1、Designation: E2744 10 (Reapproved 2015)Standard Test Method forPressure Calibration of Thermal Analyzers1This standard is issued under the fixed designation E2744; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. 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 test method describes the calibration or perfor-mance confirmation of the electronic pressure signals fromthermal analys
3、is apparatus.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 There is no ISO standard equivalent to this test method.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its us
4、e. It 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.2. Referenced Documents2.1 ASTM Standards:2D5483 Test Method for Oxidation Induction Time of Lubri-cating Greases by P
5、ressure Differential Scanning Calorim-etryD6186 Test Method for Oxidation Induction Time of Lubri-cating Oils by Pressure Differential Scanning Calorimetry(PDSC)D5720 Practice for Static Calibration of ElectronicTransducer-Based Pressure Measurement Systems forGeotechnical PurposesD5885 Test Method
6、for Oxidative Induction Time of Poly-olefin Geosynthetics by High-Pressure Differential Scan-ning CalorimetryE473 Terminology Relating to Thermal Analysis and Rhe-ologyE537 Test Method for The Thermal Stability of Chemicalsby Differential Scanning CalorimetryE1142 Terminology Relating to Thermophysi
7、cal PropertiesE1782 Test Method for Determining Vapor Pressure byThermal AnalysisE1858 Test Method for Determining Oxidation InductionTime of Hydrocarbons by Differential Scanning Calorim-etryE2009 Test Methods for Oxidation Onset Temperature ofHydrocarbons by Differential Scanning CalorimetryE2161
8、Terminology Relating to Performance Validation inThermal Analysis3. Terminology3.1 Definitions:3.1.1 The technical terms used in this test method aredefined in Terminologies E473, E1142, and E2161, includingcalibration, Celsius, differential scanning calorimetry, highpressure, linearity, oxidative i
9、nduction time, thermal analysis,and vapor pressure.3.2 Definitions of Terms Specific to This Standard:3.2.1 absolute pressure, npressure measured relative tozero pressure corresponding to empty space.3.2.1.1 DiscussionAbsolute pressure is atmospheric pres-sure plus gage pressure.3.2.2 atmospheric pr
10、essure, nthe pressure due to theweight of the atmosphere.3.2.2.1 DiscussionAtmospheric pressure varies with el-evation above sea level, acceleration due to gravity andweather conditions. Standard atmospheric pressure is101.325 kPa.3.2.3 barometer, nan instrument for measuring atmo-spheric pressure.3
11、.2.4 gage pressure, npressure measured relative to atmo-spheric pressure.3.2.4.1 DiscussionZero gage pressure is equal to atmo-spheric pressure. Gage pressure is the difference betweenabsolute pressure and atmospheric pressure.3.2.5 pressure, nthe force exerted to a surface per unitarea.3.2.6 vacuum
12、, npressure less than atmospheric pressure.4. Summary of Test Method4.1 The pressure (vacuum) signal generated by a thermalanalyzer is compared to a gage whose performance is known1This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility
13、 of Subcommittee E37.10 onFundamental, Statistical and Mechanical Properties.Current edition approved March 1, 2015. Published March 2015. Originallyapproved in 2010. Last previous edition approved in 2010 as E2744 10.DOI:101520/E2744-10R15.2For referenced ASTM standards, visit the ASTM website, www
14、.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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1and tr
15、aceable to a national metrology institute. The thermalanalyzer may be said to be in conformance if the performanceis within established limits. Alternately, the pressure signalmay be calibrated using a two-point calibration method.5. Significance and Use5.1 Most thermal analysis experiments are cond
16、ucted underambient pressure conditions using isothermal or temperaturetime rate of change conditions where time or temperature is theindependent parameter. Some experiments, however, are con-ducted under reduced or elevated pressure conditions wherepressure is an independent experimental parameter (
17、TestMethod E537). Oxidation Induction Times (Test MethodsD5483, D5885, D6186, and E1858), Oxidation Onset Tem-perature (Test Method E2009), and the Vapor Pressure (TestMethod E1782) are other examples of experiments conductedunder elevated or reduced pressure (vacuum) conditions. Sincein these cases
18、 pressure is an independent variable, the mea-surement system for this parameter shall be calibrated to ensureinterlaboratory reproducibility.5.2 The dependence of experimental results on pressure isusually logarithmic rather than linear.6. Apparatus6.1 Reference pressure gage with a range 1.2 times
19、 themaximum value to be calibrated readable to within 0.1 % of thefull range and performance of which has been verified usingstandards and procedures traceable to a national metrologyinstitute (such as the National Institute of Standards andTechnology (NIST).NOTE 1To ensure an accurate pressure meas
20、urement, the referencepressure gage shall be placed as close as practical to the thermal analysisapparatus to be calibrated and connected to the thermal analysis apparatuswith large diameter tubing such as 6.3 mm or larger especially for vacuumtesting. Ensure that there is no gas flow in the connect
21、ion (for example,due to leaking) to provide a static pressure measurement.NOTE 2Additional information on pressure gages may be found inPractice D5720.6.2 A source of pressurized inert gas, typically nitrogen,with a pressure regulator, capable of adjusting the pressuresupplied to the apparatus from
22、zero to 100 % of the gagepressure range to be calibrated, commonly 7 MPa.NOTE 3Since the calibration is performed under static flowconditions, the pressurizing gas delivery system to the thermal analysisapparatus should be of small diameter (such as 1.6 mm diameter tubing)for safety considerations.N
23、OTE 4Do not use a reactive gas such as oxygen unless all apparatus,tubing and test gage have been cleaned and are rated for oxygen service.6.3 The thermal analysis apparatus for which the pressurecalibration is to be performed.6.4 Barometer capable of measuring atmospheric pressurereadable to 60.01
24、kPa (0.1 mm Hg).7. Hazards7.1 This test poses risks associated with high pressureoperation. The thermal analysis apparatus, connecting tubingand measurement gages shall be designed to contain pressuresin excess of two times the maximum allowable workingpressure. Pressure relief shall be provided at
25、pressures nogreater than 1.2 times the maximum allowable working pres-sure.8. Preparation of Apparatus8.1 Assemble the apparatus so that the calibration pressuregage is connected in parallel with the pressure transducer of theapparatus. That is, the instrument transducer and the calibrationgage shal
26、l see the same static pressure (see Fig. 1). Equilibratethe thermal analysis apparatus pressure container, referencepressure gage and instrument transducer at ambient tempera-ture.9. Calibration9.1 Perform any pressure signal calibration procedures rec-ommended by the manufacturer of the thermal ana
27、lyzer asdescribed in the Operators Manual.10. Procedure10.1 Electronic pressure signals associated with thermalanalysis apparatus measure gage pressure relative to atmo-spheric pressure. However, absolute pressure is most oftenrequired for thermal analysis experiments. Absolute pressure isthe sum of
28、 gage pressure and atmospheric pressure. Soknowledge of atmospheric pressure is required to obtainabsolute pressure.10.2 Using a laboratory barometer, measure and record theatmospheric pressure (Patm) within one hour of the pressurecalibration in steps 10.4 10.6.NOTE 5Should a laboratory barometer b
29、e unavailable, local pressuremay often be obtained by contacting the local weather service. Thisapproach is not suitable for laboratories operating under negative gagepressure.10.3 Assemble the instrument to be calibrated, the referencepressure gage and the source of the pressurized gas accordingto
30、schematic Fig. 1.10.4 With the thermal analysis exhaust valve open toatmospheric and the source valve shut off (see Fig. 1), set thethermal analysis instrument indicated pressure to zero gagepressure.10.5 Close the thermal analyzer exhaust valve, open thesource of pressurized gas, and slowly increas
31、e the pressureregulator until the reference pressure gage reads the maximumpressure to be calibrated (often 7.00 MPa). Record this value asP2.NOTE 6Other calibration pressures may be used but shall be reported.10.6 Record the indicated pressure on the thermal analyzerpressure measuring signal (or ga
32、ge) as P3.10.7 Calculate the calibration constant (S) using Eq 2.10.8 Using the value of S from 10.7, calculate the percentconformity (C) using Eq 4 or a table of percent conformityvalues (see 11.4.1)11. Calculation11.1 For the purpose of these procedures, it is assumed thatthe relationship between
33、observed pressure (Po) and the actualpressure (P) is linear and governed by Eq 1:E2744 10 (2015)2P 5 Po 3 S (1)where:P = true gage pressure (kPa),Po = thermal analyzer observed gage pressure (kPa), andP = calibration constant (nominal value 1.00000).11.2 The calibration constant S is determined by E
34、q 2:S 5P2P3(2)NOTE 7When performing this calculation, retain all available decimalplaces in the measured value and in the value of S.11.3 Using the value of S from 11.2, the percent conformityof the pressure measurement of the instrument signal may becalculated by:C 5 S 2 1.00000! 3100% (3)11.4 Conf
35、ormity may be estimated to one significant figureusing the following criteria:11.4.1 If the value of S lies:11.4.1.1 Between 0.9990 and 0.9999 or between 1.0001 and1.0010, then conformity is better than 0.1 %;11.4.1.2 Between 0.9900 and 0.9990 or between 1.0010 and1.0100, then conformity is better t
36、han 1 %; and11.4.1.3 Between 0.9000 and 0.9900 or between 1.1000 and1.0100, then conformity is better than 10 %.11.5 Using the determined value of S, Eq 1 may be used tocalculate true gage pressure (P) from an observed signalpressure (Po), provided that the measuring gage has beenproperly “zeroed.”1
37、1.6 Absolute pressure (Pa) may be obtained from Eq 4:Pa 5 Patm1P (4)where:Pa = absolute pressure (kPa), andPatm = atmospheric pressure (kPa).12. Report12.1 Report the following information:12.2 Model number and description of the thermal analyzerused.12.3 The value of S determined in 10.7 reported t
38、o at leastfour places to the right of the decimal point.12.4 Conformity as determined in 10.8.13. Precision and Bias13.1 An interlaboratory study of pressure signal calibrationwas conducted in 2009 in which a single organization made 6duplicated determinations on 5 different instruments for a totalo
39、f 20 degrees of experimental freedom.13.2 Precision:13.2.1 Within laboratory variability may be described usingthe repeatability value (r) obtained by multiplying the repeat-ability standard deviation by 2.8. The repeatability valueestimates the 95 % confidence limit. That is, two results fromthe sa
40、me laboratory should be considered suspect (95 %confidence level) if they differ by more than the repeatabilityvalue.13.2.2 The within laboratory repeatability standard devia-tion obtained for the measurement of pressure was 3.4 kPa.The relative repeatability standard deviation was 0.098 %.13.2.3 Th
41、e between laboratory variability may be describedusing the reproducibility value (R) obtained by multiplying theFIG. 1 Schematic Diagram of ApparatusE2744 10 (2015)3reproducibility standard deviation by 2.8. The reproducibilityvalue estimates the 95 % confidence limit. This is, resultsobtained from
42、two different laboratories, operators or apparatusshould be considered suspect (at the 95 % confidence level) ifthey differ by more than the reproducibility value.13.2.4 The between laboratory reproducibility standard de-viation obtained for the measurement of pressure was 6.2 kPa.The relative repro
43、ducibility standard deviation was 0.18 %.13.3 Bias:13.3.1 Bias is the difference between the mean value ob-tained and an acceptable reference value. This test methodreports bias as conformance.13.3.2 The mean value of pressure measured was3444.5 kPA gage compared to the reference value of3447.5 kPa
44、gage. This corresponds to a bias of 3.0 Pa or0.087 %.13.4 Bias is the difference between the mean value obtainedand an acceptable reference value. This test methods reportsbias as conformance.13.5 The mean slope determined by this test method wasS = 1.00087. This corresponds to a conformance value o
45、fC = 0.0087 %.14. Keywords14.1 absolute pressure; atmospheric pressure; calibration;gage pressure; pressure; thermal analysisASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are ex
46、pressly 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 by the responsible technical committee and must be reviewed every five years andif not revi
47、sed, 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 receive careful consideration at a meeting of theresponsible technical committee, which you ma
48、y 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United Sta
49、tes. 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 through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 10 (2015)4
