1、Designation:F 78 97(Reapproved 2002)Standard Test Method forCalibration of Helium Leak Detectors by Use of SecondaryStandards1This standard is issued under the fixed designation F 78;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,th
2、e year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a procedure for calibrating amass spectrometer-type helium leak detector with a series ofc
3、ommercially available calibrated leaks without need forrecourse to a primary standard.1.2 Leak detector parameters determined by this test methodinclude:1.2.1 Minimum detectable signal,drift noise(8.5,withrecorder;8.6,without recorder),1.2.2 Response time,1.2.3 Minimum detectable leak rate,and1.2.4
4、Sensitivity.1.3 This standard does not purport to address the safetyconcerns,if any,associated with its use.It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2.Referenced Docu
5、ments2.1 ASTM Standards:E 1 Specification for ASTM Thermometers2E 425 Definitions of Terms Relating to Leak Testing33.Terminology3.1 Definitions:3.1.1 calibrated leakin leak detection,a device that per-mits leakage through it at a specified rate,of a specific gas,under specific conditions,with the d
6、ownstream side of thedevice exposed to a pressure sufficiently low to have negligibleeffect on the leak rate.3.1.2 minimum detectable signalin leak detection,thesmallest unambiguous output signal that can be derived from agiven particular leak detector.Units are detector scale divi-sions.3.1.2.1 Dis
7、cussionThe minimum detectable signal is de-termined by the noise present in,and drift of,the output signal.3.1.3 standard leak ratein leak detection,the rate of flowof atmospheric air of dewpoint less than 25C through a leakunder standard conditions specified as follows:(1)the inletpressure shall be
8、 1 standard atmosphere 65%(1016 5 kPa),(2)the outlet pressure shall be less than 1 kPa(0.01 atm),and(3)the temperature shall be 23 6 3C.3.2 Definitions of Terms Specific to This Standard:3.2.1 response timeof a leak detector,for the purposes ofthis test method,a measure of the speed of response of t
9、hedetector to an incoming helium sample.3.2.1.1 DiscussionIn this test method the cleanup timeand response time are assumed to be equal.3.2.2 sensitivityof a leak detector,for the purposes of thistest method,the ratio of the change in the output signal to theapplied helium leak rate.3.3 Other terms
10、used in this test method are defined inDefinitions E 425.4.Summary of Test Method4.1 At least three calibrated leaks are tested on a helium leakdetector,and a correlation is obtained between the outputindication of the leak detector and the leak rate of the calibratedleaks.These readings are used to
11、 plot a calibration line fromwhich intermediate values,within specified limits,may beread.5.Interferences5.1 Certain materials,particularly organic compounds,willentrap or hold helium tracer gas.Use of such materials inconnections between the calibrated leak and the leak should beminimized to avoid
12、erroneous results.(If the net outputreadings from any calibrated leak consistently lie outside theestablished limits,the leak should be returned to the supplierfor a recalibration check.)5.2 The background reading,B,should be at most onequarter of the output reading,A.If the value of B approachestha
13、t of A,the accuracy of the determination of N will suffer(see9.3.1).6.Apparatus6.1 Calibrated LeaksAt least three commercial devicesincorporating leaks,one having a leak rate of approximately109atmcm3s1(1010Pam3s1),a second having a leak1This test method is under the jurisdiction of ASTM Committee F
14、01 onElectronics and is the direct responsibility of Subcommittee F01.03 on MetallicMaterials.Current edition approved Dec.10,2002.Published May 2003.Originallyapproved in 1967.Last previous edition approved in 1997 as F 78 97.2Annual Book of ASTM Standards,Vol 14.03.3Discontinued.See 1991 Annual Bo
15、ok of ASTM Standards,Vol 03.03.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.value in the nominal range from 108to 107atmcm3s1(109to 108Pam3s1),and the third having a leak rate ofapproximately 106atmcm3s1(107Pam3s1).6.1.1 The calibrated
16、 leaks shall be obtained from at leasttwo independent suppliers.6.1.2 The calibrated leaks shall have been calibrated withhelium gas at a pressure of approximately 1 standard atmo-sphere 65%(101 6 5 kPa).6.1.3 The following information shall be provided with eachcalibrated leak:6.1.3.1 Calibrated leak rate,atmcm3s1(or Pam3s1),6.1.3.2 Date of calibration,6.1.3.3 Temperature of calibration,C,6.1.3.4 Temperaturecoefficient,atmcm3s1C1(orPam3s1C1),and6.1.3.5 If a reservoir is an integral part of the