Double-string structure vibrating wire pressure sensor and pressure calculation method thereof

Abstract

The invention discloses a double-string structure vibrating wire pressure sensor and a pressure calculation method thereof, and relates to the technical field of pressure sensors, and the pressure sensor comprises a housing, a supporting column, a sliding assembly, a transmission part, a measurement assembly and two vibrating wires. A liquid inlet is formed in one end of the shell; the supporting column is fixedly arranged in the accommodating cavity; the sliding assembly is slidably arranged outside the supporting column in a sleeving mode and can slide in the direction away from the liquid inlet under the action of liquid. The outer end, deviating from the supporting column, of the transmission part at least in the radial direction of the supporting column is a movable end which can be pushed by the sliding assembly to move. The two vibrating wires are arranged on the two sides of the supporting column, one end is fixedly connected to the side, away from the sliding assembly, of the movable end, and the other end is fixedly connected to the end, away from the liquid inlet, in the containing cavity; the measuring assembly is used for measuring the free oscillation frequency of the two vibrating wires. According to the double-string structure vibrating wire pressure sensor and the pressure calculation method thereof provided by the invention, the measurement precision, the measurement range and the sensitivity can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and particularly to a vibrating wire pressure sensor with a double-wire structure and a pressure calculation method thereof. Background Art

[0002] Vibrating wire pressure sensors are widely used in fields such as civil engineering, geological monitoring, petrochemical industry, etc., especially in occasions that require long-term stable monitoring, such as safety monitoring of dams, subways, coal, etc. A vibrating wire pressure sensor usually consists of a vibrating wire, a support member, a measurement circuit and other parts. The vibrating wire pressure sensor measures pressure by using a tensioned steel wire. Its core principle is that the natural oscillation frequency of the steel wire is related to its tension. By measuring the change in the natural frequency of the vibrating wire, the change in the tension of the steel wire caused by the external pressure is reflected. The natural frequency of the vibrating wire is related to its tension, length and mass. When an external pressure acts on the vibrating wire, the tension of the vibrating wire changes, resulting in a change in its vibration frequency. By measuring the frequency change, the magnitude of the pressure can be deduced.

[0003] The currently widely used single-wire vibrating wire pressure sensor is easily affected by external factors such as temperature. However, in the measurement, there are phenomena of ignoring the temperature influence or using a reference value in calculating the temperature compensation coefficient, introducing measurement errors and resulting in a decrease in the pressure measurement accuracy. In addition, for the single-wire vibrating wire pressure sensor, the measurement range and sensitivity are limited by the inherent characteristics of the wire. Using a thin-diameter vibrating wire with low tension has high sensitivity but a small measurement range, while using a thick-diameter vibrating wire with high tension has relatively reduced sensitivity and a wide linear range. Therefore, the single-wire vibrating wire pressure sensor usually cannot take into account both the measurement range and high sensitivity. Summary of the Invention

[0004] The purpose of the present invention is to provide a vibrating wire pressure sensor with a double-wire structure and a pressure calculation method thereof to solve the problems existing in the above-mentioned prior art, and to improve the measurement accuracy, measurement range and sensitivity.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] The present invention provides a double-string structure vibrating-wire pressure sensor, comprising a shell, a support column, a sliding assembly, a transmission component, a measuring assembly and two vibrating strings; the shell has a containing cavity, and one end of the shell has a liquid inlet connected to the containing cavity; the supporting column is fixedly arranged in the containing cavity; the sliding assembly is arranged in the containing cavity and close to the liquid inlet, the sliding assembly is slidably sleeved outside the supporting column, and the sliding assembly can slide in a direction away from the liquid inlet under the action of the liquid introduced into the liquid inlet; the transmission component is arranged in the containing cavity, and the transmission component is fixedly sleeved outside the supporting column , and is placed on the side of the sliding component away from the liquid inlet; the transmission component is set as a movable end at least along the outer end of the support column radially away from the support column, and the movable end can be connected with the sliding component and move under the push of the sliding component; the two vibrating strings are arranged in the accommodating cavity and are respectively placed on both sides of the support column; one end of the two vibrating strings is fixedly connected to the side of the movable end away from the sliding component, and the other ends of the two vibrating strings are fixedly connected to one end of the accommodating cavity away from the liquid inlet; the measuring component is used to measure the free oscillation frequency of the two vibrating strings.

[0007] Preferably, the support column, the sliding assembly and the transmission component are coaxially arranged.

[0008] Preferably, the sliding assembly is in sealing contact with the inner wall of the accommodating cavity and the outer wall of the supporting column in the circumferential direction, and can slide relative to the accommodating cavity and the supporting column in the axial direction.

[0009] Preferably, the sliding assembly includes a piston and at least one sealing ring fixedly mounted on the outer circumference of the piston, the piston is slidably and sealingly sleeved on the outside of the support column, and the piston is sealingly abutted against the inner wall of the accommodating chamber through the sealing ring; the side of the piston facing away from the liquid inlet can abut against one side of the movable end under the action of the liquid and push the movable end to move.

[0010] Preferably, the transmission component is configured as an elastomer, and a fixing piece is provided on both sides of the middle of the transmission component, and the two fixing pieces are fixedly sleeved on the outside of the support column so as to clamp and fix the middle of the transmission component; the sliding assembly can push the movable end to undergo elastic deformation under the action of liquid.

[0011] Preferably, the transmission component has two movable ends, the two movable ends are symmetrical about the axis of the support column, and the two vibrating wires are fixedly connected to the two movable ends respectively.

[0012] Preferably, a filter screen is fixedly provided at the liquid inlet, and the filter screen is used to filter the liquid passing into the accommodating cavity.

[0013] Preferably, the measurement component includes an exciting coil and a measurement circuit. The exciting coil is placed in the accommodating cavity and fixedly sleeved outside the support column. The measurement circuit can be electrically connected to the exciting coil. The measurement circuit can generate an alternating magnetic field through the exciting coil to make one of the vibrating wires receive the Lorentz force and thus vibrate. After the alternating magnetic field of the exciting coil is removed, the inertial vibration of the vibrating wire can make the exciting coil generate an induced electromotive force, and the measurement circuit obtains the free oscillation frequency corresponding to the vibrating wire according to the induced electromotive force signal.

[0014] Preferably, the two vibrating wires are made of the same material, have the same length, and different diameters.

[0015] The present invention also provides a pressure calculation method based on the double-wire structure vibrating wire pressure sensor as described above. The relationship between the liquid pressure acting on the transmission component and the tension transmitted to the vibrating wire is as follows:

[0016] Formula One: F VS1 = K1F

[0017] Formula Two: F VS2 = K2F

[0018] In the formula, F is the liquid pressure, F VS1 and F VS2 are the tensions transmitted to the two vibrating wires respectively, and K1 and K2 represent the transmission coefficients of the liquid pressure F to the tensions of the corresponding two vibrating wires;

[0019] The tensions F VS1 and F VS2 of the two vibrating wires and their own free oscillation frequencies are related as follows:

[0020] Formula Three:

[0021] Formula Four:

[0022] In the formula, f VS1 , f VS2 are the self-oscillation frequencies of the corresponding two vibrating wires respectively; ρ1, ρ2 represent the densities of the corresponding vibrating wires; σ VS1 , σ VS2 represent the stresses of the corresponding vibrating wires; l VS1 , l VS2 represent the lengths of the corresponding vibrating wires;

[0023] When there is a temperature change, let the total stresses σ1 and σ2 received by the two vibrating wires respectively be expressed as follows:

[0024] Formula Five: σ1 = (FVS1 + F0) / A1 + E(α h -α w )·ΔT

[0025] Formula Six: σ2 = (F VS2 + F0) / A2 + E(α h -α w )·ΔT

[0026] In the formula, F0 represents the external force applied to the two vibrating strings when static, that is, the tension for clamping the vibrating strings at the free end without external force; A1 and A2 represent the cross-sectional areas corresponding to the vibrating strings, D1 and D2 represent the diameters corresponding to the vibrating strings; α h is the coefficient of thermal expansion of the housing (1); α w is the coefficient of thermal expansion of the vibrating string (5); E is the elastic modulus of the vibrating string (5); ΔT is the temperature change;

[0027] Substitute Formula Five and Formula Six into Formula Three and Formula Four respectively, where σ1 = σ VS1 、σ2 = σ VS2 , and the following expressions are obtained:

[0028] Formula Seven:

[0029] Formula Eight:

[0030] When the two vibrating strings are made of the same material and have the same length, that is, ρ1 = ρ2 = ρ, l VS1 = l VS2 = l, subtracting Formula Eight from Formula Seven gives:

[0031] Formula Nine:

[0032] Obtain the free oscillation frequencies f VS1 、f VS2 of the two vibrating strings through the measuring component, substitute them into Formula Nine, and substitute Formula One and Formula Two into Formula Nine, then the value of the liquid pressure F can be obtained.

[0033] The present invention has achieved the following technical effects compared with the prior art:

[0034] The double-string structure vibrating string pressure sensor provided by the present invention adopts two vibrating strings. Under the action of liquid pressure, the sliding component causes the movable end of the transmission component to move. After the two movable ends move, they deviate from the initial state. Therefore, it can simultaneously drive the two vibrating strings to change in tension. After the measuring component obtains the free oscillation frequencies of the two vibrating strings, by calculating the free oscillation frequencies of the two vibrating strings subsequently, the measurement error caused by the external temperature change can be eliminated, and the pressure measurement accuracy can be improved.

[0035] By controlling the two vibrating strings to have different diameters, it can meet the requirement that the thin string is more sensitive to the tension change (high sensitivity) and is suitable for high-precision measurement of low ranges, and at the same time meet the effect that the thick string can withstand greater tension (high range), which is convenient for dynamically selecting the optimal signal or fusing data in the subsequent data processing process to achieve the balance between wide range and high precision.

[0036] Moreover, compared with the single-string vibrating string pressure sensor, the failure of a single string will cause the sensor to completely malfunction, and the reliability of the sensor is not high. In the double-string structure vibrating string pressure sensor, when one of the strings fails, the other string can still keep working, and the reliability of the double-string structure vibrating string pressure sensor is improved.

[0037] According to Formula 1, Formula 2, and Formula 9, the pressure calculation method of the double-string structure vibrating string pressure sensor provided by the present invention shows that when the free oscillation frequencies of the two vibrating strings are obtained, the liquid pressure value can be obtained. Moreover, the measurement error caused by the external temperature change can be eliminated through the square difference of the free oscillation frequencies of the two vibrating strings, and the influence of the external temperature change factor can be offset, improving the pressure measurement accuracy. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 It is a structural diagram of a double-string structure vibrating string pressure sensor provided in Embodiment 1 of the present invention;

[0040] Figure 2 It is a schematic diagram of the positions of the housing and the support column provided in Embodiment 1 of the present invention;

[0041] Figure 3 It is a front view schematic diagram of the transmission component provided in Embodiment 1 of the present invention;

[0042] Figure 4 It is a side view schematic diagram of the transmission component provided in Embodiment 1 of the present invention;

[0043] Figure 5 This is a schematic axial view of the sliding assembly provided in Embodiment 1 of the present invention.

[0044] In the figure: 1-shell; 11-accommodating chamber; 12-liquid inlet; 13-filter screen; 2-support column; 3-sliding assembly; 31-piston; 32-sealing ring; 4-transmission component; 41-movable end; 42-fixing part; 5-vibrating wire; 6-measuring assembly; 61-excitation coil. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The purpose of the present invention is to provide a double-string structure vibrating-wire pressure sensor and a pressure calculation method thereof, so as to solve the problems existing in the above-mentioned prior art and improve the measurement accuracy, measurement range and sensitivity.

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Embodiment 1

[0049] This embodiment provides a double-string structure vibrating wire pressure sensor, see Figure 1 and Figure 2 , comprising a shell 1, a support column 2, a sliding assembly 3, a transmission component 4, a measuring assembly 6 and two vibrating wires 5; the shell 1 has a accommodating chamber 11, and one end of the shell 1 has a liquid inlet 12 connected to the accommodating chamber 11; the support column 2 is fixedly arranged in the accommodating chamber 11; the sliding assembly 3 is arranged in the accommodating chamber 11 and close to the liquid inlet 12, the sliding assembly 3 is slidably sleeved outside the support column 2, and the sliding assembly 3 can slide in a direction away from the liquid inlet 12 under the action of the liquid introduced into the liquid inlet 12; the transmission component 4 is arranged in the accommodating chamber 11, the transmission component 4 is fixedly sleeved outside the support column 2, and is arranged On the side of the sliding component 3 away from the liquid inlet 12; the transmission component 4 is set as a movable end 41 at least along the outer end of the support column 2 radially away from the support column 2, and the movable end 41 can be connected with the sliding component 3 and move under the push of the sliding component 3; the two vibrating strings 5 are both arranged in the accommodating cavity 11 and placed on both sides of the support column 2; one end of the two vibrating strings 5 is fixedly connected to the side of the movable end 41 away from the sliding component 3, and the other ends of the two vibrating strings 5 are fixedly connected to the end of the accommodating cavity 11 away from the liquid inlet 12; the measuring component 6 is used to measure the free oscillation frequency of the two vibrating strings 5.

[0050] By adopting two vibrating wires 5, under the action of liquid pressure, the sliding assembly 3 causes the movable end 41 of the transmission component 4 to move. After the two movable ends 41 move, they deviate from the initial state. Therefore, it is possible to simultaneously drive the two vibrating wires 5 to change in tension. After the measuring assembly 6 obtains the free oscillation frequencies of the two vibrating wires 5, by calculating the free oscillation frequencies of the two vibrating wires 5 subsequently, the measurement error caused by the external temperature change can be eliminated, and the pressure measurement accuracy can be improved. By controlling the two vibrating wires 5 to have different diameters, it is possible to meet the requirement that the thin wire is more sensitive to the tension change, with high sensitivity and suitable for high-precision measurement of low ranges, and at the same time meet the effect that the thick wire can withstand greater tension and high ranges, which is convenient for dynamically selecting the optimal signal or fusing data during the subsequent data processing process to achieve the balance between wide range and high precision. Moreover, compared with the single-wire vibrating wire pressure sensor, the failure of a single wire will cause the sensor to completely malfunction, and the reliability of the sensor is not high. In the vibrating wire pressure sensor with a double-wire structure, when one of the wires fails, the other wire can still keep working, and the reliability of the vibrating wire pressure sensor with a double-wire structure is improved.

[0051] Furthermore, the vibrating wire 5 is made of a steel wire vibrating wire with a high-carbon steel material, which has a low material cost and a high elastic modulus; both ends of the vibrating wire 5 are fixed to the transmission component 4 and the housing 1 through conventional fixing components. The fixing components can adopt conventional wire clips or be fixed by means of bolt tightening, as long as the fixing of the end of the vibrating wire 5 can be achieved.

[0052] In an alternative solution of this embodiment, preferably, the support column 2, the sliding assembly 3 and the transmission component 4 are coaxially arranged. This is convenient for transmission and cooperation within the accommodation cavity 11 and ensures the measurement accuracy.

[0053] In an alternative solution of this embodiment, preferably, the sliding assembly 3 is in sealing contact with the inner wall of the accommodation cavity 11 and the outer wall of the support column 2 in the circumferential direction and can slide axially relative to the accommodation cavity 11 and the support column 2; the circumferential sealing of the sliding assembly 3 with the accommodation cavity 11 and the support column 2 can prevent liquid from entering the space where the vibrating wire 5 is located, resulting in pressure relief, and can also prevent the liquid from affecting the frequency measurement of the vibrating wire 5, ensuring the accuracy of pressure measurement.

[0054] In an alternative solution of this embodiment, preferably, please refer to Figure 5The sliding assembly 3 includes a piston 31 and at least one sealing ring 32 fixedly sleeved on the outer circumference of the piston 31. The piston 31 slides and is sealedly sleeved on the outside of the support column 2. The piston 31 is sealed against the inner wall of the accommodating chamber 11 through the sealing ring 32. The side of the piston 31 away from the liquid inlet 12 can be abutted against the side of the movable end 41 under the action of the liquid, and the movable end 41 is pushed to move. Specifically, the piston 31 is sealed with the inside of the accommodating chamber 11 through the sealing ring 32 on the outer circumference. The piston 31 and the support column 2 can be sealed by a tight fit or by using a sealing ring. The liquid pressure acts on the piston 31, and the piston 31 will move to the right along the axial direction of the support column 2. The piston 31 is a rigid piston and does not undergo elastic deformation. The piston 31 transmits the liquid pressure to the movable end 41 of the transmission component 4. The movable end 41 is deformed under the action of the liquid pressure transmitted by the piston 31, so that the tension of the vibrating string 5 changes.

[0055] In the optional scheme of this embodiment, it is more preferred that the transmission component 4 is set as an elastic body, and a fixing piece 42 is set on both sides of the middle of the transmission component 4. The two fixing pieces 42 are fixedly sleeved on the outside of the support column 2 so as to clamp and fix the middle of the transmission component 4; the sliding assembly 3 can push the movable end 41 to undergo elastic deformation under the action of the liquid. The transmission component 4 is set as an elastic body, which is convenient for the outer movable end 41 to undergo elastic deformation so as to change the tension of the vibrating string 5, and the elastic deformation method is convenient for repeated use; and the two sides of the middle of the transmission component 4 are clamped by the fixing piece 42 to prevent the overall position of the transmission component 4 from moving and affecting the measurement accuracy; specifically, the fixing piece 42 is set as a locking nut, which is threadedly connected with the support column 2 for fixing; the material of the transmission component 4 can be alloy steel 40CrNiMoA, which has the characteristics of high elastic modulus, high strength, small temperature coefficient and close to Changshu, small linear expansion coefficient, low cost, easy processing, and good fatigue resistance. Since the use environment is relatively humid, measures such as zinc / nickel plating can also be added to prevent the elastic element from rusting.

[0056] Among the optional solutions of this embodiment, it is more preferred to refer to Figure 3 and Figure 4 The transmission component 4 has two movable ends 41, and the two movable ends 41 are symmetrical about the axis of the support column 2. The two vibrating strings 5 are fixedly connected to the two movable ends 41 respectively; it is convenient to transmit the two vibrating strings 5 by setting the two movable ends 41, thereby improving the reliability of the transmission; specifically, the transmission component 4 can be set as a rectangular body, and the two ends are movable ends 41, so as to facilitate the reliable transmission of the two vibrating strings 5 under the drive of the sliding assembly 3.

[0057] In an alternative embodiment of the present example, preferably, a filter screen 13 is fixedly arranged at the liquid inlet 12. The filter screen 13 is used to filter the liquid flowing into the accommodation cavity 11, preventing impurities in the liquid from entering the accommodation cavity 11 and affecting the accuracy of pressure measurement.

[0058] Furthermore, the measurement of the free oscillation frequency of the vibrating string 5 can adopt conventional methods. Specifically, the measurement component 6 includes an exciting coil 61 and a measurement circuit. The exciting coil 61 is placed in the accommodation cavity 11 and fixedly sleeved outside the support column 2. The measurement circuit can be electrically connected to the exciting coil 61 and; the measurement circuit can generate an alternating magnetic field through the exciting coil 61 to make a vibrating string 5 vibrate under the Lorentz force; and after the alternating magnetic field of the exciting coil 61 is removed, the inertial vibration of the vibrating string 5 can make the exciting coil 61 generate an induced electromotive force, and the measurement circuit obtains the free oscillation frequency of the corresponding vibrating string 5 according to the induced electromotive force signal; for the measurement circuit, the exciting and pickup circuits applied in the frequency measurement of a conventional vibrating string type vibration sensor can be adopted. After the vibrating string 5 vibrates, the exciting signal is removed, and the subsequent micro electromotive force frequency pickup circuit amplifies and processes the weak electromotive force to obtain a frequency signal.

[0059] In an alternative embodiment of the present example, preferably, the two vibrating strings 5 are made of the same material, have the same length, and different diameters. The two vibrating strings 5 respectively adopt steel vibrating strings with two diameters; the vibrating string with a small diameter has low tension, high sensitivity, and a small measurement range, and is suitable for low-range and high-precision measurement; the vibrating string with a large diameter has high tension and relatively reduced sensitivity, and a wide linear range; this double-string structure with the same material and different string diameters enables the vibrating string pressure sensor to balance high sensitivity and wide linear range pressure measurement, facilitating dynamic selection of the optimal signal or data fusion during subsequent data processing to achieve the balance between wide range and high precision.

[0060] Embodiment Two

[0061] This embodiment provides a pressure calculation method based on the double-string structure vibrating string pressure sensor in Embodiment One;

[0062] The working principle of the double-string structure vibrating string pressure sensor in Embodiment One is as follows:

[0063] When the double-string structure vibrating string pressure sensor is working, the external liquid penetrates through the filter screen 13 and is injected between the filter screen 13 and the piston 31. The filter screen 13 can prevent external sundries from entering the sensor to ensure the normal inflow of the liquid. The sealing ring 32 is used to prevent the liquid from seeping into the cavity where the transmission component 4 and the vibrating string 5 are located. The liquid pressure acts on the piston 31, and the piston 31 will move along the support column 2 in the axial direction close to the transmission component 4. The piston 31 is a rigid piston and does not undergo elastic deformation. The piston 31 transmits the liquid pressure to the upper and lower movable ends 41 of the transmission component 4. The upper and lower movable ends 41 deform under the action of the liquid pressure transmitted by the piston 31, causing the tensions of the two vibrating strings 5 to change. Subsequently, by obtaining the free oscillation frequencies of the two vibrating strings 5, the numerical value of the liquid pressure can be obtained according to the pressure calculation method provided in this embodiment. The specific method is as follows:

[0064] The two vibrating strings 5 are respectively named VS1 and VS2. The relationship between the liquid pressure acting on the transmission component 4 and the tension transmitted to the vibrating string 5 is as follows:

[0065] Formula 1: F VS1 = K1F

[0066] Formula 2: F VS2 = K2F

[0067] In the formula, F is the liquid pressure, F VS1 and F VS2 are respectively the tensions transmitted to the two vibrating strings 5. K1 and K2 represent the transmission coefficients from the liquid pressure F to the tensions of the corresponding two vibrating strings 5 and are constants;

[0068] The tensions F VS1 and F VS2 of the two vibrating strings 5 and their own free oscillation frequency relationships are as follows:

[0069] Formula 3:

[0070] Formula 4:

[0071] In the formula, f VS1 , f VS2 are respectively the self-oscillation frequencies of the corresponding two vibrating strings 5; ρ1, ρ2 represent the densities of the corresponding vibrating strings 5; σ VS1 , σ VS2 represent the stresses of the corresponding vibrating strings 5; l VS1 , l VS2 represent the lengths of the corresponding vibrating strings 5. The two vibrating strings 5 are actually designed to have the same length, that is, l VS1 = l VS2 , according to A represents the cross-sectional area of the vibrating string 5. When the error caused by temperature change is not considered, the self-oscillation frequencies f VS1 and f VS2 of the two vibrating strings 5 are obtained through the measuring component 6, and then the value of the liquid pressure F can be obtained. The specific calculation method is as follows:

[0072]

[0073]

[0074] In the formula, A1 and A2 represent the cross-sectional areas of the corresponding vibrating strings 5. Substituting the above formulas into Formula 1 and Formula 2 respectively, the magnitude of the liquid pressure F can be obtained.

[0075] When there is a temperature change, the vibrating wire sensor usually measures the vibration frequency of the vibrating wire to reflect the change of the external pressure or strain. The frequency of the vibrating wire is related to factors such as tension, length, and linear density. When the temperature changes, the vibrating wire and the sensor housing may expand to different degrees due to different thermal expansion coefficients of the materials, resulting in additional strain or tension changes and introducing measurement errors; at the same time, there is also a temperature change in the vibrating wire itself, and the thermal expansion of the vibrating wire material causes a change in the vibrating wire tension in this case, introducing measurement errors; in this embodiment, by using two vibrating wires 5 made of the same material but different diameters, the temperature error can be eliminated. The specific calculation is as follows:

[0076] Let the total stresses σ1 and σ2 corresponding to the two vibrating wires 5 be as follows:

[0077] Formula 5: σ1 = (F VS1 + F0) / A1 + E(α h - α w )·ΔT

[0078] Formula 6: σ2 = (F VS2 + F0) / A2 + E(α h - α w )·ΔT

[0079] In the formula, F0 represents the external force received by the two vibrating wires 5 when they are static, that is, the tension of clamping the vibrating wire 5 at the free end 41 without external force. After the vibrating wire 5 is installed, F0 can be determined and will be used as a constant subsequently; A1 and A2 represent the cross-sectional areas of the corresponding vibrating wires 5, D1 and D2 represent the diameters of the corresponding vibrating wires 5. The diameter of the steel wire vibrating wire VS1 is D1. The thin-diameter vibrating wire has low tension, high sensitivity, and a small measurement range. The diameter of the vibrating wire VS2 is D2. The thick-diameter vibrating wire has high tension, relatively reduced sensitivity, and a wide linear range. In the subsequent data processing process, the optimal signal can be dynamically selected or the data can be fused to achieve the balance between wide range and high precision;; α h is the thermal expansion coefficient of the housing 1; αw α is the coefficient of thermal expansion of the vibrating string 5; E is the elastic modulus of the vibrating string 5; ΔT is the temperature change;

[0080] Substitute Equation Five and Equation Six into Equation Three and Equation Four respectively, where σ1 = σ VS1 , σ2 = σ VS2 , and the following expressions are obtained:

[0081] Equation Seven:

[0082] Equation Eight:

[0083] When the two vibrating strings 5 are made of the same material and have the same length, i.e., ρ1 = ρ2 = ρ, l VS1 = l VS2 = l, subtracting Equation Eight from Equation Seven gives:

[0084] Equation Nine:

[0085] It can be seen from Equation Nine that the temperature ΔT is eliminated by the square difference of the frequencies of the two strings. It can be seen that the double-string vibrating string pressure sensor cancels the influence of external temperature changes through two vibrating strings of the same material and different diameters, improving the pressure measurement accuracy; the free oscillation frequencies f VS1 , f VS2 of the two vibrating strings 5 are obtained through the measurement component 6, substituted into Equation Nine, and Equation One and Equation Two are substituted into Equation Nine to obtain the value of the liquid pressure F.

[0086] In the present invention, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A double-string structure vibrating string pressure sensor, characterized in that: Comprising: A housing (1) having a receiving cavity (11), one end of the housing (1) having a liquid inlet (12) communicating with the receiving cavity (11); A support column (2) fixedly arranged in the receiving cavity (11); A sliding assembly (3) arranged in the receiving cavity (11) and close to the liquid inlet (12), the sliding assembly (3) being slidably sleeved outside the support column (2), and the sliding assembly (3) being capable of sliding in a direction away from the liquid inlet (12) under the action of the liquid introduced through the liquid inlet (12); A transmission member (4) arranged in the receiving cavity (11), the transmission member (4) being fixedly sleeved outside the support column (2) and placed on the side of the sliding assembly (3) away from the liquid inlet (12); at least the outer end of the transmission member (4) radially away from the support column (2) along the support column (2) is provided as a movable end (41), and the movable end (41) can be connected to the sliding assembly (3) and move under the push of the sliding assembly (3); Two vibrating strings (5), both arranged in the receiving cavity (11) and respectively placed on both sides of the support column (2); one ends of the two vibrating strings (5) are fixedly connected to the side of the movable end (41) away from the sliding assembly (3), and the other ends of the two vibrating strings (5) are both fixedly connected to one end of the receiving cavity (11) away from the liquid inlet (12); and A measuring assembly (6) for measuring the free oscillation frequencies of the two vibrating strings (5).

2. The double-string structure vibrating string pressure sensor according to claim 1, wherein: The support column (2), the sliding assembly (3) and the transmission member (4) are coaxially arranged.

3. The double-string structure vibrating wire pressure sensor according to claim 1, characterized in that: The sliding assembly (3) is in sealing abutment with the inner wall of the receiving cavity (11) and the outer wall of the support column (2) in the circumferential direction and can slide axially relative to the receiving cavity (11) and the support column (2).

4. The double-string structure vibrating string pressure sensor according to claim 3, characterized in that: The sliding assembly (3) includes a piston (31) and at least one sealing ring (32) fixedly sleeved on the outer periphery of the piston (31), the piston (31) being slidably and sealingly sleeved outside the support column (2), and the piston (31) being in sealing abutment with the inner wall of the receiving cavity (11) through the sealing ring (32); the side of the piston (31) away from the liquid inlet (12) can abut against one side of the movable end (41) under the action of the liquid and push the movable end (41) to move.

5. The double-string structure vibrating wire pressure sensor according to claim 1, wherein: The transmission member (4) is arranged as an elastic body, and a fixing member (42) is arranged on both sides in the middle of the transmission member (4), and the two fixing members (42) are both fixedly sleeved outside the support column (2) so as to be able to clamp and fix the middle of the transmission member (4); the sliding assembly (3) can push the movable end (41) to undergo elastic deformation under the action of the liquid.

6. The double-string structure vibrating string pressure sensor according to claim 5, characterized in that: The transmission member (4) has two movable ends (41), the two movable ends (41) are symmetrical about the axis of the support column (2), and the two vibrating strings (5) are respectively fixedly connected to the two movable ends (41).

7. The double-string structure vibrating string pressure sensor according to claim 1, wherein: A filter screen (13) is fixedly arranged at the liquid inlet (12), and the filter screen (13) is used for filtering the liquid flowing into the accommodating cavity (11).

8. The double-string structure vibrating string pressure sensor according to claim 1, characterized in that: The measuring assembly (6) includes an exciting coil (61) and a measuring circuit. The exciting coil (61) is placed in the accommodating cavity (11) and fixedly sleeved outside the support column (2). The measuring circuit can be electrically connected to the exciting coil (61); the measuring circuit can generate an alternating magnetic field through the exciting coil (61) to make one of the vibrating strings (5) receive the Lorentz force and thus vibrate; and after the alternating magnetic field of the exciting coil (61) is removed, the inertial vibration of the vibrating string (5) can make the exciting coil (61) generate an induced electromotive force, and the measuring circuit obtains the free oscillation frequency corresponding to the vibrating string (5) according to the induced electromotive force signal.

9. The double-string structure vibrating string pressure sensor according to claim 1, characterized in that: The two vibrating strings (5) are made of the same material, the two vibrating strings (5) have the same length, and the two vibrating strings (5) have different diameters.

10. A pressure calculation method for a double-string structure vibrating string pressure sensor according to any one of claims 1-9, characterized in that: The relationship between the liquid pressure acting on the transmission component (4) and the tension transmitted to the vibrating string (5) is as follows: Formula 1: F VS1 = K1F Formula 2: F VS2 = K2F where F is the liquid pressure, F VS1 and F VS2 are respectively the tensions transmitted to the two vibrating wires (5), and K1 and K2 represent the transmission coefficients of the liquid pressure F to the tensions of the corresponding two vibrating wires (5); The tensions F of the two vibrating strings (5) VS1 and F VS2 and their relationship with their own free oscillation frequencies are as follows: Formula Three: Formula Four: where f VS1 and f VS2 are the self-oscillation frequencies corresponding to the two vibrating wires (5) respectively; ρ1 and ρ2 represent the densities corresponding to the vibrating wires (5); σ VS1 and σ VS2 represent the stresses corresponding to the vibrating wires (5); l VS1 and l VS2 represent the lengths corresponding to the vibrating wires (5). When there is a temperature change, let the total stresses σ1 and σ2 respectively received by the two vibrating strings (5) be as follows: Formula Five: σ1 = (F VS1 + F0) / A1 + E(α h - α w )·ΔT Formula VI: σ2 = (F VS2 + F0) / A2 + E(α h - α w )·ΔT In the formula, F0 represents the external force applied to the two vibrating strings (5) when at rest, that is, the tension for clamping the vibrating string (5) at the free state of the movable end (41) without external force; F VS1 and F VS2 are the tensions transmitted to the two vibrating strings (5) respectively; A1 and A2 represent the cross-sectional areas corresponding to the vibrating strings (5), D1 and D2 represent the diameters corresponding to the vibrating strings (5); α h is the thermal expansion coefficient of the housing (1); α w is the thermal expansion coefficient of the vibrating string (5); E is the elastic modulus of the vibrating string (5); ΔT is the temperature change amount; Substitute Formula Five and Formula Six into Formula Three and Formula Four respectively, where σ1 = σ VS1 and σ2 = σ VS2 , to obtain the following expressions: Formula VII: Formula VIII: When the two vibrating strings (5) are made of the same material and have the same length, i.e., ρ1 = ρ2 = ρ, l VS1 = l VS2 = l, subtracting Formula Eight from Formula Seven gives: Formula Nine: The free oscillation frequencies f VS1 and f VS2 of the two vibrating wires (5) are obtained by the measuring component (6), substituted into Equation (9), and Equations (1) and (2) are substituted into Equation (9) to obtain the value of the liquid pressure F.

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