A device and method for detecting SF6 decomposition products using a tunable photoacoustic spectrometer

Abstract

The invention discloses a device and method for detecting SF6 decomposition products by a tunable photoacoustic spectrometer, belonging to the field of electrical equipment fault diagnosis and evaluation, the device comprises a laser control module, a resonant cavity module, an air intake module, a gas recovery module and a data processing module; the laser control module is used to output periodic laser to the resonant cavity module; the air intake module is connected to the resonant cavity module, and is used to input the gas to be measured into the resonant cavity module; the gas recovery module is connected to the resonant cavity module, and is used to recover the gas detected by the resonant cavity module; the data processing module is respectively connected to the laser module, the laser control module and the resonant cavity module, and is used to receive the reference signal output by the laser module, and process the electrical signal output by the resonant cavity module and is used to calculate the concentration of the gas to be measured; the resonant cavity module is used to perform gas analysis. The resonant cavity of the photoacoustic spectrometer can be continuously tuned, which effectively improves the sensitivity of gas measurement.

Description

Technical Field

[0001] The present invention relates to the field of electrical equipment fault diagnosis and evaluation, and in particular to a device and method for detecting SF6 decomposition products using a tunable photoacoustic spectrometer. Background Art

[0002] In photoacoustic spectroscopy, the photoacoustic cavity plays a key role, and its function is to provide continuous and stable amplification for the acoustic signal. The built-in microphone in the photoacoustic cavity converts the acoustic wave signal into a processable electrical signal. A properly designed resonant cavity can achieve photoacoustic resonant amplification, effectively suppress background noise, and significantly improve the signal-to-noise ratio, thus showing higher practicality. However, the traditional dumbbell-shaped (H-shaped) resonant cavity design has limitations. It has buffer cavities at both ends, a resonant cavity in the middle, and a fixed length of the resonant cavity, which limits the continuous adjustability of the resonant frequency, making it impossible to accurately reach the maximum resonant frequency to obtain the strongest resonant signal, thereby affecting the sensitivity of the analysis.

[0003] In addition, the design of the traditional resonant cavity requires that the light beam emitted by the light source be collimated and pass through the resonant cavity, which makes the optical path relatively limited, reducing the chance of photoacoustic interaction between the gas molecules being measured and the incident light, thereby reducing the detection sensitivity. This type of resonant cavity also fails to effectively avoid the influence of airflow noise, resulting in large deviations in the measurement signal. Especially when conducting on-site detection of SF6 decomposition components, this fixed resonant cavity structure cannot be accurately adjusted to the optimal resonant state, and the internal gas flow and complex environmental conditions, as well as the shorter infrared optical path, may introduce additional noise interference. Therefore, in the process of gas detection, achieving the tunability of the resonant cavity and effectively extending the infrared optical path are crucial to improving the accuracy of signal measurement.

[0004] Prior art CN111380805A discloses a photoacoustic cell with adjustable resonant frequency and an adjustment method, which belongs to the field of gas detection technology. The photoacoustic cell provided by the prior art includes a first buffer chamber, a second buffer chamber, a resonant cavity, a first light window, a second light window, a first movable structure, and a second movable structure. The prior art uses piezoelectric ceramics to improve the originally fixed buffer chamber and resonant cavity into an movable structure with adjustable structural parameters. The shortcomings of the prior art documents are that multiple groups of piezoelectric ceramics are used to adjust the length of the resonant cavity. The piezoelectric ceramics are limited by their own working principles and the adjustment of the length of the resonant cavity is very limited. The introduction of multiple groups of piezoelectric ceramics has dramatically increased the manufacturing cost of the photoacoustic cell. Piezoelectric ceramics use voltage to drive the expansion and contraction of the ceramic volume to achieve the regulation of its external geometric dimensions. External noise is introduced in the regulation process, which affects the accuracy of photoacoustic spectroscopy measurement to a certain extent. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides the following technical solutions.

[0006] A first aspect of the present invention provides a device for detecting SF6 decomposition products using a tunable photoacoustic spectrometer, the device comprising:

[0007] Laser control module, resonant cavity module, air intake module, gas recovery module and data processing module;

[0008] The laser control module is used to output periodic laser to the resonant cavity module; the air intake module is connected to the resonant cavity module, and is used to input the gas to be measured into the resonant cavity module; the gas recovery module is connected to the resonant cavity module, and is used to recover the gas detected by the resonant cavity module; the data processing module is respectively connected to the laser module, the laser control module and the resonant cavity module, and is used to receive the reference signal output by the laser module, and process the electrical signal output by the resonant cavity module and calculate the concentration of the gas to be measured; the resonant cavity module is used to perform gas analysis, and is provided with a slide rail 18 and a contraction cavity 9 for adjusting the length of the resonant cavity. The module is also provided with a right-angle prism 15 with adjustable direction, which is used to increase the effective optical path of the laser and the gas to be measured. The module is also provided with a gas buffer baffle 8 for buffering the input gas.

[0009] Optionally, the laser control module includes a tunable infrared laser 1 and a function signal generator 25; the function signal generator 25 is connected to the tunable infrared laser 1, and the function signal generator 25 is also connected to the data processing module. The function signal generator 25 generates a periodic signal to make the tunable infrared laser 1 periodically output infrared laser.

[0010] Optionally, the tunable infrared laser 1 of the laser control module is a tunable semiconductor infrared laser, which is used to measure the characteristic products of SF6 gas decomposition in the infrared region, including SO 2 F 2 、SO 2 F 4 、SOF 2 、SO 2 and HF.

[0011] Optionally, the resonant cavity module includes an infrared window 2, an air inlet 7, an air outlet 14, a gas buffer baffle 8, a contraction cavity 9, a resonant cavity length adjustment knob 10, a slide rail 18, a rail base 19, a right-angle prism 15, a right-angle prism adjustment base 16, a built-in microphone 20, an infrared reflector 3 and an infrared light absorption pool 26.

[0012] Optionally, the air inlet 7 and the air outlet 14 are respectively arranged at the upper ends of the two chambers of the resonant cavity, and the gas to be tested enters the resonator through the air inlet 7, and the tested gas is discharged from the air outlet 14;

[0013] The infrared window 2 is arranged on the end surface of one end of the resonant cavity, and the infrared laser enters the resonant cavity through the infrared window 2. The right-angle prism 15 is arranged at the other end inside the resonant cavity for reflecting the infrared laser. The right-angle prism adjustment base 16 is used to control the direction of the right-angle prism 15, and it is arranged outside the resonant cavity.

[0014] The infrared reflector 3 and the infrared light absorption pool 26 are arranged outside the resonant cavity. When the infrared laser is reflected by the right-angle prism 15, it is emitted from the infrared window 2 to the infrared reflector 3, and then reflected by the infrared reflector 3 and enters the infrared light absorption pool 26.

[0015] The gas buffer baffle 8 is installed inside the resonant cavity to stabilize the airflow;

[0016] A built-in microphone 20 is provided in the middle of the resonant cavity, and the built-in microphone 20 is connected to the data processing module and is used to convert the sound wave signal into an electrical signal;

[0017] The slide rail 18 is arranged on the track base 19, the resonance cavity length adjustment knob 10 is arranged in the middle above the resonance cavity, and the contraction cavity 9 is arranged at one end of the two chambers of the resonance cavity; the resonance cavity length adjustment knob 10, the contraction cavity 9, the slide rail 18 and the track base 19 work together to adjust the length of the resonance cavity, and the resonance cavity length adjustment knob 10 is rotated, and the contraction cavity 9 of the two chambers can move freely through the slide rail 18.

[0018] Optionally, the resonant cavity length adjustment knob 10 includes:

[0019] By tuning the resonant cavity length adjustment knob 10, the symmetrical contraction cavities 9 at both ends of the resonant cavity can move freely through the slide rails 18 to adjust the contraction or extension of the resonant cavity length.

[0020] Optionally, the air intake module includes: an oil and gas cabinet 4, an air intake control valve 5 and a first gas mass flow meter 6; the oil and gas cabinet 4, the air intake control valve 5 and the first gas mass flow meter 6 are connected in sequence; wherein the first gas mass flow meter 6 is connected to the air inlet 7 of the resonant cavity module.

[0021] Optionally, the gas recovery module includes: a second gas mass flow meter 11, an air outlet control valve 12, a mechanical pump 13 and a gas recovery chamber 17; the second gas mass flow meter 11, the air outlet control valve 12, the mechanical pump 13 and the gas recovery chamber 17 are connected in sequence; wherein the second gas mass flow meter 11 is connected to the air outlet 14 of the resonant cavity module.

[0022] Optionally, the data processing module includes: a preamplifier 21, a lock-in amplifier 22, a data acquisition card 23 and a computer terminal 24;

[0023] The preamplifier 21, the phase-locked amplifier 22, the data acquisition card 23, and the computer terminal 24 are connected in sequence, wherein the preamplifier 21 is connected to the built-in microphone 20 of the resonant cavity module, and is used to amplify the electrical signal output by the built-in microphone 20 to improve the signal strength, and the phase-locked amplifier 22 is also connected to the function signal generator 25 of the laser control module, and the reference signal of the phase-locked amplifier 22 is provided by the function signal generator 25, and the phase-locked amplifier 22 is used to further amplify the electrical signal processed by the preamplifier 21;

[0024] The data acquisition card 23 collects the electrical signals processed by the preamplifier 21 and the lock-in amplifier 22 and inputs them into the computer terminal 24; the computer terminal 24 is used to further process these signals and calculate the concentration.

[0025] The second aspect of the present invention provides a method for detecting SF6 decomposition products using a tunable photoacoustic spectrometer, based on the device for detecting SF6 decomposition products using a tunable photoacoustic spectrometer according to the first aspect of the present invention, comprising the following steps:

[0026] Use standard gas, controlled by mass flow meter, to enter the tunable resonant cavity, continue to flow for a period of time, open the gas outlet module, and keep the standard gas in the cavity stable;

[0027] The signal generator outputs a specific periodic function signal and inputs it into the tunable laser array to achieve wavelength modulation and tuning output of the tunable laser. The laser with periodically modulated wavelength enters the tunable resonant cavity through the infrared window. The base of the right-angle prism is adjusted to make the laser light path pass through the infrared reflector and enter the infrared light absorption pool.

[0028] Tune the resonant cavity length adjustment knob, observe the photoacoustic signal measurement value, until the maximum photoacoustic signal is obtained, and fix the resonant cavity length adjustment knob;

[0029] Recover standard gas through the mechanical pump of the gas recovery module;

[0030] The gas to be tested is introduced through the air intake module, and the intake process of the gas to be tested and the standard gas is consistent;

[0031] The signal generator outputs a specific periodic function signal and inputs it into the tunable laser array to achieve wavelength modulation and tuning output of the tunable laser. The laser with periodically modulated wavelength enters the tunable resonant cavity through the infrared window. By adjusting the right-angle prism adjustment base, it is ensured that the laser light path can smoothly pass through the infrared reflector and enter the infrared light absorption cell.

[0032] The resonant cavity is used to amplify the photoacoustic signal inside the buffer cavity of the gas to be tested. The photoacoustic signal is transmitted to the phase-locked amplifier through the preamplifier, and then transmitted to the computer terminal through the data acquisition card. The concentration of the decomposition products of the multi-component gas to be tested is obtained by computer operation and calculation.

[0033] Compared with the prior art, the beneficial effects of the present invention include:

[0034] 1. The resonant cavity of the photoacoustic spectrometer can be continuously tuned. Compared with the traditional fixed resonant cavity with a fixed resonant frequency, this scheme can continuously find the strongest resonant position, effectively improving the sensitivity of gas measurement;

[0035] 2. The buffer chamber of the tunable photoacoustic spectrometer has a built-in gas buffer baffle, which can effectively reduce the impact of airflow disturbance on measurement accuracy.

[0036] 3. The buffer cavity of the tunable photoacoustic spectrometer has a built-in right-angle prism, which changes the direction of the light path, increases the effective optical path of the infrared light and gas, and improves the accuracy of gas measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a schematic diagram of the structure of a tunable photoacoustic spectrometer for detecting SF6 decomposition products. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0039] Embodiment 1 of the present invention provides a device for detecting SF6 decomposition products using a tunable photoacoustic spectrometer, comprising: a laser control module, a resonant cavity module, an air intake module, a gas recovery module and a data processing module;

[0040] The laser control module is used to output periodic laser to the resonant cavity module;

[0041] The air intake module is connected to the resonant cavity module and is used to input the gas to be tested into the resonant cavity module;

[0042] The gas recovery module is connected to the resonant cavity module and is used to recover the gas detected by the resonant cavity module;

[0043] The data processing module is connected to the laser control module and the resonant cavity module respectively, and is used to receive the reference signal output by the laser control module, and process the electrical signal output by the resonant cavity module and use it to calculate the concentration of the gas to be measured;

[0044] The resonant cavity module is used for gas analysis.

[0045] It is worth noting that, as the three outstanding essential features of the present invention, the present invention realizes the tunability of the resonant cavity by arranging a slide rail in the resonant cavity module; by arranging a right-angle prism with adjustable orientation in the resonant cavity module, the effective optical path of the infrared light and the gas is increased, thereby improving the accuracy of gas measurement; by arranging a gas buffer baffle in the resonant cavity module, the influence of airflow disturbance on the measurement accuracy is effectively reduced.

[0046] In a further preferred but non-limiting embodiment, the laser control module includes: a tunable infrared laser 1 and a function signal generator 25; the function signal generator 25 is connected to the tunable infrared laser 1, and the function signal generator 25 is also connected to the data processing module, and the function signal generator 25 generates a periodic signal to make the tunable infrared laser 1 periodically output infrared laser;

[0047] In a further preferred but non-limiting embodiment, the tunable infrared laser 1 of the laser control module is a tunable semiconductor infrared laser specially designed for measuring the characteristic products of SF6 gas decomposition in the infrared region, including but not limited to SO 2 F 2 、SO 2 F 4 、SOF 2 、SO 2 and HF, etc.

[0048] In a further preferred but non-limiting embodiment, the resonant cavity module includes an infrared window 2, an air inlet 7, an air outlet 14, a gas buffer baffle 8, a contraction cavity 9, a resonant cavity length adjustment knob 10, a slide rail 18, a rail base 19, a right-angle prism 15, a right-angle prism adjustment base 16, a built-in microphone 20, an infrared reflector 3 and an infrared light absorption pool 26;

[0049] The air inlet 7 and the air outlet 14 are respectively arranged at the upper ends of the two chambers of the resonant cavity. The gas to be tested enters the resonator through the air inlet 7, and the tested gas is discharged from the air outlet 14.

[0050] The infrared window 2 is arranged on the end surface of one end of the resonant cavity, and the infrared laser enters the resonant cavity through the infrared window 2. The right-angle prism 15 is arranged at the other end inside the resonant cavity for reflecting the infrared laser. The right-angle prism adjustment base 16 is used to control the direction of the right-angle prism 15, and it is arranged outside the resonant cavity.

[0051] The infrared reflector 3 and the infrared light absorption pool 26 are arranged outside the resonant cavity. When the infrared laser is reflected by the right-angle prism 15, it is emitted from the infrared window 2 to the infrared reflector 3, and then reflected by the infrared reflector 3 and enters the infrared light absorption pool 26.

[0052] The gas buffer baffle 8 is installed inside the resonant cavity to stabilize the airflow;

[0053] A built-in microphone 20 is provided in the middle of the resonant cavity, and the built-in microphone 20 is connected to the data processing module and is used to convert the sound wave signal into an electrical signal;

[0054] The slide rail 18 is arranged on the track base 19, and the chambers on both sides of the resonant cavity slide freely on the track base 19 through the slide rail 18 respectively. The resonant cavity length adjustment knob 10 is arranged in the middle above the resonant cavity, and the contraction cavity 9 is arranged at one end of the two chambers of the resonant cavity; the resonant cavity length adjustment knob 10, the contraction cavity 9, the slide rail 18 and the track base 19 act together to adjust the length of the resonant cavity, and the resonant cavity length adjustment knob 10 is rotated to compress or expand the contraction cavity 9 of the two chambers at the same time, and one end of the two chambers of the resonant cavity slides to the middle or both sides at the same time through the slide rail 18, thereby realizing the adjustment of the length of the resonant cavity;

[0055] Specifically, the length of the resonant cavity is adjusted by adjusting the resonant cavity length adjustment knob 10, the resonant cavity shrinks or stretches, and the symmetrical gas buffer cavities at both ends of the resonant cavity can move freely through the slide rail 18, thereby achieving the contraction or extension adjustment of the resonant cavity length.

[0056] In a further preferred but non-limiting embodiment, the air intake module includes: an oil and gas cabinet 4, an air intake control valve 5 and a first gas mass flow meter 6; the oil and gas cabinet 4, the air intake control valve 5, and the first gas mass flow meter 6 are connected in sequence; wherein the first gas mass flow meter 6 is connected to the air inlet of the resonant cavity module; the air intake module is used to input the gas to be measured into the resonant cavity module.

[0057] In a further preferred but non-limiting embodiment, the gas recovery module comprises: a second gas mass flow meter 11, an outlet control valve 12, a mechanical pump 13 and a gas recovery chamber 17; the second gas mass flow meter 11, the outlet control valve 12, the mechanical pump 13 and the gas recovery chamber 17 are connected in sequence; wherein the second gas mass flow meter 11 is connected to the gas outlet 14 of the resonant cavity module;

[0058] The gas recovery module is used to recover the gas detected by the resonant cavity module.

[0059] In a further preferred but non-limiting embodiment, the data processing module includes: a preamplifier 21, a phase-locked amplifier 22, a data acquisition card 23 and a computer terminal 24; the preamplifier 21, the phase-locked amplifier 22, the data acquisition card 23, and the computer terminal 24 are connected in sequence, wherein the preamplifier 21 is connected to the built-in microphone 20 of the resonant cavity module, and is used to amplify the electrical signal output by the built-in microphone 20 to improve the signal strength, and the phase-locked amplifier 22 is also connected to the function signal generator 25 of the laser control module, and the reference signal of the phase-locked amplifier 22 is provided by the function signal generator 25, and the phase-locked amplifier 22 is used to further amplify the electrical signal processed by the preamplifier 21;

[0060] The data acquisition card 23 collects the electrical signals processed by the preamplifier 21 and the lock-in amplifier 22 and inputs them into the computer terminal 24; the computer terminal 24 is used to further process these signals and calculate the concentration.

[0061] Compared with the prior art, the present invention uses a mechanical knob to adjust the length of the resonant cavity, which can achieve a large range of adjustment of the length of the resonant cavity; no vibration is generated during the knob adjustment of the length of the resonant cavity, and no external noise is introduced to interfere with the measurement accuracy. Mechanical knob adjustment has obvious cost advantages compared to the adjustment of multiple groups of piezoelectric ceramics. Compared with the prior art, the most significant beneficial effect of the present invention is that it achieves a large range of adjustment of the resonant cavity without introducing external noise interference, thereby improving the measurement accuracy. Compared with the adjustment of multiple groups of piezoelectric ceramics, this solution has obvious cost advantages.

[0062] Embodiment 2 of the present invention provides a method for detecting SF6 decomposition products using a tunable photoacoustic spectrometer, based on the device for detecting SF6 decomposition products using a tunable photoacoustic spectrometer described in Embodiment 1, comprising:

[0063] Step 1: Use standard gas, controlled by a mass flow meter, to enter the tunable resonant cavity, continue to flow for a period of time, open the gas outlet module, and keep the standard gas in the cavity stable; the standard gas contains the gas to be tested with a known concentration;

[0064] Step 2: The signal generator outputs a specific periodic function signal and inputs it into the tunable laser array to achieve wavelength modulation and tuning output of the tunable laser; the laser with periodically modulated wavelength enters the tunable resonant cavity through the infrared window, and the base is adjusted by adjusting the right-angle prism to ensure that the laser light path can smoothly pass through the infrared reflector and enter the infrared light absorption cell;

[0065] Step 3: Tune the resonant cavity length adjustment knob, observe the photoacoustic signal measurement value, until the maximum photoacoustic signal is obtained, and fix the resonant cavity length adjustment knob;

[0066] Step 4: Recover the standard gas through the mechanical pump of the gas recovery module; then introduce the gas to be tested through the air intake module, and the intake process of the gas to be tested and the standard gas is consistent;

[0067] Step 5: The signal generator outputs a specific periodic function signal and inputs it into the tunable laser array to achieve wavelength modulation and tuning output of the tunable laser; the laser with periodically modulated wavelength enters the tunable resonant cavity through the infrared window, and the base is adjusted by adjusting the right-angle prism to ensure that the laser light path can smoothly pass through the infrared reflector and enter the infrared light absorption cell;

[0068] Step 6: Use the resonance cavity to amplify the photoacoustic signal inside the buffer cavity of the gas to be tested. The photoacoustic signal is transmitted to the phase-locked amplifier through the preamplifier, and then transmitted to the computer terminal through the data acquisition card. The concentration of the decomposition products of the multi-component gas to be tested is obtained by computer operation and calculation.

[0069] In a further preferred but non-limiting embodiment, in the method, the standard gas is a gas to be tested containing a known concentration, including SO 2 F 2 、SO 2 F 4 、SOF 2 、SO 2 wait.

[0070] The main features of the present invention are as follows: 1: tunable infrared laser; 2: infrared window; 3: infrared reflector; 4: oil and gas cabinet; 5: air intake control valve; 6: first gas mass flow meter; 7: air inlet; 8: gas buffer baffle; 9: contraction cavity; 10: resonant cavity length adjustment knob; 11: second gas mass flow meter; 12: air outlet control valve; 13: mechanical pump; 14: air outlet; 15: right-angle prism; 16: right-angle prism adjustment base; 17: gas recovery cavity; 18: slide rail; 19: rail base; 20: built-in microphone; 21: preamplifier; 22: phase-locked amplifier; 23: data acquisition card; 24: computer terminal; 25: function signal generator; 26: infrared light absorption cell.

[0071] The innovative configuration of this tunable photoacoustic spectrometer not only avoids the limitations of traditional fixed resonant cavities in continuously adjusting the resonance signal, but also significantly improves the measurement accuracy.

Claims

1. A device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer, characterized in that: The device includes: Laser control module, resonant cavity module, air intake module, gas recovery module and data processing module; The laser control module is used to output periodic laser light to the resonant cavity module; the air intake module is connected to the resonant cavity module and is used to input the gas to be measured into the resonant cavity module; the gas recovery module is connected to the resonant cavity module and is used to recover the gas detected by the resonant cavity module; the data processing module is respectively connected to the laser module, the laser control module and the resonant cavity module and is used to receive the reference signal output by the laser module and the laser control module, and to process the electrical signal output by the resonant cavity module and calculate the concentration of the gas to be measured; the resonant cavity module is used to perform gas analysis, and is provided with a slide rail (18) and a contraction cavity (9) for adjusting the length of the resonant cavity; the module is also provided with a right-angle prism (15) with adjustable orientation for increasing the effective optical path of the laser and the gas to be measured; the module is also provided with a gas buffer baffle (8) for buffering the input gas; The resonant cavity module comprises an infrared window (2), an air inlet (7), an air outlet (14), a gas buffer baffle (8), a contraction cavity (9), a resonant cavity length adjustment knob (10), a slide rail (18), a rail base (19), a right-angle prism (15), a right-angle prism adjustment base (16), a built-in microphone (20), an infrared reflector (3), and an infrared light absorption pool (26); The air inlet (7) and the air outlet (14) are respectively arranged at the upper ends of the two chambers of the resonant cavity, and the gas to be tested enters the interior of the resonator through the air inlet (7), and the gas that has been tested is discharged from the air outlet (14); An infrared window (2) is arranged on an end surface of one end of the resonant cavity, and infrared laser light enters the resonant cavity through the infrared window (2). A right-angle prism (15) is arranged at the other end inside the resonant cavity and is used to reflect the infrared laser light. A right-angle prism adjustment base (16) is used to control the orientation of the right-angle prism (15), and is arranged outside the resonant cavity. The infrared reflector (3) and the infrared light absorption pool (26) are arranged outside the resonant cavity. When the infrared laser is reflected by the right-angle prism (15), it is emitted from the infrared window (2) to the infrared reflector (3), and is reflected by the infrared reflector (3) before entering the infrared light absorption pool (26). A gas buffer baffle (8) is installed inside the resonant cavity to stabilize the gas flow; A built-in microphone (20) is provided in the middle of the resonant cavity, and the built-in microphone (20) is connected to the data processing module and is used to convert the sound wave signal into an electrical signal; The slide rail (18) is arranged on the rail base (19); the resonance cavity length adjustment knob (10) is arranged in the middle above the resonance cavity; and the contraction cavity (9) is arranged at one end of the two chambers of the resonance cavity; the resonance cavity length adjustment knob (10), the contraction cavity (9), the slide rail (18) and the rail base (19) act together to adjust the length of the resonance cavity; when the resonance cavity length adjustment knob (10) is rotated, the contraction cavities (9) of the two chambers move freely through the slide rail (18).

2. The device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer according to claim 1, characterized in that: The laser control module comprises a tunable infrared laser (1) and a function signal generator (25); the function signal generator (25) is connected to the tunable infrared laser (1), and the function signal generator (25) is also connected to the data processing module; the function signal generator (25) generates a periodic signal so that the tunable infrared laser (1) periodically outputs infrared laser light.

3. The device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer according to claim 2, characterized in that: The tunable infrared laser (1) of the laser control module is a tunable semiconductor infrared laser, which is used to measure characteristic decomposition products of SF6 gas in the infrared region, including SO2F2, SO2F4, SOF2, SO2 and HF.

4. The device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer according to claim 3, characterized in that: The resonant cavity length adjustment knob (10) comprises: By tuning the resonant cavity length adjustment knob (10), the contraction cavities (9) symmetrically disposed at both ends of the resonant cavity body can move freely via the slide rails (18) to adjust the contraction or extension of the resonant cavity length.

5. The device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer according to claim 1, characterized in that: The air intake module comprises: an oil and gas cabinet (4), an air intake control valve (5) and a first gas mass flow meter (6); the oil and gas cabinet (4), the air intake control valve (5) and the first gas mass flow meter (6) are connected in sequence; wherein the first gas mass flow meter (6) is connected to the air intake port (7) of the resonant cavity module.

6. The device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer according to claim 1, characterized in that: The gas recovery module comprises: a second gas mass flow meter (11), a gas outlet control valve (12), a mechanical pump (13) and a gas recovery chamber (17); the second gas mass flow meter (11), the gas outlet control valve (12), the mechanical pump (13) and the gas recovery chamber (17) are connected in sequence; wherein the second gas mass flow meter (11) is connected to the gas outlet (14) of the resonant cavity module.

7. The device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer according to claim 2, characterized in that: The data processing module comprises: a preamplifier (21), a phase-locked amplifier (22), a data acquisition card (23) and a computer terminal (24); A preamplifier (21), a phase-locked amplifier (22), a data acquisition card (23), and a computer terminal (24) are connected in sequence, wherein the preamplifier (21) is connected to a built-in microphone (20) of the resonant cavity module and is used to amplify the electrical signal output by the built-in microphone (20) to increase the signal strength, and the phase-locked amplifier (22) is also connected to a function signal generator (25) of the laser control module, and a reference signal of the phase-locked amplifier (22) is provided by the function signal generator (25), and the phase-locked amplifier (22) is used to further amplify the electrical signal processed by the preamplifier (21); The data acquisition card (23) collects the electrical signals processed by the preamplifier (21) and the phase-locked amplifier (22) and inputs them into the computer terminal (24); the computer terminal (24) is used to further process these signals and calculate the concentration.

8. A method for detecting SF6 decomposition products by a tunable photoacoustic spectrometer, based on the device for detecting SF6 decomposition products by a tunable photoacoustic spectrometer according to any one of claims 1 to 7, characterized in that: The steps include: Use standard gas, controlled by mass flow meter, to enter the tunable resonant cavity, continue to flow for a period of time, open the gas outlet module, and keep the standard gas in the cavity stable; The signal generator outputs a specific periodic function signal and inputs it into the tunable laser array to achieve wavelength modulation and tuning output of the tunable laser. The laser with periodically modulated wavelength enters the tunable resonant cavity through the infrared window. The base of the right-angle prism is adjusted to make the laser light path pass through the infrared reflector and enter the infrared light absorption pool. Tune the resonant cavity length adjustment knob, observe the photoacoustic signal measurement value, until the maximum photoacoustic signal is obtained, and fix the resonant cavity length adjustment knob; Recover standard gas through the mechanical pump of the gas recovery module; The gas to be tested is introduced through the air intake module, and the intake process of the gas to be tested and the standard gas is consistent; The signal generator outputs a specific periodic function signal and inputs it into the tunable laser array to achieve wavelength modulation and tuning output of the tunable laser. The laser with periodically modulated wavelength enters the tunable resonant cavity through the infrared window. By adjusting the right-angle prism adjustment base, it is ensured that the laser light path can smoothly pass through the infrared reflector and enter the infrared light absorption cell. The resonant cavity is used to amplify the photoacoustic signal inside the buffer cavity of the gas to be tested. The photoacoustic signal is transmitted to the phase-locked amplifier through the preamplifier, and then transmitted to the computer terminal through the data acquisition card. The concentration of the decomposition products of the multi-component gas to be tested is obtained by computer operation and calculation.

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