1、Designation: E601 07a (Reapproved 2013)Standard Test Method forMeasuring Electromotive Force (emf) Stability of Base-MetalThermoelement Materials with Time in Air1This standard is issued under the fixed designation E601; the number immediately following the designation indicates the year oforiginal
2、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.1. Scope1.1 This test method measures emf stability of base-metalthermoelement m
3、aterials in air referenced to platinum atspecified constant elevated temperatures using dual,simultaneous, emf indicators, or using a single emf indicator,with the test and reference emf measured alternately. This testis conducted over a period of weeks.1.2 A calibrated platinum-rhodium/platinum the
4、rmocoupleis used as a reference standard to establish the test temperature.1.3 The useful life of a thermocouple depends on thestability of the emf generated at given temperatures for arequired time interval. This method provides a quantitativemeasure of the stability of individual thermoelements. B
5、ycombining the results of the positive (P) and negative (N)thermoelements, the stability of a thermocouple comprised ofboth P and N thermoelements may be obtained. The emf of anindividual thermoelement is measured against platinum, whichmay be the platinum leg of the platinum-rhodium/platinumreferen
6、ce thermocouple, or an additional platinum reference.NOTE 1Some thermoelements may show insignificant emf drift whileundergoing relatively rapid oxidation. In these cases, failure of thethermoelement may be indicated only by a large rise in the electricalresistance between joined thermoelements, as
7、measured at the referencejunctions.NOTE 2See ASTM MNL 12 for recommended upper temperaturelimits in air.2NOTE 3This test method is only applicable for initially new thermo-elements. Base-metal thermoelements exposed to temperatures above 200C become thermoelectrically inhomogeneous, and stability te
8、sting ofinhomogeneous thermoelements will give ambiguous results.1.4 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 appl
9、ica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E220 Test Method for Calibration of Thermocouples ByComparison TechniquesE230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE344 Terminology Relating to Thermome
10、try and Hydrom-etryE563 Practice for Preparation and Use of an Ice-Point Bathas a Reference TemperatureE1159 Specification for Thermocouple Materials, Platinum-Rhodium Alloys, and Platinum3. Terminology3.1 DefinitionsThe definitions given in Terminology E344shall apply to this test method.3.2 Defini
11、tions of Terms Specific to This Standard:3.2.1 emf indicator, nan instrument that measures the emfand displays the value, for example, a digital voltmeter(DVM).3.2.2 emf stability, nchange in emf (or in equivalenttemperature) with time, with the thermocouple junctions heldat fixed temperatures and w
12、ith the thermal profile along thethermoelements held constant.3.2.3 half-maximum heated length, nthe distance betweenthe tip of the temperature sensor and the position along thelength of the sensor leads or sheath where the temperatureequals the average of the calibration-point and ambient tem-perat
13、ures.3.2.4 gradient zone, nthe section of a thermocouple that isexposed during a measurement to temperatures in the rangefrom tamb+ 0.1(tm tamb)totamb+ 0.9(tm tamb), where tambis ambient temperature and tmis the temperature of themeasuring junction.3.2.5 reference thermocouple, ncalibrated Type S or
14、 TypeR thermocouple.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, 2013. Published May 2013. Originallyapproved in 1977. Last previous edition approved
15、 in 2007 as E601 07a. DOI:10.1520/E0601-07AR13.2Manual on the Use of Thermocouples in Temperature Measurement: FourthEdition, Available from ASTM Headquarters, 100 Barr Harbor Drive, WestConshohocken, PA 19428, www.astm.org.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcont
16、act 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 States13.2.6 test thermocouple
17、, nthermocouple composed of thethermoelement being tested and the platinum reference ther-moelement.3.2.7 normalize, vto mathematically adjust experimentalemf data acquired at a set of temperatures to values corre-sponding to a common reference temperature.4. Summary of Test Method4.1 In this test m
18、ethod, the emf of a test thermocouple,comprised of a base-metal thermoelement relative to a plati-num reference thermoelement, is determined as a function oftime for a specified test temperature and thermal profile. If careis taken to maintain the chemical purity and annealed metal-lurgical state of
19、 the platinum thermoelement, the platinum willbe thermoelectrically stable. In that case, variation in this emfvalue is attributed to instability of the base-metal thermoele-ment. The emf of the reference thermocouple (Eref) is used tomeasure the test temperature, and the emf (Etest) of the testther
20、mocouple is measured either simultaneously or alternatelywith Eref. The test method consists of the measurement of Etestat specified time intervals and at a specified constant value ofErefwhich corresponds to a specified, constant temperature,until the required time of the test is exceeded or until
21、an opencircuit in the base-metal thermoelement results.4.2 This test method is based on Method A of TestMethodE220, where the reference thermocouple of TestMethod E220 becomes the reference thermocouple used tomeasure the test temperature and one specified constant tem-perature replaces the series o
22、f measured temperatures of TestMethod E220.5. Significance and Use5.1 This test method is important because the accuracy of atemperature measurement by a thermocouple is directly relatedto the emf stability of the thermoelements.5.2 This test method is used to verify that the testedthermoelements me
23、et the intended requirements.5.3 This test method is useful in comparing the emf stabilityof two base metal thermoelements under the same conditions.The test and reference emf may be measured either simultane-ously or alternately.5.4 The relative stabilities of base metal thermoelementsdetermined by
24、 this test method are valid only under thespecified test conditions. Results would be affected by changesin the following conditions: (1) temperature profile or gradientalong the length of the thermoelements; (2) abundance, veloc-ity and composition of the air surrounding the test pieces; (3)thermoe
25、lectric inhomogeneity of the test thermoelements; (4)stability of the platinum thermoelement.5.5 The test method does not address the determination ofbase metal thermoelement stabilities over a series of tempera-ture changes.5.6 The reliability of this test method depends on the emfstability of the
26、reference platinum thermoelement. For testingthe relative emf stability of base-metal thermoelements, areference element of platinum that has sufficient thermoelectricstability to determine any significant change in emf of base-metal thermoelements shall be used. To ascertain that theexperimental me
27、thod protects the platinum sufficiently fromdegradation, the method shall be validated by performing theprocedure described in Appendix X1 prior to the actual test.5.7 The test result does not apply to applications in whichthe temperature distribution, for a given measuring junctiontemperature, chan
28、ges with time.6. Apparatus6.1 Thermocouple Used to Measure the TestTemperatureA reference Type S or Type R thermocouplewith 0.50 mm diameter (24 AWG) thermoelements or largershall be used to measure the test temperature. The referencethermocouple shall consist of either standard tolerance orspecial
29、tolerance wire as per Table 1 in Specification E230. Thechoice of tolerance will not affect the determination of ther-moelement drift. This thermocouple shall be of sufficientlength to minimize the effect of heat conduction along thelengths of the wires upon the measuring junction temperature.(Note:
30、 platinum is a better heat conductor than most base metalthermocouple wires.) Length shall be sufficient to enable thereference thermocouples measuring junction to be locatedwithin the test furnaces zone of nearly uniform temperature(refer to 6.5.2).6.2 Platinum Reference Thermoelement The emf of th
31、etest thermoelements shall be measured relative to a 0.50 mmdiameter (24 AWG) platinum wire. This wire may be theplatinum wire of the Type S or R reference thermocouple or asecond 0.50 mm diameter (24AWG) platinum wire. The lengthof this wire shall exceed that of the test specimen to minimizethe tra
32、nsfer of heat from the measuring junction to thereference junction during testing (see 6.3). For more informa-tion concerning a platinum reference thermoelement, Specifi-cation E1159 may be consulted.6.3 Test Specimens The test specimens shall be lengths ofwires, rods, ribbons, or strips of the coil
33、s or spools of thebase-metal thermoelements to be evaluated. Their lengths shallbe adequate to minimize the transfer of heat from the measur-ing junctions to the reference junctions during the period oftest. The lengths shall be at least 0.8 m (30 in.) depending onthe length of the testing medium an
34、d the transverse sizes of thethermoelements. The specimens shall be free of kinks or otherdefects due to mechanical deformation, and shall be continuouswithout splices between the measuring and reference junctions.6.4 Reference Junction Temperature The reference junc-tion ends of the test specimens,
35、 of the platinum referenceelement, if used, and of the reference thermocouple must bemaintained at a known constant temperature during a measure-ment cycle. The uncertainty attributable to the referencejunction temperature shall be less than 60.1 C. Ice pointreference junction baths provide a relati
36、vely simple and reli-able means for maintaining the reference junction at 0 C (32F) when proper precautions are exercised in their use. PracticeE563 provides an acceptable method for utilizing the ice pointas a reference junction bath. Section 7.3 of Test Method E220may be consulted for alternative
37、methods of providing areference junction temperature.E601 07a (2013)26.5 Tube Furnace The test shall be conducted in anelectrically heated tube furnace such as described in Section7.2.3 of E220. The furnace employed shall have the followingcapabilities: The furnace tube shall be long enough to permi
38、t adepth of immersion of the thermocouple measuring junctionsthat is sufficient to assure that the temperature of the measuringjunctions is not affected by heat conduction along the thermo-elements.6.5.1 Means shall be provided to control the temperature ofthe furnace to within 610 C (618 F) of a no
39、minal tempera-ture during the performance of the test.6.5.2 The test shall be conducted in a uniformly heatedfurnace providing a nearly isothermal work zone sufficientlylarge to maintain all junctions at the same temperature.6.5.3 To determine the uncertainty resulting from tempera-ture non-uniformi
40、ties in the work zone, measure the tempera-ture profile along the thermocouple axis in the vicinity of thework zone, using a platinum-rhodium alloy thermocouple or aplatinum resistance thermometer prior to commencement ofthe test. If the furnace temperature is not sufficiently stable toobtain a temp
41、erature profile with a single thermometer, it maybe useful to place one thermometer at a fixed half-maximumheated length, and to move a second thermometer along thefurnace-tube axis. Adjust the readings of the moveable ther-mometer by adding the correction (tfixed(time) tfixed(initial),where tfixedi
42、s the temperature indication of the thermometer atfixed half-maximum heated length.6.5.3.1 A thermoelement extending from ambient tempera-ture into an isothermal zone of a furnace will come toequilibrium with the temperature of the isothermal zonethrough radiative, convective, and conductive heat tr
43、ansferbetween the thermoelement and the surrounding furnace envi-ronment. The distance of immersion into the isothermal zoneneeded to achieve thermal equilibrium depends significantly onboth the thermoelement diameter and its thermal conductivity.The characteristic length for a wire to achieve therm
44、al equi-librium with its surroundings is given by the approximatecorrelation:Leq5 2.5 cm!Sd1mmD1/2Sk100 W/mK!D1/2(1)where k is the thermal conductivity of the thermoelement,and d is the diameter of the thermoelement. Calculate thedistance Leqfor each tested thermoelement in units ofW/(m K), and d is
45、 the diameter of the thermoelement inmillimeters. The equivalent equation in English units, with din units of inches and k in units of BTU/(hrftF) is:Leq5 1in!Sd0.04 inD1/2Sk58 BTU/hr.ftF!D1/2(2)Calculate the distance Leqfor each tested thermoelement andthe platinum reference thermoelement. The appr
46、oximate ther-mal conductivities listed in Table 1 may be used for this pur-pose. Measure the diameter dmjof the measuring junctionassembly (see 7.1). Identify the maximum Lmaxof the set ofall calculated Leqvalues and dmj.NOTE 4Eq 1 was derived for a temperature of 200 C, which is nearthe lower limit
47、 of observable thermoelement drift. For highertemperatures, the value of Leqfrom Eq 1 will give an upper limit on theactual equilibration length.6.5.3.2 The standard uncertainty due to thermal non-uniformity is the maximum temperature variation in the profilefrom Section 6.5.3 between the measuring
48、junction locationand a distance Lmaxaway from the measuring junction.6.5.3.3 Alternative methods may be used to determine thestandard uncertainty due to thermal non-uniformity, such ascomparison of results in the test furnace with results obtainedeither in fixed-point cells or in a stirred liquid ba
49、th of hightemperature uniformity; or numerical heat-transfer calcula-tions.6.6 Electromotive Force Indicator The emf measuringinstrumentation shall have a measurement uncertainty of notmore than 1 V at 1 000 V and 12 V at 50 000 V for thistest. The emf indicators may be potentiometers or digitalvoltmeters. Sections 6.2 and 7.4 of Test Method E220 may beconsulted for further discussions of thermal emf indicators andmethods of emf measurement.6.7 Connecting Wires Connecting wires from the refer-ence junctions to the emf indicator or i
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