1、Designation:B7707(Reapproved 2013)Standard Test Method forThermoelectric Power of Electrical-Resistance Alloys1This standard is issued under the fixed designation B77;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last r
2、evision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the ther-moelectric power of a metal or alloy with respect to copperwhen the temperatu
3、res of the junctions lie between 0 and100C.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to addre
4、ss all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateMaterial Safety Data Sheet(MSDS)for this product/materialas provided by the manufacturer,to establish appro
5、priatesafety and health practices,and determine the applicability ofregulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B3 Specification for Soft or Annealed Copper Wire3.Terminology3.1 thermoelectric power,Q,nthe electromotive force inan electric circuit consisting of two
6、metals when the junctionsbetween them have a difference in temperature of 1C.3.1.1 DiscussionExperimentally,it has been found thatthe thermoelectric power of two metals is not a constant butdepends on the mean temperature of the junctions.However,over a range of temperature from 0 to 100C it is usua
7、llysufficient to assume that the thermoelectric power is indepen-dent of temperature so that for this range of temperature:Q 5 E/t2t!where:E=the electromotive force developed in the circuit,t=the higher temperature at one junction,C,andt=the lower temperature at the other junction,C.4.Significance a
8、nd Use4.1 The purpose of this method is to determine the suitabil-ity of different metals for use in resistance apparatus in whicha low thermoelectric power is desired.As most electric circuitsare largely composed of copper,the thermoelectric power of aresistance metal will generally be measured aga
9、inst copper.5.Test Specimen5.1 The metal or alloy to be tested shall be in the form ofsheet,ribbon,or wire and the test specimen shall be of suchlength that the two ends can be readily maintained at differenttemperatures.At each end of the specimen a copper lead ofconvenient size shall be fastened.T
10、hese leads shall make goodelectrical contact with the specimen,such as that obtained bywelding,brazing,or soldering.Slight impurities in the copperhave a negligible effect on the thermoelectric power.NOTE1When necessary to specify the quality of the copper leads,reference should be made to Specifica
11、tion B3.6.Procedure6.1 MeasurementofTemperatureAsamatterofprecaution,the average temperature used in determining thethermoelectric power shall be approximately the same as thatto which the material will be subjected in practice,and in nocase shall the temperature difference between the two junctions
12、be less than 20C.The temperature at each of two junctionsshall be measured by a device that is sufficiently accurate todetermine the temperature difference within 5%.A convenientmethod for determining the temperatures of the junctions is toimmerse each junction in separate oil baths maintained at th
13、edesired temperatures.Baths that are stirred and the tempera-tures of which are thermostatically controlled are to bepreferred.However,beakers of oil which are supported byblocks of metal,sand baths,or other means may be used,provided the thermal capacity of these assemblies is such thatwhen the hea
14、t is cut off their temperatures will decrease at ratesless than 0.2C/min.The temperature of the oil in each bathmay be determined by a calibrated temperature measuring1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of
15、SubcommitteeB02.10 on Thermostat Metals and Electrical Resistance Heating Materials.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 1930.Last previous edition approved in 2007 as B77 07.DOI:10.1520/B0077-07R13.2For referenced ASTM standards,visit the ASTM website,www.ast
16、m.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 States1 device of suitable precision and accuracy.If the oil is notstirred,the junctions shall be placed in close proximity to thetemperature-measuring instrument.To ensure that the tempera-tures of the junctions shall not be