The cathode-ray oscillograph

The paper draws attention to three commercial forms of cathode-ray oscillograph which may be employed in the study of very high-frequency alternating or impulsive electrical phenomena. The behaviour of a stream of cathode rays in electrostatic and magnetic fields is first dealt with, and the penetrating power of cathode rays through matter is considered in relation to the velocity of the rays. Making use of this fundamental information, simple relations are obtained expressing the current and voltage sensitivities of cathode-ray oscillographs, the important features to be observed in the design of these instruments being indicated. The question of photographic sensitivity is also discussed, and calculations are made of the relative photographic effects produced by cathode rays of different velocities. It is shown that ordinary photographic plates or films are, in general, unsuitable for recording by means of low-velocity cathode rays. For this purpose a certain type of plate known as the Schumann plate, which is very rich in silver bromide relative to gelatine, is recommended for recording at very high speeds. The principal features of three oscillographs, viz. the Dufour, the Western Electric and the author´s, are described and a comparison is made of their relative advantages. A few of the numerous applications of cathode-ray oscillographs are indicated, and a number of records made by each of the three types are reproduced in illustration.