1、Designation: D4298 04 (Reapproved 2010)Standard Guide forIntercomparing Permeation Tubes to Establish Traceability1This standard is issued under the fixed designation D4298; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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-ta
3、inty of the rate 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-c
4、ess in which a 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
5、is theresponsibility 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:2D1356 Terminology Relating to Sampling and Analys
6、is ofAtmospheresD3249 Practice for General Ambient Air Analyzer Proce-duresD3609 Practice for Calibration Techniques Using Perme-ation TubesD3631 Test Methods for Measuring Surface AtmosphericPressureE1 Specification for ASTM Liquid-in-Glass ThermometersE319 Practice for the Evaluation of Single-Pan
7、 MechanicalBalancesE617 Specification for Laboratory Weights and PrecisionMass Standards3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this guide, refer toTerminology D1356.3.1.2 Definitions of Terms Specific to This Standard:3.1.2.1 working standarda standard used in the labor
8、atoryor field for periodic 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
9、 of a gaseous mixturegenerated 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 NIS
10、T standards. The validity 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
11、can be intercom-pared when 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
12、For apparatus used in the calibration of permeationdevices, refer to Practice D3609.1This guide is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.01 on Quality Control.Current edition approved July 1, 2010. Published July 2010. Origina
13、lly approvedin 1983. Last previous edition approved in 2004 as D4298 - 04. DOI: 10.1520/D4298-04R10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Do
14、cument Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.1.1 The thermometers used shall conform to SpecificationE1 and shall have calibration certificates traceable to the NIST.Measurement uncertainty
15、 should be 0.1C or less.6.1.2 The mercury barometer shall conform to Test MethodsD3631.6.2 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-
16、scale per 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-scal
17、e travel 1 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 requireme
18、nts of Prac-tices E319 and D3609.6.3.2 Analytical weights meeting the requirements of Speci-fication E617 and having a calibration certificate traceable tothe NIST.7. Materials7.1 Refer to Practice D3609.7.2 CRM Permeation Device.48. Precautions8.1 Procedural Precautions:8.1.1 The procedural precaut
19、ions described in PracticeD3609 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
20、 temperatures 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 tu
21、bes to 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 D3249.9. Calibration and Standardization9.1 Pro
22、cedure 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 D3609. Equilibrate atthe desired temperature of calibration.9.1.2 Optimize the performance of the analytical instrumentaccording to the man
23、ufacturers 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 ran
24、dom 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
25、theline 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 ca
26、libration, 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
27、the 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, period
28、ically recording themass and time of weighing, as described in Practice D3609.10.2.3 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 Pr
29、ocedure 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),3ISO GUM, Guide to the Expression of Uncertainty
30、 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 from the Office of Standard Reference
31、 Materials, National Institute ofStandards and Technology, Washington, DC 20234.D4298 04 (2010)2MW = molecular weight of permeant, andMV = 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
32、 be stated.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 (expande
33、d) uncertainty 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 NMA
34、M.511.1.4.1 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 CR
35、Mcalibration 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
36、int14,0.95= 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 de
37、tails behind 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 m
38、ade within 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 includ
39、ed because 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 li
40、sted in the CRM certificate, whereas the candidate tubescoefficient would be either measured or a conservative value of 10 % ofthe permeation rate in accordance with Practice D3609 (C), adopted.Then, uR,Tis estimated by:uR,T5 ?DR / DT? sT(6)where sT(C) is an estimate of the temperature-drift standar
41、d devia-tion. 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 coverag
42、e factor 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 slo
43、pe is the 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
44、 standards, 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 r
45、ights asserted 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 a
46、ny time by 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
47、will receive 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
48、ASTM International, 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);
49、 or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).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.D4298 04 (2010)3
