An improved method of electrically measuring by means of a wheatstone bridge

摘要

268,453. Ulitovsky, A., and Vishnevsky, G. Sokolov-. Jan. 5, 1926. Resistances. measuring. - Resistances are measured by the deflection oj of a two-coil galvanometer in a Wheatstone bridge having its two coils 1, 2 connected in twc bridges starting from two different points y, z. The arms m, n of the bridge are of constant and equal resistances, the resistances to be measured being connected between the points v, z. The source of current is connected to the points v, q. The resistances zy, yq are so adjusted that when measuring a resistance of the maximum value the resistances vz and zq are equal and no current flows through the coil 2, the soft-iron armature r being deflected by the current in the coil 1 to the highest reading on the scale. When measuring a resistance of the lowest value, no current flows in the coil 1 and the armature r is deflected to the lowest reading by the current in the coil 2. For intermediate values the armature takes up an intermediate position under the influence of both coils. The readings of the instrument are independent of changes in the voltage at the terminals v, q, since such changes vary the currents in the coils 1, 2 in the same ratio. Temperature variations also cause proportionate changes in the resistances of the coils 1. 2, so, that the ratio of the currents through them. and therefore the indication of the instrument, is unchanged. The instrument may be employed for reading the value of a resistance thermometer, the scale being calibrated in degrees. The scale values may be varied by changing the resistances zy, yq.