Patent GB-721460-A (GB)
Title: Voltage indicating valve
IPC: H03J3/14
Filed: 1951-11-30
Abstract: 721,460. Cathode-ray tubes. STANDARD TELEPHONES & CABLES, Ltd. Nov. 30, 1951 [March 20, 1951]. No. 28149/51. Class 39 (1). A voltage indicator comprises an anode coated with luminescent material, a cathode, a grid adjacent the cathode followed by a plurality of deflecting electrodes and a curved sheet electrode formed as an arc which extends parallel to the axis of the cathode over a length much less than the length of the other electrodes. In one form, Fig. 1, the device has cathode 1, grid 2, two deflecting electrodes 3, 4, beam dividing member 5 formed as a curved metal strip, and luminescent anode 7. Grid 2 is at cathode potential and dividing member 5 at positive potential; cover 6 may be connected to the potential of anode 7. A plurality of indicating systems or an indicating system and an amplifier system may be arranged radially about a common cathode; the amplifier section may however surround a different axial portion of the cathode. The dividing member 5 is carried by two supports and the electrodes 3, 4 cross over in the vicinity of 5 so that two luminous traces appear which move in opposite directions with unequal voltages, and coincide with equal voltages, to 3, 4. In a modification, Figs. 7-13 (not shown), the dividing member is near to the rim of the anode so that the two traces are of unequal lengths. The length of the upper trace can be varied by varying the voltage on 5 or 6; in the latter case the lower luminous pattern remains unchanged. In another modification, Figs. 14-22 (not shown) the dividing member 5 has side extensions to suppress the wedge shaped side traces which normally accompany the upper trace. In another modification, Fig. 23 (not shown), the grid is wound closely where it faces the crossover point of electrodes 3, 4 and more openly at other parts. In another form, Fig. 24 (not shown), the electrode 5 is split into two parts to allow for independent adjustment of the lengths of the upper and lower traces. The upper electrode 5 may have side extensions as in Figs. 14-22 (not shown). In further forms the electrode 5 and its supports are stamped in one piece from a cylinder, Figs. 30- 32 (not shown). A screen may be provided to shield the non-useful part of the electrode 5 from electron bombardment, Figs. 33-35 (not shown). The grid 2 may have variable pitch, Fig. 36 (not shown), being wound more closely at its upper end so that the upper trace is made less bright than the lower trace. In another form, Fig. 38, the device has two pairs of deflecting electrodes 3a, 4a; 3b, 4b, ring electrodes 5, 10, 11, and dish shaped or plane fluorescent anode 7. The anode 7 may be translucent and may be arranged at right angles to the direction of observation. The deflecting electrodes may be connected in various ways to obtain traces moving in the same or in opposite directions, and the lengths of the traces may be varied by varying the voltages of ring electrodes 5, 10, 11. In another form, Fig. 52 (not shown) the deflecting electrodes are inclined to the cathode axis and to one another to produce wedge shaped traces. Combinations of features of embodiments can be used e.g. the crossover deflecting electrodes may be replaced by parallel or inclined electrodes. The voltages to be measured or compared may be amplified inside or outside the envelope before being applied to the deflecting electrodes. The deflecting electrodes may be placed asymmetrically with respect to the cathode. The devices may be used to indicate the tuning of a circuit to amplitude or frequency modulated signals. In the latter case the deflecting electrodes are connected to the positive and negative voltage points of the discriminator and tuning to the centre of the carrier gives zero voltage difference between these electrodes.