Quartz enhanced photoacoustic spectrometry gas detection system embedded with off-axis resonance tube

Abstract

The utility model discloses a quartz enhanced photoacoustic spectrometry gas detection system embedded with an off-axis resonance tube, which relates to the technical field of optical fiber gas sensing and comprises a signal generator, an adder, a DFB (distributed feedback) laser, a collimator, a gas sensing device, a preamplifier, a lock-in amplifier, a data acquisition system and a computer system. One side of the signal generator is electrically connected with an adder, and one side of the adder is provided with a DFB laser. According to the gas sensing device disclosed by the utility model, a traditional resonance tube is improved into an embedded off-axis resonance tube, the DFB laser is driven by a waveform formed by superposing a high-frequency sine wave and a low-frequency sawtooth wave to generate narrow-wavelength laser of which the central wavelength is periodically changed, and the laser can scan an absorption peak of detected gas; the laser collimated by the collimator passes through the axis of the resonance tube to obtain a photoacoustic signal which is excited and enhanced by the resonance tube, so that the signal strength can be greatly improved, and the final gas detection precision can be obviously improved.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber gas sensing, in particular to a quartz-enhanced photoacoustic spectrum gas detection system embedded in an off-axis resonance tube. Background Art

[0002] With the development of society, multi-component, high-sensitivity detection of toxic and hazardous trace gases is of great significance for improving the quality of human life and the living environment. Photoacoustic spectroscopy gas detection technology is an indirect spectral detection technology based on the photoacoustic effect, which converts light energy into sound energy to detect gas concentration. Due to its advantages such as high precision and rapid response, it has attracted much attention in fields such as environmental monitoring, aerospace, and industrial production. In terms of environmental protection, the rapid development of the industrial manufacturing industry has led to increased fuel consumption and the generation of large amounts of industrial waste gas. This has caused the concentrations of gases such as carbon dioxide, carbon monoxide, and carbon disulfide in the air to rise. Therefore, monitoring toxic gases in the external environment and indoor environments has become increasingly important. In the aerospace field, the aircraft and carrier equipment used in manned space projects, such as the Chang'e Project, and manned submersibles are characterized by precise structures, high technological content, and high safety requirements. To effectively ensure the normal operation of equipment and the safety of personnel, strict real-time monitoring of trace gases is even more necessary.

[0003] In the aforementioned application areas, gas component concentrations may be at or below the part-per-million level, placing high demands on the minimum detection limit of gas sensors. Therefore, designing a trace gas sensor with an ultra-low minimum detection limit is key to achieving rapid, accurate, and effective gas concentration detection. Utility Model Content

[0004] The purpose of the utility model is to provide a quartz-enhanced photoacoustic spectroscopy gas detection system embedded in an off-axis resonance tube, so as to solve the problems raised in the above background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] A quartz-enhanced photoacoustic spectroscopy gas detection system embedded in an off-axis resonant tube comprises a signal generator, an adder, a DFB laser, a collimator, a gas sensor, a preamplifier, a lock-in amplifier, a data acquisition system, and a computer system. The system is characterized in that one side of the signal generator is electrically connected to the adder, one side of the adder is provided with a DFB laser, an output end of the DFB laser is provided with a collimator, one side of the collimator is provided with a gas sensor, the gas sensor comprises a resonant tube and a quartz tuning fork, a preamplifier is provided on the rear side of the gas sensor, the output end of the preamplifier is connected to the input end of the lock-in amplifier, the output end of the lock-in amplifier is connected to the data acquisition system, and the data acquisition system is electrically connected to the computer system.

[0007] Furthermore, the collimator is a small spot collimator with a spot diameter of 0.3 mm, and the collimator is placed at the front end of the off-axis resonant tube.

[0008] Furthermore, the resonance tube has a length of 8 mm, a height of 1 mm, an inner diameter of 1 mm, and an outer diameter of 2.8 mm, and has the function of enhancing acoustic resonance. The off-axis resonance tube and the quartz tuning fork are placed off-axis, and the side wall of the quartz tuning fork is embedded in the resonance tube. The distance between the center of the resonance tube and the center of the quartz tuning fork is 1.5 mm.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0010] The gas sensing device in the utility model is improved from a traditional resonant tube to an embedded off-axis resonant tube. The DFB laser is driven by a waveform formed by the superposition of a high-frequency sine wave and a low-frequency sawtooth wave to generate a narrow-wavelength laser with a periodic central wavelength change. The laser can scan the absorption peak of the gas to be measured. The laser, after being collimated by a collimator, passes along the axis of the resonant tube to obtain a photoacoustic signal that is enhanced by the resonant tube after excitation. This can greatly improve the signal strength, so that the final gas detection accuracy will be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the structure of a quartz-enhanced photoacoustic spectroscopy gas detection system embedded in an off-axis resonance tube;

[0012] Figure 2 This is a schematic diagram of the three-dimensional structure of a gas sensing device embedded in an off-axis resonant tube quartz-enhanced photoacoustic spectroscopy gas detection system;

[0013] Figure 3 This is a schematic diagram of the three-dimensional explosion structure of a gas sensing device embedded in an off-axis resonant tube quartz enhanced photoacoustic spectroscopy gas detection system.

[0014] In the picture:

[0015] 1. Signal generator; 2. Adder; 3. DFB laser; 4. Collimator; 5. Gas sensing device; 501. Resonance tube; 502. Quartz tuning fork; 6. Preamplifier; 7. Lock-in amplifier; 8. Data acquisition system; 9. Computer system. DETAILED DESCRIPTION

[0016] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0017] like Figure 1-3 As shown, the present invention provides a quartz enhanced photoacoustic spectroscopy gas detection system embedded in an off-axis resonant tube, comprising a signal generator 1, an adder 2, a DFB laser 3, a collimator 4, a gas sensing device 5, a preamplifier 6, a phase-locked amplifier 7, a data acquisition system 8 and a computer system 9. One side of the signal generator 1 is electrically connected to the adder 2, one side of the adder 2 is provided with the DFB laser 3, the output end of the DFB laser 3 is provided with the collimator 4, the DFB laser 3 is driven by a waveform formed by the superposition of a high-frequency sine wave and a low-frequency sawtooth wave to generate a narrow wavelength laser with a periodic change in the central wavelength, the laser light collimated by the collimator 4 passes along the axis of the resonant tube 501, and obtains a photoacoustic signal enhanced by the resonant tube 501 after excitation, the gas sensing device 5 comprises a resonant tube 501 and a quartz tuning fork 502, the current signal output by the quartz tuning fork 502 is converted into a voltage signal by the preamplifier, and the output end of the electrical signal of the quartz tuning fork 502 is connected to the input end of the preamplifier; A preamplifier 6 is provided on the rear side of the body sensing device 5. The output end of the preamplifier 6 is connected to the input end of a phase-locked amplifier 7. The phase-locked amplifier 7 is used to demodulate the voltage signal; the output end of the phase-locked amplifier 7 is connected to a data acquisition system 8, which is electrically connected to a computer system 9. The data acquisition system 8 is used to collect the demodulated voltage signal data and then transmit the data to the computer system 9 for signal processing and gas concentration calculation. In the utility model, the gas sensing device 5 is improved from the traditional resonance tube 501 to an embedded resonance tube 501. The DFB laser 3 is driven by a waveform formed by the superposition of a high-frequency sine wave and a low-frequency sawtooth wave to generate a narrow wavelength laser with a periodic central wavelength change. The laser can scan the absorption peak of the gas to be measured. The laser, after being collimated by the collimator 4, passes along the axis of the resonance tube 501 to obtain a photoacoustic signal that is enhanced by the resonance tube 501 after excitation. This can greatly improve the signal strength, so that the final gas detection accuracy will be significantly improved.

[0018] The signal generator 1 is used to generate a high-frequency sine wave and a low-frequency sawtooth wave. The adder 2 can superimpose the waveforms generated by the signal generator 1 to generate a driving waveform for wavelength modulation of the laser.

[0019] Preferably, the collimator 4 uses a small spot collimator 4 with a spot diameter of 0.3 mm, and the collimator 4 is placed at the front end of the resonance tube 501 .

[0020] Preferably, the resonance tube 501 has a length of 8 mm, a height of 1 mm, an inner diameter of 1 mm, and an outer diameter of 2.8 mm, and has the function of enhancing acoustic resonance. The resonance tube 501 and the quartz tuning fork 502 are placed off-axis, and the side wall of the quartz tuning fork 502 is embedded in the resonance tube 501. The distance between the center of the resonance tube 501 and the center of the quartz tuning fork 502 is 1.5 mm.

[0021] The preamplifier 6 converts the current signal output by the gas sensor device 5 into a voltage signal and amplifies it. The lock-in amplifier 7 demodulates the voltage signal into the second harmonic. The data acquisition system 8 collects the demodulated data and then transmits the data to the computer system 9, which finally processes the signal and calculates the gas concentration. Specific embodiment:

[0023] A photoacoustic spectroscopy gas detection system based on embedded off-axis quartz enhancement, the working steps are as follows:

[0024] S1. Signal generator 1 provides a high-frequency sine wave and a low-frequency sawtooth wave. Adder 2 superimposes the high-frequency sine wave and the low-frequency sawtooth wave to drive DFB laser 3.

[0025] S2. The laser light generated by the DFB laser 3 is then collimated by the collimator 4 and enters the resonance tube 501 and passes along the axis of the resonance tube 501 to obtain a photoacoustic signal that is enhanced by the resonance tube 501 after excitation.

[0026] S3. After the electrical signal generated by the quartz tuning fork 502 enters the preamplifier, the preamplifier 6 converts the current signal into a voltage signal and amplifies it. The phase-locked amplifier 7 demodulates the voltage signal. The data acquisition system 8 collects the demodulated voltage signal data and then transmits the data to the computer system 9 for signal processing and gas concentration calculation, ultimately completing trace gas detection.

[0027] The embodiments of the present invention are provided for purposes of illustration and description and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are selected and described to better illustrate the principles and practical applications of the present invention and to enable those skilled in the art to understand the present invention and design various embodiments with various modifications suitable for specific applications.

Claims

1. A quartz-enhanced photoacoustic spectroscopy gas detection system embedded in an off-axis resonant tube, comprising a signal generator (1), an adder (2), a DFB laser (3), a collimator (4), a gas sensor (5), a preamplifier (6), a lock-in amplifier (7), a data acquisition system (8) and a computer system (9), characterized in that: One side of the signal generator (1) is electrically connected to an adder (2), one side of the adder (2) is provided with a DFB laser (3), an output end of the DFB laser (3) is provided with a collimator (4), one side of the collimator (4) is provided with a gas sensing device (5), the gas sensing device (5) comprises a resonance tube (501) and a quartz tuning fork (502), the off-axis resonance tube (501) and the quartz tuning fork (502) are placed in an off-axis manner, a preamplifier (6) is provided on the rear side of the gas sensing device (5), the output end of the preamplifier (6) is connected to the input end of the lock-in amplifier (7), the output end of the lock-in amplifier (7) is connected to the data acquisition system (8), and the data acquisition system (8) is electrically connected to the computer system (9).

2. The quartz-enhanced photoacoustic spectroscopy gas detection system embedded in an off-axis resonance tube according to claim 1, characterized in that: The collimator (4) is a small spot collimator with a spot diameter of 0.3 mm. The collimator (4) is placed at the front end of the off-axis resonance tube (501).

3. The quartz-enhanced photoacoustic spectroscopy gas detection system embedded in an off-axis resonance tube according to claim 1, characterized in that: The resonance tube (501) has a length of 8 mm, a height of 1 mm, an inner diameter of 1 mm, and an outer diameter of 2.8 mm, and has a function of enhancing acoustic resonance. The side wall of the quartz tuning fork (502) is embedded in the resonance tube (501), and the distance between the center of the resonance tube (501) and the center of the quartz tuning fork (502) is 1.5 mm.

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