ASTM_B_84_-_07_2013.pdf

Designation:B8407(Reapproved 2013)Standard Test Method forTemperature-Resistance Constants of Alloy Wires forPrecision Resistors1This standard is issued under the fixed designation B84;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers determination of the change ofresistance with temperature of alloy wires used for resistancestandards and precision resistors for electrical apparatus.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateMaterial Safety Data Sheet(MSDS)for this product/materialas provided by the manufacturer,to establish appropriatesafety and health practices,and determine the applicability ofregulatory limitations prior to use.2.Significance and Use2.1 Procedure A covers the determination of the equation ofthe curve relating resistance and temperature where the curveapproximates a parabola.This test method may be used forwire of any metal or alloy over the temperature intervalappropriate to the material.2.2 Procedure B covers the determination of the meantemperature coefficient of resistance for wire of any metal oralloy over the temperature interval appropriate to the material.3.Apparatus3.1 The apparatus for making the test shall consist of one ormore baths for maintaining the specimen at the desiredtemperatures;thermometers for measuring the temperatures ofthe baths;and suitable means for measuring the resistance ofthe specimen.Details of the apparatus are given in Sections 4to 6.4.Baths4.1 Baths for use from 65 to+15C may consist of toluol,or equivalent.4.2 Baths for use above 15 to 250C may consist ofchemically neutral oils with a low viscosity,having a flashpoint at least 50C higher than the temperature of use.4.3 The liquid in these baths shall be of such quantity and sowell stirred that the temperature in the region occupied by thespecimen and the thermometer will be uniform within 0.5Cfor any temperature between 65 and+100C,and within1.0C for any temperature above 100 to 250C.If the tempera-ture range is less than 100C,the uniformity of temperatureshall be proportionately closer.NOTE1It is recommended that a solvent bath at room temperatureshall be used to rinse specimens before immersion in any temperaturebath.5.Temperature Measurement Apparatus5.1 The temperature shall be measured to an accuracy of60.5C,or 1%of temperature range,whichever is smaller.6.Resistance Measurement Apparatus6.1 The change of resistance of the specimen shall bemeasured by apparatus capable of determining such changes to0.001%of the resistance of the specimen if the temperaturerange is 50C or more.If the temperature range is less than50C,the accuracy of the resistance change measurementsshall be correspondingly greater.6.2 The connections from the specimen to the measuringdevice shall be such that changes in the resistance of theseconnections due to changes in their temperature do notappreciably affect the measurement of the change in resistanceof the specimen.6.3 The temperature of the measuring apparatus shall notchange during the test by an amount sufficient to introduceappreciable errors in the results.With apparatus of goodquality,a change in 1C in room temperature is allowable.6.4 The test current shall not be of such a magnitude as toproduce an appreciable change in resistance of the specimen ormeasuring apparatus due to the heating effect.To determineexperimentally that the test current is not too large,the1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.10 on Thermostat Metals and Electrical Resistance Heating Materials.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 1931.Last previous edition approved in 2007 as B84 07.DOI:10.1520/B0084-07R13.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 specimen may be immersed in a bath having a temperature atwhich it has been found that the wire has a relatively largechange in resistance with temperature.Apply the test currentand maintain until the resistance of the specimen has becomeconstant.Then increase the current by 40%and maintain atthis value until the resistance has again become constant.If thechange in resistance is greater than 0.01%,the test current istoo large and shall be reduced until the foregoing limitation isreached.6.5 The measurements shall be made in such a way that theeffects of t