A magnetostrictive liquid level sensor suitable for high temperature / high pressure environments

Abstract

The present invention is a magnetostrictive liquid level sensor suitable for high temperature / high pressure environment. The head of the sensor is an electronic compartment, in which a circuit module, a detection device and a top damping device are installed. Fe-Ga and Fe-Co magnetostrictive materials are used as waveguide wires; the device enhances the strength of the bias magnetic field generated by the annular permanent magnet through the special shape and structural setting of the permanent magnet and the magnetic yoke in the float, the structure of the permanent magnet structure, the position of the distance from the waveguide wire, the addition of the magnetic yoke and other structural designs. The magnetostrictive liquid level sensor obtained by the present invention has high measurement accuracy and good reliability under harsh working conditions such as high temperature, high pressure and strong vibration.

Description

Technical Field

[0001] The present invention belongs to the field of magnetostrictive liquid level sensors, and mainly relates to magnetostrictive liquid level sensors based on Fe-Ga materials and Fe-Co materials and float structures thereof, which can be applied to liquid level measurement under complex and severe working conditions such as high temperature, high pressure and strong vibration. Background Art

[0002] The magnetostrictive liquid level sensor is an absolute displacement sensor realized by the Wiedemann effect of magnetostrictive materials, which is mainly used for distance measurement or displacement control. As early as the 1970s, the prototype of magnetostrictive liquid level sensor had already appeared. The American MTS company first used the magnetostrictive principle to measure the oil level in the oil tank. Since then, magnetostrictive sensors have been widely used in automated production processes. By the 1980s, many manufacturers have been able to maturely use magnetostrictive technology to measure liquid level and displacement. Since the beginning of the 21st century, people's industrial technology and scientific and technological levels have been continuously improved, and the performance of magnetostrictive liquid level sensors has been continuously optimized. In recent years, the products of the American MTS company and the German Balluff company related to magnetostrictive sensors have great advantages in performance and are very popular in foreign markets.

[0003] Compared with other traditional liquid level measuring devices, magnetostrictive liquid level sensors have the following advantages: high measurement accuracy; easy to use, no need to re-zero; little influence of interference signals on the detection results; high safety. In the field of measurement, especially in the fields of chemical industry, metallurgy, pharmaceuticals, ships, aircraft, petroleum, etc., which require high measurement accuracy and the measurement process is exposed to explosive, flammable, volatile, corrosive and other conditions, the advantages of magnetostrictive liquid level sensors are particularly obvious. Magnetostrictive liquid level sensors are absolute value sensors. There is no need to set zero before measurement. The measurement data is constantly scanned and updated. Even if there is an accidental momentary interference during the measurement process, it will quickly correct itself and will not affect the measurement results. In view of the above advantages, magnetostrictive liquid level sensors have been widely used in the field of liquid level measurement.

[0004] The working environment of the current magnetostrictive displacement sensor is mostly around 100℃ and the working pressure is 2MPa. The permanent magnet in the float is basically a non-contact circular magnet. However, in harsh working conditions such as high temperature, high pressure or strong vibration, the permanent magnet will demagnetize, and the axial magnetic field strength it generates will weaken. When it meets the circumferential magnetic field formed by the current on the waveguide wire, the strength of the spiral magnetic field formed by vector superposition is not strong enough, resulting in a lower signal amplitude of the sensor's detection voltage, which is not conducive to signal detection. In order to make the magnetic field intensity of the spiral magnetic field more concentrated and the detection voltage amplitude larger, the structure of the permanent magnetic float is designed and optimized. Summary of the invention

[0005] The purpose of the present invention is to provide a magnetostrictive liquid level sensor suitable for high temperature / high pressure in view of the deficiencies in the current technology. The head of the sensor is an electronic compartment, in which a circuit module, a detection device and a top damping device are installed. Fe-Ga and Fe-Co magnetostrictive materials are used as waveguide wires. The present invention enhances the intensity of the bias magnetic field generated by the annular permanent magnet by changing the shape of the float, the structure of the permanent magnet structure, the position of the distance from the waveguide wire, the addition of a magnetic yoke and other structural designs. The magnetostrictive liquid level sensor obtained by the present invention has high measurement accuracy and good reliability under harsh working conditions such as high temperature, high pressure and strong vibration.

[0006] The technical solution of the present invention is:

[0007] A magnetostrictive liquid level sensor suitable for high temperature / high pressure environment, the sensor comprises an electronic compartment, a pulse drive circuit, a detection coil, a control sampling module, a support, a simply supported beam spring, a mounting protrusion, a thermocouple, a permanent magnetic float, a probe rod, a magnetostrictive waveguide wire, a waveguide wire insulating sleeve, and a damping device;

[0008] The electronic warehouse is in the shape of a cuboid, with a through hole in the middle of the right side, a cylindrical protrusion outside the through hole, and threads on the inner and outer sides of the cylindrical mounting protrusion; the left side of the probe rod passes through the cylindrical protrusion and the through hole to enter the inner wall of the electronic warehouse; the circuit board is fixed in the electronic warehouse; the right end of the horizontal part of the L-shaped support is fixed on the inner wall of the right side of the electronic warehouse, and the vertical short end is at the left end of the horizontal part; a simply supported spring sheet is fixed on the left side of the horizontal part of the support, and the simply supported spring sheet is provided with a first damper, and the right end of the waveguide wire sleeve is provided with a second damper, the right end of the waveguide wire passes through the second damper and is fixed to the right side of the waveguide wire sleeve, and the left end of the waveguide wire passes through the first damper and is fixed to the left end of the support; a detection coil is sleeved on the waveguide wire 3 to 5 cm away from the first damper; 2 to 5 thermocouples are evenly spaced inside the waveguide wire insulating sleeve; the permanent magnetic float is sleeved on the outside of the probe rod at a position 55 to 65% of the probe rod length from the front end of the probe rod;

[0009] The horizontal axes of the electronic compartment, the two dampers, the detection coil and the waveguide wire are all the same;

[0010] The permanent magnetic float comprises a float housing, a center tube, a magnetic yoke, a permanent magnet, a clamping block, and a clamping ring, and includes the following two structures:

[0011] The first structure is that the outer shell of the float includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the hollow rods of the three parts are coaxial and penetrate to form a central tube; a circular permanent magnet is sleeved in the middle of the central tube, and a circular yoke with the same outer diameter is respectively fitted on the upper and lower parts of the circular permanent magnet; four identical clamping blocks are evenly distributed on the inner wall of the middle part of the cylindrical shell to clamp the aggregate "circular yoke-circular permanent magnet-circular yoke" (the height of the clamping block is greater than the sum of the thickness of "circular yoke-circular permanent magnet-circular yoke" by 4 to 6 mm); the clamping ring is fixed on the inner wall of the cylindrical tube and is respectively clamped on the upper and lower ends of the clamping block;

[0012] One side of the magnetic yoke is provided with a coaxial annular groove, and the annular grooves of the two magnetic yokes are arranged facing each other and are respectively closely attached to the two sides of the annular permanent magnet;

[0013] Alternatively, the second structure: the float shell includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the hollow rods of the three parts are coaxial and penetrate to form a central tube; four identical cylindrical permanent magnets are evenly spaced and symmetrically placed in the middle of the central tube, and the upper and lower parts of each cylindrical permanent magnet are respectively connected to one end of a quarter-circle arc column, and the other end of each arc column is fixed to the central tube; the four arc columns at the same end of the cylindrical permanent magnet form a four-claw yoke; that is, four groups of "arc column-cylindrical permanent magnet-arc column" aggregates form four handle-type structures, which are respectively fixed in four directions of the central tube; each cylindrical permanent magnet is clamped by a clamping block, and the clamping block is fixed on the inner wall of the cylindrical shell;

[0014] The circuit board is provided with a pulse drive circuit and a control sampling module; the pulse drive circuit is connected to both ends of the magnetostrictive waveguide wire, the control sampling module is respectively connected to the detection coil and three thermocouples, and the control sampling module is also connected to the pulse drive circuit;

[0015] The detection coil has 200 to 1200 turns and is wound into a hollow cylinder;

[0016] The material of the permanent magnet is samarium cobalt YX28, and the material of the yoke is electrical pure iron; the waveguide wire is a filamentary Fe-Ga or Fe-Co material;

[0017] The float shell is made of TC4 titanium alloy.

[0018] The material of the probe rod is non-ferromagnetic aluminum oxide.

[0019] The waveguide wire insulation sleeve is made of glass fiber tube.

[0020] The damping device is made of mesoporous silica aerogel.

[0021] The length of the probe rod is 0.8-2m, and the diameter is 18-24mm; the length of the float is 120-220mm, the outer diameter is 40mm-80mm, and the inner diameter is 16-24mm.

[0022] The essential features of the present invention are:

[0023] The magnetostrictive liquid level sensors currently on the market and those studied by the research team all use circular permanent magnets or block permanent magnets inside their floats. Their purpose is only to provide a bias magnetic field to the waveguide wire to generate a torsional wave. However, due to harsh environments such as high temperature, high pressure, and strong vibration, the magnetism of the permanent magnet will weaken and the position of the bias magnetic field generated by the permanent magnet will change, making it impossible to ensure that the position of the bias magnetic field provided by the permanent magnet to the waveguide wire is optimal. Such a shape design will result in little change in the strain of the waveguide wire. At this time, the corresponding sensor output voltage amplitude is low, which is not conducive to signal detection. The present invention relates to two solutions. The first solution adds two circular cover magnetic yokes to the float on the basis of the current design, sandwiches the annular permanent magnet in the middle, and enhances the strength of the bias magnetic field generated by the annular permanent magnet. The other solution is improved in the permanent magnet structure, using four cylindrical permanent magnets, which are symmetrically distributed around the waveguide wire. The centers of the four cylindrical permanent magnets are 20.5 mm away from the waveguide wire. At this time, the torsional strain of the waveguide wire reaches the maximum. Similarly, magnetic yokes are added to the four cylindrical permanent magnets to enhance the strength of the bias magnetic field generated by the permanent magnets.

[0024] The innovation of the first structure is the addition of a yoke, and the shape and structure of the yoke are designed to make it more suitable for circular permanent magnets (there is currently no magnetostrictive liquid level sensor on the market that can be used inside the float);

[0025] The innovation of the second structure lies in the distribution of the permanent magnets and the most suitable distance from the waveguide wire. A yoke is added and the shape and structure of the yoke are designed to make it more suitable for cylindrical permanent magnets.

[0026] The beneficial effects of the present invention are:

[0027] The current magnetostrictive liquid level sensor is limited by the Curie temperature of the Fe-Ni magnetostrictive waveguide wire and ferrite permanent magnet ring. When the high temperature of the application environment exceeds 100°C, the magnetism of the magnetic material and the permanent magnet gradually disappears, and the magnetostrictive liquid level sensor fails immediately. The waveguide wire uses the magnetic material Fe-Ga and Fe-Co wire, and the permanent magnet uses samarium cobalt material. Since they have a higher Curie temperature, the magnetostrictive liquid level sensor can be used in high temperature environments below 500°C. Moreover, the factors that affect the measurement of the liquid level are not only high temperature, but also high pressure in high temperature environments. Therefore, the float shell outside the permanent magnet also needs to be designed in structure and size so that it will not deform in a high pressure environment, provide a better placement environment for the internal permanent magnet, and keep the bias magnetic field stable. The designed titanium alloy float shell can withstand a pressure of up to 12MPa.

[0028] Specifically reflected in:

[0029] 1. Utilize the Widman effect of magnetostrictive Fe-Ga and Fe-Co filamentary materials to convert the position of the permanent magnetic float that rises and falls with the liquid level into a time-dependent voltage signal to accurately measure the liquid level. The waveguide wire uses Fe-Ga wire and Fe-Co wire, both of which are magnetostrictive materials with high Curie temperatures, which are not less than 600°C. The permanent magnet uses samarium cobalt, and the Curie temperature is not less than 670°C. This broadens the operating temperature range of the magnetostrictive liquid level sensor.

[0030] 2. To optimize the permanent magnet magnetic circuit in the float, two structures are designed: the first one is that four cylindrical permanent magnets of equal size are placed symmetrically along the axis of the central tube inside the float. Unlike other magnetostrictive liquid level sensors on the market, which have permanent magnets with the same polarity placed relative to each other, four cylindrical permanent magnets are placed vertically, with the N pole on the top and the S pole on the bottom. The relative placement of permanent magnets with the same polarity will cause the magnetic lines to generate two main peak magnetic fields in the axial direction, so there are two peaks in the magnetic field formed inside the waveguide wire, which is not conducive to the generation of elastic waves and affects the accuracy of the magnetostrictive liquid level sensor. When the permanent magnet is placed vertically, the magnetic field on the waveguide wire has only one peak, and the magnetic field formed inside the waveguide wire is more concentrated, so that the detection signal waveform can be distributed symmetrically with a single peak and a good slope. The second one is that a circular permanent magnet is used inside the float. When placing the circular permanent magnet, try to make the waveguide wire pass through the circular permanent magnet vertically and be in the center of the circular permanent magnet. Optimization: In the first structure, an arc-shaped cylindrical yoke is connected to the central tube. An arc-shaped cylindrical yoke is placed between the two circular surfaces of each cylindrical permanent magnet and the central tube. The magnetic lines of force are more concentrated on the waveguide wire through the yoke, making the magnetic field distribution on the waveguide wire more concentrated. In the second structure, a yoke is placed on each side of the ring permanent magnet. The yoke is in the shape of a circular cover and is sandwiched between two circular cover yokes. The magnetic field strength of the ring permanent magnet biased on the waveguide wire is enhanced by the magnetic conductive material yoke, so that the magnetic field generated on the waveguide wire is more concentrated and the magnetic field strength is stronger. The purpose of designing these two permanent magnet structures is to make the magnetic field strength of the bias magnetic field generated on the waveguide wire stronger, thereby significantly improving the output voltage of the magnetostrictive liquid level sensor, which is more conducive to signal detection; the purpose of adding a magnetic yoke to these two structures is because the magnetic yoke can play a magnetic conductive effect, so that the magnetic line beam is better concentrated around the waveguide wire, and the strength of the bias magnetic field generated by the permanent magnet on the waveguide wire is better enhanced, thereby enhancing the output characteristics of the sensor and facilitating signal detection.

[0031] 3. In order to optimize the float shell of the permanent magnetic float, the float shell is designed according to the structure of the internal permanent magnet, so that the magnetostrictive liquid level sensor can work normally under high pressure. The float shell consists of two hollow hemispheres with the same radius and a hollow cylinder. The center of the two hemispheres and the center of the cylinder are provided with a center tube. The two hollow hemispheres are connected to both sides of the hollow cylinder to form a sealed float shell with a through hole in the center. The stability of the float shell under high pressure is studied to provide a basis for the structural safety of the sensor under high pressure.

[0032] 4. It is proposed to preset the magnetostrictive waveguide wire sound velocity-temperature relationship in the sensor control sampling module, add a thermocouple to measure the sensor working temperature in real time, and extract the corresponding waveguide wire sound velocity in real time according to the working temperature to calculate the displacement, thereby reducing or even eliminating the measurement error caused by the change of sound velocity when the sensor works in the high temperature range, ensuring the accuracy of the sensor in the high temperature environment and optimizing the detection signal.

[0033] 5. Based on the above improvements, after simulation analysis, the structure of the permanent magnetic float is designed and optimized, and a magnetostrictive liquid level sensor for high temperature and high pressure conditions is designed. The designed magnetostrictive liquid level sensor can work for a long time in a high temperature and high pressure environment, with a high temperature of up to 350°C and a high pressure of up to 12Mpa. It ensures the accurate measurement of the magnetostrictive liquid level sensor in a high temperature and high pressure environment and optimizes the detection voltage signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the structural diagram of the magnetostrictive liquid level sensor;

[0035] FIG. 2( a ) is a cross-sectional view of the first permanent magnetic float structure; FIG. 2( b ) is a cross-sectional view of the second permanent magnetic float structure;

[0036] FIG3(a) is a top view of the structural cross-sectional view of the circular magnetic yoke in the first permanent magnetic float structure of the magnetic yoke; FIG3(b) is a bottom view of the structural cross-sectional view of the circular magnetic yoke in the first permanent magnetic float structure; FIG3(c) is a cross-sectional view from top to bottom of the structural cross-sectional view of the circular magnetic yoke in the first permanent magnetic float structure;

[0037] FIG4(a) is a front view of the float housing; FIG4(b) is a top view of the float housing; FIG4(c) is a cross-sectional view of the float housing from top to bottom;

[0038] FIG. 5( a ) is a diagram showing a magnetic circuit structure of a first type of permanent magnet and a magnetic yoke; FIG. 5( b ) is a diagram showing a magnetic circuit structure of a second type of permanent magnet and a magnetic yoke;

[0039] FIG6(a) is a diagram showing the magnetic field intensity of a magnetic circuit structure composed of a first permanent magnet and a magnetic yoke on a waveguide wire; FIG6(b) is a diagram showing the magnetic field intensity of a magnetic circuit structure composed of a second permanent magnet and a magnetic yoke on a waveguide wire;

[0040] Figure 7 This is the simulation result diagram of the eigenvalue buckling analysis of the float shell using ANSYS software;

[0041] Figure 8 The measured and fitted curves of the torsional wave velocity of Fe-Ga and Fe-Co waveguide wires changing with temperature;

[0042] FIG9(a) is a graph comparing the output voltages of a magnetostrictive liquid level sensor whose waveguide wire is Fe-Ga and adopts different permanent magnet structures; FIG9(b) is a graph comparing the output voltages of a magnetostrictive liquid level sensor whose waveguide wire is Fe-Co and adopts different permanent magnet structures. DETAILED DESCRIPTION

[0043] The invention is further described in detail below in conjunction with the figures. This embodiment is only a specific description of the invention and is not to be regarded as limiting the scope of protection.

[0044] The structure of the magnetostrictive liquid level sensor suitable for high temperature and high pressure of the present invention is as follows: Figure 1 As shown, it includes an electronic compartment 1, a pulse drive circuit 2, a detection coil 3, a control sampling module 4, a support 5, a simply supported beam spring 6, a mounting protrusion 7, a thermocouple 8, a permanent magnetic float 9, a probe rod 10, a magnetostrictive waveguide wire 11, a waveguide wire insulating sleeve 12, and a damping device 13;

[0045] The electronic warehouse 1 is in the shape of a rectangular parallelepiped, with a through hole in the middle of the right side, a cylindrical protrusion outside the through hole, and threads on the inner and outer sides of the cylindrical mounting protrusion 7; the left side of the probe rod 10 passes through the cylindrical protrusion and the through hole to enter the inner wall of the electronic warehouse 1; the U-shaped circuit board opening faces the right wall of the electronic warehouse 1; the right end of the horizontal part of the L-shaped support 5 is fixed to the inner wall of the right side of the electronic warehouse 1, and the vertical short end is at the left end of the horizontal part; a simply supported spring sheet 6 is fixed on the left side of the horizontal part of the support 5, and a damper 13 (first damper) is provided on the simply supported spring sheet 6, Another damper 13 (second damper) is provided at the right end of the waveguide wire sleeve 12, the right end of the waveguide wire 11 passes through the second damper and is fixed to the right inner part of the waveguide wire sleeve 12, and the left end of the waveguide wire 11 passes through the first damper and is fixed to the left end of the support 5; a detection coil 3 is sleeved on the waveguide wire 4 cm away from the first damper; three thermocouples are evenly spaced inside the waveguide wire insulating sleeve 12; the permanent magnetic float 9 is sleeved on the outside of the probe rod 10 at a position of 55-65% of the probe rod length (60% in this embodiment) from the front end of the probe rod (that is, the through hole on the right side of the electronic compartment);

[0046] The horizontal axes of the electronic compartment 1, the two dampers 13, the detection coil 3 and the waveguide wire 11 are all the same.

[0047] The circuit board is provided with a pulse drive circuit 2 and a control sampling module 4; the size of each circuit board shall not exceed the housing of the sensor head and they are fastened together with screws, and the wiring shall be firm to avoid short circuit or open circuit.

[0048] The electronic compartment 1 of the magnetostrictive liquid level sensor is shaped as a cube of 200mm*160mm*200mm. The internal circuit board is equipped with the circuit of the entire sensor, including a pulse drive circuit 2, a control sampling module 4 (timing circuit part, filter circuit part, detection signal processing circuit part), etc., which can issue instructions and calculate and process these data.

[0049] The pulse drive circuit 2 is arranged in the cubic component compartment at the left end of the probe rod 10, and connects the two ends of the waveguide wire 11. The pulse drive circuit 2 is a well-known circuit, including an AC-DC switching power supply circuit and a PWM circuit, which are then integrated through a circuit board. Here is a brief introduction: the circuit is divided into two stages. The front stage is an AC-DC switching power supply circuit that converts AC220V into DC30V. The circuit topology adopts a single-ended flyback circuit. The back stage is a PWM circuit composed of a CD4013 trigger that sends a PWM signal to the gate drive of the chopper MOS tube. Through the isolation of the optical coupler 6N137, it is output through the push-pull structure of the transistor D772\D882. The obtained level signal is chopped into a square pulse wave with a pulse width of 7 microseconds by IRFP4137. After receiving the trigger signal sent by the control sampling module 4, the circuit works and outputs a square pulse wave with an amplitude of 30V and a pulse width of 7 microseconds.

[0050] The detection coil 3 is wound with 0.2mm diameter enameled wire, wound into a hollow cylinder, wound 600 turns, the finished product has an inner diameter of 4mm, an outer diameter of 8mm, and a length of 15mm. It is located on the right side of the support 5 in the electronic compartment at the left end of the probe rod 10, and is sleeved on the left end of the waveguide wire 11 to receive the elastic torsion wave signal. The time interval from the pulse generation to the reception of the torsion wave signal is calculated by controlling the sampling module 4.

[0051] The control sampling module 4 is arranged in the cubic electronic compartment at the left end of the probe rod 10, connected to the detection coil 3, and connected to the pulse drive circuit 2. The control sampling module 4 is a well-known module, including a control system circuit, a liquid crystal display module, a differential amplifier circuit, a comparison circuit, and a timing circuit, which are then integrated together through a circuit board. Here is a brief introduction: MCU is the core control system circuit, and the main control chip uses MSP430F149; RS232, ISP and JTAG interfaces are integrated on the control board, and it has a 1602 liquid crystal display module. The control system circuit transmits the starting pulse signal, and the detection coil 3 receives the pulse signal, respectively through: the differential amplifier circuit, the signal collected by the detection coil 3 is connected, and the TDA2050 excitation pulse power amplifier circuit is used as an amplifier, and the amplified output signal is used as the input signal of the comparison circuit; the comparison circuit uses a single voltage comparator LM311 for comparison output, and uses a level conversion circuit to convert the amplitude of the comparison voltage into 3.3V that meets the TDC-gp2 configuration; the timing circuit uses the TDC-gp2 time measurement chip, and the A / D conversion unit uses a 16-bit AD7705 analog voltage digital converter. The pulse signal output by the comparison circuit is used as the termination signal of the timing circuit. After the time timing is completed, the time data will be read by the control system, and the control circuit presets the waveguide wire sound velocity v-temperature T curve. According to the average temperature measured by the three thermocouples as the ambient temperature T, the sound velocity v at the corresponding temperature is extracted in real time, and according to the time interval t between the moment when the detection coil senses the torsional wave signal of the active magnetic ring and the moment when the driving pulse is generated, the measured displacement s=t*v at the corresponding temperature can be finally obtained, and the obtained position information will be displayed on the liquid crystal by the control system.

[0052] The pulse driving circuit 2 is connected to both ends of the magnetostrictive waveguide wire 11 , and the control sampling module 4 is respectively connected to the detection coil 3 and the three thermocouples 8 . The control sampling module 4 is also connected to the pulse driving circuit 2 .

[0053] A constant elastic force device is composed of a support 5, a simply supported beam spring 6 and a damper 13 (the first damper), which is located in the electronic compartment 1 on the left side of the probe rod 10 and supports the waveguide wire 11 in the waveguide wire insulating sleeve 12 to be relatively horizontal with the sleeve. The support is L-shaped, with the vertical end located on the left side of the horizontal end; a simply supported beam spring piece 6 is arranged on the upper part of the right side of the horizontal end, and a damper 13 (the first damper) is arranged on the simply supported beam spring piece 6. The right end of the horizontally arranged waveguide wire 11 passes through another damper 13 (the second damper) and is fixed to the right center of the hollow tube of the probe rod 10, and the left end passes through the damper 13 (the first damper) and is connected to the left side of the vertical end of the support 5, and the waveguide wire 11 of this part forms an angle of 25° with the horizontal; the simply supported beam spring piece 6 is made of 3J53 constant elastic alloy and has a size of 50mm*30mm*1.5mm, and is mounted under the waveguide wire 11 with the damper 13 (the first damper). The simply supported beam spring piece 6 is hinged at one end and fixed at the other end to the support 5. Due to the pre-tension of the waveguide wire 11, the simply supported beam spring piece 6 is subjected to a certain positive bending moment. The simply supported beam spring piece 6 of constant elastic alloy material applies constant stress perpendicular to the waveguide wire. When the temperature changes, the elasticity of the simply supported beam spring piece 6 does not change with the temperature, ensuring that the tension of the waveguide wire 11 is constant. The support 5 is made of stainless steel with a material grade of 430 and has a slope angle of 15° with the horizontal direction. One end of the support simply supported beam spring piece and the support are hinged and the other end is fixed. The device is suitable for high temperature environments with different temperatures, using a simply supported beam structure to adjust stress and absorb torsional wave signals reflected from the fixed end.

[0054] The cylindrical protrusion 7 is made of 45# steel, with a specification of M30*2, and is located at the connection between the electronic compartment 1 and the probe rod 10. The installation thread is to facilitate the installation of the sensor on the canned liquid equipment, strengthen the overall fixation of the sensor, and reduce the vibration of the sensor itself.

[0055] The thermocouple 8 is an OMEGACO2-K adhesive fast response thermocouple. The continuous use temperature is 550°C. Three thermocouples are provided, evenly distributed on the lower side of the inner wall of the waveguide wire insulating sleeve 12 in the right housing, and are 38cm, 68cm, and 98cm away from the detection coil respectively.

[0056] The structure of the permanent magnetic float 9 is shown in FIG. 2 , and includes a float housing 91 , a center tube 92 , a yoke 93 , a permanent magnet 94 , a clamping block 95 , and a clamping ring 96 .

[0057] The magnetic circuit composed of the permanent magnet and the magnetic yoke has two structures.

[0058] The first structure is shown in FIG2(a): the float housing 91 includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the hollow rods of the three parts are coaxial and penetrate to form a central tube 92; a circular permanent magnet 94 is sleeved in the middle of the central tube 92, and a circular yoke 93 with the same outer diameter is respectively fitted on the upper and lower parts of the circular permanent magnet 94; four identical clamping blocks 95 are evenly spaced on the inner wall of the middle part of the cylindrical shell, clamping the aggregate "circular yoke 93-circular permanent magnet 94-circular yoke 93" (the height of the clamping block 95 is greater than the thickness value of "circular yoke 93-circular permanent magnet 94-circular yoke 93" and 5mm); a clamping ring 96 is fixed on the inner wall of the cylindrical tube and is respectively clamped on the upper and lower ends of the clamping block 95;

[0059] A circular permanent magnet 94 is sleeved in the middle of the central tube. The material is samarium cobalt YX28, with an outer diameter of 44 mm, an inner diameter of 28 mm, and a height of 15 mm. The center of the circular permanent magnet is 18 mm away from the waveguide wire.

[0060] A circular yoke 93 is placed above and below the permanent magnet 94. The yoke is made of electrical pure iron, with a wall thickness of 2 mm. Its outer diameter and inner diameter are the same as those of the permanent magnet, 44 mm and 28 mm, and its height is 10 mm. A coaxial circular groove (with a rectangular cross section) is opened on one side of the yoke 93. The circular grooves of the two yokes are placed facing each other and are respectively attached to the two sides of the circular permanent magnet 94 to form their own air ring areas. The specific structure of the "hollow" circular yoke 93 is shown in FIG3 ; the outer diameter of the circular groove is 40 mm, the inner diameter is 32 mm, and the height is 8 mm;

[0061] Four clamping blocks 95 are symmetrically placed on the outer ring surface of the circular permanent magnet 94 and the yoke 93. The material is stainless steel 316L, with specifications of 10 mm in length, 6.5 mm in width and 40 mm in height. The function of the clamping blocks 95 is to fix the relative positions of the circular yoke 93 and the circular permanent magnet 94. A retaining ring 96 is placed under the clamping block 95. The material is 316L, with specifications of 57 mm in outer diameter, 24 mm in inner diameter and 2 mm in height. The inner diameter of the retaining ring matches the outer diameter of the center tube. The retaining ring 96 is a blocking device used to prevent the yoke 93, the permanent magnet 94 and the clamping block 95 from sliding in position. It can also play the role of supporting the clamping block 95. A 2.5 mm gap is set between the yoke 93 and the retaining ring 96 through the clamping block 95.

[0062] The second structure is shown in FIG2(b): the float housing 91 includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the three hollow rods are coaxial and penetrate to form a central tube 92; four identical cylindrical permanent magnets 94 are placed evenly and symmetrically (i.e., front, back, left, and right) in the middle of the central tube 92, and the upper and lower ends of each cylindrical permanent magnet 94 are respectively connected to one end of a quarter-circle arc column, and each arc column is connected to the outer diameter of the probe rod. The other end of the column is connected to the center tube 92; the four arc columns at the same end of the cylindrical permanent magnet 94 form a four-claw type yoke 93 connected; the four groups of "arc column-cylindrical permanent magnet-arc column" aggregates form four handle-type structures, which are respectively fixed in four directions of the center tube 92; each cylindrical permanent magnet 94 is clamped by a clamping block 95, and the clamping block 95 is fixed on the inner wall of the cylindrical shell; this is because there is a large space between the permanent magnet 94 and the inner wall of the middle part of the cylindrical shell of the float shell 91, and the clamping block 95 is used to fill it to further reinforce the permanent magnet 94;

[0063] Four cylindrical permanent magnets 94 are symmetrically placed at the front, back, left and right of the middle part of the central tube 92. The permanent magnet material is samarium cobalt YX28, with a diameter of 10mm and a height of 12mm. The center of the cylindrical permanent magnet is 20.5mm away from the waveguide wire; the cylindrical permanent magnet 94 is connected to the central tube through a yoke 93. The yoke material is electrical pure iron and is in the shape of a quarter of a circular ring with an outer diameter of 27mm and an inner diameter of 7mm. The diameter of the ring circular surface is 10mm, which is the same as and connected to the circular surface of the cylindrical permanent magnet. Each upper and lower circular surface of each cylinder has a yoke connected thereto, and the other end of the yoke is connected to the central tube 92; a clamping block 95 is placed outside each cylindrical permanent magnet 94. The clamping block 95 is made of 316L and has a specification of 6mm in length, 3mm in width and 6mm in height. The relative position of the permanent magnet 94 is fixed by the clamping block 95, and there is no shaking, so that the structure is more secure.

[0064] The connection between the permanent magnet 94 and the yoke 93 inside the float housing 91, as well as the connection between the yoke 93 and the center tube, are bonded using HR-8767A alumina high-temperature adhesive, which is a high-temperature resistant adhesive made from high-temperature resistant materials through a condensation reaction. It can maintain good bonding properties and corrosion resistance at high temperatures and has a long service life.

[0065] The structure of the float shell 91 is shown in FIG4 . The entire float shell is made of TC4 titanium alloy and consists of two hemispherical shells with a wall thickness of 1.5 mm and an outer diameter of 60 mm and a cylindrical shell with a wall thickness of 1.5 mm, a round surface outer diameter of 60 mm and a height of 120 mm. The cylindrical shell is combined with a hemispherical shell on the upper and lower sides, and the overall length is 180 mm. A central tube is arranged in the center of the hemispherical shell and the cylindrical shell, and then connected by riveting to form a sealed "capsule" body with a through hole in the center. The inner diameter of the central tube needs to match the outer diameter of the probe rod 10 (the matching is that the inner diameter of the central tube is 1 to 2 mm larger than the outer diameter of the probe rod), which is 22 mm, the outer diameter is 24 mm, and the wall thickness is 1 mm. The permanent magnetic float 9 is sleeved on the right end of the probe rod 10 and moves on the tubular probe rod with the liquid level to be measured.

[0066] The distribution of magnetic field intensity generated on the waveguide wire 11 by the two magnetic circuit structures composed of the permanent magnet 94 and the magnetic yoke 93 is shown in Figure 6. The magnetic lines of force generate a main peak magnetic field in the axial direction, which is reflected in the appearance of a peak in the detection voltage waveform. The detection voltage signal waveform presents a standard axially symmetrical graph. The moment when the symmetry axis displayed by the voltage waveform is detected is the propagation moment of the torsional wave generated by the permanent magnet at the object position, thereby improving the measurement accuracy of the sensor.

[0067] The finite element ANSYS software provides an eigenvalue buckling analysis method, which belongs to structural linear analysis and is currently mainly used to predict the theoretical buckling strength of an ideal linear elastic structure. The ANSYS software is used to perform an eigenvalue buckling analysis on the float shell 91 of the permanent magnetic float to predict the maximum critical pressure value that the float shell 91 can withstand under ideal conditions. The simulation results are shown in the figure. Figure 7 Before performing the characteristic value buckling analysis on the float housing 91, a pressure value of 1Pa is applied to the outside as an external pressure load. After the buckling analysis, the characteristic value can be calculated to be 0.186*10 8 Finally, it is calculated that the buckling load of the float shell 91 is 18.6MPa, that is, the maximum critical pressure that the float shell 91 can withstand is 18.6MPa, and the maximum deformation occurs in the middle part of the cylindrical body of the float shell 91.

[0068] The probe rod 10 is a hollow structure made of non-ferromagnetic alumina with a temperature resistance of 1000°C. The left side is a 200mm*160mm*200mm cubic electronic warehouse, and the right side is a hollow probe rod with an outer diameter of 20mm, a length of 1000mm, and a wall thickness of 4mm. The two are connected in the middle, closed at both ends, and have the same central axis. The waveguide wire 11 and the waveguide wire insulation protection sleeve 12 extend into the probe rod 10, and the permanent magnetic float 9 is sleeved on the probe rod 10.

[0069] The magnetostrictive waveguide wire 11 is made of filamentous Fe-Ga or Fe-Co material, 1000 mm long and 0.8 mm in diameter. The right end of the waveguide wire 11 passes through the damper 13 (the second damper) and is fixed to the right end of the sensor probe 10. The left end of the waveguide wire 11 passes through the detection coil 3 and is inserted into the damper 13 (the first damper) mounted on the simply supported beam spring piece 6. After passing the beam piece, the waveguide wire is fixed to the support 5 3 cm away from the simply supported beam spring piece at a tensile stress of 1 MPa in a direction with an angle of 25° to the horizontal.

[0070] The waveguide wire insulation sleeve 12 is located in the hollow tube on the right side of the probe rod 10, and is sleeved on the waveguide wire 11. It serves as insulation between the waveguide wire 11 and the sensor probe rod 10, and reduces the torsional friction with the probe rod. Its main function is to provide electrical insulation. It is made of glass fiber tube: temperature resistance 600℃; diameter 8mm; temperature range -30℃~+600℃; working voltage: 500V~800V; it is woven with alkali-free glass fiber yarn, and then impregnated with a small amount of silane adhesive after high temperature treatment to form an insulation tube with the characteristics of high temperature resistance and softness. It serves as insulation between the waveguide wire and the sensor housing, and reduces the torsional friction with the housing.

[0071] The damper 13 (the second damper) at the right end of the sensor probe 10 is the same as the damper 13 (the first damper) on the support 5, which is cylindrical with a diameter of 16 mm and a height of 22 mm. The material is mesoporous silica aerogel, which is nested at the head and tail ends of the waveguide wire to block heat and sound transfer and suppress echo noise.

[0072] Embodiment 1:

[0073] according to Figure 1 As shown in the figure, a high-temperature, high-pressure magnetostrictive liquid level sensor is assembled, and the shape, material and size of its related components are the same as described above, wherein the permanent magnet and the magnetic yoke form a first magnetic circuit structure, as shown in FIG2(a), and its magnetostrictive waveguide wire 11 is made of filamentous Fe-Ga;

[0074] Embodiment 2:

[0075] The other components and connection relationships are the same as those in Example 1, except that the magnetostrictive waveguide wire 11 is made of filamentous Fe-Co;

[0076] Embodiment 3:

[0077] according to Figure 1 As shown in the figure, a high-temperature, high-pressure magnetostrictive liquid level sensor is assembled, and the shape, material and size of the related components are the same as described above, wherein the permanent magnet and the magnetic yoke form a second magnetic circuit structure, as shown in FIG2(b), and a high-temperature, high-pressure magnetostrictive liquid level sensor is assembled, and its magnetostrictive waveguide wire 11 adopts filamentous Fe-Ga;

[0078] Embodiment 4:

[0079] Other components and connection relationships are the same as those in Example 3, except that the magnetostrictive waveguide wire 11 is made of filamentous Fe-Co;

[0080] Comparative Example 1:

[0081] The other components and connection relationships are the same as those in Example 1, except that the yoke structure is removed;

[0082] Comparative Example 2:

[0083] Other compositions and connection relationships are the same as those in comparison 1, except that the magnetostrictive waveguide wire 11 is made of filamentous Fe-Co.

[0084] Device performance test:

[0085] (1) Test in a high temperature environment to verify the measurement accuracy of the magnetostrictive liquid level sensor.

[0086] Experimental platform construction: The detection coil is 70mm away from the top of the waveguide wire, and the permanent magnetic float is 680mm away from the detection coil. The Fe-Ga and Fe-Co waveguide wires are placed in a high-temperature furnace and tested at a temperature range of 25℃ to 500℃.

[0087] Experimental process and results: Figure 8 As shown in the figure, the sound velocity of Fe-Ga and Fe-Co waveguide wires changes at different temperatures, and the displacement needs to be compensated for different temperature fields. According to the measured fitting curve, the sound velocity of Fe-Ga wire v = 2769.2685-0.27072*T, the sound velocity of Fe-Co wire v = 2665.45952-0.265*T, where T is the average temperature measured by the thermocouple. The time interval t between the moment when the detection coil senses the torsional wave signal of the active magnetic ring and the moment when the drive pulse is generated, the detection displacement s = t*v is obtained.

[0088] (2) The reliability of the device signal of the magnetostrictive liquid level sensor with Fe-Ga and Fe-Co waveguide wires under two permanent magnet structures at high temperature is tested respectively, and then compared with the magnetostrictive liquid level sensor with a circular ring structure of the permanent magnet inside the float. The main purpose of this embodiment is to verify the reliability of the output voltage of the two permanent magnet structures under high temperature.

[0089] Experimental platform construction: The detection coil is 70mm away from the top of the waveguide wire, and the permanent magnetic float is 680mm away from the detection coil. Fe-Ga and Fe-Co magnetostrictive liquid level sensors are used to test four devices with two designs of permanent magnet structures (i.e., Examples 1-4) and a reference permanent magnet structure (using a circular permanent magnet structure - i.e., Comparative Examples 1-2). They are placed in a high-temperature furnace for testing at 25°C to 550°C, and an external excitation is applied by a signal generator. The output voltage waveform of the detection coil is observed by an oscilloscope.

[0090] Experimental process and results: As shown in Figure 9 (a) and Figure 9 (b), the output voltage of Fe-Ga is higher than that of Fe-Co. In these two figures, the order of the measured voltage waveforms is respectively Fe-Ga (1) corresponding to the output voltage measured by using the waveguide wire of Fe-Ga and the permanent magnet structure of Figure 2 (a) (i.e., Example 1); Fe-Ga (2) corresponding to the output voltage measured by using the waveguide wire of Fe-Ga and the permanent magnet structure of Figure 2 (b) (i.e., Example 3); Fe-Ga (3) corresponding to the output voltage measured by using the waveguide wire of Fe-Ga and the permanent magnet structure of the ring permanent magnet (i.e., Comparative Example 1); It can be observed that the detection voltage signal of the structure of Figure 2 (a) is better than the detection voltage signal of the structure of Figure 2 (b), and the output voltage signals of the permanent magnets of these two structures are better than the output voltage signals of the ring permanent magnet structure.

[0091] The order of the measured voltage waveforms is respectively Fe-Co (1) corresponding to the waveguide wire of Fe-Co and the permanent magnet structure (ie, Example 2) using Figure 2 (a) to measure the output voltage; Fe-Co (2) corresponding to the waveguide wire of Fe-Co and the permanent magnet structure (ie, Example 4) using Figure 2 (b) to measure the output voltage; Fe-Co (3) corresponding to the waveguide wire of Fe-Co and the permanent magnet structure using a ring permanent magnet (ie, Comparative Example 2) to measure the output voltage; It can be observed that the detection voltage signal of the structure of Figure 2 (a) is better than the detection voltage signal of the structure of Figure 2 (b), and the output voltage signals of the permanent magnets of these two structures are also better than the output voltage signals of the ring permanent magnet structure. The experimental results show that at high temperatures, the magnetic circuit structure composed of the permanent magnet and the magnetic yoke of the magnetostrictive liquid level sensor using the two structures of Figure 2 (a) and Figure 2 (b) is much better than the output voltage signal measured by the ring permanent magnet on the market.

[0092] The software or protocols involved in the sensor application of the present invention are all well-known technologies.

[0093] The present invention aims to solve the problem that the magnetostrictive liquid level sensor may reduce the measurement accuracy under high temperature and high pressure, and improves the structure of the permanent magnetic float of the sensor to improve its applicability:

[0094] 1. The stability of the float is an important issue to be considered in practical applications. The structure of the float and its internal permanent magnet has been improved. When used in high-pressure environments, the overall structure of the float shell needs to be designed so that it has good pressure resistance and will not deform under external pressure. When subjected to external pressure, its circumferential stress manifests as compressive stress. When the compressive stress exceeds a certain critical value, the structure will lose its original geometric shape, and overall or partial buckling of the structure will occur. The purpose of studying the stability of the float shell under external pressure is to grasp its critical load and corresponding instability mode, and to provide a basis for its safety and rationality of structural design.

[0095] 2. The bias magnetic field provided by the float requires a large magnetic field strength and is not easily affected by the external temperature. In order to enhance the output characteristics of the sensor at high temperatures, the structure of the permanent magnetic float is designed and optimized. By designing the shape, size, and distance of the permanent magnet from the center tube, an optimal bias magnetic field position is selected. And a magnetic yoke is added to compensate for the weakening of the magnetism of the magnet at high temperatures. The magnetic yoke can constrain the magnetic lines generated by the permanent magnet to scatter outward, allowing the magnetic lines to be better introduced into the waveguide wire inside the center tube through the magnetic yoke, so that the magnetic line beam is concentrated around the waveguide wire to increase the magnetic field strength, thereby enhancing the output characteristics of the sensor. The axial magnetic field is the amount that characterizes the displacement of the permanent magnet in the float. After meeting the circumferential magnetic field formed by the current on the waveguide wire, the vector superposition forms a spiral magnetic field. By improving the structure of the permanent magnet and adding a magnetic yoke, the magnetic field strength of the spiral magnetic field is well concentrated and has a good peak value, which further increases the detection voltage amplitude and improves the measurement accuracy of the sensor.

[0096] 3. Three thermocouples are placed at the front, middle and rear ends of the waveguide wire protection sleeve to measure the ambient temperature of the waveguide wire in real time. In order to ensure the measurement accuracy of the sensor in a large temperature range, this patent proposes a sensor structure design suitable for high temperature environments. By presetting the measured sound velocity-temperature curve of the Fe-Ga and Fe-Co waveguide wires and saving them in the single-chip microcomputer of the detection circuit, the working temperature is detected in real time through the three thermocouples at the front, middle and rear ends of the sensor protection sleeve. The sensor extracts the corresponding waveguide wire sound velocity at this temperature to calculate the displacement, eliminating the measurement error caused by temperature.

[0097] In the present invention, when the magnetostrictive liquid level sensor is working, the pulse driving circuit generates a pulse voltage applied to both ends of the waveguide wire. The pulse can cause the waveguide wire to generate a circumferential magnetic field. When the circumferential magnetic field propagates to the position of the active permanent magnetic float, it is superimposed with the axial magnetic field generated by the permanent magnetic float to form a spiral magnetic field. Based on the Widmann effect, the waveguide wire is instantly deformed and generates a torsion wave, which propagates to both ends of the waveguide wire at a certain speed. When the detection coil senses the torsion wave signal, the time interval between this moment and the moment when the driving pulse is generated multiplied by the torsion wave sound velocity is the current position of the permanent magnetic float. The device adds a thermocouple in order to measure the temperature-corrected torsion wave sound velocity in real time and compensate for the waveguide wire sound velocity in the changing temperature field. In order to ensure that the waveguide wire is measured under constant tension at high temperature, a constant elastic force device consisting of a support, a simply supported beam spring and a damping device is set on the end face of one side of the waveguide wire detection coil. In order to optimize the permanent magnet magnetic circuit in the float, in terms of structure, the geometric parameters of the permanent magnet, the placement of the permanent magnet, and the distance between the permanent magnet and the waveguide wire should be considered to maximize the strain of the waveguide wire as much as possible. At this time, the output voltage amplitude of the sensor is high, which is conducive to signal detection; in terms of optimization, a magnetic yoke is added to the permanent magnet, which can play a magnetic conductive effect, so that the magnetic line beam is better concentrated around the waveguide wire, and the strength of the bias magnetic field generated by the permanent magnet on the waveguide wire is enhanced, thereby enhancing the output characteristics of the sensor. In order to optimize the reliability of the float shell, titanium alloy materials are selected and its structure and the dimensions of each part are designed to improve the yield strength of the structure, providing a basis for its safety and structural rationality. Based on the above improvements, the configuration of each part of the magnetostrictive liquid level sensor is optimized, and a magnetostrictive liquid level sensor for high temperature and high pressure conditions is designed. Through simulation analysis, the accurate measurement of the magnetostrictive liquid level sensor in high temperature and high pressure environments is guaranteed and the detection signal is optimized.

[0098] Based on the above improvements, after a large number of experiments and optimization of the configuration of each part, a magnetostrictive liquid level sensor suitable for high temperature and high pressure environments was designed. The sensor can obtain detection signals and optimize the detection signals.

[0099] Matters not covered by the present invention are known technologies.

Claims

1. A magnetostrictive liquid level sensor suitable for high temperature / high pressure environment, characterized by The sensor includes an electronic compartment, a pulse drive circuit, a detection coil, a control sampling module, a support, a simply supported beam spring, a mounting protrusion, a thermocouple, a permanent magnetic float, a probe rod, a magnetostrictive waveguide wire, a waveguide wire insulating sleeve, and a damping device; The electronic warehouse is in the shape of a cuboid, with a through hole in the middle of the right side, a cylindrical protrusion outside the through hole, and threads on the inner and outer sides of the cylindrical mounting protrusion; the left side of the probe rod passes through the cylindrical protrusion and the through hole to enter the inner wall of the electronic warehouse; the circuit board is fixed in the electronic warehouse; the right end of the horizontal part of the L-shaped support is fixed on the inner wall of the right side of the electronic warehouse, and the vertical short end is at the left end of the horizontal part; a simply supported spring sheet is fixed on the left side of the horizontal part of the support, and the simply supported spring sheet is provided with a first damper, and the right end of the waveguide wire sleeve is provided with a second damper, the right end of the waveguide wire passes through the second damper and is fixed to the right side of the waveguide wire sleeve, and the left end of the waveguide wire passes through the first damper and is fixed to the left end of the support; a detection coil is sleeved on the waveguide wire 3 to 5 cm away from the first damper; 2 to 5 thermocouples are evenly spaced inside the waveguide wire insulating sleeve; the permanent magnetic float is sleeved on the outside of the probe rod at a position 55 to 65% of the probe rod length from the front end of the probe rod; The permanent magnetic float comprises a float housing, a center tube, a magnetic yoke, a permanent magnet, a clamping block, and a clamping ring, and includes the following two structures: The first structure is that the outer shell of the float includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the hollow rods of the three parts are coaxial and penetrate to form a central tube; a circular permanent magnet is sleeved in the middle of the central tube, and a circular yoke with the same outer diameter is fitted on the upper and lower parts of the circular permanent magnet; four identical clamping blocks are evenly spaced on the inner wall of the middle part of the cylindrical shell to clamp the aggregate "circular yoke-circular permanent magnet-circular yoke"; the clamping ring is fixed on the inner wall of the cylindrical tube and is respectively clamped on the upper and lower ends of the clamping block; One side of the magnetic yoke is provided with a coaxial annular groove, and the annular grooves of the two magnetic yokes are arranged facing each other and are respectively closely attached to the two sides of the annular permanent magnet; Alternatively, the second structure: the float shell includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the hollow rods of the three parts are coaxial and penetrate to form a central tube; four identical cylindrical permanent magnets are evenly spaced and symmetrically placed in the middle of the central tube, and the upper and lower ends of each cylindrical permanent magnet are respectively connected to one end of a quarter-circle arc column, and the other end of each arc column is fixed to the central tube; the four arc columns at the same end of the cylindrical permanent magnet form a four-claw type yoke; that is, four groups of "arc column-cylindrical permanent magnet-arc column" aggregates form four handle-type structures, which are respectively fixed in four directions of the central tube; each cylindrical permanent magnet is clamped by a clamping block, and the clamping block is fixed on the inner wall of the cylindrical shell.

2. The magnetostrictive liquid level sensor suitable for high temperature / high pressure environment as described in claim 1 is characterized in that a pulse drive circuit and a control sampling module are distributed on the circuit board; the pulse drive circuit is connected to both ends of the magnetostrictive waveguide wire, the control sampling module is respectively connected to the detection coil and three thermocouples, and the control sampling module is also connected to the pulse drive circuit.

3. The magnetostrictive liquid level sensor suitable for high temperature / high pressure environment as described in claim 1, characterized in that the detection coil has 200 to 1200 turns and is wound into a hollow cylinder.

4. The magnetostrictive liquid level sensor suitable for high temperature / high pressure environment as claimed in claim 1, characterized in that The material of the permanent magnet is samarium cobalt YX28, and the material of the magnetic yoke is electrical pure iron; the waveguide wire is a filamentary Fe-Ga or Fe-Co material.

5. The magnetostrictive liquid level sensor suitable for high temperature / high pressure environment as claimed in claim 1, characterized in that The float shell is made of TC4 titanium alloy.

6. The magnetostrictive liquid level sensor suitable for high temperature / high pressure environment as claimed in claim 1, characterized in that The material of the probe rod is non-ferromagnetic aluminum oxide; the material of the waveguide wire insulation sleeve is a glass fiber tube; and the material of the damping device is mesoporous silica aerogel.

7. The magnetostrictive liquid level sensor suitable for high temperature / high pressure environment as described in claim 1 is characterized in that the length of the probe rod is 0.8 to 2 m and the diameter is 18 to 24 mm; the length of the float is 120 to 220 mm, the outer diameter is 40 to 80 mm, and the inner diameter is 16 to 24 mm.

8. The magnetostrictive liquid level sensor suitable for high temperature / high pressure environment as claimed in claim 1, characterized in that the height of the clamping block is greater than the sum of the thicknesses of "circular yoke-circular permanent magnet-circular yoke" by 4 to 6 mm.

9. A permanent magnetic float, characterized by comprising a float housing, a center tube, a yoke, a permanent magnet, a clamping block, and a clamping ring, including the following two structures: The first structure is that the outer shell of the float includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the hollow rods of the three parts are coaxial and penetrate to form a central tube; a circular permanent magnet is sleeved in the middle of the central tube, and a circular yoke with the same outer diameter is fitted on the upper and lower parts of the circular permanent magnet; four identical clamping blocks are evenly spaced on the inner wall of the middle part of the cylindrical shell to clamp the aggregate "circular yoke-circular permanent magnet-circular yoke"; the clamping ring is fixed on the inner wall of the cylindrical tube and is respectively clamped on the upper and lower ends of the clamping block; One side of the magnetic yoke is provided with a coaxial annular groove, and the annular grooves of the two magnetic yokes are arranged facing each other and are respectively closely attached to the two sides of the annular permanent magnet; Alternatively, the second structure: the float shell includes a cylindrical shell in the middle and hemispherical shells at the upper and lower ends, and the three parts form a sealed "capsule" body; the three parts have a hollow rod in the middle with an inner diameter matching the outer diameter of the probe rod, and the hollow rods of the three parts are coaxial and penetrate to form a central tube; four identical cylindrical permanent magnets are evenly spaced and symmetrically placed in the middle of the central tube, and the upper and lower ends of each cylindrical permanent magnet are respectively connected to one end of a quarter-circle arc column, and the other end of each arc column is fixed to the central tube; the four arc columns at the same end of the cylindrical permanent magnet form a four-claw type yoke; that is, four groups of "arc column-cylindrical permanent magnet-arc column" aggregates form four handle-type structures, which are respectively fixed in four directions of the central tube; each cylindrical permanent magnet is clamped by a clamping block, and the clamping block is fixed on the inner wall of the cylindrical shell.

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