PHASE METERS 551 



rium position. There is no moving wire and consequently no 

 necessity for taking current to and from the movable element. 



Magnetic Vane Frequency Meter. The arrangement adopted 

 in the Weston frequency meter is shown in Fig. 335. 



The crossed coils A and B are fixed and in their field is pivoted 

 a long thin needle of soft iron, N, which carries the pointer. 

 There is no controlling spring. The inductances (L) and resist- 

 ances (R) are so proportioned that the combined action of the two 



FIG. 335. Diagram for Weston magnetic vane frequency meter. 



coils sets up an elliptical rotating field. The needle takes up the 

 direction of the longer axis of the field, the angular position of 

 which changes as the frequency alters. If the frequency rises, 

 for the same total current in the circuit the current in coil A is 

 increased while that in coil B is diminished. This shifts the direc- 

 tion of the axis of the field and the pointer is thus carried over the 

 scale. 



References 



1. "Bin Phasemnessapparat fur Wechselstrome," J. TUMA, Sitzungbericht 

 der K. Akad. Wissenschaft, Vienna, vol. 106, 1897, p. 521. 



2. "Power Factor Indicator," AUG. J. BOWIE, JR., Electrical World, vol. 

 36, 1900, p. 644. 



3. "Power Factor Indicators," WILLIAM HAND BROWNE, JR., Trans. 

 A.I.E.E., vol. 17, 1901, p. 287. 



4. "Phase Meters and Their Calibration," W. E. SUMPNER, Electrician, 

 vol. 56, 1906, p. 760. 



5. "Theory of Phase Meters/' W. E. SUMPNER, Philosophical Magazine, 

 vol. 11, 1906, p. 81. 



6. "Synchronism and Frequency Indication," PAUL M. LINCOLN, Trans. 

 A.I.E.E., vol. 18, 1901, p. 255. 



7. "Resonant Circuit Frequency Indicator," W. H. PRATT and D. R. 

 PRICE. Trans. A.I.E.E., vol. 31, 1912, Part II, p. 1595. 



