Passive high-vacuum-degree online detection device and method

Abstract

The invention discloses a passive high-vacuum-degree on-line detection device and a passive high-vacuum-degree on-line detection method, and relates to vacuum state detection in the vacuum field by utilizing the temperature characteristic of a permanent magnet material, the passive high-vacuum-degree on-line detection device comprises a sensing element arranged on the inner surface of a vacuum cavity and a coil arranged on the outer surface of the vacuum cavity, one side of the coil corresponds to the outer surface of the vacuum cavity, and the other side of the coil corresponds to the outer surface of the vacuum cavity. A force sensor is fixedly arranged on the other side of the vacuum cavity, and the coil and the sensing element are located at the corresponding positions of the outer surface and the inner surface of the vacuum cavity. In the heating stage, high-frequency current is introduced into the coil to heat the induction element in an eddy current mode; in the measuring stage, direct-current large current is introduced into the coil, the sensing element and the coil generate interaction force, the sensing element is gradually cooled, and the magnetism is gradually increased. And a judgment stage: taking the numerical value change of the force sensor as a criterion or a measurement result to judge the vacuum state in the cavity. The detection method is high in universality, low in external environment dependence degree, high in detection precision, convenient, rapid and low in cost, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to vacuum state detection in the field of vacuum, and particularly to a passive high vacuum online detection device and method. Background Technology

[0002] With the development of science and technology, vacuum technology has been increasingly widely applied in industrial production, high-end manufacturing, and daily life. Vacuum refers to a gaseous state at a pressure below one atmosphere within a given space. Its core value lies in creating an environment with "nothing" or "very little matter," thereby eliminating many interferences caused by gas molecules and creating a physical environment with high insulation, low heat transfer, and no oxidation. In recent years, vacuum has been widely used in high-voltage electrical equipment, semiconductor and metal processing, advanced material manufacturing, nuclear fusion devices, and various experimental instruments. Related technologies have developed rapidly with the support of the vacuum environment. Accurate measurement of gas pressure values ​​under high vacuum conditions is a crucial prerequisite for ensuring the long-term stable and effective operation of technology and equipment, avoiding equipment failure and increased costs due to vacuum life loss, and even potentially causing major production accidents, such as abnormal power system interruptions caused by leakage in high-voltage vacuum circuit breakers.

[0003] Despite the availability of various vacuum detection techniques, several challenges remain: some methods, such as elastic deformation vacuum gauges and thermal conductivity vacuum gauges, lack sufficient accuracy in vacuum pressure detection, making it difficult to further differentiate between different vacuum environments; vacuum detection circuits are complex, instruments are intricate, and costs are high, as seen with laser-triggered plasma and ionization vacuum gauges; vacuum equipment is susceptible to interference due to its complex application scenarios; and vacuum detection solutions are highly specific, requiring placement within specialized testing equipment or embedding the measuring probe into the product under test, such as magnetron discharge and capacitive vacuum gauges. This increases the difficulty of vacuum condition detection and may even affect the structural integrity of vacuum products. Currently, many researchers are developing corresponding vacuum detection solutions for different application scenarios, aiming to improve the accuracy of vacuum condition detection. Therefore, there is an urgent need to design a passive online vacuum condition detection method that is universally applicable, has low dependence on external environments, high detection accuracy, and is convenient, fast, and low-cost. Summary of the Invention

[0004] The purpose of this invention is to provide a passive high vacuum online detection device and method to solve the problems existing in the prior art. The detection method of this invention has strong universality, low dependence on external environment, high detection accuracy, and is convenient, fast and low cost.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A passive high vacuum online detection device includes a sensing element disposed on the inner surface of a vacuum chamber and a coil disposed on the outer surface of the vacuum chamber. One side of the coil corresponds to the outer surface of the vacuum chamber, and a force sensor is fixedly disposed on the other side. The coil and the sensing element are located at corresponding positions on the outer and inner surfaces of the vacuum chamber.

[0006] Furthermore, the sensing element is a composite array composed of neodymium iron boron permanent magnet material, samarium cobalt permanent magnet material, alnico permanent magnet material, or the above-mentioned permanent magnet materials.

[0007] Furthermore, the sensing element is in the shape of a sheet structure, and the two sides with the largest area of ​​the sheet structure are the north and south poles of the magnet.

[0008] Furthermore, the direction of the central axis of the coil is aligned with the magnetic pole direction of the sensing element.

[0009] Furthermore, the sensing element is disposed on the inner surface of the vacuum chamber via a fixed point; Alternatively, the sensing element may be disposed on the surface of an object near the inner surface of the vacuum chamber.

[0010] Furthermore, the force sensor is a tension / compression sensor, a thin-film sensor, or a capacitive sensor.

[0011] A passive high vacuum online detection method for a vacuum cavity with built-in sensing elements includes a process for determining the judgment criteria under known vacuum and a process for detecting pressure under unknown vacuum. The process of determining the judgment criteria under a known vacuum degree and the process of pressure detection under an unknown vacuum degree both include a heating stage, a measurement stage, and a judgment stage. The heating stage: a high-frequency current is passed through the coil to heat the sensing element by eddy current. The high-frequency current is disconnected when the heating reaches a first preset time. The first preset time is used to heat the sensing element to a preset temperature, which is greater than 50°C and less than the maximum operating temperature of the sensing element. The measurement stage: A large DC current is then applied to the coil, and an electromagnetic interaction force is generated between the sensing element and the coil. The magnitude of the electromagnetic interaction force is read by a force sensor. The determination stage involves tracking the change in force sensor values ​​within a second preset time period and obtaining a criterion or measurement result based on the change in force sensor values. The process of determining the judgment criteria under a known vacuum level specifically includes: before the vacuum chamber is completely sealed or operated online, determining the pressures P1, P2, P3, ..., P under different pressures. n (P1, P2, P3, ..., P) nThe values ​​change linearly. The process involves heating, measuring, and determining the values ​​to obtain the force sensor value changes K1, K2, K3, ..., K within a second preset time period, corresponding to different pressures. n This will be used as the criterion. The process of pressure detection under unknown vacuum specifically includes: with the vacuum chamber completely sealed or operating online, performing a heating stage, a measurement stage, and a judgment stage under an unknown pressure P0, and comparing the change in force sensor value K0 with criteria K1, K2, K3, ..., K... n For comparison, if K i <K0<K i+1 Then P i <P0<P i+1 , where i = 1, 2, 3, ..., n-1, thus obtaining the pressure range of P0.

[0012] Furthermore, the process of determining the judgment criteria under a known vacuum degree and the process of pressure detection under an unknown vacuum degree use the same coil, the same high-frequency current and DC high current, the same first preset time and the same second preset time, and maintain the same distance between the coil and the sensing element.

[0013] Furthermore, the high-frequency current, the first preset time, and the same distance between the coil and the sensing element are determined through a process of determining the judgment criteria under a known vacuum degree, so as to ensure that the preset temperature is greater than 50°C and less than the maximum operating temperature of the sensing element.

[0014] Furthermore, the DC high current, the second preset time, and the same distance between the coil and the sensing element are determined through a process of determining the judgment criteria under a known vacuum degree, so as to ensure that the numerical value of the measurement result or criterion matches the measurement accuracy of the force sensor.

[0015] Furthermore, the sensing element relies on the Pirani vacuum gauge principle, and the magnitude of the electromagnetic interaction force is read by a force sensor. Specifically, the force sensor value is proportional to the magnetic moment of the sensing element.

[0016] in, F The electromagnetic interaction force between the sensing element and the coil, i.e., the reading value of the force sensor. m The magnetic moment of the sensing element, its magnitude and remanence B r related:

[0017]

[0018] in,μ 0、 μ r These are the vacuum permeability and relative permeability, respectively. The magnetization intensity, Residual magnetism B r The vector representation of Δ V It is a unit volume element. It is the sum of the molecular magnetic moments contained in the volume element, and the vector sum of the molecular magnetic moments of the permanent magnet material as a whole, i.e., the macroscopic magnetic moment of the permanent magnet. m Residual magnetism of sensing element B r It has a remanence temperature coefficient of 0.02~0.12% / ℃, which is the change in remanence caused by a unit temperature change.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: Unlike many traditional vacuum detection solutions, the passive high vacuum online detection device of this invention adopts a passive detection method, which does not require cumbersome wiring and components inside the vacuum chamber, nor does it require expensive detection and analysis instruments. Based on the influence of temperature on the magnetism of the permanent magnet itself, combined with the principles of electromagnetic induction and Pirani vacuum gauge, and through macroscopic design matching, the vacuum detection has high response accuracy and good application versatility.

[0020] A thin permanent magnet plate is fixed inside the vacuum chamber as the sensing element, with the two sides of the plate with the largest area representing the north and south poles of the magnet. A coil with a certain number of turns is placed outside the vacuum chamber, in close contact with a force sensor. The direction of the coil's central axis corresponds to the north and south poles of the sensing element. At the start of detection, a high-frequency alternating current is passed through the coil to heat the sensing element. After reaching a certain temperature (below the maximum operating temperature of the permanent magnet), the alternating current is disconnected, and direct current is passed through the coil. An interaction force is generated between the coil and the sensing element. As the sensing element cools, its magnetism gradually increases; the higher the gas pressure, the faster the cooling. The force sensor reads the change in electromagnetic force, thus reflecting the thermodynamic process of the sensing element's cooling and determining the gas pressure inside the vacuum chamber.

[0021] This invention avoids the problems of low detection accuracy of traditional thermal conductivity vacuum gauges, as well as the complex instrument circuits and high costs of laser-triggered plasma and ionization vacuum gauges. It utilizes a passive detection method to open up more diverse application possibilities. The invention features a simple and flexible structure, with sensing element materials possessing strong stability and temperature sensitivity, reducing environmental interference with vacuum measurements and achieving high detection accuracy. Furthermore, its thin-film structure facilitates integration and processing within the vacuum chamber. The use of an external passive coil for directional power supply and precise measurement enables online detection of vacuum instruments and equipment. This facilitates real-time monitoring of vacuum device pressure levels, proactively mitigating safety hazards, and has broad application prospects. Attached Figure Description

[0022] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a three-dimensional schematic diagram of the passive high vacuum online detection device of the present invention; Figure 2 This is a two-dimensional schematic diagram of the passive high vacuum online detection device of the present invention; Figure 3 This is another two-dimensional schematic diagram of the passive high vacuum online detection device of the present invention; Figure 4 This is a schematic diagram of the passive high vacuum online detection method of the present invention.

[0024] Among them, 1. sensing element, 2. coil, 3. force sensor, 4. vacuum chamber, 5. fixed point, and 6. object. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] Example 1 See Figure 1 and Figure 2 The sealed vacuum chamber 4 is a vacuum environment. A thin eddy current plate, serving as the sensing element 1, is placed inside. The eddy current plate is made of permanent magnet material (such as neodymium iron boron, samarium cobalt, or aluminum nickel cobalt permanent magnets), or a composite array of the aforementioned permanent magnet materials. The upper and lower planes of the eddy current plate represent its north and south magnetization poles, respectively. The sensing element 1 is fixed near the inner surface of the vacuum chamber 4 by welding, suspension, or support. The fixing point 5 between the eddy current plate and the inner surface of the vacuum chamber 4 fixes the sensing element 1 to the inner surface of the outer shell of the vacuum chamber 4 or an object 6 (not necessarily a specific component, but simply located on or near the inner surface of the outer shell of the vacuum chamber 4) on or near the inner surface. For example, Figure 2 Fixed point 5 is fixed to the inner surface of the outer shell by welding. Figure 3 The fixing point 5 is fixed to the surface of the object 6 near the inner surface by welding. Near the outer surface of the vacuum chamber 4, a multi-layered, multi-turn coil 2 is placed, with the central axis of the coil 2 aligned with the magnetic pole direction of the sensing element 1. A force sensor 3 is fixed to one side of the coil 2, and the outer coil 2 is in close contact with the force sensor 3 to read the force value exerted by the coil 2 on the force sensor 3. The force sensor 3 is a tension / compression sensor, a thin-film sensor, or a capacitive sensor.

[0028] See Figures 1-4 The principle and implementation method of the passive high vacuum online detection method of the present invention are as follows: i. In the initial state, sensing element 1, coil 2, force sensor 3, and vacuum chamber 4 are all at ambient temperature; ii. A certain amount of high-frequency current is passed through the external coil 2. Accompanied by the high-frequency changing magnetic field in the space, eddy currents appear on the surface of the sensing element 1 based on the principle of electromagnetic induction, and the eddy currents heat it. iii. After the first preset time, the sensing element 1 is heated to the preset temperature, the high-frequency current is disconnected, and the maximum heating temperature does not exceed the maximum operating temperature of the permanent magnet material; iv. A certain amount of DC current is passed through it. At this time, the external coil 2 is equivalent to an electromagnet, with the central axis in the direction of the N and S poles. v. Based on the Pirani vacuum gauge principle, the thermal conductivity of the environment varies significantly under different vacuum levels. During the second preset time period, as the sensing element 1 cools, its magnetism gradually recovers and strengthens, and the force between the sensing element 1 and the external coil 2 changes. vi. Determine the degree of vacuum inside the vacuum chamber based on the change in the value of force sensor 2.

[0029] The vacuum state detection method described in this invention combines the principles of electromagnetic induction and the Pirani vacuum gauge, utilizing the temperature characteristics of a permanent magnet for vacuum state detection. On one hand, this method offers high accuracy in vacuum pressure detection; on the other hand, it employs a passive detection approach, making it applicable to a wide range of scenarios. Furthermore, because the sensing element 1 is thin-film and located close to the inner surface of the vacuum chamber 4, it minimizes the space occupied within the chamber, facilitating integration and fabrication. This allows for flexible online vacuum state detection while instruments and equipment inside the vacuum chamber 4 are operating normally, enabling continuous monitoring of the pressure level of the vacuum device. Moreover, the number of turns and dimensions of the permanent magnet sensing element 1 and the coil 2 can be specially designed for different application scenarios and measurement products. The entire measurement process is simple and flexible to operate, easy to manufacture, requires no complex equipment, and is innovative in concept and mature in technology, showing promising application prospects.

[0030] Example 2 This invention can be applied to applications requiring a strict vacuum environment, such as high-voltage fields, nuclear industry, semiconductor fields, and metal processing.

[0031] Specifically, this invention provides a passive high vacuum online detection device, comprising a sensing element 1 fixed near the inner surface of a vacuum chamber 4, an externally fixed coil 2, and a force sensor 3, with the external coil 2 and force sensor 3 in close contact. The sensing element 1 is a thin sheet (sheet structure) and can be made of permanent magnets such as neodymium iron boron permanent magnets, samarium cobalt permanent magnets, and aluminum nickel cobalt permanent magnets, or a composite array of the above permanent magnet materials. The two sides with the largest area of ​​the sheet structure are the north and south poles of the magnet. The sensing element 1 is fixed inside the vacuum chamber 4 by a very small fixing point 5. In addition to having strong stability and mechanical reliability, the fixing point 5 also needs to reduce the heat conduction between the fixing point 5 and the sensing element 1, thereby increasing the Pirani principle heat dissipation ratio and improving the accuracy of vacuum detection.

[0032] This invention also provides a passive high vacuum online detection method for a vacuum cavity 4 with a built-in sensing element 1, including a process for determining the judgment criteria under a known vacuum degree and a process for detecting pressure under an unknown vacuum degree. Both processes include a heating stage, a measurement stage, and a judgment stage. 1) During the heating stage, a high-frequency current is passed through the external coil 2 to perform eddy current heating on the induction element 1. The high-frequency current is disconnected when the preset temperature is reached. Specifically, the induction element 1 is heated by the high-frequency current passed through the coil 2. The induction element 1 is fixed in position to ensure sufficient heating efficiency. The highest heating temperature (i.e. the preset temperature reached in the first preset time) should be greater than 50°C and less than the maximum operating temperature of the induction element 1.

[0033] 2) During the measurement phase, after the high-frequency current is disconnected, a large DC current is supplied to the external coil 2, and an electromagnetic interaction force is generated between the sensing element 1 and the coil 2. The magnitude of the electromagnetic interaction force is read by the force sensor 3.

[0034] 3) In the judgment stage, the change in the value of force sensor 3 is tracked within the second preset time. The judgment or measurement result is obtained based on the change in the value of force sensor 3. The measurement accuracy of force sensor 3 is not less than 0.1g.

[0035] The process of determining the judgment criteria under a known vacuum level specifically includes: before the vacuum chamber 4 is completely sealed or put into online operation, determining the pressures P1, P2, P3, ..., P under different pressures. n (P1, P2, P3, ..., P) n The values ​​change linearly. The heating, measurement, and judgment stages are performed to obtain the force sensor 3 value changes K1, K2, K3, ..., K within a second preset time period, corresponding to different pressures. n This will be used as the criterion. The process of pressure detection under unknown vacuum conditions specifically includes: when the vacuum chamber 4 is completely sealed or operating online, a heating stage, a measurement stage, and a judgment stage are performed under an unknown pressure P0. The change in the force sensor value K0 is compared with criteria K1, K2, K3, ..., K... n For comparison, if K i <K0<K i+1 Then P i <P0<P i+1 Where i = 1, 2, 3, ..., n-1, the pressure range of P0 is obtained from this. The larger the value of n, the more accurate the value of P0.

[0036] In both processes above, the conditions are the same: the same coil 2, the same high-frequency current and DC high current are used, the same first preset time and the same second preset time are used, and the same distance is maintained between the coil 2 and the sensing element 1.

[0037] The high-frequency current, the first preset time, and the same distance between coil 2 and sensing element 1 are determined through a process of determining the judgment criteria under a known vacuum degree. The desired effect is that the preset temperature is greater than 50°C and less than the maximum operating temperature of sensing element 1.

[0038] The DC high current, the second preset time, and the same distance between coil 2 and sensing element 1 are determined through a process of determining the judgment criteria under a known vacuum degree, so as to ensure that the numerical value of the measurement result or criterion matches the measurement accuracy of force sensor 3.

[0039] The frequency of the high-frequency current can be selected from 1k to 300kHz, and the amplitude can be selected from 1 to 20A; the DC high current can be selected from 10 to 30A, and the second preset time can be customized according to the actual situation.

[0040] The sensing element 1 relies on the Pirani vacuum gauge principle, and the sensing element 1 has residual magnetism. B r It possesses a remanence temperature coefficient of approximately 0.02~0.12% / ℃. The magnitude of the force sensor 3 value is approximately proportional to the magnetic moment of the sensing element.

[0041] F The force is the interaction force between sensing element 1 and coil 2, and the reading is that of force sensor 3. m The magnetic moment of sensing element 1, its magnitude and remanence B r related:

[0042]

[0043] in, μ 0、 μ r These are the vacuum permeability and relative permeability, respectively. The magnetization intensity, Residual magnetism B r The vector representation of Δ V It is a unit volume element. It is the sum of the molecular magnetic moments contained in the volume element, and the vector sum of the molecular magnetic moments of the permanent magnet material as a whole, i.e., the macroscopic magnetic moment of the permanent magnet. m Residual magnetism of sensing element 1 B r It has a remanence temperature coefficient of 0.02~0.12% / ℃, which is the change in remanence caused by a unit temperature change.

[0044] Example 3 See Figure 1 and Figure 3 The vacuum chamber 4 is a high-vacuum environment. A thin eddy current plate, serving as the sensing element 1, is placed inside. The eddy current plate is made of neodymium iron boron permanent magnet material, grade 40UH, with a diameter of 4cm and a thickness of 2mm. The upper and lower planes of the eddy current plate represent its north and south magnetization poles, respectively. An internal support plane (object 6) is present, and the sensing element 1 is welded to the support plane. Near the outer surface of the vacuum chamber 4, a coil 2 with 200 turns is placed, with the central axis of the coil 2 aligned with the magnetic pole direction of the sensing element 1. A force sensor 3 is fixed to one side of the coil 2, and the external coil 2 is in close contact with the force sensor 3 to read the force exerted by the coil 2 on the force sensor 3. The force sensor 3 can be a tension / compression sensor, a thin-film sensor, or a capacitive sensor.

[0045] See Figures 1-4 The principle and implementation results of the passive online vacuum degree detection method of the present invention are as follows: i. In the initial state, sensing element 1, coil 2, and force sensor 3 are all at ambient temperature; ii. A high-frequency current with a frequency of 50kHz and an amplitude of 10A is passed through the external coil 2. Accompanied by a high-frequency changing magnetic field in space, eddy currents appear on the surface of the sensing element 1 based on the principle of electromagnetic induction, and the eddy currents heat it. iii. After heating for 30 seconds, the temperature of sensing element 1 rises to 87°C, and the high-frequency current is disconnected; iv. Apply a DC current of 20A. At this time, the external coil 2 is equivalent to an electromagnet, with the central axis in the direction of the N and S poles. v. Based on the Pirani vacuum gauge principle, the thermal conductivity of the environment varies significantly under different vacuum levels. As the sensing element 1 cools down, its magnetism gradually recovers and strengthens, and the interaction force between the sensing element 1 and the external coil 2 changes. Under pressures of 0.1 Pa, 1 Pa, and 10 Pa, after 10 minutes, the readings of the force sensor 2 changed by 14.34 g, 15.48 g, and 17.24 g, respectively. vi. The experiment was repeated. Under unknown pressure, the reading of force sensor 2 changed by 14.77g, which indicated that the vacuum degree inside the cavity was between 0.1Pa and 1Pa. The actual pressure was measured to be 0.5Pa by other means, which is consistent with the detection result of this invention.

[0046] If more readings are taken under different pressure conditions in step v, then a more precise pressure range can be locked in step vi.

[0047] The vacuum state detection method described in this invention combines the principles of electromagnetic induction and the Pirani vacuum gauge, utilizing the temperature characteristics of a permanent magnet for vacuum state detection. On one hand, this method offers high accuracy in vacuum pressure detection; on the other hand, it employs a passive detection approach, making it applicable to a wide range of scenarios. Furthermore, because the sensing element 1 is thin-film and located close to the inner surface of the vacuum chamber 4, it minimizes the space occupied within the chamber, facilitating integration and fabrication. This allows for flexible online vacuum state detection while instruments and equipment inside the vacuum chamber 4 are operating normally, enabling continuous monitoring of the pressure level of the vacuum device. Moreover, the number of turns and dimensions of the permanent magnet sensing element 1 and the coil 2 can be specially designed for different application scenarios and measurement products. The entire measurement process is simple and flexible to operate, easy to manufacture, requires no complex equipment, and is innovative in concept and mature in technology, showing promising application prospects.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A passive high vacuum online detection device, characterized in that, It includes a sensing element (1) disposed on the inner surface of the vacuum cavity (4) and a coil (2) disposed on the outer surface of the vacuum cavity (4). One side of the coil (2) corresponds to the outer surface of the vacuum cavity (4), and a force sensor (3) is fixedly disposed on the other side. The coil (2) and the sensing element (1) are located at corresponding positions on the outer and inner surfaces of the vacuum cavity (4).

2. The passive high vacuum online detection device according to claim 1, characterized in that, The sensing element (1) is a composite array composed of neodymium iron boron permanent magnet material, samarium cobalt permanent magnet material, aluminum nickel cobalt permanent magnet material, or the above permanent magnet materials.

3. The passive high vacuum online detection device according to claim 2, characterized in that, The sensing element (1) is in the shape of a sheet structure, and the two sides with the largest area of ​​the sheet structure are the north and south poles of the magnet; The direction of the central axis of the coil (2) is directly opposite to the magnetic pole direction of the induction element (1).

4. The passive high vacuum online detection device according to claim 1, characterized in that, The sensing element (1) is disposed on the inner surface of the vacuum cavity (4) through a fixed point (5); Alternatively, the sensing element (1) is disposed on the surface of an object (6) near the inner surface of the vacuum cavity (4).

5. The passive high vacuum online detection device according to claim 1, characterized in that, The force sensor (3) is a tension / compression sensor, a thin film sensor or a capacitive sensor, and the measurement accuracy of the force sensor (3) is not less than 0.1g.

6. A passive high vacuum online detection method, based on the passive high vacuum online detection device according to any one of claims 1-5, characterized in that, For a vacuum cavity (4) with built-in sensing element (1), the process includes determining the judgment criteria under known vacuum degree and the pressure detection process under unknown vacuum degree; The process of determining the judgment criteria under a known vacuum degree and the process of pressure detection under an unknown vacuum degree both include a heating stage, a measurement stage, and a judgment stage. The heating stage: a high-frequency current is passed into the coil (2) to heat the sensing element (1) by eddy current. When the heating reaches the first preset time, the high-frequency current is disconnected. The first preset time is used to heat the sensing element (1) to a preset temperature. The preset temperature is greater than 50°C and less than the maximum operating temperature of the sensing element (1). The measurement stage: a large DC current is then applied to the coil (2), and an electromagnetic interaction force is generated between the sensing element (1) and the coil (2). The magnitude of the electromagnetic interaction force is read by the force sensor (3). The determination stage: track the change in the value of the force sensor (3) within a second preset time, and obtain the criterion or measurement result based on the change in the value of the force sensor (3); The process of determining the judgment criteria under a known vacuum degree specifically includes: before the vacuum chamber (4) is completely sealed or operated online, under different pressures P1, P2, P3, ..., P n The heating, measurement, and judgment stages are performed to obtain the numerical changes K1, K2, K3, ..., K of the force sensors (3) corresponding to different pressures within a second preset time period. n This will be used as the criterion. The process of pressure detection under unknown vacuum degree specifically includes: when the vacuum chamber (4) is completely sealed or running online, a heating stage, a measurement stage, and a judgment stage are performed under unknown pressure P0. The change in the force sensor (3) value K0 is compared with the criteria K1, K2, K3, ..., K n For comparison, if K i < K0 <K i+1 Then P i < P0 <P i+1 , where i = 1, 2, 3, ..., n-1, thus obtaining the pressure range of P0.

7. The passive high vacuum online detection method according to claim 6, characterized in that, The process of determining the judgment criteria under known vacuum degree and the process of pressure detection under unknown vacuum degree use the same coil (2), the same high-frequency current and DC high current, the same first preset time and the same second preset time, and maintain the same distance between the coil (2) and the sensing element (1).

8. The passive high vacuum online detection method according to claim 7, characterized in that, The high-frequency current, the first preset time, and the same distance between the coil (2) and the sensing element (1) are determined by the process of determining the judgment criteria under a known vacuum degree, so as to ensure that the preset temperature is greater than 50°C and less than the maximum operating temperature of the sensing element (1).

9. The passive high vacuum online detection method according to claim 7, characterized in that, The DC high current, the second preset time, and the same distance between the coil (2) and the sensing element (1) are determined by the process of determining the judgment criteria under a known vacuum degree, so as to ensure that the numerical value of the measurement result or criterion matches the measurement accuracy of the force sensor (3).

10. The passive high vacuum online detection method according to claim 6, characterized in that, The sensing element (1) relies on the Pirani vacuum gauge principle, and the magnitude of the electromagnetic interaction force is read by the force sensor (3). Specifically, the magnitude of the force sensor (3) is proportional to the magnetic moment of the sensing element. in, F The electromagnetic interaction force between the sensing element (1) and the coil (2), i.e., the reading value of the force sensor (3), m The magnetic moment of the sensing element (1), its magnitude and remanence B r related: in, μ 0、 μ r These are the vacuum permeability and relative permeability, respectively. The magnetization intensity, Residual magnetism B r The vector representation of Δ V It is a unit volume element. It is the sum of the molecular magnetic moments contained in the volume element, and the vector sum of the molecular magnetic moments of the permanent magnet material as a whole, i.e., the macroscopic magnetic moment of the permanent magnet. m Residual magnetism of sensing element (1) B r It has a remanence temperature coefficient of 0.02~0.12% / ℃, which is the change in remanence caused by a unit temperature change.

Images