. Practical wireless telegraphy; a complete text book for students of radio communication . the radioinspectors testing equipment. TheHartmann & Braun meter is shown in Fig. 52. It has much the appearance ^^- so—Mechanism of Alternating Current Ammeter. of a voltmeter, and, like that instrument, it is connected in shunt to the terminalsof the alternator. In this diagram the single elongated magnet winding M has joined in series withIt the coil R; the two terminals E, E are shunted across the circuit under measurement. The soft iron piece, P, P, completes the magnetic circuit for the poles of t
. Practical wireless telegraphy; a complete text book for students of radio communication . the radioinspectors testing equipment. TheHartmann & Braun meter is shown in Fig. 52. It has much the appearance ^^- so—Mechanism of Alternating Current Ammeter. of a voltmeter, and, like that instrument, it is connected in shunt to the terminalsof the alternator. In this diagram the single elongated magnet winding M has joined in series withIt the coil R; the two terminals E, E are shunted across the circuit under measurement. The soft iron piece, P, P, completes the magnetic circuit for the poles of the horse-shoe magnet, N, S, N, S, etc. A number of small vibrating reeds are placed directlym the path of the flux between the soft iron piece and the poles of the magnet Eachof these reeds have a dififerent period of mechanical vibration and, consequently areonly set into vibration by the flux of the magnet when it alternates at such rates as tocorrespond to the natural mechanical period of the reed. Four permanent horse-shoe magnets, N, S, N, S, etc., keep the core in a constant. ELECTROMAGNETIC INDUCTION. 45 state of magnetization, but when alternating current flows through winding M, thereed having a natural period corresponding to the particular frequency of the currentflowing will be set into violent oscillation. The scale reading corresponding to this particular reed is the frequency of the cir-cuit under measurement. The instrumentwill perhaps be better understood fromthe side elevation, Fig. 52. Frequencymeters of this type are very accurate. (d) The mechanism of one typeof hot wire ammeter is shown in Meters of this construction areparticularly suitable for measurementof the current at radio-frequencies. Itshould be self-evident that measure-ment instruments having bobbins orcoils of wires are totally unsuited tothis work, first, because the currentof high voltage and high frequencywould burn out the coil, and, second,the length of the windings wouldseriousl
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
