A Heterodyne Frequency Meter For 10 To 3,000 Megacycles - GenRad Experimenter July

A Heterodyne Frequency Meter For 10 To 3,000 Megacycles - GenRad Experimenter July
PEBIMENTEB
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A HETERODYNE FREQUENCY METER FOR
10 TO 3,000 MEGACYCLES
• TO MEASURE FREQUENCIES ,
(nl ll1 a l' unI..I'fi\II' ~Hllr(';' ' -UII loe
ab-.nrbnl in II c'a lil...ra ll', 1 n'i'Qnaul l"in'lIi l
111111 lIIallc to op,'m te an imli('ll1or. TIlt'
I\,~
11<)\, III \111>11'" ",,_
il1dieator call IIC an i n nu ulci'n'11 1 lamp, a
VI-:"'!'! Jr.", LIT,,, ...
6
g"lm\ tube o r II gah :\n,)/ltl'l,' r pn·('t·,It'. \ I I~ a
12
.letl'I'lor. TI.is ~i lllpic lin. I :< lrai::-IJlf')rI.anl
1I1., tI":H1 rcqllin'" appn·,·inlll,· I-""H'r allil is
liulill',1 to frcrpwlwi, '!' (01' \\ hi.,11 "'SOl\lInt ,-il'<'lIil .. III',' :Iluilalol",
III n hdero,l) Ill' frt'l,m'IIt'} meter. the IJO\\t'r nO/Jll in-,1 (I"O m Ille
un kll!ll\tI .... '(In:(' 10 prtJtlllcc hr"al nOll'S "II I, a ":lli l'I':lIt',1 o,..·illn l. ,r i;<
1;lIIall,'r h) ~·\t·r:1 1 ortlt'rs of IIl11gn il lule, ll1ul lilt' (n'qllclle) n Ul;,!'> that
can I~· ""\"'1"(',1 \\illl a sin :!le o,... illa lor, " pmlllin g a 1110 10 ()Ill' r:1r1ge .
('x lelllis "'lIl lilll1011SI) ow'r !Ol'1(' ral dl"l'a. I" !1-,
If the IIl1l..nol\ll fn' qm' n q is IOl,c r ,hall till' 10IH·,..1 fn'q ll('11('~ of Ihe
hctcroo l}III' osl'i llal or, hanllOmicl' o f the 11111.. 110\\11 an' u..(·,1 to pr.HIIII'('
Ix'al s "i lh thl' 'Jllt'iliutor fun,laIlH; 1I1:11. I f Ill<' 11111..110)\\ 11 is hig.llf'f tltal1
thc hi ~ llc;;t frequI'll t'} o f Ihc ht't c fod~ lI e o~l'i ll :ll'lr, IHII'IIII)lIi,';; ,,( tile
o;;o.:i llator are woed, In
eit her l"1Ii'C Ihe IlUrlllonif'S
nre prO(llIccd in II 11011lin(,:lr t'le lllc nl of Ihe he!('roo.l) nc fft'l llIt'nt'Y meie r,
EXI,,-,rit' I1I-C has !1-ho\\ n
Ihal hllnno ni o.:s lip 1,0 the
tlll·Hlil'l l. o nlcr ,'UI1 he
u"c·tJ in all ill511'11111CII I of
liIi;; 1~ 1}t' \lil h u n.>rrcs l)()lUling " paeillA' of 5%
oct\\l'f'n frcqu t' l1 l'il'l! \\ll i.,h
1"I\I(' r
IN THIS ISSUE
FWlni!: I. \ i"11 or thl' TH)('
i:!O-A 1It'lt,rod) ..,· Fn'(I''''II(')
"dl'r
lIi l h
OOI('r
l'1.'rt'OH'<1.
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
www.ietlabs.com
TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
GEN E RAl RADIO EXPERI ME NTE R
prod uce adj accn l beat s. It fo llows t ha t
the cali Lrated oS~ 'i lJ a tOi' sho uld ha ve a
range of a p proximate ly 100 to 200
megacyc les if un l..no" n frequcncit,s u p
10 3,000 mC/;lwyc\es arc to he Ill ca s lll"c ~ L
The cll ir f o hs taclc to producing a he t .
e roJ ) IIIl fre qlll' l\ey IlICln fo r t. his range
h ll ~ l~clI t he errat ic performance of
oscillato n; using eOI\\'c l1 l ioll a l tlll W(/ circui ts. Slifling contac ts prQducll e rralic
varililiolls in fr(' q ue m;,. and a tnl'iitttfle ,
Idri le ch anges in luhes allll sup ply volt _
a orrt's hal c milch 0" rc a ler eIT('t'ts t h an a t
lo \\ o: r fn'lj ut' w,:ies, The I1c " Ir d e H' lo pe ll
Ullw·.. fI ) C irf' uit,· howl·l e r. 11115 ma.le it
pO:lsiLlc to ~l\oi d mos t o f these llilli eultil;;;. W itll t ire Ilel\ '1' 1 I'E 120-.\ l id ·
crotl) lIc Fre llliCIlCY ::\ Ic lc r. whic h II"!:S
the Bult er/lr C irl'llil. 11 frequcnt·) or
3000 lo l e can L-c 1I11'asured as 1'011 1(' 11 iel1 l l) ami as a('c ura ld) as those ill Ihc
broadcast ra nge . T he low_freq uellc)
lilllit fo r 1I'/rI1lHIII;>.(' is ahOll1 10 I\ l c, hut
lo " e r fl~ ' fju l' Iwi\'s \'all 1.It! nlea:m red i f
mOre thaH 1 ,' olt at tile lU.l 1...n Oll ll fri' .
qU{' I1 C) is illaib.hle a l tire .ld ecHJI'
il1pu t.
The TH E 720- \ Hc tc roti.1 lLe Fre quenc) \l eter is H port lllJle halte ry.
opl' rllt ell ilis trul1Ic n l o f s lIIall size lind
light l\l' igh l, 1\ ilh un us uall r hi gh scllsit; I' it) , The pa nel vil' II o f Ihe ne w instru ment is s holHl in .Figu re 1. .\ cOlIIl'lr le
sc i of o pe ra ting ins tr uctions is mo un ted
. ~:,
" . " .I ~.,
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- 1'1", U"".,Qv Ci",m'."
t..: ... oer. 1 11. 01;"
\ "I"",~ X L\ , l\,,_ • • 'kl"r."., 1'111,
2
in Ihe ru lllol'a hle l:OI'c r, The func tiona l
cle men ts of the in stI'u men t are tt cali_~
b ral ed oscillator, a de leclo r, a nd an
audjo nllipli ficr as shown in t he sche ·
ma tit; di agra m of Figure 2, An in te rnal
,' iew of the instrument is shown in
Figure 3.
O sci ll a tor
The {req ucuey o f Ihc he le ro(l y" c oSl'ilis cOli lin llolisly vari ah le l.c t llCf' ll
](}() a ll, l 200 IIlcgac) cles, The freq ue ll cy ,
tie t{'nllining e lc me nt is a ttlnell cirnl; t of
Ihe Imth: rl1 } t) ]le, I,itlr ro lor plat es
slu'Iwd to gil'e till a pproxima lc l} loga ril.l' llI il· rrcq llf' lH'y (lis l ribut ioll . TI ll'
I'OIC)I' is 1II0 un te,L ill bl,1J lica rill gs . No
slidin g 1'01l 1l\CIS arc u",-",1. llUti liO elll'rell t
110ll s th l'Ough Ihe he arings . S rnOllth 1111 ·
j us t lllen t of freq uclH') and s tab ili l~ ,)f
e a lih mt iOI1 nrc Ihcre fore assured ,
T he mai l! (li :1I o f Ihe f,-c lplelll') mc te r
is l'a lilH'at ci lllireclly ilL IIIcgac) ('If's. The
sca le is 15" lo ng and np pl'o xi matel) lo g;I- ~
rithllli<'. The gear ra tio be l \\ecII tl ...
It/neil c il"(." "il Ullt\ the H rnie r t\iu l is ove r
200: I, Oli" - 1I1 0,~ t uf the frt' ll'!eI U' )
ru ng.' olle ·h a lf lu .... o f the ,ern.ier llia l
corresp')lllls to l o~ va l·iU lion in fre·
'\"('n<,)', nlld olle il i \' i ~ i oll of the I'e rn iur
llial 10 (t frN p"::HC) dlllngc o{ 100 pur ls
IJer lI1i\lion . Un kllOll'n fre'l'lelleics l I re
measlII'ct/ Ly prot/titli ng Lea ts "i il l the
calihra led he ICro(l ) l1e oscill u t o l·. Be a ts
11U1) I)t! produced bc h ' ccn Ibe fllnd a·
m e n ta ls o f the unkno wn source and lire
1:1I0r
FIG UI\I:: :!, Sell e-ma li(: circuit ditigru lIl of t he hc te-rod yuc frCfI'H!IlCY meler.
o."l rill". 1915, C o"t •• 1Ihd lo Coo' I" "I . C. n,J"
ld~~.
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
M... " lI.S.A .
www.ietlabs.com
TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
JULY ud AUG IJ ST, 1945
)
Iwt"I1)(ip,e oscilla tor. between IlarmOIl-
i" " of the unlmown freq uency 8111 1 IIII'
11('II'n)( I~II(,
fUlUlamcnlal , between !Ill'
unkno\\ II fwu\amen tal and harmon ic/; of
till' Il('l cl"O(l~nc oscillator. or hc l \\('('1I
hUfrnonies of both the unk llol\1I St'lln'"
I.IUlll hc hell.'rOO} III' oscillator .
Detector
The detector. in which the hnnnolli,'s
of tile known and unknown frcquCIWit'iI
and lh('ir bea l.e or dilTcrPllN' freque uei,'!!
arc pMdtl(.:cd, is a s talldanl I N2 1 B. I) 1Jt'
c r) SI3\ dNce-lor. consisting of a silicon
n }l, lal and R tungsten wire. mou nted ill
a s mnll (~ ralllic cartridge. T he 11('1('I" IOr
t'lIrlridg" is 1OC3 ..,.1 ncar the 3ntCIl li ll ill 1'111 termi nul and is held in place h) 11
ri ng-lO ha!,,!"',1 fl pring . .A spare del,ector i;;;
furni shc,l \Iith the instrument , bUI,since
Ih(' (,lIrlrillge used has stand ard dimendifrelTllt makes and types or
,1t'lt'l:lors ,'a n be s uIJslilul.ed.
\dell'Hlle input 10 the detector I"
11."11811) oblaincfl ir the instru lllc nt is
pla,'('ti in thc vicinity or the oscillator
"lubI: fre que ncy is 10 bc rnca.~llrcd. \11
illl'lIt 1IIIII'nllll of mljllslu b1.· length is
~ion.s_
l"lt:rtllllllcntl y
mOl lllted
on
tllc
fron t
panel. This ndjus t111cllt is 118<:, 1 to im·
pro\'I' "itflllli 61renglh .. hell \\orking
"itb fn-'!ll1cncics al)()\'e 1000 M e. For
frc{llIcnril'8 below 100 ) l c, il lIla y be
nf" 'I'I""lt r~ to f'Ollncet an additiona l "irc
to Ihl' "i nput" termin al.
Amplilier
TIlt' thITC-S 18!!"C andio ampli fier has an
(·frel·li\I' !JatHl "idlh of 50 kc a nd is ('onnee tf'd In IlI'nlhu:/-, a dc llc/, tiol1 of tl w
l'tUlClllU'II'r "llt' l1 a stron g 8igllul is im I'I'cI!!lCd on til .. d{'tcetor. Tilis fc u tu n: is
plirtit'III 8rly 1I-.('fl1l \\hCII the frcfltlellcy
unde r 1l1('8S Ur('lIwnt is not suOicielltly
"ta blc 10 pro<luee a s leady audible lien!.
\udihlc 1)0'11.1 " are ~ imllhul1eous l )' hcnnl
,..... in till' small d) IHllllil' 61K'nker 1Il011l1t{'(1
on Ihe frQI1 1 pancl. \\'f'ak I)('al nOl es are
FIGUIIE 3. In t.erior vjew show;,,!: I,he bull,e,n )··
Iype luned circuit and the locution or 111(> work-
ing Imd ~Jlure crrfltnt'!.
bes l obsen'ed \\ ith a pair or headphones
pll lggcll into the PII ONES jack.
Po wer Supply
One Burgess '1'''1'1, 6T .\ 6U UUIl!· f.\ i"
u;;cd 10 s upply 90 \'olta 10 ril(' plat c~ 1I11~1
1.5 \'011.8 10 the fi llline llt s of t he three
'-!It'uum l ubes uscd . \11 11l...·cssary COil·
nec tions are 1I1ade by a buttery plug a itached to a short cable. Thc filament
and plate loads an: "ell bnlanccd , and
the batt e r~ \\ill gi\'c lon g l!e n 'iL'C in
in termittent II~ . Sincc t he henling up
l i llle of the tubes is ver) I'ho rt. the ins t rument can I.Jt: turne(1 01T ir appreciahlc
lime elal)SCs be lw(''ClI 111eus ureUlt'nIS.
' I' he ins trull1e n t CI111 ulso be o perate!]
fro m II reel i fie r 1)4)\\er supply. 1111(1 :1 co m _
pile i II-C I)()\\er unjl to fit, Ihe baller.\eOltl parl1l1(,llt \\illlle u\ailllble later.
Ma king Fre quency Mea su remen ls
The process of making frt'qllenc)
mellsurcmcnLB
Ii}
Ihe he tcrodyne
IIlcllu)t1 con ~is l S fundul11l'ntall) ftr thn'\'
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
www.ietlabs.com
TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
•
GEHERAL RADIO EXPERIMENTER
,; tep", Till' fi rs t i s t oe !;.Illj, l j~h a 1}t':11 nolC
hel"ct"n tht" IJUk nO"1I "Oll rl'C allli Ihe
11I~ lcrt)(l) lit' o!'eillal or, The ;;(:eOlul s tep
i~ 10 tit-Iermine Ihe ar,ln of Ihe heat
OI'8Cr\cd, nml Ihe t hirll ste p is 10 rlelo' rIIlilll' Iht' frcq lle IH: ~ of Ihe helerod) ne
Oi'eillalor,
\\ilh til(' T\' I'E j2Q, .\ 111' I I'ro, I ) lIc
Frc'I"enC) '\ !etn the hl;;.t step " ') I1 SiS IS
merel) in read ing the di~l·tl) 'l'ali hrHlCII
main Jial of the In,,'nOllcn l. TIlt' a'·l·n·
rac~ Ihus f)btai ncrl i,. O.I o/r. . If IIIJ,;iler
UI'/'ural'1('" an' desi re /I. tilt.' tnll' fn-,
(I'h~ nt') of the helern,l ) nc ost·ill,l tnr ('an
1M' lIIeas lln'd in h: rlll" of 11 ilion' u('eurulC
10" .frrlllll· rH' } slanrlarl!. Thl' '1'\ f>~~
420·)\ thcli IS 'lU,: rl' l) a 1,.,u \C uienL
.. h'ppi ng ,;toile be l \leclI 11ll' high 1111·
~no\lll frc11llenc) anJ the 10\\ Sllllltlani
freque nt'). II hich an:: too far 1I 1)art 10
prorlu('e heal notes h ~ th'·IIlSl·hes. The
!x';; 1 pT'Ot'c,lure 10 es w hlish 1 ~llt notes
lind 10 ,1<'Ll'rllline Iheir ortler d'·IJI.'fI(is on
"Iwthl'r Ihe Unk llll\ll1 frequc ,w) isin Lht'
rang<' of 1i1(' furuiullwili al o,ot'iIIll lQr
frcqllc IH':) 'Jr aLove or bclrm. III g:e ne ral.
if the " ' I III..IIO"n" fre( l lIl'nc~ is ~llIllIn
lIpproxirnat .. I ~, a sillglc bea l is slIflkienl
to lll· terlllill(· the freqll(' lw~ at'(: lLrll.leI ,.
On IIlc ot her hall(l , if the arl'rO\imllle
\alile i8 1101 1..110\\11. il "ill be 1ll'/'CS!;ary
lu no te E'1I(·l'(";o.ehc heRt,; unlil Iheir
plilte rn ( ' lIIl he deh'rrninc(t.
Frequencies between 100 and
200 M c. \\hen Ihc fre(!llCnc~ 10 be
lIIea",uretl IiI'S \lithin the fUlul ll. lII.' Iu al
U .... ~NOWN
eoo Me
z...... HflQ.MONI C· 1600 Me
3 11'11; ' \'1I<'I>1ON IC • 01.4 00 I'lc
--
-"
>--,
N
n a;d
100
I
It"
Fr equencies over 200 M C.rodrt.:_
fl uent'ice "hidl lie al)Q\e 200 \I e the
procedure is 1,0 s larl 11. 1 IiiI' high ellil of
the fre(llIenc) range a lllli O note the SIII' '·es,.I'e 8C ll ings of st l'ong h arlll!lni\'
Ix·at,. as the frcfJ llt' llc} of the he l f' rOoI~ 11('
~t' iliator is prog rcs..ildy re(il,c(',I. I f
the fre(ln"II ('~ a l which one !.cal Ut'(' urt;
i" iii, irle(1 h.\ the frt:'1IU' II ('Y tlilTen' IICC
bc l\;('CIl it ,lIu l a SlII,'(·cs..i,c IlI'al. Ihe
rCil ull IIII1EI he an inlq!I'r and i;; thl'
harmonic 11I1lI1IIc r of the ,,1I(·ct's,.i\{: 1.II·al.
eXfllll/,It': .\ high fre qtLt' lI e~ i.<; Ilh:llslL rI·,1
lind ".I rong \'e:H5 afl! o ill ai nc(i a l 200.0
lind 160.0 \ Ir. S lIbtrac li ng' the Eec()n.1
l.!Cat from I I... first gil ",. :WO.O
160.0
- 10.0. Oi \' i,lill;::- the !ins l bt!a l h} thi s
rlilTert'nce gi\e .. 200,0 10,0 :. 5. II hit'"
is II ", Il armo ni{' nlllnlo., 1' <If tlJ(' ...·c('lml
• I I
I,
'R[QIJ[~ C I(
r UNOOo,j(N1I1l
!'IlII ge of th e 'I", t-I-: nO· \ Ilc tcI'lKI .' IH'
F reqllenc~
\l dt' r. the ullklloll n fn'·
(I Ut'lIC) is read ,lire!'I I) from the l11"ill
Ilial when a ;.I rong \)(,lI t Ii' ohtlli l,..d . III
mldi lion to Lh i ~ Iwa l lIul,e. o lhe r 1Il'1I~l'r
~a l no te;; 11m) bl' hl!a nl. For c\;lInple.
if a (u II,l al11(' lI tll l frcqllf'I1I') of 150 \Ie i;;.
lIIt'as u",,!. a Si m llg bl'at "ill I,,· ohtain"11
II I u diul S(, tt in J! o( 150,0 1
\ 1,·. !lnd lIl'n~l'r
11<'111 5 ilia) he l... arU 111 eli .. 1 5eHillg>! (J(
100 and 11 2.5 \I e. Th e~ l\t'aker bl'ltt~
arc prOlllU'ell IJI! llI'CCn the 2,1 ;m ll :~. I
" ,1 1'I1IOllie;; of tll4' UI1).. III)lI n frc(I•• e l1t:y
jl!HI Ihe 3. 1 ,111\1
Iwrmonie!! of Ihe
TWE 720· ,\
Oscilla tor, n:spCt' lil'cI~;
2 X 150 ~ I (' - :i X 100 \I e ami 3 X l aO
\I e = I X 11 2.5 ) 11',
,~
"
II
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"
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1
"
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~
re.<'
I
f
"
12O
16O
18O
"0
OtAL SETTING IN MEGACYCLES
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
1I-
200
www.ietlabs.com
TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
~
JULY anI! AUGUST , 1945
5
III!HI. Il e lln', Illc IIUkllll\11i frcq llcnq i s
5 X 160.0 = 1-100.0 L\I t'.
In IIUII ) i'aacs it \\ ill he l'0ssil,l.· to
p,ur lut'c hCllt s bet\\ CC Il harllum il 'S of tht'
11111..1101\11 fn.'ll llc m ') and hUl"Il1olli. 's o f
,
the hc tcrud)l]{' oseill;ll .\r. TllI'se beal s
\.ill IIs1Il111 ) be IlHl(·I, IH' nke r t lHlI 1 1111'
i)t; al s pro<luecd Le llfCC 11 the 1111 1.. 11 0 "11
fUII,lamc lll a l and the he l c rOf I ~ IlC har-
)
IIlcmies. The chart of Figu re I giles lhe
po~sibl,· IIt-a l s lip 10 the 3,1 harmonic of
tl H,' unl..n n\\ ll I , ~ed in the (''(a mple ubo\'c.
Frequenc i es under 100 M e. For
frnl'lI.' !I(-it'S" llie l! li{, Iw lo \\ 100 \ '1." lhe
1'1"1)cctiure is to s lar t al tlte 10\\ end of
tl lC fn:<!uCIH')' ra nge all d 10 no te the
tl!t:tc.~iH" ~c lti ll g!' of Ileal s as the fre·
'P ! I' Ill'~ of til!' 11t~ h'ru(l) l ie u;;\:illalo l" i s
IJrogn:ssi1cl} irlcrca~ d . T ilt! fre (lucllI'Y
,li rr"l'e lH" > Ile 111C1' 1I Iwu SIl .. ce~si " I· heal
,c llinge. is C(luu l 10 Ihe u nknown fre q ue lll'~. £nIllIIJ/e: A 10)11 frclluellcy is
me as u re,1 ami hea l S a re obecn .,,1 II I
L05.n_ 120.0 a mi 1 :~5.0 1\1('. The fro''1 IIC I1\: )
,liffe r<: IH'c he ll' ce n S UCCC!;!' I'·C
l.... aB is [.::;.0 \1.;' . ", hid. is the fre 'plc II C~
bci n g mcasurc, l.
Wa velen gth. T he wave le n gt h 111
/'t' nlirnete rs it< o hl ai w·,1 I\i l b s ufli"ie lL t
a cc ura cy by dil' i(lin g :J X 10 10 h ) fn'_
llw· nc}'. In Illus l a ppl io.;a l iulls cledrom agn e t ic WllW' 8 lire t' hurai·tcrizc.l b y
Ilteir frc(pwlw}. Im l in SOllie prohle ms
l ilt' usc of " ' II I' c lc n g t h HI li )' he mo re eOIl I'e nie nl. I I has bee n s hown in Ih e para_
Wa p!. e nt i t le ll " Fre(llIeno.;ics Ol'c r 200
M,,' a!Jolc . fo r in s tall/·c. Ilow a n un knol'" frNluel)('Y o ve r 200 .Al e " 1111 1)('
ll e le nn illc ,l frol ll Ihe lWO freq ue ncies of
the he tc l-od y nc useillalor \Ihic h p rodu ce
SUI'''''ssil c hea t nul es. If all freque ncies
urI:: t on lerl.e,1 i lllo wavele n g th. Il,e
" al'clc nglh of Ihe unknow n is s impl)
I he , liffcrc lH:c he lll ccn the 1\\0 .. a l',"
lc n g l!';; .. hid, pro~luce(1 I lle Sllc,;ei!siv(>
be al. 11 0 1C6. £\'IIIII[) /o>: 100 a nd 200 ' 1 ~~ ill
Ihe c .... a m ple abo\'(> co rrt'spon d 10 187. 5
:m,1 ISO t il l. The ,lifTc rc lltl'
37.5 ~:)Il
eQrrt's p' llul ;; 10 800 1\l c.
- E IW .\ltIJ K .\1U' I.US
or
SPECifiCATIONS
Fra~uenty Ranle: 'I'h,· fu", lam" lII al (rc·
'I""'WY flln e,· i.i fr(l m 11)0 I" :WO i\h:. TI,is runge
i ~ e'''·... re,1 in II ~i n ll l,· 1... ",1 .... ith "1'I'tQ~ilUulci f
logarilh,ni e fr"\l"ell"Y tli8tril,u " on. U )' hatm<l nic ,nclllt,..I~, ffe'l "<':" ci~'1! Ll'lwC('n 10 \ Ic un ,1
30lMJ 'to· ell n 1)(· ",ca6uretl.
Calibration : ThO,' 1) 1<1. " dial is~·a l'l .raleti ill
fr'·qu... ,C). 1'1I~h .Ii. i~i<ln cQrre~Jl.Qn.lin t:" to I
\ l c. '1'1,.. "'m;"r .Jia' i~ gCllrNI
Ih" Inu ing
"ne·h:.lf tur" "f [h.· ,Ii al curre_
ill't",,1 iiI I ' , change in f.~'tl" ,·nc} <I" ;' lhe
",,,jilt I' Hr~ •• f ,I,,' ' "ni"g , u" g'·. TI, e "'r,,;e r ... ,,1
~'lI rri cs !!Un u,,;rvrn , ,Ih · .......... li!.
ACcu r a e y : T I'e " ,·,:r.. l1 IIc<.:" ruc), of mc" . " ..·,
""." .. i~ 0.1 r, . C hu" I?~ ill I"I",~ or 1,;\I ' ,·r,. ,,,1 . ~ e'''' ,,,,d 'l1r; a . iv"~ .. f " ''''1",.,,1 .. ,,· ,mtl h,,_
mi,ti' )' "v,'' 11.<.: rll"g,· 1)( lal'Maltl f) (·""tI'ti.", ~
n... ",,,II ,' ,·"e..""I ...,·.1 .1" n,,1 ~rr.'C 1 Il w ,....
1.' ''''''') ;,f lit.· iuslr""ll' ut .
o at eel Dr : O n.. "a'lri,tgc.lYl" · c r/ lI tut.I CI.'t'!Ur
( IN!! I. B) is ,, ~,·tl ",,,I i ~ 8"1'1'''''' "ilt. Ih e inSln,IU(·" t.
'0
""., '0 Ill"....·
VHuum Tub es: Th .. (..I1"",i,,/; ,,,1'<':8 nrc
,,;;<>d :I"d :Ire :O "PI,I;"t1 wi ll, II I<' i,,~!run,,·" t '
I - TI'I' ~
1NSGT
I DSG'I'
I - Tyv~ 958
Balli f Y: 1\ ~in g l~- t.I O<!k BUft;1:l!<! Tn'1> ({j'AUO
n all~n' is u ~,·,1 ,,,,,I is BUl'/ ,licd wi,h II ... i" ~ tr,,.
me n!. 'n le [lOWer ":<I"i ..·( i ~ (' I,prn.~ ;"' a t t·l r liO
,.-.II ~. 6 Ill .. am/ /.1 ,·ol ls. 250
Ca 5e : '1'1". Tn'~ 120." I Icter"dy" c F'(.'(I " elle~
McI~r i~ mOlln,.·,1 in a ~ lticl. I,·, 1 c rtrry i" J; cal!<! "f
I - Tll'~
,"a.
du.a!,I.! airplan,· luggage
,uHf"''''''''
He t Wei t ht :
l"clutling!'lItlery.27 ~ ~ I,()uml ~.
(.'("J,. II u,.,l
I [,·tc. .... I ~
72U- \
'1 J,;. " •• ",,'''~,,' i. ","" .. f"<I."""
I
, S. I '~ ' '' n'
"' ... 2.J1.7J!l I.
(.'()U ~ . r"': li on .
S pare Part s: 0,11' ' N2 1 - B -l~' I 'C J" h'CIor i8
8ul'l'li e.t a~" epart· in a. ldi . ion I" lhc une in 'he
inli ln,,,,,.,,t.
Atce550ries: 11 "udl,hvnc8 "'hiel, I'll" I, ...
I'lu gg,..J iu " " th e f .. on ' pand ~n .1 B,"ret! ill the
<.: UVi·r ()f Ih f'
a'" rc..,,,,,,,,,,'ud<.:d.
Dimensions : Q,crun. (" i.hh ) 1 21~,! ' X
(I"'i!! lo t) 13 )-i" X Ctlcfl h) 1U}!i·. I',ond . (.. i.Il t. )
10 3., " X (heigh ' ) II ~~ ".
Pricc
'''' !'r"'J"enc), ,\ Icler
....1 .,,101 ",,,I.. ( I ) ..... ",•••r tf,~
I" .....·." 'I'.kl" "~'" ~" d '1',,1<1<0,.10 c.''''I'~'') ' . ",1 (2)
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,
GEHEAAl RADIO EXPERIME,HTEA
HOW HUMIDITY AFFECTS INSULATION
PART 1-0 . C. PHENOMENA
The pn'scnl increasi ng usc of clcl;trica l equipme nt in tropical c1imales has
ru ll~l e nece"su ry II ootter unolers landing
fJf the he h u\' ior of iusulaliou umler extre me condi tiolls of h umidity, General
s hll e ment s ~ uc l. as " 1\1 JOO% rela tive
IIIBnidit ) and a fretllu::ncy of 60 Cfcles,
increases as much as 50% in capuci.
tunce, or a lIlillio nfo ltl in COll4luctivit)',
and up to a dissipation factor of 1.0, a fC
(Iuite l)OMibl.· for such porous materials
as filled ulld lamin a ted the rmo-se lling
plasti ...,., man)' thermoplas tics a od ua t_
ural fibers like cotlon, wool , aod silk'"
arc (lui Ie inadequlltc. 11 01" IOIlg: tlocs il
Ilike 10 produce tbese I'banges; bow
Illllclt less is the effeet at 101ler humidities ; wha t ha ppens III o ther frequencies;
are tbere any really good insulators that
are unaffected? it is t he object of this
ll.·tide 10 gile SO IllC sort of WlS"er to
each of t hese queMiolls lind to Ulal..e a
beginning lit sorting out present com·
mcrcial insulating materiaJs according
to their resis tance 10 mois tu re.
El ect rical Pro pllfties
The elect rical property mQSt affceted
b), moisture is insulation resistance.
Thi& is lllHJe up of l wo purts, surface
resistancc and volulJle resistance, "hicb
exlti],it VHSlly diff~n:nt behal'ior. cs~ ­
cilllly with res pect to time. Volullle re sistivit), is a n inherent properly of a
mltlerinl, "hieh is HI a mnximum IIwler
tlry conditions. ami decrcai!t:1I rapidlr as
"Hter is absorbed. Su rfacc resis til'il), is
infinite for II. dean dry surface, hut decreases very ra piJly as any roreign conducting male rial ad heres to t~ surface .
Water Hdhcrcs to the surfa(;e of most illsulalol1! aud is a bsorbed by them under
' M. • . f"'....l, "1"" I'Ao.:t of lI umiod.') on JiI<rtri<.1 M~ ...
...........,..." t:-... R.I,. ~_. \ oI. XI'III ....." . JI,
'I"" 1?-41. " . S.
('ouditions uf imlllersion o r high re lali,c
humidi t). This waler fil ... , cve n Ihough
pu re init inlJ)', beeomes ionized rrom c:.rbon ~Lioxide in the atlllosphere , (rom
solu tion of sa lts on the surface or; n the
WIli e r 011 im mcrsiuII, lind from s lis.11I sulUI ion o f the insulating ma t,crial itself.
T he relutil'e imporlance of Ihese t\\O
UlOtic;; of eondlwt;on, SUr£IICC anti vol·
lunc, dcpclu~ grellt l)' 011 the ;;ha fl'" of Ihe
sample unde r leU. For du' slab uf in su lation showil in Figure l t he surface and
,0lulIlc rcsist am:cs are, respecti\cl)',
I
lind J{ = p 2(w
t)
11'1
"here a = surratt rcsi;;til ily (illlll' I.lCml.
ent of ulli ts)
p -
+
volume resis Li\ily
5in oc the ratio of surfaec tu \oll1 11l1'
sistance
s
f{
n;.
• = c'c"''--c
= ; 2 (w
+ t)
is iLlde l>cmlc Bt of palh leng th. it can bt,
millimizcd h) maki ng the slab as t hin
as jlOSsible. Thc samples uSt:d for s tud)ing iusulal ion resis tance are hCll'l!cn
~ Hud .K inch thick and ba\ e bar electrodcs so plHced that. the su rface area ios
us ually II. square, so that s urface resistiliL~' is a pproxima tely l"iC"e the lnSli latioli
rcsistance (\olu llle rcsislan\;C hci ng us·
SUllletl negligible). The electrodes are
a llacbed by a ecnll'r bolt Ihmugl. a hole
in the specimen or h y tl\O e nd holt ;;.'
Res is t ance is meas ured 011 a TYI'~;
5 11·U58 \l cgohlll Uritlge ! on I,hidl. al
500 volts, a rcsiJI tancc of 10 .\lM n can
be dis unguished fro m in fi nite re.,i.i!tam,;C.
The sa mple is mounted on the IIlt!lalto l)
of n glass d es i "'~'al or jar. The I,erminuls
lAST;\! D:!:>7- JII. 1..... I.olM>i. II ..... 'M,"'" "j ~: "'·" .... I In ... ,
",;".. .\I .......... I'l....... J • .,.1 2 •
r'J'hio. 0 """=1 b ........,.''''''' nn.., III ""_ ~., ... It.~~
,10. ,
or tbe ...mloJ'd bridle.
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534 Main Street, Westbury, NY 11590
I
S = a
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IULY anti AU G US T ,
19 4 ~
Lained. Thompson and i\ l alhcsli have rcIXllted a similar effcct. T hjs behavior i:;
shown b y polyethylene for which the
voltage was removed for L6 hours with a
J- - - - - - - - tenfold d ecrease in resistance whell Lhe
yoltage was rea pplied. But withill ] :1
minutes its resistam:e was up to the
earl ier val ue . showing lim!.. the wat.er
film djd no t change with lime. Jr, however. d ew point condeu&'ltio ll is proFl(l!)lIg I. Dinu.'nsiQII s keleh of Il'Sl ,;Ialt of duced by init ia l cooli ng of t he sample,
insu ll) l.ion.
the wuter fU m is both morc cond uct..ing
ai'll lIlo uutCj\ o n TvP£ 138- UL Bi nding
a nd t hicker, as shown b y the t.wo cun 'es
POI; l AsscmIJtics wilh the me tal lOp 0011 - for polystyrene. J)roof t hat the fil m is
ncc tc{1 to the guard term inal of the t hicker will appear in the next paraLridge. Exce pt for a few of lhe poorest graph .
1I1 ulcriui;;. tlll; inSI,lation resis tance of the Re covery !at 0% Relative Hu midit y
sample Whell dry IS greate r thao
The degree of l:lennane llce of t he water
10 .\l l\Hl.
film i" de mOIl!! Lrll ted by t ransfe rring t lte
Ellect of 100 % Rel ativ e Humidity sample to a n a tmos phe re of 0% J U I.~
WIJCIl a uy saillple is placed in a n at- For tbe ma leriliis o f Figure 4 the illili a l
lIIosphere o f 100% reillli vc hu midity,4 res is tall ce is reco vere d wit h ill 10
7
nil ion;.,xu conduc ting fi lm of wuter sceonds. E ven thi!! short l'ecOyer), tilllc
fon us \\'illlin a few 6CCOlld8. Wi thin o ne
m iJiu le it.s resis tancc drol>S 10 a value
a bo ut a decaue a bove ils fi nal equi lib·
FI r.UK6 2. Pial of surface r""islivi ' l vs. t i"'F for
rium value in t he manner sho wn in
fou r mal erial" hO"i ng nCll:lig il,l ... ' ·0 ume a u.ort'·
I~ig u rc 2 fo r four materials which e ithe r
, ion ..·ith il) the tim e i"'l icoh..... /. The left·hullt!
have no volullle absorp t.ion or a !leg - po rt io n of th e \' ]01 s hows th e s urface rCil iSliv it)"
und er t he eoru ition Olr 100% rcla t i\·c bmnidi ty
ligiblc a mou nt \\ilhin the lime indi o fo r time ul' 10 l()(lO mi,m W. where the t ime
ca ted. Tile quantity plo ued is surface &cole re peat s for tile righ l .h uml ".ort:ion. whid,
elr ow, Ibe relXwery lime at 0% relative
reSlSl1 \Til y. For some ma terials the
hnm idi ty.
e quilihri luu \'a luc is steallil y approaehed ,
\\hile (or ot he rs lhc l'C is a IIlini luu lll
\ altH: a mi a slow risco These di ffe renl
,
forms res ult from the di vergent e ffec ts
\
proclueed br tue applied voltage in
s\\ ceping iOlls 1.0 the elect rodes and in
''''''"
for ming new ions by collision, a process
D<}~M' ..
which l'Csuhs ill a voltage coe ffi cient. of
'OOK""
__'!c"!
resis tauce. Wben t be bridge voli age is
no t a pplied con tinuously but oBly mo·
me nta rily for a reading, Ihe measured
resista ucc is decreased , Lu t returns to its
l ar~I' I· va lllC whell thc voltage is Illllin·
//':
""'"~'I,
-"'''-
,, ~.L
~11"."..,.j
1>1 (,m". ,I..
~.""
t
"r d", J""k,<. ,ur jo, ~;tlJ "ole'
.",1 I.., I,,~. _ . ...., r.,. f",,, h."". '''''' ........y.
10 .. n
I..
1m....~'+----'--cil
I
I
10
I
10"0/
r-1001; III< - - ----j-0 1. ~--l
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GEIHRAl RADIO EXPERIMEN TER
15 prulHlbl) "t:t m() re b ) the 1I11111rlil ,Iifru ~ inll rltlt' of \\ a le t I al'or 011 I \\ ard 10 1he
"ili('a g..! Ihan hy (III~ 8I.11·t:ifi.; pt0I'I'ny
of Ihc~ Illate rials . For Illc Ihie !.. film
prudul'I.'11 0 11 IJol)sl) IX' lle II) Ilew po int
c·. )mll' II!!1Iti v n. th c rllpid ri!lt: in resis lillll'C
ii! h al l(' ll ll flc r 11 fell !;Cl'ontls l.,cl· a u8l.' the
!'(llnti", hllmillil y imnwll ial e ly s urroumlill ~ IIIf" f'.p:-c illlcn is no lon ge r 0% . The
film is I'C llis l rihutctl . ilnd olll y uft e r olle
min ul e docs resisla lll'\! s lltrl 10 rise again
In regain it s ini tial re~i~ I (lII t'" a.fl c r I
minu lt'li. 'f he u;;.: of forced vcnl illtlion.
Cl ell Ill. a 1'00111 hUllli.l it, o f 30% HII.
rc molCI! Ihe fi lm in 10 seconds.
Thi!' f IHlj)l' of II II' rCt:O\{' ry c ur l'C. ill
IIhieh then' is. 11 rllpid ri51'. a Aklll IlrQp
J urin g rcdis lliblltio n and a final rise to
illiti .1l va llll" se.' llIs In be dwra<'lrl'i sLi l:
of IhOf'c rIla t'; I' ial ~ hal ing no voluHlc aLsorpl ion lIithinthe timc o f the IlIc aSlI l'Cme nl S, II lie n U)' l' ariou8 IIl(' allS the fil m
is Ill udc s uflil'ie llil, thi"k, C ur l'c~ for
t\IO grades of mi eu·fill ed phe noli ... arc
gh~ " ill Fi gure 3. Sa m pic .\ rccove rs
"i lhi n 10 second" afler an c:'( pOsul'e of 90
minutes to 100% HII but rcquires 1'1
OOI.I.i".. 1 ~, I,ll",. II", I,,,....
or II" ,I_;~a" .. j., ~;II , .(1.'4
.~I.,,,II,", '''~ . "" .. '''' f....-f,~ .. h""" I~ .. ~~ ..I:,
1"l1", I",.I,~ 1. 1",0":' .1
r~;".", ...." ,1 II.. ' ''''' ,,,
rr """
Iv
1,.1.,,,,., 1.
F.eu R!; I.
,,,r,,,,'c
~,c","f.,.1
(f'i')
hu midi l )' alTl'f'I~
b) ..
""I' ~ ".>h.
PIll! ~I","in g ho" rdot h .:
Ih" eltp Oi!IIr(> " une ror t,,-,I yell,} kue.
5. (r ip-lit ) E'lu WJ, ri n,,, s" rfa ...~ re~ i~ l i, it)'
I' llo y l.. " " u~ u r" "eli"n Hr r,'lulil'{' !.",m_
.Iil), '1 ht f:~r ..",e"t;at rc1at io n ~h;r' ;b "harll{'ler.
isl'" (,f a U i"~,,lating "' <l It· ri ut ~.
FIC. I
r,).
I! Ii:
I".t ~
'\
0 _"
'.:: '
.. 0
..,
.... - J
~
..
.
."
,-
-_It._.
-"'-
..
•..
.,....
...
...
.,
. -, '",,""
\
~
," ".
"" ... ~
\,
FIG UfI ~: 3. Ex~)Os"re aUlI rceo"er)' cu""cs rnr :1
gr a, le~ of nnea·fitt et! I.heno t;". AI' I' ar~'''lt )',
diffe(enc~ in 8"rf:lce l;"i ~ h rl:li uh in torl:t"
,lilT"rences in surfae.. rc~i~ li "il }.
@malt
millutes aft e r a 16·holl f expo;; ur,;. Sarno
pic n sholl'S a 1II 111'h lowe r surface rt'sis li l'i , ), uud tilt: ly picul rt.Jeo vc r)' C Url' I'
after 011 1)' 20 minutes c:'( IKls urc to 100%
nil . Fo r('cli \'cn l i lal iOIl reIllOI'CS ' lit'
fi lms f"o lll bot h mate ri als ill 10 sc(·nllii s. ~
SCI'c ral o ther matcria ls F.IIOW t his effecl ,
88 5hown in '!'uilic I, "hich \\i l1 he Ilis('tJssed la le r. The e:,( lIc t shape of thc re·
con: .'" eurl'C ('an t':'( tcild frOIl1 Ihat of
I'in) I ch loride acctate . whieh ri scs UDOI'C
10 ~ IM n beforc I he dmp. 10 that o f
qll<lrtz afl.; r dew poin l I'ondclisa lioll ,
II hidl rc mai ns at it s 100% BII val uc for
2 minutes bcfor(' thl' final fi se 10 init ia l
I'lI luc.
Effect 01 Other Relative Hu midities
\VhclI lII ate ri ills Hrc plat'cd in 1II II IIi(l.
ilics less than 100% HII , t heir e quilihrillm rcsis t ances arc hi ghe r and t he
water films pres umahl y tliinn,·r. CUtl' i'S
o b lH inCl1 fur polydh yll! lIt! ' In; ~ ho\\n ill
Figllre 4.s The I'elu l ion l:Jt' t weeli tlU'
cq uilihrilllli Budul'e resis t ivit), (!lid rela·
Iii'll 1!ulIli/lil y is c:'(poncil t iu l. its s hm"l
in Fi gur.; S. II'lwrc t hc 1'101 of th ... loga.
· D..r",il~ 1"''''i,li l .....''' ,~, •• ;,,<.I I,) ,~ ••·i"f • •
.,'. .,.,.,"'" .".,.~
v"
f,d~, .. ":
.... 1111 3.2
4J
S:.!
s.h CaQ, " ,CO, N...cr,u,
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
",r;o,•. J ....,1". ~
. ~'''. ,,( ... ~" .... h. i" , I.. ,"""I ..·. " .. j ••. T lte .. I..."",,1 ~ ...
••
66
HI
"'fli'oU, ( 'II .h.~\).
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~l
"'.so,
,
JULY In ll AUGUS T, 1945
ri 1IIII1s of fl'!! i s ! j"i I} aglli ns l pe rcerll .-chlli,-c hurnidil } is a s t raight linc. Th is
:I!!,rL'es 4uitt' " e ll wit ll Ihe work clone U)
C url i... ill 191 5~ on t ht· a vailable iIl5ul:. lion of tM II I Ila}. lIis plol s we re m ! lIrl }
lincllr from IOOC{; 1(11 dO" 11 to II boul
50% H II !Iud the ll flatt encd 10 11 CQ II .
" Ia lll \ IIlu~ of resis llln('.c de finel l Ii)' "re
InJunII' I't'~i l! t ivil} of the 811 1l1plc. The
greatc r "cllsitivi l) of h is ap panllus ill.
101\1~ ,1 him In IU Clli3Urc 100 k l\ 1 \1 f! ull d
10 (,lIrry tllC ob;;cn' lI ti o n!l d O'''l 10
0%
UIL S urfal'c res is t ivit y nl 11 11 )' re luli l c
11I1IIIilli, ). /I %. is best de fined by s t II Iiug
the SlIdncc resist ilil )" 11[00 :1 11 00% nil
lilt' dllUlge in r('l llli n' IlIIlIIi, li l ), "
\\ h i.' I. dlUnges Ihe res iSl ivi ty by o ne
tleudc, Then
li lld
log 17 =
,....
'100
/,
"
(3)
- log 17100
Effecl of Volume Absorpll on
, col u nlc u hsorpt io ll or Ilal c l" inl o till!
IJlId ~
of an ills lliul o r pro,·illcs IJOt h ;1
1'.,lurne COIH IIICIMII.:C allil II s to ru gc (If
"alcr. " hidl 0 11 dry ing 0 111 lllUSI "a,..8
0 111 Ih rou gh the @
lI rfau'. Lo ng beforo
j' lIuug h \Ialer hal' IIl'l' 1I ub sorhCl 1 to re' II . I.. C....,... "1",,,10,,,, • •.,."1 ...." ... .of 8o" i,'
"r II"",. .. ,0( l".hJ.nl..
1I ~1""i"
, ~.,
W - I!O.
\,~ ,
I)i •
....,'191.'>.
' o..·.
11. ' .. ,3, \I .)
10',,: \ I< 1\ 1>, E' lo(r.! u,.' uII, 1 " '.'{In:ry Cll n o'f for
f... or ",ul"r;ul. hal illlt Pl'l'r',<:iul. le ,0Iu,"1' "h.
"''''1,1;,-,... S uc h ", a l o:rial ~ . ho ... ill 1;"'1"1'1,1, u
s moo th"f rc<;o," 'ry "un'I', " XIt:I1\I,"!; ." l'r "
lime oollll'prlll.I,· 10 th ... "\I>Oi!ur,' Ii",,,,
"
,
dw'c l'ol llnl1:.'
rc~ i 8 tan l'C
10 a 131\10:: al ;.11
co m parable 10 ElirfaL'e rt' ~ i S l ll n cc, Ih('
",IHlpc of Ihc "c e ol er} l'lIl'I e i .~ "'. an gNI,
IJot' e3t1se Ihe ••b;;.orbe d \\ui(: r tj"H lij 10
llIuilllllili ti,t' i) \lrfnt't' fillII, S urface fe·
sislililies for four IntlteriHls hUling- np1't'Cl'il.hlc \,O I,llIIe n l'so l' llli {ll' 1It'C II h oll l'
;11 Fig-uri' 6_ The ir rccoll' r.1 (' lIrI e::. r iji('
s iOl. I) !l lId rt' !] lIirc IIl0re d um 10 rn illul('s
to Hllain ini lial vn lucs, Sorm' lhing 1I1(.Or('
Ih a n 1I m ou n l IIr \llIler a hM)rh.,. 1 ,Ielt·r·
mines Ihe ra il' of reCOIl'r), I>i ll('c Ihe
laminalCiI PllrlC r a nd as hc~ los ·(jll c( 1 phe.
nol ie!; a hsor lJ IIIl1ch mo n; Illlte r Ih al!
g ta!lil -ho 'Hlc d mica or shed lIIi. a . This
may he Ihe mo lec ular (oret' IIhidl holtl s
Ih \' lIalt:'r (j Im 10 the IIlIrfnl'C .
Fo r high r all'~ of I'o lullli.' ah~orp l ioll of
wal .... volutllc rcsis lann: li t 1000/0 .11 11
ix-coJlle!l compurable lI ith /O urfa("C rt'"is t3111 'e hef(.Ot'C Ihe I'l lu ilih ri lllll lultle o f
s urfa('"e r('s;s l nlH:e is a llaill('~1. The
n's;s l:tnct' -lill ll' t'UrI(' 11"' 11 ~' n l\ lilll ' l'"
df)111111 ard al 11 mtt' tlqX' lId(' 1I1 " 11011 the
ra le of Wil ie r ahsor ption. Thi!; dfef'L \. ill
fi l"$ l a plX'3 r ill III!' l' UrI'C!l for Ille lo\\cr
hlllll i, Ii i iei', h"t'u lI&, II.c r:II I' of \I a le r II 11probllhl~ illdep(' nde nl of rdll1; 1(' 1IIIIII il l il .~ ;;0 1011 :;: as II Sli rfaCf' film
l'xis l s . Ilhile Ihc ;;'lIrfm'c I'('s;;; l a n cc ill -
sorplion is
Fua IU!. 7. E"I "~"'" un.1 rt;<·(' I .....
,' ''fle;!
til; l,.
CII ",.o t
,
1><) "I.so'n ... 1.
,
'. . .... 11,
fur
I.. " "'lIl cr; ~,I~ 1 ~lIilll!"" lu rF'::O • " ]"l1Ie ~h"'.rJ"
lil)rI 1h ~" PI! "(I "ilil.r;"Ul 1:010 ... "r . " r rue,' "~I~ '
T
~
"... n·
,., ... "
., ... /l
.-.
- .--.
'\3~;/ +
~~:~ ;1
'-"
~_'l"'~
000 .. n\
,
.., .. 11-
~
•
·'00 '1;
~~
0,-
I~"Il'
,
~
~' ....
... , ....
"'!.
~-
/
,
<00"/1·
; , -.x.":.J
,,-
'II .. "
-
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
··d
.-
l-
•
.00 .......
m_
"... •.
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TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
GENERH RADIO EXPERI M ENTER
t.' rease .. with IOM'red humidity. T il!!$(:
,listinctions arc !;'howli in Fig-uN' 7, Th e
lIurface rel"istivitr of Hllcanizetl fibre at
100% Ilil ill !'O 10" 111I1l e'lui lihriulIl is
ntlAint!.1 al 90 milJlI h's before vol ulIle
resi;;;tanl'e I'an ha\'e an c lTec t , "hile at
8 1% Ill! lolullIc rcsitllflllCe becume£'
f'o mparabl,' 10 surffl('e resista!l('c "ilhi"
\U mil1l1h!lI, pre""IIIS equilihriulIl , ami
('RUSCS insulRtion rC!;'is t:mce 10 ,I,'n ease
diN'Clly wilh lime. Polytlm id ~ htl'i 11 relafile! ) high s urface re!! i ~ li \' it~ . 110 Ihat
eve n at -100% IH I i ts lOlulllC resist:HlO'e
I....coll)(>s comparable to fi ll1'faec r~s i s l ­
an.-e ¥oilhin 10 minutcs aud Jlren~ llt s
1111, equi librium VAlue hd llg altAilled,
On ('onliulled eX I'08 "'~ 10 hi gh humid·
ity extending o,er dll ys a ll.1 Ileek s
rather th llll Il(lu l"S. lolul11c t:onduc ti,tjtr
s leadil} increases in proportion to t he
\I IItcr absorbed and ill most materials
d"rninatell' 0'1' 1' Sllrfat'e t:olHll lCtivily
t'H'n a l 1000{, lU I. Klin1"'o hilS given a
lillt of Ihe limes ne~!\l!ary 10 reach I'a lu _
r:Hion fDr 22 malerials, The ,'allies extt'1I11 fmm !! ,Ill} II to 2 Y1"ars. T ht·) tie .
1M·nd bOlh 011 1l1e Slnwlure of 11lf' lIIale.
rin lnud the shnpe of 111(' sa lllple. particularly the rlilio of II urface to volume.
S('hee rll hUll Illeas urcd the ins u latiOI1 reo
IIi .~tll ll ce of 8e,·c ral insulators Ol'c r It
1)(''';0.] of 30 da.\'s alul finds Ihnt resistalice e'll lilibriulll is Iisually Ittlaillell
wi thin Ihut timc. It is importanl lo note
Iha l of Ihe tOlal decrease (6 10 7 deI'a<lt'&) in in""lation rt'Sis trulce from the
initial dry v8 lu{' Stlrfat't· I"t'l'istalll'f' /l('.
t'Qu nts for lIlt> major part . "hi" h U.
Ill'ually s urli(' ient 10 rl'n,lcr u!'CIt'l!s any
in~trumCIll ill \I bich Ih" malc rial is
u,,;er!. VolulI)c ",,,i"ta nl'(' I)nl) at'collllts
for Ihe lai't olle or '\\0 decadei'. Imt
"'G, M IWoo. \. II. II ... ,,,,. II . \ . r~" ..... ";;",...,...., 01
........ by ,,.,.,........ I~"'w. fII A" ........" "'<o<io.. f,~
1r.3-1:JI:.
, ,,""a, \b ......I.. \0)1(1, ""
s._,
li P. II .
~~"o<I .. nI \I ••• ",,,, " ........"'R or ............ , ('"
"""001;', """,",I .. C""'"""" Y Il<I'''' I"I~ I. ('~"'.t;.1 M.,I.,
c..,.
R
10
m akes the reduc lion perllIunent 10 Ihc
c xte nt t bal Ihe recovery lilllc will he li t
If'as t as long as the f'xpos ure time.
Colle cted Oata
Somc 40 matc rillis nrc Ilrralwe,1
ill
o
Table I in the order of dccreas i,I"
sur_
o
fa(."e rcl>iSli ,tjty a fl er exposure to lOO%
nil , ran gi ng Jrom grca tN _111111 20 t\1 ,\1 n
1030 1\1 n. The (.losition of ce rtain mall'rials is mosl s ur prising aUfI ilia) no t Iw.'
' ypica!. ,\11 samples "c re was.lwd ill
g rlli n alcohol to re mol'e dirt, hut SOIllI'
I,.:l't!ttsc a ll rl Oil ie r substances Il lay rc IIUlill.
A t least 'hey " e re 3S clf'all as I he,
''I)lI ld be in al'tual u;;e, Olll~ one sll mpl;.
of It ki nd wa s tested so tbal Iht:rc is II()
mClIsure of _he 1lI11J.'11iIUlle of nOl'II1111
vlIrilitiollS. lI o"e \'cr, t ile rCllu lls Are 11.'I)('atable on ' he same sl'cl'imcn \\it h in
50%. ' Vbere mo", t hAn one lIample of a
ki nd is given. they arc kllowlI 10,lilTc I'
l i t are made by di lTeren t IlI tlllufactllrl'!"!',
II is k nO\\11 IllIIl \'cry 8111 all 1I1l10llnts of
plaSliri7.cr l'an grca tl ~ f' h :l llge Ih(, I' llr.
fnce !'e havi()r aud nonc of the I'a III I'ln;
WII S fu rnis.Ill'. 1 fOf t his pnrlit:ullir 1(',, 1.
'I'hf' slope of Ihe s tr:!igh l li ne plol /If
" u r fll l'C resisli l' it )' a g ain s t rdalill'
hum id ity is givl'n in IIIf' scI'olHI ('Olllili n.
an. I in the _!rird .'oll1 l11n t he re lati\'(,
IWl1Iidit.\, a l "hieh d Ie s urfa("e resj",il'
il~ is 20 i\ t \I n. SilU-e for mOl5 t of Ihe
'"lIlerilll;; t his \' lIl ltc of re lnl i \ I' h II m i, li I I
is grea lcr t han 50% nil , it is cas)' _ ose~
" hy rc latiHl h umidi lies Icss tban 50%
H II lire consilien:d 10 hal e little ('ITf'ct
0 11 i n ~ lIl lI li o n fIlHI IlI80 \\ hy Ihllt vll llIC is
a good s iaml ard room Illull i,lit,·, _\I a1e_
rials " ilh volu me absn rp lion ' III111 I,...
cOlldi tioned at t hat hU Hl irlit)' \\i l'''out
" livi ng IIny II p precia ble s u rfllt:e reais l .
a n('C.
'1'111' la!; t Ihrel' ('o l ll mn ~. gi l(~ the I'{'.
(,fHC rr li mt's in mi nu les after] hour an, 1
10 ho u rs ex posure to 100%
lItHI
nil
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
www.ietlabs.com
TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
lULY
11
r
Mllterial
% IHI
per (!Locu. l..
chll ll geof "
•
M~ln
11 ),\.ocllrl.>oll " ax. modified
Cell ulO&c llce lot e hll' y rulj,
Silicone ruhber
1'01) tctn.nuoro<:lh} le ne
>20
>20
10
,,'
% IUJ (or
20MMO
I h.
16 hre
100
100
.0
.0
.0
.0
. 17
. 17
. 13
.13
3.'
7
29
,
,"
Phenolic,
lI~ b"",t .....
IiIlnl
,p
r
P<lly'lic hlorO~ lre'H" 3_ 1
l'IH' noli.· ....... 110, ow lilli'"
Anili"c ronnaldeh) ..t". gta&l
mltll c
ci~.c,1)
Melnlll ine, glll>lll clod,
1'1"·,,oli,·. nile" filkJ
>J
.17
56
.17
J:J
"
6
77
12
51!
8J
66
7.0
57
5 .'
5 .0
,.•
<\ 2
3.6
3 7
15
:\ .1
10
12
10
30
•
2
:! <I
•6
IA
1.3
•1.23
SOU
70
'"
·IlI
42
'"
9
63
·15
. 17
00
1.5'
25
18
16
JO
"9
9
J6
50
20
0
12
57
.00
12
3·'
61
18
31
30
"
33
•••
aftcr tic" point cOrHl.,tls ation. Any timc
up l O 0.25 min ule (15 8CconJs ) iltdica tes
no \,olllllle ubsorptiolt. All} 10llge t' t ime
\Ihi c h is .. tarred (.) refers to the s hape of
rcctwery cune dHlracleristic of nonporou s m a terials, for "hich fort'cd ventilation will g ive u rectH'ery tillle of Icss
than 0.25 minute. Othe r large limes indi_
cate volume absorption unde r Ihe condi tion n otcd .
..,
32
. 11
. 17
17
. 17
"
17
lOll'
300
.5
"00
,10'
.33
.33
J 3'
..,
' 000
(.~)
300
.'
3
"
·.00
3()(1
7'
\ 1un }' illt.crest ing fac ts lIlay be gleancd
from this taUlc. T he high l:K>si l.iolt of
t;e llulose uce tatc-but) r lUe is s urpris ing
II hell it is R.'ali ...ed th at this ma lerial
Idll absorb I.Lout 1% of WItter in 24
hours at 100% HII. This water must be
kept in UllCOlUlcCtcd pockets 10 prol'c n t
couduc t io n . i \ sa ntple \Iitlt 4 % of wnter
s till has a resista n ce b'f"tla ter th an ]0
.I\. IM n. Evcntually the waler in the
IET LABS, Inc in the GenRad tradition
534 Main Street, Westbury, NY 11590
'"
20·
61
61
.0
'_.,-,
H
71
90
20·
50
68
NO
62"
13'
200
Ii....,
.5
17
II
15
6
. •7
17·
6
2110
. Ii
59
•
320
2'10
2'10
.33
1.0
6'
. 17
••9
Mil
660
"10
I'he.",I;". C
220
V"leani:«,,", Fil,fc
220
Anilin ... rornoal dd'y d ... , gla>lll
<"1mlo
200
Qnurl;/;
'90
Pheool fOTlIlaldchy<lc (1'11I~l i _
CIIl __ ( ~i nll·r..,..t )
Ciaiii' I,o,",kd lIlien
93
!!tl
Phtillol i<:. ). \.
l'henulic..., X
SI"'lI ti le (1.-4)
Phc""lic. LJ~
"hell.,I1". ",iell·fill,.,.1
Stea li li' l t-i)
COllide",,,••
. 13
11-10
<$>
HeC')\'er{ time in ",i"" tell ufte.
100% I I r for
Dcw po,nt
~iJ\ 1!?
l'ol,fil,r<'lle ("heel)
Pol) .\i.:I,lorOll ly.r.,,· 2- 5
J I y,lrocllrlK>1I WHX
Elhyl cell ulose
Cclllllo.w aeNa le
1,<,1" ;n) I chloride U"III ((~
" 01) ~ Il r,'u(' ( pI O~lici~('<1)
PI"",,) ie. ",ic .. ·filk.1
1\ nilill" (".nwldd" d,l'olplll1i,I,'
po,('I'\a;lI, glazed
Gla&tl (hi~h .... )
MiclI
Pol) ~t ) rene (",olt/e.1)
PoIYiI ' ) 'eur (1'Ip~l i ... i7.!"tI )
S teM . it e (1, .3)
Quor. ';!;
P OIH: ''') IClle
AUGUST, 1945
www.ietlabs.com
TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
12
GENERAL RADID EXPERIMENTER
isolaled pockets joins and provides norllIal volullIe resistrul(!e. G lass. quarh.:.
Slca tile and mjcn arc \Ie ll do\\'n in the
list a nd probahl) "ould he lower if their
s urfaces hall been m~l(l e pe rfectly dean
hy high teill pr-ra turc haking. Siliconc
ruhber i,; Ibird from the lOp and illustrates th e valuable II IIter·repellenl property of all silicone n:~ins. Treal meut o(
luin crill is conl 'li llin g lli licon, sllch liS
glass and quartz, by the special ;,ilicQne
,""sins \\hich prOllucc a molecul a r laycr
@c \'eral hundred lIlolcnllcs thick makes
Ihe (rt'aled surface I"ollljllcwly wa ler·
repellellt, even under hot sa lt s pray lind
sa lt watcr immersion. A simil lir Irt· lI l ·
JIlent of stealite affords great illlprO\'c.
mcnt, but is not always ent.irel y SUt'(·(,;o.sfill. A lion-porous ccra nue 1)I'OI)Crly
treated with silicone resin is lIuaffcctrtl
by moistu re and is as nearly a l)CrfC\'t
ins ulator as cxiSIS at presen t. It is qui Ie
possible thai ce rtain plns lies. espcl'ially
the silicone resins, will also IIII'd Ihis
s llCei ficat iOIl.
- l{ oat:ItT F. Fa;; •.n
Pari" ou A. C. PhCnOtllelUI \,,;11 np])Car in an early issue.
MISCELLANY
\ t Oregon Sllllc College on June 10,
the honorary degree of Doctor o( En ~ nt'('ring "as ('()n(errCll upon \I c h"ille
Eas. h am. (ou",lcr IIIII! forrncr prc;;idcnt
of thl' Gene ral Harlin Company . no\\
Chid Engineer in t"hnrg:e of n'scarch ul).1
tlc\ elOpllleli t.
• A PA PER elltitll.'ll "Wartime I'roh·
lems of a ~lanu faC Llln'r of Engineering
l'>roc lll('15" was dcli\'ercd by .\ . E.
1'hie!l~n. Vice Prt·sitlcnt of the General
•
Hadio Corn pan) , before the Ct'tlar
I{apids, lown, &(' Iion o( Ihe lnSliwte o(
nadio Enginc\'rs on \ pril 19, and al. n
IIH..'e1 ing of the Chit'ago
(·tio ll 0 11 \pril
:20.
On \ pril 27, lIoralio \y, L.un,..oll, of..-...
I he Gelleral Hud io Enginee ring Staff,
addressed tilt': HOS LOH Section of the
InSlitute of Che mical Enginl'\'rs 0 11 Ihe
subject of " Time lInti Tillie \I easuremelll."
GENERAL RADIO COMPANY
CAMBRIDGE 39
215 MASSACHUSETTS AYENUE
MA SSAC HU SETTS
TELEPHONE: TROWBRIDGE HOD
BRANCH
ENGINEERING
OffiCES
M[W YORIl I, MEW YORIt
.. WEST STun
TH. - WOATH 2. Slll
CHICAlilO S, ILliNOIS
UI IOUlH MI CHIGAN _HMO[
TH. - WHASH HlI
l OS .MGHES lI, CHIFIU NI.
UII NORtH SEWaRD SHEET
TEl. - HOLLYWOOD 1321
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534 Main Street, Westbury, NY 11590
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TEL: (516) 334-5959 • (800) 899-8438 • FAX: (516) 334-5988
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