. Practical wireless telegraphy; a complete text book for students of radio communication . r to rotate the shaft which carriesthe indicating needle. When the hot wire ammeter is usedto measure large values of current, ashunt must be supplied to sub-divide thecurrent flow, but an inductive shunt,even with one-half a turn of wire can-not be employed to measure current atradio-frequencies because the inductanceof the shunt would vary with eachchange of frequency. Consequently, hot wire meters are constructed after the de- t-- t, „ ^ • r t7 ■«»■ . -„.-., , . ^ Fig. 52—Mechanism oi Frequency Meter
. Practical wireless telegraphy; a complete text book for students of radio communication . r to rotate the shaft which carriesthe indicating needle. When the hot wire ammeter is usedto measure large values of current, ashunt must be supplied to sub-divide thecurrent flow, but an inductive shunt,even with one-half a turn of wire can-not be employed to measure current atradio-frequencies because the inductanceof the shunt would vary with eachchange of frequency. Consequently, hot wire meters are constructed after the de- t-- t, „ ^ • r t7 ■«»■ . -„.-., , . ^ Fig. 52—Mechanism oi Frequency Meter, Sign of Fig. 54, where several resistance wires are stretched in parallel between two large copper blocks, B, B^. All of these wires are of small diameter, such as No. 36 or No. 40 B. & S. gauge, hence they offer practically the same resistance to current, of radio-frequency as to a direct current; that is, irrespective of the frequency of the current, the reading in amperes will be accurate. One of the wires, C, D, is selected to work the indicating mechanism in the. -Mechanism Wattmeter.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
