Patent GB-393497-A (GB)
Title: Improvements in and relating to remote measuring apparatus
IPC: G08C19/22
Filed: 1932-11-24
Abstract: 393,497. Current and pressure meters. INTERNATIONAL GENERAL ELECTRIC CO., Inc., 120, Broadway, New York, U.S.A. -(Assignees of Allgemeine Elektricitats- Ges. ; 2, Friedrich Karl-Ufer, Berlin.) Nov. 24, 1932, No. 33287. Convention date, Nov. 24, 1931. [Class 37.] In a system in which measurements are transmitted by impulses of constant frequency but of duration proportional to the value being measured, a potential corresponding to the magnitude to be measured has superimposed thereon a potential varied in relation to time to control the discharge periods of a vapourelectric device; the impulses transmitted being of the same duration as the time taken for the varying potential to reach the potential corresponding to the magnitude to be measured. As shown in Figs. 1 and 2 the magnitude to be measured is connected through a transformer 10 and rectifying network 11 to create a direct current potential across resistance 12 which gives the discharge tube 16 a negative bias. The switch 18, which is revolving at a constant rate, closes (i) a circuit to the plate of the tube 16, (ii) a circuit through resistance 21 and (iii) a circuit through inductance 19 and resistance 20. The current flowing through 21 initiates the transmission of a high frequency 'pulse over the lines 24. The current in the circuit 19, 20 gradually builds up and when the potential drop in 20 exceeds the potential across 12 plus the potential due to the connection P2, the device 16 discharges, shorting 21 and stopping the impulse.- The building up of the current in 20 is represented diagrammatically by A in Fig. 2, where B represents the bias on the tube created by the potential of P2, shown as V1, and the potential across 12, shown as V2. An impulse of duration t is transmitted, of which to represents the unvariable bias, signals of this duration being transmitted when no potential is created in 12. At the receiving station the impulse passes through the primary 27 of the transformer and induces a voltage in the grid and anode circuits of the receiving discharge tube 30, which starts to discharge and feeds constant current to the receiving instrument 32. When the impulse ceases an impulse of reverse polarity is induced by 27 in the circuits of 30 so that the discharge stops. The condenser 33 prevents 32 from hunting. The instrument 32 is calibrated to give a zero reading when impulses of duration to are received. In the embodiment shown in Figs. 3 and 4, the discharge tube 16 is fed from an alternating current source 38, the. coupling transformer having three secondary windings 39, 40, 41 feeding the anode, cathode and grid of the tube 16 respectively. An inductance 42 is connected in circuit with the winding 41 of the transformer so that the grid potential lags behind the anode potential. The anode potential is indicated by curve C, Fig. 4, the grid potential fed from 41 by curve D and the potential to be signalled by straight line E. As the other parts of the circuit have the same functions as similar parts in Fig. 1, it follows that current flows through the resistance 21 for time t1-t3 in each cycle, the resistance being shorted by the discharge in the tube from t3-t4 and the flow in 21 being in the reverse direction for time t4-t5. Signals are sent to the remote point when the current in 21 flows in a positive direction only, that is for the time t1-t3, the period of the signal being composed of the time t1-t2, which is the " lag " time and is the period of the signal when the potential across 12 is zero, and t2-t3 which is proportional to the magnitude being measured. The receiving equipment is similar to that shown in Fig. 1.