Capacitive pressure sensor

Abstract

The utility model discloses a kind of capacitive pressure sensors, including pedestal and plug, the pedestal has open cavity and medium hole, medium hole one end is communicated with the open cavity, medium hole other end penetrates pedestal, the open cavity bottom wall of the pedestal is equipped with the installation groove for placing sealing washer, form step in the open cavity bottom of pedestal, the sealing washer is located in the installation groove, the free thickness of the sealing washer is greater than the depth of the installation groove, capacitive sensing module, circuit board are also equipped in the open cavity of the pedestal, the plug part is inserted into the open cavity of pedestal, capacitive sensing module, circuit board are limited in the open cavity of insertion pedestal, and capacitive sensing module is contacted with sealing washer.The sealing structure of the utility model reduces process compared with traditional assembly mode, impact resistance is greatly improved, and structure reliability is improved.

Description

Technical Field

[0001] This utility model relates to an industrial measurement and control device, specifically a capacitive pressure sensor. Background Technology

[0002] Existing pressure sensors typically output single-mode signals.

[0003] Currently, diffused silicon pressure sensors are widely used in industrial applications, with their core component being an oil-filled corrugated diaphragm structure. This type of sensor has the following inherent drawbacks: First, the measurement error increases significantly outside the temperature compensation range (-10℃ to 50℃), with errors generally exceeding 0.5%FS across the entire temperature range; second, the presence of the silicone oil medium prevents direct contact with corrosive liquids, and leakage is prone to occur under alternating positive and negative pressure conditions; third, traditional threaded or snap-lock sealing structures rely on precise fit of multiple components, making assembly tolerance control difficult and prone to seal failure in vibration environments. Although ceramic pressure sensing technology has emerged in recent years, it generally uses the principle of ceramic piezoresistive sensing, which has significant limitations in shock resistance. Domestically produced ceramic capacitive pressure sensors have also appeared in recent years, but existing products have not yet formed complete solutions in signal processing, structural sealing, and system integration. Utility Model Content

[0004] The purpose of this invention is to overcome at least one defect in the prior art and to provide a capacitive pressure sensor.

[0005] The technical solution of this utility model is implemented as follows: This utility model discloses a capacitive pressure sensor, including a base and a plug. The base has an opening and a medium hole. One end of the medium hole communicates with the opening and the other end of the medium hole penetrates the base. The bottom wall of the opening of the base is provided with a mounting groove for placing a sealing gasket. A step is formed at the bottom of the opening of the base. The sealing gasket is located in the mounting groove. The free thickness of the sealing gasket is greater than the depth of the mounting groove. The opening of the base is also provided with a capacitive sensing module and a circuit board. The plug is inserted into the opening of the base, limiting the capacitive sensing module and the circuit board to be inserted into the opening of the base, and the capacitive sensing module is in contact with the sealing gasket.

[0006] In some embodiments, the capacitance sensing module is a ceramic capacitance sensing module.

[0007] In some embodiments, the plug is connected to the base.

[0008] In some embodiments, the plug and the base can be connected by riveting.

[0009] In some embodiments, the capacitive pressure sensor of the present invention further includes a cylinder and / or a protective cover. The cylinder is connected to a first end of a base, one end of a plug extends into an opening in the base, and the other end of the plug is located inside the cylinder. The protective cover is connected to a second end of the base, and the medium hole of the base communicates with the inner cavity of the protective cover. The protective cover has an opening.

[0010] In some embodiments, the cylinder is detachably connected to the first end of the base;

[0011] And / or, the protective cover is detachably connected to the second end of the base;

[0012] And / or, a first sealing ring is provided between the cylinder and the base.

[0013] In some embodiments, the cylinder is threadedly connected to the base;

[0014] And / or, the protective cover is threadedly connected to the base;

[0015] And / or, the inner cavity of the cylinder is stepped, the first end of the cylinder is connected to the base, the second end port of the cylinder is provided with a second sealing ring, and the second end of the cylinder is threadedly connected with a fastener, which limits the second sealing ring inside the cylinder.

[0016] In some embodiments, a pressure plate is provided between the capacitance sensing module and the circuit board, and / or a pressure ring is provided between the circuit board and the plug.

[0017] In some embodiments, the capacitance sensing module includes a ceramic diaphragm, and the pressure plate has a groove on the side near the capacitance sensing module.

[0018] In some embodiments, the circuit board is provided with a signal conditioning circuit, the capacitance sensing module is electrically connected to the signal conditioning circuit, and the signal conditioning circuit provides an analog output interface.

[0019] In some embodiments, the capacitive pressure sensor of the present invention further includes a processor and a communication module for digital output. The processor is electrically connected to a signal conditioning circuit via IIC communication, and the processor is electrically connected to the communication module.

[0020] The present invention has at least the following beneficial effects: the sealing structure of the present invention reduces the number of steps compared with the traditional assembly method and greatly improves the impact resistance; the double O-ring design achieves an IP68 protection level and improves the structural reliability.

[0021] Furthermore, the capacitive pressure sensor converts the pressure signal into a capacitive signal through a capacitive sensing module. Combined with the signal conditioning circuit and sealed housing design, it can achieve high-precision and high-reliability pressure detection under harsh working conditions. It features strong impact resistance, high temperature resistance, corrosion resistance, and dual-mode signal output.

[0022] The device of this invention effectively solves the limitations of the prior art through its layered stacked module design, riveted integrated sealing system, and dual-mode output architecture with dual redundant CAN fieldbus and 4-20mA output. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is an exploded view of the structure of a capacitive pressure sensor disclosed in one embodiment of the present invention;

[0025] Figure 2 This is a perspective view of a capacitive pressure sensor disclosed in one embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of a capacitive pressure sensor disclosed in one embodiment of the present invention;

[0027] Figure 4 for Figure 3 A sectional view along the AA direction.

[0028] Figure 5 for Figure 3 The right view;

[0029] Figure 6 This is a circuit block diagram of a capacitive pressure sensor disclosed in one embodiment of the present invention;

[0030] Figure 7 This is a circuit diagram of the signal conditioning circuit and power input protection circuit of a capacitive pressure sensor disclosed in one embodiment of the present invention.

[0031] Figure 8 This is a schematic diagram of the peripheral circuit of the processor of the capacitive pressure sensor disclosed in one embodiment of the present invention;

[0032] Figure 9 This is a schematic diagram of the peripheral circuit of the 485 converter for a capacitive pressure sensor disclosed in one embodiment of the present invention.

[0033] Figure 10 This is a schematic diagram of the power supply circuit of a capacitive pressure sensor disclosed in one embodiment of the present invention.

[0034] In the attached diagram, 1 is the base, 1-1 is the mounting groove, 2 is the sealing gasket, 3 is the capacitive sensing module, 4 is the pressure plate, 4-1 is the groove, 5 is the pressure ring, 6 is the cylinder, 7 is the protective cover, 7-1 is the opening, 8 is the second sealing ring, 9 is the fastener, 10 is the first sealing ring, 11 is the circuit board, and 12 is the plug. Detailed Implementation

[0035] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0036] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0037] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this utility model, unless otherwise stated, "a plurality of" or "several" means two or more.

[0038] See Figures 1 to 5This utility model provides a capacitive pressure sensor, including a base 1 and a plug 12. The base 1 has an opening and a medium hole. One end of the medium hole communicates with the opening and the other end of the medium hole penetrates the base 1. The bottom wall of the opening of the base 1 is provided with a mounting groove 1-1 for placing a sealing gasket 2. A step is formed at the bottom of the opening of the base 1. The sealing gasket 2 is located in the mounting groove 1-1. The free thickness of the sealing gasket 2 is greater than the depth of the mounting groove 1-1. The opening of the base 1 is also provided with a capacitive sensing module 3 and a circuit board 11. The plug 12 is partially inserted into the opening of the base 1, limiting the capacitive sensing module 3 and the circuit board 11 within the opening of the base 1. The capacitive sensing module 3 is in contact with the sealing gasket 2.

[0039] The depth of the mounting groove 1-1 in the base 1 must match the cross-sectional dimensions (such as diameter or rectangular cross-sectional height) of the sealing gasket 2 to ensure that the sealing ring can be appropriately compressed after assembly to form an effective seal. If the mounting groove 1-1 is too deep, the sealing gasket 2 may not be compressible, leading to a risk of leakage; if it is too shallow, the sealing gasket 2 may be over-compressed, resulting in material fatigue, damage, or assembly difficulties. As a preferred embodiment, the depth of the mounting groove 1-1 is 75% to 90% of the original cross-sectional height of the sealing ring to ensure a good compression ratio and sealing performance. The step mainly serves to limit and position the sealing gasket 2, preventing damage due to excessive compression.

[0040] In some embodiments, the plug 12 is connected to the base 1. For example, the plug 12 and the base 1 can be connected by riveting.

[0041] The plug 12 is a multifunctional composite structure, serving multiple functions including signal output, electrical sealing, mechanical reinforcement, and directional positioning. The notch on the plug 12 is used as an assembly direction identification structure.

[0042] In some embodiments, the capacitive pressure sensor of the present invention further includes a cylinder 6 and / or a protective cover 7. The cylinder 6 is connected to the first end of the base 1. One end of the plug 12 extends into the opening of the base 1, and the other end of the plug 12 is connected to the second end of the base 1. The medium hole of the base 1 communicates with the inner cavity of the protective cover 7, and the protective cover 7 is provided with an opening 7-1.

[0043] In some embodiments, the other end of the plug 12 may abut against the cylinder 6.

[0044] In some embodiments, the cylinder 6 is detachably connected to the first end of the base 1. Of course, the cylinder 6 and the first end of the base 1 can also be fixedly connected, such as by welding.

[0045] In some embodiments, the protective cover 7 is detachably connected to the second end of the base 1. Of course, the protective cover 7 and the second end of the base 1 can also be fixedly connected, such as by welding.

[0046] In some embodiments, a first sealing ring 10 is provided between the cylinder 6 and the base 1.

[0047] In some embodiments, the cylinder 6 is threadedly connected to the base 1.

[0048] In some embodiments, the protective cover 7 is threadedly connected to the base 1.

[0049] In some embodiments, the inner cavity of the cylinder 6 is stepped, the first end of the cylinder 6 is connected to the base 1, the second end port of the cylinder 6 is provided with a second sealing ring 8, and the second end of the cylinder 6 is threadedly connected with a fastener 9, which limits the second sealing ring 8 inside the cylinder 6.

[0050] The electrical connection between the capacitive sensing module 3 and the circuit board 11 is achieved by soldering the pins or metal end faces to the pads of the circuit board 11.

[0051] In some embodiments, a pressure plate 4 is provided between the capacitance sensing module 3 and the circuit board 11. The pressure plate 4 has a groove 4-1 or a through slot on the side near the capacitance sensing module 3, corresponding to the portion of the capacitance sensing module 3 that will undergo elastic deformation. The depth of the groove 4-1 of the pressure plate 4 is set as needed. The bottom of the groove of the pressure plate 4 is a mechanical limiting surface. Under a sudden increase in medium pressure, the ceramic diaphragm undergoes elastic deformation and adheres to the mechanical limiting surface of the pressure plate 4, thereby forming a structural deformation limit and preventing the diaphragm from excessively deflecting and breaking.

[0052] In some embodiments, a pressure ring 5 is provided between the circuit board 11 and the plug 12. The pressure ring 5 is a plastic pressure ring 5.

[0053] In some embodiments, the capacitance sensing module 3 employs a ceramic diaphragm.

[0054] The outer casing (including base 1, protective cover 7, etc.) of this embodiment can be made of 316L stainless steel, or CuNi10Fe1Mn alloy for seawater corrosion environments. The seals are made of fluororubber (FKM) or polytetrafluoroethylene, which can withstand strong corrosive media with pH 0-14.

[0055] The pressure sensor of this invention adopts a layered stacked module design. In this embodiment, the capacitance sensing module 3 uses a D20 series ceramic diaphragm (such as the D20054DF capacitance sensing module 3 diaphragm), with a diameter of Φ19.9mm. It is rigidly connected to the stainless steel base 1 via laser welding to convert the pressure signal into a capacitance signal. The surface of the ceramic diaphragm undergoes nano-level polishing, with a contact surface roughness Ra≤0.1μm, effectively preventing media residue.

[0056] In some embodiments, the circuit board 11 is provided with a signal conditioning circuit, the capacitance sensing module 3 is electrically connected to the signal conditioning circuit, and the signal conditioning circuit provides an analog output interface.

[0057] See Figures 6 to 10 The signal conditioning circuit includes a pressure sensor signal conditioning chip. The CINP and CINN pins of the pressure sensor signal conditioning chip are connected to the capacitance sensing module 3. The VGATE pin of the pressure sensor signal conditioning chip is connected to the gate of transistor Q2. The drain of transistor Q2 is connected to the positive terminal of the input power supply. The source of transistor Q2 is connected to the negative terminal of Zener diode D1, one end of filter capacitor C10, one end of filter capacitor C20, and the AVDD pin of the pressure sensor signal conditioning chip. The other end of filter capacitor C10 is grounded. The Zener diode D1... The positive terminal and the other end of the filter capacitor C20 are connected to the negative terminal of the input power supply and one end of resistor R8, with the other end of resistor R8 grounded. The OWI pin of the pressure sensor signal conditioning chip is connected to the positive terminal of the input power supply via a series resistor R5 and capacitor C13. The VOUT pin of the pressure sensor signal conditioning chip is connected to the base of transistor U2 via resistor R6. The collector of transistor U2 is connected to the positive terminal of the input power supply. The emitter of transistor U2 is connected to one end of resistor R7 and one end of capacitor C14, with the other end of resistor R7 grounded and the other end of capacitor C14 connected to the base of transistor U2. The input power supply is a DC input power supply.

[0058] In some embodiments, the FILTER pin of the pressure sensor signal conditioning chip is grounded via a filter capacitor C15.

[0059] In some embodiments, the DVDD pin of the pressure sensor signal conditioning chip is grounded via a filter capacitor C12.

[0060] In some embodiments, the LOOPN pin of the pressure sensor signal conditioning chip is connected to the negative output terminal of the power input protection circuit.

[0061] The pressure sensor signal conditioning chip uses the NSC2860X chip. The VGATE pin of the pressure sensor signal conditioning chip is used to control the chopper, stepping down the DC 24V voltage to DC 5V to supply power to the AVDD pin of the pressure sensor signal conditioning chip, thus providing power to the NSC2860X chip. Simultaneously, capacitors C10 and C20 are used for filtering, and D1 is an avalanche diode, used here as a Zener diode to maintain the supply voltage below 7.5V to prevent high voltage damage to the chip. Pins 4 (CINP) and 5 (CINN) of the pressure sensor signal conditioning chip are connected to the capacitance sensing module 3 for acquiring capacitance signal changes. The OWI and VOUT pins of the pressure sensor signal conditioning chip are two key pins of the OWI bus. Their status and function can be adjusted by changing the values ​​of the "OWI_AC_EN" and "OWI_WINDOW" registers, thereby enabling data reading and chip configuration. U2 is an NPN power bipolar transistor. In conjunction with the OWI bus, it can adjust the loop current to calibrate the sensor with a 4-20mA output current across the pressure range from zero to full scale, ensuring high-precision sensor performance. The high-precision resistor R8, together with resistor R7, is used for current detection feedback, forming a closed-loop control that transmits the feedback signal to VOUT for signal calibration. Capacitor C15 filters the analog signal output from the DAC, reducing output noise.

[0062] In some embodiments, the circuit board 11 is further provided with a power input protection circuit, which includes a surge protection diode D4, a filter capacitor C16, a filter capacitor C17, and a reverse connection protection diode D3. One end of the surge protection diode D4 is connected to the positive terminal of the input power supply, and the other end of the surge protection diode D4 is connected to the negative terminal of the input power supply. The positive terminal of the reverse connection protection diode D3 is connected to one end of the filter capacitor C17 and the positive terminal of the input power supply, respectively. The negative terminal of the reverse connection protection diode D3 is connected to one end of the filter capacitor C16, the collector of transistor U2, and the drain of transistor Q2, respectively. The other ends of the filter capacitor C16 and the other ends of the filter capacitor C17 are connected to the negative terminal of the input power supply.

[0063] In some embodiments, the power input protection circuit further includes anti-interference ferrite beads L1 and L2 for suppressing high-frequency noise signals on the line. One end of the anti-interference ferrite bead L2 is connected to the positive terminal of the input power supply and one end of the surge protection diode D4. The other end of the anti-interference ferrite bead L2 is connected to the positive terminal of the reverse connection protection diode D3. One end of the anti-interference ferrite bead L1 is connected to the negative terminal of the input power supply and the other end of the surge protection diode D4. The other end of the anti-interference ferrite bead L1 is connected to the other end of the filter capacitor C16 and the other end of the filter capacitor C17.

[0064] In the power input protection circuit, D4 is an SD36C-01FTG bidirectional diode used for 36V surge protection. It can safely absorb repeated ESD (electrostatic discharge) shocks without performance degradation. Together with capacitor C16, it can protect against overvoltage transient pulses. D3 is a small, high-speed switching diode widely used in circuits with high signal frequencies for unidirectional conduction isolation. Here, D3 acts as a reverse connection protection diode, preventing damage to the circuit or components from reversed power supply polarity. R5 and R6 are two surge protection resistors used to protect the chip and improve its signal calibration capability. L1 and L2 are two anti-interference ferrite beads used to suppress high-frequency noise signals on the line. C16 and C17 are two filter capacitors used to filter front-end input interference, improving the system's anti-RF interference capability. C12, C13, and C14 are three filter capacitors used to suppress external noise interference and improve the chip's signal calibration and conditioning capabilities.

[0065] In some embodiments, the pressure sensor of this invention further includes a CAN bus communication module. The CAN bus communication module includes a processor and a communication module for digital output. The processor is electrically connected to the signal conditioning circuit via IIC communication, and the processor is also electrically connected to the communication module. The processor and the communication module can be mounted on the same circuit board 11 as the signal conditioning circuit, or they can be mounted on different circuit boards 11.

[0066] In some embodiments, the communication module is a 485 converter for 485 digital output, and the processor is connected to the 485 converter via 485 communication.

[0067] This utility model's pressure sensor supports dual-mode signal output, specifically: the pressure sensor supports dual-mode output of 4-20mA analog signal (loop current adjusted via NSC2860X chip) and RS-485 digital signal (based on MAX3485ESA transceiver). The 4-20mA analog output is controlled by transistor U2 in a closed loop and calibrated by high-precision resistor R8, with a linearity error ≤ ±0.1%. This meets the diverse interface requirements of shipboard equipment.

[0068] The IIC communication between the processor and the pressure sensor signal conditioning chip is established by connecting pins 13SCL and 14SDL of the NSC2860X to pins 6SCL and 7SDL of the AT32. After the NSC2860X performs data normalization processing on the output, it transmits the processed digital signal to the processor (such as the AT32) via IIC communication. The processor packages the received data and outputs it via RS-485 communication through pins 8USART2-TX and 9USART2-RX, thus achieving the digital signal output in the dual-mode output design goal.

[0069] The RS485 converter in this invention has two main functions: first, it is used for level conversion between the processor and the user equipment; second, it is used to control the reception and transmission functions of RS485 communication. The processor establishes RS485 communication by connecting pins 8 (USART2-TX) and 9 (USART2-RX) to pins 4 (USART2-TX) and 1 (USART2-RX) of the RS485 converter, transmitting digital output data to the RS485 converter. Pins 2 and 3 (PA4-DIR) are used for receiving and transmitting data in RS485 communication. Digital output is then achieved through pins 6 (RS485B) and 7 (RS485A) of the RS485 converter, enabling interface with the user.

[0070] In some embodiments, the CAN bus communication module further includes a power supply circuit, which includes a buck converter for converting DC input power to a 3.3V voltage. One embodiment uses a SY8201 synchronous buck converter with an input voltage of 4.5-27V and a regulated 3.3V output, coupled with an L1 energy storage inductor and C22-C25 filter capacitors, supporting wide-temperature operation.

[0071] The signal conditioning circuit in this embodiment integrates the NSC2860X dedicated chip, which has built-in dual 24-bit ADC channels to process capacitance signals and temperature compensation signals respectively, achieving third-order nonlinear calibration. The CAN bus communication module enables the transmission and reception of analog-to-digital data via a dual-redundant CAN bus, and provides a switchable configuration of 4-20mA analog output and dual-redundant CAN bus digital output, allowing for quick module replacement via a pluggable interface. Sealing gasket 2, along with the first sealing ring 10 and the second sealing ring 8, ensure the pressure sensor device is waterproof. The plug 12 uses a riveted integrated seal to reinforce the wiring and the top of the capacitance sensing module 3. This device has a total of 6 leads: two wires for CAN1, two wires for CAN2, and two wires for the power supply (compatible with 4-20mA).

[0072] The base 1 has a stepped limiting step inside, with the step height tolerance controlled within ±0.05mm. The fluororubber sealing gasket 2 is precisely pressed between the edge of the ceramic diaphragm and the base 1 with a compression of 30%±3%, forming a double sealing barrier. The specially designed anti-extrusion gap (1.6±0.05mm) can withstand pressure impacts below 6MPa. When the medium pressure increases suddenly, the ceramic diaphragm directly adheres to the mechanical limiting surface of the pressure plate 4 to form a mechanical limit, avoiding the diaphragm rupture problem common in traditional silicone oil-filled structures.

[0073] The pressure sensor signal conditioning chip can also incorporate a temperature-capacitance coupling compensation algorithm: by acquiring the surface temperature of the ceramic diaphragm (-40℃~150℃), it corrects the capacitance change in real time. Combined with the online calibration function of the pressure sensor signal conditioning chip (NSC2860X chip), the range ratio can be adjusted on-site via the OWI single-bus interface. During calibration, a segmented multi-point calibration method is used, acquiring data at five pressure points: 0%, 25%, 50%, 75%, and 100%. A third-order compensation curve is automatically generated and stored in a 57-byte EEPROM.

[0074] The pressure sensor signal conditioning chip consists of five parts: an analog front-end module, an integrated MCU and digital control logic module, an analog output module, a power supply and drive module, and a serial interface circuit. The analog front-end module includes a main signal channel consisting of a C / V converter and a 24-bit ADC, an auxiliary temperature measurement channel consisting of an integrated temperature sensor and a 24-bit ADC, and a digital filter, providing high-precision sensor signal and temperature acquisition. The integrated MCU and digital control logic module includes a built-in MCU, register table, EEPROM, control logic, and a high-precision internal clock source.

[0075] Based on a built-in MCU, the sensor calibration algorithm can calibrate the sensor's zero point, sensitivity, and temperature drift up to the second order, as well as nonlinearities up to the third order, with a calibration accuracy within 0.1%. Chip configuration parameters and sensor calibration coefficients are stored in a 57-byte EEPROM. The analog output module consists of a 16-bit DAC and a flexibly configurable output driver circuit with multiple voltage output modes, including 4~20mA transmission mode, PDM mode, or PWM mode.

[0076] The following discloses two specific embodiments of the pressure sensor of the present invention:

[0077] Example 1 (Marine Ballast Tank Monitoring): A Φ19.9mm ceramic diaphragm is selected to match the 0-2MPa measurement range. The shell is made of CuNi10Fe1Mn alloy, and the O-rings are made of AS113 standard fluororubber (2.62mm wire diameter). It operates continuously for 2000 hours in a salt spray test (5% NaCl, 35℃), with zero drift <0.05%FS. The signal conditioning module is equipped with dual CAN bus outputs, a bus rate of 1Mbps, and supports the MODBUS-RTU protocol.

[0078] Example 2 (Petrochemical Reactor Pressure Monitoring): A Φ19.9mm diaphragm with a PTFE sealing gasket is used, with the measurement range set to 0-500kPa. The NSC2860X chip is equipped with third-order temperature compensation, and the full-range nonlinearity error is ≤0.15%FS in a 98℃ concentrated sulfuric acid environment. The 4-20mA output circuit integrates a 22mA clamping protection circuit to prevent short-circuit damage.

[0079] According to tests conducted by a third-party testing agency, under the GJB 150A-2009 standard, the device passed the tests of 10g sinusoidal vibration (20-2000Hz) and 40g mechanical shock (11ms half-sine wave); the electromagnetic compatibility meets the requirements of GJB151B-2013RE102 / CE102; after 1000 hours of accelerated aging test (135℃ / 95%RH), the sealing performance maintains the IP68 rating.

[0080] The technical effects of this invention include:

[0081] (1) Breakthrough in measurement performance: The operating temperature range is extended to -40℃~135℃, and the error in the entire temperature range is ≤0.2%FS; the minimum range is as low as 5kPa, and the overload capacity reaches 200% of the range.

[0082] (2) Improved structural reliability: The sealing structure reduces the number of processes by 40% compared to the traditional assembly method, and improves the impact resistance by 300%; the double O-ring design achieves IP68 protection level.

[0083] (3) Optimized maintenance convenience: The modular design supports the replacement of a single functional component within 5 minutes; the unique identification code of laser marking enables full life cycle traceability.

[0084] (4) Extended media adaptability: It can measure high viscosity (≤5000cP), solid particles (particle size ≤1mm) and food-grade clean media, with an annual drift rate of <0.1%TD.

[0085] The pressure sensor of this invention is particularly suitable for measuring liquid level and pressure in harsh working environments such as ships and petrochemical plants, and has the characteristics of corrosion resistance, impact resistance and high precision.

[0086] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A capacitive pressure sensor, characterized in that: The device includes a base and a plug. The base has an opening and a medium hole. One end of the medium hole communicates with the opening and the other end penetrates the base. The bottom wall of the opening of the base has a mounting groove for placing a sealing gasket. A step is formed at the bottom of the opening of the base. The sealing gasket is located in the mounting groove. The free thickness of the sealing gasket is greater than the depth of the mounting groove. The opening of the base also contains a capacitance sensing module and a circuit board. The plug is inserted into the opening of the base, limiting the capacitance sensing module and the circuit board within the opening of the base. The capacitance sensing module is in contact with the sealing gasket.

2. The capacitive pressure sensor as described in claim 1, characterized in that: The capacitance sensing module is a ceramic capacitance sensing module.

3. The capacitive pressure sensor as described in claim 1, characterized in that: The plug is connected to the base.

4. The capacitive pressure sensor as described in claim 3, characterized in that: The plug and base can be connected by riveting.

5. The capacitive pressure sensor as described in claim 1 or 3, characterized in that: It also includes a cylindrical body and / or a protective cover, wherein the cylindrical body is connected to a first end of the base, one end of the plug extends into the opening of the base, the other end of the plug is located inside the cylindrical body, the protective cover is connected to a second end of the base, the medium hole of the base communicates with the inner cavity of the protective cover, and the protective cover is provided with an opening.

6. The capacitive pressure sensor as described in claim 5, characterized in that: The cylinder is detachably connected to the first end of the base; And / or, the protective cover is detachably connected to the second end of the base; And / or, a first sealing ring is provided between the cylinder and the base; And / or, the inner cavity of the cylinder is stepped, the first end of the cylinder is connected to the base, the second end port of the cylinder is provided with a second sealing ring, and the second end of the cylinder is threadedly connected with a fastener, which limits the second sealing ring inside the cylinder.

7. The capacitive pressure sensor as described in claim 1, characterized in that: A pressure plate is provided between the capacitance sensing module and the circuit board, and / or a pressure ring is provided between the circuit board and the plug.

8. The capacitive pressure sensor as described in claim 7, characterized in that: The capacitance sensing module includes a ceramic diaphragm, and the pressure plate has a groove on the side near the capacitance sensing module.

9. The capacitive pressure sensor as described in claim 1, characterized in that: The circuit board is equipped with a signal conditioning circuit, the capacitance sensing module is electrically connected to the signal conditioning circuit, and the signal conditioning circuit provides an analog output interface.

10. The capacitive pressure sensor as described in claim 9, characterized in that: It also includes a processor and a communication module for digital output, wherein the processor is electrically connected to a signal conditioning circuit via IIC communication, and the processor is electrically connected to the communication module.

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