Substrate applied to strain gauge and corresponding strain gauge

Abstract

The present invention relates to a substrate applied to a strain gauge and a corresponding strain gauge, wherein the substrate is composed of a first substrate section and a second substrate section with different stiffnesses, and the first substrate section and the second substrate section are respectively provided with wiring grooves for installing sensing components. When the substrate applied to the strain gauge and the corresponding strain gauge of this structure are installed on a part to be measured, the characteristics of the different stiffnesses of the two substrate sections are utilized to perform temperature measurement and strain measurement respectively, and strain and temperature can be measured simultaneously during measurement, and the measurement has good sensitivity and temperature compensation, is less affected by external temperature, has a wide range of applications, and has a simple structure and low cost.

Description

Technical Field

[0001] The present invention relates to the field of detection, in particular to the technical field of using sensors for detection, and specifically to a substrate applied to a strain gauge and a corresponding strain gauge. Background Art

[0002] In recent years, fiber Bragg gratings have developed rapidly as a new type of sensing element and have been widely used in sensing measurements under various conditions, especially in civil engineering, rail transit, petrochemical and other fields where their use has become a hot topic.

[0003] Fiber Bragg Grating uses the photosensitivity of optical fiber materials to write the incident light coherent field pattern into the fiber core through a special process, so that the refractive index along the axis of the fiber core changes periodically, thereby forming a permanent spatial phase grating. When a beam of wide-spectrum light passes through the fiber Bragg Grating, reflection and transmission will occur at the interface of the refractive index. The wavelength that meets the Bragg condition (λ = 2×n×L / N) will be reflected, and the remaining wavelengths will continue to be transmitted through the fiber Bragg Grating.

[0004] Fiber Bragg grating sensor is a kind of fiber optic sensor. The sensing process based on fiber Bragg grating is to obtain sensing information by modulating the optical fiber Bragg wavelength by external physical parameters. It is a wavelength modulated fiber optic sensor. Fiber Bragg grating power temperature sensor detects temperature value by the shift of the center wavelength of the optical signal reflected by the internal sensitive element - fiber Bragg grating. It is passive, insulated, intrinsically safe, not subject to electromagnetic interference and lightning damage. The temperature measurement accuracy and resolution are not affected by light source fluctuations and transmission line bending losses, and can be transmitted remotely.

[0005] Strain, which belongs to material mechanics, is a common technical parameter that can characterize the degree of structural change on mechanical parts. Strain measurement can provide mechanical performance indicators of various materials for components, which is of great significance in many cases.

[0006] Strain usually comes from two sources, thermal strain and elastic strain. The actual strain is the sum of the two. In structural mechanics, elastic strain is generated by the internal stress of the structure, and thermal strain is generated by the temperature change of the structure. The physical meanings of the two are different and need to be detected separately.

[0007] Conventional strain sensors cannot distinguish between thermal strain and elastic strain after being installed on components, and require a separate thermometer for temperature compensation to eliminate the influence of temperature. This method has the following problems: 1) The resolution is insufficient for small strains and they cannot be detected; 2) The thermometer and strain gauge are installed separately, and the temperature compensation is not accurate enough.

[0008] In view of the problems existing in existing optical fiber strain measurement, it is necessary to design an integrated strain gauge that can improve strain measurement sensitivity and temperature accuracy. Summary of the invention

[0009] The purpose of the present invention is to overcome at least one of the above-mentioned disadvantages of the prior art and to provide a substrate applied to a strain gauge and a corresponding strain gauge with a simple structure and good practicality.

[0010] In order to achieve the above purpose or other purposes, the substrate applied to the strain gauge and the corresponding strain gauge of the present invention are as follows:

[0011] The substrate used for the strain gauge has the following main features: the substrate is composed of a first substrate segment and a second substrate segment connected together, wherein the stiffness of the first substrate segment is much greater than the stiffness of the second substrate segment, and the first substrate segment and the second substrate segment are respectively provided with wiring grooves for installing sensing components, and the wiring grooves run through the first substrate segment and the second substrate segment.

[0012] Preferably, the difference in materials selected for constructing the first substrate segment and the second substrate segment results in different stiffness of the two; wherein the stiffness of the material selected for constructing the first substrate segment is much greater than the stiffness of the material selected for constructing the second substrate segment.

[0013] Preferably, the substrate is an integrated structure composed of a first substrate segment and a second substrate segment made of the same material, and the first substrate segment and the second substrate segment have different shapes, so that the two have different rigidities.

[0014] More preferably, the second base segment is provided with a wide groove which makes a local segment of the second base segment more susceptible to deformation due to external force.

[0015] Preferably, the portion of the sensor component installed in the wiring trough on the first substrate segment is used to measure temperature, and the portion of the sensor component installed in the wiring trough on the second substrate segment is used to measure strain.

[0016] Preferably, a fixing point for fixing the mounting sensor component is provided between the first base segment and the second base segment.

[0017] The strain gauge with the above-mentioned substrate has the following main features: the strain gauge includes a sensing component, the sensing component is an optical fiber, and the optical fiber is stretched and arranged in the wiring groove;

[0018] The portion of the optical fiber installed in the wiring trough and located on the first substrate segment is engraved with a first optical fiber Bragg grating for temperature measurement, and the portion of the optical fiber installed in the wiring trough and located on the second substrate segment is engraved with a second optical fiber Bragg grating for strain measurement.

[0019] Preferably, the strain gauge is fixed to the part to be measured through sensor mounting holes symmetrically arranged at two ends of the substrate.

[0020] More preferably, the strain gauge and the part to be measured can be connected by welding or gluing.

[0021] Preferably, the optical fiber is mounted on the substrate by metallized grating laser welding or grating gluing;

[0022] When the grating is installed by gluing, a highly strong, low-deformation strain adhesive is used for gluing.

[0023] Preferably, the strain gauge further comprises a strain protection rubber pad covering the substrate and the optical fiber.

[0024] The strain gauge with the above-mentioned substrate has the following main features: the strain gauge includes a sensing component, the sensing component is an inductive resistor module, and the inductive resistor module is arranged in the wiring groove;

[0025] The portion of the sensing resistor module installed in the wiring trough and located on the first substrate segment is a first sensing resistor for realizing temperature measurement, and the portion of the sensing resistor module installed in the wiring trough and located on the second substrate segment is a second sensing resistor for realizing strain measurement.

[0026] By using the substrate applied to the strain gauge and the corresponding strain gauge of the present invention, strain and temperature can be measured simultaneously during measurement, and the measurement has good sensitivity and temperature compensation, is less affected by external temperature, has a wide range of applications, and has a simple structure and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the schematic diagram of the fiber Bragg grating.

[0028] Figure 2 FIG. 4 is a schematic structural diagram of a substrate applied to a strain gauge in an embodiment of the present invention.

[0029] Reference numerals

[0030] 1 First basal segment

[0031] 2 Second basal segment

[0032] 3 Wireway

[0033] 4 wide slots

[0034] 5 Sensor mounting holes

[0035] 6 Fiber fixing points DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments.

[0037] The substrate applied to the strain gauge, wherein the substrate is composed of a first substrate segment 1 and a second substrate segment 2 connected together, wherein the stiffness of the first substrate segment 1 is much greater than the stiffness of the second substrate segment 2, and the first substrate segment 1 and the second substrate segment 2 are respectively provided with wiring grooves 3 for installing sensing components, and the wiring grooves 3 run through the first substrate segment 1 and the second substrate segment 2.

[0038] The first substrate segment 1 and the second substrate segment 2 may have different rigidities due to the different materials selected for the two substrate segments; wherein the rigidity of the material selected for the first substrate segment 1 is much greater than the rigidity of the material selected for the second substrate segment 2. In the above embodiment, the substrate is an integrated structure composed of the first substrate segment 1 and the second substrate segment 2 made of the same material, and the first substrate segment 1 and the second substrate segment 2 have different shapes, so that the rigidities of the two substrate segments are different.

[0039] In the above embodiment, the second base segment 2 is provided with a wide groove 4 which makes a local section of the second base segment 2 more susceptible to deformation due to external force.

[0040] In the above embodiment, the portion of the sensor component installed in the wiring trough 3 located on the first substrate segment 1 is used to measure temperature, and the portion of the sensor component installed in the wiring trough 3 located on the second substrate segment 2 is used to measure strain.

[0041] In the above embodiment, a fixing point for fixing the mounting sensor component is provided between the first base segment 1 and the second base segment 2, that is, the first base segment 1 is located on the left side of the fixing point, and the second base segment 2 is located on the right side of the fixing point.

[0042] A strain gauge having the substrate in the above embodiment, wherein the strain gauge further comprises a sensing component, wherein the sensing component is an optical fiber, and the optical fiber is stretched and arranged in the wiring trough 3. At this time, the fixing point for fixing the installation sensing component is an optical fiber fixing point 6, that is, when the optical fiber is fixed in the wiring trough 3, in addition to the two ends of the optical fiber being fixed to the two ends of the strain gauge (the two ends of the optical fiber can be fixed by the optical fiber fixing points 6 respectively arranged at the two ends of the strain gauge), the middle section of the optical fiber is also fixed between the first substrate section 1 and the second substrate section 2 through the optical fiber fixing point 6 located in the middle, so that when one section of the optical fiber is stretched by the influence of the corresponding first substrate section 1 or the second substrate section 2, the other section of the optical fiber will not be affected;

[0043] The portion of the optical fiber installed in the wiring trough 3 and located on the first substrate segment 1 is engraved with a first optical fiber Bragg grating for realizing temperature measurement, and the portion of the optical fiber installed in the wiring trough 3 and located on the second substrate segment 2 is engraved with a second optical fiber Bragg grating for realizing strain measurement.

[0044] The strain gauge is fixed on the part to be measured through sensor mounting holes 5 symmetrically arranged at both ends of the substrate.

[0045] The strain gauge and the part to be measured can be connected by welding or gluing.

[0046] The optical fiber is installed on the substrate by metallized grating laser welding or grating gluing;

[0047] When the grating is installed by gluing, a highly strong, low-deformation strain adhesive is used for gluing.

[0048] The strain gauge also includes a strain protection rubber pad covering the substrate and the optical fiber.

[0049] Combine the following Figure 1 , 2 The strain gauge in this embodiment is further described. Figure 1 This is the principle diagram of the fiber Bragg grating, which plots the characteristics of the periodic variation of the refractive index, where:

[0050] (1) Optical path difference S = n × L × 2, where n is the equivalent refractive index within the period and L is the length of the period;

[0051] (2) When the wavelength satisfies the condition: wavelength = S / N, the multi-path outgoing light forms constructive interference; N is a natural number;

[0052] (3) When the fiber Bragg grating is heated or stressed, two main effects occur: photothermal effect (change in refractive index) and photoelastic effect (change in length). The two effects work together to cause a change in wavelength.

[0053] The strain gauge in this embodiment is manufactured by applying the above-mentioned characteristics of optical fiber.

[0054] The strain gauge in this embodiment uses a fiber Bragg grating as a sensing component, which can be used to detect strain and / or temperature. At the same time, it increases the sensitivity of strain measurement and eliminates the influence of temperature. It is a dual fiber Bragg grating (optical fiber with two kinds of gratings engraved on the same optical fiber) structure that measures temperature and strain at the same time. The strain gauge adopts an integrated package. After packaging, the first fiber Bragg grating is mainly affected by temperature and expands freely to measure and supplement temperature. The second fiber Bragg grating measures elastic strain. When the optical fiber is installed in Figure 2 When the substrate is in the substrate, the first fiber Bragg grating and the second fiber Bragg grating are pre-stretched by a certain distance, about 2 to 3 nm, respectively. The specific value is adjusted according to the actual situation to ensure that the grating is in a tight state when the substrate shrinks. In the above embodiment, the sensor mounting hole 5 of the substrate can be fixed on the part to be measured by welding or gluing. When the part to be measured is deformed, the first fiber Bragg grating and the second fiber Bragg grating are deformed. The deformation of the first fiber Bragg grating is driven by the first substrate segment 1, and the deformation of the second fiber Bragg grating is driven by the second substrate segment 2. The two ends of the first fiber Bragg grating are respectively fixed on the two ends of the first substrate segment 1 (respectively fixed by the fiber fixing point 6 located on the left and the fiber fixing point 6 located in the middle), and the two ends of the second fiber Bragg grating are respectively fixed on the two ends of the second substrate segment 2 (respectively fixed by the fiber fixing point 6 located on the right and the fiber fixing point 6 located in the middle), that is, the optical fiber is divided into two sections (the first fiber Bragg grating and the second fiber Bragg grating) on ​​the substrate through three fiber fixing points 6. Since the stiffness of the first substrate segment 1 is much greater than that of the second substrate segment 2, which is about one order of magnitude greater than that of the second substrate segment 2 (about several dozen to several hundred times), assuming that the length of the first fiber Bragg grating is L1 and the stiffness is G1, and the length of the second fiber Bragg grating is L2 and the stiffness is G2, when the measured part is deformed, the first substrate segment 1 and the second substrate segment 2 respectively drive the first fiber Bragg grating and the second fiber Bragg grating to deform, and the total deformation of the optical fiber = L1 / G1+L2 / G2. In this embodiment, by setting the first substrate segment 1 and the second substrate segment 2 in different shapes, the stiffness of the two is different, and a wide groove 4 is provided on the second substrate segment 2 to make the local section of the second substrate segment 2 more susceptible to deformation by external force, as shown in FIG. Figure 2As shown, two wide grooves 4 are provided on the second substrate segment 2. The structure of the position of the wide grooves 4 is obviously finer than that of other parts, and its rigidity is relatively much smaller. In this embodiment, the rigidity of the second substrate segment 2 is changed by adjusting the size of the wide grooves 4 (in other embodiments, the rigidity of the first substrate segment 1 and the second substrate segment 2 can also be different by other means). Because G1 is much larger than G2, the deformation of the substrate caused by the measured part is mainly concentrated on the second fiber grating, and the deformation of the first fiber grating is mainly free contraction caused by temperature due to the rigidity relationship. The sensitivity enhancement (increasing measurement sensitivity) coefficient of the second substrate segment 2 is (L1+L2) / L2.

[0055] The following technical effects can be obtained through the structural design in this embodiment:

[0056] (1) The sensitivity enhancement effect of the second fiber Bragg grating part can reach more than 3 times, that is, the sensitivity is more than 3pm / uε;

[0057] (2) The temperature of the first fiber grating part is measured by the thermal expansion coefficient of the base material body, which is 13 pm / u℃;

[0058] (3) After temperature compensation, the strain accuracy is ±3uε and the temperature measurement accuracy is within 0.1℃

[0059] The strain gauge in this embodiment has the following characteristics:

[0060] (1) In the fiber grating element, there are multiple refractive index periods, and n is the equivalent refractive index of each refractive index period;

[0061] (2) The fiber grating is routed along the fiber groove to avoid fiber exposure, which may cause damage to the fiber and affect the strength;

[0062] (3) When the optical fiber is installed on the substrate, metallized grating laser welding or ordinary grating gluing can be selected, and the glue should be high-strength, low-deformation strain glue;

[0063] (4) The sensitivity enhancement coefficient can be changed by adjusting the length of the first fiber grating and the second fiber grating; the rigidity of the second substrate segment 2 can be changed by adjusting the shape of the wide groove 4.

[0064] During installation, use laser welding or gluing to install the installation hole to ensure a rigid connection between the sensor and the part to be measured. The optical fiber must not be exposed to avoid damage. A strain protection rubber pad can be used to cover it to ensure that the temperature of the sensor is consistent with that of the part to be measured and to protect the optical sensor.

[0065] The above strain gauge can not only measure strain alone, but also measure temperature and strain simultaneously.

[0066] In other embodiments, the strain gauge includes a sensing component, and the sensing component may also be an inductive resistor module, and the inductive resistor module is disposed in the wiring slot 3;

[0067] The portion of the sensing resistor module installed in the wiring trough 3 and located on the first substrate segment is a first sensing resistor for realizing temperature measurement, and the portion of the sensing resistor module installed in the wiring trough 3 and located on the second substrate segment 2 is a second sensing resistor for realizing strain measurement.

[0068] By using the substrate applied to the strain gauge and the corresponding strain gauge of the present invention, strain and temperature can be measured simultaneously during measurement, and the measurement has good sensitivity and temperature compensation, is less affected by external temperature, has a wide range of applications, and has a simple structure and low cost.

[0069] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A substrate for use on a strain gauge, characterized in that: The substrate is composed of a first substrate section and a second substrate section connected together, wherein the rigidity of the first substrate section is much greater than the rigidity of the second substrate section, and the first substrate section and the second substrate section are respectively provided with wiring grooves for installing the sensor components, and the wiring grooves run through the first substrate section and the second substrate section; The sensing component is an optical fiber, the two ends of the optical fiber are fixed to the two ends of the strain gauge, and the middle section of the optical fiber is fixed between the first base section and the second base section; Due to the difference in the materials selected for constructing the first substrate segment and the second substrate segment, the stiffness of the two is different; wherein the stiffness of the material selected for constructing the first substrate segment is much greater than the stiffness of the material selected for constructing the second substrate segment; The portion of the sensing component installed in the wiring trough on the first substrate segment is used to measure temperature, and the portion of the sensing component installed in the wiring trough on the second substrate segment is used to measure strain.

2. The substrate applied to the strain gauge according to claim 1, characterized in that: The second base segment is provided with a wide groove which makes a local segment of the second base segment more susceptible to deformation due to external force.

3. The substrate applied to the strain gauge according to claim 1, characterized in that: A fixing point for fixing the mounting sensor component is provided between the first base segment and the second base segment.

4. A strain gauge having a substrate according to any one of claims 1 to 3, characterized in that: The strain gauge includes a sensing component, the sensing component is an optical fiber, and the optical fiber is stretched and arranged in the wiring groove; The portion of the optical fiber installed in the wiring trough and located on the first substrate segment is engraved with a first optical fiber Bragg grating for temperature measurement, and the portion of the optical fiber installed in the wiring trough and located on the second substrate segment is engraved with a second optical fiber Bragg grating for strain measurement.

5. The strain gauge according to claim 4, characterized in that The strain gauge is fixed on the part to be measured through sensor mounting holes symmetrically arranged at two ends of the substrate.

6. The strain gauge according to claim 5, characterized in that The strain gauge and the part to be measured can be connected by welding or gluing.

7. The strain gauge according to claim 6, characterized in that The optical fiber is installed on the substrate by metallized grating laser welding or grating gluing; When the grating is installed by gluing, a highly strong, low-deformation strain adhesive is used for gluing.

8. The strain gauge according to claim 7, characterized in that The strain gauge also includes a strain protection rubber pad covering the substrate and the optical fiber.

9. A strain gauge having a substrate according to any one of claims 1 to 3, characterized in that: The strain gauge includes a sensing component, the sensing component is an inductive resistor module, and the inductive resistor module is arranged in the wiring groove; The portion of the sensing resistor module installed in the wiring trough and located on the first substrate segment is a first sensing resistor for realizing temperature measurement, and the portion of the sensing resistor module installed in the wiring trough and located on the second substrate segment is a second sensing resistor for realizing strain measurement.

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