Differential grating pressure sensor

Abstract

The invention relates to a differential grating pressure sensor, which is characterized in that a diaphragm is used for receiving external pressure and is connected with a sliding block, the diaphragm can drive the sliding block to move relative to a shell after being deformed due to pressure, the deformation quantity of the diaphragm in the axis direction of a fiber grating is equal to the movement quantity of the sliding block, and a pre-tightening unit is connected to the sliding block; the pre-tightening unit is used for providing pre-tightening force, through the setting of the pre-tightening force, under the condition that large pressure is externally input, the diaphragm can obtain relatively small deformation quantity so as to adapt to the change of the fiber bragg grating, and the deformation quantity is within the deformable range of the fiber bragg grating. The two ends of the fiber grating are fixedly connected to the shell, the sliding block is fixedly connected to the middle area of the fiber grating, the fiber grating is provided with an elongated section and a shortened section along with movement of the sliding block, and therefore detection and recognition of external pressure are achieved. Compared with the prior art, the purpose of preventing a pressure factor from influencing a measurement result can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of fiber grating pressure sensors, and in particular to a differential grating pressure sensor. Background Art

[0002] In recent decades, great attention has been paid to the measurement of ocean parameters, such as salinity, temperature, and depth, because these parameters have a significant impact on the physical, chemical, and biological processes of the ocean. Among them, the depth (pressure) of the ocean is an important basic parameter in oceanography, which is crucial for ocean observation, understanding and prediction of ocean processes, and protection and development of marine resources.

[0003] With the rapid development of fiber optic sensing technology, many countries have developed fiber optic sensors for use in the field of ocean sensing and detection. The fiber grating-based seabed pressure sensor is a sensor used to monitor the depth and pressure changes of the seabed. Its principle is to use the sensitivity of the fiber grating to the wavelength of light to detect changes in pressure. Specifically, the fiber grating uses the periodic refractive index change structure in the optical fiber to form the reflection and diffraction of the optical wavelength, and this periodic change in the refractive index can be changed by factors such as external pressure; when the fiber grating is subjected to external pressure, its periodic structure will change, causing the wavelength of the reflected light to shift; by measuring the change in the wavelength of this light, the magnitude of the external pressure can be determined.

[0004] When conventional fiber Bragg grating sensors identify pressure changes, because even a small change in the fiber Bragg grating will lead to a large difference in the detection results, the fiber Bragg grating sensor is often designed so that the change in external pressure will not act directly on the fiber Bragg grating, but the external pressure is converted into a change in pressure, and then the length of the fiber Bragg grating is indirectly changed through the change in pressure. However, for this method of detecting pressure by indirectly changing the length of the fiber Bragg grating through pressure, changes in temperature during detection, long-term use, and loose sealing will cause changes in the pressure inside the sensor, resulting in inaccurate detection results. Summary of the invention

[0005] In order to solve the defect that when detecting pressure by indirectly changing the length of the fiber grating through pressure, the change of temperature during detection, long-term use, and loose sealing will cause the pressure inside the sensor to change, thereby causing inaccurate detection results, the present invention proposes a differential grating pressure sensor.

[0006] The technical solution adopted by the present invention is a differential grating pressure sensor, comprising a shell, the shell having an inner cavity and the inner cavity is separated from the external environment by a diaphragm, the diaphragm is connected to a slider, the slider is slidably connected in the shell, the inner cavity has a fiber grating arranged along the sliding direction of the slider, both ends of the fiber grating are fixedly connected to the shell, the middle area of ​​the fiber grating is fixedly connected to the slider, and the slider is connected to a preload unit for providing preload force for it.

[0007] Preferably, the device further comprises a first adjusting unit for adjusting the distance between the diaphragm and the slider, and the diaphragm is connected to the slider via the first adjusting unit.

[0008] Preferably, the first adjusting unit is a threaded pair adjusting rod, and the threaded pair adjusting rod extends into the slider and is threadably connected to the slider.

[0009] Preferably, the device further comprises a second adjusting unit for adjusting the pre-tightening force of the pre-tightening unit, and the second adjusting unit is connected to the pre-tightening unit.

[0010] Preferably, the pre-tightening unit comprises an elastic member, one end of which abuts against the slider, and the other end of which is connected to the housing.

[0011] Preferably, the elastic member is connected to the housing via a pre-tightening unit, the elastic member abuts against the second adjusting unit, and the second adjusting unit can move relative to the housing in the sliding direction of the slider.

[0012] Preferably, a third adjusting unit is fixedly connected to one end of the fiber grating away from the diaphragm, the third adjusting unit is connected to the housing, and the third adjusting unit can move relative to the housing in the sliding direction of the slider.

[0013] Preferably, the housing protrudes outward at the position of the diaphragm to form a pressure inlet, and the pressure inlet is communicated with the diaphragm.

[0014] Preferably, the size of the pressure inlet is smaller than the size of the diaphragm, and the pressure inlet is arranged directly opposite the center of the diaphragm.

[0015] Preferably, washers and locking members are respectively provided on both sides of the diaphragm, and the locking members press the washers and the diaphragm onto the housing.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present application discloses a differential grating pressure sensor, wherein the diaphragm is used to receive external pressure and is connected to a slider. When the diaphragm is deformed by pressure, the slider is driven to move relative to the housing. The deformation of the diaphragm in the axial direction of the fiber grating is equal to the movement of the slider. A pre-tightening unit is connected to the slider, and the pre-tightening unit is used to provide a pre-tightening force. By setting the pre-tightening force, the diaphragm can obtain a relatively small deformation in the case of a large external input pressure to adapt to the change of the fiber grating, and the deformation is within the deformable range of the fiber grating. The two ends of the fiber grating are fixedly connected to the housing, and the slider is fixedly connected to the middle area of ​​the fiber grating. As the slider moves, the fiber grating has an extended section and a shortened section, thereby realizing the detection and identification of external pressure.

[0018] Compared with the prior art, the differential grating pressure sensor disclosed in the present application can achieve the purpose of preventing the pressure factor from affecting the measurement result. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0020] Figure 1 A schematic structural diagram of a differential grating pressure sensor provided according to an embodiment of the present invention is shown;

[0021] Figure 2 Shown according to Figure 1 A partially cutaway top view of a differential grating pressure sensor provided;

[0022] Figure 3 Shown according to Figure 1 A front view of a differential grating pressure sensor provided;

[0023] Figure 4 Shown according to Figure 1 A left side view of a differential grating pressure sensor provided;

[0024] Figure 5 The graph shows the change curve of the reflection wavelength of FBG1 and FBG2 with pressure in three pressure tests of a differential grating pressure sensor provided by an embodiment of the present invention.

[0025] Description of labels:

[0026] 1. Pressure inlet; 2. Washer; 3. Locking cylinder; 4. Fiber optic bonding block at the extension end; 5. Grating section at the extension end; 6. Slider; 7. Threaded pair adjustment rod; 8. Control block base; 9. Grating section at the compression end; 10. Fiber optic bonding block at the compression end; 11. Support rod; 12. Tail plate; 13. Armored optical cable; 14. Head end panel; 15. Diaphragm; 16. Slide base; 17. Cross roller guide; 18. Compression spring; 19. Spring compression control block; 20. X-axis steel bar ball guide type manual displacement platform; 21. Optical fiber; 22. Gland joint. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0028] The present invention discloses a differential grating pressure sensor, please refer to Figures 1 to 4 , including a shell, the shell has an inner cavity and the inner cavity is separated from the external environment by a diaphragm 15, the diaphragm 15 is connected to a slider 6, the slider 6 is slidably connected in the shell, the inner cavity has an optical fiber 21 grating arranged along the sliding direction of the slider 6, both ends of the optical fiber 21 grating are fixedly connected to the shell, the middle area of ​​the optical fiber 21 grating is fixedly connected to the slider 6, and the slider 6 is connected to a pre-tightening unit for providing pre-tightening force for it.

[0029] The diaphragm 15 is used to receive external pressure and is connected to the slider 6. When the diaphragm 15 is deformed by pressure, it will drive the slider 6 to move relative to the housing. The deformation of the diaphragm 15 in the axial direction of the optical fiber 21 grating is equal to the movement of the slider 6. The slider 6 is connected to a pre-tightening unit, which is used to provide a pre-tightening force. By setting the pre-tightening force, the diaphragm 15 can obtain a relatively small deformation in the case of a large external input pressure to adapt to the change of the optical fiber 21 grating. The deformation is within the deformable range of the optical fiber 21 grating. The two ends of the optical fiber 21 grating are fixedly connected to the housing, and the slider 6 is fixedly connected to the middle area of ​​the optical fiber 21 grating. With the movement of the slider 6, the optical fiber 21 grating has an extended section and a shortened section, thereby realizing the detection and identification of external pressure. Compared with the prior art, the differential grating pressure sensor disclosed in the present application can achieve the purpose of preventing the pressure factor from affecting the measurement result.

[0030] The main function of using the diaphragm 15 as a sensitivity enhancement element is to improve pressure sensitivity. The diaphragm 15 can effectively transmit the pressure from the outside to the fiber Bragg grating; because the diaphragm 15 is linearly deformed within a certain pressure range, when pressure acts on the diaphragm 15, it will deform, and this deformation is concentrated in the central area of ​​the diaphragm 15, so that the strain effect of the fiber Bragg grating is more significant, and the sensitivity of the sensor is improved.

[0031] The function of the slider is to transfer the deformation of the diaphragm 15 to the fiber grating. The deformation of the diaphragm 15 can be effectively applied to the fiber grating through the slider, thereby causing the wavelength of the grating to drift. Since the slider connects two gratings, one is stretched as the deformation of the diaphragm 15 increases, and the other is compressed as the deformation of the diaphragm 15 increases, thereby forming a differential mechanical structure.

[0032] The function of the preload unit is to maintain the force balance of the slider, so as to ensure that different preloads can be applied to the two gratings in their initial states, and to ensure that the motion process is still in a linear change. The pressure acts on the diaphragm 15 to cause deformation, resulting in compression of one grating. The grating will only cause wavelength drift when it is in a tensioned state. Therefore, in order to ensure that the compressed grating can work normally, the compressed grating needs to be preloaded with a greater preload than the stretched grating in advance. Setting a certain amount of spring compression in advance is used to balance the force imbalance caused by the unequal preloads of the two gratings.

[0033] It should be explained that the middle area of ​​the optical fiber 21 grating refers to any area between the two fixed ends of the optical fiber 21 grating that can achieve the purpose of lengthening one end and shortening the other end, and does not only refer to the position in the middle of the two ends.

[0034] Preferably, the material of the diaphragm 15 is 316L stainless steel, with a thickness of 2.2 mm and a diameter of Φ43 mm. It mainly serves as a pressure-bearing element of the sensor, converting the external water pressure into the axial deformation of the diaphragm 15 to cause the axial strain of the grating. The specific parameters of the diaphragm 15 can be adjusted according to actual use.

[0035] Preferably, the optical fiber 21 uses Corning single-mode optical fiber 21G.652D, which is mainly used for the transmission of optical signals. The specific parameters of the optical fiber 21 can be adjusted according to actual usage.

[0036] After the slider 6 fixes the grating of the optical fiber 21, an extension end grating segment 5 and a compression end grating segment 9 are formed on both sides thereof, respectively. Both are mainly used to convert the axial deformation of the optical fiber 21 into the variation of the optical signal.

[0037] Specifically, a grating is an optical element that uses a periodic structure to produce diffraction and interference effects on light. A typical grating is usually composed of parallel grooves or protrusions, and the spacing and shape of these grooves or protrusions determine the performance of the grating. Common methods for making gratings include mechanical etching, photolithography, electron beam exposure, and interference lithography. Among them, the Bragg grating is a special type of grating, and its production principle is based on the Bragg diffraction law. The Bragg diffraction law states that when a light wave is irradiated onto a periodic structure at a specific incident angle and wavelength, diffraction will occur in a specific direction, and only when the incident angle is equal to the Bragg angle will the diffracted wave meet the coherence condition. Bragg gratings are usually formed by exposing photosensitive materials (such as optical fibers, optical waveguides, etc.) to a light beam formed by interference fringes, and then performing photoinduced refractive index changes or local modifications of the photosensitive materials to form a periodic refractive index or equivalent refractive index structure.

[0038] Bragg wavelength λ B Determined by the following formula:

[0039] λ B =2n eff Λ

[0040] Where: n eff is the effective refractive index of light propagating in the optical fiber; Λ is the period of the Bragg grating.

[0041] When the strain of the external force on the FBG is zero and the ambient temperature changes by △T, the wavelength of light will drift. The relationship between the drift amount and the temperature change is:

[0042] Δλ B =λ B (α+ξ)ΔT

[0043] Where, α = 5.5 × 10 -7 / ℃ is the thermal expansion coefficient of FBG material; ξ=8.3×10 -6 / ℃ is the thermo-optic coefficient of FBG material; △T is the temperature change. Therefore, the temperature sensitivity coefficient of FBG is K T =α+ξ.

[0044] Without considering the temperature change, only considering the effect of strain ε on the grating period Λ when the FBG is subjected to axial tension or compression, the grating period change is:

[0045] ΔΛ=εΛ

[0046] At the same time, considering the influence of the elastic-optic effect, the effective refractive index of FBG will change with the deformation of the fiber core, and the corresponding relationship is:

[0047]

[0048] The effective elastic coefficient P of the optical fiber can be obtained by the formula: e for:

[0049]

[0050] Where P ij (i=1,j=1,2) is the elastic-optical coefficient, and ν is the Poisson's ratio.

[0051] Then the relationship between wavelength drift and pressure change can be obtained as:

[0052] Δλ B =λ B (1-P e )ε

[0053] Therefore, when strain and temperature act on FBG at the same time, the wavelength drift is:

[0054] Δλ=λ B (1-P e )ε+λ B (α+ξ)ΔT

[0055] The differential compensation method is a method of using two FBGs for temperature compensation. Specifically, the central wavelengths of the two FBGs are basically the same, and they are affected by strain and temperature at the same time. The temperature sensitivity coefficients of the two gratings are consistent. One grating FBG1 measures positive strain, and the other grating FBG2 measures negative strain. The two strains are equal in magnitude and opposite in direction.

[0056]

[0057] Δλ 1 -Δλ 2 =2λ(1-P e )ε

[0058] Where Δλ 1 and Δλ 2 are the wavelength drift of FBG1 and FBG2, λ 1 and λ 2 are the central wavelengths of FBG1 and FBG2, respectively, and λ is 1 and λ 2 Since the temperature environment of the compression end grating segment and the extension end grating segment is the same, the drift caused by the temperature effect is the same, so the compression end grating and the extension end grating can compensate each other and offset the error caused by temperature change.

[0059] For example, a 1555nm band grating can be used, the initial wavelength is 1555.0351nm, the ambient temperature is 25°C, the wavelength after stretching is 1558.8656, and the stretching amount is 3.8305nm. The specific parameters of the compression end grating segment can be adjusted according to actual usage.

[0060] In some embodiments, the end of the optical fiber 21 grating near the membrane 15 is fixedly connected to the frame through the extended end optical fiber 21 bonding block 4. The extended end optical fiber 21 bonding block 4 is mainly used to fix the position of the extended end optical fiber 21 and maintain the prestress on the extended end grating. The specific parameters of the extended end optical fiber 21 bonding block 4 can be adjusted according to actual usage.

[0061] In some embodiments, the end of the optical fiber 21 grating away from the diaphragm 15 is fixedly connected to the frame through the compression end optical fiber 21 bonding block 10, and the material of the compression end optical fiber 21 bonding block 10 is preferably aluminum alloy. It is mainly used to fix the position of the tensile section optical fiber 21, so as to maintain the prestress applied to the compression end grating. The specific parameters of the compression end optical fiber 21 bonding block 10 can be adjusted according to actual use.

[0062] In some embodiments, the slider 6 is made of aluminum alloy and is mainly used to receive the stress transmitted by the diaphragm 15 so that it can generate a movement equivalent to the axial displacement of the diaphragm 15 .

[0063] In some embodiments, an armored optical cable 13 is provided at the position where the optical fiber 21 grating extends out of the housing. The sensor uses an armored optical cable 13 with a diameter of 3 mm, which is mainly used to protect the sensor pigtail and adjust the air pressure difference so that the sensor can work normally and is not affected by the external environment. The specific parameters of the armored optical cable 13 can be adjusted according to actual use. In addition, a gland connector 22 is also provided at the position where the optical fiber 21 grating extends out of the housing, specifically an M8 stainless steel gland connector 22, which is mainly used to connect the optical cable and has the characteristics of dustproof and waterproof.

[0064] In some embodiments, a slide base 16 is fixedly connected in the inner cavity of the shell, and a cross roller guide 17 is arranged on the slide base 16. The slider 6 can slide on the cross roller guide 17, and higher precision can be obtained by using the cross roller guide 17. The slide base 16 is made of aluminum alloy and is mainly used to lock and adjust the position of the cross roller guide 17. The specific parameters of the slide base 16 can be adjusted according to actual use. The cross roller guide 17, model VPU2-65, has an overall size of 40*65mm, the table and base are made of aluminum alloy, the track material is Gcr5, the roller material is Gcr5, and the retaining frame material is SUS304. It is mainly used to fix the slider 6, and the slider 6 can move smoothly along the axial displacement direction of the diaphragm 15 after receiving the stress transmitted by the diaphragm 15. The specific parameters of the cross roller guide 17 can be adjusted according to actual use.

[0065] In some embodiments, the housing includes a support rod 11, a tail plate 12, a head end panel 14 and a side plate. The support rod 11 is made of aluminum alloy and is used to connect and fix the head end panel 14 and the tail plate 12. The tail plate 12 is made of aluminum alloy and is used to fix the gland joint 22. The tail plate 12 is made of aluminum alloy and is used to fix the pressure inlet 1.

[0066] The sensitivity test of the assembled sensor was carried out. The sensor was connected to the hydraulic pump through a high-pressure hose, and one end of the armored optical cable 13 was connected to the fiber 21 grating demodulator. The ambient temperature during the test was 25°C. In the experiment, the pressure was gradually increased from 0MPa to 2MPa in steps of 0.1MPa, and a total of three tests were conducted. Each pressure measurement point was maintained for 10 to 15 seconds; the reflection wavelengths of the tensile grating FBG1 and the compression grating FBG2 were truly recorded through the fiber 21 grating demodulation software, and the reflection spectra of FBG1 and FBG2 at each pressure measurement point were recorded.

[0067] from Figure 5 It can be seen that the wavelengths of FBG1 and FBG2 show good linear response and repeatability to pressure. The average pressure sensitivity of FBG1 is 855.13pm / MPa, and the average linear correlation coefficient is 0.9987. The average pressure sensitivity of FBG2 is 886.4pm / MPa, and the average linear correlation coefficient is 0.9988. Therefore, the sensitivity of the sensor within the working range of 2MPa is approximately (886.4+855.13)pm / MPa=1741.53.

[0068] The sensing probe is composed of a grating etched on the optical fiber 21 as a sensitive element. The all-optical fiber 21 of the submarine probe is passive, does not require on-site power supply, and can achieve long-term real-time monitoring. It adopts optical signal sensing transmission and is not subject to electromagnetic interference. The grating is a part of the transmission optical fiber 21 itself, realizing integrated sensing and transmission. Long-distance transmission can easily form quasi-distributed network monitoring and realize long-distance distributed monitoring.

[0069] The sensor can convert external pressure information into the form of light wavelength changes for detection. The laser inputs the light signal to the sensor probe through the optical fiber 21. As the pressure changes, the periodic structure of the optical fiber 21 grating changes, which causes the reflected light wavelength to shift. The reflected light wave is transmitted through the optical fiber 21 to the optical fiber 21 grating demodulation system for signal processing and data storage, so that the pressure information can be detected in real time.

[0070] The sensor integrates two fiber 21 Bragg gratings (FBG1 and FBG2) of the same specifications on one fiber 21, and adopts a differential dual grating structure. The common end of FBG1 and FBG2 is fixed on the slider 6, and the other end of FBG1, which is pre-stretched (causing a wavelength shift of about 0.5nm), is pasted and fixed between the extension end bonding block and the slider 6 to sense the positive displacement change of pressure conversion; the other end of FBG2, which is pre-stressed (causing a wavelength shift of about 4nm), is pasted and fixed between the slider 6 and the compression end bonding block to sense the negative displacement change of pressure conversion; in addition, the slide is balanced by the pressure spring to the different prestresses it is subjected to. When the ambient pressure changes, the diaphragm 15 of the sensor will drive the slider 6 to reciprocate. Since the common end of FBG1 and FBG2 is fixed to the slider 6, the length changes of the two gratings are the same, and the displacements generated are equal, that is, the strains of the gratings at the compression end and the extension end are equal. Moreover, the gratings at both ends are in the same environment, which can self-compensate for the temperature, and at the same time double the sensitivity of the sensor, thereby improving the accuracy and precision of pressure measurement.

[0071] In some embodiments, a first adjusting unit for adjusting the distance between the diaphragm 15 and the slider 6 is further included, and the diaphragm 15 is connected to the slider 6 via the first adjusting unit.

[0072] Specifically, the first adjustment module can adjust the distance between the diaphragm 15 and the slider 6, so that the length of the extended end grating segment 5 can be adjusted, thereby improving adaptability, meeting more types of test requirements, and adapting to applications in more scenarios.

[0073] In some specific embodiments, the first adjusting unit is a threaded pair adjusting rod 7 , and the threaded pair adjusting rod 7 extends into the slider 6 and is threadedly connected to the slider 6 .

[0074] Specifically, the material of the threaded pair adjusting rod 7 is aluminum alloy, and it is mainly used to transfer the axial stress of the diaphragm 15 to the slider 6, so that the slider 6 moves a distance equal to the axial displacement of the diaphragm 15. The specific parameters of the threaded pair adjusting rod 7 can be adjusted according to actual use conditions.

[0075] The threaded pair adjusting rod 7 is used for force transmission during operation, and forms a rigid connection with the slider 6 to ensure that the sliding movement produces the same displacement as the axial deformation of the diaphragm 15. During the initial setting process of manufacturing and debugging, it can be used to adjust the distance between the diaphragm 15 and the slider 6.

[0076] In other embodiments, the first adjustment unit may also be a control knob, a positioning pin, or other structures.

[0077] In some embodiments, a second adjusting unit for adjusting the pre-tensioning force of the pre-tensioning unit is further included, and the second adjusting unit is connected to the pre-tensioning unit.

[0078] The second adjustment unit can be set up to allow the operator to adjust the deformation of the diaphragm 15 by changing the preload force when it is subjected to the same pressure. Therefore, when the optical fiber 21 grating remains unchanged, the sensitivity can be changed by changing the deformation. When the preload force is small, the deformation of the diaphragm 15 is large, so that the elongation or shortening of the optical fiber 21 grating is also large, and the sensor can be more sensitive. Otherwise, the sensitivity of the sensor will be reduced, which can reduce interference and improve the stability of the sensor.

[0079] In some specific embodiments, the pre-tightening unit includes an elastic member, one end of which abuts against the slider 6 and the other end of which is connected to the housing.

[0080] The pre-tightening unit includes an elastic member. The use of the elastic member for pre-tightening has a simple structure and belongs to passive control, which is convenient for the sensor to perform data transmission and use control.

[0081] In other embodiments, the pre-tightening unit may also be a buffer cylinder or other mechanism.

[0082] In some more specific embodiments, the elastic member is connected to the housing via a pre-tightening unit, the elastic member abuts against the second adjusting unit, and the second adjusting unit can move relative to the housing in the sliding direction of the slider 6 .

[0083] Among them, the elastic member is preferably a spring, the material of the spring is spring steel, and the wire diameter, diameter and length dimensions are 1.0mm, Φ15mm and 40mm respectively. It is mainly used to fix the position of the slider 6. By applying spring resistance, the tension and compression end gratings can still maintain the position of the slider 6 after being applied with different prestresses and will not move due to uneven force. The specific parameters of the compression spring 18 can be adjusted according to actual use. In addition, the compression deformation of the spring belongs to linear elastic deformation, which ensures that the deformation acting on the grating is still a linear change under the linear deformation of the diaphragm 15.

[0084] Preferably, the second adjustment unit includes a spring compression control block 19 and a control block base 8. The spring compression control block 19 has a hole diameter of Φ15 cm and is made of aluminum alloy. It is mainly used to adjust the compression of the spring so that the spring can play its role. The control block base 8 is made of aluminum alloy. It is used to lock and adjust the position of the control block. The specific parameters of the control block base 8 and the spring compression control block 19 can be adjusted according to actual usage.

[0085] In some embodiments, one end of the optical fiber 21 grating away from the diaphragm 15 is fixedly connected to a third adjustment unit, the third adjustment unit is connected to the housing, and the third adjustment unit can move relative to the housing in the sliding direction of the slider 6.

[0086] Specifically, the third adjustment module can adjust the distance between the diaphragm 15 and the slider 6, so that the length of the extended end grating segment 5 can be adjusted, thereby improving adaptability, meeting more types of test requirements, and adapting to applications in more scenarios.

[0087] Preferably, the X-axis steel bar ball guide type manual displacement platform 20, model LGX60-L, has an overall dimension of 60*60mm and is made of aluminum alloy. It is mainly used to fix the compression end optical fiber 21 bonding block 10, and can manually adjust the displacement platform to move the compression end optical fiber 21 bonding block 10, so as to adjust the prestress applied to the compression end grating segment 9, so that the initial wavelength of the compression end grating can meet the sensor use requirements. The specific parameters of the X-axis steel bar ball guide type manual displacement platform 20 can be adjusted according to actual usage. When there is no compression end light bonding block, the X-axis steel bar ball guide manual displacement platform can directly fix and adjust the end of the optical fiber 21 grating away from the diaphragm 15.

[0088] Among them, the X-axis steel bar ball guide type manual displacement platform 20 is used to apply the initial prestress of the grating. First, the two ends of the grating string are fixed on the extension end fiber bonding block and the compression end fiber bonding block. Since the compression end fiber bonding block is fixed on the X-axis steel bar ball guide type manual displacement platform 20, the X-axis steel bar ball guide type manual displacement platform 20 can be adjusted to move to ensure that the grating string is always in a tensioned state. Then, the middle position of the grating string is bonded to the slider to ensure that the stretched grating is initially in a tensioned state. Finally, the X-axis steel bar ball guide type manual displacement platform 20 is adjusted again. Since the compression grating is between the slider and the X-axis steel bar ball guide type manual displacement platform 20, the prestress on the compression grating can be increased by moving the X-axis steel bar ball guide type manual displacement platform 20, so as to provide sufficient initial prestress to ensure that the compression grating is always in a tensioned state during the working process.

[0089] In some embodiments, the housing protrudes outward at the position of the diaphragm 15 to form a pressure inlet 1, and the pressure inlet 1 is connected to the diaphragm 15.

[0090] Preferably, the pressure inlet 1 is cylindrical and made of stainless steel. During testing, it is used to form a rigid connection with the pressure pump so that the internal water pressure can be controlled and adjusted by the pressure pump; during actual use, it is directly connected to the external environment. The specific parameters of the pressure inlet 1 can be adjusted according to actual use.

[0091] In the experimental test, a pressure hose is required to connect the sensor to the pressure calibration device, and the pressure response test of the sensor is performed by adjusting the water pressure through the pressure calibration device. Since the outer diameter of the pressure hose connector used is 20mm and the thread is 1.5m, the size of the pressure inlet depends on the size of the hose connector, and it can also be changed according to the actual situation in subsequent actual use. There is no specific requirement for the installation location.

[0092] In some specific embodiments, the size of the pressure inlet 1 is smaller than the size of the diaphragm 15 , and the pressure inlet 1 is arranged directly opposite to the center of the diaphragm 15 .

[0093] It should be noted that the size of the pressure inlet 1 is smaller than the size of the diaphragm 15, and the pressure inlet 1 is arranged opposite the center of the diaphragm 15. In this way, the external pressure can be concentrated in the center of the diaphragm 15, so that the diaphragm 15 obtains more accurate strain deformation, and thus obtains more accurate detection results.

[0094] In some embodiments, washers 2 and locking members are respectively provided on both sides of the diaphragm 15 , and the locking members press the washers 2 and the diaphragm 15 onto the housing.

[0095] Specifically, the gasket 2 is a gasket 2 made of fluororubber. It is mainly used to make the space between the diaphragm 15 and the pressure inlet 1 a sealed environment, so that the inside of the sensor is dustproof and waterproof. The specific parameters of the gasket 2 can be adjusted according to actual use.

[0096] The locking member is a locking cylinder 3 made of stainless steel, which is mainly used to lock the position of the diaphragm 15 at the exact center. The specific parameters of the locking cylinder 3 can be adjusted according to actual use.

[0097] In the description of this specification, if the terms "embodiment one", "this embodiment", "in an embodiment" and the like appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in an appropriate manner.

[0098] In the description of this specification, the terms "connect", "install", "fix", "set", "have", etc. are all understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0099] In the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0100] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. A differential grating pressure sensor, characterized in that: The invention comprises a shell, wherein the shell has an inner cavity and the inner cavity is separated from the external environment by a diaphragm, the diaphragm is connected to a slider, the slider is slidably connected in the shell, the inner cavity has a fiber grating arranged along the sliding direction of the slider, both ends of the fiber grating are fixedly connected to the shell, the middle area of ​​the fiber grating is fixedly connected to the slider, and the slider is connected to a pre-tightening unit for providing pre-tightening force for the slider.

2. A differential grating pressure sensor according to claim 1, characterized in that: The device further comprises a first adjusting unit for adjusting the distance between the diaphragm and the slider, wherein the diaphragm is connected to the slider via the first adjusting unit.

3. A differential grating pressure sensor according to claim 2, characterized in that: The first adjusting unit is a threaded pair adjusting rod, and the threaded pair adjusting rod extends into the slider and is threadedly connected to the slider.

4. A differential grating pressure sensor according to claim 1, characterized in that: It also includes a second adjusting unit for adjusting the pre-tensioning force of the pre-tensioning unit, and the second adjusting unit is connected to the pre-tensioning unit.

5. A differential grating pressure sensor according to claim 4, characterized in that: The pre-tightening unit comprises an elastic member, one end of which abuts against the slider, and the other end of which is connected to the housing.

6. A differential grating pressure sensor according to claim 5, characterized in that: The elastic member is connected to the housing via the pre-tightening unit. The elastic member abuts against the second adjusting unit. The second adjusting unit can move relative to the housing in the sliding direction of the slider.

7. The differential grating pressure sensor according to claim 1, characterized in that: A third adjusting unit is fixedly connected to one end of the fiber grating away from the diaphragm. The third adjusting unit is connected to the housing. The third adjusting unit can move relative to the housing in the sliding direction of the slider.

8. A differential grating pressure sensor according to any one of claims 1 to 7, characterized in that: The housing protrudes outward at the position of the diaphragm to form a pressure inlet, and the pressure inlet is communicated with the diaphragm.

9. The differential grating pressure sensor according to claim 8, characterized in that: The size of the pressure inlet is smaller than the size of the diaphragm, and the pressure inlet is arranged directly opposite to the center of the diaphragm.

10. A differential grating pressure sensor according to any one of claims 1 to 7, characterized in that: A gasket and a locking member are respectively arranged on both sides of the diaphragm, and the locking member presses the gasket and the diaphragm onto the housing.

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