CN114034660A - Gas detection system and method based on TDLAS - Google Patents
Gas detection system and method based on TDLAS Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 74
- 238000000041 tunable diode laser absorption spectroscopy Methods 0.000 title claims abstract description 30
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 14
- 230000000694 effects Effects 0.000 description 5
- 238000010892 electric spark Methods 0.000 description 4
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- 230000031700 light absorption Effects 0.000 description 4
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- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000003245 coal Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
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- 239000004065 semiconductor Substances 0.000 description 2
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- 238000007084 catalytic combustion reaction Methods 0.000 description 1
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- 238000009792 diffusion process Methods 0.000 description 1
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- 238000005259 measurement Methods 0.000 description 1
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 1
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Abstract
The invention discloses a gas detection system and method based on TDLAS, comprising the following steps: the two ends of the gas absorption pool are provided with conductive optical fibers; a signal generator for generating a carrier signal; the laser transmitter is used for receiving the carrier signal and generating a corresponding carrier optical signal; the photoelectric detection tube is used for converting modulated optical signals carrying gas signals to be detected into photocurrents with corresponding sizes; the non-inverting input end of the operational amplifier is connected with the signal generator, and the inverting input end of the operational amplifier is connected with the cathode end of the photoelectric detection tube; and the processing module is connected with the output end of the operational amplifier to obtain the content information of the gas to be detected. The invention can improve the accuracy of the detection result: the carrier signal is counteracted through the modulated light signal carrying the information of the gas to be detected and the synchronous action of the modulated light signal and the carrier signal, and the information of the light intensity absorbed by the gas is directly obtained.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of gas detection, in particular to a TDLAS-based gas detection system and method.
[ background of the invention ]
Based on the requirements of healthy living, safe production and the like, detection of specific gases is required in many scenes, such as formaldehyde in rooms, methane in coal mines and pipelines and the like. For methane, the existing detection sensors include catalytic combustion type, semiconductor resistance type, electrochemical and infrared gas sensors, and the like, and the products need to be powered on site, so that the potential possibility of generating static electricity and electric sparks is realized; moreover, due to the characteristics of the sensor, signals cannot be transmitted over a long distance, so that the meter body cannot be far away from the site. Because methane belongs to flammable gas, when gas detection is carried out in a closed scene, explosion can be generated due to electric sparks and static electricity, and safety accidents can be caused.
In addition, in the existing TDLAS-based gas detection method, finally, when a final output signal is processed, it is difficult to demodulate the modulated signal, a plurality of complex links are required, the cost is not counted, noise is introduced in subsequent links, signal distortion and loss are caused, the post-processing data volume is large, and the detection result is not accurate enough.
Accordingly, there is a need for a TDLAS-based gas detection system and method that overcomes the above-mentioned drawbacks.
[ summary of the invention ]
The invention aims to provide a TDLAS-based gas detection system and method, which aim to fundamentally solve the problem that the gas explosion is easily caused by power supply required during detection of the existing gas detection device, greatly simplify the difficulty of later signal processing, improve the signal-to-noise ratio and the resolution ratio and improve the accuracy of a detection result.
In order to achieve the above object, the present invention provides a TDLAS-based gas detection system, comprising:
a gas absorption cell; both ends of the gas absorption cell are provided with conductive optical fibers for being placed in an environment to be detected;
the signal generator is used for controlling the power supply to generate a corresponding carrier signal according to the characteristic absorption spectrum of the gas to be detected;
the laser transmitter is used for receiving the carrier signal sent by the signal generator and generating a corresponding carrier optical signal, so that the carrier optical signal passes through the gas absorption cell through the optical fiber; wherein, the carrier optical signal is called as modulated optical signal after passing through the gas absorption cell;
the photoelectric detection tube is used for receiving the modulated optical signal of the gas to be detected in the gas absorption cell through an optical fiber far away from one end for transmitting the carrier optical signal and converting the modulated optical signal carrying the information of the gas to be detected into a photocurrent with a corresponding size;
an operational amplifier; the non-inverting input end of the operational amplifier is connected with the signal generator so as to receive the carrier signal; the inverting input end of the operational amplifier is connected with the cathode end of the photoelectric detection tube so as to receive the photocurrent;
and the processing module is connected with the output end of the operational amplifier and is used for analyzing the signal output by the operational amplifier according to a preset algorithm so as to obtain the content information of the gas to be detected in the environment to be detected.
In a preferred embodiment, the TDLAS-based gas detection system further comprises:
and the amplitude tracking module is used for carrying out fundamental wave amplitude identification according to the output signal of the operational amplifier and then correspondingly changing the gain of a channel at the non-inverting input end of the operational amplifier so as to enable the amplitude of the signal input to the non-inverting input end of the operational amplifier to be matched with the amplitude of the signal input to the inverting input end of the operational amplifier.
In a preferred embodiment, the fundamental amplitude of the output signal of the operational amplifier is identified by a preset program algorithm, and then the channel gain of the non-inverting input of the operational amplifier is changed accordingly.
In a preferred embodiment, the anode terminal of the photo-detection tube is grounded, the cathode terminal is connected with the inverting input terminal of the operational amplifier through a resistor and forms a negative feedback circuit, and the non-inverting input terminal of the operational amplifier is further connected with the output of the signal generator through a resistor network.
In a preferred embodiment, the photo detector is a PD, converts the carrier optical signal into the corresponding photocurrent, inputs the photocurrent to an inverting input terminal of the operational amplifier, performs I/V conversion, and completes signal demodulation by combining the carrier signal of the signal generator connected to a non-inverting terminal of the operational amplifier.
In a preferred embodiment, the signal generator performs impedance matching while outputting the carrier signal.
The invention also provides a TDLAS-based gas detection method, which comprises the following steps:
putting a gas absorption cell into an environment to be detected, and enabling the gas absorption cell to absorb the gas to be detected in the environment to be detected;
placing a signal generator, a laser emitter, a photoelectric detection tube, an operational amplifier and a processing module at positions far away from the environment to be detected;
the signal generator generates corresponding carrier signals according to the information of the gas to be detected and respectively sends the carrier signals to the non-inverting input ends of the laser transmitter and the operational amplifier;
the laser transmitter generates a corresponding carrier optical signal according to the carrier signal;
the carrier optical signal is transmitted to the gas absorption cell by the optical fiber, after the gas to be detected passes through the gas to be detected, the light with the specific wavelength is absorbed by the gas to be detected, the gas concentration information is modulated on the carrier signal to obtain a modulated optical signal, and then the modulated optical signal enters from the optical fiber at the other end;
the photoelectric detection tube receives the modulated optical signal carrying the information of the gas to be detected through the optical fiber at the other end, converts the modulated optical signal into corresponding photocurrent, and converts the photocurrent into corresponding voltage through an I/V converter under the potential control of a non-inverting input end of the operational amplifier;
the operational amplifier outputs a signal to the processing module;
and the processing module confirms the content of the gas to be detected in the environment to be detected according to the magnitude of the output signal.
The TDLAS-based gas detection system and method provided by the invention have the following beneficial effects:
the optical fibers are arranged at the two ends of the gas absorption cell, so that the gas absorption cell can be placed in an environment to be detected, and other equipment is placed at a position far away from the environment to be detected, so that the risk of gas explosion of the environment to be detected due to possible generation of static electricity and electric sparks during power supply of other equipment in work is avoided, and the safety of gas detection operation is improved and guaranteed;
the carrier signal generated by the signal generator is sent to the in-phase input end of the operational amplifier, the photoelectric detection tube is connected to the anti-phase input end of the operational amplifier, and the modulated light signal received by the photoelectric detection tube is generated by the laser transmitter according to the signal rule change of the carrier signal, so that the modulated light converted by the modulated light signal carrying the gas information to be detected can act synchronously with the carrier signal, the carrier signal can be counteracted, and only the light intensity information of the gas absorption carrier light signal is left, thereby greatly simplifying the difficulty of later-stage signal processing, avoiding the signal distortion and attenuation loss generated by a subsequent circuit, and greatly improving the signal-to-noise ratio. Meanwhile, interference of carrier signals is avoided during data processing, and the accuracy of detection results is improved.
[ description of the drawings ]
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic diagram of a TDLAS-based gas detection system according to the present invention;
FIG. 2 is a flow chart of a TDLAS-based gas detection method provided by the present invention;
FIG. 3 is a diagram illustrating the waveform effect of a conventional TDLAS gas detection method;
fig. 4 is a waveform comparison diagram of output signals of the operational amplifier of the conventional TDLAS gas detection method and the detection method provided by the present invention.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantageous effects of the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and the detailed description. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
In an embodiment of the present invention, a TDLAS (Tunable Diode Laser Absorption spectroscopy) -based gas detection system 100 is provided, which is used for detecting the presence or absence and the content of a gas to be detected (for example, methane, formaldehyde, and the like) in an environment to be detected (for example, a coal mine, an underground pipe gallery, a natural gas pipe network, a gas pressure regulating station, a gas boiler, a commercial and central kitchen, and the like), and improves the accuracy of a detection result on the premise of ensuring the detection safety.
As shown in fig. 1, the TDLAS-based gas detection system 100 includes a gas absorption cell 10, a signal generator 20, a laser emitter 30, a photoelectric detection tube 40, an operational amplifier 50, and a processing module 60.
Specifically, both ends of the gas absorption cell are provided with conductive optical fibers for placing in an environment to be detected. Namely, the two ends of the gas absorption cell are both provided with optical fiber ports, and laser can enter light from one of the optical fiber ports, so that the laser enters the gas absorption cell, and enters another optical fiber through the other optical fiber port to emit light after passing through the gas environment in the gas absorption cell. Different gases have different characteristic absorption spectra, when the absorption line of the gas is found in the laser wavelength range, the curve of the optical power test has a depression, the light intensity is reduced, the type and the intensity of the gas can be judged through the wavelength (related to the characteristic absorption spectrum of the gas) and the depth (related to the content of the gas in the environment) of the depression, and the higher the gas concentration is, the higher the absorbed light intensity is. Therefore, the laser light emitted from the gas absorption cell carries the gas information in the gas absorption cell. In this embodiment, the gas absorption cell may be a natural gas diffusion type or a flow type gas absorption cell, and the measurement range is 0 to 10000 ppm.
The length of the optical fiber can be 500m, 1km or 50km, so that only the gas absorption cell can be placed in the environment to be detected, other components needing power supply are placed at positions far away from the environment to be detected, the laser signal is conducted through the optical fiber, and the detection site is ensured not to use a power supply.
And the signal generator 20 is used for controlling the power supply to generate a corresponding carrier signal according to the characteristic absorption spectrum of the gas to be detected. The signal generator is used to generate a carrier current or voltage signal to the tuning signal, for example in the form of a tuned high precision dc power supply, and then to control the laser transmitter to produce a correspondingly varying laser. By way of example, the characteristic absorption spectrum of methane gas is at 1653.72nm, so the signal can be tuned to have a lasing wavelength linewidth near 1653.72nm, and as narrow as possible.
And the laser transmitter 30 is used for receiving the carrier signal sent by the signal generator and generating a corresponding carrier optical signal, so that the carrier optical signal is transmitted to the gas absorption cell through the optical fiber. Wherein the carrier optical signal is called a modulated optical signal after passing through the gas absorption cell. In the present embodiment, the laser transmitter is an LD (laser diode). Meanwhile, the laser emitter is provided with a temperature controller. The temperature controller is used for making laser emitter's temperature stabilize at preset size to make laser wavelength scanning range more stable.
The photoelectric detection tube 40 is configured to receive a carrier optical signal of the gas to be detected in the gas absorption cell through an optical fiber far from an end where the carrier optical signal is emitted, and convert the carrier optical signal carrying the gas signal to be detected into a modulated optical current (referred to as photocurrent for short) of a corresponding magnitude. In this embodiment, the photo detector is a PD (photo diode), and converts the modulated optical signal into a corresponding optical current, and then inputs the optical current to the inverting input terminal of the operational amplifier.
An operational amplifier 50; the non-inverting input of the operational amplifier is connected to the signal generator to receive the carrier signal. It will be appreciated that if the non-inverting input has the appropriate potential and the gain is appropriate, then in the non-measuring state the output of the operational amplifier will replicate the waveform of the signal generator. The inverting input end of the operational amplifier is connected with the cathode end of the photoelectric detection tube so as to receive the modulated light current, and in the receiving process, the photoelectric detection tube can perform photoelectric conversion, so that the voltage output corresponding to the modulated light current is input to the inverting input end of the operational amplifier. It should be noted that the signal waveform change of the modulated light current is changed according to the signal waveform change generated by the signal generator in a synchronous rule, but the light intensity of the modulated light signal is reduced after the modulated light signal is absorbed by the gas. Therefore, in the operational amplifier, the original carrier signal received by the non-inverting input end and the modulated signal received by the inverting input end after gas absorption act synchronously, so that the carrier signal is offset, and only the signal change information caused by the gas absorption light intensity is carried by the output end.
Specifically, the anode end of the photoelectric detection tube is grounded, the cathode end of the photoelectric detection tube is connected with the inverting input end of the operational amplifier, a negative feedback circuit is formed by the resistor and the operational amplifier, and the non-inverting input end of the operational amplifier is further connected to the output of the signal generator through a resistor network.
Wherein the signal generator performs impedance matching when outputting the carrier signal. It should be noted that, after a carrier optical signal emitted by the laser emitter is absorbed by the photoelectric detection tube through the gas absorption cell, the carrier optical signal is compared with a carrier signal generated by the signal generator, one path is optical transmission, and the other path is directly used, which do not generate a delay to cause a phase shift, but because the optical attenuation and the parameters of the operational amplifier are different, the amplitudes of the optical attenuation and the operational amplifier may not be the same, which may cause that the carrier signal cannot be completely cancelled out, thereby affecting the detection effect.
Accordingly, the TDLAS based gas detection system also includes an amplitude tracking module. And the amplitude tracking module is used for identifying the amplitude of the fundamental wave according to the output signal (which can be independently collected or can be directly taken and received by the processing module) of the operational amplifier, judging whether the following potential is overcompensated or undercompensated, and correspondingly changing the gain of a channel at the non-inverting input end of the operational amplifier to ensure that the amplitude of the signal input to the non-inverting input end of the operational amplifier is consistent with the amplitude of the modulated signal input to the inverting input end of the operational amplifier, thereby achieving the purpose of completely offsetting the carrier signal. After the circuit parameters of the whole system are set, no intervention is needed in normal operation, and the circuit parameters can be maintained regularly or after long-term use, and can be calibrated in an auxiliary mode through an amplitude tracking module. Specifically, in an embodiment, the fundamental amplitude identification is performed on the output signal of the operational amplifier through a preset program algorithm, and then the channel gain of the non-inverting input terminal of the operational amplifier is changed accordingly, and the specific program algorithm may refer to the existing fundamental amplitude identification and channel gain change algorithm, which is not limited herein.
And the processing module 60 is connected with the output end of the operational amplifier and is used for analyzing the signal output by the operational amplifier according to a preset algorithm so as to obtain the content information of the gas to be detected in the environment to be detected. The processing module may be a device having a data processing capability such as a CPU (central processing unit). It should be noted that, since the method has extracted the valid signal completely and losslessly, the algorithm for processing the waveform signal by the processing module may refer to the prior art, and the present invention is not limited herein.
The present invention further provides a TDLAS-based gas detection method, which is performed based on the TDLAS-based gas detection system 100, and the implementation principles are consistent, so that the details are not repeated herein.
As shown in fig. 2, the TDLAS-based gas detection method includes the following steps S101-S108.
Step S101, placing a gas absorption tank into an environment to be detected, and enabling the gas absorption tank to absorb gas to be detected in the environment to be detected;
step S102, placing a signal generator, a laser emitter, a photoelectric detection tube, an operational amplifier and a processing module at a position far away from an environment to be detected;
step S103, the signal generator generates corresponding carrier signals according to the information of the gas to be detected and sends the carrier signals to the non-inverting input ends of the laser emitter and the operational amplifier respectively;
step S104, the laser transmitter generates a corresponding carrier optical signal according to the carrier signal;
step S105, the carrier optical signal is transmitted to a gas absorption cell by the optical fiber, after the gas to be detected passes through and the light with the specific wavelength is absorbed by the gas to be detected, the gas concentration information is modulated on the carrier optical signal to obtain a modulated optical signal, and then the modulated optical signal enters from the optical fiber at the other end;
step S106, the photoelectric detection tube receives a modulated light signal carrying information of the gas to be detected through the optical fiber at the other end, and converts the modulated light signal into corresponding photocurrent which is converted into corresponding voltage through an I/V converter under the potential control of the non-inverting input end of the operational amplifier;
step S107, the operational amplifier outputs signals to the processing module;
and S108, confirming the content of the gas to be detected in the environment to be detected by the processing module according to the size of the output signal.
For example, in fig. 3, the conventional gas detection waveform effect is shown, the upper waveform is the carrier signal of the signal generator, and the lower waveform is the output information of the operational amplifier with light absorption information, which is obviously very hidden in the waveform. Fig. 4 shows the waveform effect obtained by the detection method provided by the present invention, the original carrier signal and the carrier signal after light absorption simultaneously act on the non-inverting and inverting input terminals of the operational amplifier to cancel out the carrier signal, and useful information is extracted, the upper waveform is the output signal of the operational amplifier with light absorption information obtained by the conventional detection method, and the lower straight line is the output signal of the operational amplifier after the carrier signal is eliminated. It should be noted that, for the sake of clarity, the waveform parameters are not practical parameters, for example, the light absorption signal is replaced by a pulse train, the amplitude is the same as the sine wave, and the frequency is three times that of the triangle wave.
In summary, in combination with the above embodiments, the TDLAS-based gas detecting system 100 and method provided by the present invention at least have the following advantages:
the optical fibers are arranged at the two ends of the gas absorption cell, so that the gas absorption cell can be placed in an environment to be detected, and other equipment is placed at a position far away from the environment to be detected, so that the risk of gas explosion of the environment to be detected due to possible generation of static electricity and electric sparks during power supply of other equipment in work is avoided, and the safety of gas detection operation is improved and guaranteed;
the carrier signal generated by the signal generator is sent to the in-phase input end of the operational amplifier, the photoelectric detection tube is connected to the anti-phase input end of the operational amplifier, and the modulated light signal received by the photoelectric detection tube is generated by the laser transmitter according to the signal rule change of the carrier signal, so that the modulated light converted by the modulated light signal carrying the gas information to be detected can act synchronously with the carrier signal, the carrier signal can be counteracted, and only the light intensity information of the gas absorption carrier light signal is left, thereby greatly simplifying the difficulty of later-stage signal processing, avoiding the signal distortion and attenuation loss generated by a subsequent circuit, and greatly improving the signal-to-noise ratio. Meanwhile, interference of carrier signals is avoided during data processing, and the accuracy of detection results is improved.
Those of ordinary skill in the art will appreciate that the various illustrative elements and method steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The invention is not limited solely to that described in the specification and embodiments, and additional advantages and modifications will readily occur to those skilled in the art, so that the invention is not limited to the specific details, representative apparatus, and illustrative examples shown and described herein, without departing from the spirit and scope of the general concept as defined by the appended claims and their equivalents.
Claims (7)
1. A TDLAS-based gas detection system, comprising:
a gas absorption cell; both ends of the gas absorption cell are provided with conductive optical fibers for being placed in an environment to be detected;
the signal generator is used for controlling the power supply to generate a corresponding carrier signal according to the characteristic absorption spectrum of the gas to be detected;
the laser transmitter is used for receiving the carrier signal sent by the signal generator and generating a corresponding carrier optical signal, so that the carrier optical signal passes through the gas absorption cell through the optical fiber; wherein, the carrier optical signal is called as modulated optical signal after passing through the gas absorption cell;
the photoelectric detection tube is used for receiving the modulated optical signal of the gas to be detected in the gas absorption cell through an optical fiber far away from one end for transmitting the carrier optical signal and converting the modulated optical signal carrying the information of the gas to be detected into a photocurrent with a corresponding size;
an operational amplifier; the non-inverting input end of the operational amplifier is connected with the signal generator so as to receive the carrier signal; the inverting input end of the operational amplifier is connected with the cathode end of the photoelectric detection tube so as to receive the photocurrent;
and the processing module is connected with the output end of the operational amplifier and is used for analyzing the signal output by the operational amplifier according to a preset algorithm so as to obtain the content information of the gas to be detected in the environment to be detected.
2. The TDLAS-based gas detection system as defined in claim 1, further comprising:
and the amplitude tracking module is used for carrying out fundamental wave amplitude identification according to the output signal of the operational amplifier and then correspondingly changing the gain of a channel at the non-inverting input end of the operational amplifier so as to enable the amplitude of the signal input to the non-inverting input end of the operational amplifier to be matched with the amplitude of the signal input to the inverting input end of the operational amplifier.
3. The TDLAS-based gas detection system as recited in claim 2, wherein fundamental amplitude identification is performed on the output signal of the operational amplifier through a pre-programmed algorithm, and then channel gain of the non-inverting input of the operational amplifier is changed accordingly.
4. The TDLAS-based gas detection system as recited in claim 1, wherein an anode terminal of the photo-detection tube is grounded, a cathode terminal is connected to an inverting input terminal of the operational amplifier through a resistor and forms a negative feedback circuit, and a non-inverting input terminal of the operational amplifier is further connected to an output of the signal generator through a resistor network.
5. The TDLAS-based gas detection system as claimed in claim 1, wherein the photo detector is PD, and after converting the carrier optical signal into the corresponding optical current, the optical signal is inputted to the inverting input terminal of the operational amplifier for I/V conversion, and then the signal demodulation is performed by combining the carrier signal of the signal generator connected to the non-inverting terminal of the operational amplifier.
6. The TDLAS-based gas detection system as defined in claim 1, wherein the signal generator is impedance matched in outputting the carrier signal.
7. A TDLAS-based gas detection method is characterized by comprising the following steps:
putting a gas absorption cell into an environment to be detected, and enabling the gas absorption cell to absorb the gas to be detected in the environment to be detected;
placing a signal generator, a laser emitter, a photoelectric detection tube, an operational amplifier and a processing module at positions far away from the environment to be detected;
the signal generator generates corresponding carrier signals according to the information of the gas to be detected and respectively sends the carrier signals to the non-inverting input ends of the laser transmitter and the operational amplifier;
the laser transmitter generates a corresponding carrier optical signal according to the carrier signal;
the carrier optical signal is transmitted to the gas absorption cell by the optical fiber, after the gas to be detected passes through the gas to be detected, the light with the specific wavelength is absorbed by the gas to be detected, the gas concentration information is modulated on the carrier signal to obtain a modulated optical signal, and then the modulated optical signal enters from the optical fiber at the other end;
the photoelectric detection tube receives the modulated optical signal carrying the information of the gas to be detected through the optical fiber at the other end, converts the modulated optical signal into corresponding photocurrent, and converts the photocurrent into corresponding voltage through an I/V converter under the potential control of a non-inverting input end of the operational amplifier;
the operational amplifier outputs a signal to the processing module;
and the processing module confirms the content of the gas to be detected in the environment to be detected according to the magnitude of the output signal.
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