1、Designation: B 114 07Standard Test Method forTemperature-Resistance Constants of Sheet Materials forShunts and Precision Resistors1This standard is issued under the fixed designation B 114; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the changeof resistance with temperature of sheet mat
3、erials 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 approximate.1.3 Th
4、is 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 provi
5、ded by the manufacturer, to establish appropriatesafety and health practices, and determine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 84 Test Method for Temperature-Resistance Constants ofAlloy Wires for Precision Resistors3. Significance an
6、d 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 specimen shal
7、l 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 V or more. The specimen may be bent in the form of a “U” tofacilitate handling.5. Terminals5.1 A current terminal shall be attached
8、 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 of the specim
9、enfrom 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 that they a
10、re 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. Preliminary Trea
11、tment 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 (50 %) to remo
12、ve 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 desiredtemperature, thermometers for measuring the temperatures of
13、the 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 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
14、 for any temperature between0 and 80C.1This 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, 2007. Publish
15、ed June 2007. Originallyapproved in 1938. Last previous edition approved in 2001 as B 114 90 (2001).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 Do
16、cument Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8.2 In an automatically controlled bath, the temperature ofthe bath at any time during the test at any temperature levelshall not differ from its
17、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. The thermometer shall have s
18、ufficient 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 capable of determining such chang
19、es 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 introduceappreciable errors in the results.
20、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 specimen should be such that the
21、 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 largechange in resistance with temper
22、ature. 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 than0.001 %, the test current
23、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 measured by a Kelvin bridge m
24、ay 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 resistance of the specimen. In the
25、 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 circuit andsubmerge entirely
26、 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 made.When the test specimen
27、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 temperature, or byremoving the speci
28、men 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 desired descend-ing temperatu
29、re 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 observations of at least five temperat
30、ures. Forplotting a curve, six or more observations are generally made.11.5 Note the temperature of the measuring apparatus atfrequent intervals during the test of each specimen.12. Resistance-Temperature Equation12.1 Express the results in terms of the constants in anequation of the following form:
31、Rt5 R251 1at 2 25! 1bt 2 25!2# (1)where:Rt= resistance of the specimen in ohms at tempera-ture, C, t,FIG. 1 Test Specimen Showing Terminal ConnectionsB114072R25= resistance of the specimen in ohms at the stan-dard temperature of 25C,t = temperature of specimen, C, anda and b = temperature-resistance
32、 constants of the material.Temperature of maximum or minimum resistance=25C(a/2b)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, havinga temperature-
33、resistance curve approximating a parabola with a maximumnear room temperature.13. Calculation of Constants13.1 The values of a, b, and R25may be determined byselecting the measured values of Rtat three well-separatedtemperatures, inserting the values of Rtand t in the precedingsection equation to fo
34、rm three equations, and solving simulta-neously the three equations for R25, a, and b.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 temperature, from which
35、 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:K 25 2 t1! 5 t22 25 5 KDt (2)where K i
36、s, 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 at the temperatur
37、e t1, and R2isthe resistance at the temperature t2, then:a5R22 R25! 2 K2R12 R25!#/R25K K 1 1!Dt (3)b5K R12 R25! 1 R22 R25!#/R25K K 1 1!Dt!2(4)If K = 1, this simplifies to:a5R22 R1!/2 R25Dt (5)b5R11 R22 2R25!/2R25Dt!2(6)If, instead of measuring the actual resistances at the differenttemperatures, the
38、 change in resistance relative to the resistanceat 25C is measured, the above equations take a slightlydifferent form, as follows: Let DR1represent the change inresistance in ohms per ohm in going from 25C to t1, and DR2the similar change in going from 25C to t2. That is:DR15 R12 R25!/R25(7)andDR25
39、R22 R25!/R25(8)Thena5DR22 K2DR1!/KK 1 1!Dt (9)b5KDR11DR2!/KK 1 1!Dt!2(10)If K = 1, this simplifies to:a5DR22DR1!/2Dt (11)b5DR11DR2!/1Dt!2(12)NOTE 5A useful alternative method of calculation is presented asfollows: The resistance-temperature equation is referred to 0C, andrelative resistance values a
40、re used. For example, over the useful rangefrom 15 to 35C, the resistance-temperature curve of manganin isparabolic and of the form:Pt5 P01 At 1 Bt2(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 spec
41、imen at 0C to theresistance of the standard resistor at 25C, %, andA and B are constants calculated from resistance measurementsmade at different temperatures. One method of measurementused in production testing is to compare the resistance of thetest sample to that of a stable resistor of known cha
42、racteristicsmaintained at reference temperature 25C. The resistance isapproximately 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 ra
43、tiosof 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 t31 tr1 2t1!G(14)B 5P32 P1t32 t11P42 P1t42 t1
44、2 2P22 P1t22 t1t31 t42 2t2(15)The peak temperature is (A/2B) and the temperature coefficient betweentemperature t and the peak temperature in percent per degree Celsius is (A+2Bt)/2. Thena5A 1 50B!/100 (16)b5B/100 (17)14. Report14.1 Report the following information:14.1.1 Identification of specimen,
45、14.1.2 Description of material,14.1.3 Total length of specimen,14.1.4 Approximate resistance and distance between poten-tial terminals,B11407314.1.5 Tabular list of resistances or changes in resistanceand temperatures in the order taken,14.1.6 Temperature of measuring apparatus and room atstart and
46、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 the
47、 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, orTABLE 1 Illu
48、strative 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.Apparatus Kelvin bridge for comparing the specimen with s
49、tandard resistorStandard resistor No. 38472, 0.0100000 V made by Richard RoeRatio coils A = 1000; B = 1000Material Manganin, Specimen No. 1. From Shipment Received Jan. 14, 1937Maker John DoeSize 0.020 by 3 by 72 in. Approximate Resistance of Specimen 0.01 VRECORD OF TESTTimeTemperature, C Bridge ReadingResistance ofSpecimen, VChange inResistance,AppmRoom Standard Specimen Plus Minus Average10:00 25.0 25.0 25.0 1000.00 1000.02 1000.01 0.0100001B.10:30 25.0 25.0 80.2 999.60 999.62 999.61 0.0099961 39010:45 25.0
