. The practical telephone handbook and guide to the telephonic exchange . iii jok Fig. 425.—Kelvin Mirror Galvanometer ELECTRICAL MEASUREMENTS 45* up that a current passing through all, tends to turn thecombination in the same direction. The terminals of theinstrument are fixed on an ebonite base, fitted with spiritlevels and levelling screws, and the coils, etc., are covered witha case having glass sides. On top of the instrument is apair of scissors adjusting magnets, by means of which theastatic system can be very readily directed, and the sensibilityaltered. About 3 feet away from the fron
. The practical telephone handbook and guide to the telephonic exchange . iii jok Fig. 425.—Kelvin Mirror Galvanometer ELECTRICAL MEASUREMENTS 45* up that a current passing through all, tends to turn thecombination in the same direction. The terminals of theinstrument are fixed on an ebonite base, fitted with spiritlevels and levelling screws, and the coils, etc., are covered witha case having glass sides. On top of the instrument is apair of scissors adjusting magnets, by means of which theastatic system can be very readily directed, and the sensibilityaltered. About 3 feet away from the front of the instrument is set a. Fig. 426.—Lamp and Scale for Kelvin Galvanometer lamp, supported on a stand furnished with a graduated hole in the centre of the stand is furnished with a brass tube,in which a lens is fitted. Through the latter a beam of lightis made to fall on the mirror in the galvanometer, from whichit is reflected on to the graduated screen. An image of afine vertical wire, fixed close to the lamp, is focussed on thescreen, and enables the readings to be taken very 426 shows a very convenient lamp and scale. With thisan incandescent electric lamp is used, and the scale is printedon a translucent screen, so that the spot and line can be ob~ 452 PRACTICAL TELEPHONE HANDBOOK The screen is adjusted by means of served from either side. a rack and pinion. Fig. 427 shows a somewhat different arrangement of the Kelvin reflecting galvanometer made by Nalder Bros., in which the outer glass case is dis-pensed with, so that itcan be made considerablycheaper, although equallyconveni
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
