Titration control method of weight loss method in water quality on-line analyzer

Abstract

The present application relates to the technical field of water quality detection, and particularly relates to a titration control method of a weight loss weighing method in a water quality online analyzer, comprising the following steps: S1, preliminary preparation: placing an oxidizing reagent bottle on a weighing disc assembly, inputting the tare weight of the oxidizing reagent bottle and a matched connecting pipeline and performing calibration, determining a tare weight benchmark, and measuring the net weight of the oxidizing reagent in the oxidizing reagent bottle through the weighing disc assembly. In use, the present application realizes closed-loop control of the titration process through the weight loss weighing method, effectively solves the problems of large measurement error, influence by pipeline leakage, and inability to predict the reagent residual amount of the open-loop control of the traditional injection pump through the steps of tare weight calibration, pipeline initialization, real-time weight acquisition, closed-loop speed correction and the like.

Description

Technical Field

[0001] This invention relates to the field of water quality testing technology, specifically to a titration control method using the weight reduction weighing method in an online water quality analyzer. Background Technology

[0002] In the field of online water quality monitoring, titration is a commonly used quantitative analysis method, widely applied to the detection of target parameters such as COD, ammonia nitrogen, and total phosphorus in water samples. Its detection accuracy directly determines the reliability of water quality monitoring data, thus affecting the scientific validity of environmental governance decisions. Currently, most online water quality analyzers employ an open-loop control mode using a syringe pump. This mode controls the reagent dosage by presetting the syringe pump's operating time and speed, thereby calculating the target parameters in the water sample.

[0003] However, the dosing accuracy of some existing syringe pumps is easily affected by factors such as pipeline resistance, reagent viscosity changes, and pump wear, leading to deviations between the actual dosing volume and the preset value. This results in significant errors in the test results, failing to meet the requirements for accurate detection of low-concentration water samples. Secondly, existing titration systems lack effective pipeline status monitoring mechanisms. When pipeline malfunctions such as leaks or blockages occur, they cannot be detected in time, leading to reagent waste, data distortion, and disruption of the monitoring process. Furthermore, the determination of reagent remaining quantity relies heavily on manual observation, making automated prediction impossible. This often results in reagent shortages causing titration interruptions, reducing the deployment efficiency and operational stability of online water quality analyzers. Summary of the Invention

[0004] This invention achieves closed-loop control of the titration process through the tare weight method. By performing steps such as tare weight calibration, pipeline initialization, real-time weight acquisition, and closed-loop speed correction, it solves the problems of large measurement error, susceptibility to pipeline leakage, and inability to predict reagent balance in traditional open-loop control of syringe pumps.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a titration control method for the weight loss weighing method in an online water quality analyzer, comprising the following steps: Includes the following steps: S1. Preliminary preparation: Place the oxidizing reagent bottle on the weighing pan assembly, enter the tare weight of the oxidizing reagent bottle and its matching connecting pipes and calibrate it. After determining the tare weight benchmark, calculate the net weight of the oxidizing reagent in the oxidizing reagent bottle through the weighing pan assembly. S2. Piping initialization: Before starting the titration process, control the peristaltic pump to prefill the entire pipeline of the peristaltic pump with oxidizing reagent, and clean the digestion colorimetric unit to remove any overflowing reagent, ensuring that the weighing value during the titration process is consistent with the actual amount of reagent involved in the reaction. S3, Initial Titration Record: When the instrument enters the titration process, the system records the current weight of the weighing pan assembly as the initial titration weight. Then, the peristaltic pump is started, and the speed of the peristaltic pump is adjusted by controlling the stepper motor of the peristaltic pump, thereby adjusting the speed at which the peristaltic pump draws reagent from the oxidizing reagent bottle. S4. Real-time weighing and acquisition: During the titration process, the weighing pan component detects the actual weight of the oxidation reagent bottle in real time at a preset acquisition frequency and transmits the weight data to the control system of the water quality analyzer simultaneously. S5. Intermittent titration and reaction detection: The control system controls the peristaltic pump to work intermittently. After each specified amount of reagent is added, the addition is stopped and waited for 3 to 5 seconds to allow the reagent to react fully in the digestion and colorimetric unit. Then, the colorimetric sensor detects whether the reagent properties have changed abruptly. If no change has occurred, the addition continues. If a change has occurred, the addition is stopped immediately. S6. Data Calculation and Process End: After the titration stops, the system records the weight of the current weighing pan component as the titration termination weight. By the difference between the initial titration weight and the titration termination weight, the actual weight of the reagent used in this titration is calculated. This actual weight is substituted into the preset calculation model to calculate the measured value of the water sample parameters and complete the titration control process.

[0006] Further, in step S1, the weighing pan assembly includes a weighing pan, a weighing sensor, and an MCU controller. The oxidizing reagent bottle is connected to the sampling tube of the peristaltic pump via a flexible tube, and interference factors at the connection of the flexible tube are included in the tare weight record. The weighing pan is made of 304 stainless steel and is used to fix the oxidizing reagent bottle and align the center of gravity of the reagent bottle with the force measurement center of the weighing sensor. The weighing pan of the corresponding size is configured according to the different specifications of the reagent bottle. The weighing sensor is a high-precision cantilever beam resistance strain gauge sensor with a range of 1 kg, a 200% overload capacity, a repeatability of 0.05%, and the ability to achieve an accurate measurement of 0.05 grams.

[0007] Furthermore, in step S2, the running time of the peristaltic pump during pipeline initialization is preset according to the pipeline volume to ensure that the oxidizing reagent completely fills the inlet pipe, pump body and outlet pipe of the peristaltic pump. When cleaning the digestion colorimetric unit, the oxidizing reagent is used to circulate and rinse 2 to 3 times, with each rinsing time being 10 to 15 seconds, to thoroughly remove residual impurities and moisture in the digestion colorimetric unit, avoid side reactions between residual substances and titration reagent, and further ensure titration accuracy.

[0008] Furthermore, in step S3, the preset peristaltic pump extraction speed can be adjusted according to the estimated content of the target detection parameter in the water sample. When the estimated content of the target detection parameter is high, the stepper motor speed is adjusted to make the peristaltic pump extract the reagent at a high speed. When the estimated content of the target detection parameter is low, the stepper motor speed is adjusted to make the peristaltic pump extract the reagent at a low speed. The high speed is 10~15ml / min and the low speed is 2~5ml / min, so as to achieve a balance between titration efficiency and titration accuracy. At the same time, after the system records the initial weight of titration, it delays for 1~2 seconds before starting the peristaltic pump to avoid weight measurement error caused by the vibration of the weighing pan assembly during startup.

[0009] Furthermore, in step S4, the MCU controller has a built-in 24-bit high-precision AD chip with a sampling rate of 40Hz, which can achieve high-resolution weight detection of 0.01 grams. The MCU controller has a built-in RS485 interface, which transmits real-time weight data to the control system of the water quality analyzer through the MODBUS RTU slave protocol. The control system filters the received weight data to remove abnormal fluctuation data and ensure the stability of weight detection. The filtering process adopts a moving average filtering algorithm, and the filtering window is set to 5 to 8 sampling points.

[0010] Furthermore, in step S5, the inlet of the peristaltic pump extends below the liquid surface of the oxidizing reagent bottle and is close to the bottom of the bottle, 5-8 mm away from the bottom, to ensure that the oxidizing reagent in the reagent bottle can be fully extracted and reduce reagent residue. The outlet of the peristaltic pump is connected to the digestion colorimetric unit, and the outlet is 1-2 cm away from the highest liquid surface of the reaction liquid in the digestion colorimetric unit. A guide port with an inclination angle of 30-45° is set at the end of the outlet to ensure that all the liquid dripping from the outlet enters the digestion colorimetric unit, avoiding reagent loss and measurement error caused by liquid splashing.

[0011] Furthermore, in step S5, the preset acquisition frequency is 10 times per second. The control system of the water quality analyzer acquires the measurement data of the weighing pan assembly in real time through this frequency, monitors the change in the weight of the reagent bottle in real time, and at the same time, the control system calculates the reagent consumption rate based on the real-time weight change, compares it with the theoretical consumption rate corresponding to the preset extraction speed of the peristaltic pump, and corrects the operating speed of the peristaltic pump in real time to ensure that the deviation between the actual reagent consumption rate and the preset rate does not exceed ±5%.

[0012] Furthermore, step S5 includes the following sub-steps: S51. The peristaltic pump starts, extracts the oxidizing reagent at the preset speed, and adds it dropwise to the digestion and colorimetric unit; S52. When the dripping amount reaches the specified amount, the peristaltic pump stops working. The specified amount is preset according to the concentration of the oxidizing reagent and the volume of the water sample, and the range is 0.1~0.5ml. S53. Let stand for 3-5 seconds to allow the reagent to react fully in the digestion and colorimetric unit. During the standing process, control the digestion and colorimetric unit to stir at a low speed of 50-80 r / min to ensure that the reagent and water sample are mixed evenly and to avoid misjudgment of the endpoint due to insufficient local reaction. S54. The colorimetric sensor detects the properties of the reaction solution. The property mutation specifically refers to a significant change in the color of the reaction solution. The colorimetric sensor determines whether the property mutation has occurred by detecting the change in absorbance of the reaction solution. When the change in absorbance exceeds a preset absorbance threshold, it is determined to be a property mutation. S55. If no mutation occurs, return to step S51 to continue adding drops. If a mutation occurs, proceed to step S6.

[0013] Furthermore, in step S6, the difference between the initial titration weight and the final titration weight is the actual weight of the reagent used in this titration. By combining this actual weight with the concentration parameter of the oxidizing reagent, the content of the target detection parameter in this water sample is calculated. The preset calculation model is as follows: , in The concentration of the target detection parameter in the water sample. This refers to the actual mass of reagents consumed. The concentration of the oxidizing agent. For the volume of the water sample, This is the stoichiometric coefficient.

[0014] Furthermore, in step S6, after the titration process is completed, the remaining weight of the reagent bottle detected by the weighing pan assembly can be used to predict whether the remaining amount of oxidizing reagent is sufficient for the next titration. At the same time, by comparing the real-time rate of change of the reagent bottle weight during the titration process with the operating status of the peristaltic pump, the preset threshold of the weight change rate is preset according to the preset flow rate of the peristaltic pump and the reagent density. If the peristaltic pump is running but the weight change rate is lower than the preset threshold, it is predicted that there is a leakage fault in the pipeline. Beneficial effects

[0015] Compared with known public technologies, the technical solution provided by this invention has the following beneficial effects: This invention achieves closed-loop control of the titration process through the tare weight method. By performing steps such as tare weight calibration, pipeline initialization, real-time weight acquisition, and closed-loop speed correction, it effectively solves the problems of large measurement error, susceptibility to pipeline leakage, and inability to predict reagent balance in traditional open-loop control of syringe pumps. Attached Figure Description

[0016] Figure 1 This is a flowchart of the titration control method of the weight reduction weighing method in the online water quality analyzer of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0018] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: Example

[0020] like Figure 1 As shown, this invention provides a titration control method for the weight loss weighing method in an online water quality analyzer, comprising the following steps: S1. Preliminary preparation: Place the oxidizing reagent bottle on the weighing pan assembly, enter the tare weight of the oxidizing reagent bottle and its matching connecting pipes and calibrate it. After determining the tare weight benchmark, calculate the net weight of the oxidizing reagent in the oxidizing reagent bottle through the weighing pan assembly.

[0021] Furthermore, the weighing pan assembly includes a weighing pan, a weighing sensor, and an MCU controller. The oxidizing reagent bottle is connected to the sampling tube of the peristaltic pump via a flexible tube, and interference factors at this flexible tube connection are included in the tare weight record.

[0022] Specifically, the weighing pan is made of 304 stainless steel and is used to fix the oxidizing reagent bottle and align the center of gravity of the reagent bottle with the force measurement center of the weighing sensor. The weighing pan of the corresponding size is configured according to the different specifications of the reagent bottle. The weighing sensor is a high-precision cantilever beam resistance strain gauge sensor with a range of 1kg, 200% overload capacity, repeatability of 0.05%, and can achieve accurate measurement of 0.05 grams.

[0023] Further, the specific operation of tare calibration is as follows: First, assemble the empty oxidizing reagent bottle with the matching connecting tubing and place it on the weighing pan. The system records the weight at this time as the initial tare weight. Then, inject a standard weight of known weight (weight error ≤ ±0.01g) into the reagent bottle. The system records the calibration weight. The tare weight benchmark is calibrated by the difference between the initial tare weight and the calibration weight to ensure that the tare weight measurement error does not exceed ±0.02g. After calibration, remove the standard weight, inject the oxidizing reagent, and the system accurately calculates the net weight of the oxidizing reagent by subtracting the calibrated tare weight benchmark from the current total weight, avoiding reagent consumption measurement errors caused by tare weight deviation.

[0024] S2. Piping initialization: Before starting the titration process, control the peristaltic pump to prefill the entire pipeline of the peristaltic pump with oxidizing reagent, and clean the digestion colorimetric unit to remove any overflowing reagent, ensuring that the weighing value during the titration process is consistent with the actual amount of reagent involved in the reaction.

[0025] Furthermore, during pipeline initialization, the peristaltic pump's running time is preset according to the pipeline volume to ensure that the oxidizing reagent completely fills the inlet pipe, pump body, and outlet pipe of the peristaltic pump. When cleaning the digestion colorimetric unit, the oxidizing reagent is used to circulate and rinse 2-3 times, with each rinse lasting 10-15 seconds, to thoroughly remove residual impurities and moisture from the digestion colorimetric unit, avoid side reactions between residual substances and titration reagents, and further ensure titration accuracy.

[0026] Specifically, the method for calculating the pipeline volume is as follows: First, measure the inner diameter and length of the peristaltic pump's inlet pipe, pump body flow channel, and outlet pipe. Then, use the cylinder volume formula: ,in, The inner diameter of the pipe. Calculate the total volume of the pipeline based on the pipeline length. The peristaltic pump running time = total pipeline volume ÷ peristaltic pump preset flow rate × 1.2 (with a 20% margin) to ensure that the oxidizing reagent completely fills the pipeline without any air bubbles. When cleaning the digestion colorimetric unit, the rinsing flow rate of the oxidizing reagent is the same as the titration flow rate. After rinsing, completely drain the rinsing solution through the drain outlet of the digestion colorimetric unit to avoid diluting the subsequent reaction solution with residual rinsing solution.

[0027] S3. Initial Titration Record: The instrument enters the titration process, and the system records the current weight of the weighing pan assembly as the initial titration weight. Then, the peristaltic pump is started, and the speed of the peristaltic pump is adjusted by controlling the stepper motor of the peristaltic pump, thereby adjusting the speed at which the peristaltic pump draws reagent from the oxidizing reagent bottle.

[0028] Furthermore, the preset peristaltic pump extraction speed can be adjusted according to the estimated content of the target detection parameter in the water sample. When the estimated content of the target detection parameter is high, the stepper motor speed is adjusted to make the peristaltic pump extract the reagent at a high speed. When the estimated content of the target detection parameter is low, the stepper motor speed is adjusted to make the peristaltic pump extract the reagent at a low speed. The high speed is 10~15ml / min, and the low speed is 2~5ml / min, so as to achieve a balance between titration efficiency and titration accuracy. At the same time, after the system records the initial titration weight, it delays for 1~2 seconds before starting the peristaltic pump to avoid weight measurement errors caused by the vibration of the weighing pan assembly during startup.

[0029] Furthermore, the estimated content of the target detection parameter in the water sample can be initially obtained through the processing module of the online water quality analyzer. The processing module performs preliminary screening of the water sample using a rapid colorimetric method to obtain the estimated range of the target parameter, and then automatically matches the corresponding peristaltic pump extraction speed. The speed adjustment of the stepper motor is controlled by a pulse signal. Each pulse corresponds to a fixed rotation angle of the stepper motor, which in turn drives the peristaltic pump roller to rotate at a fixed angle, thereby achieving precise adjustment of the extraction speed. The speed adjustment error does not exceed ±0.5ml / min. Within 1~2 seconds after the peristaltic pump is delayed in starting, the system continuously collects the weight data of the weighing pan assembly. If the weight fluctuation is ≤±0.01g, the weighing system is considered stable and the peristaltic pump is started; otherwise, the delay time is extended until the weight stabilizes.

[0030] S4. Real-time weighing and acquisition: During the titration process, the weighing pan component detects the actual weight of the oxidizing reagent bottle in real time at a preset acquisition frequency, and transmits the weight data to the control system of the water quality analyzer simultaneously.

[0031] Specifically, the 24-bit high-precision AD chip converts the analog voltage signal output by the weighing sensor into a digital signal with a conversion accuracy of 0.001mV, ensuring high resolution for weight detection; the RS485 interface has a transmission rate of 9600bps and a transmission distance of ≤10m, and uses CRC check during transmission to avoid data loss or errors.

[0032] The specific implementation of the moving average filtering algorithm is as follows: continuously collect 5 to 8 weight data points, remove the maximum and minimum values, and calculate the average value of the remaining data as the current valid weight data. This effectively suppresses weight fluctuations caused by environmental vibration and liquid sloshing during the weighing process, ensuring the stability of the weight data.

[0033] Furthermore, the MCU controller has a built-in 24-bit high-precision AD chip with a sampling rate of 40Hz, which can achieve high-resolution weight detection of 0.01 grams. The MCU controller has a built-in RS485 interface, which transmits real-time weight data to the control system of the water quality analyzer through the MODBUS RTU slave protocol. The control system filters the received weight data to remove abnormal fluctuation data and ensure the stability of weight detection. The filtering process adopts a moving average filtering algorithm, and the filtering window is set to 5 to 8 sampling points.

[0034] S5. Intermittent titration and reaction detection: The control system controls the peristaltic pump to work intermittently. After each specified amount of reagent is added, the addition is stopped and waited for 3 to 5 seconds to allow the reagent to react fully in the digestion and colorimetric unit. Then, the colorimetric sensor detects whether the reagent properties have changed abruptly. If no change has occurred, the addition continues; if a change has occurred, the addition is stopped immediately.

[0035] Furthermore, the inlet of the peristaltic pump extends below the liquid surface of the oxidizing reagent bottle and close to the bottom of the bottle, 5-8 mm away from the bottom, to ensure that the oxidizing reagent in the reagent bottle can be fully extracted and reduce reagent residue. The outlet of the peristaltic pump is connected to the digestion colorimetric unit, and the outlet is 1-2 cm away from the highest liquid surface of the reaction liquid in the digestion colorimetric unit. A guide port with an inclination angle of 30-45° is set at the end of the outlet to ensure that all the liquid dripping from the outlet enters the digestion colorimetric unit, avoiding reagent loss and measurement errors caused by liquid splashing.

[0036] Specifically, a filter head is installed at the inlet end of the peristaltic pump. The filter head uses a 100-mesh stainless steel filter screen to filter impurities in the oxidizing reagent, preventing impurities from clogging the pipeline or affecting the titration accuracy. The guide port is made of polytetrafluoroethylene and the surface is polished to reduce liquid adsorption and ensure that each drop of reagent can be smoothly added to the digestion and colorimetric unit. A stirring device is installed in the digestion and colorimetric unit. The stirring device is linked to the working status of the peristaltic pump. After the peristaltic pump stops adding liquid, the stirring device starts to ensure that the reagent and water sample are mixed evenly.

[0037] The preset acquisition frequency is 10 times per second. The control system of the water quality analyzer acquires the measurement data of the weighing pan component in real time through this frequency, monitors the changes in the weight of the reagent bottle in real time, and calculates the reagent consumption rate based on the real-time weight changes. It compares the rate with the theoretical consumption rate corresponding to the preset extraction speed of the peristaltic pump and corrects the operating speed of the peristaltic pump in real time to ensure that the deviation between the actual reagent consumption rate and the preset rate does not exceed ±5%.

[0038] The specific method for calculating the reagent consumption rate is as follows: the real-time reagent consumption rate is obtained by dividing the difference between two adjacent weight data collections by the collection time interval (0.1 seconds). The theoretical consumption rate is calculated based on the preset flow rate of the peristaltic pump and the density of the oxidizing reagent (theoretical consumption rate = preset flow rate × reagent density). When the deviation between the actual consumption rate and the theoretical consumption rate exceeds ±5%, the control system adjusts the pulse frequency of the stepper motor to correct the peristaltic pump speed until the deviation returns to within ±5%, thereby achieving closed-loop control of the titration process.

[0039] Furthermore, the following steps are included: S51. The peristaltic pump starts, extracts the oxidizing reagent at the preset speed, and adds it dropwise to the digestion and colorimetric unit.

[0040] S52. When the dripping amount reaches the specified amount, the peristaltic pump stops working. The specified amount is preset according to the concentration of the oxidizing reagent and the volume of the water sample, and the range is 0.1~0.5ml.

[0041] The specific method for setting the specified amount is as follows: Based on the stoichiometric ratio of the oxidizing reagent to the target detection parameter in the water sample, combined with the water sample volume and the concentration of the oxidizing reagent, the amount is determined using the formula: , in, To predict the concentration for the target parameter, For the volume of the water sample, It is the stoichiometric coefficient. The concentration of the oxidizing reagent is calculated to ensure that each drop of the specified amount of reagent causes a significant change in the properties of the reaction solution, avoiding insufficient reaction due to too little addition or misjudgment of the titration endpoint due to too much addition.

[0042] S53. Let stand for 3-5 seconds to allow the reagent to react fully in the digestion and colorimetric unit. During the standing process, control the digestion and colorimetric unit to stir at a low speed of 50-80 r / min to ensure that the reagent and water sample are mixed evenly and to avoid misjudgment of the endpoint due to insufficient local reaction.

[0043] The low-speed stirring uses magnetic stirring with a stir bar made of polytetrafluoroethylene to avoid reaction with the reagents. The stirring speed is adjusted in real time by the control system. If bubbles appear in the reaction solution, the stirring speed is appropriately reduced to avoid affecting the detection accuracy of the colorimetric sensor. The settling time can be adaptively adjusted according to the reaction rate. If the absorbance of the reaction solution changes little after the previous settling, the settling time can be extended to 5 seconds to ensure a complete reaction.

[0044] S54. The colorimetric sensor detects the properties of the reaction solution. A sudden change in properties is specifically a significant change in the color of the reaction solution. The colorimetric sensor determines whether a sudden change in properties has occurred by detecting changes in the absorbance of the reaction solution. When the change in absorbance exceeds the preset absorbance threshold, it is determined to be a sudden change in properties.

[0045] The colorimetric sensor uses the visible light colorimetric principle, with a detection wavelength range of 400~700nm. The corresponding detection wavelength is selected according to the reaction characteristics of the target detection parameter (e.g., 610nm wavelength is selected when detecting COD). The preset absorbance threshold is determined based on the blank experiment. In the blank experiment, a blank water sample without the target detection parameter is injected into the digestion colorimetric unit, and the oxidizing reagent is added according to the titration procedure. The absorbance change curve is recorded, and the amount of absorbance change corresponding to the inflection point of the curve is used as the preset absorbance threshold to ensure the accuracy of phenotypic mutation determination.

[0046] S55. If no mutation occurs, return to step S51 to continue adding drops. If a mutation occurs, proceed to step S6.

[0047] S6. Data Calculation and Process End: After the titration stops, the system records the weight of the current weighing pan component as the titration termination weight. By the difference between the initial titration weight and the titration termination weight, the actual weight of the reagent used in this titration is calculated. This actual weight is substituted into the preset calculation model to calculate the measured value of the water sample parameters and complete the titration control process.

[0048] Furthermore, the difference between the initial titration weight and the final titration weight is the actual weight of the reagent used in this titration. By combining this actual weight with the concentration parameter of the oxidizing reagent, the content of the target detection parameter in this water sample can be calculated. The default calculation model is: , in The concentration of the target detection parameter in the water sample. This refers to the actual mass of reagents consumed. The concentration of the oxidizing agent. For the volume of the water sample, This is the stoichiometric coefficient.

[0049] Considering that the density of the oxidizing reagent expands and contracts with changes in ambient temperature, thus affecting the conversion between mass and volume, a temperature compensation mechanism is introduced. Specifically, the calculation of the actual mass of reagent consumed needs to deduct the effect of temperature. The control system has a built-in temperature sensor (such as a PT100 or NTC thermistor) to monitor the temperature of the reagent in the oxidizing reagent bottle in real time. The control system corrects the actual mass of reagent consumed according to a temperature-density conversion table. The correction formula is as follows: , in, To determine the mass of reagents consumed after calibration, This refers to the measured weight difference (i.e., the difference between the initial weight of the titration and the final weight of the titration). The density of the reagent at the current temperature t. The standard density of the reagent at 25℃ is used as the calibration formula to eliminate the influence of reagent density changes caused by ambient temperature fluctuations on the measurement results, ensuring the consistency of measurement results under different seasons and room temperatures.

[0050] Furthermore, after the titration process is completed, the remaining weight of the reagent bottle detected by the weighing pan component can be used to predict whether the remaining amount of oxidizing reagent is sufficient for the next titration. At the same time, by comparing the real-time rate of change of the reagent bottle weight during the titration process with the operating status of the peristaltic pump, the preset threshold for the rate of change of weight is preset based on the preset flow rate of the peristaltic pump and the reagent density. If the peristaltic pump is running but the rate of change of weight is lower than the preset threshold, it is predicted that there is a leakage fault in the pipeline.

[0051] The specific method for predicting the remaining amount of oxidizing reagent is as follows: The system presets the minimum reagent amount required for the next titration, which is set at 1.2 times the maximum reagent consumption for a single titration. The volume of the reagent corresponding to the remaining weight of the reagent bottle is calculated, and the remaining weight is divided by the reagent density. This is compared with the minimum reagent amount. If the remaining volume is greater than or equal to the minimum reagent amount, the remaining amount is considered sufficient. Otherwise, an audible and visual warning is issued to remind the staff to replenish the reagent. The preset threshold for the rate of weight change is calculated as: preset flow rate of the peristaltic pump × reagent density × 0.8 (with a 20% error margin). If the peristaltic pump is running and the rate of weight change remains below the preset threshold for 3 seconds, a leak or blockage in the pipeline is detected. The system immediately stops the titration process, issues a fault alarm signal, and records the time of the fault and the weight change data to facilitate troubleshooting by staff, such as checking whether the tubing interface is loose or whether the pipeline is blocked.

[0052] In summary, this invention achieves closed-loop control of the titration process through the tare weight method. By performing steps such as tare weight calibration, pipeline initialization, real-time weight acquisition, and closed-loop speed correction, it effectively solves the problems of large measurement error, susceptibility to pipeline leakage, and inability to predict reagent balance in traditional open-loop control of syringe pumps.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A titration control method using the weight loss weighing method in an online water quality analyzer, characterized in that, Includes the following steps: S1. Preliminary preparation: Place the oxidizing reagent bottle on the weighing pan assembly, enter the tare weight of the oxidizing reagent bottle and its matching connecting pipes and calibrate it. After determining the tare weight benchmark, calculate the net weight of the oxidizing reagent in the oxidizing reagent bottle through the weighing pan assembly. S2. Piping initialization: Before starting the titration process, control the peristaltic pump to prefill the entire pipeline of the peristaltic pump with oxidizing reagent, and clean the digestion colorimetric unit to remove any overflowing reagent, ensuring that the weighing value during the titration process is consistent with the actual amount of reagent involved in the reaction. S3, Initial Titration Record: When the instrument enters the titration process, the system records the current weight of the weighing pan assembly as the initial titration weight. Then, the peristaltic pump is started, and the speed of the peristaltic pump is adjusted by controlling the stepper motor of the peristaltic pump, thereby adjusting the speed at which the peristaltic pump draws reagent from the oxidizing reagent bottle. S4. Real-time weighing and acquisition: During the titration process, the weighing pan component detects the actual weight of the oxidizing reagent bottle in real time at a preset acquisition frequency and transmits the weight data to the control system of the water quality analyzer simultaneously. S5. Intermittent titration and reaction detection: The control system controls the peristaltic pump to work intermittently. After each specified amount of reagent is added, the addition is stopped and waited for 3 to 5 seconds to allow the reagent to react fully in the digestion and colorimetric unit. Then, the colorimetric sensor detects whether the reagent properties have changed abruptly. If no change has occurred, the addition continues. If a change has occurred, the addition is stopped immediately. S6. Data Calculation and Process End: After the titration stops, the system records the weight of the current weighing pan component as the titration termination weight. By the difference between the initial titration weight and the titration termination weight, the actual weight of the reagent used in this titration is calculated. This actual weight is substituted into the preset calculation model to calculate the measured value of the water sample parameters and complete the titration control process.

2. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 1, characterized in that, In step S1, the weighing pan assembly includes a weighing pan, a weighing sensor, and an MCU controller. The oxidizing reagent bottle is connected to the sampling tube of the peristaltic pump via a flexible tube, and interference factors at the connection of the flexible tube are included in the tare weight record. The weighing pan is made of 304 stainless steel and is used to fix the oxidizing reagent bottle and align the center of gravity of the reagent bottle with the force measurement center of the weighing sensor. The weighing pan of the corresponding size is configured according to the different specifications of the reagent bottle. The weighing sensor is a high-precision cantilever beam resistance strain gauge sensor with a range of 1 kg, a 200% overload capacity, a repeatability of 0.05%, and the ability to achieve an accurate measurement of 0.05 grams.

3. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 2, characterized in that, In step S2, the running time of the peristaltic pump during pipeline initialization is preset according to the pipeline volume to ensure that the oxidizing agent completely fills the inlet pipe, pump body and outlet pipe of the peristaltic pump. When cleaning the digestion colorimetric unit, the oxidizing agent is used to circulate and rinse 2 to 3 times, and each rinsing time is 10 to 15 seconds.

4. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 3, characterized in that, In step S3, the preset peristaltic pump extraction speed can be adjusted according to the estimated content of the target detection parameter in the water sample. When the estimated content of the target detection parameter is high, the stepper motor speed is adjusted to make the peristaltic pump extract the reagent at a high speed. When the estimated content of the target detection parameter is low, the stepper motor speed is adjusted to make the peristaltic pump extract the reagent at a low speed. The high speed is 10~15ml / min and the low speed is 2~5ml / min, so as to achieve a balance between titration efficiency and titration accuracy. At the same time, after the system records the initial titration weight, it delays for 1~2 seconds before starting the peristaltic pump.

5. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 4, characterized in that, In step S4, the MCU controller has a built-in 24-bit high-precision AD chip with a sampling rate of 40Hz, which can achieve high-resolution weight detection of 0.01 grams. The MCU controller has a built-in RS485 interface and transmits real-time weight data to the control system of the water quality analyzer through the MODBUS RTU slave protocol. The control system filters the received weight data to remove abnormal fluctuation data and ensure the stability of weight detection. The filtering process adopts a moving average filtering algorithm, and the filtering window is set to 5 to 8 sampling points.

6. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 5, characterized in that, In step S5, the inlet of the peristaltic pump extends below the liquid surface of the oxidizing reagent bottle and is close to the bottom of the bottle, 5-8 mm away from the bottom of the bottle, to ensure that the oxidizing reagent in the reagent bottle can be fully extracted and reduce reagent residue. The outlet of the peristaltic pump is connected to the digestion colorimetric unit, and the outlet is 1-2 cm away from the highest liquid surface of the reaction liquid in the digestion colorimetric unit. A guide port with an inclination angle of 30-45° is provided at the end of the outlet.

7. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 6, characterized in that, In step S5, the preset acquisition frequency is 10 times per second. The control system of the water quality analyzer acquires the measurement data of the weighing pan assembly in real time through this frequency, monitors the change in reagent bottle weight in real time, and at the same time, the control system calculates the reagent consumption rate based on the real-time weight change, compares it with the theoretical consumption rate corresponding to the preset extraction speed of the peristaltic pump, and corrects the operating speed of the peristaltic pump in real time.

8. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 7, characterized in that, Step S5 includes the following sub-steps: S51. The peristaltic pump starts, extracts the oxidizing reagent at the preset speed, and adds it dropwise to the digestion and colorimetric unit; S52. When the dripping amount reaches the specified amount, the peristaltic pump stops working. The specified amount is preset according to the concentration of the oxidizing reagent and the volume of the water sample, and the range is 0.1~0.5ml. S53. Let stand for 3-5 seconds to allow the reagents to react fully in the digestion and colorimetric unit. During the standing process, control the digestion and colorimetric unit to be stirred at a low speed of 50-80 r / min. S54. The colorimetric sensor detects the properties of the reaction solution. The property mutation specifically refers to a significant change in the color of the reaction solution. The colorimetric sensor determines whether the property mutation has occurred by detecting the change in absorbance of the reaction solution. When the change in absorbance exceeds a preset absorbance threshold, it is determined to be a property mutation. S55. If no mutation occurs, return to step S51 to continue adding drops. If a mutation occurs, proceed to step S6.

9. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 8, characterized in that, In step S6, the difference between the initial titration weight and the final titration weight is the actual weight of the reagent used in this titration. By combining this actual weight with the concentration parameter of the oxidizing reagent, the content of the target detection parameter in this water sample is calculated. The preset calculation model is as follows: , in The concentration of the target detection parameter in the water sample. This refers to the actual mass of reagents consumed. The concentration of the oxidizing agent. For the volume of the water sample, This is the stoichiometric coefficient.

10. The titration control method of the weight loss weighing method in the online water quality analyzer according to claim 8, characterized in that, In step S6, after the titration process is completed, the remaining weight of the reagent bottle detected by the weighing pan assembly can be used to predict whether the remaining amount of oxidizing reagent is sufficient for the next titration. At the same time, by comparing the real-time rate of change of the reagent bottle weight during the titration process with the operating status of the peristaltic pump, the preset threshold of the weight change rate is preset according to the preset flow rate of the peristaltic pump and the reagent density. If the peristaltic pump is running but the weight change rate is lower than the preset threshold, it is predicted that there is a leakage fault in the pipeline.

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