The modern electroplater; a complete book considering fully the elementary principles of electro deposition of metals, their practical application and industrial use . Fig. 35.—Ammeter a permanent magnet. A light pointer is fastened tothe bobbin in such manner that, when the latter isdeflected by the magnet, the free end of the formerswings over a divided scale. The scale divisions arecalibrated to represent amperes, and the value of thecurrent flowing in the bobbin winding is indicated bythe deflection of the needle. An instrument of thisnature is shown in Fig. 35. The windings of the ammeter
The modern electroplater; a complete book considering fully the elementary principles of electro deposition of metals, their practical application and industrial use . Fig. 35.—Ammeter a permanent magnet. A light pointer is fastened tothe bobbin in such manner that, when the latter isdeflected by the magnet, the free end of the formerswings over a divided scale. The scale divisions arecalibrated to represent amperes, and the value of thecurrent flowing in the bobbin winding is indicated bythe deflection of the needle. An instrument of thisnature is shown in Fig. 35. The windings of the ammeter coils cannot carry theheavy line current required for plating work. An 74 The Modern Electro plater ammeter shunt, of known resistance, is therefore used;this allows only a known small percentage of the linecurrent to pass through the meter. The ammeterscale is, however, calibrated to show the total amperesflowing through the external shunt and meter coilcombined. When the meter has once been calibrated,the same shunt must always be used; otherwise a new. Fig. 36.—External Shunt for Ammeter , (Wagner Electric Mfg. Co.) calibration must be made with another accurate in-strument as a standard. Ammeter shunts and leadsare furnished with the instrument, the latter beingconsidered as a part of the meter circuit. Externalshunts are furnished only where large currents areto be measured; instruments for currents of smallvalue are equipped with a shunt in the ammetercase. A typical ammeter shunt for use in the externalcircuit is shown in Fig. 36. THE VOLTMETER A voltmeter is an instrument employed to indicatethe current pressure. In construction it is quitesimilar to the ammeter with the exception that the Measuring Instruments 75 internal resistence is high instead of low. Hence thevoltmeter may be connected directly across the lineyet the current passing through it is practically negli-gible. A single voltmeter may be employed to indi-
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectelectro, bookyear1920
