A pore pressure sensor calibration device and method of use thereof

Abstract

This invention discloses a pore pressure sensor calibration device, including a lifting device, a liquid level cup, a hose, a calibrator, and a data acquisition instrument. The lower end of the lifting device is fixedly connected to the liquid level cup, and the lifting device is used to move the liquid level cup up and down. The calibrator has an inner cavity for placing the pore pressure sensor. The liquid level cup is connected to the upper end of the calibrator through the hose, which communicates with the inner cavity of the calibrator. The lower end of the calibrator has a lower valve. The pore pressure sensor is connected to the data acquisition instrument located outside the calibrator via a data cable. This invention allows water to be injected sequentially into the calibrator, hose, and liquid level cup through the lower valve, making it easy to expel trapped air bubbles. By using the lifting device to raise and lower the liquid level cup as needed, the invention achieves the technical effect of repeatedly calibrating the pore pressure sensor in stages and steps as needed. In the same calibration scenario, only the pressure applied to the pore pressure sensor is changed to collect calibration values, thereby increasing the convenience, reliability, and accuracy of calibration.

Description

Technical Field

[0001] This invention relates to a calibration device, specifically to a pore pressure sensor calibration device and its usage method. Background Technology

[0002] The variation of pore water pressure (hereinafter referred to as "pore pressure") in foundation soil is an important testing indicator in geotechnical engineering, often used to quantitatively evaluate groundwater level fluctuations, seepage forces, soil consolidation, and other related phenomena. Common pore pressure sensors include vibrating wire and piezoresistive types. The reading of a pore pressure sensor is directly proportional to the hydraulic pressure it experiences. Pore pressure sensors are typically calibrated using hydraulic pressure before leaving the factory. However, because the factory environment and the operating environment (temperature, medium, time) of a pore pressure sensor are not entirely the same, a second calibration is usually required before engineering applications or tests.

[0003] During the calibration of pore pressure sensors, one approach is to immerse the sensor in water and apply precise water pressure at different stages as needed. The electrical signal data of the pore pressure sensor under different pressures is then read using a data acquisition device or similar equipment. This process is repeated multiple times to determine the coefficient between the pore pressure sensor reading and the corresponding water pressure. However, during calibration, it is often difficult to ensure that the calibration device is free of enclosed air bubbles, as their presence affects calibration accuracy. Furthermore, there is currently no convenient method to apply clearly defined staged water pressures to the calibration device. Consequently, the calibration process requires numerous instruments, such as pressure pumps, making it complex and costly.

[0004] Therefore, there is an urgent need for a convenient pore pressure sensor calibration device and its corresponding usage method to solve the problems of the inability to effectively expel enclosed air bubbles in the calibration device and the complicated calibration process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a pore pressure sensor calibration device and its usage method, which solves the problems of the inability to effectively expel enclosed air bubbles in the calibration device and the cumbersome calibration process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A pore pressure sensor calibration device is characterized by comprising a lifting device, a liquid level cup, a hose, a calibrator, and a data acquisition instrument. The lower end of the lifting device is fixedly connected to the liquid level cup, and the lifting device is used to move the liquid level cup up and down. The upper end of the liquid level cup is open. The calibrator has an inner cavity for placing the pore pressure sensor. The liquid level cup is connected to the upper end of the calibrator through a hose, which communicates with the inner cavity of the calibrator. The lower end of the calibrator has a lower valve that communicates with the inner cavity. The pore pressure sensor located in the inner cavity of the calibrator is connected to the data acquisition instrument located outside the calibrator through a data cable.

[0008] To optimize the above technical solution, the specific measures also include:

[0009] Furthermore, the calibrator includes a tapered sealing top cover with the tip pointing upwards and a cylindrical body. The sealing top cover is detachably fixed to the upper end of the cylindrical body, and an overflow hole is provided in the center of the sealing top cover. The lower end of the hose is connected to the inner cavity of the calibrator through the overflow hole.

[0010] Furthermore, the sealing top cover is fixed to the upper end of the cylinder by bolts, and a sealing ring is provided at the connection.

[0011] Furthermore, the lifting device includes an electronic measuring tape, on which a rotating motor is mounted. The electronic measuring tape is equipped with a display screen for reading the extension of the scale. The electronic measuring tape is fixed above the liquid level cup, and the extended end of the scale is fixedly connected to the upper end of the liquid level cup.

[0012] Furthermore, it also includes an upper fixed pulley and a lower fixed pulley. The upper fixed pulley is fixed above the liquid level cup, and the lower fixed pulley is fixed on one side below the upper fixed pulley. The electronic measuring tape is fixed on the lower fixed pulley. The scale of the electronic measuring tape extends upward from the lower fixed pulley and passes around the upper fixed pulley to be fixedly connected to the liquid level cup located on the other side below the upper fixed pulley.

[0013] Furthermore, it also includes a cable exit device, which is installed on the side wall of the calibrator. The data line of the pore pressure sensor passes through the cable exit device, exits the calibrator, and is connected to the data acquisition instrument.

[0014] Furthermore, the calibrator is a cylindrical structure with a height of 10-20cm and an inner diameter of 20-30cm, and is made of transparent plexiglass.

[0015] Furthermore, the hose passes through the lower end of the liquid level cup, and the top of the hose is at the same height as the rim of the liquid level cup.

[0016] Furthermore, the hose is made of transparent material and has a diameter of 8–15 mm.

[0017] Furthermore, a method for using a pore pressure sensor calibration device is characterized by comprising the following steps:

[0018] (a) Place the pore pressure sensor at the bottom of the calibrator’s inner cavity and pass the pore pressure sensor’s data cable out of the calibrator;

[0019] (b) Connect the level cup to the upper end of the calibrator via a hose;

[0020] (c) Determine the fixed height of the lifting device based on the range of the pore pressure sensor;

[0021] (d) Connect the lower valve of the calibrator directly to the faucet through the water pipe, and slowly and evenly inject water into the calibrator. The water level will rise from bottom to top, and the air inside the calibrator will be discharged from bottom to top through the hose. When the water level cup is full, close the lower valve.

[0022] (e) Start the lifting device to raise the liquid level cup to the highest position, check whether there are closed air bubbles inside the calibrator and hose. If so, continue to slowly inject water and vent the air through the lower valve until there are no closed air bubbles.

[0023] (f) Connect the data cable to the data acquisition instrument, and adjust the height of the liquid level cup as needed through the lifting device to adjust the liquid level height. At each height, measure and record the reading of the electrical signal data Ωi of the data acquisition instrument and the lifting height Hi of the lifting device. Repeat the calibration result n times, where i is the i-th time (i = 1, 2, 3, 4, 5...).

[0024] (g) Calculate the coefficient of the pore pressure sensor based on the measured values. This completes the calibration of the pore pressure sensor.

[0025] The beneficial effects of this invention are:

[0026] This invention utilizes a method of sequentially injecting water into the calibrator, hose, and level cup via a lower valve. This allows enclosed air bubbles within these components to easily escape from the open top of the level cup, ensuring calibration accuracy. A lifting device raises and lowers the water-filled level cup as needed, altering its potential energy and thus the pressure applied to the pore pressure sensor located within the calibrator's cavity. This allows for repeated, step-by-step calibration of the pore pressure sensor, ensuring that calibration values ​​are collected by varying the applied pressure within the same calibration scenario, thereby increasing the convenience, reliability, and accuracy of calibration. Furthermore, the method of creating different water pressures by raising and lowering the liquid level is based on a clear principle, is economical and reliable, and allows for flexible calibration work in various locations. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of a pore pressure sensor calibration device proposed in this invention;

[0028] Figure 2 This is a top view of the calibrator of a pore pressure sensor calibration device proposed in this invention.

[0029] Attached reference numerals: 1-1, calibrator; 1-2, cable outlet; 1-3, lower valve; 2-1, sealing top cover; 2-2, overflow hole; 3-1, pore pressure sensor; 3-2, data cable; 3-3, data acquisition instrument; 4-1, hose; 4-2, level cup; 5-1, upper fixed pulley; 5-2, lower fixed pulley; 6-1, electronic tape measure; 6-2, scale. Implementation

[0030] The invention will now be described in further detail with reference to the accompanying drawings.

[0031] As attached Figure 1 As shown, a pore pressure sensor calibration device includes a lifting device, a liquid level cup 4-2, a hose 4-1, a calibrator 1-1, and a data acquisition instrument 3-3. The lower end of the lifting device is fixedly connected to the liquid level cup 4-2, and the lifting device is used to drive the liquid level cup 4-2 to move up and down. The upper end of the liquid level cup 4-2 is open. The calibrator 1-1 has an inner cavity for placing the pore pressure sensor 3-1. The lower end of the liquid level cup 4-2 is connected to the upper end of the calibrator 1-1 through the hose 4-1, so that the liquid level cup 4-2 communicates with the inner cavity of the calibrator 1-1. The lower end of the calibrator 1-1 has a lower valve 1-3 that communicates with the inner cavity. The pore pressure sensor 3-1 located in the inner cavity of the calibrator 1-1 is connected to the data acquisition instrument 3-3 located outside the calibrator 1-1 through a data cable 3-2.

[0032] In this way, by sequentially injecting water into the calibrator 1-1, hose 4-1, and level cup 4-2 through the lower valve 1-3, the closed air bubbles in the calibrator 1-1, hose 4-1, and level cup 4-2 can easily be discharged from the upper opening of the level cup 4-2, thereby ensuring the accuracy of the calibration. By raising and lowering the water-filled level cup 4-2 as needed through the lifting device, the potential energy of the level cup 4-2 is changed, thereby changing the pressure applied to the pore pressure sensor 3-1 located in the inner cavity of the calibrator 1-1. This achieves the technical effect of repeatedly calibrating the pore pressure sensor 3-1 in stages as needed. It is beneficial to ensure that in the same calibration scenario, only the pressure applied to the pore pressure sensor 3-1 is changed to collect calibration values, thereby increasing the convenience, reliability, and accuracy of the calibration.

[0033] As attached Figure 2 As shown, in another embodiment, the calibrator 1-1 includes a tapered sealing cap 2-1 with its tip pointing upwards and a cylindrical body. The sealing cap 2-1 is detachably fixed to the upper end of the cylindrical body. An overflow hole 2-2 is provided in the center of the sealing cap 2-1, and the lower end of the hose 4-1 is connected to the inner cavity of the calibrator 1-1 through the overflow hole 2-2. Thus, the tapered sealing cap 2-1 with its tip pointing upwards facilitates the removal of air bubbles from the inner cavity of the calibrator 1-1, thereby further ensuring the accuracy of the calibration.

[0034] The sealing top cover 2-1 is fixed to the upper end of the cylinder with bolts, and a sealing ring is provided at the connection; this facilitates the placement and removal of the pore pressure sensor 3-1, and at the same time ensures the tightness of the connection between the sealing top cover 2-1 and the cylinder.

[0035] In another embodiment, the lifting device includes an electronic measuring tape 6-1. A rotating motor is mounted on the scroll of the electronic measuring tape 6-1. The electronic measuring tape 6-1 has a display screen for reading the extension of its scale 6-2. The electronic measuring tape 6-1 is fixed above the liquid level cup 4-2, and the extended end of the scale 6-2 is fixedly connected to the upper end of the liquid level cup 4-2. Thus, the scale 6-2 can be extended or retracted by the rotating motor, thereby raising or lowering the liquid level cup 4-2. The extension of the scale 6-2 can be conveniently read through the display screen of the electronic measuring tape 6-1. The measuring accuracy of the electronic measuring tape 6-1 is 1.0 mm.

[0036] The device includes an upper fixed pulley 5-1 and a lower fixed pulley 5-2. The upper fixed pulley 5-1 is fixed above the liquid level cup 4-2, and the lower fixed pulley 5-2 is fixed to one side below the upper fixed pulley 5-1. An electronic measuring tape 6-1 is fixed on the lower fixed pulley 5-2. The scale 6-2 of the electronic measuring tape 6-1 extends upward from the lower fixed pulley 5-2 and passes around the upper fixed pulley 5-1 to be fixedly connected to the liquid level cup 4-2 located on the other side below the upper fixed pulley 5-1. In this way, by raising or lowering the scale 6-2, the liquid level cup 4-2 can be raised or lowered, thus raising or lowering the liquid level height in the liquid level cup 4-2. The pressure applied to the pore pressure sensor 3-1 can be changed without the need for a pressure pump or other devices. At the same time, the arrangement of the upper fixed pulley 5-1 and the lower fixed pulley 5-2 makes it easy to position the electronic measuring tape 6-1 at a height that is convenient for reading and operation, thereby increasing the ease of use of the device.

[0037] In another embodiment, a cable exit device 1-2 is also included. The cable exit device 1-2 is installed on the side wall of the calibrator 1-1. The data line 3-2 of the pore pressure sensor 3-1 passes through the cable exit device 1-2 and exits the calibrator 1-1 and is connected to the data acquisition instrument 3-3. This facilitates the transmission of the data line 3-2 without affecting the sealing of the calibrator 1-1.

[0038] In another embodiment, the calibrator 1-1 is a cylindrical structure with a height of 10-20cm and an inner diameter of 20-30cm, made of transparent plexiglass; thus, it facilitates the use of the calibrator 1-1 and the observation of its internal condition.

[0039] In another embodiment, the hose 4-1 passes through the lower end of the liquid level cup 4-2, and the top of the hose 4-1 is at the same height as the mouth of the liquid level cup 4-2. In this way, while not hindering the hose 4-1 from filling the liquid level cup 4-2 with water, the closed air bubbles can be directly discharged from the top of the hose 4-1 during the overflow process of the hose 4-1.

[0040] In another embodiment, the flexible tube 4-1 is made of transparent material and has a diameter of 8 to 15 mm; this facilitates the use of the flexible tube 4-1 and the observation of the internal closed air bubbles.

[0041] The method of using the above-described pore pressure sensor calibration device includes the following steps:

[0042] (a) Place the pore pressure sensor 3-1 at the bottom of the inner cavity of the calibrator 1-1, and pass the data cable 3-2 of the pore pressure sensor 3-1 out of the calibrator 1-1 through the cable outlet 1-2. Multiple pore pressure sensors 3-1 can be placed and calibrated at one time as needed. Then place the sealing top cover 2-1 on the top of the cylinder of the calibrator 1-1, and make a sealing connection with screws and sealing rings.

[0043] (b) Connect the level cup 4-2 to the upper end of the calibrator 1-1 via the hose 4-1;

[0044] (c) Determine the fixed height of the lifting device according to the range of the pore pressure sensor 3-1. It can be fixed in the vertical connecting area of ​​the stairwell. Specifically, the fixed height of the upper fixed pulley 5-1 can be determined according to the range of the pore pressure sensor 3-1. It can be fixed in the vertical connecting area of ​​the stairwell. The lower fixed pulley 5-2 can be fixed at a position 1.00m higher than the plane where the pore pressure sensor 3-1 is located. Then fix the electronic tape measure 6-1 at the lower fixed pulley 5-2, and connect the scale 6-2 around the upper fixed pulley 5-1 to the liquid level cup 4-2, and make the initial height of the liquid level cup 4-2 the same as that of the electronic tape measure 6-1.

[0045] (d) Connect the lower valve 1-3 of calibrator 1-1 directly to the faucet through a water pipe, and slowly and evenly inject water into calibrator 1-1. The water level will rise from bottom to top, and the air inside calibrator 1-1 will be discharged from bottom to top through hose 4-1. When the water level in hose 4-1 in liquid level cup 4-2 is full, close the lower valve 1-3.

[0046] (e) Start the lifting device to raise the liquid level cup 4-2 to the highest position, check whether there are closed air bubbles inside the calibrator 1-1 and the hose 4-1. If so, continue to slowly inject water and vent the air through the lower valve 1-3 until there are no closed air bubbles.

[0047] (f) Connect data cable 3-2 to data acquisition instrument 3-3, and adjust the height of liquid level cup 4-2 as needed through lifting device to adjust the liquid level. At each height, simultaneously measure and record the reading Ωi of electrical signal data of data acquisition instrument 3-3 and the lifting height Hi of lifting device. Repeat the calibration result n times, where i is the i-th time i = 1, 2, 3, 4, 5...; Specifically, the height of liquid level cup 4-2 can be adjusted by controlling the drive electronic tape measure 6-1, and the value of lifting height Hi can be read directly.

[0048] (g) Calculate the coefficient of pore pressure sensor 3-1 based on the measured values. This completes the calibration of the pore pressure sensor 3-1.

[0049] The present invention discloses a pore pressure sensor calibration device with a clear principle, simple structure, and economic applicability. In use, water can be directly injected into the calibrator 1-1, hose 4-1, and level cup 4-2 sequentially through the lower valve 1-3, so that the closed air bubbles in the calibrator 1-1, hose 4-1, and level cup 4-2 can easily be discharged from the upper opening of the level cup 4-2, thereby ensuring the calibration accuracy. Water injection and air venting can be completed simultaneously. The liquid level can be directly adjusted by raising and lowering the lifting device to create different water pressure environments, which can conveniently provide a stable, clear, and reliable calibration pressure.

[0050] It should be noted that the terms such as "upper", "lower", "left", "right", "front", and "back" used in the invention are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0051] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A pore pressure sensor calibration device, characterized by: The device includes a lifting device, a level cup (4-2), a hose (4-1), a calibrator (1-1), and a data acquisition instrument (3-3). The lower end of the lifting device is fixedly connected to the level cup (4-2), and the lifting device is used to drive the level cup (4-2) to move up and down. The upper end of the level cup (4-2) is open. The calibrator (1-1) has an inner cavity for placing the pore pressure sensor (3-1). The level cup (4-2) is connected to the upper end of the calibrator (1-1) through the hose (4-1), and the level cup (4-2) is connected to the inner cavity of the calibrator (1-1). The lower end of the calibrator (1-1) has a lower valve (1-3) connected to the inner cavity. The pore pressure sensor (3-1) located in the inner cavity of the calibrator (1-1) is connected to the data acquisition instrument (3-3) located outside the calibrator (1-1) through a data cable (3-2). The calibrator (1-1) includes a cone-shaped sealing top cover (2-1) with the tip pointing upward and a cylindrical body. The sealing top cover (2-1) is detachably fixed to the upper end of the cylindrical body. An overflow hole (2-2) is provided in the center of the sealing top cover (2-1). The lower end of the hose (4-1) is connected to the inner cavity of the calibrator (1-1) through the overflow hole (2-2). The lifting device includes an electronic measuring tape (6-1), on which a rotating motor is mounted. The electronic measuring tape (6-1) is equipped with a display screen for reading the elongation of the scale (6-2) of the electronic measuring tape (6-1). The electronic measuring tape (6-1) is fixed above the liquid level cup (4-2), and the extended end of the scale (6-2) is fixedly connected to the upper end of the liquid level cup (4-2). It also includes an upper fixed pulley (5-1) and a lower fixed pulley (5-2). The upper fixed pulley (5-1) is fixed above the liquid level cup (4-2), and the lower fixed pulley (5-2) is fixed on one side below the upper fixed pulley (5-1). The electronic tape measure (6-1) is fixed on the lower fixed pulley (5-2). The scale (6-2) of the electronic tape measure (6-1) extends upward from the lower fixed pulley (5-2) and passes around the upper fixed pulley (5-1) to be fixedly connected to the liquid level cup (4-2) on the other side below the upper fixed pulley (5-1). Water is injected sequentially into the calibrator (1-1), hose (4-1), and level cup (4-2) through the lower valve, causing the closed air bubbles in the calibrator (1-1), hose (4-1), and level cup (4-2) to be discharged from the upper opening of the level cup (4-2).

2. The pore water pressure sensor calibration device of claim 1, wherein: The sealing top cover (2-1) is fixed to the upper end of the cylinder by bolts, and a sealing ring is provided at the connection.

3. The pore pressure sensor calibration device according to claim 1, characterized in that: It also includes a cable exit device (1-2), which is installed on the side wall of the calibrator (1-1). The data line (3-2) of the pore pressure sensor (3-1) passes through the cable exit device (1-2) and exits the calibrator (1-1) and is connected to the data acquisition instrument (3-3).

4. The pore pressure sensor calibration device according to claim 1, characterized in that: The calibrator (1-1) is a cylindrical structure with a height of 10-20 cm and an inner diameter of 20-30 cm, and is made of transparent plexiglass.

5. The pore pressure sensor calibration device according to claim 1, characterized in that: The hose (4-1) passes through the lower end of the liquid level cup (4-2) and the top of the hose (4-1) is at the same height as the mouth of the liquid level cup (4-2).

6. The pore pressure sensor calibration device according to claim 1, characterized in that: The hose (4-1) is made of transparent material and has a diameter of 8~15 mm.

7. A method of using a pore pressure sensor calibration device according to any one of claims 1 to 6, characterized in that, Includes the following steps: (a) Place the pore pressure sensor (3-1) at the bottom of the inner cavity of the calibrator (1-1) and pass the data line (3-2) of the pore pressure sensor (3-1) out of the calibrator (1-1). (b) Connect the level cup (4-2) to the upper end of the calibrator (1-1) via the hose (4-1); (c) Determine the fixed height of the lifting device based on the range of the pore pressure sensor (3-1); (d) Connect the lower valve (1-3) of the calibrator (1-1) directly to the faucet via a water pipe, and slowly and evenly inject water into the calibrator (1-1). The water level will rise from bottom to top, and the air inside the calibrator (1-1) will be discharged from bottom to top through the hose (4-1). When the water level in the hose (4-1) inside the liquid level cup (4-2) is full, close the lower valve (1-3). (e) Start the lifting device to raise the liquid level cup (4-2) to the highest position, check whether there are closed air bubbles inside the calibrator (1-1) and the hose (4-1). If so, continue to slowly inject water and vent the air through the lower valve (1-3) until there are no closed air bubbles. (f) Connect the data cable (3-2) to the data acquisition instrument (3-3). Adjust the height of the liquid level cup (4-2) as needed through the lifting device to adjust the liquid level. At each height, simultaneously measure and record the reading Ωi of the electrical signal data of the data acquisition instrument (3-3) and the lifting height Hi of the lifting device. Repeat the calibration result n times. i For the first i Second-rate, i =1, 2, 3, 4, 5…; (g) Calculate the coefficient of the pore pressure sensor (3-1) based on the measured values. This is to complete the calibration of the pore pressure sensor (3-1).

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