ASTM B77-07(2018)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B77 − 07 (Reapproved 2018)
Standard Test Method for
Thermoelectric Power of Electrical-Resistance Alloys
This standard is issued under the fixed designation B77; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope the thermoelectric power of two metals is not a constant but
depends on the mean temperature of the junctions. However,
1.1 This test method covers the determination of the ther-
over a range of temperature from 0 to 100°C it is usually
moelectric power of a metal or alloy with respect to copper
sufficient to assume that the thermoelectric power is indepen-
when the temperatures of the junctions lie between 0 and
dent of temperature so that for this range of temperature:
100°C.
Q 5 E/ t'2t
~ !
1.2 The values stated in inch-pound units are to be regarded
as standard. The values given in parentheses are mathematical
where:
conversions to SI units that are provided for information only
E = the electromotive force developed in the circuit,
and are not considered standard.
t' = the higher temperature at one junction, °C, and
t = the lower temperature at the other junction, °C.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to become familiar
with all hazards including those identified in the appropriate 4.1 The purpose of this method is to determine the suitabil-
Safety Data Sheet (SDS) for this product/material as provided ity of different metals for use in resistance apparatus in which
by the manufacturer, to establish appropriate safety, health, a low thermoelectric power is desired.As most electric circuits
and environmental practices, and determine the applicability are largely composed of copper, the thermoelectric power of a
of regulatory limitations prior to use. resistance metal will generally be measured against copper.
1.4 This international standard was developed in accor-
5. Test Specimen
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
5.1 The metal or alloy to be tested shall be in the form of
Development of International Standards, Guides and Recom-
sheet, ribbon, or wire and the test specimen shall be of such
mendations issued by the World Trade Organization Technical
length that the two ends can be readily maintained at different
Barriers to Trade (TBT) Committee.
temperatures. At each end of the specimen a copper lead of
convenient size shall be fastened. These leads shall make good
2. Referenced Documents
electrical contact with the specimen, such as that obtained by
welding, brazing, or soldering. Slight impurities in the copper
2.1 ASTM Standards:
have a negligible effect on the thermoelectric power.
B3 Specification for Soft or Annealed Copper Wire
NOTE 1—When necessary to specify the quality of the copper leads,
3. Terminology
reference should be made to Specification B3.
3.1 thermoelectric power, Q, n—the electromotive force in
6. Procedure
an electric circuit consisting of two metals when the junctions
between them have a difference in temperature of 1°C. 6.1 Measurement of Temperature—As a matter of
precaution, the average temperature used in determining the
3.1.1 Discussion—Experimentally, it has been found that
thermoelectric power shall be approximately the same as that
to which the material will be subjected in practice, and in no
This test method is under the jurisdiction of ASTM Committee B02 on
case shall the temperature difference between the two junctions
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
be less than 20°C. The temperature at each of two junctions
B02.10 on Thermostat Metals and Electrical Resistance Heating Materials.
shall be measured by a device that is sufficiently accurate to
Current edition approved Nov. 1, 2018. Published November 2018. Originally
determine the temperature difference within 5 %.Aconvenient
approved in 1930. Last previous edition approved in 2013 as B77 – 07 (2013). DOI:
10.1520/B0077-07R18.
method for determining the temperatures of the junctions is to
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
immerse each junction in separate oil baths maintained at the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
desired temperatures. Baths that are stirred and the tempera
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