[Electric engineering.] . n-nections from it. It may be well to state here that thesmall connecting cables running from the shunt to theinstrument are sent out with the shunt. They are usuallymade long enough to reach any reasonable distance on theswitchboard. They should on no account be altered inlength; if they are too long, they should be coiled up out ofthe way; if too short, another shunt with long leads withits corresponding instrument should be obtained. Fig. 11 shows the ordinary type of shunt used. It con-sists of the two terminals a, a connected together by the flat 12 ELECTRIC LIGH
[Electric engineering.] . n-nections from it. It may be well to state here that thesmall connecting cables running from the shunt to theinstrument are sent out with the shunt. They are usuallymade long enough to reach any reasonable distance on theswitchboard. They should on no account be altered inlength; if they are too long, they should be coiled up out ofthe way; if too short, another shunt with long leads withits corresponding instrument should be obtained. Fig. 11 shows the ordinary type of shunt used. It con-sists of the two terminals a, a connected together by the flat 12 ELECTRIC LIGHTING. 17 strips b, which are made of an alloy that has practically aconstant resistance regardless of temperature changes; c, care the small flexible cables that run to the ammeter. The shunts and instruments are always numbered to cor-respond, and care should be taken to see that these numbersmatch before connecting up the instruments. Many othermakes of instrument other than the Weston are used inconnection with 11. Alternating-Current Ammeters and Voltmeters. Most of the switchboard ammeters and voltmeters foralternating current consist of a coil arranged so that themagnetic field set up through it will act on a piece of iron, 17 ELECTRIC LIGHTING. 13 the movements of which actuate a pointer. Various modifi-cations of this coil-and-plunger type are in common example, in the earlier type of Westinghouse instru-ments, Fig. 13, a vertical coil A is arranged so as to drawan iron core C into it. This core is hung on one end of abalance arm to which the pointer N is attached, and acounterweight W is hung from the other end. In the laterinstruments, the current is sent through a coil, and themagnetic field produced deflects a small iron vane placedwithin it. Fig. 14 illustrates the principle of a type ofinstrument that has been largely used by the General Elec-tric Company, both for alternating and direct current. Itis known as the Thomson inclined-coil pattern. Th
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