lENC 



[Entered at the Posi-Offlce of New York, N.Y., as Second-Class Matter.] 



A WEEKLY NEWSPAPER OF ALL THE ARTS AND SCIENCES. 



Sevknth Year. 

 Vol. XIV. No. 342. 



NEW YORK, August 23, i5 



Single Copies, Ten Cents. 

 P3.50 Per Year, in Advance. 



ARO.\'S ELECTRIC METER. 



An electric current meter which is attracting much attention in 

 this country, where it has been introduced but recently, is shown 

 in the accompanying illustrations. It is the invention of Professor 

 H. Aron of Berlin, who claims for it that it surpasses all similar 

 devices in point of reliability. It received a gold medal at the 

 Melbourne E.xhibition, and has been adopted, in preference to other 

 meters, by the Siemens & Halske and Edison electric lighting com- 

 panies of Berlin, and by the Berlin municipal electric lighting works. 

 It is also used in Paris, Vienna, Constantinople, and other cities, 

 where it has proved itself valuable for central station work. 



The Aron electric meter is made to measure both direct and al- 

 ternating currents, and from three-wire to nine- wire systems, from 

 fifteen to twelve hundred amperes, and from a hundred up to any 



FIG. I AND 2. —ARON ELECTRIC METER. 



desired number of volts. The action of the meter is based upon 

 magnetic attraction. The mechanism consists of two sets of clock- 

 work of ordinary construction, the pendulums of which swing 

 synchronously while no current is passing through the meter. The 

 left-hand pendulum is of the usual construction. The other varies 

 according to the current to be measured. The measuring pendu- 

 lum shown in Fig. i, which is an alternating-current meter, carries 

 a fork-shaped piece of brass fitted with a coil of fine wire, which 

 swings freely through the interior of a fixed coil of large wire. The 

 main current passes through the outer coil, the interior coil being 

 in a shunt-circuit. The mutual action of the two coils upon each 

 other effects a variation in the time of oscillation of the right-hand 

 pendulum proportional to the product of the electric tension and 

 the quantity of the current ; hence the measuring pendulum swings 

 faster the greater the tension and quantity of current passing 

 through the meter. While the pendulums swing in unison, the dial 

 train is idle, but when the current is passing, the dial-train registers 

 the difference in the pendulum oscillations, the latter being greater 

 or less according to the tension and quantity of the current. 



In the direct-current meter, the right-hand pendulum carries as 

 a w-eight a permanent steel magnet, which swings over a coil of 

 copper wire, through which the current passes. .\s in the other 



meter, the pendulums swing in unison until the current begins to 

 pass through the coil, when the measuring pendulum swings 

 faster, its rate of swing being governed by the amount of current. 

 The measuring-pendulum of the meter for the three-wire system 

 carries two permanent magnets attached to a cross-piece of brass. 



FIG. 3— ARON ELECTRIC METER. 



(For three-wire system. > 



each magnet swinging immediately above a coil of wire through 

 which the current passes, the main wires being connected to the 

 coils as shown in the diagram at the bottom of Fig. 3. The meters 

 for five, seven, and nine-wire systems differ only in the fact that 

 they are provided with a greater nuinber of permanent magnets on 

 the pendulum and a corresponding number of coils. 



