Keithley 1765 User manual

Test Instrumentation Group
Keithley Instrumenthlnc.
28773 Aurora Road
Cleveland, Ohio 44139
(216)248X400 . Fax: [phone]
BZiii;
Service Manual
Model 1765
Contains Servicing/Calibration Information for
Models 136and 176
Kaithley Instruments. Inc.
28775 Aurora Road/Cleveland. Ohio 44139/[phone]

WARRANTY
We warrant each of our products to be free from defects in material
and workmanship. Our obligation under this warranty is to repair
or replace any instrument or partthereof which, within a year after
shipment, proves defective upon examination. We will pay local
domestic surface freight costs.
To exercise this warranty, write or call your local Keithley repre-
sentative, or contact Keithley headquarters in Cleveland, Ohio.
You will be given ,prompt assistance and shipping instructions.
REPAIRS AND
CALIBRATION
Keithley Instruments maintains a complete repair and calibration
service as well as a standards laboratory in Cleveland, Ohio.
A Keithley service facility at our Munich, Germany office is
available for our customers throughout Europe. Service in the
United Kingdom can be handled at our office in Reading. Addition-
ally, Keithley representatives in most countries maintain service
and calibration facilities.
To insure prompt repair or recalibration service, please contact
your local field representative or Keithley headquarters directly
before returning the instrument. Estimates for repairs, normal
recalibrations and calibrations traceable to the National Bureau of
Standards are available upon request.
KeithleyIns&nents, Inc.128775Aurora Road/Cleveland, Ohio 44139/U.S.A./(216) 248400/T&x: 985469
WESTGERMANY: KeithieyInshumentrGmbH/Heiglhofstrasse S/D-8003 Mitnchen 70/@89) 7l4-4&6.5/Telex: 52121 60
GREAT BRlTAIN: Keitbley Instruments, Ltd./l, B&ton RoadlCEReadi~ Berkshire RG2 ONU(O734) 86 12 87/T&~: 847047
WCE: Keithleyhtrvments SARL12 Bis, Rue Leon Blum/B.P. 60/91121 Palaiseau C&.x/(6) 011,51,55/Tekx: 600933F
NEIHERLANDS: Keithley Instrvments B.V./Leid&raatweg 149/Postbus 1190 /NL-WcerderJ(O34EO) 13 M3/Telex: 40 311
SWITZERLAND: Keithfey Instruments SA/Filiale DttbendorflKriesbachstr. 4fCH-8603 D&zndorf/Ol 82194 44/T&x: 57 536
AUSTRIA: Keitbley Instruments HandeL+Gesekbaft m.b.H.IDbbliier Hauptstr.32/A-119C Wien/O222 314 289/T&x: 13 45 W

SECTION
1
1-l
1-4
1-6
1-E
l-i0
l-12
1-14
2
2-l
2-2
2.10
2-13
3
3-1
3-6
3.12
4
4-I
4-2
4-9
5
5-l
5-2
5-5
5-10
5-13
5.17
5-18
6
6-l
TABLE OF CONTENTS
TITLE PAGE
GENERAL INFORMATION ............................................................
iNTRODUCTlON
FEATURES.. .....................................
........................................ . . . . . . ..........................
WARRANPIINFORMATION
MANUAL ADDENDUMS .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.............................................................
SAFETY SYMBOLS AND TERMS
UNPACKING AND INSPECTING ......................................................
SPECIFICATIONS .......................................................
....................................................................
1-l
r\CCC~~““lC~ .................................................
GENERAL ......................................................
,ORlES ........................................
ESSORIES., .......................
ESSORIES
.........................
MUTUAL ACCESS
MODEL 135 EXCLUSIVE ACC
MODEL 176 EXCLUSIVE ACC
.................
.................
.................
rc”r”“I”I~NLc “CnlrlLAI I”N .......................................................
GENERAL ...........................................................................
MODEL 135 PERFORMANCE VERIFICATION ..........................................
MODEL 176 PERFORMANCE VERIFICATION ..........................................
lrlC”“T vr “rEI(CIII”N .............................................................
GENERAL ...........................................................................
MODEL 135 OVERALL FUNCTIONAL DESCRIPTION ...............................
MODEL 176 OVERALL FUNCTIONAL DESCRIPTION ............................... ::::
MODEL 135
TROUBLESH
MODEL 176 CALIE
MODEL 176 TROU
CURRENT FUSE RE
MODEL 1766 TROuurc:
MAINTENANCE (TROUBLESHOOTING. CALISRATIONI. .............
GENERAL .......................................................
CALIBRATION ......................................
DOTING .............................................
3RATION ........... ..........................
IELESHDOTING ................................
IPLACEMENT ..................................
“-‘-1HOOTING ...............................
...............
..............
..............
..............
REPLACEABLE PARTS ...............................................................
GENERAL ...........................................................................

MODELS 135/l 76 GENERAL INFORMATION
Model 135/l 76 Service Manual
Section 1. General Information
l-l. INTRODUCTION
l-2, The Modeis 135/176 are low cos,. 4-l/2 d~gt,.
LCD dtsplav digatal muitimeters. The two me!ers are
unfque in that they are sfm~lar in electromc design ye,
different I” case design. The most obvious dhiference 1s
the phvwal dilference. The 176 is designed tnro a more
,rad,I,onal DMM case whlie the 135 is designed #“to a
hand held case. The 176 has more current ranges and a
w,der frequency span for ACV. They both have a basx DC
accuracy of 0 05% and also a basic OHMS accuracy of
0.2%. They also bastcallv have the same A/D converter
l-3. Thus manual 1s a comeinatmn of sewce rnformatjon
for both DMM’s (1 35 and 176) I, contans tnformarlon
necessary to maintain. caitbrate and troubleshoa Ihe
Model 135 and the Model 176,
1-4. FEATURES
l-5. The 135 and 176 have many d,s,,nc, fearures and
advantages some 01 which are l,s,ed below:
.
.
.
.
.
A 20000 count I,.‘-1 12 d,g,t, Iiqu,d crvstal dtspiav.
[LCD) ,w,h large 0 6 ,nch numerals The 176 has
functnn and fange ,nd,cators. The 135 and 176
have a low ba,,eiv lndlcator that hghts when there
IS less than 10% battery life rema,“i”g. Appro-
prtale declmai point and minus stgn (~1areaisodls-
played, posirive polarttv IS ,mplied.
The Model 135 and 176 are bull, rugged. The hand
held case and the bench s,ze case are molded from
impact-res~stan, plastic. Effective ,npu, profection
prevents damage on ail functmns.
The 176 pushbuttons are color coded to the front
pane, for qwck and easy selecr~on of functton and
range. The 135 rotarv fun&on and range swlch
are easdy pos,r,oned to color coded functtons and
ranges. The decimal pan, is automatlcallv pow
tloned by the range pushbu,,on/rofarv switch. The
176 dlsplav annunciators indicate rhe selected
function and range. Improper range and function
comb,na,,ons are lndlcated bvcontradalng func-
bon and/or range annunc,alors appear,ng a, the
same rime.
Stare of the arr technology and stable prectsio”
components have been used I” these two DMM’s
to prov,de iong term accuracy and m,“,mtze main-
tenance. Calibration IS required only once a year.
If aikal,“e battertes are used /SIX C cells I” the 176
or one 9 volt ceil for the 1351 battery IIfe can be as
long as 1000 hours for the I 76 and 100 hours for
the 135
Opttonal accessories can be ordered To extend the
measurement capabtlttvof me 135 and 176. Some
of these accessor,es are’
Htgh lrequencv (RFI probe allows YOU< 3MM !a
measure from 0~25V 10 30V rms AC ow a Fred
quency range from 1OOKHr 10 iOOMHz
50 ampere wrren, Shun, aiiow~ YOU, DMM 10
measure up 10 50A. AC or DC
Clamp on AC curie”, probe al,ows vour 9M11 !o
measure up 10 200A rms AC
Htgh Voiiage Probe allows your DMM ,c reas;‘r
from 1OOOV 10 40KV DC
NOTE
l-6. WARRANTY INFORMATION
1-7~ The warranty is gwen on ,he instde front cover ci
,h,s instruction ma”“al~ If there IS a need 10 exercise ine
warranty contact the Kenhlev Representawe 10 vour area
to de,etm,“e the proper act,o” to be take” Kelrhiey slain-
fans serwce fac,l,,les I” the Untted Klngaom ‘.“,esr
Germany and I” ,he UnIted States Check ,ne !ns~de.roni
cover of lhls manual for addresses
l-8. MANUAL ADDENDUM8
l-9, ,mpr~vements or changes tha, affec, iqese ~nsfru-
ments which occ”r affer pil”,l”g of the I”s,rdc,,on
Manual wlil be explained on anaddendum sheelartacnea
to the jnside back cover,
l-10. SAFETY SYMBOLS AND TERMS
1-l 1~ Safe,” symbols used ,n lhis manual are as foilows
The symbol&an rhe ~nstrumen, denores lha, ihe user
should refer 10 the operarIng insfrucf~ons
The symbol 1 on the ~nswumen, denotes rhat I OCOV
or more may be present on the ,erminai~s,
The WARNING used in th,s manual explains dangers
that could resulf tn personai tn,urv or dean
The CAUTION used I” ,h,s manual expiains hazar?s :?a,
could damage the ~nsrrumen,,
l-12. UNPACKING AND INSPECTION
1 13 The Models~l 35 and 176 were carelullv 8”speclea
borh mecha”,ca,,v and eiec,wallv before snipmenl “pan
rece,w”g either or bolh of these instrumeni~. unpack a!!
items from the sh,pp’“g container and check for a”” 00~5~
ous damagethat may have occurred during ira”s8, Reoor:
any damage 10 the shtppmg age”,, Retain and use :hi
orig,“a, packag,ng ma,er,a,s ,f reshIpme”, 15 “ecessar,
The followmg ,,ems are sh,pped wr,h alI ‘35 a”3 : :<
orders~

GENERAL INFORMATION MODELS 135/176
FIGURE l-l
135 DIGITAL MULTIMETER
A. Model 135 or 176.
5, A copy ot the appiopnate Operator’s Manual,
C. SuppIled Accessmes: 176 (Mod&l 1768 Battery Pack
with batteries, Modei 1691 Test Lead Set, 135 (9V
batterv. Model 1691 Test Lead Setl
D, Installed or separate opf~onal accesso~,es. as orderea
1-14. SPECIFICATIONS
l-1 5. Detailed speclflcations for both instruments are
given on the foilowIng pages
FIGURE 1-2
176 DIGITAL MULTIMETER
176 SPECS

MODELS 1351176
135 SPECS
GENERAL INFORMATION
l-3

MODELS 135/176 ACCESSORIES
Section 2. Accessories
2-1. GENERAL
This sect,on describes the various accessor,es and
opiio”s avatlable ior use wth Ihe Models 135 and 176.
Some of the followlng accesswe are for use only vath
the Model 135 and some are for use onlvwlth the Model
176~ These accessoi~es w,ll be clearly potnted out as ,o
which instrument they are used wlth~
2-2. MUTUAL ACCESSORIES
The following accessories can be used wrh e,ther rhe
Model 135 or the Model 176.
2-3. Model 1SOOA High Voltage Probe
The Mode! 16OOA extends the DMM to 40kV. it has a
1000: 1 d,v,s,on rar,owhich means that 1 volt on the DMM
Corresponds to 1kV
To Operate: Set the DMM to DCV and 200 Volt range,
Connect the all~garor CLIP on the Model 1600Ato source
Iowa Connecl rhe probe top to so”ice high.
Specifications:Voltge Range: 0 to 40.000 volts DC
Input Reslsrance: 1000 megohms.
Dlvlsion RatlO. 1000 I
Ratto Accuracy~
1000 to 1 +2% terminated in IOMR
2000 to : +5% terminated I” I Mn
FIGURE 2-1
1600 HIGH VOLTAGE PROBE
2-4. Model 1651 50 Ampere Shunt
The Model 1651 allows current meawrements to be
made from 0 to 50 amperes DC and from 10 to 50 am-
peres AC, It 1s a 0.001 ohm *l% 4.terminal shunt. A fifty
ampere current WI,, correspond to 50 m,ll,volts~
To Operate: Connect separate current leads (not fur-
mshed) between the source and the Model 165 1 hex-
head bolts. Use leads that are rated UP 10 50 ampere
cap.xW Connect thevoltage leads ifurnlshedi between
the Model 1651 screw termmals and the DMM INPUT
terminals. Set the OMM 10 ACV and 2V range or DCV
and 2V range,
2-6. Model 1681 Clip-On Test Lead Set
The Model 1681 contains two leads I 2rr 146 inches,
long. lhat are terminated w,th banana piug and sarong-
acI10” cltp-on probes.
FIGURE 2-3
CLIP-ON TEST LEADS
2-6. Model 1682A RF Probe
Model 1682A RF Probe allows voltage measuremenrs
from 1OOkHz to 250MHz
To Operate: Set the DMM to DCV and appropriate range
Connect the Model 1682A to the DMM input ,acks
Specifications
AC to DC Transfer Accuracy: (7.3X? 5°C) tld6 !rom
1OOkHz to 250MHz at 1V. peak iespondlng. calibrated
i” ims of a slnewave. compat,ble with 1”5lr”ments wiin
1OMR Input res.,srance
Voltage Range: 0.25V to 15V rms
Maw&m Aliowable Input: 50V AC peak. 2OOV (DC+
AC ~eakl
Makmufk Common Mode Voltage. 30V rms. 42 peak
Input Capacitance: 5pF Typical
OperarIng Temperature: 0” to 50°C
Cable Length: 1~5 meters
Accessories Supplied: ENC Adapter. insuiaring TID,
IC Tip. Spring Hook. Carrymg Pouch
FIGURE 2-2
1651 50 AMPERE SHUN1 FIGURE 2-4 1662 RF PROBE

ACCESSORIESACCESSORIES
2-7. Model 1663 Universal Test Lead Kit 2-7. Model 1663 Universal Test Lead Kit
Two test leads. 1.2m (48 inches) long w,th 12 screw-inTwo test leads. 1.2m (48 tnches) long vat,, 12 screw-in
tips. 2 banana plugs. 2 spade lugs. 2 alligator clips wfhtips. 2 banana plugs. 2 spade lugs. 2 alligator clips wfh
boors. 2 needle ups w,th chucks and 4 heavy duty ftpboors. 2 needle ups w,th chucks and 4 heavy duty ftp
Plugs
plugs.
MODELS 135/176
FIGURE 2-7
1691 TEST LEAD SET
Z-10. MODEL 135 EXCLUSIVE ACCESSORIES
2-l 1. Model 1304 Soft Carrying Case and Stand.
The Model 1304 IS a soft carrying case and stand (t,lt
baili for Kelthley’s hne of hand held instruments.
The instrument can be secured Inside the case wfth the
thumbscrew (suppledI. if dewed, The thumbscrew IS
also used 10 secure the stand (tilt bail) fo set the ,nsfru-
men! upnghf.
FIGURE 2-5FIGURE 2-5
1683 TEST LEAD KIT1683 TEST LEAD KIT
2-S. Model 1686 Clamp-On AC Current Probe
2-S. Model 1686 Clamo-On AC Current Probe
The Model 1665 meawres AC current by clampIng ontoThe Model 1665 mea?.“& AC current by clampfng onto
a s,ngle conductor. Interrilptmn ot the current path ISa s,ngle conductor. Interrilptmn ot the current path IS
unnecessary, The Model 1665 detects current by sensingunnecessary, The Model 1685 detects current by sensing
the magneuc field produced by the current flow.the magneuc field produced by the current flow.
To Operate: Set the DMM to ACV and the appropriateTo Operate: Set the DMM to ACV and the appropriate
range. The DMM WI, dtsplay O.lV rms per ampere.range. The DMM WI, dtsplay O.lV rms per ampere.
FIGURE 2-S
1685 CLAMP-ON AC CURRENT PROSE
2-S. Model 1691 General Purpose Test Lead Set
The Mode, ,691 General Purpose Test Lead Se1 CO”SIS,S
of fwo 0,9 I mm (36 Inches) test leads wirh probe ups
iermlnated I” banana plugs
2-2
FIGURE 2-8
SOFT CASE AND STAND
FIGURE 2-9
1306 DELUXE CASE
2-12. Model 1306 Deluxe Carrying Case.
Model 1306 Deluxe Case is a rugged DMM carwng case
that IS large enough to accommodate the 135 plus var-
IOUS other DMM art~cies such as a spare battery. fes,
leads. ew

MODELS 135/176 ACCESSORIES
2-13. Model 1369 Spare Parts Kit
The Model 1359 is a spare parts kit for rhe Model 135
It CO”SISIS of a compIeme”t oi specially seiected spare
pans fhar wlil manta!” several 135 DMM’s for one year
The parts are INsted I” Table 6-2 of Sectlo” 6. Replace-
able Parts,
2.14. MODEL 176 EXCLUSIVE ACCESSORIES
2.16. Model 1010 Rack Mounting Kit
The Mode, 1010 Rack Mounting Kit permits the mou”,-
,ng of a single DMM to a standard 5-l 14 in x 19 i” rack
2-16. Model 1017 Rack Mounting Kit.
The Model 1017 Rack Mounting Ktt permits rhe mount-
,“g of two DMM’s s,de by sde I” a srandard 5- 1/4 I” x
19 I” lack.
2-17. Model 1684 Hard Shell Carrying Case
The Mode, 1684 hard she,, carrv~ng case IS a hard wny,
case which is 4 I” v 13 I” Y 14 I” (100mm x 300mm x
350mml~ Ii has a fltfed foam lnserf wth room for 1he
DMM. ~“struct!o” book and small accessories
FIGURE 2-10
HARD CASE
2-18. Model 1766 Battery Eliminator
The Model , 766 Batrerv Ei,m~“ator permits the user to
operate the 176 or 169 from lhne power. The 1766 pro-
vldes the necessary DC voltage to Operate the 176 or
169. The 1766 firs I” piace of the battery pack (Model
1766) so therefore, precludes the use of the battery pack
(Model 1768). The Model 1766 is capable of working
from a wde range of line voltages such as from 1OSVAC
to 250VAC to 50HZ or 60HZ.
FIGURE 2-l 1
1766 ELIMINATOR
BAmEAY
BATTERIES HOLDER
FIGURE 2-12
SAl-rERY PACK
2-20. Model 1769 Spare Parts Kit
The Model 1769 1s a spare parts ii, for ,he MOdeI : 76
it co”sIsts of a compiement of SPeclallY seiecreo space
parts that WIII ma~ntai” several 176 DMM’s lor cne veai
The parts are listeci I” Table 6~3 01 Seci~on 6 Rep!aceaale
Parts,

MODELS 135/l 76 PERFORMANCE “ERlFlCATlON
Section 3. Performance Verification
3-1. GENERAL
This secf~on gtves a Performance Verilvzat~on procedure
for both the Model 135 and the Model 176. Each proce-
dure wtil be presented separately I” order to avo,d con-
fus,on,
3-2 Performance Verlficatlon may be performed upon
recetpt of enher ~nstr~rnenf (1 35 or 1761 10 ensure that
no damage or m,sad,ustmen, has occurred dung trans,,.
Verlficatlon may also be performed whenever there IS
quewcr of elther instrument’s acculacv and foIlowIng
cahbraron. if desired.
NOTE
3-3. Environmental Conditions For Both Instruments
In order to perform the Performance Verlflcatton the
instr~men, to be venfied m”st be between 1B’C to 2B’C
at less than 80% R.H.
3-4. Recommended Test Equipment
Recommended test equipment for performance verlfl-
cat,on of both instruments IS hsted in Table 3- 1 Alternate
test equipment may be used. However. 11the accuracy IS
not at least 3 ttmes better than the instruments speclfl-
camns. addlnonal allowance mwt be made m the read-
I”@ obtalned.
WARNING
All service information is intended for qualt-
fied electronic maintenance personnel only.
WARNING
Some procedures require the use of high volt-
age. Take care to prevmt contact wth lwe
circuits which could cause electrical shock
resulting in injury or death.
CAUTION
TABLE 3-1
RECOMMENDED TEST EQUIPMEN
ITEM DESCRIPTION SPECIFICATION
A DC Calibrator 1v. 1ov. 1oov. 1ooov
i-0.002%
B AC Calibrator 1v. IOV. IOOV
+0.022%
C High Voltage Amplifier 1ooov
(Used wth Model 745Ai *0.04%
D Decade Resistor 1K. 10K. IOOK. 1000K. 10M
+.02%
E Cuirenf Calibrator 1mA. I OmA. 1OOmA. 1OOOmA.
10A
+.03% DCA. +.05% ACA
3-1

PERFORMANCE VERIFICATION MODELS 1351176
3.6. MODEL 135 PERFORMANCE VERIFICATION
3-7. DC Volts Verification
A Select ihe WV funann.
B. Connect the DC Calibrator ,ltem A. Table 3-I) to the
135 V-R and COM fermnals. Refer to Figure 3- 1
C~ Follow Table 3-2 and apply the required DC Voltage
fo, each range, “er~fy rhat each reading ISWI,,,,” spec-
iltcatlons iwed tn Table 3-2.
D, Repeat all checks with nega1,v.s voltage
TABLE 3-2
DC VOLTAGE PERFORMANCE CHECK
Range Applied
Voltage Allowable Reading at 18’C to 28°C
FIGURE 3-l
135 DC VOLTS VERIFICATION
3-6. AC Volts Verification
A~ Select the ACV functmn.
B. Connecr the AC calibrator (Item 8. Table 3-l) to the
135 V-Rand COM termlnais. Refer fo Figure 3-2,
C, Follow Table 3-3 and ~DDIY the reaulred AC Voltaae
for each range. Venfy th’ai <he reading IS wlfhtn speci-
ftca11ons Wed I” Table 3-3.
TABLE 3-3
AC VOLTAGE PERFORMANCE CHECK
Range Applied Voltage Allowable Reading
at 18°C to 28’C
l,OOOOVat 10KHz ~9885 to LO1 15
I O.OOOVat 500Hz 9,885to 10,115
2oov 100OOVat120Hz
98.85to 101,15 I
FIGURE 3-2
135 AC VOLTS VERIFICATION
746A P FIGURE 3-3
135 HI VOLTAGE ACV VERIFICATION
3-9. Resistance Verification
A. Select the OHMS funcrlon
By Conneci rhe Decade Resistor (Item 0. Table 3- 1) tothe
135 V-s2 and COM terrmnals. Refer 10 Flgure 3-4,
C. Follow Table 3-4 and apply the requfred ressstance
for each range. Vertfythat each read,ng isw,th,n soec-
lficatrons Ifsted in Table 3-4
FIGURE 3-4
135 RESISTANCE VERIFICATION

MODELS 135/l 76 PERFORMANCE VERIFICATION
TABLE 3-4
RESISTANCE PERFORMANCE CHECK
i
Range
2KR
ZOKR
200Kfl
2000KR
20MR
Allowable Reading
at 1wc to 28Y
9970 to 1,003o
9.978 to 10.022
99.78 to 100.22
997.8 to 1002.2
3.898 to 10.102
3-10. DC Amps Verification
A, Select the DC Amps function.
B. Connect the DC Calibrator ,l,em A. Table 3- 11 10 the
tnput of the Current Calibrator (Item E. Table 3-l I
Connect the OU,,,U, of ,he Current Calibrator to the
135’s mA and COM terminals. Refer 10 Figure 3-5.
C. Select the 20mA range and apply a 10,OOmA curren,
to the 135. Ver,fv that the reading IS with,” 9,93 to
10.07.
D. Select the 1OA range and connect the outp”, of the
Current Calibrator 10 the 135’s 10A Hi and 10A LO
terminals Refer to Figure 3-6
E. Apply lO.OOA to the 135 and ver,fy tha, rhe reading
IS w,,h,” 3.88 to 10.12,
3-11. AC Amps Verification
A~ Select the AC Amps functlon and the 20mA range.
8. Connect the AC Calibrator (Item B. Table 3-l) to the
mput of the Current Calibraror (Item E. Table 3-11
Connect the output of the Current Callbrafor to the
135’s mA and COM term~nais. Refer 10 Figure 3-7
C~ Apply a 10,OO mA currenr a, 500H2 and verliy lhal
the readfng IS w,th,n 9~80 to 10.20~
D. Select the 10A range and connect fhe outp”, of the
Curren, Calibrator fo the 135’s 10A HI and 1OA LO
terminals. Refer fo Figure 3-8.
E. Apply a 1O.OOA current at 500Hz and ver,fv that fhe
readang IS wfhin 9.80 10 10.20.
343A
343A
FIGURE 3-6
135 1OA DC AMPS VERIFICATION
FIGURE 3-7
135 AC AMPS VERfFlCATlON
FIGURE 3-5
135 DC AMPS VERIFICATION FIGURE 3-8
135 ,OA AC AMPS VERIFICATION

PERFORMANCE VERIFICATION MODELS 135/l 76
3-12. MODEL 176 PERFORMANCE VERlFlCATlON
3-l 3. DC Volts Verification
A. Select the OC Volts functuon.
6. Connect the DC Calibrator IItem A. Table 3-l) to the
176’s HI and LO ~npu, ierminals. Refer to Fig’ure 3.9.
C. Follow Table 3-5 and apply the required DC Voltage
for each range, Verify tha, each readtng ISwtfhin spec-
ifications Ifsted I” Table 3-5.
D. Repeat all checks wtth negatwe voltage,
TABLE 3-5
DC VOLTAGE PERFORMANCE VERIFICATION
Range
Applied
Voltage Allowable Reading
at 18°C to 28°C
I 4’ 1
I J
FIGURE 3-9
I76 DC VOLTS VERIFICATION
3- 14. AC Voltage Verification
A. Select rhe AC Volts funcuon.
By Connect the AC Calibrator and HVAmpllfier iltems B
and C. Table 3-l) to the 176’s HI and LO terminals.
Refer to Figures 3-10 and 3-1 1.
C. Follow Table 3-6 and apply the required AC Voltage
for each range. Verlfythafeach reading iswithIn spec-
lflcatlons listed ,n Table 3-6.
TABLE 3-6
AC VOLTAGE PERFORMANCE CHECK
Range Applied Voltage Allowable Reading
at 18°C to 28°C
;:: 11~OOOOVa,OOOOV at1OKHz1KHz .9885,9885 toto 1.011.01 1515
2% 11,OOOOVatO~OOOV at20KHz1KHZ 9,8859485 toto X051510,115
2ov lO.OOOVat 1OKHz 9.885 to 10.1 15
2ov 10,OOOVar 20KHz 9.485 to 10.515
2oov 100 OOV a, 1KHz 98.85 10 101,15
1ooov 1OOOOVal IKHz 988.5 to 101 1 5
FIGURE 3-10
176 AC VOLTS VERIFICATION
FIGURE 3-l 1
178 HIGH VOLTAGE ACV VERIFICATION
3-15. Resistance Verification
A, Select the OHMS funcnon.
8 Connect the Decade Re%$,or (hem 0. Table 3-I) to the
176 HI and LO ~npu, terminals. Refer to Figure 3.12.
C, Follow Table 3-7 and apply the reqwred resistance for
each ranae. Verlfv that each readina is within soeclfl-
cations ll;ted in fable 3.7~
TABLE 3-7
RESISTANCE VERIFICATION
Range Applied
Resistance
Allowable Reading
at 18’C to 28’C
I
1
FIGURE 3-l 2
176 RESISTANCE VERIFICATION
3-4

MODELS 135/176 PERFORMANCE VERIFICATION
3-16. DC Amps Verification
A. Select the DC Amps tunctton.
8. Connect the DC Calsbrator (Item A. Table 3-l I to the
,nputottheCurrentCai,bra,~r ,ltemE.Table 3-11, Con-
necf the output 01 the Current Calibraror to the 176 HI
and LO l”p”r terminals. Refer to Figure 3- 13.
C, Follow Table 3-8 and applv the required c”rrenf for
each ranges Verliy ihat each reading IS wrhln spew
flcatlons ilsted I” Table 3-8,.
TABLE 3-6
DC AMPS VERIFICATION
Range Applied
CtlrrWlt Allowable Reading at 16°C to 26°C
3-17. AC Amps Verification
A.
B.
C,
Select the !iC Amps funwon
Connect the AC Callbraror jlrem 6. Table 3-1, to the
~“puiotIheCurrentCaiibrator,ltemE,Tab,e3-ti Con-
nect the Outpu! of the Current Callbraior IO the 176 Hi
and LO termnals Refer to F,gure 3-14
Foliow Table 3-9 and apply the required curient for
each range. Vertiy that each reading 1s warhtn spew,-
cations ksted in Table 3-9
TABLE 3-9
AC AMPS VERIFICATION
I I
Range Applied Current I Allowable Reading
a* 19°C to 26°C
2mA 1~OOOmA ~993 IO 1~007 2mA 1.OOOmA at 1KHz 980 to 1320
20mA 1O~OOmA 9.93 10 10.07 20mA I O.OOmA ar 1KHz 9~80 10 IO 20
200mA 100 OmA 99.3 to loo,7 20OmA 100,OmA at 1KHz 9aoto 1023
2000mA 1000 rnA 993 to 1007 2000mA lOOO,mA at IKHz 980 10 1020
343A
FIGURE 3-13
176 DC AMPS VERIFICATION FIGURE 3.14 176 AC AMPS VERIFICATION
3-5

MODELS 135/l 76
Section 4. Theory of Operation
4-l. GENERAL
and graphs. Detacled st~emaiics of ,he Moaei 135 a”~
Model 176 are orovlded ,n Sewon 6
THEORY OF OPERATION
Th,s sect,on contatns the c,rc”~, descrtpflons for The
Model 135 and Model 176. The iollowng dlscusslons of
c,rcu,t theory veil be separated <“to 2 maw sect\ons~ The
2 map, SeCtIOnS are:
I ) Model 135 Circuu Theory
21 Model 176 Czrcutt Theory
The ~nfprmat,on contaned I” each of these 5ectto”s IS
arranged I” the following manner.
1, Overall Functional Description
7.1 Stgnal Condittonrig
3) A/D Converter
4) Display
51 Power SUPPlY
To facilnate understandtng. each descrtptton IS accom-
panted wth slmpilfied schematIcs. blockdlagrams. tables
V-Q ATTENUATOR
RESISTANCE
4-2. MODEL 136 OVERALL FUNCTIONAL
DESCRIPTION
The Mode, 135 1s a 4-1 i2 aqr. t20.000 co”“, hard
held DMM It has 4 DC voltage ranges. 4 AC voltage
ranoes. 5 res,srance ra”aes. 2 DC C”rre”l ranoes ant 2
The 135 was destgned for h#gh periormance ar zov? cosi
To meet these design goals the 135 takes advantage r,’
standard <off the shelf” components, The A/D c~)“vertel
was designed from scratch using dlscrete componenls for
lower power ‘onsumpt\on and ,mproved aeriorman:e
over prssen,ly available LSI A/D converters
Ftgure 4- 1 shops the overa,, bioce diagram 1-r xw mc^ei
135
+e.4v -5V ANALOG
IAC CONVERTER ONLY) +5V ANALOG
+5V DIGITAL
ANALOG
FIGURE 4.1
135 BLOCK DIAGRAM

THEORY OF OPERATION MODELS 135/l 76
4-3. Signal Conditioning
The Signal Condltlonlng for the Model 135 includes DC
arten~atmn iexcept on the 2 Volt range,. AC attenuation.
AC/DC conveis~an. Ohms conversion and current
ShUrxS.
A. DCV Signal Condittonlng consists of one lOMnpas-
swe dwder~ The taps tram this divider are inputted
dlrecrly to rhe A/D converter through the rotary range
watch S102. Table 4-1 state~~he associated attenua-
tton with each range, Potentiometer Rl 13 trims the
ga,n for the 20 Volt range. The overload protection
IS provided by the llmmng resistor Rl 15. C
TABLE 4-1
ACV AND DCyA7TENUATlON
Rl 1 1 establishes AC zero while R 109 determ,nes the
full scale gain (19000 counts), R105 and C 108 pro-
vlde the low pas5 f,lter ro average the half wave recw
fled outputs Overload protection IS prowded by d,odes
CR104 ahd CR105 and currentllmttlngreslstorR1 10.
Figure 4-2 shows a simplified SchematIc of the AC
cOn”erter.
Resistance Signal Condltloning 1saccomplished iax-
metrically. That IS. a precision reference resistor and
Rx are put in ser,es wth a 2,5 volt reference, There-
fore. the current developed i” the two ~BSIS~IIS 15the
same. Taking the ratlo of rhe voltage drop across Rx 10
the drop across R<e,e,en<ecoriectly caiculates ohms.
The value of the voltage reference IS irrelevant. as ,t
only serves to apply a source of currentto the ies,stors
(Rx and Rrc~ewncel. The preceding theory IS illustrated
mathematically in the following equations. Refer to
Figure 4-3,
I =
Vref
Rref + Rp + Rx
‘75OV range for ACV
B. ACV SIgnal Condmonmg consists of a 1OMR pasSwe
dwlder. AC buffer amplifier and AC co”verWr. The
scalmg IS accompi~shed by the same 10MSIwsswe
dlwder that IS used for DCV scaling, After the divider
rhe :,gna, IS AC coupled ,nto U105 the AC Buffer
Ampl~flei. The slgnai is then applied 10 the averaging
piec~~~on rectlfler U 104, It IS driven at low lmpedan.ce
by the AC coupled buffer U104 performs the AC con-
version, It then passes through a two stage low pass
filter which converts it to DC. This OC level IS applied
fo the A/D converter. Input resistance for the AC con-
verter is 1OfvUlshunrea by less than 100 pf.
Vdisplay = ;;;f;,:;;;f$ X 10,000
Vdisplay = I [Rx1 -0
lL~ref+flp+R~]-i[~p+~xJ x’o.ooo
IRX
Vdisp’av = , [Rref + Rp C Rx. Rp. Rx] x 10.000
Vdisplay = & X 10.000 = & X 10.000
lOMR DIVIDER
v2v
AC
COUPLING 7
2ov f---l* BUFFER PRECISION TWO STAGE
UlO!i - RECTIFIER - LOW PASS -
u104 FILTER
R105 Cl08
!
2oov
90KR
750v
1OKR
FIGURE 4-2
SIMPLIFIED AC CONVERTER BLOCK DIAGRAM
4-2