FEB. 4, 1921 



VINAL AND SNYDER: OSCILLOGRAPH MEASUREMENTS 



51 



ELECTRICAL ENGINEERING.— 05a7/ogra^/j measurements of the 

 instantaneous values of current and voltage in the battery circuit of 

 automobiles. G. W. Vinal and C. L. Snyder, Bureau of Stand- 

 ards.^ 

 Performance curves showing the instantaneous demands made upon 

 automobile starting and lighting batteries when cranking the engines 

 have been obtained recently at the Bureau of Standards. These 

 curves were made while preparing specifications for this type of 

 battery for the Motor Transport Division of the War Department. 

 In the course of these experiments additional information was ob- 

 tained with respect to the operation of the starter system and the 

 engine itself. 



In order to measure the rapidly fluctuating values of current and 

 voltage a 3-element oscillograph was used. The ordinary film drum 

 was replaced, however, by a camera of special construction. Time 

 was recorded by one element while the current and the battery voltage 

 were measured by the two remaining elements. The oscillograph 

 records show the instantaneous values of current and voltage which 

 cannot be obtained with the ordinary indicating instruments. 



ZETRO CURRENT VALUE 



Fig-fl- — Fluctuations of current and voltage in battery circuit when starter cranks the 

 engine. Initial value of current 125 amperes. Four cylinder car 12-volt single unit system. 

 Time scale in half seconds at top of record. 



A series of measurements under various conditions of operation was 

 made upon a number of cars of different makes. The records for the 

 various cars show different characteristics which are typical of the 

 design and condition of the engine and starter system. All of the 



^ Published by permission of the Director, Bureau of Standards. Received December 

 22, 1920. The complete paper will be published as Technological Paper No. 186 of the 

 Bureau of Standards. 



