GB374899A - Improvements in and relating to vacuum gauges - Google Patents

Abstract

374,899. Valve amplifying circuits. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London, DAVIES, L. J., .147, Murray Road, and KNIGHT, H. DE B., 39, Park Road, both in Rugby. March 17, 1931, No. 8238. [Class 40 (v).] An electric discharge tube 6 having an anode 7, cathode 8, and central electrode 9 is connected up in a bridge with a transformer 10 the primary of which is connected to a source of supply, and when contacts 20 are made by means of the current passing through the meter of a Wheatstone's bridge, a large current passes through a coil 21 controlling for instance an oil switch. The secondary winding 12 of the transformer is connected to the anode 7 through the coil 21. The cathode 8 is connected to a tapping or tappings 14 on the winding 12, the windings for heating the cathode, if necessary, not being shown. Current can only pass from anode to cathode when the potential of the electrode 9 is of the correct phase and magnitude relatively to the potentials of the other electrodes. The electrode 9 is connected through a resistance 16 to the junction between a resistance 17 and a capacity 18 in series across portions 13, 14, 15 of the winding 12 so that the point 14 lies between points 13, 15. The values of the resistance 17 and capacity 18 determine the phase of the potential applied to the anode 9. A second resistance 19 is connected in parallel with the resistance 17 through the contacts 20. When these are closed, the resistance of the combination 17, 19 is less than when the contacts are open and hence the potential of the electrode 9 with respect to electrode 8 is more nearly in phase with electrode 7 and the more current can pass through the device 6. This may be zero when the contacts are open and rise to several amperes when contacts are closed. Two modified circuits are shown by which variation of the potential of the electrode is secured.