. Popular electricity magazine in plain English. Fig. 73. Principle of WestinghouseInduction Ammeter 115 1216 POPULAR ELECTRICITY and the WORLDS ADVANCE trolling force is a coiled spring attached to thealuminum disk. In the case of the voltmeter the primary coilis wound with fine instead of coarse wire and anexternal series non-inductive resistance woundwith wire having a zero temperature coefficient isused. Hot Wire Instruments: The expansion of awire when heated by the passage of a currentthrough it is utilized in some instruments formeasuring current or voltage. About 1885, volt-meters usin
. Popular electricity magazine in plain English. Fig. 73. Principle of WestinghouseInduction Ammeter 115 1216 POPULAR ELECTRICITY and the WORLDS ADVANCE trolling force is a coiled spring attached to thealuminum disk. In the case of the voltmeter the primary coilis wound with fine instead of coarse wire and anexternal series non-inductive resistance woundwith wire having a zero temperature coefficient isused. Hot Wire Instruments: The expansion of awire when heated by the passage of a currentthrough it is utilized in some instruments formeasuring current or voltage. About 1885, volt-meters using this principle were quite generallyused for alternating current work, but of lateyears they have been superseded by the typesdescribed above. The expansion of the wirethrough which the current to be measured ispassing causes a certain amount of slack which. Fig. 74. Electrostatic Volmeter is taken up by a spring. The motion of thisspring-is transmitted to an indicating pointerthrough a small drum over which a cord instrument has some very good is no induction since the wire is notformed into coils. It is not sensitive to rapidfluctuations, hence is dead beat. Electrostatic Voltmeters: Another class ofvoltmeter suitable for alternating current workis one which depends on the attraction or re-pulsion of two surfaces carrying electrostaticcharges. They are generally employed for meas-uring unusually high voltages. The type in-vented by Lord Kelvin is shown in Fig. 74.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectelectri, bookyear1912
