Liquid level detection method and system

Abstract

The invention relates to the technical field of liquid level detection, and particularly provides a liquid level detection method and system. The liquid level detection method comprises the steps that detection light is sent; the circulator sends the detection light to the liquid level detection module, and the reflector reflects the detection light to form reflected light; the circulator sends the reflected light to a collimator for collimation to obtain collimated light; the photoelectric conversion module receives the collimated light and converts the collimated light into an electric signal; and comparing the electric signal with the initial signal to obtain a real-time liquid level value. According to the liquid level detection method, the change of the optical path in the liquid level detection module is caused according to the change of the liquid level so as to cause the change of a gas absorption signal in collimated light, and after the collimated light is converted into an electric signal, the gas absorption signal in the electric signal is demodulated by utilizing a phase locking method technology capable of demodulating a weak signal; and the detection precision and stability of the liquid level detection method are improved. The liquid level detection method is wide in adaptability and can be widely applied to various fields such as dam water level monitoring, fuel oil leakage monitoring, oil exploitation and storage and the like.

Description

Technical Field

[0001] The present application relates to the technical field of liquid level detection, and in particular to a liquid level detection method and system. Background Art

[0002] In industry, liquid level measurement is very common. In recent years, with the rapid development of high-tech technologies such as laser technology, optical fiber technology, and sensor technology, there are more and more methods for applying optical fiber sensing technology to liquid height, that is, liquid level measurement. There are many methods for traditional optical fiber liquid level measurement. Among them, common optical fiber liquid level measurement systems include light-shielded optical fiber liquid level sensors based on the principle of optical fiber pressure sensing, and optical fiber liquid level sensors based on the principle of surface reflection optical fiber sensing. With the continuous promotion and application of automation in the field of industrial production, the requirements for liquid level measurement accuracy are getting higher and higher, and more accurate, highly reliable, and real-time monitoring of liquid level measurement data is required to ensure that industrial production is controlled in a better production state. The above puts higher requirements on liquid level sensors.

[0003] Among the emerging fiber optic devices, fiber Bragg grating (FBG) has attracted people's attention due to its unique advantages. Fiber Bragg grating-based fiber sensors also have many irreplaceable advantages in liquid level measurement. At present, liquid level sensors based on fiber Bragg grating usually measure the grating wavelength drift caused by liquid level changes, and then invert the changes in liquid level. Due to many factors such as demodulation methods and equipment, the accuracy and stability of this type of sensor are often not very high. Summary of the invention

[0004] The present application provides a liquid level detection method and system to solve the technical problems of low precision and low stability in existing liquid level detection.

[0005] The liquid level detection method provided in the first aspect of the present application is applied to a liquid level detection system, and the liquid level detection method includes: a laser sends detection light to a circulator; wherein the detection light includes a low-frequency signal and a high-frequency signal; the circulator sends the detection light to a liquid level detection module, and a reflector in the liquid level detection module reflects the detection light to form reflected light; wherein the optical path in the liquid level detection module changes with the change of the liquid surface position; the circulator sends the reflected light to a collimator for collimation to obtain collimated light; the photoelectric conversion module receives the collimated light and converts the collimated light into an electrical signal; wherein the collimated light includes a gas absorption signal, and the amplitude of the gas absorption signal in the collimated light changes with the change of the optical path in the liquid level detection module; the electrical signal is compared with the initial signal to obtain a real-time liquid level value; wherein the initial signal is an electrical signal under the initial liquid level state.

[0006] In some feasible implementations, the laser sending the detection light to the circulator includes: the laser driver sending a driving signal to the laser; wherein the driving signal controls the detection light through temperature and current; and the laser sending the detection light according to the driving signal.

[0007] In some feasible implementations, the liquid level detection module contains gas of a fixed concentration, and the liquid level detection module is airtight.

[0008] In some feasible implementations, the liquid level detection module includes a reflector and an elastic diaphragm, the reflector is adhered to one side of the elastic diaphragm, and the other side of the elastic diaphragm is arranged at the bottom of the shell of the liquid level detection module, the bottom of the shell is in contact with the liquid surface, and the wavelength range of the reflected light of the reflector includes the wavelength of the detection light.

[0009] In some feasible implementations, the photoelectric conversion module includes one of a photodetector, a quartz tuning fork, or a piezoelectric film.

[0010] In some feasible implementations, before comparing the electrical signal with the initial signal, the liquid level detection method further includes: a preamplifier amplifying the electrical signal.

[0011] In some feasible implementations, comparing the electrical signal with the initial signal includes: demodulating the amplified electrical signal with a phase-locked amplifier; wherein the reference signal frequency of the phase-locked amplifier is twice the frequency of the high-frequency signal; and comparing the demodulated electrical signal with the initial signal.

[0012] The first aspect of the present application provides a liquid level detection method, wherein the detection light emitted by the laser is a low-frequency scanning signal, and a high-frequency modulation signal is superimposed, the detection light wavelength includes the absorption peak wavelength corresponding to the gas in the liquid level detection module, the optical path in the liquid level detection module changes due to the liquid level change, the detection light is absorbed by the gas in the liquid level detection module, and the reflector in the liquid level detection module can reflect the detection light. Since the gas absorption signal is different under different optical paths, the liquid level change can be converted into the gas absorption signal change, and after the collimated light is converted into an electrical signal, the phase-locked amplification technology that can demodulate weak signals is used to demodulate the gas absorption signal in the electrical signal, thereby improving the detection accuracy and stability of the liquid level detection method. The liquid level detection method has a wide adaptability and can be widely used in various fields such as dam water level monitoring, fuel leak monitoring, oil extraction and storage, etc.

[0013] The second aspect of the present application provides a liquid level detection system, comprising: a laser, configured to send detection light; a circulator, the input end of which is connected to the laser and configured to receive the detection light; a liquid level detection module, connected to the middle end of the circulator, the detection light transmitted by the circulator is absorbed by the gas in the liquid level detection module, and is reflected by the reflector in the liquid level detection module to form reflected light; wherein the optical path in the liquid level detection module changes with the change of the liquid surface position; a collimator, connected to the output end of the circulator, configured to collimate the reflected light transmitted by the circulator to obtain collimated light; The photoelectric conversion module is configured to convert the collimated light into an electrical signal, the collimated light includes a gas absorption signal, and the amplitude of the gas absorption signal in the collimated light changes with the change of the optical path of the liquid level detection module; the preamplifier is connected to the output end of the photoelectric conversion module and is configured to amplify the electrical signal; the phase-locked amplifier is connected to the output end of the preamplifier and is configured to demodulate the electrical signal; the computer is connected to the output end of the phase-locked amplifier and is configured to compare the electrical signal with the initial signal to obtain a real-time liquid level value, wherein the initial signal is the electrical signal under the initial liquid level state.

[0014] In some feasible implementations, the liquid level detection system also includes: a laser driver, connected to the laser and configured to control the laser to send a driving signal; wherein the driving signal controls the detection light through temperature and current, and the driving signal includes a low-frequency sawtooth wave signal and a high-frequency sine signal.

[0015] In some feasible implementations, the liquid level detection module also includes: a shell and an elastic diaphragm; wherein, in the liquid level detection module, the reflector is adhered to one side of the elastic diaphragm, and the other side of the elastic diaphragm is arranged at the bottom of the shell, and the bottom of the shell is in contact with the liquid surface.

[0016] The liquid level detection system provided in the second aspect of the present application has a simple structure, effectively reduces production costs, and has good stability. The liquid level detection system has wide adaptability and can be widely used in various fields such as dam water level monitoring, fuel leakage monitoring, oil extraction and storage, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 It is a flow chart of a liquid level detection method provided in an embodiment of the present application; Figure 2 is a structural schematic diagram of a liquid level detection system provided in an embodiment of the present application; Figure 3 is a schematic diagram of a laser output signal provided in an embodiment of the present application; Figure 4 This is a schematic diagram of the relationship between the amplitude and time of an electrical signal collected by a computer provided in an embodiment of the present application; Figure 5 This is a schematic diagram of the change in the amplitude of an electrical signal with the change in liquid level provided in an embodiment of the present application.

[0019] Graphic marking: 100-liquid level detection system; 10-laser; 20-circulator; 21-input end, 22-middle end; 23-output end; 30-liquid level detection module; 31-housing; 32-reflector; 33-elastic diaphragm; 40-collimator; 50-photoelectric conversion module; 60-preamplifier; 70-phase-locked amplifier; 80-computer; 90-laser driver. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, other embodiments obtained by ordinary technicians in this field without making creative work all belong to the protection scope of the present application.

[0021] In the following, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0022] In addition, in the present application, directional terms such as "upper", "lower", "inner" and "outer" are defined relative to the orientation of the components schematically placed in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to the changes in the orientation of the components placed in the drawings.

[0023] In order to solve the above technical problems, an embodiment of the present application provides a liquid level detection method, which changes the demodulation method of the liquid level signal, causes the optical path in the liquid level detection module to change according to the liquid level change, causes the gas absorption signal to change, and inverts the liquid level change by demodulating the change of the gas absorption signal in the electrical signal, thereby improving the detection accuracy and stability.

[0024] See also Figure 1 and Figure 2 The liquid level detection method provided in the embodiment of the present application can be implemented by the following steps S1 to S5.

[0025] Step S1 : the laser 10 sends detection light to the circulator 20 .

[0026] The laser 10 may be connected to the input end 21 of the circulator 20. The input end 21 of the circulator 20 may be used to receive the detection light sent by the laser 10, and the detection light may carry a low-frequency signal and a high-frequency signal.

[0027] In some specific implementations, step S1 may be implemented by the following steps S101 and S102.

[0028] Step S101 : the laser driver 90 sends a driving signal to the laser 10 .

[0029] The driving signal can detect light through temperature and current control, and the driving signal is formed by superposition of a low-frequency sawtooth wave signal and a high-frequency sine wave signal.

[0030] Step S102: the laser 10 sends detection light according to the driving signal.

[0031] In this way, various parameters in the detection light can be controlled by the laser driver 90 .

[0032] Step S2: the circulator 20 sends the detection light to the liquid level detection module 30, and the reflector 32 in the liquid level detection module 30 reflects the detection light to form reflected light.

[0033] After the detection light passes through the circulator 20, it is incident on the liquid level detection module 30, and the reflector 32 in the liquid level detection module 30 reflects the detection light to form reflected light. Among them, the reflection wavelength range of the reflector 32 in the liquid level detection module 30 includes the wavelength of the detection light. The liquid level detection module 30 can be connected to the middle end 22 of the circulator 20. In this way, the detection light received by the circulator 20 through the input end 21 can be incident on the liquid level detection module 30 through the middle end 22, and return through the middle end 22 again after forming reflected light. Among them, the liquid level detection module 30 contains a fixed concentration of gas, and the liquid level detection module is airtight and has good airtightness.

[0034] See also Figure 3 The wavelength range of the output signal of the laser 10 is 1530.2nm-1530.7nm, and the reflection wavelength range of the reflector 32 in the liquid level detection module 30 is 1500nm-1600nm.

[0035] Among them, the optical path in the liquid level detection module 30 changes with the change of the liquid surface position. Specifically, the liquid level detection module 30 includes a shell 31, a reflector 32 and an elastic diaphragm 33. In the liquid level detection module 30, the reflector 32 is attached to one side of the elastic diaphragm 33, and the other side of the elastic diaphragm 33 is arranged at the bottom of the shell 31. The elastic diaphragm 33 is elastic, and the bottom of the shell 31 can be immersed under the liquid surface. In this way, when the liquid level changes, the pressure of the liquid on the elastic diaphragm 33 changes, forcing the elastic diaphragm 33 to deform, causing the position of the reflector 32 to change, and then causing the optical path in the liquid level detection module 30 to change, causing the gas absorption signal in the collimated light to change.

[0036] Taking the rising liquid level as an example, when the liquid level rises, the liquid level pushes the elastic diaphragm 33 to deform, and the elastic diaphragm 33 generates a vertical upward thrust on the reflector 32, forcing the reflector 32 to move upward, thereby reducing the optical path of the liquid level detection module 30, the gas concentration remains unchanged, and the amplitude of the gas absorption signal decreases. Among them, the initial state of the reflector 32 can be a state where the reflector 32 is not subjected to external force.

[0037] Taking the drop of liquid level as an example, the thrust of the liquid surface on the elastic diaphragm 33 is weakened, and the vertical upward thrust of the elastic diaphragm 33 on the reflector 32 is gradually weakened, the reflector 32 moves downward, the optical path in the liquid level detection module 30 is increased, and the amplitude of the gas absorption signal is increased.

[0038] Step S3: The circulator 20 sends the reflected light to the collimator 40 for collimation to obtain collimated light.

[0039] The output end 23 of the circulator 20 is connected to the input end of the collimator 40, and the reflected light is sent from the output end 23 of the circulator 20 to the collimator 40. The reflected light is collimated to facilitate subsequent demodulation and ensure the accuracy of detection.

[0040] Step S4: the photoelectric conversion module 50 receives the collimated light and converts the collimated light into an electrical signal.

[0041] The reflected light is emitted through the collimator 40, and the collimated light output by the collimator 40 is received by the photoelectric conversion module 50. The photoelectric conversion module 50 is used to convert the collimated light into an electrical signal. In this way, when the liquid level changes, the optical path in the liquid level detection module 30 changes, and the amplitude of the gas absorption signal in the collimated light changes with the change of the optical path in the liquid level detection module 30. Since the gas absorption signal is positively correlated with the optical path, when the liquid level changes, the amplitude of the gas absorption signal in the collimated light also changes accordingly, and the electrical signal converted by the photoelectric conversion module 50 also changes accordingly.

[0042] The photoelectric conversion module 50 includes a photodetector, a quartz tuning fork or a piezoelectric film.

[0043] In a feasible implementation, after step S4, the liquid level detection method provided in the embodiment of the present application may further include step S41.

[0044] Step S41: The preamplifier 60 amplifies the electrical signal.

[0045] Amplifying the electrical signal by the preamplifier 60 can suppress interference components in the electrical signal and avoid distortion of the electrical signal.

[0046] Step S5: Compare the electrical signal with the initial signal to obtain the real-time liquid level value.

[0047] The initial signal may be an electrical signal in an initial liquid level state. The electrical signal in the initial liquid level state may be obtained through steps S1 to S41. At the beginning of the detection, an initial liquid level may be set, and the initial signal may be obtained by emitting a laser to the liquid level detection module 30. Specifically, the initial signal may be displayed on the computer 80, and the signal amplitude of the initial signal at this time may be recorded, corresponding to the liquid level value in the initial liquid level state.

[0048] Specifically, step S5 can be implemented by the following steps S501 and S502.

[0049] Step S501: The lock-in amplifier 70 demodulates the amplified electrical signal.

[0050] When the liquid level changes, the optical path in the liquid level detection module 30 changes, and the gas concentration in the liquid level detection module 30 remains unchanged, so the gas absorption signal changes, causing the amplitude of the signal demodulated by the lock-in amplifier 70 to change accordingly. The reference signal frequency of the lock-in amplifier 70 is twice the frequency of the high-frequency sinusoidal signal.

[0051] In a specific implementation, the laser driving signal may be a superposition of a low-frequency sawtooth signal with a frequency of 1 Hz and a high-frequency sinusoidal signal with a frequency of 1 kHz, wherein the reference signal frequency of the lock-in amplifier 70 is twice the frequency of the high-frequency sinusoidal signal, that is, 2 kHz.

[0052] Step S502: Compare the demodulated electrical signal with the initial signal.

[0053] By comparing with the initial signal, the real-time liquid level value can be analyzed. Specifically, if the demodulated electrical signal is smaller than the initial signal, it means that the amplitude of the demodulated electrical signal is smaller than the amplitude of the initial signal, which means that the real-time liquid level is rising, and the real-time liquid level value is greater than the initial liquid level value. Conversely, if the demodulated electrical signal is larger than the initial signal, it means that the amplitude of the demodulated electrical signal is larger than the amplitude of the initial signal, which means that the real-time liquid level is decreasing, and the real-time liquid level value is less than the initial liquid level value.

[0054] The output end of the lock-in amplifier 70 is connected to a computer 80 , and the comparison process between the electrical signal and the initial signal can be displayed in the computer 80 . The computer 80 can also be used to display a specific real-time liquid level value.

[0055] See also Figure 4 It can be seen that if the liquid level remains unchanged, the signal amplitude of the electrical signal collected by the computer 80 remains unchanged.

[0056] See also Figure 5 It can be seen that the liquid level change is negatively correlated with the signal amplitude of the electrical signal. For example, as the liquid level change increases, the signal amplitude of the electrical signal decreases.

[0057] The liquid level detection method provided in the embodiment of the present application changes the modulation mode of the laser emitted by the laser 10 so that the detection light emitted by the laser 10 is a low-frequency scanning signal and superimposed with a high-frequency modulation signal. The change in the position of the reflector 32 caused by the change in the liquid level can cause the optical path in the liquid level detection module 30 to change. Since the gas concentration in the liquid level detection module 30 is fixed, the gas absorption signal changes. In addition, the liquid level change can be converted into a change in the gas absorption signal. After the collimated light change is converted into an electrical signal, the phase-locked amplification technology that can demodulate weak signals is used to demodulate the gas absorption signal in the electrical signal, thereby improving the detection accuracy and stability of the liquid level detection method. The liquid level detection method has a wide adaptability and can be widely used in various fields such as dam water level monitoring, fuel leak monitoring, oil extraction and storage, etc.

[0058] Corresponding to the above-mentioned embodiment of the liquid level detection method, the present application also provides an embodiment of a liquid level detection system 100. Figure 2 The liquid level detection system 100 includes a laser 10, a circulator 20, a liquid level detection module 30, a collimator 40, a photoelectric conversion module 50, a preamplifier 60, a lock-in amplifier 70, a computer 80 and a laser driver 90.

[0059] The laser 10 is used to generate detection light. The wavelength range of the detection light includes the absorption peak wavelength of the gas in the liquid level detection module 30. The laser 10 can be a pump laser. When building the liquid level detection system 100, the power of each part can be turned on first.

[0060] In a specific implementation, the wavelength range of the detection light is 1530.2nm-1530.7nm. The reflection wavelength range of the reflector 32 in the liquid level detection module 30 is 1500nm-1600nm.

[0061] The input end 21 of the circulator 20 is connected to the laser 10, and is used to receive the detection light sent by the laser 10. The middle end 22 of the circulator 20 is connected to the liquid level detection module 30, and is used to transmit the detection light to the liquid level detection module 30. The detection light transmitted by the circulator is absorbed by the gas in the liquid level detection module 30, and the reflected light reflected by the reflector 32 in the liquid level detection module 30 is received, and the reflected light is transmitted to the collimator 40 through the output end 23.

[0062] The liquid level detection module 30 includes a housing 31, a reflector 32 and an elastic diaphragm 33. The reflector 32 is attached to one side of the elastic diaphragm 33, and the other side of the elastic diaphragm 33 is located at the bottom of the housing 31. The elastic diaphragm 33 is elastic, and the bottom of the housing 31 can be immersed below the liquid surface. In this way, when the liquid level changes, the pressure of the liquid on the elastic diaphragm 33 changes, pushing the elastic diaphragm 33, forcing the elastic diaphragm 33 to deform, and the deformation of the elastic diaphragm 33 causes the reflector 32 to move. Since the optical path of the liquid level detection module 30 changes with the change of the liquid surface position, the optical path in the liquid level detection module 30 changes. After the optical path in the liquid level detection module 30 changes, the gas concentration in the liquid level detection module 30 remains unchanged, and the gas absorption signal changes.

[0063] In a specific implementation, see Figure 2 The direction of the reflector 32 in the liquid level detection module 30 is pasted parallel to the direction of the elastic diaphragm 33, so that when the elastic diaphragm 33 bends, the reflector 32 will move.

[0064] The collimator 40 is connected to the output end 23 of the circulator 20 . The collimator 40 receives the reflected light from the output end 23 of the circulator 20 , and collimates the reflected light and then transmits it to the photoelectric conversion module 50 .

[0065] The photoelectric conversion module 50 converts the collimated light into an electrical signal, wherein the output end of the photoelectric conversion module 50 is connected to the output end of the preamplifier 60 .

[0066] In a specific implementation, the photoelectric conversion module 50 includes one of a photodetector, a quartz tuning fork, or a piezoelectric film.

[0067] The preamplifier 60 receives and amplifies the electrical signal, wherein the output end of the preamplifier 60 is connected to the input end of the lock-in amplifier 70 .

[0068] The phase-locked amplifier 70 receives and demodulates the electrical signal, and the output end of the phase-locked amplifier 70 is connected to the computer 80.

[0069] The computer 80 is used to display the liquid level information of the comparison between the electrical signal and the initial signal to obtain the real-time liquid level, wherein the initial signal is the electrical signal at the initial position of the liquid surface.

[0070] In some feasible implementations, the liquid level detection system 100 may further include a laser driver 90. The output end of the laser driver 90 is connected to the input end of the laser 10, and the laser driver 90 is used to send a driving signal, and the driving signal controls the detection light through temperature and current, and the reflection wavelength range of the reflector 32 includes the wavelength of the detection light emitted by the laser 10.

[0071] The liquid level detection system 100 provided in the embodiment of the present application has a simple structure, effectively reduces production costs, and has good stability. By changing the modulation mode of the laser emitted by the laser 10, the detection light emitted by the laser 10 is a low-frequency scanning signal, and a high-frequency modulation signal is superimposed. The movement of the reflector 32 caused by the liquid level change can cause the optical path in the liquid level detection module 30 to change. Since the gas concentration in the liquid level detection module 30 remains unchanged, the change in the optical path causes the change in the gas absorption signal, and then the liquid level change can be converted into a change in the gas absorption signal in the collimated light. After the collimated light change is converted into an electrical signal, the phase-locked amplification technology that can demodulate weak signals is used to demodulate the gas absorption signal in the electrical signal, thereby improving the detection accuracy and stability of the liquid level detection system 100. The liquid level detection system 100 has a wide adaptability and can be widely used in various fields such as dam water level monitoring, fuel leak monitoring, oil extraction and storage, etc.

[0072] It should be noted that those skilled in the art will easily think of other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variation, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application.

[0073] It should be understood that the present application is not limited to the precise construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof, the true scope being indicated by the present application.

Claims

1. A liquid level detection method, characterized in that: Applied in a liquid level detection system, the liquid level detection method comprises: The laser sends detection light to the circulator; wherein the detection light includes a low-frequency signal and a high-frequency signal; The circulator sends the detection light to the liquid level detection module, and the reflector in the liquid level detection module reflects the detection light to form reflected light; wherein the optical path in the liquid level detection module changes with the change of the liquid surface position; The circulator sends the reflected light to the collimator for collimation to obtain collimated light; The photoelectric conversion module receives the collimated light and converts the collimated light into an electrical signal; wherein the collimated light includes a gas absorption signal; the amplitude of the gas absorption signal in the collimated light changes with the change of the optical path in the liquid level detection module; The electrical signal is compared with the initial signal to obtain a real-time liquid level value; wherein the initial signal is an electrical signal under an initial liquid level state.

2. The liquid level detection method according to claim 1, characterized in that: The laser sending detection light to the circulator comprises: A laser driver sends a driving signal to the laser; wherein the driving signal controls the detection light through temperature and current; The laser transmits the detection light according to the driving signal.

3. The liquid level detection method according to claim 1, characterized in that: The liquid level detection module contains gas with a fixed concentration, and the liquid level detection module is airtight.

4. The liquid level detection method according to claim 1, characterized in that: The liquid level detection module includes a reflector and an elastic diaphragm, wherein the reflector is adhered to one side of the elastic diaphragm, and the other side of the elastic diaphragm is arranged at the bottom of the shell of the liquid level detection module, the bottom of the shell is in contact with the liquid surface, and the wavelength range of the reflected light of the reflector includes the wavelength of the detection light.

5. The liquid level detection method according to claim 1, characterized in that: The photoelectric conversion module includes one of a photoelectric detector, a quartz tuning fork or a piezoelectric film.

6. The liquid level detection method according to claim 1, characterized in that: Before comparing the electrical signal with the initial signal, the liquid level detection method further includes: The preamplifier amplifies the electrical signal.

7. The liquid level detection method according to claim 6, characterized in that: The comparing the electrical signal with the initial signal comprises: A lock-in amplifier demodulates the amplified electrical signal; wherein the reference signal frequency of the lock-in amplifier is twice the frequency of the high-frequency signal; The demodulated electrical signal is compared with the initial signal.

8. A liquid level detection system, characterized in that: According to any one of claims 1 to 7, the liquid level detection system comprises: a laser configured to transmit detection light; A circulator, whose input end is connected to the laser and configured to receive the detection light; A liquid level detection module is connected to the middle end of the circulator, wherein the detection light transmitted by the circulator is absorbed by the gas in the liquid level detection module and reflected by the reflector in the liquid level detection module to form reflected light; wherein the optical path in the liquid level detection module changes with the change of the liquid surface position; a collimator connected to the output end of the circulator and configured to collimate the reflected light transmitted by the circulator to obtain collimated light; a photoelectric conversion module configured to convert the collimated light into an electrical signal; the collimated light includes a gas absorption signal, and the amplitude of the gas absorption signal in the collimated light changes with the change of the optical path of the liquid level detection module; A preamplifier connected to the output end of the photoelectric conversion module and configured to amplify the electrical signal; a lock-in amplifier connected to the output of the preamplifier and configured to demodulate the electrical signal; The computer is connected to the output end of the phase-locked amplifier and is configured to compare the electrical signal with an initial signal to obtain a real-time liquid level value, wherein the initial signal is an electrical signal under an initial liquid level state.

9. The liquid level detection system according to claim 8, characterized in that: The liquid level detection system also includes: A laser driver is connected to the laser and is configured to control the laser to send a driving signal; wherein the driving signal controls the detection light through temperature and current, and the driving signal includes a low-frequency sawtooth wave signal and a high-frequency sine wave signal.

10. The liquid level detection system according to claim 8, characterized in that: The liquid level detection module also includes: A shell and an elastic diaphragm; wherein the reflector in the liquid level detection module is adhered to one side of the elastic diaphragm, and the other side of the elastic diaphragm is arranged at the bottom of the shell, and the bottom of the shell is in contact with the liquid surface.

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