Improvements in and relating to electrical apparatus for graphically demonstrating transient electrical wave forms

摘要

460,690. Valve generating circuits. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.) May 19, 1936, No. 14213. [Class 40 (v)] [Also in Group XXXVI] A surge generator circuit is coupled to the time-base circuit of an oscillograph by means of a discharge tube having a control electrode, whereby the surge is initiated whenever a charging current is initiated in a condenser forming part of the time-base circuit. By this means repeated surges may be applied to a circuit to be tested, the surges being synchronized with the timing motion of the beam of the oscillograph so as to retrace the curve and produce a brilliant image of the transient wave shape. The apparatus consists of a condenser 11 having a surge discharge circuit including the inductance 12 and resistances 13, 14. A. cathode ray, electron beam or other type of oscillograph may be employed, and the deflection may be produced electromagnetically or by electrostatic plates 16, 17 arranged at right angles. The plates 16 for producing the time sweep are connected across a condenser 15 which is charged through a resistance 25 and a valve 24 from a transformer 21. The valve 24 is preferably of the type which is triggered off when a suitable potential is applied to the plate and remains conducting as long as sufficient voltage remains between plate and cathode. The grid 26 is suitably biassed from a source 29 and the valve remains nonconducting until the voltage of the secondary winding 22 reaches approximately its peak positive valve, so that the condenser 15 is charged once in every cycle of the A.C. supply and moves the cathode ray beam correspondingly across the screen of the oscillograph. The condenser 15 is discharged through a resistance 31, the value of which is such that the return is slower than the forward movement whereby a zero line is traced on the screen. The condenser 11 is connected to the transformer winding 22 through a rectifier 32, and a valve 33, similar to the valve 24, is interposed in the discharge circuit of the condenser in series with the impedances 12, 13, 14. A second valve 38, connected oppositely with respect to the electrodes of the valve 33, is provided and operates when the discharge circuit is oscillatory. The valve 33 is tripped in synchronism with the sweeping of the cathode-ray beam along its timing axis by connecting the grid 34 to the cathode of the valve 24 through a condenser 44, so that, as soon as the valve 24 commences to conduct, a positive impulse is applied to the grid 34 to cause the valve 33 to light up. The condenser 11 discharges through the valve 33 and impedances 12, 13, 14, and the wave form is observed by connecting the deflector plates 17 of the oscillograph across the resistance 48 which is in parallel with a condenser 47 across the resistance 14.