Hydrogen and pressure on-line monitoring device used in top space of low-oil equipment

Abstract

The invention discloses a hydrogen and pressure on-line monitoring device used in a top space of oil-deficient equipment, which comprises a hydrogen sensing unit, a pressure sensing unit, an MCU (Microprogrammed Control Unit) circuit, an LORA wireless communication circuit, an antenna and a shielding shell, and is characterized in that the hydrogen sensing unit, the pressure sensing unit, the LORA wireless communication circuit and the antenna are connected with the MCU circuit; the hydrogen sensing unit, the pressure sensing unit, the MCU circuit, the LORA wireless communication circuit and the antenna are arranged in the shielding shell; the device is arranged at a top exhaust hole of the oil-deficient equipment; the on-line monitoring device is mounted at the exhaust hole of the oil storage chamber at the top of the low-oil equipment, the condition of low data generated by dead-zone sampling is avoided through the hydrogen content and the pressure in a high-concentration area at the top of the low-oil equipment, the problem of measurement errors caused by non-uniform gas distribution is solved, the response speed is increased, meanwhile, the hidden danger of oil leakage and oil seepage is avoided, and the working efficiency is improved. And the use safety of the monitoring device for the low-oil equipment is improved.

Description

Technical Field

[0001] The invention relates to the technical field of state monitoring of low-oil equipment, in particular to an online monitoring device for hydrogen and pressure in the top space of low-oil equipment. Background Art

[0002] At present, the internal status monitoring of low-oil equipment mainly monitors the hydrogen in the dissolved gas in the oil. The dissolved hydrogen content in the oil is monitored by inserting a sensor mainly for single hydrogen monitoring into the oil intake port on the low-oil equipment. Although this type of method solves the technical gap of online monitoring inside low-oil equipment, it also has some defects. Since the molecular weight of hydrogen is very small, its escape speed in the oil is very fast, resulting in the sensor response speed being slower than the change in the actual hydrogen content, causing the online monitoring data to be lower than the offline chromatographic data. By redesigning the sensor and installing it on the top vent valve of the low-oil equipment to monitor the hydrogen concentration, the sensitivity of the sensor can be improved.

[0003] In the prior art, a number of solutions have been proposed for online monitoring of hydrogen content inside low-oil equipment, ranging from single parameter monitoring to multi-parameter comprehensive monitoring, all of which are committed to achieving real-time, accurate and efficient online monitoring functions. The invention patent with patent application number 201810928528.3 integrates hydrogen micro-water sensors, pressure sensors and other components to achieve comprehensive monitoring of key parameters of oil-filled equipment; the invention patent with patent application number 202310694833.1 focuses on a low-oil electrical equipment fault monitoring system based on hydrogen sensors, combining signal processing with the k-means algorithm to perform cluster analysis on characteristic parameters to accurately divide the fault type. The above technical solution mainly inserts a sensor at the oil outlet of the casing and uses a palladium alloy sensor to measure the hydrogen content in the insulating oil. This solution has certain defects, which are mainly manifested as follows:

[0004] 1. Uneven gas distribution. In the oil storage chamber at the top of the casing, due to the natural floating characteristics of the gas, fault gases such as hydrogen may be more likely to gather at the top, thus forming a relatively high concentration area. At the casing oil outlet, the distribution of gas may be affected by multiple factors such as oil flow and temperature, resulting in the measurement value being unable to accurately reflect the actual hydrogen concentration inside the casing;

[0005] 2. The sampling is not representative enough. There is a dead zone in the oil sample at the oil sampling port. When the temperature is high, the oil flow speed inside the casing is fast. 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 discharge or thermal failure occurs inside the casing, it takes a certain amount of time for the generated hydrogen to diffuse to the oil tapping port. Therefore, measuring the hydrogen concentration at the oil tapping port may not reflect the fault inside the casing in real time, resulting in a slow response speed of the monitoring system.

[0007] 4. Risk of oil seepage and leakage. There is a certain intensity of vibration during the operation of the casing. The high temperature caused by the load current will accelerate the aging of the sealing rubber ring. Therefore, installing a measuring device at the oil extraction port may increase the risk of oil seepage and leakage, posing a threat to the safe operation of the casing. Summary of the invention

[0008] In order to overcome the above-mentioned problems, the purpose of the present invention is to provide an online monitoring device for hydrogen and pressure in the top space of low-oil equipment. The online monitoring device is installed at the exhaust hole of the oil storage chamber at the top of the low-oil equipment. By measuring the hydrogen content and pressure in the high-concentration area at the top of the low-oil equipment, the low data caused by dead zone sampling is avoided, the measurement error problem caused by uneven gas distribution is solved, the response speed is improved, and the hidden dangers of oil leakage and oil seepage are avoided, thereby improving the safety of the use of the low-oil equipment monitoring device.

[0009] The technical solution adopted by the present invention is: comprising a hydrogen sensing unit, a pressure sensing unit, an MCU circuit, a LORA wireless communication circuit, an antenna and a shielding shell, wherein the hydrogen sensing unit, the pressure sensing unit, the LORA wireless communication circuit and the antenna are connected to the MCU circuit, and the hydrogen sensing unit, the pressure sensing unit, the MCU circuit, the LORA wireless communication circuit and the antenna are installed in the shielding shell, and the device is installed at the top exhaust hole position of the low-oil equipment;

[0010] The hydrogen sensing unit and the 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 result of the sensing unit into a voltage signal and perform data processing;

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

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

[0014] Furthermore, the hydrogen sensing unit adopts a palladium alloy hydrogen-sensitive resistor using a Wheatstone full-bridge hydrogen-sensitive structure, wherein a passivation film is deposited on the surface of a group of relative bridge arm hydrogen-sensitive resistors.

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

[0016] Furthermore, the hydrogen sensing unit is encapsulated in the probe, and the probe is designed as a plunger structure with a sealing groove on the side and a boss welded on the bottom. The pin is fixed to the base by glass sintering and insulated from the base. The top of the lead is in the shape of a thumbtack. The hydrogen sensing unit is fixed in the groove of the insulation pad and is electrically connected to the pin through gold wire. An insulation cover is installed on the upper end of the hydrogen sensing unit, and the insulation pad and the insulation cover are both made of polytetrafluoroethylene.

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

[0018] Furthermore, the pressure sensing unit adopts an oil-filled medium isolation pressure sensor, which encapsulates the sensitive chip in a sealed container. 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.

[0019] Furthermore, the oil-filled medium isolation pressure sensor of the pressure sensing unit includes a pressure base, a corrugated diaphragm, silicone oil, gold wire, a pressure-sensitive chip, and a shell. The pressure base is made of 316 stainless steel and is laser welded in the shell. The sealed cavity formed by the pressure base and the corrugated diaphragm is filled with liquid pressure-conducting medium silicone oil to transmit the external medium pressure sensed by the corrugated diaphragm. The pressure-sensitive chip is adhered to the oil-filled core pressure base by patch adhesive, and the chip pins are connected to the pins through gold wires using a wire bonding process to achieve external electrical connection.

[0020] Furthermore, the MCU circuit is ADuCM362, and the ADuCM362 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 of the chip periphery.

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

[0023] Beneficial effects of the present invention:

[0024] 1. It effectively improves the sensitivity of hydrogen and pressure monitoring technology inside the low-oil equipment and reduces the response time of fault status monitoring. By installing the monitoring device at the exhaust hole on the top of the low-oil equipment, the hydrogen content and pressure in the high-concentration area on 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 hidden dangers of oil leakage and oil seepage, and improving the safety of the low-oil equipment monitoring device.

[0025] 2. The structural method adopted by 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 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 hole of the low-oil equipment directly acts on the back surface of the silicon chip. Because the silicon-silicon bond and silicon glass melting and sealing technology are used to form a cup-shaped back pressure cavity protection layer, the fluid medium is isolated from the silicon chip surface circuit, making it extremely corrosion-resistant to the measured medium, able to accurately measure the pressure, and at the same time extend the service life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 It is a schematic diagram of the structure of hydrogen sensitive resistor;

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

[0030] Figure 4 It is a schematic diagram of the arrangement of the functional units of the thin film hydrogen sensor;

[0031] Figure 5 It is a thin film hydrogen sensor probe structure;

[0032] Figure 6 is the hydrogen sensor grid model;

[0033] Figure 7 It is the temperature cloud diagram of hydrogen sensor;

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

[0035] Fig. 9 Schematic diagram of the chip cross section after optimizing the protective film structure and materials;

[0036] Fig.10 To test the response characteristics after high temperature tolerance test;

[0037] Fig.11 It is a schematic diagram of the structure of the medium-isolated pressure sensor;

[0038] Fig.12 This is the working principle diagram of the sensitive element;

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

[0040] Reference numerals

[0041] 1 gold wire, 2 pressure ring, 3 pin, 4 thin film chip, 5 filter, 6 insulation cover, 7 insulation pad, 8 sealing ring, 9 base, 10 glass sinter, 11 pressure base, 12 corrugated diaphragm, 13 silicone oil, 14 gold wire, 15 pressure-sensitive chip, 16 shell. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention is described below in conjunction with the accompanying drawings and embodiments:

[0043] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0044] At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0045] like Figures 1 to 13 As shown, it shows a specific implementation mode of the present invention: the hydrogen and pressure online monitoring device for the top space of low-oil equipment disclosed in the present invention includes 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, the pressure sensing unit, the LORA wireless communication circuit and the antenna are connected to the MCU circuit. The hydrogen sensing unit, the pressure sensing unit, the MCU circuit, the LORA wireless communication circuit and the antenna are installed in a shielding shell. The device is installed at the top exhaust hole position of the low-oil equipment.

[0046] The hydrogen sensing unit and the 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 result of the sensing unit into a voltage signal and perform data processing;

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

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

[0050] In the present invention, Figure 1 As shown, by installing the monitoring device at the exhaust hole position on the top of the low-oil equipment, the hydrogen content and pressure in the high-concentration area on the top can be monitored, avoiding the low data caused by dead zone sampling, solving the measurement error problem caused by uneven gas distribution, and improving the response speed. At the same time, it avoids the hidden dangers of oil leakage and oil seepage, and improves the safety of the use of the low-oil equipment monitoring device.

[0051] Specifically, the hydrogen sensing unit adopts a palladium alloy hydrogen-sensitive resistor using a Wheatstone full-bridge hydrogen-sensitive structure, wherein a passivation film is deposited on the surface of a group of opposite bridge arm hydrogen-sensitive resistors.

[0052] In the present invention, Figure 3 As shown, a detection element of a Wheatstone full bridge composed of four palladium alloy hydrogen-sensitive resistors is used, and a passivation film is deposited on the surface of two of the hydrogen-sensitive resistors to isolate the hydrogen-sensitive resistors from hydrogen. This method improves the sensitivity of the sensor and eliminates the drift caused by temperature changes.

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

[0054] In the present invention, Figure 2 As shown, the use of a discounted resistor structure can greatly increase the number of hydrogen-sensitive resistors, thereby increasing 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 measuring resistor on the surface of the chip. The heating resistor uses a platinum thin film resistor as a heating element, and the platinum thin film is deposited by sputtering and formed into a certain shape by etching. The temperature measuring resistor uses a nickel thin film resistor.

[0056] In the present invention, since the resistance of the palladium alloy resistor increases significantly with the increase of temperature, the constant temperature control of the hydrogen sensitive resistor is achieved by integrating the heating resistor and the temperature measuring resistor in the hydrogen sensing unit. Figure 4The figure shows the layout of the functional units of the thin film hydrogen sensor. The overall size of the heating resistor is taken into consideration during the design, and the layout is performed reasonably. At the same time, the uniformity of the temperature distribution of the substrate after heating is considered, and finally a higher temperature is obtained with a uniform distribution of the temperature field.

[0057] Platinum thin film resistors are used as heating elements. Platinum thin film is deposited by sputtering and etched to form a certain shape. The resistance of the platinum thin film heating resistor can be calculated according to the structural dimensions of the platinum thin film heating element. According to Ohm's law, the resistance of the metal conductor can be expressed as:

[0058]

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

[0060] Assuming the area of ​​the substrate containing the hydrogen-sensitive resistor, platinum thin film heating resistor and temperature measuring resistor element is A, and the thickness is D, under the condition of adiabatic, the power W required to raise the ceramic substrate from room temperature T0 to the working temperature T within the time Δt is expressed as:

[0061]

[0062] Where: density of ceramic d = 3.87g / cm 3 , specific heat C is A=4×3.5mm 2 , D=0.6mm, T0=20℃, T=80℃, Δt=10s, then W=0.8W.

[0063] According to R=U 2 / W, the ceramic substrate can be heated from room temperature to 80℃ using a heating power supply of about U=5.88V. The temperature distribution of the ceramic substrate is analyzed using the thermal analysis function of the finite element analysis software ANSYS. When the heating element is at 80℃, the temperature distribution of the ceramic substrate under different convection conditions is considered. It can be concluded that when the convection coefficient is 150W / (m2×℃), the temperature difference of the entire substrate surface does not exceed 1℃, and when the convection coefficient is 15W / (m 2 ×℃), the temperature of the entire substrate surface is basically uniform. Therefore, whether it is forced convection or natural convection, the temperature distribution in the entire device is very uniform. This heating resistor design method is reliable and effective.

[0064] In the present invention, the temperature measuring resistor measures the temperature by utilizing the property that the resistance of the thin film resistor changes with the temperature. The main materials are platinum, nickel and copper. Among them, the nickel thin film resistor has good stability and temperature measurement accuracy and can be used in high-precision temperature measurement occasions. The nickel thin film temperature sensor is designed based on the principle that the resistance value of metal nickel changes with temperature. Since the working temperature of the temperature sensor t≥0°C, the relationship between the resistance value R(t) at a certain temperature and the temperature t meets the following formula:

[0065] t≥0℃,R(t)=R(0℃)[1+At+Bt 2 ]

[0066] Where: R(0℃) is the resistance value at 0℃, 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 B value is very small, the quadratic term can be ignored, and the above formula can be simplified to R(t)=R(0℃)[1+At].

[0067] Therefore, when the temperature is not too high, the resistance of nickel resistor is approximately linearly related to temperature. Combining the resistivity of nickel and the structural size parameters of nickel film temperature measuring resistor, it can be obtained that the nickel film temperature measuring resistor is R 加 =400Ω.

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

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

[0070] Example

[0071] Low power design

[0072] The finite element analysis software ANSYS Workbench is used to analyze the temperature field of the thin film hydrogen sensor core structure, and the power consumption and thermal equilibrium time required to reach the optimal working temperature are theoretically analyzed. The thin film hydrogen sensor model is established using 3D software and imported into ANSYS Workbench. The material properties of each component and the contact relationship between them are set. The mesh is divided using tetrahedral units, and the influence of the filter on its temperature is ignored. The mesh model is as follows: Figure 6 As shown, the total number of units is 65709.

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

[0074] High temperature tolerance test design

[0075] Solid-state thin-film hydrogen sensors use 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 have pointed out that when heated in an atmospheric environment above 280°C, Pd begins to undergo an oxidation reaction and slowly forms a dark brown PdO film, which causes Pd to lose its catalytic effect on hydrogen, resulting in reduced sensor performance or even failure.

[0076] Considering the particularity of the operation of hydrogen sensors, catalysis can only occur when hydrogen contacts and adsorbs Pd, which is also a prerequisite for hydrogen detection. Therefore, from the perspective of thermal protection structure, the method of physically isolating the high-temperature gas medium that may contain hydrogen from the Pd Alloy chip has no practical significance in engineering. From the perspective of chip technology, the material structure and process of the protective film are optimized to reduce the diffusion coefficient of O2 molecules in the protective film structure and the diffusion rate, thereby avoiding the stability of Pd Alloy in a short period of time under high temperature and harsh environment, and preventing the formation of PdO film due to oxidation reaction of Pd, such as Figure 8 The figure shows the relationship between the diffusion rate of H2 and O2 molecules in Si3N4 film and temperature. At different temperatures, the diffusion coefficients of H2 and O2 molecules are very different. The protective film material and structure are optimized, and a Si3N4 protective film of appropriate thickness is deposited on the surface of the chip protective film structure. The structure is as follows: Fig. 9 As shown, a barrier for the diffusion of O2 molecules can be formed, and H2 can be ensured to pass smoothly through the protective film structure, thereby preventing the occurrence of Pd Alloy oxidation.

[0077] The samples after the optimization process were subjected to a high temperature tolerance test. According to the test requirements, the high temperature test temperature was determined to be 440°C and the test duration was 4 minutes. After the high temperature tolerance test, the Pd Alloy on the chip surface showed a metallic luster through optical microscopy, and no dark brown PdO film was generated.

[0078] like Fig.10 The figure shows the test results of the hydrogen sensitive response characteristics of the chip after the high temperature tolerance test was packaged. The zero point and sensitivity indexes of the sensor did not change significantly. Therefore, it was determined that the Pd film did not undergo oxidation reaction 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 of the solid-state thin-film hydrogen sensor, a barrier structure for the diffusion of O2 molecules is formed, thereby avoiding the oxidation reaction of Pd Alloy in a high-temperature environment, ensuring the survival of the hydrogen sensor under severe accident conditions, and meeting the functional requirements of hydrogen online monitoring and alarm after severe accidents, and being able to provide operators with stable and accurate hydrogen concentration parameters.

[0080] Specifically, the pressure sensing unit adopts an oil-filled medium isolation pressure sensor, which encapsulates a sensitive chip in a sealed container. 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 the present invention, Fig.11 As shown in the figure, the pressure acts directly on the back surface of the pressure-sensitive chip, and a cup-shaped back-pressure cavity protection layer is formed by using silicon-silicon bonding and silicon glass melting and sealing technology to isolate the fluid medium from the silicon chip surface circuit, making it extremely resistant to corrosion to the measured medium, so almost any fluid can be directly measured.

[0082] Specifically, the oil-filled medium isolation pressure sensor of the pressure sensing unit includes a pressure base 11, a corrugated diaphragm 12, silicone oil 13, a gold wire 14, a pressure-sensitive chip 15, and a shell 16. The pressure base 11 is made of 316 stainless steel and is laser welded in the shell 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 transmits the external medium pressure sensed by the corrugated diaphragm 12. The pressure-sensitive chip 15 is adhered to the oil-filled core pressure base 11 by patch adhesive, and 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 the present invention, Fig.12As shown, the basic principle of functional conversion adopts the working principle of piezoresistive pressure sensitive element (also known as "pressure sensitive core"). Pressure acts on the silicon cup diaphragm, and the diaphragm is subjected to compressive stress, which causes the geometric shape and resistivity of the semiconductor resistor made on the diaphragm to change. The potential difference signal output caused by the change in the resistance of the bridge arm is detected through the Wheatstone bridge to achieve pressure measurement.

[0084] In this embodiment, the pressure sensing unit uses TE's 89BSD series products, which adopt an oil-filled medium isolation structure, internally integrate an ASIC signal processing circuit, directly output digital signals, and have the advantages of small size, high precision, and good stability. Fig.13 This is the principle block diagram of the sensor. The core operation control unit of the pressure sensor adopts a dedicated ASIC circuit and uses digital compensation technology, which greatly reduces the measurement errors caused by test result deviations caused by temperature changes and sensor nonlinearity, so that the product output can achieve very high accuracy.

[0085] Specifically, the MCU circuit is ADuCM362, which is a fully integrated 3.9kSPS, 24-bit data acquisition system. ADuCM362 is designed to be directly connected 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 and 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 a ZM470 LORA communication module, which reduces the circuit design of the chip periphery and can reach farther than other wireless transmission methods under the same power consumption conditions, achieving the unity of low power consumption and long distance, which is 35 times higher than traditional wireless communication technology under the same power consumption.

[0087] In the present invention, the ZM470 transceiver mainly adopts the LoRaTM remote modem for ultra-long-distance spread spectrum communication, has strong anti-interference ability, and can minimize current consumption. With the help of Semtech's LoRaTM patented modulation technology, the ZM470 can obtain a high sensitivity of more than 148dBm using low-cost crystals and materials. In addition, the integration of high sensitivity and +20dBm power amplifier makes the link budget of these devices reach the industry-leading level, making them the best choice for long-distance transmission and applications with extremely high reliability requirements. Compared with traditional modulation technology, LoRaTM modulation technology also has obvious advantages in anti-blocking and selectivity, solving the problem that traditional design solutions cannot take into account distance, anti-interference and power consumption at the same time.

[0088] Specifically, the shielding shell is made of aluminum alloy material and uses a grille design to shield electromagnetic noise. The grille material is made of aluminum alloy and covers the circuit. Epoxy resin is used as insulation between the grille 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 adopts a microstrip antenna and is integrated on the MCU circuit.

[0089] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

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

Claims

1. An online monitoring device for hydrogen and pressure in the top space of low-oil equipment, characterized in that: It includes 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, the pressure sensing unit, the LORA wireless communication circuit and the antenna are connected to the MCU circuit. The hydrogen sensing unit, the pressure sensing unit, the MCU circuit, the LORA wireless communication circuit and the antenna are installed in the shielding shell. The device is installed at the top exhaust hole position of the low-oil equipment; The hydrogen sensing unit and the pressure sensing unit are used to measure the hydrogen content and pressure inside the oil storage chamber of the low-oil equipment; The MCU circuit is used to convert the measurement result of the sensing unit into a voltage signal and perform data processing; The LORA wireless communication circuit and antenna encode and transmit the signal processed by the MCU; The shielding shell balances the high electric field on the top of the low-oil device, ensuring that the operation of the electronic equipment inside the shielding shell is not affected by the external strong electromagnetic environment.

2. The hydrogen and pressure online monitoring device for the top space of low-oil equipment according to claim 1 is characterized in that: The hydrogen sensing unit adopts a palladium alloy hydrogen-sensitive resistor using a Wheatstone full-bridge hydrogen-sensitive structure, wherein a passivation film is deposited on the surface of a group of opposite bridge arm hydrogen-sensitive resistors.

3. The hydrogen and pressure online monitoring device for the top space of low-oil equipment according to claim 2 is characterized in that: The hydrogen sensing unit integrates a heating resistor and a temperature measuring resistor on the surface of the chip. The heating resistor uses a platinum thin film resistor as a heating element. The platinum thin film is deposited by sputtering and a certain shape is formed by etching. The temperature measuring resistor uses a nickel thin film resistor.

4. The hydrogen and pressure online monitoring device for the top space of low-oil equipment according to claim 3 is characterized in that: The hydrogen sensing unit is encapsulated in the probe. The probe is designed as a plunger structure with a sealing groove on the side and a boss welded on 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 is in the shape of a thumbtack. The hydrogen sensing unit is fixed in the groove of the thermal insulation pad (7) and is electrically connected to the pin (3) by a gold wire (1). The upper end of the hydrogen sensing unit is provided with a thermal insulation cover (6). The thermal insulation pad (7) and the thermal insulation cover (6) are both made of polytetrafluoroethylene.

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

6. The hydrogen and pressure online monitoring device for the top space of low-oil equipment according to claim 1 is characterized in that: The pressure sensing unit adopts an oil-filled medium isolation pressure sensor, which encapsulates a sensitive chip in a sealed container. 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.

7. The hydrogen and pressure online monitoring device for the top space of low-oil equipment according to claim 6 is characterized in that: The oil-filled medium isolation pressure sensor of the pressure sensing unit comprises a pressure base (11), a corrugated diaphragm (12), silicone oil (13), a gold wire (14), a pressure-sensitive chip (15), and a housing (16). The pressure base (11) is made of 316 stainless steel and is welded in the housing (16) by laser. 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 transmit the external medium pressure sensed by the corrugated diaphragm (12). The pressure-sensitive chip (15) is adhered to the oil-filled core pressure base (11) by patch adhesive. The chip pins are connected to the pins by the gold wire (14) by wire bonding technology to achieve external electrical connection.

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

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

10. The hydrogen and pressure online monitoring device for the top space of low-oil equipment according to claim 1, characterized in that: The shielding shell is made of aluminum alloy material and uses a grille design to shield electromagnetic noise. The grille material is made of aluminum alloy and covers the circuit. Epoxy resin is used as insulation between the grille and the circuit. The lower part of the shielding shell adopts an open hole structure. The antenna adopts a microstrip antenna and is integrated on the MCU circuit.

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