Device and method for preparing standard mixed gas using flow meter under vacuum condition

Abstract

The present invention relates to a device and method for preparing a standard mixed gas using a flow meter under vacuum conditions, the device comprising: a trace gas sampling pipeline, comprising a first gas cylinder, a first valve, a second valve, a first vacuum chamber, a third valve, a first high vacuum pump unit, a first vacuum gauge and a second vacuum gauge; other gas sampling pipelines, comprising a second gas cylinder, an eleventh valve, a ninth valve, a third vacuum chamber, a tenth valve, a second high vacuum pump unit, a fifth vacuum gauge and a sixth vacuum gauge; a mixed gas pipeline, comprising a fourth valve, a standard flow conductance element, a fifth valve, a sixth valve, a second vacuum chamber, a seventh valve, an eighth valve, a twelfth valve, a third vacuum gauge and a fourth vacuum gauge; the first vacuum chamber is connected to the fourth valve, and the third vacuum chamber is connected to the seventh valve, the eighth valve and the twelfth valve. The device of the present invention is simple, low in cost and easy to operate, and can extend the lower limit of the preparation ratio of preparing a standard mixed gas to 2×10 ‑10 .

Description

Technical Field

[0001] The invention relates to the field of vacuum measurement detection and testing, and in particular to a device and method for preparing a standard mixed gas, and in particular to a device and method for preparing a standard mixed gas by using a flow meter under vacuum conditions. Background Art

[0002] The preparation of a standard mixed gas with a trace proportion is a technical difficulty in the current vacuum metrology field. It has a wide range of applications, such as mass spectrometer calibration, obtaining a small standard gas flow rate, and detecting small leaks (see "Research on the Calibration Method of Extremely Small Leak Rate Based on Static Expansion Method", Yang Changqing). The relevant technology is particularly important in vacuum metrology, vacuum device reliability and component life evaluation. Common preparation methods for standard mixed gases include static method and dynamic method (see Chinese patents 201822178327 and 2014108381730). Static gas preparation is to fill two gases into a closed vacuum chamber at the same time according to the volume ratio or mass ratio. After a period of time, the two gas molecules are fully diffused through the free movement to achieve the purpose of mixing; dynamic gas preparation is to completely fill a gas component of a known concentration with a certain pressure and volume into a gas cylinder with a calibrated volume, and then fill it with a non-reactive dilution equilibrium gas that does not interfere with the component to be measured. According to the gas equation, the concentration of the component in the prepared gas can be obtained.

[0003] However, the above two methods have the following problems: (1) When preparing mixed standard gases, a mass flow meter is usually connected to a mixing tube or a mixing container, and standard mixed gases with different preparation ratios are obtained by adjusting the flow rate. However, the measurement uncertainty of the mass flow meter is large and the control accuracy is low, which will lead to inaccurate proportions of the prepared standard mixed gas and affect the accuracy of the test results; (2) The current measurement lower limit of commercial mass flow meters is relatively high. In vacuum measurement fields such as high-sensitivity mass spectrometer calibration and micro-leak detection, it is usually required that the proportion of He in the standard mixed gas flow rate is as small as possible. At this time, the method of using a mass flow meter to prepare a standard mixed gas is not feasible.

[0004] In order to obtain a more accurate standard mixed gas ratio and extend the lower limit of the standard mixed gas ratio used in the field of vacuum measurement, some scholars have proposed a standard small volume pressure sampling method. The minimum partial pressure of the trace gas in the obtained standard mixed gas is 10 -6 Pa level (see a 10 -5 -10 -16 Pa·m 3 / s Design of Standard Gas Flow Meter_Lu Yaowen_2021), but it is clear that there is still room for extension of this lower limit. Summary of the invention

[0005] In order to further extend the lower limit of the preparation ratio of standard mixed gases and broaden their applications in vacuum measurement and detection and related fields, the present invention aims to propose a device and method for preparing standard mixed gases using a flow meter under vacuum conditions, which can overcome the shortcomings of traditional standard mixed gas preparation technology and sample trace-content gases based on a standard gas flow meter. It also has the advantages of low lower limit of preparation ratio, low cost, easy operation, portability and low uncertainty.

[0006] In order to achieve the above-mentioned purpose, the present invention proposes a device for preparing a standard mixed gas by a flow meter under vacuum conditions, including a trace gas sampling pipeline, other gas sampling pipelines and a mixed gas pipeline, which can achieve a lower limit of the preparation ratio of 2×10 -10 The trace gas sampling pipeline comprises a first gas cylinder, a first valve, a second valve, a first vacuum chamber, a third valve and a first high vacuum pump unit connected in sequence, the volume of the first vacuum chamber is known, and a first vacuum gauge and a second vacuum gauge are installed thereon; the other gas sampling pipeline comprises a second gas cylinder, an eleventh valve, a ninth valve, a third vacuum chamber, a tenth valve and a second high vacuum pump unit connected in sequence, the volume of the third vacuum chamber is known, and a fifth vacuum gauge and a sixth vacuum gauge are installed thereon; the mixed gas pipeline comprises a fourth valve, a standard flow conductance element, a fifth valve, a sixth valve, a second vacuum chamber, a seventh valve, an eighth valve and a twelfth valve, the volume of the second vacuum chamber is known, and a third vacuum gauge and a fourth vacuum gauge are installed thereon; the second vacuum chamber is connected to the trace gas sampling pipeline through a fourth valve, a standard flow conductance element and a fifth valve connected in sequence; and is connected to the third vacuum chamber through the seventh valve, the eighth valve and the twelfth valve respectively.

[0007] According to one aspect of the present invention, the seventh valve and the eighth valve are fixed-volume sampling valves, and the sampling volumes are U7=0.5mL and U8=0.1L respectively.

[0008] According to one aspect of the present invention, the volume of the first vacuum chamber is U1=5L, the volume of the second vacuum chamber is U2=5L, and the volume of the third vacuum chamber is U3=1L.

[0009] According to one aspect of the present invention, the device further comprises a sixth valve for providing the standard mixed gas to the vacuum environment.

[0010] According to one aspect of the present invention, the first vacuum gauge, the third vacuum gauge and the fifth vacuum gauge are all capacitance film vacuum gauge combinations, and the measurement range is 1×10 5 Pa~10Pa, the measurement accuracy is better than 0.5%; the second vacuum gauge, the fourth vacuum gauge and the sixth vacuum gauge are composite monitoring vacuum gauges with a measurement range of 1×10 5 Pa~1×10-8 Pa.

[0011] According to one aspect of the present invention, the conductance value C of the standard conductance element ranges from 10 -8 Pa·m 3 / s~10 -10 Pa·m 3 / s.

[0012] According to one aspect of the present invention, a method for using a device for preparing a standard mixed gas using a flow meter under vacuum conditions as described in any one of the above technical solutions is proposed, comprising:

[0013] Step S1: measuring the background pressure P of the first vacuum chamber, the second vacuum chamber and the third vacuum chamber 01 , P 02 and P 03 ;

[0014] Step S2: Introduce the gas in the first gas cylinder into the first vacuum chamber until the pressure in the first vacuum chamber reaches P1, and then take samples based on the standard gas flow meter. Introduce the gas in the first vacuum chamber into the second vacuum chamber through the standard flow conduction element, and the ventilation time is t. According to Q = (P1-P 01 )·C can calculate the flow rate of the standard gas flow meter sampling;

[0015] Step S3: introducing the gas in the second gas cylinder into the third vacuum chamber until the pressure in the third vacuum chamber reaches P3, then sampling based on the static expansion method, and introducing the gas in the third vacuum chamber into the second vacuum chamber using the seventh valve or the eighth valve;

[0016] Step S4: Using the background pressure P of the first vacuum chamber and the third vacuum chamber 01 and P 03 , the pressure value P1 of the first vacuum chamber and the pressure value P3 of the third vacuum chamber, the pressure value P2 of the second vacuum chamber, the volume U7 of the seventh sampling valve and the volume U8 of the eighth sampling valve, the conductance value C of the standard flow conductance element, the ventilation time t, the ratio η of the standard mixed gas obtained in the second vacuum chamber and the partial pressure value P of the trace content gas x .

[0017] According to one aspect of the present invention, step S1 includes the following sub-steps:

[0018] Step S11: opening the third valve, the fourth valve, the fifth valve, the tenth valve and the twelfth valve, and starting the first high vacuum pump unit and the second high vacuum pump unit;

[0019] Step S12: turning on the second vacuum gauge, the fourth vacuum gauge and the sixth vacuum gauge, and then turning on the first vacuum gauge, the third vacuum gauge and the fifth vacuum gauge (when starting the capacitive film vacuum gauge for the first time, it should be preheated for more than 12 hours, and zeroed when the pressure in the corresponding vacuum chamber reaches the ultimate vacuum degree), and closing the fourth valve and the fifth valve;

[0020] Step S13: After the readings of the second vacuum gauge, the fourth vacuum gauge and the sixth vacuum gauge are stable, the displayed pressure values ​​are recorded as P respectively. 01 , P 02 , P 03 .

[0021] According to one aspect of the present invention, step S2 includes the following sub-steps:

[0022] Step S21: closing the third valve, opening the first valve and the second valve, and slowly introducing the gas in the first gas cylinder into the first vacuum chamber;

[0023] Step S22: When the pressure in the first vacuum chamber reaches 10Pa~1×10 5 When the vacuum gauge is within the range of Pa, the first valve and the second valve are closed, and the indicated value of the first vacuum gauge is recorded as P1 after the indicated value of the first vacuum gauge is stable;

[0024] Step S23: Open the fourth valve and the fifth valve in sequence, and introduce the gas in the first vacuum chamber into the second vacuum chamber through the standard flow conduction element. The air intake time can be 100s to 1000s. After the air intake is completed, quickly close the fourth valve and the fifth valve, and record the air intake time as t.

[0025] According to one aspect of the present invention, step S3 includes the following sub-steps:

[0026] Step S31: closing the tenth valve, opening the ninth valve and the eleventh valve, and slowly introducing the gas in the second gas cylinder into the third vacuum chamber;

[0027] Step S32: When the pressure in the third vacuum chamber reaches 10Pa~1×10 5 When the vacuum gauge is within the Pa range, the eleventh valve and the ninth valve are closed, and the indicated value of the fifth vacuum gauge is recorded as P3 after the indicated value thereof is stable;

[0028] Step S33: statically expand and sample the gas in the third vacuum chamber through the seventh valve or the eighth valve, and then introduce the sampled gas into the second vacuum chamber, and record the indicated value of the fourth vacuum gauge as P2 after the indicated value of the fourth vacuum gauge stabilizes.

[0029] According to one aspect of the present invention, in step S4, the following sub-steps are included:

[0030] Step S41: Calculate the ratio η of the standard mixed gas, the formula is:

[0031]

[0032] U′=U7 or U8

[0033] Step S42: Calculate the partial pressure value of the trace gas in the standard mixed gas as P x , the formula is:

[0034] P x =P2·η

[0035] According to one aspect of the present invention, it also includes:

[0036] Step S5: According to the steps S1 to S4, a mixture with a ratio of η and a partial pressure of P is prepared in the second vacuum chamber. x After the air pressure in the second vacuum chamber is stable for a period of time, the sixth valve is opened to provide the standard mixed gas into the vacuum environment.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] According to one solution of the present invention, a structure in which a mixed gas pipeline is connected to a trace gas sampling pipeline and other gas sampling pipelines respectively is adopted, and a device for preparing a standard mixed gas using a flowmeter under vacuum conditions is obtained. The device accurately samples trace gas and other gases based on a standard gas flowmeter and a static expansion method, and then mixes the two gases in a second vacuum chamber to obtain a standard mixed gas. The background pressure and gas pressure of the first vacuum chamber, the second vacuum chamber, and the third vacuum chamber are measured respectively according to the reference standard, and the preparation ratio of the standard mixed gas and the partial pressure value of the trace gas in the standard mixed gas can be finally calculated based on the conductance value of the standard flow conductance element and the volume of the second vacuum chamber.

[0039] Theoretically, if the minimum pressure of the first vacuum chamber is 10Pa, the minimum conductance of the standard conductance element is 1×10 - 10 Pa·m 3 / s, the minimum sampling time of the standard gas flow meter is 100s, and the maximum pressure value of the second vacuum chamber is 1×105 Pa, its volume is 5×10 -3 m 3 It can be calculated that the minimum mixing ratio of the standard mixed gas prepared by the device for preparing the standard mixed gas using a flow meter under vacuum conditions proposed by the present invention is 2×10 -10 If the gas pressure in the second vacuum chamber reaches the minimum value of 10Pa under this ratio, the minimum partial pressure of the trace gas in the standard mixed gas can be obtained to be 2×10 -9 Pa.

[0040] The present invention overcomes the bottleneck that the conventional standard small volume pressure sampling method is difficult to extend the lower limit of the preparation ratio when preparing the standard mixed gas, and extends the lower limit of the preparation ratio to 2×10 -10 The method has the advantages of simple equipment, low cost, and easy operation, and solves the problem of preparing standard mixed gases containing trace gases in vacuum measurement and detection and related application fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 It is a schematic structural diagram of a device for preparing a standard mixed gas using a flow meter under vacuum conditions according to an embodiment of the present invention.

[0043] Description of reference numerals:

[0044] G1-first vacuum gauge; G2-second vacuum gauge; G3-third vacuum gauge; G4-fourth vacuum gauge; G5-fifth vacuum gauge; G6-sixth vacuum gauge; V1-first valve; V2-second valve; V3-third valve; V4-fourth valve; V5-fifth valve; V6-sixth valve; V7-seventh valve; V8-eighth valve; V9-ninth valve; V10-tenth valve; V11-eleventh valve; V12-twelfth valve; Pump 1-first high vacuum pump unit (including TMP1-first molecular pump; RP1-first vortex pump); Pump 2-second high vacuum pump unit (including TMP2-second molecular pump; RP2-second vortex pump); VC1-first vacuum chamber; VC2-second vacuum chamber; VC3-third vacuum chamber. DETAILED DESCRIPTION

[0045] The description of the embodiments of this specification should be combined with the corresponding drawings, which should be considered as part of the complete specification. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated for simplification or convenience. Furthermore, the parts of each structure in the drawings will be described separately. It is worth noting that the elements not shown in the drawings or not described in words are in a form known to ordinary technicians in the relevant technical field.

[0046] The description of the embodiments herein shall not be construed as any limitation on the scope of protection of the present invention. The following description of the preferred embodiments may involve a combination of features, which may exist independently or in combination. The present invention is not particularly limited to the preferred embodiments. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

[0047] like Figure 1 As shown, an apparatus for preparing a standard mixed gas using a flow meter under vacuum conditions according to an embodiment of the present invention includes a trace gas sampling pipeline, other gas sampling pipelines and a mixed gas pipeline.

[0048] The trace gas sampling pipeline includes a first gas cylinder Gas1, a first valve V1, a second valve V2, a first vacuum chamber VC1, a third valve V3 and a first high vacuum pump unit Pump1 which are connected in sequence. A first vacuum gauge G1 and a second vacuum gauge G2 are installed on the first vacuum chamber VC1.

[0049] Other gas sampling pipelines include the second gas cylinder Gas2, the eleventh valve V11, the ninth valve V9, the third vacuum chamber VC3, the tenth valve V10 and the second high vacuum pump unit Pump2 which are connected in sequence. The fifth vacuum gauge G5 and the sixth vacuum gauge G6 are installed on the third vacuum chamber VC3.

[0050] The mixed gas pipeline includes a fourth valve V4, a standard flow conductance element f, a fifth valve V5, a second vacuum chamber VC2, a sixth valve V6, a seventh valve V7 and an eighth valve V8. A third vacuum gauge G3 and a fourth vacuum gauge G4 are installed on the second vacuum chamber VC2.

[0051] In this embodiment, the connection relationship between the various components is as follows: the second vacuum chamber VC2 is connected to the trace gas sampling pipeline through the fourth valve V4, the standard flow conductance element f and the fifth valve V5 which are connected in sequence. The second vacuum chamber VC2 is also connected to the third vacuum chamber VC3 through the seventh valve V7, the eighth valve V8 and the twelfth valve V12 (in parallel).

[0052] In this embodiment, the leakage rate at the connection interface between the components should be less than 1×10 -11 Pa·m3 / s(5.5×10 -12 Pa·m 3 / s).

[0053] In a preferred embodiment of the present invention, a sixth valve V6 for providing a standard mixed gas to the vacuum environment is further included.

[0054] In a preferred embodiment of the present invention, the gas in the first gas cylinder Gas1 is He with a purity of 99.9999%, and the gas in the second gas cylinder Gas2 is N2 with a purity of 99.9999%.

[0055] In a preferred embodiment of the present invention, preferably, the second valve V2 and the ninth valve V9 are fine-tuning valves for slowly controlling the pressure in the corresponding vacuum chamber to rise slowly. The seventh valve V7 and the eighth valve V8 are sampling valves with sampling volumes of 0.5 mL and 0.1 L, respectively, for controlling the sampling gas volume of N2 to ensure that the gas pressure in the second vacuum chamber VC2 rises in a step-by-step manner.

[0056] In a preferred embodiment of the present invention, the volumes of the first vacuum chamber VC1, the second vacuum chamber VC2 and the third vacuum chamber VC3 are 5L, 5L and 1L respectively.

[0057] In a preferred embodiment of the present invention, the first vacuum gauge G1, the third vacuum gauge G3 and the fifth vacuum gauge G5 are all combinations of capacitance film vacuum gauges, and the pressure test range is 1×10 5 Pa~10Pa, with a measurement accuracy of 0.5%; the second vacuum gauge G2, the fourth vacuum gauge G4 and the sixth vacuum gauge G6 are all composite monitoring vacuum gauges with a measurement range of 1×10 5 Pa~1×10 -8 Pa.

[0058] In a preferred embodiment of the present invention, the first high vacuum pump unit Pump1 and the second high vacuum pump unit Pump2 are both a combination of a turbomolecular pump and a vortex dry pump, which can obtain a vacuum of less than 1×10 -6 The ultimate vacuum degree is Pa. To save costs, the three vacuum chambers can also share a set of high vacuum pump units.

[0059] In a preferred embodiment of the present invention, all components are subjected to high-temperature dehydrogenation or high-temperature baking degassing treatment to reduce the impact on the background vacuum.

[0060] In a preferred embodiment of the present invention, the range of the conductance value C of the standard conductance element f is 10 -8 Pa·m 3 / s~10 -10 Pa·m 3 / s(e.g. 3.4×10 -10 Pa·m3 / s).

[0061] The embodiment of the present invention further provides a method for using the above device, comprising the following steps:

[0062] Step S1: Measure the background pressure P of the first vacuum chamber VC1, the second vacuum chamber VC2 and the third vacuum chamber VC3 01 , P 02 and P 03 ;

[0063] Step S2: Introduce He in the first gas cylinder Gas1 into the first vacuum chamber VC1 until the gas pressure in the first vacuum chamber VC1 reaches P1, where P1 is in the range of 10Pa to 1×10 5 Pa, then use the standard gas flowmeter to take samples, and introduce the He in the first vacuum chamber into the second vacuum chamber VC2 through the standard flow conduction element f, and the ventilation time is t;

[0064] Step S3: introducing N2 in the second gas cylinder Gas2 into the third vacuum chamber VC3 until the pressure in the third vacuum chamber VC3 reaches P3, and then sampling based on the static expansion method, using the seventh valve V7 or the eighth valve V8 to introduce the gas in the third vacuum chamber VC3 into the second vacuum chamber VC2, wherein the volumes of the seventh valve V7 and the eighth valve V8 are 0.5 mL and 0.1 L respectively;

[0065] Step S4: Using the background pressure P of the first vacuum chamber VC1 and the third vacuum chamber VC3 01 and P 03 , the pressure value P1 of the first vacuum chamber VC1 and the pressure value P3 of the third vacuum chamber VC3, the pressure value P2 of the second vacuum chamber (VC2), the volume U7 of the seventh sampling valve V7 and the volume U8 of the eighth sampling valve V8, the conductance value C of the standard conductance element, the ventilation time t, the ratio η of the standard mixed gas obtained in the second vacuum chamber VC2 and the partial pressure value P of the trace content gas He .

[0066] Before preparing the standard mixed gas, the process also includes: connecting the second vacuum chamber VC2 to a vacuum environment through a sixth valve V6; after the pressure in the second vacuum chamber VC2 is stabilized, opening the sixth valve V6 to deliver the prepared standard mixed gas to the vacuum environment at a certain flow rate.

[0067] In a preferred embodiment of the present invention, step S1 includes the following sub-steps:

[0068] Step S11: Record the temperature and humidity under the test environment conditions as 22°C and 47% respectively. Open the third valve V3, the fourth valve V4, the fifth valve V5, the tenth valve V10 and the twelfth valve V12, start the first fore-stage pump RP1 and the second fore-stage pump RP2, and perform rough pumping on the three vacuum chambers (i.e., the first vacuum chamber VC1, the second vacuum chamber VC2 and the third vacuum chamber VC3, hereinafter referred to as "three vacuum chambers");

[0069] Step S12: Turn on the second vacuum gauge G2, the fourth vacuum gauge G4 and the sixth vacuum gauge G6. After the indication values ​​of the second vacuum gauge G2 (e.g., 8.3 Pa), the fourth vacuum gauge G4 (8.6 Pa) and the sixth vacuum gauge G6 (9.2 Pa) all reach below 10 Pa, start the first vacuum gauge G1, the third vacuum gauge G3 and the fifth vacuum gauge G5, and simultaneously start the first molecular pump TMP1 and the second TMP2 to perform high vacuum extraction on the three vacuum chambers;

[0070] Step S13: When the indicated values ​​of the second vacuum gauge G2, the fourth vacuum gauge G4 and the sixth vacuum gauge G6 reach 1×10 -6 After it is below Pa and stable, record the displayed pressure value as P 01 (e.g. 9.5×10 -7 Pa), P 02 (e.g. 9.8×10 -7 Pa), P 03 (e.g. 8.7×10 -7 Pa), and close the fourth valve V4 and the fifth valve V5.

[0071] In a preferred embodiment of the present invention, step S2 includes the following sub-steps:

[0072] Step S21: close the third valve V3, open the first valve V1 and the second valve V2, and slowly introduce He in the first gas cylinder Gas1 into the first vacuum chamber VC1;

[0073] Step S22: When the pressure in the first vacuum chamber reaches 10Pa~1×10 5 Pa range, close the first valve V1 and the second valve V2, and record the indicated value of the first vacuum gauge G1 as P1 (e.g. P1 = 10Pa) after the indicated value stabilizes;

[0074] Step S23: Open the fourth valve V4 and the fifth valve V5 in sequence, and introduce the He in the first vacuum chamber VC1 into the second vacuum chamber VC2 through the standard flow conduction element f. The air intake time is 100s to 1000s. After the air intake is completed, quickly close the fourth valve V4 and the fifth valve V5, and record the ventilation time t (such as t=100s).

[0075] In a preferred embodiment of the present invention, step S3 includes the following sub-steps:

[0076] Step S31: close the tenth valve V10, open the ninth valve V9 and the eleventh valve V11, and slowly introduce the N2 in the second gas cylinder Gas2 into the third vacuum chamber VC3;

[0077] Step S32: When the pressure in the third vacuum chamber VC3 reaches 10Pa~1×10 5 Pa range, close the eleventh valve V11 and the ninth valve V9, and wait for the indication value of the fifth vacuum gauge G5 to stabilize and record its indication value as P3 (e.g. P3 = 1×10 5 Pa);

[0078] Step S33: statically expand and sample the N2 in the third vacuum chamber VC3 through the seventh valve V7 or the eighth valve V8, and then introduce it into the second vacuum chamber VC2. After the indication value of the fourth vacuum gauge G4 stabilizes, record its indication value as P2 (for example, after multiple samplings of N2, P2 = 1×10 5 Pa).

[0079] In a preferred embodiment of the present invention, step S4 includes the following sub-steps:

[0080] Step S41: Calculate the mixing ratio η of the standard mixed gas, the formula is:

[0081]

[0082] U′=U7 or U8

[0083] Step S42: Calculate the partial pressure value of He in the standard mixed gas as P He , the formula is:

[0084] P He =P2·η

[0085] According to the parameters in one embodiment of the present invention, the mixing ratio η of the standard mixed gas can be calculated to be 6.8×10 -10 , He partial pressure value P He 6.8×10 -5 Pa.

[0086] In a preferred embodiment of the present invention, it also includes:

[0087] Step S5: Prepare a mixture with a ratio of 6.8×10 -10 After the air pressure in the second vacuum chamber VC2 is stable for 5 minutes, the sixth valve V6 is opened to introduce the standard mixed gas into the vacuum environment.

[0088] Step S6: After the standard mixed gas is provided to the vacuum environment, the sixth valve V6 is closed, the two high vacuum pump groups and all vacuum gauges are turned off, and the test is completely completed.

[0089] The present invention discloses a device for preparing a standard mixed gas using a flow meter under vacuum conditions and a method for using the same. The device for preparing a standard mixed gas is obtained by connecting a mixed gas pipeline to two groups of gas sampling pipelines. The background pressure and gas pressure of the first vacuum chamber VC1, the second vacuum chamber VC2 and the third vacuum chamber VC3 are measured respectively by a first vacuum gauge G1, a third vacuum gauge G3 and a fifth vacuum gauge G5. A certain amount of He obtained based on the standard gas flow meter and a certain amount of N2 obtained based on a static expansion method are mixed in the second vacuum chamber VC2 to obtain the required standard mixed gas.

[0090] The standard mixed gas containing He prepared by the present invention has a lower limit of the preparation ratio of 2×10 -10 The minimum He pressure in the standard mixed gas can reach 2×10 -9 Pa, overcoming the bottleneck of the traditional standard small volume pressure sampling method for preparing standard mixed gas, which is difficult to extend the lower limit of the mixed gas preparation ratio, and extending the lower limit of the preparation ratio to 2×10 -10 This method has the advantages of simple equipment, low cost, and easy operation, and solves the problem of preparing standard mixed gases containing trace gases in vacuum measurement and detection and related application fields.

[0091] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for preparing a standard mixed gas using a flow meter under vacuum conditions, comprising a trace gas sampling pipeline, a mixed gas pipeline and other gas sampling pipelines connected in sequence, characterized in that: The trace gas sampling pipeline comprises a first gas cylinder (Gas1), a first valve (V1), a second valve (V2), a first vacuum chamber (VC1), a third valve (V3) and a first high vacuum pump unit (Pump1) which are connected in sequence, and a first vacuum gauge (G1) and a second vacuum gauge (G2) are installed on the first vacuum chamber (VC1); The mixed gas pipeline comprises a fourth valve (V4), a standard flow conductance element (f), a fifth valve (V5), a second vacuum chamber (VC2), a sixth valve (V6), a seventh valve (V7), an eighth valve (V8) and a twelfth valve (V12), and a third vacuum gauge (G3) and a fourth vacuum gauge (G4) are installed on the second vacuum chamber (VC2); The other gas sampling pipeline includes a second gas cylinder (Gas2), an eleventh valve (V11), a ninth valve (V9), a third vacuum chamber (VC3), a tenth valve (V10) and a second high vacuum pump unit (Pump2) connected in sequence, and a fifth vacuum gauge (G5) and a sixth vacuum gauge (G6) are installed on the third vacuum chamber (VC3); The first vacuum chamber (VC1) is connected to the fourth valve (V4), the second vacuum chamber (VC2) is connected to the third vacuum chamber (VC3) through the seventh valve (V7), the eighth valve (V8) and the twelfth valve (V12), and the seventh valve (V7), the eighth valve (V8) and the twelfth valve (V12) are connected in parallel.

2. The device for preparing a standard mixed gas using a flow meter under vacuum conditions according to claim 1, characterized in that: The sixth valve (V6) is connected to a vacuum environment, and the second vacuum chamber (VC2) can provide a configured standard mixed gas to the vacuum environment through the sixth valve (V6).

3. The device for preparing a standard mixed gas using a flow meter under vacuum conditions according to claim 1, characterized in that: The seventh valve (V7) and the eighth valve (V8) are respectively U 7 = 0.5 mL and U 8=0.1L sampling valve.

4. The device for preparing a standard mixed gas using a flow meter under vacuum conditions according to claim 1, characterized in that: The purity of the gas in the first gas cylinder (Gas1) and the second gas cylinder (Gas2) is 99.9999%.

5. The device for preparing a standard mixed gas using a flow meter under vacuum conditions according to claim 1, characterized in that: The first vacuum gauge (G1), the third vacuum gauge (G3) and the fifth vacuum gauge (G5) are all capacitance film vacuum gauge combinations, and the pressure test range is 1×10 5 Pa ~10 Pa, measurement accuracy is better than 0.5%; The second vacuum gauge (G2), the fourth vacuum gauge (G4) and the sixth vacuum gauge (G6) are all composite monitoring vacuum gauges with a measurement range of 1×10 5 Pa ~1×10 -8 Pa.

6. The device for preparing a standard mixed gas using a flow meter under vacuum conditions according to claim 1, characterized in that: The conductance value of the standard conductance element (f) C The range is 10 -8 m 3 / s 10 -10 m 3 / s.

7. The device for preparing a standard mixed gas using a flow meter under vacuum conditions according to claim 1, characterized in that: The volume of the first vacuum chamber (VC1) is U 1=5 L, the volume of the second vacuum chamber (VC2) is U 2=5 L, the volume of the third vacuum chamber (VC3) is U 3=1 L.

8. A method for preparing a standard mixed gas using a flow meter under vacuum conditions, using the device as described in any one of claims 1 to 7, characterized in that: The method comprises: Step S1: Measuring the background pressure of the first vacuum chamber (VC1), the second vacuum chamber (VC2) and the third vacuum chamber (VC3) P 01 , P 02 and P 03 ; Step S2: Introduce the gas in the first gas cylinder (Gas1) into the first vacuum chamber (VC1) until the gas pressure in the first vacuum chamber (VC1) is P 1, where P The range of 1 is 10 Pa~1×10 5 Pa; then start sampling based on the standard gas flow meter, close the second valve (V2), the sixth valve (V6), the seventh valve (V7), the eighth valve (V8) and the twelfth valve (V12), and open the fourth valve (V4) and the fifth valve (V5) at the same time, introduce the gas in the first vacuum chamber (VC1) into the second vacuum chamber (VC2) through the standard flow conduction element (f), and record the ventilation time as t ,in t The range of is 100 s~1000 s, and then the fourth valve (V4) and the fifth valve (V5) are closed; Q =( P 1- P 01 )·C can be calculated that the range of the gas flow rate sampled by the standard gas flow meter is 1×10 -3 Pa·m 3 / s ~ 1×10 -9 Pa·m 3 / s, wherein C is the conductance value of the standard conductance element (f); Step S3: Introduce the gas in the second gas cylinder (Gas2) into the third vacuum chamber (VC3) until the pressure in the third vacuum chamber (VC3) reaches P 3. Then, sampling is performed based on the static expansion method, and the gas in the third vacuum chamber (VC3) is introduced into the second vacuum chamber (VC2) by using the seventh valve (V7) or the eighth valve (V8); Step S4: Using the background pressure of the first vacuum chamber (VC1) and the third vacuum chamber (VC3) P 01 and P 03 , and the pressure value of the first vacuum chamber (VC1) P 1. Pressure value of the third vacuum chamber (VC3) P 3. Pressure value of the second vacuum chamber (VC2) P 2. Volume of the seventh valve (V7) U 7 or the volume of the eighth valve (V8) U 8. The conductance value C of the standard conductance element (f), the ventilation time t, and the mixing ratio of the standard mixed gas obtained in the second vacuum chamber (VC2) η and the partial pressure of the trace gas P x .

9. The method according to claim 8, characterized in that The step S1 comprises the following sub-steps: Step S11: opening the third valve (V3), the fourth valve (V4), the fifth valve (V5), the tenth valve (V10) and the twelfth valve (V12), starting the first high vacuum pump unit (Pump1) and the second high vacuum pump unit (Pump2), and evacuating the first vacuum chamber (VC1), the second vacuum chamber (VC2) and the third vacuum chamber (VC3); Step S12: Turn on the second vacuum gauge (G2), the fourth vacuum gauge (G4) and the sixth vacuum gauge (G6); after the indication values ​​of the second vacuum gauge (G2), the fourth vacuum gauge (G4) and the sixth vacuum gauge (G6) all reach below 10 Pa, turn on the first vacuum gauge (G1), the third vacuum gauge (G3) and the fifth vacuum gauge (G5); wherein, before the first use of the first vacuum gauge (G1), the third vacuum gauge (G3) and the fifth vacuum gauge (G5), they must be preheated for more than 12 hours, and the pressure in the corresponding vacuum chamber must be less than 1×10 -6 Pa, and then it can be used; Step S13: When the indication values ​​of the second vacuum gauge (G2), the fourth vacuum gauge (G4) and the sixth vacuum gauge (G6) all reach 1×10 -6 After the pressure drops below Pa and stabilizes, the pressure values ​​displayed by the second vacuum gauge (G2), the fourth vacuum gauge (G4) and the sixth vacuum gauge (G6) are recorded respectively. P 01 , P 02 , P 03 , and then close the fourth valve (V4) and the fifth valve (V5).

10. The method according to claim 8, characterized in that The step S2 comprises the following sub-steps: Step S21: closing the third valve (V3), opening the first valve (V1) and the second valve (V2), and slowly introducing the gas in the first gas cylinder (Gas1) into the first vacuum chamber (VC1); Step S22: When the pressure of the first vacuum chamber (VC1) reaches 10 Pa~1×10 5 Pa range, close the first valve (V1) and the second valve (V2), and record the indicated value of the first vacuum gauge (G1) after the indicated value stabilizes. P 1; Step S23: Open the fourth valve (V4) and the fifth valve (V5) in sequence, start sampling based on the standard gas flow meter, introduce the gas in the first vacuum chamber (VC1) into the second vacuum chamber (VC2) through the standard flow conduction element (f), and the ventilation time is 100 s to 1000 s. After the ventilation is completed, quickly close the fourth valve (V4) and the fifth valve (V5), and record the ventilation time t .

11. The method according to claim 8, characterized in that The step S3 comprises the following sub-steps: Step S31: closing the tenth valve (V10), opening the ninth valve (V9) and the eleventh valve (V11), and slowly introducing the gas in the second gas cylinder (Gas2) into the third vacuum chamber (VC3); Step S32: When the pressure in the third vacuum chamber (VC3) reaches 10 Pa~1×10 5 Pa range, close the eleventh valve (V11) and the ninth valve (V9), and record the indicated value of the fifth vacuum gauge (G5) after the indicated value stabilizes. P 3; Step S33: statically expand and sample the gas in the third vacuum chamber (VC3) through the seventh valve (V7) or the eighth valve (V8), and then introduce it into the second vacuum chamber (VC2). After the indication value of the fourth vacuum gauge (G4) stabilizes, record its indication value as follows: P 2.

12. The method according to claim 8, characterized in that The step S4 comprises the following sub-steps: Step S41: Calculate the mixing ratio of the standard mixed gas η , the formula is: Step S42: Calculate the partial pressure of the trace gas in the standard mixed gas: P x , the formula is: .

13. The method according to claim 8, characterized in that In the step S4, it also includes: Step S5: After the air pressure in the second vacuum chamber (VC2) is stabilized, a standard mixed gas is provided to the vacuum environment through the sixth valve (V6).

Images