. The Bell System technical journal . nces between thetwo ratio arm coils, Ri and i?2, and from each to ground, are shownas being uniformly distributed along the length of the coils symmet-rically with respect to each other. If this symmetry is perfect thesecapacitances do not affect the bridge balance. In practise, however,they will only be approximately so, with the result that the two armswill be somewhat unbalanced to alternating currents, the efifect of theunbalance increasing with the frequency. While the ratio arm capaci-tances can be made fairly small, others such as those indicated at
. The Bell System technical journal . nces between thetwo ratio arm coils, Ri and i?2, and from each to ground, are shownas being uniformly distributed along the length of the coils symmet-rically with respect to each other. If this symmetry is perfect thesecapacitances do not affect the bridge balance. In practise, however,they will only be approximately so, with the result that the two armswill be somewhat unbalanced to alternating currents, the efifect of theunbalance increasing with the frequency. While the ratio arm capaci-tances can be made fairly small, others such as those indicated atCi, d, Cz, and d will commonly be much larger and hence of greatereffect. Capacitances C\ and d are frequently comparatively large A SHIELDED BRIDGE FOR INDUCTIVE IMPEDANCE 147 due to the use of long distributing wires, encased in grounded conduit,for supplying the testing current. C3 may consist chiefly of the groundcapacitance of the outer layer of the detector coil winding and d thatof dead-end coils of the reference standard, 1. c; Fig. 6—Bridge circuit with stray admittances Some of the currents flowing along the paths provided by thesecapacitances will complete their circuits external to the bridge networkproper and will not affect the balance; for example, that throughcapacitances Ci and d in series. Other currents, however, will flowunsymmetrically through parts of the bridge circuit; for instance,that through Ci and C3 in series and the arm Zx; also, that throughC2 and Ci in series, returning through the ratio arm Ri. These lattercurrents and others of the same sort affect the potential distributionof the bridge and hence the values of the impedances required forbalance. Certain of these capacitance currents in the bridge networktend to neutralize or balance the effects of others; for example, thatthrough the arm Zx due to the series action of capacitances Ci and Czhas a balancing effect with respect to that through Ci and C4 and thearm Zs and would be without r
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
