GB600276A - Improvements in thermionic valve voltmeters - Google Patents

Abstract

600,276. Thermionic valve voltmeters. MARCONI'S WIRELESS TELEGRAPH CO.,. Ltd., and NEILSON, P. J. May 10, 1945, No. 11747. [Class 37] A valve voltmeter includes a multi-electrode valve so connected that the application to one of its electrodes of the voltage to be measured causes a simultaneous and opposite change in current to two of its other electrodes, and a current or voltage measuring instrument connected across the last-mentioned electrodes so as to indicate the resultant change. In the arrangement shown a pentode V has its cathode connected through a resistor RC to the nega. tive terminal of a source of anode current, the first grid being connected to an adjustable tapping on the resistor RC. The second grid is connected to the anode through series-connected resistors R, S,. the junction of which is connected to the positive terminal of the source of anode current, the potential of which may be 140 volts. The voltage to be measured is applied to the third grid and cathode with its negative terminal to the grid. An indicating meter M is connected across the resistors R, S. The adjustable tapping on the resistance RC enables the measuring instrument to be zeroized. The pentode V may be replaced by a pentagrid valve, the second and fourth grids of which are connected together and to the lower end of the resistor S, the third grid being connected to the negative terminal of the voltage to be measured.