Self-diagnosis method and gas sensor module

Abstract

The invention provides a self-diagnosis method and a gas sensor module, and the method comprises the steps: periodically applying an excitation signal with a specific frequency to an auxiliary electrode of an electrochemical gas sensor, or applying an excitation signal for scanning in a preset frequency range, and collecting dynamic impedance spectrums of the electrochemical gas sensor in different periods; analyzing the characteristic change of the dynamic impedance spectrum, extracting preset key parameter evolution data, comparing the key parameter evolution data with a preset health reference value, and diagnosing whether the electrochemical gas sensor is in a performance degradation fault state or not. According to the method, internal degradation caused by sensitivity reduction such as catalyst poisoning and electrolyte drying can be accurately captured, the gas concentration value is dynamically corrected in real time, measurement deviation caused by sensitivity reduction is effectively counteracted, and it is ensured that the sensor can output high-precision data from the initial state to the later attenuation period.

Description

Technical Field

[0001] This invention relates to the field of gas sensing technology, and more specifically, to a self-diagnostic method and a gas sensor module. Background Technology

[0002] In critical fields such as industrial safety and environmental monitoring, portable gas detection devices are core equipment for achieving real-time and accurate detection of specific gas concentrations. Their detection performance and stable operation directly affect on-site operational safety and the reliability of environmental monitoring data. Currently, portable gas detection devices generally suffer from insufficient intelligent management and maintenance capabilities, especially lacking autonomous diagnostics and dynamic compensation functions for sensor performance, making it difficult to meet the high-precision requirements of long-term continuous monitoring scenarios.

[0003] Patent application CN120927777A discloses a modular gas sensor and its signal processing method. This technical solution periodically collects the sensor's core operating parameters, including signal baseline drift, cumulative operating time, and temperature drift coefficient change rate, through a microcontroller unit. It also estimates the sensor's remaining lifespan based on a lifespan decay model and writes the prediction results into a non-volatile storage unit. In addition, the solution has a built-in self-diagnostic module that can monitor the sensor's electrical connection status and signal integrity in real time. When abnormal conditions such as disconnection, signal saturation, or response timeout are detected, a graded early warning mechanism can be triggered immediately.

[0004] The aforementioned invention achieves real-time estimation and replacement warning of sensor lifespan through software algorithms, and completes real-time monitoring and anomaly warning of connection status with the help of a self-diagnostic module, thus realizing intelligent management and maintenance of sensors to a certain extent. However, this technical solution still has significant limitations. It cannot effectively predict and dynamically compensate for the performance degradation (such as decreased sensitivity) of sensors during long-term use, which will cause a significant reduction in the reliability of measurement data in the later stages of equipment, making it difficult to adapt to the needs of high-precision, long-cycle gas monitoring.

[0005] In order to solve the above problems, people have been seeking an ideal technological solution. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a self-diagnostic method for performance degradation monitoring and real-time dynamic correction, as well as a gas sensor module.

[0007] To achieve the above objectives, the present invention provides a self-diagnostic method applied to an electrochemical gas sensor, comprising: A specific frequency excitation signal or a scanning excitation signal within a preset frequency range is periodically applied to the auxiliary electrode of the electrochemical gas sensor to collect the dynamic impedance spectrum of the electrochemical gas sensor under different periods. The characteristic changes of the dynamic impedance spectrum are analyzed, the evolution data of preset key parameters are extracted, and the evolution data of key parameters are compared with preset health benchmark values ​​to diagnose whether the electrochemical gas sensor is in a state of performance degradation failure.

[0008] By applying an excitation signal at a specific frequency, or by applying an excitation signal that scans within a preset frequency range, the state changes of the electrolyte and catalyst inside the sensor can be accurately captured, solving the problem that traditional methods cannot detect the internal degradation of the sensor.

[0009] As a preferred technical solution of the present invention, the preset key parameter evolution data includes the evolution data of charge transfer resistance and the evolution data of double-layer capacitance. The charge transfer resistance reflects the active state of the catalyst, and the double-layer capacitance reflects the state of the electrolyte.

[0010] This study targets the core degradation characteristics of catalysts and electrolytes in electrochemical gas sensors, providing direct data support for the accurate determination of performance degradation fault types, avoiding misjudgments caused by ambiguity in the correlation between parameters and faults, and improving the rigor of performance degradation fault diagnosis.

[0011] As a preferred embodiment of the present invention, the diagnosis of the performance degradation fault state of the electrochemical gas sensor includes the following steps: The preset health benchmark values ​​include the charge transfer resistance benchmark value and the double-layer capacitance benchmark value when the electrochemical gas sensor was calibrated at the factory. Based on the evolution data of the charge transfer resistance, the increase of the extracted charge transfer resistance relative to the reference value of the charge transfer resistance is calculated; based on the evolution data of the double-layer capacitor, the change of the extracted double-layer capacitor relative to the reference value of the double-layer capacitor is calculated. When the charge transfer resistance exhibits a continuous monotonically increasing trend for several consecutive cycles, and the increase is greater than a preset threshold: If the double-layer capacitor shows a continuous monotonically decreasing trend for several consecutive times, and the change amplitude of the double-layer capacitor is greater than a preset threshold, then it is determined that the electrochemical gas sensor has an electrolyte drying fault. If the change in the double-layer capacitance is less than a preset threshold, the electrochemical gas sensor is determined to have a catalyst poisoning fault.

[0012] Through a dual verification mechanism of trend judgment and amplitude threshold, the system accurately distinguishes between two types of core performance degradation faults: electrolyte drying and catalyst poisoning, providing users with targeted maintenance basis; the factory calibration benchmark value ensures the consistency of diagnostic standards for different batches of products, improving product quality traceability and reliability.

[0013] As a preferred embodiment of the present invention, the sensitivity decay amplitude of the electrochemical gas sensor is calculated based on the increase of the extracted charge transfer resistance relative to the reference value of the charge transfer resistance and the change amplitude of the extracted double-layer capacitance relative to the reference value of the double-layer capacitance; if the sensitivity decay amplitude is greater than a preset threshold, the electrochemical gas sensor is determined to have reached the end of its lifespan.

[0014] The increase in charge transfer resistance and the change in double-layer capacitance are directly related to the electrode reactivity and interfacial charge transport efficiency of electrochemical gas sensors, and are essential indicators reflecting sensor sensitivity decay. By quantitatively calculating the degree of change in these two parameters to deduce the sensitivity decay magnitude, compared to traditional methods relying on a single parameter or qualitative judgment, non-core factors are effectively avoided, significantly improving the accuracy and reliability of performance decay assessment. By accurately identifying the sensor's end-of-life state, missed or false alarms due to sensitivity decay in expired sensors are avoided, ensuring the validity of detection data throughout the sensor's entire lifespan.

[0015] The present invention also provides a gas sensor module, comprising: An electrochemical gas sensor, comprising a working electrode, a counter electrode, a reference electrode, and an auxiliary electrode; A spring-loaded pin, one end of which forms a stable elastic electrical contact with the corresponding electrode of the electrochemical gas sensor; The printed circuit board integrates a microcontroller, an excitation source, and a signal processing circuit. The microcontroller is electrically connected to the other end of the spring pin through the signal processing circuit, and is used to receive the current signal output by the electrochemical gas sensor; and to control the excitation source to periodically apply an excitation signal to the auxiliary electrode of the electrochemical gas sensor to perform the above-mentioned self-diagnostic method. An external solder pad is located at the bottom of the printed circuit board and serves as the external electrical interface of the gas sensor module. It is used to connect with the host device via spring pins to read data and supply power to the gas sensor module.

[0016] The use of spring-loaded pins instead of traditional pin sockets not only meets the structural requirements of miniaturization and flattening of portable devices, but also improves the module's vibration resistance and ease of assembly. The external solder pads and the spring-loaded pin tops of the host device simplify the connection structure and significantly improve the integration efficiency of the gas sensor module and the host device.

[0017] As a preferred technical solution of the present invention, the microcontroller has a preset compensation algorithm; when the electrochemical gas sensor is determined to be in a performance degradation fault state, the preset compensation algorithm analyzes the degree of sensitivity reduction based on the fault type and parameter change range, and performs coefficient compensation on the gas concentration data detected by the sensor.

[0018] The combination of performance degradation fault diagnosis and gas concentration deviation correction improves the intelligent management and maintenance level of the module, ensures the measurement accuracy of the sensor throughout its entire life cycle, significantly reduces maintenance and replacement costs, and meets the long-term stable operation requirements of portable devices.

[0019] As a preferred embodiment of the present invention, it further includes: The O-ring is assembled between the housing of the electrochemical gas sensor and the external mounting structure to achieve the airtight seal of the gas sensor module and to confine the gas to be measured within the sensing area. A waterproof and breathable membrane is fitted between the electrochemical gas sensor and the O-ring to allow gas molecules to pass through while blocking liquid water and impurities from entering.

[0020] The O-ring and the waterproof and breathable membrane work together to significantly improve the module's protective capabilities, solving the problems of low protection levels and susceptibility to environmental interference in traditional modules, and enhancing the module's adaptability and stability in complex industrial environments.

[0021] As a preferred embodiment of the present invention, the printed circuit board includes a signal processing circuit; The input terminal of the signal processing circuit is connected to the electrochemical gas sensor and is used to receive the current signal output by the electrochemical gas sensor, and to filter, amplify and convert the current signal. The output terminal of the signal processing circuit is electrically connected to the signal input terminal of the microcontroller, and is used to transmit the conditioned voltage signal to the microcontroller. The firmware algorithm is used to parse and process the voltage signal.

[0022] The signal processing circuit is specifically designed for the weak current signals of electrochemical gas sensors, solving the problems of weak signals being easily interfered with and having conversion distortion. It provides the microcontroller with a voltage signal source with high signal-to-noise ratio and high stability, ensuring the accuracy of data processing from the source.

[0023] As a preferred embodiment of the present invention, the printed circuit board further includes: a power module and an interface protection circuit; The output terminal of the power module is electrically connected to the signal processing circuit and the microcontroller respectively to provide a stable power supply. The interface protection circuit is connected in series between the external power input and the input terminal of the power module, and is electrically connected to the serial port output terminal of the microcontroller, to provide anti-static, overvoltage and reverse connection protection for power input and serial communication.

[0024] The power module provides stable power to the core circuit components, avoiding interference from external power fluctuations on signal conditioning and algorithm operation, and solving the problems of signal distortion and misdiagnosis caused by unstable power supply in traditional circuits. The interface protection circuit adopts a dual protection design of power input and serial port output, which comprehensively blocks external risks such as electrostatic discharge, overvoltage, and reverse connection. It not only protects the core components from damage, but also ensures the security and integrity of data communication, significantly extending the module's service life and adapting to the needs of various scenarios such as complex industrial environments and frequent movement of portable devices.

[0025] This invention has outstanding substantive features and significant progress compared to the prior art, specifically: (1) By periodically applying excitation signals to the auxiliary electrode, and comparing and analyzing the core parameters such as charge transfer resistance and double-layer capacitance with the factory reference values, internal degradation caused by catalyst poisoning and electrolyte drying can be accurately captured, thus enabling early prediction of performance degradation. This solves the problem that traditional methods cannot detect internal degradation of the sensor and significantly reduce the reliability of subsequent measurement data, ensuring the accuracy of data for long-term monitoring.

[0026] (2) For the diagnosed performance degradation fault, the gas concentration value is dynamically corrected in real time by a preset compensation algorithm and the remaining life prompt is generated. This effectively offsets the measurement deviation caused by the decrease in sensitivity and ensures that the sensor can output high-precision data from the initial state to the later stage of degradation. It can meet the stringent requirements of long-term gas monitoring without frequent sensor replacement and greatly reduce maintenance costs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the gas sensor module structure of the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the gas sensor module structure of the present invention. Figure 2 ; Figure 3 This is a circuit block diagram of the gas sensor module of the present invention; Figure 4 This is the signal processing circuit diagram of the present invention.

[0028] In the diagram: 1. O-ring; 2. Waterproof and breathable membrane; 3. Electrochemical gas sensor; 4. Electrode; 5. Spring pin; 6. Printed circuit board; 7. External solder pad. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0030] Example 1 In this application embodiment, a self-diagnostic method is proposed for use in electrochemical gas sensors, comprising: A specific frequency excitation signal or a scanning excitation signal within a preset frequency range is periodically applied to the auxiliary electrode of the electrochemical gas sensor to collect the dynamic impedance spectrum of the electrochemical gas sensor under different periods. The characteristic changes of the dynamic impedance spectrum are analyzed, the evolution data of preset key parameters are extracted, and the evolution data of key parameters are compared with preset health benchmark values ​​to diagnose whether the electrochemical gas sensor is in a state of performance degradation failure.

[0031] Specifically, the electrochemical response of the electrolyte and catalyst inside the sensor can be stimulated by periodically applying an excitation signal. The frequency of the excitation signal is preferably set between a low-frequency band reflecting the electrochemical reaction kinetics of the sensor and a high-frequency band reflecting the electrolyte characteristics, including a low-frequency band of 0.1Hz-10Hz and a high-frequency band of 1kHz-10kHz. The low-frequency excitation signal is mainly controlled by gas diffusion processes and slow electrochemical reaction kinetics, and is sensitive to catalytic activity and changes in electrode surface state. The high-frequency excitation signal mainly reflects electrolyte resistance and double-layer capacitance, and can be used to determine faults such as electrolyte drying or leakage.

[0032] Cyclic voltammetry can be used to scan within a preset frequency range, allowing the electrolyte ion migration and catalyst surface reaction state to exhibit a regular response to changes in bias voltage. By collecting impedance data under different bias voltages, a dynamic impedance spectrum is formed. The characteristic parameters of this spectrum, including impedance value and phase angle, are directly related to electrolyte impedance and catalyst activity, providing raw data support for subsequent state analysis.

[0033] In one optional embodiment, the preset key parameter evolution data includes the evolution data of charge transfer resistance and the evolution data of double-layer capacitance, wherein the charge transfer resistance reflects the active state of the catalyst and the double-layer capacitance reflects the state of the electrolyte.

[0034] Specifically, charge transfer resistance and double-layer capacitance are selected as core monitoring parameters. Charge transfer resistance corresponds to the charge transfer resistance of the redox reaction on the catalyst surface. The higher the catalyst activity, the smoother the charge transfer and the lower the resistance value. When the catalyst is poisoned or aged, the charge transfer resistance increases and the resistance value shows an upward trend. Double-layer capacitance originates from the double layer formed at the interface between the electrode and the electrolyte. Its capacity is positively correlated with the electrolyte contact area and electrolyte content. When the electrolyte dries up, the conditions for double-layer formation deteriorate and the capacitance value shows a downward trend.

[0035] In one optional embodiment, diagnosing the performance degradation fault state of the electrochemical gas sensor specifically includes the following steps: The preset health benchmark values ​​include the charge transfer resistance benchmark value and the double-layer capacitance benchmark value when the electrochemical gas sensor was calibrated at the factory. Based on the evolution data of the charge transfer resistance, the increase of the extracted charge transfer resistance relative to the reference value of the charge transfer resistance is calculated; based on the evolution data of the double-layer capacitor, the change of the extracted double-layer capacitor relative to the reference value of the double-layer capacitor is calculated. When the charge transfer resistance exhibits a continuous monotonically increasing trend for several consecutive cycles, and the increase is greater than a preset threshold: If the double-layer capacitor shows a continuous monotonically decreasing trend for several consecutive times, and the change amplitude of the double-layer capacitor is greater than a preset threshold, then it is determined that the electrochemical gas sensor has an electrolyte drying fault. If the change in the double-layer capacitance is less than a preset threshold, the electrochemical gas sensor is determined to have a catalyst poisoning fault.

[0036] Specifically, the charge transfer resistance and double-layer capacitance reference values ​​set during sensor factory calibration serve as health benchmarks to ensure the consistency and objectivity of the judgment standards and avoid misjudgments due to individual differences. By calculating and extracting the relative changes of parameters and reference values ​​in real time, the degree of performance degradation is quantified, rather than relying on absolute values, thereby improving the adaptability of judgment under different operating conditions.

[0037] Electrolyte drying will indirectly lead to a decrease in catalyst activity and a reduction in electrolyte content, thus exhibiting significant changes in both parameters; while catalyst poisoning only directly affects catalytic activity, and the state of the electrolyte does not change substantially, thus exhibiting a significant change in a single parameter. This difference can be used to accurately distinguish between the two types of core faults.

[0038] In one optional embodiment, the sensitivity decay of the electrochemical gas sensor is calculated based on the increase of the extracted charge transfer resistance relative to the reference value of the charge transfer resistance and the change of the extracted double-layer capacitance relative to the reference value of the double-layer capacitance; if the sensitivity decay is greater than a preset threshold, the electrochemical gas sensor is determined to have reached the end of its lifespan.

[0039] Specifically, by combining the changes in key parameters with preset thresholds, the remaining effective usage time of the sensor is calculated, and a lifespan warning message is generated to provide a basis for user maintenance or replacement. The lifespan can be set to expire when the sensor sensitivity drops to 50% of its initial state.

[0040] Example 2 like Figure 1-2As shown in the embodiment of this application, a gas electrochemical gas sensor module is proposed, including: an electrochemical gas sensor 3, an O-ring 1, a waterproof and breathable membrane 2, a spring pin 5, a printed circuit board 6, and an external solder pad 7.

[0041] O-ring 1 is installed between the housing of electrochemical gas sensor 3 and the external mounting structure. It is fixed by the fit and compression between the housing and the external mounting structure, thus achieving a mechanical seal. Waterproof and breathable membrane 2 is assembled between the housing of electrochemical gas sensor 3 and O-ring 1. The edge of the membrane is limited and fixed by the fit between the housing and O-ring 1, and it fits tightly with both. The housing of electrochemical gas sensor 3 forms a wrap-around containment and protection for the body of electrochemical gas sensor 3, realizing the physical positioning of the core component. Spring pin 5 is vertically set on the printed circuit board 6. One end is fixedly connected to the printed circuit board 6, and the other end corresponds to the electrode 4 of electrochemical gas sensor 3, forming a mechanical fit through elastic contact. External solder pad 7 is an integrated structure at the bottom of the printed circuit board 6. It achieves connectorless docking with the spring pin of the host device through physical contact, and relies on the assembly structure of the host device to form a stable limit.

[0042] The electrodes 4 of the electrochemical gas sensor 3, including the working electrode, counter electrode, reference electrode, and auxiliary electrode, respectively form electrical contact with one end of each of the four spring pins 5. The other end of the spring pins 5 is electrically connected to the printed circuit board 6. The printed circuit board 6 receives the current signal output by the electrochemical gas sensor 3 through the spring pins 5. The electronic components integrated on the printed circuit board realize the electrical interconnection of signal processing, calculation, communication, and control functions according to the preset circuit layout. The external solder pad 7 is connected to the internal circuit of the PCBA and serves as an external electrical interface to realize data transmission and power supply access with the host device.

[0043] The gas molecules to be measured penetrate the waterproof and breathable membrane 2 and enter the electrochemical gas sensor 3. Liquid water and impurities are blocked by the waterproof and breathable membrane 2 and cannot enter the interior of the electrochemical gas sensor 3. The O-ring 1 effectively confines the gas to be measured within the sensing area, preventing gas diffusion and loss and the intrusion of external interfering gases. The target gas in the sensing area diffuses into the interior of the electrochemical gas sensor 3, comes into contact with the electrolyte in the cavity and undergoes an oxidation-reduction reaction, generating a weak current proportional to the gas concentration. This weak current is transmitted to the printed circuit board 6 through the spring pin 5. After signal processing and calculation by the electronic components integrated on the printed circuit board 6, it is transmitted to the host device through the external solder pad 7 to complete the gas concentration detection.

[0044] Of the four electrodes 4 in the electrochemical gas sensor 3, the working electrode, counter electrode, and reference electrode participate in the redox reaction and potential stabilization control of the basic gas detection. The auxiliary electrode 4 serves as a monitoring probe for the internal state of the sensor. It is electrically connected to the microcontroller through the signal processing circuit of the printed circuit board 6 and is used to receive excitation signals periodically applied to the electrochemical gas sensor by the excitation source to execute the self-diagnostic method described in any one of Embodiments 1, providing raw signal evidence for fault detection, lifetime prediction, and sensitivity analysis.

[0045] In one optional embodiment, the microcontroller has a preset compensation algorithm; when the electrochemical gas sensor is determined to be in a performance degradation fault state, the preset compensation algorithm analyzes the degree of sensitivity reduction based on the fault type and parameter change amplitude, and performs coefficient compensation on the gas concentration data detected by the sensor.

[0046] The spring pin 5 replaces the traditional pin socket connection. One end forms a stable and reliable electrical contact with the four electrodes 4 of the electrochemical gas sensor 3, and the other end is connected to the printed circuit board 6. This greatly reduces the module height, meets the flat design requirements of the end product, and ensures contact stability through the continuous pressure provided by the spring. It also has better vibration resistance and the contact connection facilitates module assembly and subsequent maintenance.

[0047] The well-fitting O-ring 1, waterproof and breathable membrane 2, and electrochemical gas sensor 3 housing enable the entire unit to achieve an IP67 protection rating, providing waterproof and breathable protection while blocking impurities. The external solder pad 7 serves as the module's external electrical interface. End users can read data and power the module by connecting the matching spring pins to the solder pad, achieving connectorless docking between the module and the host device, further saving space.

[0048] Example 3 like Figure 3 As shown in the embodiments of this application, a specific implementation of the printed circuit board is given, including: a signal processing circuit, a microcontroller, a power module and an interface protection circuit, which work together to realize the functions of gas signal sensing, conditioning, calculation and diagnosis. It is electrically connected to the sensor electrode through a spring pin, and realizes data interaction and power supply through a standard serial interface and a power interface.

[0049] The sensor's C and R terminals are electrically connected to the signal processing module to receive a stable reference voltage to ensure operational stability; the sensor's W terminal is electrically connected to one end of the signal processing module as the output terminal of the current signal; the output terminal of the signal processing module is electrically connected to the signal input terminal of the microcontroller to transmit the stable voltage signal after filtering, amplification, and conversion.

[0050] The microcontroller's digital output pins are electrically connected to the sensor's auxiliary electrodes via spring-loaded pins to output pulse signals of a specific frequency, which, in conjunction with cyclic voltammetry scanning, enable status monitoring. The microcontroller's UART serial port output is electrically connected to the interface protection circuit to transmit real-time concentration, fault status, and other data to the outside world. The microcontroller's enable control pin is used to receive external enable signals, supporting the module's start and stop control and adapting to various application scenarios.

[0051] The input terminal of the power module is connected in series with the interface protection circuit and is powered by an external 3-5V wide voltage. The output terminal of the power module is electrically connected to the signal processing module, microcontroller and sensor respectively, providing stable power supply to each core component and avoiding voltage fluctuations from affecting working accuracy.

[0052] The interface protection circuit is connected in series between the external power input and the power module input to specifically protect the power input side from electrostatic discharge, overvoltage, and reverse connection risks; at the same time, it is electrically connected to the serial port output of the microcontroller to provide the same protection for the serial communication interface, ensuring data transmission security and interface stability.

[0053] Specifically, the signal processing circuit includes a first operational amplifier U1A, a second operational amplifier U1B, resistors R4, R5, R6, and R7, and capacitors C3 and C4. The output terminal of the first operational amplifier U1A is electrically connected to the C and R terminals of the electrochemical gas sensor to provide a stable reference voltage for the electrochemical gas sensor. The W terminal of the electrochemical gas sensor is electrically connected to one end of resistor R5, and the other end of resistor R5 is electrically connected to one end of resistor R4 and one end of capacitor C3. The other end of resistor R4 is connected to the... The non-inverting input terminal of the second operational amplifier U1B is electrically connected, and the other end of the capacitor C3 is grounded; the output terminal of the second operational amplifier U1B is electrically connected to one end of the resistor R6, and the other end of the resistor R6 is electrically connected to one end of the capacitor C4 and the signal input terminal of the external microcontroller module, respectively, and the other end of the capacitor C4 is grounded; a resistor R7 is connected in parallel between the inverting input terminal and the output terminal of the first operational amplifier U1A, the non-inverting input terminal of the first operational amplifier U1A is connected to a reference voltage, and the inverting input terminal and the output terminal of the second operational amplifier U1B are short-circuited.

[0054] Upon gas detection, the current flowing through terminal W changes. Noise is suppressed by resistor R5, and the current signal is converted into a voltage signal by resistor R4. Simultaneously, some high-frequency signals are filtered by capacitor C3. Finally, after secondary filtering by resistors R6 and C4, the output voltage signal Vout is sent to the microcontroller. Throughout the signal transmission process, U1B acts as a high-precision, low-noise operational amplifier, providing a stable reference for the signal while improving the overall circuit stability with minimal noise introduction.

[0055] Specifically, the microcontroller embeds firmware algorithms that receive voltage signals and execute core data processing and control logic. These firmware algorithms include: (1) Concentration calculation: The gas concentration calculation of this module relies on the linear response characteristics of the electrochemical sensor and is achieved by the two-point linear calibration method.

[0056] Before leaving the factory, the module is first placed in a clean air environment to collect the zero-point voltage output by the sensor and store it in the built-in storage unit. Then, the module is exposed to a standard gas atmosphere of known concentration to collect the characteristic voltage value of the sensor at the corresponding concentration. Based on the above two sets of voltage and concentration calibration data, linear fitting is performed using the least squares method to generate the sensor's own concentration and voltage conversion formula, which is then stored.

[0057] During application, the microcontroller acquires the voltage signal output by the signal processing module in real time, calls the pre-stored concentration and voltage conversion formulas to perform calculations, and can accurately obtain the target gas concentration value in the current environment.

[0058] (2) Temperature compensation: In order to solve the problem of detection accuracy degradation caused by temperature, the interference of ambient temperature fluctuation on the output characteristics of electrochemical sensor is eliminated.

[0059] In the compensation model construction phase, a wide temperature range (e.g., -40℃ to 60℃) is selected as the calibration range, and a reference temperature (e.g., 25℃) is set. Multi-point temperature and concentration calibration experiments are conducted on the sensor. The system measures the concentration output value of the sensor at different temperature points and calculates the concentration deviation data of each temperature point relative to the reference temperature. Based on the above calibration data, a piecewise interpolation method or a polynomial regression method is used to complete the mathematical fitting, construct a mapping relationship model between temperature and compensation parameters, and store this model in the module storage unit.

[0060] During the real-time compensation execution phase, the built-in temperature sensor collects the current ambient temperature in real time during the actual detection process. The microcontroller retrieves the pre-stored temperature and compensation parameter mapping model and matches it to obtain the compensation parameter corresponding to the current temperature. The compensation parameter is used to dynamically correct the gas concentration value calculated in real time, thereby improving the measurement consistency and detection accuracy of the sensor in the entire temperature operating range.

[0061] (3) Baseline self-correction: The core objective of this algorithm is to solve the zero-point drift problem caused by the long-term operation of electrochemical sensors, the recovery delay after exposure to high concentrations of gas, or complex operating conditions, to eliminate the systematic error introduced by the measurement baseline offset, and to ensure the measurement accuracy of the sensor throughout its entire life cycle.

[0062] During the drift pattern identification phase, the system continuously monitors the output signal of the sensor in a known clean air environment and collects baseline data in real time. Based on the initial baseline parameters calibrated at the factory, the system performs statistical analysis on the baseline data during long-term operation to identify the slow drift pattern of the baseline over time.

[0063] During the adaptive compensation execution phase, statistical algorithms are used to process the collected baseline data to determine the current actual baseline value. These algorithms include the moving average method and the trend fitting method. Based on this actual baseline value, the microcontroller performs adaptive compensation on the real-time measurement signals from the sensors, achieving automatic correction of zero-point drift.

[0064] By dynamically tracking baseline change trends and implementing real-time compensation, the long-term stability and measurement accuracy of the sensor throughout its entire lifecycle are effectively improved.

[0065] (4) Intelligent diagnosis and maintenance: This module is equipped with an intelligent diagnosis and maintenance mechanism. By periodically applying a pulse signal of a specific frequency to the auxiliary electrode of the sensor and performing a cyclic voltammetric scan, the dynamic impedance spectrum of the sensor under different bias conditions is collected.

[0066] In the fault diagnosis and life prediction stage, the system extracts key characteristic parameters from the dynamic impedance spectrum and analyzes their evolution over time. The real-time characteristic parameters are compared with the pre-stored sensor health benchmark model to accurately diagnose typical fault states such as electrolyte desiccation and catalyst poisoning. At the same time, based on the sensor sensitivity decay trend, the remaining lifespan is quantitatively predicted.

[0067] During the performance compensation execution phase, when the system detects sensor performance degradation, it automatically triggers a preset compensation algorithm to dynamically correct the real-time output gas concentration value, ensuring the module's detection accuracy and operational reliability throughout its entire lifecycle.

[0068] When a sensor is determined to have a performance degradation fault, i.e., a decrease in sensitivity, a preset compensation algorithm analyzes the sensitivity decline based on the fault type and the magnitude of parameter changes. It then calls the corresponding correction model to compensate the concentration data detected by the sensor with a corresponding coefficient. This includes addressing sensitivity decline caused by electrolyte drying, quantifying the electrolyte loss ratio through the change in the double-layer capacitance, and using the corresponding coefficient compensation to inversely correct the calculated gas concentration value.

[0069] (5) Mode Management and Communication: This module constructs a dual-mode working system of factory mode and user mode through software configuration, realizing hierarchical control and data interaction functions for module operation parameters.

[0070] Factory mode: Before leaving the factory, the authorized entity writes the core calibration parameters and algorithm benchmark data; after leaving the factory, all parameters in this mode are automatically switched to read-only status, prohibiting any tampering operations, ensuring the authority and uniqueness of the factory calibration data, and providing reliable data support for quality traceability and performance judgment throughout the product life cycle.

[0071] User mode: The initial parameters of the system are consistent with those of the factory mode; end users can adjust the calibration coefficients within a preset range based on the actual application scenario, or perform recalibration operations to optimize the adaptability of the module to different application environments.

[0072] Standardized data communication allows the module to output processed full data, including real-time gas concentration values, sensor fault status, and remaining lifespan indicators, via a standard serial interface (UART). It also supports enable control functions, enabling flexible integration with various host computer systems to meet the needs of multi-machine networking and integrated applications.

[0073] The dual-mode design achieves the dual goals of ensuring the security of factory baseline data and the flexibility of terminal applications, while taking into account both product quality control and field adaptation needs.

[0074] The working process of the gas sensor module circuit is as follows: The gas undergoes an electrochemical reaction inside the sensor to generate a weak current, which is transmitted to the sensor's W terminal output via a spring pin. The output is then sent to the signal processing module, where it undergoes filtering, IV conversion, amplification, and conditioning before being output as a stable voltage signal.

[0075] A stable voltage signal is transmitted to the microcontroller, which performs core processing such as concentration calculation, temperature compensation, baseline correction, and intelligent diagnostics. The final data is output through the standard serial interface UART. The power module provides stable power to all core components throughout the process, and the interface protection circuit provides full-process protection for both the power input and serial output, ensuring circuit safety and reliable data transmission.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A self-diagnostic method, characterized in that, Applications in electrochemical gas sensors include: A specific frequency excitation signal or a scanning excitation signal within a preset frequency range is periodically applied to the auxiliary electrode of the electrochemical gas sensor to collect the dynamic impedance spectrum of the electrochemical gas sensor under different periods. The characteristic changes of the dynamic impedance spectrum are analyzed, the evolution data of preset key parameters are extracted, and the evolution data of key parameters are compared with preset health benchmark values ​​to diagnose whether the electrochemical gas sensor is in a state of performance degradation failure.

2. The self-diagnostic method according to claim 1, characterized in that: The preset key parameter evolution data includes the evolution data of charge transfer resistance and the evolution data of double-layer capacitance. The charge transfer resistance reflects the active state of the catalyst, and the double-layer capacitance reflects the state of the electrolyte.

3. The self-diagnostic method according to claim 2, characterized in that: The diagnostic process for the performance degradation fault state of the electrochemical gas sensor includes the following steps: The preset health benchmark values ​​include the charge transfer resistance benchmark value and the double-layer capacitance benchmark value when the electrochemical gas sensor was calibrated at the factory. Based on the evolution data of the charge transfer resistance, the increase of the extracted charge transfer resistance relative to the reference value of the charge transfer resistance is calculated; based on the evolution data of the double-layer capacitor, the change of the extracted double-layer capacitor relative to the reference value of the double-layer capacitor is calculated. When the charge transfer resistance exhibits a continuous monotonically increasing trend for several consecutive cycles, and the increase is greater than a preset threshold: If the double-layer capacitor shows a continuous monotonically decreasing trend for several consecutive times, and the change amplitude of the double-layer capacitor is greater than a preset threshold, then it is determined that the electrochemical gas sensor has an electrolyte drying fault. If the change in the double-layer capacitance is less than a preset threshold, the electrochemical gas sensor is determined to have a catalyst poisoning fault.

4. The self-diagnostic method according to claim 3, characterized in that: The sensitivity decay of the electrochemical gas sensor is calculated based on the increase of the extracted charge transfer resistance relative to the reference value of the charge transfer resistance and the change of the extracted double-layer capacitance relative to the reference value of the double-layer capacitance; if the sensitivity decay is greater than a preset threshold, the electrochemical gas sensor is determined to have reached the end of its lifespan.

5. A gas sensor module, characterized in that, include: An electrochemical gas sensor, comprising a working electrode, a counter electrode, a reference electrode, and an auxiliary electrode; A spring-loaded pin, one end of which forms a stable elastic electrical contact with the corresponding electrode of the electrochemical gas sensor; A printed circuit board integrates a microcontroller, an excitation source, and a signal processing circuit. The microcontroller is electrically connected to the other end of the spring pin through the signal processing circuit, and is used to receive the current signal output by the electrochemical gas sensor; and to control the excitation source to periodically apply an excitation signal to the auxiliary electrode of the electrochemical gas sensor to perform the self-diagnostic method according to any one of claims 1-4. An external solder pad is located at the bottom of the printed circuit board and serves as the external electrical interface of the gas sensor module. It is used to connect with the host device via spring pins to read data and supply power to the gas sensor module.

6. The gas sensor module according to claim 5, characterized in that, The microcontroller has a preset compensation algorithm; when the electrochemical gas sensor is determined to be in a performance degradation fault state, the preset compensation algorithm analyzes the degree of sensitivity reduction based on the fault type and parameter change amplitude, and performs coefficient compensation on the gas concentration data detected by the sensor.

7. The gas sensor module according to claim 6, characterized in that, Also includes: The O-ring is assembled between the housing of the electrochemical gas sensor and the external mounting structure to achieve the airtight seal of the gas sensor module and to confine the gas to be measured within the sensing area. A waterproof and breathable membrane is fitted between the electrochemical gas sensor and the O-ring to allow gas molecules to pass through while blocking liquid water and impurities from entering.

8. The gas sensor module according to claim 7, characterized in that, The printed circuit board includes a signal processing circuit. The input terminal of the signal processing circuit is connected to the electrochemical gas sensor and is used to receive the current signal output by the electrochemical gas sensor, and to filter, amplify and convert the current signal. The output terminal of the signal processing circuit is electrically connected to the signal input terminal of the microcontroller, and is used to transmit the conditioned voltage signal to the microcontroller. The firmware algorithm is used to parse and process the voltage signal.

9. The gas sensor module according to claim 8, characterized in that, The printed circuit board also includes: a power module and an interface protection circuit; The output terminal of the power module is electrically connected to the signal processing circuit and the microcontroller respectively to provide a stable power supply. The interface protection circuit is connected in series between the external power input and the input terminal of the power module, and is electrically connected to the serial port output terminal of the microcontroller, to provide anti-static, overvoltage and reverse connection protection for power input and serial communication.

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