CN102052940B - Device for measuring extremely-low gas flow based on static expansion vacuum standard - Google Patents
Device for measuring extremely-low gas flow based on static expansion vacuum standard Download PDFInfo
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- CN102052940B CN102052940B CN 201010523143 CN201010523143A CN102052940B CN 102052940 B CN102052940 B CN 102052940B CN 201010523143 CN201010523143 CN 201010523143 CN 201010523143 A CN201010523143 A CN 201010523143A CN 102052940 B CN102052940 B CN 102052940B
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Abstract
The invention relates to a device for measuring an extremely-low gas flow based on the static expansion vacuum standard. The device comprises a backing pressure measurement system, a first valve, a gas pressure relief system, a second valve, a calibration chamber, a third valve, a small hole, a fourth valve, a fifth valve, a getter pump, a sixth valve, a molecular pump, a backing pump and an ionization gauge, wherein the backing pressure measurement system is connected with the gas pressure relief system through the first valve, the gas pressure relief system is connected with the calibration chamber through the second valve, the small hole is connected in parallel with the fourth valve to form a parallel structure and then one end of the parallel structure is connected with the calibration chamber through the third valve and the other end of the parallel structure is connected with a vacuum system, the getter pump is connected with the calibration chamber through the fifth valve, the backing pump is connected in series with the molecular pump and then connected with the calibration chamber through the sixth valve, and the ionization gauge is directly connected on the calibration chamber. The invention adopts the gas pressure generated by the static expansion vacuum standard to replace the introduced gas pressure of the gas flow meter in the constant conductance method, so as to further improve the gas flow measurement accuracy.
Description
Technical field
The present invention relates to a kind of apparatus and method of measuring minimum gas flow, particularly a kind of apparatus and method of the minimum gas flow of measurement based on static expanding method vacuum standard.
Background technology
In Measurement Laboratory, adopt the high-precision gas micro-flowmeter to measure and provide the known gas flow mostly.
Document " Li Detian. German federal physical technique research institute (PTB) gas micro metering review. vacuum science and technological journal 23 (4), 2003. " introduced the gas meter that is in the German PTB of international highest level at present.The gas meter of PTB development is with three kinds of different pattern work: flow is in that (the Pa.m3/s scope of 10-8~10-4) is used constant-voltage method; Flow is used the fixed flow inducing defecation by enema and suppository during less than 10-8Pa.m3/s; Flow is used constant volume method during greater than 10-4Pa.m3/s.When adopting the fixed flow inducing defecation by enema and suppository, the gaseous tension that charges into of gas meter is measured with capacitor thin film rule or magnetic suspension rotor gauge usually.The transfer coefficient of magnetic suspension rotor gauge can change along with time, gaseous species and variation of temperature; There is the thermal transpiration effect in capacitor thin film rule under low-pressure; These effects limit the accurate measurement of pressure, thereby become the uncertainty factor that influences the maximum that flow accurately measures.
Summary of the invention
The objective of the invention is to overcome the weak point of prior art; A kind of minimum gas flow measurement apparatus and method based on static expanding method vacuum standard are provided; Avoid with capacitor thin film rule or magnetic suspension rotor gauge gaging pressure; Thereby further improve the measuring accuracy of gas flow, make flow value less than 1 * 10
-8Pa.m
3The gas flow of/s can accurately be measured, and the measurement lower limit of flow has been extended to 10
-16Pa.m
3/ s magnitude.
The invention provides a kind of minimum gas flow measurement device based on static expanding method vacuum standard; Comprise forepressure measuring system, valve one, gaseous tension attenuation factor, valve two, calibration chamber, valve three, aperture, valve four, valve five, getter pump, valve six, molecular pump, forepump and ionization gauge composition; The forepressure measuring system is connected with the gaseous tension attenuation factor through valve one; The gaseous tension attenuation factor is connected with calibration chamber through valve two; Aperture links to each other with calibration chamber through valve three with valve four parallel connection backs one end, and an end links to each other with vacuum system, and getter pump links to each other with calibration chamber through valve five; Forepump is connected with calibration chamber through valve six with molecular pump polyphone back, and ionization gauge directly is connected on the calibration chamber.
Described forepressure measuring system is the standard source of the gas.
Described gaseous tension attenuation factor is made up of one-level sampling hut, secondary sampling hut and big volume vacuum chamber.
Described aperture, its molecular flow conductance is 10
-9m
3/ s magnitude.
Described valve six is the ultrahigh vacuum push-pull valve.
Described getter pump is the nonevaporable getter pump.
The measuring principle of device according to the invention is: after using molecular pump, forepump and getter pump that calibration chamber is evacuated to end vacuum; Use getter pump to keep; Because getter pump does not have pumping speed to inert gas, can make calibration chamber reach higher final vacuum; Inert gas flows out from the forepressure measuring system, expand into the gaseous tension attenuation factor, can calculate the pressure in the gaseous tension attenuation factor according to Boyle's law; Conductance and the intrasystem pressure of gas pressure attenuation through aperture can obtain gas flow.Ionization gauge is used to detect the final vacuum of calibration chamber.
The present invention also provides a kind of minimum gas flow measurement method based on static expanding method vacuum standard, may further comprise the steps:
(1) opens valve three, valve four, valve six, start forepump and molecular pump successively, calibration chamber and connection vacuum pipe are bled;
(2) carry out bakeout degassing to installing integral body, after baking temperature rises to peak respectively with the uniform speed, keep 60~80h;
(3) during the baking maximum temperature keeps, open the connection valve of getter pump, getter pump is activated; Stop after activating 2~4h, close getter pump and connect valve, and then reduce to room temperature gradually with the uniform speed; After temperature returns to room temperature; Open getter pump again and connect valve, continue the 24~48h that bleeds, in calibration chamber, reach 10
-9The end vacuum of the Pa order of magnitude;
(4) valve-off three, valve six, the interior pressure of calibration chamber this moment begins slow rising, and pressure reaches stable after a period of time;
(5) charge into the high-purity gas of certain pressure for the prime of static expanding method vacuum standard, in the gaseous tension attenuation factor, choose corresponding expansion path and expansion progression, gas expand into calibration chamber through valve two;
(6) after the indoor pressure stability to be calibrated, open valve three, valve-off four is incorporated into the indoor gas of calibration in the vacuum system through aperture;
(7) conductance and the intrasystem pressure of gas pressure attenuation according to aperture obtains gas flow.
Be 200~300 ℃ to installing the highest whole baking temperature in the step (2), the uniform speed that baking temperature rises and descends is 20~40 ℃/h.
Activationary temperature to getter pump (10) in the step (3) is 450~500 ℃.
The present invention's beneficial effect compared with prior art is:
The gaseous tension that charges into that replaces fixed flow inducing defecation by enema and suppository gas meter with the gaseous tension of static expanding method vacuum standard generation; The uncertainty of measurement of having introduced when having avoided like this with capacitor thin film rule or magnetic suspension rotor gauge gaging pressure, thus the measuring accuracy of gas flow further improved.
Description of drawings
Fig. 1 is the minimum gas flow measurement structure drawing of device that the present invention is based on static expanding method vacuum standard.
Among the figure: 1-forepressure measuring system, 2,4,6,8,9,11-valve, 3-gaseous tension attenuation factor, 5-calibration chamber, 7-aperture, 10-getter pump, 12-molecular pump, 13-forepump, 14-ionization gauge.
Embodiment
As shown in Figure 1; For the minimum gas flow measurement device based on static expanding method vacuum standard of the present invention, form by forepressure measuring system 1, valve 1, gaseous tension attenuation factor 3, valve 24, calibration chamber 5, valve 36, aperture 7, valve 48, valve 59, getter pump 10, valve 6 11, molecular pump 12, forepump 13 and ionization gauge 14.
Forepressure measuring system 1 is connected with gaseous tension attenuation factor 3 through valve 1; Gaseous tension attenuation factor 3 is connected with calibration chamber 5 through valve 24; Aperture 7 links to each other with calibration chamber 5 through valve 36 with valve 48 parallel connection backs one end, and an end links to each other with vacuum system, and getter pump 10 links to each other with calibration chamber 5 through valve 59; Forepump 13 is connected with calibration chamber 5 through valve 6 11 with molecular pump 12 polyphone backs, and ionization gauge 14 directly is connected on the calibration chamber 5.
Forepressure measuring system 1 is the standard source of the gas.
Gaseous tension attenuation factor 3 is made up of one-level sampling hut, secondary sampling hut and big volume vacuum chamber.
Aperture 7, its molecular flow conductance is 10
-9m
3/ s magnitude.
Valve 6 11 is the ultrahigh vacuum push-pull valve.
Getter pump 10 is the nonevaporable getter pump.
The measuring principle of this device is: after using molecular pump, forepump and getter pump that calibration chamber is evacuated to end vacuum, use getter pump to keep, because getter pump does not have pumping speed to inert gas, can make calibration chamber reach higher final vacuum; Inert gas flows out from the forepressure measuring system, expand into the gaseous tension attenuation factor, can calculate the pressure in the gaseous tension attenuation factor according to Boyle's law; Conductance and the intrasystem pressure of gas pressure attenuation through aperture can obtain gas flow.Ionization gauge is used to detect the final vacuum of calibration chamber.
The implementation step of present embodiment is following:
(1) opens valve 36, valve 48, valve 6 11, start forepump 13 and molecular pump 12 successively, calibration chamber 5 and connection vacuum pipe are bled;
(2) carry out bakeout degassing to installing integral body, baking temperature keeps 72h, and then reduces to room temperature gradually with the uniform speed of 30 ℃/h after rising to separately peak respectively with the uniform speed of 30 ℃/h;
(3) during the baking maximum temperature keeps, open the connection valve 9 of getter pump 10, getter pump 10 is activated; Activationary temperature is 500 ℃, stops behind the activation 2h, closes getter pump and connects valve; After temperature returns to room temperature; Open getter pump again and connect valve, continue the 48h that bleeds, this moment, calibration chamber 5 interior final vacuums were 6.7 * 10
-9Pa;
(4) valve-off 36, valve 11, this moment, calibration chamber 5 interior pressure began slow rising, and pressure reaches stationary value behind the 120min, and the reading of ionization gauge 14 is 3.2 * 10
-8Pa;
(5) high-purity He gas of charging into for the prime of static expanding method vacuum standard in gaseous tension attenuation factor 3, is chosen corresponding expansion path and expansion progression, and gas is through valve 24 introducing calibration chamber 5;
(6) after the pressure stability in the chamber 5 to be calibrated, the reading of ionization gauge 14 is 8.1 * 10
-7Pa is through the gaseous tension P of static expanding method vacuum standard generation
0Be 7.644 * 10
-7Pa.Open valve 36, valve-off 48 is incorporated into the gas in the calibration chamber 5 in the vacuum system through aperture 7, reaches mobile equilibrium behind the 10min.
(7) then the gas flow that provides of this device is calculated by (1) formula
Q=p
0·C
He..........................................(1)
In the formula: Q-flow, Pa.m
3/ s;
P
0The gaseous tension that-static expanding method vacuum standard produces, Pa;
C
He-under the molecular flow condition, aperture 7 is with respect to the conductance of He, m
3/ s.
Wherein, record C in advance
HeBe 1.26 * 10
-9m
3/ s.
With P
0=7.644 * 10
-7Pa, C=1.26 * 10
-9m
3/ s is substitution formula (1) respectively, and the measured value that calculates flow is 9.631 * 10
-16Pa.m
3/ s.
Claims (6)
1. minimum gas flow measurement device based on static expanding method vacuum standard; Comprise forepressure measuring system (1), valve one (2), gaseous tension attenuation factor (3), valve two (4), calibration chamber (5), valve three (6), aperture (7), valve four (8), valve five (9), getter pump (10), valve six (11), molecular pump (12), forepump (13) and ionization gauge (14); It is characterized in that: forepressure measuring system (1) is connected with gaseous tension attenuation factor (3) through valve one (2); Inert gas flows out from forepressure measuring system (1); Gaseous tension attenuation factor (3) through valve two (4) is connected with calibration chamber (5), aperture (7) and valve four (8) parallelly connected ends afterwards are connected with calibration chamber (5) through valve three (6); One end links to each other with vacuum system; Getter pump (10) links to each other with calibration chamber (5) through valve five (9), and forepump (13) is connected with calibration chamber (5) through valve six (11) with molecular pump (12) polyphone back, and ionization gauge (14) directly is connected on the calibration chamber (5).
2. a kind of minimum gas flow measurement device according to claim 1 is characterized in that: described forepressure measuring system (1) is the standard source of the gas.
3. a kind of minimum gas flow measurement device according to claim 1 is characterized in that: described gaseous tension attenuation factor (3) is made up of one-level sampling hut, secondary sampling hut and big volume vacuum chamber.
4. a kind of minimum gas flow measurement device according to claim 1 is characterized in that: described aperture (7), its molecular flow conductance is 10
-9m
3/ s magnitude.
5. a kind of minimum gas flow measurement device according to claim 1 is characterized in that: described valve six (11) is the ultrahigh vacuum push-pull valve.
6. a kind of minimum gas flow measurement device according to claim 1 is characterized in that: described getter pump (10) is the nonevaporable getter pump.
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CN113295575A (en) * | 2021-05-24 | 2021-08-24 | 合肥工业大学 | Getter air suction performance test integrated device based on differential pressure method |
CN117490783A (en) * | 2023-10-18 | 2024-02-02 | 北京东方计量测试研究所 | The lower limit is 5×10 -18 Pa·m 3 Flow meter of/s and method of use thereof |
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