1、Designation: D 4298 04Standard Guide forIntercomparing Permeation Tubes to Establish Traceability1This standard is issued under the fixed designation D 4298; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers two procedures for establishing thepermeation rate of a permeation tube and defining the uncer-tainty of the rat
3、e by comparison to National Institute ofStandards and Technologys Standard Reference Materials(SRM).1.2 Procedure A consists of a direct comparison of thepermeation rate of the device undergoing calibration with thatof an SRM.1.3 Procedure B consists of a gravimetric calibration pro-cess in which a
4、certified permeation tube is used as a qualitycontrol for the measurements.1.4 Both procedures are limited to the case where a suitablecertified permeation device is available.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsib
5、ility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (See 8.2 on SafetyPrecautions.)2. Referenced Documents2.1 ASTM Standards:2D 1356 Terminology Relating to Sampling and Analysis ofAtmospher
6、esD 3249 Practice for General Ambient Air Analyzer Proce-duresD 3609 Practice for Calibration Techniques Using Perme-ation TubesD 3631 Test Methods for Measuring Surface AtmosphericPressureE 1 Specification for ASTM ThermometersE 319 Practice for the Evaluation of Single-Pan MechanicalBalancesE 617
7、Specification for Laboratory Weights and PrecisionMass Standards3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this guide, refer toTerminology D 1356.3.1.2 Definitions of Terms Specific to This Standard:3.1.2.1 working standarda standard used in the laboratoryor field for perio
8、dic standardization of a measuring instrument.4. Summary of Guide4.1 Procedure AA certified SRM permeation source, ob-tained from the National Institute of Standards and Technologyis used to calibrate a continuous analyzer. The analyzer is thenused to measure the concentration of a gaseous mixturege
9、nerated from the permeation tube under calibration. Equa-tions are provided that permit calibration of the permeation rateof the latter from the test data.4.2 Procedure BThe permeation source is calibrated,gravimetrically, using temperature and mass standards trace-able to NIST standards. The validi
10、ty of the calibration isconfirmed by concurrently measuring the permeation rate of aCertified Reference Material (CRM).5. Significance and Use5.1 The accuracy of air pollution measurements is directlydependent upon accurate calibrations.5.2 Such measurements gain accuracy and can be intercom-pared w
11、hen the measurement procedures are traceable tonational measurement standards.5.3 This guide describes procedures for enhancing theaccuracy of air pollution measurements which may be specifiedby those organizations requiring traceability to national stan-dards.6. Apparatus6.1 For apparatus used in t
12、he calibration of permeationdevices, refer to Practice D 3609.6.1.1 The thermometers used shall conform to SpecificationE1and shall have calibration certificates traceable to the NIST.Measurement uncertainty should be 0.1C or less.1This guide is under the jurisdiction of ASTM Committee D22 on Sampli
13、ng andAnalysis of Atmospheres and is the direct responsibility of Subcommittee D22.01on Quality Control.Current edition approved October 1, 2004. Published October 2004. Originallyapproved in 1983. Last previous edition approved in 1999 as D 4298 - 95 (1999).2For referenced ASTM standards, visit the
14、 ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, U
15、nited States.6.1.2 The mercury barometer shall conform to Test MethodsD 3631.6.2 Apparatus for Procedure A:6.2.1 Analytical InstrumentsAn analytical instrument re-sponsive to the permeant with the following minimum perfor-mance specifications:Noise 1 % of full-scaleZero drift 64 % of full-scale per
16、daySpan drift 63 % of full-scale per dayRange 0 to 0.5 ppm (or appropriate for source strength)6.2.2 Continuous strip chart recorder with the followingminimum performance specifications:Uncertaintycomponent0.33 3 (0.25 % full-scaledeflection)Chart width no less than 6 in.Time for full-scale travel 1
17、 sNOTE 1ISO GUM3points out that with approximately normal plottedpoints, the above maximum 3 3 standard deviations is equivalent to99 % of plotted points lying within 6(0.25 % full-scale deflection) oftrue values.6.3 Apparatus for Procedure B:6.3.1 Analytical balance, meeting the requirements of Pra
18、c-tices E 319 and D 3609.6.3.2 Analytical weights meeting the requirements of Speci-fication E 617 and having a calibration certificate traceable tothe NIST.7. Materials7.1 Refer to Practice D 3609.7.2 CRM Permeation Device.48. Precautions8.1 Procedural Precautions:8.1.1 The procedural precautions d
19、escribed in PracticeD 3609 are applicable to the present guide.8.1.2 When possible, the permeation device should becompared to the CRM using the same system with identicalflow and temperature conditions. Unpredictable errors may beintroduced if permeation devices are compared at widelydifferent temp
20、eratures and flow rates (pertains to Procedure A).Intercomparisons are valid only at temperatures for which theCRM tube is calibrated.8.1.3 Equilibration of the permeation device, the calibrationequipment, and the analytical system must be assured, prior touse. During storage, avoid exposing tubes t
21、o high humidities orwide variations in temperature, that may permanently alter thepermeation rate.8.2 Safety Precautions:8.2.1 For precautions concerning the use of analytical in-struments and of cylinders containing pressurized gases, seePractice D 3249.9. Calibration and Standardization9.1 Procedu
22、re A:9.1.1 Set up a gas generation system using a CertifiedReference Material (CRM) permeation tube and apparatus andprocedure such as described in Practice D 3609. Equilibrate atthe desired temperature of calibration.9.1.2 Optimize the performance of the analytical instrumentaccording to the manufa
23、cturers instructions.9.1.3 Using dry air or nitrogen, set the zero point of theinstrument.9.1.4 Use the gas generation system to provide gas concen-trations corresponding to 20, 40, 60, and 80 % of full-scalereadings. Record the concentration and respective readings.Repeat the measurements in random
24、 order.9.1.5 Plot concentration versus instrument readings anddraw the line of best fit, or alternatively fit by linear leastsquares regression. Calculate the slope (ppm(v)/scale reading)and standard deviation estimate scal, expressed as g/min.9.1.5.1 If any point deviates by more than 61 % from the
25、line of best fit, repeat the calibration.9.2 Procedure B:9.2.1 The standard masses and the thermometer used musthave a valid calibration certificate or be calibrated prior to use.10. Procedure10.1 Procedure A:10.1.1 Place test permeation device in the system, equili-brate at the temperature of calib
26、ration, and generate gasmixtures corresponding approximately to 20, 40, 60, and 80 %of full scale readings, respectively.10.1.2 Record the instrument readings for each gas mixture.10.1.3 Using calibration curves described in 9.1.5, calculatethe concentrations of the gas mixtures.10.1.4 Calculate the
27、 permeation rates as described in 11.1.10.1.5 Repeat the measurements of 10.1.1 in random orderand record as in 10.1.2.10.2 Procedure B:10.2.1 Maintain the permeation device at constant tempera-ture, T, during the sequence of measurements described asfollows:10.2.2 Weigh permeation device, periodica
28、lly recording themass and time of weighing, as described in Practice D 3609.10.2.3 Calculate the mass loss per unit of time in the unitsof g/min at temperature, T.10.2.4 Calibrate a CRM permeation tube using the sameprocedure and concurrently with the test permeation device.11. Calculations11.1 Proc
29、edure A:11.1.1 Calculate the permeation rate for each of the eightmeasurements, using the following equation:R 5 Cppmv!F 3 MWMV(1)where:R = permeation rate, g/min,Cppm(v)= measured concentration, ppm(v) (by volume),F = total flow rate of gas (L/min),MW = molecular weight of permeant, and3ISO GUM, Gu
30、ide to the Expression of Uncertainty in Measurement, Interna-tional Organization for Standardization (ISO), available from American NationalStandards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.4Certified permeation tubes may be obtained from NIST currently only byspecial order f
31、rom the Office of Standard Reference Materials, National Institute ofStandards and Technology, Washington, DC 20234.D4298042MV = molecular volume (24.47 L at 25C and 101.3kPa).11.1.2 Calculate the mean Rof measured rates and thestandard deviation, sR. The temperature corresponding to Rmust be stated
32、.11.1.3 Calculate the standard deviation s of Ritself:s 5 =scal2/ n 1 sR2/ n (2)where n is the number (8) of R measurements or calibrationdata points.11.1.4 The uncertainty U in the measurement Rmay beexpressed in several ways, depending on the needs of the user.The purpose of the (expanded) uncerta
33、inty U is to bracket thecertified-mean Rtrueby R6 U at specified confidence. Thedegree of confidence in the minimization of bias of the specificSRM used for calibration relative to the certified-mean Rtruedepends on the application. Related material presented in(11.1.4) may be found in NMAM.511.1.4.
34、1 If U, at high (95 %) confidence in the specific CRMused for calibration, is to provide intervals bracketing Rtrueatgreater than given confidence (also 95 %) in the measurementR, then U may be taken to equal:U 5 1.960 uCRM1 ty, 0.95 s (3)where uCRMis the ratio of the uncertainty of the CRMcalibrati
35、on to the coverage factor, both values stated on theCRM certificate. y is the number of degrees of freedom in s2and ty,0.95is the student-t 95 %-quantile (giving single-sided95 % confidence limits). Here, y =23 (n 1)=14 if theanalyzer output is closely proportional to its input, resulting int14,0.95
36、= 1.761. Eq 3 holds when the CRM-|bias| confidencelimit 1.960 uCRMis comparable or larger than s/ty,0.95. Forsmall uCRM, the uncertainty U may be calculated as:U 5 ty,0.975 =1.9602uCRM2 1y1! / 1 1 ty, 0.9752 y1! 1 s2(4) ty, 0.975 =1.9602uCRM21 s2, if y1t14, 0.9755 2.145!.The statistical details behi
37、nd the above expressions areavailable as Research Report D22XXXX for this guide.11.1.4.2 If only mean confidence in the CRM is required,then U may be approximated simply as:U 5 2=uCRM21 s2(5)NOTE 2The above expressions assume that the calibrations of Section9 and measurements of 10.1 are made within
38、 a time interval such thatinstrumental drift is not significant. This requires that the permeationdevices to be calibrated should be equilibrated at the temperature ofmeasurement before insertion into the system. If this is not the case,uncertainty due to drift must be estimated and included because
39、 of thelarge dependence of the permeation rates on the temperature. TheT-uncertainty component uR,T(the standard deviation) due to drift wouldthen be estimated, using the mean temperature coefficient DR / DT ofstandard and reference tube. The standard tubes temperature coefficientmay be listed in th
40、e CRM certificate, whereas the candidate tubescoefficient would be either measured or a conservative value of 10 % ofthe permeation rate in accordance with Practice D 3609 (C), adopted.Then, uR,Tis estimated by:uR,T5 ?DR / DT? sT(6)where sT(C) is an estimate of the temperature-drift standard devia-t
41、ion. If uR,Tis of the order of scal/ =norsR/ =n , then uR,Twould bepooled into s, adjusting the student-t quantile with an effective number ofdegrees of freedom, accordingly (as described in ISO GUM).NOTE 3The uncertainty as expressed in Eq 5 is in the form consideredin ISO GUM with coverage factor
42、equal to 2, whereas strongly controllingthe bias inherent in any specific calibration standard results in the slightlydifferent form of Eq 4.11.2 Procedure B:11.2.1 Plot successive masses versus the correspondingtimes. Fit a straight line to the points by the method of leastsquares. The slope is the
43、 desired rate, R. Calculate the standarddeviation, s, of the slope.11.2.2 Express uncertainty by the following equation:U 5 2=s21 0.1/C st!2(7)11.2.3 The mean permeation rate, RCRMmeasured for theCRM permeation tube must agree with the certified value inaccordance with the users performance standard
44、s, accountingfor the limits of uncertainty of the measurement, as calculatedby 11.2.2, in order to validate the calibration.12. Keywords12.1 intercomparison; permeation tube; standard referencematerial; traceabilityASTM International takes no position respecting the validity of any patent rights ass
45、erted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time b
46、y the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will rece
47、ive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Inte
48、rnational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or throu
49、gh the ASTM website(www.astm.org).5NIOSH Manual of Analytical Methods (NMAM), Chapter P, MeasurementUncertainty and NIOSH Method Accuracy Range, available from U.S. GovernmentPrinting Office, Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop:SDE, Washington, DC 20401, or online at www.cdc.gov/niosh.D4298043
