ON PRACTICAL STANDARDS FOR ELECTRICAL MEASUREMENTS. 



Tablk XII. 



49 



If we neglect L'17 and L'lS the mean value of tlie other five coils 

 is 2-2 X 10-= ohms greater in 1908 than in 1903. 



Apart from the cause of these changes, it is interesting to form some 

 idea of what interpretation of the differences might reasonably have been 

 applied if mercury standards had not been the master standards. If the 

 mean value of the seven coils had been taken as remaining constant, the 

 error in five years would have amounted to 42 parts in 100,000. A com- 

 parison with coils of nominal values differing from unity might, however, 

 be made, and such might largely influence the result. 



The maximum changes which have taken place in the other resistance 

 standards and the difference values (1908-1903 values) are given in 

 Table XIII. 



Table XIII. 



Resistance 

 Standard 



O.W. 2196 

 O.W. 2493 



O.W. 2200 

 O.W. 2492 



O.W. 2352 

 O.W. 2484 



O.W. 738 

 O.W. 1693 



LI 9 



L-20 



O.W. 739 

 O.W. 2450 



O.W. 740 

 O.W. 2449 



O.W. 2448 



Nominal 

 Value 



0001 ohm 



001 „ 



01 „ 



01 „ 



01 

 01 



10 ohms 



10 „ 



10 „ 



10 „ 



100 „ 



100 „ 



1000 

 1000 



10000 



Maximum 



Change since 



1903. 



Parts in 100,000 



1908 Vahie 



minus 



1903 Value. 



Parts in 100,000 



Mean Difference. 

 Parts in 100,000 



22-4 

 20 



330 

 19 



20 

 80 



2-2 



80 



ll'O 



8-3 



1-2 

 18-0 



11-8 



89-4 



40'0 



22-4 

 1-8 



330 

 0-2 



1-4 

 80 



1-7 

 7-2 



96* 

 7-6* 



-10 

 180 



11-4 



89-4 



368 



+ 121 

 + 16-6 



+ 4-7 



+ 6-5 



+ 8-5 



+ 50-4 

 + 368 



Mean difference value (1908-1903 values) = + 16-5 parts in 100,000. 



Mean difference value (1908-1903 values) including the unit coils = + 12 6 parts 



in 100,000. 



1908. 



* These are the difference values (1908-J904 values), 



