US2568449A - Electronic counter - Google Patents

Description

Sept. 18, 1951 s. HANSEN ELECTRONIC COUNTER Filed Dec. 5, 1947 Fiigi.

TO POWER SU PPLY.

Inventor": 65 siecgFried Hansen, by Wig/W 12.

His Attorney.

Patented Sept. 18, 1951 ELECTRONIC COUNTER Siegfried Hansen, Los Angeles, Calif., assignor to General Electric Company, a corporation of New York Application December 5, 1947, Serial No. 789,794

4 Claims. 1

This invention. relates to. electronic counters utilizing. electron beam devices of the multipleanode type.

An. object of thisinvention is to provide a new and improved.l electronic counter.

Another object is toprovide animproved. electronic counter which is. capable of counting electric pulses. at rates up to 106 pulses per second.

.A further object is to provide an improved electronic counter which. has a greatly reduced number of, components compared to conventional counting circuits.

Another object. is to provide an improved, electronic counter which. is especially adapted for use-as. a timing. generator for television systems, and for. other purposes.

In. this, invention, there. is provided an electron beam. device of thecathode-ray type which has: a. multiple-anode. structure hereinafter described, and. an electric. circuit connected to beamedeflecting plates in. the. electron beam, device whichcontrols. the lateral movement. of the electron beam from one, anode to, another responsive. tov the pulses countedso that a counting, ratio is obtained. which depends, solely upon theconstruction. of the multiple anode. structure. In. the preferredembodiment, the anodestructure comprises a plurality of. parallel anodes arranged in a row substantiall parallelto the direction of the electronbeam... The. anodes on. each. end. of l the row function. as reversing. e1ectrodes,,while those in between. serve as. counting electrodes. All of the anodes are of material having a secondary emission ratio substantially greater than one. The controlling circuit comprisesa flip-flop,

or switching, circuit so. connected to the reversing electrodes that when either electrode is struck by the electron beam, the secondary emission current produced triggers the switching circuit which, in turn, effects a reversal in polarity ofthe voltage between beam deflecting plates of the electron-beam device: Since the polarity of voltage between the deflecting plates determines the direction of-fl'ateral movement of the electron beam,'the electron beam reverses its direc tion of lateral movement: each time a predetermined number of pulses iscounted and-the electron beam arrives at" one of the end anodes. For example", fivecounting electrodes may be-providedg which makes a total f seven anodes including the two: reversing electrodes. As pulses are counted, the electron beam moves fromthe first to: the fifth counting electrode; and" then to one oi the reversing electrodes. Thereupon the voltage between deflecting plates is: reversed in polarity, and the beam retraces its path in the opposite direction until; it reaches the. other reversing electrode; In completing a full cycle on operations, the beam passes over each count.- inge'lectrodetwice. Therefore; the counting ratio is two times the number of electrodes, or. 10:1 in the example given. This counting ratio. may be increased by simply adding more countingelectrodes. Thus, a. high counting ratio with, relatively few components is possible. The reversing electrodes not. only double the, counting ratio of the device, but also increase the maximum counting speed, since they make possible. the elim ination of the relatively long time interval which otherwise would be required to return thebeam to starting position after it passed the lastcounting electrode.

The features of the invention which. are believed to be. novel and patentable are set forth inthe appended claims. For a better understanding of the invention referenceismade in the fol.- lowing description to. the accompanying drawing, in which Figl is a diagrammatic represents..- tion of one embodiment of the inventiomliig, 2 is an illustration of a preferred anode. structure utilized in the electron. beam device. shown. in Fig. 1, Fig. 3 illustrates a modification of the anode structure of Fig. 2; Fig.4 is an. alternative anode. structure; and Fig. 5 is a-schematic, d1- agram illustrating, the changes. necessary to. utilize the anode structureof Fig.4.

Referring now to Fig. 1, an electron-[beam device lil comprises anenvelope IDA, which con..- tains. an electron emissive cathode H, a control grid I2, a pair oiv accelerating. and focussingelectrodes l3 and. I4, a pair of deflecting plates l5 and i6, andanelectrically conductive coating l1. These component partsare similar to those found in. a conventional cathode ray oscillograph. tube. The fluorescent screen which is at the large end of the envelope in an oscillograph tube may be omitted for some applications of the present device,.and may be included for others, as. xplained hereinafter. Adjacent to the large end l8 of envelope IDA is an anode structure which comprises a plurality of. parallel. anodes or targets 19, 2|], 2|, 22, 23, 24 and 25. More specifically. the targets l9 and 25 will be referred to as reversing electrodes and the targets 2 ll24 as counting electrodes. Preferably, the exposed surfaces.

of the anodes are constructed of an electrically conductive material having a secondary emission ratio substantially greater than one. For example, anodes coated with magnesium oxide or beryllium oxide may be used. The preferred configuration is illustrated in detail in Fig; 2. The number of counting electrodes 20--24 determines the counting ratio of the tube. The end or reversing electrodes l9 and 25 take part: in changing the direction of the lateral movement of the electron beam as it leaves either electrode Her 24, as-hereinafter explained.

A. conventional power supply, not. shown, connected to. terminals 26' furnishes the required voltages for operation of the" electron beam deknown to those skilled in the art pertaining to cathode ray oscillograph tubes and similar electron-beam devices.

In the embodiment illustrated in Fig. 1, a source of negative pulses to be counted is connected to input terminals 21. The negative pulses are transmitted through coupling capacitor 28 to control grid l2. Pulses to be counted should have an amplitude large enough to drive control grid l2 sufiiciently negative to momentarily interrupt the electron beam.

Potentials for controlling the lateral movement of the, electron beam are supplied to the deflect: ing plates l5 and I6 by a voltage-control circuit 29. which comprises two amplifiers which respectively include vacuum tubes 30 and 3!. Tube 36 comprises a cathode. 32, a control grid 33, a screen grid 34, a suppressor grid 35 which is connected to cathode 32, and an anode 36. Tube 3| is similar to tube 30,and comprises a cathode 31, a controlgrid 38, a-screen grid 39. a suppressor grid 40 connected to cathode 31, and an anode 4|. Both cathodes are connected to a common ground terminal 42. Anode voltage for tubes 30and 3| is supplied through resistance networks 46jand 41 from a conventional direct current supply circuit,.not shown, which has its positive terminalconnected to terminal 43 and its negative terminal connected to ground. The potentials of anodes 4| and 36 are appied to deflecting plates l5 and [6, respectively, through connections 44 and 45.

Tubes 30 and 3| are caused to operate alternately under'the control of a flip-flop circuit 48. This flip-flop circuit comprises a pair of electron discharge tubes 49 and 56 having, respectively, cathodes 5| and 52, control grids 53 and 54, and anodes 55 and 56. Anode voltages for tubes 43 and 50 are supplied from terminal 43 through the respective resistance networks 46 and 41. These tubes function as switching devices under the control of the reversing electrodes [9 and 25, as explained hereinafter. The reversing electrodes l9 and 25 are connected, respectively, by a pair of conductors 51 and 58 to the control grids 53 and 54. A resistance network 59 comprises two resistors 60 and GI of fixed value and a resistor 62 .which is connected between the first-mentioned resistors. All three resistors 66-62 are connected in series between the control grids 53 and 54. Resistor 62 is provided with an adjustable tap 63 connected through a resistor 65 and adjustable tap 66 to terminal 64, to which a source of negative bias voltage, not shown, is connected. .Tap 66 provides means to adjust, simultaneously, the bias voltage applied to the grids 53 and 54, and tap '63 is used to adjust the relative bias voltages'applied to the two grids. Terminal 64 is also utilized to supply a bias voltage to grids v 33 and 38, and is connected to these grids through a conductor 61 and resistor 68. Grids 33 and 38 are tiedtogether and connected by a conductor 69 to the counting electrodes 2024.

Fig. 2 illustrates the preferred structure of anodes l9-25. The exposed surfaces of these electrodes are made of a material, beryllium oxide for example, capable of producing secondary .emission currents when struck by the electron beam. The reversing'electrodes l9 and 25 are suitably supported within envelope IllA,.and are insulated from each other and from the counting electrodes. The counting electrodes Ell -24 may be stamped out of a Single piece of material in the form of a grid 20A havin any desired number of parallel strips (26-24), depending on the counting ratio desired as will be presently explained. The illustrated construction of the counting electrodes permits theme of very simple and straightforward supporting means, which provides a decided economy in the manufacture of such devices. Obviously, the electron receiving electrodes could be simplified further by utilizing a metallic conducting paint, applied, for example, on an insulating material such as glass. The conducting material must, of course, have a secondary emission ratio substantially greater than one. Electrons which strike the insulating material build up a small surface chargethereon. This raises the potential of the insulating sur: face a few volts, but not enough to substantially alter the path of the electron beam. The small rise in potential, however, is sufiicient to increase the secondary emission ratio of the insulating material to one, so that thereafter an equilibrium exists between the number of electrons arriving at the insulating surface and those leaving due to secondary emission. The electrons which are emitted travel to coating ll. 7

In Fig. 3 is illustrated a plurality of electronreceiving electrodes 13A, 26B and 25A arranged to be disposed on the inner surface of the portion It of the envelope IDA by vacuum evaporation of a metal, such as aluminum or silver. The

' proper electrode pattern can be arranged by making this disposition of the material through a mask designed in accordance, for example, with the electrodes illustrated in Figs. 2 and 4. Subsequently, its secondary emission ratio could be substantially increased by the evaporation through the same mask, of an extremely thin film of magnesium (Mg) or beryllium (Be), and this film, in turn, oxidized by'baking in air to produce a surface having a thin film of. MgO or BeO. Such a surface gives a high secondary emission yield. The ratio of this emission to the primary emission being substantially greater than one.

Referring to Fig. 1, assume that tube 30 is conducting and that the potential of grid 33 is such that the electron beam is directed into the space between electrodes l9 and 26. As a result, no current flows to electrode 20 and the grid 33 of the tube 30 is rapidly driven more negative 'as' the wiring and electrode capacitances discharge through resistor 68. As grid 33 becomes more negative, anode 36 becomes more positive;

' and since deflecting plate I6 is connected to'the anode 36, a right-hand deflection (with respect to the observer) of the electron beam occurs. This deflection continues until the beam strikes the counting electrode 20. If the entire crosssection of the beam should strike. electrode 26', a secondary emission current would be set up which is more than sufiicient to counteract the discharge of circuit cr-pacitances through resistor 68, and thus tends to drive grid 33rmore positive and deflects the electron beam to the left. As a 7 result, an automatic servo action exists which so interrupts the secondary-emission current. During this interruption, discharge of the circuit I causes the beam to come torest partly on and partly ofi electrode 20, in such a way that the secondary emission current is substantially equal to the current through resistor 68. The electron beam then remains on the left edge of counting electrode 20 until an impulse of negative polarity arrives at the input circuit 21. This negative impulse momentarily interrupts the electron beam by driving control grid l2 to cut-oil, and

aaeeguo capacitances. through resistor Bills resumedtso that at the end of the input pulse the electron beam: is reestablished on a path which is to the right; of electrode: 20, and: which may pass between. electrodes and. 21 if the input pulse is of thaproper duration. The beam thus travels to the left edge of electrode 2 whereupon secondary emission current arrests the laterali movement'. A tolerance of the order of plusior minus 50% in. the duration of: the input impulse is. al-

lowable; sinceif the electron beam falls anywhere in the spaces between the electrodes: or on. them, it: willi automatically seek tow the left edge: of the electrode. This relatively large tolerance of adjustment is one of the principal advantages of this counting system over the previously used chains of multi -vibrators used in radar" or'tel'evision timing generators.

The electron beam progresses from. one countting electrode to the next in response to: each i negative impulse arriving at the in ut. circuit 211, This progression continues until the" last electrode 24- is passed; whereupon the electron beam strikes the right-hand reversing electrode 25". The flow of secondary emission currentfrom this last-mentioned electrode applies a positive impulse to grid 53 of tube l9 and transfers current from. tube 50' to tube 49* by the: switching action offlip-fiop circuit 48. This reduces the potentials applied to screen grid 34 and anode 36. and raises the potentials applied to screen grid 39 and anode 41. When this-occurs, tube becomesnonconductingand tube 31 assumes control of the electron beam deflection. When this switching action occurs there is atendency to If deflect the electron beam rapidly to the left. However, capacitances' of the wiring and the defleeting plates prevent thebeam being deflected instantaneously to the left side of the anode structure; therefore, the beam in moving to the left strikes anode 24-, and produces a secondary emission current sufficient to arrest further deflection to the left. The beam may be deflected back into the space between anodes M and 25-for an instant due to sudll'en over-correction. From a symmetry conditions it is evident" that the counting tube It] will now perform just as before except that the electron beam will progress from right to left. The arrival of negative impulses at input 21 will cause the beam to jump from one counting electrode-to the next until it reaches the left reversing electrode F9 whereupon the flip-flop circuit again operates to restor'e the initial conditions.

It is evident that in completing a full cycle of operations the beam will pass over each counting electrode (20-24) twice and, therefore, the counting ratio is twice the number of counting electrodes or tento one for the structure shown in Fig. 2. This ratio may be increased to1'000 to l, for example, by simply adding more counting electrodes. This high counting ratio with relatively few components is another advantage oflthe' invention.

The countingspeed. is limitedv only by the rate of discharge of circuit capacitances through-resi'stor 68 and by the reversal time. of fii'p flop circuit 48 With this present invention it is possible-to count impulses of the order of 5 1 0 per second. If a slower counting speed. is desired for longer impulses, it is only necessary to add a capacitor H!- of appropriate"-value between ground and conductor 69 to reduce the rate of discharge of circuit capacitances through resistor 68.

envelope MA a fluorescent screen at the large end: t8 of the envelope to indicate the position of the electronnbeam. If it is desirable toreset' the system to zero before a count is made, this can be done by momentarily biasing the deflection plates through: asuitable circuit to that voltage which will: cause the beam to fall on the lefthand reversing electrode l9; When. this: biastis released, the system will be in the initialeondition.

The counter illustrated in Figs. 1 and 2 provides means :for counting: pulses of substantially uni"- form duration and either uniform or random repetition rate. In order to count impulses having random duration, it is preferable to use a counter having an anodestructure' as illustrated in Fig; .4. Referring now to Fig; 4, a counting electrode structure I I- A comprises a plurality of anodes TI to 19, inclusive; arranged in two interleavedrows in the form of a grid in which the unattached ends of the electrodes 72-, 'M, 7'8, and 18' extend into the'spacesformed' by the unattached ends of the electrodes TI, l3, 15, 1'1 and 19. A pair of reversing electrodes 80 and 8| are provided at-th'e opposite ends of" the anode structure, and operate in the same manner as the reversing'el'eotrodes I 9 and 25' of Fig; 1. The anodes may be constructed as described in connection with electrodes I9-25 or they ma We constructedasiillustrated in Fig. 3. 1

When the counting electrode structure! this utilized, the electron beam device It must incorporate, as illustrated in Fl'g; 5 an second pair of deflecting plates82 and 83; These plates provide the means, when suitably energized; to deflectthe electron beam perpendicular to: the direction of deflection; provided by plates l5 and It. Inrelation totFig; 5;.p1'ates it-and lfi-deflect'theelectron beam vertically, and plates 82 and 83 deflect the electron beam perpendicular to the plane of the drawing. Terminals 84 are provided for connecting the source of pulses counted to deflecting plates 82 and 83-, rather than to the control gri'dtas in- Fig. 1'. Terminals at andian adjustable ta rosisto'r"86" are provided for connecting to plates 82 and 83 a suitable DL-C. source, not shown, to provide proper operating potential to these deflecting plates. otherwise; the apparatus is similar to thatillustratied in Fig. 1.

The operation of the apparatusishown in Figs. 4

and 5 is essentially the same as described in connection with the embodiment of'the invention itlus-trated': in Figs. 1 and 2 Forexample-referring to Fig. 4, assume that an electron beam A is resting on the left edge of electrode H and that' the bias on the vertical plates ti -83 is arranged so where it-Wflli remain until the arrival of theinext impulse at input 84.

The positioning of the electron beam substantially between points B and C, Fig. 4, may be ac- "complished by adjusting the direct current potential applied to deflecting plates 82 and83 by adjusting the tap position on resistor 86; while positioning of the electron beam between points D and E is accomplished by limiting the amplitude of the impulse signal applied to the input circuit 84. Means for amplitude limiting is wellknown in the art and is therefore omitted from the present description.

The utilization of the electrode structure of Fig.1 4 in combination with the circuit above described enables one to count impulses of random duration and random interval such as occur in nuclear disintegration.

Other arrangements for utilizing the present invention'maysuggest themselves. For example,

Qarrangement would alternately cause the electron beam to move from midway between B and 'C to midway between D and E and so on, in accordance with the impulses applied to the flipflop circuit.

' The embodiments of the present invention which have been illustrated and described have been selected for the purpose of setting forth the principles involved. It will be obvious that the invention may be modified to meet various con: ditions for difierent specific uses andit is, therefore, intended to cover by the appended claims all such modifications which fall within the spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for counting electric pulses, comprising means to form an electron beam, an anode structure includin a plurality of counting electrodes, beam deflecting means, voltage control means connected to the deflecting means to apply thereto a deflecting voltage of variable magnitude to cause the electron beam to move laterally from one counting electrode to another responsive to the electric pulses counted, the voltage control means being connected to the counting electrodes and responsive to electric current flowing thereto to arrest lateral movement of the electron'beam between the pulses counted, reversing electrodes at respective ends of the anode structure, a flipflop circuit having respective input triggering terminals connected to saidreversing electrodes and having output terminals connected to the voltage control means, so that whenever the electron beam strikes one of the reversing electrodes the flip-flop circuit is triggered and thereby reverses the polarity of voltage applied to the beam deflect ing means, whereby the direction of lateral movement of the electron beam is reversed.

2. Apparatus for counting electric pulses, comprising meansto form an electron beam, an anode structure including a plurality of counting electrodes, beam deflecting means, voltage control means to control the magnitude of voltage applied to the deflecting means, said voltage control.

means being connected to the counting electrodes and responsive to electric current flowing thereto 7 to cause lateral movement of the electron beam file of this patent:

3. Apparatus for counting electric pulses, com-'- 7 prising means to form an electron beam, an anode structure including a plurality of counting electrodes arranged in two interleaved rows, first deflecting means to move the electron beam laterally from one counting electrode to another in the same row, voltage-control means connected to thecounting electrodes and responsive to current flow thereto to arrest such movement, second deflecting means to move the electron beam from one row to the other, input terminals'for the pulses to be counted, and a flip-flop circuit having triggerin terminals connected to said input terminals and output terminals connected to said second deflecting means, so that electric pulses applied to the input terminals trigger the flipflop circuit, thus reversing the polarity of voltage applied to the second deflecting means and moving the electron beam from one row of counting electrodes to the other, whereby the electron'beam' beam-deflecting plates arranged on opposite sides of the electron beam to deflect the beam from one counting electrode to another, two amplifiers having their output terminals connected to respective ones of the deflecting plates and their input terminals connected together and to the counting electrodes, a flip-flop circuit connected to bias to cut-ofi one-or the other of the two amplifiers selectively, said flip-flop circuit having respective triggering terminals connected to the reversing electrodes, a control grid positioned in the path of the electron beam, and input terminals for the pulses to be counted connected to said control grid. r I

SIEGFRIED HANSEN REFERENCES CITED 7 V The following references are of record in the UNITED STATES PATENTS 2,446,945 Morton et al Aug. 10, 1948

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