A fiber optic methane gas concentration measuring device and method resistant to strong interference

Abstract

The present invention discloses an optical fiber methane gas concentration measurement device and a measurement method that are resistant to strong interference, which are composed of an alarm controller, a transmitter, a methane gas sealed air chamber and a sensor probe. The transmitter includes a processor, a drive module, a light source, a temperature control module, an optical circulator, an optical switch, two photoelectric converters, a photoelectric balance detector, analog binarization, two multipliers, an analog-to-digital converter and a data transmission module. The photoelectric balance detector, analog binarization and multiplier are used to accurately locate the position of the methane gas absorption peak in the return signal of the sensor probe, and the equal-value intersection of the light intensity curve returned by the sensor probe and the methane gas sealed air chamber is used to dynamically lock the wavelength region on both sides of the methane absorption peak, thereby eliminating the serious decrease in measurement accuracy caused by the overlap of the absorption spectrum of the methane gas molecule with the absorption spectrum of water vapor and other hydrocarbons under a strong interference environment.

Description

Technical Field

[0001] The invention belongs to the technical field of gas concentration measurement, and in particular relates to an optical fiber methane gas concentration measurement device and a measurement method that are resistant to strong interference, and can realize the measurement of methane gas concentration under a strong interference environment. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Fiber optic methane gas concentration measurement is usually based on the principle of spectral absorption. It comprehensively utilizes the tunable diode laser absorption spectroscopy (TDLAS) technology and obtains the concentration of methane gas by detecting the attenuation of light intensity according to the Lambert-Beer law. Among them, gas molecule spectral absorption refers to the phenomenon that photons within a certain wavelength range are absorbed by gas molecules. Methane molecules have multiple absorption lines in the mid-infrared and near-infrared bands. In order to be suitable for transmission in ordinary quartz optical fibers, absorption lines near 1654nm are usually selected as the working wavelength of the sensing system. When light passes through the measured gas containing methane molecules, photons of a specific wavelength are absorbed by methane molecules. Therefore, after the light passes through the measured gas, the light intensity is attenuated, and the degree of attenuation is linearly related to the methane gas concentration. The gas sensing system based on spectral absorption can indirectly obtain the methane concentration value of the measured gas by measuring the attenuation of light intensity.

[0004] The tunable semiconductor laser spectral absorption technology mainly utilizes the narrow line width and wavelength of the tunable semiconductor laser that changes with the injected current. By modulating the wavelength of the laser, the wavelength of the laser is scanned across the absorption peak of the gas molecules to be measured, so that the gas molecules absorb the modulated laser based on the Lambert-Beer law, and the concentration of the gas molecules is measured according to the absorption amount. The physical meaning of the Lambert-Beer law is that when a beam of parallel monochromatic light passes vertically through a uniform non-scattering absorbing substance, such as methane gas, its absorbance, that is, the amount of light intensity attenuation, is proportional to the concentration of the absorbing substance.

[0005] The inventors found that due to the absorption line of methane gas molecules, water vapor, other hydrocarbons (such as ethane (C2H6), propane (C3H8) and butane (C4H 10)) have many overlapping areas of absorption spectra. Therefore, when the fiber optic methane gas concentration measurement system is used in some special environments with strong interference, such as underground urban integrated pipe corridors with gas pipelines, gas stations, gas stations, etc., the measurement results will be greatly affected by other gas components. Moreover, the absorption spectrum of methane gas molecules overlaps with water vapor, other hydrocarbons (such as ethane (C2H6), propane (C3H8) and butane (C4H 10 ))’s absorption spectra are very similar, and this influence cannot be eliminated using traditional differential measurement methods. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide an optical fiber methane gas concentration measurement device and a measurement method that are resistant to strong interference.

[0007] To solve the above technical problems, one or more embodiments of the present invention provide the following technical solutions:

[0008] In a first aspect, the present invention provides an optical fiber methane gas concentration measurement device resistant to strong interference, comprising: a detection module, a transmitter and an alarm controller which are sequentially signal-connected;

[0009] Wherein, the detection module includes at least one sensor probe and a gas-sealed air chamber, and the sensor probe and the gas-sealed air chamber are both connected to the optical circulator of the transmitter through an optical fiber;

[0010] In the transmitter:

[0011] The processor, the driving module, the light source and the optical circulator are signal-connected in sequence;

[0012] The optical circulator, the optical switch, the optical balance detector, the analog binarization, the multiplier component, the analog-to-digital converter and the processor are sequentially connected in signal, wherein the multiplier component includes a multiplier 1 and a multiplier 2, which are connected in parallel;

[0013] The optical switch, the photoelectric converter 1 and the multiplier 1 are signal connected in sequence;

[0014] The optical circulator is respectively connected to the optical balance detector and the photoelectric converter 2 signal;

[0015] The optical switch and the data sending module are connected with the processor signal, and the data sending module is connected with the data receiving module of the alarm controller signal.

[0016] In a second aspect, a method for measuring methane gas concentration in an optical fiber that is resistant to strong interference is provided, comprising the following steps:

[0017] The light source generates a continuous light signal under the stimulation of the ramp signal of the driving module, and the continuous light signal covers the absorption peak of methane gas;

[0018] The optical circulator receives the continuous optical signal from the light source, divides it into N+1 paths, and transmits it to each sensor probe and gas sealing chamber through optical fiber; transmits the optical signal reflected by the sensor probe to the optical switch, and transmits each optical signal to the photoelectric balance detector in turn through the optical switch; transmits the optical signal reflected by the gas sealing chamber to the photoelectric balance detector;

[0019] The photoelectric balanced detector converts two optical signals into one electrical signal and outputs it to analog binarization;

[0020] Analog binarization outputs an analog electrical signal with a constant voltage between two peaks, and outputs an analog electrical signal of 0V outside the two peaks; multipliers 1 and 2 receive the analog electrical signal;

[0021] The photoelectric converter 1 receives the optical signal returned by the sensor probe transmitted by the optical switch, and outputs it to the multiplier 1;

[0022] The photoelectric converter 2 receives the optical signal returned by the methane gas sealed chamber and outputs it to the multiplier 2;

[0023] Multipliers 1 and 2 transmit the electrical signals in the optical wavelength range on two adjacent sides of the methane absorption peak to the analog-to-digital converter;

[0024] The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor;

[0025] The processor uses the digital quantity obtained by the light signal reflected from the gas-sealed air chamber as a reference, calibrates the digital quantity obtained by the light signal returned from the sensor probe, and calculates the methane gas concentration value;

[0026] The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller.

[0027] Compared with the prior art, the above one or more technical solutions of the present invention have achieved the following beneficial effects:

[0028] The optical fiber methane gas concentration measurement method and device with strong interference resistance is composed of an alarm controller, a transmitter, a methane gas sealed chamber and a sensor probe. The alarm controller and the transmitter are encapsulated in the mainframe box and placed in safe areas such as monitoring rooms and offices; the methane gas sealed chamber and the sensor probe are placed in dangerous areas where methane gas may leak; the methane gas sealed chamber contains methane gas of standard concentration, which is used to return the light intensity curve with the correct absorption peak position; the sensor probe is used to measure the methane gas concentration at close range. A passive long-distance optical fiber connection is used between the mainframe and the probe.

[0029] The transmitter includes a processor, a driver module, a light source, a temperature control module, an optical circulator (1*(N+1)*(N+1)), an optical switch (1*N), two photoelectric converters, a photoelectric balance detector, an analog binarization, two multipliers, an analog-to-digital converter, and a data transmission module. The photoelectric balance detector, the analog binarization, and the multiplier are used to accurately locate the position of the methane gas absorption peak in the return signal of the sensor probe. The equal intersection of the light intensity curve returned by the sensor probe and the methane gas sealed gas chamber is used to dynamically lock the wavelength region on both sides of the methane absorption peak, eliminating the absorption spectrum of the methane gas molecule and water vapor, other hydrocarbons (such as ethane (C2H6), propane (C3H8) and butane (C4H 10 ))'s absorption line overlap causes a serious decrease in measurement accuracy.

[0030] The strong interference-resistant optical fiber methane gas concentration measurement method and device use infrared light signals to measure the methane gas concentration. Its signal transmission medium (optical fiber) and probe are completely passive, do not require power supply, do not have heating or combustion phenomena, and can be placed in dangerous locations near methane gas leakage areas, solving the inherent contradiction between the safety and monitoring needs of traditional methane gas alarm devices.

[0031] The optical fiber methane gas concentration measurement method and device with strong interference resistance realizes methane gas concentration detection by using the intensity change of infrared light signal, and there is no problem of probe poisoning, thus extending the working life and reducing maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 is a schematic diagram of the overall structure of an embodiment of the present invention;

[0034] Figure 2 is a structural diagram of an alarm controller according to an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of the structure of the transmitter according to the embodiment of the present invention. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] In a first aspect, the present invention provides an optical fiber methane gas concentration measurement device resistant to strong interference, comprising: a detection module, a transmitter and an alarm controller which are sequentially signal-connected;

[0039] Wherein, the detection module includes at least one sensor probe and a gas-sealed air chamber, and the sensor probe and the gas-sealed air chamber are both connected to the optical circulator of the transmitter through an optical fiber;

[0040] In the transmitter:

[0041] The processor, the driving module, the light source and the optical circulator are signal-connected in sequence;

[0042] The optical circulator, the optical switch, the optical balance detector, the analog binarization, the multiplier component, the analog-to-digital converter and the processor are sequentially connected in signal, wherein the multiplier component includes a multiplier 1 and a multiplier 2, which are connected in parallel;

[0043] The optical switch, the photoelectric converter 1 and the multiplier 1 are signal connected in sequence;

[0044] The optical circulator is respectively connected to the optical balance detector and the photoelectric converter 2 signal;

[0045] The optical switch and the data sending module are connected with the processor signal, and the data sending module is connected with the data receiving module of the alarm controller signal.

[0046] In some embodiments, the transmitter further comprises a temperature control module connected to the light source, and used to control the temperature of the light source to keep the temperature of the light source constant, so as to prevent the wavelength and power of the optical signal from being affected by changes in ambient temperature.

[0047] In some embodiments, the optical fiber is a passive long-distance transmission optical fiber.

[0048] In some embodiments, a data receiving module, a display module, a relay group and a power supply module are provided in the alarm controller, and the display module, the relay group and the power supply module are all connected to the data receiving module.

[0049] Furthermore, the power module is connected to the transmitter to supply power to the transmitter.

[0050] Furthermore, the alarm controller also includes a button module.

[0051] Furthermore, the alarm controller also includes an audible and visual alarm, an indicator light and a fan, all of which are connected to the relay group.

[0052] Furthermore, the indicator light includes an operation indicator light, a fault indicator light and a power indicator light.

[0053] In a second aspect, a method for measuring methane gas concentration in an optical fiber that is resistant to strong interference is provided, comprising the following steps:

[0054] The light source generates a continuous light signal under the stimulation of the ramp signal of the driving module, and the continuous light signal covers the absorption peak of methane gas;

[0055] The optical circulator receives the continuous optical signal from the light source, divides it into N+1 paths, and transmits it to each sensor probe and gas sealing chamber through optical fiber; transmits the optical signal reflected by the sensor probe to the optical switch, and transmits each optical signal to the photoelectric balance detector in turn through the optical switch; transmits the optical signal reflected by the gas sealing chamber to the photoelectric balance detector;

[0056] The photoelectric balanced detector converts two optical signals into one electrical signal and outputs it to analog binarization;

[0057] Analog binarization outputs an analog electrical signal with a constant voltage between two peaks, and outputs an analog electrical signal of 0V outside the two peaks; multipliers 1 and 2 receive the analog electrical signal;

[0058] The photoelectric converter 1 receives the optical signal returned by the sensor probe transmitted by the optical switch, and outputs it to the multiplier 1;

[0059] The photoelectric converter 2 receives the optical signal returned by the methane gas sealed chamber and outputs it to the multiplier 2;

[0060] Multipliers 1 and 2 transmit the electrical signals in the optical wavelength range on two adjacent sides of the methane absorption peak to the analog-to-digital converter;

[0061] The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor;

[0062] The processor uses the digital quantity obtained by the light signal reflected from the gas-sealed air chamber as a reference, calibrates the digital quantity obtained by the light signal returned from the sensor probe, and calculates the methane gas concentration value;

[0063] The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller.

[0064] In some embodiments, the wavelength of the absorption peak of methane gas is 1654 nm.

[0065] In some embodiments, the constant voltage analog electrical signal is a 1V analog electrical signal.

[0066] Example

[0067] like Figure 1 As shown in the figure, the strong interference-resistant optical fiber methane gas concentration measurement device consists of an alarm controller, a transmitter, a methane gas sealed chamber and a sensor probe. The alarm controller and the transmitter are encapsulated in the mainframe box and placed in safe areas such as monitoring rooms and offices; the methane gas sealed chamber and the sensor probe are placed in dangerous areas where methane gas may leak; the methane gas sealed chamber contains methane gas of standard concentration to return a light intensity curve with the correct absorption peak position; the sensor probe is used to measure the methane gas concentration at close range. A passive long-distance optical fiber is used to connect the mainframe and the probe.

[0068] like Figure 2 As shown in the figure, the alarm controller is divided into a data receiving module, a display module, a button module, a relay module, an audible and visual alarm module and a power module according to its functions. The data receiving module receives the measured data of the methane gas concentration; the display module displays the methane gas concentration value, the alarm threshold, the alarm and fault information; the button module is used to set the alarm threshold; the relay module controls the on and off of the power light, the operating light and the fault light according to the working status of the alarm controller, as well as the on and off of the peripheral audible and visual alarm and the fan. The power module is used to power the alarm controller and the transmitter.

[0069] like Figure 3 As shown, the transmitter includes a processor, a drive module, a light source, a temperature control module, an optical circulator (1*(N+1)*(N+1)), an optical switch (1*N), two photoelectric converters, a photoelectric balance detector, an analog binarization, two multipliers, an analog-to-digital converter and a data sending module.

[0070] The processor controls the driving module to generate a suitable driving current signal, receives the digital signal sent by the analog-to-digital converter, and calculates the methane gas concentration value.

[0071] Under the control of the processor, the driving module generates the current signal required to drive the light source. The waveform of the current signal is a ramp signal, which makes the wavelength of the continuous light emitted by the light source scan from λ1 to λ2, covering the absorption peak of methane gas near the wavelength of 1654nm.

[0072] Under the stimulation of the driving module, the light source generates a continuous optical signal and transmits it to the optical circulator.

[0073] The temperature control module is used to control the temperature of the light source to keep the temperature constant and prevent the wavelength and power of the optical signal from being affected by changes in ambient temperature.

[0074] The optical circulator receives the optical signal from the light source, divides the optical signal into N+1 paths, and transmits them to N sensing probes and 1 methane gas sealed air chamber in the detection area through long-distance optical fibers, and transmits the N optical signals reflected from the sensing probes to the optical switch, and transmits the 1 optical signal reflected from the methane gas sealed air chamber to the photoelectric balance detector input port 1. Under the control of the processor, the optical switch sequentially transmits the optical signals returned from the N sensing probes to the optical balance detector input port 2.

[0075] The optical balance detector converts two input optical signals into one electrical signal output, and when the two input optical signal intensities are the same, the output electrical signal amplitude is the highest. In a single ramp cycle, as the wavelength scans from λ1 to λ2, covering the absorption peak of methane gas near the wavelength of 1654nm, the intensity curve of the optical signal reflected from the methane gas sealed air chamber undergoes a process from strong to weak and then to strong; for the optical signal returned by the sensor probe, since the concentration of methane gas in the air is unknown and affected by the absorption spectrum of water vapor and other hydrocarbons, when the optical wavelength scans from λ1 to λ2, the intensity curve changes irregularly, but there will always be two equal-value intersections with the intensity curve of the optical signal reflected from the methane gas sealed air chamber, and the two intersections must be on both sides of the adjacent methane absorption peak.

[0076] The analog binary receives the electrical signal output by the photoelectric balance detector, outputs an analog electrical signal of 1V between the two peak points, and outputs an analog electrical signal of 0V outside the two peak points, and the output is connected to two multipliers.

[0077] Photoelectric converter 1 receives the optical signal returned by one sensing probe transmitted by the optical switch, and outputs it to another input port of multiplier 1. Photoelectric converter 2 receives the optical signal returned by the methane gas sealed chamber, and outputs it to another input port of multiplier 2.

[0078] The two multipliers, under the control of the high and low levels of the analog binary output, only output the relevant electrical signals of the optical wavelength range on both sides of the methane absorption peak to the analog-to-digital converter (when the optical wavelength range is not on both sides of the methane absorption peak, the electrical signals output by the two multipliers are both 0V).

[0079] The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor. The processor uses the digital value obtained by the light signal reflected from the methane gas sealed chamber as a reference to calibrate the methane gas concentration corresponding to the digital value obtained by the light signal returned by the sensor probe. The data transmission module transmits the methane gas concentration value calculated by the processor to the alarm controller.

[0080] The optical fiber methane gas concentration measurement method with strong interference resistance specifically includes the following steps:

[0081] Step 1: The light source generates a continuous light signal under the stimulation of the ramp signal of the driving module and transmits it to the optical circulator. The wavelength of the continuous light emitted by the light source is scanned from λ1 to λ2, which can cover the absorption peak of methane gas near the wavelength of 1654nm.

[0082] In step 2, the optical circulator receives the optical signal from the light source, divides it into (N+1) paths and transmits it to N sensing probes and 1 methane gas sealed air chamber in the detection area through long-distance optical fiber. At the same time, the N optical signals reflected from the sensing probes are transmitted to the optical switch, and the 1 optical signal reflected from the methane gas sealed air chamber is transmitted to the photoelectric balance detector input port 1. Under the control of the processor, the optical switch sequentially transmits the optical signals returned from the N sensing probes to the optical balance detector input port 2.

[0083] Step 3: The optical balance detector converts the two input optical signals into one electrical signal output, and when the two input optical signal intensities are the same, the output electrical signal amplitude is the highest. In a single ramp cycle, as the wavelength scans from λ1 to λ2, covering the absorption peak of methane gas near the wavelength of 1654nm, the intensity curve of the optical signal reflected from the sealed gas chamber of methane gas undergoes a process from strong to weak and then to strong again; for the optical signal returned by the sensor probe, since the concentration of methane gas in the air is unknown and is affected by the absorption spectra of water vapor and other hydrocarbons, when the wavelength of light scans from λ1 to λ2, the intensity curve changes irregularly, but there will always be two equal-value intersections with the intensity curve of the optical signal reflected from the sealed gas chamber of methane gas, and the two intersections must be on both sides of the adjacent methane absorption peak.

[0084] Step 4: Analog binary receives the electrical signal output by the photoelectric balance detector, outputs a 1V analog electrical signal between the two peak points, and outputs a 0V analog electrical signal outside the two peak points, and the output is connected to two multipliers. Photoelectric converter 1 receives the optical signal returned by the 1-way sensor probe transmitted by the optical switch, and outputs it to another input port of multiplier 1. Photoelectric converter 2 receives the optical signal returned by the methane gas sealed chamber, and outputs it to another input port of multiplier 2. Under the control of the high and low levels of the analog binary output, the two multipliers only output the relevant electrical signals with the optical wavelength range on both sides of the adjacent methane absorption peak to the analog-to-digital converter (when the optical wavelength range is not on both sides of the adjacent methane absorption peak, the electrical signals output by the two multipliers are both 0V).

[0085] Step 5: The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor.

[0086] Step 6: The processor uses the digital value obtained by the light signal reflected from the methane gas sealed chamber as a reference to calibrate the methane gas concentration corresponding to the digital value obtained by the light signal returned by the sensor probe. The data transmission module transmits the methane gas concentration value calculated by the processor to the alarm controller.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical fiber methane gas concentration measurement device resistant to strong interference, characterized in that: include: The detection module, transmitter and alarm controller are connected in sequence; Wherein, the detection module includes at least one sensor probe and a gas-sealed air chamber, and the sensor probe and the gas-sealed air chamber are both connected to the optical circulator of the transmitter through an optical fiber; In the transmitter: The processor, the driving module, the light source and the optical circulator are signal-connected in sequence; The optical circulator, the optical switch, the optical balance detector, the analog binarization, the multiplier component, the analog-to-digital converter and the processor are sequentially connected in signal, wherein the multiplier component includes a multiplier 1 and a multiplier 2, which are connected in parallel; The optical switch, the photoelectric converter 1 and the multiplier 1 are signal connected in sequence; The optical circulator is respectively connected to the optical balance detector and the photoelectric converter 2 signal; The optical switch and the data sending module are connected to the processor signal, and the data sending module is connected to the data receiving module of the alarm controller signal; The transmitter also includes a temperature control module, which is connected to the light source; The optical fiber is a passive long-distance transmission optical fiber.

2. The optical fiber methane gas concentration measuring device resistant to strong interference according to claim 1 is characterized in that: The alarm controller is provided with a data receiving module, a display module, a relay group and a power supply module, and the display module, the relay group and the power supply module are all connected to the data receiving module.

3. The optical fiber methane gas concentration measuring device resistant to strong interference according to claim 2 is characterized in that: The power module is connected to the transmitter.

4. The optical fiber methane gas concentration measuring device resistant to strong interference according to claim 2 is characterized in that: The alarm controller also includes a button module.

5. The optical fiber methane gas concentration measuring device resistant to strong interference according to claim 2 is characterized in that: The alarm controller also includes an audible and visual alarm, an indicator light and a fan, all of which are connected to the relay group.

6. The optical fiber methane gas concentration measuring device resistant to strong interference according to claim 5 is characterized in that: The indicator lights include a running indicator light, a fault indicator light and a power indicator light.

7. A method for measuring methane gas concentration by optical fiber with strong interference resistance, characterized in that: The steps include: The light source generates a continuous light signal under the stimulation of the ramp signal of the driving module, and the continuous light signal covers the absorption peak of methane gas; The optical circulator receives the continuous optical signal from the light source, divides it into N+1 paths, and transmits it to each sensor probe and gas sealing chamber through optical fiber; transmits the optical signal reflected by the sensor probe to the optical switch, and transmits each optical signal to the photoelectric balance detector in turn through the optical switch; transmits the optical signal reflected by the gas sealing chamber to the photoelectric balance detector; The photoelectric balanced detector converts two optical signals into one electrical signal and outputs it to analog binarization; Analog binarization outputs an analog electrical signal with a constant voltage between two peaks, and outputs an analog electrical signal of 0V outside the two peaks; multipliers 1 and 2 receive the analog electrical signal; The photoelectric converter 1 receives the optical signal returned by the sensor probe transmitted by the optical switch, and outputs it to the multiplier 1; The photoelectric converter 2 receives the optical signal returned by the methane gas sealed chamber and outputs it to the multiplier 2; Multipliers 1 and 2 transmit the electrical signals in the optical wavelength range on two adjacent sides of the methane absorption peak to the analog-to-digital converter; The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor; The processor uses the digital quantity obtained by the light signal reflected from the gas-sealed air chamber as a reference, calibrates the digital quantity obtained by the light signal returned from the sensor probe, and calculates the methane gas concentration value; The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller.

8. The optical fiber methane gas concentration measurement method with strong interference resistance according to claim 7 is characterized in that: The wavelength of the absorption peak of methane gas is 1654nm.

Images