. Report of the Electric Railway Test Commission to the president of the Louisiana Purchase Exposition . ssential feature a strong magneticfield produced biy the current to be measured and proportionalthereto. The current flows through a few rectangular turns ofcopper bar, and the range of the instrument may be changed byconnecting these turns in series or in parallel. When in series,the range is 600 amperes, and when in parallel, 1,200 this magnetic field is supported a movable coil consisting ofabout eighty turns of fine wire and carrying a direct currentwhich is maintained at a c
. Report of the Electric Railway Test Commission to the president of the Louisiana Purchase Exposition . ssential feature a strong magneticfield produced biy the current to be measured and proportionalthereto. The current flows through a few rectangular turns ofcopper bar, and the range of the instrument may be changed byconnecting these turns in series or in parallel. When in series,the range is 600 amperes, and when in parallel, 1,200 this magnetic field is supported a movable coil consisting ofabout eighty turns of fine wire and carrying a direct currentwhich is maintained at a constant value of one ampere. The 72 ELECTRIC RAILWAY TEST COMMISSION current for the movable coil is supplied by a storage battery. Inthe same circuit are an adjustable resistance and a sensitiveindicating ammeter. By means of the resistance the current isadjusted by an attendant. The moving coil is suspended by acontrolling spring at the top, and it is guided at the bottom by asmall shaft which hangs freely in a bearing when the instrumentis in use. The coil is protected from excessive vibration by. Fig. 24. — General Electric Companys Recording Ammeter. flexible guides, and it is rendered dead beat in its motion bymeans of an eddy-current brake consisting of a copper arm carriedby the moving coil and swinging in the field of a pair of auxiliaryelectro-magnets. Current is carried to and from the moving coilthrough spiral conductors which exert no appreciable controllingeffect upon the coil. The movement of the coil is controlled bya spiral spring, by the adjustment of which the pointer of theinstrument may be restored to its proper zero position. SERVICE TESTS OF ELECTRIC CARS 73 The movable coil carries an aluminum pointer, approximately10 inches in length, which is hinged horizontally near its centerin order to give it the necessary flexibility. The two parts of thepointer are connected by means of a delicate adjustable springwhich may be made to support the entire weight
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Keywords: ., bookauthorlouisian, bookcentury1900, bookdecade1900, bookyear1906
