ASTM B267-90(2001)
(Specification)Standard Specification for Wire for Use In Wire-Wound Resistors
Standard Specification for Wire for Use In Wire-Wound Resistors
SCOPE
1.1 This specification covers round wire and ribbon with controlled electrical properties for use in wire-wound resistance units and similar applications, but not for use as electrical heating elements.
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Designation: B 267 – 90 (Reapproved 2001)
Standard Specification for
Wire for Use In Wire-Wound Resistors
This standard is issued under the fixed designation B 267; 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.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 7. Nominal Electrical Resistance per Unit Length
1.1 This specification covers round wire and ribbon with 7.1 The nominal resistance per unit length for round wire
controlled electrical properties for use in wire-wound resis- shallbecalculatedfromthenominalresistivityandthenominal
tanceunitsandsimilarapplications,butnotforuseaselectrical cross-sectional area.
heating elements.
NOTE 1—When ribbon or flat wire is produced by rolling from round
wire, the cross section departs from that of a true rectangle by an amount
2. Referenced Documents
depending on the width-to-thickness ratio and the specific manufacturing
2.1 ASTM Standards:
practice. The conventional formula for computing ohms per foot and feet
perpoundistoconsiderthecrosssectionas17%lessthanatruerectangle
B63 Test Method for Resistivity of Metallically Conduct-
when width is more than 15 times the thickness and 6% less than a true
ing Resistance and Contact Materials
rectangle in other cases. This is not valid in view of modern rolling
B77 Test Method for Thermoelectric Power of Electrical-
equipment and practices, but still is widely used as a basis of description.
Resistance Alloys
Ribbonactuallyismadetoaspecifiedresistanceperfoot,andnotolerance
B84 Test Method for Temperature-Resistance Constants of
isspecifiedforthickness.Analternativeandacloserapproximationwould
Alloy Wires for Precision Resistors
be that for ribbon rolled round wire, the electrical resistance would be
calculated on a cross 6% less than a true rectangle.
3. Significance and Use
8. Temperature Coefficient of Resistance
3.1 This specification on wire and ribbon contains the
generic chemistry and requirements for resistivity, temperature 8.1 The change in resistance with change in temperature,
coefficient of resistance, thermal emf versus copper resistance expressed as the mean temperature coefficient of resistance
tolerances, and mechanical properties of bare wire, as well as basedonthereferencetemperatureof25°C,shallbewithinthe
thewireenamelsandinsulationsofalloysnormallyusedinthe limits specified in Table 1, Columns 4 and 6, over the
manufacture of wound resistors. corresponding temperature ranges specified in Columns 5 and
7. The mean temperature coefficient of resistance referred to
4. Alloy Classes
25°C is defined as the slope of a chord of an arc. This slope is
4.1 Fifteenclassesofalloysarecoveredbythisspecification
determined from the following equation:
as listed in Table 1.
a 5 ~DR/R DT! 310
m 25
5. Elongation
where:
5.1 The wire shall conform to the requirements for elonga-
a = mean temperature coefficient of resistance, ppm/
m
tionasprescribedinTable1,whentestedona10-in.(254-mm)
°C, Table 1, Columns 4 and 6,
length.
DR = change in resistance over temperature range indi-
cated in Table 1, Columns 5 and 7,
6. Resistivity
R = resistance at 25°C,
6.1 The bare wire shall conform to the requirements for DT = temperaturerangeindicatedinTable1,Columns5
and 7.
nominal resistivity as prescribed in Table 1.
6.2 Actual resistivity shall not vary from nominal resistivity 8.2 ForAlloyClasses1,2,and5,thetemperaturecoefficient
by more than 65% for Alloy Classes 1 to 4 inclusive, and as specified in Table 1 of any 10-ft (3-m) length shall not vary
610% for Alloy Classes 5 to 11 inclusive. more than 3 ppm/°C from that of any other 10-ft length on the
same spool or coil.
This test method is under the jurisdiction of ASTM Committee B02 on
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
B02.10 on Thermostat Metals.
Current edition approved May 25, 1990. Published July 1990. Originally
published as B267–52 T. Last previous edition B267–83.
Annual Book of ASTM Standards, Vol 03.04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 267
TABLE 1 Classes of Alloys and Requirements
Mean Temperature Coefficient of Resistance, a ppm for Maximum Thermal emf
m
Elongation in 10 in., min, %
B
° C Over Temperature Range,D T versus Copper, mV/°C
Resistivity,
Alloy Alloy Composition,
Over 0.002 to 0.0009
V·cmil/ft
A
D
Class approximate, %
Temperature 0.002 0.001 in. in
(µV·m)
DT a DT mV/°C
m C D D
Range, DT in. in in. in Diameter
Diameter Diameter and Finer
12 3 4 5 6 7 8 9 10 11 12
1a nickel base, nonmagnetic 800 (1.330) 0, 620 +25 to−55 0, 620 + 25 to + 105 + 0.003 −65 to + 250 10 5 3
1b nickel base, nonmagnetic 800 (1.330) 0, 610 +25 to−55 0, 610 + 25 to + 105 + 0.003 −65 to + 150 10 5 3
1c nickel base, nonmagnetic 800 (1.330) 0, 65 + 25 to−55 0, 65 + 25 to + 105 + 0.003 −65 to + 150 10 5 3
2a iron base, magnetic 800 (1.330) 0, 620 +25 to−55 0,6 20 + 25 to + 105 −0.004 −65 to + 200 10 5 3
2b iron base, magnetic 800 (1.330) 0, 610 +25 to−55 0, 610 + 25 to + 105 −0.004 −65 to + 150 10 5 3
3a 80 nickel, 20 chromium 650 (1.081) + 80, 620 +25 to−55 + 80, 620 + 25 to + 105 + 0.006 −65 to + 250 15 5 3
3b 80 nickel, 20 chromium, 675 (1.122) + 60,6 20 +25 to−55 + 60, 620 + 25 to + 105 + 0.006 −65 to + 250 15 5 3
stabilized
4 60 nickel, 16 chromium, 675 (1.122) + 140, 630 + 25 to − 55 + 140, 630 + 25 to + 105 + 0.002 −65 to + 200 15 5 3
balance iron
5a 55 copper, 45 nickel 300 (0.499) 0, 620 +25 to−55 0, 620 + 25 to + 105 −0.045 −65 to + 150 15 5 3
5b 55 copper, 45 nickel 300 (0.499) 0, 640 +25 to−55 0, 640 + 25 to + 105 −0.045 −65 to + 150 15 5 3
EE EE
6 manganin type 290 (0.482) 0, 615 0, 615 −0.003 + 15 to + 35 15 5 3
7 77 copper, 23 nickel 180 (0.299) + 180, 630 + 25 to − 55 + 180,6 30 + 25 to + 105 −0.037 −65 to + 150 15 5 3
8 70 nickel, 30 iron 125 (0.199) + 3600, 6400 + 25 to − 50 + 4300, 6400 + 25 to + 104 −0.040 −50 to + 100 15 5 3
9 90 copper, 10 nickel 90 (0.150) + 450, 650 + 25 to − 55 + 450, 650 + 25 to + 105 −0.026 −65 to + 150 15 5 3
10 94 copper, 6 nickel 60 (0.100) + 700, 6200 + 25 to − 55 + 700,6 200 + 25 to + 105 −0.022 −65 to + 150 15 5 3
11 98 copper, 2 nickel 30 (0.050) + 1400, 6300 + 25 to − 55 + 1400, 6300 + 25 to + 105 0.014 −65 to + 150 15 5 3
A
Alloy Classes 1a to 8 inclusive are designed to provide controlled temperature coefficients. Values shown for other classes are for information only. All values are based
on a reference temperature of 25°C.
B
Alloy Classes 1a, 1b, 1c, 2a, 2b, 3a, 4, and 6 are designed to give a low emf versus copper. Values shown for other classes are for information only. Maximum indicates
the maximum deviation from zero and the plus or minus sign the polarity of the couple.
C
The maximum temperature values listed apply to the alloy wire only. Caution should be exercised pending knowledge of the maximum temperature of use forthe
coating material involved.
D
If metric sizes are desired, 1 in. = 25.4 mm.
E
Alloy Class 6 (manganin type for resistors), has a temperature-resistance curve of parabolic shape with the maximum resistance normally located between 25 and
m
30°C. Thus, Columns 5 and 7 cannot indicate 25°C as a limit but a may be expressed as a maximum of + 15 ppm for 15°C to the temperature of maximum resistance
and a maximum of − 15 ppm from the temperature of maximum resistance to 35°C. All of the information included in this note is based on measurements made in
accordance with Test Method B 84.
9. Thermal EMF with Respect to Copper per unit length, rather than the dimensions, are of prime
importance. The electrical resistance per unit length can be
9.1 The thermal electromotive force (emf) with respect to
determined more accurately than the dimensions of very small
copper shall fall within the limits shown in Table 1, in the
wire.
corresponding temperature ranges.
12. Finish
10. Permissible Variations in Electrical Resistance
10.1 The actual resistance per unit length of any wire 12.1 Thewireshallbeasuniformandfreefromkinks,curls,
furnished under these specifications shall not vary from the andsurfacedefectssuchasseams,laminations,scale,andother
nominal resistance by more than the following amounts: irregularities as the best commercial practice will permit.
Form Permissible
Variation, 6%
13. Enamel Coatings
Over 0.005 in. (0.127 mm) in diameter 5
13.1 Enamel coatings shall include any baked-on film of
0.002 to 0.005 in. (0.051 to 0.127 mm) in diameter, incl 8
Under 0.002 in (0.051 mm) in diameter 10
insulating material, such as varnish enamel, polyurethane,
Ribbon 5
vinyl acetal, etc. and shall conform to the requirements
10.2 ForAlloyClasses1to4inclusive,theactualresistance prescribed in 13.2 to 13.7.
of any 1-ft length of wire in one spool or coil shall not vary by 13.2 The physical dimensions of the enamel film shall
more than 3% from the actual resistance of any other 1 ft of
conform to the requirements specified in Table 2.
wire in the same spool or coil.
13.3 The continuity of dielectric strength of medium or
10.3 For Alloy Classes 5 to 11 inclusive, the actual resis-
heavyenamelshallshowamaximumof10breaks/100ftwhen
tance of any 1-ft length of wire in one spool or coil shall not
tested with a potential of 150 V applied between a single
vary by more than 5% from the actual resistance of any other
mercury cup and the bared end of the wire. In the dielectric
1 ft of wire in the same spool or coil.
strength test, 100 ft of the wire shall be drawn through the
mercury or equivalent at a speed that will permit the recording
11. Permissible Variations in Dimensions
of 600 counts/min. The test circuit shall have a recording
11.1 Permissible variations in dimensions of bare wire are sensitivityof30
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