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INSTRUCTION MANUAL
MODEL I65
DIGITAL MULTIMETER
0 COPYRIGHT 1975 KEITHLEY INSTRUMENTS, INC.
PRINTED JANUARY, 1977, CLEVELAND, OHIO U. S. A.
CONTENTS MODEL
165
CONTENTS
Tit12 Page . 4. Accessories
CO"td"LS . . . 4-1. General. . 15
LiSC Of IllusCrac.ions. . . 4-2. operating Instructions . 15
Specifications . . . . . 4-3. Model 1651 50-Ampere S~UOL 15
4-4. Model 1653 Rack Mounting K~L 15
1. General DeSCriprion
1-l. Introduction . . 5. Maintenance
l-2. warranty Information 5-1. General. . . . 16
1-3. Change sotice. . . 5-2. Recommended Tesr Equipment 16
1-4. Features . . . 5-3. Performance YerificaLia" . 16
5-4. Calibration. . 20
5-5. companenr an* Calibration
4 Layouts . . . 27
5 5-b. some Semiconductor case ouc1ines
5 and Pin Identificarions . 29
5 5-7. Tra"bleshoati.ng. . 31
5
6 6. Replaceable P,,CS
7 b-l. General. . . . . 34
. 8 b-2. Electrical Schematics and
. 9 Diagrams. . . . . . . 34
9 b-3. How to "se the Parts list. . 34
b-4. How LO Order Parts . . 34
3. circuit Descripeion 6-5. Chassis Pares List . 35
3-1. General. . . . . . . 10 b-6. Electrical Parts List. . . 35
3-2. *c-"o1cs Preamplifier. . . 10 6-7. Mechanical Parts IAt. 49
3-3. DC-vo1rs PraamplFfLer. . . 10 b-8. Code-to-Name List, . . . 50
3-4. OhrnPcircuitry . . . . . . 11
3-5. 1-d currene source. . 11 7. scbmatic Diagrams
3-b. DC-r\mpsPreamplifier . . 11 7-l. 253950 Block DFagram. . . . . 52
3-7. *c-Amps Preamplifier . . . 11 7-2. 2539ZE AC & DC Preampltiier
3-8. hipolar Amplifier . . . 11 SwiCchtig . . . . . . 53
3-9. AD ConverCer . . . . . 12 7-3. 253930 "*ipolar Amplifier 61
3-m. Clock. . . . . . . . . 13 A-D canverrer . . . 54
3-11. Logic. . . . . . . . . . 13 7-4. 255080 Clack & Switching Logic. 55
3-12. Display. . . . . . . . . . 13 7-5. 25511D Re y b Drivers. . . 56
1-13. Power supply . . . . . . . 13 7-6. 25394E Readout and logic. 57
7-7. 25391c Power supply . . . 58
ILLUSTRATIONS
`ii
t .
SPECIFICATIONS
AS A DC VOLTMETER
SECTION 1. GENERAL DESCRIPTION
I4 h,.:, ,`,I,.,.:\' 165 AUTORANGING MULTIMETER
I
POWERON CR""Nu INPUT INPUT
s-301 3403 `0 HI SOURCE S40lA S4OlB
5402 3401 5402
CAL CONTROLS ANALOG CAL POWER LINE LINE FLiSE
OUTPUTS CONTROL INPUT SWITCH SWITCH F301
P304 5303 s302
MODEL 165
SECTION 2. OPERATION
b). AC Ke,ecrim. The Model 165 provides
artenuation of line frequency noise superimpose*
on a dc input signal. The ac re,ection Of the
165 is specified as follows:
NOWL MODE kE.lECTION RATIO (NMI(Io: Greater
than 60 dB above one digit for a voltage of
line frequency o= twice line frequency with
at leas= 10% of full-range dc applied.
COMmN MODEREJECTION RATlO (cxea): 120 dB
on the 10 mv, 100 mv. and 1" ranges; 80 da 0"
the 10" range; 70 da on the 100" range; and
60 dB an the 1000" range; far a dc, 50 HZ, o=
60 Hz voltage with at least 10% of full-range
dc applkd.
3. Magnetic-fFeld Noise. The presence of strong
magnetic fields can be a possible so"=ce of obJec-
eionable ac noise. The Model 165 has been suffi-
ciently sbialded from typical magnetic incerfarence;
1. Tbermoelecrric Naise. Potentials generate* however, additional shielding may be required at the
by rhermal differences Bf rtle junction a= ,unctions eo"rce or in the cabling to the 165. Magnetic flux
of Ed0 dissimilar metals are thermoelectric noises, lines which cue a conductor --- like an input cable
more commn1y called thermal mm. These potencia1s --- can produce large ac noise, especially at power
may be significant when making millivolt or mic=o- line frequencies. me voltage induced due to nag-
volt mea*uremencs. TO minimize ehermal nOiS* --- neric flux is proportional to the area enclosed by
which may appear as a drift --- caused by thermal the Circuit *s well as the rate of change of mag-
FXYO, use PUT* capper circuirry emi tswinaricms netic flux. POC example, the motion of a ,-inch
thrau*iw*t the source an* in a11 connectians to *iemeeer loop in the earth'. magnetic field will
ehe 165. The KeicNey accessory Model 1483 Low induce a signal of several tenths of a microvolt.
Thermal Connection Kit contains all necessa=y ma- The ac rejecrion characteristics of ebe Model 165
cerias for making very law-thermal copper connec- vi.11 help minimize specific effects of magnetio
tions for minimir*n* tharmal mm.. fields. Magnetic pickup may be furthe= minimized,
by arranging all so"=ce and input-cable wiring so
2. AC Power Line Noise. The presence of electric L&E the loop area enclosed 18 BB small as possible
fields generated by power lines o= other power (such as by rwisring input leads). "sing conetic
.9O"TceB can haYe an effect 0" inaaur,ent operarim. (magnetic) shielding in cables and around cirwia-j
Also ac vok?.ges presenr in Ehe BOUrCe which are may further help in seve=e cases.
very large vith reapact. to the full-scale range
sensitivity of the Model 165 could drive the analog b. Effective Shielding. Here are general shielding
amplifier into sa~uracio". producing an e==OneO"a rules fo consider far measurements in the three func-
digiral display. tion categories of the 165. Be sure that shielding
is even needed before proceeding.
a). Shielding. Proper shielding of the sowxe
or cabling can minimize noise pickup when the 1. Yolemeeer maaurements. Consider shielding
instrument is in tile presence of large ac fields input leads when sou=ce resistances a=e g=eaCe= than
or when very seneirive me*e"rements are being 100 kilc,hm o= when long input cables are used. Avoid
rude. `ornoiae shielded cable, such as Keith+, even slight movements of input cabling a= Ct\e oource
SC-9 cable, should do a sufficient job of shield- when making high s.au=ce resistance measurements.
ing rhe inpur signal. Metal shields may be re-
quired LO be installed arD""d the BOUIICB. me 2. C"rrenC Mea8"reme"C*, on the mA and ii.4 current
shields of the inpur cable and source should be ranges, generally no ape&a1 shielding precautions
connected together co ground at ooe point only, need ba taken. However, consider shielded input
typically at the input of the Model 165. This leads for me~~"=ements an the lowese ranges.
one-point-ground method ia a frtree'f configuracio",
which minimi=es ground L,ape in the measured cir- 3. Reeiscance *easuremenc*. Shielding Of the
cuiery. Ground loops are a secondary source of input cabling and sou=`ce may be necessary far meas-
interfering noise Which may also be considered in "remente on the 10 megohm and 100 megohm ranges.
larle"el meee"reme"ts.
4 1073
.~.
P .
C. If 400 HZ line "OlrageS are LO be used, COnSUlt
the factory applications deparcmenr or your local
Keithley rrpresenrarive for instructions.
d. Turn ox power Switch 5301.
2-3. CONNECTIONS. (refer ta Figures 2 and 3).
a. Innut. Three binding posts are provided an
the frO"C piln.21 LOT input connections. The cermina1s
are color-coded a* follows: red = input high (HI)
5401, black = input low (LO) ,402, and green = power-
line ground (Clm) ,403. These terminals mace Wifh
individual "ban*"*" plugs similar LO Keichley Parr
NO. c-5, The from pane1 terminals are spaced with
,/Ii-inch bewee" centers to mate wit,, a standard
dual "banana" plug such as Keitbley Part No. Lx-,.
Banana-plug-co-alligator-clip cables (available
through my local electronics supply house), such as
two Keithley Part No. 181620 cables, are ideal for
fast connections to the 165 input. The shorting link
provided at the input should be connected between LO
and cm for grounded operacian. IC is preferable,
to minimize rhe pas5ible effects of ground loops
(small mrrents flowing in the ground system), that
there be only one ground point in the measuring
syseem. If possible, connect all grounds together
at one poinr, ideally ac the CND input terminal of
the 165. 'Tire input ShorrFng link should be removed
for floaLi"g OpcrdLiO".
b. AC VOLTS OwraCion. The Model 165 provide5
five and one-half decades (six ranees, of ac vo1caee
T .
2. I"WL Resistance. me input reSiSCa"ce of
the 165 on all ac voltage ranges is I megohm 110%
shunted by less rhan 75 picafarads of capacirance.
3. Accuracy. The Model 165 detects the average
value Of a" applied input ac waveform. The display
of the 165 is calibcnted LO indicate the n,,s value
of an applied sinewave. The accuracy (error Limit)
calculations given in Paragraph Z-ha, ah.0 apply
far ac measurements, except cilai 20 HE and ZOlcHZ,
the specified accuracy is asymmetica1. Reference
the specified ac-volts accuracy ranges a~ 20 Hz,
lkkiz, an* 20w*. Typical aCCUraCy bands at non-
specified frequencies ace shown in Figure 6.
5. rlaximum Allowable Input. Ihe maximum contin-
uous or i"termifLe"t input voltage which calI be
safely applied 0" manually selected l-volt and lower
ranges is 250 "0lt.S rms. when aperacing manually
on the 10 volt to 500 volt mls ranges or in the
auroranging mode on a11 ranges, the maximum con-
cinuous or inrermiCce*t inpur voltage which can
be safely applied is 1200 volts peak ac + dc. on
the 5O&volc rms range (1000 volt range pasitio")
in either ranging mode, the 165 display will flash
when the inpui exceeds 499 volts rms, although a
reading beyond this level is displayed.
2-7. OPERATION AS AN AXXETER. The Xodel 165 can be
used to measure C"rre"L from 21 nanoamp to t2 amps 3. Accuracy. The dc-current accuracy Of the
dc and 100 nanoamps to 2 amps C"S ac. 165 is t(o.3% of reading + 0.3% Of range). The
error limit of a given measurement can b< Cal-
culated using this specifiearia" (see Paragraph
Z-6=3) and the voltage burden (see Paragraph Z;i,l,
OPERXION NODEt 165
diodes Will prorect the sensing resistors from cur- wise. As the RANGEswitch is rotated counterclock-
renfs UP to levels which cause excessive heating or wise. the 165 resistance sensitivity is increased.
vaporization of pc-board tapes. Automatic selection of range is accomplished by
rotating the RANGEswitch to rhe extreme clockwise
position marked AUTO.
a. Measurement Procedure. Select the OHMSfunc-
tion "siw, the FUNCTION switch. set the RANGEswitch.
and make input c""necrio"s t" ;he front-pa"el ter-
minals. The digital d$splay indicates decimal 1
location and engineering units of a reading. ':
POlEdry sign "ill not light when ohms is selec:~
If the display exceeds 1999 "n any range, the three
right-band digits will blank and the overrange "1"
*igir Will remain Iit. 1" the AUTO mode or manually
on the oueside IOO-megobm position, a" open-circuit
input ca"~es a flashing 01.7 W display. With an
open in~ue, the inside IN,-megohm range, the third
p"si~ion from full clockwise, may flash or blank de-
pending a" whether it was entered from the outside
lOO-megobm renge or the lo-megohm range. Also, if
the RANGE switch is rotated rapidly while in the AUTO
made, the display may blank. Neither candician just
discussed represents a problem or malfunction.
aa shown in Table 2-4. The HI input t&inal 5401 is.
1. Measuremenr Procedure. Selecr ehe AC AMPS negative with respect to the LO input terminal 3402.
function using the FUNCTION switch, set the RANGE The rermina1 voltage is 100 mulLvolts at full ranz>.
switch. and make input connections to the front- (200 millivolta at maximum overrange reading).
pane1 cermina1s. The digital display indicates maximum open-circuit voltage is less than 1 volt.
the decimal point locaeion and engineering units
Of a reading. The polarity Lag" "ill not light TABLE 2-4.
when AC amps is eeleceed. If the display exceeds Ohm Test C"rrenr
1999 on the 100 milliamp or lower raoges, the three
right-hand digits will blank and ehe overrange "1" Full Pull-Range Teat
digit will remain lit. See Paragraph 2-?a5 far Range Terminal VAtaga Current
details af the maximum allowable Fnpur.
100 n 100 In" lm.4 ,.
2. Input Resistance. See Paragraph 2-7a2. 1 k0 100 02" 100 "A
1~0k" I"0 rn" 10 p.4
3. Accuracy. The aC-C"rre"f accuracy apecifi- 100 kn 100 I"" 1 UA
cation of the 165 is used co calculate the error 1 I% 100 r&Y 100 "A
limit of a Specific mea*ureme"t (see Paragraph 10 MO 100 mv 10 "A
2-6a3). except at 20 Hz and 2OkHz where specified 100 ML-z 100 mv 1"A
accuracy is asymmtri~al. Reference the specified
ac-amps accuracy ranges a~ 20 "z, lkI+z, and 2O&. C. *muracY. The accuracy far all abms ranges is
Typical accuracy bands af non-specified frequencies as specified. This apecificario" applies far envi-
are shown in Figure 6, alrhough rhe 10-1000 mA ronmental conditions of 35'C at up to 10% relative
ran8e has somewhar flatter responsa at 2Ok"z than humidify. Accuracy on the l-megohm and higher ranges
char shawn. Voltage burden (see Paragraph 2-7b2) is typically two-times better than specifications.
can also produce error, depending on the level of The error limit of a given mea*urement can be cal-
rhe source "alcage. culatcd using the specified accuracies as described
in Paragraph 2-6~~3.
4. Half-dIgit I"terpo1ari.o". see Paragraph 2-74.
d. Half-digit Interwlation. When the m"st right-
5. Marimum Allowable Input. See Paragraph 2-7a5. hand digit of the 165 display is flashing berwee" two
adjacen; numbers, the percentage of time spent on each
2-8. OPERATION AS AN OHMMETER. The Model 165 can be is a half-digit intarpalario" of zhe incoming signal
used CO measure resistance from 0.1 ohm co 200 meg- level. POT example, 1.000 kilOhmS flashing in near-
ohms. The Model 165 ~ravides se"en full-range decades equal intervals LO 1.001 kilobms would indicate a
of resisrance fram 100 ahms LO 100 megohms. Range reading of 1.0005 kilobma.
seleccio" can be accomplished either manually x
autamarically. w selection is accomplished by e. Maximum Allowable Input. The maximum Yolrage
setting the RANGEswitch S401B LO any ""e of seven which can be applied to the input Fn the OHMSfunc-
positions, g including the secand position from tion ia 250 va1ts rms on any range. This voltage
full clockwise. i"his wsicion may be used but it may be applied continuously or ineermictenely with-
just duplicates the operarion of the 100 megohm out damage or degradation af ~pecificati""s.
runs, which is the third position from full clock-
* 1073
7,.
MODEL 165 OPERATION
2-9. OPERATION THE l-m.4 SOURCE. The ImA front-pane1
OF
pushbutton aCti"*fes * cLIrre*t source of +1 mA *10x.
The current 18 internally injected into the HI input DO NOT DEFRESS THE 1mA POS"B"TTON WHENMTWJAL
terminal 5401. voltage compliance is cypica11y *rearer VOLTAGE IS APPLIED TO THE INPUT TERMINALS.
than 4 vo1r.s.
Z-10. OPERATIONS SUMMARY. Condensed operating in-
a. Reeiarance Measurements. If the DC VOLTS func- structions are found on rhe botton cover of the Model
tion is selected while usinp. the 1 mA current BOUXCB, 165. They are repeated here with a little more detail.
the Model 165 becomes a dir&-reading autora"ginS z For complete details of operation. see 2-l Lbrou$h
manual ranging ohmmeter having 100% overran&g on ranges 2-9.
from 10.00 ohs co 1.000 kilohms full-scale (corresponding
respectively co 10.00 millivolr through 1.000 volt dc e. Power. Set Lhe rear-psoel line witches 5302
***ges). Useful measurements are available to 4.00 and S303 to the proper line voltage ~etti"Ss. Check
kilohms (corresponding LO 4.00 volts on the 10.00 volt the fuse F301 for proper rating. Connecr the line
dc range). I" any c**e. the Yoltage compliance limif cord CD-7 to 50 or 60 Hz power. Set the power switch
is also the 1iraiL of resistance measurements using S301 to ON.
the 1mA C"rre"t source. Note that rhe engineerI."*
uni~a on the display will scFll indicate volts, which b. Co*"aCfio".9. connacr to the fro"=-pane1 "I
is the voltage compliance at which maaauremenrs are tied) 5401 and LO (black) J402 binding poet Fnput
being made. Af the 8-a time, the displayed numbers Cemlinals . Connect the ground link between CND
in the reading indicate the value of the resistance (sreen) 5403 and LO (black) for grounded operation.
being measured. For example, * reading of 100.0 milli- discon"ecting rbe link for floating operation.
volts dc indicates the meaeured resistance is 100.0 Haximum allowed voltage becvaen CND and "I or LO is
ohms and a reading of 1.999 volts dc indicates 1.999 l200" peak.
kildlm.
C. Function Selection. Set the outer dial to the
1. Measuremanr Procedure. The ImA current source desired function: DC VOLTS, AC VOLTS, DC ANPS, AC
feature of rhe Model 165 may be used to measure low Ams, or OHMS. The digital LED display automatically
resistances or to check continuity. A" open cir- indicates decimal point, polarity, and-e"$ineering
C"it or resisrsnce grearer aaLl the range limit is U"5LS. Lack of polericy on the display on YOLTS or
indicated by a display of the full compliance volt- AMPS functions Fndicatas ac readLngs.
age. This voltage ia eaefly determined by open-
cFccuiting in the input terminals of the 165 and d. Range Selection.
depressing the lmA pushburro" "bile operating in
the DC YOLTS~funcfio" eithsr manvally on the IO-
volt range or in the AUTO range mode.
2. Compensaring for Lead Resistance. A precise
value of the ImA current source (I) can be obtained 2. Automatic. Set the inner dial to the fully-
by open-circuiting the input terminals, eelecting clockwise position (AUTO). In this position. the
the DC AMPS function, and depressing rbe ImA push- 165 automatically "prangea at 2000 digits and _
button; The resistance of the test leads and in- dawnranges at 179 digirs.
ternal connections (P& CB" be directly measured
by shorting the teat leads'while in the DC VOLTS e. lmA current source. If the front-panel In.4
function and depressing the 1mA pushbucto". The" wabbutto" is depressed. arwroximatelv +ImA is in-
the measured resistance (R) cm be more arrnrately jected into the i,I input t&minal at ;p to appror-
defermined as follows: imarely 4 volts compliance. Set the RANGE switch
co DC VOLTS. For semiconductor tests. forward
voltage at ImA is read direcrly. For continuity or
resisLance measurements, resistance is read in ohms
using millivolt dc ranges in kilohmn using volts dc
where " is the observed voltage during the actual ranges (limited to compliance voltage level). With
measurement of R. an open-circuited input actual compliance and current
can be meaaurad on DC VOLTS and DC AMPS respectively.
b. Semiconductor Testi"~. In the DC YOLTS function
and AUTO range mode, the ImA current source may be NOTE
used to determine polarity of a semiconductor junc-
tion. The forward voltage drop of this juncria" at DO NOT DEPRESS THE 1mA P"SHB"TTON WHENMTERNAl
lti is displayed a" the Model 165 if Lhe junction is VOLTAGE IS APPLLm TO THE INPUT TERMINALS.
connecred between the input terminals in the foward
polarity. Note thaf the lmA c"rre"f *.a"rce is inter- f. Zero. The DC ZERO potentiometer R431 on the
nally injected into the HI input terminal 5401. I" rear panel may be adjusted for a +O display with the
the m palartty position, Lhe display will ,."- Fnput shorted on the 10 millivolt dc range or with
dicafe the compliance voltage limit of the current B" open input on cbe 1 microamp dc range.
source> which can be measured as described in Para-
graph Z-gal.
1073 9
T \
CIRCUIT DESCRIPTIdN MODEL
SECTION 3. CIRCUIT DESCRIPTION
3-1. GENERAL. The block diagram of the Model 165 is d. 0" the 10 Volt Se"*e. On rhe 10 vole **"Se,
shown in Scbemaric 25395D. The eiS"*l applied to the K401 *"d K403.are off, K402 is on. Thus, RN403
input rerminals first goes rhrough en input switchinS attenuates the siSn*l by a factor of 100. The eigr
network and then ie applied to'* dc or ac preamplifier. ie then applied to the emplifier chain QA403 and
A ""ipolar amplifier co""er`c8 the signal to a positive QA404, "ith Q407 on, selectinS the xlO,S*i" for cb,
dc signal which ie the" applied to *" a-d converter. chain. Thus, the signal ia attenuered by 100 and
The s-d control and display logic ie contained in the amplified by 10 for e "et atreauatio" of a factor
LSI cirx"iZ. snd on the display printed circuit boards. of 10 bafore going to the unipolar smplifier.
The numerical information corresponding to the input
signal is displayed a" LED digits. The logic properly e. 0" the 100 Volt Range. 0" the 100 volt **age
positions the decimal point and indicates engineering K403 is on, K402 and K401 *re off, end the input
""its. The inpur swircbitq network is cootrolled from signal is attetuated by a factor of 1000 before
the logic in the AUTO range mode or from the front being applied to the x10 amplifier chain. Q407
panel manual range switch. remains on and the *et *cte"u*cio" ie a factor of
100.
3-2. AC-VOLTS PWLIFIKR.. (see Schprmaric 2539%).
The signal applied *c ebe Fnput tenninela is coupled f. 0" the 500 Volt P.ewSe. On the 500 Volt range:
through cepaci~or C401 CO a" *c-compensated ae~enuator K403 remains on, and 9406 is on selectinn the xl
consisting of RN403 and C402 through C405. TN* ie gain for the amplifier chain. Thus, the-net ecte"-
shunted by en input resietence consisting of R401 and uafio" LB a factor of 1000. C402 and C403 *re ad-
R437, and switchi"* is accomollshed bv meene of PUNC- justed to *c-compensate the *ttenu*tor KN403.
TION awitch S4Ol.A Deck No. 2: Table i-1 show* the
attenuation end gain factors ee well *a relay aate* 3-3. DC-"OLTS PREAMPLLFISR. (see SCbemaLiC 25392E)
for each *c-volt* range. The inpur signal is applied to the sttenuetor RN403
e8ein t,,rooSh ewiccb S4Ol.A Deck No. 2. The outp"t c
TABLE 3-1. the attenustor, e.8 selected by K401 through K403, ie
AC Volts: Gains and Relay St*ce* applied tbroqh S4OlA Deck No. 4 and limiting resie-
tars R420 and R421 to the input of * dc amplifier *L
RN403 AMP. S401A Deck No. 5, "`DC INPUT".
;F.ANGE ATTENUATION K401 K402 K403 GAIN Q406 9407 Q40R
a. DC Amolifier. The dc amplifier consists of a
lO@lV I:1 ON OFF OFF xl00 OFF OFF ON FET modulator Q4OLA end QLIOlB, protected by D410
1Oh" 1:1 ON OFF OFF x 10 OFF ON OFF through 0413, e" ac empltiier QA403 through QA405
1" 1:1 ON OFF OFF x 1 ON OFF OFF whose bW.n is controlled as in Paregraphs 3-2, e
10 V 100 : 1 OFF ON OFF x 10 OFF ON OFF demodulator 9409, and a final dc ampIFfier coosis-
100 " 1000 : 1 OFF OFF ON x 10 OFF ow OFF ring of QA406. The output of this mep1if1er "DC
500 " 1000 : 1 OFF OFF ON x 1ON OFF OFF PREAMPOUTPUT" is fed back to the input by resistanct
elements in RN403, selected by K404 and K405. These
a. On the 1 Volt Range. On the 1 volt range, K401 relays select Paine of 1, 10, or 100. Table 3-2
16 closed, K402 and K403 *re open, end the siSn*l is shows the attenuario" gain fsctors ** well a* relay
applied through resistors R405 end K406 to the input states for each dc-volts **"Se.
of s Xl amplifier QA403. The input to this amplifier
is limited to the power supply level* by D419 end TABLE 3-2
D420. Overload voltages applied *c the input are DC volts: Gains and Relay Stetee
dissipated in R40S and R406. SwitchinS ie accomplished
throuSh S4OLA Deck No. 6. On the 1 volt range Q406 RN403 AMP.
is on, 9407 and Q4OS *re off. The output is coupled UNGE ATTENIIATION K401 K402 K403 GAIN K404 K40
fo the unipolar amplifier through c422 end swirching
ie accomplished through S401.4 Deck Nos. 7 and 8. 1hnV 1:1 ON OFF OFF x100 OFF OFF
1oomv 1:1 ON OFP OFF Y 10 ON OFF
b. On the 100 Millivolt R*n*e. On the 100 milli- 1" 1:l ON OFF OFF x 1 OFF ON
"olL ran8e. the ouLp"t of QA403 is applied co a *LO 10 v 100 : 1 OFF ON OFF 1 10 ON OFP
amplifier Q.4404. Q407 as on, Q406 and 9408 are off. 100 " 1000 : 1 OFF OFF ON xl0 ON OFF
therefore the input siS"a1 ie amplified by * facror of 1000 v 1000 : 1 OFF OFF ON x 1 OFF ON
10 before being applied to the unipolar amplifier aSsin
through C422. b. Modulator and Demodulator. The modulator and
demodulator are operated at e frequency of 220 Kz.
C. 0" the 10 Millivolt Range. 0" the 10 mini- This is developed at the "t44" output of the LSI
volt ran@, a second x 10 amplifier 9.4405 further chip *"d appears in the middle of Schematic 25392E
amplifies the signal and it 16 applied tbrouSh 4408 "ear the bottom. S4OU Deck No. 1 disable8 the sig-
co the unipolar amplifier. nal on ec functions. On dc functions, fwo phase8
10
MODEL 165 CIRCUIT DESCRIPTION
are developed by QA601, 9402, and Q4lO. They sre The reference resistance consists of F.409. and R414
coupled to the modulator gates by c417 and C418, and rbrouSh R419. .The specific value of the resistance
to the demodulator by c409. 0421 an* 0422 clamp the is determined by the state of relays K409 through
gate *rives co a reference level equal to the feed- K415. The rota1 resisfsnce is equal to the full-
back "olrsge. developed by QA409, a Xl amplifier ran8e resistance. Note that this circuit applies
whose input is connected to the feedback point. a ne$sti"e reference currant through the unknown
resi*Lance.
c. Input Zeroing. Input seroing is accomplished
by R431 which determines rhe current throunh R428 and 3-5. le. CURRENTSO"RCE. bee Schemetic 25392E).
R429. The voltage ,vzneraced by this c"rr&t across The lmA current is developed by 9404, R411 through
R428 is added to the feedback "olLaSe developed R413 and D405. It is applied LO the HI renninal by
across the lo-kilohm element ,,f RN403 between pins mean8 of rile fronr pane1 BWitCh S402. R410 ad D406
6 and 7. "se a pure copper wire end a dual banana protect 9404 if S402 is eccidantally depressed while
plug for a shorting plug. the voltage is applied to the HI terminal.
d. Input Offset Current. Input offset current is 3-6. DC-AMPS PREAMPLIFIER. (see Schematic 25392E).
comwnsated for b" ad,usrinp. R424 "hich develow a The Fnput c"rre"t passes rbro"Sh S4OlA Deck No. 2
"o&e referenceh to-the f;edback point at the o"t- to a reference resistance selected by K406 throush
put of QA409. This voltage generates a compensafing K411. The voltage across chin reference resistance
current through R423 which is applied to the common is sensed by the dc amplifier in B 4-terminal method
node of the FET modulators, Q4OU and Q4OlB. between terminal 1 of RN401 (at circuit LO) and junc-
Cio" of K411 end R415, which is applied to the inpur
e. Offset "olra*es. Offset "oltaSes within the dc of the amplifier through S401A Deck No. 4, R420, and
amplifier loop are compensated for by R434 which ap- R421. 0" the I-microamp through 1OO-milliamp ranges.
plies a volrage to the positi"e input terminal of the dc preamplifier is set to a gain of 100, COP
QA406, the final dc amplifier. The controlling time respondinS co a full-range voltage of 10 millivolts.
constant within the loop is determined by C413 and On these radges, K406 through K411 select the refer-
R427 in the negative feedback loop of Q.4406. ence resistance which covers s span from 0.1 ohm
(in RN401) through 9 kilohms u(415). On rha IOOO-
3-4. OHMSCIRC"ITRY. (sea Schematic 25392E). on a11 mflliamp range, K406 selects the 0.1 ohm resistance
ahms ranges, K404 and 9407 are on, firing the dc "alt- in RN401, and the gain of the dc preamplifier is
age preamplifier at 100 millivolts full range. D416 changed to 10. correspondinS LO 100 millivolts full
near QA406 limits the output of this amplifier such ran$a, as indicated in ParaSraphs 3-3. D401 rhrouSh
that no more than 1 volt appears at the ioput under D404 protects rhe relays and the sensing resistances
open-circuit conditions. The ohms circuit in the from overcurrent.
lower left corner of Schematic 25392E generates a
reference current at the input terminals. This ref- 3-7. AC-Am3 PRWLHPLIFIRR. (see Schematic 25392E).
erence c"rre"f is generated by a "oleage at "0 OUT" As in the case of dc amps. the BC input current is
G4OU Deck No. 3) divided by a reference resistance passed tbraugh S4OU Deck No. 2 to a sensing resis-
selected by K409 through K415. tance selected by relays. In this cE.se, only re1#ys
K406 thrc."Sh K409 are used. The output voltage is ,
8. Reference Voltage. The reference voltage is sensed at S4Ol.A Deck No. 3 and coupled through C401,
the sunnnacion of 0.1 times the "DC PRW OUTPUT", S4OU Deck No. 2, and R455 to the AC Preamplifier,
and a fixed lOO-millivolt reference. QA402 performs chain. The ac preamplifier is set to a gain of 100
this summafion. R462 and R463 provide an output of corresponding to IO millivolts full range on the 100
0.08 times "DC PW OUTPUT" BL their iunction. microamp rhrouSh 100 milliamp ranges. a Sain of 10
This voltage is applied to rhe positive-input terminal corresponding to 100 milli"olLs full range on rhe 1000
of QA402 which has a non-in"errinS gain of 1.25 de- rsilliamp ac amps range, selected as in Paragraphs 3-2.
termined by R407 and R461. 9405 is on in normal As in the case of dc amps, D401 throuSh D404 protect
OperaLion. The lOO-milli"alt reference is developed the relays and sensing resista"ce from a"erc"rreoL.
from an aftenuaeor scros~ the g-volt reference diode Note that since the capacitor-couplin8 through C401
D408 consisrin~ of R458. R402, and R465. The "olt- OCC"rs I." the circuit folloving the sensing resis-
age at R465 is about -1.6 volts. This is amplified tances, dc or ac ~"ercurrents .3 A may hsve danaSing
by -0.25 using QA401, and by another -0.25 with QA402. affects on either DC AEIPS or AC AMPS functions.
b. Overload Conditions. Under negati"e overloads, 3-8. "NIPOLAR AMPLIFIER. bee Schematic 25393D).
D418 blocks current flow to 9405 or QA402 output, and This circuit, consistinS of QUO2 and QA203. is shown
0415 limits the input "oILage at the naSafi"e terminal in the left-half of Schematic 253930. The preampli-
of QA402 to the supply "olfaSe. Under positive o"er- fier output is applied to 3201. an analog outp"t
loads, D414 limits the neSari"a input of QA402 to the at the rear panel, and fo X213. R213 and R404 (on
positive voltage. This drives the output of QA402 Sehemstie 25392E. near S401A Deck No. 8) attenuate
negative until it is limited by D426. AC that level, dc signals to the 0.91-volt level corresponding Co
the c"rrenf flow in the emitter of Q405 is determined 1 "Ok full range. Note chat the positive terminals
by voltage across D426, rhe base-emitter drop in 4405, of QA202 and QA203 are essentially at LO. thus the
R454. and R408. These elements limit the collector feedback loops around each op-amp rend LO constrain
current in 9405 LO abo"f 1.2 milliamps. This current the neSsri"e inputs also to the LO level. Since
is essentially independent of the voltage appaariwj terminals 3 and 16 of RN.01 are connected to these
at the collector of Q405, which ie determined by the ne&ati"e inputs, we may consider the IO-kilobm ele-
po~itive voltage at the HI terminal and the voltage ments connected co terminal 2 88 a siwle 5-kilOInn
drop of the 1.2 milllamps in the reference resistance. element to LO. The 5 kilohm element from Le"r.i~Ul
1073 11
l .
CE+.XIT DESCRIPTION
1 to 2 of RN201 and this 5 kilohm equivalent element
farm a divider such that rhe volta*e at terminal 2 of
RN201 is half the voltage af. ceminal 1. For positive
si&nals, the o"fpu~ of QA202 will *o negative. DZOl
will be on, Q201 will be off. So if we define
"2.~2 Z the outpur of QA202.
"2 E rhe "olcage SC terminal 2 Of RmOl,
"203 E the ourpur of QAZO,,
"1 z rhe volra*e af terminal 1 of RN201 and
also the preamplifier ourput;
v203 = -2 W202) -2v2
where V202 = -2V2, therefore
"203 - +4v2 -2Y2 - +2v2 - "1
For negative si&nals, the outwt of 98202 will *o
positive. 1,201 will be off. Q201 will be on. In
this case, the voltage at the o"tp"t of QA203 is
-2 times the volCa&e at terminal 2 of RN201. Thus,
From this. the ""ipolar OUtpUt at J202 pravides a
positive signal equal in m*nitude to the value of
the preamplifier output 5201. regardless of sign.
For SC si&nals, Q&.202 acts as a full-wave rectifier,
and QA203 as a filter "sin* C203. The avera*e value
of the ac waveform appears at 5202 as 8 positi"e dc
signal. Nate that Q201 is off for eosirive signals,
on for negative signals. Thus the "polarity" line
is HI for negative sipnals, LO for positive signals.
This information is passed throu*h ewe tramisfms
of QA201 and R207, and presenred to the logic on the
Fl line on the right side of Schemaric 25393D.
3-9. A-D CONVERTER. (see Schematic 25393D). The
unipo1ar output J202 creates a non-negative current ,
in the 1-kilohm resistors between terminals 1 and 8
of RN202. This current is always applied to the ne*-
aLive input terminal of i"Le*raLor Q.4204. If the
diode between terminals 1 and 3 of QUO1 is off. this
si*nal currenf. is Lhe only current applied to the
integrator. If this diode is an, there is also a
reference current at the Lnput node of the integrator.
This reference c"rrent is determined from the -9 volt
reference, the emitter-follower between terminals 6
and 7 of QA201, the 9-kilohm resistance between fer-
minds 5 and 3 of RN202. and the setting of R205. v, - inregrstor output voltage.
The stare of the diode between terminals 1 to 3 of
QA201 1s de~emined by the state of rhe CS-line VA - threshold level of threshold detecror.
corni"& from the LSI logic. If CS is high, terminal
3 of QA201 will be high, and the diode from terminals FIGURE 8. Integrator Characteristics for Small
1 to 3 will be off. Figure 7 shows ehe pertinent Input Signals.
logic Fnternal to the LSI chip along with the cir-
cufrry shown on Schemaric 253930 for the a-d converter.
Note that LS will change state an rhe next clock pulse
after TH has changed state. The state of TH is deter- If the input si*nal is very small. TH will *o HI im-
mined by a zero-crossin* detector QA205 which follows mediaLely after the reference current is turned on,
the intekrator Q&204. For small inputs, the signal and at the next clock pluse, the reference current
current makes rhe InLegraCor slowly ramp negative, un- will he turned off. For large signals approaching
til the integrator oucpuc CIOSS~S zero (see Figure 8). end scale (2000 counts), when the reference current
During this time, the reference current is off (CS 1s is off, the si*nal current will cause the inte*raror
HI) .3"d 'TH is 81. When the integrator OUrpUt cr0**e* to ramp SC a faster rate in the negative direction
zero, 'IH Bees LO, and on the next clock p1use CS Will bee Figure 10). when the reference c"IrenZ t"r"S
alSo go LO. This vi11 turn on the negative reference on after sero crossing and a clock pluse, the dif-
current Which Will cause the integrator LO ramp posi- ference between the positive signal current and neg-
tin? SC a much `aster rate (see Figure 9). arive reference current will be very emall since the
12
MODEL 165
3-12. DISPLAY. (see Schematic 25394E). Q&501
&e"erates four m"lCiplexin* lines, T-O CO T-3, and
each is hi&h for an 800 microsecond CLme interval.
Durink T-O the, the funcrion is indicsred by DSlOl
Chrou*h.OS107, and the polarity and most si*nificanC
1 are displayed by LED DN103. During T-l, T-2, and
T-3, DN104, DN105, and DN106 =especCively display
the numericaL digifs with decimal p"inCs.
3-13. POWERSUPPLY. (sea Schemaric 2539X). 5302
end 5303 select the appropriate primary combinations
for the line volCa*es indicated. The outpur of ~301
and C301 is a + 10 volt unre&uleced su,qaly used fo=
the display md for the +6 volt supply QA410 (see
v, - i"cegracor 0"Cp"C voltage. Schematic 25392E). Q&301 &e."erac~s a regulated +5
v, - threshold level of threshold detector. volt supply. This powers TTL. LSI, end some analog
circuitry. 9.002 re&ulatos Che ""Cp,,C of D301 and
PICURE 9. lncesrecor Characteristics for D302 CO -12 volts. 5301 provides a mes"8 of dis-
Full-Ran&a lnpuc s*gna1*. connecCin& Che power supplies so ChaC Chey may be
tested independently from the logic and analog ci=-
cuicry.
"0
"*.D"
_----
__--
P 2.000CO"NTS
-1
"0 - ince*racor c."CP"C "olca*e.
"d - Chreshold level of threshold detector.
FIGURE 10. lnCe&raCor Characrerisrics for End-
Scale (2000 Co"ncs) Input Signals.
reference cu==enC is set to be ,ust greater Ghan 2000
co""Cs. Thus. the inCe*=aCo= will slowly r`amp in the
posiCive direction. In Chin case, the reference CUT-
rent is on most of Che Cime; TH and CS are LO most of
the Cime. Near full range, Che reference current is
on for 1 clock pluse and off for 1 clock pluse.
3-10. CLOCK. (see SchemaCic 255080). The clack con-
sists of QA503, QA602, RSOZ Cbmugh X,505, and C503, at
Che left edge of Schematic 255080. This *ene=aCes a
low-duty-cycle 9.680 Hz clock for Che tSI lo*ic QA501.
3-11. LOGIC. (see Schemaric 25508D). QA501 contains
all logic for the a-d conve=Ce= and auCoran*in* ci=-
cuitry. Ran&e lines Rl, RZ, and R4 a=e conrralled
eiChe= by the a"Ca=an*in* circuitry on QA5Ol o= by
the range swirch S401B Deck No. 10. On manual ran&es,
the MR line is connected CO LO which inhibifs the out-
puts to Rl, R2, and R4 in the LSI cup, The *uncricm
is selected by S4OI.A Deck No. 1. Table 3-3 indicaes
the complete Crurh table for all functions and ran&es
of the Model 165. Q&502 decodes Chis logic into con-
trol lines far various relays and analog switches
shown on Schmsti~ 255110. Also see SchemaCic 25392E.
1073
TABLE 3-3.
F"ncLi""lRan.elRela" Decoder Truth Table
Co"tr"l Li"es/Co"crolled Devices
Function Lines Range Lines %'I/ SW21 SW/ FCC/ SW41 SW5/ SW61 SW71 SW81 SW9/ SWlOl SWlll SW13/ SW14/ SW151
'unctian F4 F2 Fl U"W R4 K2 Kl K401 K402 K403 Q408 K404 K405 K406 K407 K408 K409 K410 K411 K413 K414 K415
-
+ocv 0 0 0 lots" 0 0 0 1 0 0 1 0 0 __ _- -- -- -- -- -- -_ --
-DC" 0 0 1 107s" 0 0 1 1 0 0 1 0 0 __ _- -- -_ _- __ -- __ -_
AC" 0 1 0 lam" 0 1 0 1 0 0 1 0 0 __ -_ _- -_ -- -_ -- __ --
loom" 0 1 I 1 0 8-J 0 1 0 __ __ _- __ __ -_ __ __ -_
1" 10 0 1 0 0 0 0 1 __ __ _- -- - -- -- __ -_
10" 1 0 1 0 1 0 0 1 0 -- _- _- -- - _- -- - --
100 Y 1 1 0 0 0 1 0 1 0 __ __ __ -_ __ -_ _- __ _-
lKv111 0 0 1 0 0 1 -_ -_ __ _- __ -- _- -_ __
ACA 0 1 1 1OOUA 0 0 0 - 0 0 10 0 0 0 0 1 0 0 0 0 0
lOO"A 0 0 1 -- 0 0 1 0 0 o,o 0 1 0 0 0 0 0
100"A 0 1 0 -- 0 0 10 0 0 0 0 1 0 0 0 0 0
1OOllA 0 1 1 -- 0 0 1 0 0 0 0 0 1 0 0 0 0 0
ImA 1 0 0 -- 0 0 10 0 0 0 1 0 0 0 0 0 0
lOmA 1 0 1 -- 0 0 10 0 0 1 0 0 0 0 0 0 0
look4 1 1 0 -- 0 0 10 0 1 0 0 0 0 0 0 0 0
1.4 1 1 1 -- 0 0 0 1 0 1 0 0 0 0 0 0 0 0
+DCA 1 0 0 1LlA 0 0 0 -- 0 0 10 0 0 0 0 0 0 1 0 0 0
-DCA 1 0 1 lll.4 0 0 1 -- 0 0 10 0 0 0 0 0 0 1 0 0 0
lOUA 0 10 -- 0 0 1 0 0 0 0 0 0 1 0 0 0 0
1OO"A 0 1 1 -- 0 0 1 0 0 0 0 0 1 0 0 0 0 0
1mA 10 0 - 0 0 10 0 0 0 1 0 0 0 0 0 0
1omA 1 0 1 -- 0 0 10 0 0 1 0 0 0 0 0 0 0
lOOm.4 1 1 0 -- 0 01 0 0 1 0 0 0 0 0 0 0 0
1A 11 1 - 0 0 0 10 1 0 0 0 0 0 0 0 0
omfs 1 1 0100n000 - 0 0 0 10 0 o-o 10 0 0 0 0
1m 0 0 1 -- 0 0 0 1 0 0 0 0 0 1 0 0 0 0
1oK.n 0 1 0 -- 0 0 0 1 0 0 0 0 0 0 1 0 0 0
1OOKn 0 1 1 - 0 0 0 1 0 0 0 0 0 0 0 1 0 0
M 1 0 0 -- 0 0 0 1 0 0 0 0 0 0 0 0 1 0
1Om I. 0 1 -- 0 0 0 10 0 0 0 0 0 0 0 0 1
lOoK 1 1 0 -- 0 0 0 1 0 0 0 0 0 0 0 0 0 0
1oOm 1 1 1 -- 0 0 0 10 0 0 0 0 0 0 0 0 0
SECTION 4. ACCESSORIES
4-l. GENERAL. The following Keithley accessories
can be used with the Model 165 co provide additional
convenience and Versatility.
4-3. MODEL 1651 SO-AMPERESHUNT. The Model 1651 pic-
tured in *igure 11 is an opLiona1 acceesory chat ex-
pands the ac and dc current measuring capability of
the 165 from 2 amps to 50 amps. The 1651 is a 4-ter-
minal 0.001 ohm flX shunt that is connected externally
to the 165 input terminals. The 165 is operated in
the ac or dc volts mode manually on the 10 m,.Ui"olc
and 100 millivolt ranges or in the AUTO mode for the
convenience of automaric ranging. The voltage drop
y:"'" the 165 inpuf, "sing the 1651 shunt is very
- only 10 mLllivolce at 10 amps. The Model
1651 18 approximately 6 inches long, l-114 inches
deep, and l-3/8 inches high. and may be m&nred t.,
a hard surface using the 15/64-inch diameter mounting
hole an,either end of rhe shunt. A cable is provided
to ~omect the input terminals of the Model 165 to
the inner voltage-sensing terminals of the shunt.
TNa cable is ap,mximaCely 58 inches long. The outer
current-sensing terminals of the shunt should be used
to connect to the c"rrenf source. FIGURE 11. Model 1651 SO-Ampere Shunt.
4-4. MODEL 1653 RACK NOUNTINS KIT. The Model 1653 inside edges of the Rack Mounting Panels fit around
picfured in Figure 12 is a single rack mounting kit the front-panel ednea of the 165. Now mo"llL the
which converts the Model 165 from bench maunt.ing to entire sss&bly of-the 1653 and 165 in a 19-inch.
standard 3-112 inch x 19 inch reck mounting, with 15 tidth rack.
inches (300 mm) depzh behind the front panel.
a. Parts List. see Table 4-1.
TABLE 4-1.
Model 1653 Parts Li