GB602592A - Modified sweep circuit for cathode ray tubes - Google Patents

Abstract

602,592. Cathode-ray oscillographs, MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Feb. 12, 1945, No. 3522. Convention date, Sept. 10, 1943. [Class 37] [Also in Group XL (c)] An arrangement for expanding a short duration pulse for examination on a cathode-ray oscillograph, so that it may cover the entire screen width, comprises means for reshaping the pulse and applying the reshaped pulse to control the sweep circuit so as to give a forward trace of the same order of duration as the pulse. Pulses from the line L are applied to the triggershaping circuit comprising the valves V1, V2, which are cross-coupled by resistances RL1, RL2; Rd1, Rd2, RH1 and the condensers CH1, CH2. In the stable state the valve V1 is rendered non-concluctive by the biassing means - Ec, and the valve V2 is conductive. The application of a negative pulse to the cathode of the valve V1 causes it to become conductive, and the valve V2 non-conductive for period mainly determined by the condenser CH2 and resistance Rd2. The diode D provides a low resistance shunt path to the cathode resistance R when the valve V1 is conductive, rendering the operating period of the trigger circuit independent of the duration of the triggering pulse. Reshaped pulses from the anode of the valve V1 are applied over the condensers C4, C3 and resistance R3 to the grids of the valves V3, V4. The valves V3, V4 are conductive in the stable state, being biassed by the resistance R5 connected to the positive source +Eb, and become non-conductive for the duration of application of the negative reshaped pulses to their grids. When the valve V4 is non- conductive, the condenser C5 charges through a resistance R4, the sweep voltage so produced being applied over an amplifier AMP to one pair of the deflecting plates of the tube CRO. The rendering of the valve V3 non-conductive causes a positive pulse to be transferred from the anode circuit to the grid of the tube CRO, making visible the trace, which is normally suppressed by biassing potentials applied over the resistance R7. The pulse to be examined may be applied over a delay network TL to the second pair of deflecting plates of the tube CRO. The system may alternatively be oper. ated synchronously with a source of periodically recurring pulses, by provision of a sinusoidal source, a phase-shifter and a clipper amplifier (not shown) supplying sharp pulses to the line L. Specification 602,267, [Group XL (c)], is referred to.