GB477664A - Automatic control arrangements for thermionic valves - Google Patents

Abstract

477,664. Automatic control; variable resistances ; current and pressure meters. STANDARD TELEPHONES & CABLES, Ltd. Feb. 1, 1937, No. 2881. Convention date, Feb. 1, 1936. [Class 38 (iv)] [Also in Group XXXVI] Current; oscillation frequency.-In athermionic valve oscillation generator in which the frequency is dependent upon the emission from the cathode, a variable resistance in the cathode heating circuit is controlled in response to variations in electron current to a positive electrode of the valve so as to maintain the generated frequency constant. A Barkhausen oscillator consists of a valve 13 whose anode and grid are coupled over wires 10 by a slider 11. The anode is maintained at a negative potential with respect to the cathode by a battery 20 and the grid is maintained at a positive potential by a battery 21 in series with a relay winding 19. The winding 19 controls a contact 51 operating between two fixed contacts 49, 50 controlling the circuits of two heating coils 43, 44 which surround the upper bulbous parts of a U-tube 33 containing mercury. One leg of the U-tube contains a resistance element 32 and the cathode heating circuit includes this resistance and a contact terminal 34 and battery 37. Variations in the grid current cause energization of one or other of the coils 43, 44 to produce expansion of a gas such as pentane in one or other of the bulbs of the U-tube so as to vary the resistance 32 in the cathode heating circuit to bring the grid current, and hence the frequency of the oscillations back to normal. In a modification, Fig. 2, circuits in shunt with the contacts 49, 50 include tapped resistances 60, 63, the tappings of which are connected to terminals inside the legs of the U-tube so that when the mercury rises sufficiently in these legs a parallel circuit for the corresponding heating coil is maintained through a part of the resistance 60 or 63. The coil is then heated sufficiently to maintain the mercury in this position irrespective of the opening of the relay contacts 49 or 50 so as to reduce hunting. The Specification as open to inspection under Sect. 91 disclosed an arrangement in which the U-tube resistance of Fig. 1 is used in the measurement of voltage or current. The relay 19, 51 is a differential relay, one coil of which carries the current to be measured and the other coil is connected across a resistance in series with the variable U-tube resistance 32, a battery and a recording meter. Variations in the current to be measured cause variations in the resistance 32 and hence in the current through the recording meter and opposing coil to return the relay 51 to its zero position, so that the current through the recording meter is proportional to the current to be measured. This subject-matter does not appear in the Specification as accepted.