ABSTRACTS 



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 this issue. 



ELECTRICITY. — Outline of design of deflection potentiometers, with 



notes on the design of moving-coil galvanometers. H. B. Brooks. 



Bulletin Bureau of Standards 8: No. 2. 1911. 



This paper outlines the principles on which deflection potentiometers 



are designed, and gives a numerical example. It includes some notes 



on the fundamental constants of the moving-coil galvanometer, and 



shows how to change the field strength, spring strength and size of wire 



in order to secure a desired galvanometer performance. A procedure 



is outlined which is intended to facilitate the production in quantity 



of galvanometers whose resultant performance is satisfactory, while 



allowing some latitude in the values of individual constants. H. B. B. 



ELECTRICITY. — Deflection potentiometers for current and voltage meas- 

 urements. H. B. Brooks. Bulletin Bureau of Standards, 8: No. 

 2. 1911. 

 The deflection potentiometer differs from the usual potentiometers 

 in one essential feature, viz., the use which it makes of the galva- 

 nometer. The greater portion of the electromotive force under observa- 

 tion is compensated, but the galvanometer deflection indicates the 

 remainder. The accuracy obtainable by the potentiometer method is 

 thus combined with the ease and speed of reading a deflection. In pre- 

 vious papers (Bulletin of Bureau of Standards, 2 : 225. 1906, and 4 : 275 

 1908) the writer has described two forms of deflection potentiometer, 

 both intended for voltage measurements only. This paper describes 

 two new instruments, each of which is suitable for both current and 

 voltage measurements. The theory of the deflection potentiometer 

 used with current shunts is developed, and a special set of values for 

 such shunts is shown to give economy of time in testing, with reduced 

 computation and liability of error. J. H. Dellinger. 



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