US2675500A - Quantizing bias insertion circuit - Google Patents

Description

5 Sheets-Sheet 1 Filed Feb. 11, 1952 INVENTOR. J'AuL K ucm/vs rr ATT ENE) April 3, 1954 s. KUCHINSKY 2,675,500

QUANTIZING BIAS INSERTION CIRCUIT Filed Feb. 11, 1952 3 Sheets-Sheet 2 FIG. 2.

/9 ff f 20 n INVENTOR. 5A (/4 Ma /Mix Y ATTOQNEY April 13, 1954 s. KUCHINSKY QUANTIZING BIAS INSERTION CIRCUIT 3 Sheets-Sheet 3 Filed Feb. 11, 1952 muNbOm I lNVENTOR. JAz/L A ucH/Ms/rr BY 4 ra /A ATTORNEY Patented Apr. 13, 1954 QUANTIZING BIAS INSERTION CIRCUIT Saul Kuchinsky, Philadelphia, Pa., assignor to National Union Radio Corporation, Orange, N. J., a corporation of Delaware Application February 11, 1952, Serial No. 270,946

11 Claims. 1

This invention relates to voltage sampling systems and more especially to such systems employing cathode ray tubes.

The invention is in the nature of an improvement on the type of voltage sampling system disclosed in application Ser. No. 80,694, filed March 8, 1949, and issued as Letters Patent No. 2,564,908. There is disclosed in said patent an arrangement for sampling the voltage of a rapidly varying input signal by employing a special dual input holding circuit for the cathode ray beam. That dual circuit requires the use of two separate holding grids which are differentially excited by the primary electrons of the beam so as to produce a resultant beam holding voltage. This voltage which is derived directly from the beam, is fed back through respective amplifiers so as to hold the beam at the sampled deflected position. One

of the requirements for proper operation of the prior arrangement is that two separate feed-back tubes are required, and both tubes must receive primary electron current from the beam in order to produce the differential holding voltage which is fed back to the respective beam deflecting plates. That may require a very precise adjustment of the various voltages, of the beam crosssection, beam intensity and a symmetric relation between the beam and both holding grids and their respective grid openings.

Accordingly, one of the principal objects of the present invention is to provide a voltage sampling arrangement using a defiectable cathode ray beam, wherein the beam can be accurately held at the sampling position by a single holding grid, and with a single grid wire or lateral for each such position. In other words, the feedback circuit utilizes the primary beam current and a single input feed-back circuit.

Another object is to provide improved beam holding arrangements for voltage sampling systems of the cathode ray tube kind, which arrangements are simple to operate and exhibit a high degree of beam holding efficiency, rendering them mor effective for such uses as pulse counting, direction finders, direct current regulators and the like.

A feature of. the invention relates to a voltage sampling system employing cathode ray sampling, and wherein the sampling can be effected without presampling or without removing the voltage to be sampled.

A. further feature relates to the novel organization, arrangement and relative locations and interconnections of parts which cooperate toprovide an improved voltage sampling system.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

In the drawing which represents, by Way of examples, certain preferred embodiments,

Fig. 1 is a schematic diagram of a voltage sampling system according to the invention.

Figs. 1a, lb, and 1c are diagrams explanatory of various operating conditions of the system of Fig. 1.

Fig. 2 is a modifications of Fig. 1.

Fig. 3 is another modifications of Fig. 1.

Referring to Fig. 1, the numeral Ill represents any well known form of evacuated enclosing envelope, such as is used in the construction of cathode ray tubes. Mounted within the tube at one end thereof is a conventional electron gun H for developin a focused beam [2 of electrons. As is well known, such a gun includes an electron emitting cathode Is, for emitting primary electrons, a beam intensity control grid l4, and a beam accelerating and beam focusing system comprising, for example, first and second anodes I5, It. Itwill be understood, of course, that any other well known beam accelerating and focusing arrangements can be used. The beam l2 passes between a pair of deflector plates l1, [8 for deflecting it vertically, that is, in a plane parallel to the plane of the drawing, and, if desired, an additional pair of deflector plates I9, 29 may be provided for controlling the position of the beam in a plane perpendicular to the drawing.

Suitably mounted at the opposite end of the tube is a ladder-like grid which may consist of a pair of metal side rods 2|, 22 between which extend the various parallel and equally spaced grid laterals 23, one of which is shown in crosssection in Figs. 1a, 1b, and 1c, and there being one such lateral for each sampling position of the beam and at which the beam is to be held during sampling, as will be described hereinbelow. If desired, a plate electrode 24 is mounted in spaced relation to the holding grid on the side opposite that facing the gun and this plate electrode can be given a small positive bias, for example 50 volts, with respect to the cathode l3. If desired, a target electrode may be mounted to replace the electrode 2d, and this target electrode may be coated with fluorescent material so as to give a visual indication of the held position of the beam. Alternatively a series of such target electrodes may be provided, one for each grid lateral, and each such target electrode may be connected to a corresponding signaling output circuit.

In accordance with the well known operation of a cathode ray tube, the beam 62 will be deflected in a plane parallel to the drawing, by varying the potential difference between the deflector plates IT, IS. If this potential difference is a fluctuating or alternating signal voltage to be sampled, the beam will change its deflected position instantaneously to correspond with that voltage. In many cases, however, it is desirable to be able to hold the beam at the particular clefiected position corresponding to the value of the voltage at the instant of sampling. Thus, there is disclosed in said U. S. Letters Patentan arrangement for effecting such beam holding. -H.owever, the system of the said patent requires'for the holding function a pair of beam holding grids and corresponding amplifiers to whose input circuits the respective holding grids are connected. The holding action is effected according to the present invention by employing a, single holding grid and by using the primary electron'beam current intercepted by the wires of the ,grid .to control a single multi-grid tube.

The various potentials iorthe electrodes of .the tube can be derived from any well known direct currentpower supply, which for convenience is shown in the drawing by the various batteries. The cathode i3 is returned to the control grid l4 through a beam intensity control potentiometer which is connected'to the power supply so. as

to be able to vary .the beam intensity. Thisreturn circuit also includes a parallel path. oneleg of which is comprised of a resistor 2", and the other leg of which is comprised of the direct current potential 27 poled as shown, and also the on-off micro-switch 28. When the switch'28 is closed to the beam ofi position, sufficient negative bias is applied to the control grid i l, to completely cut off the beam l2. However, when switch '28.is open, the grid I4 is biased so that the beam [2 is on and impinges on the holding grid.

A grid controlled tube 29 is provided, the oathode of which is connected directly to cathode it,

while the dual control grids 3!, 32 are directly connected and both these grids 'areconnected through abias potentiometer 33 poled, as shown. Acathode load resistor is provided for another vgrid'controlled tube 36 which has its anode 3;

positively biased with respect to its cathode'fid 'by means of the direct current potentials 39, lil.

The control grid 4! is connected through the grid resistor 42 to the'adjustable biasgpotentiometer contact :33 by means of which the normal space currentbetween cathode 38 and anode 3'? can be adjusted to a predetermined value. Thus, the bias'on grid 4! is a function noton y of the plate current of tube 36 .but'also of tube 29. In other words, the resistor and the plate-to-cathode circuit'of tube 29 may be consideredas a composite voltage divider.

Tube 36 is of the multi-grid kind, such as is known in'the art as a triple grid tube. The three grids are successively traversed by the electrons passing from the cathode to the anode. The second grid 44 may be connected to the positive potential point 45 so as to cause it to act as a shield grid. The third grid 45 is arranged to act as a second control grid and is connected'to one endof the secondary windingl! of a signal input transformer 48. The primary winding 49 is con nected to the source 50 whose voltages are to be sampled.

The anode3l is connected to the power supply through a load resistor 5| and it is also'connected to the beam deflector. 7. Thus, the potential anplied to deflector I7 is a function of the instantaneous voltage appearing at anode 31 which in turn is dependent on the normal bias on the first control grid 4! and the voltage on grid 54 from the signal source 53. The other beam deflector I8 is connected to the anode 52 of another triple grid tube 53 similar to tube .35. The cathode 5a is connected'to the negative terminal 55 of the power supply, and the first control grid 58 is returned to the cathode through an adjustable resistor 51 which is also connected to the beam holding grid. Thus, the negative potential of grid 581s a function of the intensity of the electron beam as it strikes a grid lateral and also a function of the amount of intercept between the grid 45 is connected. In other words, the input voltages to be sampled are applied to the'second controlgrids 46 and 59 in balanced or push-pull relation. Furthermore, the anode'52 is connected to the power supply through a load resistor .59

similar to resistor 55 l The operation of the system .to sample is along thefollowing lines. The signal'inp-utsource'iifi is continuously connected to the grids' iE, 59. As long as micro-switch'28 is closed, the grid is and the grids 3!, 32 are biased'to cut-oiian'd no'plate current flows through tube 29. The grids "4! and 56 are at "zero bias, therefore the monitoring meter 5| which maybe a vacuum tube voltmeter will vary its indication'to correspond with the signal voltages from source 56.

Should it be desired to produce a .steadyindication of the voltag at any given sampling instant without regardto the fact that the signal from source Elimay be varying in amplitude in either direction with respect to zeroor some other predetermined base potential, the.microswitch 28 is opened. This causes the beam [2 and also the plate current of tube 29 to be switched on.

This results in an average bias being applied to fromsource 5D is alternating or fluctuating, the

potential at anode 52 assumes an average potential which is a function of'the amount of intercept of that beam with the' particular grid lateral it strikes at the instant of sampling. As an illustration, assume that the signal at the secondary winding ll varies from 10 volts positive, to I0 volts negative. Then, by suitable choice of values for the various circuit components, the plate current of tube 35 will be'such as to-maintain the beam 12 at its uppermost position where it strikes the first or top grid lateral, assuming at that instant that the grid 46 is at the limit of its negative swing of 10 volts. The beam electrons which are intercepted .by'the grid lateral correspondingly increase the negative bias on grid 56 and tend to decrease the plate current of tube 53, but since at this instant grid 59 is .positive, the potential at plate52 is at its lowest value, as is also the deflector l8. Should the beam start to move downwardly away from the first grid lateral, the amount of intercept between the beam and that lateral will decrease as is evident from Fig. 1a, then the negative'bias on grid 56- likewise decreases and results in a corresponding drop inpotential of anode 52 which causes the beam to move back upwardly in the direction of the dotted arrow (Fig. la) until the average potential at anode 52 remains such as just to maintain the beam centered on the top grid lateral. This holding condition of the beam remains stable as long as the micro-switch 28 is open.

A similar action takes place no matter at which grid lateral the beam finds itself at the instant of sampling, and it is independent of the direction of change of the signal before the sampling instant. In other words, the electron holding current applied to grid 56 is capable of holding the beam at the particular grid lateral at which it appears at the instant of sampling regardless of the direction from which the beam has approached the said lateral at the sampling instant.

It should be noted that while the holding grid is connected only to tube 53, the tube 36 controls the necessary insertion of the beam intensity 7 control bias so as to minimize the effect of the signal swing on grid 45 to a point where the potential variation at anode 31 from its desired average holding voltage is small enough to be more than compensated by the beam holding action of tube 53. This is one of the distinct advantages of the invention since it does not require the signal input from source 55 to be removed or pre-sampled prior to opening switch 28.

Furthermore, while the holding feed-back is a function primarily of the amount of intercept between the beam and the grid lateral, if this amount is increasing with the beam above the lateral, and approaching it in the direction of the full line arrow (Fig. 1b), the action of tube 53 by the resultant increase in negative bias on grid 56 is to increase the positive potential on deflector l8, thus insuring that the beam continues to move downwardly until it reaches the central or stable holding relation with respect to the lateral. input is such at the instant of sampling, as to swing the grid 46 positively, that is, the beam is approaching the lateral in the direction shown in Fig 1c, the increased plate current of tube 36 resulting from the increasing intercept between beam and lateral increases the negative bias on grid 4|. Thus, the beam is constrained to continue its upward movement until it reaches the center or stable holding intercept with the grid lateral. In that condition the holding system is in equilibrium and the beam stays in contact with the grid lateral.

Referring to Fig. 2, there is shown a system similar to that of Fig. 1 except thatinstead of controlling the tube 53 by negative or primary or electron current from the holding grid, it is controlled by positive or secondary electron current from the holding grid. The parts of Fig. 2, which are the same as those of Fig. 1, bear the same designation'numerals. In Fig. 2 th electrode 24, instead of being biased positive, for example 50 volts, with respect to the cathode, is held at the same potential as the second anode so that when the primary electrons of the beam strike the holding grid laterals they release secondary electrons. If desired, the surface of the grid laterals may be coated with high efficiency secondary electron emission material as is Well known in the art. Therefore, the holding grid lateral assumes a positive potential and the grid 55, instead of receiving a negative current by the beam intercept, receives a positive current. The operation of holding is similar to that described 7 for Fig. 1. However, the grid 56, instead of being returned through resistor 5'! directly to the On the other hand, if the signal cathode 54, as in Fig. l, is returned to the adjust- (iii able contact 62 of a bias potentiometer 63 connected in the cathode load circuit of tube 53. This resistor is connected to the anode 34 of tube 29 to provide the desired grid bias for grid 56. When the beam I2 is not impinging on a grid lateral, that is, with no positive current flowing to grid from the holding grid, the contact 62 can be adjusted to bias the tube 53 to cut-off. Therefore, when the beam impinges on a lateral at the sampling instant, it reduces the negative bias on grid 56. In other words, whereas in Fig. 1 the tube 53 has a normal average anode potential which is reduced by applying a negative electron current to grid 56, in Fig. 2 the tube 53 has a normal average anode potential which is reduced when the positive electron current flows to the grid 55. The holding operation is, therefore, the same as that described for Fig. 1.

Certain of the beam holding features above described are not limited to tubes having a single holding grid. Thus, there is shown in Fig. 3 a cathode ray tube similar to th tube of Fig. 2, with the exception that instead of using a single set of grid laterals all connected to the #1 control grid of tube 53, two sets of grid laterals are employed. Thus, one set of grid laterals 23a can be attached to a side rod 2|, and a second set can be attached to the other side rod 22, with the respective laterals arranged in interspersed relation so that the two sets of laterals are insulated from one another. If desired, two sepa-- rate grids, like the holding grid of Fig. 2, may be mounted in closely spaced parallel relation and with the laterals of one grid located midway between the laterals of the other grid. The parts of Fig. 3, which are the same as corresponding parts of Fig. 2, bear the same designation numerals. The anode 24 is connected to the same positive potential as the second anode l6 of the electron gun, and the grid laterals 23a and 23b can be coated or can be of a suitable metal or alloy so as to be ehicient emitters of secondary electrons when struck by primary electrons from the beam i 2. The beam holding action of Fig. '3 is similar to that of Fig. 2, except that the cathode load resistor 35 is connected in common between the cathodes 38 and 54, and the anode 34 of tube 29, so that, when the beam I 2 is not impinging on any grid laterals, both tubes 36 and 53 are biased to cut-ofi.

Assume, for example, that at the instant of opening of switch 28, the beam I 2 finds itself impinging on the first or top lateral 23a. Since both tubes 36 and 53 had been previously adjusted to plate current cut-01f when the beam is 01f (or when it is not striking a lateral), when it does strike the lateral 23a, positive current flows to the control grid 4!, thus tending to increase the plate current of that tube and lower its anod potential. This causes a drop in the potential of the deflector l1 and the beam tends to move downwardly until it strikes the next lateral 23b. The potential of deflector I7, therefore, again rises while the potential of anode 52 drops, thus causing the beam to move back upwardly towards lateral 23a. Therefore, the beam finally assumes a stabilized holding position where its intercept with lateral 23a and its intercept with lateral 23b prevents it moving beyond the holding area between the two adjacent laterals.

While certain preferred embodiments have been described, it will be understood that various changes and modifications may be made therein r-c e zeasoo without 'departing from the spirit and scopeof r the invention.

What isclaimed is: .-l..-A beam holding arrangement for the beam "of .acathode ray tube, comprising means to develop a beam-or" focused electrons, a single beam holding electrode on which said beam is arranged toimpinge and having a series of spaced conduc- "tors one for each holding position of'thebearn, a

pairof beam deflectors, a pair of grid-controlled tubes each having first and second input circuits andeach having an output circuit, a source of variable voltage, means connecting said source in opposed balanced relation to the first input circuit of each of said' pairof tubes, means connectingthe said holding grid to only the second input =olaim 1, in which means are provided for mainttaining said third tube and said electron beam atcut-ofi except when said beam is to be held .at a position determined by the instantaneous value of said variable voltage.

.3. A beam holding arrangement according to claim 1, in which the first input circuit for said other tube of said pair has a control grid which is returned to an adjustable connection on a volt- .age divider, which divider is constituted in part of the anode-cathode resistance of said third tube.

14.. A beam holding arrangement according to claim 1, in wh ch the first input circuit of said other tube of said pair has a control grid which .isreturncd toan adjustable connection on a voltage divider which divider is constituted in part of the anode-cathode resistance to said third tube and the cathode load resistance of said other tube of said pair.

.5. A voltage sampling system comprising means to develop a beam of electrons, a pair of beam deflectors for shifting the beam trajectory, a pair of beam ho ding electrodes upon which the beam impinges and providing a series of similar spaced elements each corresponding to a particular position at which the beam is to be held for sampling, a grid controlled tube, a second grid con trolled tube, a third grid controlled tube, means connecting the output electrodes of said first and second tubes to respective deflector elements, each of said first and second tubes having first and second control grids, means connecting one holding electrode to the first control grid of the first tube,

.ans connecting the other holding grid to the control electrode of the second tube, a source of variable voltage to be sampled connected in opposed balanced relation to the second control grids. of the first and second tubes, the cathodes of the first and second tubes being connected to common cathode load resistor, and means connecting the first control grids of the first and second tubes to the plate-to-cathode circuit of said third tube.

6. A voltage sampling system comprising means to develop a beam of electrons, a pair of beam deflectors for shifting the beam trajectory, a beam holding electrode upon which the beam impinges and having a series of similar spaced elements, each corresponding to a particular position at which the beam is to be held for sampling, a first grid controlled tube, a second grid controlled tube, a third grid controlled tube, means connecting the output electrodes of said first and :second -:tubes to respective deflector elements,

means'to-control the output :of the first tube by the primary beam electrodes impinging on the spaced'elements of said holding electrode, means to control the output of said second tube by the internalresistance of said third tube, each of said ffirst and second tubes having first and 'second control grids, means connecting the first control grid of the first tube to said'holding electrode,

: means connecting thefirst control grid of thesec- 0nd tube to the-plate toecathode circuitof said third tube, and means connecting a source of voltage to be sampled in balanced relation to the second control grids "of :said first and second tubes.

'7. 1A voltage sampling system ccmprisingmeans to develop a "beam of electrons, apair of beam deflectors for shifting :the beam trajectory, 'a beam holding'electrode upon which the beam impinges and havinga serieszofsimilar spaced elements, "each corresponding to aparticular -position at which thelbeam is to'beheld for sampling,

a first grid controlled tube, a second grid 'controlled tube, a third grid controlled tube, means connecting the output electrodes of said first and second tubes to respective deflector elements, means to control the output of "the first tube'by the primary beam electrodes impingingon the spaced elements of saidh'ol'ding electrode, means to control the output of 'sai'dsecond tube by' the internal resistance of said third tube,the control grid of the first tube being connected to "said holding electrode, and the control grid of the secend tube'being returned to the cathode thereof through a cathode load which is connected in series with the plate-to-cathode circuit of said third tube.

8. A voltage sampling system comprising means "to develop a beam of electrons, a pair of beam deflectors for shifting the beam trajectory, a beam holding electrode upon which the beam impingesand having a series of similar spaced elements, each corresponding to a particular'pm sition at which the'beam is to be held for sampling, a first grid controlled tube, a second grid controlled tube, a third grid controlled tube, means connecting the output electrodes of said first and second tubes to respective deflector elements, means to control the output of the first tube by the primary beam electrodes impinging on the spaced elements of said holding electrode, means to control the output of said second tube by the internal resistance of said. third tube, said holding electrode comprising a wire grid having a series of spaced grid laterals, all connected to the control grid of the first tube to cause the plate voltage/of said first tube to be controlled by the amount '(Jf intercept be impinges'and 'havinga series of similar spaced elements, each corresponding toa particular position at which the beam is to be held for sampling, a first grid controlled tube, a second grid controlled tube, a third grid controlled tube, means connecting the output electrodes of said first and second tubes to respective deflector elements, means to control the output of the first tube by the primary beam electrodes impinging "on the spaced elements of said holding electrode, :means to control the output of said second tube by the internal resistance of said third tube, the control grid of the first tube being connected to said holding electrode, and the control grid of the second tube being returned to the cathode thereof through a resistor which is connected in series with the plate-to-cathode circuit of said third tube, and means for biasing said third tube to plate current cut-off except when a voltage is being sampled.

10. A voltage sampling system according to claim 9, in which means are provided for cutting ofi said electron beam as well as biasing said third tube to cut-off except when a voltage is being sampled.

11. A voltage sampling system comprising means to develop a beam of electrons, a pair of beam deflectors for shifting the beam trajectory, a beam holding electrode upon which the beam impinges and having a series of similar spaced elements, each corresponding to a particular position at which the beam is to be held for sampling, a first grid controlled tube, a second grid controlled tube, a third grid controlled tube, means connecting the output electrodes of said first and second tubes to respective deflector elements, means to control the output of the first tube by the primary beam electrodes 'ing a surface for emitting a copious supply of secondary electrons when struck by said beam, said first grid controlled tube being biased to plate current cut-off when the said electron beam is not impinging on said holding electrode, a second grid controlled tube, a third grid controlled tube, means connecting the output elec trodes of said first and second tubes to respective deflector elements, means to control the output of the first tube by the secondary electron emission from said holding electrode, and means to control the output of said second tube by the internal resistance of said third tube.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,436,677 Snyder Feb. 24, 1948 2,446,945 Morton et a1. Aug. 10, 1948 2,463,535 Hecht Mar. 8. 1949 2,507,590 Clark May 16, 1950 2,599,949 Skellett June 10, 1952

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