peb ime nteb - iet labs a world standard in metrology ... · peb ime nteb volume xvi no. j...

$: PEB IME NTEB - IET Labs a World Standard In Metrology ... · PEB IME NTEB VOLUME XVI No. J DECEMBER. 1941 IMPEDANCE BRIDGES ASSEMBLED FROM r ... Ita \e here a 8; llIalioll analugous$
z: c:>

I-

"" <.> ..... ""-"" ..... "" "" l-V')

= e z:

"" ... ::c l-

e z:

"" V')

Iz: ... :E ... "" = V')

"" ... :E ..... "" <.>

PEB IME NTEB VOLUME XVI No. J DECEMBER . 1941

IMPEDANCE BRIDGES ASSEMBLED FROM r-----....., LABORATORY PARTS

At.s6 IN THIS I SS UE

Pflf/,C US I NG TU~ CATIlOIH, •

n " y OSCII.\..OG I'Af'1I , .... FIIIl(l UENr. V

Co,w .• ",sor-.s 5

PART VI-INDUCTANCE MEASUREMENTS

INDEPENDENCE OF BAlANCE

• IN ANY AlTERNATING ·CU RRENT B RID G E Ihere arc IWO cOlillilioll8 lhat lIlus t be simultaneously satisfi ed to obtain a

, rue null ba lanoc. ror maximum convenience in the IISC of the brid ge it is desirable that the Iwo adjus tments (or balance be indc llCndcnt of ellch o ther, so that the e!c lIH'nt that is varied to secure one balunce to hall not alTect the o lher b,alance. Othcrwi~. the condition commonly known as a "slidin g zero" OCCurs. J t is charac lcri .. .ed by the fact that balancc must be approached by comparing a number of successive adj ustments for lJlillillllUll. T he degree of dependency of the IWO component s of halanl'c

FU;UHE J. Schem atic diagrams of <Ill the Owen I.ridge. li nd (b) the" Schering:' or parallel, ronn of the Owen hridge. The OOrl"cllliooal form o r the O wen hridge I)alane'" the 100!IIe8 in l h" P 'IU'" by II c"ndcn~er in !leriel! "ith H ... while the cirCllit $hown in (I.) nliiizL'8 " l,arulJd CQ" d .. n~cr across the A-ann. Circui t rei!i, I,, ;,I ~ nre r"presen ted lo y R ,I-, C'A and en in I>oth diagralllil. The "Pl'ro!<imatc C<1"lItions of b .. lance arc

0 , Owrn: I ,,, ... UAH. oc. .. ·; Q,. - , + D .. (Qs + V,I_ + Q'Al

.. ." HAR nC" I Schermg : I." - I + Q .. ~; Qr - QA + Qn + no\"

c, c,

R,

(0 ) (b)

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GENERAL RADIO 2

1)11 ('3(' 11 ull.l'r (i.e .. the UIllOUlIl of ··slid· ing") is dq)('uticIII oll l ~ 011 the "Iorage (al'lnr. Q. of the unknown illlpcJanC(',1

The hie:lH'f th e 810 fll ge ht'lo r o f tlU' unknown impl"flanc(', the Ie!!(/' I'rollou H" ctl ji' Ihe i' lillillg cITel·1.

It (' jill he 6110\\11 that trill} irl(lq~nll. CI1 I IH. lunccs Uf e 0 1.1I 8illl,.1 on I} " hell

Ihe l'o\O nlljll s lmcnt~ for balullIX> (Ire

mml" in Ihe some arm. Of" "hen o lle 3ll. jUSI TlI(' 1I1 jl; marlc in ('Beh (.'omplex arm.

\n "XB lllpJ(' of the fir,.t ILIc tlH:H 1 is the 0",(,11 hrir lb<e. "hilc a hrill{!c lic\ i;;ctl b) ~i ndllir2 illustrates t he sccOlUI.

T he 1110 denwll is Ihal provirlc ind.·, 111,-' 1111 0.'111 ba lances I'u n be mmll" ,lire," 1·,'II.lillg f(lf the resis l i.·c and rCllc li vc (or ('onduc lill' a llli SIISt"(' pliIC) cOI1lI'oIlI'lIl " of Ihe IIlIknol'.1I impcfllllll'c, ill

dq)Cndent nf ..-aeh ,)ther , \ 11 an "'I;3mple, ('olll'i,I,'r the II ' I} tUIII

\!.Ix" cli bri"g:es, alread~ Ilis,'u5e('d, Uoth brillge~ a rc subject til 3 ~ Iidillg

bulluw,', 1>1111'0.' tl ... {' ICIII(!lIt s thllt nrc v(lri, 'd to secure ba!tllll'c .In nOI IW Li ll fy IIII' "o.uli li,m" 81aled IIboH', The lI a~

ci r"ul l il'o ,'nrnmolll~ " .... :d for iu. lut;lors uf high Q, lI lIIl Ihe clTc.,t is nol prouoIIIH'''' ' 1. T he \1u,"cl1 bridg,', hm\c vt' r. iii fre;'ll1,, "tl~ II t'1.',1 for meaSllreme nl s of 10" Qtur:lgc factors, and in Ihis .:as!: the <; Iitlillg ... .ero 11t'{.'OlIIcs \cr} noti,~ablc, H C.\ allli It .\ (" Iltrc .v is tllC arm nppoei lC II,,' l. nl... lO\\n ill.luf'tallt'e) lI rc ,·ho.;;en 118 \ nria lJICiI, Illc 1\\ 0 (,olll l)()lI l'Ilt @; ofbu lanl'e .I r.· "OlllpIC lcl ~ in(lcpcmlclli. as pointed out IIl;n,(" Thi .. methOl1. hO\lc\'(; r. rc · ' 1'I ir,'~ a II talHl;or,I "Oliolctl.'wr of IIII' v!l ri· abl .... dCI'utie I) pc. In gc neral, Illc lISC of ,;llf'h a "UlulclIscr II ill IIW;III .. OIllC sac ·

ITh ... , . '.n"Rl ... fHo ." .118 J; ____ no. t .. iolu .. "fo ,w" ••• "nl'''~ ....... I' Ih ....... _~ ....... k ...... ""' • . ,,,.. .1 .. _ " , .... ' .. nd ..... ,. .. ~ .. pt_" .n 0 ......... h., _ .... "'"""lic .... 1 f., .. "",.

·n. 1I. ~""'laor," , K.,J;.,. t"""1""""''' ........... , .. . ",,,,,.1 . • u""' \I~ .... r.-"'. fro ... I()O "Oloo:t~1o,. ,,, IN M ... · ~l ' ... . " " ,..,.. ',R."' .. 'Me.nlle<. 1910. 1"" .,',)1-503.

rifice in accuracy of ;lIliuctancc lUcasIUCmel1t8, 118 OOlllparc(1 to Ihe aCf'l1r11c) allainaLIt: w; lh II fixe. 1 s ia nda rd con· denser. Furthermore, the bridge 110

longer "311 be lII a.lc (Ii rcct reading. for Q. For these rca!'on8, tl, is arrange mcnt ;~

not COIIIIIIOlll y usc, l, III1lI tlte me thod suggci! ted ea rl ier (varying 1(.1. :11111 R,\,) iii gellerall y prl' fc' rrc.1 ill spi l.e of II,e t:on. COllljt lU1t sli;liug 7.c ro.

THE OWEN BRIDGE

l\lIo lhe r 1\I·lI.l..no"n cir,'uit for the measurement of inductancc i" the O\ICII

bridge 5hollll in Figure I(a). In this circuit t he rcsis li,·c cOlll l)olIe n t of the un· I..no\\ u iU'I>cda ncc is h!l lnnec.1 by a ('apacila ncc in ser ics wi llt 0 11 ;: of d,e n'sisl ivc tlrlns, If lite reacli,7c hlllulI!.:e i8 oh laillctl by vllr) iug Ihis rcsisti,'c arm , thc 1\\ 0 bll lmlt.~8 are indf' lJCllclclIl , us sholl II by tile CCJwllions of Figure l. \Vc Ita \e here a 8; llIalioll analugous to t hat poinlc.1 (lU i 111)0\1' for Ihe \rnwcll bridge,,, herein illllcpendellt halalU~s arc ~cure( 1 if t he rCil isllUIf 'C ami ca pacitance of tlte I! tan dard !lrlll IIrc boll. ,aricd,

For th ... Owell l' irellil Ihe ,ariahle CUll · den;;cr (l c l .crlll i Il C~ the resi8Ian,-c laa l. IIllee, whereas f(lf Ihc \lnx"'e ll hridgc the varia Llc ('I) IHI('II~r dc te rmines tlte induc.t3n~ 1.,11]a IlL'C, \ ,ICt'lIlle .... o n.lenser. "ilh il il relali,cI) !,llOr accuracy (t}pi. "all ) l ('{,), is gencrall) sa lisJa"lory for the rcsi;;; l ll ru 'c measuremc nl , ho"c ,'c r, 118 larger errors from ot her soun:.'Cs gcnernil) dClcrminc Ihe am'ural'} of II1cas· urcment of tltis cOIllI}Ollcn t.

An{,t lt(' r \\ ell rccognilcil a,l"a nlagc or lhe Owen hrillge is thlll it is a cOllll'ara· li vc ly easy mallcr 10 pass dirclll current through 11,;: unkno" n coil. This Lridge is cOllse(IUCUII~ s lIilaM., for mcasuring iron-core indu(,tof'8 " illt polarizi ng current nowing,

The cir,'u its so f:l r .Iiscusscd, ho\\("\cr. arc a ll subjcct 10 the sa nw limitation in



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-

-

mellBuIing coils o f hi gh Q. namely that the error ill the Ile lcrmiualiOIl of Q (or of resis tance) is directly proportional to Q. :lUll Ull error of 25%, 50%. or even great er is lIot 1I1lcouunOIJ wile n Q is of the order of 100 or greater.

THE RESONANCE BRIDGE

The resonance brill gc, shown in suies form in Figure 2. is umloublcdl y tile m ost. nt.-curalc lIIe thod u,-ailubtc for

measurillg coil rcsis tnru;c a t audio frequencies. Si nce th t.> rcacl:lllcc of the P arm is reduced \0 approximately zero, the resiSlu m:c balullCc becomes Lhe .Iominan l one, and the circui t residuals have onl} a St!cond-onlcr e ffec t 011 iI , wbil(' buving a compara ti vely large effect 0 11 tlw fl!Ut' l llI lce ba lance. This lIIetholl, ,hell. although (Iuite accurah: ror r.: . sis laJl('c lIleasuremen ts, is nOl vcry lI CC U· rate for inducta nce measuremen t,s.

To ob tain t he coil resista lLce, when the lolat P arm resistance is kilO" II , 01,· viollsty requires a knowledge o f the ef· fe cti ve resistance of the tuning "011 · denscr. Additional OleaSllreme nt s are thus req uired, untess. ()Omtensers of knowli ,Iissipation fae tor are IISCll , or lIu less He is uegligihlc wi th rl'spect tn R, ..

THE " SCHER ING " CIRCUIT

The analogue of the Schering (ca. pucilance) Lridgc di scussed in II previous article is lhe ci rcuit I;ho""n in Figure J(b)_* II t rc the inlluc tallce is balanccd Lr II precision nir ('Ullfle nscr in the oppo. site arm, \\ hilc till: r("sis la ll(,:e of the un· " no\\11 is !.tula nee,1 by a cu pacitance ucross one of the fi.xed resis lullc(" Mms. Ail is the case for the lI ay bridge, lhe t wo '-ollll)(me nt s o f j,nlance are ,lepell!l. cn t Oil CIH:11 other. I,U I, fo r s torage fa l;.

' 'I'll .. ~;..,u;, no. y •• , ... 11, ... 111", """.OJ."..d ••• " .,. 11.1 ..... " , .. f 'he 0 ... " wid ••.

3 EXPERIMENTER

tors gretHer thau 10, tile 3nlloplOceirol1l Ihe sliding Imlnucc is II(H serious.

l~or ca paci ulllcc IIlcnSllrClIlcnts, one of the nehuutages o f t he Schcring ('i rcui l lics in the fu cl that i t is a relaliw-I, simple IIl utter tocI' t a hlish 1111 in itial hal· 1111ce by adj us ting the Jiff(" r<: ncl; QA -Qu, 115ill 15 trim Iller c:ondcnsc rs across the rulio It rll1 s. For inu ueta lll-(' measure · ment !>. Ilo\\I::ve r, the Q's of the resis t:II1 OX arm s nnd the condc n~'r arc direc tl ) additive, as l'oi Ulcd out in a prc \· jous article . Th us, in this case, it is nol pos· sible to use parallel capal'ilun cc across lhe resista nce arms. The l}Ossibilily im _ mediately 8uggesls itsc lf, ],m\ever, of using series iluillcronce in oue of the reo s is ta nec arms~ to cOllljle lU,n tc for t he residual Q-s of the circuit. The estuL · lishmcut of the iuili al halanec rC(jllircs a n induc la, .. :c of high Q. thc value of whicll is kno\\11 to a llloJcrnte accuracy, or, ah erllalil'cly, n moderate vlI llIe of Q. accura tely "no" u. This. in turn , reo

.'1' ...... "",,,,.,.r.hle '" Gruv •• •• ", .. "~em~,, ' f.,.. ".i", .... 0.. '"duc'."'" ,u • 'Ot;'" ~'''' ,<> U".'UI'<O ,h., D . .. { . ,",,, . de" ... .

to',eu .... 2. The llerietl ·rdOllll11CC Lri.lpc, Th,. "'lllIt:i I.""Cdi C,h CSt lind eN UTe ci rCUli re~i,l · " s s. The "'''It'' ulion~ of hslance :ore

R I/IlN I Q,, 2 U _

" Rt I + Q.v(Q" + QN) + Q.1Q8 I

L,. - ~ (apllroxi .nalcly) "' .... "



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GENERAL RADIO 4

quires Ull independent me thod of meas· uring resistancc accurately. bUl fortunately such a method is avai lable in the series-resonancc bridge .

A compensa ted circuit oC the type OUl·

lined, using the sa me COIlIPOlicu ts as the Schcring ca pucitallce bridge already described,' is sho ..... n schematica ll y in Figure 3. The secondary shield-to-ground capncituncc of the transformer is placed across the resistance arm A, witl1 tbe smaller (10 ~J,d) terllljnu l ca pacituncc across the ca paci ti ve arm N (TYI'I:: 722·0 Precisioll Condenser). A fi..\:cd inductance, LA. is used, with an additional trimmer capacitor C',4, to make the final adjustlllent in establishing the ioitial balallce. Eor an A ann resistance of 20,000 ohms, a 50 or 100 mh choke& may conve niently l>e used for I~A' together with a 100 p.p. r condenser used for CA'

FICUR,£ 3. Connections for a bench set·up of a parallel form of Owen bridge.

, ,--- - -" "

TYPE 722-0

TYPE 713'9 OSCILLATOR

p

TYPE 814 - A AMPLIFIER

Thc s tray ca pacitance placed across the stand ard condenser ca ll be determined by a me thod similar to that used wi lh the capaci tallce bridges. If two balanccs are made for a gi\'en L p •

one with the standard condcnser disconnected at its high terminal. the ot her in the usual manne r, with CN se t at about t OO ppf. the s tray calHlcit.ancc Co wi ll be given b)

I Co = eNl Bz _ 1

n, Here B! is the reading of the IJ fi rm

resista nt.'e box " 'ith CN disconnected , Hz its reading with the s ta ndard se t at a

value of C,... Wi th this arrallgemcnt an initi al bal

ancc was eS I,ablished agai lls t a Q of 20 (knO\,'n to aLout ± l%. from resonance bridge measurements) . The Q's of se\' · eral other coils were then measured, t he results checking the known va lues wit hin esse ntially the accuracy or reading of the condenser CA' Additionsl correc tion terms arc introduced into the inductance equation by the tnmsforrnc r capacitance shunting tbe se ries inductance LA' For the case cited, tbis correction is negligible, but it can become significa nt i f large inductances are uscd ill the A arm. - h ' A.N G. EA.STON

'Th • .-io, • • _ of tho choke mIlO'. "I "" ..... , be . ddc<l '0 R". 1·", cbok.""''',.n"" io .m.1I ",,"'pored.o H".I ..... ·e •••• a"d 'he ,1< •• 1"" ""Y be ....,.j ,.i,h",u. ;n ' rodu";" •• any . p!""C"i.ble .rT'Or.

THERMOCOUPLES \Ve regrc t tuat, owing to circulll

stances beyond our control , wc can 0 0

10llger supply vacu um thcrmocouples. Consequentl y. all models of TYPE 493 "'""' The rmocouples arc discolltiuued. e ffec-tive Oeceml>er 1.



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5 EXPERIMENTER

US IN G CATHODE· RAY OSCIL LOG RAP H THE FREQUENCY

IN

_IN MENT

FREQUENCY MEASU RE· AND CALIBRATIO N,

"here an Wlimowil (requency is 10 be compared \Iith, or atljuslcd to, a staudard frequency, the cathode-ray oscillograph offers a COllvcnicnl and precise meaDS of making the uCl:e!ll!nry compuri llOl1. The follo\\ ing sununary of tbe \' luioll8 ways ill "hich a cathoJe-ray olwi llograph can be used ad\'1I111ugcously in (requeuey meas urement prescnts no new methOtI",. The methods lli.scussed are presented purlieulsrl), for those who llIay have available a cathode -fur oscillograph, but who may not appreciate its po tentia lities in this [.eld .

I LISSAJOUS FIGURES

S tarting with the lIunples tcomparison, if a voltage (roUl a freque ncy &Lllndurd is applied 10 o lle pair of the dc(icc liug plates (say, the hOt"izolital) of the cat hode-ray oscillograph and a ,'o ttage from a source whose frc(lucney is to be adjustcd ill terms o f lhc s tandard to the o ther pair, pa tterns of the tYlJe illus tra ted in Figure I will be obtained.

Thcse are the "ell-known Liyajous fi gures. For simple frequcucy ralios, cxpressible by Slllall whole 1H11IILx:rs, the 1)lIttcrlls are not too complica ted, aud identification of the frequeuey ratio is possible, eveu ... bell the pallc-ru is rotating slowly.

If the Jllllle ru r:all be Illude to be nearl ) stationary, by UdjllSltllClit of the freq uency to be checked, then the fre-

COMPARISON S quelley ra tio is fOlUld as follo .... s: Count the horizontal tangent poin lJl (s lich as A, IJ, C, Figure 1) ; count the vertical taugent points (such as D). The Crc· qucncy ratio is the ratio of the number of horizontal poinlJl to the number of vertical points, ... hich, for thc example of Fi /:.'llre I. is 3 : I. II the unknowu freq uelley is 00 the vertical plates, then the unknown is three times (as illus trated in Figure 1) the s tandard frequency.

As indicated by the BUCCCS8iH~ parts of Figure 1, the appearance of tlie pa t · tern changes progressi" ely ir there is a e.light difference in (rNlucucy bet .... een the unkno\\ II and s tandard frequeucies, Under slich l.:ondiliOllS the tan gent poinlJl can be oounted onl y for simple frcl.luency ralioe.. H a frequency ratio of 7 : 5 is ohtained, for example, the pat. te rn appears almost as a nc t ... ork cov_ ering the arca And, unless the pallern is s teady, it is ve ry difficult t Q COUlit the tange nt poinll!.

II MODULATED WAVE PATTERNS

A "ariation or tbis procedure occu rs

in tile problem of matching a low beat frequency, obtained as a result of com _ paring an unknown radio fre(IUenC) .... itli a s tandard frequency, If this beat is obtained ill all oscilla tin g recei ,,!r. Lhe oscillating frequcucy beiog offse t apprcciably (by u kilocyclc or 80 frolll Loth of the radio frequencies), tbcll the out· put of the receiver is an aud ible tone, the

f lCURE L tillu jous figurel!l for II frequency ra tio of 3 ; I. At the left , the two fretluenciee II rt: shown ill phase; a t the center, 51ightly out of "hllM;; awl lit t he righ l. in 'l"a tlrll lure.

,--AB CAB C

~IDOOO° I



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illI1pJilud~ of I'hid. \\3\7C8 and '\lilies a t n ralt' Cl l1l31 to the 10" kal {relJlIc llt ·~

,liffcr~lll,\: (Jf the "'0 radio {n·lI" t·lI ... j,· ...

If Dill' of the l"O radio frl'(lu~"ci('8 is of 601I h~\\ Illil greater ampli tUll e ,1 11111 I lIe olll"f, lind if Ihe rceciler uu tpu l is eu!! · Ul'ctcd to lhe H·rlica l plates II hill' n cuI . ihnllcd audio o..cillntc)r is ('Umleck, ] to

lilt.' Imrizrm la l "law,;!. thell pulterns of th,' I ) p" ;,,110\\ II in Figure 2 an' uluaincd.

Tile ree~i'cr ou tput i" Cllui\lllcni to 311 aLldio-rrcqllcllI':~ carrier IIIQtlulille(1 b) the belll.frequent') dirrcrcnl.~·. The pallern of Figure 2 is familiar 1111 II IIlNIIJ" of

("!Jet'kin g the percen tage rnooululiun IUlll indi('nting rouglll) the 1IIIIIIil' of lIuttlu Inlion. The ull"anlagc of II. is IIII-ihod in frc'luCIll') comparisons is thai Iht' audio-fn.'qu('m.:y S)S Ic!1lI of the rCt'ei\ cr is 11M called ulx.n to tranSlIlit a rrc_ (lucnC') of ouly II fe" C) elcs; it tran!;mil S we [Iudihlc i'arrier, II hi("h IIlII} be plaoetl an} II here in Ihe 3mli blc rangc, A 1.-0, thc malching osci llator Cll n be operlltcd at a lHullipl{' of the ocat frCI IUC IIC}, in a runge II here the IIt'I'U rIlC} o r it" ca libration is usunlly much impruvt'd ,

111 fi g- uft' 2, the illu;; l ru l ioll is ill/Hie

for a l'li8l' in II hieh one r;HI ;u rrCIIUl'II<:}

it; foughl} IlIi('c til .. amplitude of the other. rel>uit..ing in II 1lI{1(luiJlI;on or the [Huli hl(' carrier of . 1/ 11 "'"' 0,5 upproxi. lIIald~, or SOC(, lr Ill(' lIul\1'hi ng osci llator fre'IUl'IH''Y i;; not t· ... s('ti) i'l l"al to Ihe Io('ul rrNIUCIIC), tht, 1'II 11 cru " ill ,,1(11 1) I'rugrl'SS through tilt, &:tlllt' I1('e ill,

FIGUIU; 2, \ IMulated "'"1'1' pHll er" , I .... rl. ill I'h1O&e; ce,U;'r, 1I1iSIIII ,. oul or I'lm~; right, in

.!'uHlral ure.

~RRIER FREOUENCY / TRACE

d icuted. Tile illusion of a threc-tl.illlcll' sionlll figure is s lrollg; the pattern uppean. lil..e u lUII(', "ilh III(' e nds t'ut at all angle 10 the a:l.is.

I f I h{' ma td ling OM:i ll a lvr rreque ll"~ is adjus le,l 10 II multi plc nL or in si lllple ra lios 10. the Lea l frC(llieIlC), l he pa l . tern dc \'cl0IJC.1 III t he .. lids o f lite fig-uft,

corresponds Iv tin:> Lisslljous liglll'C8 fo r the sa me ra lios. If IIII' III1t1ching' osr-il.

laLor is :uljuSlcll 10 tllice the belli fn '. <lm'ne},. a plillcru of I III' tyJle sho" n ill Figure 3 rcsul\il , II "ill I:", seen that a --.,,·(l ·lo-olle·' pa ll,{'rn is Ilc\'c!011C1 1 at Cltch e lltl of the fi gure or t hai, ill illu ... ioll, I" 0 lubes are tle\l ' lollCtl. t;i .le U} "ille. If Ihe maLchin g frct ILl NH'} is not e:l.lIc tl ) I" ;('() Ihe heat rr;'Ij1I1:ne~. t ile pa ttcrn changes progr~~s i,'d } through Ihe &!.

qucncc indira led.

III CIRCULAR SWEEP PATTERN

Vcr,}, 1I1>4!ful ptll LerllS a rc o lJlaiued if u ci rcular SI\ CC P is used. These patterns are or 3 fOrm in \1 hich llll; freque nt'} ra lio is easil } itiell tifie ti , ~ven when t hc rli lio is l'x pressc,1 by 1IIII1II.Jcrs II hit.:h arc not 8mllil iuteger'S,

To prod lU 'C a circul ar s"l.:e p. it is net'· essary to o lJtain 111 0 eqmtl ,olt:lgt!s hal . iug a phase tlifTercnl'C of 90 tlegrt·cs rrolH the s tmulard frequency solln:e. 0 111' mcthod is illus ira tcli in Figure I.

The s tandard rre(lu(-llr-y is sUI'plil'l l through transformer '1'.1. In malcl l the Inial load, i( CS;';;IIIIU"'S, Il. a nd reaci.

auces. C. are Illude el ill al in nragni lulle.

f'U;UHE 3, 5 IJ tt~'Uivc l,hu&eiI or 0 ",od,,\a\e(1 ",'ovll pattern w hen Ihe malehi"g freq uency IS

t",ioe the .uoJuilllion fre<:julmcy.



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fOf ~ 'on\el1i~ ' lIn;, \ "IIII1C uf 10,UUO ohm8 IH lhe SllInoanl frC(IIICIH '~ i .. hall~I }, The ph:l8CS of Ihe \ol tn~('e tal.. (' 11 to lilt' priUl aries of 7'_2 a n,1 '1'-3 lire 1.1 ~Icgree .. uheall amI bc hin,1 the ' O It Il~C slIl'l'lie ,1 from '1'-1. or hal(' a pllll!'" differNII'e of 90 tlegn'es, I f tl'e im pcfllllwes of T-2 nnd '1'-3 art high (illlenllagc coupl ing Iran;;former~ \\ itll a Slep-up ra tio of 6 : I nrc suitable), the ll ('onnccl iug them across tllc dCIHcnts It IHl~1 C I, illllo t mu teri nll ) a ffect the pi lase of thc volt ages. The combined j·lfct' ll,i o f Ill(' t ran r;;{ormcr 101ll1-ing: 31HI of the impl'flall c,t·,. anoss the 1'C~ -Ollda ri l!S g:elle rall y lIIal..c it nc("'Cssar}

to readj us t the cJ('IIleuts of Ihe phase sl,i (II' r some" hn t.

If Illc st andnnl ff"'1"e ll tl~ slIppl~ i ~ di~turlt:11 in IlltV/' form , u f' in'lIlnr 8\\ t'(' P CllllllOt 1-", uiJl ai llc'!. A 10\\ - pll ll~ filtt' r is Ihell lle(-e88ury, as ilulicu leJ 111 Ihe

diagram. If a I·a lho..le-nl) Q~ci liogra l'll 1,,11 iug

a ra~lial Ileflec lor i8 Use41. Ihe IIIII..IH)" II fre'lu"nc~ i'un be plal'efl nil Ihal clt,~ ·

" -odc. In the 1Il0fC generll l CiI!ie. i t is COIl I(' nienll o inlforllH'e Ihc IIlIl..nO\\n on lilt'. n'r tical pl atcs tI" silo" n li t '1'-1.

Tile t~l)(' of pa lll'rn ,o; ohl ain('~1 ,\illl a I·i r l'ulaf S\\\'c jJ art illu:. trilled in Fig nrc

fl. \\ ilh no unl..uo" II frt'\l'lI'n" ~ int rodlll."'.1. the pattern i;o. a ~ ·i n· le . l.jlh Ihe .sl'o t Iral·clill ~ 0lH1' uro lltltl tlu' l'ir<'1e f.w eaeh n cll" of the Ii tllml"r.J frcqtu'nc). I r a fr{'ql~enc~ ('flu alto fi\ e I;Ules Ihe s l1llu lani freque ll(,) ill illtrotiul1·d 0 11 Ihe \'er· tical plates. a pall,crtl a~ illu8'lrnlcfl inl l,c SCcOIHII ,art of Ihe fi gure "il l resull , ' I'lle frc(I'lenq ratio ('a n Iw .le lermine,1 b) ,'oullting the 1( 1)@ of the '\lI VeI!', as a t . 1, H. C. /). e. (If rmlial 11(·/1(' ('I.ion is 11 :.1" 1. lit ... pattern is lIo td i8tor lerl, and Ihe {rel l lle l H'~ ra lio ill founll b} ('ounling: the uuler ti l';; o f the " Inc;::.)

i\o te Ihat. e H ' U \dlc li the IInl..nO\\ 1I fr('\IUC Ilt·~ iil llot se t cxu ~ ' II } lu file time>; the s laIH lanl fn.·ll"e nq, Ihe I'lIl1erll tlocs

-

. ! Lfl~:'=::::::: !

.i

F1GUKE ,I. ConnCCLion! {Of' oiJ, ,,inins a ,'ire,,_ illr !!Wee'll.

1101 ,·IHlng.e f,}rm . but a l}I)(,UfS 1.0 rotc/Ie

;;Jo\\ lr. TIll' s l1t'l'CS8i,-e lranJl. iti(ms frolU one line tv tll O lines (as in l~ igurc 1) ll(l nOI Oo'I.' lIr. The pal tern rt mll ius n "one· linc" palt ern :16 lung a8 t he frequene} rlilio is nol fa r fro m all ) inlcgrul Biul-1;1'1,' of lhe s lan,l llrd freqlll' lIey,

If lllf' 1IIII..nowII \I(' rc IIdjus led to uu. ·_ fiflh the Silindard frN I"cncy, :1 set or fi ve nC:lrI ~ ('Olll'i'nlri l' l'j rt"l e!1- \,oultl be seCIi. (Not illus tr:ilcd,)

'l'hl' " OIl1'-lillf'" pa lll' rn is eX lrt'l\w l} t'onvt'nie ll t \, hell lI.E'i ng cl(uipmen t "hose calihratiotl is k no\' n to be nearly correct. For example, an audio-frequency oscill a tor muy he 1..110\\ n 10 h;1I'e no error grea ter Ihall a \er~ fell cycles 111

(111) !,oin t in its range, If it i .. , I ('~i rcd 10 k' i Ihis iti't:illlllur tu. 8:1}. 1700 (' ~t ' I('" in lerlilS of the "tan.larll (SU~ 100 c~des) . 11 \0' 11 8impl~ "", I the o ... ·illatur to IiOO qclell b~ its t'ulihrnlion . ' l' l1{' PIIU Crll "i llihen I .. , a "une·linc" I'all " r n ( ilavi u!; 17 "tops:' bUI i t i", 1I0t IIc' '('.E'8Hry to

FIG I 11K 5. Circull1r ~wt" 'r "IlIIM".. Lef, . etumlll r,l_fr<'qucncy circ"I"r sweep ' c~'nt cr. circull1r l,lIllo' ''' wil l. s"pcrimpo!!c.1 frNIIH'II<' y t'fIU:,1 to fh'c limes the !!t u,,,lanl; righ l. wi,h SU1)Crill1 JlO11C(I frequency ''-<1' , .. 1 lO 9 / 2 the

~ lI"\(I,,r' l .

• • •

J EXPERIMENTER



TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988

GENERAL RADIIl 8

Muilipl. (H+ II S Ifl9le1lne

" SO.-.

~ 4/5 F;~. Ii.,. 3/4 F_ tiM

I-- 213 Tho'H line

f- '" Fin 'M t--1/2 T., lin,

f- '" f iv, ,~

t--- 1/3 ThrH line

~ '" F_ , .. '" Flv. "M

hl ull'l>le N 5. lin, 01 Slondol'cI

flGUNK 6. T able sliow;IIg the lI«Jue lH:e or /,u l . t crll& in each I tIlQdard.frc(jllcney ;nlcrvlI .

('Ou nl them), rotating at a rate depend . ing on Ihl' error of the oscilla tor at the ..clli ng of 1700 cycles. Headjus l the osci lla tor p-lightl ) until the pattern s tands S1 il1, \\ he o tbe frC(IUcncy \I ill be 1700 c~de8 in lerms of the s tandArd .'

1t \\i ll be see n (rom the noove lilat Ull

audio.frcfluency oscili lltor i'll n be cal ibratef) using "si ngle -line" patte rns onl y. a l every ]00 c~de8 (from II 100· (·"de s tandard) tip 10 Ihe 11ighcSl fre lluency a l wbich Ihe slIc(.'f!6!!i\ c

\\8"('6 00 the pattern I'n n S l i ll IX' di stingllisil('d.

If the ol8(:illalOr is set to an 04"111 multiple of one-half tbe standard fre (l'le ney. a .. t .... C>- line" pattern_ illus trated in the third part. of Figure 5. is oh tuined. Using "one·" and .. t .... o-line·· paUerns. the osci llator eao be ca librated a t every

50 e}'des up to a limit determincd b~

the abil ity of the obscn 'cr to distinguish the paltt'ru.

In n similar malllll'r, " three-li ne" pUI·

terns a rc ohtainefl whcn the osci llator is 84! t at onc·thinl and t .... o·thirds of Ihe II'ay ~, t II ,~e ll s lIcct'ssivc l00-cyclc poi n IS; "four·lille' · PUtlCl'IlS IIhen set at o lle· quarter a lHI thrcc'<lllIlrters, e tc.

Tbe illll)Qrllll1t fCil I life of this mcthod is Iha I the 6Cqllc llce of pal ter m. repea ts in CtlC" lOO-crde inlen' aJ. as illustrated in Figure 6. Since the JOO.cycic mult iplcs arc readil) iflen I ifie' l. i I bet:o mcs a si m pic \Ua t tcr to cul ibru It' 11 11 oscillator wi tbill 20 cycles of ull y (ICI, ired audio frcquency.

For purposcs of illustra tion. referc ll l-e has bee n mudc throughou t the abol'C to a s tamlanl fl 'C(llI l'ncy o f 100 c} clcs. which is a "OI1\I'l1i,'llt I'aillo for usc ill measu rements up 10 a few thou;;a nd cycles. I f the standartl frC(llIcm::y Uc multiplied by 10, thc pallcrns obtainc,1 ... ilI be irlentical a t fre(luencies len timcs higher than before, gi\-ing a uscful rallge up to the low radio fre(lliellcies.

'flU' Generlll Ha,l io TYI'E 699 COlli . parison 0 8-t'illost:Opc has becn tlesigncd parlicu larl ) for list: .... ; Ih the CI.,I SS C·21. 11 LD I'rilllary Frequency Stand. a rd and Frcquenc} J'l le81'Uring Equip_ ment. PrOl' i8iOli ;s IIIl1de fo r perma nent shicldell .... iri ng to 1111 neccssary coml)Qncllls of the ... Ia ntlartl and mcasu ring equipment , B} mean;; of key sl,itch!:';;. thc desired sourccs anti me thod of I:om _ parison can be sclected, One hundred · cycle and OIlC thollsallll -,'ydc filters lind phase shi fters are providl' ,1 fo r ob tai ning circul ar s" ec ps lit either frl'quellcy,

- J. K , C L,II'I'

GENERAL RADIO COMPANY 30 STATE STREET CAMBRIDGE A. MASSACHUSETT S

BRANCH ENGINEERING OFFICES

to WEST STREET, NEW YORK CITY

1000 NORTH SEWARD STREET, lOS ANGElES, CALIFORNIA



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