An anti-interference method and device for a dual-wavelength laser detector for detecting pyrolysis particles in electrical fires.

Abstract

This invention discloses an anti-interference method and device for detecting pyrolysis particles in electrical fires using dual-wavelength lasers. The method includes: alternately emitting laser beams from short-wavelength and long-wavelength lasers into a detection chamber to acquire the dual-wavelength scattering signal intensities s1 and s2 of pyrolysis particles; calculating the total particle concentration C based on a pre-calibrated multivariate linear function; calculating the ratio R of the dual-wavelength scattering signal intensities; and combining C and R to intelligently distinguish between pyrolysis particles and environmental interference particles, and to perform fire status classification and early warning. This invention uses a time-division multiplexing method to alternately emit lasers into the detection chamber, utilizing the difference in scattering sensitivity of short-wavelength lasers to small particles and long-wavelength lasers to large particles to effectively compensate for measurement errors caused by changes in particle size distribution. While ensuring high sensitivity, it significantly improves anti-interference capability and measurement stability, achieving accurate quantitative monitoring of pyrolysis particle concentration in the very early stages of electrical fires.

Description

Technical Field

[0001] This invention relates to the field of electrical fire monitoring technology, and in particular to an anti-interference method and device for a detector that uses dual-wavelength lasers to detect pyrolysis particles in electrical fires. Background Technology

[0002] Electrical fires are a major cause of various fire accidents. Cables and electrical equipment insulation materials release micron to nano-sized pyrolysis particles in the early stages of overheating and aging. Accurate detection of these particles is key to achieving early warning of electrical fires.

[0003] Currently, the field of electrical fire monitoring and pyrolysis particle detection typically uses a single-wavelength laser light source combined with simple scattered light intensity detection, or only monitors single parameters such as temperature and residual current. This makes it difficult to effectively distinguish between particles generated by the pyrolysis of cable insulation materials and non-fire-related interfering particles such as dust and water mist in the environment, resulting in a high false alarm rate under complex working conditions.

[0004] For example, Chinese Patent Publication No. CN110706444A proposes a comprehensive method for monitoring electrical fires caused by pyrolysis particles. This method uses a weighted calculation based on temperature, gas concentration, and multiple particle concentration levels (PM1.0, PM2.5, PM10) to comprehensively monitor electrical fires caused by pyrolysis particles. However, this method relies on data acquisition from multiple independent sensors and dynamic weight analysis, resulting in a complex system structure and lacking optimization for the differences in particle scattering characteristics caused by light source wavelengths.

[0005] For example, Chinese Patent Publication No. CN104459817A discloses a fire hazard detection device. Its scheme adopts a structure of dual-emitting tubes and multiple photosensitive sensors, mainly using a complex labyrinth optical path and stray light absorption structure to improve the signal-to-noise ratio. However, its scheme relies on a specific light shield and extinction trap design, and the identification of pyrolysis particles with different properties is mainly based on the ratio of scattered light intensity in spatial distribution, lacking a quantitative correction for the relationship between light source wavelength and particle concentration.

[0006] In summary, existing electrical fire pyrolysis particle detection technologies have not yet achieved a synergistic unity of high-sensitivity small particle detection, strong environmental interference resistance, simple hardware architecture, and accurate quantitative monitoring. There is a need for an interference-resistant detection method and device that is based on the difference between light source wavelength and particle scattering characteristics, distinguishes particle types from their physical nature, and has a simple and reliable algorithm, in order to solve the technical pain points of high false alarm rate and insufficient early warning capability under complex working conditions. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide an anti-interference method and device for a detector used for detecting pyrolysis particles in electrical fires using dual-wavelength lasers. This solves the problem that existing technologies cannot simultaneously achieve high-sensitivity small particle detection, strong environmental anti-interference, a simple hardware architecture, and accurate quantitative monitoring. By utilizing the differences in scattering characteristics of particles of different sizes and compositions to two different wavelengths of laser light, the invention distinguishes pyrolysis particles from environmental interference particles from a physical perspective. This simplifies the hardware structure, reduces the false alarm rate under complex operating conditions, and improves the early warning capability for electrical fires.

[0008] The objective of this invention can be achieved through the following technical solution: an anti-interference method for a detector used for detecting pyrolysis particles in electrical fires using a dual-wavelength laser, comprising:

[0009] S1: Laser beams are alternately emitted by a short-wavelength laser and a long-wavelength laser into the detection gas chamber to obtain the dual-wavelength scattering signal intensities s1 and s2 of the gas in the detection gas chamber, respectively;

[0010] S2: Calculate the total particle concentration C based on a pre-calibrated multivariable linear function;

[0011] S3: Calculate the intensity ratio R of the two-wavelength scattered signals;

[0012] S4: Combine the total particle concentration C and the ratio R to distinguish between pyrolysis particles and environmental interference particles, and conduct fire status classification and early warning.

[0013] As a further aspect of the present invention:

[0014] The center wavelength of the short-wavelength laser is preferably 450 nm;

[0015] The center wavelength of the long-wavelength laser is preferably 850 nm.

[0016] As a further embodiment of the present invention: the multivariable linear function for calculating the total particle concentration C is expressed as:

[0017] C = a0 + a1s1 + a2s2

[0018] Where s1 and s2 are the scattering signal intensities corresponding to short-wavelength and long-wavelength lasers, respectively, and a0, a1 and a2 are calibration coefficients.

[0019] As a further aspect of the present invention: the calibration coefficient calibration process of the multivariable linear function includes:

[0020] S21: Prepare standard polystyrene latex microspheres of known concentration, measure the intensity of dual-wavelength scattering signal s1 and s2 at different concentrations, and obtain datasets at different concentrations;

[0021] S22: Using datasets at different concentrations, perform multiple linear regression on the multivariate linear function using the least squares method to solve for the calibration coefficients a0, a1, and a2.

[0022] As a further aspect of the present invention: the fire status classification and early warning includes:

[0023] C≤C th When the time is right, it is considered normal;

[0024] C>C th When, calculate the average rate of change of C. s C s ≥C sth And R≥R th If the fire continues, it is considered a fire alarm, and R < R th This is then judged as interference;

[0025] C>C th At that time, C s <C sth And R≥R th If this continues, it is determined to be a pyrolysis particle warning, where R < R th This is then judged as interference;

[0026] Where C is the total particle concentration, C th C is the total particle concentration threshold. s C is the average rate of change of total particle concentration. sth R is the average rate of change threshold; R is the ratio of the intensity of the two-wavelength scattered signals. th This is the baseline threshold for the intensity ratio.

[0027] An anti-interference device for a dual-wavelength laser detector for detecting pyrolysis particles in electrical fires, applied to the above-mentioned method, comprising:

[0028] A detection chamber is placed between the upper and lower covers of the detector, and the detection chamber has an air inlet and an air outlet.

[0029] A suction fan, placed between the upper and lower covers of the detector, is used to force the gas in the environment to be tested into the detection chamber.

[0030] The photoelectric receiving component, placed in the detection chamber, includes a long-wavelength laser emitter, a short-wavelength laser emitter, and a photoelectric receiver, used to perform dual-wavelength laser detection on the gas entering the detection chamber and acquire the scattered electrical signal;

[0031] The processing and control unit is used to control the photoelectric receiving component to perform dual-wavelength laser detection on the gas entering the detection chamber, and to perform calculation, processing and analysis on the received scattered electrical signals.

[0032] As a further embodiment of the present invention, the main receiving direction of the photoelectric receiver forms an angle of 120°-170° with the optical axis of the dual-wavelength laser, preferably 160°.

[0033] As a further embodiment of the present invention, the photodetector is provided with a cutoff filter in the light source receiving direction, and the passband range of the filter matches the wavelength range of the dual-wavelength laser.

[0034] As a further embodiment of the present invention, the inner wall of the detection chamber is made of a corrosion-resistant, high-absorbency black material.

[0035] As a further embodiment of the present invention, the processing and control unit includes a laser driving circuit, a preamplifier circuit, an analog-to-digital converter circuit, and a microprocessor, wherein:

[0036] The laser driving circuit is connected to a short-wavelength laser and a long-wavelength laser respectively, and is controlled by a microprocessor to output a constant current driving signal to realize time-division triggering of the dual-wavelength laser;

[0037] The preamplifier circuit is connected to the output terminal of the photodetector and is used to amplify and filter the weak scattered electrical signal through transimpedance.

[0038] The analog-to-digital converter circuit converts the processed analog signal into a digital signal for the microprocessor to read.

[0039] The beneficial effects of this invention are:

[0040] 1. The method proposed in this invention employs an emission module containing two independent semiconductor lasers, one with a short wavelength and the other with a long wavelength. Lasers are alternately emitted into the detection chamber in a time-division manner, and a quantitative functional relationship between the total particle concentration and the dual-wavelength scattering signal is established. Through alternating dual-wavelength emission and signal processing, the method effectively compensates for measurement errors caused by changes in particle size distribution by utilizing the difference in scattering sensitivity of the short-wavelength laser to small particles and the long-wavelength laser to large particles. Compared to existing technologies that rely solely on multi-sensor data fusion or single-wavelength scattering detection, this method significantly improves anti-interference capability and measurement stability while maintaining high sensitivity, achieving accurate quantitative monitoring of the concentration of pyrolysis particles in the very early stages of electrical fires.

[0041] 2. This invention alternates between short-wavelength (e.g., 450nm) and long-wavelength (e.g., 850nm) laser emission and calculates the total particle concentration C using a pre-calibrated multivariable linear function (C=a0+a1s1+a2s2). The short-wavelength laser is more sensitive to the scattering of micron / nano-sized carbonaceous pyrolysis particles generated in the early stages of cable overheating, while the quantitative model established by combining the two wavelengths effectively compensates for measurement errors caused by changes in particle size distribution. Compared to traditional single-wavelength or single-parameter detection methods, this method can more accurately reflect the comprehensive mass concentration of particulate matter per unit volume, providing stable and reliable basic data for fire identification and significantly improving the detection sensitivity for very early signs of electrical fires. It achieves precise quantitative monitoring and high-sensitivity detection of pyrolysis particles in electrical fires.

[0042] 3. In actual early warning judgment, this invention intelligently distinguishes between fire pyrolysis particles and environmental interference particles. The system combines the total particle concentration C and the ratio R for comprehensive judgment: only when C exceeds the threshold and R remains at a high level is it judged as a fire alarm or pyrolysis particle warning; if C exceeds the limit but the R value is low, it is judged as interference. This discrimination method, which starts from the essential physical characteristics of particle scattering, can effectively eliminate interference from non-fire particles, thereby significantly reducing the probability of false alarms in complex operating conditions, possessing strong environmental anti-interference capabilities, and effectively reducing the false alarm rate.

[0043] 4. The method of this invention employs a graded early warning mechanism, which can provide early warning for slowly developing insulation overheating hazards as well as emergency alarms for rapidly developing fire hazards. Simultaneously, it can filter out simple interference, thereby comprehensively improving the accuracy, reliability, and early response capability of the electrical fire monitoring system. It provides intelligent graded early warning of fire conditions, enhancing the reliability of detection and early response capabilities. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the principle of the method of the present invention;

[0045] Figure 2 This is a flowchart of the fire status classification and early warning process of the present invention;

[0046] Figure 3 This is a schematic diagram of the appearance of the device of the present invention;

[0047] Figure 4 This is a schematic diagram of the internal assembly of the device of the present invention;

[0048] Figure 5 This is an exploded view of the components of the device of the present invention;

[0049] Figure 6 This is a schematic diagram of the area division of the enclosure according to the present invention;

[0050] Figure 7This is a schematic diagram of the installation of the photoelectric receiving component of the present invention;

[0051] Figure 8 This is a schematic diagram showing the location of the photoelectric receiver of the present invention.

[0052] 110. Top cover; 120. Bottom cover; 121. Detector air inlet;

[0053] 210. Detection chamber; 220. Enclosure; 230. Upper shell of the chamber; 240. Bottom shell of the chamber; 250. Air inlet; 260. Air outlet;

[0054] 300. Optoelectronic receiving component; 310. Long-wavelength laser emitter; 320. Short-wavelength laser emitter; 330. Optoelectronic receiver; 340. Mounting substrate; 350. Gas chamber partition; 360. Cut-off filter;

[0055] 400. Exhaust fan;

[0056] 500. PCB control board;

[0057] 600. Parts and Accessories Area. Detailed Implementation

[0058] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0059] Example 1:

[0060] This embodiment presents an anti-interference method for a dual-wavelength laser detector used to detect pyrolysis particles in electrical fires, such as... Figure 1 As shown, the steps include:

[0061] S1: Laser beams are alternately emitted by a short-wavelength laser and a long-wavelength laser into the detection gas chamber to obtain the dual-wavelength scattering signal intensities s1 and s2 of the gas in the detection gas chamber, respectively.

[0062] The processing and control unit controls the short-wavelength laser and the long-wavelength laser to alternately emit laser beams, and collects the scattered light signals of pyrolysis particles in the detection chamber at the two wavelengths respectively. The alternating emission ensures that the signal acquisition of the two wavelengths does not interfere with each other.

[0063] The processing and control unit controls the emission of the short-wavelength laser and collects the net scattered light intensity s1 (baseline removed); then controls the emission of the long-wavelength laser and collects the net scattered light intensity s2 (baseline removed). In addition, s1 and s2 can also be calculated using the corresponding channel voltage value or digital quantity.

[0064] Preferably, the center wavelength of the short-wavelength laser is 450 nm; the center wavelength of the long-wavelength laser is 850 nm.

[0065] The short wavelength of 450nm light exhibits stronger scattering efficiency for micron- and submicron-sized particles. This matches the size of nanoscale carbonaceous pyrolysis particles generated in the early stages of electrical equipment overheating, ensuring high sensitivity detection of early fire signs. Meanwhile, the long wavelength of 850nm light shows relatively gradual changes in scattering efficiency for larger particles (such as some dust particles), is less affected by small-sized interfering particles in the environment (such as some water mist), and provides a more stable contrast signal. Furthermore, the sufficient wavelength separation between 450nm and 850nm results in significant differences in the scattering responses of pyrolysis particles (mainly small-sized carbonaceous particles) and common interfering particles (such as dust and water mist) to these two wavelengths. Both 450nm and 850nm lasers are mature, cost-effective, and compact commercial devices, easily integrated into detection devices.

[0066] Therefore, the preferred choice of the dual-wavelength combination of 450nm and 850nm is a balance between maximizing the optical recognition of pyrolysis particles and interfering particles, ensuring the detection sensitivity of small-diameter fire particles, and meeting the requirements of productization in terms of cost, size, and reliability.

[0067] S2: Calculate the total particle concentration C based on the pre-calibrated multivariate linear function.

[0068] The total particle concentration C is a function of s1 and s2, expressed by the formula:

[0069] C = a0 + a1s1 + a2s2

[0070] The total particle concentration C is expressed in μg / m³. 3 ; s1 and s2 are the scattering signal intensities corresponding to short-wavelength and long-wavelength lasers, respectively; a0, a1 and a2 are calibration coefficients, obtained by calibrating the standard particle concentration under different environments.

[0071] The multivariable linear function is a linear function. The method of calculating the total particle concentration C by using this linear function can reduce the computational load on the processing and control unit while ensuring calculation accuracy, thus meeting the low-cost and low-power operation requirements of the detector.

[0072] The total particle concentration C reflects the comprehensive mass concentration of all scattering particles in a unit volume of air. The total particle concentration calculation result obtained by collecting net scattering signals separately by dual-wavelength lasers can accurately reflect the overall distribution of particles in the monitoring environment. It retains the high sensitivity response of laser detection to particles, and eliminates the deviation of single-wavelength detection which is easily affected by non-fire particles such as water vapor and dust through parameter calibration. This provides accurate basic data support for subsequent abnormal identification of electrical fires.

[0073] S3: Calculate the ratio R of the intensity of the two-wavelength scattered signals.

[0074] After obtaining the scattered signal intensities s1 and s2, the processing and control unit calculates the ratio R of the net scattered light intensities of the two wavelengths, which is the ratio of s1 to s2, and is expressed as:

[0075] R=s1 / s2

[0076] The ratio R of the intensity of the two-wavelength scattering signal can characterize the particle size and optical properties, and is used to distinguish particle types. Particles with different properties have different scattering responses to short-wavelength (e.g., 450 nm) and long-wavelength (e.g., 850 nm) lasers.

[0077] Pyrolysis particles: The carbonaceous pyrolysis particles generated in the early stage of overheating of electrical equipment have a small particle size and are more sensitive to the scattering of short-wavelength light, resulting in a relatively strong short-wavelength scattering signal s1, thus making the ratio R at a high level.

[0078] Environmental interference particles, such as dust and water mist, have a wide particle size distribution or different optical properties. Their response to dual-wavelength light is relatively balanced, so their R value tends to be stable and usually low.

[0079] The ratio R can be used as one of the important criteria for distinguishing between dangerous early pyrolysis particles and common environmental disturbance particles.

[0080] S4: Combine the total particle concentration C and the ratio R to distinguish between pyrolysis particles and environmental interference particles, and conduct fire status classification and early warning.

[0081] By alternately emitting laser beams from short-wavelength and long-wavelength lasers into the detection chamber, the scattering signal intensities s1 and s2 of the particulate matter under test are obtained after filtering and noise reduction at the two wavelengths.

[0082] The total particle concentration C is calculated based on the pre-calibrated multivariable linear function relationship C=a0+a1s1+a2s2. This C value reflects the comprehensive concentration level of particulate matter per unit volume and serves as a basic indicator for judging the intensity of pyrolysis activity. At the same time, the ratio of the dual-wavelength net scattered signal R=s1 / s2 is calculated. This ratio R reflects the average particle size characteristics and optical response characteristics of the particulate matter group.

[0083] Since the carbonaceous pyrolysis particles released by electrical equipment insulation materials in the early stage of pyrolysis are mostly small-sized, irregularly structured carbon-containing particles, they are more sensitive to the scattering of short-wavelength light, exhibiting a relatively strong s1, resulting in a high ratio R. In contrast, common environmental interference particles such as dust and water mist have a wider particle size distribution or a higher refractive index, and their response to dual-wavelength light is relatively balanced, with R values ​​tending to be stable and usually lower than the response ratio of the pyrolysis particle group.

[0084] By combining the total particle concentration C and the net scattered signal ratio R, carbonaceous pyrolysis particles generated by electrical equipment pyrolysis and interfering particles in the environment can be effectively distinguished. When the total particle concentration C exceeds the preset alarm threshold, it is further determined whether the ratio R is within the characteristic range corresponding to pyrolysis particles. If R also meets the judgment condition, it is confirmed that a valid pyrolysis particle signal has been detected, and an electrical overheating warning is output. If only the concentration C exceeds the limit but R does not fall into the characteristic range, it is determined to be a signal introduced by environmental interference, and no warning is triggered. This significantly reduces the probability of false alarms caused by environmental interference and improves the accuracy and reliability of early detection of electrical fires.

[0085] Example 2:

[0086] This embodiment optimizes the calibration process of the calibration coefficients a0, a1, and a2 of the multivariable linear function of the total particle concentration C, based on Embodiment 1. Specifically, it includes:

[0087] S21: Prepare standard polystyrene latex microspheres of known concentration and measure the intensity of dual-wavelength scattering signals s1 and s2 at different concentrations.

[0088] The purpose of coefficient calibration is to establish a quantitative relationship between the scattering signal intensities s1 and s2 and standard particles of known concentration.

[0089] The calibrated particles use a known concentration C ture The standard polystyrene latex microspheres cover the typical particle size range of the expected pyrolysis particles and common interfering particles (e.g., particle sizes of 0.1 μm, 0.3 μm, 0.5 μm, 1.0 μm, etc.), ensuring the adaptability of the calibration model to particles with different particle size distributions.

[0090] Configure a series of known concentrations (C true The standard calibration particle aerosol covers the full range of detector design, from near the minimum detection limit to saturation concentration, and allows for the setting of 8-10 uniform concentration gradients.

[0091] S22: Using datasets at different concentrations, perform multiple linear regression on the multivariate linear function using the least squares method to solve for the calibration coefficients a0, a1, and a2.

[0092] Place the detector in a calibration environment and continuously acquire data for multiple periods for each concentration gradient, for example:

[0093] A known concentration gradient C is introduced. true(i) After the standard particles have stabilized at a certain concentration, the detector is controlled to collect the dual-wavelength net scattering signal s. 1(i) s 2(i) .

[0094] Repeat the above process for each concentration gradient point to obtain N sets (N is the number of concentration gradients) of calibration datasets {s 1(i) s 2(i) and C true(i)}, where i = 1, 2, ..., N.

[0095] Using the multivariate linear function C = a0 + a1s1 + a2s2, the N sets of calibration datasets {s 1(i) s 2(i) and C true(i) Substitute the values ​​into the function to form N equations.

[0096] Using the least squares method for multiple linear regression, we solve for the coefficients a0, a1, and a2. Essentially, we seek a set of coefficients that minimizes the sum of squared residuals between the predicted and actual values.

[0097] The calibration coefficients a0, a1, and a2 are obtained using the above method, optimized, and then stored in the non-volatile memory unit of the detector to complete the calibration process.

[0098] In actual detection, after the detector acquires the intensity of the dual-wavelength scattered signals s1 and s2 in the current environment, these signals can be substituted into a multivariate linear function with pre-calibrated coefficients to directly calculate the true concentration of smoke particles in the current environment, thus completing an accurate measurement. By combining dual-wavelength signal intensity with multivariate linear regression calibration, the influence of interfering particles with different particle size distributions on smoke concentration measurement can be effectively offset, enabling accurate detection of early-stage smoke in electrical fires, improving the detector's anti-interference capability, and reducing the probability of false alarms.

[0099] Example 3:

[0100] This embodiment optimizes the fire status classification and early warning process based on Embodiment 1. Based on dual-wavelength laser detection, it achieves accurate identification of pyrolysis particles, environmental interference particles, and potential fire conditions generated during the initial stage of electrical equipment overheating or insulation material pyrolysis by collaboratively analyzing the ratio R of the total particle concentration C and the dual-wavelength scattering signal. Specifically, as follows... Figure 2 As shown, it includes:

[0101] By alternately emitting laser beams from short-wavelength and long-wavelength lasers into the detection chamber, the scattering signal intensities s1 and s2 of the particulate matter under test are obtained after filtering and noise reduction at the two wavelengths.

[0102] The total particle concentration C is calculated based on the pre-calibrated multivariable function relationship C=a0+a1s1+a2s2. This C value reflects the comprehensive concentration level of particulate matter per unit volume and serves as a basic indicator for judging the intensity of pyrolysis activity.

[0103] Simultaneously, the intensity ratio of the dual-wavelength scattered signals, R = s1 / s2, is calculated. This ratio R reflects the average particle size characteristics and optical response features of the particle group. Since the carbonaceous pyrolysis particles released by the insulating materials of electrical equipment in the early stage of pyrolysis are mostly small-sized, irregularly structured carbon-containing particles, they are more sensitive to the scattering of short-wavelength light, resulting in a relatively strong s1 and a higher ratio R. In contrast, common environmental interference particles such as dust and water mist have a wider particle size distribution or higher refractive index, and their response to dual-wavelength light is relatively balanced. Their R values ​​tend to be stable and are usually lower than the response ratio of the pyrolysis particle group.

[0104] During the intelligent discrimination process, when the total particle concentration C is detected to be less than or equal to the preset total particle concentration threshold C th At that time, the test result was normal;

[0105] When C>C th When the concentration C>C th The average rate of change of data C in the 5 seconds before time C s If C s Not lower than the preset average rate of change threshold C sth And the ratio R is consistently not lower than the preset benchmark threshold R th When R < R, it is determined to be a fire. th This is then judged as interference;

[0106] When C>C th And C s <C sth At this time, R≥R th If the phenomenon persists, it is determined that there are typical electrical fire pyrolysis particle characteristics, which is confirmed as an early sign of overheating of electrical equipment or pyrolysis of insulation layer, and a pyrolysis particle warning is issued; otherwise, it is determined to be interference.

[0107] Based on the above, the total particle concentration C and the average rate of change of total particle concentration C s By combining the criterion with the ratio R, this invention achieves specific identification of pyrolysis particles, effective elimination of interfering particles, and graded early warning of fire status, significantly improving the accuracy, reliability, and early response capability of electrical fire detection.

[0108] Example 4:

[0109] This embodiment discloses an anti-interference device for a dual-wavelength laser detector used to detect pyrolysis particles in electrical fires, used to implement the anti-interference detection methods in embodiments 1 to 3, such as... Figures 3 to 8 As shown, the device includes a detection chamber 210, a suction fan 400, a photoelectric receiving component 300, and a processing and control unit, etc.

[0110] Specifically, such as Figure 3 The device shown has an upper cover 110 and a lower cover 120 on the outside. The upper cover 110 is fixed to the mounting surface to form a stable mounting structure. The lower cover 120 is connected to the upper cover 110 by screwing or snapping. The lower cover 120 has multiple detection air inlets 121. The detection air chamber 210 is fixed below the upper cover 110 and is located in the space formed by the upper cover 110 and the lower cover 120.

[0111] like Figure 4 and Figure 6 As shown, it also includes a enclosure 220, an upper chamber shell 230 and a lower chamber shell 240. The upper chamber shell 230 is fixed on the upper cover 110. The enclosure 220 is divided into a detection chamber area, a fan area and an accessory area 600.

[0112] The detection chamber 210 is composed of the enclosure 220 of the detection chamber area, the upper shell 230 of the chamber, and the bottom shell 240 of the chamber, forming a relatively closed area. The detection chamber 210 has an air inlet 250 and an air outlet 260. The gas to be detected enters the detection chamber 210 only through the air inlet 250, reducing the interference of external environmental airflow fluctuations on the laser detection path, and is discharged from the air outlet 260, which is far away from the suction fan 400.

[0113] The suction fan 400 is fixed in the fan area. When running, it can actively draw in outside air through the air inlet 250 and send it into the detection gas chamber 210, ensuring that there is always fresh gas to be tested flowing through the gas chamber and improving the detection response speed.

[0114] The photoelectric receiving component 300 is installed inside the detection gas chamber 210, such as... Figure 7 As shown, the photoelectric receiving component 300 includes a long-wavelength laser emitter 310, a short-wavelength laser emitter 320, and a photoelectric receiver 330, which together perform dual-wavelength laser detection on the gas entering the detection chamber 210 to obtain the scattered electrical signal.

[0115] Specifically, such as Figure 5As shown, the long-wavelength laser emitter 310, the short-wavelength laser emitter 320, and the photoelectric receiver 330 are respectively fixed on the mounting base plate 340. The working ends of the long-wavelength laser emitter 310, the short-wavelength laser emitter 320, and the photoelectric receiver 330 pass through the gas chamber partition 350 into the detection gas chamber 210. The gas chamber partition 350 completely separates the wiring terminals of the photoelectric components of the emitter and receiver from the detection gas chamber 210, ensuring the airtightness of the detection gas chamber 210 and preventing the photoelectric components from affecting the detection accuracy during application. The mounting base plate 340 is fixed inside the upper shell 230 of the gas chamber, which facilitates the pre-assembly and calibration of each photoelectric component before overall assembly, and facilitates later maintenance and replacement.

[0116] Preferably, such as Figure 8 As shown, the photoelectric receiver 330 is positioned at an angle of 120°-170° (preferably 160°) between its main receiving direction and the optical axis of the dual lasers, receiving the scattered light signal generated by the air sample in the air chamber on the laser.

[0117] Choosing a wide angle of 120°-170° effectively avoids direct light paths, significantly reducing background noise. Within this angle range, the difference in scattering intensity ratios of short-wavelength (450nm) and long-wavelength (850nm) lasers by particles of different sizes and compositions becomes more pronounced, enhancing the algorithm's ability to distinguish small-diameter pyrolysis particles from large-diameter interference particles using the R-value. Tests showed that the scattering intensity ratio difference was most significant at 160°, achieving the highest distinction between different particle types, effectively reducing false alarm rates and improving the detector's overall reliability and anti-interference capability.

[0118] The photodetector 330 is a photodiode used to convert the received optical signal into a weak electrical signal. A cutoff filter 360 is provided in front of the photodetector. The passband range of the filter matches the wavelength range of the dual-wavelength laser to filter out incoherent light interference in the ambient light and allow only the laser scattered light to pass through.

[0119] Preferably, such as Figure 6 As shown, the detector chamber is designed with a cuboid structure, which consists of a enclosure 220. The enclosure 220 has a reserved air inlet 260 and an air outlet 250. Together with the upper shell 230 and the lower shell 240 of the chamber, it effectively prevents external stray light from directly entering the receiver.

[0120] The air inlet 250 of the detection chamber is located between the laser emitter and the photoelectric receiver 330. The air inlet 250 of the detection chamber is connected to the air outlet of the suction fan 400, which forces the air sample in the environment to be tested into the detection chamber.

[0121] Furthermore, the inner wall of the detection chamber is made of a corrosion-resistant, high-absorbency black material to minimize interference from background stray light.

[0122] The suction fan 400 is fixedly installed next to the rectangular detection gas chamber 210, which can actively draw air from the area to be detected into the detection gas chamber 210 to ensure the real-time and representativeness of the gas sample in the chamber.

[0123] The processing and control unit is used to control the photoelectric receiving component 300 to perform dual-wavelength laser detection on the gas entering the detection chamber 210, and to perform calculation, processing and analysis on the received scattered electrical signals.

[0124] The processing and control unit is deployed within a PCB control board 500, which is fixed to a mounting substrate 340. The processing and control unit includes a laser drive circuit, a preamplifier circuit, an analog-to-digital converter (ADC), and a microprocessor (MCU), among other components.

[0125] The laser drive circuit connects to both the short-wavelength and long-wavelength lasers, and is controlled by the microprocessor to output a constant current drive signal, enabling time-division triggering of the dual-wavelength lasers. The preamplifier circuit connects to the output of the photodetector and amplifies and filters the weak scattered electrical signal across impedance. The analog-to-digital converter (ADC) converts the processed analog signal into a digital signal for the microprocessor to read. Based on the received digital signal, the microprocessor calculates the total particle concentration C and the ratio R, distinguishing between pyrolysis particles and environmental interference particles.

[0126] The device of this invention combines the differences in the scattering signal intensity of different fire characteristic particles and interfering particles under two wavelengths, and distinguishes between smoke particles and interfering particles such as water vapor and dust generated by real fires through a preset algorithm. Finally, it outputs accurate fire detection results, effectively reducing the probability of false alarms and improving the reliability of early detection of electrical fires.

[0127] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An anti-interference method for a detector used for detecting pyrolysis particles in electrical fires using dual-wavelength lasers, characterized in that, Including the following steps: S1: Laser beams are alternately emitted by a short-wavelength laser and a long-wavelength laser into the detection gas chamber to obtain the dual-wavelength scattering signal intensities s1 and s2 of the gas in the detection gas chamber, respectively; S2: Calculate the total particle concentration C based on a pre-calibrated multivariable linear function; S3: Calculate the intensity ratio R of the two-wavelength scattered signals; S4: Combine the total particle concentration C and the ratio R to distinguish between pyrolysis particles and environmental interference particles, and conduct fire status classification and early warning.

2. The method according to claim 1, characterized in that: The center wavelength of the short-wavelength laser is preferably 450 nm; The center wavelength of the long-wavelength laser is preferably 850 nm.

3. The method according to claim 1, characterized in that: The multivariable linear function for calculating the total particle concentration C is expressed as follows: C = a0 + a1s1 + a2s2 Where s1 and s2 are the scattering signal intensities corresponding to short-wavelength and long-wavelength lasers, respectively, and a0, a1 and a2 are calibration coefficients.

4. The method according to claim 3, characterized in that: The calibration coefficient calibration process for the multivariable linear function includes: S21: Prepare standard polystyrene latex microspheres of known concentration, measure the intensity of dual-wavelength scattering signal s1 and s2 at different concentrations, and obtain datasets at different concentrations; S22: Using datasets at different concentrations, perform multiple linear regression on the multivariate linear function using the least squares method to solve for the calibration coefficients a0, a1, and a2.

5. The method according to claim 4, characterized in that: The aforementioned fire status classification and early warning includes: C≤C th When the time is right, it is considered normal; C>C th When, calculate the average rate of change of C. s C s ≥C sth And R≥R th If the fire continues, it is considered a fire alarm, and R < R th This is then judged as interference; C>C th At that time, C s <C sth And R≥R th If this continues, it is determined to be a pyrolysis particle warning, where R < R th This is then judged as interference; Where C is the total particle concentration, C th C is the total particle concentration threshold. s C is the average rate of change of total particle concentration. sth R is the average rate of change threshold; R is the ratio of the intensity of the two-wavelength scattered signals. th This is the baseline threshold for the intensity ratio.

6. An anti-interference device for a dual-wavelength laser detector for detecting pyrolysis particles in electrical fires, characterized in that: The method applied to any one of claims 1 to 5 includes: A detection chamber is placed between the upper and lower covers of the detector, and the detection chamber has an air inlet and an air outlet. A suction fan, placed between the upper and lower covers of the detector, is used to force the gas in the environment to be tested into the detection chamber. The photoelectric receiving component, placed in the detection chamber, includes a long-wavelength laser emitter, a short-wavelength laser emitter, and a photoelectric receiver, used to perform dual-wavelength laser detection on the gas entering the detection chamber and acquire the scattered electrical signal; The processing and control unit is used to control the photoelectric receiving component to perform dual-wavelength laser detection on the gas entering the detection chamber, and to perform calculation, processing and analysis on the received scattered electrical signals.

7. The apparatus according to claim 6, characterized in that, The main receiving direction of the photoelectric receiver forms an angle of 120°-170° with the optical axis of the dual-wavelength laser, preferably 160°.

8. The apparatus according to claim 6, characterized in that, The photodetector has a cutoff filter in the light source receiving direction, and the passband range of the filter matches the wavelength range of the dual-wavelength laser.

9. The apparatus according to claim 6, characterized in that, The inner wall of the detection chamber is made of a corrosion-resistant, high-absorbency black material.

10. The apparatus according to claim 6, characterized in that, The processing and control unit includes a laser driving circuit, a preamplifier circuit, an analog-to-digital converter circuit, and a microprocessor, wherein: The laser driving circuit is connected to a short-wavelength laser and a long-wavelength laser respectively, and is controlled by a microprocessor to output a constant current driving signal to realize time-division triggering of the dual-wavelength laser; The preamplifier circuit is connected to the output terminal of the photodetector and is used to amplify and filter the weak scattered electrical signal through transimpedance. The analog-to-digital converter circuit converts the processed analog signal into a digital signal for the microprocessor to read.

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