1、Designation: B114 07 (Reapproved 2018)Standard Test Method forTemperature-Resistance Constants of Sheet Materials forShunts and Precision Resistors1This standard is issued under the fixed designation B114; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the changeof resistance with temperatu
3、re of sheet materials used forshunts and precision resistors for electrical apparatus. It isapplicable to materials normally used in the temperature rangeof from 0 to 80C.1.2 The values stated in inch-pound units are to be regardedas the standard. The metric equivalents of inch-pound unitsmay be app
4、roximate.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 appropriateSafety Data Sheet (SDS) for this product/material as
5、 providedby the manufacturer, to establish appropriate safety, health,and environmental practices, and determine the applicabilityof regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization establi
6、shed in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B84 Test Method for Temperature-Resistance Constants ofAlloy Wire
7、s for Precision Resistors3. Significance and Use3.1 This test method covers the determination of the changeof resistance with temperature for precision resistors andshunts made from sheet materials.3.2 Materials normally used in the temperature range from 0to 80C may be tested using this test method
8、.4. Test Specimen4.1 The test specimen shall be of such dimensions that itselectrical resistance can be measured to the required accuracy.NOTE 1Measurements are simplified if the specimen has a resistanceof 0.01 or more. The specimen may be bent in the form of a “U” tofacilitate handling.5. Terminal
9、s5.1 A current terminal shall be attached to each end of thespecimen. These terminals shall be either soldered or clampedin such a manner that there will be no change of currentdistribution in the specimen during the test.5.2 Potential terminals, one at each end, shall be located ata distance not le
10、ss than two times the width of the specimenfrom the current terminals. These terminals shall be attached atthe center of the width of the specimen either by soldering toears cut out of the specimen (Note 2) as shown in Fig. 1 or byclamps, each of which presses a single sharp point into thematerial.N
11、OTE 2The ears shall be cut so that they are about12 in. (12.7 mm)in length and18 in. (3.2 mm) in width. The cut shall be clean and free fromslivers at the junction of the ear and the specimen. Before cutting the ears,it is desirable to drill two small holes with a sharp drill where the ear willbe jo
12、inted to the specimen.6. Preliminary Treatment for Manganin Samples6.1 In the case of manganin materials, after all the mechani-cal work has been finished, the specimen shall be given oneheat treatment of 48 h at 140 6 5.0C and then cooled to roomtemperature.6.2 The specimen shall then be given a di
13、p in a nitric acidsolution (50 %) to remove the copper film (which can bejudged by the color of the specimen) and then thoroughlyscrubbed in running water.7. Apparatus7.1 The apparatus for making the test shall consist of one ormore baths for maintaining the specimen at the desired1This test method
14、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 April 1, 2018. Published April 2018. Originallyapproved in 1938. Last previo
15、us edition approved in 2013 as B114 07 (2013).DOI: 10.1520/B0114-07R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe AST
16、M website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopmen
17、t of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1temperature, thermometers for measuring the temperatures ofthe baths, and suitable means for measuring the resistance ofthe specimen.8. Baths8.1 Each bath shal
18、l consist of chemically neutral oil. The oilshall be of such quantity and so well stirred that the tempera-ture in the region occupied by the specimen and the thermom-eter shall be uniform within 0.2C for any temperature between0 and 80C.8.2 In an automatically controlled bath, the temperature ofthe
19、 bath at any time during the test at any temperature levelshall not differ from its mean temperature by more than 0.2C.In a manually controlled bath, the rate of change of tempera-ture shall not exceed 0.2C/min.9. Temperature Measurement9.1 The temperature shall be measured by a calibratedtemperatur
20、e measuring device of suitable precision and accu-racy. The thermometer shall have sufficient sensitivity toindicate temperature changes of 0.1C. It shall be sufficientlyaccurate to measure temperature differences to 0.2C in therange from 0 to 80C.10. Resistance Measurements10.1 The change of resist
21、ance of the specimen shall bemeasured by apparatus capable of determining such changes to0.001 % of the resistance of the specimen. A Kelvin doublebridge, digital ohmmeter, or equivalent is suitable for thispurpose (see Appendix X1).10.2 The temperature of the measuring apparatus shall notchange dur
22、ing the test by an amount sufficient to introduceappreciable errors in the results. With apparatus of goodquality, a change of 1C in its temperature is allowable.10.3 The test current shall not be of such a magnitude as toproduce an appreciable change in resistance of the specimen ormeasuring appara
23、tus due to the heating effect. The dimensionsof the specimen should be such that the power dissipated shallnot exceed 0.02 W/in.2(0.003 W/cm2) of exposed surface. Todetermine experimentally that the test current is not too large,the specimen may be immersed in a bath having a temperatureat which it
24、has been found that the sheet has a relatively largechange in resistance with temperature. The test current shall beapplied and maintained until the resistance of the specimen hasbecome constant. The current shall then be increased by 40 %and maintained at this value until the resistance has againbe
25、come constant. If the change in resistance is greater than0.001 %, the test current is too large and shall be reduced untilthe foregoing limitation is reached.10.4 The measurements shall be made in such a way that theeffects of thermoelectromotive forces and parasitic currents areavoided. When these
26、 effects are small, the resistance of thespecimen when measured by a Kelvin bridge may be obtainedby either of two methods. In the first method, the galvanometerzero shall be obtained with the galvanometer key open. Thebridge shall be balanced both with the direct and reversedconnection of the batte
27、ry, the average value of the two resultsbeing the resistance of the specimen. In the second method, thezero of the galvanometer shall be obtained with the galvanom-eter key closed and the battery key open. A single balance ofthe bridge is then sufficient to obtain the resistance of thespecimen.11. P
28、rocedure11.1 Connect the test specimen in the measuring circuit andsubmerge entirely in the oil bath. For a check on the constancyof the specimen, make an initial resistance measurement atroom temperature. Raise the temperature of the oil bath ortransfer the specimen to a bath maintained constant at
29、 thehighest temperature at which measurements are to be made.When the test specimen has attained a constant resistance,record the reading of the measuring device and the temperatureof the bath.11.2 Decrease the temperature of the test specimen to thenext lower temperatures either by cooling the bath
30、 and main-taining it constant at the next lower temperature, or byremoving the specimen to another bath maintained at the lowertemperature. When the resistance of the specimen has becomeconstant, again make observations of resistance and tempera-ture.11.3 In this manner make a series of determinatio
31、ns of thechange of resistance with temperature for the desired descend-ing temperature range.11.4 Take measurements at a sufficient number of tempera-tures to determine the characteristics of the material. In order tocalculate a resistance-temperature equation, tests at threetemperatures are require
32、d. If an independent check is to bemade, make observations of at least five temperatures. Forplotting a curve, six or more observations are generally made.FIG. 1 Test Specimen Showing Terminal ConnectionsB114 07 (2018)211.5 Note the temperature of the measuring apparatus atfrequent intervals during
33、the test of each specimen.12. Resistance-Temperature Equation12.1 Express the results in terms of the constants in anequation of the following form:Rt5 R2511t 2 25!1t 2 25!2# (1)where:Rt= resistance of the specimen in ohms at temperature,C, t,R25= resistance of the specimen in ohms at the standardte
34、mperature of 25C,t = temperature of specimen, C, and and = temperature-resistance constants of the material.Temperature of maximum or minimum resistance=25C(2)NOTE 3This equation will yield either a maximum or a minimum,depending on which exists in the temperature range in question. However,this equ
35、ation is normally used for those alloys such as manganin, havinga temperature-resistance curve approximating a parabola with a maximumnear room temperature.13. Calculation of Constants13.1 The values of , , and R25may be determined byselecting the measured values of Rtat three well-separatedtemperat
36、ures, inserting the values of Rtand t in the precedingsection equation to form three equations, and solving simulta-neously the three equations for R25, , and .13.2 When the measurements have not been made at exactly25C, or at other suitable temperatures, the calculation may besimplified by plotting
37、 a curve from the observed values ofresistance and temperature, from which curve R25may be readdirectly. Two additional points may then be selected on thecurve, preferably one at t1, at least 5C below the referencetemperature of 25C, and a second temperature, t2near thehighest temperature measured b
38、ut satisfying the followingrelation:K25 2 t1! 5 t22 25 5 Kt (2)where K is, for ease of calculation, generally taken as aninteger.NOTE 4ExampleIf t1is 10C below the reference temperature thent2should be 10 or 20 or 30C etc., above the reference temperature forgreatest ease of calculation, so that K =
39、 1 or 2 or 3, respectively.13.3 If R1is the resistance at the temperature t1, and R2isthe resistance at the temperature t2, then: 5 R22 R25! 2 K2R12 R25!#/R25KK11!t (3) 5 KR12 R25!1R22 R25!#/R25KK11!t!2(4)If K = 1, this simplifies to: 5 R22 R1!/2R25t (5) 5 R11R22 2R25!/2R25t!2(6)If, instead of measu
40、ring the actual resistances at the differenttemperatures, the change in resistance relative to the resistanceat 25C is measured, the above equations take a slightlydifferent form, as follows: Let R1represent the change inresistance in ohms per ohm in going from 25C to t1, and R2the similar change in
41、 going from 25C to t2. That is:R15 R12 R25!/R25(7)andR25 R22 R25!/R25(8)Then 5 R22 K2R1!/KK11!t (9) 5 KR11R2!/KK11!t!2(10)If K = 1, this simplifies to: 5 R22 R1!/2t (11) 5 R11R2!/1t!2(12)NOTE 5A useful alternative method of calculation is presented asfollows: The resistance-temperature equation is r
42、eferred to 0C, andrelative resistance values are used. For example, over the useful rangefrom 15 to 35C, the resistance-temperature curve of manganin isparabolic and of the form:Pt5 P01At1Bt2(13)where:Pt= ratio of the resistance of the specimen at t C to theresistance of the standard resistor at 25C
43、,% ,P0= ratio of the resistance of the specimen at 0C to theresistance of the standard resistor at 25C, %, andA and B are constants calculated from resistance measure-ments made at different temperatures. One method of measure-ment used in production testing is to compare the resistance ofthe test s
44、ample to that of a stable resistor of known character-istics maintained at reference temperature 25C. The resistanceis approximately the same as the test sample and measurementsusually are made directly in percentages (for example,100.008 %). If measurements are made at four temperatures t1,t2,t3, a
45、nd t4between 15 and 35C, and the corresponding ratiosof test sample resistance to standard resistor are measured inpercentages as P1,P2,P3, and P4, then the constants A and B,the peak temperature, and temperature coefficient may becalculated from the following equations:A 512FP32 P1t32 t11P22 P1t42
46、t12 t31tr12t1!G (14)B 5P32 P1t32 t11P42 P1t42 t12 2P22 P1t22 t1t31t42 2t2(15)The peak temperature is (A/2B) and the temperature coeffi-cient between temperature t and the peak temperature in per-cent per degree Celsius is (A +2Bt)/2. Then 5 A150B!/100 (16) 5 B/100 (17)14. Report14.1 Report the follo
47、wing information:14.1.1 Identification of specimen,14.1.2 Description of material,14.1.3 Total length of specimen,14.1.4 Approximate resistance and distance between poten-tial terminals,B114 07 (2018)314.1.5 Tabular list of resistances or changes in resistanceand temperatures in the order taken,14.1
48、.6 Temperature of measuring apparatus and room atstart and finish of the test,14.1.7 Temperature of the specimen at which the change ofresistance with temperature is zero (“peak temperature”), ifsuch occurs within the measured range, and14.1.8 Results expressed in one of the forms given inSection 15
49、.15. Record15.1 The results shall be reported in one of the followingforms and recorded on a data sheet similar to that shown inTable 1 and Fig. 2.15.1.1 The maximum percentage change within the tem-perature range, or15.1.2 A curve, plotted with temperature as abscissas, andthe percentage or parts per million change in resistance asordinates, or15.1.3 The constants, , , etc., in a resistance-temperatureequation may be calculated from the data and recorded as thecons
