Liquid level transmitter and method of manufacturing the same

Abstract

This invention belongs to the field of transmitter technology and discloses a level transmitter and its manufacturing method. It includes a protective cap, a pressure sensor, a conversion circuit, and a cable encapsulation unit. The protective cap is a cylindrical structure, located on one side of the transmitter and connected to the pressure sensor. The pressure sensor is positioned between the protective cap and the conversion circuit, with one end fixedly connected to the protective cap and the other end connected to the conversion circuit. A circular metal shell is provided outside the conversion circuit, and the conversion circuit is connected inside the circular metal shell via a transmitter plate. The cable encapsulation unit is located on the other side of the transmitter and fixedly connected to the metal shell. The structure and method of this level transmitter and its manufacturing method simplify the process and assembly of the level transmitter, reduce the outer diameter of the level transmitter, improve sealing performance, and make the detection results of the level transmitter more accurate.

Description

Technical Field

[0001] This invention belongs to the field of transmitter technology, specifically relating to a liquid level transmitter and its manufacturing method. Background Technology

[0002] Silicon piezoresistive pressure sensors are widely used due to their high sensitivity, low cost, and accuracy that meets most measurement needs. Level transmitters are one type of instrument developed using these characteristics of silicon piezoresistive pressure sensors. In level detection applications, level transmitters developed using silicon piezoresistive pressure sensors are widely used due to their advantages such as high sensitivity, low cost, and ease of use.

[0003] Currently, there are various types of liquid level transmitters on the market that can achieve high-precision liquid level measurement. However, they all use oil-filled core pressure sensors assembled or welded through a housing. The pressure sensor needs to be encased in a housing, and a corresponding conversion circuit and cable seal ring are assembled inside the housing to form a complete liquid level transmitter. However, during the assembly process, the pressure sensor needs to be placed into the housing containing the conversion circuit, resulting in an excessively large housing diameter for the liquid level transmitter and increasing assembly and other process costs. Furthermore, due to the poor sealing effect of the cable seal ring in some liquid level transmitters, the detection results of the liquid level transmitter have a large error. Summary of the Invention

[0004] The purpose of this invention is to provide a level transmitter and its manufacturing method to solve the problems in the prior art;

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A level transmitter includes a protective cap, a pressure sensor, a conversion circuit, and a cable encapsulation unit, wherein:

[0007] The protective cap has a cylindrical structure and is disposed on one side of the level transmitter and connected to the pressure sensor;

[0008] The pressure sensor is disposed between the protective cap and the conversion circuit, with one end of the pressure sensor threadedly connected to the protective cap and the other end connected to the conversion circuit;

[0009] The conversion circuit is provided with a circular metal shell on the outside, and the conversion circuit is connected to the cable in the cable encapsulation unit through wires inside the circular metal shell.

[0010] The cable encapsulation unit is located on the other side of the transmitter and is fixedly connected to the metal housing.

[0011] Furthermore, the protective cap includes a cap body, a filter, a retaining ring, and an O-ring, wherein,

[0012] The cap body is a hollow cavity structure, the retaining ring is disposed inside the cavity, one end of the cap body is a closed end and the other end is an open end, an external thread is provided on the outer circular surface of the open end, and a through liquid inlet hole is provided on the cap body between the open end and the closed end.

[0013] The filter screen is disposed within the cavity and located on one side of the retaining ring;

[0014] The O-ring is fitted onto the bottom of the external thread.

[0015] Furthermore, the number of liquid inlet holes is four, and the four liquid inlet holes are evenly distributed on the cap body, and the four liquid inlet holes are located between the filter screen and the closed end of the cap.

[0016] Furthermore, the pressure sensor includes a base, an insulating corrugated diaphragm, a conductive medium, a tube socket, a pressure chip, and a compensation plate, wherein...

[0017] One end of the base is a closed end and the other end is an open end. A through hole is provided at the center of the open end and the closed end. A hollow boss is provided inside the open end. A diaphragm connector with an annular structure is welded to the end face of the closed end.

[0018] The conductive medium is disposed within the first through hole;

[0019] The isolation corrugated diaphragm is fixedly disposed within the annular region of the diaphragm connector of the annular structure and is fixedly connected to the closed end face of the base;

[0020] The tube base is fixedly mounted on the hollow boss surface, and a ceramic seat is provided inside the hollow boss of the base, with one end face in contact with the ceramic seat.

[0021] The pressure chip is fixedly disposed inside the hollow boss;

[0022] The compensation plate is located at the port of the open end and is fixedly connected to the base via pins.

[0023] Furthermore, the conductive medium is silicone oil.

[0024] Furthermore, the tube base has a through second hole at its center, a vent pipe is fixedly installed on the second through hole, and a plurality of pins and medium injection holes are evenly arranged around the second through hole. One end of the plurality of pins is fixedly installed on the tube base, and the other end passes through the compensation plate and is fixedly connected to the compensation plate. The plurality of pins are connected to the pressure chip by bonding alloy wires, and a sealing member is provided on the medium injection hole.

[0025] Furthermore, the sealing component is a stainless steel ball.

[0026] Furthermore, the conversion circuit includes a conversion circuit housing and a transmitter board, an insulating sleeve, a vent pipe, and an outer sleeve disposed within the conversion circuit housing. The transmitter board is fixedly disposed within the insulating sleeve. One end of the vent sleeve is connected to a vent pipe on a pipe seat, and the other end faces the cable encapsulation unit. One end of the transmitter board is connected to a pin via an input wire. The conversion circuit housing is filled with potting compound.

[0027] Furthermore, the cable encapsulation unit includes a conductor sealing sleeve and a rubber sheath, wherein one end of the rubber sheath is a fixed end and the other end is a free end, and the fixed end of the rubber sheath is detachably connected to the conductor sealing sleeve; concentrically distributed through holes for the passage of ventilated cables are respectively provided in the center of the conductor sealing sleeve and the rubber sheath, and a first rubber ring, a conductor sealing gasket, a second rubber ring, and a conductor sealing fastener are sequentially arranged between the conductor sealing sleeve and the rubber sheath.

[0028] A method for manufacturing a level transmitter includes:

[0029] S1: The ceramic base and pressure chip are bonded to the tube socket of the pressure sensor unit, and the pins on the tube socket are electrically connected to the pressure chip by bonding wire.

[0030] S2: A base is set on one side of the pressure sensor unit tube seat, and a conversion circuit is set on the other side. Conductive medium is injected into the medium injection hole of the base and the medium injection hole is sealed with a sealing component. A compensation plate is welded on the pin. The compensation plate is electrically connected to the transmitter board inside the housing of the conversion circuit with a wire. An insulating sleeve is installed in the sleeve of the conversion circuit and potting compound is filled in the insulating sleeve.

[0031] S3: On the other side of the conversion circuit, a wire sealing sleeve and a rubber sheath are provided, and a first rubber ring, a wire sealing gasket, a second rubber ring and a wire sealing fastener are sequentially provided between the wire sealing sleeve and the rubber sheath.

[0032] S4: Install a protective cap on the other side of the pressure sensor. Insert a filter screen and a retaining ring for the holes into the inside of the protective cap. Insert an O-ring into the bottom of the threaded part of the protective cap and connect the protective cap to the diaphragm connector to complete the manufacturing of the level transmitter.

[0033] Compared with the prior art, the advantages of the present invention are:

[0034] This invention discloses a level transmitter comprising a protective cap, a pressure sensor, a conversion circuit, and a cable encapsulation unit. The protective cap is positioned on one side of the level transmitter and connected to the pressure sensor. The cable encapsulation unit is positioned on the other side of the level transmitter, with the pressure sensor and conversion circuit positioned between the protective cap and the cable encapsulation unit. The cable encapsulation unit is connected to the metal housing of the conversion circuit. The outer diameter of the conversion circuit sleeve is the same as that of the pressure sensor base, thereby reducing the outer diameter of the level transmitter. The pressure sensor is configured as a separate unit, positioned between the protective cap and the conversion circuit, allowing the pressure sensor to be directly connected to both the protective cap and the housing of the conversion circuit, thus simplifying the manufacturing process and assembly. The structure of the cable encapsulation unit improves the sealing performance of the cable within the level transmitter, resulting in more accurate level transmitter readings. Attached Figure Description

[0035] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0036] Figure 1 This is a schematic cross-sectional view of the overall structure of a level transmitter according to the present invention;

[0037] Figure 2 This is a schematic diagram of the cap structure of a level transmitter according to the present invention;

[0038] Figure 3 This is a schematic cross-sectional view of the pressure sensor structure of a level transmitter according to the present invention;

[0039] Figure 4 This is a schematic diagram of the tube socket chip bonding structure of a level transmitter according to the present invention;

[0040] Figure 5 This is a schematic diagram of the structure of a wire sealing fastener for a level transmitter according to the present invention;

[0041] The components include: 11. Protective cap; 111. Liquid inlet hole; 112. Connecting thread; 12. Filter screen; 13. Hole retaining ring; 14. O-ring; 21. Diaphragm connector; 22. Isolation corrugated diaphragm; 23. Conducting medium; 24. Bonding wire; 25. Ceramic base; 26. Base; 261. Diaphragm welding station; 262. Base welding station; 27. Tube seat; 271. Pin; 272. Vent tube; 273. Medium injection hole; 274. Sealing component; 28. Pressure chip. 29. Compensation plate; 31. Transmitter plate; 311. Input lead; 312. Output lead; 32. Insulating sleeve; 33. Potting compound; 34. Vent sleeve; 35. Sleeve; 351. Sleeve welding station; 41. First rubber ring; 42. Conductor sealing gasket; 43. Second rubber ring; 44. Conductor sealing sleeve; 441. Sheath groove; 45. Conductor sealing fastener; 46. Rubber sheath; 47. Vent cable; 471. Core wire; 472. Cable vent pipe. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0043] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0044] A level transmitter according to the present invention includes a protective cap 11, a pressure sensor, a conversion circuit, and a cable encapsulation unit. The protective cap 11 is disposed on one side of the level transmitter and connected to the pressure sensor. The cable encapsulation unit is disposed on the other side of the level transmitter. The pressure sensor and the conversion circuit are disposed between the protective cap 11 and the cable encapsulation unit, so that the cable encapsulation unit is connected to the metal shell of the conversion circuit. The outer diameter of the conversion circuit sleeve is the same as that of the pressure sensor base, thereby reducing the outer diameter of the level transmitter. The pressure sensor is disposed as a separate unit between the protective cap 11 and the conversion circuit, so that the pressure sensor can be directly connected to the protective cap 11 and the shell of the conversion circuit, thereby simplifying the process and assembly flow. Furthermore, the structure of the cable encapsulation unit improves the sealing performance of the cable in the level transmitter, making the detection results of the level transmitter more accurate.

[0045] Specifically, the protective cap 11, pressure sensor, conversion circuit and cable encapsulation unit are all cylindrical structures, and the outer diameter of the cylindrical structures is the same.

[0046] Specifically, such as Figure 1 and Figure 2 As shown, the cap 11 includes a cap body, a filter screen 12, a retaining ring 13, and an O-ring rubber ring 14. The cap body is a hollow cavity structure with one end being a closed end and the other end being an open end. Threads are provided on the outer circumference of the open end. A through-hole liquid inlet 111 is provided on the cap 11 between the open end and the closed end. The retaining ring 13 is disposed inside the cavity. The filter screen 12 is disposed on one side of the retaining ring 13. The O-ring rubber ring 14 is fitted onto the bottom of the external threaded surface. Several through-hole liquid inlets 111 are provided on the cap 11, and the liquid inlets 111 are located between the filter screen 12 and the closed end. Preferably, there are four liquid inlet holes 111; that is, the cap 11 is equipped with a filter screen 12 and is fixed with a retaining ring 13; the cap 11 has four symmetrical liquid inlet holes 111, and the whole is connected to the diaphragm connector 21 at the front end of the silicon piezoresistive pressure sensor through the connecting thread 112; its main function is to protect the pressure sensor isolation corrugated diaphragm 22, and to isolate impurities and conduct liquid; depending on the properties of the measured liquid, the cap 11 is preferably made of injection molded parts such as nylon, and at the same time, depending on the needs, the cap can be made of metal materials including but not limited to 304 stainless steel, 316L stainless steel, titanium alloy and other metal materials.

[0047] Specifically, such as Figure 1 and Figure 3As shown, the pressure sensor includes a diaphragm connector 21, an insulating corrugated diaphragm 22, a conductive medium 23, a bonding wire 24, a ceramic seat 25, a base 26, a tube seat 27, a pressure chip 28, and a compensation plate 29. The base 26 has a closed end and an open end, with a through hole at the center of both ends. A hollow boss is located inside the open end, and an annular diaphragm connector 21 is welded to the closed end face. The conductive medium 23 is disposed within the first through hole. The insulating corrugated diaphragm 22 is fixedly disposed within the annular region of the annular diaphragm connector 21 and is fixedly connected to the closed end face of the base 26. The tube seat 27 is fixedly disposed on the hollow boss surface, and a ceramic seat 25 is disposed within the hollow boss of the base 26, with one end face contacting the ceramic seat 25. The pressure chip 28 is fixedly disposed within the hollow boss. The compensation plate 29 is disposed at the open end port and is fixedly connected to the base 26 via a cover plate. Preferably, the pressure sensor is an isolated oil-filled silicon piezoresistive pressure sensor. Preferably, the tube seat 27 is a TO tube seat. This configuration converts the pressure generated by the liquid level height into a linear output voltage signal, realizing the pressure-electrical signal conversion function. Its rear electrical components are connected to the transmitter board 31 via pins 271, the vent pipe 272 on the tube seat 27 is connected to the vent sleeve 34, and the outer casing is connected to the outer casing of the conversion circuit 3 via a welding station 262. Specifically, the tube seat 27 has a through second through hole at its center, the vent pipe 272 is fixedly installed on the second through hole, and a plurality of pins 271 and medium injection holes 273 are evenly arranged around the second through hole. One end of the plurality of pins 271 is fixedly installed on the tube seat, and the other end passes through the compensation plate 29 and is fixedly connected to the compensation plate 29. The plurality of pins 271 are connected to the pressure chip 28 via bonding wires 24, and a sealing member 274 is provided on the medium injection hole 273.

[0048] Preferably, the sealing element 274 is a stainless steel ball.

[0049] Specifically, a diaphragm welding station 261 is provided on the left side of the base 26, and a base welding station 262 is provided on the right side. The diaphragm welding station 261 is welded to the diaphragm connector 21, and the base welding station 262 is welded to the sleeve 35.

[0050] Specifically, a sleeve welding station 351 is provided on the right side of the sleeve 35, and the sleeve welding station 351 is welded to the wire sealing sleeve 44.

[0051] Preferably, the conductive medium 23 is an oil-based liquid such as silicone oil.

[0052] Specifically, such as Figure 1 and Figure 4As shown, the conversion circuit comprises a transmitter board 31, an insulating sleeve 32, potting compound 33, a venting sleeve 34, and a sleeve 35. The conversion circuit includes a conversion circuit housing and the transmitter board 31, insulating sleeve 32, venting sleeve 34, and sleeve 35 disposed within the housing. The transmitter board 31 is fixedly disposed within the insulating sleeve 32. One end of the venting pipe 34 is connected to the venting pipe 272, and the other end faces the cable encapsulation unit. One end of the transmitter board 31 is connected to the pin 271 via an input wire. The conversion circuit housing is filled with potting compound 33. The transmitter board 31 powers the pressure sensor and converts the voltage signal output by the pressure sensor into a standard signal. In practical applications, depending on the requirements, the standard signal output by the transmitter board 31 includes, but is not limited to, 4mA~20mA, 0~5V, RS485, and I... 2 C; The sleeve 35 is equipped with an insulating sleeve 32 inside to enhance the insulation of the transmitter plate 31 and prevent the transmitter plate 31 from short-circuiting with the housing; and a venting sleeve 34 is provided inside the sleeve 35 to ensure that the pressure reference chamber is in communication with the atmosphere; potting compound 33 is filled between the transmitter plate 31 and the insulating sleeve 32 to enhance the sealing of the transmitter plate 31 and the pressure sensor and prevent the transmitter plate 31 from being affected by moisture.

[0053] Specifically, the reference cavity refers to the pressure reference standard inside the vent sleeve 34. The gas inside the vent sleeve 34 must be in communication with the outside atmosphere. In this preferred embodiment, the pressure refers to the gauge pressure. If it is absolute pressure, then venting is not required.

[0054] Specifically, such as Figure 1 As shown, one end of the cable encapsulation unit is a fixed end, and the other end is a free end. A through hole is provided between the fixed end and the free end. A vent cable 47 is fixedly installed in the through hole. The vent cable 47 is connected to the transmitter board 31 through an output conductor and a core wire 471. The fixed end is fixedly connected to the housing of the conversion circuit. The cable encapsulation unit includes a conductor sealing sleeve 44 and a rubber sheath 46, which are detachably connected. Inside the fixed end and the free end, a first rubber ring 41, a conductor sealing gasket 42, a second rubber ring 43, and a conductor sealing fastener 45 are arranged in sequence. Specifically, the function of the cable encapsulation unit is to seal and fix the vent cable 47 to prevent liquid from entering the transmitter and to ensure electrical continuity. The conductor 471 of the internal vent cable 47 is connected to the output end 312 of the circuit board 31, and the external conductor sealing sleeve 44 is welded to the rear step 301 of the sleeve 35. The outer conductor sealing sleeve 44 has a groove 441 at the rear. The rubber sheath 46 is inserted into the groove 441 to prevent the ventilation cable 47 from bending excessively and to form an aesthetically pleasing streamlined shape.

[0055] Specifically, a sheath groove 441 is provided on the right side of the wire sealing sleeve 44, and the sheath groove 441 is an annular groove provided inside the wire sealing sleeve 44.

[0056] Specifically, the structure of the wire sealing fastener 45 is as follows: Figure 5 As shown, a stepped shaft structure consisting of an upper cylinder and a lower cylinder is provided. An external thread is provided on the outer circular surface of the lower cylinder, and a horizontal platform is provided on the two symmetrical sides at the top of the upper circular surface. Concentric through holes of equal size are provided in the center direction of the upper and lower cylinders. By tightening and compressing the rubber ring, the rubber ring is deformed, thereby achieving the purpose of sealing.

[0057] A method for manufacturing a level transmitter includes:

[0058] S1: Attach the ceramic base 25 and the pressure chip 28 to the tube seat of the pressure sensor unit, and electrically connect the pins 271 on the tube seat 27 to the pressure chip 28 via the bonding wire 24.

[0059] S2: A base 26 is set on one side of the pressure sensor unit tube seat, and a conversion circuit is set on the other side. Conductive medium 23 is injected into the medium injection hole 273 of the base 26, and the medium injection hole 273 is sealed with a sealing member 274. A compensation plate 29 is welded on the pin 271. The compensation plate 29 is electrically connected to the transmitter board 31 inside the housing of the conversion circuit with a wire. An insulating sleeve 32 is installed in the sleeve 35 of the conversion circuit, and potting compound 33 is filled in the insulating sleeve 32.

[0060] S3: On the other side of the conversion circuit, a wire sealing sleeve 44 and a rubber sheath 46 are provided. A first rubber ring 41, a wire sealing gasket 42, a second rubber ring 43 and a wire sealing fastener 45 are sequentially provided between the wire sealing sleeve 44 and the rubber sheath 46.

[0061] S4: Set a protective cap 11 on the other side of the pressure sensor. Install a filter screen 12 and a retaining ring 13 for the hole inside the protective cap 11. Install an O-ring rubber ring 14 at the bottom of the thread of the protective cap 11 and thread the protective cap 11 onto the diaphragm connector 21 to complete the manufacturing of the level transmitter.

[0062] Specifically, a method for manufacturing a level transmitter according to the present invention comprises four parts: an isolated oil-filled silicon piezoresistive pressure sensor 2, a protective cap 11 installed in front of it, a conversion circuit component 3 welded to it, and a cable encapsulation component 4 welded to the conversion circuit component 3. The implementation process is detailed according to one of its production flows, including the following steps:

[0063] (1) Implementation method of isolated oil-filled silicon piezoresistive pressure sensor 2: First step is to complete the assembly of pressure chip 28, bond pressure chip 28 to tube seat 27, and then bond ceramic seat 25 to protect pressure chip 28. After bonding and curing, the electrical connection between pressure chip pad and pin 271 is completed; Second step is to complete the sealing of tube seat and metal base. The tube seat 27 and base 26 completed in the first step are sealed using irregular sealing technology; Third step is to complete diaphragm welding. The front part of base 26 completed in the second step is placed with isolation The process involves several steps: First, the corrugated diaphragm 22 and diaphragm connector 21 are aligned using a mold and laser-welded. Second, vacuum oil injection is performed, filling the silicon pressure sensor assembly with pressure-conducting oil in a high-vacuum environment. The oil type can be varied, including but not limited to silicone oil and fluorinated oil. The oil injection hole 273 is then sealed using steel balls or ejector pins 274. Third, temperature compensation for the oil-filled pressure sensor is completed, and the compensation plate 29 is assembled within the step of the base 26. The lead wire 271 is soldered to the compensation plate 29. The isolated oil-filled silicon piezoresistive pressure sensor 2 converts the pressure generated by the liquid level into a linear output voltage signal, achieving pressure-electrical signal conversion. The base 26, diaphragm 22, and diaphragm connector 21 all adopt a circular, symmetrical, and uniform design structure, eliminating the need for positioning, resulting in high assembly efficiency and low production costs.

[0064] (2) The implementation steps of the conversion circuit component 3 are as follows: First, connect the lead 271 on the tube seat 27 to the input lead 311 on the transmitter board 31, leaving the output lead 312; connect the vent sleeve 34 to the vent pipe 272, then line the inner sleeve 35 with the insulating sleeve 32, and connect the sleeve 35 to the base 26 at step 262 and weld it with laser or argon arc welding; the welded sensor transmitter assembly is placed vertically, and potting compound 33 is injected. After potting, only the output line 312 and the vent sleeve 34 are left. This setting allows the outside atmosphere to communicate with the pressure sensor through the vent pipe 272.

[0065] (3) The implementation steps of the cable encapsulation component 4 are as follows: Cut the ventilated cable 47 to the required length, and peel off the outer sheath to the required length, leaving the inner core wire 471 and the cable vent tube 472. Insert the ventilated cable 47 into the conductor sealing sleeve 44, and then install the rubber ring 41, conductor sealing gasket 42, and rubber ring 43 in sequence, and install the conductor sealing fastener 45, tightening it with a wrench. Then install the rubber sheath 46 and snap it into the slot 441 to complete the assembly of the cable encapsulation component 4. The purpose of this process is to fix and seal the ventilated cable, so that the protection level reaches the IP68 protection level; and the double sealing ring sandwiched conductor sealing gasket compression structure can prevent liquid leakage for a long time and ensure the reliability of the seal.

[0066] (4) The core wire 471 of the vent cable 47 is connected to the output wire 312 of the transmitter board 31; and the cable encapsulation 4 is welded to the conversion circuit component at 301. The rear of the conversion circuit component has a spare cavity, which is conducive to the placement of the docking leads and the formation of a conductive path in the gauge pressure sensor vent pipe in the cavity. The vent sleeve 34 and the cable vent pipe 472 can also be directly connected here to achieve the purpose of interconnection.

[0067] (5) Perform pressure testing and commissioning on the transmitter.

[0068] (6) Insert the filter screen 12 into the cap 11 and insert the retaining ring to secure it; put the O-ring rubber ring 14 on the thread of the cap 11 to prevent the cap 11 from loosening, and then screw in the diaphragm connector 21 to complete the fabrication of a liquid level transmitter of the present invention.

[0069] The present invention discloses a level transmitter and its manufacturing method, which uses an integrated isolated oil-filled silicon piezoresistive pressure sensor. The sensor employs a base 26 and a Kovar alloy tube seat 27 sealing structure. The Kovar alloy tube seat 27 is used to bond a pressure chip 28 and a ceramic seat 25, and completes the bonding connection. The base 26 has a pressure guiding hole at its center and an isolation corrugated diaphragm 22 at its front. Vacuum conduction medium is filled through the medium injection hole 273 on the Kovar alloy tube seat 27, and a silicon pressure sensor is formed through compensation. The pressure sensor has a protective cap 11 at the front, with a liquid inlet hole 111 on the cap, and a filter screen 12 and a retaining ring 13 inside. The pressure sensor has a transmitter plate 31, an insulating sleeve 32, potting compound 33 and a vent sleeve 34 at the rear, with the front end of the vent sleeve 34 fitted onto the vent pipe 272 at the rear of the pressure sensor. The conversion circuit has a vent cable seal at the rear, with the vent cable 47 using a double rubber ring with a wire sealing gasket in the middle, and fastened with a wire sealing fastener 45. The wire sealing fastener 45 has a rubber sheath 46 at the rear, realizing an integrated design of the level transmitter, simplifying the production process of the silicon piezoresistive pressure sensor and the transmitter, reducing process costs, and reducing the outer diameter.

[0070] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

[0071] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A level transmitter, characterized in that, Includes a protective cap (11), a pressure sensor, a conversion circuit, and a cable encapsulation unit, wherein, The protective cap (11) is a cylindrical structure. The protective cap (11) is disposed on one side of the level transmitter and connected to the pressure sensor. The pressure sensor is disposed between the protective cap (11) and the conversion circuit. One end of the pressure sensor is fixedly connected to the protective cap (11), and the other end is connected to the conversion circuit. The conversion circuit is provided with a circular metal shell on the outside, and the conversion circuit is connected to the cable in the cable encapsulation unit through wires inside the circular metal shell. The cable encapsulation unit is located on the other side of the level transmitter and is fixedly connected to the metal housing. The pressure sensor includes a base (26), an isolation corrugated diaphragm (22), a conductive medium (23), a tube seat (27), a pressure chip (28), and a compensation plate (29), wherein, The base (26) has a closed end at one end and an open end at the other end. A through hole is provided at the center of the open end and the closed end. A hollow boss is provided inside the open end. A diaphragm connector (21) with an annular structure is welded to the end face of the closed end. The conductive medium (23) is disposed in the first through hole; The isolation corrugated diaphragm (22) is fixedly disposed in the annular area of ​​the diaphragm connector (21) of the annular structure and is fixedly connected to the closed end face of the base (26); The tube seat (27) is fixedly disposed on the hollow boss surface, and a ceramic seat (25) is disposed in the hollow boss of the base (26), with one end face in contact with the ceramic seat (25). The pressure chip (28) is fixedly disposed inside the hollow boss; The compensation plate (29) is disposed at the port of the open end and is fixedly connected to the base (26) via pin (271); The tube base (27) has a through second hole at its center. A vent tube (272) is fixedly installed on the second hole. Several pins (271) and a medium injection hole (273) are evenly arranged around the second hole. One end of each pin (271) is fixedly installed on the tube base (27), and the other end passes through the compensation plate (29) and is fixedly connected to the compensation plate (29). The pins (271) are connected to the pressure chip (28) by a bonding wire (24). A sealing member (274) is provided on the medium injection hole (273). The conversion circuit includes a conversion circuit housing and a transmitter board (31), an insulating sleeve (32), a vent sleeve (34), and a sleeve (35) disposed within the conversion circuit housing. The transmitter board (31) is fixedly disposed within the insulating sleeve (32). One end of the vent sleeve (34) is connected to the vent pipe (272) on the pipe seat (27), and the other end faces the cable encapsulation unit. One end of the transmitter board (31) is connected to the pin (271) through an input wire. The conversion circuit housing is filled with potting compound (33).

2. The level transmitter according to claim 1, characterized in that, The protective cap (11) includes a cap body, a filter (12), a retaining ring, and an O-ring, wherein, The cap body is a hollow cavity structure, the retaining ring is disposed inside the cavity, one end of the cap body is a closed end and the other end is an open end, an external thread is provided on the outer circular surface of the open end, and a through liquid inlet hole (111) is provided on the cap body between the open end and the closed end. The filter (12) is disposed in the cavity and located on one side of the retaining ring; The O-ring is fitted onto the bottom of the external thread.

3. A level transmitter according to claim 2, characterized in that, The number of liquid inlet holes (111) is four. The four liquid inlet holes (111) are evenly distributed on the body of the cap (11) and are located between the filter screen (12) and the closed end of the cap (11).

4. A level transmitter according to claim 1, characterized in that, The conductive medium (23) is silicone oil.

5. A level transmitter according to claim 1, characterized in that, The tube seat (27) has a through second hole at its center. A vent tube (272) is fixedly installed on the second hole. Several pins (271) and a medium injection hole (273) are evenly arranged around the second hole. One end of each pin (271) is fixedly installed on the tube seat (27), and the other end passes through the compensation plate (29) and is fixedly connected to the compensation plate (29). The pins (271) are connected to the pressure chip (28) by a bonding wire (24). A sealing member (274) is provided on the medium injection hole (273).

6. A level transmitter according to claim 5, characterized in that, The sealing element (274) is a stainless steel ball.

7. A level transmitter according to claim 1, characterized in that, The cable encapsulation unit includes a wire sealing sleeve (44) and a rubber sheath (46), wherein one end of the rubber sheath (46) is a fixed end and the other end is a free end, and the fixed end of the rubber sheath (46) is detachably connected to the wire sealing sleeve (44); concentrically distributed through holes for the passage of a ventilated cable (47) are respectively provided in the center of the wire sealing sleeve (44) and the rubber sheath (46), and a first rubber ring (41), a wire sealing gasket (42), a second rubber ring (43) and a wire sealing fastener (45) are sequentially arranged between the wire sealing sleeve (44) and the rubber sheath (46).

8. A method for manufacturing a level transmitter as described in any one of claims 1-7, characterized in that, include, S1: Attach a ceramic base (25) and a pressure chip (28) to the tube base of the pressure sensor unit, and electrically connect the pins (271) on the tube base (27) to the pressure chip (28) through a bonding wire (24); S2: A base (26) is set on one side of the pressure sensor unit tube seat, and a conversion circuit is set on the other side. Conductive medium (23) is injected into the medium injection hole (273) of the base (26), and the medium injection hole (273) is sealed with a sealing member (274). A compensation plate (29) is welded on the pin (271). The compensation plate (29) is electrically connected to the transmitter board (31) inside the housing of the conversion circuit with a wire. An insulating sleeve (32) is installed in the sleeve (35) of the conversion circuit, and potting compound (33) is filled in the insulating sleeve (32). S3: On the other side of the conversion circuit, a wire sealing sleeve (44) and a rubber sheath (46) are provided. A first rubber ring (41), a wire sealing gasket (42), a second rubber ring (43) and a wire sealing fastener (45) are arranged sequentially between the wire sealing sleeve (44) and the rubber sheath (46). S4: Set a protective cap (11) on the other side of the pressure sensor. Insert a filter screen (12) and a retaining ring (13) for the hole into the inside of the protective cap (11). Insert an O-ring (14) into the bottom of the thread of the protective cap (11) and thread the protective cap (11) onto the diaphragm connector (21) to complete the fabrication of the level transmitter.

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