US2644886A - Electronic counting circuit - Google Patents

Description

July 1953 E. o. HOLLAND 2,644,886

ELECTRONIC COUNTING cmcux'r Filed Aug. 30, 1949 Inventor Ernest Oliver Holland mmmu A ltorneys Patented July 7, 1953 UNITED sTAras orncr:

ELECTRONIC 2,644,886 I p COUNTING, CIRCUIT,

Ernest Oliver Holland, Cambridga iEnglan'd, as-

signor to Pye Limited, Cambridge, England, a

British company Application Argue so, 1949, serial No. ii a i z's' In Great Britain August 31, 1948 1 Claim. (Cl. 250-27) tions in the load affect the triggering of the valves and experiments have shown that these variations cause instability with resultant inaccuracies in the counting.

The present invention has for its object to provide a resistance-coupled multivibratorcircuit for electronic counting which is stable in operation and, to this end, consists in incorporating multi-grid valves in the multivibrator and connecting the output and input circuits to separate electrodes of the valves.

In the preferred form of the invention, the multivibrator comprises a pair of pentode valves of which the anodes and control grids are crossconnected, the input triggering signals being fed to the anodes and the output signals being taken from the screening grids of the two valves.

The preferred circuit arrangement is illustrated in the accompanying drawing, in which V1 and V2 comprise two pentode valves, the anodes A1Az of the two valves being cross-connected respectively to the control grid GlGZ of the other valve through the resistancecapacity networks R1C1, R202 respectively. The control The multivibrator is triggered by the application of negative pulses to the point I, each negative pulse causing the valves to switch over alternately from the conducting to the non-conducting condition andvice versa in the manner common to multivibrator circuits. As each change-over occurs, 'an output signal appears alternately in the output circuits connected to the screen grids of the two valves. Thus, if the output from one of the screen grids is con- I sidered, one pulse is produced in this output grids G1G2 are also connected to the negative high tension lead or earth potential through the resistors R3R4 respectively. The anodes of the two valves are connected through resistors R 116 to the point I to which the input signals are fed, the point I being connected to the high tension positive supply lead through the resistance .R7. The suppressor grids P1P: of the two valves are connected to their respective cathodes C1C2 which are commoned and connected to the high tension negative lead through the resistance Ra shunted by the condenser C3. The outputsfrom the two valves are taken from the screening grids SIS-2 respectively through the condensers 0405. The screening grids are maintained at the desired positive potential through the voltage dropping resistors RQRIO connected to the high tension positive supply lead. I

circuit for each two negative pulses which are applied to the input I. Thus, the system efiects a division by two according to the binary system. The connection of the output circuit to the screen grid, however, separates the output circuit from the input circuit so that any variations in the output load do not afiect the stable operation of the arrangement and accurate counting can be obtained. -With the circuit described, the valve of the resistance R3 is not critical as in previously known counting circuits.

The use of a multi-grid valve also reduces inter-electrode capacities and, due to the additional gain and greater slope of the valve, the build-up time of the pulses is shorter which consequently results in more abrupt change over from one valve to the other. A'plurality of units as described may be connected in series for effecting higher counts, and

the pulses from a later stage may be fed 'back to a preceding stage in the manner described in the aforesaid publication in order to obtain a desired count which may not be a multiple of two.

While a particular embodiment has been described, it will be understood that various modifications may be made without departing from the spirit of the invention. For example, the input pulses may be applied to the suppressor grid, or a hexode or heptode valve may be used instead of a pentode. When using hexodes or heptodes, the second mixing electrodes may be joined together and the triggering pulses injected there. I 1

In a modification, the arrangement may be used for a symmetric operation by connecting the resistances Re and R6 direct to the high tension supply lead instead of through the common resistor R7, and applying separate triggering pulses directly to the anodes of the two valves.

3 ing a pair of pentode valves arranged in a trigger-pair circuit, means comprising a resistor connecting the anode of each valve to a high tension positive supply, means comprising a resistance shunted by a capacity connecting each anode to the grid nearest to the cathode in the other valve, means connecting the suppressor grid in each valve to the cathode of that valve,

means for applying the pulses to be counted togrid being connected to the high tension posi tive supply through a resistor.

References Cited in the file of this patent UNITED STATES PATENTS I OTHER REFERENCES Article, The Eccles-Jordan Trigger Circuit, pages, 54 to 57 of Time Bases, by Puckle, published December 1947.

Radiation Laboratory series, vol. 19, published ERNEST OLIVER 15 194 9, pages 6116:608.

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