Page:The Bell System Technical Journal, Volume 1, 1922.pdf/23

Rh The excess of one direct capacity C$12$ over another C$55$ is readily determines by connecting terminals 1 and 5 to corner, terminals 3, 4, 7, 8, to corner  or , and then balance with terminals 2 and 6 on  and , respectively, and repeat, with their connections reversed.

The required direct capacity C$12$ is balanced against one of its associated direct capacities, augmented by a standard direct capacity

C$1$, and the measurement is repeated with the required direct capacity and standard interchanged. Let R′, R″ be the resistance required in arm of the bridge for the first and second balance, then, S being the total slide wire resistane and G$1$ the grounded capacity of terminal 1:

This ratio method requires for the bridge a variable or slide wire resistance and a constant condenser, and it may be employed as an improvised bridge, when sufficient variable capacity is not available for the Colpitts method. Not being a substitution method, however,