US2350069A

US2350069A - Oscillograph sweep circuit

Info

Publication number: US2350069A
Application number: US431626A
Authority: US
Inventors: Harold J Schrader; Ranald D Scheldorf
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1942-02-20
Filing date: 1942-02-20
Publication date: 1944-05-30
Anticipated expiration: 1961-05-30

Description

Patented m so, 1944 2,350,069 I OSCILLQGBAPH SWEEP Harold]; Schrader, liaddonileld, and Ronald D. Scheldorl, Haddon Heights, N. J., authors of America, a corporation 'to Radio Oormration of Delaware Application February 20, 1942, Serial No. 431,826

14 Claims. 1 (on. 1-11-95) This invention relates generally to cathode ray oscillo'graphs and particularly to sweep circuits for cathode ray oscillographs in which a source of electric phenomena to be observed is caused to produce instantaneously a single timing voltage to provide a single traversal of the fluorescent screen by the cathode ray.

More particularly, the invention relates to a circuit and method for producing such a .single timing voltage substantially instantaneously with the application of the initial portion of the electric phenomena to beobserved, and or duration and rate dependent on the time constant 01' the circuit.

Other methods and circuits for producing single timing pulses have been used heretofore, but they have been characterized generally by considerable time delay between the application of the starting potential and the beginning of the timing pulse.

This invention therefore has great utility over other systems when the measurement of signals of short duration or transients is required. In all such systems the transient is often used to start the timing pulse. It is obvious that any time delay between the start of the transient and the start oi the timing pulse, both measured at the oscillograph. would prevent any useful indication of the transient during this interval.

Another problem innmeasuring transient voltages is caused by their customarily short duration. This necessitates an extremely rapid traversal oi the screen by the cathode ray with necessarily a low amount of light energy available to the observer, resulting in poor visibility, because the cathode ray intensity must be limited during absence of scanning signal to prevent burning of the fluorescent screen. This invention provides means for increasing the intensity of the cathode ray only during the time interval of the single timing pulse which is in turn under control ofthe transient voltage under measurement. This arrangement permits greatly increased illumination of the fluorescent screen during the scanning interval and at the same time permits low normal cathode ray intensity to prevent burning of the screen.

An object of the invention is to provide means for producing a single timing pulse for cathode rayoscillograph seaming which is started in response to an initial portion of the signal under measurement and the duration or rate of which is controlled by the time constant of an associated circuit.

Another object of. the invention is to provide a circuit or method for producing a single timing.

pulse for use in cathode ray oscillograph measurements oLtransients, in which the beginning of thetransi tsubstantiallyinstantlystartsthe timing pulseand at the same time causes an increase in the intensity of the cathode ray for the duration of the timing pulse.

Still another object is to provide means for producing a single non-oscillatory timing pulse for osciilograph use. in response to an initial portion of a starting signal or a transient ot a selected polarity wherein the rate or duration of the pulse is determined by the time constant of the pulse circuit. An additional object is to provide manual switching means for reconditioning the circuit after each actuation by the starting potential.

In describing the invention, reference will be made to the drawing, which shows a schematic diagram of one embodiment of the system.

Referring to the drawing, the wave form shown at the extreme left is that of a typical transient or starting signal under measurement. This signal is applied to the vertical deflecting element H of the conventional oscillograph l2 and to the input it of wide band amplifier tube T1. The output of tube T1 is coupled in any conventional manner to the input of the conventional phase inverter circuit containing tube T2. The singlepole double-throw throw switch S1 provides signals of either polarity to the cathode of diode rectifier T: by utilizing either the input or output of phase inverter tube T: as desired.

The anode of the diode T: establishes and applies a voltage of only one polarity to the grid of tube T4 of the trigger circuit comprised of the tubes T4 and T5. It will be seen that the position of switch 81 controls the startingpolarity of the transient signal.

When a signal is applied to the input circuit of tube T1 the diode tube '1; will conduct on each negative cycle. The position of the switch S1 is determined by the polarity of the input signal. The value of the variable resistor R: varies the bias, and determines the voltage at which the diode T; will conduct. When sufiicient signal voltage is applied to the diode Ts, it becomes conducting and the voltage developed across the variable resistor R: causes trigger tube T4 to become non-conducting because of the resultant high negative grid bias applied. The value of resistance of Ra determines the sensitivity of the trigger circuit. When tube T4 becomes non-conducting, tube Ts becomes conducting. With tube Ts conducting, the grid potential of tube T4 is made even more negative to maintain the cut-oil condition. This in turn increases the bias on the diode tube '1: so that it becomes non-conducting except for much higher signal voltage than is required to first actuate it. When tube Ta is conducting, the bias of the D.-C. amplifier tube- To is decreased, causing the anode current to i increase. The increase 0! anode-cathode current in tube Te causes the voltage across the resistor serving transient voltages, means 'for producingin said circuit a single non-oscillatory timing voltage pulse in response to an initial portion of said transient voltages, a time constant circuit,

means for deriving from said time constant cir- 75 e v l 1 9 9 l- I I ll-torise,whichraises the potential or the oathcult a timing vol 1, 1 15, 1 'odeoithediode'tube'rr. andnianuallyoper rtedmeanstor Frict onditionin The anode potentialoi diode T1 rises,to offset 1 said circuit after each applicati Q13, m. the riseinits cathode potential, at arate dete'rsient.volta ge.- w mined by. the time constant oi resistorRi and 5 3.. In aesthetic h! cscilloarili 'circuitior ob-z capacitor or in the anode circuit oi. the diode. -scrving transient voltages having. menu for pm. a

The amplitude of the pulse developed across ducinga single timing voltage pulse in A the-capacitor or is determined by the static" to an initial portion or said'tr'an sient'voltagg characteristic of the diode tube- Tr. Although and or duration-determined bythetimeoonstant the substitution of a triode, having sharp cut- 10 oithe'circuit, a triode actuatedbysaid transient ofl characteristics, would be desirable from the 1 1 vo1tage,a-phase'inverter inthe output circuit-otstandpoints of sensitivity and gain, the diode said triode,- a'diode selectively "connected 1, ,1.

has been Ioundto be preferable because of its, tween the output oi either said triode or-saidinherently sharper cut-oi! features. The di--- phase inverter and the input of a polarized trlg ode circuit. ompri t e 1'': n the i e d 1 sercircuit, a n. c. amplifier between the output lay circuit R1, Ci, can. ior special purposes, be or said trigger circuitandthe cathod r a m. caused to produce a train of pulses similar to the ond diode,a time constantcircuit in. the anode single pulse described heretofore, by driving the circuit or said second [diode for. determining the diode with voltage pulses of square wave io'rm. rate of said singletiming uiseendzmeem' f r irom aconventiohal square wave generator 20. impressing said timing pulse on' a deflecting eleconnected; across the resistor I ll through the I merit of said cathode ray oscillogi'apli.v 'f switch 2!. The individual. pulses of thetrain 4. In a cathode'ray osciilog raph, circuit for 6h.- would be limited in amplitude by the cut-of! serving transient voltages having means for proq characteristics of the diode and of rate or duraducingv a single timing voltage pulse in response tion determined by the time constant or the diode to an initial portion or said transient voltages anode circuit, -,'ihe amplifier tube To is driven andorduration determined byt'he time constant" by th V lta developed across p itor C1. of thecircuit, a triode actuated by said transient Output'i'or use on the horizontal deflecting elevoltage, a-phase inverter in the output circuit orment l4 oi'the cathode ray oscillograph I2 is said-triode, adiode selectively connected between taken between a' point I! onresistor It and the output of either said triode or said phase inground. 7 verter and the input oi'a polarized trigger cir- A typical timing pulse devel ped by the circuit cuit, a D. C. amplifier between the output of said. is shown at the extreme right side or the draw- 1 trigger circuit and the cathode of a second .dimg. 1 It is apparent that the pulsestarts as soon ode, a time constant circuit in the anode circuit as, the driving signal reaches a predetermined or said second diode for determining the rate or potential the polarity of which is controlled by said single timing pulse, means for impressing the position or the switch S1 and the amplitude; said timing pulse on a deflecting element-oi said by the values oi the variable resistors R2 and Ra. cathode ray oscillograph, and means ror'control- The pulse will then continue to rise for an interling the intensity of the cathode ray in said oscil val determined bythe time constant or the cir- 40 lograph by voltages derived from said timing cult comprised of resistor 7R1 and capacitor C1. pulse circuit. i f after which it will remain at maximum'potential 5 In a cathode ray 'oscillograph circuit for. ob-' I determined by the normalpotential across re- 7 serving transientvoltages having means iorpro sistor II. I a U ducing a single non-oscillatory timing voltage In order to recondition the circuit for actuapulse in. response to'an portion of said tion by a subsequent transient or starting sigtransient voltages and oi duration determined by I nal, a reset switch S2 is connected between the g the time constant orthe I circuit, a triode actugrid 01 trigger tube'Ts and nd; Temporary ated by said transient voltages, aphase inverter closing of this switch, which is normally open. in the output circuit of saidtriode, adiode se shorts the grid drcifl of tu e To, restores tubes lectively'connected between the output or either Ta', T and To to-normalop rati n, and causes said triode or said phase inverter and the input the cathode trace to return to its original posiof aIpolarized trigger circuit. a D. 0. amplifler tion. voltage for increasing the intensity or the between the output or said trigger circuit and cathode ray during the operation interval ofthe the cathode of a second diode,.a time constant circuit, to provide increased illumination, is decircuit in the anode circuitotsaid second -diode rived from the anode circuit or tube T4 andapior determining the rate .01 said single timing plied to the control grid. I! of the oscilloscope .12. pulse, and means tor impressing said timing Similar control voltage could be obtained from pulse on adefiectin'g element of said cathode ray;

other suitable points in thecircult. oscillograph'. A we claimv as our invention: a 6. In a cathode ray oscillogr'aplr circuit for obi 1. In a cathode ray oscillograph circuit ior observing transient voltages having means for pro- 'serving transient voltages, means for producing ducing a single non-oscillatory timing voltage in said. circuit a single timing voltage pulse in pulse in response to aninitial portion of said tranresponse to an i tial portion of saidtransient sient voltages and of duration determined by the voltages, a tim onstant circuit, means for detime constant of the circuit, atriode actuated by riving from said. time constant circuita timin Said nsient voltage. Phase i v 1!! e voltage pulse for said transient, and manually output circuit of said triode, a, diode H selectively operable means .ior reconditioning said circuit connected between the output of 'either'said'tri- I after each application or said transient voltages. ode or said phase inverter and the input oi a 2, In a cathode ray oscillograph circuit for obpolarized trigger circuit, a D.v C. amplifier be-.

I tween the output of'said trigger circuitjand the cathode of a second diode, a time constant circuit, in the anode circuit of said second diode for de-r.

termining'th'e rate of said single timing pulse, means for impressing said timingjpulse on a dc;

fleeting element of said cathode ray oscillograph,

means for controlling the intensity of the cathode ray in said oscillograph by voltages derived from said timing pulse circuit.

'7. In a circuit for producing a single pulse of predetermined duration, a source of starting potential, a polarized trigger circuit comprising a diode having a cathode and anode, a first triode having a cathode, a control electrode and an anode, a second triode having a cathode, a control electrode and an anode, a connection from the anode of said diode to the control electrode of said first triode, a resistor from said control electrode of said first triode to the anode of said second triode, a resistor from the anode of said first triode to the control electrode of said second triode, means for providing control electrode and anode potentials to each of said triodes, a circuit for applying the starting potential to the cathode of said diode, means connecting the control electrode of said second triode to the cathode of a second diode, a time delay circuit in the anode circuit of said second diode, and means for utilizing pulses developed across said second diode.

8. In a cathode ray oscillograph circuit for measuring transient voltages, means for producing a single timing voltage pulse in response to an initial portion of said transient voltages and of duration determined by the time constant of the circuit, comprising, in combination, a triode actuated by said transient voltage, a phase inverter in the output circuit of said triode, a diode selectively connected between the output of either said triode or said phase inverterand the input of a polarized trigger circuit, a D. C. amplifier between the output of said trigger circuit and the cathode of a second diode, a time constant circuit in the anode circuit of said second diode for determining the rate of said single timing pulse, means for impressing said timing pulse on a deflecting element of said cathode ray oscillograph, and manually operable means for reconditioning said circuit after each application of said transient voltages.

9. In a cathode ray oscillograph circuit for observing transient voltages having means for producing a single timing voltage pulse in response to an initial portion of said transient voltages and of duration determined by the time constant of the circuit, a triode actuated by said transient voltage, a phase inverter in the output circuit of said triode, a diode selectively connected between the output of either said triode or said phase inverter and the input of a polarized trigger circuit, a D. C. amplifier between the output of said trigger circuit and the cathode of a second diode, a time constant circuit in the anode circuit of said second diode for determining the rate of said single timing pulse, means for impressing said timing pulse on a deflecting element of said cathode ray oscillograph, means for controlling the intensity of the cathode ray in said oscillograph by voltages derived from said timing pulse circuit, and manuallv operable means for reconditioning said circuit after each application of said,

the time constant of the circuit, a triode actuated by said transient voltage, a phase inverter in the output circuit of said triode, a diode selectively connected between the output of either said triode or said phase inverter and the input of a polarized trigger circuit, a D. C. amplifier between the output of said trigger circuit and the cathode of a second diode, a time constant circuit in the anode circuit of said second diode for determining the rate of said single timing pulse, means for impressing said timing pulse on a deflecting element of said cathode ray oscillograph, and manually operable means for reconditioning said circuit after each application of said transient voltages.

11. In a cathode ray oscillograph circuit for observing transient voltages having means for producing a single non-oscillatory" timing voltage pulse in response to an initial portion of said transient voltages and of duration determined by the time constant of the circuit, a triode actuated by said transient voltage, a phase inverter in the output circuit of said triode, a diode selectively connected between the output of either said triode or said phase inverter and the input of a polarized trigger circuit, a D. C. amplifier between the output of said trigger circuit and the cathode of a second diode, a time constant circuit in the anode circuit of said second diode for determining the rate of said single timing pulse, means for impressing said timing pulse on a deflecting element of said cathode ray oscillograph, means for controlling the intensity of the cathode ray in said oscillograph by voltages derived from said timing pulse circuit, and manually operable means for reconditioning said circuit after each application of said transient voltages.

12. In a circuit for producing a single pulse of predetermined duration, a source of starting po tential, means for producing said pulse in response to an initial portion of said starting potential and of duration determined by the time constant of the circuit, and manually operable means for reconditioning said circuit after each application of said starting potential.

13. In a circuit for producing a single nonoscillatory pulse of predetermined duration, a source of starting potential, means for producing said pulse in response to an initial portion of said starting potential and of duration determined by the time constant of the circuit, and manually operable means for reconditioning said circuit after each application of said starting potential.

14. An oscilloscope deflection circuit for producing a single sweep deflection potential in response to a transient phenomenon comprising a non-oscillatory control impulse generating device responsive to the initial part of the transient phenomenon for generating a single control impulse, means including a time constant circuit for producing a substantially constant rate of change of potential in a predetermined polarity direction in response to the generated control impulse, and means to reset the control impulse generating mean: and to produce a change of potential in the opposite polarity direction in order that the J circuit may berendered responsive to the next succeeding transient phenomenon.