US2113011A - Thermionic valve apparatus - Google Patents

Description

April 5, 1938. I E. C, wHn-E .2,113,011

v THERMIONIC VALVE APPARATUS April 5, 1938. E. c. WHITE THERMIONIC VALVE APPARATUS Filed Nov. 28, 195e 2 sheets-sheet 2 INVENTQR ERIC L.c.wHrre.

ATTO RN EY ...WH l

UNITED STATES PATENT OFFICE land, assigner to Electric & Musical Industries Limited, Hayes, Middlesex, England, a British Company Application November 28, 1936, Serial'No. 113,211 In Great Britain December 4, 1935 5 Claims.

The present invention relates to pulse-operated thermonic valve apparatus, such n f o ergarplglas frequency dividers, ments and tlleulikww 5 A frequency d ider is known which comprises a condenser arranged in series with the anodecathode path of a thermionic valve, a resistance and a source of steady potential, the condenser being shunted by a discharge device, such as a l neon lamp, of the kind in which a discharge only takes place when the potential between the electrodes is greater than a critical value. Controlling pulses are fed to the control grid of the valve; the arrangement being such that anode current l only flows when a pulse is present; the condenser charges up during the time within which anode current is flowing. A

In this known arrangement, provided that the controlling pulses are of substantially constant duration and amplitude, it can be arranged that the potential across the condenser does not reach the :dash-over potential of the discharge device until a plurality of pulses have been operative on the control grid of the valve; there can accordingly be derived from the terminals of the condenseran oscillation at a frequency which is a sub-multiple of the frequency of the controlling pulses. In such an arrangement, if the duration or amplitude of the controlling pulses is changed, the number of pulses necessary to enable the condenser to charge Aup sufliciently for the discharge device to flash over changes also, so that the factor of frequency division is dependent upon the duration and amplitude of the controlling pulses.

It is an object of the present invention to provide pulse controlled thermipnicmvalve,apparatus, such as a frequency dividerLan electricalpounter 0r the like thfenratipn'fiiihich substan- 40 tially independent o jill dulationN I amplitude of the applied pulses, providedthat boftljithejduration and amplitude.exceed pregdetermnd minimum valuesjdthus the pulses may be of varying amplitudes and durations, pro `ded`that the It is a furth''object of the invention to provide pulse-controlled thermionic valve apparatus, the operation of which is substantially independ- 50 ent, over a wide range, of variations Ain vali/e characteristics and the potent1als of associated sources of current supply. www

According to the present invention, apparatus for counting or measuringdtherfrequency of elec- 55 tric pulses comprises means forwdelimvetringma charge on the occurrence of a pulse independently of the amplitude or duration of the pulse to a circuit which for the purpose of counting the pulses integrates the charges, a device for measuring the integrated charge being provided, or for the pur- 5 pose of measuring the frequency, measures the amount of charge delivered in unit time. Further, according to the invention, apparatus for generating electric pulses at a frequency which is a sub-multiple n of the frequency of applied pulses, comprises means for delivering a charge on the occurrence of a pulse independently of the amplitude or duration of the pulse to a circuit which integrates the charges and generates a pulse after the integration of n pulses and dissi- 15 pates the integrated charge.

In the case of apparatus for counting according to the invention, a rst condenser is charged from a source of current 9f constaip'tntial, the condenser biiigNdidslchar/gedin"the; interyals 20 between pulses ,andwthe means fwr"integrating the chargesy comprises da" furthergcondensenmand a unilaterallyconductingdeyice ,in.thecharging path of said first condenser. allflagdevicegwhich is associated witnsaidrurthernc. denserjsfie- 25 sponsive to a xpredetermined, ptentalvvalue; across said further condensenw'f'hefirst ,condenser is discharged'by;aswitching device inse:- ries with a unilaterally Yf.:Ondjuting device .and the switching devicemay b ef thermioni ,xa1ve 30 having the pulses to beountedl5`l51ic l between its grid and cathode. The devices associated with the further condenser may consist of an electro-static voltmeter, a thermionic voltmeter,

a multi-Vibrator or other relaxation oscillator. 35

In a particular thermionic valve apparatus embodying the invention the switching device is constituted by a pentode valveMarr/anwgedwinnsnhunt with said first condenser. In this arrangement each pulse caussdan increment of charge to flow 40 into the second condenser, and it can be arranged that successive increments are substantially equal in magnitude. The charge held by the second condenser, and hence the potential across it, is thus dependent on the number of pulses applied to the switching device, and apparatus according to the invention is thus readily applicable as an electrical counter.

The potential set up across the second condenser may be caused to initiate secondary pulses, each of which represents a plurality of pulses applied to the switching device. The apparatus may thus be employed as a frequency divider. In such an arrangement means are provided for discharging the second condenser after the plurality of pulses have been applied to it.

In order that the invention may be more clearly understood and readily carried into effect circuit arrangements embodying the invention will now be described by way of example with reference to the accompanying drawings in Which:

Fig. 1 shows apparatus accorcli1;1 g t,o tlgginvention for use in an electriwunter,

Fig. 2 shows apparatus according to the invention suitable for useas amfreguendcymdiyider,

Fig. 3 shows an alternative form of frequency divider, 'MW' Fig. 4 shows apparatus according to the invention suitable for use for freguepdcuygneasuring, purposes, and

Fig. 5 is an alternative form of frequency measuring circuit.

Referring to Fig. 1, a pentode valve V1 has its anode and screening grids connected to points at suitable positive potentials in a source of current B1, the negative terminal of which is connected to the cathode of the valve V1 which is earthed. The anode circuit includes a resistance R, the end of which remote from source B1 is connected to one terminal of a condenser C1, the other terminal of which is connected to the cathode of a diode V2 and the anode of a diode V3. The anode of diode V2 is earthed, and the cathode of diode V3 is connected through a condenser Cz to earth, condenser C2 being shunted by a device X, such as an electrostatic voltmeter or other high impedance indicating device, which is capable of indicating the potential set up across condenser C2 and hence the number of pulses which has been operative.

The control grid of valve V1 is arranged, in the absence of pulses, to be at substantially earth potential, and the controlling pulses are applied in negative sense and at such a level as to be capable of swinging the control grid potential to beyond anode current cut-oli. A pentode is chosen for V1 and the anode resistance is made large so that between pulses the anode current owing is limited by the anode resistance rather than the valve and the anode potential is low compared with the potential at the upper end of the resistance R. When the anode current is cut off by the applied pulses the potential of the anode rises to the potential of the upper end of the resistance R. The more nearly the change of potential of the anode approaches the high tension potential the less is the possible percentage effect of variation in this change caused by a change of valve characteristics. A low impedance triode valve could be used with the large anode resistance but would obviously require a very much greater amplitude of applied pulse to cut oi the anode current. 1n the analysis which follows it is assumed that the anode potential between pulses is so low that the change of anode potential at the occurrence of a pulse is substantially equal to the high tension voltage.

The operation of the arrangement is as follows: assuming condenser C2 initially to bedis; charged, on the arrival at Vt he gor1trolm,gridw nof valve V1 of a negative pulse of sufficient amplitude, the anode current 'of Visjhutpftandthe anode potential rises to rEihthe potential of the source B1, in a time determined by the'timeoonstant of C1 and C2 in series, and R. The negative pulse should lastmforma time equal atmleast to a multiple of (say ve times) this time ccn- Stant.

The condensers C1 and C2 charge up through the diode V3 to the potential E1, the potential across C2 being 'Ihe capacity of C2 is preferably about 10 to 100 times the capacity of C1.

At the end of the negative pulse, the potential at the anode of valve V1 is again brought down nearly to earth potential, due to valve V1 conducting once more, and C1 is discharged through V2 and V1 in series, the right hand plate of condenser C1 being brought substantially to earth potential. Condenser C2, however, retains its charge, which is increased by a further incrementldue to the next pulse. The second increment is not quite as big as the first, and causes an increase in potential equal to .C1 C2 E C1+C2 1Xc1+c1 'I'he increase in potential across condenser C1 due to the increment of charge resulting from the nth pulse is The potential of condenser C2 after n increments of charge is ElCl The number of pulses which have been operative upon valve V1 can be as gertainedwbymmers:

potential, it may be,, arrangr-lcthav operates to dischaLgeQzntlll-l's'm er, the deviselbsinearra es to generate appulsenwhi M a further cpuntinggpluevige.

The device X may, for this purpose, comprise a neon or other like discharge tube, a grid controlled gas discharge tubglvajglwopking oscillator valve V4 being thus biased so that no anode current ilows in valve V4 until the potential dierence across condenser Cz reaches a pre-determined magnitude.

A multivibrator comprising valves V5 and Vs is provided as shown, valve V5 being a pentode, the screen grid of which serves as an anode for the purpose of the multivibrator, while its anodecathode path serves to discharge condenser C2. The screening grid of valve V5 and the anode of valve V4 are connected through resistance R4 to a positive terminal in source B1. The anode of valve V6 is connected through bias battery Bz ...,.amf

E1R2 RVi-R1 Thus n (the number of increments of charge occurring before C2 is discharged) is determined by L H-Cz )l RztRi-El 1 Cri-Ci Hence R2 C2 R1 10g 1+1) Cri-C1 1 and 11:# R2+R1 10g 1+g-) Thus n depends substantially only on the ratios 1i d a R1 an C2 and it should be' particularly noticed that n is substantially independent of the voltage of the high tension source. Either or both of these ratios may be made variable if desired. The arrangement operates as a frequency divider, pulses of of the frequency of the pulses applied to valve V1 being set up at the anode of valve Ve; this point may if desiredbe' connected to a further counter. Thevalve V of Fig. 2 may be replaced by two separate valves, which may be triodes, having their grids connected together; the anode of one Valve may then be used in the multivibrator circuit and the other may be used for discharging Cz.

The upper limit to the interval between successive pulses at which counting is satisfactory is set by stray leakage resistances across C2, and by attention to the insulation this interval may be made very long. 1f in a particular application the intervals are short, the battery Bz may be replaced by a condenser and grid leak of a suitably long time constant.

The length of the pulse which discharges condenser Cz is set by the time constant of C: and R3, and is preferably arranged to be less than the minimum interval between the pulses applied to valve V1.

An example of a two stage frequency divider embodying blocking oscillators isshown innljig. 3 in which the valve Vfi: Mablocking oscillator of known type and replaces the'valves V4, Vsand Vs and also acts as the valve corresponding to V1 in the second counting stage. Diodes V2 and V'3 perform exactly similar functions as the diode valves V2 and V3 in the first counting stage which correspond with the similarly lettered valves in Figs. 1 and 2.

Referring now to Fig. 4 of the accompanying drawings, a continuous current meterme/iis connected across a condenserY (liinplace of tliel'intermittently conductivadevicew The reading of the meter M is directly proportional to the frequency of the applied pulses Vand dependent upon the supplyvgltagenirginvthe.battery B. As in the case of a, circuit for pulse counting, it is assumed that in the arrangement of Fig. 3 the nanlplitnde of the applied pu1ses isp sucignt to `duce anode current cut oi in theyale V1".m M

Fig. 5 illustrates tliedapplication of contact rectifiers in a bridge circuit to a frequency measuring circuit embodying the invention. The use Iof such a rectier provides twice the amount of current to be passed to the meter M than in the case of the diode connections shown in the previous figures. It will be seen that in this figure there is no condenser equivalent to C2 in the preceding gures, although such a condenser may be connected across the meter M.

It will be understood that while particular applications of the invention have been described and illustrated in detail the invention may nd application in numerous circuits not specifically described, thus for example, although the switching device in the circuits described takes the form of a thermionic valve, a mechanically operated switch or relay may be employed.

I claim:-

1. In combination, a storage condenser, a charging condenser, a unilaterally conducting device connected between one plate of each of said condensers for admitting current from said charging condenser to said storage condenser, a second unilaterally conducting device connected between the junction of the charging condenser and the first-mentioned conducting device and the other plate of said storage condenser for discharging said charging condenser, means to impress a pulsating current between said other plate of the storage condenser and the other plate of the charging condenser, and a loading impedance across the storage condenser for discharging the storage condenser following a predetermined charge on said storage condenser.

2. Apparatus as claimed in claim l wherein said unilaterally conducting devices comprise electron discharge tubes each having a cathode and anode.

3. Apparatus for frequency division comprising a storage condenser, a nresis 'tgnlHaj/ol-tager* source between one plate ffsaid storagevcondenser and said resistor to apply. a..negative..vo1tage t plate, a charging condenser, one plate Aof is connected to the end of said resistor remote from said voltage source, aunilaterally conducting device connected -between the` otherplatelof said charging condenser and theA other plate `of said storage condensxeruforw charging said storage condenser, a switchingf deviceiresponsiveto z,coritrolling impulses connected between 'the'. junction of the resistor and the rst-mentioned plate of said storage condenser, a secondunilatgrallLqQnducting device connected between theV unction of the charging condenserand the I'ilSi/ S M laterally conducting device and the said other plate of the storage condenser for discharging said charging condenser, and aloading impedance across the storage condenser forvdischarging the storage condenser followinga` predetermined charge on said storagecorndenser.

4. Apparatus for indicating electric pulses comprising a storage condenser, a rectier having an anode and a cathode, said cathode being connected to one plate of said storage condenser, a resistor, a charging condenser connected between said resistor and the anode oi said rectifier, a voltage source connected between the other plate of said storage condenser and the end of said resistor remote from the charging condenser to apply a negative voltage to said other plate of the storage condenser, a switching device responsive to controlling impulses connected between the junction of the resistor and said charging condenser and said other plate of the storage condenser, a unilaterally conducting device between the anode of said rectifier and said other plate of the storage condenser for discharging said second condenser, and a loading impedance across the storage condenser for discharging the storage condenser following a predetermined charge on said storage condenser.'

5. Apparatus as claimed in claim 4 wherein the said switching device comprises a thermionic valve having at least a grid, cathode and anode, the pulses being applied in a negative sense between the grid and cathode.

ERIC LAWRENCE CASLING WHITE.

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