Gas detector and method of controlling the same

Abstract

This invention discloses a gas detector and its control method, belonging to the field of gas detection technology. The detector includes an electrochemical sensor and a metal-oxide-semiconductor (MODS) sensor for detecting the same target gas. The method includes: acquiring two output signals; calculating the correlation coefficient of the two signals within a preset sliding time window; determining a sensor fault when the correlation coefficient is lower than a preset threshold and continues to exceed a preset fault confirmation time; calculating the signal change rate of the two signals; determining interference and suppressing an alarm when the change rate of the MODS sensor exceeds a preset fast threshold and the change rate of the electrochemical sensor is lower than a preset slow threshold; and determining a real leak and triggering an alarm when both signals exceed the alarm threshold. This invention utilizes the inherent differences in response speed and selectivity between the two sensors, balancing detection accuracy and long-term reliability, and effectively suppressing false alarms caused by interfering gases.

Description

Technical Field

[0001] This invention relates to the technical field of gas detection, and in particular to a gas detector and its control method. Background Technology

[0002] The core performance indicators of gas detectors are detection accuracy and long-term reliability. Existing detectors typically use a single type of sensor: electrochemical sensors have high accuracy and good selectivity, but a short lifespan, usually 2 to 3 years; metal oxide semiconductor sensors (MOS sensors) have a long lifespan, up to 10 years or more, but poor selectivity and are susceptible to interference gases such as ethanol, which can cause false alarms.

[0003] When improved reliability is required, the conventional approach is to configure two identical sensors for the same gas, i.e., homogeneous redundancy. However, this approach cannot solve the fundamental problem: both electrochemical sensors will age simultaneously, and both MOS sensors will be triggered false alarms simultaneously by the same interfering gas.

[0004] In existing technologies, Sifang Optoelectronics (CN119915973A) discloses a gas detection scheme using sensor combinations with different detection principles, but it does not limit the heterogeneous redundancy configuration for the same gas, nor does it reveal an interference identification mechanism based on response speed differences. Hefei University of Technology (CN116519872A) discloses a method for using multiple gas sensors in combination, but the differences between different sensor models are used to identify gas types rather than for fault diagnosis of the same gas. China Coal Technology & Engineering Group (CN115308288B) discloses an anti-interference scheme based on a cross-interference compensation algorithm, but this scheme uses a combination of similar electrochemical sensors and compensates for interference through mathematical formulas rather than utilizing response speed differences to identify interference. Yantai Chuangwei (CN112129893B) discloses an online calibration method for CO sensors, but it relies on a big data platform and neural networks, and is a homogeneous redundancy scheme, lacking interference identification functionality.

[0005] There has long been a technological bias in this field: that MOS sensors are susceptible to interference and should be avoided when designing high-precision detectors. This has, in turn, limited the approach of using combinations of different types of sensors to solve problems. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to balance the detection accuracy and long-term reliability of gas detectors, while effectively suppressing false alarms caused by environmental interference gases, and realizing online diagnosis of sensor faults.

[0007] To address the aforementioned technical problems, this invention provides a control method for a gas detector, the gas detector comprising an electrochemical sensor and a metal oxide semiconductor sensor for detecting the same target gas, the control method comprising: The output signal of the electrochemical sensor and the output signal of the metal oxide semiconductor sensor are acquired.

[0008] The correlation coefficient between the two output signals is calculated within a preset sliding time window. When the correlation coefficient is lower than a preset threshold and this state continues for more than a preset fault confirmation time, a sensor fault is determined, and a fault alarm signal is output. The delay judgment condition is set to avoid false judgments caused by short-term fluctuations in the correlation coefficient due to factors such as instantaneous airflow disturbances.

[0009] When no sensor malfunction is determined, the signal change rate of both sensors is calculated. If the signal change rate of the metal oxide semiconductor sensor exceeds a preset fast threshold and the signal change rate of the electrochemical sensor is below a preset slow threshold, interference is identified and the alarm output is suppressed. This judgment utilizes the inherent difference in response speed between the two sensors: the MOS sensor responds quickly to interfering gases such as ethanol, while the electrochemical sensor responds slowly, thus identifying interference events.

[0010] When the output signals of both the electrochemical sensor and the metal oxide semiconductor sensor exceed a preset alarm threshold, a real gas leak is detected, and an alarm is triggered. In the event of a real leak, both sensors respond to the target gas, and the signal trends are consistent.

[0011] In the above method, the fault diagnosis step (correlation coefficient judgment) is executed before the interference identification step (rate of change judgment) to avoid logical conflicts that may be caused by abnormal rate of change characteristics of the two signals when the sensor fails.

[0012] Furthermore, when the electrochemical sensor is determined to be faulty, the alarm threshold of the metal oxide semiconductor sensor is automatically raised to a preset degradation mode threshold, and the output of the metal oxide semiconductor sensor is used as the main detection basis to ensure that the detector can still maintain basic detection functions after the electrochemical sensor fails.

[0013] Furthermore, when interference is detected and alarm output is suppressed, interference must be detected and alarm output suppression is executed only if the signal change rate of the metal oxide semiconductor sensor exceeds a preset fast threshold and the signal change rate of the electrochemical sensor is below a preset slow threshold for more than a preset interference confirmation time. Setting an interference confirmation time can avoid frequent interference detection and alarm suppression switching caused by instantaneous signal fluctuations.

[0014] Furthermore, the target gas is a combustible gas or toxic gas that can be detected by both the electrochemical sensor and the metal oxide semiconductor sensor.

[0015] Preferably, the target gas is carbon monoxide and / or hydrogen.

[0016] The present invention also provides a gas detector, comprising a housing, at least one gas detection unit, and a processor. The gas detection unit is used to detect a target gas and includes a first sensor based on an electrochemical detection principle and a second sensor based on a metal-oxide-semiconductor (MODS) detection principle. The processor is electrically connected to both the first and second sensors and is configured to execute the aforementioned control method.

[0017] In summary, the present invention has at least one of the following beneficial technical effects: By using a heterogeneous redundancy configuration of electrochemical and MOS sensors, the high precision of electrochemical sensors and the long lifespan of MOS sensors are combined, thus extending the effective lifespan of the detector.

[0018] By taking advantage of the inherent difference in response speed between the two types of sensors, the MOS sensor responds quickly to interfering gases while the electrochemical sensor responds slowly, thus achieving accurate identification and alarm suppression of interfering gases and reducing the false alarm rate.

[0019] By leveraging the consistent response trends of the two sensors to the target gas but inconsistent response trends to the interfering gas, online diagnosis of sensor faults is achieved through correlation coefficients, without interrupting monitoring.

[0020] After the electrochemical sensor fails, it can automatically switch to degrade mode to maintain basic detection function with the MOS sensor, thereby improving the system's reliability and fault tolerance.

[0021] This invention overcomes the technical bias in the field of avoiding the use of MOS sensors, and realizes the transformation of technical defects into technical advantages. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the structure of the gas detector in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram illustrating the exploded structure of a gas detector in an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the explosion structure of the dual gas detector in Embodiment 3 of the present invention.

[0025] Figure 4 This is a flowchart illustrating the control method of the present invention.

[0026] Explanation of reference numerals in the attached drawings: 1. Housing; 2. Gas detection unit; 21. First sensor; 22. Second sensor; 3. Processor. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be regarded as limiting the scope of protection of the present invention.

[0028] Example 1: Gas Detector Structure like Figure 1 and Figure 2 As shown, the gas detector includes a housing 1, and a gas detection unit 2 and a processor 3 are provided inside the housing 1.

[0029] Gas detection unit 2 is used to detect a target gas. This embodiment uses carbon monoxide (CO) detection as an example. Gas detection unit 2 includes a first sensor 21 and a second sensor 22. The first sensor 21 is an electrochemical CO sensor, which has high accuracy and high selectivity. The second sensor 22 is a metal-oxide-semiconductor (MOS) CO sensor, which features fast response and long lifespan.

[0030] The output signals from the two sensors are sent to processor 3 after passing through a signal conditioning circuit (including amplification, filtering, and analog-to-digital conversion circuits). Processor 3 is a microcontroller configured to execute the control method described in Example 2.

[0031] Example 2: Control Method like Figure 2 As shown, processor 3 performs the following steps: S1: Acquire signals. The output signals of the first sensor 21 and the second sensor 22 are acquired at a period of 1 second. In other embodiments, the sampling period can be set according to actual needs, such as 0.5 seconds or 2 seconds.

[0032] S2: Fault Diagnosis. Within a 60-second sliding time window, the two output sequences are stored, and the correlation coefficient is calculated. Experimental verification shows that, under normal pairing, the correlation coefficients of the two output signals from the electrochemical CO sensor and the MOS CO sensor are both above 0.9 within a concentration range of 0-200 ppm. When the sensitivity of the electrochemical sensor decreases by half, the correlation coefficient drops below 0.5. Based on this, the correlation coefficient threshold is set to 0.7. If the correlation coefficient remains below 0.7 for more than 300 seconds, a sensor fault is determined, and a fault alarm signal is output. The 300-second delay is set to avoid misjudgments caused by momentary fluctuations in the correlation coefficient due to instantaneous airflow disturbances.

[0033] It should be noted that the correlation coefficient threshold of 0.7 mentioned above was determined based on experimental data from the CO sensor. For other target gases such as H2, the corresponding threshold can be set according to the actual sensor pairing calibration results. The setting of the correlation coefficient threshold follows these principles: within the full range of normal sensor operation, the correlation coefficient between the two signals should be higher than this threshold; when the performance of either sensor deteriorates significantly, the correlation coefficient should be lower than this threshold.

[0034] S3: Interference Identification. Without determining sensor malfunction, calculate the signal change rate of both sensors. In this embodiment, the signal change rate is expressed as the amount of signal change per unit time (1 second) (ppm / s). In an ethanol vapor pulse experiment: facing 50ppm ethanol interference, the peak change rate of the MOS sensor exceeded 8ppm / s, while the change rate of the electrochemical sensor remained below 0.3ppm / s. In a real CO leak (concentration change rate of approximately 2ppm / s), the change rates of both sensors exceeded 1ppm / s. Based on this, a fast threshold of 5ppm / s and a slow threshold of 0.5ppm / s are set. When the change rate of the MOS sensor exceeds 5ppm / s and the change rate of the electrochemical sensor is below 0.5ppm / s, and this state persists for more than 3 seconds, it is determined to be interference. At this time, the processor suppresses the alarm output, i.e., temporarily freezes the alarm signal, and does not trigger an audible or visual alarm, but data acquisition and recording continue normally.

[0035] It should be noted that the aforementioned rapid threshold of 5 ppm / s and slow threshold of 0.5 ppm / s are based on data obtained from the CO sensor under specific experimental conditions. For other target gases such as H2 or different sensor models, the corresponding thresholds can be set according to the actual calibration results. The basic principle for threshold setting is: under normal leakage, the rate of change of both sensors should be higher than the slow threshold and not lower than half of the rapid threshold; when the interfering gas appears alone, only the rate of change of the MOS sensor should be significantly higher than the rapid threshold, while the rate of change of the electrochemical sensor should be lower than the slow threshold.

[0036] If the interference persists for more than 120 seconds, the processor will reassess: if the electrochemical sensor signal also starts to rise, it may be an early stage of a real leak, and the processor will automatically switch to a conservative monitoring mode (i.e., lower the alarm threshold or shorten the alarm confirmation time).

[0037] S4: Real Leakage Detection. When the output signals of the first sensor 21 and the second sensor 22 both exceed the preset alarm threshold (in this embodiment, the CO alarm threshold is set to 50ppm), it is determined to be a real gas leak, triggering an audible and visual alarm.

[0038] S5: Degradation Mode. During normal operation, the output of the first sensor 21 (electrochemical sensor) is used as the primary basis for concentration detection. When the first sensor 21 is determined to be faulty, the processor automatically raises the alarm threshold of the second sensor 22 (MOS sensor) from 50ppm to 80ppm, and uses the output of the second sensor 22 as the primary detection basis to ensure that the detector can continue to operate after the electrochemical sensor fails. After replacing the sensor and confirming that the two signals have regained high correlation (correlation coefficient greater than 0.7), it automatically switches back to normal operation mode.

[0039] Example 3: Dual Gas Detector Applying the above solution to both CO and H2 target gases simultaneously constitutes a preferred embodiment of the present invention—a dual-gas detector. This dual-gas detector is particularly suitable for early warning scenarios of lithium battery thermal runaway in energy storage containers, because lithium battery thermal runaway releases both CO and H2 characteristic gases simultaneously in the early stages.

[0040] like Figure 3 As shown, two gas detection units 2 are installed inside the housing 1, used to detect CO and H2 respectively. Each detection unit includes an electrochemical sensor (corresponding to CO and H2 respectively) and a MOS sensor. The processor 3 independently runs the fault diagnosis and interference identification logic described in Example 2 for each of the two detection units. When either detection unit determines that there is a real leak, it triggers an alarm signal for the corresponding gas.

[0041] In this embodiment, the electrochemical sensor for the CO channel is City Technology's 3CO-F, and the MOS sensor uses a CO-sensitive element made of a specific MOS material; the electrochemical sensor for the H2 channel is City Technology's 3H2, and the MOS sensor uses a MOS material sensitive to H2. Actual testing in an energy storage container environment (temperature -20°C to 55°C, relative humidity 10% to 95%) showed that this dual-gas detector can effectively distinguish between interference signals caused by electrolyte evaporation (mainly alcohols and esters) and CO / H2 leakage signals generated by lithium battery thermal runaway, reducing the false alarm rate by approximately 85% compared to a single-sensor solution.

[0042] Example 4: Verification Experiment of Threshold Setting To further illustrate the basis and scope of application of the correlation coefficient threshold and the rate of change threshold in this invention, this embodiment provides verification experimental data.

[0043] Experimental conditions: temperature 25℃±2℃, relative humidity 50%±5%.

[0044] (1) Correlation coefficient threshold verification: Ten pairs of electrochemical CO sensors were paired with MOS CO sensors, and gradient tests were conducted within the CO concentration range of 0-200 ppm. The results showed that under normal sensor conditions, the mean correlation coefficient of the ten pairs was 0.95, the standard deviation was 0.03, and the minimum value was 0.91. After the electrochemical sensor was accelerated to 500 hours in a high temperature and high humidity environment (60℃, 95%RH), its sensitivity decreased to 50% of the initial value, and the correlation coefficient dropped to the range of 0.42-0.55. Therefore, setting the correlation coefficient threshold to 0.7 can reliably distinguish between normal and fault states, and also reserves sufficient redundancy for individual differences between different sensor pairs.

[0045] (2) Verification of the rate of change threshold: Ten identical pairs of sensors were used to test two scenarios: CO leakage (concentration change rate of approximately 2 ppm / s) and ethanol interference (ethanol vapor pulses with a concentration change rate of approximately 3 ppm / s). The results showed that the ratio of the rates of change between the two sensors (MOS / EC) was 0.8-1.2 during CO leakage and 15-30 during ethanol interference. Based on this, setting the fast threshold to 5 ppm / s and the slow threshold to 0.5 ppm / s can ensure reliable differentiation between the two scenarios, and this differentiation threshold remains effective under different temperature and humidity conditions (-20℃ to 55℃, 10%-95%RH).

[0046] It should be noted that the above embodiments use CO and H2 as examples to illustrate the present invention. However, those skilled in the art should understand that the core of the present invention lies in utilizing the correlation and difference in response speed between electrochemical sensors and MOS sensors to the same target gas to achieve fault diagnosis and interference identification. The above control method is applicable as long as the target gas can be detected simultaneously by both electrochemical and MOS sensors, and is not limited to CO and H2. For example, the solution of the present invention can be implemented for gases such as H2S, NO2, SO2, and CH4, which can be detected simultaneously by both types of sensors, and the corresponding technical effects can be achieved.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a gas detector, characterized in that, The gas detector includes an electrochemical sensor and a metal oxide semiconductor sensor for detecting the same target gas, and the control method includes: Acquire the output signal of the electrochemical sensor and the output signal of the metal oxide semiconductor sensor; The correlation coefficient of the two output signals is calculated within a preset sliding time window. When the correlation coefficient is lower than a preset threshold and the state continues for more than a preset fault confirmation time, the sensor is determined to be faulty and a fault alarm signal is output. When no sensor fault is determined, the signal change rate of the two sensors is calculated. When the signal change rate of the metal oxide semiconductor sensor exceeds a preset fast threshold and the signal change rate of the electrochemical sensor is lower than a preset slow threshold, it is determined to be interference and the alarm output is suppressed. When the output signals of both sensors exceed the preset alarm threshold, it is determined to be a real gas leak and an alarm is triggered.

2. The control method according to claim 1, characterized in that: When the electrochemical sensor is determined to be faulty, the alarm threshold of the metal oxide semiconductor sensor is automatically raised to the preset degradation mode threshold, and the output of the metal oxide semiconductor sensor is used as the main detection basis.

3. The control method according to claim 1, characterized in that: To determine if interference is being detected and to suppress alarm output, the state of the signal change rate of the metal oxide semiconductor sensor exceeding a preset fast threshold and the signal change rate of the electrochemical sensor being below a preset slow threshold must continue for more than a preset interference confirmation time before interference is detected and the alarm output is suppressed.

4. The control method according to claim 1, characterized in that: The target gas is a combustible or toxic gas that can be detected by both the electrochemical sensor and the metal oxide semiconductor sensor.

5. The control method according to claim 1, characterized in that: The target gas is carbon monoxide and / or hydrogen.

6. A gas detector, characterized in that: The device includes a housing, at least one gas detection unit, and a processor. The gas detection unit is used to detect a target gas and includes a first sensor based on an electrochemical detection principle and a second sensor based on a metal oxide semiconductor detection principle. The processor is electrically connected to the first sensor and the second sensor, respectively, and is configured to perform the control method according to any one of claims 1 to 5.

7. The gas detector according to claim 6, characterized in that: The gas detection unit consists of two units, used to detect carbon monoxide and hydrogen respectively.

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