ASTM B84 - 07 (2025) 精密电阻器用合金丝温度电阻常数的标准试验方法

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Designation: B84 −07 (Reapproved 2025)

Standard Test Method for

Temperature-Resistance Constants of Alloy Wires for

Precision Resistors

This standard is issued under the ﬁxed designation B84; 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.

1. 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 appro-

priate safety, health, and environmental practices and deter-

mine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accor-

dance with internationally recognized principles on standard-

ization established in the Decision on Principles for the

Development of International Standards, Guides and Recom-

mendations issued by the World Trade Organization Technical

Barriers to Trade (TBT) Committee.

2. 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.

3. Apparatus

3.1 The apparatus for making the test shall consist of one or

more baths for maintaining the specimen at the desired

temperatures; thermometers for measuring the temperatures of

the baths; and suitable means for measuring the resistance of

the specimen. Details of the apparatus are given in Sections 4

to 6.

4. Baths

4.1 Baths for use from −65 °C to +15 °C may consist of

toluol, or equivalent.

4.2 Baths for use above 15 °C to 250 °C may consist of

chemically neutral oils with a low viscosity, having a ﬂash

point at least 50 °C higher than the temperature of use.

4.3 The liquid in these baths shall be of such quantity and so

well stirred that the temperature in the region occupied by the

specimen and the thermometer will be uniform within 0.5 °C

for any temperature between −65 °C and +100 °C, and within

1.0 °C for any temperature above 100 °C to 250 °C. If the

temperature range is less than 100 °C, the uniformity of

temperature shall be proportionately closer.

NOTE 1—It is recommended that a solvent bath at room temperature

shall be used to rinse specimens before immersion in any temperature

bath.

5. Temperature Measurement Apparatus

5.1 The temperature shall be measured to an accuracy of

60.5 °C, or 1 % of temperature range, whichever is smaller.

6. Resistance Measurement Apparatus

6.1 The change of resistance of the specimen shall be

measured by apparatus capable of determining such changes to

0.001 % of the resistance of the specimen if the temperature

range is 50 °C or more. If the temperature range is less than

50 °C, the accuracy of the resistance change measurements

shall be correspondingly greater.

6.2 The connections from the specimen to the measuring

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.

6.3 The temperature of the measuring apparatus shall not

change during the test by an amount sufficient to introduce

appreciable errors in the results. With apparatus of good

quality, a change in 1 °C in room temperature is allowable.

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 and Electrical Resistance Heating Materials.

Current edition approved July 1, 2025. Published July 2025. Originally approved

in 1931. Last previous edition approved in 2019 as B84 – 07 (2019). DOI:

10.1520/B0084-07R25.

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.

6.4 The test current shall not be of such a magnitude as to

produce an appreciable change in resistance of the specimen or

measuring apparatus due to the heating effect. To determine

experimentally that the test current is not too large, the

specimen may be immersed in a bath having a temperature at

which it has been found that the wire has a relatively large

change in resistance with temperature. Apply the test current

and maintain until the resistance of the specimen has become

constant. Then increase the current by 40 % and maintain at

this value until the resistance has again become constant. If the

change in resistance is greater than 0.01 %, the test current is

too large and shall be reduced until the foregoing limitation is

reached.

6.5 The measurements shall be made in such a way that the

effects of thermoelectromotive forces and parasitic currents are

avoided. When these effects are small, the resistance of the

specimen may be obtained by either of the following methods:

6.5.1 Obtain the galvanometer zero with the galvanometer

key open. Balance the bridge both with the direct and reversed

connection of the battery, the average value of the two results

being the resistance of the specimen.

6.5.2 Obtain the zero of the galvanometer with the galva-

nometer key closed and the battery key opened. A single

balance of the bridge is then sufficient to obtain the resistance

of the specimen.

7. Sampling

7.1 Take one test specimen from each continuous length of

the material to be tested.

8. Test Specimen

8.1 The test specimen shall be of a length that will give a

resistance that can be measured to the required accuracy.

8.2 If the wire is insulated, it may be wound in a circular,

open coil not less than 50 mm in diameter.

8.3 If the wire is not insulated, it may be wound on an

insulating form of a type that will not introduce strains in the

wire when subjected to temperature changes.

8.4 The tension used in winding shall be no more than

sufficient to produce a neat coil of insulated wire or to prevent

the touching of adjacent turns when bare wire is wound on an

insulating form.

8.5 For ﬁne wires of sufficiently high-resistivity alloys,

straight wire specimens may be used. Precautions should be

taken to avoid the introduction of strains in the sample during

preparation.

9. Terminals

9.1 For specimens having a resistance so large that the

resistance of the leads is negligible, a copper wire may be

brazed, soldered, or welded to each end of the specimen for use

as a terminal. The resistance of the copper terminals shall be

less than 0.02 % of the resistance of the specimen.

9.2 If the resistance of the specimen is less than 10 Ω, so

that it is necessary to use both current and potential terminals

in measuring the resistance, two copper wires may be brazed,

soldered, or welded to each end of the specimen for use as

terminals. The terminals shall be placed so that the measured

potential does not include the potential drop in the current

connections.

9.3 In coils made of ﬁne wire where there is not sufficient

rigidity in the coil itself to furnish a satisfactory support for the

terminals, short lengths of thin glass or ceramic rods may be

found across the coil to act as struts and furnish an anchorage

for the terminals.

10. Preliminary Treatment of Specimen

10.1 The ﬁnished specimen shall be subjected to a baking

treatment as necessary to stabilize the resistance of the speci-

men. For manganin the treatment shall be at 140 °C 610 °C

continuously for a period of 48 h.

11. Procedure A

11.1 Connect the test specimen in the measuring circuit and

submerge entirely in the bath. For a check on the constancy of

the specimen, make an initial resistance measurement at 25 °C.

Raise the temperature of the bath or transfer the specimen to a

bath maintained constant at the highest temperature at which

measurements are to be made. When the specimen has attained

a constant resistance, record the reading of the measuring

device and the temperature of the bath.

11.2 Decrease the temperature of the test specimen to the

next lower temperature either by cooling the bath and main-

taining it constant at the next lower temperature, or by

removing the specimen to another bath maintained at the lower

temperature. When the resistance of the specimen has become

constant, again make observations of resistance and tempera-

ture.

11.3 In this manner, make a series of determinations of the

change of resistance with temperature for the desired descend-

ing temperature range, measurements being taken at intervals

of approximately 10 % of the temperature range or any

temperature interval speciﬁed by agreement between producer

and consumer.

11.4 Test at not less than four temperatures.

11.5 Note the temperature of the measuring apparatus at

frequent intervals during the test of each specimen.

12. Procedure B

12.1 See Section 11, except 11.4. Tests shall be made at not

less than three temperatures, including 25 °C.

13. Resistance-Temperature Equation

13.1 Express the results in terms of the constants in an

equation of the following form:

11α

t225

1β

t225

(1)

where:

= resistance of the specimen in ohms at temperature,

°C, t,

= resistance of the specimen in ohms at the standard

temperature of 25 °C,

B84 − 07 (2025)

t= temperature of specimen, °C, and

αand β= temperature-resistance constants of the material.

Temperature of maximum or minimum resistance

= 25°C − (α⁄2β)

NOTE 2—This equation will yield either a maximum or a minimum,

depending on which exists in the temperature range in question. However,

this equation is normally used for those alloys such as manganin, having

a temperature-resistance curve approximating a parabola with a maximum

near room temperature.

14. Calculation of Constants

14.1 The values of α,β, and R

may be determined by

selecting the measured values of R

at three well-separated

temperatures, inserting the values of R

and tin the above

equation to form three equations, and solving simultaneously

the three equations for R

,α, and β.

14.2 When the measurements have not been made at exactly

25 °C, or at other suitable temperatures, the calculation may be

simpliﬁed by plotting a curve from the observed values of

resistance and temperature, from which curve R

may be read

directly. Two additional points may then be selected on the

curve, preferably one at t

, at least 5 °C below the reference

temperature of 25 °C, and a second temperature, t

near the

highest temperature measured but satisfying the following

relation:

25 2t

225 5K∆t(2)

where Kis, for ease of calculation, generally taken as an

integer.

NOTE 3—Example: If t

is 10 °C below the reference temperature then

should be 10 °C or 20 °C or 30 °C etc., above the reference temperature

for greatest ease of calculation, so that K= 1 or 2 or 3, respectively.

14.3 If R

is the resistance at the temperature t

, and R

the resistance at the temperature t

, then:

α5

K11

∆t(3)

β5

K11

∆t

(4)

If K= 1, this simpliﬁes to:

α5

/2R

∆t(5)

β5

22R

/2R

∆t

(6)

If, instead of measuring the actual resistances at the different

temperatures, the change in resistance relative to the resistance

at 25 °C is measured, the above equations take a slightly

different form, as follows: Let ∆R

represent the change in

resistance in ohms per ohm in going from 25 °C to t

, and ∆R

the similar change in going from 25 °C to t

. That is:

∆R

(7)

and

∆R

(8)

Then

α5

∆R

K11

∆t(9)

β5

K∆R

1∆R

K11

∆t

(10)

If K= 1, this simpliﬁes to:

α5

2∆R

/2∆t(11)

β5

∆R

1∆R

∆t

(12)

NOTE 4—A useful alternative method of calculation is presented as

follows: The resistance-temperature equation is referred to 0 °C, and

relative resistance values are used. For example, over the useful range

from 15 °C to 35 °C, the resistance-temperature curve of manganin is

parabolic and of the form:

1At1Bt

(13)

where:

= %, ratio of the resistance of the specimen at t°C to the resistance

of the standard resistor at 25 °C, expressed in percent,

= %, ratio of the resistance of the specimen at 0 °C to the resistance

of the standard resistor at 25 °C, expressed in percent, and

Aand Bare constants calculated from resistance measurements made at

different temperatures. One method of measurement used in production

testing is to compare the resistance of the test sample to that of a stable

resistor of known characteristics maintained at reference temperature

25 °C. The resistance is approximately the same as the test sample and

measurements usually are made directly in percentages (for example,

100.008 %). If measurements are made at four temperatures t

, t

,and

between 15 °C and 35 °C, and the corresponding ratios of test sample

resistance to standard resistor are measured in percentages as P

, P

and P

, then the constants Aand B, the peak temperature, and temperature

coefficient may be calculated from the following equations:

A51

12t

(14)

22P

22t

(15)

The peak temperature is − (A/2B) and the temperature coefficient be-

tween temperature tand the peak temperature in percent per degree

Celsius is (A+ 2Bt)/2. Then

α5

A150B

/100 (16)

β5B/100 (17)

15. Procedure A—Report

15.1 Report the following information:

15.1.1 Identiﬁcation of specimen,

15.1.2 Description of material and its insulation,

15.1.3 Length of wire in specimen and approximate

resistance,

15.1.4 Tabular list of resistances and temperatures in the

order taken,

15.1.5 Temperature of measuring apparatus and room at

start and ﬁnish of test,

15.1.6 Values of tand ∆Rused in calculating αand β,

15.1.7 Values calculated for the temperature-resistance con-

stants αand β, and

15.1.8 Temperature of the specimen at which the change of

resistance with temperature is zero, if such occurs within the

measured range.

16. Procedure B—Report

16.1 Report the following information:

16.1.1 Identiﬁcation of specimen,

16.1.2 Description of material and its insulation,

16.1.3 Length of wire in specimen and approximate

resistance,

16.1.4 Tabular list of resistance and temperatures in the

order taken,

B84 − 07 (2025)

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标签： #合金 #标准试验 #试验方法

摘要：

ASTM B84 - 07 (2025) 是一项由美国材料与试验协会发布的标准试验方法，专门用于测定精密电阻器用合金丝的电阻温度常数。该标准适用于制造精密电阻器所需的金属合金丝材，通过规定统一的测试条件与计算程序，评估合金丝在温度变化下电阻值的相对稳定性，即温度电阻常数。这一参数对于确保电阻器在精密仪器、电子电路及计量设备中的长期可靠性与温度补偿性能至关重要。标准详细描述了试验装置、试样制备、测试温度范围、电阻测量步骤以及数据处理方法，旨在帮助用户准确、可重复地获得合金丝的温度系数特性。该方法对

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