| 摘要 |
286,666. Brillouin, L. N. March 8, 1927, [Convention date]. Producing transient current impulses. -A constant current is applied for a predetermined time, for medical diagnosis for example, by an arrangement comprising a thermionic valve the grid potential of which is controlled by an auxiliary circuit Fig. 1 comprising two condensers c<1>, c<2> each shunted by a resistance (r<1>, r'), a battery 1 of negligable resistance and a switch 2; two inductances L<1>, L<2> each associated with a series resistance (r<1>, r<2>) may be employed as an alternative Fig. 5. The grid 6 of the first valve in the arrangement shown in Fig. 7 is given a negative potential e, Fig. 8, from battery 5 which on closing switch 2 is immediately increased to a value determined by the condenser ratio and then falls exponentially to a value, Fig. 9, dependent on the resistance ratio. The resultant variation in potential drop ri in the plate circuit resistance 8, is applied to the grid 10 of a second valve in series with a control-battery 14, and the grid battery voltages are adjusted to produce an impulse of constant current i<1> as shown in Fig. 11 each time the switch 2 is closed. A modification with resistance and capacity coupling of the valves is also described. An arrangement employing one valve is shown in Fig. 13. In this the point 14 on a battery 1 is selected to afford a voltage V<1>, Fig. 14, such that the valve will pass a saturation current directly the switch 2 is closed which current is maintained for a period, Fig. 15, during the exponential fall of grid voltage, followed by a short period in which the current falls to zero, Figs. 14, 15. The value of the output current and the period of application may be adjusted in all the arrangements described. |
