Wirie coefficient measuring device based on continuous expansion method

Abstract

The invention provides a villi coefficient measuring device based on a continuous expansion method. In the device, an air source, a plurality of expansion chambers and an air extractor unit are sequentially connected in series; the measuring module controls an air extractor set to open all stop valves to vacuumize an expansion chamber at the beginning of measurement; then all the stop valves are closed, and a fixed amount of gas provided by the gas source is sequentially introduced into the expansion chambers by controlling the stop valves from the expansion chamber closest to the gas source, so that the expansion chambers are gradually communicated according to the connection sequence; and when a new expansion chamber is communicated, data of the pressure gauge and the thermotank are recorded. After inflation of all the expansion chambers is completed, linear fitting is carried out by using recorded data, and two coefficients of a fitting straight line are two Wirie coefficients. According to the invention, the first virie coefficient and the second virie coefficient suitable for different gases in the static expansion method can be obtained, and accurate calibration of the vacuum gauge by the static expansion method is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum metrology, and in particular to a device for accurately measuring virial coefficients. Background Art

[0002] In vacuum metrology, the calibration of rough and low vacuum measuring instruments adopts the static expansion method. The basic principle of the static expansion method is based on the Boyle-Maliott theorem, that is, under isothermal conditions, a certain amount of gas obeys pV=C, p is the gas pressure, V is the volume occupied by the gas, and C is a constant. The static expansion method requires that the gas temperature remains unchanged during the calibration process, which places high demands on the environmental conditions of the calibration laboratory. At present, it is difficult to strictly meet the isothermal conditions during the static expansion method calibration process, so it is necessary to use the virial coefficient to correct the static expansion method formula.

[0003] For a certain amount of gas, its state can be described by three parameters: p, V, and T, satisfying pVnRT, that is, p is the gas pressure, V is the volume occupied by the gas, n is the number of moles, R is the gas constant, and T is the temperature. Since the isothermal condition is not met during static expansion, the actual gas state A is the first virial coefficient, B is the second virial coefficient, Vm is the molar volume, VmV / n, Vm expands with volume.

[0004] In order to achieve accurate calibration of a rough low vacuum measuring instrument using a static expansion method, the present invention measures the first virial coefficient and the second virial coefficient so as to correct the calibration result of the static expansion method. Summary of the invention

[0005] In view of this, the present invention provides a virial coefficient measuring device based on the continuous expansion method to realize the measurement of the first virial coefficient and the second virial coefficient applicable to different gases in the static expansion method, thereby ensuring the accurate calibration of the vacuum gauge by the static expansion method, and solving the technical problems of accurate value transmission and traceability of capacitance film vacuum gauges, magnetic levitation rotor vacuum gauges, ionization vacuum gauges, thermal conductivity vacuum gauges, etc. in the field of vacuum testing technology in China.

[0006] In order to solve the above technical problems, the present invention is implemented as follows.

[0007] A virial coefficient measuring device based on a continuous expansion method, the measuring device comprises a gas source, M expansion chambers, a pressure gauge, an air pumping unit and a measuring module; M is an integer greater than or equal to 3; the gas source, each expansion chamber and the air pumping unit are connected in series in sequence; a stop valve is provided between the gas source and the expansion chamber, between each of the expansion chambers, and between the expansion chamber and the air pumping unit; the expansion chamber, the stop valve and the pressure gauge are arranged in a thermostatic box to keep the temperature constant during the measurement process; the pressure gauge selects the same pressure indication of various gases of the same volume in the same expansion chamber at the same temperature;

[0008] The measuring module connects each gas source, each stop valve, pressure gauge and vacuum unit; the measuring module controls the vacuum unit to open all the stop valves to evacuate the expansion chamber at the beginning of the measurement; then close all the stop valves, and start from the expansion chamber closest to the gas source, by controlling the stop valves, introduce a fixed amount of gas provided by the gas source into each expansion chamber in sequence, so that each expansion chamber is gradually connected in the connection sequence; each time a new expansion chamber is connected, the pressure gauge indication p is recorded after the pressure stabilizes. m The temperature of the thermostat is T m ; The gas state at the current stage is expressed as:

[0009]

[0010] Let the dependent variable of the current stage be Independent Variable

[0011] Among them, V i is the volume of the ith expansion chamber, n is the number of moles, R is the gas constant, Vm m is the molar volume, m means that the first m expansion chambers are currently connected;

[0012] After all the expansion chambers are inflated, the dependent variables y1~y M and independent variables x1~x M Perform linear fitting and obtain the linear function ya+bx, where a is the value of the first virial coefficient A, and b is the value of the second virial coefficient B.

[0013] Preferably, the pressure gauge is connected to the expansion chamber closest to the gas source.

[0014] Preferably, the gas source provides multiple independent high-purity gases, and the purity of the gas sample is ensured not to change during the process of being introduced into the expansion chamber.

[0015] Preferably, the stop valves are all made of metal and have an internal and external leakage rate of less than 1×10 -9 Pam 3 / s.

[0016] Preferably, the expansion chamber is a metal container of known volume, the volume of each expansion chamber is the same or different, the minimum volume is not less than 0.1L, and the maximum volume is not more than 100L.

[0017] Preferably, the vacuum unit (14) exhausts air so that the vacuum background in the device is no greater than 1×10 -3 Pa.

[0018] Preferably, the constant temperature box (15) controls the temperature of the environment in the box during the measurement process with an accuracy of 0.01°C and a temperature fluctuation of less than ±0.01°C.

[0019] Preferably, there are five expansion chambers.

[0020] Beneficial effects:

[0021] The present invention proposes a virial coefficient measuring device based on the continuous expansion method, which realizes the accurate measurement of the first virial coefficient and the second virial coefficient applicable to different gases in the static expansion method, corrects the non-isothermal situation in the actual calibration process, and ensures the accurate calibration of the vacuum gauge by the static expansion method; due to the use of a pressure gauge without discrimination effect, the measurement of the virial coefficients of different gases can be realized; and the technical difficulties in the field of vacuum testing technology in my country for the accurate value transmission and traceability of capacitance film vacuum gauges, magnetic suspension rotor vacuum gauges, ionization vacuum gauges, thermal conductivity vacuum gauges, etc. are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of a Virial coefficient measuring device based on a continuous expansion method according to the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0024] The present invention provides a device for measuring the virial coefficient based on the continuous expansion method, such as Figure 1 As shown, the measuring device includes an air source 1, M expansion chambers 3, 6, 8, 10, 12, an exhaust unit 14 and a measuring module. The air source 1, each expansion chamber and the exhaust unit 14 are connected in series in sequence; stop valves 2, 5, 7, 9, 11, 13 are provided between the air source 1 and the expansion chamber, between each of the expansion chambers, and between the expansion chamber and the exhaust unit 14; the expansion chamber, the stop valve, and the pressure gauge are arranged in a constant temperature box 15 to keep the temperature constant during the measurement process. The measuring module connects each air source 1, each stop valve, the pressure gauge 4 and the exhaust unit 14, so as to realize the data acquisition, equipment control and measurement calculation of the measurement.

[0025] The pressure gauge 4 should have no discrimination effect on various gases, that is, the pressure indications of various gases of the same amount in the same expansion chamber at the same temperature are the same, and the measurement of the virial coefficients of different gases can be realized. For example, a capacitance film vacuum gauge in the field of vacuum measurement can be selected. In a preferred embodiment, the pressure gauge 4 is connected to the expansion chamber closest to the gas source 1, so that one pressure gauge can be used to complete the measurement of each stage, avoiding the inconsistency problem caused by using multiple pressure gauges.

[0026] The gas source 1 can provide multiple independent high-purity gases, and the purity of the gas sample is guaranteed not to change during the process of being introduced into the expansion chamber 3.

[0027] The stop valves are all made of metal, and the internal and external leakage rate is less than 1×10 -9 Pam 3 / s to ensure the accuracy of the data.

[0028] The expansion chamber adopts a metal container with a known volume. The volume of each expansion chamber can be the same or different, with the minimum volume not less than 0.1 L and the maximum volume not more than 100 L. There are at least 3 expansion chambers. The more expansion chambers there are, the more accurate the theoretically calculated virial coefficient will be. However, the more expansion chambers there are, the higher the sealing and precision of the pipelines and devices are required to avoid attenuation that should not exist. Therefore, through experiments, 5 expansion chambers are determined to be the preferred one.

[0029] Preferably, the thermostatic box 15 is selected to ensure that the temperature control accuracy of the environment in the box is 0.01° C. and the temperature fluctuation is less than ±0.01° C. during the measurement process, so as to ensure stable temperature control.

[0030] Preferably, the vacuum unit 14 makes the vacuum background in the device no greater than 1×10 -3 Pa.

[0031] The scheme for realizing the measurement of the virial coefficient of the device is as follows: the measuring module controls the vacuum unit 14 to open all the stop valves at the beginning of the measurement to first evacuate the expansion chamber, and then close all the stop valves, and then start from the expansion chamber closest to the gas source in sequence, and control the stop valves to sequentially introduce a fixed amount of gas provided by the gas source 1 into each expansion chamber of known volume, so that each expansion chamber is gradually connected in the connection sequence; after each new expansion chamber is connected, assuming that the currently connected expansion chamber is the mth expansion chamber, the pressure gauge 4 indication p is recorded after the pressure stabilizes. m The temperature of the thermostat is T m ; The gas state at the current stage is expressed as:

[0032]

[0033] Let the dependent variable of the current stage be Independent Variable

[0034] Among them, V i is the volume of the i-th expansion chamber, is the sum of the capacities of the first m expansion chambers that have been opened; n is the number of moles, R is the gas constant, Vm m is the molar volume,

[0035] After all the expansion chambers are inflated, the dependent variables y1~y M and independent variables x1~x MPerform linear fitting and obtain the linear function ya+bx, where a is the value of the first virial coefficient A, and b is the value of the second virial coefficient B.

[0036] The following is an example of a method including five expansion chambers to describe the implementation scheme of the present invention in detail. The method includes the following steps:

[0037] Step 1: Turn on the thermostat 15 and keep the temperature fluctuation less than ±0.01°C during the measurement.

[0038] Step 2: Open all stop valves 5, 7, 9, 11, 13, and use the vacuum unit 14 to evacuate all expansion chambers 3, 6, 8, 10, 12 until the vacuum reading on the pressure gauge 4 is less than 1×10 -3 Pa.

[0039] Step 3: Close all stop valves 5, 7, 9, 11, 13, open stop valve 2, introduce the high-purity gas in the gas source 1 into the expansion chamber 3 with a known volume of V1, and close valve 2 after judging that the pressure is stable according to the reading of the pressure gauge 4, and record the indication p1 of the pressure gauge 4 and the temperature indication T1 of the thermostat. The gas state at this time is expressed by formula (1), where Vm1 is the molar volume, n is the number of moles, and R is the gas constant.

[0040]

[0041] Step 4: Open the stop valve 5 and introduce the high-purity gas in the expansion chamber 3 into the expansion chamber 6 with a known volume of V2. After the pressure stabilizes, record the pressure gauge 4 reading p2 and the constant temperature box temperature reading T2. The gas state at this time is expressed by formula (2), where Vm2 is the molar volume.

[0042]

[0043] Step 5: Open the stop valve 7 and introduce the high-purity gas in the expansion chamber 6 into the expansion chamber 8 with a known volume of V3. After the pressure stabilizes, record the pressure gauge 4 reading p3 and the constant temperature box temperature reading T3. The gas state at this time is expressed by formula (3), where Vm3 is the molar volume.

[0044]

[0045] Step 6: Open the stop valve 9 and introduce the high-purity gas in the expansion chamber 8 into the expansion chamber 10 with a known volume of V4. After the pressure stabilizes, record the pressure gauge 4 reading p4 and the constant temperature box temperature reading T4. The gas state at this time is expressed by formula (4), where Vm4 is the molar volume.

[0046]

[0047] Step 7: Open the stop valve 11, introduce the high-purity gas in the expansion chamber 10 into the expansion chamber 12 with a known volume of V5, and record the pressure gauge 4 indication p5 and the thermostat temperature indication T5 after the pressure stabilizes. The gas state at this time is expressed by formula (5), where Vm5 is the molar volume.

[0048]

[0049] Step 8: Solve.

[0050] make,

[0051] Take y1, y2, y3, y4, y5 as dependent variables and x1, x2, x3, x4, x5 as independent variables, and perform linear fitting on the 5 groups of data to obtain the linear function ya+bx, then a is the value of the first virial coefficient A, and b is the value of the second virial coefficient B.

[0052] The virial coefficient measurement scheme of the present invention is based on the continuous expansion method, and can correct the temperature inconsistency in the actual calibration process to realize the measurement of the first virial coefficient and the second virial coefficient applicable to different gases in the static expansion method, thereby ensuring the accurate calibration of the vacuum gauge by the static expansion method, and solving the technical problems of accurate value transmission and traceability of capacitance film vacuum gauges, magnetic levitation rotor vacuum gauges, ionization vacuum gauges, thermal conductivity vacuum gauges, etc. in the field of vacuum testing technology in China.

[0053] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in the description may be different and are not limited. Therefore, those skilled in the art in the field of the present invention may modify or replace the technical solutions recorded in the above embodiments; and these modifications and replacements do not deviate from the creative purpose and technical solutions of the present invention and should all fall within the protection scope of the present invention.

Claims

1. A Virial coefficient measurement device based on the continuous expansion method, characterized in that: The measuring device comprises a gas source (1), M expansion chambers (3, 6, 8, 10, 12), a pressure gauge (4), an air pumping unit (14) and a measuring module; M is an integer greater than or equal to 3; the gas source (1), each expansion chamber and the air pumping unit (14) are connected in series in sequence; stop valves (2, 5, 7, 9, 11, 13) are provided between the gas source (1) and the expansion chambers, between each of the expansion chambers, and between the expansion chambers and the air pumping unit (14); the expansion chambers, the stop valves and the pressure gauge are arranged in a thermostatic box (15) to keep the temperature constant during the measurement process; the pressure gauge selects various gases of the same volume in the same expansion chamber at the same temperature and has the same pressure indication; The measuring module is connected to each gas source (1), each stop valve, a pressure gauge (4) and an exhaust unit (14); the measuring module controls the exhaust unit (14) to open all the stop valves at the beginning of the measurement to first evacuate the expansion chamber; then all the stop valves are closed, and starting from the expansion chamber closest to the gas source, a fixed amount of gas provided by the gas source (1) is sequentially introduced into each expansion chamber by controlling the stop valves, so that each expansion chamber is gradually connected in a connection sequence; each time a new expansion chamber is connected, the pressure gauge (4) reading p is recorded after the pressure stabilizes. m The temperature of the thermostat is T m ; The gas state at the current stage is expressed as: Let the dependent variable of the current stage be Independent Variable Among them, V i is the volume of the ith expansion chamber, n is the number of moles, R is the gas constant, Vm m is the molar volume, m means that the first m expansion chambers are currently connected; After all the expansion chambers are inflated, the dependent variables y1~y M and independent variables x1~x M Perform linear fitting and obtain the linear function y=a+bx, where a is the value of the first virial coefficient A, and b is the value of the second virial coefficient B.

2. The measuring device according to claim 1, characterized in that The pressure gauge (4) is connected to the expansion chamber closest to the gas source (1).

3. The measuring device according to claim 1, characterized in that The gas source (1) provides multiple independent high-purity gases, and the purity of the gas sample is guaranteed not to change during the process of being introduced into the expansion chamber (3).

4. The measuring device according to claim 1, characterized in that The stop valves are all made of metal and the internal and external leakage rate is less than 1×10 -9 Pam 3 / s.

5. The measuring device according to claim 1, characterized in that The expansion chamber is a metal container with a known volume. The volume of each expansion chamber is the same or different, the minimum volume is not less than 0.1L, and the maximum volume is not more than 100L.

6. The measuring method according to claim 1, characterized in that: The vacuum unit (14) exhausts air to make the vacuum background in the device no greater than 1×10 -3 Pa.

7. The measuring method according to claim 1, characterized in that: The constant temperature box (15) controls the temperature of the environment in the box with an accuracy of 0.01°C during the measurement process, and the temperature fluctuation is less than ±0.01°C.

8. The measuring method according to claim 1, characterized in that: The number of the expansion chambers is 5.

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