US2977541A - Counting system - Google Patents

Description

March 28, 1961 R. A COLA COUNTING SYSTEM Filed Aug. 29, 1957 IN VEN TOR. RUDOLPH A COL A KM am 2,911,541 COUNTING SYSTEM Rudolph A. Cola, Philadelphia, Pa., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Aug, 29, 1957, Ser. No. 31,010

. l 2 Claims. o|. 328-52) This invention relates to counting systems employing electron-beam switching tubes and particularly to an improved arrangement for coupling a plurality of such tubes in a unitary counting chain. p 1 Electron beam switching tubes of the type employed in the presentinvention are shown in 11.8. Patent No. 2,721,955 to Fan et;al. These tubes include a central longitudinally elongated electron emitting cathode and a pluralityof groups of electrodes arrayed about the cathode. Each group of electrodes includes an electron beam forming electrode known as a spade electrode, an electron target electrode, and an electron beam switching electrode. Acylindrical permanent magnet surrounds each tube and provides an axially aligned magnetic field withinthe tube. This magnetic field andthe electric field provided by;electrode potentials operate .to switch an electron beam from one group of electrodes to the next.

Tubes; of the type'described above are particularly useful as counters and two or more of them may be cascaded to provide a count on-any desired scale, for example, ascaleof ten, one hundred, one thousand, or the like. In the past, the cascade connection of the tubes has been made, for example, by direct coupling, by capacitive coupling, by means of coupling transformers, orthe like. However, under certain conditions and particularly when the tube supply voltages fluctuate, none of these arrangements provides completely satisfactory coupling of a switching signal from on'etube to another in the counting chain.

, Accordingly, one object of the present invention is to provide an improved counting system employing a plu-' rality of serially connected electron beam switching tubes. Another object of the invention is to provide an improved coupling and switching arrangement for a counting system employing serially connected electron beam switching tubes, the operation of the system being characterized by uniformity and efiiciency in coupling of signals from one tube to the next.

, ln brief, asystem embodying the invention includes a plurality of serially connected electron beam switching tubes which are operated to perform a unitary counting function. According to the invention, the tubes are coupled by a voltage standardizer having square-loop characteristics. Such a standardizer comprisesa magnetic core-wound inductive means having a generally rectangular. magnetization curve and providing constant energy outputalthough its input energizing current might vary Over a comparatively wide range with time. This type of magnetic inductive means may also be employed to couple an; input signal to the first tube of the counting chain of tubes.

2,977,541 Patented lVlar. 28, 1961 age standardizer of the type employed in the system of Fig. l; and

Fig. 3 is a schematic representation of a circuit which may be employed in the system of Fig. 1.

The system shown in Fig. l, for the purposes of illustrating the invention, is a decade counter having a scale of 100 and employs electron beam switching tubes of the type shown in US. Patent No.'2,721,955' to Sin-pih Fan et. al. In Fig. 1, two such tubes 10 and 12 are shown which operate as units and tens counters, respectively. In actual construction, the tubes 10 and 12 are cylindrical in form; however, for convenience, they are shown schematically in linear form; The tube 10 includes a cathode 14 and ten groups of electrodes, each of which receives, in turn, an electron beam emitted by the cathode. In the interest of simplifying the drawing, only three of these groups of electrodes are shown, numbered 1, 2, and 0. In tube 10, each group of electrodes includes a generally U-shaped longitudinally elongated beam forming and holding electrode 16,

called a spade electrode, a generally L-shaped longitudinally elongated target or output electrode 18, and a rod-like switching grid electrode 20. An open-ended cylindrical permanent magnet (not shown) surrounds the tube 10 and is coaxial therewith and provides. an axial magnetic field within the tube which is oriented to urge electrons from the cathode either clockwise or counterclockwise, as desired. The magnetic field strength is selected to provide a desired magnetron cut-off and operating tube current. The second tube 12 is a duplicate of the first tube 10 and includes a cathode 1'4, spade electrodes 16', target electrodes 18, switching electrodes '1 The invention isdesoribed in greater detail by refer- 20', and vacylindrical magnet (not shown).

' In the counter system shown in Fig. l, and particularly referring to the tube 10, the cathode 14 of the tube is connected through a degeneration resistor 22 to a source of reference potential such as ground. A bypass capacitor 24 is connected across the resistor 22. The cathode is provided with a supply voltage V of the order of +45 volts. Each spade electrode is connected through a load resistor 26, which is paralleled by a capacitor 28, to a common spade buss 30. The spade buss is connected to a source (not shown) of spade supply voltage, V of the order ofvolts above cathode voltage.

All of the target electrodes 18, except the last 18a, are connected through load resistors 32 to a common target buss 34 to which a supply voltage, V of about +300 volts is coupled. An output terminal 36 is provided at each target electrode for connection to a suitable utilization device which may be a visual indicator, for example, a glow tube such as type 6449 gaseous indicator tube. The connection of the last target electrode 18a in the circuit is described below. The switching grid electrodes 20 are connected together and are coupled to a source (not shown) of supply voltage, V of the order of +300 volts and to a source (not shown) of switching pulses 38 such as a one-shot multivibrator.

The tube 12 is connected to substantially the same circuitry as the tube 10. The cathode 14' of the tube 12 is connected through a degeneration resistor 22 to ground and the resistor 22' is by-passed by a capacitor 2 4'. The cathode is also provided with a supply voltage, V of the order of +45 volts- The spades 16 are connected through load resistor 26 in parallel with capacitor 28' to a common spade buss 30'. A spade supply Vol tage V of the order of 100 volts over cathode voltage is suitably coupled to the spade buss. The targets 18' are connected through load resistors 32' to a common target buss 34' at which a target supply voltage, V of about +300 volts is provided. Output terminals 36' are provided at each of the target electrodes for con;

nection to a suitable utilization device (not shown). The switching electrodes 20' of tube 12 are connected together and are suitably coupled by a capacitor 40 to the "output or position of the tube 10. This coupling is described in greater detail below.

Each of the tubes and 12 of the counting chain is provided with a zero-setting means, that is, means for interrupting the counting operation of the tube and for starting the count at a predetermined first position. Various means for zero-setting a beam switching tube of the type described above are shown in Bethke US. Patent No. 2,794,147. One suitable zero-setting arrangement shown in Fig. l for the tubes 10 and 12, respectively,

comprises a parallel combination of resistors 42, 42 and capacitors 44, 44' connected in series between the spade resistors 26, 26' and the spade busses 30, 30" at the position in the tube at which it is desired to initiate the count. The junction points of the two resistors 26 and 42, 26' and 42', are connected through reverse-biased diodes 46, 46' to sources (not shown) of negative pulses 48, 48. The diodes 46, 46 are oriented so that the direction of easy current flow is from the junction points of resistors 26, 42 and 26', =42 to the source of zero- set pulses 48 and 48.

In the system shown in Fig. 1, the tube 10 is the units counter and the tube 12 is the tens counter. Of course, additional tubes may be provided to operate as counters of hundreds and thousands. In operation of the counter system, the units counter tube 10 is set in operation and, after the electron beam has been moved from position to position under the control of pulses 38 applied to the switching electrodes 20 and the tube 10 has completed its counting cycle, that fact is recorded in the tens counter tube 12 by the switching of the electron beam one position under the influence of a signal pulse transmitted to its connected switching electrodes 20 from the units counter. The present invention provides improved circuit means for signal-coupling the two tubes 10 and 12 so that a switching pulse 50 of optimum characteristics is transferred properly from one tube to the next and the desired counting operation is performed accurately and efficiently.

across the target resistor 52 when the electron beam strikes the target 18a and serves to increase the initial target current. According to the invention, the coupling circuit also includes a voltage standardizer which comprises, essentially, a magnetic inductive element which is known as a bistable square loop magnetic core. The bistable square loop core 60 includes two coils of wire 66 and 68 wound on a magnetic toroid or core 70 which has a generally rectangular magnetization curve. The magnetic core 70 may compnise, for example, a material known as rnolypermalloy which is an alloy of 4% molybdenum, 79% nickel, and 17% iron. This type of core, having a rectangular magnetization curve, provides constant energy output, that is, no matter what range of input current energizes the core, only a predetermined constant maximum magnetic flux change takes place in the core and an output pulse is provided which has an area which remains constant with respect to time.

Referring to Fig. 1, the coil 66 of the inductive coupling element 60 is a bias winding for the core 70 and is connected to the target voltage supply V The coil 68, which is the output coil of the magnetic element 60, is connected across the resistor-diode (58, 56) combination. The resistor 58 and diode 56 serve to damp the output signal pulses from the output coil 68.

A typical magnetization curve for a square loop inductive element of the type described above is shown in Fig. 2. The magnetization curve is generally rectangular in form and is related to the operation of the magnetic element 60 in the following manner. With a constant DC. current flowing through the bias coil 66, a. constant level of maximum negative magnetic flux (B,-) is maintained in the core 70 and is represented at point A on the curve. When the electron beam in the tube 10 reaches the last target 18a in the counting cycle, current flows through the second coil 68 Initially, as current flows to the target 18a, the magnetic flux remains constant at the maximum negative value until the positive intensity portion of the curve is reached. Then, 'the magnetic flux increases rapidly to a 'maximum'positive value l-B for example, to point B When the electron beam in the tube 10 is switched from the last targewo" fo the next one 1" to start the countingcycle again, the square loop core 60 returns along the line of maximum fiux to the negative intensity region and then to the bias condition at point A. These changes in magnetic flux produce the voltage pulse 50, the area of which remains constant since the area 'of the magnetization curve remains constant regardless of the magnitude of the magnetizing current. Pulse 50 is basically asawtooth.

The voltage pulse '50, applied to the grids 20' of the tube 12, switches "an electron beam from one position to the next. When'the tube 10 completes its counting cycle and its electron beam reaches the 0 position, another 'pulse 50 is generated and the electron beam in the tube 12 is switched to the next position.

A square loop magnetic element of the type described above for coupling the tubes 10 and 12 may also be employed to couple an input switching signal into the tube 10. A circuit for performing this operation is shown in Fig. 2 and includes 'a one-shot multivibrator comprising essentially two electron discharge tubes 72 and 74. The tubes include cathodes 76 and 78 which are connected together and to ground through a suitable bias resistor 80. Tube 72 includes -a control grid 82 which is connected to ground through a par allel combination of a bias resistor '84 and diode 86 and the grid 82 is also coupled to a source of input signal pulses 88 by means'of a coupling capacitor 90. The tube 72 also includes an anode 92 which is cross-connected through a timing capacitor 94 to grid 96 of tube 74. The tube 74 includes an anode 98 which is connected through a load resistor 100 to one end 102 of a bias coil 104 wound on a core 105 of a magnetic square loop inductive element 106, the end 108 of which is connected to a positive D.C. supply voltage B+. The control grid 96 of tube 74 is also connected through a bias resistor 114 to 'the positive B voltage. The anode 9-2 of tube 72 is connected through a load resistor 116 in parallel with a capacitor 117 to one end 118 of the output coil 120, the other end 122 of which is connected to the B+ voltage supply. The end of the second coil is also connected through a coupling capacitor 124 to the switching grids (not' shown) of a counting tube.

In operation of the circuit of Fig. 3, in the quiescent state, tube 74 conducts current because its grid 96 is biased through its connection to B+ and the electron current flow path is from ground through cathode bias resistor through the tube and the coil 104 to 13+. The resultant voltage drop across the cathode bias resistor 8i) cuts oif tube 72, the control grid 82 of which is at ground potential due to its connection to ground through the parallel combination of resistor 84 and diode 86. When a positive pulse 8 8 is applied to the grid of tube 72, the tube 72 conducts current and the resultant pulse of current through the coil provides a voltage pulse 126 which is coupled through the capacitor 124 to the grids of a beam switching tube. The pulse of current through the tube 72 provides a voltage drop across the tubeload resistor 116 and coil 120 which is coupled through the capacitor 94 to the grid 96 of tube 74. This coupled voltage cuts off tube 74. The time constant of the combination of resistor 114 and capacitor 94 determines the length of time required for the return of tube 74 to the conducting state and the return of the multivibrator to the quiescent state.

With respect to the characteristics of the switching pulses which are transmitted from one tube to another in a counting chain, it is essential, of course, that the amplitude of the pulse be sufficient to depress the switching grid electrodes enough to cause an electron beam to switch from one position to the next. The square loop magnetic inductor may be readily selected to provide the desired switching pulse amplitude. It is also necessary to control the time duration of the pulse so that the beam is switched by only one position when all of the switching electrodes are connected together. The bypass capacitors for the spade load resistors play an important part in controlling this characteristic.

The present invention thus provides a counting system in which reliable and accurate transmission of a counting signal from one counting unit to another is achieved. This accuracy results from the provision of a transmitted counting or switching signal of constant energy which is substantially unaffected by voltage or current fluctuations in its electronic environment.

What is claimed is:

1. A counting system comprising a plurality of cascadecon-nected magnetron beam switching tubes each having a cathode and a plurality of groups of electrodes; each group including a target electrode which receives an electron beam and produces an output signal therefrom, a spade electrode which holds an electron beam on its associated target electrode, and a switching electrode which serves to switch an electron beam from one group of electrodes to the next; all of the switching electrodes in each tube being connected together whereby a single source of driving signals maybe employed to switch an electron beam in each tube, the driving signals provided by a single source having a comparatively critical energy content to insure the switching of an electron beam by only one position in each tube; a source of beam switching pulses coupled between first and second adjacent beam switching tubes; said source comprising a magnetic core having a bias winding and an output winding and having a generally rectangular characteristic magnetization curve which insures the production of constant energy output pulses; said output winding of said source being coupled between a target electrode of said first tube and the commonly connected switching electrodes of said second tube whereby a pulse applied by said lastmentioned target electrode to said source of beam switching pulses causes the generation and application of a required switching signal to said last-mentioned commonly connected switching electrodes; all of the pulses produced by said source thus having substantially the same energy content.

2. The system defined in claim 1 and including a re sister and a clamping diode connected across said output 7 winding of said source of switching pulses.

References Cited in the file of this patent UNITED STATES PATENTS Television for Radiomen, Noll, The MacMillan Company, New York, 1952, pages 252, 253.

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