PEAK VALUES OF A SHORT-TIME LIGHT TRANSIENT SIGNAL
D. F. ALEXANDER
PULSE AVERAGING CIRCUIT
Original Filed Nov. 30, 1942
UNITED STATES PATENT 0FEICE
,' ;..'' 2,521,890 "•;';.:;;;".;,;' ,';f.,,!;.,'./ •
PULSE AVERAGING CIRCUIT
Donald P. Alexander, Oakwood, (Ohio,:assignor:to
General Motors Corporation,, Dayton,; ,-C>hio.f a
corporation of Delaware .,., .;; '...;.' ...;.', .;.;,';.i v'.,;" ;.,
Original application November 30,1942, Serial No-.
467,422, now Patent No. 2,422,766, dated Jmie
24,1947. Divided^and this application-Novem-
ber 23,1946, Serial No. 711i904..? •'•:• : nsr ; ri
''' '. '•'• '"' :-1 Claim. (Cl. 171—95)
.. . ... .
This invention relates to a direct current Volt meter.. '... ...' ..."..' ' .'•"';..."'.„ .. ..-,• ';;'" . V
TMs application is. a division of my cpperiding, application S. N. 467,422, filed November 30,1942,: now Patent No. 2,422,766, issued June 24,.1947!.;,' 5 • The particular invention to whiph the present application is directed relates to the circuit 'arrangements' of .the..averaging and, amplifying means. , ', "";..! . ,',";' . ...'.. ''"'/ .,. .','..., .'.
It is one object of this.invention to providfe.'an, ib improved form of direct',current amplifier,for use in combination with aii electron tube jndicator.. .„,.,
One.object of; this invention is tp,.,prqvide.;a'n" instrument capable of. checking the intensjty..of peak voltages of shortduration..,., •! .''..;'.. 'r, 15
Another object of this invention Is. to'provide'a portable low cost instrument for measuring and indicating the "peak voltage values, of art intermittent voltage source. ,".: .": - , ''''.'].'•
Still another object of, this inyentibn, is t6;prb-' io vide a portable, compact, light weight, 'completely battery operated, voltmeter.";,, . .Y; ,, ',,•'•',., 'A further object'of .this invention; is'Jp!,prpVi8e an indicator which does not re'quire1'the' use."cif delicate and expensive indicating elements^ ,;•'.";': 25 -'A'further object of this inv|ritioti'is to provide a direct current volt meter in Wh^ch, the readings; afe'independerit of battery and tube chariges dtir4 ing use.' -" • :'"'' • '•"'•'• _ :-"•"-'' t '"' •"''
Further objects arid advantages of the1:'present, 30 invention will be appareht from thei •follbwing description; reference being had to the a'ccbmpahying; drawings, wherein ;a preferred form of the present invention is clearly^shown. -= •• ~< ••.:;'••
In the drawings: •'•'•-'> >'"; 35
Fig. 1 is a diagrammatic view'shdwing a light source and the main elements of a pe'ak'transient; light-meter constructed; in accordance witrY m^1 invention;' . .'•' '..•:-'•'••'- .•••'- ••••-'• r- ,i-3:h;:.',-:-p
Fig. 2 represents a graph showing' light'yalues'' 40 as ordinates and time"as abscissa; and
•Fig. 3 is a detailed circuit diagram of a'light meter constructed in accordance with' my inveh^ tion;. .••'•••:- '.;: :" . '':" '•• '" • ..'"-• •' ""•'•
The light meter described herein iis primarily 45 intendedto measure the intensity of a light signal; emitted by a flasher type of signalling'apparatus.; MOre particularly'it! is Iritended for use''inr":'a:I flasher type of' signalling system wherein ^thfr' flashes consist;of intensive flashes' of extremely''; &o short duration which may last less than 25 ^inicroseconds. The flashes emanate from the soiirbe i(S and may for example occur at a. rate 6'f abotit' ten per second anrd may 'be"either 'visible br; ... invisible light rays. ;Because'of th'e small aniount: 56
of 'energ^^ih 1ea,ch:.,pe^k,.;ordinary,;iig^ means would not give a proper measurement.. ;of, the. signal. Since the... flashes. emanating. frprnl an ordinary 'flashe;r^wi|(;.vHry; some1 in intensity, the. light meter is .designe^' ts>., average a. succession ,of these. peak^yalvies.. Thus. the ,,ligiit meter, is. intended io. translate JhV light In' each - peakl.irito ,a| yoltage impulse w'iiich '.''"'is; proppr(t;ipnal tp. J.the height of. the pe,ak ^liCtrie in,tensity' of , the ligiit,^ Due tq the shprtnes^lof ,the.duratipn, of each,flashi: and due; ;to the.^mail;!ainquiit of. energy ayaftabte fQr,;measuremenij.;it.,is; desi^rabjfe .to' ..so ; cpjistr,u.ct; and operate the ^ppajjat^s a^,"tC( ^embrace iri . '.tjiiei measurement a;'.?etie,s,:pf,. light peaks. .This ;way,; one in effect ... pealc ^/alue ,0^ the,flashes. ... ,pb;tiaj^s. a'niore porrect eyalui' atipn J^ian /woiild,^, gi*e^ ty •% ?in.feI0::,'p£afe.'\;$& shown diagrammatically'iti Fig. 2 the p^aks of 'the flash.es vary Spm.e. in, height, and. , the ;energy;;:bf tjiai' pprjiph; of .-.' eac,h,;,Rea.k ^hicli projects'. rab'pve, t^e iUpper, horizpntaf line is, very'smalL ;:; ,,;; _ ;.'.'. ..'': Yt'haye 'fpund,tha^ ,thes,e| pgak.light values, .may, . be; ... .mea^s^.pf -.a. liglit; -,: meter ,.,wjiich comprise? % ... '2 ;i ;'an; ;integratpr; designate'd ;by; the ££fy?r.ence flum'e^l,.'..! 4," ah plifler/i 6 V'^'nd ... as,idiagram^a^iGaj}yfs&^nin 'Fig.; 1. .The. elec-.; trie '.circuits \^re siif?^ 'in,:detan;;ih-.Fig, .3..:'^^ cir.cu.it. arr.ang'e'mient,:.may..;be .used. .for measuring; either visijale pranyjsible;, radiatio,naf by .selecting! the /proper, phptoceljY, Th.e ; type of photoc.elLused.. will. ... .nature , of .the, radiations tp be .measured, ^.nd.. the sensitivity rer, auired... .;,">?,';.',', ^ ,,,v,-..r,' , ',.',,. r>,?.V^ '•:•.'•• '••••.. -^ . A.,ca,}ibra);ed .thr.eshpld ., sensitive i adjiistment,.f,t;is i pjEoyiciexl s ... l.?;,^s' shown' in ihe "diag^Pi £$$$.. P.ermits , determi^a- \ tipn ,pf . the|.sjgna}_s;(;iiepgl;h. fey suitable, calibration , of , the ', adj.ustijieiit, ,pqsJ,tiprj,s. ., ,If ,;; desir.e,d, ;,a -.: vblt'-^. met,er . (i. ..may, bel cpriftjected: .as ;.;.sh;pw:h in .which' ." case, it ..is, npt ne.c7e.ss;ary, tp niafe., changes :'ip thg; calibration ;p;f ...the Insjjrifmerit, tp ,Jcpmp.ensa|ie f,pr! . chariges in ;the vbltage, pf ;.b.attery :7^, since adjust,-! .:. ... ra.ainiain the, voltage';. ''' '"; '''
.
..^ jinterf ering .
trpra',;ti^e tp tiiije, pj;pyjsion has. .
r;eliwfeatin^
ing .light ,sbur.c;es as; ^expjaingd hereinafter. . 'Kbw-' eyer, these interf ^erirxg, 'light. sourceg, dp^notmgi,; teriaHy". affect., . the '.fsperaition.; pf . ,the, light meterri under: nbrmal. :cbnai,tip,ns,,,. since, ; .thjej mfer;|.ering light, sources ... liaye, •&, steaiay 5 vahi^ whichj.. |s ^elatiyeiy jinsignifw^pt.to.^the .value, ', of the light' "pekizs" to be ni'easurea. " As shown' in
Fig. 2 the interfering light may be represented by a substantially horizontal straight line, whereas the light flashes to be'measured are represented by a series of high peaks.
The integrators 1 4'cPmprisesi'a^pjmtptleltube 20 3 having a •filamentary' cathode -an& -riiay, for ex^ ample, be a tube of the type commonly known as 1E5GP. The rather unusual "space-chargeV,.., tetrode connection is used wherein the first ois" signal grid is fixed at average filament'potentialTffy by means of the resistors 17 and 19, and the second or screened-grid is useb^asftps^etuM -feigfi&F' grid. A zero plate-current setting^harbeen- pro- . vided for the tube 20 which comprises a potentiometer 15 arranged in circuit* 'asi shown;?. By;- 13 virtue of this arrangement :the!p6tentiofnetetv 1 5 may be adjusted so that n^ plate Jeu'rrent^can'' flow through tube 20 until a signal is receivedfrom the photocell circuit. ;..-;•••
Voltmeter 1 1 in conjunction with the adjustable, rheostat. 9. aypids-the necessity of: changing ''''!''i
battery vpltagev . ..,. . _.. _ , .,. ......... ,...
The atepUfief :indicat6f' stake as;;shov^;pn"th;e'; diagra;m: includes ^o'. peittode tubes 21 aJHd- 22 which may, . f or example bfe; tyj&W: 6S J7 attd' aii; electrbn-ray indicatiiigxttib'e 2'4r'1whicri;im'ay.':b'e: type;6E5; Trie ;twb" pentbd6:tube;s'2l and 2l2;are connected'; in' circuit -iiLstictr a rd.a'teeif tSat. a; singi4 .battery; may"b'e; us£d^tb~si^iy,bPth' of; trie; aitiSdesV Th'e "amplifier; arraTigtemc-rit .makes;. it ^ la^^ sta'ntialiyt etiuiyalerit; to: the'; voltage; galfr of' a
2,521,890 - 'v,':g|" ,:-li .'.:•-••: "-.-•%:r' :'1
4'"
resistor 31, and the polarity is such that decreased bias-drop due to receipt of a negative direct current signal on the grid of the first tube increases the plate-current of the second tube. Tiie^mpunt o| tftis increaise is nearly eqiual to the ambunt1 of decrease in'the-plate-current in the first tube due to the decreased bias-drop. Since .the two plate-currents are additive through the cathode-resistor, the effect of using the second tuSe'ls 'tb: minimize changes in bias-drop, that is, to reduce the .feedback to zero. This arrange ... amplification. By virtue of 'tKfeiafito'gijment, the voltage gain is the same as that for a tube with a fixed battery-bias, that is? there^is-no ^negative feedback despite the use df;a-cathoae-resistbr type of bias. A further advantage in .usift^ above circuit is that the voltage^ output is; zero when the signal is zero, .;•••••. or.canrjbe made of small value and of a polarity 20 to suit the no-signal setting of the visible target of .tube^.f by adjustment' of the first .tube screen vplfage' by adjusting the pbtehtiometer 38 :asr shown. The above arrangement obviates trieVrreqjiirenient fbr a separate-fai'as battery", fbr tube.
'' '''
The ''indicator portion of tfie circuit-makes iise^ of'a cbnvehtioiial cathode-ray tube 24'suchas the &E5tube in which.the.fiiameht,is energized'from'' the same 'battery 40'which energizes the filaments' 30 of the amplifier tubes 21 and-22. A 90 volt'plate battery 42Hs used with!tufe24-'as shown,
Th&f>E5 'indicator stage; was. designed ;tp; avoid f the'us6''pi;.ah.osc'fllbscb|iebr ^sensitive micrpammeter for, such, indication. To :obtain maximum^
tube .single."stage: afliplitter, without" any' 35i sensitivity,' a lo\v pla'te;voltage supply. (90, yolis).
degeneration' of'the; slgrial;' tliferefey1' making;; a: "; was.used consistent 'w.ltlt bbtaiiiing a .clear .'image.
singie:stSge: requiring' p;n^' tKeioite".attptle;'ba;ti: A smali.lamount of 'A. cr..iriduc'tive":iniage flutter
t8ry.;t6'pfoVtde the voltage5gain0of'two'of more" wa:s avoided; by, the addition of' an input filter
stages.; . .. v>: ..;•... ,...,., comprising a' 1 megohm resistor 41 in series witii
Fof best operatibn; I have; fbtrrid ttrdeslrable: |q. the grid, and 0.1. mfd.. capacitof 43i connected tb^^ connect the otitput'ca-p^cltb^ 3tf bettyeen tlie;
anode ..battery 331 arid;; the" aTipde;. 32A of;
32;lii theline l£a;ffi^ 20^
to' thV. amplifier; circuit:; .Sesistby"'32',must;'.tie?
selected of !such";a~yaluVthtfifi cdiijiffliitlbtfwith"
grid1; resistor 35J:tHe ca;pacitpr;;.3,b; wijl; remain;
charged" to - a: voltage "p'rppbrtipnal tp"" tKefsjrver agej
peak value"of;the'sighals;bfeint; recelvfed:; , Grid'
resistor 35l may; for exantpief haye'a;'
vaiue-pf" "•""'";i—--:-:: -:"•••>-•••-*'*•'--• -^i-
the:charge on" ... 30=.whlcH'riiay;:ber£i; .037 iriicrofara'd'ednderiser? change in grid-bias. voltage will result ffpw^ Pf aJi'unwa&ted"grid-cutrfeiitilas^ fflicrV-aimperfe-thrbugh-rtn'e' g^ftf resistb'r^SBj-lt'il irripdrtant' to' user a-i ... ; btes;, rather;: than a nxed battery—bias. •. yy Ith sucJi~an,arrange-^ m'eiit laVge increases iii^iat^cu'rjretits; due' td'tW" u;nwahted grid'; currents, a!fec seif-cdrriperisating~ in a degree, through'...the^^;increase iii^ nfegatiye; grid-bias due to increased ... fio^irig; through the cathodiei'registbr^""In_: a;n;v.ordiiiai?y'v. amplifier circuit" the use" of "a cathbde-bias;; resistor common to the input and'tile;output;'ciicititfe 'of atr ainplifie'r prb:ducels;:an unwanted neM"tiv;e;fee;dback; effect. -,In:;A.. C. aniplifiirs; this is'; avbided; by: suiiably shuntiifg the resistdr w;th a capacitor which by^pasge:gi;;thei signal' currents3" without' disturbing.the; direct current .bias. In drFetit" current amplifiers "th'is;.caniiot! be; done; . As shown in Fig; 3 applicaiit's dircuit" includes twP duplicate tubes pppbsed''tp each other,in. a
from;f rid to eathode as:sripwn,
The resistors' 47 'and,48" are:
loading, resistprsi; This^^ arrangement permits the
use of a common, plate battery, f or rth&tubes-2-1.-.
45 ahd'22... ... .... —-,',;i,lV: • .-, •• _-.\' ;.;:'-:'.
The-values of-the resistanGes;. capacitor>: etc. are given for purposes of -. illustration only as",.ifr, is-obyipus. that other values iirtay-be used -withoati^ departirig from' the spirit of my invention.. . f.;
no By-virtue;, of the aboye described.-arrangement the-instrumeht is capable of averaging-a-succesr' sibn -of -peak light,values; >rathe-r- than;measuring;-,a single ^peak value; Furthermore the: readings^ are independent.of- batteryjand tube'.changesrdur^^
~'~> ing use. ..:•-,.•.-. .,-.-,'
While thfrform of empodiment-of the invention as-hereinjdisclpsed,-constitutes;a preferred:fornv/r it is tpvbe understood tnat-;otheriforms-mighttbef! adopted, as may come within the scopg-bf rtrrer claim whteh"follows.'; •'•••:.•:•:••; "''•
What is claimed is :as-followsT :•.-••.••:•••••
r Means-,for developing.-.-the?average -value of' a varying signal; of unidireetiona] ... • ing two signal input conductors, capacitor meanss* permanently connected (between'said; input ePnductors,jresistaiice«means5permanently connected:! itt•series':.with:!erne- of Mnput-;conductors- beyoridr; the capacitor means connection therewithyia secy:vr ond.Tesistance means haying-pn&end permanent-
70 . ly- connected to,the output side?of the-rfirst men* ;-•?
tioned..resistanee.means-and -its-other'e
manentiy. connected ,tp, :the second:
ductbr in parallel; circuit with said capacitory.
meansr to form with ithe,first .mentioned resistr-,!
push-pull circuit^ butvhavirig" a ;cPmnion cathode- 75 ance-means a permanent-passive storage'Circuit,;;;
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