Full-automatic capacitance film vacuum gauge calibration device

Abstract

The utility model discloses a full-automatic capacitance film vacuum gauge calibration device which comprises an inflation unit, a calibration unit, a measurement unit, an air exhaust unit and a control unit. The inflation unit is connected with the measuring unit, the calibration unit and the control unit. The control unit is respectively connected with the calibration unit, the measurement unit and the air exhaust unit; and the air exhaust unit is connected with the calibration unit. According to the utility model, the technical problem of how to carry out calibration test on a plurality of capacitance film vacuum gauges with different measuring ranges and realize real-time pressure, temperature and linearity performance parameter measurement on the capacitance film vacuum gauges is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of thin film vacuum gauge calibration, in particular to a full-automatic capacitance thin film vacuum gauge calibration device. Background Art

[0002] Vacuum science and technology is a crucial component of modern science and technology, encompassing four key areas: vacuum acquisition, vacuum leak detection, vacuum application, and vacuum metrology. Vacuum metrology relies heavily on various types of pressure sensors, one of the most widely used sensors. During use, sensors require calibration and verification to achieve high measurement accuracy. Sensor calibration involves using state-certified, higher-level testing equipment to calibrate the sensor's static and dynamic indicators.

[0003] In recent years, many researchers have done little research on the accuracy calibration and test result correction of capacitance film vacuum gauges. The test standards for capacitance film vacuum gauges have not yet been unified, which leads to uncertainty in the output electrical signal value of capacitance film vacuum gauges. For example, Liu Beibei et al. of Shanghai Institute of Metrology and Testing Technology used the static expansion method to establish a set of measurement range of 10 based on the Boyle-Maurit law. -1 -10 4 Pa, and a capacitance film vacuum gauge calibration device with an expanded uncertainty of 0.22% to 0.06%. The device's volume ratio and the uncertainty of the capacitance film vacuum gauge were tested, providing guidance for the traceability of absolute pressure capacitance film vacuum gauge measurement values. At the same time, due to the interference of various factors on the test results during the testing process, some calibration standards can no longer meet the testing requirements of low-range, high-precision capacitance film vacuum gauges. At present, the production of capacitance film vacuum gauges in China mainly relies on manual manufacturing and assembly. High-precision film vacuum gauges are often assembled, resulting in low yields, extremely low production efficiency, and low levels of intelligence and information technology. Therefore, it is necessary to develop intelligent manufacturing and precision testing, establish standardized multi-range measurement and calibration equipment, and achieve the goals of mass production and consistency. Therefore, based on the above technical problems, it is urgent to propose a fully automatic capacitance film vacuum gauge calibration device to solve the technical problems of how to calibrate multiple capacitance film vacuum gauges of different ranges and realize the real-time pressure, temperature, and linearity performance parameter measurement of capacitance film vacuum gauges. Utility Model Content

[0004] The main purpose of the utility model is to propose a fully automatic capacitance film vacuum gauge calibration device, which aims to solve the technical problem of how to calibrate and test multiple capacitance film vacuum gauges with different ranges and realize the real-time pressure, temperature and linearity performance parameter measurement of the capacitance film vacuum gauges.

[0005] To achieve the above-mentioned object, the present invention provides a fully automatic capacitance film vacuum gauge calibration device, wherein the fully automatic capacitance film vacuum gauge calibration device comprises:

[0006] Inflating unit, calibration unit, measuring unit, exhaust unit and control unit;

[0007] The inflation unit is connected to the measuring unit, the calibration unit and the control unit respectively; the control unit is connected to the calibration unit, the measuring unit and the air extraction unit respectively; the air extraction unit is connected to the calibration unit.

[0008] In one preferred embodiment, the inflation unit includes a pressure stabilizing chamber, a first stop valve, a first inflation pipeline, and a second inflation pipeline;

[0009] The pressure stabilizing chamber is connected to the measuring unit and the first stop valve respectively, and the other end of the first stop valve is connected to the first inflation pipeline and the second inflation pipeline respectively.

[0010] In one of the preferred solutions, the first inflation pipeline includes a pressure reducing valve and a steel cylinder; one end of the pressure reducing valve is connected to the stop valve, and the other end of the pressure reducing valve is connected to the steel cylinder; the steel cylinder is equipped with a detection gas of a capacitance diaphragm vacuum gauge; the second inflation pipeline includes a second stop valve; one end of the second stop valve is connected to the first stop valve, and the other end of the second stop valve is provided with an inflation interface, and the inflation interface is used to connect to an external standard detection steel cylinder.

[0011] In one preferred embodiment, a high-pressure inflation pipeline is used between the first inflation pipeline, the second inflation pipeline and the pressure stabilization chamber.

[0012] In one of the preferred solutions, the inflation unit further includes a first flow meter and a second flow meter; one end of the first flow meter and the second flow meter is connected to the pressure stabilizing chamber, and the other end of the first flow meter and the second flow meter is connected to the calibration unit.

[0013] In one preferred embodiment, the measuring unit includes a vacuum gauge A, a vacuum gauge B and a temperature sensor;

[0014] The vacuum gauge A is connected to the calibration unit, and the vacuum gauge B is connected to the inflation unit.

[0015] In one of the preferred solutions, the calibration unit includes a calibration chamber and at least one standard vacuum gauge; the standard vacuum gauge is connected to the calibration chamber, and the calibration chamber is connected to the inflation unit and the exhaust unit respectively.

[0016] In one preferred embodiment, the calibration unit further comprises a calibration interface, an air extraction valve and a flow limiting orifice;

[0017] The calibration interface adopts KF16 interface design;

[0018] The air extraction valve includes a pneumatic plug-in valve and an electromagnetic pressure differential valve; one end of the pneumatic plug-in valve and the electromagnetic pressure differential valve is connected to the calibration chamber, and the other end of the pneumatic plug-in valve and the electromagnetic pressure differential valve is connected to the air extraction unit;

[0019] The flow limiting hole is placed between the pneumatic plug-in valve and the air extraction unit.

[0020] In one preferred embodiment, the air extraction unit includes a first pump, a second pump, an electromagnetic isolation valve and a pneumatic air release valve;

[0021] The first pump is connected to the pneumatic gate valve, the other end of the first pump is connected to the electromagnetic isolation valve, the other end of the electromagnetic isolation valve is connected to the second pump, and the other end of the second pump is connected to the electromagnetic pressure differential valve; the pneumatic air release valve is connected to the calibration chamber.

[0022] One of the preferred solutions, the control unit includes an industrial computer, a protocol converter, a PID controller, a digital-to-analog converter, a pressure transmitter and a vacuum gauge controller; the industrial computer is connected to the PID controller and the digital-to-analog converter respectively through the protocol converter, the digital-to-analog converter is connected to the vacuum gauge controller, the inflation unit and the pressure transmitter respectively, and the vacuum gauge controller and the PID controller are connected to the calibration unit.

[0023] In the above-mentioned technical solution of the present invention, the fully automatic capacitance diaphragm vacuum gauge calibration device includes: an inflation unit, a calibration unit, a measuring unit, an exhaust unit, and a control unit; the inflation unit is connected to the measuring unit, calibration unit, and control unit respectively; the control unit is connected to the calibration unit, measuring unit, and exhaust unit respectively; and the exhaust unit is connected to the calibration unit. This utility model solves the technical problem of how to calibrate and test multiple capacitance diaphragm vacuum gauges of different ranges, and achieves real-time pressure, temperature, and linearity performance parameter measurement of the capacitance diaphragm vacuum gauges.

[0024] In the present invention, the inlet and outlet gas flows are automatically controlled, that is, the inlet and outlet gas flows are controlled by the inflation unit and the exhaust unit, thereby achieving control of the inlet and outlet pressures, so that they can quickly reach a dynamic equilibrium point, avoiding pressure deviations and slow adjustment caused by human factors; and the minimum pressure in the calibration chamber of the calibration unit can reach 1×10 -3 Pa, can detect capacitance film vacuum gauges with a full scale as low as 1Torr, and has a wide detection range.

[0025] In the present invention, the fully automatic capacitance diaphragm vacuum gauge calibration device uses pressure, temperature, linearity and dynamic stability as the main measurement and adjustment parameters, which can meet the functional requirements of simultaneously calibrating multiple capacitance diaphragm vacuum gauges and can quickly and accurately measure the real-time pressure, temperature, linearity and other performance parameters of the capacitance diaphragm vacuum gauge. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the implementation methods or the description of the prior art. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0027] Figure 1 This is a structural diagram of a fully automatic capacitance film vacuum gauge calibration device according to an embodiment of the present utility model;

[0028] Figure 2 Schematic diagram of a control unit according to an embodiment of the present invention.

[0029] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] It should be noted that all directional indications (such as up, down, etc.) in the implementation mode of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0032] In addition, in this utility model, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of such features.

[0033] Moreover, the technical solutions between the various embodiments of the present invention can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0034] See also Figure 1-Figure 2 According to one aspect of the present invention, the present invention provides a fully automatic capacitance film vacuum gauge calibration device, wherein the fully automatic capacitance film vacuum gauge calibration device comprises:

[0035] A cabinet, and an inflation unit, a calibration unit, a measuring unit, an exhaust unit and a control unit placed on the cabinet; the inflation unit is respectively connected to the measuring unit, the calibration unit and the control unit; the control unit is respectively connected to the calibration unit, the measuring unit and the exhaust unit; the exhaust unit is connected to the calibration unit.

[0036] Specifically, in this embodiment, a plurality of steering wheels are provided at the bottom of the cabinet. By providing the steering wheels at the bottom of the cabinet, the full-automatic capacitance film vacuum gauge calibration device can be moved and turned in any direction.

[0037] Specifically, in this embodiment, the inflation unit includes a pressure-stabilizing chamber, a first stop valve, and a first inflation pipeline and a second inflation pipeline; the pressure-stabilizing chamber is respectively connected to the measuring unit and the first stop valve, and the other end of the first stop valve is respectively connected to the first inflation pipeline and the second inflation pipeline; the first stop valve is a 1 / 4 corrugated tube stop valve, and the pressure-stabilizing chamber adopts a cylindrical structure design with a volume of not less than 1.5L and a working pressure of 10Pa-0.2MPa. The present utility model does not make specific limitations and can be set according to needs.

[0038] Specifically, in this embodiment, the first inflation pipeline includes a pressure reducing valve and a cylinder; one end of the pressure reducing valve is connected to the stop valve, and the other end of the pressure reducing valve is connected to the cylinder; the cylinder has a built-in detection gas of a capacitance diaphragm vacuum gauge; the detection gas can be nitrogen, and the cylinder is a 4L, 10MPa standard cylinder; the outlet pressure of the pressure reducing valve is below 0.6MPa, and the accuracy is 2.5%; the second inflation pipeline includes a second stop valve; one end of the second stop valve is connected to the first stop valve, and the other end of the second stop valve is provided with an inflation interface, and the inflation interface is used to connect to an external standard detection cylinder; the external standard detection cylinder is a 40L, 15MPa standard detection cylinder, and the second stop valve is a 1 / 4 corrugated tube stop valve. The present utility model does not make specific limitations and can be set according to needs.

[0039] Specifically, in this embodiment, high-pressure inflation pipelines are used between the first inflation pipeline and the second inflation pipeline and the pressure stabilization chamber, and vacuum pipelines are used in other parts.

[0040] Specifically, in this embodiment, the inflation unit also includes a first flow meter and a second flow meter; one end of the first flow meter and the second flow meter is connected to the pressure stabilizing chamber, and the other end of the first flow meter and the second flow meter is connected to the calibration unit; the specifications of the first flow meter and the second flow meter are different, and the flow rate is measured by the first flow meter and the second flow meter while measuring and adjusting the pressure of the pressure stabilizing chamber and the calibration chamber to achieve flow control.

[0041] Specifically, in this embodiment, the measuring unit includes a vacuum gauge A, a vacuum gauge B, and a temperature sensor; the vacuum gauge A is connected to the calibration unit, the vacuum gauge B is connected to the inflation unit, and the temperature sensor is installed on the cabinet; the vacuum gauge A is used to measure the pressure of the calibration chamber. The vacuum gauge A adopts a capacitance film vacuum gauge. The vacuum gauge A has three ranges, namely 0.1, 10, and 1000 Torr, and the measurement range is 1×10 -3 -1×10 5 Pa; the vacuum gauge B is used to measure the pressure in the stabilizing chamber. The vacuum gauge B adopts a Pirani vacuum gauge. The measurement range of the vacuum gauge B is 1×10 -2 -1×10 5 Pa; the temperature sensor adopts a platinum resistance temperature sensor, which is not specifically limited in the present invention. The vacuum gauge A, vacuum gauge B and temperature sensor can be set as needed.

[0042] Specifically, in this embodiment, the calibration unit includes a calibration chamber and at least one standard vacuum gauge; the standard vacuum gauge is connected to the calibration chamber, and the calibration chamber is respectively connected to the inflation unit and the exhaust unit; the standard vacuum gauge includes an MKS capacitance diaphragm vacuum gauge, the model of the capacitance diaphragm vacuum gauge is 690A, and during operation, the range of the standard vacuum gauge is selected according to the range of the diaphragm vacuum gauge being measured.

[0043] Specifically, in this embodiment, the calibration chamber is the core part of the calibration unit. The gas enters the calibration chamber from the cylinder through the pipeline, and then is evacuated by a pump group, that is, an exhaust unit, so that a dynamic balance effect is achieved in the calibration chamber, allowing the capacitance diaphragm vacuum gauge to obtain the required pressure value.

[0044] Specifically, in this embodiment, the calibration unit also includes a calibration interface, an air extraction valve and a flow limiting orifice; the calibration interface adopts a KF16 interface design; the air extraction valve includes a pneumatic plug-in valve and an electromagnetic pressure differential valve; one end of the pneumatic plug-in valve and the electromagnetic pressure differential valve is connected to the calibration chamber, and the other end of the pneumatic plug-in valve and the electromagnetic pressure differential valve is connected to the air extraction unit; the flow limiting orifice is placed between the pneumatic plug-in valve and the turbomolecular pump, and the flow limiting orifice is designed by opening a hole on an oxygen-free copper sealing ring.

[0045] Specifically, in this embodiment, during the entire testing process of the calibration device, it is necessary to quickly adjust the inlet and outlet gas pressures within the calibration chamber so that the calibration chamber quickly reaches a dynamic pressure equilibrium state, shortening the preparation time before the capacitance diaphragm vacuum gauge calibration work and thus performing subsequent work more efficiently. To this end, the device is provided with an exhaust unit to meet the pressure requirements of the calibration device. The exhaust unit includes a first pump, a second pump, an electromagnetic isolation valve, and a pneumatic bleed valve. The first pump is connected to the pneumatic gate valve, the other end of the first pump is connected to the electromagnetic isolation valve, the other end of the electromagnetic isolation valve is connected to the second pump, and the other end of the second pump is connected to the electromagnetic pressure differential valve. The pneumatic bleed valve is connected to the calibration chamber. The first pump uses a molecular pump as the main pump, and the second pump uses a vortex pump as the roughing pump. The molecular pump and the vortex pump work together, taking advantage of the advantages of the vortex pump, such as simple structure, light weight, and insensitivity to system pressure fluctuations, to provide a good foreline pressure for the device. At the same time, the molecular pump, as a high vacuum pump, has the advantages of ease of use and strong gas delivery capacity, and can provide a good calibration pressure environment for the capacitance diaphragm vacuum gauge and the required vacuum environment for the device.

[0046] Specifically, in this embodiment, in order to avoid or reduce the influence of human factors on the detection results and improve the efficiency of the calibration device in measuring the capacitance film vacuum gauge, the control unit is set, and the control unit is coordinated with the inflation unit, the exhaust unit, and the calibration unit to have the functions of vacuum degree regulation and flow regulation, and realize the requirements of functional control such as pressure, temperature, flow and speed; the control unit includes an industrial computer, a protocol converter, a PID controller, a digital-to-analog converter, a pressure transmitter and a vacuum gauge controller; the industrial computer is connected to the PID controller and the digital-to-analog converter respectively through the protocol converter, the digital-to-analog converter is connected to the vacuum gauge controller, the inflation unit and the pressure transmitter respectively, and the vacuum gauge controller and the PID controller are connected to the calibration unit; in the utility model, the protocol converter is an RS232 / RS485 protocol converter, and the control unit also includes a PLC and a switch. The PLC is connected to the switch and the industrial computer respectively; when the calibration device starts working, the cylinder in the charging unit starts to supply gas and is throttled through the first stop valve. At this time, a pressure difference will be generated in the pressure stabilizing chamber, and the pressure transmitter converts the pressure value into an electrical signal, which is output to the industrial computer through the digital-to-analog converter and the protocol converter. The industrial computer controls the first flow meter and the second flow meter according to the received model to allow the gas in the cylinder to enter the pressure stabilizing chamber. During the test flow, the amount of incoming flow can be controlled by controlling the opening of the 1 / 4 stop valve A between the pressure stabilizing chamber and the calibration chamber. The vacuum gauge A installed on the calibration chamber converts the real-time pressure value into an electrical signal and transmits it to the digital-to-analog converter. The digital-to-analog converter then transmits the electrical signal to the industrial computer via the protocol converter in a serial communication manner. The industrial computer receives the signal and converts it into a vacuum value, compares the vacuum value with the vacuum threshold set by the system, and thus controls the opening of the exhaust unit and the valve to reach the specified pressure value.

[0047] Specifically, in this embodiment, the opening of the air extraction unit and the valve is controlled to reach the specified pressure value, specifically: open the electromagnetic pressure differential valve and the second pump to roughly pump the calibration chamber, and close the electromagnetic pressure differential valve when it reaches 20Pa; open the first pump and the pneumatic plug-in valve to pump the calibration chamber to the background pressure. This process is to vacuum the calibration chamber; at the beginning of the test, first close the first pump and the pneumatic plug-in valve, open the 1 / 4 stop valve A, and control the first flowmeter and the second flowmeter to make the calibration chamber reach the set pressure; at the same time, the calibration chamber is maintained within the error range of the specified pressure by opening and closing the 1 / 4 stop valve A and the pumping speed of the second pump, as well as the gas release rate of the leak. When you want to lower the set pressure, A second pump is used to pump air. When the second pump pumps the pressure in the calibration chamber to the working pressure range of the first pump, the second pump stops working. If the pressure is less than the set value, the first flow meter and the second flow meter are controlled to intake air. If it is still greater than the set value, the first pump works. By automatically controlling the gas flow at the inlet and outlet, the inlet and outlet pressures are controlled, so that they can quickly reach a dynamic equilibrium point, avoiding pressure deviations and slow adjustments caused by human factors; and by changing the internal structure of the calibration chamber, the gas is evenly distributed everywhere, thereby making the internal pressure evenly distributed, avoiding inaccurate pressure readings of the capacitance diaphragm vacuum gauge due to pressure errors.

[0048] Specifically, in this embodiment, the linearity of the capacitance diaphragm vacuum gauge is obtained by setting pressure points at intervals of 10% within the measuring range through a calibration device, obtaining a voltage output corresponding to the pressure at each point, and thus obtaining a calibration curve of the diaphragm vacuum gauge. The maximum deviation between the curve and the fitting straight line and the percentage of the full-scale output is the linearity.

[0049] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural transformations made based on the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, within the scope of the present invention are included in the patent protection scope of the present invention.

Claims

1. A fully automatic capacitance film vacuum gauge calibration device, characterized in that: include: Inflating unit, calibration unit, measuring unit, exhaust unit and control unit; The inflation unit is connected to the measuring unit, the calibration unit and the control unit respectively; the control unit is connected to the calibration unit, the measuring unit and the air extraction unit respectively; the air extraction unit is connected to the calibration unit.

2. The fully automatic capacitance film vacuum gauge calibration device according to claim 1, characterized in that: The inflation unit includes a pressure stabilizing chamber, a first stop valve, a first inflation pipeline and a second inflation pipeline; The pressure stabilizing chamber is connected to the measuring unit and the first stop valve respectively, and the other end of the first stop valve is connected to the first inflation pipeline and the second inflation pipeline respectively.

3. The fully automatic capacitance film vacuum gauge calibration device according to claim 2, characterized in that: The first inflation pipeline includes a pressure reducing valve and a cylinder; one end of the pressure reducing valve is connected to the stop valve, and the other end of the pressure reducing valve is connected to the cylinder; the cylinder contains a detection gas of a capacitance diaphragm vacuum gauge; the second inflation pipeline includes a second stop valve; one end of the second stop valve is connected to the first stop valve, and the other end of the second stop valve is provided with an inflation interface, and the inflation interface is used to connect to an external standard detection cylinder.

4. The fully automatic capacitance film vacuum gauge calibration device according to claim 2, characterized in that: A high-pressure inflation pipeline is used between the first inflation pipeline, the second inflation pipeline and the pressure stabilization chamber.

5. The fully automatic capacitance film vacuum gauge calibration device according to claim 2, characterized in that: The inflation unit further includes a first flow meter and a second flow meter; one end of the first flow meter and the second flow meter is connected to the pressure stabilizing chamber, and the other end of the first flow meter and the second flow meter is connected to the calibration unit.

6. A fully automatic capacitance film vacuum gauge calibration device according to any one of claims 1 to 5, characterized in that: The measuring unit includes a vacuum gauge A, a vacuum gauge B and a temperature sensor; The vacuum gauge A is connected to the calibration unit, and the vacuum gauge B is connected to the inflation unit.

7. A fully automatic capacitance film vacuum gauge calibration device according to any one of claims 1 to 5, characterized in that: The calibration unit includes a calibration chamber and at least one standard vacuum gauge; the standard vacuum gauge is connected to the calibration chamber, and the calibration chamber is connected to the inflation unit and the exhaust unit respectively.

8. The fully automatic capacitance film vacuum gauge calibration device according to claim 7, characterized in that: The calibration unit also includes a calibration interface, an air extraction valve and a flow limiting orifice; The calibration interface adopts KF16 interface design; The air extraction valve includes a pneumatic plug-in valve and an electromagnetic pressure differential valve; one end of the pneumatic plug-in valve and the electromagnetic pressure differential valve is connected to the calibration chamber, and the other end of the pneumatic plug-in valve and the electromagnetic pressure differential valve is connected to the air extraction unit; The flow limiting hole is placed between the pneumatic plug-in valve and the air extraction unit.

9. The fully automatic capacitance film vacuum gauge calibration device according to claim 8, characterized in that: The air extraction unit includes a first pump, a second pump, an electromagnetic isolation valve and a pneumatic air release valve; The first pump is connected to the pneumatic gate valve, the other end of the first pump is connected to the electromagnetic isolation valve, the other end of the electromagnetic isolation valve is connected to the second pump, and the other end of the second pump is connected to the electromagnetic pressure differential valve; the pneumatic air release valve is connected to the calibration chamber.

10. A fully automatic capacitance film vacuum gauge calibration device according to any one of claims 1 to 5, characterized in that: The control unit includes an industrial computer, a protocol converter, a PID controller, a digital-to-analog converter, a pressure transmitter and a vacuum gauge controller; the industrial computer is connected to the PID controller and the digital-to-analog converter respectively through the protocol converter, the digital-to-analog converter is connected to the vacuum gauge controller, the inflation unit and the pressure transmitter respectively, and the vacuum gauge controller and the PID controller are connected to the calibration unit.

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