614 abstracts: electricity 



ELECTRICITY. — A system of remote control for an electric testing lab- 

 oratory. P. G. Agnew, W. H. Stannard, and J. L. Fearing. 

 Bureau of Standards Scientific Paper No. 291 (Bull. Bur. Stds., 

 13:581-597). 1916. 

 This paper describes a system of remote control which was developed 

 primarily for use in testing electrical measuring instruments. Small 

 multiple lever controllers, which may be operated in any one of several 

 laboratory rooms, give complete control of the output of a group of 

 motor-generator sets. For example, in testing a wattmeter, or an a.c. 

 watthour meter on low power factor, the five levers of a controller 

 give both a coarse and a fine adjustment of frequency, current, voltage, 

 power factor, and an auxiliary d.c. voltage, respectively. The field 

 rheostats are very long slide-wire resistances. They are tubular in 

 form and are wound helically with the resistance wire. They are 32 

 mm. in outside diameter, and as much as 12 meters in length. When 

 necessary they are cooled by circulating water through the tube. Spe- 

 cial laminated brushes, which bear directly on the winding, are oper- 

 ated by small worm-geared motors which pull them along the tubes by 

 means of cord and pulley. The phase relation of current to voltage 

 is controlled by a motor-operated worm drive. A large, motor-oper- 

 ated, low voltage rheostat for currents up to 10,000 or 12,000 amperes 

 is included in the system. P. G. A. 



ELECTRICITY. — A variable self and mutual inductor. H. B. Brooks 



and F. C. Weaver. Bureau of Standards Scientific Paper No. 



290 (Bull. Bur. Stds., 13: 569-580). 1916. 



The instrument consists of two pairs of fixed coils held in stationary 



hard rubber disks between which a third disk carrying two coils is 



arranged to be rotated. The form and the spacing of the coils were 



determined so as to secure the following advantages: (1) high ratio of 



inductance to resistance; (2) scale divisions of uniform length reading 



directly in units of inductance; (3) astatic arrangement of the coils, 



which reduces the liability of errors caused by the proximity of other 



instruments or of conductors carrying currents. Diagrams and data 



are given from which instruments of this type can be designed for given 



uses. Comparison is made of the new instrument and of some other 



older forms of variable inductor, including the Ayrton-Perry. 



H. B. B. 



