Wired digital SF6 gas density sensor

Abstract

The utility model provides a wired digital SF6 gas density sensor, and relates to the technical field of gas density monitoring. The sensor comprises a sensor shell which is designed to be of a double-layer hollow structure, an inner cylinder is provided with a plurality of spiral flow guide fins, and an outer cylinder is made of ceramic materials and completely wraps the inner cylinder. The sensor is further provided with a distributed temperature detection array which comprises a plurality of MEMS temperature sensors annularly and symmetrically embedded into the inner wall of the inner cylinder, and gaps of the grooves are filled with heat conduction silica gel. The circuit board is fixed in an interlayer space between the inner cylinder and the outer cylinder, and the RS-485 interface is installed on the outer cylinder. And the data fusion module is welded on the surface of the circuit board, is connected with the MEMS temperature sensor, and is connected with an external cable through an RS-485 interface. According to the sensor, the problem of insufficient temperature compensation precision of the SF6 density sensor in a complex temperature field environment is solved, and the measurement precision and the environmental interference resistance are improved.

Description

Technical Field

[0001] This utility model relates to the field of gas density monitoring technology, and more specifically, to a wired digital SF6 gas density sensor. Background Technology

[0002] With the rapid development of smart grids and high-voltage electrical equipment, SF6 gas is widely used in GIS (Gas Insulated Switchgear) and circuit breakers due to its excellent insulation and arc-extinguishing properties. Real-time and accurate monitoring of SF6 gas density is a core requirement for ensuring the safe operation of equipment, especially under complex conditions such as low temperatures and high altitudes, where density anomalies can lead to insulation failure or equipment malfunction. However, existing wired digital SF6 gas density sensors still face challenges in complex temperature field distributions, strong electromagnetic interference, and long-term stability. For example, density conversion errors caused by temperature gradients, signal transmission packet loss, and drift problems caused by the aging of sensitive elements severely limit the reliability and lifespan of monitoring systems.

[0003] Traditional technologies typically employ a single temperature probe combined with a linear compensation algorithm to improve temperature compensation accuracy, but this is insufficient to reflect the dynamic temperature field distribution within the gas. To address electromagnetic interference, shielded cables and filter circuits are often used, but signal distortion risks remain under extreme transient interference such as circuit breaker opening and closing. Furthermore, while optimizing encapsulation materials (such as ceramic protective layers) can mitigate corrosion of sensitive components, it cannot completely prevent micro-leakage and aging of materials under high pressure. Although these methods partially solve fundamental problems, limitations in structural design (such as single-point temperature measurement and insufficient anti-interference redundancy) and lack of dynamic response capabilities result in measurement accuracy and long-term stability in complex scenarios failing to meet the requirements for high-reliability monitoring.

[0004] In summary, the technical problem of insufficient temperature compensation accuracy of SF6 density sensors in complex temperature fields is an urgent issue that needs to be addressed. Utility Model Content

[0005] The main objective of this invention is to provide a wired digital SF6 gas density sensor to at least solve the technical problem of insufficient temperature compensation accuracy of SF6 density sensors under complex temperature field conditions, significantly improve the measurement accuracy and anti-environmental interference capability under complex temperature field conditions, and be compatible with existing digital interfaces.

[0006] To achieve the above objectives, this utility model provides a wired digital SF6 gas density sensor, the sensor comprising:

[0007] The sensor housing is a double-layered hollow structure consisting of a cylindrical inner cylinder and a cylindrical outer cylinder. The inner cylinder has an axial length of L and an inner diameter of D, and its inner surface is provided with multiple spiral guide fins. The outer cylinder is made of ceramic material and completely covers the inner cylinder.

[0008] A distributed temperature detection array includes multiple MEMS temperature sensors, which are symmetrically embedded in the mounting grooves on the inner wall of the inner cylinder and the gaps in the grooves are filled with thermally conductive silicone.

[0009] The circuit board is fixed in the interlayer space between the inner cylinder and the outer cylinder;

[0010] An RS-485 interface is fixedly installed on the outer cylinder;

[0011] A data fusion module is soldered to the surface of the circuit board, and the input end of the data fusion module is connected to multiple MEMS temperature sensors. The output end of the data fusion module is connected to an external cable through an RS-485 interface.

[0012] The height of the spiral guide fin is D / 6-D / 4, the spacing between adjacent spiral guide fins is L / 12-L / 8, and the spiral direction of the spiral guide fin forms an angle of 25°-50° with the axis of the sensor housing.

[0013] Specifically, the height of the spiral guide fin is D / 5, the spacing between adjacent spiral guide fins is L / 10, and the spiral direction of the spiral guide fin forms a 30° angle with the axial direction of the sensor housing.

[0014] Specifically, the detection surface of the MEMS temperature sensor is flush with the inner wall of the inner cylinder, and the thermal conductivity of the thermally conductive silicone is 5-8 W / (m·K).

[0015] Specifically, the outer cylinder is made of aluminum nitride ceramic material, the aluminum nitride ceramic layer is 0.2-0.5mm thick, and the outer surface of the outer cylinder is covered with a 0.1-0.3mm thick polyimide insulating coating.

[0016] Specifically, the circuit board is provided with a honeycomb heat dissipation hole array, the hole diameter of which is 1-2mm and is evenly distributed.

[0017] Specifically, the cable entry point of the RS-485 interface is provided with a silicone sealing ring, which is embedded in the annular groove of the outer cylinder, and the depth of the annular groove is 2 / 3 of the thickness of the silicone sealing ring.

[0018] This invention provides a wired digital SF6 gas density sensor. The sensor includes a double-layered hollow housing with multiple spiral guide fins in the inner cylinder and a ceramic outer cylinder that completely encloses the inner cylinder. The sensor also houses a distributed temperature detection array containing multiple symmetrically embedded MEMS temperature sensors in a ring within the inner cylinder, with thermally conductive silicone filling the gaps to ensure good contact. A circuit board, fixed in the space between the inner and outer cylinders, handles data processing. An RS-485 interface is mounted on the outer cylinder for communication with external devices. A data fusion module is soldered to the circuit board surface, connected to the MEMS temperature sensors, and outputs data via the RS-485 interface. This unique sensor design effectively solves the temperature compensation accuracy problem of SF6 density sensors in complex temperature fields, improving measurement accuracy and anti-interference capabilities, while remaining compatible with existing digital interfaces. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0020] Figure 1 This is a schematic diagram of a longitudinal section of an optional wired digital SF6 gas density sensor according to an embodiment of the present utility model;

[0021] 10. Sensor housing; 11. Inner cylinder; 111. Spiral guide fins; 12. Outer cylinder; 13. Interlayer space; 20. Distributed temperature detection array; 21. MEMS temperature sensor; 22. Thermally conductive silicone; 14. Circuit board; 15. RS-485 interface; 30. Data fusion module. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] According to the embodiments of this utility model, the GIS air chamber SF6 micro-water density monitoring sensor, such as Figure 1As shown, this utility model provides a wired digital SF6 gas density sensor. The sensor includes: a sensor housing 10, a distributed temperature detection array 20, and a data fusion module 30. The sensor housing 10 is a double-layer hollow structure composed of a cylindrical inner cylinder 11 and a cylindrical outer cylinder 12. The axial length of the inner cylinder 11 is L, the inner diameter is D, and multiple spiral guide fins 111 are provided on the inner surface. The outer cylinder 12 is made of ceramic and completely covers the inner cylinder 11. The distributed temperature detection array 20 includes multiple MEMS temperature sensors 21. The MEMS temperature sensors 21 are symmetrically embedded in the mounting grooves on the inner wall of the inner cylinder 11, and the grooves are filled with thermally conductive silicone 22. The system includes: a circuit board 14 fixed in the interlayer space 13 between the inner cylinder 11 and the outer cylinder 12; an RS-485 interface 15 fixedly mounted on the outer cylinder 12; a data fusion module 30 soldered to the surface of the circuit board 14, with its input terminal connected to multiple MEMS temperature sensors 21, and its output terminal connected to an external cable via the RS-485 interface 15; the height of the spiral guide fins 111 is D / 6-D / 4, the spacing between adjacent spiral guide fins 111 is L / 12-L / 8, and the spiral direction of the spiral guide fins 111 forms an angle of 25°-50° with the axis of the sensor housing 10.Specifically, the wired digital SF6 gas density sensor provided in this embodiment includes a sensor housing 10, a distributed temperature detection array 20, and a data fusion module 30. The sensor housing 10 includes a double-layer hollow structure consisting of a cylindrical inner cylinder 11 and a cylindrical outer cylinder 12. The axial length of the inner cylinder 11 is L and its inner diameter is D. Multiple spiral guide fins 111 with a height of D / 6-D / 4 are provided on the inner surface of the inner cylinder 11. The spacing between adjacent spiral guide fins 111 is L / 12-L / 8. The spiral direction of the spiral guide fins 111 forms an angle of 25°-50° with the axial direction of the sensor housing 10 to promote gas flow. Uniformity and accelerated heat exchange; the outer cylinder 12 is made of ceramic and completely covers the inner cylinder 11 through a sintering process to resist electromagnetic interference and corrosion; the distributed temperature detection array 20 includes 16 annularly symmetrical MEMS temperature sensors 21 embedded in circular mounting grooves on the inner wall of the inner cylinder 11, each MEMS temperature sensor 21 is filled with thermally conductive silicone 22 to improve temperature conduction efficiency and fix the device; the circuit board 14 is fixed in the interlayer space 13 between the inner cylinder 11 and the outer cylinder 12 by stainless steel screws; the RS-485 interface 15 is fixed in the rectangular through hole on the side wall of the outer cylinder 12 by epoxy resin adhesive; data fusion module. 30 STM32F103 chips are soldered onto the copper foil pads of circuit board 14. The input of data fusion module 30 is connected to the pins of 16 MEMS temperature sensors 21 via 0.5mm diameter silver-plated copper wires. The output of data fusion module 30 is connected to the SP3485 chip of RS-485 interface 15 via PCB traces of circuit board 14. Data fusion module 30 processes the detection data of 16 MEMS temperature sensors 21 using a weighted average algorithm. Specifically, it multiplies the measured value of each MEMS temperature sensor 21 by its corresponding weighting coefficient, sums the results, and then divides by the total weighting coefficient. The coefficients are inversely proportional to the distance between each sensor and the gas contact surface. The processed temperature data is transmitted to an external monitoring system via the Modbus protocol of the RS-485 interface 15. The tilt angle and dense distribution of the spiral guide fins 111 create turbulence in the SF6 gas to eliminate temperature gradients. The ceramic outer cylinder 12 isolates the measurement core from the influence of external temperature abrupt changes. The filling of thermally conductive silicone 22 ensures tight contact between the MEMS temperature sensor 21 and the metal wall of the inner cylinder 11. The multi-point weighted algorithm of the data fusion module 30 eliminates local temperature anomalies, ultimately achieving accurate measurement of SF6 gas density in complex temperature fields. This sensor solves the problem of insufficient temperature compensation accuracy of SF6 density sensors in complex temperature fields, improving measurement accuracy and resistance to environmental interference.

[0024] Specifically, the height of the spiral guide fins 111 is D / 5, the spacing between adjacent spiral guide fins 111 is L / 10, and the spiral direction of the spiral guide fins 111 forms a 30° angle with the axial direction of the sensor housing 10. Specifically, the wired digital SF6 gas density sensor provided in this embodiment includes a sensor housing 10, which includes a cylindrical inner cylinder 11 and a cylindrical outer cylinder 12. Spiral guide fins 111 with a height of D / 5 are disposed on the inner surface of the inner cylinder 11. The spacing between adjacent spiral guide fins 111 is L / 10, and the spiral direction of the spiral guide fins 111 forms a 30° angle with the axial direction of the sensor housing 10. The spiral guide fins 111 are evenly distributed circumferentially on the inner surface of the inner cylinder 11 and continuously extend to the axis of the inner cylinder 11. Spiral guide fins 111 at 30° angles at both ends create a spiral flow path for SF6 gas within the inner cylinder 11 to uniformly distribute the gas temperature field. The outer cylinder 12 is made of ceramic and completely encloses the inner cylinder 11, forming a sandwich space 13 between the outer cylinder 12 and the inner cylinder 11. The distributed temperature detection array 20 includes multiple MEMS temperature sensors 21, which are embedded in circular mounting grooves on the inner wall of the inner cylinder 11. Each MEMS temperature sensor 21 fills the gap in the mounting groove with thermally conductive silicone 22 to eliminate air gap thermal resistance. Circuit board 14 is fixed within the interlayer space 13 and connected to the outer wall of the inner cylinder 11 by screws; RS-485 interface 15 is installed in a through hole in the side wall of the outer cylinder 12, and the metal shell is fixed to the ceramic wall of the outer cylinder 12 by adhesive; data fusion module 30 is soldered to the surface of circuit board 14, the input end of data fusion module 30 is directly connected to the pin of MEMS temperature sensor 21 through wires, and the output end of data fusion module 30 is connected to the pin of RS-485 interface 15 through copper foil traces on circuit board 14; spiral guide fins 11 The D / 5 height and L / 10 spacing of the 1 reduce gas flow resistance by 20% while maintaining turbulence intensity. The 30° spiral angle extends the residence time of the gas in the inner cylinder 11 to fully facilitate heat exchange. The ceramic outer cylinder 12 isolates the MEMS temperature sensor 21 from the influence of sudden temperature changes in the external environment. The thermally conductive silicone 22 conducts the heat of the MEMS temperature sensor 21 to the metal wall of the inner cylinder 11 to achieve rapid temperature response. The data fusion module 30 outputs the measurement data of multiple MEMS temperature sensors 21 after arithmetic averaging.

[0025] Specifically, the detection surface of the MEMS temperature sensor 21 is flush with the inner wall of the inner cylinder 11, and the thermal conductivity of the thermally conductive silicone 22 is 5-8 W / (m·K). Specifically, the wired digital SF6 gas density sensor provided in this embodiment includes a sensor housing 10, which includes a cylindrical inner cylinder 11 and a cylindrical outer cylinder 12. The inner surface of the inner cylinder 11 is a smooth metal surface with an axial length of L and an inner diameter of D. The distributed temperature detection array 20 includes multiple MEMS temperature sensors 21. The detection surface of the MEMS temperature sensors 21 is flush with the inner wall of the inner cylinder 11. The MEMS temperature sensors 21 are embedded in a circular mounting groove on the inner wall of the inner cylinder 11. The depth of the mounting groove is equal to the thickness of the MEMS temperature sensor 21's encapsulation shell. The inner edge of the mounting groove is chamfered by 0.1 mm to prevent scratching the sensor during installation. The thermally conductive silicone 22 has a thermal conductivity of 5-8 W / (m·K). The thermally conductive silicone 22 is injected into the mounting groove through a syringe and completely fills the 0.05 mm gap between the MEMS temperature sensor 21 and the side wall of the mounting groove. After curing, the surface of the thermally conductive silicone 22 is flush with the detection surface of the MEMS temperature sensor 21. The circuit board 14 is a rectangular PCB. The circuit board 14 is fixed to four threaded holes on the outer wall of the inner cylinder 11 by four M2 stainless steel screws. The mounting position of the circuit board 14 is located in the middle of the interlayer space 13 between the inner cylinder 11 and the outer cylinder 12. The metal shell of the RS-485 interface 15 is embedded in an 8mm×5mm rectangular through hole machined in the side wall of the outer cylinder 12. The pins of the RS-485 interface 15 pass through the through hole and are connected to the copper foil pads of the circuit board 14 by solder. The data fusion module 30 is a surface mount chip and is soldered to the circuit board 14. In the left area, the input pins of the data fusion module 30 are connected one-to-one with the output pins of the MEMS temperature sensor 21 via silver-plated wires with a diameter of 0.15mm. The detection surface of the MEMS temperature sensor 21 is flush with the inner wall of the inner cylinder 11 to avoid local eddies caused by gas flow. The thermally conductive silicone 22 with a thermal conductivity of 5-8W / (m·K) reduces the temperature conduction delay to less than 0.2 seconds. The data fusion module 30 collects real-time data from multiple MEMS temperature sensors 21 and outputs it to the RS-485 interface 15.

[0026] Specifically, the outer cylinder 12 is made of aluminum nitride ceramic material, the aluminum nitride ceramic layer has a thickness of 0.2-0.5mm, and the outer surface of the outer cylinder 12 is covered with a polyimide insulating coating of 0.1-0.3mm thickness. The sensor housing (10) of this embodiment includes a cylindrical outer cylinder 12. The outer cylinder 12 is made of aluminum nitride ceramic and is coated on the outer surface of the inner cylinder 11 by plasma spraying. The thickness of the aluminum nitride ceramic layer is 0.2-0.5 mm and the thickness deviation is ≤ ±0.02 mm. The outer surface of the outer cylinder 12 is covered with a polyimide insulating coating with a thickness of 0.1-0.3 mm by dip coating. The surface roughness Ra of the polyimide insulating coating is ≤1.6 μm. The thermal conductivity of the aluminum nitride ceramic layer is 170-200 W / (m·K) to achieve rapid heat dissipation. The thickness of 0.2-0.5 mm makes the compressive strength of the outer cylinder 12 ≥300 MPa. The volume resistivity of the polyimide insulating coating is ≥1×10^16 Ω·cm and the breakdown voltage is ≥3000 V / mm. The thickness of 0.1-0.3 mm makes the surface withstand voltage of the outer cylinder 12 reach AC 3000 V / 1 min without breakdown.

[0027] Specifically, the circuit board 14 is provided with a honeycomb heat dissipation hole array, the hole diameter of the heat dissipation hole array is 1-2mm and it is evenly distributed. In this embodiment, the circuit board 14 is a rectangular substrate made of FR-4 material. The thickness of the circuit board 14 is 1.6mm, and a honeycomb-shaped heat dissipation hole array is provided on its surface. The diameter of the honeycomb-shaped heat dissipation hole array is 1-2mm, and the tolerance is controlled within ±0.05mm. The heat dissipation hole array adopts a hexagonal honeycomb arrangement. The center-to-center distance between adjacent heat dissipation holes is 1.5 times the diameter of the hole, and they are evenly distributed in the non-wiring area of ​​the circuit board 14. The heat dissipation holes are formed by CNC drilling machine. During the machining, the drill bit speed is 30000rpm and the feed rate is 0.02mm / revolution. The inner wall of the heat dissipation hole is plated with a 30μm thick chemical copper plating layer to improve heat dissipation efficiency. The 1-2mm hole diameter design of the honeycomb-shaped heat dissipation hole array increases the effective heat dissipation area of ​​the circuit board 14 by 45%, and the hexagonal honeycomb arrangement improves the air convection efficiency by 25%. The edge of the heat dissipation hole is kept 2mm away from the pin pads of the components on the circuit board 14 to prevent drilling damage. The heat dissipation hole array covers 85% of the effective area of ​​the surface of the circuit board 14 and avoids the installation positions of the RS-485 interface 15 and the data fusion module 30.

[0028] Specifically, the RS-485 interface 15 has a silicone sealing ring at its cable inlet. This silicone sealing ring is embedded in an annular groove in the outer cylinder 12, and the depth of the annular groove is 2 / 3 of the silicone sealing ring's thickness. In this embodiment, the metal casing of the RS-485 interface 15 has a cable inlet hole with a diameter of 5mm. The outer edge of the cable inlet hole is machined with an annular groove 3mm wide, 2.5mm deep, and with an inner wall surface roughness Ra = 3.2μm. The silicone sealing ring has a wire diameter of 3.75mm and a hardness of 70±5 Shore A. The silicone sealing ring is pressed into the annular groove using a special crimping tool. During crimping, an axial compression of 30% is used to cause radial expansion of the silicone sealing ring. The depth of the annular groove is designed to be 2 / 3 of the silicone sealing ring's thickness (a silicone sealing ring thickness of 3.75mm corresponds to a groove depth of 2.5mm). The bottom of the annular groove is far from the outer surface of the outer cylinder 12. Maintaining a wall thickness of 1.25mm ensures structural strength; the outer diameter of the installed silicone sealing ring expands to 4.2mm and forms an interference fit with the cable outer sheath; the compression permanent deformation rate of the silicone sealing ring is ≤10% to maintain long-term sealing effect; the chamfer radius of the annular groove is 0.3mm to prevent tearing of the silicone sealing ring edge during crimping; the cable inlet hole axis is arranged perpendicularly to the radial center line of the outer cylinder 12 at 90°; the volume resistivity of the silicone sealing ring is ≥1×10^14Ω·cm to maintain electrical insulation performance; the 70ShoreA hardness ensures that the sealing ring does not undergo plastic deformation when the cable is bent; the 2 / 3 depth annular groove design increases the sealing ring fixing firmness by 40% and the pull-out force is ≥50N.

[0029] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A wired digital SF6 gas density sensor, characterized in that, The utility model relates to a kind of temperature sensor, including: Sensor housing (10), the sensor housing (10) is made of double-layer hollow structure of cylindrical inner tube (11) and cylindrical outer tube (12), the axial length of the inner tube (11) is L, inner diameter is D, and inner surface is equipped with multiple spiral flow guide fins (111), the outer tube (12) is ceramic material and completely covers inner tube (11); Distributed temperature detection array (20) includes multiple MEMS temperature sensors (21), the MEMS temperature sensor (21) is embedded in the mounting groove of inner wall of the inner tube (11) in annular symmetry, and the gap between grooves is filled by heat-conducting silica gel (22); Circuit board (14) is fixed in the interlayer space (13) between the inner tube (11) and the outer tube (12); RS-485 interface (15) is fixedly installed on the outer tube (12); Data fusion module (30) is welded on the surface of the circuit board (14), and the input end of the data fusion module (30) is connected with multiple MEMS temperature sensors (21), and the output end of the data fusion module (30) is connected with external cable through RS-485 interface (15); The height of the spiral flow guide fin (111) is D / 6-D / 4, the distance between adjacent spiral flow guide fins (111) is L / 12-L / 8, and the spiral direction of the spiral flow guide fin (111) and the axial direction of the sensor housing (10) form an angle of 25°-50°.

2. The sensor of claim 1, wherein, The height of the spiral flow guide fin (111) is D / 5, the distance between adjacent spiral flow guide fins (111) is L / 10, and the spiral direction of the spiral flow guide fin (111) and the axial direction of the sensor housing (10) form an angle of 30°.

3. The sensor of claim 1, wherein, The detection surface of the MEMS temperature sensor (21) is flush with the inner wall of the inner tube (11), and the thermal conductivity of the heat-conducting silica gel (22) is 5-8 W / (m·K).

4. The sensor of claim 1, wherein, The outer tube (12) is made of aluminum nitride ceramic material, the thickness of the aluminum nitride ceramic layer is 0.2-0.5 mm, and the outer surface of the outer tube (12) is covered with a 0.1-0.3 mm thick polyimide insulating coating.

5. The sensor of claim 1, wherein, The circuit board (14) is provided with a honeycomb-shaped array of heat dissipation holes, and the hole diameter of the heat dissipation hole array is 1-2 mm and uniformly distributed.

6. The sensor of claim 1, wherein, A silica gel sealing ring is provided at the cable inlet of the RS-485 interface (15), the silica gel sealing ring is embedded in the annular groove of the outer tube (12), and the depth of the annular groove is 2 / 3 of the thickness of the silica gel sealing ring.

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