,.. THE GENERAL RADIO

VOLUME 42. NUMBERS /

SEPT 1968

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

thel ~ I Experirnenter

Volume 42 NOli. 8, 9 August-September 1 988

Publ ishe d

monthly

General

Red lo

Company

<il
lK, _ G-".llodloC-_y,

w CO<OCO<d,

Mo. !./SA

CONTENTS

A Unique DC Voltmeter.. ..
Transistor Measurements with the 1650-B. _.. ".. A New Audio-Frequency and DC Microvolter. ..

GR Product Noles. ,..

"
The Central Itarlio t:,/;p~rimf"(fr i~ Jllailed each month wilhlHlt charge 10 engineer.>., ~eie"l i.1t~, t(l('h"ida,,~, edueat<lf'll, and others inlere>!ted in the jn~t r llment~ lLnd techl1illue~ or electrirnl Rud elect '"nics l11eft __ uremenl~. Addre,,-~ all eorrcsponden~ to Ediwr, Gc,urallladlQ E.r.f1Tillumler, Geneml Hadio Co., West Concc)I"(l, i\l1ll>S. 01 i SI.

----===~~--I.

A UNIQUE DC VOLTMETER
Among t he in st rum ent~ t hat. ca n he clnssiftC'd as basic or essent ial to any electrical or C'\(>clron ic:'l la boratory or prod uc tion test fac ili ty is the de vo l t~ mete r. Yl'l, wit h tiw stat(' of t il(' art in till' electronic ind ustry df'Jl1:luc:i ing incrt'::J.f;ingly spcciaii1.ro in strulllC'nts. it is difficul t to fi nd 011 (' "basic" voltmeter to mret lhe 11('('(\8 of ('W'n sc\"cra l p rojects ill a ginn resea rch a nd de\clopmcnt {'ente r. Gcnern l Radio' s ne w TYl' ~; 1807 DC' :\licrovoltmctcr ~n ll oa mmcte r was designed to fi ll t his.< \'crs.'lliiity gap." It combines til(' features of microvoltmeter, na noammcte r, null de tect or, and
diffcrt:'lllin l \oltmctcr, all wit h 0.2% tlCCu racy. \ s a mic rovoltmelC'r it. offers nine d('('ac:it' rang('s, fro m l:i ~ \ r (with rcsolutioll of 0 ,0,-, j.l V ) to 1::;00 volts ull-St'3\(,. \ 1\ input fi lter is also p rovided for noi&' suppression. As a II:Uloanlllletcr it ca n rcad currents from I:") pA (O.05-pA resolut ion ) to 10 111.\ fu ll-sea le.\ 5 a null delft'tor it has a commonmode rejl'ct ion ratio of greate r t ha n ]()() d B ami a th rf'(,-8econd rceo\'cry time for a lOS owrload.\ 5 a d ifT{'rent ial \'oltmclcr il. offers nCClI fn{"y 10 li mes hettN t ha n t hat of conventional vollmet('f:;.

the[;j Expe rimenter

. OUT..

L __ _ ______

@ ___ o

_ __________.1I

,,' v 0-

""UV

The instrument can be operated from a 11:).-22Q.yolt ac line or from a 2.Jvolt dc supply. ,.,.
Meter ood Outp ut Circ uits
FL.. 1. BLock d L olrom 01 TYP I 1101 DC M l. oyolt. t./ No noom. t.

GENERAL DESCRIPTION

Figure I shows the block diagram of the 1807. What. may not. be obvious from lhi!! diagram is the method of achic\'ing such n high commonmode rejection ratio, The key is Teflon' insula tion to ground at. nil connections to the high and low terminals. for example, lh(' meter is ('omplet('ly iso-lated by T('flon from the front panel. E"en in the power transformer, Teflon is used as the insu lation bet.ween wind ings.
An unusual meter scale (sec Figure 2) helps to impro\'e the aeetlrtl.cy of read ing and to provide higher resolution for null detection, ~ote that the meter is logarithmic above 10% of full sca le and linear below 10% of full sca le, The zero

fi.. 2 , M it. teotl of Ih l l.07.

";"<11

_~':'O~:'~~~':'__r--ll__
+-j;~Uf!;;'<>---r--- ~~

Si mplifi ed

dl o g. "m of th. 1101.
is othet by about 20 degrees to allow the user to wke read ings about zero and still I'('SC-r\"C most of the meter movement for higher resolution. A frontpaneil>olarit.y switch enables the user to utilize the proper region of t he meter. The de outpu t amplifier (:lI1l suppl,\' 2.5 vol ts or l rn A, enough to drive most recorders. This voltnge is adjustable at t he front. pllnel. Any load , even a sho rt circu it. at the recorder terminals, will have no effect 011 the operation of the instrument.
,.., Interpola tion-Offset feoture
1'h(' interpolation-oifset feature a llows the llser LO read t he d iffere nce betwccn two signals to wit hin 0.1 % of reading plus 0. 1% of full-scale accuracy. T he uscr, in setting t he interpolation. offset. switch, subtracts from the input. u calibrated voltage equal to the most. significant figure of t he unknown ; he then reads t he differencc in t he COlwell tional man ner (sec Figu re I), With this feature , t he lS07 achieves nccu rncies usually associat.ed with digit-n. 1 tech niques, while preserving t he versatility of nn analog instrument.
Input Circuitry and Connectors
J>Cdance of the series--shunt. cadmiumselellide (CdSc) photochoppcrs used at Lhe input. of the instrument. The selection of n photochoppcr modulator was made in order to min imize noise, drift, a nd offset. Figure -4 shows a recording of the output. noise of t.he IS07 in t he pieonlllpere range with no sigllill appl ied to the in put. (T here is n I-megohm resistor ac ross the input terminals Oil this range.) One very annoying problem in the measu rement of low-level dc is the presence of thermoelectric ,oltages generated when junctions of dissimilar metals are at. d iffere nt temperatures. Since it is difficu lt to keep all parts of the instrument at the same temperature, care was taken in t he design of the 1807 to tlSC copperf.Q.-copper junctions at all points of the input circuitry. Thus, the input binding I)()sts are goldplated copper and tbe photocell leads

----- -

The high in put impedance of the IS07, even down to t he microvolt. level, eliminatcs a lmost. all loading errors. T his impedance is achieved by Illeans ~ f the high loop gain in the error :1m plifier (sec Figure 3) and t he high im-
FIV"'. Ruo.d ln, 01 'h. o,,'p,,' noi ~ "". n' I. d '0 'h. Inp'" wl'h 1 M fl 0 ~' 0 1l ' h. In p'" '. ,m lno t .

the[;j Experirnenter

APPLICATIONS
Because of its versstility, the 1807 ,.-. will undoubtedly fmd applications in physics, biology, a nd chemistry, as well as in electronics. Thus the applications discussed below shou ld 1101. be interpreted as being the prime uses of this instrument.
Diode or Transistor Matching
FI"u 5. lI.co.din" of 'h. I. o~o". cUff.n l for "Typ. IN 3604 dl od. cycl.d Ih,ou"h" I. mp.'o'u ,. chon". C 0C.
arc Dumct, which bas a thermoelectric voltage coefficient similar to that of copper. The high inpu t. impedance of the instrument make::; it feasibll:' to uS(' nn RC low-pass filter with n cutoff frequencyof 1.5 Hz at the input. This will fi lter out any ac noise that may be superposed on thl:' de signal. For fu ster rcsponse time, the filter can be switched out by means of a front-pane l switch. As an nid for routine voltage :md current measurements, a Tektronix 1:1 probe (no attenuation) is available as an accessory. ~ote that this probe should not be used at extremely low voltage and cu rrent levels.
Quite often it is desirable to match a pair of diodes for leakage current. or forward vo l t~'lge drop (emitter-la-base voltage ill case of transistors). The 1807 can be used to measure the forward voltuge drop with a high degree of accuracy (using the interpolation fcature) and thc reverse leakage currcnt. with high sensitivity. Figure.5 shows a recording of leakagc current for a typc I ~360-1 diodc cycled through IO"C to 4.0"C.
law level Differential Measure ments
For com parison of various standard cells (c.g., saturated ycrsus unsaturated), one is interested in making d e differential measurements of a few hundred microvolts with accuracies of about. 1 or 2 p.V. Figure 6 shows a recording of differential measurements

,-.~.-

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" !I

"I ,

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!I 1 I ;

': i ' : ; ! : ,

fltur. 6. Roc o,dint of Ih. d.lft of Ih. voll"t. difh,.nco b.lwOIn IW" un""lu,,,,. d oIond",d UUl "I 2S oC.
AU ljl u et-September 1968

.,. !1

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! I , , it-.

I,I I, i i.
over a Due-hour period, shows the thermoelectric voltage betwccn t he two junctions of t he t hermocouple to va ry between +81J.V and - 28IJ.V. Thu s, t he temperature va riation is concluded to heaboutO.9C.

High-Value Re$islance Measurements
Flgu 7. Ru o,ding of th e th. rmo e lec l,;c v o llag. g e n '.ol,d by " th t, mocoup t

'"

Figur.

'0Tu t l-u p

f".
m e """;"11 II n.nown
The low-Cllrrent sensitivity and the high accuracy of the 1807 make it. suitable fo r \'ery-high-resistan cc measurements. Figure 8 is a typical setup for such measurcments. A nominal current i of pA at 50C was measured with the 1807, using the in terpolation feature (Figure 9). Thus, the value of f? at :lODe is calculated to be \ n.7.j X n. _ s the temperature was dropped to O C, the cu rrent measured by the 1807 decreased to 376 pA. The resislfill ce of R. at OC, therefore, is 1.00 X 1011 U. 1\. C. Ih.: IWJ IAN
r\ brief biography of :\ Ir. l3alekdjian Ilppeared in the :\I&y 1965 issue of the P.xperim~ '!ltr.

1$10. II.

for two unsuturated standard cells. Th is recordinK, taken over a two-hour period, shows that. the cells difTercd by :~8.1 p.V at the beginning of the test and by 36.8 p. V nt the end of two hours. The test. temperature was 25"C.

Temperature Measurements

li'igurc 7 is a recording of the thermoelectric voltages generated by temperature differcllce between two points in a non-nir-conditioned room. A copperconstantan t hermocouple with a temperature coeffi cien t of :19 j.I V;oC was used in t.his test. The recording, taken
fig ",. 9. R.cluding.ho. ing th e change I" c"" e nl i (Figu re. ) a. th e Q ambl e nl tempe".I. e ch ang n "am 50 C to OQ C.

SPECIFICATIONS

. -. - Vo ltag e (either polarity ): 15 ",V to 1500 V rll11 scale in 9 de<:we rlUlges ; O.05-~N Idiv rC!!Olution near zero o n m()!ltllensitive ra nge.
Cu"ent (either I)()lnrity ): 15 pA to 1.5 rnA full scale in! t deude TILuge!!. O.05-pA / div fC!!Olutiou !lelLf ~ero on most genllitive rnuge.

the [;jExpe ri men ter

ACCU l ACY
1t. " _Cu.. t lnp.. TI.,. (t.ypical): 0.1
.c.,.-C. ". lI.. '!'y : (O.II( of reading 0.5 ~V). ,.,po ,. , [O.I (' r of fulllltale (ra nge ) + 0.1 '{ of reading + 0.5 ~Vl. 0 1,. ( L5f( of re!Ld1ll1t; + 0.5. V) above 10"" o f fulileale. (0.15~~ of full acale + 0.5

"ith filter (0.6-111 bandwidth)

. V ) belo\\

of fulillCale.
To.,p h. C ff lcl.nh (' y p l I). C. h D. lfl : (0.001 % of full
+ 0.15. V ) per d egree C. + 0.001 ", of fullacale + 0.15.V ) per degree C. 01. : (0.02'1- of reading + 0.001 'f of full leale + 0.15. V) per degree C.
I",. ,polo'" (o.ool C} of reading
.ithout input filter ( 1.5-Ih; bandv';dth ), 0.3 II 011 all rangee abo\'e 15. V; 10 timeelliower on 15-. V range. M. I.,.., 0. : Voltage: 150 V on L5-V range a nd belo"', 1500 \' on 15-V range IUId above. Current: 10 rnA max all rangetl. O.. I d. ~.. y TI. : Approx 3 II for 10" overload. It. ,d. , o"'pu' : Adjulltnblc UI) to 2.5 V open circuit for fullllCllle meter d eflection; 1 rnA into 1.5 kn max load. GENERAL T., I. I., Gold-plAted coppe r binding poeUl on front and reAr p:mela. GfO\lod eODlIection ou rear panel only. Battery I:Cn llection on rea r
INI'UT IM"lDANCl V. It , 150-. V to !.Ii. V ra~ee, > 500 )lfl on direet IUId typically 5,000 Ma on interpolate: lS.~V range, > 50 :\10; IS-V to 1500-V r&!l~, 10.5Mn. Cu".,,', Internal Shuntll, 1 : O in pA-,wA range., U I kOil! nAomA rangea. M.,." Single Kille f rom -1.5 to 15. l.ogtlri lhmic (20 dB) above 10"4 of fullllCale. I. p. ' Cu. I: Leu than 5 pA. N. I J TYlJieally 0.5 ,wV for 3<r with 1 IUl aer08R input. c .,.,. M. > 160 dB for d c. ith up to 600 \' dc max above ground ; > 120 dll for OO-HI common. mode 8ign,.J. of <8 V pit with input filter.
".w Itoq.,. , lOS to 125,205 to 250 V, 50 to

panel.

"i"".n :
60 Hs, 5 W. Aiao operatea from extern!!.1 2-1-V d e Bupply ; 153S-P3 Battery a ud Charger recommended. Au. ". 5. pp ll. , 2N-QBJ adapt.ll binding poet.ll to B~C ; fu8C ; power co rd. A. 'I. A. II.bl" Input 1)l'obe, Tektronix type P6028 ; 1538- 1 Batwry and Cha rger. '3 M.. U. " Convert.i.bl&- Bench Cabi net. Dim. I.n. ( \I\idtb x height x depth ): Deneh, 12 x 5J{ x 10),{ in. (305 x 150 x 200 mm); rack, 19 x 5 J~ x 81~ in. (~ 86 x 135 x 2'20 mm). N. I W.iehl : Bench, !)li Ib (~A kg); rack, 101~ Ib (~.9 kg ). Shlpp l., W.I,hI : Bench, 16 1'2lb (7.5 kg ); rack, IS lb (8.5 kg ).

DacriptioPi

1107. 1107'170' 1107 960' 1'07 DC M lcr.""'. '. / N.n "''''. '

kn. h Mod. 1

Itack Mod.1
Inpw-l probo, Toktro<tlJllyp.
"6028, Cal. No. 0 10.0074_00
TRANSISTOR MEASUREMENTS WITH THE 1650-B

As mentioned in the ;\fay h'xperj.
menter, the new TYPE 1650-B I mpedance Bridge is useful not only for routine measurements on passive com. poneots but. also for measurements of transistor h-parametcrs. The special test jig required for such measurements, as well as the procedure, is described

below.

ind icate how to obtain the rou r. tcrmina l parameters hI. nnd h from two-. terminal measu rements appea r in Figure 2. Some thought about biasing the

____- L__~-+~~_"

The h-parameters are defined in Figure I , and the calculations that.
f l,. I. E"u l. I. , cI. 1t.1. ".n. II ' ,. h. wl. , h.w Ih. c.,. n-. I" h.p.,.,. nn.

-"

h"

I;"

V1 Vir!

y"

substitute and combine to get

h i/'hC)t' - /lf~hn

"'"
hrt' "'" Rir/ (hOI! -
transistor SO as to isolnw t he particular impedance we want. to meas ure yields t he test circuits of Figure 3. These may be built into n conven ient test jig using rotary switches or toggle switches with shielded leads going to tJIC 16.50-B'5 unknown terminals. The shields should be connected 1.0 the 1650-B casc to guard out. the stray capllciumce 00~twccn the center conductors. 1t. is helpul to have the 1650-8 plastic-con ted
condensed instruct ion sheet. handy during measurements so t hat Il"" the ratio-arm rcsiswn'Cc, CU ll be determined. The procedure is as foll ows: n. Usc the /(., bridge llnd the h" test jig ( Figure 311), Turn the ose I. En:L control way dowl1 to ensu re a s mall signal measurement. of the forwardbiased base-t<HmitU!r jU llction. The diffusion capacitance of the junction is balanced using an ex ternal capacitance

the [;JExperirnenter

~E$Qf<.,.t

OM. 10

SII Un ' "G

""

FIIU,. 30.

"i, '.0'111.

".

cU)S( SW'TPI TO MU$Ull:t Y. Of'(N MU~ft.

",

Fllur. 3b. Th. It. , , III.

n."DARD

g.".
decade box connected betwccn the HlGII UNK terminal and the 1650-13 ground. h,. is usually a few thousand ohms and 10 kfl Cill = - - Cd.de , fl. where Il.t is the value of the ratio arm in kilohms ( 10 kfl on the I-kf! multiplier range), b. Throw a switch tbat connects the base to the collector with a large capacitor and measure R ;'" which will be about 26 ohms for an emitter current of I mA. Calculate: tor level for increased sensitiv ity Measure h. directly in micromhos and balance the outpu t capacitance, C., with the external capacitance decade

"'0=

Cd. de , II. where IlN is t he reading on the CGRI, dial (0- k) in kilohms and R.t is the value of the ratio arm in kilohms (100 kf! on the X IO-micromhos range). d. Throw a switch that connects the base to the em itter with a large capacitor and mensure Y in micromhos. Calculate: h = Hi" (h~. - V). -C. H AVE NER

box. Calculate: Co

c. Usc the G". bridge and the h test. jig (Figu re 3b) and turn up t he oscilla10
A brief biography of " Ir. Havener appeared in the :\lay 1%8 i.'l!!ue of the ";.r;perim(!nur.

.:.:::=----~

A NEW AUDIO-FREQUENCY AND DC MICROVOLTER*
Just. as in 1933 when the first. Genernl Radio :\ticrovolter W/18 designed. thert' is still a need for an independent metered Ilttcnufitor to obtain de and audio-frequency \'oltnges at til{' microvolt level. :\Iany modern sources of no signals, particularly of nOllsinusoidnl oncs, nrc not metered and do not have an nttcnuutor with the range or the shielding rtXluired for working at micro\'olt potentials. Yet the nccd for such a low-voltage source is cleaf, especially with loony's wide usc of v('ry high-gnin operlllionlll-nmplifier techniques. A :\Iicro\'oltor i!'i simply a seUcontained step nttcnuator preceded by (l meter and 11 continuously adjustable potentiometer. Th" meter Ilnd poten~ tiomctcr establish the input \'ohage of the nt.tcnuator over a olle-dccadc range,
and this is then reduced to the desired len!'1 in decade steps by the at.tcnuator. The range of the instrument. is determill()d by the hilt-scale sensitivity of the meter and by the amount of attenuation. The new 1:J46 Audio-Frequency ;'I licrovolter, the third generation to follow the originaI5W, has many Ilew features, of which the two most important. are a dc meter scale and an internal battery, making it a self-contnined "floatable" dc source. Output is adjustable from I ~\' to 10 \' with either polarity. Goldplated copper hinding posts and careful COllstruction keep thermal emfs ncgligibleeven nt. the lowest. microvolt. levels. An on-off switch, which in the ofT posi T.. ~m. r. recittered ill USA.

the [;l Ex pe rim e nte r
tion maintains thc GOO-ohm output impedancc, permits casy dc zcro setting. Since the impedanc(' of the source remain s the same, any offset. \"oltage due to input current. will be the same wit h or without the signa l applied and will not. affect. incrementnl gain measuremcnts. The floatnbility makes it. easy to f~pply a common-mode signal to measure common-mode rejection for various dc inpu ta. The bat.tery elUi be removed !\lId an external d e 8upply used if complete isolation is not needed or if )lacement. is an periodic bat.te ry f'(1 inCOll'"cn iencc. The abilit.y to superpose a small ac signal 011 the dc grClltly increases the usefu lncss of the :\Jicrovolter. If one wants to know when a d c amplificr is operating in ils linea r region and when it is in saturation, he CB Il simply superpose n small ae signal 011 the dc t hrough the input binding posts and check for t he presence of this ac at the output. wit h an oscilloscope. Ac operation is improved also. A fu ll 10 volts ac is available when the Microvolter is uscd wit h the common 20-\'0It, 6OO-ohm aud io oscillators on t he Io-volt nc full-scale range. A I-volt ac fu ll-scale range is pro\'ided for sources t.hat. hnve lower out.puts. The mini mum fu ll-scale outputs are 1 and 10 respectively. T he meter is calibrated for t he rms value of :l sinusoidal input, with t he s tated accuracy extending over !l frequency range of 10 li z to 100 k Hz. The- nttenuat.or is accurate to c \'cn higher frc<luencies, but. lenkage from the source oscillator, radiation from connectors. and ground-loop effects of~n exceed microvolt. levels at fro-qllcneies aoo\'e 100 k Hz. Distortion in t rod uced in t he signal of the ~ Ii c ro vo l tc.r is reduced to a level consistent with t hat of typical sources with which it. may be used. The output.

Il"

f l. ", 1. aro. ~ clr m of th. 1346.

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.eo O(

"01-'

"."IIT

L[I/(\.

August-Septe mber 1968

on-off switch that can reduce the outpu t to zero while maintaining the Stlille GOO-ohm output impedance is fully ns useful with n.c signals as wi th d c. Noisc ~urces due to ac pickup and ground loops nre much casier to measure and to locatA:! with the signal relllo\'ed and with the impedance level , shielding, and circuit configuration relllaining the same. In addition to positions for the one de lind two ac sensitivities, the meter has an ATT t :S ON"Ll' position in which the meter is out of the circuit, leaving just the step altA:!l1uator bet.wccn the input and output term inals. This is desirable when the signal is of unusual wavesbape, as for example, a. tone burst.

Figure 1 is n block diagram of the
1:)46, show ing the circuits used in t he
differen t modes of operation. Note that. the battery is used in the de nnd 1- V nc posit ions only; the meter is 3C1fpo\\'cred 011 the to-V tiC range. This is t he range most oftell used, beca use of the profusion oi 20-vol t audio oscillators available, and t he battery thus should normally ha ve a very long life. The battery is an inexpensive nnd readily available type. - R. E. OWEN
A brief bi()Jl;!liphv or.\lr. Owen BPI~red in t he J an uar}' 1008 i~le or the EZPf!tHMnkr.

ACKNOWLEDGEMENT

The Buthor IIcknowlcdges the alMistance of Peter Young on the att.enuator and Alan Ombrello 00 the meter de!ign.!l.
SPECIFICAT I ON S "'unction
Opon.C I.ouil Oulpul \10110, 0 Acc u.oo., olU oe

1.0 "Y W

10 Y!I.e

10 l' ac ~--

.ltl4:n Only

1.0 " V to 10 V de

0.1 "V w 1.0 V ao

O to -l 20dll

20 d 13/800(1
(0.0.t d lJ!.tel) + lMdUbelowinJiut level) de to 100 Idlz
(.100". 10% 01 do lull. al.)
(4%+0.2jN ) (o& %+O.0'2,11 V) (3%+0.2 "V) 10 l iz to 100 k ill External ae requirod 1.0 V into.'iSO 0.

10.0 V io w

&15 11

Inpul Imp.donco

(opp." )"
Internal ballery or ell E,xt ac or d~iource d c lIOurce 10 V max 10 V DIU illl)ut
Co lO n to 25 kll \\'ith iot bllttery removed

005 n w 25 kll

to 5 kl1
Inpu~ ImpedaoH.an. oh. i. lahlo. ,\.b MU. 01 input If\'fl ~. ttol. ('u bt adjuUed 1<1.tonai. (ODlIan t. h. "'Y'''. the oloop atWlluatoo. 10. l-t impedallcD 01 ","SO U.

Dld , IDo.

(at I klh ): < 0.01 '1, io I-V_ac mode, <0.05'1. io IO-"-ac mode. wilh level con t rol III
mllX !letting. Oll'pul I. pod o". : 0001"1 0.5"}.
Po"'o' Rtq"I d: ~'one te(llIired. ror 10-V-uc rMllge. In other modell, 12-V dry batlery: F, \'ereIW\' 228, RCA VS329, or BlItge8!I PM8. Approx iife, 3.1 bours at 2h / day in either d c OIode. 316 houl'll at 2b / day in I-V-ac mode. Mou. I1", : Convertible-l3ench Cabinet.
.0. S. ppll. oI , Ilnttery; OIoo nling hArdwith rack model. e. o. Avo llabl.: nit 1301J-A Ilnd lalO-A OacillAtol'!l, 139&-1} T OIle- Hurst GenerAtor, 1381 lind 1:l82 1tn.lLtlom.~oi!!e Gcnerntol'$. OI. e". lo". ( w x h x d): Hench, 81~ x 7 1, X 7~ in. (220 x 100 x 100 mm); rack, t9 x 6 x i i i in. (.tS5 x 155 x 195 mOl). Wol,hl : ~et, 51 ~ III ( 2.' kg); !hipping, 9 Ib (.t. l kg).

Ducription

1346 A"dlo. F.equo" ., Mlelo".U "

13169700 13169701

b" ch Mod.1 la ,," Mod.1

lhe [;J Expel'imenter

NEW SHiElDED SWITCH MODULE
The I ;72-(>3 module extends the capabilities of the 1770 Scanner System to the automatic scanning of signullincs by providing high isolation of "ignals up to 100 )'1IIz. Isolation betw('('n lines is 120 dB at. 500 kHz, 100 dB at. 1 MHz and 60 dB at. 100 ),1 1L Pulse reflections z. are typically less than 15%. Othcr switc h modules, the 1772-PI and 1772-P2, accept input lincs in n singlc shielded bundle; j he Ilew 1772-P:~ accepts H'\"('-terminalCd cables. All three will switch 10 cha nnels per module, thus providing up tl) 100 channels in n single 1770 Scunner System. The ~yst.em has six scnnning modes, with frontpanel mode selection. The 1772-P3 switch modu le contains ten dry-reed relay switches. Each relay requires I:") Vat 30 mA to opera te. The module i'l a special-order item , and the customer can specify the program boards, !Switching methods, lind 8hielding tbat su it his application.

-. ~ j -.

~."

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Iloh.lio" betw. " cho"" , th , 1772. '3 (d"". I" ed b,. " ,;2;", 0", ch,,"" ,I, o,pl,I", a 11,. al Ihra. ,h II, and. a. I. ' th ,.1,. 01 On " , " " ,I ud ch a"" ,1 with 50_11 d , t,do, ).
Typica l of the ma ny uses for the 1i72-P:~ is that of mak ing automatic frcclue ncy-stability tests on many oscil.-"'"" laton, or R ignal generators. While tbe shielded modules connec(, the oscillator outputs in sequencc to a single counter, the output data from the counter could also be switched, in order, to severnl recorders 01 to other logging devices through other modules.

PRECISION CAPACITOR

The 1'12Z-CE is a stable and precise variable air capacitor intended for use as a continuously adjustable standard of capacitance. It is a dual-range, threet('rminal capacitor with shielded eOi\xial terminals for use in three-terminal measurements. The calibrated direct capacitance is independent. of terminal capacitance to ground and losses are very low. This lowcapacitnnce member of the 1422 family has ranges of O.OO.j to 0.11 pI" and 0.05 t.o J.J pr, resolution of
0.00002 a nd 0.0002 pF per division, rcspccti\'ely, a nd will s.'H isfy thc special requirements for usc in the Harris ultralow-frequency capacitallce bridge'" built at the National Bureau of Standards. Specifications arc comparable to other models of the alt 1422 and arc given in full in Catalog '1'.
I'. 1l1UTlI. '.'\ S.. I'lt.lo. ~'Hqueney Hr;d '~ DleleeVic Me).tu"""eftt." 196/1 A~". al N.,.rt. CuI' "" Hlffl";tOl f".wali~" ond f)i.l.cen< I'Ao"n. u. , 1 ~e72.
NEW DIGITAL LIMIT COMPARATOR FOR 1681 AUTOMATIC IMPEDANCE COMPARATOR SYSTEMS
00010 DOOIO 01!00 OlO"
Thl' 1783 Digital Limit Comparator is !<imilnr to the 1781 (an ncc('!o;sor,Y to tile 1680 ('npnciwncc Bridg('I), but it hn~ (''l:pnndcd cupabilit ies for uS(' with tile IGSI.\uto01ali(' Impe<iall("c Com

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The limits are SC't manually on rows of
thumh. whccl swit.chcs. A 1681 impc<iance comparator and Oil(' or more 1783 limit comp:1rtltors
\\"h('11 \I'it'd with tile 1681 l'omplU"a torI til(' li8a automatically m:tkt,~ ("om
pnri'-l()II>; l)('tw('('11 th(' metl!:;III"{'(1 digit,., und th~' limit digits and pre.''nls thl' re~ult., us n panel-Inmp di"play and II!' ,,-.rd:ly-contncl ('io!<ur('s at :I rellr.paut'l ('OI1lH'("tor. Thl;' 1783 has incl{'jl{'ndC'ul uPI~r and IOWN ;j-digit limHs for hoth impNlulI(,(, Illllgnitucll' ami phtlM' 1I1l~1("
form a complete testing system thut allowl! nil opcrator to sort componelltR IlUlIlllUlly into preciS(' cat('gori('~. The&' in~trttmentr; (':In illso h(' uS<'d with nutolllntie hundling ClIUipllU'lIt. Till' I 78:i i" :l~mhled on 5pc('ial ord('r. [t j.; lwailablc citll('r alone or in :l.~-,,~k>m ('II!';tom d('~ignNi hy Grllcral Hadio for your npplication.

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DC LEVEL CONTROL FOR THE 1398 PULSE GENERATOR
.\ IlCW ncc('~ry call l>t~ u.scd to l'on trol th' dc h~\'cl of thl' output puiS(' of n 1:~9g.:\ Pulse Generator. TIl(' ('on trollcd p:Jramcl<'r may lx' :l\rrag(" positivc lX'ak, or negative Ix'ak, and ('ontrol is independent of duty rntio and prf Tim(' ('on stant of thl:' rf'gulnting eirnLit (':)n hc ~lect('(1 according to (IUtput pulS<' durn lion. TIl('.:mSPl 1)(' C'OIll I)OIlCnl COIlnol :ltt:)che~ ~() the !';icit, of, and derives POW('f from, the pulse genrrator.

,OVERSEAS)

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