A is used to control the suction and push operation of the first syringe pump (4) according to the first control signal sent by the host computer, and the first syringe pump (4) is used to control the standard mother liquor according to the first control signal The bottle is sucked, and after the sucking, the liquid is pushed into the mixed solution pool (1) according to the first control signal.

The second control module B is used to control the suction and push operation of the second syringe pump (5) according to the second control signal sent by the host computer, and the second syringe pump (5) is used to dilute the diluent according to the second control signal. The bottle is sucked, and after the sucking, the liquid is pushed into the mixed solution pool (1) according to the second control signal.

The third control module C is used to control the peristaltic pump (6) to suck the mixed solution pool (1) according to the third control signal sent by the host computer;

The circuit control board is used to control the electromagnetic stirrer (7) to stir according to the fourth control signal sent by the host computer;

The water quality analyzer is used to detect the liquid coming in from the detection liquid pipe (8), and upload the detection result to the host computer;

The host computer is used to send a first control signal, a second control signal, a third control signal and a fourth control signal to the first control module A, the second control module B, the third control module C and the circuit control board; at the same time The upper computer is used to receive the detection result of the water quality analyzer, and obtain the judgment report of the water quality analyzer according to the detection result and the technical indicators of the national verification regulations.

A water quality online analyzer calibration method, comprising the following steps:

Step 1: The inspector connects the communication port of the tested water quality analyzer with the communication port of the upper computer of the calibration device, and connects the sampling system of the tested water quality analyzer with the detection liquid pipe (8).

Step 2, the standard mother liquor bottle that standard solution mother liquor is housed is communicated with the first liquid inlet pipe (41); The diluent liquid bottle that diluent is housed is communicated with the second liquid inlet pipe (51); And the diluted solution concentration is input to the host computer.

Step 3, the host computer calculates and obtains the amount of the standard solution mother solution and the amount of the diluent according to the concentration of the standard solution mother solution and the diluted solution concentration, and then obtains the feed rate of the first syringe pump (4) and the second syringe pump (5) ) feeding amount; the upper computer sends the first control signal to the first control module A according to the feeding amount of the first syringe pump (4), and sends the second control signal to the second control module B according to the feeding amount of the second syringe pump (5). For the control signal, the upper computer sends the fourth control signal to the circuit control board, and sends the fourth control signal to the second control module B.

Step 4, the first control module A controls the first syringe pump (4) to draw the standard solution mother solution from the standard mother solution bottle according to the first control signal; the second control module B controls the second syringe pump (5) from the diluted solution according to the second control signal The liquid bottle absorbs the diluent; the second control module B controls the second syringe pump (5) to inject the diluent into the mixed solution pool (1) according to the second control signal, and then the first control module A controls the second injection pump (5) according to the first control signal. A syringe pump (4) injects the mother solution of the standard solution into the mixed solution pool (1), and the mother solution of the standard solution is injected at least when the injection of the diluent is completed.

Step 5, the circuit control board controls the electromagnet (72) to stir and drive the stirring bar (73) according to the fourth control signal, and then stirs the liquid in the mixed solution pool (1).

Step 6: After the solution preparation is completed, the computer sends a sampling command to the tested water quality analyzer, and the tested water quality analyzer accepts the command to sample the solution in the mixed solution pool (1), and the tested water quality analyzer collects the water quality analysis information Upload to the host computer; and analyze the indication error, zero drift, indication stability, etc. After the analysis is completed, the analysis data will be sent to the computer.

Step 7: The upper computer analyzes, detects and automatically calibrates the tested water quality analyzer according to the analysis information of the tested water quality analyzer, and generates a judgment report, and the data results are traceable.

Automatic calibration means that the calibration device realizes the instruction sending and data receiving of the instrument through the communication protocol provided by the water quality online analyzer manufacturer, and completes the "indication error", "zero drift" and For the testing of items such as "indicating value stability", the calibration items can be adjusted according to the different instruments to be tested, not limited to the above three items. Automatically means that after the experimenter selects the experiment option, during the entire calibration process, there is no need to manually replace reagents, do not need to be on duty, and do not need to manually record data. The whole process is automatically completed by the calibration device.

The items analyzed and detected by the host computer to the tested water quality analyzer include indication error, zero drift, and indication stability.

7.1 Detection process and calculation method of indication error (COD)

After the water quality analyzer runs stably, introduce COD standard solutions with mass concentrations of C _S (50, 150, 500mg/L) in sequence for measurement, each solution is measured continuously for 3 times, and the indication error is calculated according to the following formula :

Among them, ΔC represents the indication error, Indicates the average value of the concentration measured by the tested water quality analyzer, and C _S indicates the concentration of the diluted solution.

7.2 Detection process and calculation method of zero drift (COD):

After the water quality analyzer is running stably, the computer controls the first syringe pump (4) and the second syringe pump (5) to prepare a zero-point calibration solution to the mixed solution pool (1), and introduce the prepared zero-point calibration solution into the tested water quality analysis Measure the zero-point calibration liquid with the instrument, record the measured initial zero value Z ₀ , introduce the zero-point calibration liquid into the tested water quality analyzer every 30 minutes within 4 hours, measure the zero-point indication value Z _i , and take the zero-point indication value that deviates from Z ₀ the most Z _i is used as the maximum zero indication value Z _max , and the difference between the maximum zero indication value Z _max and the initial zero value Z ₀ is taken as the zero drift.

7.3 Detection process and calculation method of index stability (COD):

After the water quality analyzer runs stably, the computer controls the first syringe pump (4) and the second syringe pump (5) to prepare a standard calibration solution to the mixed solution pool (1); import the prepared standard calibration solution into the tested water quality analyzer Solution, record the initial measurement value S0, and run continuously for 24 hours; introduce a standard calibration solution to the tested water quality analyzer every 1 hour within 24 hours, measure the measurement value Si, and take the measurement value Si that deviates from the initial measurement value S0 as the maximum measurement Value Smax, calculate the indication stability according to the following formula:

ΔS represents the stability of the indication, S _max represents the maximum measured value, and S ₀ represents the initial measured value.

Indication error, zero drift, and indication stability indicators are the evaluation indicators of the measurement performance of the instrument in the measurement specification. During the manual evaluation, it needs to be manually on duty for 40 hours and process the data. This calibration device can replace the manual and automatically complete the evaluation of the above measurement performance. .

In the present invention, the replacement of detection solutions of different concentrations corresponding to different detection items of the same water quality analyzer to be tested is realized through the solution automatic preparation function of the calibration device, so there is no need to manually replace reagents, and the present invention uses the same device to prepare Compared with the detection solutions of different concentrations, it reduces the human error of the zero drift, the stability of the indication value and the detection results of the error of the indication value.

In addition, the host computer of the present invention can adopt computer or other central processing units, and each function can be based on Windows and Win The operating system is implemented, which can send sample making instructions and receive data, and form a report after processing and calculating the data, and can give a conclusion whether the water quality analyzer to be tested is qualified or not.

Step 8, after the detection of a certain concentration solution is completed, the upper computer sends a third control signal to the third control module C, and the third control module C controls the peristaltic pump to discharge the waste liquid in the solution mixing tank, and closes after the waste liquid is discharged Peristaltic pump for preparation of the next detection concentration point;

After the waste liquid is discharged and before the preparation of the next detection concentration point, it also includes cleaning and drying the solution mixing tank, and the method is as follows: the control template B controls the second syringe pump (5) to draw the diluent from the diluent bottle and inject it into the mixed solution tank In (1), the upper computer sends the fourth control signal to the circuit control board, starts the electromagnetic stirrer (7) to clean the mixed solution pool (1), after cleaning, the peristaltic pump is controlled by the third control signal to discharge, and the cleaning is done for 3 At last, the peristaltic pump is controlled by the third control signal, and the electromagnetic stirrer (7) is started by the fourth control signal, so that the stirring bar (73) rotates, and then the mixed solution pool (1) is dried rapidly.

In the present invention, the uncertainty of the solution obtained by diluting the calibration device is less than 3% (k=2), and can be traced to the national standard through comparison with the national secondary standard substance, so its data data results can be traced.

In the present embodiment, the first syringe pump (4) and the second syringe pump (5) of the present invention adopt quantitative pump, quantitative pump volume: 10ml, when the quantitative pump specification is selected between 5ml, 10ml and 25ml, the test shows The quantitative syringe pump adopts two specifications of 10ml, and the operability and precision of solution preparation are the highest. Quantitative pump accuracy: 2uL/step. The speed of the quantitative pump motor can be adjusted according to the actual needs. The speed of this instrument is 30 rpm (adjustable), and the test shows that the volume accuracy of the pump at this speed is the highest.

Reset mode: The quantitative pump is equipped with a photoelectric switch at the maximum push point (reset position), and the quantitative pump is reset before dosing to ensure that there is no residual liquid in the quantitative pump and each pipeline is filled with diluent before each solution is prepared .

Control of remaining liquid in the pipeline: During the preparation process, when the quantitative pump is pushing, the pipeline is always kept full of liquid, and through program optimization, the pushing of the mother liquor is always completed first, and the pushing of the diluent is completed last, ensuring that the pipeline is full The liquid used is always the diluent (pure water) to improve the reproducibility of the preparation to achieve the purpose of controlling the accuracy.

While taking into account the efficiency, choose the pipeline with a diameter of 2mm, the total length of the connecting pipeline should be as short as possible, and the diameter of the pipe should be as small as possible to reduce the dead volume. All components are connected by high temperature, acid and alkali resistant PTFE tubes, and the pipeline interface is sealed with a pressure ring, so the contact area of the connection is small and the dead volume is small. Compared with the raw material tape sealing method, the sealing performance is more reliable and the operation is more convenient. During the whole sample making process, this connection method makes the pipeline completely fixed without loosening and reduces the detection failure rate. The size of the PTFE tube is 2.85*1.25mm.

Calibration device dosing liquid, tested by the absorbance of potassium dichromate solution, the solution preparation error is less than ± 2%, the whole system has systematic deviation, at this time, when the host computer generates the first control signal and the second control signal through the repeat test, the middle The introduction of the system correction factor K can reduce the error of the mechanical liquid distribution system, making the overall error better than ±1%.

The water quality on-line analyzer of the present invention includes but not limited to chemical oxygen demand (COD) on-line analyzer, ammonia nitrogen on-line analyzer and other on-site non-laboratory water quality parameter analysis applied to water sources, industrial sewage outlets, and water body environmental monitoring points instrument.

The invention can be pushed by a single person to calibrate the water quality analyzer on site, and the mobility of the calibration device ensures that the solution can be prepared and used immediately during analysis. Compared with the traditional artificially prepared solution brought to the site for analysis, it is no longer necessary to consider low-concentration detection Solution preservation problems and site requirements for solution preparation, solution preparation has higher reproducibility.

The present invention realizes the fully automatic calibration of the online water quality analyzer, unattended, according to predetermined standards or requirements (such as national metrology verification regulations, calibration specifications and other technical specifications), and performs a series of calibration on all measurement indicators of the water quality online analyzer. Continuous and uninterrupted analysis and testing, collecting data and analyzing and processing, and judging whether the calibration results meet the relevant index requirements, and generating corresponding original calibration reports. An output port for external data communication is reserved to realize the preparation for remote collection of calibration results. The entire process is intelligently processed without manual intervention. At the same time, the device has the function of automatic maintenance, which can automatically clean and maintain during the running interval or standby state, so as to improve the reliability and stability of the device operation.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (3)

1. a kind of error of water quality online analyzer self-checking device reduces method, which is characterized in that includes the following steps：It is logical Water quality online analyzer self-checking device compound concentration is crossed as c₀Potassium bichromate solution mother liquor measures solution under certain wavelength Absorbance A₀, solution is prepared under different distribution ratios using calibrating installation, the theoretical absorbance A of solution is calculated using distribution ratio_s1- A_si, practical absorbance A is measured under similarity condition_X1-A_Xi, according to theoretical absorbance A_s1-A_siWith practical absorbance A_X1-A_XiIt obtains Improvement factor K under different distribution ratios₁-K_i, when matching solution, by this improvement factor, play the work for reducing systematic error With.

2. the error of water quality online analyzer self-checking device reduces method according to claim 1, it is characterised in that：System Unite correction factor K_iCalculation formula is：

K_i=A_xi/A_si

Wherein, the volume x of mother liquor is drawn according to the first syringe pump (4)：The volume y that second syringe pump (5) draws dilution is obtained Theoretical thinner ratio i_n(x：y)；Thinner ratio i_n=x/ (x+y), theoretical absorbance A_si=A₀*i_n, solution theory concentration c after dilution_si= c₀*i_n, practical compound concentration c_xi=K_i*c_si, practical thinner ratio l_n=K_ii_n。

3. the error of water quality online analyzer self-checking device reduces method according to claim 2, it is characterised in that：When Mother liquid concentration is fixed, and selects specific objective solution concentration c_iWhen, first calculate theoretical distribution ratio i_n, reuse K_iIt is modified, repaiies Thinner ratio I after just_n；Thinner ratio I is added in when host computer generates first control signal and second control signal_n, change calibrated shot The stepper motor steps of pump change dv values, I_n=(x+dv)/(x+dv+y-dv), the solution concentration prepared after correcting at this time are missed Difference reduces systematic error part.