The measurement of small potential differences by means of a double triode valve in a bridge circuit

The paper discusses a balanced bridge circuit which was first described by J. C. M. Brentano. It introduces a modification in that the two valves used in the original circuit are replaced by a single double triode valve of special design. In this way the fluctuations due to the random character of the discontinuities of emission from the two filaments are eliminated in the same way as they are in the circuits using one single tetrode. At the same time the advantages of simple balancing and of better compensation of the effect of transient E.M.F.'s which are characteristic of the symmetrical circuit are retained.