US3500115A - Electronic graticule for cathode ray tubes - Google Patents

Description

March 10, 1970 M. E. AUGER. JR 3,

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES Filed June 10, 1968 6 Sheets-Sheet 1 I00 IIO I20 T0 VERTICAL MIXER 24 T0 HORIZONLAL MIXER 22 MIXER I RING RING COUNTER COUNTER I a2 as HQ 4 MONOSTABLE RAMP MULTIVIBRIIIOP GENERATOR RATE ADJUST 30 v" INVENTOR MEDERIC E. AUGER,JR.

BY @02 @vda FROM SWITCH I6 ATTORNEY March 10, 1970 M. E. AueER, JR

ELECTRONIC GRATICULE FOR cmnom: RAY TUBES 6 Sheets-Sheet 2 Filed June 10, 1968 INVENTOR BY MEDERIC E.AUGER,JR. wad,

ATTORNEY @359 ZOEHEQ 2535:

March 10, 1970 M. E. AUGER, JR

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES 6 Sheets-Sheet 5 Filed June 10. 1968 VERTICAL AMPLIFIER MIXER WAVEFORM 8 VERTICAL LINE TRACING CIRCUIT I HORIZONTAL AMPLIFIER HORIZONTAL LINE TRACING CIRCUIT SOURCE ATTORNEY 1, 1970 M. E. AUGER. JR

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES 6 Sheets-Sheet 4 Filed June 10, 1968 TIME TIME

N 0 N P hnyai o ATTORNEY -FROM MULTIVIBRATOR 32 .QRRING COUNTER 34 y 3% M. E. Auem, JR 3,@,E i

ELECTRONIC GRATICULE FOR CATHODE RAY TUBES Filed June 10, 1968 6 Sheets-Sheet 5 To VERTICAL MIXER 24 TO HORIZONTAL MIXER 22 MIXER 76 MIXER I I l 4 DISCHARGE PEAK E DETECTOR SW'TCH AND DRIVER w j GATE RAMP /@L+' I I 82 RATE I GEN I PULSE M ADJUST I I SHAPER MONO A I MV. L 72 66 sNITcII I4 0 '9' MAIN SYNC.

RESET GATE MAIN SYNC. WAIIEEORM RESET K I x ID. BISTABLE MV. N 56 5 MAIN SYNC. l4 SY c RESET sIIIITcH INvEIITOR MEDERIC E. AU6ER,JR.

FROM swITcII I6 BY 4 @WJMH ATTORNEY.

Pig-Mk2}! y 19% M. E. AUGER, JR 35am ELECTRONIC GRATICULE FOR CATHODE RAY TUBES Filed June 10, 1968 6 Sheets-Sheet 6 k hHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH L Q/l/l/l/l/l/M/l/I/l/l/l/l/I/l/l/l/l/I/I/l/l/l/l/l/1/l/l/l/l/l/\/l/l/l HIIHIIIIHHHI Will 111i TIME INVENTOR MEDERIC E. AUGER,JR.

BY F M ATTORNEY 3,500,115 ELECTRONIC GRATHCULESFOR CATHODE RAY TUBE Mederic E. Auger, .lr., Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed June 10, 1968, Ser. No. 735,648 Int. Cl. Htllj 29/70 U.S. Cl. 315-18 4 Claims ABSTRACT OF THE DISCLOSURE A technique and circuitry for the generation of an electronic graticule and display of such on the screen of a cathode ray tube oscilloscope with a waveform to be measured thereagainst is based on time-sharing established by the production of a cyclical time interval and a number of smaller time intervals within for the display of vertical lines, horizontal lines and the waveform or waveforms in any permutation. In one embodiment, the cyclical time interval is established by counting from a 60 Hz. signal and the smaller time intervals by energization of a switch by a signal having the cyclical time interval. The horizontal lines may be generated by sweeping the outputs of modified ring counters stepped by an oscillator, the spacing between the lines being determined by the step amplitude differences in the ring counter outputs. In the remainder of the cyclical time interval, a waveform and the vertical lines may be displayed by suitable gating means driven by a time base circuit. The vertical lines may be repetitively generated by sweeping the output of a peak detector which converts a series of spikes modulated by a sweep voltage into a series of step voltages.

BACKGROUND OF THE INVENTION This invention relates generally to graticules or scales for cathode ray tubes and more particularly, to a method and means for electronically producing such a graticule.

From the days of introduction of Oscilloscopes employing cathode ray tubes for signal display and measurement, the accurate and precise measurement of waveform levels from visual inspection of the signal trace has been a roblem. The earliest Oscilloscopes employed an auxiliary transparent plastic window which was placed in front of the cathode ray tube screen. The plastic window had a graticule inscribed on its rear surface and made visible by means of edge illumination. A serious drawback, however, was that a large parallax error was possible in visual measurement, due to the thickness of the cathode ray tube envelope interposed between the cathode ray tube screen and the transparent plastic window. In order to make an accurate measurement, the observer had to remain stationary when calibrating the instrument and measuring the waveform.

More recently, oscilloscope and instrument manufacturers have turned to cathode ray tubes having graticules which are internally scribed in the cathode ray tube screen. As the observer can therefore move freely while making measurements, due to the absence of parallax error, these instruments are vastly more convenient to use than those utilizing transparent plastic windows.

Nevertheless, this advance has brought the problem of inflexibility of measurement. That is, the waveforms traced by the electron beam can be measured only against the internally scribed graticule. Where the internally scribed graticle is linear and the waveform desired to be displayed has a logarithmic characteristic, such as would be obtained from a logarithmic amplifier, calibration and measurement of the waveform cannot be made. Certainly, logarithmic scale could be internally scribed, but the number of 3,50%,115 Patented Mar. 10, 1970 decades thereof would be fixed and the graticule would then be useless for linear measurements.

A recent attempt to solve this problem resulted in a device which is externally attached to the oscilloscope and which projects a graticule on the face of the cathode ray tube. The graticules may be varied by inserting different transparent slides in the device. However, as with the earliest Oscilloscopes, this device again may produce a large parallax error. Further, the device is cumbersome and the resultant graticule is barely visible, due to poor reflection from the cathode ray tube face.

In other art, it has been proposed to generate a series of lines for simulating in a CRT display an approaching runway. While the techniques for producing such lines may be applicable to graticule displays, they do not allow for the display of both a graticule and a waveform to be measured thereagainst.

SUMMARY OF THE INVENTION Therefore, it is an object of this invention to provide a graticule for use in cathode ray tube measurements which produces no parallax error and which may be varied for different measurements.

It is a further object of this invention to provide such a graticule which may include logarithmic, linear or other types of scales, either singly or in combination.

Briefly, these objects are achieved, according to one embodiment of the invention, by electronically producing signals by time-sharing techniques which include components representative of the wave-form to be displayed and of the horizontal and vertical lines of the graticule, then applying the signals sequentially to the deflection means of the cathode ray tube so that both the waveform and the graticule appear to the eye to be superimposed on the cathode ray tube screen.

BRIEF DESCRIPTION OF THE DRAWINGS The subject matter of the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. For a complete understanding of an emboditment of the invention together with further objects and advantages thereof, reference should be made to the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a front view of a cathode ray tube screen showing thereon the electronic graticule of this invention and a superimposed waveform;

FIGURE 2 is a diagram showing the waveforms of the signals applied to the deflection means of a cathode ray tube for one embodiment of graticule and waveform dis- P y;

FIGURE 3 illustrates a block diagram of a means for producing these signals;

FIGURE 4 is a block diagram of a means for producing the horizontal lines of the graticule;

FIGURE 5 is a timing diagram to be used with FIG- URE 4;

FIGURE 6 is a schematic diagram of an element of the means in FIGURE 4;

FIGURE 7 shows a block diagram of a means for displaying the waveform and the vertical lines of the graticule:

FIGURE 8 is a timing diagram to be used with FIG- URE 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGURE 1, a sample electronic graticule produced according to the teachings of this invention is illustrated. The graticule comprises a plurality of spaced, vertical lines which are intersected by a plurality of spaced, horizontal lines. Each line is traced n the phosphor screen of the cathode ray tube, hereinafter CRT, by means of signals applied to the deflection means thereof. The particular graticule illustrated in FIGURE 1 includes linear spacing of the vertical lines and a repetitive logarithmic spacing of the horizontal lines at 1, 2, 3, 4, 6 and 8 divisions. But, this invention is in no way limited to such a graticule; for instance, the graticule may comprise logarithmic spacing of the vertical lines and linear spacing of the horizontal lines. Furthermore, this invention has such flexibility that practically any spacing between the lines can be accomplished.

The waveform to be displayed is normally traced so as to appear superimposed on the graticule by a time-sharing technique. The signals necessary to accomplish both waveform and graticule tracing are illustrated in FIGURE 2.

FIGURE 2a depicts waveforms of the signals applied to the horizontal deflection means of the CRT and FIG- URE 2b shows the signals applied to the vertical deflection means. The display of both the graticule and the waveform is cyclical, repeating every T seconds. The interval T may be divided into three smaller intervals:

( 1) An interval 1,; (2) An interval 1 (3) An interval t In FIGURE 2, the horizontal lines of the graticule are displayed during the first time interval, the waveform or information signal is displayed during the second and the vertical lines during the third. As will be more clearly seen when the formation of the signals to produce such a display is explained, the invention is not limited to such a time sequence, but indeed contemplates any permutation thereof.

Again referring to the graph of FIGURE 2, the horizontal lines are formed during the interval 21., by applying to the vertical deflection means a series of step voltages, progression through the series being made with respect to time. Simultaneously, the electron beam is swept horizontally for each step voltage by a varying sweep voltage applied to the horizontal deflection means.

More particularly, the logarithmic scale of FIGURE 1 may be generated by applying a voltage having a level 1 to the vertical deflection means and sweeping the beam by means of a simultaneous sw ep voltage applied to the horizontal deflection means. The lines 2, 3, 4, 6 and 8 are formed in a similar manner, the spacing between the voltages applied to the vertical deflection means determining the vertical scale divisions of the horizontal lines. The logarithmic characteristic may be reiterated at 10, 100, 1000, and so forth, by applying a fixed voltage representative of the decade and repeating the step voltage variation as depicted in FIGURE 2.

At the end of the first time interval the display of the horizontal lines is terminated. Thereafter, during the sec- 0nd time interval 1 the waveform or information signal is displayed by applying this waveform to the vertical deflection means and sweeping the beam conventionally by a single sweep voltage applied to the horizontal deflection means. At the end of the second time interval, the waveform display is ended and the third time interval is initiated wherein the vertical lines may be displayed in the same manner as were the horizontal lines, with the step voltages now being applied to the horizontal deflection means and the sweep voltages to the vertical deflection means. In FIGURE 2, the steps are equidistantly spaced to display linear scale divisions of the vertical lines. Moreover, the vertical lines have been retraced a number of times, the purpose of which will be fully explained hereinafter. At the completion of the third time interval, the cycle T of graticule and waveform display repeats.

It should be noted that display of each portion of the graticule and display of the waveform is accomplished only for a time interval t, smallpr than the total cyclical i te val I- One sen en ent alue f he t me i e v I 4 may be that obtained from a 60-cycle sine wave, or approximately thirty-five milliseconds. For convenience, the first time interval may equal one-half of the total interval T. In order to avoid a flickering display at this low duty cycle, a CRT may be used whose phosphors have a high persistence for a given amount of voltage excitation.

Necessarily, such a long interval T places limitations upon the transient waveform displaying ability of the oscilloscope, for the time interval t is but a small portion of the total time interval T. Thus, a long time exists in which no signal can be displayed. It is toward this result that other embodiments of the invention may be drawn which will be described hereinafter, For purposes of illustration, the teachings of this invention will be further described in terms of the embodiment illustrated in FIG- URE 2. Such a method of display is most useful when the waveform to be displayed is that obtained from a pulsegenerating circuit for applications such as shock-excited, ultrasonic transducers or modulators in which the pulse originates at the initiation of time interval 1 In addition, the embodiment of FIGURE 2 is eminently suitable for display of steady state signals or those whose transient times are significantly longer than that of the time interval T, which may be milliseconds.

One may now see the reason for repetitive display of the vertical lines in the time interval t Although the eye acts as an effective integrator of the varying graticule and waveform displays, it has been found that persistence problems may be encountered with conventional cathode ray tubes. Particularly is this so when the electron beam is swept across the phosphor screen at a high rate. It can be said that in FIGURE 2, wherein the first time interval t =T/2 and the sum of the second and third time intervals also equals T/2, time sharing between the waveform display and vertical line display results in a decreased time of sweep of any one particular line as contrasted with the sweep time of a horizontal line during the first time interval. Therefore, the phosphors in each line may not be excited to a degree suflicient to effect persistence for the rest of the third time interval. To obviate this problem, each particular line may be swept a number of times.

In the general case, the number of lines displayed in both the vertical and horizontal scales may be varied by changing either the frequency of line display within each individual time interval or the magnitude of each step voltage applied to the deflection means. In a practical case, the frequency of line display is fixed and the number of lines are varied by adjusting the final amplification of the step voltages before application to the deflection means.

Turning now to FIGURE 3, a means for implementation of the method illustrated by the graph of FIGURE 2 is shown. A cathode ray tube 1 includes a phosphor screen 2 on an inner surface of the glass envelope thereof, a vertical deflection means comprising a pair of deflection plates having terminals 3 and a horizontal deflection means comprising a pair of plates having terminals 4. Connected to the terminals 3 are pushpull outputs from a vertical amplifier 5; connected to the terminals 4 are push-pull outputs from a horizontal amplifier 6. The elements 1 through 6 may comprise elements of any currently marketed, standard oscilloscope or they may be integrated with a fraticule generation means 10 which has power and signal input from an alternating current source 12. The frequency of source 12 may comprise Hz or power line frequency. The signal from source 12 is fed to a main sync circuit 14 which may either count up or count down from the frequency of the source 12 to provide an output signal which has a time interval T. As previously mentioned, T serves as the main time basis for establishing time sharing of the graticule and waveform display. In a pre-. ferred embodiment, main sync 14 provides a 30 Hz. square a e at its outp t t r inal hi is on ect d in turn to a switch circuit 16. An electronic switch, such as a flip-flop or bistable multivibrator, may comprise switch 16 but any other means for producing two separate output signals at the initiation of each half-cycle of the square wave from main sync 14 could be used. In FIGURE 2, one switch output is provided during the first time interval t the other switch output is provided during the second and third time intervals t and r Alternately, main sync 14, together with switch 16, may divide the signal from source 12 into a plurality of portions so that flexibility in the display may be accomplished.

One output from switch 16 is fed to a horizontal line tracing circuit 13 and the other output from switch 16 is fed to a waveform or information signal and vertical line tracing circuit 20. Horizontal line tracing circuit 18 produces both horizontal and vertical output voltages which are fed, respectively, to a horizontal mixer 22 and a vertical mixer 24. Horizontal mixer 22 is connected to the input of horizontal amplifier 6 and vertical mixer 24 is connected to the input of vertical amplifier 5. In like vein, the waveform and vertical line tracing circuit has both horizontal and vertical output voltages which are connected in turn to horizontal mixer 22 and vertical mixer 24 and thence to horizontal amplifier 6 and vertical amplifier 5. Finally, circuit 20* has the waveform to be displayed as an input thereof.

In operation, switch 16 provides, at the beginning of the output signal from main sync 14, or the beginning of t an output signal to horizontal line tracing circuit 18. Thereafter, the horizontal circuit 18 produces the horizontal lines of FIGURE 2. At the end of t and the beginning of t the output signal is removed from horizontal circuit 18 and applied to waveform and vertical line tracing circuit 20 which thereafter displays the waveform and vertical lines until the end of r at which time switch 16 removes the output signal from circuit 20 and reapplies it to circuit 18 to repeat the display. Mixers 22 and 24 perform a simple function of coupling the voltages from circuits 1 S and 29 to the appropriate inputs of the oscilloscope amplifiers 5 and 6.

Variations on the circuitry of FIGURE 3 can easily be visualized; for instance, the waveform could be displayed during the first time interval t by coupling it to amplifiers 5 and 6 through the horizontal line tracing circuit 18 instead of circuit 20. Or, main sync 14 and switch 16 could provide four distinct signals in each time interval T. In response to the first signal, the horizontal line tracing circuit 18 could be energized. In response to the second and third signals, the waveform could be applied to the amplifiers 5, 6 through a separate gating circuit energized by switch 16. Finally, during the time interval of the fourth signal, the vertical line tracing circuit 20 could be energized.

Appreciation of this invention then reveals no restriction on the broad aspect of graticule and waveform display utilizing time sharing techniques. The particular method and means used will depend on the nature of the waveform; where the main sync 14 and switch 16 provided four signals per time interval T, display of transient waveforms would be facilitated. On the other hand, the method in FIGURE 2 and the circuitry of FIGURE 3 provide a more flexible display of the graticule.

Returning now to FIGURE 3, the voltages present at the outputs of mixers 22 and 24 are those represented by the waveshapes of FIGURE 2. The number and relative magnitude of the graticule lines and of the waveforms actually displayed depend on the gain of amplifiers 5 an 6. By knowing the magnitude of the output voltages from mixers 22 and 24 and the gain of the amplifiers 5 and 6, the graticule can be calibrated. Thereafter, the waveform may be measured thereagainst by visual inspection.

Means are pictured in FIGURE 4 for implementing the horizontal line tracing circuit 18, although these means could equally be applicable to display of vertical lines in embodiments other than those illustrated in FIGURE 3. The output signal from switch 16 is applied to a sync switch 30 which in turn connects a positive voltage supply V+ to a monostable multivibrator or oscillator 32. Oscillator 32 then produces a plurality of pulses at a predetermined repetition rate which are coupled both to a ring counter 34 and to a ramp generator 36 which has one output coupled back to oscillator 32. The frequency at which changes in the voltage steps applied to the vertical deflection means of the CRT, as illustrated in FIGURE 2, is governed by the repetition rate of the pulses from oscillator 32. Ramp generator 36 converts these pulses into sweep voltages and may be adjusted by means of a rate adjust control so that one complete sweep is made for every step. The sweep voltages are coupled through horizontal mixer 22 to horizontal amplifier 6 and their waveforms appear as seen in FIGURE 2a during the first time interval t When the pulses from oscillator 32 are applied thereto, ring counter 34 produces the step voltages illustrated in FIGURE 2b in the first time interval t Simply, ring counter 34 produces a slightly higher voltage at its output terminal for each pulse; the number of step increases before resetting is determined by the number of stages in the ring counter. By varying the step voltage produced by each stage as hereinafter related, the number of lines to be displayed can be changed. Spacing between step voltages is accomplished by means internal to the ring counter, also described hereinafter.

The output from ring counter 34 is fed to a mixer 38 and to a second ring counter 40 which has as a resetting input a second output from sync switch 30. Ring counter 40 in turn has its output coupled to mixer 38 Whose output is connected through vertical mixer 24 to vertical amplifier 5. By means of this circuitry, logarithmic or other scales can be easily displayed. For instance, the spacing and number of lines within a single decade of a log scale can be varied by adjustment of ring counter 34. When ring counter 34 resets from its highest value of voltage, ring counter 40 is shifted thereby to its next highest voltage output. Thereafter, ring counter 34 reiterates its voltage steps. By combining these voltage in mixer 33, an ascending staircase waveform can be produced.

Reference should be made to FIGURE 5 for depiction of outputs from ring counters 34 and 40. FIGURE 5a shows the output voltage from ring counter 34 when that counter has been adjusted to provied a logarithmic decade with steps at l, 2, 3, 4, 6 and 8. FIGURE 5b shows the output voltage from ring counter 40 when that counter has been adjusted to provide uniform decade steps at 1, 10, 100, 1000, etc. The 1 step of counter 34 can be chosen at a convenient reference level; thereafter, when the output from ring counter 34 shifts to the 1 step, ring counter 40 advances to the next decade. By summation of these voltages in mixer 38-, the waveform of FIGURE 2b can be produced.

Ring counters 34 and 41) may comprise any of those well-known to the art, with slight modification. Such a modified counter is illustrated in FIGURE 6 and comprises a plurality of transistors Q Q Q The number of such transistors depends on the number of ring counter stages and thus upon the maximum number of steps to be produced thereby. Each of the transistors Q through Q has its emitter connected to a reference bus -41 which is in turn connected to a conducting electrode of a switch, such as transistor 42. The other conducting terminal of transistor 42 is coupled to a source of reference potential, such as ground. The base electrodes of transistors Q through Q are connected to a first biasing voltage supply V by appropriate biasing resistors R through R In addition, the collector of each transistor Q through Q is coupled to the base of an immediately succeeding transistor in the ring by a capacitor C through C Disposed between a second biasing voltage supply V and the collectors of transistors Q through Q are potentiometers P through P whose taps are connected to a common output point 43 through diodes D through D Finally, an input to the ring counter is coupled to the electrode of transistor 42 through a resistor 44.

In operation, the reception of a pulse at the input, as from either multivibrator 32 or ring counter 34, places transistor 42 in a non-conducting state as long as the input pulse is present. Each pulse thus steps the ring counter from one count state to another. Assuming that all transistors Q through Q have been set in a nonconducting condition, and that transistor Q is conducting, non-conduction of transistor 42 turns off transistor Q The anode voltage of Q rises to the value of supply V The positive transient produced thereby is coupled to Q by means of capacitor C Meanwhile, the input pulse is removed and transistor 42 is placed in a conducting state. If transistor 42 conducts before the transient voltage coupled to Q has decayed below the turn-on voltage of Q Q is placed in a conducting condition. In thi manner, transistor 42 steps conducting states around the ring counter at a rate determined by multivibrator 32 or ring counter 34.

The different step voltages of the ring counter output may be obtained by adjusting the setting of potentiometers P through P thereby varying the voltage dropped thereacross and supplied to common point 43 upon conduction of the associated transistors Q through Q The maxi mum number of lines displayed is dependent on the number of stages in each ring counter. If a lesser number is desired to be displayed, as within a logarithmic decade, the potentiometers of the two or more adjacent stages may be adjusted to provide the same step voltage so that one line is thereby retraced.

Referring again to FIG. 4, switch 16 removes its output signal from sync switch at the end of interval I sync switch 30 in turn removes the voltage V+ from oscillator 32 and provides a reset signal to ring counter 40.

In FIG. 7, a means for the implementation of the graph of FIG. 2 during intervals t and r is illustrated. This means may comprise block 20 of FIG. 3.

At the end of first time interval t as previously described, switch 16 provides an output signal to circuit 20. In FIG. 7, this output signal is applied directly to a sync switch which then connects the positive voltage supply V+ to a time base circuit 51 for providing a time base throughout the second and third time intervals via a time delay 56, a bistable multivibrator 54 and a switch 55. Time base circuit 51 comprises a monostable multivibrator 52 and a ramp generator 53 which are interconnected in the same manner as are monostable multivibrator 32 and ramp generator 36 of FIG. 4. Monostable multivibrator 52 in turn has its output connected to an input of a bistable multivibrator 57, a time delay 59, and a pulse shaper 9% In this embodiment, the second and third time intervals are derived from the output of time base circuit 51. To this end, switch 55 provides V+ to energize the monostable multivibrator 52. Monostable multivibrator 52 controls ramp generator 53 whose output is fed to gates 64 and 62. Bistable multivibrator 57 is turned on at the end of period 2, by the Main Sync Reset 14 and i turned off at the end of period t by the monostable multivibrator 52. The output of bistable multivibrator 57 feeds gates 60 and 64 to allow their respective signals to pass only during the second time period t Gate 60 thus passes the wave form 63 to mixer 76 and gate 64 thus passes only the 1st ramp generated by ramp generator 53 to mixer 78. In like manner monostable multivibrator 52 turns on switch 66 via time delay 59 and bistable multivibrator 61 which applies V+ to energize monostable multivibrator 72 which is coupled to ramp generator 74. The time base 68 is independent of time base 51 except for synchronization. The inputs to gate 62 are the square wave from bistable multivibrator 57 and the ramp produced at the output of ramp generator 53. The output of gate 62 is therefore all the ramps from ramp generator 53 with the exception of the first one. This is now period r The output of gate 62 is coupled to gate The output of ramp generator 74 is connected to mixer 76. The output of monostable multivibrator 72 is connected to a pulse shaper 82 whose output controls the gate 89. In turn, the output of gate 80 is connected to a peak detector and driver 84 whose output is connected to mixer 76. Driver 84 is controlled by a discharge switch 86 which has as an input thereto the output of a pulse shaper 99 controlled by monostable multivibrator 52. Finally the output of mixer 76 is coupled to horizontal mixer 22 and the output of mixer 73 is coupled to vertical mixer 24.

To understand how the circuit of FIG. 7 functions to produce the voltages of FIG. 2, reference should be made to the timing chart of FIG. 8 in which relative magnitudes of the signals illustrated have been ignored. The plot of FIG. 8 begins at some arbitrary time within the first time interval t and ends at an arbitrary time within the third time interval t FIG. 8a shows the output signal applied to the input of sync switch 50 from switch circuit 16. FIG. 8b shows the voltage V4- which energizes monostable multivibrator 52 at the beginning of the second time interval t FIG, 8c shows the voltage V+ which energizes gate 62 at a time within the second time interval as determined by bistable multivibrator 57. FIG. 8d illustrates the output of multivibrator 52 which comprises a plurality of recurrent, positive pulses having a repetition rate which is greater than that of the pulse output from switch circuit 16. The duration of the first recurrent pulse equals that of t and the pulses continue throughout the third interval t FIG. 8a illustrates the ramp output voltages obtained from ramp generator 53 and coupled to the inputs of gates 62 and 64. The rate adjust control of ramp generator 53 is varied to suit the time display, l to observe the waveform (in much the same manner as ramp generator 36 is adjusted with respect to the pulses from oscillator or multivibrator 32).

In FIG. 8], the output of bistable multivibrator 57 comprises only the first pulse from monostable multivibrator 52, or that marking the second interval t The second and all succeeding pulses are blocked by gate 64 which is controlled by 57. To accomplish this result, gate 64 may comprise any circuitry which, upon absence of a voltage such as V+, allows a pulse to be coupled from its input to its output and which, upon cessation of that pulse and a prior application of the voltage V+ blocks all succeeding pulses from its output.

This pulse from bistable multivibrator 57 controls gates 60, 62 and 64.

FIG. 8g shows the output of gate 60 for a typical waveform applied to the input thereof. It should be noted that the input waveform is coupled to the output thereof only during the second time interval 11,, or, the duration of the pulse from bistable multivibrator 57. Similarly, FIG. 8h illustrates the output from gate 64 which comprises one sweep of the ramp voltage from ramp generator 53 during the second time interval t By means of mixers 76 annd 24, the waveform at the output of gate 60 is coupled to the vertical amplifier 5 and thus to the vertical deflection means terminals 3 of the CRT 1. The sweep voltage appearing at the output of gate 64 is likewise coupled through mixers 78 and 22 to horizontal amplifier 6 and thus to the horizontal deflection means terminals 4 of CRT 1. In this manner, the waveform is displayed during the second time interval t and the waveforms in FIGS. 8g and 8h correspond exactly to the waveforms of FIGS. 2b and 2a during the second time interval.

FIG. 81 shows the output pulses from multivibrator 52, beginning at the initiation of time interval t and recurring thereafter throughout the interval, terminating at end of t FIG. 8i shows the output of gate 62 which comprises the recurring sweep voltage from ramp generator 53, beginning at the initiation of time interval z, and recurring thereafter throughout the interval. FIGS. 8g and 811 show that during the third time interval, no signal is present at the outputs of gates 60 and 64. Therefore, by means of bistable multivibrator 57, gates 60 and 64 assure that the waveform only is displayed during the second time interval and that thereafter during the third time interval the waveform and a sweep signal or another waveform are blocked from the deflection terminals 3, 4 of the CRT 1 and that voltages representing the vertical lines may be produced.

Pulses from monostable multivibrator 52 energize sync switch 66 via the variable time delay 59 and bistable multivibrator 61 to apply the voltage V+ to time base circuit 68. During this pulse and during succeeding pulses, monostable rnultivibrator 72 and ramp generator '74 of time base circuit 68 oscillate at a frequency higher than that of time base circuit 51. The number of pulses produced by multivibrator 72 during one pulse from multivibrator 52 determines the maximum number of vertical lines which can be displayed. The pulses from multivibrator 72 are illustrated in FIGURE 8k, and by comparison with FIGURE 8i, ten such pulses are produced for one pulse from multivibrator 52. Therefore, the maximum number of lines displayed in this embodiment would be ten, as is the case with the voltages of FIGURE 2.

Ramp generator 74 is adjusted by means of its rate adjust control to provide one sweep voltage for every pulse from multivibrator 72. These sweep voltages are illustrated in FIGURE 81 and are coupled to the vertical deflection means terminals 3 through mixers 76 and 24 and vertical amplifier 6. The pulses from monostable multivibrator 72 are connected to pulse shaper 82 whose output is illustrated in FIGURE 8m. Pulses shaper 82 may comprise any circuitry for converting each of the pulses from multivibrator 72 into a sharp, relatively large amplitude spike. For instance, pulse shaper 32 could include any known differentiating circuiting. The plurality of spikes in FIGURE 8m are applied to the gate terminal of permissive gate 80. As the sweep voltages illustrated in FIGURE 81' are applied to the input of gate 80 during the third time interval, the output from gate 80 comprises a series of spikes occurring at a rate equal to that present at the gate terminal thereof and varying in amplitude proportionally to the instantaneous value of each sweep voltage. FIGURE 8n depicts the output. These spikes present at the output of gate 80 are in turn fed to the peak detector and driver 84 which converts each spike into a step voltage proportional to the maximum amplitude thereof, as illustrated in FIGURE 80. This output is fed to the horizontal deflection means terminals 4 through mixers 78 and 22 and horizontal amplifier 6. Therefore, the waveform appearing at FIG- URE 80 is identical with that appearing in FIGURE 2a during the third time interval t At the beginning of time interval t the pulses from monostable multivibrator 52 are also coupled to pulse shaper 98 which differentiates these pulses into a series of spikes in the same manner as does pulse shaper 82 with respect to the output of multivibrator 72. The output of pulse shaper 90 is seen in FIGURE 8p and comprises a sharp spike occurring at a rate equal to that of mlutivibrator 52. These spikes in turn energize discharge switch 85 to provide a discharge path for the voltage accumulated in peak detector and driver 84 at those times so that the step voltage progression may be reiterated in order to retrace each of the vertical lines in the display.

Therefore, the circuitry illustrated in FIGURE 7 provides a means for implementation of a technique using time sharing between the waveform and line displays. In addition to the fact that recurrent traces are made 10 of the vertical lines to insure persistence thereof, the circuitry of FIGURE 7 also provides that the vertical lines accurately depict time markers without distortion thereof. For instance, if the simple step voltage display used for the horizontal lines in the embodiment of FIG- URES 4, 5 and 6 were used for display of time markers, any departure from a linear progression thereof would produce corresponding errors in spacing of the time markers. When the markers are displayed with respect to a timebase, such as circuit 68 of FIGURE 7, this problem is eliminated. Of course, if time accuracy were desired in the display of horizontal lines, the circuitry of FIG- URE 4 could be replaced by the circuitry of FIGURE 7. If time accuracy were required in the display of the entire graticule, the circuitry of FIGURE 7 alone could be used, the output voltages thereof being coupled to the deflection means of the CRT 1 through a switch which would be energized by switch circuit 16.

The embodiment of FIGURE 7 uses a fixed unit of time which is established by time base circuit 51 for determining time sharing between the display of the waveform and of the vertical lines. However, this time sharing could be established by obtaining a sync signal from the waveform by trigger means well known to the art, particularly where the wavefrom were a highly transient signal. To implement this technique, the time base circuit 51 could be replaced by the trigger means and gates 60, 62 and and 64 could be designed to alternately display the waveform and the lines.

On the other hand, if time accuracy were not especially important, triggering could again be obtained from the waveform and applied to a step voltage generator circuit, such as that illustrated in FIGURES 4 and 6, for display of the entire graticule. Time sharing could then be accomplished by a simple gating means coupling the waveform to the mixers, amplifiers and deflection means during certain portions of the cycle T.

Finally, it would not be necessary to provide a sweep voltage through gate 64 to the vertical deflection means if two waveforms were desired to be displayed simultaneously, such as in Lissajous figures; one waveform could be applied to gate 60 and the other to gate 64. Of course, such a means of display would be accurate only if both waveforms were nontransient but it can clearly be seen that the variations of the embodiment just mentioned for display of transient signals could be applied with equal facility to the display of two transient waveforms, the time base for time sharing being established by triggering signal obtained from either or both of the waveforms.

From the foregoing specification, it should be clearly recognized by those skilled in the art that this invention is not limited to the specific methods and means illustrated, but is intended to encompass the broad aspect of utilizing time sharing techniques in the display on a cathode ray tube screen of a waveform or waveforms and of a graticule on which measurement of the waveforms is to be made. The circuitry illustrated in the foregoing specification illustrates merely a preferable embodiment from the standpoint of steady state waveforms or those having a low repetition rate, as well as possessing other additional advantages such as accurate establishment of time markers and persistence of vertical lines displayed. However, it is to be understood by those skilled in the art that the invention is not limited thereto and is intended to be bounded only by the limits of the appended claims.

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

1. A graticule and waveform display means for use with a cathode ray oscilloscope including a cathode ray tube having horizontal and vertical deflection means, a horizontal input coupled to the horizontal deflection means through a horizontal amplifier, and a vertical input L lli coupled to the vertical deflection means through a vertical amplifier, comprising:

(a) means providing a first signal having a cyclical time interval;

(b) means coupled to said first signal, dividing said ode ray tube during a portion of the cyclical time interval and the waveforms may be displayed during the remainder of said cyclical time interval.

12 being disposed between the other conducting electrode of one of said semiconductor switching devices and the control electrode of an immediately suceeding one of said semiconductor switching devices; (c) a biasing voltage supply;

cyclical time interval into a plurality of shorter time a (d) a plurality of potentiometers, each of said potcn intervals and producing a separate output pulse for tiometers being connected between the other coneach of said shorter intervals; ducting electrode of one of said semiconductor (c) vertical line tracing means energized by said outswitching devices and said biasing voltage supply;

put pulses throughout at least one of said shorter (e) a plurality of unilateral conducting means conintervals to produce at its horizontal output a series nected from the taps of said potentiometers to a of first step voltages, wherein changes in the step common output point; amplitudes thereof occur with respect to time, the (f) asource of reference potential; spacing between the step amplitudes being deter- (g) a second semiconductor switching means having mined by the horizontal scale divisions desired, and 1,3 its conducting electrodes connected to the reference to produce at its vertical output a first sweep voltage bus and said source of reference potential and its for each of said first step voltages; control electrode connected to the input of said first (d) horizontal line tracing means energized by said or second ring counters, whereby, either of said first output pulses throughout at least another of said or second step voltages are obtained at the output shorter intervals to produce at its vertical output a point, the spacing between step voltage amplitudes series of second step voltages, wherein changes in the being determined by adjustment of said potentiostep amplitudes thereof occur with respect to time, meters. the spacing between the step amplitudes being deter- 3. A graticule and waveform display means for use mined by the vertical scale divisions desired, and to with a cathode ray oscilloscope including a cathode ray produce at its horizontal output a second sweep tube having horizontal and vertical deflection means, a voltage for each of said second step voltages; horizontal input coupled to the horizontal deflection means (e) each of said vertical and horizontal line tracing through a horizontal amplifier, and a vertical input coumeans comprising pled to the vertical deflection means through a vertical (i) an oscillator actuated by one of said output amplifier, comprising:

pulses to thereby produce a plurality of first (a) means providing a first signal having cyclical time pulses at a predetermined rate, interval;

(ii) a ramp generator coupled to said oscillator (b) means coupled to said first signal, dividing said to produce one of said first or second sweep cyclical time interval into a plurality of shorter time voltages for each of said first pulses, and intervals and producing a separate output pulse for (iii) means including a first ring counter having each of said shorter intervals;

its input coupled to said oscillator and produc- (c) vertical line tracing means energized by said outing at its output a series of third step voltages put pulses throughout at least one of said shorter whose step amplitudes reiterate with respect to intervals to produce at its horizontal output a series time, the spacing between the step amplitudes of first step voltages, wherein changes in the step being determined by the horizontal or vertical amplitudes thereof occur with respect to time, the scale divisions desired Within the reiteration, a spacing between the step amplitudes being detersecond ring counter having its input coupled t mined by the horizontal scale divisions desired, and the output of said first ring counter and producto produce at its vertical output a first sweep voltage ing at its output a series of fourth step voltages for each of said first step voltages; whose step amplitudes change with respect to (d) horizontal line tracing means energized by said outeach reiteration of said first ring counter output, put pulses throughout at least another of said shorter and a mixer having as inputs thereto the outputs intervals to produce at its vertical output a series of of said first and second ring counters and prosecond step voltages, wherein changes in the step ducing at its output either of said first or second amplitudes thereof occur with respect to time, the step voltages, spacing between the step amplitudes being deter- (iv) said means being coupled to said oscillator mined by the vertical scale divisions desired, and to to produce one of said first or second step voltproduce at its horizontal output a second sweep voltages for each of said first pulses; age for each of said second step voltages;

(f) waveform gating means, energized by the output (e) at least one of said vertical or horizontal line tracpulses during the remainder of said shorter intervals ing means comprising in said cyclical interval, having as inputs thereto the (i) a first time base circuit which is energized by waveforms to be displayed and coupling said waveone of said output pulses and which produces forms to its horizontal and vertical outputs; and at its outputs a plurality of second pulses and a (g) means coupling the horizontal and vertical outputs third sweep voltage for each of said second of vertical line tracing means, said horizontal line pulses, tracing means and said waveform gating means to (ii) a second time base circuit which is energized respective horizontal and vertical inputs of the cathby each of said second pulses and which proode ray oscilloscope, whereby vertical and horizonduces at its outputs a plurality of third pulses tal lines may be displayed on the screen of the cath- G which occur at a rate greater than that of said second pulses and either of said first or said second sweep voltages for each of said third pulses, (iii) a pulse shaper converting said plurality of 2. The graticule and waveform display means of claim 1 wherein each of said first and second ring counters comprises: 79

(a) a plurality of semiconductor switching devices,

each of said semiconductor switching devices having one of its conducting electrodes connected to a reference bus;

(b) a plurality of capacitors, each of said capacitors third pulses into a corresponding plurality of first spikes,

(iv) first gating means having as an input thereto said third sweep voltages and having as an input to a gating terminal thereof said plurality of first spikes, whereby said first gating means produces at its output a plurality of second spikes which occur at a rate equal to that of said first spikes and which occur at a rate equal to that of said first spikes and which vary in amplitude proportionately to the instantaneous value of each of said third sweep voltages,

(v) peak detector and driver means producing from said second spikes either of said first or second step voltages, and

(vi) means for discharging said peak detector and driver means upon reception of each of said second pulses;

(f) waveform gating means, energized by the output pulses during the remainder of said shorter intervals in said cyclical interval, having as inputs thereto the waveforms to be displayed and coupling said waveforms to its horizontal and vertical outputs; and

(g) means coupling the horizontal and vertical outputs of said vertical line tracing means, said horizontal line tracing means and said waveform gating means to respective horizontal and vertical inputs of the cathode ray oscilloscope, whereby vertical and horizontal lines may be displayed on the screen of the cathode ray tube during a portion of the cyclical time interval and the waveforms may be displayed during the remainder of said cyclical time interval.

4. The graticule and waveform display means of claim 3 wherein said vertical or horizontal line tracing means and said waveform gating means are combined, further comprising:

(a) switch means having as an input thereto said plu rality of second pulses, said switch means being controlled by one of said output pulses to produce a control signal at its output having a time duration corresponding to the first of said plurality of second pulses;

(b) second and third gating means having said control signal coupled to their gating terminals and blocking respectively said second pulses and said third sweep voltages from their outputs when said control signal is present at their gating terminals;

(c) fourth gating means having said control signal coupled to its gating terminal and permitting the first of said third sweep voltages to be coupled to its output when said control signal is present at its gating terminal;

(d) said control signal also being applied to the gating terminal of said waveform gating means to permit the waveform to be coupled to its output only when said control signal is present;

(e) means coupling said third gating means to said second gating means;

(f) means coupling said second gating means to said second time base circuit;

(g) means coupling said fourth gating means to the horizontal output of said waveform gating means;

(h) whereby, the waveform is displayed throughout the first of said second pulses and the lines are displayed during the remainder of said shorter time interval.

References Cited UNITED STATES PATENTS 2,504,852 4/1950 Lewis 315-24 2,666,868 1/1954 McMillan 315-22 2,741,722 4/1956 Shields 315-22 2,967,263 1/ 1961 Steinhauser 315-26 3,404,309 10/1968 Massel et a1. 315-18 RODNEY D. BENNETT, 111., Primary Examiner I. G. BAXTER, Assistant Examiner US. Cl. X.R. 315-24

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