Medium isolation type back pressure sensor

Abstract

The invention discloses a medium isolation type back pressure sensor, a sensor core comprises a core base, a core assembly and a middle separator, the core base is provided with an accommodating cavity and a circulation cavity, the core assembly is arranged in the accommodating cavity and is used for detecting the pressure in the circulation cavity, the middle separator is fixed in the core base, and the core assembly is used for detecting the pressure in the circulation cavity. A circulation channel is arranged between the middle partition piece and the core body base, one end of the circulation channel is communicated with the circulation cavity, the core body assembly is arranged corresponding to the other end of the circulation channel, and the core body assembly comprises a circuit board, a pressure sensing chip and a signal conditioning chip, and a signal shielding cover made of a metal material covers the outer sides of the pressure sensing chip and the signal conditioning chip. The pressure sensing chip and the signal conditioning chip can be protected, and the problem of electromagnetic interference can be effectively solved in the signal processing and pressure data calculation process of the pressure sensing chip and the signal conditioning chip, so that the pressure detection precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a pressure sensor. Background Art

[0002] The prior art discloses a pressure sensor, comprising a base, a sealing glass component and a diaphragm, wherein a pressure-sensitive chip is loaded in a sealed space; the sealing glass component is fixed with a 0-potential guide pin and at least one electrical signal output guide pin, and the electrical signal output end of the pressure-sensitive chip is connected to the electrical signal output guide pin; the pressure-sensitive chip is installed on the sealing glass component through a chip mounting component, and an equipotential protection sleeve is provided at a peripheral position or a part of a peripheral position of the pressure-sensitive chip, the equipotential protection sleeve and the chip mounting component are an integrated structure, and the 0-potential guide pin is in direct contact with the chip mounting component to achieve electrical connection.

[0003] The equipotential protection sleeve is connected to the 0-potential guide pin, which can completely contain the pressure-sensing chip inside, thus forming an equipotential space. When subjected to external interference, it can effectively protect the internal circuit from interference or reduce interference, thereby ensuring the output stability of the sensor. However, on the one hand, the equipotential protection sleeve only forms an equipotential space, and its ability to resist signal interference is limited. On the other hand, other chips of the sensor, such as the signal conditioning chip, cannot resist interference. Summary of the invention

[0004] In view of the defects of the prior art, the technical problem to be solved by the present invention is to provide a medium-isolated back-pressure pressure sensor to further improve the anti-interference ability of the chip mounted on the pressure sensor.

[0005] In order to solve the above technical problems, the present invention adopts the following technical scheme: a medium-isolated back-pressure pressure sensor, including a sensor core, the sensor core including a core base, a core assembly and an intermediate partition, the core base having a accommodating cavity and a flow cavity, the core assembly being arranged in the accommodating cavity, the core assembly being used to detect the pressure in the flow cavity, the intermediate partition being fixed in the core base, a flow channel being provided between the intermediate partition and the core base, one end of the flow channel being connected to the flow cavity, the core assembly being arranged corresponding to the other end of the flow channel, the core assembly including a circuit board and a pressure sensing chip and a signal conditioning chip connected to the circuit board, the outer covers of the pressure sensing chip and the signal conditioning chip being provided with a signal shielding cover made of metal material.

[0006] Preferably, the circuit board is provided with a grounding wire, and the signal shielding cover is connected to the grounding wire of the circuit board.

[0007] Preferably, the surface of the signal shielding cover is covered with a plastic layer.

[0008] Preferably, the pressure sensing chip is an unpackaged bare chip, and the inner leads of the pressure sensing chip are directly connected to the circuit board; and / or, the distance between the pressure sensing chip and the signal conditioning chip is H, where H ≤ 1.5 mm.

[0009] Preferably, the intermediate separator serves as a pressure sensing chip encapsulation seat, and the pressure sensing chip and the pressure sensing chip encapsulation seat are eutectically bonded together.

[0010] Preferably, the intermediate separator is made of ceramic material; and / or, the core base is made of stainless steel material; and / or, the intermediate separator is welded or bonded to the core base.

[0011] Preferably, an upper mounting step is provided on the upper side of the middle part of the core base, and the circuit board is mounted on the upper mounting step; and / or, a lower mounting step is provided on the lower side of the middle part of the core base, and the intermediate separator is mounted on the lower mounting step; and / or, the flow channel is a through hole penetrating the center of the intermediate separator, and this through hole corresponds to the central area of the diaphragm.

[0012] Preferably, the sensor core further includes a diaphragm and a damping pressure ring provided at the lower opening of the core base; a circular pressure-resistant piece is provided on the diaphragm corresponding to the position of the through hole, and the diameter of the pressure-resistant piece is larger than the diameter of the through hole; and / or, the diaphragm and the damping pressure ring are laser welded as an integral part to the lower opening of the core base to achieve sealing.

[0013] Preferably, a central convex column penetrating upward into the accommodation cavity is provided at the upper center of the intermediate separator, a cylinder is provided at the lower part of the intermediate separator, a radial gap is provided between the cylinder and the inner wall of the core base, an oil filling port is provided on the core base corresponding to the radial gap position, and the distance between the lower end surface of the cylinder and the diaphragm is L, where L ≤ 1.5 mm.

[0014] Preferably, the pressure sensor further includes a protective housing, a lower housing and a sensor plug. A limiting flange is provided in the middle of the inner wall of the protective housing. The sensor core is arranged in the protective housing, and the outer edge of the core base abuts against the lower end surface of the limiting flange. The sensor plug is fixed to the upper part of the protective housing and abuts against the upper end surface of the limiting flange. The sensor plug is connected to the circuit board, and the upper end of the lower housing is inserted into the inner side of the protective housing and abuts against the core base.

[0015] The technical solution adopted by the present invention has the following beneficial effects:

[0016] 1. The intermediate separator is arranged in the core base. There is a flow channel between the intermediate separator and the housing. One end of the flow channel is communicated with the flow cavity, and the core assembly is arranged corresponding to the other end of the flow channel. Thus, it is convenient to use the core assembly to detect the pressure in the flow cavity.

[0017] The outer side of the pressure sensing chip and the signal conditioning chip is provided with a signal shielding cover made of metal material. By using the reflection, absorption and skin collection effects of the metal shielding layer, electromagnetic interference and electromagnetic radiation can be prevented, protecting the pressure sensing chip and the signal conditioning chip. During the signal processing and pressure data calculation processes of the pressure sensing chip and the signal conditioning chip, the problem of electromagnetic interference can be effectively solved, thereby improving the accuracy of pressure detection.

[0018] 2. The signal shielding cover is connected to the circuit board ground wire to ensure that the signal shielding cover realizes the function of preventing electromagnetic interference and electromagnetic radiation.

[0019] 3. The surface of the signal shielding cover is coated with a plastic layer to protect the metal material and enable the signal shielding cover to be used for a long time and play a signal shielding role.

[0020] 4. The pressure sensing chip is an unpackaged bare chip, and the inner leads of the pressure sensing chip are directly connected to the circuit board, reducing the chip packaging process. Finally, it is enclosed with a signal shielding cover, which can reduce the packaging cost.

[0021] The signal conditioning chip and the pressure sensing chip are encapsulated in adjacent areas. Specifically, the distance between the pressure sensing chip and the signal conditioning chip is H, and H ≤ 1.5 mm, which can effectively avoid the distortion problem of weak signals. At the same time, the timeliness of temperature response helps with the temperature compensation of the pressure sensing chip and improves the accuracy in the full temperature range.

[0022] 5. The pressure sensing chip and the pressure sensing chip packaging seat are eutectically bonded into one body. The eutectic bonding is more reliable than traditional glue bonding and has less long-term drift.

[0023] 6. The intermediate separator is made of ceramic material, using aluminum oxide ceramic with a certain purity, which has the advantages of good insulation performance, low dielectric constant, low thermal expansion coefficient, high thermal conductivity, excellent airtightness and chemical stability, and is very suitable for the packaging of high-reliability, high-frequency, high-temperature resistance and airtight products.

[0024] The intermediate separator is fixedly connected to the core body base through welding or bonding, such as brazing or epoxy material bonding, so that the structure can be sealed without using a sealing ring. With the above structure, the connection between the intermediate separator and the core body base does not leak, which can improve the sealing effect of the structure. There is no need to set components such as elastic retaining rings, gasket rings and sealing rings, which is convenient for assembly and can simplify the production process.

[0025] 7. The circuit board is positioned through the upper mounting step, and the intermediate separator is positioned through the lower mounting step to ensure the distance between the lower end face of the pressure sensing chip packaging seat and the diaphragm.

[0026] The intermediate separator serves as a pressure sensing chip encapsulation base, which has through holes connecting to the bottom surface of the pressure sensing chip. The through holes are on the central axis of the pressure sensing chip encapsulation base and also on the central axis of the diaphragm. When the system pressure is extremely high, the area near the central axis of the diaphragm deforms the most, directly blocking the through holes, and the force acting on the bottom surface of the chip no longer increases, protecting the safety of the sensor.

[0027] 8. Usually, the diaphragm is relatively thin and has insufficient pressure resistance. Therefore, a pressure-resistant sheet with a certain thickness is bonded or welded to the diaphragm. The diameter of the pressure-resistant sheet is larger than the diameter of the through hole, improving the pressure resistance of the diaphragm.

[0028] 9. A cylinder is provided at the lower part of the intermediate separator. There is a radial gap between the cylinder and the inner wall of the core base. Therefore, the pressure sensing chip encapsulation base is made of ceramic material. The surfaces for the medium to transfer heat by oil only include two directions, namely the lower end surface and the annular surface surrounding the oil-filled cavity. Therefore, the heat transfer area is small and the heat dissipation area is large. The ceramic material and silicone oil have low thermal conductivity, and the medium has little influence on the temperature of the chip.

[0029] The lower end surface of the cylinder on the pressure sensing chip encapsulation base limits the upward movement distance of the diaphragm. The distance between the lower end surface of the cylinder and the diaphragm is L, where L ≤ 1.5 mm. The reasonable distance between the bottom of the ceramic base and the diaphragm can reduce the amount of oil filled and prevent oil leakage caused by the diaphragm breakage in extreme cases (leakage occurs in the oil-filled cavity).

[0030] 10. The sensor core is arranged inside the protective housing, and the outer edge of the core base abuts against the lower end surface of the limiting flange. The upper end of the lower housing is inserted into the inner side of the protective housing and abuts against the core base, thereby fixing the sensor core inside the protective housing and making it not easy to shift.

[0031] The specific technical solutions adopted by the present invention and the beneficial effects brought by them will be detailedly disclosed in the following specific embodiments in combination with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the drawings and specific embodiments:

[0033] Figure 1 is a schematic structural diagram of the sensor core;

[0034] Figure 2 is a schematic structural diagram of the circuit board Figure 1 ;

[0035] Figure 3 is a schematic structural diagram of the circuit board Figure 2 ;

[0036] Figure 4 is a schematic structural diagram of the circuit board Figure 3 ;

[0037] Figure 5 Schematic diagram of the external structure of the sensor core Figure 1 ;

[0038] Figure 6 Schematic diagram of the external structure of the sensor core Figure 2 ;

[0039] Figure 7 Schematic diagram of the external structure of the sensor core Figure 3 ;

[0040] Figure 8 Cross-sectional view of the sensor core;

[0041] Figure 9 General structure schematic diagram of the pressure sensor;

[0042] In the figure: sensor core 100, core base 1, accommodation cavity 11, flow cavity 12, upper mounting step 13, lower mounting step 14, intermediate separator 2, central convex column 21, through hole 22, eutectic bonding 23, cylinder 24, diaphragm 3, damping compression ring 4, circuit board 5, steel ball 6, signal shielding cover 7, pressure sensing chip 8, signal conditioning chip 9, connection terminal 10, protective housing 200, limiting flange 201, flexible connecting plate 300, sensor plug 400, lower housing 500, pressure guiding threaded head 600. Specific implementation mode

[0043] The technical solutions of the embodiments of the present invention will be explained and described below with reference to the accompanying drawings of the embodiments of the present invention. However, the following embodiments are only the preferred embodiments of the present invention and not all of them. Based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative efforts all fall within the protection scope of the present invention.

[0044] Those skilled in the art can understand that, without conflict, the features in the following embodiments and implementation manners can be combined with each other.

[0045] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For example, the terms such as "upper", "lower", "inner", "outer", etc. indicating the orientation or position relationship are only based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device / component referred to must have a specific orientation or be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention.

[0046] In the present invention, unless otherwise clearly specified and defined, terms such as "installation", "connection", "fixation" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] As Figures 1 to 9 shown, a medium-isolated backpressure pressure sensor includes a sensor core body 100. The sensor core body 100 includes a core base 1, a core component, and an intermediate partition 2. The core base 1 has a receiving cavity 11 and a flow cavity 12. The core component is disposed in the receiving cavity 11. The core component is used to detect the pressure in the flow cavity. The intermediate partition 2 is fixed in the core base 1. There is a flow channel between the intermediate partition 2 and the core base 1. One end of the flow channel communicates with the flow cavity 12, and the core component is disposed corresponding to the other end of the flow channel. The core component includes a circuit board 5, a pressure sensing chip 8, and a signal conditioning chip 9 connected to the circuit board 5.

[0048] It can be understood that connection terminals 10 and other electronic components are also provided on the circuit board. Among them, the electronic components are soldered onto the circuit board by SMT (the process of assembling components onto a printed (or other substrate) is called SMT process) reflow soldering process, and the signal conditioning chip 9 is connected to the circuit board 5 through a semiconductor chip packaging process.

[0049] Compared with the prior art, in this embodiment, a signal shielding cover 7 made of a metal material is provided outside the pressure sensing chip 8 and the signal conditioning chip 9. The signal shielding cover 7 can be adhered to the circuit board 5.

[0050] In the above technical solution, the intermediate partition is disposed in the core base. There is a flow channel between the intermediate partition and the housing. One end of the flow channel communicates with the flow cavity, and the core component is disposed corresponding to the other end of the flow channel. In this way, it is convenient to use the core component to detect the pressure in the flow cavity.

[0051] Since a signal shielding cover made of a metal material is provided outside the pressure sensing chip and the signal conditioning chip. By using the reflection, absorption, and skin collection effects of the metal shielding layer, electromagnetic interference and electromagnetic radiation can be prevented, which can protect the pressure sensing chip and the signal conditioning chip. During the signal processing and pressure data calculation processes of the pressure sensing chip and the signal conditioning chip, the problem of electromagnetic interference can be effectively solved, thereby improving the accuracy of pressure detection.

[0052] Specifically, the circuit board 5 is provided with a ground wire, and the signal shielding cover 7 is connected to the ground wire of the circuit board. This ensures that the signal shielding cover can prevent electromagnetic interference and electromagnetic radiation. The surface of the signal shielding cover 7 is coated with a plastic layer. The plastic layer can protect the metal material, enabling the signal shielding cover to be used for a long time and play the role of signal shielding.

[0053] In this embodiment, the pressure sensing chip 8 is an unpackaged bare chip, and the inner leads of the pressure sensing chip are directly connected to the circuit board 5. This reduces the chip packaging process. Finally, it is enclosed with a signal shielding cover, which can reduce the packaging cost. Moreover, the signal conditioning chip and the pressure sensing chip are packaged in adjacent areas. Specifically, the distance between the pressure sensing chip 8 and the signal conditioning chip 9 is H, and H ≤ 1.5 mm. This can effectively avoid the distortion problem of weak signals. At the same time, the timeliness of temperature response helps with the temperature compensation of the pressure sensing chip and improves the accuracy in the full temperature range.

[0054] In this embodiment, the intermediate separator 2 serves as the packaging seat for the pressure sensing chip, and the pressure sensing chip and the pressure sensing chip packaging seat are eutectically bonded 23 into one body. Because eutectic bonding is more reliable than traditional glue bonding and has less long-term drift.

[0055] Specifically, the intermediate separator 2 is made of ceramic material. The core base is made of stainless steel material. The intermediate separator is welded or bonded to the core base. The intermediate separator is made of ceramic material, using a certain purity of aluminum oxide ceramic, which has the advantages of good insulation performance, low dielectric constant, low thermal expansion coefficient, high thermal conductivity, excellent airtightness, and chemical stability. It is very suitable for the packaging of high-reliability, high-frequency, high-temperature resistance, and airtight products. The intermediate separator is fixedly connected to the core base through welding or bonding, such as brazing or epoxy material bonding. In this way, the structure can be sealed without using a sealing ring. With the above structure, the connection between the intermediate separator and the core base does not leak, which can improve the sealing effect of the structure. There is no need to set elastic retaining rings, gasket rings, and sealing rings and other components, which is convenient for assembly and can simplify the production process.

[0056] Specifically, an upper mounting step 13 is provided on the upper side of the middle part of the core base 1, and the circuit board 5 is mounted on the upper mounting step 13. A lower mounting step 14 is provided on the lower side of the middle part of the core base 1, and the intermediate separator 2 is mounted on the lower mounting step 14. In this way, the circuit board is positioned by the upper mounting step, and the intermediate separator is positioned by the lower mounting step, ensuring the distance between the lower end face of the pressure sensing chip packaging seat and the diaphragm. The accommodation cavity 11 and the flow cavity 12 are separated by the intermediate separator.

[0057] Furthermore, the sensor core further includes a diaphragm 3 and a damping compression ring 4 provided at the lower opening of the core base. The core base 1 is provided with an oil filling port communicating with the circulation cavity. Silicone oil is filled through the oil filling port. After the oil filling is completed, the sealing steel ball 6 is sealed to achieve the sealing of the entire sensor core. Among them, the diaphragm 3 and the damping compression ring 4 are laser welded with the lower opening of the core base as an integral part to achieve sealing, which is convenient for installation and ensures the sealing effect. The pressure medium acts on the diaphragm, so that the silicone oil acts on the bottom surface of the pressure sensing chip through the circulation channel, that is, a back-pressure type MEMS pressure sensing chip is adopted. The circulation channel is a through hole 22 with a circular structure penetrating the center of the intermediate separator. The through hole 22 corresponds to the central area of the diaphragm. The through hole is on the center line of the packaging substrate of the pressure sensing chip and also on the central axis of the diaphragm. When the system pressure is extremely high, the area near the central axis of the diaphragm deforms the most, directly blocking the through hole, and the force acting on the bottom surface of the chip no longer increases, protecting the safety of the sensor.

[0058] Generally, the diaphragm is relatively thin and has insufficient pressure resistance. Therefore, the diaphragm 3 can also be provided with a circular pressure-resistant piece at the position corresponding to the through hole 22, and the diameter of the pressure-resistant piece is larger than the diameter of the through hole. In this way, a pressure-resistant piece with a certain thickness is bonded or welded and fixed on the diaphragm. The diameter of the pressure-resistant piece is larger than the diameter of the through hole, improving the pressure resistance of the diaphragm.

[0059] As Figure 1 and Figure 8 shown, the upper center of the intermediate separator 2 is provided with a central convex column 21 that penetrates upward into the accommodation cavity. The lower part of the intermediate separator is provided with a cylinder 24. The outer edge of the upper end surface of the cylinder abuts against the lower installation step 14. A radial gap is provided between the cylinder 24 and the inner wall of the core base. The core base is provided with an oil filling port corresponding to the radial gap. Silicone oil is filled through the oil filling port. After the oil filling is completed, the sealing steel ball 6 is sealed to achieve the sealing of the entire sensor core. The packaging substrate of the pressure sensing chip is made of ceramic material. The surfaces for the medium to transfer heat to the oil only include two directions, that is, the lower end surface and the annular surface surrounding the oil filling cavity. Therefore, the heat transfer area is small and the heat dissipation area is large. The thermal conductivity of the ceramic material and the silicone oil is low, and the influence of the medium on the temperature of the chip is small. The lower end surface of the cylinder on the pressure sensing chip packaging seat limits the upward movement distance of the diaphragm. The distance between the lower end surface of the cylinder and the diaphragm is L, L≤1.5mm. The distance between the bottom of the ceramic base and the diaphragm is reasonable, which can reduce the amount of oil filled and prevent oil leakage caused by diaphragm breakage in extreme cases (leakage occurs in the oil filling cavity).

[0060] As Figure 9As shown, the pressure sensor further includes a protective housing 200, a lower housing 500, and a sensor plug 400. A limiting flange 201 is provided in the middle of the inner wall of the protective housing. The sensor core is arranged inside the protective housing, and the outer edge of the core base abuts against the lower end surface of the limiting flange. The sensor plug 400 is fixed to the upper part of the protective housing and abuts against the upper end surface of the limiting flange. The sensor plug 400 is connected to the circuit board 5 through a flexible connecting plate 300, and the flexible connecting plate 300 is connected to the connecting terminal 10. The upper end of the lower housing 500 is inserted into the inside of the protective housing 200 and abuts against the core base 1. In addition, the lower housing 500 is connected with a pressure-introducing threaded head 600.

[0061] As described above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the drawings and the above specific implementation manner. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A dielectric isolation type back pressure sensor, characterized in that, It includes a sensor core body, and the sensor core body includes a core base, a core component and an intermediate separator. The core base has a receiving cavity and a circulation cavity. The core component is arranged in the receiving cavity. The core component is used to detect the pressure in the circulation cavity. The intermediate separator is fixed in the core base. There is a circulation channel between the intermediate separator and the core base. One end of the circulation channel is communicated with the circulation cavity. The core component is arranged corresponding to the other end of the circulation channel. The core component includes a circuit board, a pressure sensing chip and a signal conditioning chip connected to the circuit board. The outside of the pressure sensing chip and the signal conditioning chip is covered with a signal shielding cover made of a metal material.

2. The backpressure pressure sensor of the dielectric isolation type according to claim 1, wherein: The circuit board is provided with a ground wire, and the signal shielding cover is connected to the ground wire of the circuit board.

3. The back pressure type pressure sensor with dielectric isolation according to claim 1, characterized in that: The surface of the signal shielding cover is coated with a plastic layer.

4. A medium-isolated back-pressure type pressure sensor according to claim 1, characterized in that: The pressure sensing chip is an unpackaged bare chip, and the inner leads of the pressure sensing chip are directly connected to the circuit board; and / or, the distance between the pressure sensing chip and the signal conditioning chip is H, and H≤1.5mm.

5. A medium-isolated backpressure pressure sensor according to claim 1, characterized in that: The intermediate separator serves as a pressure sensing chip packaging seat, and the pressure sensing chip and the pressure sensing chip packaging seat are eutectically bonded into one body.

6. A medium-isolated back-pressure type pressure sensor according to claim 1, characterized in that: The intermediate separator is made of ceramic material; and / or, the core base is made of stainless steel material; and / or, the intermediate separator and the core base are welded or bonded.

7. A medium-isolated backpressure pressure sensor according to claim 1, characterized in that: An upper mounting step is provided on the upper side of the middle part of the core base, and the circuit board is mounted on the upper mounting step; and / or, a lower mounting step is provided on the lower side of the middle part of the core base, and the intermediate separator is mounted on the lower mounting step; and / or, the circulation channel is a through hole penetrating the center of the intermediate separator, and this through hole corresponds to the central area of the diaphragm.

8. A medium-isolated back-pressure type pressure sensor according to claim 7, characterized in that: The sensor core body further includes a diaphragm and a damping compression ring arranged at the lower opening of the core base; the diaphragm is provided with a circular pressure-resistant piece corresponding to the position of the through hole, and the diameter of the pressure-resistant piece is larger than the diameter of the through hole; and / or, the diaphragm and the damping compression ring are laser welded as an integral part to the lower opening of the core base to achieve sealing.

9. A medium-isolated back-pressure type pressure sensor according to claim 8, characterized in that: A central convex column penetrating upward into the receiving cavity is provided at the upper center of the intermediate separator. A cylinder is provided at the lower part of the intermediate separator. There is a radial gap between the cylinder and the inner wall of the core base. The core base is provided with an oil filling port corresponding to the position of the radial gap. The distance between the lower end surface of the cylinder and the diaphragm is L, and L≤1.5mm.

10. A medium-isolated back-pressure type pressure sensor according to claim 1, characterized in that: The pressure sensor further includes a protective shell, a lower shell and a sensor plug. A limiting flange is provided in the middle of the inner wall of the protective shell. The sensor core body is arranged in the protective shell, and the outer edge of the core base abuts against the lower end surface of the limiting flange. The sensor plug is fixed to the upper part of the protective shell and abuts against the upper end surface of the limiting flange. The sensor plug is connected to the circuit board. The upper end of the lower shell is inserted into the inner side of the protective shell and abuts against the core base.

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