On-line monitoring device for hydrogen, pressure in the headspace of low oil equipment

Abstract

This invention discloses an online monitoring device for hydrogen and pressure in the top space of a low-oil equipment. The device comprises a hydrogen sensing unit, a pressure sensing unit, an MCU circuit, a LoRa wireless communication circuit, an antenna, and a shielding shell. The hydrogen sensing unit, pressure sensing unit, LoRa wireless communication circuit, and antenna are connected to the MCU circuit. These components are housed within the shielding shell. The device is installed at the exhaust port on the top of the low-oil equipment. This online monitoring device, installed at the exhaust port of the oil storage chamber at the top of the low-oil equipment, monitors the hydrogen content and pressure in the high-concentration area at the top of the equipment. This avoids the low data caused by dead-zone sampling, solves the measurement error problem caused by uneven gas distribution, improves response speed, and prevents oil leakage and seepage hazards, thus enhancing the safety of the low-oil equipment monitoring device.

Description

Technical Field

[0001] This invention relates to the field of condition monitoring technology for low-oil equipment, and in particular to an online monitoring device for hydrogen and pressure in the top space of low-oil equipment. Background Technology

[0002] Current internal status monitoring of low-oil equipment primarily focuses on monitoring hydrogen in dissolved gases within the oil. This is achieved by inserting a single-hydrogen sensor into the oil inlet of the equipment. While this method fills the technological gap in online monitoring within low-oil equipment, it also has some drawbacks. Due to the extremely small molecular weight of hydrogen, its escape velocity in oil is very fast, causing the sensor's response speed to lag behind the actual change in hydrogen content. This results in online monitoring data being relatively lower than offline chromatographic data. By redesigning the sensor and installing it on the vent valve at the top of the low-oil equipment to monitor hydrogen concentration, the sensor's sensitivity can be improved.

[0003] In existing technologies, several solutions have been proposed for online monitoring of hydrogen content inside low-oil equipment, expanding from single-parameter monitoring to multi-parameter comprehensive monitoring. All aim to achieve real-time, accurate, and efficient online monitoring. Patent application number 201810928528.3 integrates components such as hydrogen micro-water sensors and pressure sensors to achieve comprehensive monitoring of key parameters of oil-filled equipment. Patent application number 202310694833.1 focuses on a fault monitoring system for low-oil electrical equipment based on hydrogen sensors. It combines signal processing and the k-means algorithm to perform cluster analysis on feature parameters to accurately classify fault types. The above technical solutions mainly insert sensors at the bushing oil inlet and use palladium alloy sensors to measure the hydrogen content in the insulating oil. This approach has certain drawbacks, mainly:

[0004] 1. Uneven gas distribution: In the oil storage chamber at the top of the casing, due to the natural upward floating characteristic of gas, fault gases such as hydrogen may more easily accumulate at the top, thus forming a relatively high concentration area. At the oil outlet of the casing, the gas distribution may be affected by various factors such as oil flow and temperature, resulting in the measurement value not being able to accurately reflect the true hydrogen concentration inside the casing.

[0005] 2. Insufficient representativeness of the sampling. There is a dead zone in the oil sample at the oil sampling port. When the temperature is high, the oil flow velocity inside the casing is fast, and the oil sample at the oil sampling port may be significantly different from the oil sample in other areas of the casing.

[0006] 3. Slow response speed: When a discharge or thermal fault occurs inside the casing, the generated hydrogen gas needs a certain amount of time to diffuse to the oil tap. Therefore, measuring the hydrogen concentration at the oil tap may not reflect the fault condition inside the casing in real time, resulting in a slow response speed of the monitoring system.

[0007] 4. Risk of oil seepage and leakage: During the operation of the casing, there is a certain intensity of vibration. Combined with the high temperature brought about by the load current, the sealing rubber ring will age faster. Therefore, installing a measuring device at the oil outlet may increase the risk of oil seepage and leakage, which poses a threat to the safe operation of the casing. Summary of the Invention

[0008] To overcome the above problems, the purpose of this invention is to provide an online monitoring device for hydrogen and pressure in the top space of a low-oil equipment. This online monitoring device is installed at the exhaust port of the oil storage chamber at the top of the low-oil equipment. By monitoring the hydrogen content and pressure in the high-concentration area at the top of the low-oil equipment, it avoids the problem of low data caused by dead zone sampling, solves the measurement error problem caused by uneven gas distribution, improves the response speed, avoids the risk of oil leakage and seepage, and improves the safety of the monitoring device for low-oil equipment.

[0009] The technical solution adopted in this invention is as follows: it comprises a hydrogen sensing unit, a pressure sensing unit, an MCU circuit, a LORA wireless communication circuit, an antenna, and a shielding shell. The hydrogen sensing unit, pressure sensing unit, LORA wireless communication circuit, and antenna are connected to the MCU circuit. The hydrogen sensing unit, pressure sensing unit, MCU circuit, LORA wireless communication circuit, and antenna are installed in the shielding shell. The device is installed at the top exhaust port of the low-oil equipment.

[0010] The hydrogen sensing unit and pressure sensing unit are used to measure the hydrogen content and pressure inside the oil storage chamber of the low-oil equipment.

[0011] The MCU circuit is used to convert the measurement results of the sensing unit into voltage signals and perform data processing.

[0012] The LORA wireless communication circuit and antenna encode and transmit the signals processed by the MCU.

[0013] The shielding shell equalizes the high electric field at the top of the low-oil equipment, ensuring that the electronic equipment inside the shielding shell is not affected by the strong external electromagnetic environment.

[0014] Furthermore, the hydrogen sensing unit adopts a palladium alloy hydrogen sensor with a Wheatstone full-bridge hydrogen sensor structure, wherein a passivation film is deposited on the surface of the hydrogen sensor of an opposite pair of bridge arms.

[0015] Furthermore, the hydrogen sensing unit integrates a heating resistor and a temperature sensing resistor on the surface of the chip. The heating resistor uses a platinum thin film resistor as the heating element, which is formed into a certain shape by sputtering and depositing a platinum thin film and etching. The temperature sensing resistor uses a nickel thin film resistor.

[0016] Furthermore, the hydrogen sensing unit is encapsulated in a probe, which is designed as a plunger structure with a sealing groove on the side and a boss welded to the bottom. The pins are fixed to the base by glass sintering and are insulated from the base. The tip of the lead wire is pin-shaped. The hydrogen sensing unit is fixed in the groove of the heat insulation pad and electrically connected to the pins by gold wire. The upper end of the hydrogen sensing unit is equipped with a heat insulation cover. Both the heat insulation pad and the heat insulation cover are made of polytetrafluoroethylene.

[0017] Furthermore, the hydrogen-sensitive resistor is fabricated on the surface of an Al2O3 ceramic substrate using microfabrication technology to form a zigzag resistor structure with a total length of 5000 mm.

[0018] Furthermore, the pressure sensing unit employs an oil-filled medium-isolated pressure sensor. This sensor encapsulates the sensitive chip in a sealed container, and the medium pressure is transmitted to the sensitive element through a corrugated diaphragm, thus completely isolating the measured medium from the sensitive element and protecting the sensitive element from damage by the medium.

[0019] Furthermore, the oil-filled medium isolated pressure sensor of the pressure sensing unit includes a pressure base, a corrugated diaphragm, silicone oil, gold wire, a pressure-sensitive chip, and a housing. The pressure base is made of 316 stainless steel and is laser-welded into the housing. The sealed cavity formed by the pressure base and the corrugated diaphragm is filled with liquid pressure-conducting medium silicone oil, which transmits the external medium pressure sensed by the corrugated diaphragm. The pressure-sensitive chip is attached to the oil-filled core pressure base with a surface mount adhesive, and the chip pins are connected to the pins with gold wires using a wire bonding process to achieve external electrical connection.

[0020] Furthermore, the MCU circuit is an ADuCM362, which is a fully integrated 3.9kSPS, 24-bit data acquisition system.

[0021] Furthermore, the LORA wireless communication circuit is a ZM470 LORA communication module, which reduces the circuit design required around the chip.

[0022] Furthermore, the shielding shell is made of aluminum alloy and uses a grid design for electromagnetic noise shielding. The grid material is made of aluminum alloy and covers the circuit. Epoxy resin is used as insulation between the grid and the circuit. The lower part of the shielding shell adopts an open structure. The antenna is a microstrip antenna and is integrated on the MCU circuit.

[0023] The beneficial effects of this invention are:

[0024] 1. Effectively improves the sensitivity of hydrogen and pressure monitoring technology inside low-oil equipment, reduces the response time of fault condition monitoring. By installing this monitoring device at the exhaust port on the top of the low-oil equipment, the hydrogen content and pressure in the high-concentration area at the top can be monitored, avoiding the low data caused by dead zone sampling, solving the measurement error problem caused by uneven gas distribution, improving the response speed, avoiding the risk of oil leakage and seepage, and improving the safety of the low-oil equipment monitoring device.

[0025] 2. The structure of the hydrogen sensing unit can greatly increase the number of hydrogen-sensitive resistors, improve the sensitivity of the hydrogen sensing unit, and ensure a sufficiently fast response speed, thereby ensuring the real-time performance and accuracy of the monitoring results of the online monitoring device.

[0026] 3. In the measurement of the pressure sensing unit, the pressure at the exhaust port of the low-oil device directly acts on the back surface of the silicon chip. Because a cup-shaped back pressure cavity protective layer is formed by using silicon-silicon bonding and silicon glass fusion sealing technology, the fluid medium is isolated from the circuit on the surface of the silicon chip, which makes it have excellent corrosion resistance to the measured medium, can accurately measure pressure, and extend the service life of the device. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure;

[0028] Figure 2 This is a schematic diagram of a hydrogen-sensitive resistor structure;

[0029] Figure 3 This is a schematic diagram of the Wheatstone full-bridge hydrogen-sensitive structure.

[0030] Figure 4 A schematic diagram showing the functional unit layout of a thin-film hydrogen sensor.

[0031] Figure 5 This is the structure of a thin-film hydrogen sensor probe;

[0032] Figure 6 A grid model for a hydrogen sensor;

[0033] Figure 7 Temperature cloud map of hydrogen sensor;

[0034] Figure 8 A schematic diagram showing the diffusion coefficients of H2 and O2 molecules in Si3N4 medium;

[0035] Figure 9 A schematic diagram of the chip cross-section after optimizing the protective film structure and materials;

[0036] Figure 10 This is a test of response characteristics after a high-temperature tolerance test;

[0037] Figure 11 This is a schematic diagram of a medium-isolated pressure sensor.

[0038] Figure 12 This is a schematic diagram of the working principle of the sensitive element;

[0039] Figure 13 This is a block diagram of the 89BSD sensor principle.

[0040] Figure Labels

[0041] 1. Gold wire, 2. Pressure ring, 3. Pin, 4. Thin film chip, 5. Filter screen, 6. Heat insulation cover, 7. Heat insulation pad, 8. Sealing ring, 9. Base, 10. Glass sintering, 11. Pressure base, 12. Corrugated diaphragm, 13. Silicone oil, 14. Gold wire, 15. Pressure-sensitive chip, 16. Housing. Detailed Implementation

[0042] The specific embodiments of the present invention are described below with reference to the accompanying drawings and examples:

[0043] It should be noted that the structures, proportions, sizes, etc. illustrated in the accompanying drawings of this specification are only used to complement the content disclosed in the specification, so that those skilled in the art can understand and read them, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0044] Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0045] like Figures 1-13 As shown, a specific embodiment of the present invention is illustrated: The hydrogen and pressure online monitoring device for the top space of a low-oil equipment disclosed in the present invention comprises a hydrogen sensing unit, a pressure sensing unit, an MCU circuit, a LORA wireless communication circuit, an antenna, and a shielding shell. The hydrogen sensing unit, pressure sensing unit, LORA wireless communication circuit, and antenna are connected to the MCU circuit. The hydrogen sensing unit, pressure sensing unit, MCU circuit, LORA wireless communication circuit, and antenna are housed in the shielding shell. The device is installed at the top exhaust port of the low-oil equipment.

[0046] The hydrogen sensing unit and pressure sensing unit are used to measure the hydrogen content and pressure inside the oil storage chamber of the low-oil equipment.

[0047] The MCU circuit is used to convert the measurement results of the sensing unit into voltage signals and perform data processing.

[0048] The LORA wireless communication circuit and antenna encode and transmit the signals processed by the MCU.

[0049] The shielding shell equalizes the high electric field at the top of the low-oil equipment, ensuring that the electronic equipment inside the shielding shell is not affected by the strong external electromagnetic environment.

[0050] In this invention, such as Figure 1 As shown, by installing this monitoring device at the exhaust port on the top of the low-oil equipment, the hydrogen content and pressure in the high-concentration area at the top can be monitored. This avoids the low data caused by dead zone sampling, solves the measurement error problem caused by uneven gas distribution, improves the response speed, avoids the risk of oil leakage and seepage, and improves the safety of the low-oil equipment monitoring device.

[0051] Specifically, the hydrogen sensing unit uses a palladium alloy hydrogen resistor with a Wheatstone full-bridge hydrogen sensing structure, wherein a passivation film is deposited on the surface of the hydrogen resistor of opposite bridge arms.

[0052] In this invention, such as Figure 3 As shown, the detection element of the Wheatstone full bridge is composed of four palladium alloy hydrogen resistors. Two of the hydrogen resistors have passivation films deposited on their surfaces to isolate them from hydrogen gas. This method improves the sensor sensitivity and eliminates drift caused by temperature changes.

[0053] Specifically, the hydrogen-sensitive resistor is fabricated on the surface of an Al2O3 ceramic substrate using microfabrication technology to form a zigzag resistor structure with a total length of 5000 mm.

[0054] In this invention, such as Figure 2 As shown, the use of a refractive resistor structure can greatly increase the number of blocks in the hydrogen resistor, which can improve the sensitivity of the hydrogen sensing unit while ensuring that it has a sufficiently fast response speed.

[0055] Specifically, the hydrogen sensing unit integrates a heating resistor and a temperature sensing resistor on the surface of the chip. The heating resistor uses a platinum thin film resistor as the heating element, which is formed into a certain shape by sputtering and depositing a platinum thin film and etching. The temperature sensing resistor uses a nickel thin film resistor.

[0056] In this invention, since the resistance of the palladium alloy resistor increases significantly with increasing temperature, a method is adopted to integrate a heating resistor and a temperature-sensing resistor in the hydrogen sensing unit to achieve constant temperature control of the hydrogen resistor, such as... Figure 4The diagram shows the functional unit layout of the thin-film hydrogen sensor. The overall size of the heating resistors was considered during the design process, and their arrangement was optimized. The uniformity of the substrate temperature distribution after heating was also taken into account, ultimately resulting in a higher temperature and a more uniform temperature field.

[0057] A platinum thin-film resistor is used as the heating element. A platinum thin film is deposited by sputtering and etched into a specific shape. Based on the structural dimensions of the platinum thin-film heating element, the resistance value can be calculated. According to Ohm's law, the resistance of a metallic conductor can be expressed as:

[0058]

[0059] For platinum, its resistivity ρ = 10.6 × 10⁻⁶ 6 Ω·cm, combined with the structural dimensions of the platinum thin-film heating resistor, yields the platinum heating resistor R. 加 =10Ω actual value.

[0060] Let the area of ​​the substrate containing the hydrogen sensor, platinum thin-film heating resistor, and temperature sensing resistor be A, and the thickness be D. Under adiabatic conditions, the power W required to raise the ceramic substrate from room temperature T0 to operating temperature T within time Δt is expressed as:

[0061]

[0062] In the formula: the density of ceramic d = 3.87 g / cm³ 3 Specific heat C is Using A = 4 × 3.5 mm 2 Given D = 0.6 mm, T0 = 20℃, T = 80℃, Δt = 10 s, then W = 0.8 W.

[0063] According to R=U 2 A heating power supply of approximately U = 5.88V can be used to heat the ceramic substrate from room temperature to 80℃. Using the thermal analysis function of the finite element analysis software ANSYS, the temperature distribution of the ceramic substrate was analyzed. Considering different convection conditions, the temperature distribution of the ceramic substrate at 80℃ was analyzed. It was found that when the convection coefficient is 150W / (m²×℃), the temperature difference across the entire substrate surface does not exceed 1℃. When the convection coefficient is 15W / (m²×℃), the temperature difference is significantly lower. 2 At a temperature of ×℃, the temperature of the entire substrate surface is basically uniform. Therefore, whether under forced convection or natural convection, the temperature distribution within the entire device range is very uniform. This heating resistor design method is reliable and effective.

[0064] In this invention, the temperature-sensing resistor measures temperature by utilizing the characteristic that the resistance of a thin-film resistor changes with temperature. The main materials are platinum, nickel, and copper, among others. Nickel thin-film resistors, in particular, exhibit excellent stability and temperature measurement accuracy, making them suitable for high-precision temperature measurement applications. The nickel thin-film temperature sensor is designed based on the principle that the resistance of metallic nickel changes with temperature. Since the operating temperature of the temperature sensor is t ≥ 0℃, the relationship between the resistance value R(t) at a given temperature and the temperature t conforms to the following formula:

[0065] t≥0℃,R(t)=R(0℃)[1+At+Bt 2 ]

[0066] In the formula: R(0℃) is the resistance value at 0℃, and A and B are constants. By measuring the resistance value of the nickel resistor at a certain temperature, its temperature value can be obtained. When the temperature is not too high, since the value of B is very small, the quadratic term can be ignored. The above formula can be simplified to R(t)=R(0℃)[1+At].

[0067] Therefore, at relatively low temperatures, the resistance of a nickel resistor has an approximately linear relationship with temperature. Combining the resistivity of nickel and the structural dimensions of the nickel thin-film thermocouple, the resistance of the nickel thin-film thermocouple can be calculated as R. 加 =400Ω.

[0068] Specifically, the hydrogen sensing unit is encapsulated in a probe. The probe is designed as a plunger structure with a sealing groove on the side and a boss welded to the bottom. The pin 3 is fixed to the base 9 by glass sintering 10 and is insulated from the base 9. The tip of the lead wire is pin-shaped. The hydrogen sensing unit is fixed in the groove of the heat insulation pad 7 and is electrically connected to the pin 3 by gold wire 1. The upper end of the hydrogen sensing unit is equipped with a heat insulation cover 6. Both the heat insulation pad 7 and the heat insulation cover 6 are made of polytetrafluoroethylene.

[0069] In this invention, such as Figure 5 As shown, the top of the lead wire is pin-shaped, which increases the end face area and facilitates the connection process of the gold wire 1, resulting in a more stable and reliable connection effect. The heat insulation pad 7 and the heat insulation cover 6 are made of polytetrafluoroethylene, whose high specific heat capacity and low thermal conductivity can slow down heat loss. The filter 5 at the top of the heat insulation cover 6 can prevent dust and liquid water in the environment from entering the sensor core. The pressure ring 2, filter 5, and base 9 are fused together by laser welding technology. This design meets the low power consumption heating capability when the hydrogen sensing unit is working.

[0070] Example

[0071] Low power design

[0072] The temperature field of the thin-film hydrogen sensor core structure was analyzed using ANSYS Workbench finite element analysis software. The power consumption and thermal equilibrium time required to reach the optimal operating temperature were theoretically analyzed. A 3D model of the thin-film hydrogen sensor was created and imported into ANSYS Workbench, with the material properties of each component and their contact relationships set. Tetrahedral elements were used to mesh the sensor, ignoring the influence of the filter on its temperature. The mesh model is shown below. Figure 6 As shown, the total number of units is 65,709.

[0073] By applying boundary conditions, the simulation showed that when the ambient temperature is 25℃, the power consumption required for the hydrogen sensor core to reach its operating temperature of 80℃ is approximately 0.2W. Figure 7 The image shows the temperature cloud diagram of the hydrogen sensor probe structure. The power consumption level of the thin-film hydrogen sensor prototype was tested. At an ambient temperature of 25℃, the heating power consumption is about 0.25W to heat the probe to 80℃.

[0074] High temperature tolerance test design

[0075] Solid-state thin-film hydrogen sensors utilize the catalytic effect of palladium alloy (Pd Alloy) on hydrogen. Therefore, the stability of Pd Alloy determines the working characteristics of the hydrogen sensor. Relevant studies at home and abroad indicate that when heated in an atmospheric environment above 280°C, Pd begins to undergo an oxidation reaction, slowly forming a dark brown PdO film. This causes Pd to lose its catalytic effect on hydrogen, leading to a decrease in sensor performance or even failure.

[0076] Considering the unique operating characteristics of hydrogen sensors, catalysis only occurs when hydrogen comes into contact with and adsorbs Pd, a prerequisite for hydrogen detection. Therefore, from a thermal protection perspective, physically isolating the potentially hydrogen-containing high-temperature gas medium from the Pd Alloy chip is not practically feasible. Optimizing the material structure and process of the protective film at the chip manufacturing level reduces the diffusion coefficient and rate of O2 molecules within the protective film, thereby mitigating the instability of Pd Alloy under harsh high-temperature conditions in a short period and preventing the formation of a PdO film due to Pd oxidation. Figure 8 The figure shows the relationship between the diffusion rates of H2 and O2 molecules in a Si3N4 thin film and temperature. The diffusion coefficients of H2 and O2 molecules differ significantly at different temperatures. By optimizing the protective film material and structure, a Si3N4 protective film of appropriate thickness is deposited on the surface of the chip protective film structure, as shown in the figure. Figure 9 As shown, it can form a barrier to the diffusion of O2 molecules and ensure that H2 can pass through the protective film structure smoothly, thereby preventing the oxidation of Pd Alloy.

[0077] The optimized process samples were subjected to a high-temperature tolerance test. According to the test requirements, we determined the high-temperature test temperature to be 440℃ and the test duration to be 4 minutes. After the high-temperature tolerance test, the Pd Alloy on the chip surface showed a metallic luster under an optical microscope and no dark brown PdO film was formed.

[0078] like Figure 10 The results show the hydrogen sensitivity response characteristics of the chip after high-temperature tolerance test and subsequent packaging. The zero point and sensitivity of the sensor did not change significantly, therefore it was determined that the Pd film did not undergo oxidation at high temperature, and the sensor successfully survived in the high-temperature environment.

[0079] By optimizing the structure and process of the protective film material for the solid-state thin-film hydrogen sensor, a barrier structure for O2 molecule diffusion is formed, thereby preventing the oxidation reaction of Pd Alloy under high-temperature conditions. This ensures the survival capability of the hydrogen sensor under severe accident conditions, meets the functional requirements of online hydrogen monitoring and alarm after a severe accident, and can provide operators with stable and accurate hydrogen concentration parameters.

[0080] Specifically, the pressure sensing unit uses an oil-filled medium-isolated pressure sensor. This sensor encapsulates the sensitive chip in a sealed container, and the medium pressure is transmitted to the sensitive element through a corrugated diaphragm, so that the measured medium is completely isolated from the sensitive element and the sensitive element is not damaged by the medium.

[0081] In this invention, such as Figure 11 As shown, the pressure acts directly on the back surface of the pressure-sensitive chip. A cup-shaped back pressure cavity protective layer is formed by using silicon-silicon bonding and silicon glass fusion sealing technology to isolate the fluid medium from the circuit on the silicon wafer surface, giving it excellent corrosion resistance to the measured medium. Therefore, almost any fluid can be directly measured.

[0082] Specifically, the oil-filled medium isolated pressure sensor of the pressure sensing unit includes a pressure base 11, a corrugated diaphragm 12, silicone oil 13, gold wire 14, a pressure-sensitive chip 15, and a housing 16. The pressure base 11 is made of 316 stainless steel and is laser-welded into the housing 16. The sealed cavity formed by the pressure base 11 and the corrugated diaphragm 12 is filled with liquid pressure-conducting medium silicone oil 13, which conducts the external medium pressure sensed by the corrugated diaphragm 12. The pressure-sensitive chip 15 is attached to the oil-filled core pressure base 11 with a patch adhesive. The chip pins are connected to the pins through the gold wire 14 using a wire bonding process to achieve external electrical connection.

[0083] In this invention, such as Figure 12As shown, the basic principle of the function conversion adopts the working principle of the piezoresistive pressure sensitive element (also known as "pressure sensitive core"). When pressure is applied to the silicon cup diaphragm, the diaphragm is subjected to compressive stress, which causes the geometry and resistivity of the semiconductor resistor fabricated on the diaphragm to change. Then, the potential difference signal output caused by the change in the resistance of its bridge arms is detected by the Wheatstone bridge to realize the pressure measurement.

[0084] In this embodiment, the pressure sensing unit is selected from TE Connectivity's 89BSD series product. It adopts an oil-filled medium isolation structure, integrates ASIC signal processing circuitry internally, and directly outputs digital signals. It has advantages such as small size, high accuracy, and good stability. Figure 13 This is a block diagram of the sensor's principle. The core operation and control unit of the pressure sensor adopts a dedicated ASIC circuit and uses digital compensation technology, which greatly reduces the measurement error caused by factors such as temperature changes and sensor nonlinearity, enabling the product output to achieve a very high accuracy.

[0085] Specifically, the MCU circuit is an ADuCM362, which is a fully integrated 3.9kSPS, 24-bit data acquisition system. The ADuCM362 is designed to connect directly to external precision sensors. The device has an on-chip 32kHz oscillator and an internal 16MHz high-frequency oscillator. The high-frequency oscillator is routed through a programmable clock divider, which generates the processor core clock operating frequency. The maximum core clock speed is 16MHz, which is not limited by operating voltage or temperature.

[0086] Specifically, the LORA wireless communication circuit is the ZM470 LORA communication module, which reduces the circuit design of the chip's external components and achieves a longer range than other wireless transmission methods under the same power consumption conditions. It achieves a balance between low power consumption and long distance, and is 35 times faster than traditional wireless communication technologies under the same power consumption conditions.

[0087] In this invention, the ZM470 transceiver primarily employs a LoRa™ remote modem for ultra-long-range spread spectrum communication. It boasts strong anti-interference capabilities and minimizes current consumption. Leveraging Semtech's patented LoRa™ modulation technology, the ZM470 achieves a high sensitivity exceeding 148dBm using low-cost crystals and components. Furthermore, the integration of high sensitivity with a +20dBm power amplifier enables these devices to achieve industry-leading link budgets, making them the optimal choice for long-distance transmission and applications with extremely high reliability requirements. Compared to traditional modulation techniques, LoRa™ modulation technology also offers significant advantages in terms of anti-blocking and selectivity, solving the problem that traditional designs cannot simultaneously balance distance, anti-interference, and power consumption.

[0088] Specifically, the shielding shell is made of aluminum alloy and uses a grid design to shield electromagnetic noise. The grid material is made of aluminum alloy and covers the circuit. Epoxy resin is used as insulation between the grid and the circuit. The lower part of the shielding shell adopts an open structure to facilitate the transmission and reception of radio frequency signals, realize high voltage field strength shielding and provide an electromagnetic radiation channel. The antenna is a microstrip antenna and is integrated on the MCU circuit.

[0089] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0090] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A device for online monitoring of hydrogen and pressure in the top space of a low-oil equipment, characterized in that, It consists of a hydrogen sensing unit, a pressure sensing unit, an MCU circuit, a LORA wireless communication circuit, an antenna, and a shielding shell. The hydrogen sensing unit, pressure sensing unit, LORA wireless communication circuit, and antenna are connected to the MCU circuit. The hydrogen sensing unit, pressure sensing unit, MCU circuit, LORA wireless communication circuit, and antenna are installed in the shielding shell. The device is installed at the top exhaust port of the low-oil equipment. The hydrogen sensing unit and pressure sensing unit are used to measure the hydrogen content and pressure inside the oil storage chamber of the low-oil equipment. The hydrogen sensing unit employs a palladium alloy hydrogen resistor using a Wheatstone full-bridge hydrogen sensing structure. A passivation film is deposited on the surface of opposite bridge arms of the hydrogen resistor. The hydrogen sensing unit integrates a heating resistor and a temperature-sensing resistor on the chip surface. The heating resistor uses a platinum thin-film resistor as the heating element, formed into a specific shape through sputtering deposition of the platinum thin film and etching. The temperature-sensing resistor uses a nickel thin-film resistor. The hydrogen sensing unit is encapsulated in a probe. The probe is designed as a plunger structure with a sealing groove on the side and a boss welded to the bottom. The pin (3) is fixed to the base (9) by glass sintering (10) and is insulated from the base (9). The top of the lead wire is pin-shaped. The hydrogen sensing unit is fixed in the groove of the heat insulation pad (7) and electrically connected to the pin (3) by gold wire (1). The upper end of the hydrogen sensing unit is equipped with a heat insulation cover (6). The heat insulation pad (7) and the heat insulation cover (6) are both made of polytetrafluoroethylene. The pressure sensing unit employs an oil-filled, media-isolated pressure sensor. The sensitive chip is encapsulated in a sealed container, and the media pressure is transmitted to the sensitive element through a corrugated diaphragm, completely isolating the measured media from the sensitive element and protecting the sensitive element from damage. The oil-filled medium isolated pressure sensor of the pressure sensing unit includes a pressure base (11), a corrugated diaphragm (12), silicone oil (13), gold wire (14), a pressure-sensitive chip (15), and a housing (16). The pressure base (11) is made of 316 stainless steel and is laser-welded into the housing (16). The sealed cavity formed by the pressure base (11) and the corrugated diaphragm (12) is filled with liquid pressure-conducting medium silicone oil (13) to conduct the external medium pressure sensed by the corrugated diaphragm (12). The pressure-sensitive chip (15) is attached to the oil-filled core pressure base (11) with a patch adhesive. The chip pins are connected to the pins by gold wire (14) using a wire bonding process to achieve external electrical connection. The MCU circuit is used to convert the measurement results of the sensing unit into voltage signals and perform data processing. The LORA wireless communication circuit and antenna encode and transmit the signals processed by the MCU. The shielding shell equalizes the high electric field at the top of the low-oil equipment, ensuring that the electronic equipment inside the shielding shell is not affected by the strong external electromagnetic environment. The shielding shell is made of aluminum alloy and uses a grid design to shield electromagnetic noise. The grid material is made of aluminum alloy and covers the circuit. Epoxy resin is used as insulation between the grid and the circuit. The lower part of the shielding shell adopts an open structure.

2. The online monitoring device for hydrogen and pressure in the top space of a low-oil equipment according to claim 1, characterized in that, The hydrogen-sensitive resistor is fabricated on the surface of an Al2O3 ceramic substrate using microfabrication technology to form a zigzag resistor structure with a total length of 5000 mm.

3. The online monitoring device for hydrogen and pressure in the top space of a low-oil equipment according to claim 1, characterized in that, The MCU circuit is an ADuCM362, which is a fully integrated 3.9kSPS, 24-bit data acquisition system.

4. The online monitoring device for hydrogen and pressure in the top space of a low-oil equipment according to claim 1, characterized in that, The LORA wireless communication circuit is the ZM470 LORA communication module, which reduces the need for peripheral circuit design.

5. The online monitoring device for hydrogen and pressure in the top space of a low-oil equipment according to claim 1, characterized in that, The antenna is a microstrip antenna, integrated on the MCU circuit.

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