US2477848A

US2477848A - Delayed control system for cathode-ray oscillographs

Info

Publication number: US2477848A
Application number: US640958A
Authority: US
Inventors: John J Borek; Abe M Zarem
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1946-01-12
Filing date: 1946-01-12
Publication date: 1949-08-02
Anticipated expiration: 1966-08-02

Description

DELAYED CONTROL SYSTEM FOR CATHODE-RAY OSCILLOGRAPHS iled Jan. 12, 1946 1949- I J. J. BOREK ET'AL 2,477,843

A TORNEY Patented Aug. 2, 1949 DELAYED .CONTEOL SYSTEM FOR CATHODIEJCAY OSCILLOGRAPHS- John J.- Borek,-.Mil waukee;- Wis,- and -Abe -Mo Zarem, Pasadena, Calif.; .assig'nors: to Allis-; Chalmers Manufacturing Company; Milwaukee, Wis.,- acorporation. of Delaware..-

Appli'cati'on January 12, 1946; Serial No; 640,958

of a disturbance in'an operating condition by means of a cathode ray oscilloscope in'wh'ich the. trace of the beam on a screen has a substantial time of persistence, the-persistent trace being photographed-under the-control of an abnormal conditionafiecting the' condition beingobserved or in response 'to the latter condition; If records of successive occurrences of'a disturbance are thus to be obtained-at-infrequent intervals, it becomes advantageous to provide the oscillograph with suitable control elements for enabling itto operate unattended" to: produce records oi all suchdisturbances occurring 1 between periodic inspections as well as records-of. their tim'e of occurrence; The desired result may be'obtained by :pointing the: camera toward the oscilloscopeand. l atimeindicating :device disposed adjacent thereto,- and bi -providing 'automatic means re sponsive totheoccurrence oia-transientcondii'w tion" to; cause 1 opening of 'the camera shutten: momentary" suppression of the 1 cathode ray beam of thezoscilloscope, momentary illumination. of; theztime indicating device reclosure of the shutter, winding. of .the'exposed .film; and-zresettingrot:

the entire system; Additional. meansiare prefer-a ably provided forlocking.out the'system when. the entire film has been exposed;

In a. preferred embodiment. i of theinvention. the-shutter is 'causedito open by means of athyra; tron connecting: a charged capacitor: with a trip; coil for releasing; the shutter, and. thearemaining control operations are .efiected response .to .dis-. charge of- .the capacitor by meansxof :thyratrons connected with the capacitor dischargingthyras tron through .timedelay circuits:

It is therefore an objector the:pr-esent. invention tocprovide a control systems-for-acathoderay oscillograph, for producingrecords of a transient condition of an4-electriccircuit showing the course oftheconditionover an adjustable length of. time;

Another :obj ect of the present inventiomis T110 provide acontrol system fori'a'ncathode ray. oscil-. lograph having; an adjustable time .of exposure vof the Tfilm' to thetracetobephotographed;

Anothersobject 1 of :the present invention. .is...to:;

provide controLlsystemin which :a control .elee ment :may; bet-actuatedswith an adiustable'etimei delayinresponse to asubstantially instantaneous current impulse:

Objects and advantages-othenthan those above set forth will be apparent from the followinglde'esoriptiOn-When read inconnection withithesaae companying drawing which? diagrammatically. represents one embodiment .of the present; irwene tion -sh'owns connected for recording;ethezvoltage of an electric-."circuit in response tOithB. flow-pi current above. a; predetermined; value there-.: through;-

Referringv more; particularly: touthe drawing: by, characters of] referencaanumeral 6 ;generally.;des; i'g nates a cathode ray oscilloscope 0 suitable known: type, which isrepresentied; conventionally-- omtl-i'e drawings. Oscilloscope 6 comprises anodes 6a, a catbode. Eb; a control grid 160,, two pairsofdeflection plates 6d, Seand a screen .6 The necessary potentialsxfor: energizing -,anodes 6a and: grid fic'may beobtained from any suitable source such as a voltage divider-I energized.fromadirect. current generator 8 having its positive terminal. connected to ground;- The cathode raybeam may"; be .caused. continually, to; sweep across screenafif by impression: on deflectionplates lie, for example; of aperiodic potential froma suitablesource COD-5 ventionally represented-asagenerator;9.. The other .pair .of deflection plates is impressed. .with'. potential; representing any desired .operating. con.- dition: to :beobserved; andwhich cooperates. :with the sweep potentialwto. causethe cathode .-ray to; produce a continual: :succession: of luminoustraces on screenfifi. The screenis'chosen of such; material -that each; trace produced :thereonaby: the cathode .raythas a substantial timeofpersistence,:so that any trace may still be-photographed: withimian: appreciable length of time, after it. has=.beerr;produced:;. Tube' szmaya be assumed: for .example; torbe used-ion recording variations. initheivoltageiof an :alternatingcurrent generator. I! in response to abnormal iflowotcurrentube tweenithe generatoranda load device-l 2 through atswitch i3 and. aacurrent. transformer I;

Photographic :copies :of- :selected .Itraces :may;v be obtained by means of acamera I5 pointed-toward. screen; if and properly". focused; thereon; ItiwllL be :understood. that simultaneous recordss oil a. plurality of=.:related-foperatlngconditions; may 'be obtained .ibyi. disposingizwithirr the .field of'icameral5'a plurality of-oscilloscopes which areesi-milar. toz-tube .Su-and. similarly; controlled inresponseetd a;-.: common. 1 abnormal condition. To obtaim on each-photograph- .-ai =record;;.of;.the time rot. occur-.- renceaof the condition in response-atmwhich the.

camera isucontrolled; asuitable:timeJndicatina.

device may be disposed within the field of camera I adjacent tube 6. The time indicating device is represented on the drawing as an electric clock i6 comprising the usual reluctance type motor I! energized from an alternating current supply circuit I8;

Camera I5 is provided with a shutter [9 of any suitable type such as the gravity operated type shown on the drawing. Shutter I9 is held in the closed position by a latch 2| which may be withdrawn by means of a trip coil 22. The shutter may be reclosed by means of an electric motor 23 through a mechanism comprising a cam 24 and a lever 25. Motor 23 also serves to drive the mechanism for Winding the exposed portion of a roll of film 26 on a spool and thereby expose a fresh film portion to the lens. It will be understood, however, that the film Winding mechanism may be suitably modified if the records are to be obtained on individual pieces of film or on plates.

.Motor 23 .may be momentarily energized from circuit I8 through contacts 21b of a relay 2'! to start the motor rotating. The motor thereafter remains energized through holding contacts 28 controlled by a cam 29 to cause cam 24 to effect a complete revolution. Camera l5, tube 6 and clock It are preferably disposed within a light tight enclosure (not shown) and clock I6 is momentarily illuminated by means of a small electric lamp 3! during the opening of shutter l9. Lamp 35 may be supplied with current from circuit'iB through a transformer 32 and through the contacts of a relay 33. 33 may be coordinated in any suitable manner with the operation of shutter l9 as by connecting relay coil 33a with a charged capacitor 34 through contacts 35 which are closed by the shutter.

Unidirectional current for charging capacitor 34 and for energizing the control elements of the system may be obtained from circuit l8 through a rectifying system generally designated 36. The rectifying system may be of any suitable known type and may comprise a transformer 31 and a rectifying tube 38 associated with filtering means comprising a series reactor 39 and a shunt capacitor 4|. A loading resistor 42 prevents excessive rise of the rectifier voltage between operations of the system. Charging current for capacitor 34 is obtained from rectifier 36 through a resistor 43. As a relatively large current is required in trip coil 22 to operate latch 2i, current for the trip coil is preferably obtained from a capacitor 44 which may be gradually charged from rectifier 36 through a resistor 45. Capacitor 44 may be discharged abruptly through contacts 46b of a resetting relay 46, trip coil 22, a shield-grid thyratron 41 and a'resistor 48 to actuate latch 2!. The plate circuit of thyratron 41 and the associated circuits are preferably grounded to the frame on which the elements of the system are mounted, as indicated at 49.

The operation of thyratron 47 may be controlled in any suitable manner in dependence upon an abnormal condition affecting the operation of generator II or of any other circuit under observation. For example, control grid 41c of the thyratron may be connected through a current limiting resistor 51 with a grounded resistor 52 supplied with current from current transformer I4. A'capacitor 53 is preferably connected between grid 41c and ground to divert accidental surge potentials which might cause undesired operation of thyratron 41. Anode 41a and shield-grid 41d are preferably likewise connected to ground through capacitors 54, 55, respectively. Shield- Operation of relay grid 41d is maintained at a predetermined potential with respect to ground by means of a battery 56 to impart to grid 4'i'c the desired characteristic.

Cathode 41b is connected through a current limiting resistor 51 with the control grid 580 of a second thyratron 58 to cause thyratron 58 to become continuously conductive in response to the discharge of capacitor 44 through thyratron 41. Thyratron 58 completes a circuit from the positive terminal of rectifier 36 to ground through contacts d, a current limiting resistor 59, a plate resistor 5i and a cathode resistor 62. The plate potential of thyratron 58 is maintained at a substantially constant value by means of a regulating glow tube 63. Anode 58a is connected to ground through a surge diverting capacitor 64, and shield-grid 5865 is connected with battery 56 through a current limiting resistor 65.

.The control grid 660 of a third thyratron 66 is connected with resistor 62 through a current limiting resistor 67 and through an adjustable time delay circuit comprising a variable resistor 68 and a capacitor 83 to cause thyratron 65 to become conductive an adjustable time after thyratron 58 becomes conductive. The plate circuit of thyratron 65 is connected between anode 63a and ground through a plate resistor H and a cathode resistor 12. Cathode 66b and shieldgrid 6611 may be jointly connected with anode 53a through a resistor 13.

The potential variations of anode 66a are utilized in any suitable known manner for controlling the potential of grid to to cause momentary suppression of the cathode ray beam a predetermined time interval after thyratron 41 is rendered conductive. For example, grid may be connected with anode a through a capacitor 14 and with voltage divider I through a resistor 15 to cause impression of a negative transient voltage on grid when thyratron becomes conductive.

The control grid 160 of a fourth thyratron i6 is connected with resistor 12 through a current limiting resistor 17 and through a second adjustable time delay circuit comprising a variable resistor 78 and a capacitor F9. The plate circuit of thyratron 16 is connected between the positive terminal of rectifier 36 and ground through contacts 46d, 2, current limiting resistor 8|, coil 21a and a cathode resistor 82 to cause operation of relay 2? a predetermined time interval after thyratron 41 becomes conductive. Shield-grid d and cathode 16b may be jointly connected with anode 63a through a resistor 83.

To render the system inoperative and provide a, signal when the supply of film of camera I5 is exhausted, transformer 3'1 is disconnected from circuit I8 after a predetermined adjustable number of operations of motor 23. For the latter purpose, motor 23 drives a cam 84 controlling contacts 85 for connecting circuit is} with the coil 86a of a step relay 85 controlling the connection of transformer 37 with circuit :18. A lamp 8! may also be controlled by relay 86 to indicate whether or not the system is in operating condition.

Coil 45a is connected in parallel with coil 36a to cause resetting of the system after each operation of motor 23. A pushbutton switch 88 connected in parallel with contacts 85 may conveniently be utilized for resetting the system manually during trial operation thereof.

A considerable latitude 'is allowable in the choice of the electrical characteristics of the elements of the herein described system. The following engineering data relate to the essential elements :of a system which has been found to same-4e ep'era'te saliis'factofily and are 'giVli' only by way of example:

Cathode ray tube B-type 5BP1 Glow tube 63-type VR150 H Thyratrons 41, 58, 66, 18-type 2050 Resistor 81-1000 ohms Resistor 59-2900 ohms Resistor 82-4 kilo-ohms Resistor 83-6 kilo-ohms Resistor 65-10 kilo-ohms Resistors 62, 12-15 kilo-ohms Resistor 52-25 kilo-ohms Resistor 1l-31.5 kilo-ohms Resistor 61-45 kilo-ohms I Resistors 42, 45, 5|, 48, 61, 11', 51-50 kilo-ohms Resistor 13-10 kilo-ohms Resistors 43, -100 kilo-ohms Resistor 68-500 kilo-ohms Resistor 18-600 kilo-ohms Voltage divider 1-2.5 megohms Capacitor 54-00005 microfarad Capacitors 53, 64-0001 microfarad Capacitor 09-01 microfarad Capacitors 55, 19-05 microfarad Capacitor 34-10 microfarads Capacitors 4|, 44-20 microfarads Capacitor 14-0.5 microfarad Generator 8-1500 volts Battery 53-8 /2 volts Rectifier 36 -300 volts Reactor 39-20 henries' Before the system is placed inoperation, camera I5 is loaded with film and relay 86'is set in the position shown in the drawing. Circuit I8 is energized and clock I6 is set to show standard time or any other convenient time indication. Resistor '15 is connected with a suitable point of voltage divider 1 to cause impression on grid 80 of apotential having the value required for focus ing the cathode ray beam of tube 8 on screen 6f as is well known. The cathode ray beamis caused to sweep across screen 6 by the voltage impressed between plates 69 and the voltage impressed be-" tween deflection plates 6d causes the beam to produce onscreen iii a succession of traces having a substantial time of persistence. Rectifier 36 supplies unidirectional potential for maintainin'g capacitors 34, 44 in'charged condition and also supplies plate potential for the different flow of

current throughresistors

83 and 82, with theresult that thyratrons' 6B, 16 also remain-non conductive.

The connections between" thyratron 41 and generator I i are so efiected that upon occurrence of a predetermined abnormaI condition in the circuit of generator H and load 12 grid 41c reaches a sufficient potential to render thyratron 41' conductive. Capacitor 44 thereupon abruptly discharges through contacts 466, trip co'i1'22'f thyratron fl and resistor 48!- Trip c'oil 22 with drawszlatch 2 l thereby allowing shutter l9-*'-to' conductive.

6 dropanu expose =filrii 26- the tracesappearing ons'creen" 5f. The speed of operation of shutter 19 'is prefe'rably so-relatedtothe time of persisten'ce of the traces that-when theshutte'r opens the particular traces afi'ected by the abnormal condition which caused openingof the shutter are still'of sufficient intensitytoproduce a record on'film 26 When shutter l 9"reaches the open position, contacts 3d are "closed todischarge capacitor 34 throughrelay coil 3 3a. Relay 33- is thereby cause'd momentarilyto clos'e-its contacts to connect' la'rnp- 3i with transformer'32; Lamp 3| momentarily illuminates clock- 16, thereby causing" a record of thetim'e of operation of relay 33- to appear on film-26, The time indicated-by clock 16' may be taken as thetim'eof occurrence of the abnormal conditionbut' the time taken by the operation of shutter Hand of relay 33 may be subtracted therefrom ii greater accuracy is desired' Discharge of capacitor 44' through thyratro'n 41- and resistor 48 causes grid 580 to reach a potential which is sufficient to render thyratron 58 As the plate potential of thyratron 53 is supplied from rectifier 36, thyratron 58 remains conductive after thyrat'ron' 41 ceases to carry current of appreciable intensity; The continuous flow of current through thyratron 5'9 and resistor 52 causes the potential of' grid 65c to rise gradually at a rate depending'on the time con-'- s'tant 'of the combination of resistor 68 with capacitor 69. After a predetermined time delay, the-grid potential" becomes sufficiently high to I cause thyr'atron 66 to become conductive.

The flow of current from" rectifier 36 through thyratron 6G is established abruptly, thereby abruptly lowering the potential of anode 63a to a predetermined value. The potential drop of anode 66a is transmitted to grid Go through capacitcr 14. The cathode ray beam is thus suppressed, and remains suppressed until grid again'rises beyond a predetermined potential by the gradual partial-discharge of capacitor 14.

'The discharge current of capacitor 14 flows through'thyratron 6 6; resistor 12, voltage divider 1 and resistor 15,-and'ceases when grid 6c has again the same potentialas the tap of voltage divider 1 connected with resistor 15'.

Resistor 68' is so adjusted that the cathode ray beamds suppressed when'the desired number of traces have been produced on screen 6f following the occurrence of the abnormal conditions to which the system is responsive. The number of traces photographed simultaneously by camera [5 isthus limited so as to prevent the record so obtained from becoming confused.

Then'ow of current through thy'ratron and resistor 12 likewise causes thyratro'n 16 to become conductive a predeter'mined'time after thyratron depending on the adjustment of resistor 18 Shutter I9 is thus caused to reclose after film 26 has been exposed to the persistent traces for a sufficient length of time butbefore the cathode ray 'beam'is released by restoration of the normalpotential on grid 60.

Thyra'tron "receives current from rectifier 36 throughresistor BI and coil 21a to cause relay 21 to close contacts 21b. Current is thus supplied to motor 23 from circuit [8. Motor 23 actuates' cam 29, which closes contacts 28 to maintain motor 23 energized independently. of relay 21. Cam 24' raises shutter 19 through lever 25, and

the -shutter is again held closedby latch 2 I' as coil if is "then substantially withofitburr'ntfi Motor 23 also causes winding of the exposed portion of film 26 to expose a fresh film portion to the lens. Return of shutter l9 to the closed position opens contacts 35, thereby enabling rectifier 36 gradually to recharge capacitor 34 in anticipation of another operation of the system.

During rotation of motor 23, cam 84 momentarily closes contacts 85. Current is thereby momentarily supplied to coil 86a to cause the armature 86b thereof to rise and fall and thereby progress contact 86c by one step. At the same time relay 46 is momentarily actuated to momentarily disconnect the thyratrons from rectifier 36.

Contact 460 also momentarily grounds the circuits of thyratrons 58, 6G, 16 to remove all charges from the capacitive elements thereof. The thyratrons return to the nonconductive condition and remain in such condition when relay 46 returns to the position shown. Relay 27 is deenergized and returns to the position shown. Capacitor 44 is gradually recharged from rectifier 36 in anticipation of another operation of the system. When cam 24 has completed its revolution, contacts 28 open to cause motor 23 to stop in the position shown. The system is then reset for another operation thereof responsive to another occurrence of an abnormal operating condition of the circuit of generator Ii and load i2.

Each operation of the system causes contact 830 to progress by one step. When the system is placed in operation, contact 850 is so adjusted that the number of operations of the system which results in complete exposure of film 26, also results in contact 860 being moved out of engagement with contact 86d. A connection between transformer 3! and circuit 18 is thereby opened and the system is rendered inoperative. Lamp 37, which was bright as long as transformer 3'! was energized, then becomes dark, indicating that the system has been locked out. The system may then be returned to the operative condition by replacing film 25 with an unexposed film and resetting contact 860 to a position in engagement with contact 86d corresponding to the length of the film.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. Features disclosed but not claimed herein are claimed in an application of A. M. Zarem and R. D. Weinhold, Serial No. 640,333, filed January 10, 1946.

It is claimed and desired to secure by Letters Patent:

1. In an oscillograph comprising a system for producing a succession of traces responsive to a predetermined operating condition of an electric circuit, each of said traces having a substantial time of persistence, and a camera having a shutter, the combination of control means responsive to an abnormal condition afiecting the operation of said circuit for causing opening of said shutter. means for interrupting the operation of said trace producing system, and time delay means responsive to operation of said control means for causing operation of said interrupting means a predetermined time after operation of said control means.

2. In an oscillograph comprising a system for producing a succession of traces responsive to a predetermined operating condition of an electric circuit, each of said traces having a substantial ter, means for interrupting the operation of saidtrace producing system, means for reclosing said shutter, and time delay means responsive to operation of said control means for causing operation of said interrupting means and of said shutter reclosing means at predetermined times after operation of said control means.

3. In an oscillograph comprising a system for producing a succession of traces responsive to a predetermined operating condition of an electric circuit, each of said traces having a substantial time of persistence, and a camera having a shutter, the combination of control means responsive to an abnormal condition afiecting the operation of said circuit for causing opening of said shutter, means for interrupting the operation of said trace producing system, time delay means responsive to operation of said control means for controlling the operation of said interrupting means, means for reclosing said shutter, and a second time delay means responsive to operation of said interrupting means for controlling the operation of said shutter reclosing means.

4. In an oscillograph comprising a system for producing a succession of traces responsive to a predetermined operating condition of an electric circuit, each of said traces having a substantial time of persistence, and a camera having a shutter, the combination of a trip coil for said shutter, a capacitor, means for charging said capacitor, and means comprising a thyratron responsive to an abnormal condition affecting the operation of said circuit for discharging said.

capacitor through said trip coil.

5. In an oscillograph comprising a system for producing a succession'of traces responsive to a predetermined operating condition of an electric circuit, each of said traces having a substantial time of persistence, and a camera having a shut ter, the combination of a trip coil for said shutter, a capacitor, means for charging said capacitor, and means comprising a first thyratron responsive to an adnormal condition afiecting the operation of said circuit for discharging said capacitor through said trip coil, a source of unidirectional current, a second thyratron connected with said source and with said first thyratron to become conductive in response to discharge of said capacitor through said first thyratron, means comprising a third thyratron for interrupting the operation of said trace producing means, and a time delay circuit connecting said second and third thyratrons to cause operation of said interrupting means a predetermined time after occurrence of said abnormal condition.

6. In an oscillograph comprising a system for producing a succession of traces responsive to a predetermined operating condition of an electric circuit, each of said traces having a substantial time of persistence, and a camera having a shutter, the combination of a trip coil for said shutter, a capacitor, means or charging said capacitor, and means comprising a first thyratron responsive to an abnormal condition afiecting the operation of said circuit for discharging said capacitor through said trip coil, a source of unidirectional current, a second thyratron connected with said source and with said first thyratron to become conductive in response to discharge of said capacitor through said first thyratron, means comprising a third thyratron for interrupting the operation of said trace producing means, a time delay circuit connecting said second and third thyratrons to cause operation of said interrupting means a predetermined time after occurrence of said abnormal condition, means comprising a fourth thyratron for causing reclosure of said shutter, and a second time delay circuit connecting said third and fourth thyratrons to cause reclosure of said shutter a predetermined time after operation of said interrupting means.

'7. In a control system, the combination of a capacitor, means for charging said capacitor, means comprising a first electric valve responsive to a predetermined operating condition for discharging said capacitor, a source of unidirectional current, a second electric valve connected with said source and with said first valve to become conductive in response to discharge of said capacitor through said first valve, a control element, means comprising a third electric valve for controlling the operation of said control element, and a time delay circuit connecting said second and hird valves to cause operation of said control element a predetermined time after occurrence of said abnormal condition.

JOHN J BOREK.

ABE M. ZAREM.

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

UNITED STATES PATENTS Number Name Date 2,186,268 Pakala Jan. 9, 1940 2,264,615 Bryce Dec. 2, 1941