CN115839916A - Gas detection alarm system and method for temperature change of immune laser - Google Patents
Gas detection alarm system and method for temperature change of immune laser Download PDFInfo
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Abstract
The invention relates to the technical field of gas detection and alarm, in particular to a gas detection and alarm system and method for temperature change of an immune laser. The microcontroller is adopted to detect various gases simultaneously by presetting the full width at half maximum of the gas to be detected, and a digital thermoelectric cooler is carried, so that the laser can be immune to the influence of self temperature, the accurate wavelength and stable light power are kept, meanwhile, a demodulation algorithm is arranged in the microcontroller, the absorption peak is judged by Lorentz line type fitting, the gas concentration is obtained, an audible and visual alarm is controlled, and the response speed and the accuracy of a gas detection alarm system are ensured.
Description
Technical Field
The invention relates to the technical field of gas detection alarm, in particular to a gas detection alarm system and method for temperature change of an immune laser.
Background
At present, toxic and harmful gases are generated in a plurality of domestic industrial production processes, such as electric welding, electroplating, smelting, chemical industry, petroleum and other industries. The hazards of different toxic and harmful gases are different, and even the main hazards of the same gas are different in different environments or aiming at different phenomena. The hazard of common toxic and harmful gases can be roughly divided into the following aspects: corrosiveness, irritation, flammability, explosiveness, etc.
Therefore, in the industries of petroleum, chemical industry, coal mine, smelting and the like, the prevention of the escape, the overflow, the dripping and the leakage of toxic and harmful gases is the prevention key point for avoiding accidents, the current laser gas detection device needs to be matched with a high-power precise temperature control device in order to realize that a laser beam does not change along with the change of the environmental temperature, and the temperature control device has larger current and is not beneficial to the intrinsic safety detection of equipment; meanwhile, most laser gas detection devices adopt a closed gas chamber or provide a reference gas chamber, namely, the laser gas detection devices must work on a non-open circuit, and equipment cost is increased.
Therefore, the research on the gas detection system and the algorithm which are applied to an open circuit and are not influenced by the ambient temperature and the temperature of the laser has very important significance for ensuring industrial safety production and reducing accidents and life and property losses.
Disclosure of Invention
In order to solve the problems, the invention provides a gas detection alarm system and a gas detection alarm method for temperature change of an immune laser.
The scheme of the invention is as follows:
a gas detection alarm system for immunological laser temperature changes, the system comprising:
a microcontroller: generating a modulated sawtooth wave with appropriate corresponding frequency and amplitude according to the preset half-width height of the gas to be detected; receiving the electric signal, the data information and the temperature value; the received electric signals are processed to obtain the concentration of the gas to be detected, and when the concentration of the gas exceeds a threshold value, an audible and visual alarm is controlled to give an alarm;
the laser driving module: loading a modulated sawtooth wave to generate a constant current and a modulated voltage;
a laser: generating emergent light covering the plurality of absorption peaks;
thermoelectric coolers: controlling the temperature of the laser in an active heat dissipation mode to maintain the stability of the emergent wavelength;
air chamber: for providing a spatial light path with a detection gas;
photodiode detector: the photoelectric conversion module is used for receiving the transmitted light with the gas absorption information and transmitting the received light information to the photoelectric conversion module;
a photoelectric conversion module: the optical fiber receiving device is used for receiving an optical signal and converting the optical signal into an electrical signal;
a data acquisition module: the microcontroller is used for acquiring an electric signal and transmitting the electric signal to the microcontroller;
a temperature detection module: the microcontroller is used for acquiring an environmental temperature value and transmitting the temperature value to the microcontroller;
audible and visual alarm: used for receiving the signal of the microcontroller and giving sound and light alarm.
After the laser driving module receives the modulated sawtooth wave of the microcontroller, the driving circuit generates constant current to load the laser to enable the laser to emit light, modulation voltage is applied to piezoelectric ceramics in the laser to change the length of the cavity in the laser, and therefore the emitting wavelength is changed.
The laser generates emergent light by loading constant current on a power modulation cathode pin; and loading a modulation voltage to the wavelength modulation cathode pin to enable the laser to generate laser with a preset wavelength.
The temperature acquisition module calculates the resistance value of the thermistor in the bridge circuit, fits a formula of temperature and resistance value according to a resistance value temperature mapping table to obtain the ambient temperature, and transmits the ambient temperature value to the microcontroller.
A gas detection alarm method of temperature change of an immunity laser, the method comprising the steps of:
(1) Analyzing the electric signal with the gas absorption information to obtain spectral data, loading the spectral data of a scanning period to obtain a period length, and slicing the period 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, and obtaining the incident spectrum intensity by adopting high-order polynomial fitting according to transmission signals which are not absorbed and are on two wings of the preset transmission spectrum;
(4) According to the intensity of the incident spectrum, carrying out intensity normalization by using a Lambert beer law to obtain an absorption spectrum;
(5) Taking the initial position of the normalized data as the central position of the Lorentz line type, and obtaining corresponding point numbers as step length according to the width of the full width at half maximum of the absorption peak of the gas at the wavelength, and determining the central position of the Lorentz;
(6) Fitting the absorption spectrum through a Lorentzian line type to obtain the Lorentzian line type fitting full width at half maximum;
(7) Comparing the Lorentz line type fitting full width at half maximum with that of the standard gas, if the Lorentz line type fitting full width at half maximum is similar to that of the standard gas, judging that the fitting full width at half maximum is an absorption peak, accumulating the identification mark bit, if the fitting full width at half maximum is not similar to that of the standard gas, judging that the fitting full width at half maximum is not an absorption peak, and repeating the steps (6) - (7) after advancing a step length until the absorption peak appears;
(8) Determining a real gas absorption peak through an absorption peak mark position;
(9) And acquiring the peak value of the obtained absorption peak, performing temperature compensation, calculating to obtain the gas concentration through a calibrated inversion formula, judging whether the gas concentration exceeds a threshold value, and controlling an audible and visual alarm to give an alarm if the gas concentration exceeds the threshold value.
Preferably, the slicing process includes setting a start position of the first slicing to i 0 Slice length of L q Judging whether the slice end position is greater than the cycle length L z If the data is not larger than the cycle length, the operations of the steps (2) - (8) are carried out on the slice processing unit, and if the data is larger than the cycle length, the data in the whole cycle is completely processed, and then the next cycle is reloaded.
Preferably, the higher order polynomial fit is determined by the tuning characteristics of the laser, the order being determined from the wavelength response and power response curves.
Preferably, the lorentz center position is judged, and according to whether the lorentz center position is greater than the slice length or not, if so, the slice initial position parameter is updated, and the operation in the step (1) is performed again; and (5) if the length of the slice is smaller than the length of the slice, performing the operation of the step (6) to fit the Lorentzian line type.
Preferably, the absorption peak judgment is carried out by comparing the fitting full width at half maximum with the full height of the standard gas according to the Lorentz line type, if the comparison result meets the relative error range, the potential absorption peak is identified, if the comparison result is not similar, the potential absorption peak is not the absorption peak, the full width at half maximum is taken as the step length to step forward the Lorentz central position, and the steps (6) - (7) are repeated, so that whether the whole spectrum data has the absorption peak or not is judged; and (3) if no absorption peak exists in one scanning period, reloading the next period to perform the operation of the step (1).
Preferably, the true gas absorption peak is determined, when the slice processing unit in a certain period is determined as a potential absorption peak, the flag bit of the absorption peak is identified and counted, when the same slice in the next 4 periods is determined as a potential absorption peak at the same position, and the flag bit of the absorption peak is counted for 5 times, the absorption peak is determined as a true gas absorption peak; if the judgment of one occurrence is not a potential absorption peak, the judgment is that the occurrence is noise, and the flag bit of the absorption peak is recalculated.
Has the advantages that: the invention adopts the microcontroller to realize the simultaneous detection of various gases by presetting the full width at half maximum of the gas to be detected, and carries the digital thermoelectric cooler, so that the laser can be immune to the influence of self temperature, the accurate wavelength and the stable light power are kept, meanwhile, the microcontroller is internally provided with a demodulation algorithm, the absorption peak is judged and the gas concentration is obtained by Lorentz linear fitting, an audible and visual alarm is controlled, and the response speed and the accuracy of a gas detection alarm system are ensured.
Drawings
FIG. 1 is a schematic structural diagram of a gas detection alarm system for temperature variation of an immunity laser provided by the invention;
FIG. 2 is a flow chart of a mediation algorithm of the gas detection alarm system for the temperature change of the immunological laser provided by the invention;
FIG. 3 shows three absorption peaks for methane;
Detailed Description
The following detailed description is to be read with reference to the drawings, in which preferred embodiments are shown.
As shown in fig. 1, the system of the present application includes:
a Microcontroller Unit (MCU) adopts a low-power consumption STM32L chip, generates a modulated sawtooth wave with moderate corresponding frequency and amplitude according to the preset half-width height of the gas to be detected, and loads the modulated sawtooth wave to a laser driving module; receiving an electric signal and data information of a data acquisition module and a temperature value of a temperature detection module; the received electric signals are processed to obtain the concentration of the gas to be detected, and when the concentration of the gas exceeds a threshold value, an audible and visual alarm is controlled to give an alarm;
the laser driving module is composed of an error amplifier, an MOS tube and a current measuring resistor, wherein the error amplifier and the MOS tube form a constant current source, the positive input end of the error amplifier is connected with the source electrode of the MOS tube and one section of the current measuring resistor, the reverse input end of the error amplifier is connected with the other end of the current measuring resistor, the current measuring resistor is connected in series with the source electrode (S pole) of the MOS tube, the branch current forms a driving circuit, and the voltage difference of the two sections of the current measuring resistor is the monitoring voltage of the laser power. After the monitoring voltage amplified by the error amplifier is repeatedly compared with the set voltage through the comparator, the grid (G pole) voltage of the MOS tube is adjusted, and then the drain (D pole) and the source of the MOS tube are controlled to be conducted, so that the constant current drive of the laser is realized;
the Laser is a T0 packaged VCSEL (Vertical Cavity Surface Emitting Laser) without a tail fiber, and the VCSEL loads constant current on a power modulation cathode pin to generate emergent light; the required emergent wavelength is generated by loading a modulation voltage on a wavelength modulation cathode pin;
a thermoelectric Cooler (TEC for short) is a digital thermoelectric Cooler controlled by a low power consumption DS4830A light controller, and maintains the stability of the emission wavelength by controlling the temperature of the VCSEL laser in an active heat dissipation manner;
the gas chamber is an open space light path, the TO-packaged VCSEL laser is arranged at one end of the device, the photodiode detector is arranged at the other end, two ends of the TO-packaged VCSEL laser form concentric circles and are aligned, the laser and the photodiode detector are aligned, and the formed section of space is also used as a gas chamber for gas absorption;
the model of the photodiode detector is IG17X2000G1i, the photodiode detector generally responds to infrared light, the response coefficient is about 0.9A/W, the gain is flat, the photodiode detector receives transmitted light of a VCSEL laser passing through an open light path of the air chamber, and meanwhile, received optical signals are transmitted to the photoelectric conversion module;
the photoelectric conversion module is used for receiving optical signals, converting the optical signals into electric signals and transmitting the electric signals to the data acquisition module, the photoelectric conversion module is composed of a dual-channel operational amplifier, a transconductance amplifier is formed in the first channel, the cathode of a photodiode detector is connected with a power supply level VCC, the anode of the photodiode detector is connected with the negative input end of a first operation amplifier channel, VCC/2 is used as virtual ground in the positive input end, the output end of the first channel is connected with the reverse input end of a second channel through a resistor, the output end of the second channel is connected with the output end of the second channel to form a reverse proportion amplifier, the photoelectric signals are further zoomed, and the VCC/2 is used as virtual ground in the positive input end;
the data acquisition module is AD7606BSTZ, comprises an Analog-to-Digital Converter (ADC) and a peripheral circuit, can accurately acquire an electric signal at the output end of the photoelectric conversion module, and transmits the acquired signal to the MCU;
the temperature detection module is a bridge formed by a thermistor with a B value of 3950 and a thermistor with a temperature of 25 ℃ corresponding to 10K omega, the fixed resistor 1 and the fixed resistor 2 are connected in series for voltage division, and the level of a serial node is collected by the MCU and used as a reference level V ref The fixed resistor 3 is connected in series with the thermistor, and the series node is also acquired by the MCU and is called as an acquisition level V aq The two branches are connected between VCC and GND in parallel, the resistance of the thermistor in the bridge circuit is calculated, and a formula of temperature and resistance is fitted according to a resistance-temperature correspondence table to obtainThe ambient temperature and the ambient temperature value are transmitted to the MCU;
and the audible and visual alarm is used for receiving the signal of the microcontroller and giving audible and visual alarm.
In one embodiment, the method of the present application comprises the steps of:
(1) Analyzing the electric signal with the gas absorption information to obtain spectral data, loading the spectral data of a scanning period to obtain a period length, and slicing the period length to obtain a processing unit with a fixed slice length;
more specifically, the slicing process includes setting a start position of the first slice to i 0 Slice length of L q Judging whether the slice end position is greater than the cycle length L z And if the data processing time is not larger than the preset time, performing the operations in the steps (2) to (8) on the slice processing unit, and if the data processing time is larger than the preset time, indicating that the data processing of the whole time is finished and reloading the next time.
(2) Filtering the processing unit, and removing high-frequency noise by adopting a Savitzky-Golay (SG) filter;
(3) Taking the filtered processing unit as a transmission spectrum, and obtaining the incident spectrum intensity by adopting high-order polynomial fitting according to transmission signals which are not absorbed and are on two wings of the preset transmission spectrum;
wherein the higher order polynomial fit is determined by the tuning characteristics of the laser, and the order is determined from the wavelength response and power response curves.
(4) According to the intensity of the incident spectrum, intensity normalization is carried out by utilizing a Lambert beer law to obtain an absorption spectrum;
(5) Taking the initial position of the normalized data as the central position of the Lorentz line type, and obtaining corresponding point numbers as step length according to the width of the full width at half maximum of the absorption peak of the gas at the wavelength, and determining the central position of the Lorentz;
further specifically, according to whether the lorentz center position is greater than the slice length or not, if so, updating the slice initial position parameter, and performing the operation of the step (1) again; and (5) if the length is smaller than the slice length, performing the operation of the step (6).
(6) Fitting the absorption spectrum through a Lorentzian line type to obtain the Lorentzian line type fitting full width at half maximum;
(7) Comparing the half-height width of the Lorentzian line fitting with the half-height width of the standard gas, and identifying the comparison result as a potential absorption peak if the comparison result meets a relative error range; if not, the spectrum data are not absorption peaks, the Lorentz central position is progressively increased by taking the full width at half maximum as a step length, and the steps (6) - (7) are repeated, so that whether the whole spectrum data have absorption peaks or not is judged; and (3) if no absorption peak exists in one scanning period, reloading the next period to perform the operation of the step (1).
(8) Determining a real gas absorption peak through an absorption peak mark position;
more specifically, when a slice processing unit in a certain period is judged to be a potential absorption peak, the absorption peak flag bit is subjected to identification counting, when the same slices in the following 4 periods are judged to be the potential absorption peak at the same position, and the absorption peak flag bit is counted for 5 times, the absorption peak is judged to be the true gas absorption peak; if the judgment of one occurrence is not a potential absorption peak, the judgment is that the occurrence is noise, and the flag bit of the absorption peak is recalculated.
(9) And acquiring the peak value of the obtained absorption peak, performing temperature compensation, calculating to obtain the gas concentration through a calibrated inversion formula, judging whether the gas concentration exceeds a threshold value, and controlling an audible and visual alarm to give an alarm if the gas concentration exceeds the threshold value.
An exemplary embodiment of the present invention will now be described in more detail, using methane as an example, and with reference to the illustration of FIG. 2:
(1) Presetting the half-height width of methane gas, generating a modulated sawtooth wave with the frequency of 5hz and the moderate amplitude by the MCU, and loading the modulated sawtooth wave to the laser driving module;
(2) The laser driving module drives the laser to generate emergent light covering a plurality of methane absorption peaks (1653.7 nm,1650.9nm and 1648.2nm), and meanwhile, the digital TEC controls the temperature of the VCSEL laser in an active heat dissipation mode to maintain the stability of emergent wavelength;
(3) Emergent light of the laser passes through an open light path of the air chamber, and the photodiode detector receives transmitted light with gas absorption information at the other end of the air chamber and transmits the received light information to the photoelectric conversion module;
(4) The photoelectric conversion module converts the optical signal into an electric signal, and the electric signal is transmitted to the MCU through the data acquisition module;
(5) The temperature detection module calculates the resistance value of the thermistor in the bridge circuit, fits a formula of temperature and resistance value according to a resistance value and temperature corresponding table to obtain the ambient temperature, and transmits the ambient temperature value to the MCU; the temperature detection module comprises the following processing procedures:
the resistance value of the thermistor is calculated as follows:
wherein, V ref Is a reference level, V aq To acquire the electrical level;
fitting a calculation formula of temperature and resistance according to the resistance temperature corresponding table:
T＝61.84438-17.86124*ln(R the -1.68917)
(6) The MCU is internally provided with a demodulation algorithm, when information data of the data acquisition module are received, the concentration of the gas to be detected is obtained through the demodulation algorithm, the temperature value of the temperature detection module is received to effectively correct the concentration error, and when the gas concentration reaches a preset early warning critical value, the audible and visual alarm is controlled to give an alarm;
the demodulation algorithm is processed as follows:
step one, analyzing and processing the electric signal with the gas absorption information to obtain spectrum data of a plurality of scanning periods, loading the spectrum data of a first scanning period to obtain period length L z For the length L of the first period z Performing slicing processing to obtain a processing unit with fixed slice length, and setting the initial position of the first slice as i 0 Slice length of L q Repeatedly judging whether the slice end position is greater than the period length L z If not, processing the sliceThe unit enters the operation of the next step, if the length of the unit is larger than the cycle length, the data processing of the whole cycle is finished, and the next cycle is reloaded;
step two, removing high-frequency noise by adopting a Savitzky-Golay (SG) filter for the processing unit;
step three, taking the filtered processing unit as a transmission spectrum I t In 1 with t The two wings of the laser are regarded as transmission signals without participating in absorption, and according to the tuning characteristics of the VCSEL laser, the wavelength and the power response curve of the VCSEL laser are determined to obtain the incident spectral intensity I by adopting second-order polynomial fitting 0 ；
Step four, utilizing the fitted incident spectrum intensity I according to the Lambert Beer law (Beer-LambertLaw) 0 The intensity normalization is carried out to obtain an absorption spectrum,
I t ＝I 0 exp[S(T)α(v)CL]
when the absorption is small, according to the first order taylor expansion, the above equation can be expanded approximately,
I t ＝I 0 exp[-S(T)α(v)CL]≈I 0 [1-S(T)α(v)CL]
wherein, I t ，I 0 Respectively transmitted light intensity and incident light intensity, 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, and alpha (v) represents the absorption spectrum;
the absorption spectrum satisfies the lorentzian line type,
wherein, y 0 Is an offset amount, x 0 For parameters defining the position of the distribution peak, w is the full width at half maximum and a is the area;
step five, taking the initial position of the normalized data as the central position of the Lorentz line type to judge the central position of the Lorentz line typeAccording to whether the Lorentz center position is larger than the slice length L q If it is larger than the slice length L q Then, according to the width of the full width at half maximum of the absorption peak of the gas at the wavelength, the number of points corresponding to 400 is obtained as the step length s, and the slice starting position is i 0 Update slice start position i n Parameter, i n ＝i 0 + s, repeating the operation of the first step; if less than the slice length L q Performing the operation of the sixth step to fit the Lorentzian line type;
sixthly, fitting an absorption spectrum through a Lorentzian line type to obtain a Lorentzian line type fitting half-height width m;
seventhly, comparing the full width at half maximum with the full width at half maximum of methane gas (the full width at half maximum of the methane gas at 1638.2nm is 48pm, the full width at half maximum at 1650.9nm is 52pm, and the full width at half maximum of the methane gas at 1653.7nm is 34 pm) through Lorentz line type fitting, if the comparison result meets a relative error range, identifying an absorption peak, accumulating identification marker positions, changing the central position of the Lorentz by taking the full width at half maximum as a step length, and repeating the fifth step to the sixth step; if the whole scanning period judges that no potential absorption peak exists, reloading the next period to perform the operation of the first step;
step eight, marking a flag bit n by a potential absorption peak in a main program i Continuously reaching 5 times, and judging that the absorption peak is a real gas absorption peak;
and step nine, when the absorption peak is judged to be a real gas absorption peak, acquiring the peak value of the obtained absorption peak, substituting the ambient temperature into a system correction coefficient, calculating to obtain the gas concentration according to a calibrated inversion formula, judging whether the gas concentration exceeds a concentration threshold preset by a program, and when the gas concentration exceeds the concentration threshold preset by the program, sending a starting signal to the audible and visual alarm by the MCU, and controlling the audible and visual alarm to give an alarm.
The invention adopts the microcontroller to realize the simultaneous detection of various gases by presetting the full width at half maximum of the gas to be detected, and carries a digital thermoelectric cooler, so that the laser can be immune to the influence of self temperature, the accurate wavelength and the stable light power are kept, meanwhile, a demodulation algorithm is arranged in the microcontroller, the absorption peak is judged and the gas concentration is obtained by Lorentz line type fitting, an audible and visual alarm is controlled, the response speed and the accuracy of a gas detection alarm system are ensured, the industrial safety production is ensured, and the occurrence of accidents and the loss of lives and properties are reduced.
Claims (10)
1. An immunological laser temperature change gas detection alarm system, comprising:
a microcontroller: generating a modulated sawtooth wave with moderate corresponding frequency and amplitude according to the preset half-width height of the gas to be detected; receiving the electric signal, the data information and the temperature value; the received electric signals are processed to obtain the concentration of the gas to be detected, and when the concentration of the gas exceeds a threshold value, an audible and visual alarm is controlled to give an alarm;
the laser driving module: loading a modulated sawtooth wave to generate a constant current and a modulated voltage;
a laser: generating emergent light covering the plurality of absorption peaks;
thermoelectric coolers: controlling the temperature of the laser in an active heat dissipation mode to maintain the stability of the emergent wavelength;
air chamber: for providing a spatial light path with a detection gas;
photodiode detector: the photoelectric conversion module is used for receiving the transmitted light with the gas absorption information and transmitting the received light information to the photoelectric conversion module;
a photoelectric conversion module: the optical signal receiving module is used for receiving an optical signal and converting the optical signal into an electrical signal;
a data acquisition module: the microcontroller is used for acquiring an electric signal and transmitting the electric signal to the microcontroller;
a temperature detection module: the microcontroller is used for acquiring an environmental temperature value and transmitting the temperature value to the microcontroller;
audible and visual alarm: used for receiving the signal of the microcontroller and giving sound and light alarm.
2. The gas detection alarm system of claim 1, wherein after the laser driving module receives the modulated sawtooth wave of the microcontroller, the driving circuit generates a constant current to load the laser to emit light, and applies a modulation voltage to the piezoelectric ceramic inside the laser to change the cavity length inside the laser, so as to change the emission wavelength.
3. The gas detection alarm system of claim 1, wherein the laser generates the emitted light by applying a constant current to a power modulated cathode pin; and loading a modulation voltage to the wavelength modulation cathode pin to enable the laser to generate laser with a preset wavelength.
4. The gas detection alarm system of claim 1, wherein the temperature acquisition module obtains the ambient temperature by calculating the resistance of the thermistor in the bridge circuit and fitting a formula of the temperature and the resistance according to a resistance-temperature correspondence table, and transmits the ambient temperature value to the microcontroller.
5. A gas detection alarm method for temperature change of an immunity laser is characterized by comprising the following steps:
(1) Analyzing the electric signal with the gas absorption information to obtain spectral data, loading the spectral data of a scanning period to obtain a period length, and slicing the period 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, and obtaining the incident spectrum intensity by adopting high-order polynomial fitting according to transmission signals which are not absorbed and are on two wings of the preset transmission spectrum;
(4) According to the intensity of the incident spectrum, intensity normalization is carried out by utilizing a Lambert beer law to obtain an absorption spectrum;
(5) Taking the initial position of the normalized data as the central position of the Lorentz line type, obtaining corresponding point numbers according to the width of the half-maximum and full-width of the absorption peak of the gas at the wavelength as step length, and determining the central position of the Lorentz;
(6) Fitting the absorption spectrum through a Lorentzian line type to obtain the Lorentzian line type fitting full width at half maximum;
(7) Comparing the half-height width of Lorentz line fitting with the half-height width of standard gas, judging that the gas is an absorption peak if the gas is similar to the standard gas, accumulating identification mark bits, judging that the gas is not an absorption peak if the gas is not similar to the standard gas, and repeating the steps (6) - (7) after a step length is increased until the absorption peak appears;
(8) Determining a real gas absorption peak through an absorption peak mark position;
(9) And acquiring the peak value of the obtained absorption peak, performing temperature compensation, calculating to obtain the gas concentration through a calibrated inversion formula, judging whether the gas concentration exceeds a threshold value, and controlling an audible and visual alarm to give an alarm if the gas concentration exceeds the threshold value.
6. The gas detection alarm method of claim 5, wherein the slicing process includes setting a start position of a first slicing to i 0 Slice length of L q Judging whether the slice end position is greater than the cycle length L z And if the data processing time is not larger than the preset time, performing the operations in the steps (2) to (8) on the slice processing unit, and if the data processing time is larger than the preset time, indicating that the data processing of the whole time is finished and reloading the next time.
7. The gas detection alarm method of claim 5, wherein the higher order polynomial fit is determined by a tuning characteristic of the laser, the order being determined from a wavelength response and a power response curve.
8. The gas detection alarm method according to claim 5, wherein the Lorentz center position is determined, and according to whether the Lorentz center position is greater than the slice length, if so, the slice starting position parameter is updated, and the operation in step (1) is performed again; and (5) if the length of the slice is smaller than the length of the slice, performing the operation of the step (6) to fit the Lorentzian line type.
9. The gas detection alarm method according to claim 5, wherein the absorption peak judgment is performed by comparing the full width at half maximum of the Lorentzian line fitting with the full height of the standard gas, if the comparison result meets the relative error range, the potential absorption peak is identified, and the Lorentzian center position is changed by taking the full width at half maximum as the step length and the steps (5) - (6) are repeated; and (4) if the result judges that the absorption peak is not a potential absorption peak, reloading the next cycle to perform the operation of the step (1).
10. The gas detection alarm method according to claim 5, wherein the true gas absorption peak is determined, when a slice processing unit in a certain period is determined as a potential absorption peak, the flag bit of the absorption peak is identified and counted, and when the same slice in the following 4 periods is determined as a potential absorption peak at the same position, the flag bit of the absorption peak is counted up to 5 times, and the absorption peak is determined as a true gas absorption peak; if the judgment of one occurrence is not a potential absorption peak, the judgment is that the occurrence is noise, and the flag bit of the absorption peak is recalculated.
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| CN117387673A (en) * | 2023-12-08 | 2024-01-12 | 山东星冉信息科技有限公司 | Fiber bragg grating demodulation method and device based on reference air chamber |
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| CN117387673B (en) * | 2023-12-08 | 2024-02-23 | 山东星冉信息科技有限公司 | Fiber bragg grating demodulation method and device based on reference air chamber |
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