CN205280058U - Differential type fiber grating hydrostatic level appearance - Google Patents

Abstract

The utility model discloses a differential optical fiber grating static level, which comprises several optical fiber grating static level devices with the same structure and connected in series. The valves are connected. Each fiber grating static leveling device is a cylindrical cavity, which is divided into an upper cavity and a lower cavity. In the upper cavity, the upper cover is fixed along the diameter direction of the upper cover. Fiber Bragg grating 1 is pasted on the upper surface of beam 1 of equal strength, and fiber Bragg grating 2 is pasted on the lower surface of beam 2 of constant strength. A float is arranged in the lower cavity, and the float includes a buoy and a push rod. The upper end of the push rod passes through the partition and is located directly below the connection end points of the first equal-strength beam and the second equal-strength beam. The side of the lower chamber fixes the liquid level indicating tube in the vertical direction. The utility model has the advantages of simple structure, high sensitivity and temperature self-compensation function for the differential fiber grating static force level.

Description

A Differential Fiber Bragg Grating Static Level

technical field

The utility model belongs to the technical field of optical fiber sensing, in particular to a differential optical fiber grating static level.

Background technique

Fiber Bragg grating sensing technology is a technology that utilizes the wavelength shift of the grating under the influence of external factors to realize quasi-distributed sensing and measurement. As a new type of passive sensing element, fiber Bragg grating has the advantages of anti-electromagnetic interference, anti-corrosion, high reliability, high measurement accuracy, and strong series networking capabilities. Therefore, fiber grating sensors play an important role in power systems, natural resource exploitation, and water conservancy projects.

Bridges, tunnels, dams, etc. will deform under external factors or natural conditions. The local or overall deflection changes in the vertical direction reflect the unevenness of the force in the vertical direction, which will affect the deformation of bridges, tunnels, dams, etc. Adversely affect safety and usability. At present, the static level is mainly used to monitor the displacement of the structure in the vertical direction. The static level is mainly composed of liquid cylinders, buoys, sensitive devices and other components, and is suitable for measuring the relative displacement of the substrate between the reference point and the test point in the vertical direction. . During use, the static level uses the principle of the connector, and the liquid levels of the multiple static levels connected together through the connecting pipe and the liquid storage tank are always at the same level. By measuring the height of the internal liquid level of different static levels The change indirectly measures the vertical displacement change of the measuring point. Traditional static levels mostly use weighing, capacitive and pressure-type sensors. Due to poor anti-electromagnetic interference, poor long-term stability, serious attenuation of long-distance transmission signals, and difficulty in building sensor networks, these electrical sensors are often used in some cases. Use is limited. The fiber grating static level solves the problems of the above-mentioned traditional static level. The Chinese patent No. 201520094700.1 "multi-channel static level device based on fiber grating sensor" adopts a float type, and a fixed pulley transmits force and changes direction. By stretching the metal sheet, the wavelength of the grating attached to it is shifted, so as to detect the change of the liquid level. However, the friction of the fixed pulley mechanism cannot be ignored, which affects the measurement accuracy and repeatability of the sensor. Since no temperature compensation measures are taken, the measurement results of the sensor are greatly affected by temperature. Patent No. 201120149877.9 Chinese patent "a grating static level" adopts a float-type double-grating structure. The buoyancy acts on the equal-strength beam through the float, and the strain of the grating pasted on the equal-strength beam changes. The strain change causes the wavelength to drift. In this way, there is a corresponding relationship between the liquid level change and the wavelength drift, and the double grating structure has a temperature compensation function. However, due to the limitation of the material of the equal-strength beam itself, the strain change is limited, so the wavelength change is limited, so the sensitivity of the static level is not great.

Utility model content

Aiming at the problems in the prior art, the utility model provides a differential fiber grating static level instrument, which has simple structure, high sensitivity and the function of temperature self-compensation.

The technical scheme adopted by the utility model to solve the technical problem is: to provide a differential fiber grating static level, which includes several fiber grating static level devices with the same structure and connected in series, adjacent fiber grating static level devices The lower chambers are connected through the liquid three-way valve. The liquid three-way valve is set at the lower part of the lower chamber of the fiber grating static level device. Each fiber grating static level device is a cylindrical cavity and is divided into an upper chamber. and the lower chamber, the upper chamber and the lower chamber are separated by a partition, the upper chamber includes the upper cover, the first equal-strength beam, the second equal-strength beam, the first fiber grating, the second fiber grating, the first fiber outlet tube, and the second fiber outlet tube , the equal-strength beam 1 and the equal-strength beam 2 are fixed in the upper cover along the diameter direction of the upper cover. The structures and sizes of the equal-strength beam 1 and the equal-strength beam 2 are symmetrically arranged, and their ends close to each other are fixedly connected. Fiber Bragg Grating 1 is pasted on the upper surface of beam 1, and Fiber Bragg Grating 2 is pasted on the lower surface of equal-intensity beam 2. Fiber Bragg Grating 1 and Fiber Bragg Grating 2 are respectively connected to external testing instruments through fiber outlet tube 1 and fiber outlet tube 2 located on the side of the upper cover. ;A float is set in the lower cavity, the float includes a buoy and a push rod, the lower end of the push rod is fixed at the center of the upper surface of the buoy, the upper end of the push rod passes through the partition, and is located at the connection end point with the first equal-strength beam and the second equal-strength beam directly below; the side of the lower chamber is vertically fixed with a liquid level indicator tube; the upper part of the lower chamber of each fiber grating static leveling device is respectively provided with a venting three-way valve.

According to the above technical solution, the upper end and the lower end of the liquid level indicating tube are respectively communicated with the lower chamber through a two-way valve.

According to the above technical scheme, the buoy is horizontally limited by the first snap ring and the second snap ring, so that the buoy is located in the middle of the lower cavity.

According to the above technical solution, the two-way valves at the upper end and the lower end of the liquid level indicating pipe are connected with the lower chamber by threads, and a sealing ring is provided respectively.

According to the above technical solution, a small boss is arranged on the bottom surface of the lower chamber, and the bottom surface of the lower chamber contacts with the lower bottom surface of the buoy through the small boss.

According to the above technical scheme, the material of the push rod is aluminum.

The working principle of the utility model is that a plurality of fiber grating static leveling devices are connected in series through the liquid three-way valve to form a connecting device, and the liquid levels in all the fiber grating static leveling devices are kept at the same level and at the same level as the reference base point. On the horizontal plane, when the vertical displacement of the detection point where any FBG static leveling device is located changes, the liquid level in each FBG static leveling device is still at the same level, but the FBG static leveling device at this detection point When the depth of the liquid changes, the buoyancy of the buoy in the fiber grating static leveling device changes, so the force acting on the first and second equal-strength beams changes, and corresponding deformation occurs on the first and second equal-strength beams , the surface strain also changes. At the same time, grating 1 and grating 2 pasted on the surface also produce strain changes synchronously. According to the principle of fiber grating sensing, the wavelength of grating 1 and grating 2 drifts. Because grating 1 is pasted on the upper surface of equal-strength beam 1, and grating 2 is pasted on the lower surface of equal-strength beam 2, during the deformation process of equal-strength beam 1 and equal-strength beam 2, one grating is pulled, and the wavelength becomes larger. The other grating is compressed, the wavelength becomes smaller, and since they are in the same temperature field, the temperature affects them equally. Subtracting the wavelength variation of grating 1 and grating 2, on the one hand, eliminates the influence of temperature change and achieves the effect of temperature compensation; on the other hand, the magnitude of strain is amplified to achieve the effect of increasing sensitivity.

The beneficial effects produced by the utility model are: the fiber grating is used as the key sensing element of the differential fiber grating static level instrument, and its advantages of strong anti-interference ability, high sensing measurement accuracy, strong durability and convenient networking are brought into play ; Double fiber grating, with temperature self-compensation; differential structure, improve the measurement sensitivity.

Description of drawings

The utility model will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is a schematic structural view of a differential fiber grating static level instrument according to an embodiment of the present invention;

Fig. 2 is the sectional view of Fig. 1;

Fig. 3 is the structural representation of clasp one;

In the drawings: 1-fiber outlet pipe, 2-upper cover, 3-lower chamber, 4-ventilation three-way valve, 5-liquid level indicator tube, 6-liquid three-way valve, 7-two-way valve, 8- Equal-intensity beam one, 9-fiber grating one, 10-ejector, 11-fiber grating two, 12-equal-strength beam two, 13-partition, 14-pontoon, 15-clasp one, 16-clasp two.

detailed description

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

In the embodiment of the utility model, a differential fiber grating static level is provided, which includes several fiber grating static level devices with the same structure and connected in series. The liquid three-way valve is connected, and the liquid three-way valve is set at the lower part of the lower cavity of the fiber grating static level device. Each fiber grating static level device is a cylindrical cavity, which is divided into an upper cavity and a lower cavity. The lower cavity is separated by a partition, and the upper cavity includes the upper cover, the first equal-strength beam, the second equal-strength beam, the first fiber grating, the second fiber grating, the first fiber outlet tube, the second fiber outlet tube, and the middle edge of the upper cover The first and second equal-strength beams are fixed in the diameter direction of the constant-strength beam. The first and second equal-strength beams have the same structure and size and are symmetrically arranged. Their ends close to each other are fixedly connected. 1. Fiber Bragg Grating 2 is pasted on the lower surface of equal-intensity beam 2. Fiber Bragg Grating 1 and Fiber Bragg Grating 2 are respectively connected to external detection instruments through fiber outlet tube 1 and fiber outlet tube 2 located on the side of the upper cover; a float is set in the lower chamber, The float includes a buoy and a push rod, the lower end of the push rod is fixed at the center of the upper surface of the buoy, the upper end of the push rod passes through the partition, and is located directly below the connection end point with the equal-strength beam 1 and equal-strength beam 2; the lower chamber The liquid level indicator tube is fixed vertically on the side; the upper part of the lower cavity of each fiber grating static leveling device is respectively provided with a venting three-way valve.

Further, the upper end and the lower end of the liquid level indicating tube are respectively communicated with the lower chamber through a two-way valve.

In the embodiment of the utility model, further, the buoy is horizontally limited by the first snap ring and the second snap ring, so that the buoy is located in the middle of the lower chamber.

Further, the two-way valves at the upper end and the lower end of the liquid level indicator tube are connected to the lower chamber by threads, and a sealing ring is provided respectively.

In the embodiment of the utility model, further, a small boss is provided on the bottom surface of the lower chamber, and the bottom surface of the lower chamber and the lower bottom surface of the buoy are in contact with each other through the small boss.

Further, the ejector rod is made of aluminum.

In a preferred embodiment of the present utility model, as shown in Figures 1-3, the differential fiber grating static level includes several fiber grating static level devices with the same structure and connected in series, and the adjacent fiber grating static levels The lower chambers of the device are connected through the liquid three-way valve 6. The liquid three-way valve is arranged at the lower part of the lower chamber of the fiber grating static leveling device. Each fiber grating static leveling device is in the shape of a cylindrical cavity and is divided into The upper cavity and the lower cavity 3 are separated by a partition 13. The upper cavity includes an upper cover 2, an equal-intensity beam 18, an equal-intensity beam 2 12, a fiber grating 9, a fiber grating 2 11, Fiber outlet pipe 1, fiber outlet pipe 2, equal strength beam 1 and equal strength beam 2 are fixed in the upper cover along the diameter direction of the upper cover, and the structure and size of equal strength beam 1 and equal strength beam 2 are the same and symmetrically arranged. The ends close to each other are fixedly connected, the upper surface of the equal strength beam 1 is pasted with the fiber grating 1, and the lower surface of the equal strength beam 2 is pasted with the fiber grating 2, and the fiber grating 1 and the fiber grating 2 respectively pass through the fiber outlet tube 1 located on the side of the upper cover 2. The fiber outlet tube 2 is connected with the external testing instrument; a float is set in the lower chamber, the float includes a buoy and a push rod, the lower end of the push rod is fixed at the center of the upper end surface of the buoy, and the upper end of the push rod passes through the partition and is located at the same strength Just below the connection end points of the first beam and the second equal-strength beam, the ejector rod is made of aluminum. The side of the lower cavity is vertically fixed with a liquid level indicating tube, and the upper and lower ends of the liquid level indicating tube 5 communicate with the lower cavity through a two-way valve 7 respectively. The two-way valves at the upper end and the lower end of the liquid level indicating pipe are connected with the lower chamber through threads, and a sealing ring is respectively provided. A ventilation three-way valve 4 is respectively arranged on the upper part of the lower chamber of each fiber grating static leveling device. The buoy is horizontally limited by snap ring one 15 and snap ring two 16, so that the buoy 14 is located in the middle of the lower cavity. A small boss is arranged on the bottom surface of the lower chamber, and the bottom surface of the lower chamber is in contact with the lower bottom surface of the buoy through the small boss. Among them, the vent three-way pipe is threadedly connected with the lower chamber, and a sealing ring is installed, the liquid three-way valve is threadedly connected with the lower chamber, and a sealing ring is installed, and the two two-way valves are threadedly connected with the lower chamber, and installed There is a sealing ring, the liquid level indicating pipe is coaxially arranged with two two-way valves and connected by interference fit, the partition plate is connected with the lower chamber through threads, and the snap ring 1 and snap ring 2 are connected with the lower chamber through threads. The ejector rod is connected with the buoy by threads. The ejector rod 10 is in clearance fit with the partition plate 13, the buoy 14 is in clearance fit with snap ring 1 15, and the buoy 14 is in clearance fit with snap ring 2 16. It is ensured that the buoy 14 will not shake horizontally or swing from side to side, thereby ensuring the measurement accuracy of the static level. The lower bottom surface of the buoy 14 is in contact with the inner bottom surface of the lower chamber 3 through a small boss instead of a large plane, which ensures that the buoyancy 14 can be fully affected by the buoyancy. The partition 13 plays the role of isolating the upper cavity and the lower cavity, and at the same time plays a position-limiting role in the upward movement of the buoy 14, and plays a protective role for the first beam of equal strength and the second beam of equal strength, the first fiber grating and the second fiber grating . As shown in Figure 3, the inner circular end face of the snap ring one 15 is provided with a transition fillet, which ensures that the frictional resistance between the buoy 14 and the snap ring one 15 is very small when the buoy 14 moves in the vertical direction, and the snap ring two 16 It has the same structure and effect as snap ring one 15. The ejector rod is in contact with equal-strength beam 1 and equal-strength beam 2 and has a certain pre-tightening force. The buoy is made of a material with a low density and a certain strength.

The liquid enters from one fiber grating static level device to another fiber grating static level device through the liquid three-way valve 6. After the liquid in the lower chamber 3 rises to a certain height, a part of the buoy 14 is gradually immersed in the liquid and is subjected to upward pressure. When the buoyancy force is greater than the self-gravity of the buoy 14, the buoy 14 starts to move upward and exerts a force on the two equal-strength beams, and the equal-strength beam one 8 and the equal-strength beam two 12 produce upward deflection under the action of force change, the fiber grating-9 is compressed on the upper surface of the equal-strength beam-8, so it is compressed and produces a negative strain. The lower surface of the equal-strength beam 2 12 is stretched to produce positive strain, so the reflection wavelength of the fiber grating 2 11 becomes larger. At the same time, the wavelengths of the two fiber gratings are also affected by the ambient temperature, but when the wavelength changes of the two fiber gratings are subtracted, the influence of temperature changes can be eliminated, and the temperature self-compensation of the fiber grating static leveling device is achieved. At the same time, the result of the subtraction increases the sensitivity of the fiber grating static leveling device and improves the measurement sensitivity. In this way, when multiple fiber Bragg grating static level devices are connected in series, the internal liquid level of each fiber Bragg grating static level device is at the same level. The depth of the liquid inside the leveling device increases, the buoyancy of the internal buoy increases, and the wavelength of the fiber grating drifts, while the depth of the liquid inside the other fiber grating static level devices does not change, and the liquid level in each fiber grating static level device is still the same In this way, the vertical displacement change of the point to be measured is measured.

The beneficial effects of the preferred embodiment of the utility model are: (1) the fiber grating is used as the key sensing element of the static level, and its strong anti-interference ability, high sensing measurement accuracy, strong durability and easy networking are brought into play. Advantages; (2) The three-layer circumferential clearance fit structure is adopted, which reduces the error and improves the measurement accuracy; (3) The lower bottom surface of the buoy and the inner bottom surface of the lower cylinder are in contact with a small boss instead of a large plane. It is beneficial to the buoyancy of the buoy; (4) the partition has a position limiting function, and has a self-protection function in the case of over-range use; (5) adopts double fiber gratings, which has a temperature self-compensation function; (6) adopts a differential structure, Improved measurement sensitivity. The differential fiber grating static level in the embodiment of the utility model can measure the displacement of the point to be measured in the vertical direction, and is especially suitable for detecting the deflection changes in the vertical direction of bridges, tunnels, and dams.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present utility model.

Claims (6)

1. A differential fiber grating static level is characterized in that it comprises several fiber grating static level devices that are identical in structure and connected in series, and the lower chambers of adjacent fiber grating static level devices pass liquid through three The through valve is connected, and the liquid three-way valve is set at the lower part of the lower chamber of the fiber grating static level device. They are separated by partitions. The upper cavity includes the upper cover, the first equal-strength beam, the second equal-strength beam, the first fiber grating, the second fiber grating, the first fiber outlet tube, and the second fiber outlet tube. The diameter of the upper cover along the upper cover The first and second equal-strength beams are fixed in direction. The first and second equal-strength beams have the same structure and size and are arranged symmetrically. Their ends close to each other are fixedly connected. The lower surface of the equal-intensity beam 2 is pasted with the fiber grating 2, and the fiber grating 1 and the fiber grating 2 are respectively connected to the external detection instrument through the fiber outlet tube 1 and the fiber outlet tube 2 located on the side of the upper cover; a float is arranged in the lower cavity, and the float includes The buoy and the ejector rod, the lower end of the ejector rod is fixed at the center of the upper end surface of the buoy, the upper end of the ejector rod passes through the partition, and is located directly below the connection end point with the equal-strength beam 1 and equal-strength beam 2; the side of the lower chamber is along the The liquid level indicator tube is fixed vertically; the upper part of the lower cavity of each fiber grating static leveling device is respectively provided with a venting three-way valve. 2. The differential fiber grating static level according to claim 1, characterized in that the upper end and the lower end of the liquid level indicating tube communicate with the lower cavity through a two-way valve respectively. 3. The differential fiber grating static level according to claim 1 or 2, characterized in that, the buoy is horizontally limited by the snap ring 1 and the snap ring 2, so that the buoy is located in the middle of the lower chamber. 4. The differential fiber grating static level according to claim 2, characterized in that the two-way valves at the upper end and the lower end of the liquid level indicating tube and the lower cavity are all connected by threads, and a sealing seal is provided respectively. lock up. 5. The differential fiber grating static level according to claim 1 or 2, characterized in that a small boss is arranged on the bottom surface of the lower chamber, and the bottom surface of the lower chamber and the lower bottom surface of the buoy are in contact with each other through the small boss . 6. The differential fiber grating static level according to claim 1 or 2, characterized in that the ejector rod is made of aluminum.