Composite vacuum gauge combining metal diaphragm capacitor and barometer

Abstract

The invention relates to a composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer, and relates to the technical field of vacuum measurement. The composite vacuum gauge combining the metal diaphragm capacitive sensor and the barometer comprises a first shell, an electrode, a metal diaphragm, a second shell, a third shell, the barometer, a flange, a connecting pipe fitting and a vacuum pipe, the first shell, the second shell and the third shell are sequentially arranged from top to bottom, the connecting pipe fitting is fixedly connected with the lower end of the third shell, and the connecting pipe fitting is composed of a connecting pipe and a standard vacuum chuck used for being connected with a tested vacuum cavity interface. The composite vacuum gauge has the advantages of being large in measuring range, good in repeatability, high in precision, good in sensitivity, small in size, convenient to install, excellent in corrosion resistance, capable of being used under different working conditions, capable of directly conducting vacuum measurement without preheating, beneficial to developing new application technical fields and capable of meeting the requirements of customers for diversity and individuation.

Description

Technical Field

[0001] The present invention relates to the technical field of air pressure sensors, and more specifically, to a composite vacuum gauge combining a metal diaphragm capacitance sensor and an air pressure gauge. Background Art

[0002] A vacuum gauge is an instrument for measuring vacuum degree, which is widely used in industrial production and scientific research. According to the measurement principle of vacuum gauge, it mainly includes vacuum gauges using charged particle effect, vacuum gauges made using gas dynamic effect and vacuum gauges using mechanical properties. Vacuum gauges using charged particle effect include hot cathode ionization vacuum gauges and cold cathode ionization vacuum gauges, which have the advantages of wide range and high measurement accuracy, but they are large in size and complex in electrode structure. Typical vacuum gauges made using gas dynamic effect include Pirani resistance gauges and thermocouple gauges, which have a small range and are suitable for high vacuum degree measurement, and have the advantage of high accuracy. Typical vacuum gauges using mechanical properties include Bourdon gauges and film capacitance gauges, which have the advantage of using mechanical deformation caused by pressure changes to indicate or measure vacuum degree, have a large measurement range and good reproducibility, low production cost and fast response time. Thin film capacitance gauge products mainly include ceramic diaphragm capacitors and metal diaphragm capacitance sensors. The core component of the diaphragm capacitance vacuum gauge is a variable capacitor formed between the diaphragm and the electrode. The capacitance changes due to changes in pressure. However, due to the large range of vacuum, products with a large range will result in poor accuracy, while products with high accuracy will have a small range.

[0003] In order to overcome the shortcomings of a single type of vacuum gauge, a composite vacuum gauge with two different principles has also been developed in the prior art. The composite vacuum gauge is a product made using two or three of the above physical principles, with a full range, high precision and a wide range of applications, which makes up for the shortcomings of a single-core vacuum gauge and has a wider range of applications.

[0004] CN116412956A and CN116399505A disclose bimetallic diaphragm capacitance sensor type composite vacuum gauges, which use two metal diaphragm capacitance sensors to achieve large-range and high-precision measurements, can directly measure different gases, have fast response, simple maintenance, and good product repeatability; however, the process of the bimetallic diaphragm composite vacuum gauge is difficult and the cost is high, which does not have an advantage in commercial promotion. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the object of the present invention is to provide a composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer.

[0006] The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer of the present invention comprises a first shell, an electrode, a metal diaphragm, a second shell, a third shell, a barometer, a flange, a connecting pipe and a vacuum tube; the first shell, the second shell and the third shell are arranged in sequence from top to bottom, the connecting pipe is fixedly connected to the lower end of the third shell, and the connecting pipe is composed of a connecting tube and a standard vacuum chuck for connecting to the interface of the measured vacuum chamber; the metal diaphragm is arranged between the first shell and the second shell, and an open groove is arranged in the middle of the lower end of the first shell for placing the electrode, and the metal diaphragm separates the open groove from the internal space formed by the second shell and the third shell, and the open groove The space formed with the metal diaphragm constitutes a reference absolute pressure vacuum cavity; an electrode is arranged in the reference absolute pressure vacuum cavity, the electrode is composed of an electrode sheet and an electrode column arranged on the electrode sheet, the electrode sheet and the metal diaphragm are arranged adjacent to each other, and the electrode is connected to the main circuit through a lead wire, and the vacuum tube is connected to the reference vacuum cavity; a pressure sensor base PCB board is arranged in the third shell, and the barometer is installed on the pressure sensor base PCB board; a connecting terminal is welded on the outer wall of the third shell, the connecting terminal leads out the pins of the barometer through a lead pin insulated from the third shell, and the connecting terminal is connected to the main circuit through a transfer PCB board.

[0007] The metal diaphragm of the metal diaphragm capacitive sensor is made of incolnel alloy with a thickness of 20-50 μm, and the barometer is a piezoresistive silicon microelectric sensor.

[0008] The Inconel alloy contains 14-17wt% Cr, 6-10wt% Fe, 3-5wt% Nb, less than 0.15wt% C, and the remainder is Ni and inevitable impurities.

[0009] The Inconel alloy is obtained by annealing the quenched and tempered Inconel alloy, wherein the annealing treatment is to apply a tensile stress of 120 to 150 MPa in the length direction of the Inconel alloy and anneal at a temperature of 600 to 720°C.

[0010] Wherein, the barometer is a piezoresistive silicon micro-electric sensor filled with silicone.

[0011] Among them, the second shell is arranged on the step surface at the upper end of the third shell and is fixed by laser welding; the connecting pipe is fixed to the lower end of the third shell by laser welding through a flange; the outer periphery of the metal diaphragm is laser welded to the first shell and the second shell respectively; the adapter PCB board is welded inside the third shell.

[0012] Among them, a glass insulator is arranged on the periphery of the electrode column, and the glass insulator is sealed and connected to the upper end opening of the first shell through a seal; the vacuum tube is connected to the reference absolute pressure vacuum cavity through a seal, and the vacuum tube is used to evacuate the reference vacuum cavity to a set vacuum degree.

[0013] Wherein, a protective diaphragm is further provided in the third shell, and the protective diaphragm is welded to the inner lower end of the third shell; the protective diaphragm is fixed to the inner wall of the third shell by resistance welding.

[0014] Wherein, the protective membrane is made of Inconel alloy.

[0015] Compared with the prior art, the composite vacuum gauge combining the metal diaphragm capacitive sensor and the barometer of the present invention has the following beneficial effects:

[0016] The metal diaphragm capacitive sensor of the composite vacuum gauge of the present invention has the advantages of low nonlinear error, large range, good repeatability and high precision within the measuring range of 0.01Pa to 2000Pa, and the barometer has the advantages of low nonlinear error, large range, good repeatability and high precision within the measuring range of 2kPa to 103kPa. The composite vacuum gauge product has good sensitivity, small size, and easy installation. It has excellent corrosion resistance and vacuum performance, can meet the use of different working conditions, does not require preheating, can directly measure vacuum, does not require frequent calibration, is simple to install and maintain, and is conducive to the development of new application technology fields to meet the diverse and personalized needs of customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The cross-sectional structure diagram of the composite vacuum gauge combining the metal diaphragm capacitance sensor and the barometer of the present invention is shown.

[0018] The meanings of the reference numerals in the figure are: 1-glass insulator, 2-seal, 3-electrode, 4-first shell, 5-metal diaphragm, 6-second shell, 7-third shell, 8-connecting terminal, 9-adapter PCB board, 10-barometer (piezoresistive silicon pressure sensor), 11-pressure sensor base PCB board, 12-protective diaphragm, 13-flange, 14-connecting pipe fittings, 15-vacuum tube. DETAILED DESCRIPTION

[0019] The composite vacuum gauge combining the metal diaphragm capacitive sensor and the barometer of the present invention will be further described below in conjunction with specific embodiments to help those skilled in the art to have a more complete, accurate and in-depth understanding of the technical solution of the present invention.

[0020] like Figure 1As shown, the composite vacuum gauge combining the metal diaphragm capacitive sensor and the barometer of this embodiment includes a glass insulator 1, a seal 2, an electrode 3, a first shell 4, a metal diaphragm 5, a second shell 6, a third shell 7, a connecting terminal 8, a transfer PCB board 9, a barometer 10 (a piezoresistive silicon microelectric sensor filled with silicone, with a measuring range of 1kPa to 110kPa), a pressure sensor base PCB board 11, a protective diaphragm 12, a flange 13, a connecting pipe 14 and a vacuum tube 15. The first shell 4, the second shell 6 and the third shell 7 are arranged in sequence from top to bottom, and the connecting pipe 14 is fixed to the lower end of the third shell 7 by laser welding through the flange 13. The connecting pipe 14 is assembled by a connecting pipe and a standard vacuum chuck, and the standard vacuum chuck is used to connect to the interface of the vacuum chamber to be measured. The metal diaphragm 5 is arranged between the first shell 4 and the second shell 6, and the outer periphery of the metal diaphragm 5 is laser welded to the first shell 4 and the second shell 6 respectively. An open groove is provided in the middle of the lower end of the first shell 4. The metal diaphragm 5 separates the open groove from the internal space of the second shell 6 and the third shell 7, and the open groove and the metal diaphragm 5 form a reference vacuum cavity. An electrode 3 is provided in the reference vacuum cavity. The electrode 3 is composed of an electrode sheet and an electrode column provided on the electrode sheet. The electrode sheet and the metal diaphragm 5 are arranged adjacent to each other, and the electrode 3 is connected to the main circuit through a lead wire. A glass insulator 1 is provided on the periphery of the electrode column, and the glass insulator 1 is sealed and connected to the upper end opening of the first shell 4 through a seal 2. The vacuum tube 15 is connected to the reference vacuum cavity through the seal 2. The reference vacuum cavity can be evacuated to a set vacuum degree through the vacuum tube 15. The set vacuum degree is <10 -3 pa, at this time, the metal diaphragm is tightly attached to the first shell 4 and the lower surface of the electrode 3 due to the effect of atmospheric pressure. The protective diaphragm 12 is welded to the lower end of the inner part of the third shell 7 to prevent foreign objects from entering the third shell 7 to protect the barometer 10 and the metal diaphragm 5. The protective diaphragm 12 is fixed to the inner wall of the third shell 7 by resistance welding. The second shell 6 is arranged on the step surface at the upper end of the third shell 7 and is fixed by laser welding. A pressure sensor base PCB board 11 is arranged in the third shell 7, and the barometer 10 is installed on the pressure sensor base PCB board 11. A connecting terminal 8 is welded on the side wall of the third shell 7, and the connecting terminal 8 leads the pins of the barometer 10 through the lead pin insulated from the third shell 7, and the connecting terminal 8 is connected to the main circuit through the transfer PCB board 9, and the main circuit is responsible for processing the data of the sensor and the barometer and converting them into the required output. The transfer PCB board 9 is welded on the outer wall of the third shell 7.

[0021] The metal diaphragm capacitor in the composite vacuum gauge of the present invention, when measuring the vacuum degree, when the vacuum degree of the vacuum chamber to be measured gradually increases, the pressure on both sides of the metal diaphragm 5 close to the first shell 4 and the lower surface of the electrode 3 decreases, and due to its own material properties, it will gradually return to a natural state. The change in the distance between the diaphragm 5 and the electrode sheet of the electrode 3 will cause the capacitance generated between the two to change, and the change in the vacuum degree can be measured by the change in capacitance. The main circuit includes a capacitance-voltage conversion module, an amplifier module, a demodulation module, a filter module, a comparison module and other main parts. The difference in the gas pressure to be measured will cause the capacitance to change, and the main circuit part is processed and converted into the required output. The pressure range measured by the metal diaphragm capacitance sensor in the present invention is 0-2000Pa, and the thickness of the metal diaphragm is 20-50μm. The metal diaphragm is made of Inconel alloy, and its chemical composition is 14-17wt% Cr, 6-10wt% Fe, 3-5wt% Nb, <0.15wt% C, and the remainder is Ni and unavoidable impurities. The metal diaphragm adopts Inconel alloy, which not only has good corrosion resistance and thermal stability, but also can be applied to the present invention to obtain high precision and small nonlinear error. The barometer 10 in the present invention can stably output reliable output within the pressure range of 1kPa to 110kPa. The silica gel filled on the surface of the piezoresistive silicon can effectively prevent the adhesion of condensed water during the vacuum measurement process, ensuring that the barometer works stably and reliably. When measuring the pressure in the range of 1000 to 2000Pa, the metal diaphragm capacitor sensor and the barometer 10 can detect the vacuum value. The main circuit analyzes, compares and processes the collected data from the two sensors, determines the appropriate sensor data to use and outputs the required data.

[0022] Specifically, the material used in the present invention is an Inconel alloy coil, which is subjected to a quenching and tempering treatment at 1050°C to obtain a quenched and tempered Inconel alloy coil, and then a tensile stress of 120 to 150 MPa is applied along the length direction of the Inconel alloy coil, and annealing treatment is performed at a temperature of 600 to 720°C for 90 to 120 seconds. By applying the above-mentioned tensile stress annealing treatment in the coil direction, it can be confirmed by X-ray diffraction that the surface layer has a small (0 to 15 MPa) positive residual stress, and a plate with a flat surface and basically no deformation can be obtained by cutting. Unexpectedly, the above-mentioned tensile stress annealing treatment can expand the linear region between the voltage and pressure obtained by capacitance conversion, ensuring high accuracy within the range of 0.01 to 2000 Pa.

[0023] As an example, an Inconel alloy coil (chemical composition is 15wt% Cr, 8wt% Fe, 3wt% Nb, 0.05wt% C, the balance is Ni and inevitable impurities) is hot rolled to obtain a coil with a thickness of 0.05mm, and tempered at 1050°C to obtain a tempered Inconel alloy coil, and then a tensile stress of 150MPa is applied along the length direction of the coil, and annealed at 720°C for 90 seconds or 600°C for 90 seconds. X-ray diffraction method can confirm that the surface layer has a small (0-15MPa) positive residual stress, and then a smooth surface and basically no deformation of the Inconel alloy substrate can be obtained by cutting. The Inconel alloy substrate is used as the capacitor diaphragm in the present invention. In the measuring range of 0.01 to 1000 Pa, the non-linear error between the voltage and the gas pressure (the maximum deviation between the sensor calibration curve and the fitting straight line and the percentage of the full-scale output is defined as "non-linear error") is less than 2.0%, and in the measuring range of 1000 Pa to 2000 Pa, the non-linear error between the voltage and the gas pressure is less than 3.0%.

[0024] As another example, an Inconel alloy coil (chemical composition is 15wt% Cr, 6wt% Fe, 5wt% Nb, 0.05wt% C, the balance is Ni and inevitable impurities) is hot rolled to obtain a coil with a thickness of 0.05mm, and tempered at 1050°C to obtain a tempered Inconel alloy coil, and then a tensile stress of 120MPa is applied along the length direction of the coil, and annealed at 720°C for 90 seconds or 600°C for 90 seconds. X-ray diffraction method can confirm that the surface layer has a small (0-15MPa) positive residual stress, and then a Inconel alloy substrate with a smooth surface and basically no deformation can be obtained by cutting. The Inconel alloy substrate is used as the capacitor diaphragm in the present invention. In the measuring range of 0.01 to 1000 Pa, the nonlinear error between the voltage and the gas pressure is less than 1.5%, and in the measuring range of 1000 Pa to 2000 Pa, the nonlinear error between the voltage and the gas pressure is less than 3.0%.

[0025] As a comparative example, an Inconel alloy coil (chemical composition is 15wt% Cr, 8wt% Fe, 3wt% Nb, 0.05wt% C, and the balance is Ni and inevitable impurities) is hot rolled to obtain a coil with a thickness of 0.05mm, and is tempered at 1050°C to obtain a tempered Inconel alloy coil, and then a tensile stress of 20MPa is applied along the length direction of the coil, and annealed at 720°C for 90 seconds, and then an Inconel alloy substrate is obtained by cutting. The Inconel alloy substrate is used as a capacitor diaphragm. In the measuring range of 0.01 to 1000Pa, the non-linear error between the voltage and the gas pressure is 5.9%, and in the measuring range of 1000Pa to 2000Pa, the non-linear error between the voltage and the gas pressure is greater than 10.0%.

[0026] As another comparative example, an Inconel alloy coil with the same chemical composition as above (chemical composition is 15wt% Cr, 8wt% Fe, 3wt% Nb, 0.05wt% C, and the balance is Ni and inevitable impurities) is hot rolled to obtain a coil with a thickness of 0.05mm, and then tempered at 1050°C to obtain a tempered Inconel alloy coil, and then a tensile stress of 200MPa is applied along the length direction of the coil, and annealed at 720°C for 90 seconds, and then an Inconel alloy substrate with a smooth surface and basically no deformation is obtained by cutting. The Inconel alloy substrate is used as a capacitor diaphragm, and the non-linear error between the voltage and the gas pressure is 5.3% in the measuring range of 0.01 to 1000Pa, and the non-linear error between the voltage and the gas pressure is greater than 15.0% in the measuring range of 1000Pa to 2000Pa.

[0027] As another comparative example, for an Inconel alloy with a thickness of 0.05 mm and the same chemical composition (chemical composition is 15wt% Cr, 8wt% Fe, 3wt% Nb, 0.05wt% C, and the remainder is Ni and inevitable impurities), a tempering treatment is performed at 1050°C to obtain a tempered Inconel alloy, followed by annealing treatment at 720°C for 90 seconds (without applying tensile stress), and an Inconel alloy substrate with a smooth surface and essentially no deformation is obtained by cutting. The Inconel alloy substrate is used as a capacitor diaphragm, and the non-linear error between the voltage and the gas pressure is 5.5% in the measuring range of 0.01 to 1000 Pa, and the non-linear error between the voltage and the gas pressure is greater than 15.0% in the measuring range of 1000Pa to 2000Pa.

[0028] As another comparative example, an Inconel alloy coil (chemical composition is 15wt% Cr, 6wt% Fe, 0.05wt% C, the balance is Ni and inevitable impurities) is subjected to hot rolling to obtain a coil with a thickness of 0.05mm, and a tempering treatment is performed at 1050°C to obtain a tempered Inconel alloy coil, and then a tensile stress of 120MPa is applied along the length direction of the coil, and annealing treatment is performed at a temperature of 720°C for 90 seconds or at a temperature of 600°C for 90 seconds, and then a surface-flat and substantially non-deformed Inconel alloy substrate is obtained by cutting. The Inconel alloy substrate is used as the capacitor diaphragm in the present invention, and the nonlinear error between the voltage and the gas pressure is 3.5% in the range of 0.01 to 1000Pa, and the nonlinear error between the voltage and the gas pressure is 7.6% in the range of 1000Pa to 2000Pa.

[0029] For ordinary technicians in this field, the specific embodiments are only illustrative descriptions of the present invention. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concepts and technical solutions of the present invention, or the concepts and technical solutions of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A composite vacuum gauge combining a metal diaphragm capacitance sensor and a barometer, characterized in that: The invention comprises a first shell, an electrode, a metal diaphragm, a second shell, a third shell, a barometer, a flange, a connecting pipe and a vacuum tube; the first shell, the second shell and the third shell are arranged in sequence from top to bottom, the connecting pipe is fixedly connected to the lower end of the third shell, and the connecting pipe is composed of a connecting tube and a standard vacuum chuck for connecting to the interface of the measured vacuum chamber; the metal diaphragm is arranged between the first shell and the second shell, an open groove is arranged in the middle of the lower end of the first shell for placing the electrode, the metal diaphragm separates the open groove from the internal space formed by the second shell and the third shell, and the space formed by the open groove and the metal diaphragm A reference absolute pressure vacuum chamber is formed; an electrode is arranged in the reference absolute pressure vacuum chamber, the electrode consists of an electrode sheet and an electrode column arranged on the electrode sheet, the electrode sheet is arranged adjacent to the metal diaphragm and opposite to it, and the electrode is connected to the main circuit through a lead wire, and the vacuum tube is connected to the reference vacuum chamber; a pressure sensor base PCB board is arranged in the third shell, and the barometer is installed on the pressure sensor base PCB board; a connecting terminal is welded on the outer wall of the third shell, the connecting terminal leads out the pin of the barometer through a lead pin insulated from the third shell, and the connecting terminal is connected to the main circuit through a transfer PCB board.

2. The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer according to claim 1, characterized in that: The metal diaphragm of the metal diaphragm capacitive sensor is made of Inconel alloy with a thickness of 20-50 μm, and the barometer is a piezoresistive silicon micro-electric sensor.

3. The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer according to claim 2, characterized in that: The Inconel alloy contains 14-17wt% Cr, 6-10wt% Fe, 3-5wt% Nb, less than 0.15wt% C, and the balance is Ni and inevitable impurities.

4. The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer according to claim 3, characterized in that: The Inconel alloy is obtained by annealing the quenched and tempered Inconel alloy. The annealing treatment is to apply a tensile stress of 120 to 150 MPa in the length direction of the Inconel alloy and perform the annealing treatment at a temperature of 600 to 720°C.

5. The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer according to claim 2, characterized in that: The barometer is a piezoresistive silicon micro-electric sensor filled with silica gel.

6. The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer according to claim 1 or 2, characterized in that: The second shell is arranged on the step surface at the upper end of the third shell and is fixed by laser welding; the connecting pipe is fixed to the lower end of the third shell by laser welding through a flange; the outer periphery of the metal diaphragm is laser welded to the first shell and the second shell respectively; the adapter PCB board is welded to the inside of the third shell.

7. The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer according to claim 1 or 2, characterized in that: A glass insulator is arranged on the periphery of the electrode column, and the glass insulator is sealed and connected to the upper end opening of the first shell through a seal; the vacuum tube is connected to the reference absolute pressure vacuum cavity through a seal, and the vacuum tube is used to evacuate the reference vacuum cavity to a set vacuum degree.

8. The composite vacuum gauge combining a metal diaphragm capacitive sensor and a barometer according to claim 1 or 2, characterized in that: A protective diaphragm is also provided in the third shell, and the protective diaphragm is welded to the inner lower end of the third shell; the protective diaphragm is fixed to the inner wall of the third shell by resistance welding.

9. The composite vacuum gauge combining a metal diaphragm capacitance sensor and a barometer according to claim 8, characterized in that: The protective diaphragm is made of Inconel alloy.

Images