GB478200A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

478,200. Cathode-ray tubes. WESTINGHOUSE ELECTRIC & MANUFACTURING CO. July 10, 1936, No. 19136. Convention date, Aug. 24, 1935. [Class 37] [Also in Group XL] An image of uniform intensity is produced on the screen or photographic plate of a cathoderay oscillograph by varying the density or velocity of the rays in accordance with the rate of traverse of the beam across the screen &c., the signal &c. to be observed being applied across the tube deflecting means and a potential divider, the potential derived from the latter being rectified and the positive impulses applied to a control electrode in the tube through an electrical device the effective impedance of which varies inversely as the frequency of the pulsations, the magnitude of these pulsations being directly dependent on the rate of change of the varying electrical potential derived from the signal &c. under observation. The oscillograph 1, which is provided with the usual heated electron source 5, control electrodes 79 and deflecting plates 11, 13 may be furnished with an additional control electrode 19 which is disposed adjacent the source 5 and is negatively biassed from a battery 21. The voltage under observation is connected to the deflecting plates 13 and also to a potential divider 23, the centre point of which is earthed and on which variable tappings 27, 29 are provided which are also connected to the anodes 31, 33 of a full wave rectifier 35. The control electrode 19 is connected to the earthed filament of the rectifier 35 through a condenser 43 so that positive impulses are transmitted to the electrode 19, the magnitudes of which increase with increase in the frequency of the impulses. This frequency is the same as that of the wave under observation, so that when the rate of change of the voltage of this wave is high a larger positive potential is applied to the electrode 19 than when the rate of change is low and the density of the beam is thus dependent on the rate of change of the voltage under observation. The potential producing the constant intensity of the picture may be applied to a control electrode situated between the screen and the last set of deflecting plates in which case it serves to vary the velocity of the electrons. The Specification as open to inspection under Sect. 91 discloses also the use of a transformer in place of the condenser 43, the primary of which is connected between the filament 37 and the ground while the secondary is connected in place of the resistance 41. The brightness of the picture obtained may be rendered uniform by increasing the intensity of certain parts and decreasing it in others, in which case both positive and negative potentials are applied to the electrode 19, the rectifier 35 then being omitted and the wave under observation being suitably applied to give the variations desired. This subject-matter does not appear in the Specification as accepted.