r>4 ALTKUX. \TI\C (TRREXTX 



and upper portions of the scale, however, are usually of such 

 magnitude that they may be read with a high degree of precision. 



This dynamometer-type of voltmeter takes about five times as 

 much current as a direct-current voltmeter of the same rating and 

 consumes an appreciable amount of power. As the moving coil 

 operates in a comparatively weak field, this type oj" instrument 

 is very susceptible to stray fields. Unless the instrument is 

 shielded, wires carrying currents, inductive apparatus and even 

 iron alone, if brought too near, may cause large errors in the 

 indications of this type of voltmeter. 



This instrument may be used for direct current as well as 

 for alternating current. Reversed direct-current readings should 

 be taken in order to eliminate the effect of the earth's field and 

 of any other stray fields. As the deflections depend upon the 

 square of the voltage, the instrument reads effective values. 



30. Inclined-coil Voltmeters. The inclined-coil type of volt- 

 meter operates on the dynamometer principle. It differs from the 



. ~~ , Spindle 



Moving Coil. 



Fixed Coll 



Pointer 



Fio. 51. General Electric inclined-coil instrument. 



previous types only in the geometrical relations of its fixed and 

 moving coils. The axis of the fixed coil, Fig. 51, is set at a con- 

 siderable angle with the vertical. The axis of the moving coil 

 makes a considerable angle with the spindle. This moving coil 

 is connected in series with the fixed coil, the current being carried 

 to the moving coil through light springs. A resistance to limit 

 the current is connected in series with the instrument. 



When the pointer is at the zero position there is a considerable 

 angle between the axes of the fixed and the moving coils. When 

 current flows through the instrument, the moving coil tends to 



