CN113916802A - Automatic calibration open-circuit type laser gas detection device and implementation method - Google Patents
Automatic calibration open-circuit type laser gas detection device and implementation method Download PDFInfo
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Abstract
The invention discloses an automatic calibration open-circuit type laser gas detection device and an implementation method in the technical field of gas detection, wherein in the gas detection device, a circuit control processing system drives a laser to emit working wavelength laser, an optical fiber coupler is used for splitting the working wavelength laser emitted by the laser into signal light and reference light, the signal light is incident to a first photoelectric detector after passing through an open-circuit environment, and the reference light is incident to a second photoelectric detector after passing through a standard gas chamber; the implementation method comprises the steps of emitting laser signals, enabling the laser signals to respectively penetrate through an open-circuit environment and a standard air chamber, comparing detection results, calibrating and the like. The invention overcomes the defect that the detection system of the open-circuit environment in the prior art can not be calibrated, and the detection of the open-circuit environment is calibrated and calibrated through the standard air chamber, so that the whole system is more reliable and intelligent.
Description
Technical Field
The invention relates to the technical field of gas detection, in particular to an automatic calibration open-circuit type laser gas detection device and an implementation method.
Background
In recent years, the economic strength of China is increasing day by day, the energy demand is increasing continuously, and in order to promote sustainable development and green development, China has gradually adjusted the energy distribution structure, and the energy is changed from the previous coal energy to the current natural gas energy. The cumulative natural gas yield of China all year round in 2020 exceeds 1888 billion cubic meters, the same ratio increases by 9.8%, the yield increase of China all year round continuously exceeds 100 billion cubic meters, the cumulative natural gas import amount of China all year round in 2020 reaches 10166 million tons, and the same ratio increases by 5.3%. Natural gas is mainly composed of alkanes, most of which are methane, and small amounts of ethane, propane and butane, as well as some other gases (such as hydrogen sulfide, carbon dioxide, etc.). In the exploitation, transportation and storage of natural gas, various leakage problems always exist inevitably, once the gas leakage is not found and treated in time, serious consequences (including causing environmental pollution and explosion accidents) can be brought, which not only brings huge economic loss, but also greatly harms the life safety of people and causes adverse social effects. Therefore, in order to reduce environmental pollution and guarantee social safety, the problem of timely detecting gas leakage through a detector is in the trend.
The detectors commonly used at present for detecting natural gas include catalytic combustion type detectors, semiconductor type detectors, electrochemical type detectors and the like, but the detectors have the defects of low sensitivity, slow response speed, poor anti-interference capability, easy interference or toxic effect of other gases and the like. In order to reduce environmental pollution and ensure social stability, a detector capable of timely, stably and accurately detecting the concentration of gases such as methane is needed, and an open-circuit gas detection system can meet the requirements.
The existing open circuit detection system mainly comprises a transmitter, a receiver and a reflector, wherein: the transmitter consists of a distributed feedback optical fiber, a collimator, a singlechip control circuit and the like; the receiver is composed of a detector, a small signal amplifying circuit, a signal extracting circuit, a single chip microcomputer signal processing and the like. In the detection process, a light source is collimated and then transmitted to an open-circuit environment with gas to be detected, incident light is absorbed and attenuated by the gas to be detected and then received by a photoelectric detector, detected optical signals are converted into electric signals, the electric signals are amplified through a circuit, and finally, a CPU is used for processing and analyzing the amplified electric signals.
The existing open-circuit gas detection system cannot carry out calibration and calibration in the detection process, because the open-circuit gas detection system is applied to the open-circuit environment, the whole open-circuit environment cannot be completely filled with standard gas for calibration, and the mode of completely filling gas is difficult to realize and can cause environmental pollution. In addition, in order to ensure the accuracy and stability of the system, calibration is often required to be performed frequently, which consumes a large amount of labor and material costs.
The above-mentioned drawbacks need to be solved.
Disclosure of Invention
In order to overcome the defect that the detection system of the open circuit environment in the prior art cannot automatically calibrate and calibrate, the invention provides the automatic calibration open circuit type laser gas detection device and the realization method thereof, which can calibrate and calibrate the detection of the open circuit environment in real time through the standard gas chamber, so that the whole system is more reliable and intelligent.
The technical scheme of the invention is as follows:
an automatic calibration open-circuit laser gas detection device, which comprises an optical path system and a circuit control processing system connected with the optical path system, and is characterized in that,
the optical path system comprises a laser, an optical fiber coupler, a standard air chamber, a first photoelectric detector connected with an open-circuit environment and a second photoelectric detector connected with the standard air chamber, wherein standard gas is sealed in the standard air chamber, working wavelength laser emitted by the laser is split by the optical fiber coupler to form signal light and reference light, the signal light is incident to the first photoelectric detector after passing through the open-circuit environment, and the reference light is incident to the second photoelectric detector after passing through the standard air chamber;
the circuit processing system is connected with the laser and drives the laser to emit working wavelength laser, and the circuit processing system is connected with the first photoelectric detector and the second photoelectric detector and realizes real-time automatic calibration of the product value of the concentration and the length of the gas to be measured in the open-circuit environment through the product value of the concentration and the length of the gas in the standard gas chamber.
The present invention according to the above aspect is characterized in that the laser and the fiber coupler are connected by fusion splicing.
The optical path system further includes a wavelength division multiplexer and a visible light source, the optical fiber coupler and the visible light source are connected with the wavelength division multiplexer in an optical fiber fusion mode, signal light output by the optical fiber coupler is connected with one input end of the wavelength division multiplexer, laser with an indication wavelength emitted by the visible light source is connected with the other input end of the wavelength division multiplexer, the wavelength division multiplexer is used for combining the signal light and the laser with the indication wavelength and outputting the combined laser with an optical fiber, and the combined light irradiates the open-circuit environment.
On the other hand, a parabolic reflector is arranged at the light incidence end of the open circuit environment, and the wavelength division multiplexer and the composite light output by the optical fiber are reflected by the parabolic reflector and then are collimated and emitted into the open circuit environment.
The invention according to the above scheme is characterized in that the light collimation incident end and the light receiving end of the open-circuit environment are both located on the same side, a reflector is arranged on the other side of the open-circuit environment, and the light collimated and incident to the open-circuit environment is reflected by the reflector and then incident to the first photoelectric detector of the receiving end.
The invention according to the above aspect is characterized in that the standard gas is a pure gas to be measured, or a mixture of a gas to be measured and an inert gas.
The invention according to the above scheme is characterized in that a modulation circuit is arranged in the circuit control processing system, and the modulation circuit is used for controlling the laser wavelength generated by the laser to automatically scan within the central wavelength range of the absorption peak of the gas to be measured.
On the other hand, the implementation method for automatically calibrating the open-circuit type laser gas detection is characterized by comprising the following steps of:
s100, controlling a laser to emit a laser signal by a circuit control processing system;
s200, respectively acquiring an optical signal of a laser signal passing through an open-circuit environment and an optical signal of the laser signal passing through a standard air chamber;
s300, comparing detection results of the two paths of optical signals, and calibrating the detection result of the optical signal passing through the open-circuit environment through the detection result of the optical signal passing through the standard air chamber.
The invention according to the above scheme is characterized in that in step S100, the modulation circuit in the circuit control processing system controls the wavelength scanning of the laser, so as to realize the automatic reciprocating scanning of the laser wavelength near the central wavelength of the absorption peak of the gas to be measured; the working wavelength laser emitted by the laser is respectively sent to the open circuit environment and the standard air chamber through the optical fiber coupler, and the laser passing through the open circuit environment and the standard air chamber comes from the same laser light source, so that synchronous same-frequency wavelength scanning of two paths of air chamber gases is realized.
The invention according to the above scheme is characterized in that in step S300, two paths of photodetectors respectively receive an optical signal passing through an open-circuit environment and an optical signal passing through a standard air chamber, and convert the corresponding optical signals into electrical signals, thereby realizing synchronous same-frequency acquisition of the two paths of optical detection signals; and after the electric signal is amplified by the small signal amplifying circuit, extracting relevant characteristic information of the electric signal for comparison and calculation to obtain the information of the product value of the concentration and the length of the gas to be measured in the open-circuit environment, which is calibrated by the standard gas chamber.
The open circuit detection system has the advantages that the laser light source is adopted, the open circuit detection system has the advantages of long detection distance, high detection precision, high response speed, no interference of external environment, no interference of other gas components and the like, light is split through the optical fiber coupler, signal light and open circuit environment are calibrated and calibrated through the reference light and the standard air chamber, the accuracy and the real-time performance of the detection process of the system are guaranteed, and the whole system is more reliable and intelligent.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
fig. 2 is a schematic structural diagram of the invention.
In the figures, the various reference numbers are:
1-a circuit control processing system; 2-a laser; 3-a fiber optic coupler; 4-a source of visible light; 5-wavelength division multiplexer; 6-parabolic mirror; 7-a reflector; 8-a first photodetector; 9-a fiber collimator; 10-a standard air chamber; 11-second photodetector.
Detailed Description
The invention is further described with reference to the following figures and embodiments:
as shown in fig. 1 and 2, an automatic calibration open-circuit laser gas detection device includes an optical path system and a circuit control processing system 1 connected with the optical path system, the optical path system includes a light source (laser) and a photoelectric detector, wherein the circuit control processing system 1 is used for controlling a light source generator to generate a light source, the photoelectric detector is used for receiving a light signal passing through a gas environment to be detected and converting the detected light signal into an electric signal, and after the electric signal is sent to the circuit control processing system 1, the electric signal is amplified through the circuit control processing system 1, so as to realize detection and identification functions.
In actual detection, many factors affect the detection accuracy and sensitivity to different degrees, including fluctuation of light power of a light source, drift of light wavelength, disturbance of open-circuit environment, detection noise of a light detector, temperature drift and time drift of a circuit, and the like. The invention adopts the tunable semiconductor laser absorption spectroscopy (TDLAS) technology, and then utilizes the optical fiber coupler to divide a path of reference light to realize the automatic and real-time calibration and calibration functions on the detection result through the standard air chamber, thereby reducing the influence caused by the factors to a certain extent.
Specifically, in the light source generating process, the circuit control processing system 1 is connected with the laser 2, a modulation circuit is arranged in the circuit control processing system 1, and the laser wavelength generated by the laser 2 is controlled by the modulation circuit to automatically scan back and forth near the central wavelength of the absorption peak of the gas (such as methane) to be detected. When the laser emitted by the laser 2 does not pass through the gas to be detected, the intensity of the optical signal detected by the photoelectric detector is kept consistent at all times; when laser passes through gas to be detected, the intensity of an optical signal of the photoelectric detector at the central wavelength of an absorption peak of the gas to be detected is reduced, the intensity of the optical signal is unchanged when other wavelengths are detected, the phenomenon is that the optical signal is a high-level signal in most of time in the performance condition of an electric signal, a low-level signal appears in the middle of the optical signal, the alternating high-level signal and the alternating low-level signal have periodicity, and the concentration multiplied by the length of the gas to be detected corresponding to the output of the electric signal is fixed. Then the photoelectric detector converts the detected optical signal into an electric signal, the obtained electric signal is amplified through the circuit control processing system 1, then high level and low level signal values are extracted, and the corresponding optical information is the initial light intensity and the light intensity value at the absorption peak.
Preferably, the laser 2 is a tunable semiconductor laser, and the laser light source emitted by the laser is good in monochromaticity, and the laser output laser wavelength range is narrow and can be adjusted, so that only the central wavelength of the laser needs to be selected as a certain absorption line wavelength of a certain gas to be detected. Therefore, the tunable semiconductor laser is adopted, so that the whole detection system has the advantages of long detection distance, high detection precision, high response speed, no interference from external environment, no interference from other gas components and the like.
The invention selects the laser signal generated by the laser 2 as the detection light, detects the gas concentration based on infrared spectrum absorption, and because different gas molecules have different band electron energy level structures, the gas molecules can only absorb photons with energy exactly equal to the energy difference of two energy levels of the gas molecules, and because the different energy levels of the gas with different molecular structures can absorb the photons with different frequencies, the gas has strong selective absorption characteristics to the laser wavelength. In addition, the laser signal has the advantages of long detection distance, high detection precision, high response speed, no interference of external environment, no interference of other gas components and the like, so that a stable detection result can be obtained.
In order to realize calibration and calibration of the detection result of the open-circuit environment, the light path emitted by the laser 2 is divided into a signal light path and a reference light path, the signal light path passes through the open-circuit environment with unknown gas parameters, the reference light path passes through the standard environment with known gas parameters, and the detection result of the signal light path is calibrated and calibrated through the detection result of the reference light path. Correspondingly, the photoelectric detector in the invention comprises a first photoelectric detector 8 connected with the open-circuit environment and a second photoelectric detector 11 connected with the standard gas cell 10, wherein the first photoelectric detector 8 is used for detecting the signal light signal, and the second photoelectric detector 11 is used for detecting the reference light signal.
The optical path system further comprises an optical fiber coupler 3 and a standard gas cell 10, and the photoelectric detector comprises a first photoelectric detector 8 connected with the open-circuit environment and a second photoelectric detector 11 connected with the standard gas cell 10. The circuit control processing system 1 is connected with the laser 2 and drives the laser 2 to emit laser with working wavelength, the laser 2 is connected with the optical fiber coupler 3, the optical fiber coupler 3 is used for splitting the laser emitted by the laser 2 into signal light and reference light, the signal light is incident to the first photoelectric detector 8 after passing through an open-circuit environment to realize detection of the open-circuit environment, the reference light is incident to the second photoelectric detector 11 after passing through the standard air chamber 10, the circuit control processing system 1 compares the signals obtained by the first photoelectric detector 8 and the second photoelectric detector 11, and calibration are carried out on the gas detection result of the open-circuit environment.
The splitting ratio of the selected optical fiber coupler 3 in the invention is 90: 10, the energy of the signal light occupies 90% of the whole, and the energy of the reference light occupies 10% of the whole, which does not affect the detection accuracy of the signal light to the open-circuit environment, and can ensure the consistency of the laser information of the open-circuit environment and the standard gas cell 10.
In a preferred embodiment, the laser 2 is fusion spliced to the fiber coupler 3. The laser beam output by the laser 2 can be connected with the optical fiber coupler 3 through the optical fiber output end by using the optical fiber fusion splicer, so that the laser light source can be replaced, the subsequent collimation light path does not need to be adjusted after the laser 2 is replaced, and the switching is very convenient to realize the detection of different gases.
In the signal light path, the signal light passes through the open-circuit environment and is absorbed by the gas to be detected, and then enters the first photodetector 8. In a preferred embodiment, the optical path system further includes a wavelength division multiplexer 5 and a visible light source 4, the optical fiber coupler 3 and the visible light source 4 are connected with the wavelength division multiplexer 5 through optical fiber fusion, the signal light output by the optical fiber coupler 3 is connected with one input end of the wavelength division multiplexer 5, the visible light source 4 emits laser light indicating wavelength and is connected with the other input end of the wavelength division multiplexer 5, the wavelength division multiplexer 5 is used for combining the signal light output by the first output end and the visible light emitted by the visible light source 4 and outputting the combined signal light and the visible light with the optical fiber so that the signal light and the visible light are completely overlapped, and the light output by the wavelength division multiplexer 5 irradiates an open circuit environment. By inputting the signal light and the visible light emitted from the visible light source 4 to the wavelength division multiplexer 5, the wavelength division multiplexer 5 couples the two lights into one light. The visible light is used for indicating light rays, and is convenient to view and adjust.
The light incidence end of the open circuit environment is provided with a parabolic reflector 6, the working wavelength laser and the indicating wavelength laser are emitted from the same optical fiber output end of the wavelength division multiplexer, and are collimated and emitted into the open circuit environment after being reflected by the parabolic reflector 6. Because the light that the laser passes through the fiber coupler 3 output is gaussian light, in order to avoid the light spot from becoming bigger after the signal light is transmitted in the open circuit environment of too far distance, the invention adopts the parabolic reflector 6 to collimate the signal light, make its output be parallel light, because the parabolic reflector 6 is stable and there is no dispersion effect of light, so after multiplexing the signal wavelength laser and the indicating wavelength laser into a path of light through the wavelength division multiplexer 5, adopt the parabolic reflector 6 to collimate, can guarantee the light path of the signal light and the indicating light keeps the complete unanimity.
Preferably, the surface of the parabolic reflector 6 is plated with gold, so that the reflecting effect is ensured, and the processing difficulty is reduced.
In the invention, the light incident end (the parabolic reflector 6) and the light emergent end (the first photoelectric detector 8) of the open circuit environment are both positioned at the same side, the other side of the open circuit environment is provided with the reflector 7, and the light incident to the open circuit environment is reflected by the reflector 7 and then is emitted from the light emergent end (the first photoelectric detector 8). The surface of the reflector 7 is made of special materials, and the reflector has a plurality of optical physical properties such as good imaging and cleanability, so that laser can penetrate through the open-circuit environment and then is reflected by the reflector 7 to enter the initial end part of the open-circuit environment again, the requirement that the parabolic reflector 6 and the first photoelectric detector 8 are located at the same end part of the open-circuit environment is met, the light source and the first photoelectric detector 8 adopt the same circuit control processing system, and the reflector has good synchronism and real-time performance.
In the reference light path, the second output end of the fiber coupler 3 is connected to the fiber collimator 9, and the light (reference light) output by the fiber collimator 9 irradiates the standard gas cell 10. Compared with the signal light, the transmission distance of the reference light in the standard gas chamber 10 is short, so the reference light is directly collimated by the optical fiber collimator 9, passes through the standard gas chamber 10 and is received by the second photoelectric detector 11.
The standard gas chamber 10 of the present invention can be replaced with different standard gases for detecting different gases. The standard gas chamber 10 comprises a gas chamber shell and standard gas filled in the gas chamber shell, wherein the gas chamber shell is of a cuboid structure formed by organic glass plates, and the length of the gas chamber shell is known and can be selected according to specific needs. Optical window sheets with high transmissivity near the central wavelength of the absorption peak of the gas to be measured are arranged at the light path inlet and outlet (the left port and the right port in the figure) of the gas chamber shell, and the optical window sheets are used for replacing organic glass to ensure that light rays can well pass through. Based on this, can very convenient change standard air chamber, the laser light source and the narrowband filter of different center wavelength, and then realize the detection of different gases.
The standard gas in the present invention may be a pure test gas, or a mixture of a test gas and an inert gas (such as nitrogen) may be selected as the standard gas, and the contents of the test gas and the inert gas in the mixture are known, so that the test gas in the standard gas chamber 10 may be calibrated as a standard value. The standard gas is related to the length of the standard gas chamber and is not limited in detail. The standard gas can avoid the interference of moisture and other impurities in the air, the concentration of the gas to be detected is high, and the calibration test can reach more than half of the full range of the detector by only using a short standard gas chamber as reference. In order to ensure the use safety, the concentration of the pure gas to be measured or the mixture of the gas to be measured and the inert gas is higher and is not controlled in the gas explosion range.
After the first photoelectric detector 8 detects the signal light and the second photoelectric detector 10 detects the reference light, the corresponding optical signals are converted into electric signals, and the electric signals are amplified by a small signal amplifying circuit and then relevant characteristic information of the electric signals is extracted.
The invention utilizes Lambert beer's law, when laser passes through the gas to be measured, if the laser output laser wavelength is the same as a certain absorption peak of the gas, the gas to be measured can absorb the laser, wherein the absorption intensity is related to the concentration of the gas, the length of the gas and the absorption coefficient of the gas at the wavelength, the absorption coefficient of each gas to be measured at each absorption line is fixed, so that the gas absorption intensity is only related to the product of the concentration of the gas to be measured and the gas length. Therefore, the reflective laser open circuit detection system is calibrated and calibrated by comparing and analyzing the electric signals output by the signal light detector and the reference light detector, so that the whole system is more reliable and intelligent.
Based on the automatic calibration open-circuit laser gas detection device, the standard gas chamber is added in the system, under the condition that the detection effect of the main light path is not influenced, the light with certain energy is separated by the optical fiber coupler to be used as the reference light, the reference light generates the reference signal after passing through the standard gas chamber, and the reference signal and the detection signal are used for contrastive analysis, so that the detection signal can be calibrated and calibrated in real time, and the whole system is more reliable and intelligent.
Based on the above automatic calibration open-circuit laser gas detection device, the invention also provides a realization method of automatic calibration open-circuit laser gas detection, which comprises the following steps:
and S100, controlling the laser to emit a laser signal by the circuit control processing system.
In the process, a modulation circuit in the circuit control processing system controls the laser to realize laser wavelength scanning, and the laser wavelength generated by the laser is automatically scanned in a reciprocating manner near the central wavelength of the absorption peak of the gas to be detected; the working wavelength laser emitted by the laser is respectively sent to the open circuit environment and the standard air chamber through the optical fiber coupler, and the laser passing through the open circuit environment and the standard air chamber comes from the same laser light source, so that synchronous same-frequency wavelength scanning of two paths of air chamber gases is realized.
In order to realize the calibration and calibration of the system, the invention designs a signal light path to be compared with a reference light path. Specifically, a laser signal emitted by the laser is split by the optical fiber coupler, wherein the signal light enters an open-circuit environment, and the reference light enters the standard air chamber.
In the signal light path, in order to realize the indication of the signal light, the signal light and the visible light emitted by the visible light source are simultaneously transmitted into the wavelength division multiplexer, and the wavelength division multiplexer optically couples the two paths of light into one path of light. The coupled light directly enters an open-circuit environment, and can also enter the open-circuit environment after being reflected by a parabolic reflector.
S200, after the system is started, the first photoelectric detector obtains an optical signal (namely a detection optical signal) of a laser signal passing through an open-circuit environment, and the second photoelectric detector obtains an optical signal (namely a reference optical signal) of the laser signal passing through the standard air chamber.
And then the first photoelectric detector converts the detection optical signal into an electric signal and sends the electric signal to the circuit control processing system, and the second photoelectric detector converts the reference optical signal into an electric signal and sends the electric signal to the circuit control processing system.
S300, the circuit control processing system compares the detection results of the two paths of optical signals (namely the results of the two paths of optical signals), and the detection results of the optical signals passing through the open-circuit environment are calibrated and calibrated according to the detection results of the optical signals passing through the standard air chamber. The method calibrates and calibrates the product value of the gas concentration and the length corresponding to the optical signal passing through the open-circuit environment through the product value of the standard gas concentration and the length corresponding to the optical signal passing through the standard gas chamber.
In the process, the two paths of photoelectric detectors respectively receive the optical signal passing through the open-circuit environment and the optical signal passing through the standard air chamber, so that synchronous same-frequency acquisition of the two paths of optical detection signals is realized; and the corresponding optical signal is converted into an electric signal, the electric signal is amplified by a small signal amplifying circuit, then the related characteristic information of the electric signal is extracted, and comparison calculation is carried out to obtain the information of the product value of the concentration and the length of the gas to be measured in the open-circuit environment after the calibration of the standard gas chamber.
In an open-circuit environment, signal light with 90% of energy reaches the reflector through the open-circuit environment, and is reflected by the reflector to be detected by the first photoelectric detector. When the gas to be detected does not exist in the open-circuit environment, the detected electric signal is always at a high level, and the product value of the corresponding gas concentration and the length is 0; when the gas to be detected leaks in the open-circuit environment, the intensity of the optical signal of the laser at the central wavelength of the absorption peak of the gas to be detected is reduced, so that the detection result is similar to that of the reference light path, most of the electrical signals detected by the first photoelectric detector in the open-circuit environment are high-level signals, and a periodic low-level signal appears in the middle. The amount of change of the low level signal with respect to the high level signal at this time can be detected and extracted by the signal photodetector and the circuit system.
Since the length of the standard gas chamber and the gas concentration are determined and known, the product of the reference gas concentration to be measured and the length is fixed, and the variation of the low-level signal detected by the reference photoelectric detector and the signal photoelectric detector relative to the high-level signal is analyzed and calculated through a fitting function. Specifically, when calculating the product value of the concentration and the length of the gas to be measured in the open-circuit environment, the specific calculation data expression is as follows:
wherein C is1Is the concentration of the gas to be measured in an open-circuit environment, L1Is the length value, C, that the gas to be measured in the open-circuit environment passes through0Is the concentration of the gas to be measured in the standard gas chamber, L0Is the length of the standard gas cell, the f () function is the fitting function, X1X is the variation of the low level signal relative to the high level signal of the signal light (the variation of the absorption peak light intensity relative to the initial light intensity), and0the amount of change of the low level signal relative to the high level signal (the amount of change of the absorption peak light intensity relative to the initial light intensity) of the reference light.
The f () function is obtained by fitting experimental data, which is related to the absorption coefficient of each gas in different absorption spectra, and due to C0、L0Is known as X1And X0The product value of the concentration and the length of the gas to be detected in the open-circuit environment can be accurately obtained in real time through the calculation expression.
According to the invention, the standard air chamber is added in the system for reference, so that the automatic calibration and calibration of the reflective laser open-circuit gas detection system can be realized, the stability and accuracy of the whole system are ensured, and the problems that the open-circuit laser gas detection system is difficult to calibrate and is frequently calibrated are effectively solved, thereby reducing the burden of maintenance and after-sales engineers and reducing the use of manpower and material resources.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
The invention is described above with reference to the accompanying drawings, which are illustrative, and it is obvious that the implementation of the invention is not limited in the above manner, and it is within the scope of the invention to adopt various modifications of the inventive method concept and technical solution, or to apply the inventive concept and technical solution to other fields without modification.
Claims (10)
1. An automatic calibration open-circuit laser gas detection device, which comprises an optical path system and a circuit control processing system connected with the optical path system, and is characterized in that,
the optical path system comprises a laser, an optical fiber coupler, a standard air chamber, a first photoelectric detector connected with an open-circuit environment and a second photoelectric detector connected with the standard air chamber, wherein standard gas is sealed in the standard air chamber, working wavelength laser emitted by the laser is split by the optical fiber coupler to form signal light and reference light, the signal light is incident to the first photoelectric detector after passing through the open-circuit environment, and the reference light is incident to the second photoelectric detector after passing through the standard air chamber;
the circuit processing system is connected with the laser and drives the laser to emit working wavelength laser, and the circuit processing system is connected with the first photoelectric detector and the second photoelectric detector and realizes real-time automatic calibration of the product value of the concentration and the length of the gas to be measured in the open-circuit environment through the product value of the concentration and the length of the gas in the standard gas chamber.
2. The self-calibrating, open-path laser gas detection device of claim 1, wherein the laser is fusion spliced to the fiber coupler.
3. The self-calibrating open laser gas detection device according to claim 1, wherein the optical system further comprises a wavelength division multiplexer and a visible light source, the optical fiber coupler and the visible light source are all connected with the wavelength division multiplexer through optical fiber fusion, the signal light output by the optical fiber coupler is connected with one input end of the wavelength division multiplexer, the visible light source emits the laser light with the indicated wavelength and is connected with the other input end of the wavelength division multiplexer, the wavelength division multiplexer is configured to combine the signal light and the laser light with the indicated wavelength and output the combined light with the optical fiber, and the combined light irradiates the open environment.
4. The self-calibrating open laser gas sensor according to claim 3, wherein a parabolic mirror is disposed at the light incident end of the open environment, and the composite light output from the wavelength division multiplexer and the optical fiber is reflected by the parabolic mirror and then collimated into the open environment.
5. The apparatus according to claim 1, wherein the light collimating and incident end and the light receiving end of the open-circuit environment are both located on the same side, and a reflector is disposed on the other side of the open-circuit environment, so that the light collimated and incident to the open-circuit environment is reflected by the reflector and then incident to the first photodetector of the receiving end.
6. The self-calibrating open laser gas detection device according to claim 1, wherein the standard gas is a pure test gas or a mixture of a test gas and an inert gas.
7. The self-calibrating, open-path laser gas detection device of claim 1, wherein the circuit control processing system comprises a modulation circuit for controlling the laser wavelength generated by the laser to automatically scan within the central wavelength range of the absorption peak of the gas to be detected.
8. An implementation method for automatically calibrating open-circuit laser gas detection is characterized by comprising the following steps:
s100, controlling a laser to emit a laser signal by a circuit control processing system;
s200, respectively acquiring an optical signal of a laser signal passing through an open-circuit environment and an optical signal of the laser signal passing through a standard air chamber;
s300, comparing detection results of the two paths of optical signals, and calibrating the detection result of the optical signal passing through the open-circuit environment through the detection result of the optical signal passing through the standard air chamber.
9. The method for implementing automatic calibration open laser gas detection according to claim 8, wherein in step S100, the modulation circuit in the circuit control processing system controls the laser wavelength scanning to implement the automatic reciprocating scanning of the laser wavelength near the central wavelength of the absorption peak of the gas to be detected; the working wavelength laser emitted by the laser is respectively sent to the open circuit environment and the standard air chamber through the optical fiber coupler, and the laser passing through the open circuit environment and the standard air chamber comes from the same laser light source, so that synchronous same-frequency wavelength scanning of two paths of air chamber gases is realized.
10. The method according to claim 8, wherein in step S300, two photodetectors respectively receive the optical signal passing through the open-circuit environment and the optical signal passing through the standard air chamber, and convert the corresponding optical signals into electrical signals, thereby realizing synchronous same-frequency acquisition of the two optical detection signals; and after the electric signal is amplified by the small signal amplifying circuit, extracting relevant characteristic information of the electric signal for comparison and calculation to obtain the information of the product value of the concentration and the length of the gas to be measured in the open-circuit environment, which is calibrated by the standard gas chamber.
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