Fiber bragg grating osmometer package structure with built-in temperature compensation

Abstract

The utility model discloses a kind of built-in temperature compensation's fiber grating osmotic pressure gauge packaging structure, it is related to engineering monitoring technical field, its technical scheme main point is: protective shell, protective shell inside is formed with osmotic pressure gauge internal structure, packaging structure further include with the structure head end connected with pressure measurement part and with the structure tail end connected with temperature measurement part, sensing component is set in protective shell, for the deformation generated by osmotic pressure is transmitted to pressure measurement part, pressure measurement part is set in protective shell, pressure measurement part is the cantilever force frame structure coupled by double bending frame, the both sides of pressure measurement part are symmetrically provided with the installation groove of the placement pressure measurement fiber grating;Temperature measurement part is set in protective shell, solve the problem that the measurement accuracy of existing sensor is significantly influenced by environmental temperature change due to lack of temperature compensation function, significantly improve the long-term measurement accuracy and reliability of osmotic pressure gauge under complex temperature environment.

Description

Technical Field

[0001] This utility model relates to the field of engineering monitoring technology, and more specifically, it relates to a fiber optic grating piezometer packaging structure with built-in temperature compensation. Background Technology

[0002] In the field of civil engineering, long-term and stable seepage pressure monitoring of major infrastructure such as dams, slopes, and tunnels is a key link in ensuring their construction and operation safety. Achieving high-precision and high-reliability pressure measurement is of great significance for structural health monitoring.

[0003] Traditional resistance strain gauges or vibrating wire piezometers used in engineering, while technically mature, have inherent drawbacks such as weak electromagnetic interference resistance, susceptibility to lightning strikes, short signal transmission distance, and insufficient long-term stability. They are difficult to meet the high-reliability monitoring requirements in complex environments. Fiber optic grating sensing technology, with its advantages of electromagnetic interference resistance, corrosion resistance, lightning protection, long signal transmission distance, and suitability for multiplexing and networking, provides a new solution for piezometer monitoring.

[0004] However, existing fiber Bragg grating piezometers still have significant shortcomings: First, in terms of structural design, most products still use complex mechanical transmission structures (such as cantilever beams, levers, etc.), resulting in numerous internal components, complex assembly processes, and bulky overall size of the sensor, making it difficult to meet the application requirements of embedded installation or space-constrained occasions. More importantly, in terms of measurement accuracy, common fiber Bragg grating piezometers lack an effective temperature compensation mechanism. Fiber Bragg gratings are sensitive to both ambient temperature and strain. In actual working conditions, temperature changes will cause a shift in the center wavelength of the grating. This shift is coupled with the wavelength change caused by pressure. If it is not distinguished and compensated, it will introduce significant measurement errors, reduce the reliability of the data, and fail to meet the requirements of high-precision long-term monitoring.

[0005] Therefore, in order to solve the above-mentioned technical problems, this application proposes a fiber optic grating piezometer packaging structure with built-in temperature compensation. Utility Model Content

[0006] To address the problems of numerous internal components and bulky overall size caused by the complex mechanical structures such as cantilever beams commonly used in existing fiber Bragg grating piezometers, this invention aims to provide an integrated and compact packaging solution through optimized structural design. Furthermore, to address the issue of insufficient measurement accuracy caused by the lack of an effective temperature compensation mechanism in existing sensors, this invention aims to effectively distinguish and compensate for center wavelength shifts caused by temperature changes through a built-in temperature compensation design. Therefore, this invention provides a fiber Bragg grating piezometer packaging structure with built-in temperature compensation.

[0007] To achieve the above objectives, this utility model provides the following technical solution: a fiber optic grating piezometer packaging structure with built-in temperature compensation, comprising: Protective casing; Pressure measuring unit is installed inside the protective housing; Temperature measuring unit disposed within the protective housing; The sensing component installed inside the protective housing is used to transmit the deformation caused by seepage pressure to the pressure measuring unit; Some of the optical fibers are housed inside the protective housing; A pressure measurement fiber grating coupled to the pressure measurement unit for sensing the deformation of the pressure measurement unit; A temperature measurement fiber grating coupled to the temperature measurement unit for sensing temperature changes; The pressure measurement fiber grating and the temperature measurement fiber grating are fabricated on the optical fiber.

[0008] Preferably, the pressure measuring unit is a suspension frame structure formed by coupling two bending frames, and mounting slots for placing the pressure measuring fiber optic grating are symmetrically opened on both sides of the pressure measuring unit.

[0009] Preferably, the packaging structure further includes a structural head end connected to the pressure measuring unit and a structural tail end connected to the temperature measuring unit.

[0010] Preferably, the sensing element is a pressure-sensitive diaphragm that deforms in response to external seepage pressure.

[0011] Preferably, the tail end of the structure has a connecting portion, and the pressure-sensitive diaphragm is disposed at the connecting portion.

[0012] Preferably, the tail end of the structure is provided with a permeable water-permeable element, which is made of porous material. The water-permeable element is connected to the pressure-sensitive membrane and transmits external osmotic pressure to the pressure-sensitive membrane.

[0013] Preferably, the permeable element is permeable stone.

[0014] Preferably, the pressure measuring fiber grating is encapsulated and attached to the inner wall of the suspension frame of the pressure measuring part in a pre-loaded stress state, while the temperature measuring fiber grating is encapsulated and fixed to the temperature measuring part in a free state.

[0015] Preferably, the inner wall of the suspension frame of the pressure measuring unit is provided with high-temperature adhesive to make the pressure measuring fiber optic grating adhere tightly to the inner wall of the suspension frame as one piece; The surface of the temperature measuring part is provided with high-temperature adhesive to fix the stress-free temperature measuring fiber optic grating to the surface of the temperature measuring part.

[0016] Preferably, the protective housing is provided with a tail sleeve terminal for connecting to an external device, and the optical fiber extends through the tail sleeve terminal to the outside of the protective housing.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. In this utility model, by using different packaging processes, the two gratings are placed in different mechanical states, with the pressure grating in a pre-stretched state and the temperature grating in a stress decoupling state. Real-time compensation is performed using the pure temperature reference signal provided by the temperature grating, which effectively distinguishes the optical response caused by pressure and temperature changes. This solves the problem that the measurement accuracy of existing sensors is significantly affected by changes in ambient temperature due to the lack of temperature compensation function, and significantly improves the long-term measurement accuracy and reliability of the piezometer in complex temperature environments.

[0018] 2. In this utility model, by integrating the pressure and temperature measuring gratings into the same optical fiber and adopting a simplified structure in which the pressure-sensitive diaphragm is directly mechanically coupled to the fiber optic grating, the number of mechanical parts inside the sensor is effectively reduced, the assembly complexity is lowered, and the sensor structure is miniaturized and lightweighted, making it more suitable for installation and use in space-constrained monitoring scenarios. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the present invention and form part of this application, illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the present invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the overall internal structure of this utility model; Figure 3 This is a structural schematic diagram of the overall interior of this utility model from another perspective; Figure 4 This is a schematic diagram of the pressure measuring unit and the temperature measuring unit in this utility model.

[0020] 1. Protective casing; 20. Structural head end; 21. Structural tail end; 22. Pressure measuring unit; 23. Temperature measuring unit; 24. Mounting slot; 30. Optical fiber; 31. Pressure measurement fiber grating; 32. Temperature measurement fiber grating; 4. Permeable stone; 5. Pressure-sensitive diaphragm; 6. Tail sleeve terminal. Detailed Implementation

[0021] like Figure 1-4 As shown, this utility model provides a fiber Bragg grating piezometer packaging structure with built-in temperature compensation, comprising: The protective housing 1 contains an internal structure of a piezometer. The encapsulation structure also includes a structural head end 20 connected to the pressure measuring unit 22 and a structural tail end 21 connected to the temperature measuring unit 23. A sensing component is disposed within the protective housing 1 to transmit the deformation generated by osmosis to the pressure measuring unit 22. The structural tail end 21 has a communication point, and a pressure-sensing diaphragm 5 is disposed at the communication point. The end of the structural tail end 21 is provided with a permeable water-permeable element. The water-permeable element is made of porous material and is connected to the pressure-sensing diaphragm 5 to transmit external osmosis to the pressure-sensing diaphragm 5. The water-permeable element is a permeable stone 4, which can be a sintered metal permeable stone 4 or a ceramic permeable stone 4. The pressure measuring unit 22 is installed inside the protective housing 1. The pressure measuring unit 22 is a suspension frame structure formed by double bending frame coupling. The two sides of the pressure measuring unit 22 are symmetrically provided with mounting slots 24 for placing the pressure measuring fiber optic grating 31; the temperature measuring unit 23 is installed inside the protective housing 1. It should be noted that the deformation of the sensing diaphragm caused by the seepage pressure from the permeable stone 4 directly acts on the temperature measuring unit 23. The temperature measuring unit 23 and the pressure measuring unit 22 are coupled. Due to its robust structure, the temperature measuring unit 23 transmits the deformation pressure from the sensing diaphragm to the pressure measuring unit 22. Since the pressure measuring unit 22 is a double-bend suspension frame structure, the suspension frame structure also deforms when the sensing diaphragm deforms. It should be noted that in this embodiment, the protective shell 1 is made of stainless steel with precision machining. Its interior forms a sealed accommodating chamber. The whole has good mechanical strength and corrosion resistance, and is suitable for long-term installation in harsh engineering environments. One end of the protective shell 1 is provided with an installation interface for fixing the permeable stone 4. The permeable stone 4 is preferably a loose and porous structure made of sintered stainless steel or ceramic material, which can effectively filter impurities and allow the liquid or gas medium to be tested to permeate.

[0022] In this embodiment, the pressure-sensitive diaphragm 5 is made of a metal sheet or a polymer material sheet with good elasticity and high stability. It can undergo significant and recoverable deformation under external seepage pressure. It is sealed and fixed to the inner end face of the protective shell 1 by laser welding or high-temperature brazing process and is located inside the permeable stone 4. The pressure-sensitive diaphragm 5 has good elasticity and fatigue resistance characteristics and can generate recoverable deformation in response to changes in external seepage pressure.

[0023] A pressure measuring fiber grating 31 is coupled to the pressure measuring unit 22 to sense the deformation of the pressure measuring unit 22; a temperature measuring fiber grating 32 is coupled to the temperature measuring unit 23 to sense temperature changes; the pressure measuring fiber grating 31 is encapsulated and bonded to the inner wall of the suspension frame of the pressure measuring unit 22 in a pre-loaded stress state, and the temperature measuring fiber grating 32 is encapsulated and fixed to the temperature measuring unit 23 in a free state; a high-temperature adhesive is provided on the inner wall of the suspension frame of the pressure measuring unit 22 to make the pressure measuring fiber grating 31 adhere tightly to the inner wall of the suspension frame and form an integral whole; a high-temperature adhesive is provided on the surface of the temperature measuring unit 23 to fix the stress-free temperature measuring fiber grating 32 to the surface of the temperature measuring unit 23. The pressure measurement fiber grating 31 is encapsulated and fixed in a preloaded stress state. The preloaded stress state of the pressure measurement fiber grating 31 is achieved by applying axial prestress to it during encapsulation to measure the pressure change. The temperature measurement fiber grating 32 is encapsulated and fixed in a stress decoupling state. The stress decoupling state of the temperature measurement fiber grating 32 is achieved by fixing it in a region inside the optical fiber that is not affected by mechanical deformation, so that its optical signal only responds to the change of ambient temperature. The pressure measurement fiber grating 31 is cured and encapsulated under pre-stress by a high-bonding epoxy resin adhesive, while the temperature measurement fiber grating 32 is cured and encapsulated under free state by a high-bonding epoxy resin adhesive. It should be noted that the pressure measuring fiber optic grating 31 measures pressure through optical signals. It does not directly receive pressure itself, but rather transforms physical quantities such as the deformation of the pressure-sensing diaphragm 5 and the prestress applied by the pressure measuring fiber optic grating 31 itself into strain that it can sense, and finally presents it through changes in optical signals. The packaging state of the pressure sensing component is different from that of the temperature reference component. The pressure sensing module acquires optical signals related to osmotic pressure, and the temperature compensation module acquires optical signals related to temperature. The two signals are processed together to eliminate errors and realize temperature self-compensation for osmotic pressure measurement. In the embodiments, the key packaging processes are described as follows: After the pressure measuring fiber optic grating 31 is placed in an axial pre-stretched state by a special fiber optic clamp, it is firmly bonded and fixed to the inside of the fiber optic and the temperature measuring part 23 by a high-strength epoxy resin adhesive, thereby sensitively receiving the strain transmitted by the pressure-sensitive diaphragm 5. The temperature measurement fiber grating 32 is fixed inside the fiber 30 under natural stress (i.e., free state) and is located in the non-stressed area of ​​the internal structure of the piezometer, so that its optical response is only sensitive to changes in ambient temperature and is decoupled from mechanical stress.

[0024] The protective housing 1 is provided with a tail sleeve terminal 6 for connecting to external devices, and an optical fiber extends through the tail sleeve terminal 6 to the outside of the protective housing 1; It should be noted that the pressure measuring fiber grating 31 and the temperature measuring fiber grating 32 are engraved on the same optical fiber 30. The optical fiber 30 passes through the tail sleeve terminal 6 located at the other end of the protective housing 1 and leads out to the outside. The tail sleeve terminal 6 is filled with sealant to ensure the airtightness of the housing.

[0025] Its specific working principle is as follows: External seepage pressure changes are transmitted to the pressure-sensing diaphragm 5 through the permeable stone 4. The diaphragm deforms under the pressure from the permeable stone 4, and this deformation directly acts on the temperature measuring unit 23. The temperature measuring unit 23 and the pressure measuring unit 22 are coupled. Due to its robust structure, the temperature measuring unit 23 transmits the deformation pressure from the diaphragm to the pressure measuring unit 22. Since the pressure measuring unit 22 is a double-bend suspension frame structure, the suspension frame structure also deforms when the diaphragm deforms. This deformation is further transmitted to the pressure measuring fiber optic grating 31 coupled with it, causing a change in its grating pitch, which in turn causes a shift in its center wavelength. This wavelength shift includes the optical response caused by both the actual seepage pressure change and the temperature change. Ambient temperature changes affect both the pressure measurement fiber grating 31 and the temperature measurement fiber grating 32. Since the temperature measurement fiber grating 32 is encapsulated in a stress-decoupled state, the offset of its center wavelength is caused only by temperature changes, and therefore it can be used as a pure temperature reference signal. An external fiber optic demodulator (an instrument used for fiber optic grating measurement in the prior art) synchronously acquires the center wavelengths of the pressure measuring fiber optic grating 31 and the temperature measuring fiber optic grating 32. The data processing of the fiber optic demodulator first calculates the current change in ambient temperature based on the center wavelength offset of the temperature measuring fiber optic grating 32 and its known temperature sensitivity coefficient. Then, based on the known temperature sensitivity coefficient of the pressure measuring fiber optic grating 31, it calculates the wavelength offset caused by the temperature change to the pressure channel. Finally, by subtracting the thermally induced offset from the total wavelength offset of the pressure channel, the true wavelength offset caused only by the change in osmotic pressure can be obtained. Then, the accurate external osmotic pressure value is calculated based on its pressure sensitivity coefficient.

[0026] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model in any way. Those skilled in the art can readily implement this utility model based on the accompanying drawings and the above description. However, any modifications, alterations, or equivalent variations made by those skilled in the art without departing from the scope of the utility model's technical solution, utilizing the disclosed technical content, are considered equivalent embodiments of this utility model. Furthermore, any equivalent changes, alterations, or variations made to the above embodiments based on the essential technology of this utility model are still within the protection scope of this utility model's technical solution.

Claims

1. A fiber Bragg grating piezometer packaging structure with built-in temperature compensation, characterized in that, include: Protective housing (1); The pressure measuring unit (22) is installed inside the protective housing (1); Temperature measuring unit (23) is installed inside the protective housing (1); The sensing component installed inside the protective housing (1) is used to transmit the deformation caused by seepage pressure to the pressure measuring unit (22). Optical fiber (30) partially disposed inside the protective housing (1); A pressure measurement fiber grating (31) is coupled to the pressure measurement unit (22) for sensing the deformation of the pressure measurement unit (22); A temperature measurement fiber grating (32) is coupled to the temperature measurement unit (23) for sensing temperature changes. The pressure measuring fiber grating (31) and the temperature measuring fiber grating (32) are written on the optical fiber.

2. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 1, characterized in that: The pressure measuring unit (22) is a suspension frame structure formed by double bending frames coupled together. The pressure measuring unit (22) has mounting slots (24) symmetrically opened on both sides for placing the pressure measuring fiber optic grating (31).

3. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 2, characterized in that: The encapsulation structure also includes a structural head end (20) connected to the pressure measuring unit (22) and a structural tail end (21) connected to the temperature measuring unit (23).

4. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 3, characterized in that: The sensing component is a pressure-sensitive diaphragm (5) that deforms in response to external seepage pressure.

5. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 4, characterized in that: The tail end (21) of the structure has a connection point, and the pressure-sensitive diaphragm (5) is disposed at the connection point.

6. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 5, characterized in that: The end of the tail end (21) of the structure is provided with a permeable water-permeable element. The water-permeable element is made of porous material. The water-permeable element is connected to the pressure-sensitive membrane (5) and transmits external osmotic pressure to the pressure-sensitive membrane (5).

7. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 6, characterized in that: The permeable component is permeable stone (4).

8. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 2, characterized in that: The pressure measuring fiber grating (31) is encapsulated and attached to the inner wall of the suspension frame of the pressure measuring part (22) in a preloaded stress state, while the temperature measuring fiber grating (32) is encapsulated and fixed on the temperature measuring part (23) in a free state.

9. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 8, characterized in that: The inner wall of the suspension frame of the pressure measuring unit (22) is provided with high-temperature adhesive to make the pressure measuring fiber optic grating (31) stick tightly to the inner wall of the suspension frame and become one piece. The surface of the temperature measuring part (23) is provided with high-temperature adhesive that fixes the stress-free temperature measuring fiber optic grating (32) to the surface of the temperature measuring part (23).

10. The packaging structure of a fiber Bragg grating piezometer with built-in temperature compensation according to claim 1, characterized in that: The protective housing (1) is provided with a tail sleeve terminal (6) for connecting to external devices, and the optical fiber (30) extends through the tail sleeve terminal (6) to the outside of the protective housing (1).

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