Zero drift calibration device and method for gas sensor

Abstract

The invention discloses a gas sensor zero drift calibration device and method, a catalytic sensor detects gas and outputs an original sensor signal voltage, a signal processing circuit receives the sensor signal voltage and outputs a processed signal voltage, a DAC module generates an adjustable zeroing reference voltage, an ADC module collects the processed signal voltage in real time, and the zeroing reference voltage is used for calibrating zero drift of a gas sensor. The signal zeroing circuit receives the zeroing reference voltage and performs zeroing control on the processed signal voltage, and the calibration control module controls the DAC module to adjust the zeroing reference voltage during power-on, so that the processed signal voltage is maintained in a preset zero point range, and the processed signal voltage is continuously monitored in an operation stage; if the processed signal voltage continuously exceeds the limit for N times, the calibration process is re-triggered, a hardware simplification means that a single-path DAC is directly connected with a feedback loop to replace a traditional resistance network is adopted, and a software closed loop stepping control and dynamic monitoring mechanism is combined, so that the problem of lack of environment temperature excursion and aging dynamic compensation caused by hardware complexity is solved.

Description

Technical Field

[0001] The present application relates to the field of gas detection technology, and in particular to a gas sensor zero drift calibration device and method. Background Art

[0002] Catalytic gas sensors are widely used in gas leak monitoring and toxic and hazardous gas detection. Their core performance metric, zero-point voltage, is extremely sensitive to changes in ambient temperature, humidity, and sensor aging. Drift in this zero-point voltage can lead to significant errors in gas concentration detection, affecting measurement accuracy and potentially causing false or missed alarms, posing a potential risk to industrial safety monitoring and public safety.

[0003] To overcome zero-point drift, existing technologies commonly employ a hardware zeroing solution based on a multi-resistor network. In this solution, multiple resistors of varying values ​​are connected to the zeroing circuit of the signal conditioning circuit. The system microcontroller controls an analog switch array connected to its multiple input / output ports to select specific resistor combinations for access to the circuit. During system startup, the MCU sequentially switches resistor combinations and reads the output voltage of the signal circuit in real time using an analog-to-digital converter. When Vout falls within the preset zero-point voltage tolerance range, the MCU locks the switch configuration for the current resistor combination, completing initial calibration.

[0004] However, the above traditional solutions have significant shortcomings: First, the hardware structure is complex, relying on multiple precision resistors, analog switch chips and MCU-specific IO ports, which not only increases material costs and circuit board space occupancy, but also increases the system failure rate due to the increase in the number of components and solder joints; second, the calibration process is time-consuming, because it is necessary to switch multiple resistor combinations in sequence and wait for the circuit parameters to stabilize before performing ADC sampling, resulting in equipment startup delays and affecting response efficiency; third, it lacks dynamic adaptability. Its calibration is only a one-time operation during the startup phase. During continuous operation, the equipment cannot compensate in real time for dynamic changes in temperature and humidity or accumulated drift caused by sensor aging, resulting in long-term operation accuracy reduction and necessitating power-off and restart for recalibration, making it difficult to meet the application requirements of continuous, high-precision monitoring. Summary of the Invention

[0005] The purpose of this application is to provide a gas sensor zero drift calibration device and method in order to overcome the existing technical defects, by replacing the traditional resistor network with a hardware simplification method through a single DAC direct feedback loop, combined with software closed-loop step control and dynamic monitoring mechanism, to solve the problem of lack of dynamic compensation for environmental temperature drift and aging caused by hardware complexity.

[0006] The purpose of this application is achieved through the following technical solutions:

[0007] In a first aspect, the present application proposes a gas sensor zero drift calibration device, the device comprising:

[0008] Catalytic sensor, used to detect gas and output the original sensor signal voltage;

[0009] a signal processing circuit connected to the catalytic sensor, for receiving the sensor signal voltage and outputting a processed signal voltage;

[0010] A microcontroller includes a DAC module and an ADC module, wherein the DAC module generates an adjustable zero reference voltage and the ADC module collects and processes the signal voltage in real time;

[0011] The signal zeroing circuit is arranged between the output end of the DAC module of the microcontroller and the signal processing circuit, and is used to receive a zeroing reference voltage and perform zeroing control on the processed signal voltage based on the zeroing reference voltage;

[0012] The calibration control module is used to control the DAC module to adjust the zero reference voltage in a step-by-step manner when powered on, and cyclically read the processed signal voltage so that the processed signal voltage is maintained within the preset zero point range. During the operation phase, the processed signal voltage is continuously monitored. If the processed signal voltage exceeds the limit for N consecutive times, the calibration process is re-triggered.

[0013] In a possible implementation, the signal zeroing circuit includes a filtering circuit, and the zeroing reference voltage output by the DAC module is connected to a feedback input terminal of an operational amplifier in the signal processing circuit via the filtering circuit.

[0014] In a possible implementation, the microcontroller has a built-in 12-bit DAC module with an output range of 0 to 3.3 V, and the output end of the DAC module is directly connected to the signal zeroing circuit.

[0015] In one possible implementation, the output voltage terminal of the signal processing circuit is connected to an input pin of an ADC module of the microcontroller to form a closed-loop feedback path.

[0016] In a second aspect, the present application proposes a gas sensor zero drift calibration method, characterized in that the method is applied to the gas sensor zero drift calibration device according to any one of the first aspects, and the method includes:

[0017] Step S1, setting the DAC initial output value and reading the signal voltage;

[0018] Step S2: If the signal voltage is not within the preset zero point range, adjust the DAC initial output value according to the preset step size, wait for the stabilization time after each adjustment, and then read the signal voltage;

[0019] Step S3: until the signal voltage stabilizes within the preset zero point range, save the current DAC initial output value and use it as a calibration reference value.

[0020] In one possible implementation, the method further includes:

[0021] Step S4: reading the signal voltage at periodic intervals;

[0022] Step S5: If the signal voltage exceeds the preset zero point range N times in a row, then re-execute steps S1-S3.

[0023] In one possible implementation, the method further includes:

[0024] Before re-triggering the calibration, perform a signal stability check:

[0025] The signal voltage is collected M times continuously. If the fluctuation difference of adjacent sampling values ​​is less than the threshold δ, it is determined to be in a stable state and the calibration process is started.

[0026] In a possible implementation, the preset step size is dynamically adjusted according to a deviation between the actual voltage and the target range.

[0027] The above-mentioned main scheme of this application and its further options can be freely combined to form multiple schemes, all of which are schemes that can be adopted and protected by this application; and in this application, (non-conflicting options) can also be freely combined with each other and with other options. After understanding the scheme of this application, those skilled in the art will understand that there are many combinations based on existing technology and common knowledge, all of which are technical solutions to be protected by this application, and they are not exhaustive here.

[0028] The present application discloses a gas sensor zero drift calibration device and method, in which a catalytic sensor detects gas and outputs an original sensor signal voltage, a signal processing circuit receives the sensor signal voltage and outputs a processed signal voltage, a DAC module generates an adjustable zero adjustment reference voltage, an ADC module collects the processed signal voltage in real time, a signal zero adjustment circuit receives the zero adjustment reference voltage, and performs zero adjustment control on the processed signal voltage, a calibration control module controls the DAC module to adjust the zero adjustment reference voltage when powered on, so that the processed signal voltage is maintained within a preset zero point range, and continuously monitors the processed signal voltage during operation, and re-triggers the calibration process if the processed signal voltage exceeds the limit N times in a row, replaces the traditional resistor network with a hardware simplification method by a single DAC direct-connected feedback loop, and combines software closed-loop step control and a dynamic monitoring mechanism to solve the problem of lack of dynamic compensation for environmental temperature drift and aging caused by hardware complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A schematic structural diagram of a gas sensor zero drift calibration device proposed in an embodiment of the present application is shown.

[0031] Figure 2 A flow chart of a gas sensor zero drift calibration method proposed in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0032] The following describes the embodiments of the present application through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0033] Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of this application.

[0034] In the prior art, multiple resistors (such as R1, R2, and R3) are set in the zero adjustment circuit of the sensor, and the analog switches are controlled by the multiple IO ports of the microcontroller to select different resistor combinations, thereby adjusting the feedback input voltage of the signal output circuit. When powered on, the microcontroller switches the resistor combinations in sequence, and reads back the output voltage (Vout) of the signal circuit through the analog-to-digital converter (ADC). When Vout falls within the preset range, the corresponding resistance position is locked. The problems it has are: First, the hardware is complex: multiple resistors, analog switches, and IO ports are required, which increases the circuit cost and failure rate. Second, the calibration speed is slow: the resistor switching and stabilization time are long, which affects the startup efficiency of the equipment. Third, there is a lack of dynamic compensation: the zero point cannot be adjusted in real time during operation, and the accuracy decreases due to temperature drift or aging after long-term use.

[0035] Therefore, in order to solve the problems of complex hardware, low calibration efficiency and lack of dynamic compensation in the traditional multi-resistance network voltage regulation solution, the embodiment of the present application proposes a gas sensor zero drift calibration device and method, which realizes fast power-on calibration and dynamic zeroing during operation through hardware simplification and software closed-loop control.

[0036] Please refer to Figure 1 , Figure 1 The following is a schematic diagram showing the structure of a gas sensor zero drift calibration device proposed in an embodiment of the present application, the device comprising:

[0037] Catalytic sensor, used to detect gas and output the original sensor signal voltage;

[0038] a signal processing circuit connected to the catalytic sensor, for receiving the sensor signal voltage and outputting a processed signal voltage;

[0039] A microcontroller includes a DAC module and an ADC module, wherein the DAC module generates an adjustable zero reference voltage and the ADC module collects and processes the signal voltage in real time;

[0040] The signal zeroing circuit is arranged between the output end of the DAC module of the microcontroller and the signal processing circuit, and is used to receive a zeroing reference voltage and perform zeroing control on the processed signal voltage based on the zeroing reference voltage;

[0041] The calibration control module is used to control the DAC module to adjust the zero reference voltage in a step-by-step manner when powered on, and cyclically read the processed signal voltage so that the processed signal voltage is maintained within the preset zero point range. During the operation phase, the processed signal voltage is continuously monitored. If the processed signal voltage exceeds the limit for N consecutive times, the calibration process is re-triggered.

[0042] A gas sensor zero drift calibration device proposed in this application can solve the problems of complex hardware, low calibration efficiency and lack of dynamic compensation in the prior art, and realize fast calibration in the power-on initialization phase and dynamic zeroing in the operation phase to ensure the zero point stability of the gas sensor. The catalytic sensor is used to detect gas and output the original sensor signal voltage, which is connected to the signal processing circuit to convert the detected gas signal into an electrical signal.

[0043] The signal processing circuit receives the original signal voltage output by the catalytic sensor, processes it (such as amplification, filtering, etc.), and outputs the processed signal voltage Vout. The signal processing circuit is connected to the catalytic sensor and the signal zeroing circuit to perform preliminary processing on the sensor signal.

[0044] The microcontroller includes a DAC (digital-to-analog converter) module and an ADC (analog-to-digital converter) module. The DAC module generates an adjustable zero-adjustment reference voltage (Vref), which is used to adjust the feedback input of the signal processing circuit to calibrate the sensor's zero point. The ADC module collects the processed signal voltage (Vout) output by the signal processing circuit in real time and feeds it back to the calibration control module. The DAC module output is connected to the signal zero-adjustment circuit, and the ADC module input is connected to the output of the signal processing circuit.

[0045] The signal zeroing circuit receives a zeroing reference voltage (Vref) from the microcontroller's DAC module and uses this voltage to zero-adjust the processed signal voltage output by the signal processing circuit. It is located between the microcontroller's DAC module output and the signal processing circuit. After being processed by the filtering circuit, the zeroing reference voltage output by the DAC is input to the feedback input pin of the signal voltage op amp, thereby adjusting the output voltage of the signal processing circuit.

[0046] The calibration control module controls the entire calibration process, including power-on initialization calibration and dynamic calibration during operation. During power-on initialization calibration, the DAC output zero-adjustment reference voltage Vref is gradually adjusted. Through closed-loop feedback control, the signal processing circuit output voltage Vout quickly converges to the preset zero-point range. The calibrated Vref value is then saved as a reference. During operational monitoring, Vout is periodically monitored (e.g., every 30 seconds). If Vout exceeds the limit for N consecutive times (e.g., 6 times), the calibration process is retriggered.

[0047] During the power-on calibration process, the initial DAC output value Vref_initial is set (e.g., 1.0V). The ADC module then reads the signal processing circuit's output voltage, Vout. If Vout is not within the preset zero-point range (Vmin, Vmax), Vref is adjusted by a step size of ΔV until Vout stabilizes within the target range. The current Vref value is then saved as the calibration reference value.

[0048] During the run-time calibration process, Vout is read every time T (e.g., 30 seconds). If Vout exceeds the preset range for N consecutive times (e.g., 6 times), the power-on calibration process is re-executed to compensate for zero-point drift caused by environmental changes or sensor aging.

[0049] The signal zeroing circuit includes a filtering circuit, and the zeroing reference voltage output by the DAC module is connected to the feedback input terminal of the operational amplifier in the signal processing circuit through the filtering circuit.

[0050] The filter circuit smoothes the zero-adjustment reference voltage output by the DAC module, filtering out high-frequency noise and ripple to ensure its stability and accuracy. During the power-on initialization and calibration phase, the microcontroller controls the DAC module to output an initial zero-adjustment reference voltage. This voltage, after processing by the filter circuit, is then fed into the feedback input of the operational amplifier in the signal processing circuit. Based on the comparison of the feedback zero-adjustment reference voltage and the sensor signal voltage, the operational amplifier adjusts the output voltage of the signal processing circuit to gradually approach the preset zero-point range.

[0051] The microcontroller uses the ADC module to collect the output voltage of the signal processing circuit in real time and adjusts the output voltage of the DAC module based on the collected results until the output voltage of the signal processing circuit stabilizes within the preset zero-point range. During normal operation of the device, the signal zeroing circuit continues to operate. If factors such as environmental temperature drift or sensor aging cause zero-point offset, the microcontroller monitors the output voltage change of the signal processing circuit through the ADC module, restarts the calibration process, and controls the DAC module to adjust the zeroing reference voltage. After processing by the filter circuit, the voltage is re-input into the feedback input of the operational amplifier, bringing the output voltage of the signal processing circuit back into the preset zero-point range, achieving dynamic zeroing.

[0052] The microcontroller has a built-in 12-bit DAC module with an output range of 0 to 3.3V, and the output end of the DAC module is directly connected to the signal zeroing circuit.

[0053] The microcontroller's output range covers 0 to 3.3V, sufficient to meet the zero-adjustment reference voltage requirement. The DAC module output is directly connected to the signal zero-adjustment circuit, ensuring that the zero-adjustment reference voltage is quickly and accurately transmitted to the signal zero-adjustment circuit, where it is then applied to the feedback input of the operational amplifier in the signal processing circuit. This design enables the microcontroller to precisely zero the output voltage of the signal processing circuit by directly controlling the DAC module's output voltage. The 12-bit DAC module provides high output accuracy, which helps improve zero-adjustment accuracy. Furthermore, this direct connection reduces signal loss and interference in intermediate links, further enhancing the efficiency and stability of zero-adjustment.

[0054] The output voltage terminal of the signal processing circuit is connected to the input pin of the ADC module of the microcontroller to form a closed-loop feedback path.

[0055] The closed-loop feedback path enables the microcontroller to acquire the output voltage of the signal processing circuit in real time and compare it with the preset zero-point range. During power-up initialization, the microcontroller adjusts the output voltage of the DAC module to quickly converge the output voltage of the signal processing circuit to the preset range. During operation, the microcontroller continuously monitors zero-point drift based on the feedback voltage information. If an out-of-range zero-point offset is detected, a recalibration process is immediately triggered, ensuring that the zero point of the gas sensor remains accurate at all times, effectively improving detection accuracy and reliability.

[0056] It's worth noting that the STM32G031 microcontroller is a good choice. Its advantage lies in its built-in 12-bit DAC with an output voltage range of 0 to 3.3V, which meets the accuracy and range requirements of the zero reference voltage. The catalytic sensor can be the NAP55 model, with its signal output pin connected to the input of the signal op amp circuit, which converts the detected gas signal into an electrical signal for preliminary processing.

[0057] Please refer to Figure 2 , Figure 2 A flow chart of a gas sensor zero drift calibration method proposed in an embodiment of the present application is shown, and the method includes:

[0058] Step S1, setting the DAC initial output value and reading the signal voltage;

[0059] Step S2: If the signal voltage is not within the preset zero point range, adjust the DAC initial output value according to the preset step size, wait for the stabilization time after each adjustment, and then read the signal voltage;

[0060] Step S3: until the signal voltage stabilizes within the preset zero point range, save the current DAC initial output value and use it as a calibration reference value.

[0061] First, the initial output value of the DAC is set. For example, it can be set to an intermediate value or a reasonable value estimated based on historical data. Then, the signal voltage output by the signal processing circuit is read through the microcontroller's ADC module. This signal voltage reflects the current zero point state of the sensor.

[0062] If the signal voltage reading is outside the preset zero-point range, the current DAC output value cannot adjust the sensor signal to the ideal zero point. In this case, adjust the DAC output value according to the preset step size (for example, 0.01V). After each DAC output adjustment, wait for a period of time to allow the signal processing circuit and sensor signal to stabilize before rereading the signal voltage. This wait time depends on the response characteristics of the sensor and circuit, and is generally in the millisecond range.

[0063] Repeat step S2, continuously adjusting the DAC output and verifying the signal voltage until the signal voltage stabilizes within the preset zero-point range. Once this condition is met, the current DAC output value is saved as a calibration reference value for subsequent testing and calibration. This reference value is used for comparison during device operation to determine whether the zero-point has shifted, thereby determining whether the calibration process needs to be restarted.

[0064] Gas sensor zero drift calibration method also includes:

[0065] Step S4: reading the signal voltage at periodic intervals;

[0066] Step S5: If the signal voltage exceeds the preset zero point range N times in a row, then re-execute steps S1-S3.

[0067] After completing initial calibration and saving the calibration reference value, the microcontroller enters the operational monitoring phase. During this phase, the microcontroller reads the signal voltage output by the signal processing circuit at a preset periodic interval (for example, every 30 seconds). This periodic reading operation continuously monitors the sensor's zero point status to ensure its stability during long-term operation.

[0068] Each signal voltage reading is compared to a preset zero-point range. If the signal voltage exceeds the preset zero-point range N times (e.g., six times) in a row, this indicates that the sensor's zero point has shifted significantly, possibly due to environmental changes or aging, and has exceeded the normal fluctuation range. At this point, the microcontroller triggers a recalibration process, re-executing steps S1 through S3. This involves resetting the initial DAC output value and adjusting the DAC output by a preset step size until the signal voltage stabilizes within the preset zero-point range. The new calibration reference value is then saved.

[0069] The method further includes:

[0070] Before re-triggering the calibration, perform a signal stability check:

[0071] The signal voltage is collected M times continuously. If the fluctuation difference of adjacent sampling values ​​is less than the threshold δ, it is determined to be in a stable state and the calibration process is started.

[0072] Before re-triggering the calibration process, in order to ensure the accuracy of the calibration and avoid frequent calibration due to accidental interference, a signal stability determination needs to be performed. Specifically, the signal voltage is continuously collected M times, and the number of collections M can be set according to the actual application scenario and stability requirements. During the collection process, a certain time interval is maintained between each sampling to ensure the independence and representativeness of the sampling. After the collection is completed, the fluctuation difference between adjacent sample values ​​is calculated, that is, the absolute difference between two adjacent sample values. If the fluctuation difference of all adjacent sample values ​​is less than the set threshold δ, the value of δ is usually determined according to the noise level and zero point stability requirements of the sensor, then the current signal voltage is considered to be in a stable state. At this point, it can be determined that the zero point of the sensor has indeed shifted, and the calibration process needs to be started and steps S1 to S3 need to be re-executed to adjust the DAC output so that the signal voltage returns to the preset zero point range.

[0073] The preset step size is dynamically adjusted based on the deviation between the actual voltage and the target range.

[0074] During the gas sensor zero-point calibration process, the preset step size can be dynamically adjusted based on the deviation between the actual voltage and the target range. Specifically, when the actual signal voltage differs significantly from the preset zero-point range, the step size ΔV can be increased to quickly bring the DAC output value closer to the target range, shortening calibration time. If the actual voltage is already close to the target range, the step size ΔV can be reduced, allowing for more refined adjustments to ensure the signal voltage remains within the preset range, improving calibration accuracy.

[0075] In one possible embodiment, during power-on initialization, the DAC output Vref is first set to 1.0V, and the zero-point range of the signal output voltage Vout is set within (Vmin, Vmax), corresponding to 5% of the sensor zero point Vzero. Next, the initial DAC adjustment step size ΔV is set to 0.01V. During execution, the step size ΔV can be dynamically adjusted based on the difference between Vout and the preset zero-point range. The Vout voltage is then read. If Vout is not within the preset zero-point range, it is adjusted according to the set step size ΔV, moving closer to the preset zero-point range. After each adjustment, Vout is read again after a 20ms wait. This cycle continues until Vout stabilizes within the preset zero-point range. Calibration is complete, and the current DAC output Vref value is saved and continuously output. During normal operation, the Vout value is continuously monitored. If Vout exceeds the preset zero-point range, voltage stability determination is initiated. When Vout is stable and has no fluctuations, the calibration process is executed again, that is, the above steps are repeated. The stable and no-fluctuation judgment can be set according to the actual situation. For example, Vout is read every 30 seconds. If the difference of Vout read for 6 consecutive times is within 5mV, it can be considered that Vout is in a stable and no-fluctuation state.

[0076] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0077] First, only a single DAC is needed to implement the zero adjustment function, reducing pin occupancy and component count, thereby significantly reducing hardware costs, with an estimated cost reduction of more than 20%.

[0078] Second, the use of DAC for digital adjustment is faster than the traditional resistor switching method, which greatly shortens the power-on calibration time and increases efficiency by 50%, effectively improving the startup efficiency of the device.

[0079] Third, during operation, it can compensate for the effects of ambient temperature drift and sensor aging in real time, ensuring that the long-term zero drift rate is controlled within ±0.5% of the full scale, significantly improving the accuracy and reliability of detection.

[0080] Fourth, the DAC stepless zero adjustment calibration circuit device and method avoids the limitations of traditional multi-resistance networks and provides a more flexible and accurate zero adjustment solution.

[0081] Fifth, the calibration control module uses a stepped increment to adjust the DAC output voltage. The step size ΔV can be dynamically adjusted according to actual conditions, achieving fast and accurate calibration and improving the intelligence level of the calibration process.

[0082] Sixth, under normal operating conditions, the signal voltage is continuously monitored and the calibration process is automatically executed when a zero offset is detected, ensuring long-term stable operation of the equipment and reducing maintenance costs and workload.

[0083] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A gas sensor zero drift calibration device, characterized in that: The device comprises: Catalytic sensor, used to detect gas and output the original sensor signal voltage; a signal processing circuit connected to the catalytic sensor, for receiving the sensor signal voltage and outputting a processed signal voltage; A microcontroller includes a DAC module and an ADC module, wherein the DAC module generates an adjustable zero reference voltage and the ADC module collects and processes the signal voltage in real time; The signal zeroing circuit is arranged between the output end of the DAC module of the microcontroller and the signal processing circuit, and is used to receive a zeroing reference voltage and perform zeroing control on the processed signal voltage based on the zeroing reference voltage; The calibration control module is used to control the DAC module to adjust the zero reference voltage in a step-by-step manner when powered on, and cyclically read the processed signal voltage so that the processed signal voltage is maintained within the preset zero point range. During the operation phase, the processed signal voltage is continuously monitored. If the processed signal voltage exceeds the limit for N consecutive times, the calibration process is re-triggered.

2. The gas sensor zero drift calibration device according to claim 1, characterized in that: The signal zeroing circuit includes a filtering circuit, and the zeroing reference voltage output by the DAC module is connected to the feedback input terminal of the operational amplifier in the signal processing circuit through the filtering circuit.

3. The gas sensor zero drift calibration device according to claim 1, characterized in that: The microcontroller has a built-in 12-bit DAC module with an output range of 0 to 3.3V, and the output end of the DAC module is directly connected to the signal zeroing circuit.

4. The gas sensor zero drift calibration device according to claim 1, wherein: The output voltage terminal of the signal processing circuit is connected to the input pin of the ADC module of the microcontroller to form a closed-loop feedback path.

5. A gas sensor zero drift calibration method, characterized in that: The method is applied to the gas sensor zero drift calibration device according to any one of claims 1 to 4, and the method comprises: Step S1, setting the DAC initial output value and reading the signal voltage; Step S2: If the signal voltage is not within the preset zero point range, adjust the DAC initial output value according to the preset step size, wait for the stabilization time after each adjustment, and then read the signal voltage; Step S3: until the signal voltage stabilizes within the preset zero point range, save the current DAC initial output value and use it as a calibration reference value.

6. The gas sensor zero drift calibration method according to claim 5, wherein: The method further comprises: Step S4: reading the signal voltage at periodic intervals; Step S5: If the signal voltage exceeds the preset zero point range N times in a row, then re-execute steps S1-S3.

7. The gas sensor zero drift calibration method according to claim 5, wherein: The method further comprises: Before re-triggering the calibration, perform a signal stability check: The signal voltage is collected M times continuously. If the fluctuation difference of adjacent sampling values ​​is less than the threshold δ, it is determined to be in a stable state and the calibration process is started.

8. The gas sensor zero drift calibration method according to claim 5, wherein: The preset step size is dynamically adjusted based on the deviation between the actual voltage and the target range.

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