1、Designation: E207 08 (Reapproved 2015)1Standard Test Method forThermal EMF Test of Single Thermoelement Materials byComparison with a Reference Thermoelement of SimilarEMF-Temperature Properties1This standard is issued under the fixed designation E207; the number immediately following the designatio
2、n indicates the year oforiginal adoption or, in the case of revision, the year 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.1NOTEEditorial changes were made throughout in J
3、une 2015.1. Scope1.1 This test method covers a test for determining thethermoelectric emf of a thermoelement versus NIST platinum67 (Pt-67) by means of measuring the difference between theemf of the test thermoelement and the emf of a referencethermoelement (previously referred to as a secondarystan
4、dard), which has a known relationship to NIST Pt-67.1.2 This test is applicable to new thermocouple materialsover the temperature ranges normally associated with thermo-couples and their extension wires. The table on SuggestedUpper Temperature Limits for Protected Thermocouples inSpecification E230
5、lists the ranges associated with the letter-designated types of thermocouples. ASTM MNL-122lists thetemperature range of extension circuit materials.1.3 This test is not applicable to stability testing or inhomo-geneity testing.1.4 The values stated in SI units are to be regarded as thestandard. The
6、 values given in parentheses are for informationonly.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility o
7、f regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E77 Test Method for Inspection and Verification of Ther-mometersE220 Test Method for Calibration of Thermocouples ByComparison TechniquesE230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardize
8、d ThermocouplesE344 Terminology Relating to Thermometry and Hydrom-etryE563 Practice for Preparation and Use of an Ice-Point Bathas a Reference Temperature3. Terminology3.1 DefinitionsThe terms used in this test method aredefined in Terminology E344.3.2 Definitions of Terms Specific to This Standard
9、:3.2.1 reference facility, nNIST, or a testing laboratorywhose physical standards are traceable to NIST or anothernational standards laboratory.3.2.2 test temperature, nthe temperature of the measuringjunction.3.2.2.1 DiscussionIn reporting the results, the value of thetest temperature may be rounde
10、d off, provided the stated testtemperature is within the bounds indicated in 10.10.4. Summary of Test Method4.1 The emf of a thermoelement sample is determined bycomparison to a reference thermoelement that has similarSeebeck coefficients.4.2 This test is conducted on one or more lengths ofspecimens
11、 connected to a single length of the referencethermoelement at a single point. The joined ends are held at thetest temperature, and their opposite ends are held at a constantreference temperature.4.3 The emf of the reference thermoelement relative toPt-67 at several test temperatures are provided by
12、 a referencefacility.1This test method is under the jurisdiction of ASTM Committee E20 onTemperature Measurement and is the direct responsibility of Subcommittee E20.04on Thermocouples.Current edition approved May 1, 2015. Published May 2015. Originallyapproved in 1962 . Last previous edition approv
13、ed in 2008 as E207 08. DOI:10.1520/E0207-08R15E01.2Manual on the Use of Thermocouples in Temperature Measurement, ASTMMNL-12, Fourth Edition, ASTM, April 1993. (Revision of STP 407B).3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.
14、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 States14.4 The emf of the test thermoelement relative to Pt-67 isdeterm
15、ined by algebraically adding the measured emf to theemf of the reference thermoelement at each test temperature.5. Significance and Use5.1 This test method is designed to calibrate a thermoele-ment at one or more test temperatures. The data obtained aresometimes referred to as initial values of emf
16、because the timeat the test temperature is limited.5.2 This test method is employed mainly by providers ofspools or coils of wire or strips of thermoelectric material.Generally more than one specimen at a time is tested, and theresultant emfs of individual thermoelements are used to matchto companio
17、n thermoelements for use as thermocouples or inextension wiring.5.3 The emf of a thermocouple comprised of two differentthermoelements as tested with this test method may be deter-mined by algebraically subtracting the emf of the negativethermoelement from the emf of the positive thermoelement ata p
18、articular temperature. The emf of a thermocouple may alsobe determined by the test described in Test Method E220, butTest Method E220 does not take into account the values of theemf of the individual thermoelements relative to Pt-67.5.4 This test method is normally used for the calibration ofthermoc
19、ouple materials during their production or distribution,not for the accurate determination of the properties of a usedthermocouple. If the test samples were subjected to previoususe, the test results may not reflect the same emf as thethermocouple did while in service. For example, inhomogene-ities
20、may have been induced in the wires because of a chemicalor metallurgical reaction while in service. Since emf is devel-oped in the thermal gradient, and it is unlikely that thetemperature profile along the wire under testing conditions willbe the same as it was while in service, the test results may
21、 bemisleading.5.5 The test results are suitable for specification acceptance,manufacturing control, design, or research and developmentpurposes.6. Test Specimen6.1 Each sample shall represent one continuous spool, coil,or strip of thermoelectric material. The sample shall consist oftwo specimens, on
22、e cut from each end of the spool, coil, orstrip. The extreme ends shall not be acceptable if they aredistorted or have been subjected to processing dissimilar to thebulk of the spool, coil, or strip.6.2 Insulation or covering shall be removed with care if itinterferes with the test. Straining the te
23、st specimen shall beavoided.6.3 The specimens shall be cleaned of any extraneoussurface contamination.6.4 The specimens and the reference thermoelement shall belong enough to extend continuously from the measuringjunction to the reference junction. A length of 600 to 1200 mm(2 to 4 ft) is generally
24、satisfactory. The exact length dependsupon the depth of immersion in the testing medium and thetransverse size (for example, diameter of round wire, width ofstrip) of the thermoelement.6.4.1 Heating of the measuring junctions shall not affect thetemperature of the reference junctions during the peri
25、od of test.7. Reference Thermoelement7.1 The reference thermoelement has its emf establishedrelative to NIST Pt-67 over the temperature range of itsintended use. A specific lot of thermoelement material isusually reserved for use as reference thermoelements.7.2 The emf of the reference thermoelement
26、 versus plati-num (Pt-67) shall conform to Specification E230 within onehalf the standard tolerance specified for the related thermo-couple type. For example, the tolerance for KP versus Pt-67 is6 1C or 6 0.375% of temperature from 0 to 1260C,whichever is greater.7.3 The cross section of the base me
27、tal thermoelement shallbe sufficiently large so that oxidation caused by the tempera-tures of testing would not significantly affect its emf over theperiod of the test.7.4 To provide some assurance that the reserved lot isuniform in emf from end to end, it shall be manufactured in onecontinuous leng
28、th with no in-process welds. . Cold working ofthe material after the final anneal shall be minimized7.4.1 A specimen from each end of the reserved lot shall betested using this test method. The test temperatures shallinclude the extremes of the intended range of use and addi-tional test points that
29、are no more than 260C (500F) apart.7.4.2 The emf difference between the specimens of 7.4.1 ateach test temperature shall not exceed the equivalent of 0.33C(0.6F) for that thermocouple type or 0.05 % of the value of thetest temperature in degrees Celsius, whichever is the greater.7.5 From the lot tha
30、t meets the stated uniformityrequirements, at least one unused 1 m (3-ft) section shall becertified by a reference facility to document its emf relative toPt-67. Traceability shall be required in the form of a certificateissued by the reference facility.7.5.1 Emf data shall be provided every 50C (10
31、0F) or atintervals that do not exceed 25 % of the test temperature range,whichever is the lesser. If fewer than the aforementionednumber of points are taken, then the data are applicable only ator near the measured temperatures, and interpolation beyondthem should not be attempted.7.5.2 The emf of t
32、he reference thermoelement at intermedi-ate values of temperature may be determined by one of thefollowing methods.7.5.2.1 For the letter-designated thermocouple types, emffunctions for thermoelements versus Pt-67 are given in Speci-fication E230. In these cases, the deviation of the referencethermo
33、element emf from the function value is first calculated atthe test temperatures. At an intermediate temperature, thedeviation of emf is calculated either by linear interpolation orby fitting a polynomial to the deviation of emf using themethod of least squares, and evaluating the polynomial at thein
34、termediate temperature. For the least squares method, thenumber of data points shall equal or exceed twice the numberof parameters fitted. Addition of the deviation of emf to theE207 08 (2015)12function value at the intermediate temperature gives the emfvalue of the reference thermoelement at the in
35、termediatetemperature.7.5.2.2 For the thermoelements for which there is no emffunction for that thermoelement versus Pt-67, a function maybe determined by fitting a polynomial to the emf valuesreported by NIST for the reference thermoelement versusPt-67, using the method of least squares. The number
36、 of datapoints shall equal or exceed twice the number of parametersfitted. Evaluation of the polynomial at the intermediate tem-perature gives the emf of the reference thermoelement. In caseswhere the deviations of the fitted data from the polynomial aresignificant compared to other uncertainties in
37、 the test, asubcomponent of uncertainty shall be added to the uncertaintybudget equal to:u 5 F1NdfiEi2 Efit!2G(1)where:u = uncertainty,Ei= the emf at the ith calibration temperature value of thereference thermoelement that has been calibrated rela-tive to NIST Pt-67,Efit= the emf of the fitted polyn
38、omial, andNdf= the number of degrees of freedom in the fit = numberof data points number of fitted parameters.7.5.2.3 Linear interpolation of the reference thermoelementemf, rather than the deviation of emf, may also be done, but useof this method requires inclusion of an additional uncertaintycompo
39、nent to account for the interpolation error. This uncer-tainty component may be estimated by calculating the error oflinear interpolation of the emf values obtained from the emffunctions for thermoelements versus Pt-67 in SpecificationE230 or another source. This error may be as large as all otherer
40、rors combined.7.6 The segment of reference thermoelement that is used foreach test shall be unaffected by a prior test. For example, anysegment of a KP, EP, or JP thermoelement, exposed totemperatures exceeding 260C (500F) shall not be reused.However, if it shows no evidence of its test environment
41、and noeffects of strain, the remainder may be reused. For noble metalsand their alloys, the number of reuses depends upon theamount of strain or contamination of the segment. Noble metalreference thermoelements should be checked for emf confor-mity after ten uses or less against another noble metal
42、referencesegment that was not subjected to routine use.8. Reference Temperature Unit8.1 The reference temperature unit shall maintain the tem-perature of the reference junctions within 5C (9F) of theassumed value of reference temperature. The reference tem-perature unit shall be designed so that the
43、 temperatures of allthe reference junctions will be isothermal.NOTE 1The preferred reference junction temperature is 0C (32F).This may be approximated with an ice bath (see Practice E563),“automatic ice point” unit or a “zone box” (see MNL-12). Care should beexercised to maintain the reference junct
44、ion temperatures for both thereference and test thermocouples at the same temperature.9. Measuring Junction9.1 The measuring junction shall consist of an electricalconnection of the test specimens at one of their ends to thereference thermoelement. Welding is the preferred method ofjoining, particul
45、arly for test temperatures above 260C(500F).9.2 The number of test specimens that may be tested at onetime is limited mainly by the thermal capacity of the system.The thermal conduction along the assembly of test thermoele-ments shall not be so large as to impair isothermal conditionsat the measurin
46、g or reference junction.10. Test Temperature Medium10.1 Normally, both the test and reference thermoelementshave the same nominal composition and consequently haveapproximately the same values of Seebeck coefficients.Therefore, the measured emf is expected to be small inmagnitude (compared to the em
47、f relative to Pt-67) and varyonly slightly as a function of temperature. Therefore, it is notnecessary to control the test temperature precisely.10.2 The immersion media, insulation materials, supports,and adjacent materials shall not interact with or electricallyshunt the thermoelements.10.3 For te
48、sting in the range of 160 to 75C (250to 100F), a liquid nitrogen bath may be used. Refer to thedevices and precautions in Test Method E77, Appendix X1, onDiscussion of Apparatus for Verification of Liquid-in-GlassThermometers and Fig. X1.3 on Comparator for TemperatureRange from 160 to 75C (256 to 1
49、03F).10.4 For testing in the range of 80 to +5C (110to +40F), use an apparatus as depicted in Test Method E77,Appendix X1, on Discussion of Apparatus for Verification ofLiquid-in-Glass Thermometers and Fig. X1.4 on Comparatorfor Temperature Range from 80 to +5C (112 to +41F),using dry ice and a suitable liquid.10.5 For testing in the range of room temperature to 95C(200F), a heated bath using demineralized water may be used.10.6 In the range of 5 to 300C (40 to 600F), a stirred bathof an oil with a flash point higher than the tes
