GB354788A - Improvements in alternating current bridges - Google Patents

Abstract

354,788. Capacitance measurements. STANDARD TELEPHONES & CABLES, Ltd. and NIELSEN, N. P., Columbia House, Aldwych, London. May 14, 1930, No. 14811. [Class 37.] A bridge for measuring capacity unbalance, for example in a telephone cable, is so arranged that substantially equal capacities may be added to each of two opposite arms and subtracted from each of the other two opposite arms. Fig. 2 shows a bridge in which the four arms A .. D are formed of four separate condensers mechanically connected, as by being mounted on the same spindle. The two pairs of one quad in the cable are connected to the points 1, 2 and the two pairs of the second quad to the points 3, 4. A modification is shown in Fig. 4 in which the bridge has two movable sets of plates 9, 10 and four fixed sets A .. D. The sets A, C and B, D may be combined as shown in Fig. 6. The bridges shown in Figs. 2, 4, and 6 may be connected as shown in Figs. 3, 5, and 7 for measuring phantom to side circuit unbalances. The bridge may be shielded. The direct capacities between the corners of the bridge may be rendered equal by known methods, and equality of the direct capacities of the corners to earth may be ensured. The arms may be adjusted to have equal initial capacities by the use of separate fixed or variable condensers, and similar condensers may be used for varying the range. Instead of mounting the movable plates on the same spindle, gearing may be employed so as to allow for initial adjustment of the capacities of each of the arms.