1、Designation: B114 07 (Reapproved 2013)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 appropriateMaterial Safety Data Sheet (MSDS) for this product/m
5、aterialas provided by the manufacturer, to establish appropriatesafety and health practices, and determine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B84 Test Method for Temperature-Resistance Constants ofAlloy Wires for Precision Resistors3. S
6、ignificance 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.4. Test Specimen4.1 The test
7、 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. Terminals5.1 A current terminal shall
8、 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 less than two times the width o
9、f 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.NOTE 2The ears shall be cut so
10、 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 jointed to the specimen.6. Prel
11、iminary 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 dip in a nitric acidsolution (5
12、0 %) 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 is under the jurisdiction of
13、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 1938. Last previous edition approved in 2007 as B1
14、14 07. DOI:10.1520/B0114-07R13.2For 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 ASTM website.Copyright ASTM International,
15、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1temperature, thermometers for measuring the temperatures ofthe baths, and suitable means for measuring the resistance ofthe specimen.8. Baths8.1 Each bath shall consist of chemically neutral oil. The oilshall be of s
16、uch 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 bath at any time during the test at any temperature leve
17、lshall 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 calibratedtemperature measuring device of suitable precision and accu-racy. T
18、he 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 resistance of the specimen shall bemeasured by apparatus capabl
19、e 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 during the test by an amount sufficient to introduceapprecia
20、ble 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 apparatus due to the heating effect. The dimensionsof the speci
21、men 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 has been found that the sheet has a relatively largechang
22、e 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 againbecome constant. If the change in resistance is greater tha
23、n0.001 %, 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 effects are small, the resistance of thespecimen when me
24、asured 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 battery, the average value of the two resultsbeing the resista
25、nce 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. Procedure11.1 Connect the test specimen in the measuring c
26、ircuit 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 thehighest temperature at which measurements are to be m
27、ade.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 and main-taining it constant at the next lower temperatu
28、re, 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 determinations of thechange of resistance with temperature for the de
29、sired 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 required. If an independent check is to bemade, make observation
30、s of at least five temperatures. Forplotting a curve, six or more observations are generally made.FIG. 1 Test Specimen Showing Terminal ConnectionsB114 07 (2013)211.5 Note the temperature of the measuring apparatus atfrequent intervals during the test of each specimen.12. Resistance-Temperature Equa
31、tion12.1 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 standardtemperature of 25C,t = temperature of specimen, C, and and
32、= 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 equation is normally used for those alloys such as manganin
33、, 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-separatedtemperatures, inserting the values of Rtand t in the precedingse
34、ction 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 a curve from the observed values ofresistance and tempe
35、rature, 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 but satisfying the followingrelation:K25 2 t1! 5 t22 25 5
36、 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 = 1 or 2 or 3, respectively.13.3 If R1is the resistance a
37、t 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 measuring the actual resistances at the differenttemperatures
38、, 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 going from 25C to t2. That is:R15 R12 R25!/R25(7)andR25
39、 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 referred to 0C, andrelative resistance values are used. F
40、or 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,% ,P0= ratio of the resistance of the specimen at 0C to
41、 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 sample to that of a stable resistor of known character-is
42、tics 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, and t4between 15 and 35C, and the corresponding ratiosof
43、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 t12 t31tr12t1!G (14)B 5P32 P1t32 t11P42 P1t42 t12 2P22 P
44、1t22 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 following information:14.1.1 Identification of specimen,14.1.
45、2 Description of material,14.1.3 Total length of specimen,14.1.4 Approximate resistance and distance between poten-tial terminals,B114 07 (2013)314.1.5 Tabular list of resistances or changes in resistanceand temperatures in the order taken,14.1.6 Temperature of measuring apparatus and room atstart a
46、nd 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 15.15. Record15.1 The results shall be reported in one of
47、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 Th
48、e constants, , , etc., in a resistance-temperatureequation may be calculated from the data and recorded as theconstants of the temperature-resistance curve.16. Precision and Bias16.1 The instrumentation and operators skill play a largepart in the precision and bias attainable. There are no dataavail
49、able to determine a precision and bias figure for this testmethod.17. Keywords17.1 resistance change; resistance constants; resistors; sheetresistors; shunts; temperature coefficient; temperature resis-tanceTABLE 1 Illustrative Form for Reporting Test Data and CalculationsNOTE 1The following table, with test values inserted for purpose of illustration, is only a suggested form for recording test data and calculations ontemperature-resistance characteristics.Apparat
