Laboratory Apparatus

142 Pages·2012·13.04 MB·English

by  Howard Skolnik

Catalog of
Laboratory Apparatus
GENERAL RADIO CO.
CAMBRIDGE, MASS.
I
Printed in U. S. A. SEPTEMflF.,R, 1928.
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FOREW ORD
('ollllllcrc:iai acceptahility has Lccn tile primary thought ill the dcsigll
of Genel'al Hadio instnl1HC'llts. T his should not be taken to mean' that
they arc not precision instnllll(!llls find. aecol'(lillgiy. lack (tCCtlnICY, hut
rathel' tllnt lIIlUSU"! ruggedness has been incol'pol'l.Itcd in their deSIgn.
They Iw\'c becH designed lo stand ordinary commercial laboratory usc,
without loss of nCCUrilc:\',
~-\ gcncnd Chlssi(icHtioll of nil instruments as laboralo,'y working
shlndards would. of COtll'SC, be impractical. The "cry nntul'C of some
illsinnncnts 11S reference st:lIldal'ds makC's it necessary to give sPCCitlJ
attention 10 their precision. Even ill these illslnllllcnts. the construction
is such that they may be referred to rcgulllriy. without the danger of in
jury to their accurilcy of cillibriltioll .
.- \ feature of pnrti('ular interest in our line of I"borntory equipment
is the specilll parts thHt arc <In\iIHhlc 1"01' (t\lick Iabonltory set-ups. These
padS consist of quick chHnge-O\·cr switches . .<:;pccial plug and jack com
binatiolls. and bolllc-nel·k binding posl~. In a IHborutory equipped
with a fel\" of these IIlTessories it is possible to get ,dong with a sm<lller
!lumber of instruments than would be required if pel"man("ll~ set-ups were
uscd. This class of eqlliplllcnt will be found pilrticulllrly useful where
comparisons ,He heing lllade between different kinds or instruments.
In looking through this cablog it. is evident <It on("e that the
illstl"utl1ents listed arc \;1I·gely sp('('ialized ones fOI" measurements at audio
and radio frcquencies. The filet. hOWC\·Cl"l should not be lost sight of
that mllny of these instrulllents arc also particularly ilclnpted for usc
at cOllllllercill1 frequellcies find in direct currcnt work.
Aside from thc items listed in this catalog. we manufacture a
large Ilumbel· of special instruments unci pieces of HpP;Il"atus. These are
built either to the customer's specificatiolls or to meet his particular
requi,·cll1ents. Yom p,·oblems in this field arc solicited.
SHIPMENT and TERMS
Unless specific shipping instructions accomp~lll.r an order, we will
lISC QUI" best judgment ltS to the method of shipment. .All prices lHC
1<'. O. B. Camhridge, ) la55. T here is no domestic packing c1wl'gc and
no charge for shipping cases ullless so stated with the price of the in
strument.
When o]"dcl'ing hy Idcgl'ilph, please specify qU<lIlt.ity unci OUl' code
word. l"ol'cign customers will find it cOllvenient to usc Bentley's Code.
Om cable Mldrcss is Gcnradco. Boston.
T enlls HI'C net thirty days 01' with 27c discount fol' payment within
ten (by5 from date of shipment. \\'hell cash accompanies the order, we
will pay transportatioll <:hllrg'cs anywlH'l'c in the L llitcd States 01'
Cl.Inadll in plllcc of allowing the USllU! cash discount.
Unless credit has already hcen established wc witt IlHtkc shipments
c. o. D.
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A OiVE PRICE POLlcr
The items listed in this catalog arc of such a nature that they are
best distributed on a direct from Illl.lnufacturer to COllsumer basis. There
fore. with the exception of a co-opcratiyc pltlll with the Central Scientific
COmpuIIY, of Chicngo. Illinois, our instrullIents arc not sold through
dcaJc.]·s bl'oke)'s.
0)'
:\1<111\' of lhe instnllllCllls l'cquil'c special engineering correspondence
to determine their adllpblbility to the particular conditions of the p I'OS
pecLi,'c user. ~·\..s these problems arc strictly of an engineering nature,
maintain all engineering stafr lo gi\'c pfU'ticuial' attention to Stich
11"(,
pl'ohlems. Your correspondence is solicited .
..:-\ 5 our instruments arc not sold through defilers, pnces ha\'c ueen
made on basis thut docs !lot permit discount. All prices tire,
It tilly
therefore, strictly net. Quantity discounts as gl\'en in the next para
graph arc the only discounts 1IlIo\\"(xl.
\Vhen tell to nineteen of tilly item arc ordered at the same time for
a single shipment, there is :\ 5% discount, In quantities of twenty to
nindy-nine, the discount is l Dl;7r, Tn qUlintities of one hundred Or O\'CI',
special prices will ue quoted on request.
Unless otherwise sUtled, quotutions rell1UlIl open for thirty days,
Delivery promises arc made subject to the usual classi(ic~ttion of c~luses
beyond our control. Catalog prices Iwvc been rel'ised to J uly 1, 1928,
but ,He subject to change without notice,
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CONDENSERS
The requirements of communications hboratol-ies hlw(' called for a
wide yariety of capacity units. These include precision units for capacity
<Illel frequency stanciurds, and units for' tuning of oscillator and filter
circuits. The httcr requirements alone necessitate a n,ricty of condensers
in order to the wide frequency I'ange used.
(;O\'CI'
The larger capacities required for low frequency circuits arc neces
sarily of paper or lllica dielectric sillce air condensers of such capacity
would irwolve great hulk.
TYPE 219 DECADE CONDENSEHS
E\·cl')' college and labol'lllol"Y has need of a \"ul'iable con
1'(,5('I.II'(;h
denser of large capacitance and reasonable accuracy for temporary set
ups where it is inexpedient to use the pr"ccisioll types. l'or ma:-:illlum
utility and rapidity or adjustment this unit should have the same flexi
bility-as the fttmiliar dial-decade type of rcsistance box.
In the Type 219 Decade Condenser this highly desinilile feature is
obtained by means of a CtllH switch which makcs it definite contact with
the successive units, determined by a bi.dl and socket locking combination.
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GEl\"ElIAL IIADIO COJII'ANY
This permits the construction of a unit possessing the samc characleristics
liS the standard dial-decade type of ]'csistnllcc bo .... , The capacitance
ill microfarl.lds is read directly opposite the end of the switch pointer.
The complete unit is mounted in ft wtt1nut case with btlkelitc PtlllCI.
The condensers used in the 0.001 steps arc the mic.l type. Holled,
paruffill-impl'egnaled }Japel' condCllscrs IIrc used in the higher capacitance
steps. While this type of condenser is inferior to that using mica dielec
tric, a well built paper condenser is so satisfactory for a wide "ariel),
of inboralol'Y uses that the expense of the micfl type in the hll'gcr capa
citances is seldom justified. '1'11(.'5(' units supplied adjusted to within
1I1'C
ole
in the .00] )IF., tlml within:2 £jt ill the 0.01 i\IF. <.Incl 0.1 ).1.1:'. steps,
which is 11 f;\il· indication of their cOllstancy undel· \"Iuious conditions
of tCll1pel"Hturc and frequency.
T he rolled paper comienSCl"S used ill the Type :H!) units repl·escnt the
ocst of their type. The paper and foil IlI·e fed r!"Om the rolls through
an impregnating Lath of moltcn pltl"affin. The thOl·ough impregnatioll
thus outaill('(1 not Dilly increases the dielech·ic strength. but 1IIso makes
the unit mOl·C cOllsistent in its behln·ior. due to its gl·eater homogeneity.
Sufficient o\"lnlap is allowed on the roil so tllItt the sliccessi\-c laycl·s of
<'itch plate may be bent O'-CI· for conbtel with endl olhel·. Connection
is nwcle to the side of the plate. that is, to aHlllyers in the roll. Because
of its lower resistance, this method of assembly is nlllch superior for
laborntOl·Y and filter wOI"k to Ihat which makes use of a connection at
Ihe ends of the plates only. Thc side cOllllcction also H'·oids the incrcase
of phase angle ,,·jlh frcqucllcy ,,·hich OCCllrs with the ('lid cOllncctiOIl. Thc
phasc angle of thesc condcnscrs lit 1000 cyclcs is approximutely .2570_
The complcted condcnscr tlllits HI"C sCHlcfl in metal cans \\"hen finllllv
motlntcci . .. l, rigid moistul·e~pl"Oof Ilssclllhly is thus asslired.
T he ,·oltagc rating of all lIllits is 300 mlts (I'. Ill. s.).
l·SES. T he Typc iH) Dccude Condenscr is extremciy llscful in
,·nClllUll-lllhc oscillators of \"I1l·iublc frcquency. It pl·o,·idcs the largc capa
citance l"c·quircci for low frequency. a.nd providcs com·cnicnt \-arialion
O'·C1" a capacital](·c rangc of ]000 10 1. It is also lIseful III tcmpOritry
filtcr SCt.-lIpS lind in tuning circuits to low frequcncics.
Type 219~F DCC;ldc ('ondcn5('1" ............. . .......... Price $40.00
TCIl 0.1 :'II F. steps.
Ten 0.01 ".\IJ'. steps.
Dimcnsions 9¥2" x 5" x ;3% ". W·eight 51,4 Ibs.
Corle Wonl: COrEll.
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GE,YERAL RADIO CO.lf/'ANY
Type 219-G Condenser .... . . PI'ice $60.00
Tell 0.001 :II F. steps.
'1'el1 O.OJ 1\11<'. steps.
'f en 0.1 :IIF. steps.
Dill'H:I1Siolls l:l:* " x :3" x Un. n rcight 7 Ibs.
Code Word: llHIEH.
-- 00
AIR CONDENSERS
Ylniablc '1Il" condensers arc generally used 1\S seconda,'." sbilldurds
for all labol'lI~ory purposes fot' cftpllcitnnces lip to sCH~l'al hundredths
microfanld. Condensers for tiJis purpose must first of aI! be of such
rugged mcchnnical construction to withstand the handling of ordi
;IS
Itil!"y laboratory llM', \\-ithout suffering changes in c.ilibnltion. It is also
impol·tant that the phase angle be as 101\" as is consistent wilh phy!>ical
strength <lnd that the field tlnough the dielectric remain substftlltially
constant with changes ill ctlpHcit.\",
Hcalizing that there is an economic as well a physic:d p]'ohlem
HS
in\'oh'ed, the Gcncnd Badio Compa1l} has tlil'idee! its hboratory air
.
condcnscrs into three classes. designcd to lllCCt diffc]'Cllt. rCCjuircments of
\Jrecisioll and COllstanc.\', T h.e '1',,\) e 21:l Prccision Condenser is desi<rnccl
for usc liS II lauon.llol'Y standard and in precision Wal'cllleters, \\'here
labonttory work of less exacting character is plHnlled, the T ype ~!6 or
the T ype 2:30 rariablc ~-\ir Condenser will be founel satisf:'lctory, All
t.hree typcs arc ldike in gener;d electrical design,
TYPE 222 PHECISION CONDENSEH
Condense]'s used as stanellnels ane! 1'0]' precision meaSurCllll.:!nts must
11<I"e ]IWIIY feulun~s 1I0t usually fOll]HJ in on:1inal'Y Inboratory condensers,
For nlrillb!e standards it is essential that the plates be sufficicnUy rigid
;wel In:1I spaced so that handling the condenser \\'ill not C:luse n ch:Ulge
in capacitnnce. It is not alone sufficient that thc ])O\\'CI' fador be low,
but it is also important that the dielectric losst.:s be subslunLi(tlly I,;on
stnnt throughout the entire mnge of the condenser,
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GEXEIIAL 1111 010 COJ1IT'!l.\T
The General fbdio Type 222 Precision CondCHSCl' IS intended for
usc whcl"(, I"'ccisioll is essential. rathel' than fol' lISC as 1111 ol'(lilllHY
laboratory experimental condenser. In its design. the Illcchanic .. 1i us \\'ell
flS the e1ectric;.d fCHlul'cs hn\'c l"CcciH'd special attention.
The plates :HC of hea\'y aluminum, widely separated by acclll'atcly
tnrned SI)/Iccn:. lind fintl!." clamped hel ween suLslHntial east. mctHl end
plates. .-\ sleel shaft, clllTying the rotating plates. turllS in COlIc-shaped
brollze bearings. The adjustment is locked arlcl' the condenser has been
subjccted to it ,'olation lest to inSlIl'C the propel' filling of the ix>lII"ings.
The rotH!'." plates arc turned Ly a worm <Inc! geAr, thlls permitting
nne control. 'fhe worm is held by spring tension ill position agl\inst
lhe gear to j11"e\"cnt LllcklHsh" This is the salllc method used in aCClll"ute
di\"iding engines" T he worm is lapped in to insure perfect (il. find lhe
condellser then tested for brtcklash ill lhe I"boralol')".
ELECTRIC.-\ !... The statol" plate assembly is insulated frolll the
rigid end plates, cUlTying the rotor Assembly, hy isolnntit<- hlocks" .As
these blocks fll"e small in Yolullle, I1.lId placed in 1.\ weuk, nO'H'al'ying
electrostatic field. the condenser has 11 \"cry low power fad01', "001%
at 1000 lIMF.
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GESEIIAL RAD/O CO.llPJL\T
" fhen using this condenscl' in mCl.IslIl"ing the power fador of ab
sorbing cOJlCicnscl's the /'flct that the ficld, where the isolnntite supports
IHC localed, docs 1I0t vary with condenser setting is of importance, be
Ci.lllse it permits the tlSSlIlllption that th~ precision condenser is the equiv
alent of two condense."s in pamUel, one being a perfect condenser of
\'ol'i:\blc ca.pl.Icily, the other a small fixed condenser with which is Ilssocialed
all the dielectric losses.
The tcmpcn\ture coefficient of this cQlldcnSCI' is practically lIil,
and Ulcrc is no change in capacity with fl'cqucncy. The equivalent sel'ies
resistance at 1000 cycles and 1000 :"\1:\11:'. is approximately 11 ohms.
The breakdown potential is about 1000 wits.
Ill.'"
SCALES A="'V C,I I.IIlH..ITJO:\. Attached to lhe shuft
is a scale, divided into 2:3 equal parts. while on the \l'orm shaft is a
second scaic, the cil'cumference of which is divided into 100 cqUtl! parts.
Sincc onc complete ttli'll of the shuft moves the main scale through
WOl'lll
one di"isioll, the position of the rotary plates may be read directly to
1 part ill 2500- equint!ellt to about O.G l'd i\IF'. Since these sllb-scale
cii"isions are 1/16 of an inch {lpal't, it is easy to estimate to olle-fifth of a
division. Each condenser is supplied with v. cll1.11·t giving, with an ac
curacy of 1 l\Il\lF., the condenser caiibl'ulioll III 26 points.
Iii
MOUNTING. The condenser is mounted on a inch l.lluminulll
plate finished in pel'manC'nt crystalline blu.ck. This plate forllls the
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