Keithley 195 User manual

Model 195
Instruction Manual
Contains Operating and Servicing Information for the
Model 195 Digital Multimeter
Publication Date: August 1983
Document Number: 195-90%OIC

WARRANTY
Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year from
date of shipment.
Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batter-
ies, diskettes, and documentation.
During the warranty period, we will, at our option, either repair or replace any product that proves to be defective,
To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Cleveland, Ohio. You
will be given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service facility.
Repairs will he made and the product returned, transportation prepaid. Repaired or replaced products are warranted for the balance
of the original warranty period, or at least 90 days.
LIMITATION OF WARRANTY
This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or misuse
of any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from battery leak-
age, or problems arising from normal wear or failure to follow instructions.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PROVIDED HEREIN
ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.
NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT,
INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRU-
MENTS AND SOFTWARE EVEN IF KEITHLBY INSTRUMENTS. INC.. HAS BEEN ADVISED IN ADVANCE OF THE POS-
SIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES’sHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS
OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAM-
AGE TO PROPERTY.
Road - Cleveland, OH 44139 - 440-248-0400 -Fax: 440-24X-6168 * http://www.keithley.com

Instruction Manual
Model 195
Digital Multimater
01992, Keithley Instruments, Inc.
Cleveland, Ohio, U.S.A.

SPECIFICATIONS
MAXIMLIM ALLOWABLE INPUT: IWDV peak
BENCH READING RATE: 5 readbwlaecond.
2Mo 10 n -2LmnA -2v o.oJ+ 7 o.ayI+ 1 0.015+1
*oMn Irn ” -x0* -1v 0.06+ 5 o,1m+ 5 o.m+*
+Afterpu&b”tto” orbusrrminx.
*I” wldktigitnwdr. counts-*2 bcept *t4 0” x-a rangeafterZerobIg,.
CONFRXJRATlON: Automatic 2- or 44erminal.
MAXM”M ALLOWABLE INT’DT: 36oVpeak or 250, nns.
BEN~NdEADWG RATE: 3 readb&sRand except2OMOrange, 1reading/
TRMS AC VOLTS (Option 19.50)
w/aEigiw ACCURACY(1YEAR),
*~%rd*+cwnal
,I” rv..di#t mode. divide cmlm error by 10. Above Irn”.
TEMPERAnJRE coEFFIclBNr loo-ISOC& 2ax5owz Leu tha” rt(O.lX
applicable accuracyspeeificatlonl/‘C.
RESPONSE:True mot mea” squarr, AC coupled.
CRESTFACTOR (ratio of peak to rmsl: Up to 3:l allowable.
INPUT IMPEDANCE: 2Mn shuntedby lea than 75pF.
MAXIMUM ALLOWABLE fNf%T: IWOV peak. IO’V.Hz.
BENCH READING RATE: 3 rexlii/seco”d.
CMRRzGreater than @dB at DC, 50 or 6OHz(with IkR in either lead).
BANDWIDTH: -3dB at 2SOkHztypical.
DC AMPS (Option 1950)
w/1wa, -TURF
ACamAcY(1YEAR,,* coEFRm MAnMuM
RESO *Pkd~+rounw
*,%rd*+cemw/‘c VOLTAGE
RANGE LvnON 18’28’C wwc b 28Be5oQc BmEN
20!A me. 0.14+40* 0.01+7. 0.03”
?m#t‘4 InA W-9+10 0.01+0.5 0.25v
2m.4 lti 0.09+10 0.0110.5 0.25v
x&A 0.09+10
222, 0.01+0.5 02.5v
0.09+10 0.01+0.5 0.28v
2.4 lOP.4 O.C9+lO o.ol+o.5 1 ”
t,n 4vdkit mode,coun*- *:2 kxapl 24 0” 2Qx.4nnxe afterzeroinn).
t4fm pushbuttonorbuszeroins.
OVERLOAD PROTECTION: 2A fuseLXOV), externally accessible
BENCH READING RATE: 5 r&i”gs/recond.
2.4 $4 Oh+353 0.04+10 1 v
,I” ‘Ivldt@tmode,dividecounte”vr by 10.Above0.5%Range.
RESPONSE:True mot meansquare, AC coupled.
CRESTFACTOR (ratio of peak to rms): Up to 3:l allowable.
OVERLOAD PROTECTION: 2A fure UOVI, externally acceaible.
BENCH READING RATE: 3 read&/second.
IEEE488 BUS IMPL!ZMENTATlON
MuMIne Cad: DCL, LLO, SIX. GET, GTL. LINT. UNL, SPE.SPD.
Unlllne Commands:IFC. REN. EOI. SRQ. ATN.
Interface Fwuttow: SHI, AHl. T5, TEO. L4, LEO,SRl. RLI, PPO,DCI,
DTI. co. El.
PTble Paramemr: Range.Function,Zero. integration Period, Ave+
EOI, T r. Terminator, Delay’, loo-rdg. Storage, Calibration,
i%i$,, Multl~Off. Status,ServtceRequest.SelfTest,Output Fannat.
‘First reading is cotsct when step input is c~incldemwith trigger.
Ccwemhm Rates(DC Volta): UbnnmmA
tReadt&&nd. V.&mat.%Hz.
Addrw Modes: TALK ONLY and ADDRESSABLE.
FRONT PANEL PROGRAMS
0 Clear - Camels program mode.
1 Non-volattle RAM st.,,age- Storeprograms3.4.5 and8datain NVRAM
2 MuhI lex - Defeatainput amplifier multlplexlw
3 IEEE1w mode- ADDRESSABLE and TALK ONLY entry.
4 Lhe frequency- Selects5si7. or tQH2 operation.
5 Caltbntlo” - Perfonnr digital calibration.
6 Extendedprognms - Enablerentry to aptiwal expanricn
7 Data lq&Sf7- Allows 1co.readlq storage*t 9 pm*amma rogams. POle rate%alw
storeshighest, lowest and average reading.
8 Dla~rtoatice- TmublesbooHngaid and self-test.
9 Trlggp: - Enablesfmnt panel or extemal tripgeflw.
GENERAL
DISPLAY: SIX0.5” LED digiti with de&md
ec?
oint,
Functionand IEEEbus statusalso display exponent and polarity.
- -.
ISOLATION: Input LO to IEEELO or
V*M; gnater tba” lO*Il paralleled owe?It&round: 5ooVA, 5 x lo’ ! y X’@F.
WARMup: 1 hour to rated accuracy.
OzTpG ENVIRONMENT: O”-5WC.0% to 80% relative humidity up
0
.- -- -.
STORAGE ENVIRONMENT: -25’ to 65%.
POWER: 10542sv or 21&?50v (internal switch &ctEd), 5042 to 4wfiz.
24V.A maximum. ‘9&llOV and lBo22OV version avatlable upon reauest.
CONNECTORS: Amlog: Stitch selectablefront or rear, 5wa; Sold piated
binding posts. Digttal: ‘Tririgger”input and %ltmeter Complete” output
on rear panel, BNCs.
DIMENSIONS, WEIGHT: 127mml&h X 216mmwide X 35%~” deep(5”
X 8’S” X 14%“).Net wetit 3.2kp.(7 Ibs.).

Safety Precautions
‘The following safety precautions should be observed before using
this product and any associated instrumentation. Although some in-
struments and accessories would normally be used with non-haz-
ardous voltages, there am situations where hazardous conditions
may be present.
This product is intended for use by qualified personnel who recog-
nize shock hazards and are familiar with the safety precautions re-
quired to avoid possible injury. Read the operating information
carefully before using the product.
The types of product users am:
Responsiblebody is the individual OIgroup responsible for the use
and maintenance of equipment, for ensuring that the equipment is
operated within its specifications and operating limits, and for en-
suring that operators BT~adequately trained.
Operators use the product for its intended function. They must be
trained in electrical safety procedures and proper use of the instm-
ment. They must be protected from electric shock and contact with
hazardous live circuits.
Maintenance personnel perform routine procedures on the product
N keep it operating, for example, setting the line voltage or mplac-
ing consumable materials. Maintenance procedures are described in
the manual. The procedures explicitly state if the operator may per-
form them. Otherwise, they should be performed only by service
personnel.
Servicepersonnel are trained to work on live circuits, and perform
safe installations and repairs of products. Only properly trained ser.
vice personnel may perfm’m installation and service procedures.
Exercise extreme caution when a shock hazard is present. Lethal
voltage may be present on cable connector jacks or tat fixtures. The
American National Standards Institute (ANSI) states that a shock
hazard exists when voltage levels greater than 3OV RMS, 42.4V
peak, or 60VDC are present. A good safety practice is to expect
that hazardous voltage ispresent in any unknown circuit before
measuring.
Users of this product must be protected from electric shock at all
times. The responsible body must ensure that users are prevented
accessand/or insulated from every connection point. In some cases,
connections must be exposed to potential human contact. Pmduct
users in these circumstances must be trained to protect themselves
from the risk of electric shock. If the circuit is capable of operating
ator above 1000 volts, no conductive part of the circuit may be
exposed.
As described in the International Electrotechnical Commission
@EC) Standard IEC 664, digital multimeter measuring circuits
(e.g., Keithley Models l75A, 199,ZOOQ2001, 2002, and 2010) are
Installation Category II. All other insmnnents’ signal terminals are
Installation Category I and must not he connected to mains.
Do not cmmect switching cards directly to unlimited power circuits.
They am intended to be used with impedance limited sources.
NEVER connect switching cards directly to AC mains. When con-
necting sourcesto switching cards, install protective devices to lim-
it fault current and voltage to the card.
Before operating an instrument, make sure the line cord is connect-
ed to a properly grounded power receptacle. Inspect the connecting
cables, test leads, and jumpers for possible wear, cracks, or breaks
before each use.
For maximum safety, do not touch the product, test cables, or any
other instruments while power is applied to the circuit under test.
ALWAYS remove power from the entire test system and discharge
any capacitors before: connecting or disconnecting cables or jump-
ers, installing or removing switching cards, or making internal
changes, such as installing or removing jumpers.
Da not touch any object that could provide a current path to the
common side of the circuit under test or power line (earth) ground.
Always make measurements with dry hands while standing on a
dry, insulated surface capable of withstanding the voltage being
measured.

The instrument and accessories must be used in accordance with its
specifications and operating instmctions or the safety of the equip-
ment may be impaired.
Do not exceed the maximum signal levels of the instruments and ac-
cessories, as defined in the specifications and operating informa-
tion, and as shown on the instrument or test fixture panels, or
switching card.
When fuses are used in a product, replace with sametype and rating
for continued pmtection against fire hazard.
Chassis connections must only be used as shield connections for
measuring circuits, NOT as safety earth ground connections.
If you are using a test fixture, keep the lid closed while power is ap-
plied to the device under test. Safe operation requires the use of a
lid interlock.
lfa@ screw is present, connect it to safety earth gmund using the
wire recommended in the user documentation.
Then symbol on an btstmment indicates that the user should re-
fer to the operating instructions located in the manual.
TheA symbol on an instrument shows that it can source or mea-
sure 1000 volts or more, including the combined effect of normal
and c~mrn~n mode voltages. Use standard safety precautions to
avoid personal contact with these voltages.
The WARNING heading in a manual explains dangers that might
result in personal injury or death. Always read the associated infor-
mation very carefully before performing the indicated procedure.
The CAUTION heading in a manual explains hazards that could
damage the instrument. Such damage may invalidate the warranty.
Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and
all test cables.
To maintain protection from electric shock and fire, replacement
components in mains circuits, including the power transformer, test
leads, and input jacks, must be purchased from Kcithley Ins&w
mats. Standard fuses, with applicable national safety approvals,
may be used if the rating and type are the same. Other components
that are not safety related may be purchased from other suppliers as
long asthey are equivalent to the original component. (Note that se-
lected pats should be purchased only through Keithley Instruments
to maintain accuracy and functionality of the product.) If you are
unsure about the applicability of a replacement component, call a
Keithley Instruments office for information.
To clean an insuument, use a damp cloth or mild, water based
cleaner. Clean the exterior of the instrument only. Do not apply
cleaner directly to the instrument or allow liquids to enter or spill
on the instrument. Products that consist of a circuit board with no
case or chassis (e.g., data acquisition board for installation into a
computer) should never require cleaning if handled according to it-
stmctions. If the board becomes contaminated and operation is af-
fccted, the board should be returned to the factory for proper
cleaning/servicing.
Rev. 7.199

TABLE OF CONTENTS
Paragraph Title Page
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.8.1
1.8.2
1.8.3
1.8.4
1.85
1.9
1.10
1.11
1.11.1
1.11.2
1.11.3
1.11.4
1.11.5
1.11.6
1.11.7
1.11.8
1.11.9
1.11.10
1.11.11
1.11.12
SECTION 1 GENERAL INFORMATION
Introduction .................................................................................
Model196Features ...........................................................................
WarrantyInformation .........................................................................
Manual Addenda .............................................................................
Safety Symbolsand Terms .....................................................................
Specifications. ...............................................................................
Unpackingandlnspection ......................................................................
PreparationForUse ...........................................................................
LinePower ........................................................................ . .......
LineVoltageSelection .......................................................................
LineFrequency .............................................................................
IEEEPrimaryAddress .......................................................................
Model185OptionPreparation.. ..............................................................
RepackingForShipment .......................................................................
Using the Model 195 Instruction Manual ..........................................................
Accessories ..................................................................................
Model1301TemperaturaProbe ...............................................................
ModellOlSRackMountingKit ................................................................
Model1600AHighVoltageProbe.. ...........................................................
Model1641KelvinTestLeadSet ..............................................................
Model165150-AmpereShunt ................................................................
Model1681Clip-OnTestLeadSet .............................................................
Model1682ARFProbe ......................................................................
Model1683UniversalTestLeadKit ............................................................
Model 1685 Clamp-On AC Current Probe .......................................................
Model 1691 General Purpose Test Lead Kit. .....................................................
Model 1950 AC Voltage; AC and DC Current Option .............................................
Model7008IEEE-488Cable.. ................................................................
SECTION 2 BASIC OMM OPERATION
Introduction .................................................................................
FrontPanelFamiliarization .....................................................................
Controls ...................................................................................
Terminals ..................................................................................
Displayandlndicators .......................................................................
TiltBail ....................................................................................
RearPanelFamiliariration ......................................................................
ConnectorsandTerminals ...................................................................
INPUTSSwitch ............................................................................
Fuses .....................................................................................
Power-UpProcedure ..........................................................................
DisplayMessage ..............................................................................
OverflowIndication.. .......................................................................
NoOptionMessage .........................................................................
ControlSelection .............................................................................
Function ..................................................................................
Range ....................................................................................
UsingZero .................................................................................
Filtering ...................................................................................
DisplayResolution.. ........................................................................
InputTerminalSelection .....................................................................
Triggering.. .................................................................................
l-l
l-l
l-l
l-l
l-1
l-l
1-2
1-2
l-2
1-2
1-2
l-2
l-2
l-2
1-3
l-3
l-3
1-3
1-3
1-3
13
1-3
13
1-3
l-3
l-3
1-3
l-3
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.3
2.3.1
2.3.2
2.3.3
2.4
2.5
2.5.1
2.5.2
Zl
2:6:2
2.6.3
2.6.4
2.6.5
2.6.6
2.7
2-l
2-1
2-1
2-2
2-2
2-2
2-2
2-3
2-3
2-3
2-3
24
El
2-6
2-5
2-6
2-5
2-6
2-7
2-7
2-7
i

2.7.1
2.7.2
2.7.3
2.7.4
2.8
2.8.1
2.8.2
2.8.3
2.8.4
2.8.5
2.9
2.9.1
2.9.2
t:
3:3
3.4
3.5
3.5.1
35.2
3.5.3
3.5.4
3.5.5
3.5.6
3.5.7
3.5.8
3.5.8
3.5.10
3.6
4.1
4.2
4.3
4.3.1
4.3.2
4.3.3
4.4
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.5
4.6
4.6.1
4.6.2
4.8.3
4.7
4.7.1
4.7.2
4.7.3
4.7.4
4.8
4.8.1
4.8.2
TABLE OF CONTENTS (CONT.)
FrontPanelTriggering ....................................................................... 2-7
ExternalTrigger ............................................................................ 2-7
VoltmeterComplete.............................................................~ ........... 2-8
TriggeringExample ......................................................................... 2-8
BasicMeasurements.. ........................................................................ 2-9
OCVoltageMeasurements ................................................................... 2-9
ResistanceMeasurements .................................................................. 2-10
ACVoltageMeasurements .................................................................. 2-11
OCCurrentMeasurements .................................................................. 2-11
ACCurrentMeasurements .................................................................. 2-11
TRMSConsiderations ........................................................................ 2-12
TRMSMeasurementComparison ............................................................ 2-12
CrestFactor .............................................................................. 2-13
SECTION 3 FRONT PANEL PROGRAMS
Introduction ................................................................................. 3-l
ProgrammingControls ........................................................................ 3-1
Front Panel Program Display Messages .......................................................... 3-1
ProgrammingNotes ........................................................................... 3-1
ProgramDescription .......................................................................... 3-3
ProgramO.Clear ............................................................................ 3-3
Program 1. Non-Volatile Storage .............................................................. 3-3
Program2.Multiplex ........................................................................ 3-3
Program 3. IEEEAddress and Talk-Only Mode ................................................... 33
Program4.LineFrequency ................................................................... 3-4
Program 5. Digital Calibration ................................................................. 3-4
Program6.Expansion ........................................................................ 3-5
Program7.OataLogger.. ................................................................... 3-5
ProgramS.Oiagnostics ...................................................................... 3-7
ProgramS.TriggerMode .................................................................... 3-8
ProgremmingScalingFactors .................................................................. 3-8
SECTION 4 IEEE-488 OPERATION
Introduction ................................................................................. 4-l
BusDescription .............................................................................. 4-l
IEEE488BusLines ........................................................................... 4-2
SusManagementLines ...................................................................... 4-2
HandshakeLines ........................................................................... 4-2
DataLines ................................................................................. 4-3
BusCommends.. ............................................................................ 4-3
UnilineCommands .......................................................................... 4-3
UnivenalCommands ........................................................................ 4-3
AddressedCommands ...................................................................... 4-4
UnaddressCommands ...................................................................... 4-4
Device-DependentCommands ................................................................ 4-4
Command Codes ............................................................................. 44
CommandSequence .............................................................. . ........... 4-4
Addressed Command Sequence ............................................................... 46
UniversalCommandSequence ............................................................... 4-6
Device-Dependent Command Sequence ....................................................... 4-6
Hardwareconsiderations ...................................................................... 4-6
Typical Controlled Systems .................................................................. 4-6
BusConnections.. ......................................................................... 4-6
PrimaryAddressProgramming ................................................................ 4-8
Talk-Only Mode ............................................................................ 49
Softwareconsiderations ....................................................................... 4-9
Controller Interface Routines ................................................................. 4-9
HP-85BASlCStatements .................................................................... 4-9
ii

4.03
4.8.4
4.9
4.9.1
4.9.2
4.9.3
4.8.4
4.9.5
4.9.6
4.9.7
4.9.8
4.10
4.10.1
4.10.2
4.10.3
4.10.4
4.10.5
4.10.8
4.10.7
4.10.8
4.10.9
4.10.10
4.10.11
4.10.12
4.10.13
4.10.14
4.10.15
4.10.16
4.10.17
4.10.18
4.10.19
4.10.20
4.11
4.11.1
4.11.2
4.11.3
4.12
5.1
5.2
5.3
5.4
5.5
55.1
5.5.2
5.5.3
5.54
5.5.5
6.1
2
6:3.1
6.3.2
6.3.3
6.3.4
TABLE OF CONTENTS (CONT.1
InterfacaFunctionCodas ................................................................... 410
Model 195 Interface Commands .............................................................. 4-10
General Bus Command Programming ........................................................... 411
REN (Remote Enable) ...................................................................... 4-11
IFClInterfaceClear) ........................................................................ 4-11
LLOlLocalLockout) ....................................................................... 4-12
GTL(GoToLocall ......................................................................... 4-12
DCL(DeviceClear) ......................................................................... 4-12
SDC (Selective Device Clear) ................................................................ 412
GETlGroupExecuteTriggsrJ ................................................................ 4-13
Serial Polling (SPE, SPD) ................................................................... 413
Device-Dependent Command Programming ..................................................... 4-13
Execute(X) ............................................................................... 4-14
FunctionfF) ...................................................................... . ....... 4.14
Range(R) ................................................................................ 4-14
Rate(S) .................................................................................... 4-16
ZeroCommandIZ) ......................................................................... 4-17
Filter. .................................................................................... 4-17
Triggering (Tl ............................................................................. 4-17
EOIIK) ................................................................................... 4-18
Multiplex(A) .............................................................................. 4-18
Delay(W) ................................................................................ 4-18
StatusWord ........................................................................... 4-19
SRQ Mode (M) and Status Bvte Format. ...................................................... 4-20
BufferCommand (Qand El ................................................................. 4-21
DateFormat ........................................................................... 4-22
DigitalCalibration ......... ..i .......................................................... 4-23
Non-VolatileMemorvStoragefL) ............................................................ 4-24
SelfTest .............................................................................. 4-24
ProgrammingTerminator(Y). ............................................................ 4-24
HitBunonlH) ............................................................................. 4-26
Display(D) ............................................................................... 4-25
FrontPanelErrorMessages ................................................................... 426
IDDCError ............................................................................... 4-26
IDDCOError .............................................................................. 4-26
NoRemoteError .......................................................................... 4-26
ReadingRates .............................................................................. 4-27
SECTION 6 PERFORMANCE VERIFICATION
Introduction ................................................................................. 5-l
EnvironmentalConditions ...................................................................... 51
RecommendedTestEquipment ................................................................. 6-l
InitialConditions .............................................................................. 5-l
Verificationprocedure ......................................................................... 5-l
DCVoltageAccuracyCheck .................................................................. 5-2
ResistanceAccuracyCheck .................................................................. 52
AC Voltage Accuracy Check (with Model 1950 Option) ............................................ 6-3
DC Current Accuracy Check (with Model 1950 Option) ........................................... 6-4
AC Current Accuracy Check (with Model 1950 Option) ........................................... 6-6
SECTION 6 THEORY OF OPERATION
Introduction .................. . .............................................................. 6-l
Overall Functional Description ................................................................. 8-1
AnalogCircuitF/ .............................................................................. 6-l
InputSwitchingandMultiplexer .............................................................. 6-l
InputBufferAmpiifier ....................................................................... 8-3
-2VReferenceSource ....................................................................... 6-3
AIDConverter ............................................................................. 6-3
iii

6.4
6.4.1
6.4.2
6.4.3
6.4.4
6.4.5
6.4.6
6.4.7
6.4.8
:i
6:7
8.7.1
6.7.2
6.7.3
6.7.4
7.1
7.2
7.3
7.3.1
7.3.2
7.4
7.5
7.5.1
7.5.2
7.5.3
7.5.4
7.5.5
7.5.6
7.5.7
75.8
7.5.9
7.8
7.7
7.8
7.8.1
7.8.2
7.83
7.8.4
7.8.5
7.8.8
7.8.7
7.8.8
7.8.9
7.8.10
8.1
8.2
8.3
8.4
8.5
TABLE OF CONTENTS (CONT.1
DigitalCircuitry ............................................................................... 8-5
Microcomputer Block Diagram ................................................................ 8-5
MemoryMapping ........................................................................... 65
AddressDecoding.. ........................................................................ 6-5
MicrocomputerReset ....................................................................... 6-7
6522VIA .................................................................................. 6-7
IEEElnterface ............................................................................... 6-7
Display Board .............................................................................. 6-7
Serial-Parallel Conversion .................................................................... 6-7
PowerSupply ................................................................................ 6-8
Modell950AClCurrentOption ................................................................. 6-8
Circuit Operation During Measurements. ......................................................... 6-8
DCVoltageMeasurement .................................................................... 8-8
Circuit Operation During Resistance Measurements .............................................. 6-9
2- and 4-Terminal Resistance Considerations ................................................... 6-l 1
Circuit Operation During Model 1950 Option Measurements ....................................... .8-11
SECTION 7 MAINTENANCE
Introduction.. ............................................................................... 7-l
LineVoltageSelection ......................................................................... 7-1
FuseReplacement ............................................................................ 7-l
LineFuse...............................................................................~ .. 7-1
AmpsFuse ................................................................................ 7-2
Model 1950 AC/Amps Option Installation ........................................................ 7-2
CaObration ................................................................................... 7-3
Recommended Calibration Equipment ......................................................... 7-3
Environmental Conditions .................................................................... 7-3
WarmUpPeriod ........................................................................... 7-3
DCVoltageCalibration ...................................................................... 7-4
ResistanceCalibration ....................................................................... 74
ACVoltegeCalibration ...................................................................... 7-5
AC and DC Current Calibration ................................................................ 7-8
Non-Volatile Storage of Calibration Constants. .................................................. 7-6
CalibrationJumpers ......................................................................... 7-8
Special Handling of Static Sensitive Devices ...................................................... 7-7
Disassembly Instructions ....................................................................... 7-7
Troubleshooting ............................................................................ 7-0
RecommendedTestEquipment ............................................................... 7-8
Power-Up Self Diagnostics ................................................................... 7-8
SelfDiagnosticProgram ..................................................................... 7-9
PowerSupplyChecks ....................................................................... 7-9
A/DConverrerandDisplay ................................................................... 7-9
Input Attenuator and Ohms Source Checks ..................................................... 7-9
Input Multiplexer and Buffer Amplifier ......................................................... 7-9
Digital Circuitry. ............................................................................ 7-9
Modell950AC/AmpsOption.. .............................................................. 7-9
BufferAmplifierGainChecks ................................................................ 7-15
SECTION 8 REPLACEABLE PARTS
Introduction ................................................................................. El
PartsList .................................................................................... 8-I
Orderinglnformation .......................................................................... 9-l
Facton/Service ............................................................................... 8-l
Schematic Diaarams and Component Location Drawinas ........................................... 8-l
iv