ELECTRIC METER 



1994 



ELECTRIC MOTOR 



ELECTRIC ME'TER, a machine used to 

 measure the quantity of electric energy con- 

 sumed. Electric service companies charge for 

 their service according to the readings of the 

 electric meters in the premises of their cus- 

 tomers. Since the kilowatt-hour is the unit 

 of electrical energy, the meter measures kilo- 

 watt-hours or watt-hours, and for this reason 

 it is sometimes called a watt-hour meter. See 

 WATT; KILOWATT. 



Description of the Meter. The principal 

 parts of the watt-hour meter are the field coils 

 a a, the vertical shaft b, to the lower end of 

 which is attached a' horizontal circular disk c, 

 and the dials d. These are shown in the first 

 illustration. The field coils are wound with 

 coarse wire and are connected with the elec- 

 tric circuit in series. They are without cores 

 and they carry the whole volume of the cur- 

 rent. The armature is mounted on the shaft 

 b and is wound with very fine wire, which 

 forms a shunt circuit between the two wires 

 of the main circuit and carries a current of 

 small volume, but one that represents the full 

 pressure by which the branches of the current 



MECHANISM OF A METER 

 Explanation of the figure appears in the text. 



are driven. The difference in pressure in the 

 field coils and the armature causes the arma- 

 ture to revolve. The vertical shaft is con- 

 nected with a system of clock work which 

 moves the . needles over dials, as described 

 in the paragraph below. 

 Reading a Meter. An electric meter usually 



has either three or four pointers on the dial. 

 Each pointer moves over a circular scale hav- 

 ing ten spaces. The pointer on the right 

 moves over one space while one kilowatt-hour 

 is being used. When this pointer makes one 

 complete revolution ten kilowatt-hours have 

 been used. The second pointer makes one 



METER DIALS 





A SMALL METER 

 The reading indicates fifteen kilowatt-hours. 



revolution while the first makes ten revolu- 

 tions, so that each space of the second scale 

 indicates ten kilowatt-hours and one complete 

 revolution of the second pointer indicates one 

 hundred kilowatt-hours. Each space of the 

 third scale indicates a hundred kilowatt-hours 

 and each space of the fourth scale 1,000. In the 

 illustration the number above the circular 

 scale is the amount recorded by one complete 

 revolution of the pointer. 



To read a meter, note the number of com- 

 plete spaces or divisions of the scale passed 

 over by each pointer and write them down in 

 order, beginning at the left. The result will 

 be the number of kilowatt-hours. If a pointer 

 is near a mark of the scale consult the pointer 

 to the right to find out whether the mark has 

 been passed or not. Unless the pointer to the 

 right has reached or passed the zero, or, in 

 other words, has completed a revolution, the 

 other has not completed the division which 

 it appears to have completed. See the sec- 

 ond illustration for example of meter reading. 



ELECTRIC MOTOR, mo'ter. By attaching 

 a dynamo to a steam engine or a water wheel 

 and applying the necessary power, the power 

 of the steam or water is transformed into 

 electric energy. This energy can be carried 

 long distances by wires and connected to an- 

 other dynamo, transmitting to it a motive 

 power that may be used in the operation of 

 machinery. An electric motor is a dynamo 

 deriving its power from an electric current. 

 It may be called a dynamo reversed. 



