Multifunctional gas leak detector based on variable magnetic field

Abstract

The invention discloses a multifunctional gas leak detector based on a variable magnetic field, relates to the technical field of gas leak detection, and solves the problems that when an existing gas leak detector adopts a permanent magnet to provide a constant magnetic field, high-voltage safety risks exist and are difficult to obtain through a conventional circuit when acceleration voltage required by gas detection is too high. According to the technical scheme, a main control board is connected with an ion source amplifier, an operation touch screen, a magnetic induction sensor and a control circuit, the control circuit is connected with an electromagnet, the electromagnet is used for providing a magnetic field for a mass spectrum chamber, and the magnetic induction sensor is used for monitoring the actual magnetic induction intensity in the mass spectrum chamber; wherein the main control board is used for calculating a set current and a set voltage according to a set magnetic induction intensity transmitted by the operation touch screen, sending the set current and the set voltage to the control circuit, and adjusting the set current and the set voltage according to an actual magnetic induction intensity transmitted by the magnetic induction sensor; the electromagnet is adopted to adjust the magnetic induction intensity so as to adapt to the detection requirements of different gases, and the flexibility and safety of the leak detector are improved.

Description

Technical Field

[0001] The invention relates to the technical field of gas leak detection, and more particularly to a multifunctional gas leak detector based on a variable magnetic field. Background Art

[0002] The mass spectrometer leak detector is a high-precision leak detection device that uses gas as a tracer gas and mass spectrometry analysis technology to detect tiny leak rates in the system. The working principle of the mass spectrometer leak detector is based on the principle of mass spectrometry, using special gases as leak detector gases. When the external gas enters the mass spectrometer chamber of the leak detector, the gas is ionized to produce ions. These gas ions are accelerated and enter the magnetic field. Due to the different charge-to-mass ratios of different ions, their paths will be deflected accordingly. By setting a slit, only the ions of the special gas can pass through and reach the collector. The ion flow signal obtained by the collector is proportional to the amount of special gas entering the leak detector, thereby realizing the measurement of the leak rate.

[0003] Existing mass spectrometer leak detectors generally use permanent magnets to provide a constant magnetic field. The constant magnetic field causes single-charged special gas ions to first pass through the orifice, then through the exit slit, and finally hit the detector. When detecting different gases, it is necessary to adjust the acceleration voltage U to change the path of the ions and achieve selective deflection and detection of specific gas ions. However, when the acceleration voltage U required for gas detection is too high, there is a high-voltage safety risk and it is difficult to obtain through conventional circuits. That is, existing mass spectrometer leak detectors cannot meet the leak detection needs of multiple gases.

[0004] Therefore, the present application provides a multifunctional gas leak detector based on a variable magnetic field to solve the above problems. Summary of the invention

[0005] The purpose of this application is to provide a multifunctional gas leak detector based on a variable magnetic field, so as to solve the problem that the existing gas leak detector uses a permanent magnet to provide a constant magnetic field. When the acceleration voltage required for gas detection is too high, there is a high-voltage safety risk and it is difficult to obtain through conventional circuits. This application replaces the traditional permanent magnet with an electromagnet, and adjusts the magnetic induction intensity to adapt to the detection needs of different gases, thereby improving the flexibility and safety of the leak detector.

[0006] The above-mentioned technical purpose of the present application is achieved through the following technical scheme: including: a main control board, a control circuit, a magnetic induction sensor, an electromagnet, an operating touch screen, a leak detection port, a molecular pump, a mass spectrometry chamber and an ion source amplifier; the inlet end of the leak detection port is connected to the test piece, the output port of the leak detection port is connected to the molecular pump, the molecular pump is connected to the mass spectrometry chamber, and the mass spectrometry chamber is connected to the ion source amplifier; the main control board is respectively connected to the ion source amplifier, the operating touch screen, the magnetic induction sensor and the control circuit, the control circuit is connected to the electromagnet, the electromagnet is used to provide a magnetic field for the mass spectrometry chamber, and the magnetic induction sensor is used to monitor the actual magnetic induction intensity in the mass spectrometry chamber; wherein the main control board is used to calculate the set current and the set voltage according to the set magnetic induction intensity transmitted by the operating touch screen and send them to the control circuit, adjust the set current and the set voltage according to the actual magnetic induction intensity transmitted by the magnetic induction sensor, calculate the leakage rate of the test piece according to the current transmitted by the ion source amplifier and send it to the operating touch screen for display.

[0007] In a possible implementation, the set current and the set voltage are calculated based on the set magnetic induction intensity transmitted by the operating touch screen, including: calculating the set current based on the set magnetic induction intensity, the magnetic permeability of air or vacuum, the relative magnetic permeability of the iron core, and the turns density of the coil; calculating the set voltage based on the set current and the resistance of the coil.

[0008] In one possible implementation, the control circuit includes: a constant power supply circuit, an adjustable voltage and current circuit, and a feedback circuit; the constant power supply circuit is used to convert the power supply VCC into a power supply voltage to power the feedback circuit; the feedback circuit is used to receive the set voltage and set current of the main control board, the feedback voltage and feedback current of the adjustable voltage and current circuit, compare the set voltage with the feedback voltage, compare the set current with the feedback current, and output a feedback signal; the adjustable voltage and current circuit is used to convert the power supply VCC into a set voltage according to the feedback signal and output it to the electromagnet.

[0009] In a possible implementation, the adjustable voltage and current circuit includes: a buck switching regulator chip, wherein the VIN terminal of the buck switching regulator chip is connected to a power supply VCC, the VC terminal is connected to the VIN terminal through a capacitor, the GND terminal is grounded, the SW terminal is connected to a first terminal of an inductor, the second terminal of the inductor serves as an output terminal of the adjustable voltage and current circuit, and the FB terminal is connected to a feedback signal and is grounded through a resistor.

[0010] In a possible implementation, the output end of the adjustable voltage and current circuit is grounded through a voltage divider composed of two resistors, and the connection point between the two resistors is led out as a voltage feedback point of the adjustable voltage and current circuit, and the voltage feedback point is used to output a feedback voltage.

[0011] In a possible implementation, the output end of the adjustable voltage and current circuit is grounded through a sampling resistor, and both ends of the sampling resistor are led out as current feedback points of the adjustable voltage and current circuit, and the current feedback points are used to output feedback current.

[0012] In a possible implementation, the feedback circuit includes: a voltage feedback circuit and a current feedback circuit; the voltage feedback circuit includes: a first operational amplifier, the inverting input terminal of the first operational amplifier is connected to the main control board through an RC filter circuit, the non-inverting input terminal is connected to the voltage feedback point of the adjustable voltage and current circuit, and the output terminal is connected to the FB terminal of the adjustable voltage and current circuit through a diode; the current feedback circuit includes: a second operational amplifier and an operational amplifier integrated chip, the inverting input terminal of the second operational amplifier is connected to the main control board through a filter circuit, the non-inverting input terminal is connected to the output terminal of the operational amplifier integrated chip, the output terminal is connected to the FB terminal of the adjustable voltage and current circuit through a diode, and the positive input terminal and the negative input terminal of the operational amplifier integrated chip are connected to the current feedback point of the adjustable voltage and current circuit.

[0013] In a possible implementation, the constant power supply circuit includes: two low voltage dropout linear regulators, which respectively convert the power supply VCC into positive and negative power supply voltage outputs.

[0014] In a possible implementation manner, the electromagnet is a water-cooled electromagnet.

[0015] In a possible implementation, the main control board is placed in the shielding cover, and the main control board is connected to the ion source amplifier, the operation touch screen, the magnetic induction sensor and the control circuit through a power line or a signal line with a shielding ring.

[0016] Compared with the prior art, the present application has the following beneficial effects: first, an electromagnet is used to replace the traditional permanent magnet, and the magnetic induction intensity can be changed by adjusting the current / voltage of the electromagnet to adapt to the detection of different gases; second, a constant control current / control voltage is provided by the control circuit to form a stable magnetic field; third, a magnetic induction sensor is set to monitor the actual magnetic induction intensity of the mass spectrometer chamber, and the set current and set voltage are adjusted by feedback of the monitored actual magnetic field intensity to ensure that the magnetic field generated by the electromagnet can reach the set magnetic induction intensity; fourth, a user-friendly operation touch screen is set, and the user can input the set magnetic induction intensity on the operation touch screen according to the type of gas to be detected, so as to realize the detection of different gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings: Figure 1 It is a structural schematic diagram of a multifunctional gas leak detector based on a variable magnetic field; Figure 2 It is a circuit diagram of a multifunctional gas leak detector based on a variable magnetic field; Figure 3 This is the control schematic diagram of the electromagnet; Figure 4 is the circuit diagram of the feedback circuit; Figure 5 A circuit diagram of a constant power supply circuit; Figure 6 This is the control schematic diagram of the electromagnet.

[0018] Marks and corresponding parts names in the attached drawings: 1. Electromagnet; 2. Ion source amplifier; 3. Mass spectrometer chamber; 4. Molecular pump; 5. Leak detection port; 6. Operation touch screen. DETAILED DESCRIPTION

[0019] Hereinafter, the term "include" or "may include" used in various embodiments of the present application indicates the presence of the function, operation or element applied for, and does not limit the increase of one or more functions, operations or elements. In addition, as used in various embodiments of the present application, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or the possibility of increasing one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items.

[0020] In various embodiments of the present application, the expression "or" or "at least one of B or / and C" includes any combination or all combinations of the words listed at the same time. For example, the expression "B or C" or "at least one of B or / and C" may include B, may include C, or may include both B and C.

[0021] The expressions (such as "first", "second", etc.) used in various embodiments of the present application may modify various constituent elements in various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of various embodiments of the present application, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0022] It should be noted that if it is described that one component element is “connected” to another component element or is “connected to” another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element or is “directly connected to” another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0023] The terms used in the various embodiments of the present application are only used for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present application. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the meanings commonly understood by ordinary technicians in the field to which the various embodiments of the present application belong. Terms (such as terms defined in generally used dictionaries) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in the various embodiments of the present application.

[0024] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

[0025] Embodiment 1 provides a multifunctional gas leak detector based on a variable magnetic field. First, the feasibility of this application is analyzed and explained. This application replaces the traditional permanent magnet with an electromagnet and adjusts the magnetic induction intensity to meet the detection requirements of different gases.

[0026] According to the Lorentz force and circular motion formula, the formula for the magnetic deflection radius can be derived as: ; Among them, r is the magnetic deflection radius, that is, the radius of the charged particle's circular motion in the magnetic field; m is the mass of the charged particle; U is the accelerating electric field voltage; q is the charge of the charged particle; and B is the magnetic induction intensity of the magnetic field.

[0027] In traditional mass spectrometer leak detectors, the deflection radius in the mass spectrometer chamber is often the same. If a permanent magnet is used, the magnetic induction intensity is also the same. To detect different gases, the only way is to change the accelerating electric field voltage. Taking hydrogen ion and helium ion detection as an example, the hydrogen ion and helium ion acceleration voltage and mass have the following relationship: ; Among them, U His the hydrogen ion accelerating voltage; U He is the helium ion accelerating voltage; m He is the mass of helium ion; m H is the mass of hydrogen ions.

[0028] Assuming the accelerating voltage of helium ions is 130V, it is known that: ; The hydrogen ion accelerating voltage can be calculated as: ; Such a high voltage is difficult to obtain for the circuit, and high voltage poses a safety risk.

[0029] Therefore, the present application proposes another way to detect different gases, that is, to change the permanent magnet into a variable electromagnet. Assuming that the accelerating electric field voltage U and the magnetic deflection radius r are constant, the magnetic induction intensity B has the following relationship: ; Among them, B H is the magnetic induction intensity required for hydrogen ions; B He is the magnetic induction intensity required for helium ions.

[0030] Assumption B He =1T, then B H =0.25T; for the electromagnet, there is the following relationship: ; Where B is the magnetic induction intensity inside the coil; μ0 is the magnetic permeability of air or vacuum, and the value of μ0 is approximately 4π×10 −7 T·m / A;μ r is the relative magnetic permeability of the core, which is related to the core material; n is the number of coil turns per unit length, that is, the turn density of the coil; I is the current passing through the coil.

[0031] The core material is pure iron, the relative magnetic permeability of pure iron is about 7000 ~ 10000, and the relative magnetic permeability μ r Take 8000, and the coil turn density n is 30. Then, to obtain a magnetic induction intensity of 1 T, a current of about 3.3 A is required. 3.3 A current is easy to achieve for circuit design.

[0032] From the above discussion, it can be seen that it is feasible for the present application to replace the traditional permanent magnet with an electromagnet and to adapt to the detection requirements of different gases by adjusting the magnetic induction intensity.

[0033] See also Figure 1 and Figure 2 As shown, Figure 1 It is a structural diagram of a multifunctional gas leak detector based on a variable magnetic field. Figure 2 The invention discloses a circuit diagram of a multifunctional gas leak detector based on a variable magnetic field. The multifunctional gas leak detector based on a variable magnetic field provided by the present application comprises: a main control board, a control circuit, a magnetic induction sensor, an electromagnet, an operation touch screen, a leak detection port, a molecular pump, a mass spectrometer chamber and an ion source amplifier; the inlet end of the leak detection port is connected to the inspected object, the output port of the leak detection port is connected to the molecular pump, the molecular pump is connected to the mass spectrometer chamber, and the mass spectrometer chamber is connected to the ion source amplifier; the main control board is respectively connected to the ion source amplifier, the operation touch screen, the magnetic induction sensor and the control circuit, the control circuit is connected to the electromagnet, the electromagnet is used to provide a magnetic field for the mass spectrometer chamber, and the magnetic induction sensor is used to monitor the actual magnetic induction intensity in the mass spectrometer chamber; wherein the main control board is used to calculate the set current and the set voltage according to the set magnetic induction intensity transmitted by the operation touch screen and send them to the control circuit, adjust the set current and the set voltage according to the actual magnetic induction intensity transmitted by the magnetic induction sensor, calculate the leakage rate of the inspected object according to the current transmitted by the ion source amplifier and send it to the operation touch screen for display.

[0034] Specifically, Figure 1 As shown, the inlet end of the leak detection port 5 is used to connect the inspected object, the output port of the leak detection port 5 is connected to the molecular pump 4, the molecular pump 4 is connected to the mass spectrometer chamber 3, and the mass spectrometer chamber 3 is connected to the ion source amplifier 2. When the leak detector is working, the gas of the inspected object passes through the leak detection port 5 and the molecular pump 4 and reaches the mass spectrometer chamber 3. The electrons emitted by the filament in the mass spectrometer chamber 3 collide with the gas in the chamber to ionize. The ions generated by the ionization are accelerated by the accelerating electric field and enter the magnetic field generated by the electromagnet 1. They are deflected by the Lorentz force and hit the inlet of the ion source amplifier 2 through the narrow slit. The ion source amplifier 2 receives the ion signal and converts and amplifies it into an electrical signal for output.

[0035] like Figure 2 As shown, the main control board can use STM32F407VET6. Its ADC1 port is connected to the ion source amplifier, its Usart1 port is connected to the operating touch screen, the SPI1 port is connected to the magnetic induction sensor, and the DAC1 and DAC2 ports are connected to the control circuit. The operating touch screen is used to set the magnetic induction intensity and display the leakage rate of the test piece, the ion source amplifier is used to convert and amplify the ion signal into an electrical signal for calculating the leakage rate, the magnetic induction sensor is used to monitor the actual magnetic induction intensity in the mass spectrometer room, and the control circuit is used to provide the electromagnet with a set voltage V_DAC and a set current I_DAC according to the set magnetic induction intensity. Ideally, the magnetic induction intensity generated by the electromagnet at the set voltage and set current is the set magnetic induction intensity, but in reality, affected by factors such as device aging and electromagnetic interference, the magnetic field magnetic induction intensity generated by the electromagnet at the set voltage and set current may have an error with the set magnetic induction intensity, so feedback adjustment is performed through the magnetic induction sensor.

[0036] The improvements of the present application are that, first, an electromagnet is used instead of a traditional permanent magnet, and the magnetic induction intensity can be changed by adjusting the current / voltage of the electromagnet to adapt to the detection of different gases; second, a constant control current / control voltage is provided by a control circuit to form a stable magnetic field; third, a magnetic induction sensor is set to monitor the actual magnetic induction intensity of the mass spectrometer chamber, and the set current and set voltage are adjusted by feedback of the monitored actual magnetic field intensity to ensure that the magnetic field generated by the electromagnet can reach the set magnetic induction intensity; fourth, a user-friendly operation touch screen is set, and the user can input the set magnetic induction intensity on the operation touch screen according to the type of gas to be detected, so as to achieve the detection of different gases.

[0037] The magnetic field stability and uniformity of the electromagnet are not as good as those of the permanent magnet. Therefore, the present application optimizes the stability and uniformity of the magnetic field through precise coil winding and magnetic circuit design to ensure the accuracy and repeatability of the leak detector.

[0038] Solenoid control does not require complex software development, user-friendly control software and intuitive user interface make operation easy.

[0039] In a possible implementation, the set current and the set voltage are calculated based on the set magnetic induction intensity transmitted by the operating touch screen, including: calculating the set current based on the set magnetic induction intensity, the magnetic permeability of air or vacuum, the relative magnetic permeability of the iron core, and the turns density of the coil; calculating the set voltage based on the set current and the resistance of the coil.

[0040] Specifically, the set current can be calculated based on the set magnetic induction intensity, the magnetic permeability of air or vacuum, the relative magnetic permeability of the iron core, and the turns density of the coil: ; Where I is the set current, B is the set magnetic induction intensity; μ0 is the magnetic permeability of air or vacuum, and the value of μ0 is approximately 4π×10 −7 T·m / A;μ r is the relative magnetic permeability of the core, which is related to the core material; n is the number of coil turns per unit length, that is, the coil turn density; U is the set voltage, and R is the resistance of the coil. Under the set voltage, the electromagnet generates a set current, and then generates a magnetic field with a set magnetic induction intensity.

[0041] In a possible implementation, the control circuit includes: a constant power supply circuit, an adjustable voltage and current circuit, and a feedback circuit; the constant power supply circuit is used to convert the power supply VCC into a power supply voltage to supply power to the feedback circuit; the feedback circuit is used to receive the set voltage and set current of the main control board, the feedback voltage and feedback current of the adjustable voltage and current circuit, compare the set voltage with the feedback voltage, compare the set current with the feedback current, and output a feedback signal; the adjustable voltage and current circuit is used to convert the power supply VCC into a set voltage according to the feedback signal and output it to the electromagnet. Figure 3 , 4 and 5, and explain in detail each part of the control circuit.

[0042] See also Figure 3 As shown, Figure 3 The circuit diagram of the adjustable voltage and current circuit is shown in FIG. The adjustable voltage and current circuit includes: a buck switching regulator chip, the VIN terminal of the buck switching regulator chip is connected to the power supply VCC, the VC terminal is connected to the VIN terminal through a capacitor, the GND terminal is grounded, the SW terminal is connected to the first terminal of the inductor, the second terminal of the inductor is used as the output terminal of the adjustable voltage and current circuit, and the FB terminal is connected to the feedback signal and grounded through a resistor.

[0043] Specifically, the step-down switching regulator chip can use XL4016. The power supply VCC is input to the chip VIN terminal after RC filtering, the chip VC terminal is connected to the VIN terminal through a bypass capacitor, the SW terminal outputs the voltage VOUT through the inductor, the FB terminal receives the feedback signal FB, the FB terminal is grounded through a resistor, and the GND terminal is grounded. The first end of the inductor can also be grounded through a diode to suppress the reverse current in the circuit. The second end of the inductor can also be grounded through multiple parallel capacitors to filter out high-frequency noise in the output and output a stable voltage.

[0044] Furthermore, the output end of the adjustable voltage and current circuit is grounded through a voltage divider composed of two resistors, and the connection point between the two resistors is led out as a voltage feedback point of the adjustable voltage and current circuit, and the voltage feedback point is used to output a feedback voltage.

[0045] Furthermore, the output end of the adjustable voltage and current circuit is grounded through a sampling resistor, and both ends of the sampling resistor are led out as current feedback points of the adjustable voltage and current circuit, and the current feedback points are used to output feedback current.

[0046] Specifically, Figure 3 In the example, the voltage feedback point is V_FB, which is also connected to VOUT through a resistor and a capacitor. The current feedback points are IN+ and IN-, and the two ends of the sampling resistor lead to the current feedback point through a resistor.

[0047] See also Figure 4 As shown, Figure 4The circuit diagram of the feedback circuit is shown in FIG. The feedback circuit includes: a voltage feedback circuit and a current feedback circuit; the voltage feedback circuit includes: a first operational amplifier, the inverting input terminal of the first operational amplifier is connected to the main control board through an RC filter circuit, the in-phase input terminal is connected to the voltage feedback point of the adjustable voltage and current circuit, and the output terminal is connected to the FB terminal of the adjustable voltage and current circuit through a diode; the current feedback circuit includes: a second operational amplifier and an operational amplifier integrated chip, the inverting input terminal of the second operational amplifier is connected to the main control board through a filter circuit, the in-phase input terminal is connected to the output terminal of the operational amplifier integrated chip, the output terminal is connected to the FB terminal of the adjustable voltage and current circuit through a diode, and the positive input terminal and the negative input terminal of the operational amplifier integrated chip are connected to the current feedback point of the adjustable voltage and current circuit.

[0048] Specifically, the inverting input terminal of the first operational amplifier is connected to the set voltage V_DAC of the main control board through an RC filter circuit, and the non-inverting input terminal is connected to the voltage feedback point V_FB of the adjustable voltage and current circuit. The inverting input terminal of the second operational amplifier is connected to the set current I_DAC of the main control board through a filter circuit, and the non-inverting input terminal is connected to the output terminal OUT of the operational amplifier integrated chip U1 through a resistor, the positive input terminal IN+ and the negative input terminal IN- of the operational amplifier integrated chip U1 are connected to the current feedback point of the adjustable voltage and current circuit, the power supply terminal VS of the operational amplifier integrated chip U1 is connected to the +5V power supply voltage through a resistor, the power supply terminal VS of the operational amplifier integrated chip U1 is grounded through a capacitor, and the ground terminal GND of the operational amplifier integrated chip U1 is grounded.

[0049] See also Figure 5 As shown, Figure 5 The circuit diagram of the constant power supply circuit is shown in FIG. The constant power supply circuit includes two low voltage drop linear regulators, which convert the power supply VCC into positive and negative power supply voltage outputs respectively.

[0050] Specifically, two low voltage drop linear regulators U2 and U3 convert the power supply VCC into a +5V supply voltage and a -5V supply voltage to provide supply voltages for the first operational amplifier, the second operational amplifier and the operational amplifier integrated chip of the feedback circuit.

[0051] It should be noted that the control circuit of the present invention is not a common electromagnet control circuit. Common electromagnet control circuits generally use MOS tubes or relays to output a voltage to drive the electromagnet, use the electromagnet's attraction ability to attract the armature, and achieve the on-off function, and do not involve the control of the magnetic field strength. In order to achieve the control of the magnetic field strength, the present invention sets a voltage feedback circuit and a current feedback circuit to output a stable voltage to drive the electromagnet to generate a stable magnetic field. Please refer to Figure 6 As shown, Figure 6The control principle diagram of the electromagnet. This application uses magnetic field feedback Bf, current feedback If, and voltage feedback Uf to jointly control the current flowing through the electromagnet. The main control board first calculates the set current and set voltage according to the set magnetic induction intensity transmitted by the operating touch screen and sends them to the control circuit. On the one hand, the voltage and current applied to the electromagnet are feedback-controlled through the current feedback circuit and voltage feedback circuit of the control circuit; on the other hand, the set current and set voltage are adjusted through the feedback of the actual magnetic induction intensity monitored by the magnetic induction sensor to control the electromagnet to generate a magnetic field with a set magnetic field intensity.

[0052] In a possible implementation, the electromagnet is a water-cooled electromagnet. It should be noted that the electromagnet is prone to generate heat during use, and heat accumulation may affect the accuracy of leak detection; therefore, the electromagnet of the present invention can be a water-cooled electromagnet, which can quickly reduce the temperature of the electromagnet, and the electromagnet can be set to a power-off state when the leak detector is not working, thereby reducing system power consumption and reducing the heat generated by the electromagnet.

[0053] In a possible implementation, the main control board is placed in a shielding cover, and the main control board is connected to the ion source amplifier, the operating touch screen, the magnetic induction sensor, and the control circuit through a power line or a signal line with a shielding ring. It should be noted that the magnetic field strength of the electromagnet is easily affected by external factors, such as the interference of the surrounding electromagnetic field; therefore, the present invention reduces the interference of the external magnetic field by designing a shielding cover and a shielding ring to ensure the stability of the control.

[0054] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multifunctional gas leak detector based on a variable magnetic field, characterized in that: include: Main control board, control circuit, magnetic induction sensor, electromagnet, operation touch screen, leak detection port, molecular pump, mass spectrometer room and ion source amplifier; The inlet end of the leak detection port is connected to the inspected object, the output end of the leak detection port is connected to the molecular pump, the molecular pump is connected to the mass spectrometer chamber, and the mass spectrometer chamber is connected to the ion source amplifier; The main control board is respectively connected to the ion source amplifier, the operation touch screen, the magnetic induction sensor and the control circuit, the control circuit is connected to the electromagnet, the electromagnet is used to provide a magnetic field for the mass spectrometry chamber, and the magnetic induction sensor is used to monitor the actual magnetic induction intensity in the mass spectrometry chamber; Among them, the main control board is used to calculate the set current and set voltage according to the set magnetic induction intensity transmitted by the operating touch screen and send them to the control circuit, adjust the set current and set voltage according to the actual magnetic induction intensity transmitted by the magnetic induction sensor, calculate the leakage rate of the test piece according to the current transmitted by the ion source amplifier and send it to the operating touch screen for display.

2. A multifunctional gas leak detector based on a variable magnetic field according to claim 1, characterized in that: Calculating a set current and a set voltage according to the set magnetic induction intensity transmitted by the operating touch screen includes: Calculate the set current according to the set magnetic induction intensity, the magnetic permeability of air or vacuum, the relative magnetic permeability of the iron core, and the turns density of the coil; The set voltage is calculated based on the set current and the resistance of the coil.

3. The multifunctional gas leak detector based on variable magnetic field according to claim 1, characterized in that: The control circuit includes: a constant power supply circuit, an adjustable voltage and current circuit and a feedback circuit; The constant power supply circuit is used to convert the power supply VCC into a supply voltage to supply power to the feedback circuit; The feedback circuit is used to receive the set voltage and set current of the main control board, the feedback voltage and feedback current of the adjustable voltage and current circuit, compare the set voltage with the feedback voltage, compare the set current with the feedback current, and output a feedback signal; The adjustable voltage and current circuit is used to convert the power supply VCC into a set voltage according to the feedback signal and output it to the electromagnet.

4. The multifunctional gas leak detector based on variable magnetic field according to claim 3, characterized in that: The adjustable voltage and current circuit comprises: a buck switching regulator chip, wherein the VIN terminal of the buck switching regulator chip is connected to a power source VCC, the VC terminal is connected to the VIN terminal through a capacitor, the GND terminal is grounded, the SW terminal is connected to a first terminal of an inductor, the second terminal of the inductor serves as an output terminal of the adjustable voltage and current circuit, and the FB terminal is connected to a feedback signal and is grounded through a resistor.

5. The multifunctional gas leak detector based on variable magnetic field according to claim 4, characterized in that: The output end of the adjustable voltage and current circuit is grounded through a voltage divider composed of two resistors, and the connection point between the two resistors is led out as a voltage feedback point of the adjustable voltage and current circuit, and the voltage feedback point is used to output a feedback voltage.

6. The multifunctional gas leak detector based on variable magnetic field according to claim 5, characterized in that: The output end of the adjustable voltage and current circuit is grounded through a sampling resistor, and both ends of the sampling resistor are led out as current feedback points of the adjustable voltage and current circuit, and the current feedback points are used to output feedback current.

7. The multifunctional gas leak detector based on variable magnetic field according to claim 6, characterized in that: The feedback circuit includes: a voltage feedback circuit and a current feedback circuit; The voltage feedback circuit comprises: a first operational amplifier, wherein the inverting input terminal of the first operational amplifier is connected to the main control board through an RC filter circuit, the non-inverting input terminal is connected to the voltage feedback point of the adjustable voltage and current circuit, and the output terminal is connected to the FB terminal of the adjustable voltage and current circuit through a diode; The current feedback circuit includes: a second operational amplifier and an operational amplifier integrated chip, the inverting input terminal of the second operational amplifier is connected to the main control board through a filter circuit, the non-inverting input terminal is connected to the output terminal of the operational amplifier integrated chip, the output terminal is connected to the FB terminal of the adjustable voltage and current circuit through a diode, and the positive input terminal and the negative input terminal of the operational amplifier integrated chip are connected to the current feedback point of the adjustable voltage and current circuit.

8. The multifunctional gas leak detector based on variable magnetic field according to claim 3, characterized in that: The constant power supply circuit comprises: two low voltage difference linear regulators, which respectively convert the power supply VCC into positive and negative power supply voltage outputs.

9. The multifunctional gas leak detector based on variable magnetic field according to claim 1, characterized in that: The electromagnet is a water-cooled electromagnet.

10. The multifunctional gas leak detector based on variable magnetic field according to claim 1, characterized in that: The main control board is placed in the shielding cover, and the main control board is connected with the ion source amplifier, the operation touch screen, the magnetic induction sensor and the control circuit through a power line or a signal line with a shielding ring.

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