Measurement of Vacuum-Tube Capacities by a Transformer Balance

A complete, portable equipment is described for the measurement of the direct capacities of vacuum tubes in laboratory or factory testing. The tube capacity is compared with a standard variable condenser by means of a transformer-balance (Neutrodyne) circuit, whose balance is independent of the frequency (about 1600 kc. being preferred). Designs are proposed for the standard condenser and the transformer, and suggestions are made for the further improvement of this equipment.