High-precision fiber bragg grating liquid level sensor suitable for small measuring range

Abstract

The high-precision fiber grating liquid level sensor comprises a shell, an elastic membrane is arranged in the shell and divides the space in the shell into a liquid cavity and a pressure cavity, the shell is provided with a liquid port, the liquid port is communicated with the liquid cavity, and the pressure cavity is communicated with the liquid port. A fiber bragg grating sensor is arranged on the elastic diaphragm, and the fiber bragg grating sensor is sequentially connected with a signal transmission fiber, a signal transmission cable and a fiber cold joint. The liquid pressure is converted into the deformation of the fiber Bragg grating sensor through the elastic membrane, so that the purpose of measuring the liquid pressure is achieved, the change of the liquid level of the surrounding environment of the sensor can be monitored in real time, and high-resolution and high-precision long-term monitoring of the small-range liquid level can be achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of optical fiber sensors, and in particular relates to a high-precision optical fiber Bragg grating liquid level sensor suitable for a small range. Background Art

[0002] In-situ test pit water injection testing is an important method for assessing groundwater levels, permeability, and other hydrogeological parameters. Initial test methods and equipment were relatively simple, relying primarily on manual operation and simple measuring equipment to measure the liquid level.

[0003] Traditional liquid level measurement primarily involves mechanical float level sensors, electronic level sensors, and radar / ultrasonic level sensors. Mechanical float level sensors utilize transmission devices such as mechanical reeds, magnets, and electronic or optoelectronic devices to convert float height information into pulse or continuous signals. While these sensors offer advantages such as low cost and high reliability, they also suffer from low sensitivity and limited intelligence. Electronic level sensors convert changes in liquid level into changes in electrical parameters, using measurement circuits to monitor the output of these parameters to measure the liquid level signal. These sensors, primarily capacitive and resistive, offer advantages such as high measurement accuracy and a wide range, but drawbacks include being based on electrical signals, susceptible to electromagnetic interference, and exhibiting poor reliability. With the advancement of fiber grating (FBG) sensing technology, using FBG sensors for liquid level measurement can simplify detection processes and significantly shorten measurement cycles. They also offer advantages such as fast response, ease of networking, and resistance to high-temperature corrosion and electromagnetic interference. However, current FBG level sensors still have limitations for monitoring the level of small-scale liquid storage tanks, including low sensitivity, resolution, and accuracy. Utility Model Content

[0004] Therefore, the present invention aims to solve the problems of low sensitivity, low resolution and poor accuracy in measuring liquid level in the prior art.

[0005] To this end, the technical solution adopted is that the utility model is a high-precision fiber Bragg grating liquid level sensor suitable for a small range, comprising: a housing, an elastic diaphragm arranged in the housing, the elastic diaphragm dividing the space in the housing into a liquid chamber and a pressure chamber, a liquid port provided on the housing, the liquid port being connected to the liquid chamber, a fiber Bragg grating sensor provided on the elastic diaphragm, and the fiber Bragg grating sensor being connected in sequence to a signal transmission optical fiber, a signal transmission cable and an optical fiber cold joint.

[0006] Preferably, the signal transmission cable and the optical fiber cold connector are located outside the housing.

[0007] Preferably, both ends of the fiber Bragg grating sensor are fixed on the elastic diaphragm by fixing glue.

[0008] Preferably, a filter screen is provided on the liquid port.

[0009] Preferably, the fiber Bragg grating sensor has a core diameter of 6-10 μm, a cladding diameter of 125 μm, a coating diameter of 250 μm, and a grating diameter of 10 mm.

[0010] Preferably, the elastic membrane has a diameter of 15-25 mm and a thickness of 50-200 μm.

[0011] The technical solution of the utility model has the following advantages: the sensor uses a polymer film as the elastic diaphragm of the sensor. Due to the excellent parameter performance of the polymer film, the sensitivity of the bare optical fiber can be enhanced, and the fiber Bragg grating is laterally pasted to the elastic diaphragm, making the sensor structure simple and easy to manufacture.

[0012] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0013] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0015] Figure 1 It is a structural diagram of the utility model;

[0016] Figure 2 This is a working state diagram of the elastic diaphragm in the utility model;

[0017] Among them, 1. Shell; 2. Elastic diaphragm; 3. Liquid chamber; 4. Pressure chamber; 5. Liquid port; 6. Fiber Bragg grating sensor; 7. Signal transmission optical fiber; 8. Signal transmission cable; 9. Fiber cold joint; 10. Fixing glue; 11. Filter. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] It should be noted that when a component is referred to as being “fixed to” or “disposed on” another component, it can be directly on the other component or indirectly on the other component. When a component is referred to as being “connected to” another component, it can be directly or indirectly connected to the other component.

[0020] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0022] The utility model provides a high-precision fiber Bragg grating liquid level sensor suitable for small range, such as Figure 1-2 As shown, the device comprises a housing 1, within which is disposed an elastic diaphragm 2, which divides the space within the housing 1 into a liquid chamber 3 and a pressure chamber 4. A liquid port 5 is provided on the housing 1, communicating with the liquid chamber 3. A fiber Bragg grating sensor 6 is disposed on the elastic diaphragm 2, which is sequentially connected to a signal transmission optical fiber 7, a signal transmission cable 8, and a fiber cold connector 9. This fiber Bragg grating liquid level sensor has a measuring range of 500 mm, a liquid level resolution of 1 mm, and an accuracy of 0.2% FS.

[0023] The beneficial technical effects of the above technical solution are as follows: the housing 1 is placed in the liquid to be measured, the liquid enters the liquid chamber 3 through the liquid port 5, the elastic diaphragm 2 is deformed under the action of the liquid pressure, and the liquid pressure is converted into stress changes on the fiber Bragg grating sensor 6, which is then transmitted through the signal transmission optical fiber 7, the signal transmission cable 8 and the optical fiber cold connector 9. After signal processing, the liquid level measurement result is displayed, thereby realizing accurate measurement of small-scale liquid levels.

[0024] In one embodiment, Figure 1As shown, a signal transmission cable 8 and a fiber optic cold connector 9 are located outside the housing 1 for signal transmission. The ends of the fiber Bragg grating sensor 6 are fixed to the elastic diaphragm 2 with adhesive 10. Due to the deformation of the elastic diaphragm 2 caused by liquid pressure, the fiber Bragg grating sensor 6 experiences uniform stress, causing the center wavelength of the fiber Bragg grating sensor 6 to drift. Liquid level measurement is achieved by monitoring the drift of the center wavelength. A filter 11 is provided on the liquid port 5. The filter 10 is a stainless steel mesh with a pore size of 0.5 mm and a thickness of 5 mm. It filters out impurities and other particulate matter in the surrounding liquid of the measured environment.

[0025] The fiber Bragg grating sensor 6 has a core diameter of 6-10 μm, a cladding diameter of 125 μm, a coating diameter of 250 μm, a grating diameter of 10 mm, an operating wavelength of 1528-1568 nm, a reflectivity greater than 90%, and a coating structure composed of fluorinated acrylic resin. The output spectrum of the fiber Bragg grating sensor 6 has a resonant peak that responds to external pressure changes. The elastic diaphragm 2 is a polymer elastic film (PI film, PE film, PP film) with a diameter of 15-25 mm, a thickness of 50-200 μm, and a Young's modulus below 4 GPa. The elastic diaphragm 2 can transfer the tiny strains generated by millimeter-level liquid level changes to the fiber Bragg grating sensor 6 attached to it, thereby enhancing the sensitivity of the fiber Bragg grating sensor 6. The deformation range of the elastic diaphragm 2 determines the liquid level measurement range of the sensor, enabling the fiber Bragg grating sensor 6 to monitor millimeter-level liquid level changes within a small measurement range, achieving high-resolution and high-precision monitoring of small-scale liquid levels. The polymer elastic film also exhibits excellent heat and moisture resistance, as well as good chemical stability, is insoluble in organic solvents, and is corrosion-resistant. Signal transmission optical fiber 7 is a core-clad single-mode quartz optical fiber with a core refractive index of 1.4680, a core diameter of 6-10 µm, a cladding refractive index of 1.4444, a diameter of 125 µm, and a numerical aperture of 0.22, used for transmitting optical signals.

[0026] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.

Claims

1. A high-precision fiber Bragg grating liquid level sensor suitable for small-scale measurement, characterized in that: include: A housing (1) is provided with an elastic diaphragm (2) in the housing (1), the elastic diaphragm (2) divides the space in the housing (1) into a liquid chamber (3) and a pressure chamber (4), a liquid port (5) is provided on the housing (1), the liquid port (5) is communicated with the liquid chamber (3), a fiber Bragg grating sensor (6) is provided on the elastic diaphragm (2), and the fiber Bragg grating sensor (6) is connected to a signal transmission optical fiber (7), a signal transmission cable (8) and an optical fiber cold connector (9) in sequence.

2. A high-precision fiber Bragg grating liquid level sensor suitable for a small range according to claim 1, characterized in that: The signal transmission cable (8) and the optical fiber cold connector (9) are located outside the housing (1).

3. The high-precision fiber Bragg grating liquid level sensor suitable for a small range according to claim 1, characterized in that: Both ends of the fiber Bragg grating sensor (6) are fixed on the elastic diaphragm (2) by fixing glue (10).

4. The high-precision fiber Bragg grating liquid level sensor suitable for a small range according to claim 1, characterized in that: A filter screen (11) is provided on the liquid port (5).

5. The high-precision fiber Bragg grating liquid level sensor suitable for a small range according to claim 1, characterized in that: The fiber Bragg grating sensor (6) has a core diameter of 6-10 μm, a cladding diameter of 125 μm, a coating diameter of 250 μm, and a grating diameter of 10 mm.

6. The high-precision fiber Bragg grating liquid level sensor suitable for a small range according to claim 1, characterized in that: The elastic diaphragm (2) has a diameter of 15-25 mm and a thickness of 50-200 µm.

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