Annular thermotank for calibrating fiber bragg grating temperature sensor

Abstract

The invention relates to an annular constant-temperature box for calibrating a fiber grating temperature sensor, and belongs to the technical field of optical fiber sensing measurement. Comprising an annular heat insulation shell, an annular supporting cylinder, n annular test tubes, a heat insulation upper cover and n strings of fiber grating temperature sensors, the annular heat insulation shell is of a hollow barrel-shaped structure which is vertically arranged in the axial direction. An opening is formed in the top end of the annular heat-insulating shell; the annular supporting cylinder is of a columnar structure. The annular supporting cylinder is placed in an inner cavity of the annular heat insulation shell. The n annular test tubes are embedded into the annular supporting cylinder from top to bottom; a string of fiber bragg grating temperature sensors are placed in each annular test tube; the heat insulation upper cover covers the top end opening of the annular heat insulation shell for sealing; a heat transfer medium is introduced into the annular heat insulation shell for heating, so that temperature calibration of the fiber grating temperature sensor is realized; the problem of batch calibration of the fiber grating temperature sensors is solved, and the calibration efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing and measurement, and relates to an annular constant temperature box for calibrating an optical fiber Bragg grating temperature sensor. Background Art

[0002] The fiber Bragg grating temperature sensor has a serial structure, and multiple sensors are connected and signals are transmitted through a single optical fiber. Compared with thermocouples and platinum resistance sensors, it is light in weight and has strong anti-electromagnetic interference capabilities. It is an ideal temperature sensor to replace thermocouples and platinum resistance sensors on satellites and spacecraft. It can significantly reduce the weight of the original sensor while effectively increasing the payload weight.

[0003] Because fiber Bragg grating temperature sensors are serially structured, with multiple sensors connected and transmitting signals through a single optical fiber, temperature calibration requires simultaneous calibration of multiple sensors on a single fiber, and batch calibration is required. However, the sensor market currently lacks corresponding measurement equipment. Therefore, research into batch calibration equipment for fiber Bragg grating temperature sensors is imperative. Summary of the Invention

[0004] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and propose an annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, thereby solving the difficulty of batch calibration of fiber Bragg grating temperature sensors and improving calibration efficiency.

[0005] The solution of the present invention is:

[0006] An annular constant temperature box for calibrating a fiber Bragg grating temperature sensor comprises an annular heat-insulating shell, an annular support tube assembly, n annular test tubes, an insulation upper cover and n strings of fiber Bragg grating temperature sensors;

[0007] Among them, the annular thermal insulation shell is a hollow cylindrical structure arranged axially vertically; the top of the annular thermal insulation shell is provided with an opening; the annular support tube assembly is a columnar structure; the annular support tube assembly is placed in the inner cavity of the annular thermal insulation shell; n annular test tubes are embedded in the annular support tube assembly from top to bottom; a string of fiber grating temperature sensors is placed in each annular test tube; the thermal insulation upper cover is covered on the top opening of the annular thermal insulation shell to seal it; a heat transfer medium is introduced into the annular thermal insulation shell for heating to realize temperature calibration of the fiber grating temperature sensor; and n is a positive integer.

[0008] In the above-mentioned annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, the annular support tube assembly includes a limit sleeve and n support tubes; wherein, the limit sleeve is a vertically placed cylindrical structure; the support tube is an annular cylindrical structure; the diameters of each support tube are different; the limit sleeve is located at the center; the n support tubes are coaxially mounted in sequence; a limit column is provided at the center of the inner cavity of the annular thermal insulation shell; the concentric assembly of the annular support tube assembly and the annular thermal insulation shell is achieved through the cooperation of the limit column and the limit sleeve; n is greater than or equal to 3.

[0009] In the above-mentioned annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, annular gaps are left between two adjacent supporting tubes and between the limiting sleeve and the adjacent supporting tubes.

[0010] In the above-mentioned annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, the limiting sleeve and the n supporting tubes are all made of stainless steel; the side walls of the limiting sleeve and the n supporting tubes are provided with through holes distributed in a matrix; and the heat transfer medium is circulated through the through holes.

[0011] In the above-mentioned annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, the heat transfer medium is liquid, solid or gas; when it is liquid, the heat transfer medium is water or oil; when it is solid, the heat transfer medium is nanographene powder.

[0012] In the above-mentioned annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, the annular test tube is an annular double-layer cylindrical structure with a U-shaped cross-section; the top of the double-layer cylindrical structure is open and the bottom is sealed to form an annular sandwich cavity; the annular inner wall of the annular test tube is a straight cylindrical structure, and the top of the annular outer wall of the annular test tube is provided with a flange; n annular test tubes are embedded one by one in the corresponding n annular gaps; each annular test tube is overlapped on the corresponding support tube by the flange to complete the assembly.

[0013] In the above-mentioned annular constant temperature box for calibrating fiber Bragg grating temperature sensors, each string of fiber Bragg grating temperature sensors includes an optical fiber and m fiber Bragg grating temperature sensors; the optical fiber passes through each fiber Bragg grating temperature sensor in sequence along the axial direction; m is a positive integer and is not less than 5.

[0014] In the above-mentioned annular constant temperature box for calibrating fiber Bragg grating temperature sensors, during assembly, each string of fiber Bragg grating temperature sensors is formed into a ring and then installed in the annular inner cavity of the corresponding annular test tube, and is filled with thermal insulation material to achieve thermal insulation of the annular test tube.

[0015] In the above-mentioned annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, the minimum bending radius of each string of fiber Bragg grating temperature sensors formed into a ring is 100 mm. The fiber Bragg grating temperature sensor with the minimum bending radius is located in an annular test tube between the limiting sleeve and the adjacent support tube. The annular inner cavity diameter of the annular test tube is greater than 200 mm.

[0016] In the above-mentioned annular constant temperature box for calibrating a fiber Bragg grating temperature sensor, the bending radius of each remaining string of fiber Bragg grating temperature sensors after forming a ring is greater than 100 mm, and the bending radius increases from the inner ring to the outer ring; the annular inner cavity diameter of each annular test tube increases from the inner ring to the outer ring.

[0017] The beneficial effects of the present invention compared with the prior art are:

[0018] (1) The fiber Bragg grating temperature sensor of the present invention has a serial structure, and multiple sensors are connected and signal transmitted through a single optical fiber. Compared with thermocouples and platinum resistors, it has the characteristics of light weight and strong anti-electromagnetic interference ability. It is an ideal temperature sensor to replace thermocouples and platinum resistors on satellites and spacecraft, which can significantly reduce the weight of the original sensor while effectively increasing the payload weight.

[0019] (2) The present invention can achieve simultaneous calibration of multiple grating temperature sensors on a string of optical fibers by placing the fiber Bragg grating temperature sensor and its connecting optical fiber into an annular test tube. Batch calibration of fiber Bragg grating temperature sensors can be achieved by placing multiple annular test tubes into an annular support tube;

[0020] (3) The present invention achieves continuous stability of the calibration temperature by filling the opening of the annular test tube with thermal insulation material. The constant temperature box solves the problem of the fiber Bragg grating temperature sensor being unable to accurately calibrate the temperature, and improves the accuracy and reliability of the calibration temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an overall schematic diagram of the annular constant temperature box of the present invention;

[0022] Figure 2 This is a schematic diagram of the annular support cylinder assembly of the present invention;

[0023] Figure 3 This is a schematic diagram of the annular test tube structure of the present invention;

[0024] Figure 4 This is a schematic diagram of an annular test tube installed in an annular support cylinder assembly according to the present invention;

[0025] Figure 5 Schematic diagram of each string of fiber Bragg grating temperature sensors of the present invention;

[0026] Figure 6 This is a schematic diagram of each string of fiber Bragg grating temperature sensors of the present invention being installed in a corresponding annular test tube. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the embodiments.

[0028] The present invention provides an annular constant temperature chamber for calibrating fiber Bragg grating (FBG) temperature sensors. By placing a fiber Bragg grating (FBG) string in an annular test tube, multiple FBG temperature sensors on a single optical fiber string can be calibrated simultaneously. Using an annular support tube to house multiple annular test tubes enables batch calibration of fiber Bragg grating (FBG) temperature sensors. Filling the openings of the annular test tubes with thermal insulation material ensures a constant and stable calibration temperature. This annular constant temperature chamber solves the problem of accurate temperature calibration of fiber Bragg grating (FBG) temperature sensors and improves the accuracy and reliability of calibration temperature. It solves the problem of batch calibration of fiber Bragg grating (FBG) temperature sensors and improves calibration efficiency.

[0029] Fiber Bragg grating temperature sensor calibration uses a ring constant temperature box, such as Figure 1 As shown, the apparatus specifically comprises an annular thermal insulation shell 1, an annular support tube assembly 2, n annular test tubes 3, an insulating upper cover 4, and n strings of fiber Bragg grating temperature sensors 5. The annular thermal insulation shell 1 is a hollow cylindrical structure arranged axially and vertically; the top of the annular thermal insulation shell 1 is provided with an opening; the annular support tube assembly 2 is a columnar structure; the annular support tube assembly 2 is placed in the inner cavity of the annular thermal insulation shell 1; the n annular test tubes 3 are inserted into the annular support tube assembly 2 from top to bottom; a string of fiber Bragg grating temperature sensors 5 is placed in each annular test tube 3; the insulating upper cover 4 covers the top opening of the annular thermal insulation shell 1 to seal it; a heat transfer medium is introduced into the annular thermal insulation shell 1 to heat it and achieve temperature calibration of the fiber Bragg grating temperature sensors 5, where n is a positive integer greater than or equal to 3.

[0030] like Figure 2 As shown, the annular support tube assembly 2 includes a limiting sleeve 21 and n supporting tubes 22. The limiting sleeve 21 is a vertically placed cylindrical structure; the supporting tubes 22 are annular cylindrical structures; each supporting tube 22 has a different diameter; the limiting sleeve 21 is located at the center; the n supporting tubes 22 are coaxially arranged in sequence; a limiting post is provided at the center of the inner cavity of the annular thermal insulation shell 1; the limiting post cooperates with the limiting sleeve 21 to achieve concentric assembly of the annular support tube assembly 2 and the annular thermal insulation shell 1. Annular gaps are left between adjacent supporting tubes 22 and between the limiting sleeve 21 and adjacent supporting tubes 22.

[0031] In the present invention, the limiting sleeve 21 and the n supporting tubes 22 are all made of stainless steel. The sidewalls of the limiting sleeve 21 and the n supporting tubes 22 are provided with through-holes arranged in a matrix pattern. These through-holes allow the circulation of a heat transfer medium. The heat transfer medium can be liquid, solid, or gas. For liquids, the heat transfer medium is water or oil; for solids, the heat transfer medium is nanographene powder.

[0032] like Figure 3As shown, the annular test tube 3 is an annular double-layer cylindrical structure with a U-shaped cross section; the double-layer cylindrical structure is open at the top and sealed at the bottom, forming an annular sandwich cavity; the annular inner wall of the annular test tube 3 is a straight cylindrical structure, and the top of the annular outer wall of the annular test tube 3 is provided with a flange; n annular test tubes 3 are embedded in the corresponding n annular gaps one by one; each annular test tube 3 is overlapped on the corresponding support tube 22 by the flange to complete the assembly, as shown in FIG. Figure 4 shown.

[0033] like Figure 5 As shown, each string of fiber Bragg grating temperature sensors 5 includes an optical fiber and m fiber Bragg grating temperature sensors 5 ; the optical fiber passes through each fiber Bragg grating temperature sensor 5 in sequence along the axial direction; m is a positive integer, and m is not less than 5.

[0034] The fiber Bragg grating temperature sensor has a serial structure, and multiple sensors are connected and signals are transmitted through a single optical fiber. Compared with thermocouples and platinum resistance sensors, it is light in weight and has strong anti-electromagnetic interference capabilities. It is an ideal temperature sensor to replace thermocouples and platinum resistance sensors on satellites and spacecraft. It can significantly reduce the weight of the original sensor while effectively increasing the payload weight.

[0035] Because fiber Bragg grating temperature sensors are serially structured, with multiple sensors connected and transmitting signals via a single optical fiber, temperature calibration requires simultaneous calibration of multiple sensors on a single fiber, and batch calibration is possible. However, metrology institutes and sensor manufacturers currently lack the necessary metrology equipment. Therefore, research into batch calibration equipment for fiber Bragg grating temperature sensors is imperative. This invention addresses the challenge of accurate temperature calibration for fiber Bragg grating temperature sensors, improving the accuracy and reliability of calibration temperatures. This solves the challenge of batch temperature calibration for fiber Bragg grating temperature sensors and improves calibration efficiency.

[0036] like Figure 6 As shown, during assembly, each string of fiber Bragg grating temperature sensors 5 is arranged in a ring and then installed in the annular inner cavity of the corresponding annular test tube 3. The ring is then filled with thermal insulation material to provide thermal insulation to the annular test tube 3. The minimum bend radius of each ring-shaped string of fiber Bragg grating temperature sensors 5 is 100 mm. The fiber Bragg grating temperature sensor 5 with the minimum bend radius is located in the annular test tube 3 between the retaining sleeve 21 and the adjacent support tube 22. The annular inner cavity of the annular test tube 3 has a diameter greater than 200 mm. By filling the opening of the annular test tube with thermal insulation material, the calibration temperature is continuously stabilized.

[0037] The bending radius of the remaining strings of fiber Bragg grating temperature sensors 5 after forming a ring is greater than 100 mm, and the bending radius increases from the inner ring to the outer ring; the diameter of the inner cavity of each ring test tube 3 increases from the inner ring to the outer ring.

[0038] After actual production practice, very good results have been achieved. The details are as follows:

[0039] 1) High-precision temperature calibration of fiber Bragg grating temperature sensors is achieved, with a calibration accuracy of ±0.01°C.

[0040] 2) Batch temperature calibration of fiber Bragg grating temperature sensors is realized, calibrating 60 at a time.

[0041] 3) The normalization and standardization of temperature calibration of fiber Bragg grating temperature sensors are realized.

[0042] The present invention can realize simultaneous calibration of multiple grating temperature sensors on a string of optical fibers by placing the fiber grating string in an annular test tube. By using an annular support tube to place multiple annular test tubes, batch calibration of fiber grating temperature sensors can be realized.

[0043] This annular constant temperature box solves the problem of inaccurate temperature calibration of fiber Bragg grating temperature sensors, improves the accuracy and reliability of calibration temperature, solves the problem of batch calibration of fiber Bragg grating temperature sensors, and improves calibration efficiency.

[0044] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor, characterized in that: It comprises an annular heat-insulating shell (1), an annular support tube assembly (2), n annular test tubes (3), a heat-insulating upper cover (4), and n strings of fiber optic Bragg grating temperature sensors (5); The annular heat-insulating shell (1) is a hollow cylindrical structure arranged vertically in an axial direction; an opening is provided at the top end of the annular heat-insulating shell (1); the annular support tube assembly (2) is a columnar structure; the annular support tube assembly (2) is placed in the inner cavity of the annular heat-insulating shell (1); n annular test tubes (3) are embedded in the annular support tube assembly (2) from the top downward; a string of fiber Bragg grating temperature sensors (5) is placed in each annular test tube (3); a heat-insulating upper cover (4) is covered at the top end opening of the annular heat-insulating shell (1) to seal it; a heat transfer medium is introduced into the annular heat-insulating shell (1) to heat it, thereby achieving temperature calibration of the fiber Bragg grating temperature sensor (5); and n is a positive integer.

2. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 1, characterized in that: The annular support cylinder assembly (2) comprises a limiting sleeve (21) and n supporting cylinders (22); wherein the limiting sleeve (21) is a vertically placed cylindrical structure; the supporting cylinder (22) is an annular cylindrical structure; the diameters of the supporting cylinders (22) are different; the limiting sleeve (21) is located at the center; the n supporting cylinders (22) are coaxially mounted in sequence; a limiting column is provided at the center of the inner cavity of the annular heat-insulating shell (1); the concentric assembly of the annular support cylinder assembly (2) and the annular heat-insulating shell (1) is achieved by the cooperation of the limiting column and the limiting sleeve (21); and n is greater than or equal to 3.

3. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 2, characterized in that: Annular gaps are left between two adjacent support cylinders (22) and between the limiting sleeve (21) and the adjacent support cylinders (22).

4. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 2, characterized in that: The limiting sleeve (21) and the n supporting cylinders (22) are both made of stainless steel; the side walls of the limiting sleeve (21) and the n supporting cylinders (22) are both provided with through holes distributed in a matrix; and the heat transfer medium is circulated through the through holes.

5. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 1, characterized in that: The heat transfer medium is liquid, solid or gas; when it is liquid, the heat transfer medium is water or oil; when it is solid, the heat transfer medium is nanographene powder.

6. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 3, characterized in that: The annular test tube (3) is an annular double-layer cylindrical structure with a U-shaped cross section; the top of the double-layer cylindrical structure is open and the bottom is sealed, forming an annular interlayer cavity; the annular inner wall of the annular test tube (3) is a straight cylindrical structure, and the top of the annular outer wall of the annular test tube (3) is provided with a flange; n annular test tubes (3) are embedded in the corresponding n annular gaps one by one; each annular test tube (3) is overlapped on the corresponding support tube (22) through the flange to complete the assembly.

7. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 6, characterized in that: Each string of fiber Bragg grating temperature sensors (5) comprises an optical fiber and m fiber Bragg grating temperature sensors (5); the optical fiber passes through each fiber Bragg grating temperature sensor (5) in sequence along the axial direction; m is a positive integer, and m is not less than 5.

8. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 7, characterized in that: During assembly, each string of fiber optic Bragg grating temperature sensors (5) is formed into a ring and then installed in the ring inner cavity of the corresponding ring test tube (3), and is filled with heat-insulating material to achieve heat insulation of the ring test tube (3).

9. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 8, characterized in that: The minimum bending radius of each string of fiber optic Bragg grating temperature sensors (5) formed into a ring is 100 mm. The fiber optic Bragg grating temperature sensors (5) with the minimum bending radius are located in the ring-shaped test tube (3) between the limiting sleeve (21) and the adjacent support tube (22). The diameter of the ring-shaped inner cavity of the ring-shaped test tube (3) is greater than 200 mm.

10. The ring-shaped constant temperature box for calibrating a fiber Bragg grating temperature sensor according to claim 9, characterized in that: The bending radius of the remaining strings of fiber optic Bragg grating temperature sensors (5) after forming a ring is greater than 100 mm, and the bending radius increases from the inner ring to the outer ring; the diameter of the annular inner cavity of each annular test tube (3) increases from the inner ring to the outer ring.

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