Near-zero temperature excursion fiber bragg grating humidity sensor

Abstract

The utility model relates to the technical field of fiber bragg gratings, in particular to a near-zero temperature drift fiber bragg grating humidity sensor. Comprising a packaging shell and an optical fiber arranged in the packaging shell. According to the sensor, a double-fiber grating structure is arranged on the same optical fiber, so that a temperature compensation effect can be achieved, and double parameters can be measured at the same time. The measurement precision is improved. The humidity sensing element adopts a fiber bragg grating coated with a polyimide film, and the humidity is measured by utilizing the wet expansion characteristic of the film. The packaging shell is provided with vent holes and a looped network, dust pollution is effectively avoided, internal humidity distribution is balanced, and measurement accuracy is improved. Two ends of the optical fiber are connected with armored optical fibers to improve tensile and compressive strength. The packaging shell and the ring net are made of stainless steel materials, so that the structural strength and the corrosion resistance are enhanced. The fiber bragg grating humidity sensor solves the problems that an existing fiber bragg grating humidity sensor is prone to being polluted and has temperature cross sensitivity when humidity is measured, improves measurement accuracy and stability, and is suitable for humidity measurement of various environments.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of fiber grating sensor, concretely relates to a near zero temperature drift fiber grating humidity sensor. BACKGROUND

[0002] With the continuous progress of industry, agriculture and science and technology, the demand for accurate detection of environmental humidity is increasingly urgent. As a kind of optical passive device, fiber grating has excellent characteristics such as small size, anti-electromagnetic interference, strong corrosion resistance, high sensitivity and good stability. When the fiber grating is affected by external temperature or stress, the center wavelength of its reflection or transmission spectrum will drift, and the drift amount is linearly related to the change of temperature or stress.

[0003] The existing grating humidity sensors are various, mainly including resistance type, capacitance type, ceramic type, etc. These sensors perceive the humidity change in the environment through different physical or chemical principles, and convert it into an electrical signal for output. However, the existing humidity sensors still have some shortcomings in practical application. On the one hand, the packaging of the humidity-sensitive film in the grating humidity sensor is easily contaminated by dust and particles, resulting in low reliability of long-term measurement results. In addition, some humidity sensors also have temperature cross-sensitivity problem in the measurement process. The fiber grating humidity sensor is sensitive to both temperature and humidity, resulting in reduced measurement accuracy. INVENTION CONTENTS

[0004] The utility model provides a kind of near zero temperature drift fiber grating humidity sensor, it can solve the problem that existing fiber grating humidity sensor is easily contaminated by dust and particles and has temperature cross-sensitivity in measurement process.

[0005] According to the near zero temperature drift fiber grating humidity sensor of the utility model, it comprises: a packaging shell, and a fiber arranged in the packaging shell, the packaging shell is a hollow cylindrical shell;The fiber has a fiber grating humidity sensing element at one end for measuring the humidity of the environment, and a first fiber grating at the other end for measuring the temperature of the environment.

[0006] In the utility model, the packaging shell is hollow cylindrical, which not only protects the internal fiber grating structure, but also ensures good interaction between the sensor and the external environment. The design of the packaging shell enables the sensor to work stably in harsh environments, improving the durability and reliability of the sensor. The fiber is fixed in the packaging shell by fiber coupling technology, ensuring stable transmission of optical signals.

[0007] This invention incorporates humidity and temperature sensing elements at both ends of the optical fiber, with all fiber Bragg grating temperature / humidity sensing elements connected in series. The sensor employs a dual fiber Bragg grating structure, serving both as a temperature compensation mechanism and simultaneously measuring two parameters. This design not only improves the sensor's integration but also effectively eliminates the influence of temperature on humidity measurement through temperature compensation technology, thereby enhancing measurement accuracy.

[0008] In this invention, the fiber optic humidity sensing element includes a second fiber optic grating disposed on the outer surface of the fiber, and the outer wall of the second fiber optic grating is provided with a polyimide film with a thickness of 10-30 μm.

[0009] The fiber optic humidity sensing element in this invention is made of a fiber optic grating coated with a polyimide film, utilizing the moisture expansion characteristics of polyimide to measure humidity. The temperature sensing element uses an uncoated fiber optic grating, reflecting changes in ambient temperature by measuring the Bragg wavelength shift of the grating. The thickness of the polyimide film is controlled within the range of 10-30 μm, ensuring good moisture-sensing linear expansion characteristics while avoiding measurement and delay errors caused by excessively thick films.

[0010] In this invention, the number of the first fiber grating, the second fiber grating, and the polyimide film is at least one.

[0011] By increasing the number of fiber Bragg gratings and polyimide films in this invention, the measurement accuracy and stability of the sensor can be further improved, or functions such as multi-point measurement can be achieved. In practical applications, the number of fiber Bragg gratings and polyimide films can be determined according to specific needs. In applications requiring high-precision measurement, multiple fiber Bragg gratings can be used for averaging or redundant measurement; in applications requiring multi-point measurement, multiple humidity sensing elements can be set at different locations.

[0012] In this utility model, the encapsulation housing includes an encapsulation shell and a ring mesh disposed on the inner wall of the encapsulation shell. The encapsulation shell is provided with a first mounting cavity for installing optical fibers. The outer wall of the encapsulation shell is provided with a plurality of first vent holes spaced circumferentially along the length of the encapsulation shell. The ring mesh is provided with a plurality of second vent holes spaced circumferentially along the length of the ring mesh. The diameter of the first vent holes is larger than the diameter of the second vent holes.

[0013] The fiber optic grating is encapsulated in the packaging shell of this invention, which not only protects the sensing element from contamination but also makes the entire sensor more robust, providing it with a certain degree of resistance to pressure and tension. The packaging shell first protects the sensing part from damage, and the mesh structure effectively prevents dust and particles from contaminating the humidity-sensitive film and affecting the test results. Furthermore, the mesh structure facilitates ventilation, reduces response time and hysteresis, helps balance the humidity distribution and ventilation effect inside the sensor, and improves measurement accuracy. The first vent ensures the humidity sensor can detect the humidity of the wall environment. Since small particles of sand and gravel may still pass through the first vent on the packaging shell, a ring mesh is added inside the stainless steel tube. The small second vents on the ring mesh protect the humidity-sensing element without affecting humidity measurement.

[0014] In this utility model, both ends of the encapsulation shell are provided with threaded sleeves that communicate with the first mounting cavity. Both ends of the threaded sleeves away from the encapsulation shell are provided with openings, and the openings are provided with the second mounting cavity.

[0015] The threaded sleeve design in this invention not only facilitates the installation and disassembly of the sensor, but also enables reliable connection between the sensor and other devices or systems through its internal threaded structure.

[0016] In this invention, armored optical fibers are fixedly connected to both ends of the optical fiber, and the armored optical fibers pass through the second mounting cavity and are embedded in the encapsulation shell.

[0017] The armored optical fiber in this invention provides additional protection and support for the optical fiber, improving its tensile and compressive strength and ensuring stable transmission within the sensor.

[0018] In this invention, both ends of the first mounting cavity are provided with hollow sealing blocks, and the outer diameter of the armored optical fiber is adapted to the inner diameter of the sealing block and the inner diameter of the second mounting cavity.

[0019] The matching design of the inner diameters of the second mounting cavity and the sealing block in this invention ensures stable installation and fixation of the armored optical fiber, preventing loosening and detachment during transmission. The armored optical fiber is firmly fixed using adhesive injection, ensuring that vibrations and tension of the encapsulation shell do not affect the fiber optic humidity sensing element and the first fiber optic grating.

[0020] In this invention, both the outer casing and the ring mesh are made of stainless steel.

[0021] The fact that the outer shell and ring network of this invention are made of stainless steel not only improves the structural strength and durability of the sensor, but also reduces physical damage and chemical corrosion of the sensor in harsh environments due to its good corrosion resistance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a near-zero temperature drift fiber Bragg grating humidity sensor.

[0023] Figure 2 This is a schematic diagram of an optical fiber.

[0024] Figure 3 This is a schematic diagram of a fiber Bragg grating humidity sensing element.

[0025] Figure 4 This is a schematic diagram of the encapsulated casing.

[0026] Figure 5 This is a cross-sectional view of the enclosure.

[0027] Figure 6 This is a schematic diagram of a ring network. Detailed Implementation

[0028] To further understand the content of this utility model, a detailed description of the utility model is provided in conjunction with the embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the utility model.

[0029] Example 1

[0030] like Figures 1-6 As shown, this embodiment provides a near-zero temperature drift fiber Bragg grating humidity sensor, which includes: a housing 100 and an optical fiber 200 disposed within the housing 100. The housing 100 is a hollow cylindrical housing. One end of the optical fiber 200 is provided with a fiber Bragg grating humidity sensing element 210 for measuring the humidity of the surrounding environment, and the other end of the optical fiber 200 is provided with a first fiber Bragg grating 220 for measuring the temperature of the surrounding environment.

[0031] In this embodiment, the encapsulation housing 100 is a hollow cylindrical shape, which protects the internal fiber Bragg grating structure while ensuring good interaction between the sensor and the external environment. The design of the encapsulation housing 100 enables the sensor to operate stably in harsh environments, improving its durability and reliability. The encapsulation housing 100 can be made of corrosion-resistant, high-strength materials such as stainless steel to ensure the long-term stability of the sensor. The optical fiber 200 is fixed inside the encapsulation housing 100 using fiber optic coupling technology, ensuring stable transmission of the optical signal.

[0032] In this embodiment, humidity and temperature sensing elements are respectively set at both ends of the optical fiber 200, and all fiber Bragg grating temperature / humidity sensing elements are connected in series. The sensor adopts a dual fiber Bragg grating structure, which can serve as a temperature compensation function and simultaneously measure two parameters. This configuration not only improves the integration of the sensor, but also effectively eliminates the influence of temperature on humidity measurement through temperature compensation technology, thereby improving measurement accuracy.

[0033] In this embodiment, the fiber optic humidity sensing element 210 includes a second fiber optic grating 211 disposed on the outer surface of the fiber, and the outer wall of the second fiber optic grating 211 is provided with a polyimide film 212 with a thickness of 10-30 μm.

[0034] In this embodiment, the fiber optic humidity sensing element 210 is made of a fiber optic grating coated with a polyimide film 212, utilizing the moisture expansion characteristics of polyimide to achieve humidity measurement. The temperature sensing element uses an uncoated fiber optic grating, reflecting changes in ambient temperature by measuring the Bragg wavelength shift of the grating. The thickness of the polyimide film 212 is controlled within the range of 10-30 μm, ensuring good moisture-sensing linear expansion characteristics while avoiding measurement and delay errors caused by excessively thick films. The polyimide film 212 can be coated onto the outer surface of the fiber optic grating using methods such as spin coating, spray coating, or dip coating. Strict control of process parameters, such as coating speed, temperature, and humidity, is required during the coating process to ensure film uniformity and thickness accuracy.

[0035] In this embodiment, the number of the first fiber grating 220, the second fiber grating 211, and the polyimide film 212 is at least one.

[0036] By increasing the number of fiber Bragg gratings and polyimide films 212 in this embodiment, the measurement accuracy and stability of the sensor can be further improved, or functions such as multi-point measurement can be achieved. In practical applications, the number of fiber Bragg gratings and polyimide films 212 can be determined according to specific requirements. For example, in applications requiring high-precision measurement, multiple fiber Bragg gratings can be used for averaging or redundant measurement; in applications requiring multi-point measurement, multiple humidity sensing elements can be set at different locations.

[0037] In this embodiment, the encapsulation housing 100 includes an encapsulation shell 110 and a ring network 120 disposed on the inner wall of the encapsulation shell 110. The encapsulation shell 110 is provided with a first mounting cavity 111 for mounting the optical fiber 200. The outer wall of the encapsulation shell 110 is provided with a plurality of first vent holes 112 arranged circumferentially at intervals along the length direction of the encapsulation shell 110. The ring network 120 is provided with a plurality of second vent holes 121 arranged circumferentially at intervals along the length direction of the ring network 120. The diameter of the first vent holes 112 is larger than the diameter of the second vent holes 121.

[0038] The encapsulation shell 110 in this embodiment encapsulates the fiber Bragg grating, protecting the sensing element from contamination and making the entire sensor more robust, providing it with a certain degree of resistance to pressure and tension. The encapsulation shell 110 first protects the sensing part from damage. Simultaneously, the mesh structure of the ring 120 effectively prevents dust and particles from contaminating the humidity-sensitive film and affecting the test results. Furthermore, the mesh structure facilitates ventilation, reduces response time and hysteresis, helps balance the humidity distribution and ventilation effect inside the sensor, and improves measurement accuracy. The first vent 112 ensures that the humidity sensor can sense the humidity of the wall environment. Since small particles of sand and gravel may still pass through the first vent 112 on the encapsulation shell 110, a ring 120 is added inside the stainless steel tube. The small second vent 121 on the ring 120 protects the fiber Bragg grating humidity sensing element 210 and the first fiber Bragg grating 220 without affecting humidity measurement.

[0039] In this embodiment, both ends of the encapsulation housing 100 are provided with threaded sleeves 130 that communicate with the first mounting cavity 111. Both ends of the threaded sleeves 130 away from the encapsulation housing 100 are provided with openings 131, and the openings 131 are provided with second mounting cavities 132.

[0040] The threaded sleeve 130 in this embodiment not only facilitates the installation and removal of the sensor, but also enables reliable connection between the sensor and other devices or systems through its internal threaded structure. The second mounting cavity 132 can be customized and adjusted according to specific needs to adapt to the connection requirements of different interface components.

[0041] In this embodiment, armored optical fibers 230 are fixedly connected to both ends of the optical fiber 200, and the armored optical fibers 230 pass through the second mounting cavity 132 and are embedded in the encapsulation housing 100.

[0042] In this embodiment, the armored optical fiber 230 provides additional protection and support for the optical fiber, improving its tensile and compressive strength and ensuring stable transmission within the sensor.

[0043] In this embodiment, both ends of the first mounting cavity 111 are provided with hollow sealing blocks 113, and the outer diameter of the armored optical fiber 230 is adapted to the inner diameter of the sealing block 113 and the inner diameter of the second mounting cavity 132.

[0044] The matching design of the inner diameters of the second mounting cavity 132 and the sealing block 113 in this embodiment ensures the stable installation and fixation of the armored optical fiber 230, preventing the optical fiber from loosening and falling off during transmission. The armored optical fiber 230 is firmly fixed by injection molding, ensuring that vibrations and tensions in the encapsulation shell 110 do not affect the fiber optic humidity sensing element 210 and the first fiber optic grating 220.

[0045] In this embodiment, both the outer casing 110 and the ring network 120 are made of stainless steel.

[0046] In this embodiment, both the housing 110 and the ring network 120 are made of stainless steel, which not only improves the structural strength and durability of the sensor, but also reduces physical damage and chemical corrosion of the sensor in harsh environments through its good corrosion resistance.

[0047] It is readily understood that those skilled in the art can combine, split, or reorganize the embodiments provided in this application to obtain other embodiments, all of which do not exceed the protection scope of this application.

[0048] In summary, the above description is only a preferred embodiment of the present utility model. All equivalent changes and modifications made within the scope of the patent application of the present utility model shall fall within the scope of the patent of the present utility model.

Claims

1. A near zero temperature drift fiber (200) grating humidity sensor characterized by: The application relates to a fiber-optic humidity and temperature sensor, which comprises a packaging shell (100) and a fiber (200) arranged in the packaging shell (100), the packaging shell (100) is a hollow cylindrical shell; one end of the fiber (200) is provided with a fiber-optic grating humidity sensing element (210) for measuring the humidity of the environment, and the other end of the fiber (200) is provided with a first fiber-optic grating (220) for measuring the temperature of the environment.

2. The near-zero temperature drift fiber grating humidity sensor according to claim 1, wherein: The fiber-optic grating humidity sensing element (210) comprises a second fiber-optic grating (211) arranged on the outer surface of the fiber (200), and the outer wall of the second fiber-optic grating (211) is provided with a polyimide film (212) with a thickness of 10-30 mu m.

3. A near zero temperature drift fiber grating humidity sensor according to claim 2, characterized in that: The number of the first fiber-optic grating (220), the second fiber-optic grating (211) and the polyimide film (212) is at least one.

4. The near-zero temperature drift fiber grating humidity sensor of claim 1, wherein: The packaging shell (100) comprises a packaging shell (110) and a ring network (120) arranged on the inner wall of the packaging shell (110), the packaging shell (110) is internally provided with a first mounting cavity (111) for mounting the fiber (200), the outer wall of the packaging shell (110) is provided with a plurality of first air holes (112) arranged in the length direction of the packaging shell (110) and spaced apart in the circumferential direction, the ring network (120) is provided with a plurality of second air holes (121) arranged in the length direction of the ring network (120) and spaced apart in the circumferential direction, and the diameter of the first air hole (112) is larger than that of the second air hole (121).

5. A near zero temperature drift fiber grating humidity sensor according to claim 4, characterized in that: Both ends of the packaging shell (100) are provided with a threaded sleeve (130) communicating with the first mounting cavity (111), the threaded sleeve (130) is provided with an opening (131) away from both ends of the packaging shell (100), and the opening (131) is internally provided with a second mounting cavity (132).

6. A near zero temperature drift fiber grating humidity sensor according to claim 5, characterized in that: Both ends of the fiber (200) are fixedly connected with armored optical fibers (230), the armored optical fibers (230) pass through the second mounting cavity (132) and are embedded in the packaging shell (100).

7. A near zero temperature drift fiber grating humidity sensor according to claim 6, characterized in that: Both ends of the first mounting cavity (111) are provided with a plugging block (113) with an internal hollow, and the outer diameter of the armored optical fiber (230) is matched with the inner diameter of the plugging block (113) and the inner diameter of the second mounting cavity (132).

8. The near-zero temperature drift fiber grating humidity sensor of claim 4, wherein: The packaging shell (110) and the ring network (120) are made of stainless steel.

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