Jan. 14, 1947. n. E. KENYON 2,414,107 ELECTRONIC TIMING APPARATUS Filed June §50, 1944 3 ShèetS-Sheet 1 ¿am M9' ÍIM‘Ã l D. È. KENYGN ÉÁÄ‘É’ÄÜ? ELECTRONIC TIMING APPARATUS Filed June 50, 1.944 S'Sì'zeeüsßsheet 2 Jan. 14, 1947. 2,414,107 n. E. KENYoN ELECTRONIC TIMAING APPARATUS 3 sheets-sheet 5 Filed June a0, 1944 TIME» TIME-5 lnf' mUïîu TIME-.v TIME-h TIME-'P U INVENTOR B à DAViD E. KENYON BY ATTORNE Patented Jan. 14, .1947 ^ '2,414,107 UNITED sTATEs PATENT AOFFICE ELECTRONIC TIMING APPARATUS David E. Kenyon, Smithtown, N. Y., assíg'nor to Sperry Gyroscope Company, Inc., a corporation of New York Application June 30, 1944, Serial No. 543,034 16 Claims. (Cl. 161--15) 2 The present invention relates to counting and timing devices, and concerns particularly elec caused by spurious current leakage into or out of the charge-collecting capacitor. tronic means Ifor the precise measurement and continuous indication of recurrent time inter vals. ’ The employment of electron tubes to control the charging or discharging of a capacitor and the subsequent measurement of the change in Still another object of the present invention lies in the provision of novel time sweep generat Ui ing means synchronized by those pulses of stable frequency which are employed to measure a pe riodic interval in terms of the number generated during the same, the sweep generating means per potential across the capacitor as a function of mitting interpolation between the individual the elapsed time of current flow is a common 10 pulses whose sum defines the interval and there method of determining a time interval. Although by affording an interval measurement of in very short intervals may be measured in this creased accuracy. f manner, the accuracy of a direct reading instru Other objects and advantages of the inven ment in terms of the useable fraction of full scale tion will become more apparent in connection indication is limited to perhaps one percent by with the following detailed description of the the galvanometer employed in the vacuum tube illustrated embodiment thereof, together with voltmeter which measures the potential left on the accompanying drawings, wherein: the capacitor. Fig. 1 is a block diagram of a recurrent inter The prior art also teaches the measurement of val measuring system embodying the present time by counting pulses derived from a standard 20 invention; frequency source, such as the domestic alternat Fig. 2 is a block diagram of a circuit which may ing current supply, and the utilization of trigger be substituted for that portion of Fig. 1 indi circuits which “scale down” or divide the rate of cated by dash lines 45 to adapt the structure of occurrence of the impressed pulses to make pos the latter iìgure to the measurement of low fre sible their summation by relatively slow acting quencies; electromechanical counters. Devices operating Fig. 3 is a schematic diagram of a typical step on this principle are well adapted to measure counter employed in the structure of Fig. 1; accurately long time intervals, but they are not Figs. Liii-4E are graphs of wave shapes illus suited for indicating the length of recurrent short trating the operation of the step counter shown periods with precision. 30 in Fig. 3; It is, therefore, an object of the present inven Fig. 5 is a schematic diagram of an electronic tion to provide means for measuring a recur switch and indicating circuit employed in the rent time interval by counting the number of structure of Fig. 1; pulses of a precisely known frequency contained Figs. 6A-6D are graphs of wave shapes illus within the unknown interval, the total count be trating the operation of the electronic switch and ing proportioned among a plurality of indicating indicating Fig. 7 is circuit a schematic showndiagram in Fig. of 5; aand time sweep " meters for the purpose of providing a reading many times more accurate than the accuracies generator employed in the structure of Fig. 1 of the individual meters. to provide a fine scale indication. Another object is to provide an electronic inter 40 Similar reference characters are employed in val meter having charge collecting capacitors ` all the above ñgures to designate corresponding which are placed at a reference potential by a parts and arrows are provided to indicate the pulse generated in response to the commence direction of energy i‘low. ment of the recurrent time interval that is to be In its essential function, the electronic appara measured and indicating means which are re sponsive to the potentials on the capacitors only after the conclusion of this interval for indicat ing the average length thereof. A further object is to provide recurrent inter val measuring means adapted to iurnish a con 45 tus hereinafter disclosed measures a recurrent time interval. This interval may be that between any two periodic events having substantially the same repetition rate no matter what their origin if they are capable of initiating electrical im Thus, if the events are the occurrences of corresponding portions of different waves hav ing the same predetermined frequency, then the present apparatus may, if desired, indicate the length of the recurrent interval between such 50 pulses. tinuous indication proportional to the potential appearing across a charge collecting capacitor at the termination of the charging interval and sam pled for such a short period thereafter as to provide a reading substantially free from errors 55 wave portions in terms of relative phase angle. 2,414,107 4 0n the other hand, if the present device responds to similar portions of the same wave, then the indicating scales may be calibrated in terms of -the frequency of the measured wave. This inter val between the two periodic events is embodied in a control wave having a length precisely equal to the interval to be measured. The control wave causes impulses of a stable frequency to be ap gular control wave, while the other series of pulses acts to terminate this wave. Devices having the properties of generator I6 are well known and may be dcrived from the Eccles-Jordan trigger circuit. The length of the wave provided by gen erator I6 is, therefore, precisely equal to the pe riod which it is desired to measure. A frequency standard Il provides waves of some precise radio frequency, such as 100 kilo This counting circuit comprises a series of Ih cycles or 1 megacycle, to an electronic switch I8 normally blocking passage of these waves. In charge collecting capacitors interconnected by the particular embodiment of the invention illus blocking oscillators and adapted to be- charged plied to an impulse counting circuit. f in steps by applied impulses.- Each of the oscil trated in Fig. 1, the periodicity of the pulses which lators is arranged to be triggered by a critical ' initiate the control wave bears a definite though potential placed on the preceding capacitor cor l5 not necessarily harmonic relationship to the fre quency of the standard I1. The rectangular con responding to a predetermined number of im trol wave is supplied from generator I5 to the pulses for the purpose of discharging this ca switch I8 to permit passage of the standard fre pacitor and for concurrently supplying a charging quency waves for precisely the duration of the impulse to the succeeding capacitor. This charg ing and discharging action continues as long as 20 interval to be measured. The intermittent out put of the electronic switch I8 is fed to a block the control wave permits the pulses to be applied ing oscillator I9 of a conventional design. The to the counter chain. Upon the conclusion of the blocking oscillator I9 is normally quiescent, but interval, however, the momentary charge on each adapted to be synchronized at one-half the fre capacitor in the series remains substantially un changed until the beginning of the next interval. 25 quency of standard source I'I by the substantially sinusoidal triggering -waves, every alternate one These charges reveal the electrical position of of which it converts into a sharp pulse or voltage the counter and the residual potential on each spike which is passed on to a step counter 2|. capacitor is a measure of the number of im The step counter .2I, of a type discussed in de pulses applied thereto in excess of an integral multiple, including zero, of the predetermined> 30 tail with reference to Fig. 3, has a capacitor adapted to be charged in discrete voltage incre number necessary to cause a discharge of the ments by each applied impulse- 'I‘he potential capacitor through its associated blocking oscil on the charge collecting capacitor increases in lator. Thus, it is evident that the indication of steps until it exceeds that corresponding to a pre-Y a potential corresponding to a single impulse left on a particular capacitor represents a plurality of 35 determined number of impulses. In the case of counter 2|, this number is designated as five. impulses originally applied to the beginning of the chain numerically equal to that factor by This critical potential triggers a blocking oscilla tor which serves to discharge the capacitor and at the same time supply a voltage pulse to another The total count 40 step counter 22. Counter 22 is similar to counter which the pulses have been “scaled down” or divided in the process of passing down the chain to the capacitor in question. may, therefore, be determined with precision from a. knowledge of the number of impulses stored on each capacitor and the factor associated there with. The residual potentials on the capacitors 2|, but acts to divide only by two, and feeds a series of impulses to a step counter 23. Counter 23 divides the pulses it receives by a factor of ñve and passes on the diminished number to a are measured after the conclusion of the interval 45 counter 24, which like device 22, reduces the re- ' ceived impulses by a half. A iìnal counter 25 and indicated on a plurality of meters each indi performs a division by live. It is evident that cating a convenient portion, such as a decimal the series of counters may be extended to increase place, of the total count. i the number of pulses that may be counted either A resetting impulse at least equal to the above mentioned critical potential is generated in re 50 for lengthening the maximum period which may be unambiguously indicated or for providing more sponse to the commencement of each interval scales if the precision and frequency of the stand and applied to all capacitors to discharge theml ard source I'I warrants them. simultaneously to a reference potential corre The counting and dividing action of counters sponding to a zero reading of the counter in prep- ` aration for a new count. The indicating circuits, 55 2l through 25 continues as long as the electronic switch I8 through the control of the interval de however, have a time constant such as to pro iining control wave produced by-generator I6 per vide a continuous indication despite the inter mits pulses to be supplied to the counting chain. mittent flow of information from the counting Upon the termination of the unknown interval, chain. ' Referring now to Fig. 1, there is shown an ap 60 a potential is left upon the charging capacitor associated with each step counter which ls a paratus which responds to a ñrst- source II of measure of the electrical position of that counter periodic signals and a second source I2 of sig ~at the time of the interval termination. nals having substantially the same period. The In the illustrated embodiment of the invention, apparatus serves to measure the recurrent inter it is desired to indicate the time interval on scales val between these signals and indicates the length thereof with a high degree of precision on a coarse scale meter I3, a medium scale meter I4 and a line scale meter I5. 'I'he ratios of the full scale readings of the indicating devices- I3, I4 and I5 are powers of ten; consequently the meas having maximum readings which are some power of ten units of time, e. g., microseconds. In order that the various scales may be decimally related, it is, of course, possible to adjust each step coun 70 ter so that it divides by a factor of 10 and to ured interval is indicated to at least three decimal employ separate indicating circuits responding places. to the potential on each capacitor whose charge increases in 10 steps before discharging through Sources II and I2 supply their pulses to an interval wave generator I6, wherein one series the associated blocking oscillator. However, this of pulses serves to initiate a substantially rectan 75 is not the most reliable arrangement since a rel 5 `2,414,107' ativeiy small change in operating conditions may cause such a counter to miscount, dividing in stead by a factor of 9 or 11. It is, therefore, pref erable for reasons of stability, to count to 10 in two operations as is illustrated. Under these conditions, a uniform decimal scale may be ob tained by adding the voltages across the capaci tors of adjacent two step and live step counters in suitable proportions, the potential correspond 6 its zero position to its full scale position in a smooth manner. If, for example, the interval is zero and in creases constantly, then meters I3 and I4 lic steady at zero indication. While meter I5 gradu ally attains its maximum indication. When the interval exceeds this ñne scale' maximum, meter I5 drops suddenlyto zero While meter I4 jumps to its iirst index. The line scale meter then pro ing to an impulse on the capacitor of a two step 10 gresses to its maximum again, at which point counter being adjusted to equal one-half the potential corresponding to a step on the capaci tor of the next succeeding five step counter. Leads 26 and 21 supply potentials correspond ing to the voltages on the charge collecting ca the medium scale meter jumps to its second posi tion as the meter .I5 drops again to zero. When the medium scale meter I4 attains its maximum indication, it'falls tc zero, while the coarse scale It is evident that the three meters may be read from an electronic switch 28. Switch 28 is controlled right to left to obtain a highly precise summa by a wave provided by a metering wave gener tion of the pulses of standard frequency which ator 29, which is synchronized after a short de are contained within the measured interval. lay created by delay circuit 3I by the termina 20 At the commencement of each interval all the tion of the wave issuing from generator I6. The counters are set to zero by discharging their as switching wave created by generator 29 permits sociated capacitors. This is accomplished by the the sum of the potentials on leads 26 and 21 to provision of a resetting pulse generator 42 which be applied to a D. C. amplifier 32 only for a short is act .ated by the leading edge of the substan time after the termination of the counting cycle. tially rectangular control Wave from Ygenerator Limiting the time during which the voltages on I6 and is adapted to create a sharp pulse in re the capacitors are sampled is a precaution against sponse thereto. This pulse is applied over a lead stray current leakages in these capacitors which 43 to all counters simultaneously. The action of ' may cause the voltages to drift upward or down the resetting pulse is discussed in more detail in ward slightly before the recurrence of another 30 Fig. 3, but it may be noted that since this zero timing cycle. . ‘ setting of the counters occurs at the commence The ampliñer 32 is adapted to have a long time ment of the measured interval, the deleterious constant so that the output voltage of the am effects of stray current leakage through the ca pliiier suffers substantially no change between pacitor circuits are minimzed. successive periods of the same duration. The Fig. 2 illustrates an alternate input circuit ar meter I3 is connected to the output of amplifier rangement 45’ which may be substituted for that 32 and provides a continuous indication of the portion of Fig. l which is enclosed by dashed lines recurrent charge condition of the counters 24 and and designated by the reference numeral 45. The 25. The charge potentials on the capacitors as structure of Fig. 2 is adapted for the precise sociated with step counters 22 and 23 are im-> 40 measurement of audio frequencies. A source of pressed over leads 34 and 35, respectively, on an low frequency 46 is supplied to a square wave electronic switch 33 similar to switch 28. A D. C. shaper 41 which corresponds to the interval wave amplifier 36 like device 32 ampliñes the selective generator I6 in Fig. 1. The square wave shaper ly applied potential and drives the meter I4. 41 forms the wave supplied by source 46 into It is evident that the coarse reading meter I3 substantially _rectangular pulses having lengths and the medium scale meter I4 indicate only at corresponding to one-half the period of the ap discrete points jumping from one position to the plied waves. The waves produced by wave shaper next highest as the counters whose potential they 41 are employed as control waves in a manner reveal pass from one charge condition to the next similar to Fig. 1. In lieu of frequency standard possible higher charge condition. It is desirable 50 I1 and electronic switch I8, a stable shock-ex that the fine scale meter I5 indicate smoothly cited oscillator 48 is preferably provided. With throughout its range interpolating between dis this circuit, the control waves from device 41 ex crete points on its scale. Thus, if the fine scale cite the standard frequency oscillations rather meter I5 may be read to an accuracy of one per than merely control their passage. The advantage arising from the employment of cent, then the three meters enable the count to be determined to four decimal places. This inter the shock-excited 4oscillator 48 is that the lead polation on fine scale I5 is accomplished through « ing edge of the control wave determines the phase the employment of a sawtooth generator 31. of the generated waves as well as the moment when these waves are applied to the counting The saw tooth generator 31 produces a linear time sweep voltage which is initiated by output 60 chain. If the initial phase is not maintained constant, the interval between the resetting pulse pulses supplied over a lead 50 _from step counter and the first pulse provided by the blocking os 2|. The interval wave generator I6 suspends or cillator I9 does not remain fixed. Under these freezes the action of the saw tooth generator 31 conditions meter I5 indicates only at discrete at the instantaneous conclusion of the measured points like meters I3 and I4 and the interpolat interval by application of the control wave over ing action of sawtooth generator 31 is rendered a lead 40. A potential corresponding to the posi ineffectual. For this reason, the use of the elec tion of the saw tooth wave as stopped in its linear tronic switch I8 in Fig. 1 is preferably restricted charging cycle somewhere between the zero ref _ to those applications Where the periodicity of the erence potential and full charge condition is ap pulses initiating the control wave bears a deñnite 70 plied over lead 38 to an electronic switch 39 and though notl necessarily harmonic relationship to D. C, amplifier 4I similar to the devices previ the frequency of the standard source I1. ously discussed. The meter I5 is actuated by the When the counter is employed with the input amplifier 4I so that as the measured interval circuit 45’ rather than 45 then the meters I3, I4 changes, this meter follows these changes from 75 and I5 may be calibrated directly in `frequency pacitors of counters 24 and 25, respectively, to 15 meter jumps to its ilrst indicating position. 2,414,107 7 rather than merely indicating the time occupied negative potential with- respect to ground is pre by a half cycle of the low frequency wave from vented by the low impedance oñered by the series source 46. combination of the two diodes and the small out- -- The step counter 23 which is typical of counters 2| through 25 is shown in detail in Fig. 3. An in put impedance of the cathode follower 65 which dissipates all charge more negative than the ref-put lead 5I is connected through a capacitor 52 to erence potential on cathode 84. The regenera a cathode 53 and an anode 54_of two diodes con tive action of the blocking oscillator continues tained within a common vacuum envelope 55. A until the anode current reaches its saturation cathode 56 associated with the anode 54 is at value. The voltage induced across transformer tached toa charge collecting capacitor 51 whose 10 62 then becomes zero. Stray and interwinding other side is held at ground potential. The ñoat capacitors discharge quickly because they are _ ing side of the capacitor 51 is also connected t0 small. The anode current then starts to decrease, a grid 58 of a triode whose anode 59 is coupled thus creating a positive voltage in the cathode through a feed-back transformer 62 to its cathode circuit, regeneration being now in the opposite 6| to form a blocking oscillator` circuit. An an 15 direction. The potential difference between the ode 63 associated with the cathode 53 is attached grid 68 Yand cathode 6I is quickly carried below to a cathode 64 of a triode 65 which has no plate the cut-oir point and the regeneration stops. The load but merely a cathode resistor 66 suitably . negative reference potential on the capacitor 51 chosen to provide a cathode follower action. Tri holds the oscillator in a quiescent condition until ode 65 has a grid 61 connected through a grid 20 triggered by the next charge accumulation. resistor 68 to an adjustable voltage divider 69 A facsimile of the voltage excursion of the grid placed between a source of negative potential and ' 58 is impressed across the cathode load 15. The ground. The adjustable connection between re lead 35 therefore supplies the indicating circuits sistors 68 and 69 permits the bias of tube 65 to be with a wave corresponding to Fig. 4E. The lead controlled so that the cathode 64 is maintained at 25 11 attached to the blocking oscillator anode 59 some suitable negative reference potential. The provides the next succeeding step counter with lead 43 carrying the resetting pulses is con pulses as shown at 85 in Fig. 4D, occurring at each nected through a blocking capacitor 1 I to the grid discharge ofthe blocking oscillator. The numeri 61. Another cathode folower circuit is provided cal ratio of pulses 85 to pulses 8| is determined, to measure the potential across the charge col 30 of course, by the number of pulses which capaci-` lecting capacitor 51 without drawing current tor 51 accepts before reaching the critical poten therefrom. This latter cathode follower com prises a triode 12 whose grid 13 is connected to the ungrounded side of capacitor 51, and whose cath ode 14 is provided with a load resistor 15. The lead 34 supplying the indicating circuits is at tached to the cathode 14. . In the operation of the step counter illustrated l in Fig. 3, pulses shown in Fig. 4B as‘at 8l, are` ap tial, in this instance after iive steps. , The resetting pulse shown at 86 in Fig. 4C and aligned with the lead edge> of the control wave 82 produces a momentary positive voltage across the load resistor 66 which causes a current ñow -through the two diodes in envelope 55, and charges .the capacitor 51 to a potential equal or exceeding the critical value necessary -to dis plied to the input lead 5I for the duration of the 40 charge the blocking oscillator. The , effect of time interval deñned by a control wave 82 shown the resetting pulse 86 is therefore to discharge in Fig. 4A. The negative portions of the applied the capacitor 51 no matter what its charge con pulses are readily passed by the diode combina dition. tion of cathode 53 and anode 63 and applied to the The details of a circuit suitable for the elec cathode load 66. Since the effective output lm tronic switch 33 and the amplifier 36 are shown pedance of a cathode follower corresponds to the in Fig. 5. Leads 34 and 35 attached tothe cath combination of the cathode resistor in parallel ode followers in step counters 22 and 23, respec with a fictitious resistor approximately equal to tively, are connected through decoupling re the reciprocal of the variational transconduct ance of the tube, the impedance between the cathode 64 and ground is low. The negative pulses are therefore substantially snorted to sistors- 9| and 92, respectively, to the control grid 93 of a .triode 94. Trlode 94 acts as a cath ode follower stage and has a cathode load resistor 95 shunted by, a large value capacitor 96. This ground.` The positive portions of input pulses 9| load circuit is connected to a grid 91 of a second are barred from this circuit by the action of the cathode follower 98 which, in turn, has a load re diode, but are free to pass from anode 54 to cath sistor 99. The load 99 is attached to an adjust ode 56 and charge the capacitor 51 in steps. 'I'he able voltage divider IOI. The meter I4 is coninitial bias on the blocking oscillator is equal to nected together with a resistor |02 in series with ' the negative potential of cathode 64 and is such the voltage divider I0| and a second voltage di as to keep the blocking oscillator quiescent. The vider I03 interposed between a negative potential potential on the capacitor 51 increases according 60 source and ground. to the wave 83 shown in Fig. 4E. Upon applica y 'I'he grid 93 of triode 94 is also connected to the tion of every ñfth pulse, however, the voltage anode |04 of a rectifier |05 formed by connecting across capacitor 51 reaches a critical or triggering the grid of a triode to its plate. The cathode |06 potential such’as indicated by reference numeral of the rectiñer |05 is attached to the anode |01 84. of a triode amplifier |08 having a» plate load re At this voltagel amplitude plate current com sistor I 09. The gri-d III of triode |08 has a grid mences to flow through the transformer 452. This resistor II2 which is coupled through a blocking action induces a negative voltage between the capacitor II3 to the lead 30 upon which is im cathode 6I and ground, which causes a further pressed the metering wave lfrom generator 29. rise in plate current flow. This action is regen 70 In the operation o_f the circuit shown in Fig. 5, erative and the grid 58 swings highly positive with respect to the cathode 6I and permits current ñow which discharges the capacitor 51 to the negative reference potential. Any attempt on the part of the discharge to place capacitor 51 at a more 75 the step voltages from the two step counter 22 and the iive step counter 23 are mixed by the par allel feed of leads 34 and 35 through the resistors 9| and 92 which can be adjusted to provide a uniform ten-step Wave form. Figs. 6B and 6C 9 2,414,107 illustrate the wave shapes ||5 and |20, respec tively, impressed on leads 34 and 95, respectively, and Fig. 6D shows with dashed lines ||6 the summation of these voltages in such proportion as to provide a. uniform scale. The wave shape ||6 does not, however, appear on the grid 93 be cause during the timing interval tube |08 is con ducting, causing a voltage drop across .the load resistor |09 such as to keep the anode |01 at sub , 10 counter 2| is connected through a coupling ca .pacitor |33 to the pentode grid |3 | , The potential on the charge collecting capacitor |2| is meas ured without drawing current therefrom by means of a cathode follower stage |34 which has a cathode load |35 to whose high potential side the lead 38, supplying the switching, amplifying and indicating circuits 39, 4| and I5, respectively, is attached. stantially the negative reference potential al 10 In the operation of the circuit shown in Fig. '1, though, of course, at a positive potential with the interval wave generator I6 supplies the con respect to its cathode. Under these conditions, trol wave with a positive polarity over lead 40. any potential applied by leads 34 or 35 to .the This wave flows through the series resistors |21, grid 94 more positive than this negative reference | 26 and |25 and causes the potential on the potential is conducted through the rectifier |05 15 anode |24 of the diode |23 to be displaced in to ground. ' After the conclusion of the interval 82 shown in Fig. 4A, the metering wave illustrated in Fig. 6A at ||1 is applied with a negative polarity to to the grid ||| of the tube |08 thereby cutting ofï current flow -through resistor |09 and render ing the rectifier |05 inoperative. The tube 94 is thus permitted to respond to the voltages supplied over leads 34 and 35. These voltages correspond to the residual charges on the capacitors in the ~ step counters as mixed by resistors 9| and 92. The capacitor 96 assumes a voltage in accordan-ce with a positive direction. This allows diode |23 to con duct, drawing current through the high resistance of resistor |26 and gradually charging capacitor |2|. The increase in potential across capacitor | 2| is substantially linear with respect to time. This charging action continues for the dura tion of the measured interval. Meanwhile, how ever, pulses from the counter 2| are periodically impressed upon control grid |3| of pentode |29. Tube | 29 is thereby made momentarily conductive and effectively shorts the capacitor |2| to ground. The potential across capacitor |2| therefore is this charge as indicated by the solid line ||8 in very rapidly reduced to zero and immediately Fig. 6D. The metering wave allows this voltage starts to recharge through the diode |23. It is to be applied for a short period at the termina 30 evident that substantially saw-tooth waves are tion of which the connection between the step generated across capacitor i 2| as long as the counters and the cathode follower 94 is removed measured interval lasts. At the termination of and all further voltages on the grid 93 are short` ed by the combined action of -tubes |08 and |05. As has been mentioned, this momentary sam- ‘ pling of the residual potentials shortly after the end of the measured interval is designed to render the indicating circuit substantially independent of leakage in and around the charge collecting capacitors. Therefore, the charge on the capaci tor 96 is readjusted for a short interval having the same repetition rate as the measured interval. The time constant of the parallel combination of resistor 95 and capacitor 96 is very long and the potential on the grid 91 is substantially free from ñuctuations. The cathode follower 98 drives the meter I4 without loading the capaci tor 96. The calibration of meter |4 may be ad justed by the voltage divider |0|, while the zero setting may be corrected by the voltage divider |03. The meter |4 may be placed at a point re mote from the remainder of the apparatus with out resorting to shielded cables, since the circuit impedance is relatively low. the interval. however, the control wave from gen erator I6 stops charging the capacitor and no more discharging pulses are supplied from the counter 2|. Under these conditions, the capaci tor |2| is neither allowed to accumulate charge nor is it discharged, and therefore retains what ever intermediate charge it has acquired at the instant the interval ends. Although the cathode follower |34 impresses a replica of the potential across capacitor |2| over lead 38, it is only this last charge condition which the electronic switch 39 permits the fine scale meter |5 to indicate. The present invention has been disclosed as embodied in an apparatus which is not limited in its speed of response by the inertia of mechanical elements, which is well adapted to provide remote indication, which affords highly accurate meas urements while utilizing circuits comprising corn ponents having liberal electrical tolerances, and whose principle of operation finds application in such apparently different fields as 10W frequency measurement and high speed photoelectric count A suitable circuit for the time sweep generator , ing or sorting. 31, is shown in detail in Fig. 7. A charge collect Since many changes could be made in the above ing capacitor |2| is connected between the cath construction and many apparently widely differ ode |22 of a diode |23 and ground. The diode |23 ent embodiments of this invention could be made has an anode |24 which is attached to the junc without departing from the scope thereof, it is tion of resistors |25 and |26. Another resistor intended that all matter contained in the above |21 is joined to the end of resistor |26 opposite 60 description or shown in the accompanying draw ings shall be interpreted as illustrative and not in resistor |25, the three resistors |21,` |26 and |25 a limiting sense. forming a series circuit placed between positive What is claimed is: and negative sources of potential. The point of 1. Apparatus for measuring a time interval by attachment of anode | 24 is arranged to be at sub stantially zero potential. The control lead 40 “ counting the numberof waves of known fre quency contained within said interval comprising from generator |6 has a connection incommon a source of waves of said known frequency, a step with resistors |26 and |21. counter having a capacitor adapted to be charged The ungrounded side of the capacitor |2| is in discrete voltage increments by each cycle of also attached to an anode |28 of a pentode |29. said waves, means for placing a reference poten The pentode |29 is maintained in a nonconduc tial on said capacitor at the commencement of tive condition by a negative bias placed on its said interval, means for applying said waves to control grid |3| .and supplied from a negative said counter during said interval, and means source through a grid resistor |32 attached responsive to the difference between the poten thereto. The lead 50 coming from the step tial present on said capacitor upon the conclusion 9,414,107 1l of said interval and said reference potential to indicate Ithe number yof cycles applied to said counter. - 2. In apparatus for counting a recurrent series of impulses, a capacitor, means for charging said capacitor in steps to successively higher potentials ing impulse to the succeeding capacitor, meter ing means responsive only between said groups of impulses for measuring the residual potentials on said capacitors to determine the number of impulses applied thereto in excess of integral multiples of said predetermined number> of im pulses, means generating a resetting impulse at sive to a critical potential for discharging said least equal to said critical potentials, and means capacitor after a predetermined number of im for applying said resetting impulse at the com pulses, means responsive only between said recur-> 10 mencement of the' next group of impulses to dis rent series of impulses for measuring the residual charge all said capacitors simultaneously. potential on said capacitor to determine the num 7. Apparatus for measuring a time interval by ber of impulses in excess of an integral multiple counting the number of waves of known ireof said predetermined number of impulses, and quency occurring during said interval compris means generating a resetting impulse at least ing means for generating waves of said known equal to said critical potential for discharging said frequency, means for forming a substantially rec capacitor at the commencement of the next series tangular wave having a duration equal to said of said impulses. interval, a capacitor, means responsive to the 3. In apparatus for counting a recurrent series leading edge of said rectangular wave for plac of impulses, a capacitor, means for charging said 20 ing said capacitor at a reference potential, means capacitor in steps to successively greater poten controlled fromsaid wave forming means for tials in response to successive impulses, a block applying said waves of known frequency to said ing oscillator arranged to discharge said capaci capacitor only during said interval, means for tor when the potential exceeds that correspond altering the potential on said capacitor from said ing to a predetermined number of impulses, me reference potential in steps in response to said tering means responsive only between said recur applied Waves,- and means responsive to the dif rent series of impulses for measuring the residual ference between the potential _present on said potential on said capacitor to determine the num capacitor upon the conclusion of said interval ber of impulses in excess of an integral multiple and said reference potential to indicate the num- of said predetermined number, and means pro 30 ber of cycles applied to said counter. ` ducing a resetting impulse for discharging said ca_ 8. In apparatus for measuring a time interval pacitor at the commencement of the next series by counting the number of timing waves of known of said impulses. frequency generated during said interval, means 4. In apparatus for counting a recurrent series for interpolating between adjacent, periods of of impulses, a capacitor, means for altering the said timing waves comprising means for forming potential on said capacitor from a reference po a. control wave characterizing said interval, a tential in steps in response to said impulses, a . charge collecting capacitor, means responsive to blocking oscillator arranged to return said ca said control wave for gradually charging said pacitor to said reference potential when the po capacitor throughout said interval, capacitor dis tential reaches a magnitude corresponding to a ,predetermined number of impulses, metering 40 charging means, means responsive to said con trol wave for applying said timing waves to said means responsive only between said series of im discharging means during said interval to dis pulses for measuring the residual potential on charge said capacitor periodically and abruptly, said capacitor to determine the number of im and means for measuring the charge potential on pulses impressed thereon in excess of an integral said capacitor after the conclusion of said inter multiple of said predetermined number, and in response to successive impulses, means respon means producing a resetting impulse for return ing said capacitor to said reference potential Vat the commencement of the next series of said im ‘val to determine the duration of the same in excess of an integral number of said timing periods. 9. In apparatus for measuring a time interval ` 5. In impulse counting apparatus wherein a 50 by counting the 'number of timing waves of known frequency generated during said interval, means series of capacitors are charged one from another for determining the duration of said interval in in progression, each receiving an impulse upon excess of an integral number of periods of said the discharge of the preceding capacitor until timing waves comprising means for forming a a predetermined number of charging impulses have been received and then discharging to pro.- 55 substantially rectangular control wave having a, duration equal to said interval, a charge collect vide the succeeding capacitor with a charging» ing capacitor, means responsive to said control impulse, the combination of cathode follower cir wave for continuously and gradually charging cuits each comprising a grid controlled electron said capacitor only during said interval, capaci tube having a cathode load, rectifying means connected between said'capacitors and said cath 60 tor discharging means, means responsive to said control wave for applying said timing waves to ode loads, said rectifying-meansand said cath said discharging means only during said inter ode loads providing low impedance paths shunt val to discharge said capacitor periodically and ing said capacitors for impulses of undesired abruptly, means for measuring the charge poten polarity, and means for applying a resetting im tial on'said capacitor, and means providing a pulse to the grids of said cathode followers to Acontinuous indication of said charge potential discharge all said capacitors simultaneously. present at the conclusion of said interval as a 6. Apparatus for counting recurrent groups of function of said excess duration. impulses comprising a series of charge collecting l0. In apparatus for measuring a time inter capacitors adapted to be charged in steps by applied impulses, blocking oscillators intercon 70 val by counting the number of waves of known. frequency generated during said interval, means necting said capacitors, each of said oscillators for forming a control wave characterizing said being triggered by a critical potential on the pre interval, an oscillator for generating waves of a ceding capacitor corresponding to a predeter known frequency in response to said control wave, mined number of impulses for discharging said capacitor and for concurrently supplying a charg 75 a step counter supplied Waves from said oscil pulses. 13 2,414,107 lator, said step counter having a capacitor adapt ed to be charged in steps by each cycle of said waves, means responsive to the front edge of said control wave for placing a referenœ charge on said capacitor, means responsive to the rear edge of said control wave for momentarily sampling the charge on said capacitor, and means for indicating the momentarily sampled charge con dition. 14 means responsive to a critical potential for dis charging said capacitor after a predetermined number of impulses, means responsive only be tween said recurrent series of impulses for meas uring the residuaI potential on said capacitor to determine the number of impulses in excess of an integral multiple of said predetermined number ofimpulses, and means generating a resetting -impulse at least equal to said critical potential 11. Apparatus for counting recurrent groups 10 for discharging said capacitor. of impulses comprising a series of charge col 14. In apparatus for counting a recurrent se lecting capacitors adapted to be charged in steps ries of impulses, a capacitor, means for altering by applied-impulses, blocking oscillators inter the potential on said capacitor from a reference connecting said capacitors, -each of said oscil potentialin steps in response to said impulses, lators being triggered -by a critical potential on1 15 means for returning said capacitor to'said rei' the preceding capacitor corresponding to a pre erence potential when the potential reaches a determined number of impulses for discharging magnitude corresponding to a predetermined said capacitor and for concurrently supplying a number of impulses, metering means responsive charging impulse to the succeeding capacitor, only between said series of impulses for meas metering means responsive only between said 20 uring the residual potential on said capacitor groups of impulses for adding in ñxed propor to determine the number of impulses impressed tions the residual potentials on said capacitors thereon in excess of an integral multiple of said to determine the number of impulses applied to predetermined number, and means producing a said series in excess of an integral multiple of resetting impulse for returning said capacit-or to the product of the predetermined number of im 25 said reference potential in preparation for the pulses necessary to discharge each capacitor of next series of said impulses. said series, means generating a resetting impulse 15. In impulse counting apparatus, a capaci at least equal to said critical potential, and means tor, means for altering the charge on said ca for applying said resetting impulse at the com pacitor in steps in response to applied impulses, mencement of the next group of impulses to dis 30 means for returning said capacitor to its original charge all said capacitors simultaneously. charge condition when the charge potential 12. Apparatus for counting a group oi.' im . pulses comprising a series oi' charge collecting capacitors adapted to be charged in potential steps by applied impulses, blocking oscillators interconnecting said capacitors, each of said os cillators being triggered by a critical potential on the preceding capacitor corresponding to a predetermined number of impulses for discharg ing said capacitor and >for concurrently supply ing a charging impulse to the succeeding capac itor, and measuring means responsive only after the application of said groups of impulses for adding in fixed proportions the residual poten tials on said capacitors to determine _the number of impulses applied to said series in excess of an integral multiple of the product ot the pre reaches a magnitude corresponding to a prede termined number of applied impulses, a cathode „follower circuit comprising a grid controlled elec 35 tron tube -having a cathode load, rectifying means connected between said capacitor and said load, said rectifying means and said cathode load providing a low impedance path shunting said capacitor for impulses of undesired polarity, and means for applying a resetting impulse to the grid of said cathode follower to return said ca pacitor to its original charge condition irrespec tive of the number of applied impulses. ' 16. In apparatus for timing an interval the combination comprising a charge collecting ca pacitor, means for continuously and gradually charging said capacitor during said interval, means for periodically and abruptly discharging charge each capacitor of said series. said capacitor during said interval, and means 13. In apparatus for counting a recurrent se 50 forl measuring the charge potential present on ries of impulseava capacitor, means for charg _ said capacitor at the conclusion of said interval. determined number of impulses necesary to dis- ' ing said capacitor in steps to successively higherA potentials in response to successive impulses, DAVID E. KENYYON.