Temperature self-correction device and method for an optical fiber strain gauge

Abstract

The present invention relates to the field of fiber optic sensing technology, and particularly to a temperature self-correction device and method for a fiber optic strain gauge. The device utilizes two relatively spaced temperature compensation sheets, and the two temperature compensation sheets are fixed to the substrate through their respective outer end faces (the end faces away from the other temperature compensation sheet). It can mount two fiber optic strain gauges, and each fiber optic strain gauge is fixed through two fixed points, wherein the distances between the fixed points of the two fiber optic strain gauges are different. The thermal expansion coefficients of the two temperature compensation sheets are the same and greater than the thermal expansion coefficient of the substrate, ensuring the difference in the temperature sensitivities of the two fiber optic strain gauges. The thermal expansion between the temperature compensation sheet and the substrate can at least partially offset. While increasing the strain sensitivity, it can reduce the temperature sensitivity, reduce and eliminate the influence of thermal output on the measurement result of the fiber optic strain gauge, and has a simple structure and is convenient to install. The self-correction method can eliminate the influence of thermal output on the measurement result of the fiber optic strain gauge.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber sensing, and in particular to a temperature self-correction device and method for an optical fiber strain gauge. Background Art

[0002] Optical fiber sensors have the advantages of anti-electromagnetic interference, high temperature resistance, small size, high precision, etc., and have been widely used in high-precision measurements in many fields such as aerospace, aviation, navigation, and energy. Optical fiber sensors can detect a variety of physical quantities, including pressure, temperature, strain, vibration, etc. Among them, optical fiber strain gauges have been widely used in the health monitoring of structures such as bridges and the measurement of thermal stress of structures in extremely low / high temperature environments. However, when accurately measuring the structural stress using an optical fiber strain gauge in a variable temperature environment, the influence of temperature changes on the structure and the optical fiber strain gauge must be considered. Therefore, the temperature correction of the optical fiber strain gauge is a key technology.

[0003] For an optical fiber strain gauge installed on a base structure, when the temperature changes, both the strain gauge and the base structure will undergo thermal deformation, thereby generating a thermal output, which affects the accurate measurement of strain by the optical fiber strain gauge in a variable temperature environment. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] The first object of the present invention is to provide a temperature self-correction device for an optical fiber strain gauge, which can at least reduce the influence of thermal output on the measurement result of the optical fiber strain gauge.

[0006] The second object of the present invention is to provide a temperature self-correction method for an optical fiber strain gauge, which can at least eliminate the influence of thermal output on the measurement result of the optical fiber strain gauge.

[0007] (II) Technical Solutions

[0008] To achieve the first object of the present invention, in a first aspect of the present invention, a temperature self-correction device for an optical fiber strain gauge is provided. In a first implementation manner, the temperature self-correction device for an optical fiber strain gauge includes:

[0009] A first temperature compensation sheet, on which two parallel and spaced optical fiber routing grooves are provided, namely a first optical fiber routing groove and a second optical fiber routing groove. A first optical fiber fixing point is provided in the first optical fiber routing groove, and a second optical fiber fixing point is provided in the second optical fiber routing groove;

[0010] A second temperature compensation sheet, on which two parallel and spaced optical fiber routing grooves are provided, namely a third optical fiber routing groove and a fourth optical fiber routing groove. A third optical fiber fixing point is provided in the third optical fiber routing groove, and a fourth optical fiber fixing point is provided in the fourth optical fiber routing groove;

[0011] The first temperature compensation piece and the second temperature compensation piece are spaced and relatively fixed on the upper side of the substrate, so as to form an expansion gap between the first temperature compensation piece and the second temperature compensation piece, and when the first temperature compensation piece and the second temperature compensation piece undergo thermal expansion deformation, it is avoided that the first temperature compensation piece and the second temperature compensation piece are in direct contact;

[0012] The first temperature compensation piece is fixed to the substrate through the end face far away from the second temperature compensation piece, and the second temperature compensation piece is fixed to the substrate through the end face far away from the first temperature compensation piece;

[0013] The first optical fiber routing groove and the third optical fiber routing groove are spaced and opposite to each other in the same groove direction, and are used to accommodate the first optical fiber strain gauge. The first optical fiber strain gauge is fixed at the first optical fiber fixing point and the third optical fiber fixing point. The sensitive head of the first optical fiber strain gauge is located between the first optical fiber fixing point and the third optical fiber fixing point, and the distance between the first optical fiber fixing point and the third optical fiber fixing point is the first installation distance;

[0014] The second optical fiber routing groove and the fourth optical fiber routing groove are spaced and opposite to each other in the same groove direction, and are used to accommodate the second optical fiber strain gauge. The second optical fiber strain gauge is fixed at the second optical fiber fixing point and the fourth optical fiber fixing point. The sensitive head of the second optical fiber strain gauge is located between the second optical fiber fixing point and the fourth optical fiber fixing point, and the distance between the second optical fiber fixing point and the fourth optical fiber fixing point is the second installation distance;

[0015] The first installation distance is less than the second installation distance;

[0016] The first temperature compensation piece and the second temperature compensation piece have the same coefficient of thermal expansion and are greater than the coefficient of thermal expansion of the substrate.

[0017] The temperature self-correction device of the optical fiber strain gauge can ensure the difference in temperature sensitivity of the two optical fiber strain gauges. The thermal expansion between the temperature compensation piece and the substrate can at least partially offset. While increasing the strain sensitivity, it can reduce the temperature sensitivity, reduce and eliminate the influence of the thermal output on the measurement result of the optical fiber strain gauge, and has a simple structure and is convenient for installation.

[0018] Combined with the first implementation manner of the first aspect of the present invention, in the second implementation manner of the first aspect of the present invention, the first optical fiber strain gauge is fixed at the first optical fiber fixing point and the third optical fiber fixing point by welding or bonding, and the second optical fiber strain gauge is fixed at the second optical fiber fixing point and the fourth optical fiber fixing point by welding or bonding. It is convenient to install the optical fiber strain gauge.

[0019] Combined with the first implementation manner or the second implementation manner of the first aspect of the present invention, in the third implementation manner of the first aspect of the present invention, grooves are provided at the first optical fiber fixing point, the second optical fiber fixing point, the third optical fiber fixing point and the fourth optical fiber fixing point. It is convenient to determine the optical fiber fixing point and convenient to perform the fixing operation on the optical fiber strain gauge.

[0020] Combined with any one of the first to third implementation manners of the first aspect of the present invention, in the fourth implementation manner of the first aspect of the present invention, the temperature self-correction device of the fiber optic strain gauge further includes at least one connecting arm, one end of the connecting arm is connected to the first temperature compensation piece, and the other end is connected to the second temperature compensation piece, so that the positions between the first temperature compensation piece and the second temperature compensation piece are relatively fixed.

[0021] Combined with any one of the first to fourth implementation manners of the first aspect of the present invention, in the fifth implementation manner of the first aspect of the present invention, the first temperature compensation piece is welded or adhered to the upper side surface of the base through the end surface away from the second temperature compensation piece, and the second temperature compensation piece is welded or adhered to the upper side surface of the base through the end surface away from the first temperature compensation piece.

[0022] Combined with any one of the first to fifth implementation manners of the first aspect of the present invention, in the sixth implementation manner of the first aspect of the present invention, two spaced first protrusions are provided on the end surface of the first temperature compensation piece away from the second temperature compensation piece, and the lower side surfaces of the two first protrusions are lower than the lower side surface of the first temperature compensation piece. The first temperature compensation piece is welded or adhered to the upper side surface of the base through the end surface of the first protrusion away from the second temperature compensation piece;

[0023] Two spaced second protrusions are provided on the end surface of the second temperature compensation piece away from the first temperature compensation piece, and the lower side surfaces of the two second protrusions are lower than the lower side surface of the second temperature compensation piece. The second temperature compensation piece is welded or adhered to the upper side surface of the base through the end surface of the second protrusion away from the first temperature compensation piece;

[0024] The lower side surfaces of the two first protrusions are flush with the lower side surfaces of the two second protrusions and are in contact with the upper side surface of the base.

[0025] To achieve the second object of the present invention, the second aspect of the present invention provides a temperature self-correction method for a fiber optic strain gauge, which uses the temperature self-correction device of the fiber optic strain gauge in any one of the first to sixth implementation manners of the first aspect of the present invention for temperature self-correction, including the following steps:

[0026] S1. Determine the theoretically ideal installation distance L2 of the two fiber optic strain gauges through the formula L1·α1 - (L1 - L2)·α2 = 0;

[0027]

[0028] Wherein, α1 is the thermal expansion coefficient of the base, α2 is the thermal expansion coefficient of the first temperature compensation piece and the second temperature compensation piece, and L1 is the distance between the installation point of the first temperature compensation piece and the installation point of the second temperature compensation piece;

[0029] S2. Determine the first installation distance L3 and the second installation distance L4:

[0030] L3 = L2 - ΔL3;

[0031] L4 = L2 + ΔL4;

[0032] Wherein, 0 < ΔL3 < L2 - L5, 0 < ΔL4 < L1 - L2, L5 is the width of the expansion gap, and it satisfies the following relationship: 0 < L5 < L2;

[0033] S3. According to Step S1 and Step S3, obtain the relationship between the strain of the first fiber optic strain gauge and the second fiber optic strain gauge, the strain of the substrate, and the temperature change:

[0034]

[0035] Wherein, ε 基底 is the strain of the substrate, ε3 is the strain of the first fiber optic strain gauge, ε4 is the strain of the second fiber optic strain gauge, and ΔT is the temperature change;

[0036] S4. Solve the relationship in Step S3 to obtain the relationship independent of temperature as follows:

[0037]

[0038] Wherein, ε sum is the coupled strain of the first fiber optic strain gauge and the second fiber optic strain gauge.

[0039] (III) Beneficial Effects

[0040] The above technical solution of the present invention has the following advantages: The temperature self-correction device of the fiber optic strain gauge provided by the present invention uses two relatively spaced temperature compensation sheets. The two temperature compensation sheets are fixed to the substrate through their respective outer end faces (the end faces away from the other temperature compensation sheet). It can install two fiber optic strain gauges, and each fiber optic strain gauge is fixed through two fixed points. Among them, the fixed distances of the two fiber optic strain gauges (the distances between the two fixed points of each fiber optic strain gauge) are different. The thermal expansion coefficients of the two temperature compensation sheets are the same and greater than the thermal expansion coefficient of the substrate, ensuring the difference in the temperature sensitivities of the two fiber optic strain gauges. The thermal expansion between the temperature compensation sheet and the substrate can at least partially offset. While increasing the strain sensitivity, it can reduce the temperature sensitivity, reduce and eliminate the influence of the thermal output on the measurement result of the fiber optic strain gauge, and has a simple structure and is convenient to install.

[0041] The temperature self-correction method of the fiber optic strain gauge provided by the present invention utilizes the temperature self-correction device of the fiber optic strain gauge, which can eliminate the influence of thermal output on the measurement results of the fiber optic strain gauge, improve the test accuracy, and the method is simple and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings of the present invention are provided only for illustrative purposes, and the proportions and quantities of the components in the drawings are not necessarily consistent with the actual products.

[0043] Figure 1 is a front view structural schematic diagram of a temperature self-correction device of a fiber optic strain gauge in Embodiment 1 of the present invention;

[0044] Figure 2 is a three-dimensional structural schematic diagram of the temperature self-correction device of the fiber optic strain gauge in Embodiment 1 of the present invention;

[0045] Figure 3 is a front view structural schematic diagram of another temperature self-correction device of a fiber optic strain gauge in Embodiment 1 of the present invention;

[0046] Figure 4 is a front view structural schematic diagram of a temperature self-correction device of a fiber optic strain gauge in Embodiment 2 of the present invention;

[0047] Figure 5 is a bottom view structural schematic diagram of the temperature self-correction device of the fiber optic strain gauge in Embodiment 2 of the present invention;

[0048] Figure 6 is a three-dimensional structural schematic diagram of the temperature self-correction device of the fiber optic strain gauge in Embodiment 2 of the present invention;

[0049] Figure 7 is a structural schematic diagram of the combination of the temperature self-correction device of the fiber optic strain gauge and the fiber optic strain gauge in Embodiment 2 of the present invention.

[0050] In the figure: 1: First temperature compensation piece; 11: First optical fiber routing groove; 12: Second optical fiber routing groove; 13: First optical fiber fixing point; 14: Second optical fiber fixing point;

[0051] 2: Second temperature compensation piece; 21: Third optical fiber routing groove; 22: Fourth optical fiber routing groove; 23: Third optical fiber fixing point; 24: Fourth optical fiber fixing point;

[0052] 3: Expansion gap; 4: Connecting arm; 5: First protrusion; 6: Second protrusion;

[0053] 100: Substrate; 200: First fiber optic strain gauge; 300: Second fiber optic strain gauge. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0055] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0056] Embodiment 1

[0057] Refer to Figure 1 and Figure 2 As shown, the temperature self-correction device of the fiber optic strain gauge provided by the embodiment of the present invention includes a first temperature compensation sheet 1 and a second temperature compensation sheet 2.

[0058] Among them, two parallel and spaced fiber optic routing grooves are provided on the first temperature compensation sheet 1, namely a first fiber optic routing groove 11 and a second fiber optic routing groove 12. A first fiber optic fixing point 13 is provided in the first fiber optic routing groove, and a second fiber optic fixing point 14 is provided in the second fiber optic routing groove 12.

[0059] Two parallel and spaced fiber optic routing grooves are provided on the second temperature compensation sheet 2, namely a third fiber optic routing groove 21 and a fourth fiber optic routing groove 22. A third fiber optic fixing point 23 is provided in the third fiber optic routing groove 21, and a fourth fiber optic fixing point 24 is provided in the fourth fiber optic routing groove 22.

[0060] The first temperature compensation sheet 1 and the second temperature compensation sheet 2 are relatively fixed at intervals on the upper side of the base 100, and an expansion gap 3 is formed between the first temperature compensation sheet 1 and the second temperature compensation sheet 2. When the first temperature compensation sheet 1 and the second temperature compensation sheet 2 undergo thermal expansion deformation, the expansion gap 3 can prevent the first temperature compensation sheet 1 and the second temperature compensation sheet 2 (the end faces on both sides of the expansion gap) from directly contacting. The first temperature compensation sheet 1 is fixed to the base 100 through the end face away from the second temperature compensation sheet 2, and the second temperature compensation sheet 2 is fixed to the base 100 through the end face away from the first temperature compensation sheet 1.

[0061] The first optical fiber raceway 11 and the third optical fiber raceway 21 are respectively located on both sides of the expansion gap 3, and the first optical fiber raceway 11 and the third optical fiber raceway 21 have the same groove direction, forming a long groove with a structural interruption (at the expansion gap) for accommodating the first optical fiber strain gauge 200. When placing the first optical fiber strain gauge 200, the first optical fiber strain gauge 200 is fixed at the first optical fiber fixing point 13 and the third optical fiber fixing point 23, and it is ensured that the sensitive head of the first optical fiber strain gauge 200 is located between the first optical fiber fixing point 13 and the third optical fiber fixing point 23. The distance between the first optical fiber fixing point 13 and the third optical fiber fixing point 23 is the first installation distance L3.

[0062] The second optical fiber raceway 12 and the fourth optical fiber raceway 22 are also respectively located on both sides of the expansion gap 3, and the second optical fiber raceway 12 and the fourth optical fiber raceway 22 have the same groove direction, also forming a long groove with a structural interruption (at the expansion gap) for accommodating the second optical fiber strain gauge 300. When placing the second optical fiber strain gauge 300, the second optical fiber strain gauge 300 is fixed at the second optical fiber fixing point 14 and the fourth optical fiber fixing point 24, and it is ensured that the sensitive head of the second optical fiber strain gauge 300 is located between the second optical fiber fixing point 14 and the fourth optical fiber fixing point 24. The distance between the second optical fiber fixing point 14 and the fourth optical fiber fixing point 24 is the second installation distance L4.

[0063] In this embodiment, the first installation distance L3 is less than the second installation distance L4, and the thermal expansion coefficients α2 of the first temperature compensation sheet 1 and the second temperature compensation sheet 2 (the thermal expansion coefficients of the two are the same) are greater than the thermal expansion coefficient α1 of the substrate.

[0064] The temperature self-correction device of the optical fiber strain gauge provided in this embodiment uses two relatively spaced temperature compensation sheets. The two temperature compensation sheets are fixed to the substrate through their respective outer end faces (the end faces away from the other temperature compensation sheet). It can install two optical fiber strain gauges, and each optical fiber strain gauge is fixed by two fixing points. Among them, the fixing distances of the two optical fiber strain gauges (the distances between the two fixing points of each optical fiber strain gauge) are different. The thermal expansion coefficients of the two temperature compensation sheets are the same and greater than the thermal expansion coefficient of the substrate, ensuring the difference in the temperature sensitivities of the two optical fiber strain gauges. The thermal expansion between the temperature compensation sheet and the substrate can at least partially offset. While increasing the strain sensitivity, it can reduce the temperature sensitivity, reduce and eliminate the influence of the thermal output on the measurement result of the optical fiber strain gauge, and has a simple structure and is convenient to install.

[0065] It should be noted that the temperature self-correction device of the fiber optic strain gauge provided by the present invention does not require the type of the installed fiber optic strain gauge, and the first fiber optic strain gauge and the second fiber optic strain gauge can be the same or different. For example, both fiber optic strain gauges can be fiber Bragg grating strain gauges or fiber Fabry-Perot strain gauges, or one can be a fiber Bragg grating strain gauge and the other can be a fiber Fabry-Perot strain gauge.

[0066] In some preferred embodiments, two spaced points are selected on the end face of the first temperature compensation sheet away from the second temperature compensation sheet as the fixing points of the first temperature compensation sheet 1 and the substrate 100. Similarly, two spaced points are selected on the end face of the second temperature compensation sheet away from the first temperature compensation sheet as the fixing points of the second temperature compensation sheet 2 and the substrate 100.

[0067] In some preferred embodiments, the first fiber optic strain gauge 200 is fixed at the positions of the first fiber optic fixing point 13 and the third fiber optic fixing point 23 by welding or bonding. Preferably, the first temperature compensation sheet 1 is fixed to the upper side of the substrate 100 by welding or bonding through its end face away from the second temperature compensation sheet 2.

[0068] The second temperature compensation sheet 2 is welded or bonded to the upper side of the substrate through its end face away from the first temperature compensation sheet 1.

[0069] The second fiber optic strain gauge 300 is fixed at the positions of the second fiber optic fixing point 14 and the fourth fiber optic fixing point 24 by welding or bonding.

[0070] In some preferred embodiments, see Figure 1 and Figure 2 As shown, grooves are provided at the first fiber optic fixing point 13, the second fiber optic fixing point 14, the third fiber optic fixing point 23, and the fourth fiber optic fixing point 24, which facilitate determining the fixing positions and facilitate the fixing operation.

[0071] To facilitate fixing the relative positions of the two temperature compensation sheets, see Figure 3 As shown, in some preferred embodiments, the temperature self-correction device of the fiber optic strain gauge further includes at least one connecting arm 4. One end of the connecting arm 4 is connected to the first temperature compensation sheet 1, and the other end is connected to the second temperature compensation sheet 2, so that the positions between the first temperature compensation sheet 1 and the second temperature compensation sheet 2 are relatively fixed.

[0072] Preferably, there are two connecting arms 4, which are symmetrically arranged on opposite sides respectively. Both ends of each connecting arm 4 are such that one end is connected to the first temperature compensation sheet 1 and the other end is connected to the second temperature compensation sheet 2.

[0073] Embodiment 2

[0074] As Figures 4 - 6As shown, the second embodiment is basically the same as the first embodiment, and the same parts will not be described again. The differences are as follows: On the basis of any implementation manner in the first embodiment, the end surface of the first temperature compensation sheet 1 away from the second temperature compensation sheet 2 has two first protrusions 5 arranged at intervals, and the lower side surfaces of the two first protrusions 5 are lower than the lower side surface of the first temperature compensation sheet 1. The first temperature compensation sheet 1 is welded or adhered to the upper side surface of the substrate 100 through the end surface of the first protrusion away from the second temperature compensation sheet 2.

[0075] The end surface of the second temperature compensation sheet 2 away from the first temperature compensation sheet 1 is provided with two second protrusions 6 arranged at intervals, and the lower side surfaces of the two second protrusions 6 are lower than the lower side surface of the second temperature compensation sheet 2. The second temperature compensation sheet 2 is welded or adhered to the upper side surface of the substrate 100 through the end surface of the second protrusion away from the first temperature compensation sheet 1.

[0076] See Figure 5 As shown, when the first temperature compensation sheet 1 and the second temperature compensation sheet 2 are installed on the substrate 100, the lower side surfaces of the first temperature compensation sheet 1 and the second temperature compensation sheet 2 contact the upper side surface of the substrate 100 through the lower side surfaces of the four protrusions (two first protrusions and two second protrusions), and the lower side surfaces of the four protrusions are flush, so that the two temperature compensation sheets are installed parallel to the upper side surface of the substrate 100, that is, the two temperature compensation sheets only contact the upper side surface of the substrate 100 through the lower side surfaces of the four protrusions, and the lower side surfaces of the two temperature compensation sheets do not directly contact the upper side surface of the substrate 100 and have a certain gap (the gap height is equal to the height of the lower side surface of the protrusion below the lower side surface of the temperature compensation sheet). When the substrate 100 is bent and deformed, it can be ensured that the lower side surfaces of the first temperature compensation sheet 1 and the second temperature compensation sheet 2 do not contact the upper side surface of the substrate 100, thereby avoiding interference between the two and further improving the measurement accuracy.

[0077] See Figure 7 As shown, it is a schematic structural diagram of installing two temperature compensation sheets on a substrate and installing two fiber optic strain gauges on the temperature compensation sheets. The structure of wrapping the fiber optic strain gauges at the positions of the first fiber optic fixing point 13, the second fiber optic fixing point 14, the third fiber optic fixing point 23, and the fourth fiber optic fixing point 24 in the figure is a schematic structure of a welding or bonding method. The inclined surface structure of the end surfaces of the four protrusions is also a schematic structure of a welding or bonding method.

[0078] The temperature self-correction device provided in this embodiment fixes the temperature compensation sheet to the substrate at the end face of the protrusion, which can reduce the limitation of the installation sequence. Two temperature compensation sheets can be fixed on the substrate 100 first, and then the fiber optic strain gauge can be installed. It is also possible to install the fiber optic strain gauge on the two temperature compensation sheets first, and then install the temperature compensation sheet with the fiber optic strain gauge installed on the substrate 100, which can avoid the fiber optic strain gauge blocking the installation area of the temperature compensation sheet and make the installation more convenient and accurate.

[0079] Embodiment III

[0080] The temperature self-correction method of the fiber optic strain gauge provided in this embodiment uses any one of the temperature self-correction devices of the fiber optic strain gauge in Embodiment I and Embodiment II for temperature self-correction, and includes the following steps:

[0081] S1. Determine the theoretically ideal installation distance L2 between the two fiber optic strain gauges through the formula L1·α1 - (L1 - L2)·α2 = 0;

[0082]

[0083] Wherein, α1 is the thermal expansion coefficient of the substrate, α2 is the thermal expansion coefficient of the first temperature compensation sheet and the second temperature compensation sheet, and L1 is the distance between the installation points of the first temperature compensation sheet and the second temperature compensation sheet;

[0084] S2. Determine the first installation distance L3 and the second installation distance L4:

[0085] L3 = L2 - ΔL3;

[0086] L4 = L2 + ΔL4;

[0087] Wherein, 0 < ΔL3 < L2 - L5, 0 < ΔL4 < L1 - L2, and L5 is the width of the expansion gap.

[0088] It should be noted that from the range limitation of ΔL3, it can be obtained that the width of the expansion gap satisfies the following relationship: 0 < L5 < L2. Generally speaking, setting the expansion gap is to avoid direct contact between the first temperature compensation sheet 1 and the second temperature compensation sheet 2 during thermal expansion deformation. For those skilled in the art, based on the materials of the two selected temperature compensation sheets and the substrate and the use environment of the fiber optic strain gauge temperature self-correction device, the width of the expansion gap can be determined on the basis of satisfying 0 < L5 < L2.

[0089] S3. According to steps S1 and S2, obtain the relationship between the strain of the first fiber optic strain gauge and the second fiber optic strain gauge, the strain of the substrate, and the temperature change:

[0090]

[0091] wherein, ε 基底 is the strain variable based on the base, ε3 is the strain variable of the first fiber optic strain gauge, ε4 is the strain variable of the second fiber optic strain gauge, and ΔT is the temperature change amount;

[0092] S4. Solve the relational expression in step S3 to obtain the relational expression independent of temperature as follows:

[0093]

[0094] wherein, ε sum is the coupling strain variable of the first fiber optic strain gauge and the second fiber optic strain gauge.

[0095] The temperature self - correction method of the fiber optic strain gauge provided by this embodiment can eliminate the influence of thermal output on the measurement result of the fiber optic strain gauge.

[0096] In a specific embodiment, the highest temperature in the application environment of the fiber optic strain gauge temperature self - correction device is 100 °C, the thermal expansion coefficient α1 of the base is 10.6×10 -6 / °C, the thermal expansion coefficient α2 of the first temperature compensation sheet 1 and the second temperature compensation sheet 2 is 18×10 -6 / °C, L1 is 4 mm, then L2 is 1.69 mm, L5 can be taken as 1.5 mm, ΔL3 is taken as 0.09 mm, ΔL4 is taken as 0.11 mm, then L3 is 1.6 mm, and L4 is 1.8 mm.

[0097] It should be noted that the theoretically ideal installation distance L2 described in this embodiment is the ideal installation distance obtained by calculation. However, in practice, the installation points have spatial dimensions, so it is impossible to achieve the ideal installation distance.

[0098] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: not every embodiment only contains an independent technical solution. In the case of no conflict between the solutions, the technical features mentioned in each embodiment can be combined in any way to form other embodiments that can be understood by those skilled in the art.

[0099] In addition, without departing from the scope of the present invention, modifying the technical solutions recorded in the foregoing embodiments, or equivalently replacing some of the technical features, does not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present invention.

Claims

1. A temperature self-correction method for an optical fiber strain gauge, characterized in that: Temperature self - correction is performed using a temperature self - correction device with fiber optic strain gauges. The temperature self - modification device includes a first temperature compensation piece, on which there are two fiber optic wire grooves arranged in parallel at intervals, namely a first fiber optic wire groove and a second fiber optic wire groove. A first fiber optic fixing point is provided in the first fiber optic wire groove, and a second fiber optic fixing point is provided in the second fiber optic wire groove; A second temperature compensation piece, on which there are two fiber optic wire grooves arranged in parallel at intervals, namely a third fiber optic wire groove and a fourth fiber optic wire groove. A third fiber optic fixing point is provided in the third fiber optic wire groove, and a fourth fiber optic fixing point is provided in the fourth fiber optic wire groove; The first temperature compensation piece and the second temperature compensation piece are relatively fixed at intervals on the upper side of the base, so that an expansion gap is formed between the first temperature compensation piece and the second temperature compensation piece. When the first temperature compensation piece and the second temperature compensation piece undergo thermal expansion deformation, direct contact between the first temperature compensation piece and the second temperature compensation piece is avoided; The first temperature compensation piece is fixed to the base through the end face away from the second temperature compensation piece, and the second temperature compensation piece is fixed to the base through the end face away from the first temperature compensation piece; The first fiber optic wire groove and the third fiber optic wire groove are opposite to each other in the same groove direction with the expansion gap in between, for accommodating a first fiber optic strain gauge. The first fiber optic strain gauge is fixed at the first fiber optic fixing point and the third fiber optic fixing point. The sensitive head of the first fiber optic strain gauge is located between the first fiber optic fixing point and the third fiber optic fixing point, and the distance between the first fiber optic fixing point and the third fiber optic fixing point is a first installation distance; The second fiber optic wire groove and the fourth fiber optic wire groove are opposite to each other in the same groove direction with the expansion gap in between, for accommodating a second fiber optic strain gauge. The second fiber optic strain gauge is fixed at the second fiber optic fixing point and the fourth fiber optic fixing point. The sensitive head of the second fiber optic strain gauge is located between the second fiber optic fixing point and the fourth fiber optic fixing point, and the distance between the second fiber optic fixing point and the fourth fiber optic fixing point is a second installation distance; The first installation distance is less than the second installation distance; The first temperature compensation piece and the second temperature compensation piece have the same coefficient of thermal expansion and are greater than the coefficient of thermal expansion of the base; The temperature self - correction method includes the following steps: S1. Determine the theoretically ideal installation distance L2 of the two fiber optic strain gauges through the formula L1·α1-(L1 - L2)·α2 = 0; Where α1 is the coefficient of thermal expansion of the base, α2 is the coefficient of thermal expansion of the first temperature compensation piece and the second temperature compensation piece, and L1 is the distance between the installation point of the first temperature compensation piece and the installation point of the second temperature compensation piece; S2. Determine the first installation distance L3 and the second installation distance L4: L3 = L2 - ΔL3; L4 = L2 + ΔL4; Where 0 < ΔL3 < L2 - L5, 0 < ΔL4 < L1 - L2, L5 is the width of the expansion gap, and it satisfies the following relationship: 0 < L5 < L2; S3. Obtain the relationship between the strain of the first fiber optic strain gauge and the second fiber optic strain gauge, the strain of the substrate, and the temperature change according to steps S1 and S2: where ε 基底 is the strain variable based on the base, ε3 is the strain variable of the first fiber optic strain gauge, ε4 is the strain variable of the second fiber optic strain gauge, and ΔT is the temperature change; S4. Solve the relationship in step S3 to obtain the relationship independent of temperature as follows: where ε sum is the coupling strain of the first fiber optic strain gauge and the second fiber optic strain gauge.

2. The temperature self-correction method of the fiber optic strain gauge according to claim 1, wherein: Fix the first fiber optic strain gauge at the first fiber fixing point and the third fiber fixing point by welding or bonding; Fix the second fiber optic strain gauge at the second fiber fixing point and the fourth fiber fixing point by welding or bonding.

3. The temperature self-correction method of the fiber optic strain gauge according to claim 1 or 2, characterized in that: Grooves are provided at the first fiber fixing point, the second fiber fixing point, the third fiber fixing point, and the fourth fiber fixing point.

4. The temperature self-correction method of the fiber optic strain gauge according to claim 1, characterized in that: It further includes at least one connecting arm, one end of the connecting arm is connected to the first temperature compensation sheet, and the other end is connected to the second temperature compensation sheet to relatively fix the positions between the first temperature compensation sheet and the second temperature compensation sheet.

5. The temperature self-correction method of the fiber optic strain gauge according to claim 1 or 4, characterized in that: The first temperature compensation sheet is welded or bonded to the upper side of the substrate through the end face away from the second temperature compensation sheet; The second temperature compensation sheet is welded or bonded to the upper side of the substrate through the end face away from the first temperature compensation sheet.

6. The temperature self-correction method of the fiber optic strain gauge according to claim 4, characterized in that: On the end face of the first temperature compensation sheet away from the second temperature compensation sheet, there are two first protrusions arranged at intervals, and the lower sides of the two first protrusions are both lower than the lower side of the first temperature compensation sheet. The first temperature compensation sheet is welded or bonded to the upper side of the substrate through the end face of the first protrusion away from the second temperature compensation sheet; On the end face of the second temperature compensation sheet away from the first temperature compensation sheet, there are two second protrusions arranged at intervals, and the lower sides of the two second protrusions are both lower than the lower side of the second temperature compensation sheet. The second temperature compensation sheet is welded or bonded to the upper side of the substrate through the end face of the second protrusion away from the first temperature compensation sheet; The lower sides of the two first protrusions are flush with the lower sides of the two second protrusions and are in contact with the upper side of the substrate.

Images