A laser spectroscopy device for trace monitoring of acetylene in oil based on a tuning fork

Abstract

The present application relates to a kind of laser spectroscopy devices based on oil in trace monitoring of acoustic pick-up, photoacoustic detection module, signal processing module and reset module;Degassing module: for separating out from insulating oil the sample gas to be measured containing acetylene, comprising: degassing oil tank: the cylindrical sealed cavity of top opening, the bottom of cavity is equipped with stirring motor, heating rod is wound outside, the inner wall of cavity is equipped with float oil level gauge, top is equipped with first gas port and second gas port.High-precision detection: using 1531.6nm center wavelength DFB laser, accurately match acetylene strong absorption peak, avoid coexisting gas interference;Collaborate 32.768kHz high Q value tuning fork sensor, combined with lock-in amplification technology, signal-to-noise ratio is improved 10-15 times, can realize 0.1ppm grade trace acetylene detection.

Description

Technical Field

[0001] This invention belongs to the field of acetylene trace monitoring, specifically a laser spectrometer for monitoring acetylene traces in oil based on a tuning fork. Background Technology

[0002] Oil-immersed power transformers are core equipment in power systems, and their safe and stable operation directly determines the reliability of power supply. When faults such as overheating or arc discharge occur inside the transformer, the insulating oil and insulating paper undergo a cracking reaction, producing characteristic gases such as acetylene, methane, and ethane. Among these, acetylene is a hallmark gas for severe arc discharge faults, and its concentration change directly reflects the severity of the fault. Therefore, high-precision, continuous online monitoring of trace acetylene in insulating oil, whose concentration is usually below 1 ppm, is a key means of achieving early warning of transformer faults.

[0003] Current mainstream acetylene monitoring technologies have significant drawbacks: 1. Gas chromatography: Although it is the standard for laboratory testing, the equipment is large, requires regular maintenance, and has a long testing cycle, usually >1 hour, which cannot meet the needs of online real-time monitoring. 2. Near-infrared direct absorption spectroscopy: Acetylene's absorption peak in the near-infrared band is overtone absorption, with weak signal intensity and is easily interfered with by coexisting gases such as methane and ethane, resulting in a low signal-to-noise ratio for trace detection. 3. Traditional photoacoustic spectroscopy devices use microphones as acoustic sensors, which have inherently high noise and poor resistance to environmental vibration, requiring complex sound insulation and vibration reduction structures; moreover, the photoacoustic gas chamber is large in volume and requires a large amount of sample gas, resulting in slow system response and difficulty in modular integration.

[0004] In the existing technology, there is a lack of a trace acetylene monitoring device that is compact, highly sensitive, has strong anti-interference ability and is suitable for online monitoring. Therefore, a laser spectroscopic device for monitoring trace acetylene in oil based on a tuning fork is proposed. Utility Model Content

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] Given the following technical problems in the existing technology: traditional photoacoustic spectroscopy devices use microphones as acoustic sensors, which have high inherent noise and poor resistance to environmental vibration, requiring complex sound insulation and vibration reduction structures; and the photoacoustic gas chamber is large in volume, usually >10ml, requiring a large amount of sample gas, resulting in slow system response and difficulty in modular integration.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a laser spectrometer for monitoring trace amounts of acetylene in oil based on a tuning fork, comprising a degassing module, a photoacoustic detection module, a signal processing module and a reset module; Degassing module: Used to separate acetylene-containing test gas from insulating oil, including: Degassed oil tank: It is a cylindrical sealed cavity with an open top. A stirring motor is installed at the bottom of the cavity, and a heating rod with a power of 50-100W is wrapped around the outside. A float oil level gauge with a range of 0-500ml is installed on the inner wall of the cavity, and a first air port and a second air port are installed at the top. Oil inlet assembly: includes an oil inlet pump with a flow rate of 1500ml / min and an oil inlet pipeline. One end of the oil inlet pump is connected to the transformer body oil circuit through the oil inlet pipeline, and the other end is connected to the oil inlet at the bottom of the degassed oil tank through the oil inlet pipeline. Vacuum assembly: includes an air pump and a first three-way valve. The air pump has both suction and air pumping functions, with a vacuum degree ≤100Pa. The first port of the first three-way valve is connected to the first air port on the top of the degassed oil tank through an air pipe, the second port is connected to the air pump through an air pipe, and the third port is connected to an external clean air source through an air pipe. Pressure sensor: Fixed to the inner wall of the top of the degassed oil tank, used to measure the gas pressure inside the tank in the range of 0-101kPa, and the signal output terminal is connected to the signal processing module through a wire.

[0008] Photoacoustic detection module: Used for the spectroscopic detection of acetylene in the sample gas, including: Photoacoustic air chamber: It is a miniature sealed cavity with a volume of 1-2ml. The photoacoustic air chamber is made of quartz glass. One end of the cavity has an air inlet and the other end has an air outlet. A tuning fork sensor is fixed in the center of the cavity. Tuning fork sensor: It is a quartz material through-hole structure with a natural resonant frequency of 32.768kHz. The pins are passed through the outer wall of the photoacoustic chamber by wires and connected to the signal processing module. Laser components: include a distributed feedback laser, which includes a DFB laser and a laser driving circuit. The center wavelength of the DFB laser is 1531.6nm, and the output end is aligned with the entrance window of the photoacoustic gas chamber. The signal input end of the laser driving circuit is connected to the signal processing module, and the output end is connected to the DFB laser through a wire. Gas path switching component: includes a second three-way valve, the first port of the second three-way valve is connected to the second gas port on the top of the degassed oil tank through a gas pipe, the second port is connected to the air inlet of the photoacoustic gas chamber through a gas pipe, and the third port is connected to the outside atmosphere through a gas pipe.

[0009] Signal processing module: Used to control the operation of each module and process detection signals, including: Main control chip: STM32F4 series microcontroller is used. The pins are connected to the float oil level gauge, pressure sensor, heating rod, stirring motor, oil pump, air pump, first three-way valve, second three-way valve and laser drive circuit through wires respectively. Lock-in amplifier: Model SR830. The signal input terminal is connected to the pin of the tuning fork sensor via a wire, the reference signal input terminal is connected to the main control chip via a wire, and the signal output terminal is connected to the main control chip via a wire. Storage unit: It adopts an AT24C64E EPROM chip, which is connected to the main control chip via I2C bus to store calibration parameters (zero-point offset, slope ratio). Human-machine interaction unit: includes an LCD display screen, which is connected to the main control chip via an SPI bus, and is used to display concentration data and set monitoring parameters.

[0010] Reset Module: Used to restore the initial state after a single monitoring cycle, including: Purging Component: Shares an air pump, a first three-way valve, and a second three-way valve with the photoacoustic detection module. Clean air is pumped in through the air pump to purge the photoacoustic chamber; Oil Return Component: Includes an oil return pump with a flow rate set to 1500 ml / min and an oil return pipeline. One end of the oil return pump is connected to the oil outlet at the bottom of the degassed oil tank through the oil return pipeline, and the other end is connected to the transformer body's oil return line through the oil return pipeline.

[0011] Mechanical assembly: Fix a 500ml degassed oil tank to the left side of the machine box, fix a 1ml photoacoustic gas chamber to the right side of the machine box, and fix the oil inlet pump, oil return pump, and air pump to the bottom of the machine box; fix the tuning fork sensor to the center of the photoacoustic gas chamber with bolts, fix the DFB laser to the bracket, and the distance between the light output end and the incident window of the photoacoustic gas chamber is 5mm. Air circuit connection: The oil inlet pump is connected to the transformer oil circuit and the oil inlet of the degassed oil tank through a φ6mm oil-resistant hose; the first three-way valve is connected to the first air port of the degassed oil tank, the air pump, and the clean air source through a φ4mm air pipe; the second three-way valve is connected to the second air port of the degassed oil tank, the air inlet of the photoacoustic air chamber, and the outside atmosphere through a φ4mm air pipe; the return oil pump is connected to the oil outlet of the degassed oil tank and the transformer return oil circuit through a φ6mm oil-resistant hose; Circuit connections: The main control chip is connected via wires to the float level gauge, the MPX5010 pressure sensor, the 80W heating rod, the 12V rated voltage stirring motor, the 12V rated voltage oil pump, the 12V rated voltage air pump, the first three-way valve, and the second three-way valve, all of which are electromagnetic. The input of the SR830 lock-in amplifier is connected to the AB32768 tuning fork sensor, and the output is connected to the main control chip. The storage unit is AT24C64, and the LCD display is connected to the main control chip via the SPI bus.

[0012] With parameters of "air chamber volume 1-2ml, delivery rate 1ml / s", the air pump's operating time must be fixed at 2 seconds. 2 seconds × 1 ml / s = 2 ml of sample gas, which is exactly 1-2 times the volume of the gas chamber. For example, if the volume of the gas chamber is 1 ml, filling it with 2 ml can completely replace the residue; if the volume is 2 ml, filling it with 2 ml can completely fill the chamber. Compared to longer durations, such as 3 seconds, 2 seconds avoids excessive sample gas leading to increased chamber pressure and exceeding standard atmospheric pressure, thus preventing disruption to the stability of the photoacoustic effect. Compared to shorter durations, such as 1.5 seconds, 2 seconds ensures complete sample gas filling, preventing residual gas from diluting the acetylene concentration. Detection only occurs after the gas in the photoacoustic chamber has lost its initial kinetic energy and reached a steady state. During reset, the main control chip switches the second three-way valve to the "photoacoustic chamber - external atmosphere" path, while the first three-way valve switches to the "clean air source - air pump" path. After the air pump starts, clean air, filtered by the filter element and free of acetylene and solid impurities, is pumped into the photoacoustic chamber, and residual sample gas is discharged from the outlet in a "forward flushing" manner. Key parameters: The purge gas volume is "more than 10 times the gas chamber volume" (gas chamber volume 1-2ml, purge volume 20-30ml), and "intermittent purging" is used, with pumping for 2 seconds and stopping for 1 second, and the cycle is repeated 3 times - this design can ensure that the residual sample gas in every corner of the gas chamber is flushed out, avoiding "dead corner residue".

[0013] The beneficial effects of the laser spectrometer for monitoring trace amounts of acetylene in oil based on a tuning fork according to the present invention are as follows: High-precision detection: A DFB laser with a center wavelength of 1531.6nm is used to accurately match the strong absorption peak of acetylene and avoid interference from coexisting gases; Combined with a 32.768kHz high-Q tuning fork sensor and lock-in amplification technology, the signal-to-noise ratio is improved by 10-15 times, and trace acetylene detection at the level of 0.1ppm can be achieved; Compact structure: The photoacoustic gas chamber has a volume of only 1-2ml, and the degassing oil tank, laser components, and signal processing module can be integrated into a 300×200×150mm chassis, making it suitable for the limited installation space of transformer sites; Practical and reliable: Through the coordinated degassing of heating, stirring and depressurization, the sample gas separation efficiency is improved by 20%; the reset module realizes the automation of sample gas purging and oil sample return; Cost-controllable: The tuning fork sensor replaces the traditional microphone and complex vibration reduction structure, reducing the overall cost of the device and facilitating mass production and application. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 : Overall structural block diagram of this utility model; Figure 2 Schematic diagram of the photoacoustic gas chamber structure of this utility model Figure 1 ; Figure 3 Schematic diagram of the photoacoustic gas chamber structure of this utility model Figure 2 .

[0015] Figure reference numerals: 1-Degassed oil tank; 2-Stirring motor; 3-Heating rod; 5-Oil inlet pump; 6-Air pump; 7-First three-way valve; 9-Photoacoustic gas chamber; 10-Tuning fork sensor; 11-DFB laser; 13-Second three-way valve; 14-Main control chip; 15-Lock-in amplifier; 17-LCD display screen; 18-Return oil pump; 19-Stirring rod; 20-Transformer; 21-Air inlet; 22-Exhaust port. Detailed Implementation

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0018] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0019] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0020] like Figures 1-3As shown, this invention proposes a laser spectroscopy device for monitoring trace amounts of acetylene in oil based on a tuning fork, comprising a degassing module, a photoacoustic detection module, a signal processing module, and a reset module; The degassing module includes a degassing oil tank 1, an oil inlet assembly, a vacuum assembly, and a pressure sensor. The oil inlet assembly includes an oil inlet pump 5, and the vacuum assembly includes an air pump 6 and a first three-way valve 7. The inner wall of the degassing oil tank 1 is equipped with a float oil level gauge, the outer side is equipped with a heating rod 3, and the inner side is equipped with a stirring motor 2 and a stirring rod 19. The photoacoustic detection module includes a photoacoustic chamber 9, a tuning fork sensor 10, a laser component, and a gas path switching component. The laser component includes a DFB laser 11, which extends into one end of the photoacoustic chamber 9. The gas path switching component includes a second three-way valve 13. The photoacoustic chamber 9 is provided with an air inlet 21 and an air outlet 22. The tuning fork sensor 10 is fixed in the middle of the inside of the photoacoustic chamber 9. The signal processing module includes a main control chip 14 and a lock-in amplifier 15. The input terminal of the lock-in amplifier 15 is connected to the tuning fork sensor 10, and the output terminal is connected to the main control chip 14. The reset module includes a purging assembly and an oil return assembly. The purging assembly shares an air pump 6, a first three-way valve 7, and a second three-way valve 13 with the photoacoustic detection module. The oil return assembly includes an oil return pump 18 and an oil return pipeline. The degassed oil tank 1 is connected to the transformer 20 through an oil circuit.

[0021] The degassed oil tank 1 is a cylindrical sealed cavity with a volume of 500ml. It has a first air port and a second air port at the top, and an oil inlet and an oil outlet at the bottom. The oil inlet is connected to the oil pump 5 through a pipeline, and the oil outlet is connected to the return oil pump 18 through a pipeline.

[0022] The laser assembly includes a distributed DFB laser 11 and a laser driving circuit. The center wavelength of the DFB laser 11 is 1531.6 nm, and the modulation frequency output by the laser driving circuit is 16.384 kHz. The light-emitting end of the DFB laser 11 is aligned with the incident window of the photoacoustic gas chamber 9.

[0023] The tuning fork sensor 10 is made of quartz and has a natural resonant frequency of 32.768kHz. Its pins pass through the outer wall of the photoacoustic chamber 9 via wires and are connected to the lock-in amplifier 15.

[0024] The internal chamber of the photoacoustic gas chamber 9 is a miniature sealed cavity with a volume of 1-2 ml, symmetrically distributed on both sides of the photoacoustic gas chamber 9. The exhaust port 22 of the photoacoustic gas chamber 9 is connected to the second three-way valve 13 through a pipeline, and the exhaust port 22 is connected to the external atmosphere through the second three-way valve 13.

[0025] The vacuum assembly includes an air pump 6 and a first three-way valve 7. The air pump 6 has both pumping and air-blowing functions, with a vacuum degree ≤100Pa. The first three-way valve 7 is electromagnetic and can switch between the "degassed oil tank 1-air pump 6" and "clean air source-air pump 6" paths.

[0026] The gas path switching component includes a second three-way valve 13, which is electromagnetic and can switch between the "degassed oil tank 1 - photoacoustic gas chamber 9" and "photoacoustic gas chamber 9 - external atmosphere" paths.

[0027] The signal processing module also includes a human-computer interaction unit, which includes an LCD display screen 17 and buttons, and is connected to the main control chip 14 via an SPI bus.

[0028] The oil return component of the reset module includes an oil return pump 18 and an oil return pipeline. The oil return pump 18 has a flow rate of 1500 ml / min and is connected to the oil outlet of the degassed oil tank 1 and the transformer 20 through the oil return pipeline.

[0029] The heating rod 3 of the degassing module is located in the middle of the degassing oil tank 1 and has a power of 50-100W. The stirring motor 2 has a speed of 1000-2000rpm and the power output end of the stirring motor 2 is fixedly connected to the stirring rod 19.

[0030] A heat-resistant ceramic baffle is provided on the surface of the photoacoustic gas chamber 9 corresponding to the DFB laser 11. The heat-resistant ceramic baffle can absorb the laser light from the DFB laser 11.

[0031] The laser beam from the DFB laser 11 passes through the space between the two detection rods of the tuning fork sensor 10.

[0032] The laser drive circuit is electrically connected to the main control chip 14.

[0033] The specific implementation method includes the following process: S1. Oil sample degassing: The main control chip 14 controls the start of the oil inlet pump 5 to extract the insulating oil of the transformer 20 until the liquid level of the degassing oil tank 1 reaches 375ml. The float oil level gauge triggers a signal, and the oil inlet pump 5 stops. The heating rod 3 starts and heats the oil sample to 60±1℃ through PID control, and holds the temperature for 1 minute. The first three-way valve 7 switches to the "degassing oil tank 1-air pump 6" passage, and the air pump 6 starts to pump air. When the pressure sensor detects that the air pressure in the tank drops to 4000Pa, the air pump 6 stops. The stirring motor 2 starts and is set to a speed of 1500rpm, driving the stirring rod 19 to stir for 5 minutes. Acetylene escapes from the oil and forms the sample gas to be tested at the top of the degassing oil tank 1.

[0034] S2. Sample Gas Detection: The second three-way valve 13 switches to the "Degassed Oil Tank 1 - Photoacoustic Gas Chamber 9" path, and the first three-way valve 7 switches to the "Clean Air Source - Air Pump 6" path. The air pump 6 starts pumping air, pushing the sample gas to be tested into the photoacoustic gas chamber 9 with a pushing volume of 2ml. Then the air pump 6 stops, and the second three-way valve 13 closes. The laser drive circuit of model DFB-LD-DR1550 starts, providing a 50mA DC current and a 16.384kHz modulation current to the DFB laser 11. The laser passes through the incident window of the photoacoustic gas chamber 9 and irradiates the sample gas to be tested. Acetylene molecules absorb the laser energy and generate a 32.768kHz sound pressure wave, triggering the resonance of the tuning fork sensor 10 in the photoacoustic gas chamber 9. The tuning fork sensor 10 outputs a microvolt-level electrical signal. The lock-in amplifier 15 processes the electrical signal output by the tuning fork sensor 10, extracts the DC voltage amplitude, and the DC voltage amplitude characterizes the acetylene concentration, which is then transmitted to the main control chip 14.

[0035] S4. Concentration Calculation: The main control chip 14 reads the calibration parameters, the zero-point offset b=0.02V and the slope ratio a=0.05ppm / V from the storage unit; according to the formula C2H2 concentration=a×amplitude+b, the acetylene concentration in the sample gas to be tested is calculated. For example, when the amplitude is 0.5V, the concentration = 0.05×0.5+0.02=0.045ppm; the concentration data is displayed on the LCD screen 17 and stored in the storage unit, and is also uploaded to the background monitoring system.

[0036] S5. Reset Preparation: The second three-way valve 13 is switched to the "Photoacoustic Chamber 9 - External Atmosphere" passage, and the first three-way valve 7 is switched to the "Clean Air Source - Air Pump 6" passage. The air pump 6 is started, and clean air is pumped in to purge the photoacoustic chamber 9. The cycle of "pumping air for 2 seconds - stopping for 1 second" is repeated 3 times. Then the air pump 6 is stopped, and the second three-way valve 13 is closed. The return oil pump 18 is started, and the oil sample in the degassed oil tank 1 is returned to the transformer 20. After the return is completed, the return oil pump 18 is stopped. The device enters the standby state and waits for the next monitoring cycle. The cycle can be set to 4-24 hours.

[0037] S6. Calibration process: High-purity nitrogen gas without acetylene is introduced into the inlet 21 of the photoacoustic gas chamber 9, and the above detection steps are performed. The output amplitude of the lock-in amplifier 15 is recorded as V0=0.02V, i.e., the zero-point bias b=0.02V. Standard acetylene gas of 1ppm, 5ppm, and 10ppm is introduced sequentially through the inlet 21 of the photoacoustic gas chamber 9, and the corresponding output amplitudes of the lock-in amplifier 15 are recorded as V1=0.04V, V5=0.12V, and V10=0.22V. The exhaust gas generated during calibration is discharged from the exhaust port 22 of the photoacoustic gas chamber 9. The slope ratio a=0.05ppm / V is obtained by least squares fitting, and a and b are stored in the memory unit associated with the main control chip 14.

[0038] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0039] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork, characterized in that, It includes a degassing module, a photoacoustic detection module, a signal processing module, and a reset module; The degassing module includes a degassing oil tank (1), an oil inlet assembly, a vacuum assembly, and a pressure sensor. The oil inlet assembly includes an oil inlet pump (5), and the vacuum assembly includes an air pump (6) and a first three-way valve (7). The inner wall of the degassing oil tank (1) is equipped with a float oil level gauge, the outer side is equipped with a heating rod (3), and the inside is equipped with a stirring motor (2) and a stirring rod (19). The photoacoustic detection module includes a photoacoustic chamber (9), a tuning fork sensor (10), a laser component and a gas path switching component. The laser component includes a DFB laser (11), which extends into one end of the photoacoustic chamber (9). The gas path switching component includes a second three-way valve (13). The photoacoustic chamber (9) is provided with an air inlet (21) and an air outlet (22). The tuning fork sensor (10) is fixed in the middle of the inside of the photoacoustic chamber (9). The signal processing module includes a main control chip (14) and a lock-in amplifier (15). The input end of the lock-in amplifier (15) is connected to the tuning fork sensor (10), and the output end is connected to the main control chip (14). The reset module includes a purging assembly and an oil return assembly. The purging assembly shares an air pump (6) and a first three-way valve (7) and a second three-way valve (13) with the photoacoustic detection module. The oil return assembly includes an oil return pump (18) and an oil return pipeline. The degassed oil tank (1) and the transformer (20) are connected through an oil circuit.

2. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The degassed oil tank (1) is a cylindrical sealed cavity with a volume of 500ml. It has a first air port and a second air port at the top, and an oil inlet and an oil outlet at the bottom. The oil inlet is connected to an oil pump (5) through a pipeline, and the oil outlet is connected to a return oil pump (18) through a pipeline.

3. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The laser assembly includes a distributed DFB laser (11) and a laser driving circuit. The center wavelength of the DFB laser (11) is 1531.6nm, and the modulation frequency output by the laser driving circuit is 16.384kHz. The light-emitting end of the DFB laser (11) is aligned with the incident window of the photoacoustic gas chamber (9).

4. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The tuning fork sensor (10) is made of quartz and has a natural resonant frequency of 32.768kHz. Its pins pass through the outer wall of the photoacoustic chamber (9) via wires and are connected to the lock-in amplifier (15).

5. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The internal chamber of the photoacoustic gas chamber (9) is a miniature sealed chamber with a volume of 1-2 ml, symmetrically distributed on both sides of the photoacoustic gas chamber (9). The exhaust port (22) of the photoacoustic gas chamber (9) is connected to the second three-way valve (13) through a pipeline.

6. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The vacuum assembly includes an air pump (6) and a first three-way valve (7). The air pump (6) has both pumping and air blowing functions, and the vacuum degree is ≤100Pa. The first three-way valve (7) is electromagnetic and can switch between the "degassed oil tank (1) - air pump (6)" and "clean air source - air pump (6)" paths.

7. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The gas path switching component includes a second three-way valve (13), which is electromagnetic and can switch between the "degassed oil tank (1) - photoacoustic chamber (9)" and "photoacoustic chamber (9) - external atmosphere" paths.

8. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The signal processing module also includes a human-machine interaction unit, which includes an LCD display screen (17) and is connected to the main control chip (14) via an SPI bus.

9. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The return oil component of the reset module includes a return oil pump (18) and a return oil pipeline. The return oil pipeline connects the oil outlet of the degassing oil tank (1) to the transformer (20) via the return oil pipeline.

10. The laser spectroscopic device for monitoring trace amounts of acetylene in oil based on a tuning fork according to claim 1, characterized in that, The heating rod (3) of the degassing module is located in the middle of the degassing oil tank (1), and the power output end of the stirring motor (2) is fixedly connected to the stirring rod (19).

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