ELECTRICITY METERS 



489 



For high capacities, meters of 10 amp. are used with shunts 

 provided with heavy connecting cables. For obtaining the final 

 adjustment of the multiplying power of the shunt the high- 

 resistance wire N and sliding terminal T are provided. 



The full-load drop through the armature of a 10-ampere meter 

 without a shunt is about 30 millivolts; in the 20 to 80-ampere 

 meters with internal shunts it is about 60 millivolts; for the 





V\c,. 281. Sangamo direct-current watt-hour meter. 



external shunts the drop is about 75 millivolts. This higher 

 drop is necessitated by the resistance of the connecting cables. 

 The loss in the potential circuit of a 110- volt meter is about 4.5 

 watts; with 220-volt and 550-volt meters it is about 9 and 22 

 watts, respectively. In the two latter, the larger part of the loss 

 is in the added wire resistance. The full-load torque is about 6 

 cni.-gm. " 



In this meter the drag magnets are fixed in position, and a 25 

 per cent variation in the braking action may be obtained by 

 the use of a magnetic shunt on the drag magnets. The shunt 



