A gas detection alarm system and method for temperature changes in an immunoassay laser

Abstract

This invention relates to the field of gas detection and alarm technology, and particularly to a gas detection and alarm system and method that is immune to changes in laser temperature. A microcontroller, by pre-setting the half-width at half-maximum (WHM) of the gas to be detected, enables simultaneous detection of multiple gases. Equipped with a digital thermoelectric cooler, the laser is immune to the effects of its own temperature, maintaining accurate wavelength and stable optical power. Simultaneously, the microcontroller incorporates a demodulation algorithm that uses Lorentz line fitting to determine the absorption peak and obtain the gas concentration, controlling the audible and visual alarms, thus ensuring the response speed and accuracy of the gas detection and alarm system.

Description

Technical Field

[0001] This invention relates to the field of gas detection and alarm technology, specifically to a gas detection and alarm system and method for temperature changes in an immune laser. Background Technology

[0002] Currently, many industrial production processes in China generate toxic and harmful gases, such as those in welding, electroplating, smelting, chemical, and petroleum industries. Different toxic and harmful gases pose different hazards, and even the same gas can have different primary hazards depending on the environment or the specific phenomena observed. Common toxic and harmful gases can be broadly categorized by their hazards as follows: corrosiveness, irritation, flammability, and explosiveness.

[0003] Therefore, in industries such as petroleum, chemical, coal mining, and metallurgy, preventing the leakage, spillage, dripping, and seepage of toxic and harmful gases is a key focus of accident prevention. Currently, laser gas detection devices require high-power precision temperature control devices to ensure that the laser beam does not change with the ambient temperature. However, the large current of the temperature control device makes it difficult for the equipment to pass intrinsic safety testing. At the same time, most laser gas detection devices use closed gas chambers or provide reference gas chambers, which means they must operate in non-open circuits, increasing equipment costs.

[0004] Therefore, researching gas detection systems and algorithms that can be applied to open circuits and are unaffected by ambient temperature and the temperature of the laser itself is of great significance for ensuring safe industrial production and reducing accidents and loss of life and property. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a gas detection alarm system and method for temperature changes in an immune laser.

[0006] The present invention is as follows:

[0007] A gas detection alarm system for temperature changes in an immune laser, the system comprising:

[0008] Microcontroller: Generates a modulated sawtooth wave with appropriate frequency and amplitude based on the preset half-width and height of the gas to be measured; receives electrical signals, data information and temperature values; processes the received electrical signals to obtain the concentration of the gas to be measured; when the gas concentration exceeds the threshold, controls the audible and visual alarm to sound an alarm.

[0009] Laser drive module: Loads a modulated sawtooth wave to generate a constant current and modulation voltage;

[0010] Laser: Generates emitted light covering multiple absorption peaks;

[0011] Thermoelectric cooler: It controls the temperature of the laser through active heat dissipation to maintain the stability of the emitted wavelength;

[0012] Gas chamber: Used to provide a spatial optical path for detecting gases;

[0013] Photodiode detector: Used to receive transmitted light carrying gas absorption information and transmit the received light information to the photoelectric conversion module;

[0014] Photoelectric conversion module: used to receive optical signals and convert them into electrical signals;

[0015] Data acquisition module: used to acquire electrical signals and transmit them to the micro controller;

[0016] Temperature detection module: used to collect ambient temperature values ​​and transmit them to the micro controller;

[0017] Audible and visual alarm: Used to receive signals from a microcontroller and provide audible and visual alarms.

[0018] After receiving the modulated sawtooth wave from the microcontroller, the laser driving module generates a constant current to apply to the laser, causing it to emit light. It also applies a modulation voltage to the piezoelectric ceramic inside the laser to change the internal cavity length, thereby changing the output wavelength.

[0019] The laser generates emitted light by applying a constant current to the power modulation cathode pin; and generates laser light of a preset wavelength by applying a modulation voltage to the wavelength modulation cathode pin.

[0020] The temperature acquisition module calculates the resistance value of the thermistor in the bridge circuit, fits the temperature-resistance formula according to the resistance-temperature correspondence table, obtains the ambient temperature, and transmits the ambient temperature value to the microcontroller.

[0021] A gas detection alarm method for temperature changes in an immune laser, the method comprising the following steps:

[0022] (1) The electrical signal with gas absorption information is analyzed and processed to obtain spectral data. The spectral data of one scanning cycle is loaded to obtain the cycle length. The cycle length is sliced ​​to obtain a processing unit with a fixed slice length.

[0023] (2) Filter the processing unit to remove noise;

[0024] (3) The filtered processing unit is used as the transmission spectrum. Based on the fact that the two wings of the preset transmission spectrum are transmission signals that do not participate in absorption, the incident spectrum intensity is obtained by fitting with a high-order polynomial.

[0025] (4) Based on the incident spectral intensity, the intensity is normalized using Beer-Lambert law to obtain the absorption spectrum;

[0026] (5) Take the starting position of the normalized data as the center position of the Lorentz line and use the number of points corresponding to the full width at half maximum (FWHM) of the absorption peak of the gas at this wavelength as the step size to determine the center position of the Lorentz line.

[0027] (6) The full width at half maximum (FWHM) of the Lorentz line-fitted absorption spectrum was obtained by fitting the Lorentz line-fitted absorption spectrum;

[0028] (7) Compare the full width at half maximum (FWHM) of the Lorentz line fitting with the FWHM of the standard gas. If they are similar, it is determined to be an absorption peak and the marker position is accumulated. If they are not similar, it is not an absorption peak. Then, step (6)-(7) is repeated after advancing one step size until an absorption peak appears.

[0029] (8) Determine the absorption peak of the real gas by the absorption peak marker position;

[0030] (9) Obtain the peak value of the absorption peak, perform temperature compensation, calculate the gas concentration using the calibrated inversion formula, determine whether the gas concentration exceeds the threshold, and if it does, control the sound and light alarm to sound an alarm.

[0031] Preferably, the slicing process includes setting the starting position of the first slice as i0 and the slice length as L. q Determine if the end position of the slice is greater than the period length L. z If it is not greater than the length of the slice, perform the operation of steps (2)-(8) on the slice processing unit. If it is greater than the cycle length, it means that the data processing of the entire cycle is completed and the next cycle is reloaded.

[0032] Preferably, the higher-order polynomial fitting is determined by the tuning characteristics of the laser, and the order is determined based on the wavelength response and power response curves.

[0033] Preferably, the Lorentz center position determination is based on whether the Lorentz center position is greater than the slice length. If it is greater than the slice length, the slice start position parameter is updated and step (1) is repeated; if it is less than the slice length, step (6) is performed to fit the Lorentz line shape.

[0034] Preferably, the absorption peak determination is based on comparing the full width at half maximum (FWHM) of the Lorentz line fitting with the FWHM of the standard gas. If the comparison result meets the relative error range, it is identified as a potential absorption peak. If they are not similar, it is not an absorption peak. The Lorentz center position is advanced step by step with the FWHM as the step size, and steps (6)-(7) are repeated to determine whether the entire spectral data has an absorption peak. If there is no absorption peak in a scanning cycle, the next cycle is reloaded and the operation of step (1) is performed.

[0035] Preferably, in determining the real gas absorption peak, when a slice processing unit in a certain period is determined to be a potential absorption peak, the absorption peak flag is marked and counted. When the same slice in the same position in the next 4 periods is determined to be a potential absorption peak and the absorption peak flag count reaches 5 times, the absorption peak is determined to be a real gas absorption peak. If it is determined once that it is not a potential absorption peak, it is considered to be noise and the absorption peak flag is recalculated.

[0036] Beneficial effects: This invention uses a microcontroller to simultaneously detect multiple gases by presetting the half-width at half-maximum (WHM) of the gas to be tested. It is also equipped with a digital thermoelectric cooler, which enables the laser to be immune to the influence of its own temperature, maintaining accurate wavelength and stable optical power. At the same time, the microcontroller has a built-in demodulation algorithm that uses Lorentz line fitting to determine the absorption peak and obtain the gas concentration, and controls the audible and visual alarm, ensuring the response speed and accuracy of the gas detection alarm system. Attached Figure Description

[0037] Figure 1 A schematic diagram of a gas detection alarm system for temperature changes in an immune laser provided for the invention;

[0038] Figure 2 A flowchart of the adjustment algorithm for a gas detection alarm system for temperature changes in an immune laser, provided for the invention.

[0039] Figure 3 These are the three absorption peaks of methane; Detailed Implementation

[0040] The following is a detailed description of the preferred embodiments with reference to the accompanying drawings.

[0041] like Figure 1 As shown, the system described in this application includes:

[0042] The microcontroller unit (MCU) uses a low-power STM32L chip. Based on the preset half-width and height of the gas to be measured, it generates a modulated sawtooth wave with a corresponding frequency and appropriate amplitude, and loads it into the laser driver module. It receives electrical signals and data information from the data acquisition module and temperature values ​​from the temperature detection module. After processing the received electrical signals, it obtains the concentration of the gas to be measured. When the gas concentration exceeds the threshold, it controls the audible and visual alarm to sound an alarm.

[0043] The laser drive module consists of an error amplifier, a MOSFET, and a current-sensing resistor. The error amplifier and MOSFET form a constant current source. The positive input of the error amplifier is connected to the source of the MOSFET and one end of the current-sensing resistor, while the negative input is connected to the other end of the current-sensing resistor. The current-sensing resistor is connected in series with the source (S) of the MOSFET. The current in this branch constitutes the drive circuit, and the voltage difference between the two ends of the current-sensing resistor is the monitoring voltage for the laser power. By repeatedly comparing the monitoring voltage amplified by the error amplifier with the set voltage through a comparator, the gate (G) voltage of the MOSFET is adjusted, thereby controlling the drain (D) and source of the MOSFET to conduct, thus achieving constant current drive of the laser.

[0044] The laser is a T0 packaged VCSEL laser (Vertical Cavity Surface Emitting Laser) without a pigtail. The VCSEL laser generates emitted light by applying a constant current to the power modulation cathode pin; and generates the desired emitted wavelength by applying a modulation voltage to the wavelength modulation cathode pin.

[0045] The thermoelectric cooler (TEC) is a digital thermoelectric cooler controlled by a low-power DS4830A optical controller. It maintains the stability of the emitted wavelength by actively cooling the VCSEL laser.

[0046] The gas chamber is an open space optical path. The TO-packaged VCSEL laser is at one end of the device, and the photodiode detector is at the other end. The two ends form concentric circles and are collimated, so that the laser and the photodiode detector are aligned. This space also serves as a gas chamber for gas absorption.

[0047] The photodiode detector, model IG17X2000G1i, has a general response to infrared light with a response coefficient of approximately 0.9 A / W and a relatively flat gain. The photodiode detector receives the transmitted light from the VCSEL laser through the open optical path of the gas cell and transmits the received optical signal to the photoelectric conversion module.

[0048] The photoelectric conversion module is used to receive optical signals and convert them into electrical signals for transmission to the data acquisition module. It is constructed using a dual-channel operational amplifier. The first channel forms a transconductance amplifier. The negative terminal of the photodiode detector is connected to the power supply level VCC, and the positive terminal is connected to the negative input terminal of the first operational amplifier channel. The positive input terminal uses VCC / 2 as "virtual ground". The output terminal of the first channel is connected to the inverting input terminal of the second channel through a resistor, and then connected to the output terminal of the second channel to form an inverting proportional amplifier, which further amplifies the photoelectric signal. The positive input terminal uses VCC / 2 as "virtual ground".

[0049] The data acquisition module is AD7606BSTZ, which includes an analog-to-digital converter (ADC) and peripheral circuitry. It can accurately acquire the electrical signal at the output of the photoelectric conversion module and transmit the acquired signal to the MCU.

[0050] The temperature detection module consists of a 10KΩ thermistor (B value 3950) for 25℃ and a 10KΩ fixed resistor forming a bridge circuit. Fixed resistor 1 and fixed resistor 2 are connected in series to divide the voltage. The voltage level at the series junction is acquired by the MCU and used as the reference voltage V. ref Fixed resistor 3 is connected in series with the thermistor, and the series connection point is also acquired by the MCU, which is called the acquisition level V. aq These two branches are connected in parallel between VCC and GND. By calculating the resistance value of the thermistor in the bridge circuit, and according to the resistance-temperature correspondence table, the formula of temperature and resistance is fitted to obtain the ambient temperature, and the ambient temperature value is transmitted to the MCU.

[0051] The audible and visual alarm is used to receive signals from the microcontroller and trigger an audible and visual alarm.

[0052] In one embodiment, the method of this application includes the following steps:

[0053] (1) The electrical signal with gas absorption information is analyzed and processed to obtain spectral data. The spectral data of one scanning cycle is loaded to obtain the cycle length. The cycle length is sliced ​​to obtain a processing unit with a fixed slice length.

[0054] More specifically, the slicing process includes setting the starting position of the first slice as i0 and the slice length as L. q Determine if the end position of the slice is greater than the period length L. z If it is not greater than the length of the slice, perform the operation of steps (2)-(8) on the slice processing unit. If it is greater than the cycle length, it means that the data processing of the entire cycle is completed and the next cycle is reloaded.

[0055] (2) The processing unit is filtered by using a Savitzky-Golay (SG) filter to remove high-frequency noise;

[0056] (3) The filtered processing unit is used as the transmission spectrum. Based on the fact that the two wings of the preset transmission spectrum are transmission signals that do not participate in absorption, the incident spectrum intensity is obtained by fitting with a high-order polynomial.

[0057] The higher-order polynomial fitting is determined by the tuning characteristics of the laser, and the order is determined based on the wavelength response and power response curves.

[0058] (4) Based on the incident spectral intensity, the intensity is normalized using Beer-Lambert law to obtain the absorption spectrum;

[0059] (5) Take the starting position of the normalized data as the center position of the Lorentz line and use the number of points corresponding to the full width at half maximum (FWHM) of the absorption peak of the gas at this wavelength as the step size to determine the center position of the Lorentz line.

[0060] More specifically, depending on whether the Lorenz center position is greater than the slice length, if it is greater than the slice length, the slice start position parameter is updated and step (1) is repeated; if it is less than the slice length, step (6) is performed.

[0061] (6) The full width at half maximum (FWHM) of the Lorentz line-fitted absorption spectrum was obtained by fitting the Lorentz line-fitted absorption spectrum;

[0062] (7) Compare the full width at half maximum (FWHM) of the Lorentz line fitting with the FWHM of the standard gas. If the comparison result meets the relative error range, it is marked as a potential absorption peak. If they are not similar, it is not an absorption peak. The Lorentz center position is advanced step by step with the FWHM as the step size, and steps (6)-(7) are repeated to determine whether the entire spectral data has an absorption peak. If there is no absorption peak in a scanning cycle, the next cycle is reloaded and step (1) is performed.

[0063] (8) Determine the absorption peak of the real gas by the absorption peak marker position;

[0064] More specifically, in determining the real gas absorption peak, when a slice processing unit in a certain period is identified as a potential absorption peak, the absorption peak flag is marked and counted. When the same slice in the same position in the next 4 periods is identified as a potential absorption peak and the absorption peak flag count reaches 5 times, the absorption peak is determined to be a real gas absorption peak. If it is determined once that it is not a potential absorption peak, it is considered to be noise, and the absorption peak flag is recalculated.

[0065] (9) Obtain the peak value of the absorption peak, perform temperature compensation, calculate the gas concentration using the calibrated inversion formula, determine whether the gas concentration exceeds the threshold, and if it does, control the sound and light alarm to sound an alarm.

[0066] The following will use methane as an example, and see [link / reference]. Figure 2 Exemplary embodiments of the present invention are described in more detail below:

[0067] (1) The half width at half maximum (WHM) of methane gas is preset, the MCU generates a modulated sawtooth wave with a frequency of 5 Hz and an appropriate amplitude, and loads the modulated sawtooth wave onto the laser driver module.

[0068] (2) The laser driver module drives the laser to generate emitted light covering multiple methane absorption peaks (1653.7nm, 1650.9nm, 1648.2nm). At the same time, the digital TEC controls the temperature of the VCSEL laser through active heat dissipation to maintain the stability of the emitted wavelength.

[0069] (3) The laser beam passes through the open optical path of the gas chamber, and the photodiode detector receives the transmitted light with gas absorption information at the other end of the gas chamber and transmits the received light information to the photoelectric conversion module.

[0070] (4) The photoelectric conversion module converts the optical signal into an electrical signal, and the electrical signal is transmitted to the MCU through the data acquisition module;

[0071] (5) The temperature detection module calculates the resistance value of the thermistor in the bridge circuit, fits the temperature-resistance formula according to the resistance-temperature correspondence table, obtains the ambient temperature, and transmits the ambient temperature value to the MCU; the processing procedure of the temperature detection module is as follows:

[0072] The resistance of the thermistor was calculated to be:

[0073]

[0074] Among them, V ref As the reference level, V aq The level to be acquired;

[0075] Based on the resistance-temperature correspondence table, the formulas for calculating temperature and resistance are fitted:

[0076] T = 61.84438 - 17.86124 * ln(R) the -1.68917)

[0077] (6) The MCU has a demodulation algorithm. When it receives information data from the data acquisition module, it obtains the concentration of the gas to be measured through the demodulation algorithm and receives the temperature value from the temperature detection module to effectively correct the concentration error. When the gas concentration reaches the preset warning threshold, it controls the sound and light alarm to sound an alarm.

[0078] The demodulation algorithm processes the data as follows:

[0079] Step 1: Analyze the electrical signal containing gas absorption information to obtain spectral data for multiple scanning cycles. Load the spectral data from the first scanning cycle to obtain the cycle length L. z For the first period length L z Slicing is performed to obtain a processing unit with a fixed slice length. The starting position of the first slice is set to i0, and the slice length is L. q Repeatedly check whether the end position of the slice is greater than the period length L.z If the value is not greater than the cycle length, proceed to the next step for the slice processing unit; if the value is greater than the cycle length, it means that the data processing for the entire cycle is complete and the next cycle is reloaded.

[0080] Step 2: Use a Savitzky-Golay (SG) filter on the processing unit to remove high-frequency noise;

[0081] Step 3: Use the filtered processing unit as the transmission spectrum I. t , with I t The two wings are considered to be transmitted signals that do not participate in absorption. Based on the tuning characteristics of the VCSEL laser, its wavelength and power response curves are determined by fitting a second-order polynomial to obtain the incident spectral intensity I0.

[0082] Step four: According to Beer-Lambert Law, the intensity of the fitted incident spectrum I0 is normalized to obtain the absorption spectrum.

[0083] I t =I0exp[S(T)α(v)CL]

[0084] When the absorption is small, the above equation can be approximately expanded according to the first-order Taylor expansion.

[0085] I t =I0exp[-S(T)α(v)CL]≈I0[1-S(T)α(v)CL]

[0086] Among them, I t I0 and S(T) are the transmitted light intensity and the incident light intensity, respectively. S(T) is a function of temperature T, v is the frequency of the laser, C is the gas concentration, L is the optical path length, and α(v) represents the absorption spectrum.

[0087]

[0088] The absorption spectrum conforms to the Lorentz line type.

[0089]

[0090] Where y0 is the offset, x0 is the parameter defining the location of the distribution peak, w is the full width at half maximum (FWHM), and A is the area;

[0091] Step 5: Using the starting position of the normalized data as the center position of the Lorentz line, determine the Lorentz center position based on whether it is greater than the slice length L. q If it is greater than the slice length L qThe number of points corresponding to 400 is obtained based on the full width at half maximum (FWHM) of the absorption peak of the gas at this wavelength, and the step size s is used. The starting position of the slice is i0, and the starting position of the slice is updated to i. n Parameter, i n =i0+s, repeat step one; if it is less than the slice length L q Then proceed to step six to fit the Lorentz line shape;

[0092] Step 6: Obtain the full width at half maximum (FWHM) m of the Lorentz line-fitted absorption spectrum;

[0093] Step 7: Compare the full width at half maximum (FWHM) of the Lorentz line fitting with the FWHM of methane gas (48 pm at 1638.2 nm, 52 pm at 1650.9 nm, and 34 pm at 1653.7 nm). If the comparison result meets the relative error range, it is marked as an absorption peak, and the marker position is accumulated. At the same time, the Lorentz center position is changed with the FWHM as the step size, and steps 5 and 6 are repeated. If no potential absorption peak is found in the entire scanning cycle, the next cycle is reloaded and step 1 is performed.

[0094] Step 8: In the main program, add the potential absorption peak flag n. i If the absorption peak is reached five times consecutively, it is determined to be a real gas absorption peak.

[0095] Step 9: When the absorption peak is determined to be a real gas absorption peak, the peak value of the obtained absorption peak is obtained. By substituting the ambient temperature into the system correction coefficient, the gas concentration is calculated according to the calibrated inversion formula. It is then determined whether the gas concentration exceeds the preset concentration threshold of the program. If it exceeds the preset concentration threshold, the MCU sends a start signal to the audible and visual alarm to control the audible and visual alarm to sound an alarm.

[0096] This invention employs a microcontroller that presets the half-width at half-maximum (WHM) of the gas to be tested, enabling simultaneous detection of multiple gases. It also incorporates a digital thermoelectric cooler, allowing the laser to be immune to the effects of its own temperature, maintaining accurate wavelength and stable optical power. Furthermore, the microcontroller features a built-in demodulation algorithm that uses Lorentz line fitting to determine absorption peaks and obtain gas concentration, controlling the audible and visual alarms. This ensures the response speed and accuracy of the gas detection alarm system, guaranteeing safe industrial production and reducing accidents and loss of life and property.

Claims

1. A gas detection alarm system that is immune to temperature variations of a laser, characterized by, The system comprises: Microcontroller: according to the preset half-width of the measured gas, generate corresponding frequency, amplitude modulation sawtooth wave; receive electrical signals, data information and temperature value; after processing the received electrical signals, get the concentration of the measured gas, when the gas concentration exceeds the threshold, control the sound and light alarm to alarm; Laser drive module: load modulation sawtooth wave, generate constant current and modulation voltage; Laser: generate the outgoing light covering multiple absorption peaks; Thermoelectric cooler: control the temperature of the laser through active cooling, maintain the stability of the outgoing wavelength; Gas chamber: for providing a space light path with detection gas; the gas chamber is an open space light path, the laser and the photodiode detector are aligned, and the space formed serves as the gas chamber for gas absorption; Photodiode detector: for receiving the transmitted light with gas absorption information, and transmitting the received light information to the photoelectric conversion module; Photoelectric conversion module: for receiving optical signals and converting optical signals into electrical signals; Data acquisition module: for collecting electrical signals and transmitting the electrical signals to the microcontroller; Temperature detection module: for collecting environmental temperature values and transmitting the temperature values to the microcontroller; Sound and light alarm: for receiving signals from the microcontroller and performing sound and light alarm; The microprocessor obtains the concentration of the measured gas through a demodulation algorithm, and the processing method of the demodulation algorithm is as follows: Step one, the electric signal with gas absorption information is analyzed to obtain spectral data of multiple scanning periods, the spectral data of the first scanning period is loaded to obtain a period length L z The first period length L z is sliced to obtain a processing unit with a fixed slice length Step two, remove high-frequency noise from the processing unit; Step three, the filtered processing unit as a transmission spectrum I t , the two wings of I t The transmission signal without participating in the absorption is fitted with a second-order polynomial to obtain the incident light spectrum intensity I0; Step four, according to the Lambert-Beer law, use the fitted incident spectral intensity I0 to perform intensity normalization to obtain the absorption spectrum; Step five, take the starting position of the normalized data as the center position of the Lorentz line, and perform Lorentz center position judgment; Step six, fit the absorption spectrum through Lorentz linearity to obtain the Lorentz linearity fitting half-width m; Step seven, compare the Lorentz linearity fitting half-width with the half-width of the methane gas, if the comparison result meets the relative error range, identify it as an absorption peak, and accumulate the identification flag bit, and change the Lorentz center position by half-width as a step and repeat steps five to six; if there is no potential absorption peak in the whole scanning period, reload the next period to perform the operation of step one; Step eight, in the main program, potential absorption peak identification flag bit n i Continuous 5 times, determine the absorption peak is a real gas absorption peak; Step nine, when the absorption peak is determined to be a real gas absorption peak, obtain the peak value of the absorption peak, input the environmental temperature into the system correction coefficient, calculate the gas concentration according to the calibrated inversion formula.

2. The gas detection alarm system of claim 1, wherein, After the laser drive module receives the modulation sawtooth wave from the microcontroller, the drive circuit generates a constant current to load the laser to make it emit light, and applies a modulation voltage to the piezoelectric ceramic inside the laser to change the cavity length inside the laser, thereby changing the outgoing wavelength.

3. The gas detection alarm system of claim 1, wherein, The laser generates outgoing light by loading a constant current to the power modulation cathode pin; and generates laser of preset wavelength by loading modulation voltage to the wavelength modulation cathode pin.

4. The gas detection alarm system of claim 1, wherein, The temperature acquisition module calculates the resistance value of the thermistor in the bridge circuit, fits the formula of temperature and resistance value according to the resistance value-temperature correspondence table, obtains the environmental temperature, and transmits the environmental temperature value to the microcontroller.

5. A method of detecting a gas and alarming of temperature change of an immune laser, characterized by, The method comprises the following steps: (1) Analyzing and processing the electric signal with gas absorption information to obtain spectral data, loading the spectral data of a scanning cycle, obtaining the cycle length, and performing slice processing on the cycle length to obtain a processing unit with a fixed slice length; (2) Filtering the processing unit to remove noise; (3) Taking the filtered processing unit as a transmission spectrum, using a high-order polynomial fitting to obtain the incident spectrum intensity according to the two wings of the preset transmission spectrum being transmission signals not participating in absorption; (4) Using the Lambert-Beer law to perform intensity normalization to obtain an absorption spectrum according to the incident spectrum intensity; (5) Taking the starting position of the normalized data as the center position of the Lorentz line type, and determining the corresponding point number as a step length according to the width of the half-height full width of the absorption peak of the gas at the wavelength to determine the Lorentz center position; (6) Fitting the absorption spectrum by the Lorentz linearity to obtain the Lorentz linearity fitting half-height width; (7) Comparing the Lorentz linearity fitting half-height width with the half-height width of the standard gas, if they are similar, determining that it is an absorption peak and accumulating an identification flag, and if they are not similar, it is not an absorption peak, and a step length is advanced to repeat steps (6)-(7) until an absorption peak appears; (8) Determining the real gas absorption peak through the absorption peak flag; (9) Obtaining the peak value of the absorption peak, performing temperature compensation, calculating the gas concentration through the calibrated inversion formula, and judging whether the gas concentration exceeds the threshold value, if it exceeds, controlling the acousto-optic alarm to alarm.

6. The gas detection alarm method of claim 5, wherein, The slice processing includes setting the start position of the first slice as i0 and the slice length as L q , judging whether the slice end position is greater than the cycle length L z , if not, performing the operations of steps (2)-(8) on the slice processing unit, and if greater than the cycle length, indicating that the data processing of the whole cycle is completed, and the next cycle is reloaded.

7. The gas detection alarm method of claim 5, wherein, The high-order polynomial fitting is determined by the tuning characteristics of the laser, and the order is determined according to the wavelength response and power response curve.

8. The gas detection alarm method of claim 5, wherein, The Lorentz center position determination, whether the Lorentz center position is greater than the slice length, if greater than the slice length, updating the slice starting position parameter and re-performing the operation of step (1); if less than the slice length, performing step (6) to fit the Lorentz linearity.

9. The gas detection alarm method of claim 5, wherein, The absorption peak determination, comparing the Lorentz linearity fitting half-height width with the half-height of the standard gas, if the comparison result meets the relative error range, identifying it as a potential absorption peak, changing the Lorentz center position by the half-height width as a step length and repeating steps (5)-(6); if the result is not a potential absorption peak, re-loading the next cycle to perform step (1).

10. The gas detection alarm method of claim 5, wherein, The determination of the real gas absorption peak, when the slice processing unit of a certain cycle is determined to be a potential absorption peak, the absorption peak flag is identified and counted, when the same slice of the next four cycles is determined to be a potential absorption peak, the absorption peak flag count reaches 5 times, and the absorption peak is determined to be a real gas absorption peak; If it is determined once that it is not a potential absorption peak, it is determined that this place is noise, and the absorption peak flag is recalculated.

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