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BELL SYSTEM TECHNICAL JOURNAL 



TABLE III 

 Determination of K at 2,000 Cycles 



\ n 



Final value of K 1.00032 ± .00003.* 



d = deviation from mean 



Av. 1.00026 

 a- .000035 

 3<r .00010 



The resistance of the coils used for r was determined before and after 

 each set of tests. Although the best grade of commercial resistance 

 wire was used in making up the resistance coils they were found to have 

 an appreciable temperature coefficient for work of such high precision, 

 and due allowance had to be made for temperature variations in the 

 computation of the results. The temperature coefficients of the 

 resistances used are contained in Table IV. 



TABLE IV 



Temperature Coefficients of Resistance Coils Used as r 



Nominal Resistance Temp. Coeff. % per ° C. at 



of Coil 20° C. 



500 ohms -.0016 



400 " +.0083 



690 " +.0013 



800 " +.0013 



1000 " +.0013 



The temperature of the room in which all the tests except the 

 measurement of resistance, were made, was held within ± 1° C. As the 

 condensers in the capacitance bridge and the special unit condensers 



* The final value was obtained by adding .00002 for a known error in frequency 

 and .00004 for the ratio arm error of the bridge to the average of the above determina- 



3(r 

 tions. The accuracy of the final value is equal to ± — p • 



