Zirconium oxide sensor oxygen content measurement self-correction method and system

Abstract

The invention discloses a zirconia sensor oxygen content measurement self-correction method and system. The method comprises the following steps: respectively conveying high standard gas and low standard gas into a zirconium oxide sensor, reading an output current value and a current actual temperature after the output current value is stable, and if the current actual temperature does not meet a preset threshold value, performing temperature compensation to obtain a corrected current value; obtaining a range correction coefficient through the actual concentration and the correction current value of the high standard gas; a zero point correction coefficient is obtained through the actual concentration of the low standard gas, the correction current value and the range correction coefficient; judging the accuracy of the range correction coefficient and the zero point correction coefficient, if not accurate, not updating the system, continuing to use the last effective coefficient and re-calibrating; if so, storing the range correction coefficient and the zero point correction coefficient, and calculating the real-time oxygen content; by calibrating time, a range correction coefficient and a zero correction coefficient and calibrating whether the health index of the zirconium oxide sensor is calculated, an alarm is given when the health index is smaller than a preset value.

Description

Technical Field

[0001] This application relates to the interdisciplinary field of gas detection and combustion control, and more specifically, to a self-calibration method and system for measuring oxygen content in a zirconia sensor based on online calibration and real-time self-correction using a two-point calibration with dual-standard gas. Background Technology

[0002] Zirconia sensors, as key components for gas component detection, are widely used in combustion control-related fields, especially in advanced process scenarios such as ultra-low nitrogen combustion and oxygen-enriched combustion. They provide core oxygen content measurement data for combustion optimization control systems, directly affecting the stability of the combustion process, energy consumption control, and emission compliance.

[0003] Currently, zirconia sensors are often calibrated using a standard gas of one concentration, plus air (default 20.9%). Another method is the air zero-point reference method, which uses ambient air as a zero-point reference (theoretically containing approximately 20.9% O2), combined with the single-point calibration mentioned above to achieve sensor calibration. Both methods are mainstream calibration approaches in the industry. However, in practical applications, existing calibration schemes have significant technical flaws, including: First, the zero-point reference is susceptible to environmental interference. The oxygen content of ambient air fluctuates with altitude, temperature, humidity, and atmospheric pressure, leading to uncontrollable zero-point drift and introducing systematic biases. Second, full-range nonlinear errors cannot be effectively compensated. Single high-concentration standard gas calibration ignores the sensor's sensitivity decay in low-oxygen regions, making extrapolation distortion and significantly increasing measurement uncertainty. Third, there is a lack of a verification mechanism for the effectiveness of the calibration process. Real-time monitoring of ventilation status, response speed, and signal stability is not implemented, leading to "pseudo-calibrations" in cases of standard gas leaks or pipeline blockages, contaminating subsequent measurement data and making traceability difficult. Fourth, there is no historical parameter retention or performance degradation early warning capability. Fifth, current technology lacks automatic calibration logic judgment and verification, requiring manual judgment of oxygen measurement accuracy. These flaws collectively cause a continuous decline in the long-term operating accuracy of the zirconia measurement system, severely impacting the decision reliability of the combustion optimization control system. Summary of the Invention

[0004] The main objective of this application is to provide a self-calibration method and system for measuring oxygen content in a zirconia sensor based on online calibration and real-time self-correction using a two-point calibration with dual-standard gas. This method enables end-to-end error suppression and verifiable correction from the original signal to the final output value, significantly improving measurement stability and long-term reliability.

[0005] To achieve the above objectives, the first aspect of this application proposes a self-calibration method for measuring oxygen content in a zirconia sensor, comprising the following steps: Step one, supplying a high-standard gas with an oxygen concentration of 8%-12% into the zirconia sensor; after the output current value of the zirconia sensor stabilizes, reading the output current value. If the actual temperature of the zirconia sensor does not meet the preset threshold, temperature compensation is performed to obtain a corrected current value. Step two, using the actual concentration of the high-standard gas and the corrected current value. The range correction coefficient is obtained. Step 3: Turn off the high-grade standard gas and introduce low-grade standard gas with an oxygen concentration of 1%-3% into the zirconia sensor. After the output current value of the zirconia sensor stabilizes, read the output current value. The current actual temperature of the zirconia sensor is used. If the current actual temperature does not meet the preset threshold, temperature compensation is performed to obtain a corrected current value. Step four: Correct the current value by adjusting the actual concentration of the low-standard gas. Range correction factor The zero-point correction coefficient is obtained. Step 5: Determine the range correction coefficient based on the preset deviation range. and zero-point correction factor If the calibration coefficients are inaccurate, the system will not update them; instead, it will continue using the previous valid coefficients and recalibrate. If the calibration coefficients are accurate, the calibrated values ​​will be updated. and zero-point correction factor Store and calibrate and zero-point correction factor Calculate real-time oxygen content; Step 6, calibrate time, Zero-point correction factor The system checks whether the calibration is successful, calculates the health index of the zirconia sensor, and issues an alarm when the health index is less than a preset value.

[0006] In some embodiments, in steps one and three, the corrected current value can be obtained by the following step: measuring the current actual temperature of the zirconia sensor. and output current value ; Calculated using the following formula: ; in, Represents the output current value and , Represents the corrected current value and ; This represents the temperature compensation coefficient, with a value range of 1.2 × 10⁻⁶.-4 ~1.8×10 -4 / ℃; This represents the optimal operating temperature for zirconia sensors. This represents the current actual temperature of the zirconia sensor.

[0007] In some embodiments, in step two, the range correction coefficient is calculated. The method is as follows: ; in, The value range is 0.5~5.0%O2 / mA.

[0008] In some embodiments, step four involves generating zero-point correction coefficients. The method is as follows: .

[0009] In some embodiments, step five, the method for calculating real-time oxygen content, includes: ; Where n is the self-learning correction parameter, and the initial value of n ranges from 0.9 to 1.5.

[0010] In some embodiments, in step six, the zirconia sensor health index ranges from 0 to 1, wherein the zirconia sensor health index can be obtained by the following method: ; in, Represents the health index of zirconia sensors; represent Normalization factor, This represents the normalization factor for the nonlinear exponential term.

[0011] In some embodiments, The normalization factor is obtained by the following method: ; in, The initial range coefficients are used for the first calibration of the zirconia sensor; the normalization factor for the nonlinear exponential term is obtained by the following method: ; in, To correct the initial values ​​of the parameters for self-learning, These are the current self-learning correction parameters.

[0012] In some embodiments, in step five, the range correction factor is determined. and zero-point correction factor The methods for determining whether calibration is successful include: recording the stabilization time from switching the standard gas to the output current value of the zirconia sensor; if the stabilization time is greater than a preset threshold, an alarm is issued; comparing the oxygen concentration corresponding to the corrected current value with the actual oxygen concentration of the standard gas; if the error exceeds a preset threshold, an alarm is issued; if either of the two judgment conditions triggers an alarm, the calibration is considered to have failed; otherwise, the calibration is considered successful.

[0013] In some embodiments, the method further includes: installing two zirconia sensors at the outlet and inlet of the device being tested, respectively; automatically initiating a calibration procedure when the oxygen levels at the outlet and inlet deviate abnormally, or if the oxygen level at the outlet is lower than that at the inlet; or setting a calibration time period, passing a standard gas through the gas for verification within the calibration time period, and ending the calibration if the verification measurement result is accurate. If the measurement is inaccurate, the calibration is repeated.

[0014] In some embodiments, the method further includes the steps of: determining whether the output pressure of the standard gas meets a preset threshold; if not, prohibiting the start of the calibration process of the zirconia sensor; if yes, determining whether the heating temperature of the zirconia sensor meets a preset threshold; if not, prohibiting the start of the calibration process of the zirconia sensor; if yes, determining whether the zirconia sensor is faulty; if yes, prohibiting the start of the calibration process of the zirconia sensor; if not, starting the calibration process of the zirconia sensor.

[0015] A second aspect of this application proposes a zirconia sensor oxygen content measurement self-calibration system, applied to the aforementioned zirconia sensor oxygen content measurement self-calibration method, comprising: a zirconia sensor for measuring the oxygen content in flue gas within a flue; a temperature sensor disposed inside the heating chamber of the zirconia sensor for measuring the heating temperature of the zirconia sensor; a standard gas supply device connected to the zirconia sensor, the standard gas supply device including at least two independently controllable standard gas output channels, the two independently controllable standard gas output channels being used to output high standard gas with an oxygen concentration of 8%-12% and low standard gas with an oxygen concentration of 1%-3%, respectively; and a data acquisition unit for receiving the output current of the zirconia sensor and transmitting raw data to a central processing unit, the central processing unit being used to perform preset processing on the raw data.

[0016] The technical solutions provided by the embodiments of this application may include the following beneficial effects: The self-calibration method and system for measuring oxygen content using a zirconia sensor according to embodiments of the present invention have the following advantages: 1) By introducing dual constraints (known values ​​at high and low concentration points) to reconstruct the linear relationship of the measurement, the systematic bias caused by the assumption of a fixed zero point in the prior art is eliminated, allowing the geometric similarity of the measurement model to be maintained even under non-ideal working conditions, thereby effectively compressing the residual error bandwidth. Compared with single-point calibration, which only corrects the gain term and ignores the bias drift, this method is equivalent to redefining the origin and scale factor of the coordinate system, thereby significantly suppressing the composite error caused by zero-point drift and sensitivity decay, especially in low-oxygen areas where extrapolation distortion is avoided, thus improving measurement fidelity. 2) It fundamentally solves the zero-point drift problem caused by changes in altitude, temperature, and humidity, achieving wider adaptability. 3) It introduces a dual verification mechanism of temperature compensation linkage correction and response time monitoring to prevent dynamic performance degradation caused by temperature deviation or sensor hysteresis from affecting the authenticity of the calibration results. The calibration process is verifiable, reproducible, and traceable, meeting the requirements of industrial safety and quality management systems. 4) By saving historical correction coefficients, a sensor health record can be established, enabling performance degradation early warning and lifespan prediction, reducing the risk of unexpected downtime. 5) The zirconia sensor oxygen content measurement self-calibration method and system of this invention can also form automatic verification and automatic calibration functions by introducing standard verification gas and setting a calibration cycle. 6) The algorithm is entirely based on mature mathematical modeling and standard communication protocols, and can be quickly integrated into existing DCS platforms as a software package without replacing hardware, exhibiting good compatibility and scalability. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 A flowchart illustrating the steps of the self-calibration method for measuring oxygen content using a zirconia sensor provided in this application; Figure 2 A flowchart of the DCS-side verification logic for the self-calibration method for measuring oxygen content using a zirconia sensor provided in this application; Figure 3 A flowchart of the automatic calibration conditions for the self-calibration method for measuring oxygen content in a zirconia sensor provided in this application; Figure 4 A flowchart illustrating the start-up conditions for the calibration procedure of the self-calibration method for measuring oxygen content in a zirconia sensor provided in this application. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application 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 for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover 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.

[0020] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0022] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linked," and "socketing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] The zirconia sensor oxygen content measurement self-calibration method 100 provided in this application can be applied to a zirconia sensor oxygen content measurement self-calibration system. This system may include: a zirconia sensor for measuring the oxygen content in flue gas and converting it into a current value; a temperature sensor disposed inside the heating chamber of the zirconia sensor for measuring the heating temperature of the zirconia sensor; a standard gas supply device connected to the zirconia sensor, the standard gas supply device including at least two independently controllable standard gas output channels, the two independently controllable standard gas output channels being used to output high standard gas with an oxygen concentration of 8%-12% and low standard gas with an oxygen concentration of 1%-3%, respectively. In this application, the on / off switching of the two independently controllable standard gas output channels can be achieved using a solenoid valve assembly and controlled by a central processing unit. A data acquisition unit (e.g., a signal converter (secondary meter)) is used to receive the output current of the zirconia sensor and transmit raw data to the central processing unit, which performs preset processing on the raw data.

[0024] In this application, the central processing unit can be a programmable logic controller (PLC) or a DCS system, which is capable of performing logical judgments to determine the accuracy of the zirconia sensor measurement and automatically calibrate it. This application may also include a human-machine interface (HMI) for displaying the current calibration status, correction coefficients, alarm information, and historical trend graphs.

[0025] Based on the above system, Figure 1 A flowchart of a self-calibration method 100 for measuring oxygen content using a zirconia sensor according to this application is shown. Figure 1 As shown, the self-calibration method 100 for measuring oxygen content using a zirconia sensor according to an embodiment of the present invention includes the following steps: Step S1: High-standard gas with an oxygen concentration of 8%-12% is introduced into the zirconia sensor. After the output current value of the zirconia sensor stabilizes, the output current value is read. If the actual temperature of the zirconia sensor does not meet the preset threshold, temperature compensation is performed to obtain a corrected current value. .

[0026] For example, in practical applications, the standard operating temperature for zirconia sensors is typically 750°C. If... Temperature compensation is required.

[0027] In step S1, the corrected current value can be obtained by measuring the current actual temperature of the zirconia sensor. and output current value ; Calculated using the following formula: ; in, Represents the output current value , Represents the corrected current value ; This represents the temperature compensation coefficient, with a value range of 1.2 × 10⁻⁶. -4 ~1.8×10 -4 / ℃; This represents the optimal operating temperature for zirconia sensors. This represents the current actual temperature of the zirconia sensor.

[0028] Step 2, S2, involves using the actual concentration of the high-standard gas and the corrected current value. The range correction coefficient is obtained. .

[0029] In step S2, the range correction coefficient is calculated. The method is as follows: ; in, The value range can be 0.5~5.0%O2 / mA.

[0030] In practical use, zirconia sensors may exhibit inconsistent output signals at the same concentration due to differences in manufacturing processes (such as electrode area, zirconia electrolyte purity, and gas path resistance). This application addresses this issue by recalibrating this ratio through range correction, bringing the actual output-to-concentration ratio of the zirconia sensor back to its ideal value. Specifically, range correction coefficients are generated through calibration with high-standard gas. This ensures that the ratio of the output change to the concentration change of the zirconia sensor meets the design requirements.

[0031] Step 3 (S3): Turn off the high-standard gas and introduce low-standard gas with an oxygen concentration of 1%-3% into the zirconia sensor. After the output current value of the zirconia sensor stabilizes, read the output current value. The current actual temperature of the zirconia sensor is used. If the current actual temperature does not meet the preset threshold, temperature compensation is performed to obtain a corrected current value. .

[0032] Similarly, for example, in practical applications, the standard operating temperature for zirconia sensors is typically 750°C. If... Temperature compensation is required.

[0033] In step S3, the corrected current value can be obtained by measuring the current actual temperature of the zirconia sensor. and output current value ; Calculated using the following formula: ; in, Represents the output current value , Represents the corrected current value ; This represents the temperature compensation coefficient, with a value range of 1.2 × 10⁻⁶. -4 ~1.8×10 -4 / ℃; This represents the optimal operating temperature for zirconia sensors. This represents the current actual temperature of the zirconia sensor.

[0034] Step 4 (S4): Correct the current value by adjusting the actual concentration of the low-standard gas. Range correction factor The zero-point correction coefficient is obtained. .

[0035] In step S4, the zero-point correction coefficient is generated. The method is as follows: .

[0036] In practical use, zirconia sensors can experience baseline drift over long-term use due to environmental interference (such as residual temperature drift, slight electrode oxidation, and residual gas in the gas path), leading to completely inaccurate low-concentration measurements. Zero-point correction subtracts this fixed offset, allowing the measured value of the low-standard gas to return to the true concentration. Zero-point correction coefficients are generated through low-standard gas calibration. This can offset the fixed offset and ensure accurate measurements at low or zero concentrations.

[0037] In this application, during the standard gas delivery process in steps S1 and S3, the gas needs to pass through a filter for ash removal, a pressure valve for pressure stabilization, and a flow meter for flow rate stabilization. Specifically: Filtration of Standard Gas Delivery: The system applying the self-calibration method of this invention may further include a filtration device (e.g., a microporous metal sintered filter), which is installed at the end of the standard gas output channel on the standard gas supply device. The filtration device according to this application can have a pore size of 5 μm to intercept dust and droplets. Its specific principle is as follows: when the dust-laden airflow passes through the porous metal medium, particles undergo inertial collisions due to abrupt changes in flow direction within the tortuous channels and are adsorbed by the pore walls. Simultaneously, small-diameter particles are captured in the gaps between the fiber structures through Brownian diffusion, achieving efficient interception of PM10 and larger particles in the flue gas, preventing them from entering the sensor and causing micropore blockage or electrode contamination, thus ensuring long-term operational stability.

[0038] Pressure stabilization of standard gas delivery: The system applying the self-calibration method of this embodiment may further include a pressure feedback pressure reducing valve, which is respectively installed on the high-standard gas and low-standard gas output channels, and the output pressure is kept constant. This setting is used to maintain consistent pressure conditions for the standard gas. Pressure fluctuations alter gas density and viscosity, affecting the mass transfer rate of oxygen to the sensor surface and introducing additional measurement bias. Closed-loop pressure control ensures highly consistent gas pressure conditions for each calibration, thereby eliminating external disturbances from affecting the concentration and current relationship, improving calibration repeatability, and enhancing the consistency of calibration results under different measurement conditions.

[0039] Stable flow rate of standard gas delivery: The system applying the self-calibration method of this invention may further include a float flowmeter, which is respectively installed on the standard gas output channels for high-standard gas and low-standard gas, with a range of 0–2 L / min, to ensure consistent standard gas flow rate and absence of turbulence disturbance. This setting maintains constant gas flow rate conditions. If the difference in flow rate between high-standard gas and low-standard gas is too large, it will lead to inconsistent sensor response time and deviation in steady-state value. By setting a uniform standard flow rate (e.g., 1.2 L / min), the residence time of gas in the sensing cavity is kept stable, ensuring that the two measurements are under the same mass transfer kinetic conditions, thus improving calibration accuracy.

[0040] The system applying the self-calibration method of this invention may further include a buffer device, which is disposed on the outlet of the solenoid valve used to control the opening and closing of the standard gas output channel. The buffer device may consist of a two-stage buffer assembly composed of a compression helical spring and a silicone damping pad. The compression helical spring may be sleeved on the outer periphery of the standard gas output channel, with an inner diameter 0.3-0.7 mm larger than the outer diameter of the standard gas output channel, a free length of 28-32 mm, and a stiffness coefficient of 7-9 N / mm. The buffer cavity of the buffer device may have a Venturi structure with an inlet diameter of 5-7 mm and an outlet diameter of 2-4 mm, and a porous silicone damping pad with a thickness of 1.3-1.7 mm and a porosity of 38%-42% may be embedded downstream of the throat. The entire buffer device is sealed between the solenoid valve and the tee connector using an O-ring, thereby achieving a smooth airflow transition. Through the above configuration, the structure utilizes a composite structure of compression spring, venturi, and damping pad to form a dual suppression mechanism of mechanical inertia and viscous dissipation. This mechanism enables spatial diffusion and energy absorption of the step pressure impact generated during the opening and closing of the solenoid valve, reducing transient overshoot caused by airflow turbulence. Consequently, it avoids false responses from the sensor caused by pressure fluctuations and improves signal stability and data reliability during the calibration process.

[0041] Step 5 (S5): Determine the range correction coefficient based on the preset deviation range. and zero-point correction factor If the calibration coefficients are inaccurate, the system will not update them; instead, it will continue using the previous valid coefficients and recalibrate. If the calibration coefficients are accurate, the calibrated values ​​will be updated. and zero-point correction factor Perform storage (i.e., synchronize to the DCS database), and pass the calibrated and zero-point correction factor Calculate real-time oxygen content.

[0042] In step S5, the range correction factor is determined. and zero-point correction factor The methods for determining whether calibration is successful include: recording the stabilization time from switching the standard gas to the output current value of the zirconia sensor; if the stabilization time is greater than a preset threshold (e.g., more than 120 seconds), an alarm is issued; comparing the oxygen concentration corresponding to the corrected current value with the actual oxygen concentration of the standard gas; if the error exceeds a preset threshold (e.g., more than 0.5%), an alarm is issued; if either of the two judgment conditions triggers an alarm, the calibration is considered to have failed; otherwise, the calibration is considered successful.

[0043] In step S5, the method for calculating the real-time oxygen content includes: ; Where n is the self-learning correction parameter, and the initial value of n ranges from 0.9 to 1.5.

[0044] In this application, the "current-oxygen concentration" relationship of the zirconia sensor is not absolutely linear (especially in low-oxygen regions or after sensor aging). 'n' is a parameter used to correct this nonlinear bias, ensuring that the calculation results accurately match the actual concentration across the entire oxygen concentration range (0~25% O2), thus avoiding the problem of "accurate in high-oxygen regions, biased in low-oxygen regions" or vice versa. Therefore, 'n' is an "exponential term autonomously optimized by the system through historical calibration data," requiring no manual intervention; the core logic is "iteratively correcting the bias using data."

[0045] In this application, a self-learning module for the newly added self-learning correction parameter 'n' addresses the issue of inaccurate measurements caused by prolonged use of zirconia sensors. As the sensor's lifespan increases, internal electrolyte aging and electrode catalytic capacity decline, causing the output current-concentration relationship to change from a linear curve to a curve (i.e., nonlinear distortion), particularly noticeable in the low-oxygen (1-5%) and high-oxygen (8-12%) ranges. During each calibration, the self-learning module learns the current level of distortion and automatically adjusts the correction parameter 'n', ensuring the calculated results closely match the actual concentration. In this application, 'n' is initially set to approximately 1.0. After each dual-standard gas calibration, the 'n' value is adaptively adjusted by comparing the error between theoretical and actual concentrations, ultimately converging to a reasonable range of 0.9–1.5, achieving accurate measurement of total oxygen concentration. Based on the sensor model preset, the default value of 'n' can be 1.0, which can be manually modified by the user through the HMI. The adaptive step size of 'n' can be 0.01–0.05.

[0046] Step 6 (S6): calibrate the time... Zero-point correction factor The system checks whether the calibration is successful, calculates the health index of the zirconia sensor, and issues an alarm when the health index is less than a preset value.

[0047] In step S6, the health index of the zirconia sensor ranges from 0 to 1, and the health index of the zirconia sensor can be obtained by the following method: ; in, Represents the health index of zirconia sensors; represent Normalization factor, This represents the normalization factor for the nonlinear exponential term.

[0048] In some embodiments, The normalization factor is obtained by the following method: ; in, The initial range coefficients are used for the first calibration of the zirconia sensor; the normalization factor for the nonlinear exponential term is obtained by the following method: ; in, To correct the initial values ​​of the parameters for self-learning, These are the current self-learning correction parameters (as described above).

[0049] For example: initial calibration of a zirconia sensor =1.0%O2 / mA, currently =1.2, current self-learning correction parameter =1.1: =0.8; =0.8; =0.8 (Health status "Excellent"). When This can trigger a "sensor lifespan warning".

[0050] In this application, the sensor health index is calculated. Specifically, this can be understood as: 1) Store the correction coefficients securely to prevent loss and facilitate retrieval: After calibration is successful, the system will... and The two core correction parameters are stored in two locations, essentially a "double backup." One is stored in the sensor's accompanying "secondary table" (which can be understood as a "data processor") in memory that retains data even in the event of a power outage, facilitating quick retrieval during real-time calculations. The other is synchronized to the factory's "central data system" (DCS database), allowing engineers to easily access historical calibration records and preventing complete data loss should local memory fail.

[0051] 2) Calculate the true oxygen concentration using a correction factor: When the zirconia sensor is working normally, it does not directly calculate the oxygen concentration using the raw current value (the raw value is inaccurate), but instead uses the calibrated value. and Make corrections.

[0052] 3) Record history and predict lifespans to provide early warnings: After each calibration, the system records a "calibration log" for easy tracking, including: the calibration time (what time it was done); and the calculated values. and The specific values; whether the calibration passed (qualified / unqualified); the actual concentrations of high-standard gas and low-standard gas (to avoid forgetting which standard gas was used when checking data later); the response time of this calibration (to determine how fast the sensor responds); the temperature of the sensor heater (to check if the temperature is normal).

[0053] After the above, use the health index HI to determine whether the zirconia sensor needs to be replaced: HI can be set to a number between 0 and 1, the closer it is to 1, the healthier the sensor is; if HI < 0.8, an alarm will be triggered.

[0054] Please refer to Figure 2 and Figure 3 In some embodiments, the method further includes the following steps: installing two zirconia sensors at the outlet and inlet of the device being tested, respectively; automatically initiating a calibration procedure when the oxygen levels at the outlet and inlet deviate abnormally, or if the oxygen level at the outlet is lower than that at the inlet; or setting a calibration time period (e.g., once every 7 days or every 30 days), passing standard gas through the gas during the calibration time period for verification; ending the calibration if the verification measurement result is accurate; and recalibrating if the measurement is inaccurate.

[0055] In this application, after the standard gas for verification is injected, the gas supply must be maintained until the signal stabilizes (fluctuation ≤ 0.01% / 10 seconds) before recording the actual response value. Typically, the gas supply duration is not less than the time from switching the standard gas to the output current value of the zirconia sensor. +5 seconds.

[0056] Through the methods described in the above steps, the self-calibration method for measuring oxygen content in a zirconia sensor according to this invention can also form an automatic verification and automatic calibration function by introducing a standard verification gas and setting a calibration cycle.

[0057] Please refer to Figure 4 In some embodiments, the method further includes the following steps: determining whether the output pressure of the standard gas (standard gas cylinder pressure) meets a preset threshold (standard gas cylinder pressure not less than 0.18-0.22 MPa); if not, prohibiting the initiation of the zirconia sensor calibration process; if yes, determining whether the heating temperature of the zirconia sensor meets a preset threshold (not less than 615°C); if no, prohibiting the initiation of the zirconia sensor calibration process; if yes, determining whether the zirconia sensor is faulty; if yes, prohibiting the initiation of the zirconia sensor calibration process; if no, initiating the zirconia sensor calibration process.

[0058] A second aspect of this application proposes a zirconia sensor oxygen content measurement self-calibration system, applied to the aforementioned zirconia sensor oxygen content measurement self-calibration method, comprising: a zirconia sensor for measuring the oxygen content in flue gas within a flue; a temperature sensor disposed inside the heating chamber of the zirconia sensor for measuring the heating temperature of the zirconia sensor; a standard gas supply device connected to the zirconia sensor, the standard gas supply device including at least two independently controllable standard gas output channels, the two independently controllable standard gas output channels being used to output high standard gas with an oxygen concentration of 8%-12% and low standard gas with an oxygen concentration of 1%-3%, respectively; and a data acquisition unit for receiving the output current of the zirconia sensor and transmitting raw data to a central processing unit, the central processing unit being used to perform preset processing on the raw data.

[0059] According to the system described in this application, a dedicated calibration operation screen can be developed on the DCS operator station, providing a clear and convenient human-machine interaction. This screen mainly includes: a "One-Click Calibration" button: the operator can trigger the complete automatic calibration process by clicking this button, without any intermediate steps. A calibration status display area: displaying the current status in real time using color and text, such as "Ready," "High Standard Gas Calibration in Progress," "Low Standard Gas Calibration in Progress," "Calibration Successful," and "Calibration Failed." Parameter settings and display: displaying the current oxygen value, calibration cycle setting, and the date, time, and correction amount of the most recent calibration.

[0060] This application may include two zirconia sensors, which are respectively installed on the outlet and inlet sides of the device being tested, to measure the oxygen content in the flue gas. If the oxygen content on the outlet side is lower than that on the inlet side, the calibration program will be automatically started.

[0061] In summary, the self-calibration method and system for measuring oxygen content using a zirconia sensor according to embodiments of the present invention have the following advantages: 1) By introducing dual constraints (known values ​​at high and low concentration points) to reconstruct the linear relationship of the measurement, the systematic bias caused by the assumption of a fixed zero point in existing technologies is eliminated. This allows the geometric similarity of the measurement model to be maintained even under non-ideal operating conditions, thereby effectively compressing the residual error bandwidth. Compared to single-point calibration, which only corrects the gain term and ignores bias drift, this method is mathematically equivalent to redefining the origin and scale factor of the coordinate system. This significantly suppresses the combined error caused by zero-point drift and sensitivity decay, especially in the low-oxygen region, where it avoids extrapolation distortion and improves measurement fidelity.

[0062] 2) By abandoning the assumption that the air has a fixed oxygen content of 20.9%, the problem of zero-point drift caused by changes in altitude, temperature and humidity is fundamentally solved, and a wider range of adaptability is achieved.

[0063] 3) A dual verification mechanism of temperature compensation linkage correction and response time monitoring is introduced to prevent dynamic performance degradation caused by temperature deviation or sensor hysteresis from affecting the authenticity of the calibration results. The calibration process is verifiable, reproducible, and traceable, meeting the requirements of industrial safety and quality management systems.

[0064] 4) By saving historical correction coefficients, sensor health records can be established to enable performance degradation early warning and lifespan prediction, reducing the risk of unexpected downtime.

[0065] 5) The algorithm is based entirely on mature mathematical modeling and standard communication protocols (such as Modbus and OPCUA), and can be quickly integrated into the existing DCS platform as a software package without replacing hardware, thus having good compatibility and scalability; 6) The self-calibration method and system for measuring oxygen content of the zirconia sensor of the present invention can also form an automatic verification and automatic calibration function by introducing a standard verification gas and setting a calibration cycle.

[0066] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0067] Obviously, those skilled in the art should understand that the various units or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device, or fabricating them separately as individual integrated circuit modules, or fabricating multiple modules or steps into a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0068] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A self-calibration method for measuring oxygen content using a zirconia sensor, characterized in that, Includes the following steps: Step 1: Introduce high-standard gas with an oxygen concentration of 8%-12% into the zirconia sensor. After the output current value of the zirconia sensor stabilizes, read the output current value. If the actual temperature of the zirconia sensor does not meet the preset threshold, temperature compensation is performed to obtain a corrected current value. ; Step two, using the actual concentration of the high-standard gas and the corrected current value. The range correction coefficient is obtained. ; Step 3: Turn off the high-standard gas and introduce low-standard gas with an oxygen concentration of 1%-3% into the zirconia sensor. After the output current value of the zirconia sensor stabilizes, read the output current value. The current actual temperature of the zirconia sensor is used. If the current actual temperature does not meet the preset threshold, temperature compensation is performed to obtain a corrected current value. ; Step four: Correct the current value by checking the actual concentration of the low-standard gas. Range correction factor The zero-point correction coefficient is obtained. ; Step 5: Determine the range correction coefficient based on the preset deviation range. and zero-point correction factor If the calibration coefficients are inaccurate, the system will not update them, will continue to use the previous valid coefficients, and will recalibrate; if the calibration coefficients are accurate, the calibrated coefficients will be updated. and zero-point correction factor Store and calibrate and zero-point correction factor Calculate real-time oxygen content; Step six, by calibrating the time, Zero-point correction factor The system checks whether the calibration is successful, calculates the health index of the zirconia sensor, and issues an alarm when the health index is lower than a preset value.

2. The self-calibration method for measuring oxygen content using a zirconia sensor according to claim 1, characterized in that, In steps one and three, the corrected current value can be obtained through the following steps: Measuring the current actual temperature of the zirconia sensor and output current value ; Calculated using the following formula: ; in, Represents the output current value and , Represents the corrected current value and ; This represents the temperature compensation coefficient, with a value range of 1.2 × 10⁻⁶. -4 ~1.8×10 -4 / ℃; This represents the optimal operating temperature for zirconia sensors. This represents the current actual temperature of the zirconia sensor.

3. The self-calibration method for measuring oxygen content in a zirconia sensor according to claim 2, characterized in that, In step two, the range correction coefficient is calculated. The method is as follows: ； in, The value range is 0.5~5.0%O2 / mA.

4. The self-calibration method for measuring oxygen content in a zirconia sensor according to claim 3, characterized in that, In step four, the zero-point correction coefficient is generated. The method is as follows: 。 5. The self-calibration method for measuring oxygen content in a zirconia sensor according to claim 4, characterized in that, In step five, the method for calculating the real-time oxygen content includes: ； Where n is the self-learning correction parameter, and the initial value of n ranges from 0.9 to 1.

5.

6. The self-calibration method for measuring oxygen content in a zirconia sensor according to claim 5, characterized in that, In step six, the health index of the zirconia sensor ranges from 0 to 1, and the health index of the zirconia sensor can be obtained by the following method: ； in, Represents the health index of zirconia sensors; represent Normalization factor The normalization factor for the nonlinear exponential term; The normalization factor is obtained by the following method: ； in, The initial range coefficient for the first calibration of the zirconia sensor; The normalization factor for the nonlinear exponential term is obtained by the following method: ; in, To correct the initial values ​​of the parameters for self-learning, These are the current self-learning correction parameters.

7. The self-calibration method for measuring oxygen content in a zirconium oxide sensor according to any one of claims 1-6, characterized in that, In step five, the range correction coefficient is determined. and zero-point correction factor Methods to determine if calibration was successful include: Record the settling time from switching the standard gas to the output current value of the zirconia sensor. If the settling time is greater than a preset threshold, an alarm will be issued. Compare the oxygen concentration corresponding to the corrected current value with the actual oxygen concentration of the standard gas. If the error exceeds the preset threshold, an alarm will be issued. If either of the two judgment conditions issues an alarm, the correction is deemed to have failed; otherwise, the correction is deemed to have succeeded.

8. The self-calibration method for measuring oxygen content using a zirconia sensor according to claim 1, characterized in that, The method further includes the following steps: Two zirconia sensors are installed at the outlet and inlet of the equipment being tested, respectively. When the oxygen levels at the inlet and outlet deviate abnormally, or if the oxygen level at the outlet is lower than that at the inlet, the calibration program is automatically initiated; or... Set a calibration time period, and pass standard gas through the gas during the calibration time period for verification. If the verification measurement result is accurate, the calibration is completed; if the measurement is inaccurate, the calibration is repeated.

9. The self-calibration method for measuring oxygen content in a zirconia sensor according to claim 1, characterized in that, The method further includes the following steps: Determine if the output pressure of the standard gas meets the preset threshold; if not, prohibit the start of the zirconia sensor calibration process; if yes, determine if the heating temperature of the zirconia sensor meets the preset threshold; if not, prohibit the start of the zirconia sensor calibration process; if yes, determine if the zirconia sensor is faulty; if yes, prohibit the start of the zirconia sensor calibration process; if no, start the zirconia sensor calibration process.

10. A self-calibration system for measuring oxygen content in a zirconia sensor, applied to the self-calibration method for measuring oxygen content in a zirconia sensor according to any one of claims 1 to 9, characterized in that, include: Zirconia sensor, used to measure the oxygen content in flue gas; A temperature sensor is disposed inside the heating chamber of the zirconia sensor and is used to measure the heating temperature of the zirconia sensor. A standard gas supply device is connected to the zirconium oxide sensor. The standard gas supply device includes at least two independent and controllable standard gas output channels. The two independent and controllable standard gas output channels are used to output high standard gas with an oxygen concentration of 8%-12% and low standard gas with an oxygen concentration of 1%-3%, respectively. A data acquisition unit is used to receive the output current of the zirconia sensor and transmit the raw data to the central processing unit, which is used to perform preset processing on the raw data.

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