ASTM B193-02(2008)
(Test Method)Standard Test Method for Resistivity of Electrical Conductor Materials
Standard Test Method for Resistivity of Electrical Conductor Materials
ABSTRACT
This test method covers the determination of the electrical resistivity of metallic electrical conductor material. Weight resistivity accuracy may be adversely affected by possible inaccuracies in the assumed density of the conductor. The definition of resistivity and the equations for calculating volume resistivity and weight resistivity are given. Resistance shall be measured using an apparatus with a circuit configuration and instrumentation that has a resistance measurement capability of the prescribed accuracy. The test specimen requirements and the test procedure including: (1) determination of dimensions (such as length and cross-section), weight, and density, and (2) resistance measurement are detailed. The formula for calculating the corrected resistance, when the measurement is made at any temperature other than a reference temperature, is given. No statement of precision has been made and no work has been planned to develop such a statement. This test method has no bias because the value for resistivity is determined solely in terms of this test method.
SCOPE
1.1 This test method covers the determination of the electrical resistivity of metallic electrical conductor material. It provides for an accuracy of ±0.30 % on test specimens having a resistance of 0.00001 Ω (10 μΩ) or more. Weight resistivity accuracy may be adversely affected by possible inaccuracies in the assumed density of the conductor.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B193 − 02(Reapproved 2008)
Standard Test Method for
Resistivity of Electrical Conductor Materials
This standard is issued under the fixed designation B193; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope for Electrical Purposes—Annealed and Intermediate Tem-
pers
1.1 This test method covers the determination of the elec-
2.2 NIST Document:
trical resistivity of metallic electrical conductor material. It
NBS Handbook 100 — Copper Wire Tables
provides for an accuracy of 60.30 % on test specimens having
a resistance of 0.00001 Ω (10 µΩ) or more. Weight resistivity
3. Resistivity
accuracy may be adversely affected by possible inaccuracies in
3.1 Resistivity (Explanatory Note 1) is the electrical resis-
the assumed density of the conductor.
tance of a body of unit length, and unit cross-sectional area or
1.2 This standard does not purport to address all of the
unit weight.
safety concerns, if any, associated with its use. It is the
3.2 VolumeResistivity is commonly expressed in ohms for a
responsibility of the user of this standard to establish appro-
theoretical conductor of unit length and cross-sectional area; in
priate safety and health practices and determine the applica-
inch-pound units in Ω·cmil/ft and in acceptable metric units in
bility of regulatory limitations prior to use.
Ω·mm /m. It may be calculated by the following equation:
2. Referenced Documents
ρ 5 A/L R
~ !
v
2.1 ASTM Standards:
where:
A111 Specification for Zinc-Coated (Galvanized) “Iron”
ρ = volume resistivity, Ω·cmil/ft or Ω·mm /m,
v
Telephone and Telegraph Line Wire
A = cross-sectional area, cmil or mm ,
A326 Specification for Zinc-Coated (Galvanized) High Ten-
L = gage length, used to determine R,ftorm,and
sile Steel Telephone and Telegraph Line Wire (Withdrawn
R = measured resistance, Ω.
1990)
3.3 Weight Resistivity is commonly expressed in ohms for a
B9 Specification for Bronze Trolley Wire
theoretical conductor of unit length and weight. The method
B105 Specification for Hard-Drawn CopperAlloy Wires for
for calculating weight resistivity, based on resistance, length,
Electric Conductors
and weight measurements, of a test specimen is given in
B298 Specification for Silver-Coated Soft orAnnealed Cop-
Explanatory Note 2.
per Wire
B355 SpecificationforNickel-CoatedSoftorAnnealedCop-
4. Apparatus
per Wire
B415 Specification for Hard-Drawn Aluminum-Clad Steel 4.1 Resistance shall be measured with a circuit configura-
tion and instrumentation that has a resistance measurement
Wire
B566 Specification for Copper-Clad Aluminum Wire capability of 60.15 % accuracy.
B800 Specification for 8000 Series Aluminum Alloy Wire
5. Test Specimen
5.1 The test specimen may be in the form of a wire, strip,
This test method is under the jurisdiction of ASTM Committee B01 on
rod, bar, tube, or shape. It shall be of uniform cross section
Electrical Conductors and is the direct responsibility of Subcommittee B01.02 on
throughout its length within 60.75 % of the cross-sectional
Methods of Test and Sampling Procedure.
Current edition approved Sept. 1, 2008. Published September 2008. Originally area. Wherever possible it shall be the full cross section of the
approved in 1944. Last previous edition approved in 2002 as B193 – 02. DOI:
material it represents, if the full cross section is such that the
10.1520/B0193-02R08.
uniformity of the cross-sectional area can be accurately deter-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
mined.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 4
The last approved version of this historical standard is referenced on Available from National Institute of Standards and Technology (NIST), 100
www.astm.org. Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B193 − 02 (2008)
5.2 The test specimen shall have the following characteris- δ 5 W 3d / W 2 W
~ ! ~ !
a a l
tics:
where:
5.2.1 A resistance of at least 0.00001 Ω (10 µΩ) in the test
δ = density of the specimen, g/cm ;
length between potential contacts,
W = weight of the specimen in air, g;
a
5.2.2 A test length of at least 1 ft or 300 mm,
W = weight of the specimen in the liquid, g; and
l
5.2.3 A diameter, thickness, width, or other dimension
d = density of the liquid at the test temperature, g/cm .
suitable to the limitations of the resistance measuring
instrument, 6.4 When potential leads are used, make sure the distance
5.2.4 No surface cracks or defects visible to the unaided between each potential contact and the corresponding current
normal eye, and substantially free from surface oxide, dirt, and contact is at least equal to 1 ⁄2 times the cross-sectional
grease, and perimeter of the specimen. Make sure the yoke resistance
5.2.5 No joints or splices. (between reference standard and test specimen) is appreciably
smaller than that of either the reference standard or the test
6. Procedure
specimen unless a suitable lead compensation method is used,
6.1 Make all determinations of the dimensions and weight
or it is known that the coil and lead ratios are sufficiently
of the test specimen using instruments accurate to 60.05 %. In
balanced so that variation in yoke resistance will not decrease
order to assure this accuracy in measuring the length between
the bridge accuracy below stated requirements.
potential contacts, the surface in contact with the test specimen
6.5 Make resistance measurements to an accuracy of
shall be a substantially sharp knife-edge when using a Kelvin-
60.15 %. To ensure a correct reading, allow the reference
type bridge or a potentiometer.
standardandthetestspecimentocometothesametemperature
6.2 The cross-sectional dimensions of the specimen may be
as the surrounding medium. (If the reference standard is made
determined by micrometer measurements, and a sufficient
of manganin it is possible to obtain correct readings with the
number of measurements shall be made to obtain the mean
test specimen at reference temperatures other than room
cross section to within 60.10 %. In case any dimension of the
temperature). In all resistance measurements, the measuring
specimen is less than 0.100 in. and cannot be measured to the
current raises the temperature of the medium. Therefore, take
requiredaccuracy,determinethecross-sectionfromtheweight,
care to keep the magnitude of the current low, and the time of
density, and length of the specimen.
its use short enough so that the change in resistance cannot be
6.3 When the density is unknown, determine the density by detected with the galvanometer. To eliminate errors due to
weighing a specimen first in air and then in a liquid of known contact potential, take two readings, one direct and one with
density at the test temperature, which shall be room tempera- current reversed, in direct succession. Check tests are recom-
turetoavoiderrorsduetoconvectioncurrents.Exercisecarein mended whereby the specimen is turned end for end, and the
removing all air bubbles from the specimen when weighing it test repeated. Surface cleaning of the specimen at current and
in the liquid. Calculate the density from the following equa- potential contact points may be necessary to obtain good
tion: electrical contact.
TABLE 1 Resistivity and Conductivity Conversion
NOTE 1—These factors are applicable only to resistivity and conductivity values corrected to 20°C (68°F). They are applicable for any temperature
when used to convert between volume units only or between weight units only. Values of density, δ, for the common electrical conductor materials, are
listed in Table 2.
Given N→ Volume Resistivity at 20°C Weight Resistivity at 20°C Conductivity at 20°C
Perform indicated % IACS % IACS
2 2 2
Ω·cmil/ft Ω·mm /m µΩ·in. µΩ·cm Ω·lb/mile Ω·g/m
operation to obtain↓ (Volume Basis) (Weight Basis)
Volume Resistivity at 20°C
Ω·cmil/ft . . . N × 601.52 N × 15.279 N × 6.0153 N × 0.10535 × N × 601.53 × (1/N) × 1037.1 (1/N) × 9220.0
(l/δ) (1/δ) × (l/δ)
Ω·mm /m N × 0.0016624 . . . N × 0.025400 N × 0.010000 N × 0.00017513 N ×(1/δ)(1/N) × 1.7241 (1/N) × 15.328
×(1/δ) ×(1/δ)
µΩ·in. N × 0.065450 N × 39.370 . . . N × 0.39370 N × 0.0068950 N × 39.370 × (1/N) × 67.879 (1/N) × 603.45
×(1/δ) (1/δ) ×(1/δ)
µΩ·cm N × 0.16624 N × 100.00 N × 2.5400 . . . N × 0.017513 × N × 100.00 × (1/N) × 172.41 (1/N) × 1532.8
(1/δ) (1/δ) ×(1/δ)
Weight Resistivity at 20°C
Ω·lb/mile N × 9.4924 ×δ N × 5710.0 ×δ N × 145.03 ×δ N × 57.100 ×δ . N × 5710.0 (1/N) × 9844.8 (1/N) × 87520
×δ
Ω·g/m N × 0.0016624 N ×δ N × 0.025400 N × 0.010000 N × 0.00017513 . . . (1/N) × 1.7241 (1/N) × 15.328
×δ × δ × δ ×δ
Conductivity at 20°C
% IACS (volume basis) (1/N) × 1037.1 (1/N) × 1.7241 (1/N) × 67.879 (1/N) × 172.41 (1/N) × 9844.8 (1/N) × 1.7241 . N × 0.11249
×δ ×δ ×δ
% IACS (weight basis) (1/N) × 9220.0 (1/N) × 15.328 (1/N) × 603.45 (1/N) × 1532.8 (1/N) × 87520 (1/N) × 15.328 N 8.89 × (1/δ) .
×(1/δ) ×(1/δ) ×(1/δ) ×(1/δ)
B193 − 02 (2008)
TABLE 2 Density and Temperature Coefficien
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:B 193–01 Designation:B 193–02 (Reapproved 2008)
Standard Test Method for
Resistivity of Electrical Conductor Materials
This standard is issued under the fixed designation B 193; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope
1.1 This test method covers the determination of the electrical resistivity of metallic electrical conductor material. It provides
for an accuracy of 60.30 % on test specimens having a resistance of 0.00001 V (10 µV) or more. Weight resistivity accuracy may
be adversely affected by possible inaccuracies in the assumed density of the conductor.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
A111Specification for Zinc-Coated (Galvanized) “Iron” Telephone and Telegraph Line Wire
A 111 Specification for Zinc-Coated (Galvanized) Iron Telephone and Telegraph Line Wire
A 326 Specification for Zinc-Coated (Galvanized) High Tensile Steel Telephone and Telegraph Line Wire
B 9 Specification for Bronze Trolley Wire
B 105 Specification for Hard-Drawn Copper Alloy Wires for Electric Conductors
B 298 Specification for Silver-Coated Soft or Annealed Copper Wire
B 355 Specification for Nickel-Coated Soft or Annealed Copper Wire
B 415 Specification for Hard-Drawn Aluminum-Clad Steel Wire
B 566 Specification for Copper-Clad Aluminum Wire
B 800 Specification for 8000 Series Aluminum Alloy Wire for Electrical Purposes—Annealed and Intermediate Tempers
2.2 NIST Document:
NBS Handbook 100— Copper Wire Tables
3. Resistivity
3.1 Resistivity (Explanatory Note 1) is the electrical resistance of a body of unit length, and unit cross-sectional area or unit
weight.
3.2 Volume Resistivity is commonly expressed in ohms for a theoretical conductor of unit length and cross-sectional area; in
inch-pound units in V·cmil/ft and in acceptable metric units in V·mm /m. It may be calculated by the following equation:
r 5 ~A/L!R
v
where:
r = volume resistivity, V·cmil/ft or V·mm /m,
v
A = cross-sectional area, cmil or mm ,
L = gage length, used to determine R,ftorm,and
This test method is under the jurisdiction of ASTM Committee B01 on Electrical Conductors and is the direct responsibility of Subcommittee B01.02 on Methods of
Test and Sampling Procedure.
Current edition approved Apr. 10, 2001. Published May 2001. Originally published as B193–44T. Last previous edition B193–00.
Current edition approved Sept. 1, 2008. Published September 2008. Originally approved in 1944. Last previous edition approved in 2002 as B 193 – 02.
Annual Book of ASTM Standards, Vol 01.06.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. ForAnnualBookofASTMStandards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Annual Book of ASTM Standards, Vol 02.03.
Withdrawn
Available from the National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899.
Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 193–02 (2008)
R = measured resistance, V.
3.3 Weight Resistivity is commonly expressed in ohms for a theoretical conductor of unit length and weight. The method for
calculating weight resistivity, based on resistance, length, and weight measurements, of a test specimen is given in Explanatory
Note 2.
4. Apparatus
4.1Resistance shall be measured with a Kelvin-type double bridge or a potentiometer if the resistance of the specimen is below
1 V.Ifitis1 V or more, a Wheatstone bridge may be used. Where applicable, a Hoopes conductivity bridge may be used.
4.1 Resistance shall be measured with a circuit configuration and instrumentation that has a resistance measurement capability
of 60.15 % accuracy.
5. Test Specimen
5.1 Thetestspecimenmaybeintheformofawire,strip,rod,bar,tube,orshape.Itshallbeofuniformcrosssectionthroughout
its length within 60.75 % of the cross-sectional area. Wherever possible it shall be the full cross section of the material it
represents, if the full cross section is such that the uniformity of the cross-sectional area can be accurately determined.
5.2 The test specimen shall have the following characteristics:
5.2.1 A resistance of at least 0.00001 V (10 µV) in the test length between potential contacts,
5.2.2 A test length of at least 1 ft or 300 mm,
5.2.3 A diameter, thickness, width, or other dimension suitable to the limitations of the resistance measuring instrument,
5.2.4 No surface cracks or defects visible to the unaided normal eye, and substantially free from surface oxide, dirt, and grease,
and
5.2.5 No joints or splices.
6. Procedure
6.1 Make all determinations of the dimensions and weight of the test specimen using instruments accurate to 60.05 %. In order
to assure this accuracy in measuring the length between potential contacts, the surface in contact with the test specimen shall be
a substantially sharp knife-edge when using a Kelvin-type bridge or a potentiometer.
6.2 The cross-sectional dimensions of the specimen may be determined by micrometer measurements, and a sufficient number
of measurements shall be made to obtain the mean cross section to within 60.10 %. In case any dimension of the specimen is less
than 0.100 in. and cannot be measured to the required accuracy, determine the cross-section from the weight, density, and length
of the specimen.
6.3 When the density is unknown, determine the density by weighing a specimen first in air and then in a liquid of known
density at the test temperature, which shall be room temperature to avoid errors due to convection currents. Exercise care in
removing all air bubbles from the specimen when weighing it in the liquid. Calculate the density from the following equation:
d5 ~W 3d!/~W 2W !
a a l
where:
d = density of the specimen, g/cm,;
W = weight of the specimen in air, g, g;
a
W = weight of the specimen in the liquid, g,g; and
l
d = density of the liquid at the test temperature, g/cm .
6.4 When potential leads are used, make sure the distance between each potential contact and the corresponding current contact
is at least equal to 1 ⁄2 times the cross-sectional perimeter of the specimen. Make sure the yoke resistance (between reference
standard and test specimen) is appreciably smaller than that of either the reference standard or the test specimen unless a suitable
lead compensation method is used, or it is known that the coil and lead ratios are sufficiently balanced so that variation in yoke
resistance will not decrease the bridge accuracy below stated requirements.
6.5 Make resistance measurements to an accuracy of 60.15 %. To ensure a correct reading, allow the reference standard and
the test specimen to come to the same temperature as the surrounding medium. (If the reference standard is made of manganin it
is possible to obtain correct readings with the test specimen at reference temperatures other than room temperature). In all
resistance measurements, the measuring current raises the temperature of the medium. Therefore, take care to keep the magnitude
of the current low, and the time of its use short enough so that the change in resistance cannot be detected with the galvanometer.
Toeliminateerrorsduetocontactpotential,taketworeadings,onedirectandonewithcurrentreversed,indirectsuccession.Check
tests are recommended whereby the specimen is turned end for end, and the test repeated. Surface cleaning of the specimen at
current and potential contact points may be necessary to obtain good electrical contact.
7. Temperature Correction
7.1 When the measurement is made at any other than a reference temperature, the resistance may be corrected for moderate
temperature differences to what it would be at the reference temperature, as follows:
R
t
R 5
T
11a ~t —T!
T
B 193–02 (2008)
where:
R = resistance at reference temperature T,
T
R = resistance as measured at temperature t,
t
a = known or given temperature coefficient of resistance of the specimen being measured at reference temperature T,
T
T = reference temperature, and
t = temperature at which measurement is made.
NOTE 1—The parameter a , in the above equation, varies with conductivity and temperature. For copper of 100 % conductivity and a reference
T
temperature of 20°C, its value is 0.00393.Values at other conductivities and temperatures will be found inNBSHandbook100. Table 1 lists temperature
coefficients for the common electrical conductor materials.
8. Report
8.1 For referee tests, report the following information:
8.1.1 Identification of test specimen,
8.1.2 Kind of material,
8.1.3 Test temperature,
8.1.4 Test length of specimen,
8.1.5 Method of obtaining cross-sectional area:
8.1.5.1 If by micrometer, the average values of micrometer readings, or
8.1.5.2 If by weighing, a record of length, weight, any density determinations that may be made, and calculated cross-sectional
areas.
8.1.6 Weight, if used,
8.1.7 Method of measuring resistance,
8.1.8 Value of resistance,
TABLE 1 Resistivity and Conductivity Conversion
NOTE 1—These factors are applicable only to resistivity and conductivity values corrected to 20°C (68°F). They are applicable for any temperature
when used to convert between volume units only or between weight units only. Values of density, d, for the common electrical conductor materials, are
listed in Table 3 2.
Given N→ Volume Resistivity at 20°C Weight Resistivity at 20°C Conductivity at 20°C
Perform indicated % IA
...
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