US2578258A - Sweep generator - Google Patents

Description

Dec. 11, 1951 Filed Nov. 29, 1945 INVENTORS ROBERT A. MECONNELL VERLAND A. OLSON W BY ATTORNEY Patented Dec. 11, 1951 UNITED STATES SWEEP GENERATOR Application November 29, 1945, Serial No. 631,736

This invention relates to sweep generators and more particularly to those providing a spiral sweep for cathode ray tube indicators.

Heretofore sweep generators in use were limited to a succession of comparatively short sweeps alternating with fiyback sweeps during which the scanning beam was blanked out. In the operation and'testing of storage and related tubes it was desirable to use a sweep of longer duration, the period of which was uninterrupted by fiyback or blanking. It was further desirable to have the electron beam scanning the mosaic screen of such tubes more uniformly and completely covering that portion of the mosaic screen from which the least distorted results may be expected.

The general object of the present invention is toprovide a sweep generator which will furnish a versatile spiral sweep. Another object of the present invention is to provide a sweep generator capable of controlling the displacement of the beginning of the spiral sweep with respect to the point of rotation.

A furtherobject of the present invention is to provide a sweep generator capable of supplying sweeps spiraling outwardly from a center or spiraling inwardly toward a center. A still further object of the present invention is to provide a sweep generator capable of supplying sweeps with a greater or lesser number of spiral turns for a given screen area.

A still further object of this invention is to provide a sweep generator capable of supplying acircular sweep of variable diameter. In accordance with this invention it has been found that these objects may be attained by the ,use of a gated transitron oscillator with variable oscillatory characteristics and the appropriate, driving, switching, damping and phase shifting circuits to provide voltages which when applied to the proper deflection system of an oscilloscope will produce a spiral sweep possessing variable characteristics. Such a spiral sweep allows a greater length of base line on a given sized oscilloscope tube. "-Other and further objects will appear during the following description when taken with the accompanying drawing which is a schematic diagram of an embodiment of the invention.

In the drawing an electron tube circuit I2 comprises a single-shot multivibrator, responsive to a negative trigger pulse from pulse terminal H.

7 Claims. (Cl. 250-36) pacitor combination l5, rendering normally nonconducting electron tube 30 conducting to cause a negative square wave gate voltage to appear on its plate IT. The length of the negative gate voltage depends upon the charging time of capacitor [8 charged through resistors l9 and 2 l, and can be varied by changing the position of the movable contact on a sweep length control resistor 2|.

The resistor capacitor combination I5 is for the purpose of sharpening the leading and trailing edges of the gate voltage pulse. Thus the single shot multivibrator passes through one complete cycle of operation each time a trigger pulse is received at terminal H returning to and remaining in its normal state until actuated-by a succeeding negative trigger pulse. The singleshot multivibrator, each time it is triggered; produces simultaneously a negative square wave gate voltage at plate IT. and a negative exponential wave gating voltage pulse of the same duration as the gate voltage, at the ground side of capacitor I8.

The negative exponential wave is coupled to grid lZ of normally conducting electron tube BB through resistor 4|. Tube 40 is thus rendered non-conductive by the negative exponential wave for the duration of the gate voltage pulse, and produces a positive square wave of gate length at plate id rising to 3+ voltage allowing electron transitron oscillator tube 60 with its associated resonant tank 19 to oscillate. Electron tube 40 acts as a driver and switching tube for transitron oscillator tube andfor electron tube 5!]. Electron tube 50 normally conducting is rendered non-conducting simultaneously by the negative gate voltage applied to grid 5| and a positive square wave from plate 44 applied to cathode 53. Tube 50 being connected in parallel with resonant tank ill of transition oscillator tube damps the oscillations in the tank by loadingthe tank between gate pulses, plate 52 being directly connected to the positive or plate side of resonant tank H3 and cathode 53 directly connected to the grid side of resonant tank 10. Electron tubes 40 and 5E] rendered non-conductive for the duration of the gate, allow resonant tank '10 to ring or oscillate at the resonant frequency for the duration of the gate. At the end of the gate electron tubes 36 and 50 return to their normally conducting state, loading tank TE] and damping the oscillations therein. Thus tank 10 can only ring for the duration of the gate. The amount of the rise or amplitude of the initial positive oscillation is determined by the positioning of drive control resistor 43 inthe cathode of electron tube 40.

Voltage regulator tube 80 and associated circuit maintain a regulated voltage for electron tubes 40 and 50 and transitron oscillator 60. The positive square wave from electron tube 46 is directly connected to grid 6! and capacitively coupled to suppressor grid 62 of transitron tube to, the amplitude of this positive square wave being controlled by the drive control resistor 53 in the cathode of tube All. As the resonant tank rings, the energy for maintaining the oscillations is supplied by tube 60. The amount of feed back between suppressor grid 62 and control grid GI and whether it is positive or negative in action is determined by the positioning of Q control p0.- tentiometer 64 and oscillator bias control potentiometer 63. The positioning of controls 63 and 64 determine whether the oscillations in the resonant tank increase in amplitude, decrease in amplitude or remain constant in amplitude.

Resonant tank 70 comprises a number of capacitors and inductances the combinations of which are controlled by range switch 12. Thus the resonant frequency may be varied by shifting switch 72 through the four positions. The selection of frequencies for the tanks is made with the knowledge that each oscillation in the tank will, when fed through the. deflection system of an oscilloscope, produce. one spiral revolution of the electron beam. Thus each revolution of the electron beam may be so, timed by the oscillations in the tank that it acts-as range indication.

In position I the resonant frequency is such as to give an indicated range of twenty miles for each oscillation, position 2 an indicated range of ten miles for each oscillation, position 3 five miles for each oscillation, and. position 4 two miles for each oscillation. Thus the output from resonant tank 10 at. terminal 96 comprises. a variable sinusoidal wave continuous for the duration of the gate voltage pulse.

Part of the output oftank in. is fed to a differentiating circuit; comprising capacitor 2 and variable resistor 93 and thence to terminal 9|. In thisv circuit the sinusoidal output of tank 10 is shifted in phase substantially a' quarter cycle. Thus. the output. at terminal 9| of amplitude as determined by adjustment of the tap of resistor 93 comprises a cosinusoid-al wavecontinuous for the duration of the gate voltage pulse, the output at terminal 90. being sinusoidal.

This sinusoidal output from terminal 90 and the cosinusoidal output from terminal Hi When appliedsimultaneously in the appropriate defiection system of an oscilloscope will cause the electron beam. to-follow a spiral sweep. The character of the spiral sweep being determined by sweep length control 2 I-, drive control 43, Q control 64, oscillator bias control 63, and the positioi of range switch 12.

The invention is only to be limited by the appended claims.

What is claimed is:

1 A spiral sweep generator, comprising a source of trigger voltage, a first electron tube circuit, responsive to said trigger voltage, for supplying; a gate voltage pulse, a transitron. oscillator, means for maintaining said transitron oscillator operative during said gate, means for maintaining said transitron oscillator inoperative during the interval between said gate pulses, means for controlling the variations of the amplitude of the, oscillations of said transitron oscil'lator, means for phase shifting part of the output of said transitronv oscillator substantially a. quarter 02618,. the output. of said transitron oscillator and the output of said phase shifting means providing sine and cosine wave voltages which when applied to deflection system of an oscilloscope will produce a spiral sweep with variable characteristics.

2. The combination of claim 1 wherein said transitron. oscillator has a multiple resonant tank comprising a plurality of capacitors and inductances so arranged that different combinations of said capacitors and inductances are resonant to different frequencies and a range control switch for selecting one of said combinations of capacitors. and inductances.

3. The combination of claim 1 wherein said transitron oscillator has an electron tube and a variable Q control potentiometer for determining the amount of feedback from the suppressor to the grid of said tube and whether this feedback is positive or negative in action, a bias control potentiometer in the cathode circuit of said tube, the adjustment of said two potentiometers determining whether the oscillations in said resonant tank increase in amplitude, decreasein amplitude or remain constantin amplitude during the-operative period or said transitron oscillator.

4. A spiral sweep generator, comprising a source of trigger voltage, a first electron tube circuit, responsive to said trigger voltage for supplying a gate voltage pulse, a variable sweep length control resistor in said first circuit. for controlling the length of said gate voltage pulse, a transitron oscillator including a tank circuit, a second and a thirdnormally conductin electron tube circuits rendered non-conductive by and for the duration'of said gate voltage pulse, said second circuit acting as a driver and electronic switch on said transitron oscillator, said third circuit connected in parallel with said tank circuit of said transitron oscillator for damping the oscillations in said tank circuit during the intervals between said gate voltage pulses, said third circuit rendered non-conductive by said first circuit gate voltage and voltagefrom said second circuit applied thereto simultaneously, said transitron oscillator being maintained inoperative by conduction of said second and third circuits, between said gate voltage pulsesand said transitron oscillator bein rendered operative by the simultaneous non-conductance of said second and third circuits during said gate voltage pulses, a variable resistor drive control in the cathode of said second circuit to determine the height of the initial oscillation rise in said tank of said transitron oscillator, a bias control potentiometer in the cathode circuit of said transitron oscillator, a Q control potentiometer in the grid circuit of said transitron oscillator, said last mentioned two potentiometersbeing adjustable to control the variation in amplitude of the. oscillations in said tank circuit, and a circuit for phase shifting part. of the output of said tank of said transitron oscillator by substantially a quarter cycle.

5. In a cathode ray tube spiral sweep generator, an oscillator circuit. comprising a. transitron oscillator, a source of power connected tosaid oscillator, a source. of timed negative pulses, an electron switch tube normally conducting to damp the oscillations of said oscillator, a. second electron switch tube. normally conducting. to shunt said transitron, oscillator, and means applying said pulses tobias; said switch tubesto cut ofi thereby applyin a positive. voltage; pulse to said transitron. oscillator to. initiateoscillations:

therein;

said pulses to bias said switch tubes to cut-off, I

thereby applying a positive voltage pulse to said transitron oscillator to initiate oscillations therein, and means to adjust the normally conducting bias of said second switch tube, thereby adjustiiig the amplitude of said positive voltage pulse and the initial amplitude of said oscillations.

7. In a cathode ray tube spiral sweep generator, an oscillator circuit comprising a transitron oscillator, a source of power connected to said oscillator, a source of timed negative pulses, an electron switch tube normally conducting to damp the oscillations of said oscillator, a second electron switch tube normally conducting to shunt said transitron oscillator, and means applying said pulses to bias said switch tubes to cut-off, thereby applying a positive voltage pulse to said transitron oscillator to initiate oscillations therein, and means to adjust the normally conducting bias of said second switch tube, thereby adjusting the amplitude of said positive voltage pulse and the initial amplitude of said oscillations, and means to adjust the amount and direction of feedback in said transitron osci1lator to control whether the amplitude of oscillations is increasing or decreasing.

ROBERT A. MCCONNELL.

VERLAND A. OLSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,171,150 Shelby Aug. 29, 1939 2,389,004 Schroeder Nov. 13, 1945 2,407,475 Charrier Sept. 10, 1946 2,448,543 Moore Sept. 7, 1948 2,470,573 Moore May 17, 1949

Images