High-precision fire pool liquid level sensor based on fiber bragg grating

Abstract

The utility model discloses a high-precision fire pool liquid level sensor based on a fiber bragg grating, which belongs to the technical field of liquid level sensors and comprises a water inlet net, four sides of the water inlet net are connected onto a water inlet net mounting frame, and a front mounting frame, a pressure film, a rear mounting frame and an air box are sequentially arranged behind the water inlet net mounting frame. A strain sensing grating is pasted on the surface, close to the rear mounting frame, of the pressure film, a temperature compensation grating is pasted on the surface of the rear mounting frame, the pressure film separates liquid from the air box to form a cavity, the liquid transmits pressure to the pressure film through the water inlet net, then the strain sensing grating deforms, and the liquid level height is calculated. The liquid level sensor is simple in structure, easy to machine, convenient and fast to assemble and convenient to install on site, the liquid level height is obtained by directly measuring the deformation of the pressure film through the strain sensing grating, the sensitivity and the precision are high, and the influence of the environment temperature on the measurement precision is eliminated due to the arrangement of the temperature compensation grating.

Description

Technical Field

[0001] The utility model belongs to the technical field of liquid level sensors, and in particular relates to a high-precision fire water pool liquid level sensor based on optical fiber Bragg gratings. Background Art

[0002] To ensure adequate firefighting water, the liquid level in a building's firewater tank must remain within the permitted range. This requires a liquid level sensor to monitor the level. Existing liquid level sensors are primarily categorized as float sensors and pressure sensors. Fiber Bragg grating sensors are being adopted for pressure level sensors due to their excellent stress and strain sensing capabilities, corrosion resistance, immunity to electromagnetic interference, and low cost.

[0003] For example, the ultra-high-precision fiber Bragg grating (FBG) liquid level sensor proposed in application No. 202321357648.5 includes a water inlet base, a base membrane mounting base disposed on the water inlet base, the upper end of the base membrane mounting base being connected to an outer cylinder, a deformable base membrane disposed at the upper end of the base membrane mounting base and located within a cavity, and a strain-sensitive fiber Bragg grating disposed on the base membrane. Liquid height differences directly act on the strain-sensitive fiber Bragg grating through the base membrane to monitor minute changes in height differences. In this application, the FBG is perpendicular to the base membrane, and the strain measured by the FBG is much smaller than the actual deformation of the base membrane, resulting in low accuracy. The FBG is fixed between the upper and lower covers of the base membrane by end bonding, which has a limited bonding length and questionable long-term bonding effectiveness. There is no FBG for temperature compensation, and the measurement results are easily affected by ambient temperature.

[0004] Therefore, we propose a high-precision fire water tank level sensor based on fiber Bragg grating to solve the above problems. Summary of the Invention

[0005] In order to solve the above-mentioned defects, the utility model discloses a high-precision fire water tank level sensor based on fiber grating, which aims to solve the problems in the above-mentioned background technology that the strain measured by the fiber grating is much smaller than the actual deformation of the pressure membrane, resulting in limited measurement accuracy, as well as the questionable bonding effect of the fiber grating and the measurement results are affected by the ambient temperature.

[0006] The technical solution of the utility model is as follows:

[0007] The utility model provides a high-precision fire water tank level sensor based on optical fiber Bragg grating, comprising a water inlet network, wherein the four sides of the water inlet network are connected to a water inlet network mounting frame, and the water inlet network mounting frame is followed by a front mounting frame, a pressure membrane, a rear mounting frame and an air box. A strain sensing grating is adhered to the surface of the pressure membrane close to the rear mounting frame, and a temperature compensation grating is adhered to the surface of the rear mounting frame. The pressure membrane isolates the liquid from the air box to form a cavity. The liquid transmits pressure to the pressure membrane through the water inlet network, thereby causing the strain sensing grating to deform, thereby calculating the liquid level height.

[0008] Furthermore, the air box is a hollow rectangular parallelepiped structure with one side open, and a bottom mounting frame for connecting to other parts is provided around the opening.

[0009] Furthermore, the water inlet network mounting frame, front mounting frame, rear mounting frame, and bottom mounting frame are all rectangular plates with a hollow middle, having the same cross-sectional dimensions, and a circle of bolt holes at the same position. They are connected to each other in sequence through mounting bolts, and the mounting bolts have waterproof washers.

[0010] Furthermore, the inner sides of the bolt holes on the side of the front mounting frame and the rear mounting frame facing the pressure membrane are provided with inner waterproof rubber rings surrounding the center, and the inner waterproof rubber rings of the front mounting frame and the rear mounting frame clamp the four sides of the pressure membrane in the middle.

[0011] Furthermore, outer sides of the bolt holes on both sides of the rear mounting frame are provided with outer waterproof rubber rings surrounding the center.

[0012] Furthermore, a vent pipe is provided on the top of the air box, and the vent pipe is connected to a position above the liquid level that will not be immersed.

[0013] Furthermore, the strain sensing grating is pre-stretched and adhered to the surface of the pressure membrane facing the rear mounting frame in the pre-stretched state, and the temperature compensation grating is adhered to the surface of the rear mounting frame.

[0014] Furthermore, the strain sensing grating and the temperature compensation grating are connected in series through optical fibers, extend along the ventilation tube to above the liquid surface, and are connected to a fiber Bragg grating demodulator.

[0015] Furthermore, the four corners of the air box are provided with fixing seats, and the fixing seats fix the device of the utility model to the bottom of the container through fixing bolts.

[0016] Beneficial effects

[0017] The utility model provides a high-precision fire water tank liquid level sensor based on fiber optic Bragg grating, comprising a water inlet network, wherein the four sides of the water inlet network are connected to the water inlet network mounting frame, and the water inlet network mounting frame is followed by a front mounting frame, a pressure membrane, a rear mounting frame, and an air box. The surface of the pressure membrane near the rear mounting frame is affixed with a strain sensing grating, and the surface of the rear mounting frame is affixed with a temperature compensation grating. The pressure membrane isolates the liquid from the air box to form a cavity. The liquid transmits pressure to the pressure membrane through the water inlet network, thereby causing the strain sensing grating to deform, thereby calculating the liquid level. The utility model provides a high-precision fire water tank liquid level sensor based on fiber optic Bragg grating, which has a simple structure, is easy to process, is convenient to assemble, and is convenient for on-site installation. The strain sensing grating is affixed to the pressure membrane along its entire length, having a good bonding effect. The strain sensing grating directly measures the deformation of the pressure membrane and infers the liquid level, with high sensitivity and accuracy. The temperature compensation grating is provided to eliminate the influence of ambient temperature on measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the three-dimensional structure of a high-precision fire water tank level sensor based on fiber Bragg grating provided in a specific embodiment of the present utility model;

[0019] Figure 2 This is a front exploded schematic diagram of a high-precision fire water tank level sensor based on fiber Bragg grating provided by a specific embodiment of the utility model;

[0020] Figure 3 This is a back exploded schematic diagram of a high-precision fire water tank level sensor based on fiber Bragg grating provided by a specific embodiment of the present utility model.

[0021] Explanation of the accompanying symbols: 1. Water inlet net; 2. Water inlet net mounting frame; 3. Front mounting frame; 4. Pressure membrane; 5. Rear mounting frame; 6. Air box; 7. Ventilation pipe; 8. Mounting bolt; 9. Waterproof gasket; 10. Fixing seat; 11. Fixing bolt; 12. Outer waterproof rubber ring; 13. Inner waterproof rubber ring; 14. Bottom mounting frame; 15. Strain sensing grating; 16. Temperature compensation grating. DETAILED DESCRIPTION

[0022] The following describes the implementation of the present invention in conjunction with the accompanying drawings and examples. Obviously, the examples are only used to introduce the technical solution of the present invention in detail, rather than to limit the scope of protection of the present invention.

[0023] Example

[0024] refer to Figure 1As shown in the figure, a high-precision fire pool liquid level sensor based on fiber grating comprises a water inlet net 1, the water inlet net 1 is connected to a water inlet net installation frame 2 at four sides, the water inlet net installation frame is followed by a front installation frame 3, a pressure film 4, a rear installation frame 5 and an air box 6 in sequence.

[0025] Reference Figure 2 As shown in the figure, the air box 6 is a hollow cuboid structure with one side open, a bottom installation frame 14 for connecting other parts is arranged around the opening, and a breather pipe 7 is arranged on the top of the air box 6, the breather pipe 7 is connected to a position above the liquid surface that will not be submerged, so that the air pressure in the air box 6 is equal to the outside air pressure.

[0026] Reference Figure 2 And Figure 3 As shown in the figure, the water inlet net installation frame 2, the front installation frame 3, the rear installation frame 5 and the bottom installation frame 14 are all hollow rectangular plates in the middle, have the same cross-sectional size, and have a circle of bolt holes at the same position, and are connected in sequence through mounting bolts 8, and the mounting bolts 8 have waterproof gaskets 9.

[0027] Reference Figure 2 And Figure 3 As shown in the figure, the pressure film 4 is clamped between the front installation frame 3 and the rear installation frame 5, the inside of the bolt holes on the side of the front installation frame 3 and the rear installation frame 5 facing the pressure film 4 is surrounded by an inner waterproof rubber ring 13, and the inner waterproof rubber ring 13 of the front installation frame 3 and the rear installation frame 5 clamps the four edges of the pressure film 4 in the middle, separates the liquid from the air box 6 to form a cavity.

[0028] Reference Figure 2 And Figure 3 As shown in the figure, the outside of the bolt holes on both sides of the rear installation frame 5 is surrounded by an outer waterproof rubber ring 12, so as to prevent leakage at the connecting parts between the rear installation frame 5 and the front installation frame 3 and the rear installation frame 5 and the bottom installation frame 14.

[0029] Reference Figure 3 As shown in the figure, the strain sensing grating 15 is pre-tensioned, and is pasted on the surface of the side of the pressure film 4 facing the rear installation frame 5 in the pre-tensioned state, and the temperature compensation grating 16 is pasted on the surface of the side of the rear installation frame 5 facing the pressure film 4, the strain sensing grating 15 and the temperature compensation grating 16 are connected in series through an optical fiber, and extend along the breather pipe 7 to above the liquid surface, and are connected with a fiber grating demodulator.

[0030] Reference Figure 1 As shown in the figure, four corners of the air box 6 are provided with fixing seats 10, and the fixing seats 10 are fixedly installed on the bottom of the container through fixing bolts 11.

[0031] Working principle:

[0032] When the liquid level of the container changes, the force of the liquid acting on the pressure film 4 through the water inlet net 1 changes, the pressure film 4 deforms accordingly, the strain sensing optical grating 15 pasted on the inner side of the pressure film 4 deforms coordinately with the pressure film 4, and the center wavelength changes accordingly, the center wavelength change value of the strain sensing optical grating 15 measured by the fiber grating demodulator is subtracted by the center wavelength change value of the temperature compensation optical grating 16, and then divided by the sensitivity coefficient of the fiber grating, so that the strain value of the pressure film 4 eliminating the influence of the ambient temperature is obtained, and finally the liquid level height of the container is inversely deduced through the relationship between the strain value of the pressure film 4 and the liquid level height marked in advance.

[0033] The above is only the preferred embodiment of the utility model, and is not a limitation on the protection scope of the utility model, and any equivalent replacement improvement made on the basis of the technical solutions claimed in the utility model should be included in the protection scope of the utility model.

Claims

1. A high-precision fire water tank level sensor based on fiber Bragg grating, characterized in that: The invention comprises a water inlet net (1), wherein the four sides of the water inlet net (1) are connected to a water inlet net installation frame (2), and the water inlet net installation frame (2) is followed by a front installation frame (3), a pressure membrane (4), a rear installation frame (5) and an air box (6). A strain sensing grating (15) is attached to the surface of the pressure membrane (4) close to the rear installation frame (5). The pressure membrane (4) separates liquid from the air box (6) to form a cavity. The liquid transmits pressure to the pressure membrane (4) through the water inlet net (1), thereby causing the strain sensing grating (15) to deform, thereby realizing liquid level monitoring.

2. A high-precision fire water tank level sensor based on fiber Bragg grating according to claim 1, characterized in that: The air box (6) is a hollow rectangular parallelepiped structure with one side open. A bottom mounting frame (14) is provided around the opening for connecting to other parts. A vent pipe (7) is provided on the top of the air box (6). The vent pipe (7) is connected to a position above the liquid level that will not be immersed.

3. The high-precision fire water tank level sensor based on fiber Bragg grating according to claim 1 is characterized in that: The water inlet network mounting frame (2), the front mounting frame (3), the rear mounting frame (5), and the bottom mounting frame (14) are all rectangular plates with a hollow center, have the same cross-sectional dimensions, and are provided with a circle of bolt holes at the same position. They are connected to each other in sequence by mounting bolts (8), and waterproof washers (9) are provided on the mounting bolts (8).

4. The high-precision fire water tank level sensor based on fiber Bragg grating according to claim 1, characterized in that: The pressure membrane (4) is sandwiched between the front mounting frame (3) and the rear mounting frame (5). The inner sides of the bolt holes on the sides of the front mounting frame (3) and the rear mounting frame (5) facing the pressure membrane (4) are each provided with an inner waterproof rubber ring (13) surrounding the center. The inner waterproof rubber ring (13) of the front mounting frame (3) and the rear mounting frame (5) sandwich the four sides of the pressure membrane (4) and isolate the liquid from the air box (6) to form a cavity. The outer sides of the bolt holes on both sides of the rear mounting frame (5) are each provided with an outer waterproof rubber ring (12) surrounding the center.

5. The high-precision fire water tank level sensor based on fiber Bragg grating according to claim 1 is characterized in that: The strain sensing grating (15) is adhered to the surface of the pressure membrane (4) facing the rear mounting frame (5) in a pre-tensioned state, and the temperature compensation grating (16) is adhered to the surface of the rear mounting frame (5) facing the pressure membrane (4). The strain sensing grating (15) and the temperature compensation grating (16) are connected in series via optical fibers, extended along the vent pipe (7) to above the liquid surface, and connected to a fiber Bragg grating demodulator.

6. The high-precision fire water tank level sensor based on fiber Bragg grating according to claim 2, characterized in that: The four corners of the air box (6) are provided with fixing seats (10), and the fixing seats (10) are used to fix the device to the bottom of the container through fixing bolts (11).

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