Self-calibration sulfur dioxide tester
By self-calibrating the working circuit of the sulfur dioxide meter and using the temperature and flow detection modules for signal acquisition and dynamic feature extraction, the problems of temperature drift of the heating module and abnormal nitrogen flow control are solved, and the accuracy of the test results is achieved.
Patent Information
- Application Number
- CN202510789550.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-13
- Publication Date
- 2025-09-05
AI Technical Summary
Existing sulfur dioxide detectors may experience temperature drift in the heating module and abnormal nitrogen flow control after long-term use, resulting in low test results and difficulty in calibration.
A self-calibrating sulfur dioxide meter is used to collect signals through the temperature detection module and the flow detection module, perform dynamic feature extraction and fault judgment, use the composite decision module to adjust the control parameters of the actuator and the feedforward compensation of the nitrogen flow, and regularly correct the measurement error through the calibration verification module.
It realizes the identification and self-calibration of heating module temperature drift and nitrogen flow control anomalies, ensuring the accuracy of test results.
Smart Images
Figure CN120594739A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of sulfur dioxide measuring instruments, in particular to a self-calibrating sulfur dioxide measuring instrument. Background Art
[0002] The sulfur dioxide detector based on the pharmacopoeia distillation-titration method is mainly used to detect the residual amount of sulfur dioxide in food or medicine. It includes a heating module and a nitrogen module. Its working principle is to first distill the sulfur dioxide in the sample through a distillation device. Specifically, the sample is placed in a distillation flask, added with an appropriate amount of water and heated for distillation. The sulfur dioxide is distilled out along with the water vapor, and then absorbed by the absorption liquid after condensation. Subsequently, the sulfur dioxide in the absorption liquid is quantitatively analyzed by titration. Starch is usually used as an indicator and titrated with an iodine standard solution. The titration end point is determined based on the color change during the titration process, and the sulfur dioxide content in the sample is then calculated. The detector strictly follows the distillation and titration conditions specified in the pharmacopoeia, can ensure the accuracy and reliability of the test results, and is widely used in food quality testing, drug quality control and other fields. It is of great significance to ensure food safety and drug quality.
[0003] In actual use, sulfur dioxide detectors based on the pharmacopoeial distillation-titration method are often used for large-scale sample testing. The long-term operation of the heating module, coupled with high temperatures, accelerates the aging of circuit components, leading to unstable heating power output. Furthermore, nitrogen gas line blockage or valve wear, combined with circuit signal distortion, can cause flow control failure. This can lead to a combined failure of heating module temperature drift and nitrogen flow control anomalies. This combined failure, due to incomplete acid hydrolysis caused by insufficient temperature and insufficient nitrogen flow rate, prevents all released sulfur dioxide from entering the absorption liquid. The combined effect can lead to significantly low final test results. Even through calibration and parameter adjustment, it is difficult to compensate for the synchronization deviation between the two modules.
[0004] Therefore, a self-calibrating sulfur dioxide meter is proposed to solve or alleviate the above problems. Summary of the Invention
[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a self-calibrating sulfur dioxide measuring instrument.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A self-calibrating sulfur dioxide meter includes a housing, a human-machine interface disposed on the housing, and a working circuit disposed within the housing and coupled to the human-machine interface. The working circuit includes a temperature detection module, a flow detection module, a composite decision module, a dynamic compensation module, a calibration verification module, and an actuator for controlled regulation of heating, nitrogen volume, a nitrogen main path, and a nitrogen branch path. The temperature detection module collects three redundant temperature signals and transmits them to the composite decision module; The flow detection module synchronously collects the Coriolis mass flow signal and the differential pressure compensation flow signal and transmits them to the composite decision module; The composite decision module extracts dynamic features from the temperature signal and the flow signal, and determines the temperature drift fault, nitrogen flow abnormality fault or composite fault level based on preset threshold rules; The dynamic compensation module adjusts the proportional-integral-differential control parameters of the heating in the actuator and the feedforward compensation amount of the nitrogen flow in the actuator according to the fault level; The calibration verification module regularly injects reference signals into the temperature detection module and the flow detection module to correct system measurement errors.
[0007] Preferably, the temperature detection module collects three redundant temperature signals and transmits them to the composite decision module, including the following steps: By synchronously collecting three redundant temperature signals and transmitting them to the composite decision module; A dynamic threshold is used to eliminate abnormal temperature data, the median of the three temperature signals is calculated, and the root mean square value of half the sum of the squares of the deviations of the three redundant temperature signals from the median is calculated as the standard deviation; If the deviation between one redundant temperature signal and the median value exceeds three standard deviations, the redundant temperature signal is shielded.
[0008] Preferably, the flow detection module synchronously collects the Coriolis mass flow signal and the differential pressure compensation flow signal and transmits them to the composite decision module, including the following steps: Multiply the phase difference value with the calibration coefficient and the inverse of the excitation frequency to obtain the main flow measurement value; The main flow value is subjected to median filtering with a sliding window length of three points, and the middle value of the data at the current moment and the two moments before it is taken as the final flow value.
[0009] Preferably, the composite decision module extracts dynamic features from the temperature signal and the flow signal, and determines the temperature drift fault, the nitrogen flow abnormality fault, or the composite fault level based on a preset threshold rule, including the following steps: To calculate the temperature drift rate, take the difference between the current temperature value and the temperature value twice the sampling period ago, and divide it by twice the sampling period time; Calculate the flow fluctuation variance by calculating one-fifth of the sum of squares of the deviations of the flow measurement values from the window average within a five-point sliding window; If the temperature drift rate exceeds 0.5 degrees Celsius per minute and the absolute deviation between the current temperature and the set value exceeds two degrees Celsius, a temperature fault is determined. If the flow fluctuation variance exceeds 0.01 per liter per minute squared and the absolute deviation between the current flow and the set value exceeds 0.1 liter per minute, a flow fault is determined.
[0010] Preferably, the dynamic compensation module adjusts the proportional-integral-derivative control parameters of the heating in the actuator and the feedforward compensation amount of the nitrogen flow in the actuator according to the fault level, including the following steps: When the fault level reaches or exceeds level 1, it switches to the anti-integral windup control mode, retaining only the proportional and differential control items and disabling the integral control item; The coupled compensation of temperature to flow rate is performed, and a compensation amount is generated according to the temperature drift rate at a ratio of 0.05 liters per minute per degree Celsius second, and the compensation amount is limited to a range of plus or minus 10% of the set value.
[0011] Preferably, the calibration verification module periodically injects a reference signal into the temperature detection module and the flow detection module to correct the system measurement error, comprising the following steps: Temperature calibration uses a single-point reference correction, and the ratio of the original measurement value of the temperature detection module to the standard voltage value of the reference source is used as the calibration coefficient; Flow calibration is performed by adjusting the proportional factor, using the ratio of the original measurement value of the flow meter detection module to the calibration value of the standard flow device as the calibration coefficient.
[0012] Preferably, the actuator includes a solid-state relay, a heater arranged in the housing, a proportional valve for connecting to the nitrogen main line to dynamically adjust the nitrogen flow rate, and an electrically controlled needle valve for connecting the nitrogen main line and the nitrogen branch line to switch the nitrogen gas line and limit the heating efficiency; The coil of the solid-state relay is connected to the drain of the MOS tube IRF540 in the dynamic compensation module, the main circuit end of the solid-state relay is connected in series with the heater, the controlled end of the proportional valve is connected to the output end of the H-bridge circuit L298N in the dynamic compensation module, and the controlled end of the stepper motor in the electric-controlled needle valve is connected to the output end of the A4988 stepper motor driver in the dynamic compensation module.
[0013] The present invention has the following beneficial effects: The present invention can utilize the temperature detection module and the flow detection module to collect data through the working circuit in the self-calibrating sulfur dioxide meter, and perform dynamic feature extraction on the temperature signal and the flow signal, determine the temperature drift fault, the nitrogen flow abnormality fault or the composite fault level based on the preset threshold rule, and then adjust the proportional-integral-differential control parameters of the heating in the actuator and the feedforward compensation amount of the nitrogen flow in the actuator according to the composite fault level, and regularly inject a reference signal into the temperature detection module and the flow detection module to correct the system measurement error, so that the sulfur dioxide meter can finally identify the composite fault of the heating module temperature drift and the nitrogen flow control abnormality, and perform self-calibration, so that the sulfur dioxide meter can be used normally without any data accuracy problems. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.
[0015] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a structural block diagram of the working circuit in the present invention.
[0016] In the figure, 1. housing; 2. human-computer interaction interface; 3. actuator; 4. temperature detection module; 5. flow detection module; 6. calibration verification module; 7. composite decision module; 8. dynamic compensation module. DETAILED DESCRIPTION
[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.
[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.
[0019] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.
[0020] In the description of the present invention, it should be understood that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when in use, or are the orientation or position relationship commonly understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.
[0021] Furthermore, the terms “first,” “second,” “third,” etc., are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.
[0022] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.
[0023] A self-calibrating sulfur dioxide meter, such as Figure 1 As shown, it includes a housing 1, a human-computer interaction interface 2 provided on the housing 1, and a working circuit provided in the housing 1 and coupled to the human-computer interaction interface 2, as shown in FIG. Figure 2 As shown, the working circuit includes a temperature detection module 4, a flow detection module 5, a composite decision module 7, a dynamic compensation module 8, a calibration verification module 6, and an actuator 3 for controlled regulation of heating, nitrogen volume, nitrogen main path and nitrogen branch path; The temperature detection module 4 collects three redundant temperature signals and transmits them to the composite decision module 7; the flow detection module 5 synchronously collects the Coriolis mass flow signal and the differential pressure compensation flow signal and transmits them to the composite decision module 7; the composite decision module 7 extracts dynamic features of the temperature signal and the flow signal, and determines the temperature drift fault, the abnormal nitrogen flow fault or the composite fault level based on the preset threshold rules; the dynamic compensation module 8 adjusts the proportional-integral-differential control parameters of the heating in the actuator 3 and the feedforward compensation amount of the nitrogen flow in the actuator 3 according to the combined fault level; the calibration verification module 6 regularly injects reference signals into the temperature detection module 4 and the flow detection module 5 to correct the system measurement error.
[0024] The present invention can utilize the temperature detection module 4 and the flow detection module 5 to collect data through the working circuit in the self-calibrating sulfur dioxide meter, and perform dynamic feature extraction on the temperature signal and the flow signal, determine the temperature drift fault, the nitrogen flow abnormality fault or the composite fault level based on the preset threshold rule, and then adjust the proportional-integral-differential control parameters of the heating in the actuator 3 and the feedforward compensation amount of the nitrogen flow in the actuator 3 according to the composite fault level, and regularly inject a reference signal into the temperature detection module 4 and the flow detection module 5 to correct the system measurement error, so that the sulfur dioxide meter can finally identify the composite fault of the heating module temperature drift and the nitrogen flow control abnormality, and perform self-calibration, so that the sulfur dioxide meter can be used normally without data accuracy problems.
[0025] Preferably, the temperature detection module 4 collects three redundant temperature signals and transmits them to the composite decision module 7, including the following steps: By synchronously collecting three redundant temperature signals and transmitting them to the composite decision module 7; A dynamic threshold is used to eliminate abnormal temperature data, the median of the three temperature signals is calculated, and the root mean square value of half the sum of the squares of the deviations of the three redundant temperature signals from the median is calculated as the standard deviation; If the deviation between one redundant temperature signal and the median value exceeds three standard deviations, the redundant temperature signal is shielded.
[0026] The temperature detection module 4 includes three sets of PT1000 temperature sensors, an LM334 constant current source, a bridge circuit, three sets of AD623 instrumentation amplifiers, a CD4051 multiplexer, an STM32F4 microcontroller, and a first ADS1256 digital-to-analog converter; The positive electrodes of the three PT1000 temperature sensors are connected to the output of the LM334 constant current source, and the negative electrodes of the PT1000 temperature sensors are grounded. The output pins of the three PT1000 temperature sensors are connected to the input of the AD623 instrumentation amplifier through a bridge circuit. The output of the three AD623 instrumentation amplifiers are connected to the channels of the CD4051 multiplexer. The REF pin of the AD623 instrumentation amplifier is connected to the 2.5V reference. The common end of the CD4051 multiplexer is connected to the first ADS1256 digital-analog converter. The input end of the converter, the channel selection end of the CD4051 multiplexer and the connection pin of the STM32F4 microcontroller, the output end of the first ADS1256 digital-to-analog converter are connected to the input end of the composite decision module 7, the connection section of the STM32F4 microcontroller is connected to the serial peripheral interface, chip select end, and clock end of the MCP41010 digital potentiometer, the output end of the STM32F4 microcontroller is connected to the 24LC256 memory chip in the calibration verification module 6, and the STM32F4 microcontroller is coupled to the human-computer interaction interface 2.
[0027] Three sets of PT1000 temperature sensors are connected to a bridge circuit constructed with an LM334 constant current source via a three-wire system. Each set of PT1000 temperature sensors is connected to the output of the LM334 constant current source to obtain a 0.5mA excitation current. The output of each set of PT1000 temperature sensors is connected to the bridge circuit, and the negative terminal of the PT1000 temperature sensor is grounded. The differential signal output by the bridge circuit is amplified 200 times by three sets of AD623 instrumentation amplifiers. The analog signal output is input into each channel of the CD4051CD4051 multiplexer. The STM32F4 microcontroller dynamically selects the active channel through the channel selector of the CD4051 multiplexer. When the deviation of the sensor data from the median value exceeds three times the standard deviation, the backup channel is automatically switched. The filtered signal is sent to the first ADS1256 digital-to-analog converter for digital conversion. The converted digital signal is transmitted to the Spartan-6 chip in the composite decision module 7 for real-time processing.
[0028] Preferably, the flow detection module 5 synchronously collects the Coriolis mass flow signal and the differential pressure compensation flow signal and transmits them to the composite decision module 7, including the following steps: Multiply the phase difference value with the calibration coefficient and the inverse of the excitation frequency to obtain the main flow measurement value; The main flow value is subjected to median filtering with a sliding window length of three points, and the middle value of the data at the current moment and the two moments before it is taken as the final flow value.
[0029] Flow detection module 5 includes FS4000 Coriolis flowmeter, LTC6992 voltage-controlled oscillator, push-pull amplifier, AD8302 phase detector, MPX5100DP differential pressure sensor, OPA2188 instrumentation amplifier, LTC1562 filter, RMS detector ADL5511, and second ADS1256 digital-to-analog converter; The excitation coil drive end of the FS4000 Coriolis flowmeter is connected to the output of the LTC6992 voltage-controlled oscillator through a push-pull amplifier. The phase detection end of the FS4000 Coriolis flowmeter is connected to the input of the AD8302 phase detector. The output of the AD8302 phase detector is connected to the input of the second ADS1256 digital-to-analog converter. The output of the MPX5100DP differential pressure sensor is connected to the input of the OPA2188 instrumentation amplifier. The output of the OPA2188 instrumentation amplifier is connected to the input of the RMS detector ADL5511 after passing through the LTC1562 filter. The output of the RMS detector ADL5511 is connected to the input of the second ADS1256 digital-to-analog converter.
[0030] The FS4000 Coriolis flowmeter in flow detection module 5 receives a 40kHz square wave signal generated by the LTC6992 voltage-controlled oscillator through its excitation coil. This signal is driven by a push-pull amplifier constructed from MOSFET tubes to form a high-power excitation magnetic field. The phase difference signal induced by the detection coil of the FS4000 Coriolis flowmeter is converted into a voltage signal by the AD8302 phase detector and input into the second ADS1256 digital-to-analog converter. The MPX5100DP differential pressure sensor working in parallel amplifies its auxiliary flow signal by 50 times through the OPA2188 instrumentation amplifier. The signal is then band-pass filtered with a 1-100Hz bandpass filter by the LTC1562 filter. The effective value signal is then extracted by the ADL5511 RMS detector and input into the second ADS1256 digital-to-analog converter. The dual-mode flow data is processed by sliding median filtering in the Spartan-6 chip of the composite decision module 7 and enters the decision process synchronously with the temperature data.
[0031] Preferably, the composite decision module 7 performs dynamic feature extraction on the temperature signal and the flow signal, and determines the temperature drift fault, nitrogen flow abnormality fault or composite fault level based on a preset threshold rule, including the following steps: To calculate the temperature drift rate, take the difference between the current temperature value and the temperature value twice the sampling period ago, and divide it by twice the sampling period time; Calculate the flow fluctuation variance by calculating one-fifth of the sum of squares of the deviations of the flow measurement values from the window average within a five-point sliding window; If the temperature drift rate exceeds 0.5 degrees Celsius per minute and the absolute deviation between the current temperature and the set value exceeds two degrees Celsius, a temperature fault is determined. If the flow fluctuation variance exceeds 0.01 per liter per minute squared and the absolute deviation between the current flow and the set value exceeds 0.1 liter per minute, a flow fault is determined.
[0032] The composite decision module 7 includes a spartan-6 chip, an AD835 analog multiplier, an AD5260 digital potentiometer, a CD4532 priority encoder, a CD4013 D flip-flop, and an optocoupler TLP521-4; The input end of the spartan-6 chip is connected to the output end of the first ADS1256 digital-to-analog converter in the temperature detection module 4 and the output end of the second ADS1256 digital-to-analog converter in the flow meter detection module. The X input end and the Y input end of the AD835 analog multiplier are respectively connected to the output end of the spartan-6 chip. The output end of the AD835 analog multiplier is connected to the input end of the spartan-6 chip. The first input end of the CD4532 priority encoder is connected to the output end of the spartan-6 chip and receives the temperature over-limit signal. The first input end of the CD4532 priority encoder is connected to the output end of the spartan-6 chip. The output end of the chip is connected to and receives the flow rate excess signal, the output end of the CD4532 priority encoder is connected to the D input end of the D flip-flop CD4013, the start and end pins of the D flip-flop CD4013 are connected to the output end of the spartan-6 chip, and the output end of the D flip-flop CD4013 is connected to the control end of the dynamic compensation module 8 through the optocoupler TLP521-4. The chip select end, clock end, and serial data input end of the AD5260 digital potentiometer are respectively connected to the connection end of the spartan-6 chip, and the sliding end of the AD5260 digital potentiometer is connected to the Y input end of the AD835 analog multiplier to dynamically adjust the multiplier gain.
[0033] The Spartan-6 chip in the composite decision module 7 first performs dynamic baseline calibration on the three temperature signals, adjusts the gain coefficient of the AD835 analog multiplier through the AD5260 digital potentiometer, and uses a three-point exponentially weighted moving average algorithm to filter the temperature signals in real time. At the same time, the backward differential temperature drift rate is calculated. When the temperature change rate exceeds 0.5°C / min and the absolute deviation exceeds 2°C, the temperature anomaly flag is triggered. The flow signal is analyzed through a five-point sliding window variance calculation to analyze the fluctuation energy. If the variance value exceeds 0.01 (L / min), the flow rate is automatically detected. 2 If the flow rate deviates from the set value by more than 0.1L / min, the flow rate is marked as abnormal. The two abnormal signals are input into the CD4532 priority encoder for logic arbitration. The temperature fault is given a higher priority. The arbitration result is locked by the D flip-flop CD4013 and isolated and output to the dynamic compensation module 8 through the optocoupler TLP521-4.
[0034] Preferably, the dynamic compensation module 8 adjusts the proportional-integral-differential control parameters of the heating in the actuator 3 and the feedforward compensation amount of the nitrogen flow in the actuator 3 according to the fault level, including the following steps: When the fault level reaches or exceeds level 1, it switches to the anti-integral windup control mode, retaining only the proportional and differential control items and disabling the integral control item; The coupled compensation of temperature to flow rate is performed, and a compensation amount is generated according to the temperature drift rate at a ratio of 0.05 liters per minute per degree Celsius second, and the compensation amount is limited to a range of plus or minus 10% of the set value.
[0035] The dynamic compensation module 8 includes an ADN8830 thermoelectric controller, an OPA2188 operational amplifier, an A4988 stepper motor driver, an IXDD404 MOSFET driver, an IRF540 MOS tube, and an L298N H-bridge circuit. The serial peripheral interface, chip select terminal, and clock terminal of the ADN8830 thermoelectric controller are connected to the connection terminal of the Spartan-6 chip in the compound decision module 7. The output terminal of the ADN8830 thermoelectric controller is connected to the input terminal of the MOSFET driver IXDD404. The output terminal of the MOSFET driver IXDD404 is connected to the gate of the MOS tube IRF540 to control the power supply of the actuator 3. The input terminal of the OPA2188 operational amplifier is connected to the output terminal of the Spartan-6 chip in the compound decision module 7. The output terminal of the OPA2188 operational amplifier is connected to the input terminal of the H-bridge circuit L298N. The H-bridge circuit L298N is connected to the actuator 3. The STEP pin and DIR pin of the A4988 stepper motor driver are respectively connected to the output terminals of the Spartan-6 chip in the compound decision module 7. The output terminal of the A4988 stepper motor driver is connected to the actuator 3.
[0036] Dynamic compensation module 8 implements differentiated control strategies based on the fault level. For a level 1 fault (single parameter anomaly), the ADN8830 thermoelectric controller receives the PID parameters sent by the Spartan-6 chip in the composite decision module 7 and dynamically adjusts the heating power using an anti-integral windup algorithm. The output signal is amplified by the MOSFET driver IXDD404 and then drives the MOSFET transistor IRF540 to control the on-off frequency of the solid-state relay. Simultaneously, the OPA2188 operational amplifier generates a feedforward compensation value based on the temperature drift rate at a ratio of 0.05 (L / min) / (°C / s). The nitrogen flow rate is adjusted via the H-bridge circuit L298N proportional valve. For a level 2 composite fault, the A4988 stepper motor driver is activated to drive the electronically controlled needle valve at a 200Hz pulse frequency to switch to the backup gas path.
[0037] Preferably, the calibration verification module 6 regularly injects a reference signal into the temperature detection module 4 and the flow detection module 5 to correct the system measurement error, including the following steps: Temperature calibration uses a single-point reference correction, and the ratio of the original measurement value of the temperature detection module 4 to the standard voltage value of the reference source is used as the calibration coefficient; Flow calibration is performed by adjusting the proportional factor, using the ratio of the original measurement value of the flow meter detection module to the calibration value of the standard flow device as the calibration coefficient.
[0038] Calibration verification module 6 includes LM335Z temperature reference, OP07 buffer, ADR445 voltage reference, DAC8554 digital-to-analog converter, AD9833 waveform generator, and 24LC256 memory chip; The output end of the LM335Z temperature reference is connected to the positive input end of the OP07 buffer, the negative input end of the OP07 buffer and its output end are short-circuited to form a voltage follower, the output end of the OP07 buffer is connected to the connection end of the first ADS1256 digital-to-analog converter in the temperature detection module 4, the output end of the ADR445 voltage reference is connected to the connection end of the first ADS1256 digital-to-analog converter in the temperature detection module 4, the serial peripheral interface, chip select end, and clock end of the DAC8554 digital-to-analog converter are connected to the connection end of the STM32F4 microcontroller, the output end of the DAC8554 digital-to-analog converter is connected to the channel pin of the CD4051 multiplexer in the temperature detection module 4 for calibration signal injection, the output end of the AD9833 waveform generator is connected to the input end of the LTC6992 voltage-controlled oscillator in the flow detection module 5 to inject a disturbance signal, and the 24LC256 memory chip is connected to the connection end of the STM32F4 microcontroller in the temperature detection module 4 to read and write calibration parameters.
[0039] The actuator 3 includes a solid-state relay, a heater disposed in the housing 1, a proportional valve connected to the nitrogen main line to dynamically adjust the nitrogen flow rate, and an electrically controlled needle valve connected to the nitrogen main line and the nitrogen branch line to switch the nitrogen gas path and limit the heating efficiency; The coil of the solid-state relay is connected to the drain of the MOS tube IRF540 in the dynamic compensation module 8, the main circuit end of the solid-state relay is connected in series with the heater, the controlled end of the proportional valve is connected to the output end of the H-bridge circuit L298N in the dynamic compensation module 8, and the controlled end of the stepper motor in the electric control needle valve is connected to the output end of the A4988 stepper motor driver in the dynamic compensation module 8.
[0040] Calibration verification module 6 automatically performs benchmark calibration upon power-up. The 10mV / °C signal output by the LM335Z temperature reference source is input into the first ADS1256 digital-to-analog converter in temperature detection module 4 via a voltage follower formed by an OP07 buffer. This signal is compared with the measured value of the PT1000 temperature sensor to calculate the calibration coefficient. The ADR445 voltage reference provides a 5V reference signal through a voltage divider network to verify ADC linearity. The DAC8554 digital-to-analog converter automatically generates a standard temperature curve of 0-100°C and injects it into the CD4051 multiplexer. The AD9833 waveform generator synchronously generates a frequency disturbance signal to test the dynamic response of the flow detection loop. All calibration parameters are stored in the 24LC256 memory chip. The solid-state relay in actuator 3 uses a zero-crossing trigger method to control the heater power. In a fault state, the MOSFET driver IXDD404 outputs a forced shutdown signal. The proportional valve is in the H-bridge circuit L29. Driven by an 8N PWM signal, the opening control is achieved with an accuracy of 0.1%. The electronically controlled needle valve receives the subdivision control signal through the A4988 stepper motor driver to complete the gas path switching. When the temperature detection module 4 identifies an abnormal drift exceeding 5°C / min, the Spartan-6 chip in the composite decision module 7 completes the fault decision within 200ms and starts the compensation program, stabilizing the nitrogen flow to within ±0.05L / min of the set value. The calibration verification module 6 will automatically perform online calibration and write the error data into the 24LC256 memory chip. The STM32F4 microcontroller regularly reads the historical data in the 24LC256 memory chip for trend prediction and life assessment, forming a complete closed-loop control from sensor detection, feature extraction, fault decision to dynamic compensation, ensuring that the sulfur dioxide distillation titration process strictly meets the requirements, can identify and calibrate composite faults, and ensure the accuracy of the final measurement results of the sulfur dioxide meter.
[0041] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.
Claims
1. A self-calibrating sulfur dioxide meter, characterized in that: The invention comprises a housing (1), a human-machine interaction interface (2) arranged on the housing (1), and a working circuit arranged in the housing (1) and coupled to the human-machine interaction interface (2), wherein the working circuit comprises a temperature detection module (4), a flow detection module (5), a composite decision module (7), a dynamic compensation module (8), a calibration verification module (6), and an actuator (3) for controlled regulation of heating, nitrogen volume, a nitrogen main path, and a nitrogen branch path; The temperature detection module (4) collects three redundant temperature signals and transmits them to the composite decision module (7); The flow detection module (5) synchronously collects the Coriolis mass flow signal and the differential pressure compensation flow signal and transmits them to the composite decision module (7); The composite decision module (7) extracts dynamic features from the temperature signal and the flow signal, and determines the temperature drift fault, the nitrogen flow abnormality fault or the composite fault level based on a preset threshold rule; The dynamic compensation module (8) adjusts the proportional-integral-differential control parameters of the heating in the actuator (3) and the feedforward compensation amount of the nitrogen flow in the actuator (3) according to the fault level; The calibration verification module (6) regularly injects a reference signal into the temperature detection module (4) and the flow detection module (5) to correct system measurement errors.
2. A self-calibrating sulfur dioxide meter according to claim 1, characterized in that: The temperature detection module (4) collects three redundant temperature signals and transmits them to the composite decision module (7), comprising the following steps: By synchronously collecting three redundant temperature signals and transmitting them to the composite decision module (7); A dynamic threshold is used to eliminate abnormal temperature data, the median of the three temperature signals is calculated, and the root mean square value of half the sum of the squares of the deviations of the three redundant temperature signals from the median is calculated as the standard deviation; If the deviation between one redundant temperature signal and the median value exceeds three standard deviations, the redundant temperature signal is shielded.
3. A self-calibrating sulfur dioxide meter according to claim 1, characterized in that: The flow detection module (5) synchronously collects the Coriolis mass flow signal and the differential pressure compensation flow signal and transmits them to the composite decision module (7), comprising the following steps: Multiply the phase difference value with the calibration coefficient and the inverse of the excitation frequency to obtain the main flow measurement value; The main flow value is subjected to median filtering with a sliding window length of three points, and the middle value of the data at the current moment and the two moments before it is taken as the final flow value.
4. A self-calibrating sulfur dioxide meter according to claim 1, characterized in that: The composite decision module (7) extracts dynamic features from the temperature signal and the flow signal, and determines the temperature drift fault, nitrogen flow abnormality fault or composite fault level based on a preset threshold rule, including the following steps: To calculate the temperature drift rate, take the difference between the current temperature value and the temperature value twice the sampling period ago, and divide it by twice the sampling period time; Calculate the flow fluctuation variance by calculating one-fifth of the sum of squares of the deviations of the flow measurement values from the window average within a five-point sliding window; If the temperature drift rate exceeds 0.5 degrees Celsius per minute and the absolute deviation between the current temperature and the set value exceeds two degrees Celsius, a temperature fault is determined. If the flow fluctuation variance exceeds 0.01 per liter per minute squared and the absolute deviation between the current flow and the set value exceeds 0.1 liter per minute, a flow fault is determined.
5. A self-calibrating sulfur dioxide meter according to claim 1, characterized in that: The dynamic compensation module (8) adjusts the proportional-integral-differential control parameters of the heating in the actuator (3) and the feedforward compensation amount of the nitrogen flow in the actuator (3) according to the fault level, including the following steps: When the fault level reaches or exceeds level 1, it switches to the anti-integral windup control mode, retaining only the proportional and differential control items and disabling the integral control item; The coupled compensation of temperature to flow rate is performed, and a compensation amount is generated according to the temperature drift rate at a ratio of 0.05 liters per minute per degree Celsius second, and the compensation amount is limited to a range of plus or minus 10% of the set value.
6. A self-calibrating sulfur dioxide meter according to claim 1, characterized in that: The calibration verification module (6) regularly injects a reference signal into the temperature detection module (4) and the flow detection module (5) to correct the system measurement error, including the following steps: The temperature calibration adopts single-point reference correction, and the ratio of the original measurement value of the temperature detection module (4) to the standard voltage value of the reference source is used as the calibration coefficient; Flow calibration is performed by adjusting the proportional factor, using the ratio of the original measurement value of the flow meter detection module to the calibration value of the standard flow device as the calibration coefficient.
7. A self-calibrating sulfur dioxide meter according to claim 1, characterized in that: The actuator (3) includes a solid-state relay, a heater arranged in the housing (1), a proportional valve for connecting to the nitrogen main line to dynamically adjust the nitrogen flow rate, and an electrically controlled needle valve for connecting the nitrogen main line and the nitrogen branch line to switch the nitrogen gas line and limit the heating efficiency; The coil of the solid-state relay is connected to the drain of the MOS tube IRF540 in the dynamic compensation module (8), the main circuit end of the solid-state relay is connected in series with the heater, the controlled end of the proportional valve is connected to the output end of the H-bridge circuit L298N in the dynamic compensation module (8), and the controlled end of the stepping motor in the electric control needle valve is connected to the output end of the A4988 stepping motor driver in the dynamic compensation module (8).