Temperature effect correction method of static leveling instrument system

Abstract

The invention discloses a method for correcting a temperature effect of a static level gauge system, relates to the technical field of correction and calibration of the static level gauge system, and considers shrinkage and expansion in the length direction and the radial direction of a communicating pipe between static level gauges, shrinkage and expansion of communicating liquid and shrinkage and expansion of a bowl body of the static level gauge. The method can reduce the influence of the temperature effect on the hydrostatic level data, and has reference significance for improving the temperature adaptability and precision of the hydrostatic level monitoring method.

Description

Technical Field

[0001] The invention relates to the technical field of correction and calibration of a static level system, and in particular to a temperature effect correction method for a static level system. Background Art

[0002] A static level is an automated settlement monitoring device used to measure the relative elevation change between two or more points. It is widely used in vertical displacement monitoring of structures such as large storage tanks, dams, nuclear power plants, high-rise buildings, foundation pits, tunnels, bridges, and subways. A static level system usually consists of multiple static levels. Based on the principle of communicating vessels, each sensor container is connected to each other through a connecting pipe. In connected containers, liquids naturally seek the same potential energy level. When settlement occurs at each observation point, this will cause the liquid level or pressure in each storage tank to change. The sensor of the static level can sense the change in the relative height of the liquid level in the storage tank at each test point, thereby calculating the differential settlement of each static level relative to the reference point.

[0003] The common types of static levels on the market include: differential transformer type, photoelectric type (CCD), magnetostrictive type, vibrating wire type, capacitive type, ultrasonic type and differential pressure type static levels. Except for the differential pressure type static level, which determines the elevation of the measured point by measuring the pressure of the liquid surface on the deformation sensor, other types of static levels mainly measure the liquid level height. In recent years, with the advancement of technology, static leveling technology has developed rapidly. Looking back on the development history of static levels, their accuracy and stability mainly depend on the following aspects: Sensor accuracy: the measurement accuracy of the static level sensor itself. Data acquisition and correction method: effective data acquisition strategy and appropriate correction algorithm are crucial to improve the accuracy of measurement results. Temperature sensitivity and durability of system materials: the material selection of system accessories including Unicom liquid and Unicom pipes will affect the long-term stability and reliability of the system. External environmental factors: external conditions such as temperature difference between different static levels, temperature gradient changes, tidal effects, etc. will affect the measurement. Construction quality: factors including the installation position of the static level, whether the installation height is correct, whether the bubbles are completely discharged, etc. will also affect the final measurement results. Among them, the temperature effect has a significant impact on the accuracy of the static level system. Temperature changes will cause the volume of the connected liquid to expand or contract, the inner diameter of the connected pipe to change, and the inner diameter of the static level bowl to change, all of which will affect the liquid level height. Since the static level is a precision measuring instrument with a measurement sensitivity generally higher than 0.1 mm, the temperature effect may significantly reduce the measurement accuracy of this method. For this reason, developing a reliable temperature effect correction method is one of the key technical challenges to improve the practicality of static levels. Summary of the invention

[0004] Technical problem to be solved by the invention

[0005] The technical problem to be solved by the present invention is to provide a temperature effect correction method for reducing the influence of temperature effect on the data of static level, which can take into account the influence of the expansion and contraction in the length direction and radial direction of the connecting tube between the static level, the expansion and contraction of the connecting fluid, and the expansion and contraction of the bowl of the static level on the data.

[0006] Technical Solution

[0007] To solve the above problems, the technical solution provided by the present invention is:

[0008] A method for correcting the temperature effect of a static level system comprises the following steps:

[0009] S1. Set assumptions. Assumption 1: Ignore the evaporation of the interconnecting fluid during the monitoring process. Assumption 2: The thermal expansion and contraction of the interconnecting fluid does not affect the water pressure balance between the static level. Assumption 3: The absolute value of the temperature gradient change is no more than 2℃ / h, and the effect of the temperature gradient on the thermal expansion of the material is not considered. Assumption 4: Ignore the vertical expansion and contraction of the static level bowl. Assumption 5: The temperature measured by the temperature sensor represents the temperature of the static level bowl and the nearby interconnecting pipe.

[0010] S2. The static level system has n static levels. At t0, the readings of the static levels are h1…hi…hj…hn, and the installation heights are H1…Hi…Hj…Hn. The distances between static level i and static level j and the previous static level are Li and Lj respectively.

[0011] S3. Calculate the volume change of the interconnecting fluid, formula 1-1: ΔV = (1 + α V,w )VΔT, where ΔV is the volume change of the connecting fluid; α V,w is the volume expansion coefficient of the communication fluid; ΔT is the temperature change;

[0012] S4. Calculate the size change of the connecting tube and the bowl of the static level, formula 1-2: ΔL = (1 + α L )LΔT, where L and ΔL are the size and the change in size; α L is the linear expansion coefficient of the connecting tube and the bowl of the static level. The linear expansion coefficient of the connecting tube is α L,P , the linear expansion coefficient of the static level bowl is α L,B ;

[0013] S5. According to assumption 2, when the temperature changes, the connecting fluid between the static level i and the static level j will reach a water pressure balance at the midpoint MM line. Consider the circuit of a single static level i, and divide the connecting fluid into three parts according to the different positions. The volume change of the connecting fluid includes the front tube part V1i of the connecting tube, the rear tube part V2i of the connecting tube, and the bowl part V3i of the static level. Consider the i-th static level. At time t0, the inner diameter of the connecting tube is The inner diameter of the bowl of the static level is The length of the front tube of the connecting tube is The length of the connecting pipe is When the unit temperature changes, the radius of the hydrostatic level bowl becomes The radius of the connecting pipe becomes The length of the front tube of the connecting tube is The length of the connecting pipe is

[0014] S6. Calculate the overflow volume of the front pipe of the connecting pipe, formula 1-3:

[0015]

[0016] S7. Calculate the overflow volume of the connected pipe, formula 1-4:

[0017]

[0018] S8. Calculate the overflow of the bowl of the static level, formula 1-5:

[0019]

[0020] S9. Calculate the change in the liquid level of the static level under unit temperature change, formula 1-6: Similarly, Δhj is obtained. Let the static level i be the reference level and its elevation be 0. Then the elevation of the static level j is hi-hj, and the temperature correction of the static level j is Δhi-Δhj.

[0021] Optionally, if i=1 in S2, then L1=0.

[0022] Optionally, the application condition of Formula 1-1 is i≠1. When i=1, the overflow of the front pipe of the connecting pipe is 0.

[0023] Optionally, the application condition of Formula 1-2 is that bowl i+1≤n, that is, bowl i+1 cannot be the last bowl; when i+1>n, the overflow of the connecting pipe and the rear pipe is 0.

[0024] As an option, after the connecting fluid is replenished, the height of the connecting fluid changes, and hi' of each static level is replaced by hi.

[0025] As an option, when the material expansion coefficient varies with temperature, α V and α L Replace it with a function of temperature.

[0026] As an option, the size changes of the connecting tube and the static level bowl are changes in the inner diameters or lengths of the connecting tube and the static level.

[0027] As an option, the hydrostatic level can be equipped with a temperature sensor with an accuracy of better than 0.01 degrees Celsius.

[0028] Beneficial Effects

[0029] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0030] The technical solution provided by the present invention takes into account the thermal expansion effect of the connecting tube and the bowl of the static level, as well as the length of the connecting tube between the static levels, and establishes a temperature effect correction model suitable for complex scenarios. The model is intuitive and has great scalability, which is convenient for further analysis and research. The application of this technical solution can reduce the impact of temperature effects on static level data, which has reference significance for improving the temperature adaptability and accuracy of static level monitoring methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic structural diagram of a static level system proposed in an embodiment of the present invention;

[0032] Figure 2 A parameter diagram of a temperature effect correction method for a static level system proposed in an embodiment of the present invention;

[0033] Figure 3 An implementation method of three static levels for a temperature effect correction method of a static level system proposed in an embodiment of the present invention;

[0034] 1. The first static level; 2. The i-th static level; 3. The j-th static level; 4. The n-th static level; 5. Connecting tube; 6. Bowl; 7. Reference static level; 8. The second static level; 9. The third static level. DETAILED DESCRIPTION

[0035] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.

[0036] Example 1

[0037] Combined with Figure 1-3 , a temperature effect correction method for a static level system, comprising the following steps:

[0038] S1. Set assumptions. Assumption 1: Ignore the evaporation of the connecting fluid during the monitoring process. Assumption 2: The thermal expansion and contraction of the connecting fluid does not affect the water pressure balance between the static level. Assumption 3: The absolute value of the temperature gradient change is no more than 2°C / h, and the effect of the temperature gradient on the thermal expansion of the material is not considered. Assumption 4: Ignore the vertical expansion and contraction of the static level bowl. Assumption 5: The temperature measured by the temperature sensor represents the temperature of the static level bowl and the nearby connecting pipe 5.

[0039] S2. The static level system has n static levels. The accuracy of the temperature sensor of the static level is above 0.01 degrees Celsius. At t0, the readings of the static levels are h1…hi…hj…hn, and the installation heights are H1…Hi…Hj…Hn. The distances between static level i and static level j and the previous static level are Li and Lj, respectively. If i=1, L1=0. The n static levels are: the first static level 1, the i-th static level 2, the j-th static level 3, and the n-th static level 4.

[0040] S3. Calculate the volume change of the interconnecting fluid, formula 1-1: ΔV = (1 + α V,w )VΔT, where ΔV is the volume change of the connecting fluid; α V,w is the volume expansion coefficient of the connecting fluid; ΔT is the temperature change. The application condition of formula 1-1 is i≠1. When i=1, the overflow of the front pipe of the connecting pipe 5 is 0.

[0041] S4. Calculate the size change of the connecting pipe 5 and the bowl of the static level, formula 1-2: ΔL = (1 + α L )LΔT, where L and ΔL are the size and the size change, and the size change of the connecting tube 5 and the static level bowl is the change in the inner diameter or length of the connecting tube 5 and the static level. L is the linear expansion coefficient of the connecting tube 5 and the bowl of the static level, and the linear expansion coefficient of the connecting tube 5 is α L,P , the linear expansion coefficient of the static level bowl is α L,B The application condition of formula 1-2 is that the bowl i+1≤n, that is, the bowl i+1 cannot be the last bowl; when i+1>n, the overflow of the tube after connecting tube 5 is 0. When the material expansion coefficient changes with temperature, α V and α L Replace it with a function of temperature.

[0042] S5. According to assumption 2, when the temperature changes, the connecting fluid between the i-th static level 2 and the j-th static level 3 will reach a water pressure balance at the midpoint MM line. Investigate the circuit of a single i-th static level 2, divide the connecting fluid into three parts according to the different positions, and the volume change of the connecting fluid includes the front tube part V1i of the connecting tube 5, the rear tube part V2i of the connecting tube 5 and the bowl part V3i of the static level. Investigate the i-th static level 2, at time t0, the inner diameter of the connecting tube 5 is The inner diameter of the bowl of the static level is The length of the front tube of the connecting tube 5 is The length of the rear tube of the connecting tube 5 is When the unit temperature changes, the radius of the hydrostatic level bowl becomes The radius of the connecting pipe 5 becomes The length of the front tube of the connecting tube 5 is The length of the rear tube of the connecting tube 5 is

[0043] S6. Calculate the overflow volume of the front pipe of the connecting pipe 5, formula 1-3:

[0044]

[0045] S7, calculate the overflow volume of the pipe after connecting pipe 5, formula 1-4:

[0046]

[0047] S8. Calculate the overflow of the bowl of the static level, formula 1-5:

[0048]

[0049] S9. Calculate the liquid level change of the ith static level gauge 2 under unit temperature change, formula 1-6: Similarly, Δhj is obtained. Let the i-th static level 2 be the reference level, and the elevation be 0. Then the elevation of the j-th static level 3 is hi-hj, and the temperature correction of the j-th static level 3 is Δhi-Δhj. After the connecting fluid is replenished, the height of the connecting fluid changes, and the hi' of each static level is replaced by hi.

[0050] When the temperature is 20°C, the inner diameter of the connecting pipe 5 is 4 mm and the outer diameter is 6 mm. i The horizontal distance L2 between the second static level 8 and the reference static level 7 is 20m, and the horizontal distance L1 between the third static level 9 and the second static level 8 is 20m.

[0051] The bowl of the static level is made of austenitic 304 stainless steel, and the connecting pipe 5 is made of silicone hose. The expansion coefficient of the stainless steel material is basically a constant value at room temperature, and the expansion coefficient of the silicone hose can be roughly considered constant. In the embodiment, the linear expansion coefficient of the bowl is taken as 1.7×10 -5 / K, the linear expansion coefficient of the connecting tube 5 is 5.9×10 -4 / K. If a material with a non-constant expansion coefficient is used, the linear expansion can be calculated using the integral method.

[0052] The communication fluid is a mixture of GLYSANTIN antifreeze and water, with a dilution ratio of 1:3.

[0053] Under the conditions of the embodiment, the ambient temperature changes. The temperature of the bowl of the reference static level 7 is slowly increased from 20°C to 30°C; the temperature of the bowl of the second static level 8 is slowly increased from 20°C to 28°C; the temperature of the bowl of the third static level 9 is slowly increased from 20°C to 25°C. The actual elevations of the three static levels do not change.

[0054] The expansion coefficient of the communication fluid changes with temperature. Generally, the expansion coefficient of the communication fluid such as water changes significantly with temperature. Here, a mixture of GLYSANTIN antifreeze with excellent thermal expansion performance and water is selected, and the dilution ratio is 1:3. In the range of 20℃~30℃, when mixed according to the dilution ratio of 1:3, the expansion coefficient formula is α=3.8×10 -6 T+3.3×10 -5 Since the temperature variation range is small, the volume expansion coefficient is considered constant. V,w Take the expansion coefficient at 25°C, which is 1.28×10 -4 / K. If a connecting fluid with a large change in expansion coefficient is used, the volume expansion can be calculated by the integral method.

[0055] Inspection reference static level 7

[0056] The temperature at time t0 is 20°C, the same as during installation. 2mm, the inner radius of the static level bowl The liquid level in the bowl of the reference static level 7 is 49.5 mm. The length of the front tube of the connecting tube 5 is 0. The length of the rear tube of the connecting tube 5 is It is 10.2m.

[0057] t k At this time, the temperature rises uniformly to 30°C. According to formula (1-2), the inner radius of the bowl of the static level is calculated The inner radius of the connecting tube 5 is 2.00118 mm. It is 49.50084mm.

[0058] i=1, calculated according to formula (1-3), the unit temperature change ΔV 11 is 0. According to formula (1-4), the unit temperature change ΔV 21 -210.60mm 3 According to formula (1-5), the unit temperature change ΔV 31 -13.09mm 3 .

[0059] From t0 to t k The temperature rose uniformly by 10°C. According to formula (1-6), Δh1 was calculated to be -0.2905mm.

[0060] Inspection of the Second Static Level 8

[0061] The temperature at time t0 is 20°C, the same as during installation. k At this moment, the temperature rises uniformly to 28°C. According to the calculation method of the reference static level 7, ΔV 12 -210.60mm 3 , ΔV 22 -210.60mm 3 , ΔV 32 43.41mm 3 . Δh2 is -0.3926mm.

[0062] Inspection of the third static level 9

[0063] The temperature at time t0 is 20°C, the same as during installation. k At this moment, the temperature rises uniformly to 28°C. According to the calculation method of the reference static level 7, ΔV 13 -210.60mm 3 , ΔV 23 =0, ΔV 33 -14.39mm 3 . Δh2 is -0.1461mm.

[0064] The temperature correction amount of the i-th static level is Δhi-Δhj, and finally the correction amount of the second static level 8 is 0.1020mm, and the correction amount of the third static level 9 is 0.1444mm.

[0065] Example 2

[0066] Combined with Figure 3 Compared with the technical solution of Example 1, the temperature effect correction method of a static level system in this embodiment can be improved as follows:

[0067] The horizontal spacing of the static level is 10m, the installation height is 200mm, and the inner radius of the connecting pipe 5 is 2mm.

[0068] Example 3

[0069] Combined with Figure 3 Compared with the technical solution of Embodiment 1 or 2, the temperature effect correction method of a static level system in this embodiment can be improved as follows:

[0070] The horizontal spacing of the static level is 20m, the installation height is 300mm, and the inner radius of the connecting pipe 5 is 2mm

[0071] Example 4

[0072] Combined with Figure 3 , a temperature effect correction method for a static level system in this embodiment can be improved as follows compared with any one of the technical solutions in embodiments 1-3:

[0073] The horizontal spacing of the static level is 20m, the installation height is 200mm, and the inner radius of the connecting pipe 5 is 2.5mm.

[0074]

[0075] In summary, examples 1-4 show that the temperature effect correction method of the present invention is affected by the static level spacing, installation height, and the inner radius of the connecting pipe. The correction method significantly corrects the static level spacing and the inner radius of the connecting pipe, and can improve the accuracy by more than 0.1 mm.

[0076] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A method for correcting the temperature effect of a static level system, characterized in that: The following steps are involved: S1. Set assumptions. Assumption 1: Ignore the evaporation of the interconnecting fluid during the monitoring process. Assumption 2: The thermal expansion and contraction of the interconnecting fluid does not affect the water pressure balance between the static level. Assumption 3: The absolute value of the temperature gradient change is no more than 2℃ / h, and the effect of the temperature gradient on the thermal expansion of the material is not considered. Assumption 4: Ignore the vertical expansion and contraction of the static level bowl. Assumption 5: The temperature measured by the temperature sensor represents the temperature of the static level bowl and the nearby interconnecting pipe. S2. The static level system has n static levels. At t0, the readings of the static levels are h1…hi…hj…hn, and the installation heights are H1…Hi…Hj…Hn. The distances between static level i and static level j and the previous static level are Li and Lj respectively. S3. Calculate the volume change of the interconnecting fluid, formula 1-1: ΔV = (1 + α V,w )VΔT, where ΔV is the volume change of the connecting fluid; α V,w is the volume expansion coefficient of the communication fluid; ΔT is the temperature change; S4. Calculate the size change of the connecting tube and the bowl of the static level, formula 1-2: ΔL = (1 + α L )LΔT, where L and ΔL are the size and the change in size; α L is the linear expansion coefficient of the connecting tube and the bowl of the static level. The linear expansion coefficient of the connecting tube is α L,P , the linear expansion coefficient of the static level bowl is α L,B ; S5. According to assumption 2, when the temperature changes, the connecting fluid between the static level i and the static level j will reach a water pressure balance at the midpoint MM line. Consider the circuit of a single static level i, and divide the connecting fluid into three parts according to the different positions. The volume change of the connecting fluid includes the front tube part V1i of the connecting tube, the rear tube part V2i of the connecting tube, and the bowl part V3i of the static level. Consider the i-th static level. At time t0, the inner diameter of the connecting tube is The inner diameter of the bowl of the static level is The length of the front tube of the connecting tube is The length of the connecting pipe is When the unit temperature changes, the radius of the hydrostatic level bowl becomes The radius of the connecting pipe becomes The length of the front tube of the connecting tube is The length of the connecting pipe is S6. Calculate the overflow volume of the front pipe of the connecting pipe, formula 1-3: S7. Calculate the overflow volume of the connected pipe, formula 1-4: S8. Calculate the overflow of the bowl of the static level, formula 1-5: S9. Calculate the change in the liquid level of the static level under unit temperature change, formula 1-6: Similarly, Δhj is obtained. Let the static level i be the reference level and its elevation be 0. Then the elevation of the static level j is hi-hj, and the temperature correction of the static level j is Δhi-Δhj.

2. The temperature effect correction method of a static level system according to claim 1, characterized in that: In S2, if i=1, then L1=0.

3. The temperature effect correction method of a static level system according to claim 1, characterized in that: The application condition of formula 1-1 is i≠1. When i=1, the overflow volume of the pipe in front of the connecting pipe is 0.

4. The temperature effect correction method of a static level system according to claim 1, characterized in that: The application condition of formula 1-2 is that bowl i+1≤n, that is, bowl i+1 cannot be the last bowl; when i+1>n, the overflow of the connecting pipe and the rear pipe is 0.

5. The temperature effect correction method of a static level system according to claim 1, characterized in that: After replenishing the connecting fluid, the height of the connecting fluid changes, and the hi' of each static level is replaced by hi.

6. The temperature effect correction method of a static level system according to claim 1, characterized in that: When the material expansion coefficient changes with temperature, α V and α L Replace it with a function of temperature.

7. A method for correcting the temperature effect of a static level system according to any one of claims 1 to 6, characterized in that: The size change of the connecting tube and the bowl of the static level is the change of the inner diameter or length of the connecting tube and the static level.

8. A method for correcting the temperature effect of a static level system according to any one of claims 1 to 6, characterized in that: The temperature sensor of the hydrostatic level has an accuracy of better than 0.01 degrees Celsius.

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