Oscillographic Study of Electron Tube Characteristics

A special oscillograph is used to record simultaneously the plate current and the grid current of an electron tube. By superposing a slow audio frequency variation of voltage on the regularly increasing grid voltage during the photographing of the oscillogram, corresponding audio frequency variations are produced in the plate current, the amplitudes of which are proportional to the amplification of the tube at that setting. Detector action can similarly be studied by applying a rising radio frequency voltage to the grid, and periodically interrupting it at a low audio frequency. The study of tubes containing gas, and the recording of kinks in their characteristics is particularly facilitated by the use of the apparatus described.