A Condenser Bridge for Factory Inspection of Variable Condensers

A capacity bridge designed for routine factory testing of variable air condensers of the "gang" type, as used in modern radio receivers, is described in this paper. Setting the bridge involves a capacity balance and a phase-angle adjustment. The capacity balance is effected by a balancing condenser which gives directly the capacity difference between two condensers connected to the bridge for test. The phase-angle adjustment is made by rheostats in series with the condensers, and by an arrangement whereby the phase angles of the ratio resistances can be varied slightly for precise adjustment. Design and construction of some of the more important parts, and testing and calibration of the bridge, are described, and installation and use of the bridge are discussed.