ASTM B84-07(2019)

Standard Test Method for Temperature-Resistance Constants of Alloy Wires for Precision Resistors

SIGNIFICANCE AND USE
2.1 Procedure A covers the determination of the equation of the curve relating resistance and temperature where the curve approximates a parabola. This test method may be used for wire of any metal or alloy over the temperature interval appropriate to the material.  
2.2 Procedure B covers the determination of the mean temperature coefficient of resistance for wire of any metal or alloy over the temperature interval appropriate to the material.
SCOPE
1.1 This test method covers determination of the change of resistance with temperature of alloy wires used for resistance standards and precision resistors for electrical apparatus.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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.

General Information

• Status: Published
• Publication Date: 31-Mar-2019
• ICS: 29.050 - Superconductivity and conducting materials
• Technical Committee: B02 - Nonferrous Metals and Alloys
• Drafting Committee: B02.10 - Thermostat Metals and Electrical Resistance Heating Materials

Relations

• Replaces: ASTM B84-07(2013) - Standard Test Method for Temperature-Resistance Constants of Alloy Wires for Precision Resistors
• Effective Date: 01-Apr-2019
• Referred By: ASTM B114-07(2018) - Standard Test Method for Temperature-Resistance Constants of Sheet Materials for Shunts and Precision Resistors
• Effective Date: 01-Apr-2019
• Referred By: ASTM B267-07(2018) - Standard Specification for Wire for Use In Wire-Wound Resistors
• Effective Date: 01-Apr-2019
• Referred By: ASTM B1015-20 - Standard Practice for Form and Style of Standards Relating to Refined Nickel and Cobalt and Their Alloys
• Effective Date: 01-Apr-2019

Overview

ASTM B84-07(2019): Standard Test Method for Temperature-Resistance Constants of Alloy Wires for Precision Resistors sets forth recognized procedures for determining how the electrical resistance of alloy wires changes as their temperature varies. Administered by ASTM International, this important standard is widely used to evaluate wires intended for resistance standards and precision resistors, which are key components in the calibration and operation of electrical apparatus.

This test method includes two procedures:

• Procedure A: Determines the equation that relates resistance to temperature when the relationship is approximately parabolic, applicable to any metallic wire over a relevant temperature range.
• Procedure B: Establishes the mean temperature coefficient of resistance for wires over a specified temperature interval.

All measurements and results under this standard are expressed in SI units, and the method is developed in accordance with internationally recognized principles on standardization, supporting global trade and regulatory harmonization.

Key Topics

• Temperature-Resistance Relationship: The standard defines methodologies to accurately characterize changes in resistance as temperature varies, particularly for alloys with parabolic resistance-temperature curves.
• Apparatus and Procedures: Detailed recommendations are provided for the preparation and setup of baths and measuring apparatus to ensure precise thermal and electrical conditions.
• Measurement Accuracy: High standards for measurement accuracy are mandated, including strict temperature uniformity in baths and resistance measurement to 0.001% or better.
• Specimen Preparation: Guidance addresses the preparation of test specimens, including the length, winding method, insulation, and terminal attachment, to minimize measurement artifacts.
• Reporting Format: The standard prescribes a comprehensive format for reporting data, ensuring consistency across laboratories and manufacturers.
• Safety Considerations: Users are reminded to assess and address all health, safety, and environmental risks appropriate to their specific applications.

Applications

This test method is critically important in several domains where wire stability and precision are essential.

• Manufacture of Precision Resistors: Ensures that resistance wire materials used in high-accuracy electrical resistors for scientific, industrial, and calibration purposes have known and stable temperature-resistance characteristics.
• Quality Control: Provides wire manufacturers and end-users with a reliable tool for verifying material consistency and suitability when producing resistance standards.
• Metrology and Calibration: Used in national and company standards laboratories to ensure that reference resistors function predictably across specified temperature ranges, supporting accurate electrical measurements.
• Research and Development: Utilized in materials science to compare and improve the temperature performance of different alloys intended for electronic applications.

The standard helps designers and engineers select appropriate alloys and manufacturing processes to achieve the minimal temperature coefficient necessary for high-stability resistors and references.

Related Standards

Several other standards complement ASTM B84-07(2019) in the field of electrical resistance materials and measurement techniques:

• ASTM B258: Standard Specification for Silver-Coated Soft or Annealed Copper Wire for Electrical Purposes
• ASTM B193: Standard Test Method for Resistivity of Electrical Conductor Materials
• IEC 60468: Temperature Coefficient Measurement Standard for Resistors
• ASTM E2877: Guide for Digital Contact Thermometers for Calibration

By following ASTM B84-07(2019), manufacturers, laboratories, and quality control professionals ensure that the alloy wires they use or produce for precision resistors are accurately characterized for temperature-resistance behavior, supporting performance, reliability, and traceability in critical electronic applications.

Keywords: ASTM B84, temperature-resistance constants, alloy wires, precision resistors, resistance change, temperature coefficient, electrical measurement standards, resistor wire testing.

Standards Content (Sample)

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: B84 − 07 (Reapproved 2019)
Standard Test Method for
Temperature-Resistance Constants of Alloy Wires for
Precision Resistors
ThisstandardisissuedunderthefixeddesignationB84;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope the baths; and suitable means for measuring the resistance of
the specimen. Details of the apparatus are given in Sections 4
1.1 This test method covers determination of the change of
to 6.
resistance with temperature of alloy wires used for resistance
standards and precision resistors for electrical apparatus.
4. Baths
1.2 The values stated in SI units are to be regarded as
4.1 Baths for use from −65 to +15°C may consist of toluol,
standard. No other units of measurement are included in this
or equivalent.
standard.
4.2 Baths for use above 15 to 250°C may consist of
1.3 This standard does not purport to address all of the
chemically neutral oils with a low viscosity, having a flash
safety concerns, if any, associated with its use. It is the
point at least 50°C higher than the temperature of use.
responsibility of the user of this standard to establish appro-
4.3 Theliquidinthesebathsshallbeofsuchquantityandso
priate safety, health, and environmental practices and deter-
well stirred that the temperature in the region occupied by the
mine the applicability of regulatory limitations prior to use.
specimen and the thermometer will be uniform within 0.5°C
1.4 This international standard was developed in accor-
for any temperature between −65 and +100°C, and within
dance with internationally recognized principles on standard-
1.0°C for any temperature above 100 to 250°C. If the
ization established in the Decision on Principles for the
temperature range is less than 100°C, the uniformity of
Development of International Standards, Guides and Recom-
temperature shall be proportionately closer.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. NOTE 1—It is recommended that a solvent bath at room temperature
shall be used to rinse specimens before immersion in any temperature
bath.
2. Significance and Use
2.1 ProcedureAcovers the determination of the equation of 5. Temperature Measurement Apparatus
the curve relating resistance and temperature where the curve
5.1 The temperature shall be measured to an accuracy of
approximates a parabola. This test method may be used for
60.5°C, or 1% of temperature range, whichever is smaller.
wire of any metal or alloy over the temperature interval
appropriate to the material.
6. Resistance Measurement Apparatus
2.2 Procedure B covers the determination of the mean 6.1 The change of resistance of the specimen shall be
temperature coefficient of resistance for wire of any metal or
measuredbyapparatuscapableofdeterminingsuchchangesto
alloy over the temperature interval appropriate to the material. 0.001% of the resistance of the specimen if the temperature
range is 50°C or more. If the temperature range is less than
3. Apparatus 50°C, the accuracy of the resistance change measurements
shall be correspondingly greater.
3.1 The apparatus for making the test shall consist of one or
6.2 The connections from the specimen to the measuring
more baths for maintaining the specimen at the desired
temperatures; thermometers for measuring the temperatures of device shall be such that changes in the resistance of these
connections due to changes in their temperature do not
appreciably affect the measurement of the change in resistance
of the specimen.
This test method is under the jurisdiction of ASTM Committee B02 on
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
6.3 The temperature of the measuring apparatus shall not
B02.10 on Thermostat Metals and Electrical Resistance Heating Materials.
change during the test by an amount sufficient to introduce
Current edition approved April 1, 2019. Published April 2019. Originally
appreciable errors in the results. With apparatus of good
approvedin1931.Lastpreviouseditionapprovedin2013asB84–07(2013).DOI:
10.1520/B0084-07R19. quality, a change in 1°C in room temperature is allowable.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B84 − 07 (2019)
6.4 The test current shall not be of such a magnitude as to soldered, or welded to each end of the specimen for use as
produceanappreciablechangeinresistanceofthespecimenor terminals. The terminals shall be placed so that the measured
measuring apparatus due to the heating effect. To determine potential does not include the potential drop in the current
experimentally that the test current is not too large, the connections.
specimen may be immersed in a bath having a temperature at
9.3 In coils made of fine wire where there is not sufficient
which it has been found that the wire has a relatively large
rigidityinthecoilitselftofurnishasatisfactorysupportforthe
change in resistance with temperature. Apply the test current
terminals, short lengths of thin glass or ceramic rods may be
and maintain until the resistance of the specimen has become
found across the coil to act as struts and furnish an anchorage
constant. Then increase the current by 40% and maintain at
for the terminals.
thisvalueuntiltheresistancehasagainbecomeconstant.Ifthe
change in resistance is greater than 0.01%, the test current is
10. Preliminary Treatment of Specimen
too large and shall be reduced until the foregoing limitation is
10.1 The finished specimen shall be subjected to a baking
reached.
treatment as necessary to stabilize the resistance of the speci-
6.5 The measurements shall be made in such a way that the
men. For manganin the treatment shall be at 140 6 10°C
effectsofthermoelectromotiveforcesandparasiticcurrentsare
continuously for a period of 48 h.
avoided. When these effects are small, the resistance of the
specimen may be obtained by either of the following methods: 11. Procedure A
6.5.1 Obtain the galvanometer zero with the galvanometer
11.1 Connect the test specimen in the measuring circuit and
key open. Balance the bridge both with the direct and reversed
submerge entirely in the bath. For a check on the constancy of
connection of the battery, the average value of the two results
thespecimen,makeaninitialresistancemeasurementat25°C.
being the resistance of the specimen.
Raise the temperature of the bath or transfer the specimen to a
6.5.2 Obtain the zero of the galvanometer with the galva-
bath maintained constant at the highest temperature at which
nometer key closed and the battery key opened. A single
measurementsaretobemade.Whenthespecimenhasattained
balance of the bridge is then sufficient to obtain the resistance
a constant resistance, record the reading of the measuring
of the specimen.
device and the temperature of the bath.
11.2 Decrease the temperature of the test specimen to the
7. Sampling
next lower temperature either by cooling the bath and main-
7.1 Take one test specimen from each continuous length of
taining it constant at the next lower temperature, or by
the material to be tested.
removingthespecimentoanotherbathmaintainedatthelower
temperature. When the resistance of the specimen has become
8. Test Specimen
constant, again make observations of resistance and tempera-
8.1 The test specimen shall be of a length that will give a
ture.
resistance that can be measured to the required accuracy.
11.3 In this manner, make a series of determinations of the
8.2 If the wire is insulated, it may be wound in a circular,
change of resistance with temperature for the desired descend-
open coil not less than 50 mm in diameter.
ing temperature range, measurements being taken at intervals
of approximately 10% of the temperature range or any
8.3 If the wire is not insulated, it may be wound on an
temperature interval specified by agreement between producer
insulating form of a type that will not introduce strains in the
and consumer.
wire when subjected to temperature changes.
11.4 Test at not less than four temperatures.
8.4 The tension used in winding shall be no more than
sufficient to produce a neat coil of insulated wire or to prevent
11.5 Note the temperature of the measuring apparatus at
the touching of adjacent turns when bare wire is wound on an
frequent intervals during the test of each specimen.
insulating form.
12. Procedure B
8.5 For fine wires of sufficiently high-resistivity alloys,
straight wire specimens may be used. Precautions should be
12.1 See Section 11, except 11.4. Tests shall be made at not
taken to avoid the introduction of strains in the sample during
less than three temperatures, including 25°C.
preparation.
13. Resistance-Temperature Equation
9. Terminals
13.1 Express the results in terms of the constants in an
9.1 For specimens having a resistance so large that the equation of the following form:
resistance of the leads is negligible, a copper wire may be
R 5 R @11α~t 2 25!1β~t 2 25! # (1)
t 25
brazed,soldered,orweldedtoeachendofthespecimenforuse
where:
as a terminal. The resistance of the copper terminals shall be
R = resistanceofthespecimeninohmsattemperature,
less than 0.02% of the resistance of the specimen.
t
°C, t,
9.2 If the resistance of the specimen is less than 10 Ω,so
R = resistanceofthespecimeninohmsatthestandard
that it is necessary to use both current and potential terminals
temperature of 25°C,
in measuring the resistance, two copper wires may be brazed,
B84 − 07 (2019)
β 5 ∆R 1∆R /1 ∆ t (12)
~ ! ~ !
t = temperature of specimen, °C, and 1 2
NOTE 4—A useful alternative method of calculation is presented as
α and β = temperature-resistance constants of the material.
follows: The resistance-temperature equation is referred to 0°C, and
Temperature of maximum or minimum resistance
relative resistance values are used. For example, over the useful range
=25°C−(α⁄2β) from 15 to 35°C, the resistance-temperature curve of manganin is
parabolic and of the form:
NOTE 2—This equation will yield either a maximum or a minimum,
dependingonwhichexistsinthetemperaturerangeinquestion.However, P 5 P 1At1Bt (13)
t 0
this equation is normally used for those alloys such as manganin, having
where:
atemperature-resistancecurveapproximatingaparabolawithamaximum
P = %, ratio of the resistance of the
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