Keithley 197A User manual

Model 197A AutorangingMicrovolt DMM
User’sManual
MYMY
A GREATER MEASURE:~OF CONFIDENCEA GREATER MEASURE:~OF CONFIDENCE

Model 197AAutoranging Microvolt DMM
User’s Manual
01990, Keithley Instruments, Inc.
All rights reserved.
Cleveland, Ohio, U.S.A.
Third Printing, February 2001
Document Number: 197A-901.01 Rev. C

SAFETY PRECAUTIONS
The following safety precautions should be observed before operating the Model 197A.
This instrument is intended for useby qualified personnel who recognize shock hazards and arefamiliar with the safety
precautions required to avoid possible injury. Readover the manual carefully before operating this instrument.
Exercise extreme caution when ashock hazard is present at the instrument’s input. The American National Standards
Institute (ANSI) statesthat ashock hazard exists when voltage levels greater than 30V ms or 424V peak are present. A
good safety practice is to expect that ahazardous voltage is present in any unknown circuit before measuring.
Inspect the test leads for possible wear, cracksor breaks before eachuse.If any defects arefound, replace the testleads.
For optimum safety do not touch the testleads or the instrument while power isapplied to the circuit under test.Turn the
power off and discharge all capacitors, before connecting or disconnecting the instrument.
Do not touch any object which could provide acurrent path to the cmnmon side of the circuit under test or power line
(earth) ground. Always make measurements with dry hands while standing on adry, insulated surface, capable ofwith-
standing the voltage being measured.
Exercise extreme safety when testing high energy power circuits (AC line or mains, etc).Refer to High Energy Circuit
Safety Precautions found in paragraph 2.2.
Do not exceed the instrument’s maximum allowable input asdefined in the specifications and operation section.
Instrumentation and accessoriesshould not be connected to humans.

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 are situations whcrc 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
cweiully beiorc using the product.
The types of product osers arc:
Responsible body is the individual or group responsible for the use
and maintenance oi equipment, for ensuring that the equipment is
operated within its specifications and operating limits, and ior en-
suring that operators are adequately trained.
Operators use the product ior its intended function. They most be
trained in electrical safety procedures and proper use of the instn-
ment. They most bc protected from electric shock and contact with
hazardous live circuits.
Maintenance personnel perform routine procedures on the product
to keep it operating, ior example, setting the line voltage or replac-
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
pCIS”tttEl.
Service personnel arc trained to work on live circuits, and perform
safe installations and repairs of products. Only properly trained ser-
vice personnel may perform installation and service procedures.
Keitbley products are designed ior “se with electrical signals that
are rated Installation Category I and Installation Category II, as de-
scribed in the International Electratechnical Commission (IEC!)
Standard IEC 60664. Most measurement, conaol, and data I/O sig-
nals are Installation Category I and most not be directly connected
to mains voltage or to voltage sowces with high transientovcr-volt-
ages. Installation Category II connections require protection for
high transient over-voltages often associated with local AC mains
connections. The user should assome all measurement, control, and
data I/O connections zwefor connection to Category 1sources un-
less otherwise marked or described in the Manual.
Exercise extreme caution when a shock hazard is present. Lethal
voltage may be present on cable connector jacks or test fixtures. The
American National Standards Institute (ANSI) states that a shock
hazard exists when voltage levels greater than 30V RMS, 42.4V
peak, or 60VDC are present. A good safety practice is to expect
that hazardous voltage is present in any unknown circuit before
measuring.
Users oi 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. Product
users in these circumstances must be trained to protect themselves
from the risk of electric shock. If the circuit is capable of operating
at or above 1000 volts, no conductive part of the circuit may be
exposed.
Do not connect switching cards directly to unlimited power circtdts.
They are intended to be used with impedance limited sources.
NEVER connect switching cards directly to AC mains. When con-
necting sources to switching cards, install protective devices to lim-
it fault current and voltage to the card.
Before operating an instrument, make sorethe 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.
When installing equipment where accessto the main power cord is
restricted, such asrack mounting, a separate main input power dis-
connect device must be provided, in close proximity to the equip-
ment and within easy reach of the operator.
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.
Do not touch any object that could provide a current path to the com-
mon side oitbe circuit under testor power line (earth) ground. Always
make mea~uremem with dry handswhile standing on adry, insulated
surface capable of withstanding the voltage being measured.

The instrument and accessories must be used in accordance with its
specifications and operating instructions 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 inform%
lion, and as shown on the instrument or test fixture panels, or
switching card.
When fuses are usedin a product, replace with same type and rating
for continued protection against fire hazard.
Chassis connections must only he 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.
Ifa@ screw is present, connect it to safety earth ground using the
wire recommended in the user documentation.
The n ! symbol on an instrument indicates that the user should re-
fer to the operating instructions located in the manual.
Then symbol on an instrument shows that it can source or mea-
sure 1000 volts or more, including the combined effect of normal
and common 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.
lnslrumentation 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 Keithley Instru-
merits. 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 parts should be purchased only through Keithley Instruments
to maintain accumcy 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 instrument, 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 insrmment. 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 in-
structions. If the board becomes contaminated and operation is af-
fected, the board should be returned to the factory for proper
cleaning/servicing.
7JOl

197A5%-D&$ Mukimeter Specifications
DCVOLTS .4CC”RMx”*
*(?&r*g+CO”rm,
DCAMPS

Table of Contents
SECTION 1 - General Information
1.1 INTRODUCTION ...................................................
1.2 FEATURES .........................................................
1.3 WARRANTY INFORMATION ........................................
1.4 MANUALADDENDA ...............................................
1.5 SAFETY SYMBOLS AND TERMS .....................................
1.6 SPECIFICATIONS.. .................................................
1.7 UNPACKING AND INSPECTION .....................................
1.8 USING THE MODEL 197A MANUAL .................................
1.9 INITIALOPERATION ...............................................
1.10 ACCESSORIES ......................................................
SECTION 2 - Bench Operation
2.1 INTRODUCTION ......................................................................... 2-l
2.2 HIGH ENERGY CIRCUIT SAFETY PRECAUTIONS ........................................... 2-l
2.3 PREI’ARATIONFORUSE .................................................................. 2-2
2.3.1 LinePower ............................................................................. 2-2
2.3.2 BatteryPackPower ...................................................................... 2-2
2.3.3 BatteryCharging ........................................................................ 2-2
2.4 FRONT AND REAR PANEL FAMILIARIZATION ............................................. 2-2
2.4.1 Display ................................................................................ 2-2
2.4.2 FrontPanelControls ..................................................................... 2-4
2.4.3 InputTerminals ......................................................................... 2-4
2.4.4
Current FuseReplacement ................................................................ 2-4
2.4.5 RearPanelSwitches ..................................................................... 2-5
2.5 ERRORMESSAGES ....................................................................... 2-5
2.6 OPERATINGCONDITlONS ................................................................ 2-5
2.6.1 Environmental Conditions ................................................................ 2-5
2.6.2 MaximumAllowableInputs .............................................................. 2-5
2.6.3 warmup ............................................................................... 2-b
2.7 BASICBENCHMEASUREMENTS .......................................................... 2-b
2.7.1 PowerUp .............................................................................. 2-b
2.7.2 Relative Mode .......................................................................... 2-b
2.7.3 DCVoltageMeasurement ................................................................. 2-7
2.7.4 TRMSACVoltageMeasurements .......................................................... 2-8
2.7.5 Microvolt Measurement Considerations .................................................... 2-8
2.7.6 ResistanceMeasurements.. ............................................................... 2-9
2.7.7 Current Measurements (DC or TRMS AC) .................................................. z-11
2.7.8 ACI’lusDCMeasurements ............................................................... z-12
2.7.9 dB Measurements ....................................................................... 2-13
2.7.10 dB Measurement Considerations and Applications ........................................... 2-15
2.7.11 MIN/MAX and 100 Point Data Logger Operation ........................................... 2-16
2.7.12 DiodeTest .............................................................................. 2-16

2.8 TRMSCONSIDERATIONS ................................................................. 2-17
2.8.1 ACVoltageOffset ....................................................................... Z-17
2.8.2 TRMSMeasurementComparison .......................................................... 2-17
2.8.3 CrestFactor ............................................................................ 2-17
2.8.4 Extended Frequency Response ............................................................ 2-17
SECTION 3 - Performance Verification
3.1 INTRODUCTION.. ..................... ................................................. 3-l
3.2 ENVIRONMENTAL CONDITIONS ....... ................................................. 3-l
3.3 RECOMMENDED TEST EQUIPMENT ..... ................................................. 3-1
3.4 INITIAL CONDITIONS .................. ................................................. 3-l
3.5 VERIFICATION PROCEDURE ............ ................................................. 3-2
3.5.1 DC Voltage Accuracy Check ............ ................................................. 3-2
3.5.2 AC Voltage Accuracy Check ............ ................................................. 3-3
3.5.3 Resistance Accuracy Check ............. ................................................. 3-4
3.5.4 DC Current Accuracy Check ............ ................................................. 3-6
3.5.5 AC Current Accuracy Check ............ ................................................. 3-7
SECTION 4 - Maintenance
4.1 INTRODUCTION ......................................................................... 4-1
4.2 DISASSEMBLY INSTRUCTIONS ............................................................ 4-l
4.3 BATTERY PACK (Model 1978) INSTALLATION ............................................... 4-3
4.4 LINE VOLTAGE SELECTION ............................................................... 4-4
4.5 FUSEREPLACEMENT .................................................................... 4-5
4.5.1 LineFuseReplacement ................................................................... 4-5
4.5.2 Current Fuse Replacement ................................................................ 4-5
4.6 FRONTPANELCALIBRATION ............................................................. 4-5
4.6.1 Recommended Calibration Equipment ..................................................... 4-6
4.6.2 Environmental Conditions ................................................................ 4-6
4.6.3 CalibrationSwitch ....................................................................... 4-6
4.6.4 DC Voltage Calibration ................................................................... 4-6
4.6.5 ACVolageCalbration ................................................................... 4-7
4.6.6 FrequencyCompensation ................................................................ 4-7
4.6.7 Resistance Calibration ................................................................... 4-9
4.6.8 CalibrationStorage ...................................................................... 4-10

List of Illustrations
SECTION 2 - Bench Operation
Figure 2-l
Figure 2-2
Figure 2-3
Figure 2-4
Figure 2-5
Figure 2-6
Figure 2-7
Figure 2-8
Figure 2-9
Figure Z-10
Model 197A Front Panel
Model 197A Rear Panel
DC Voltage Measurements
TRMS AC Voltage Measurements
Four Terminal Zeroing
Two Terminal Resistance Measurement
Four Terminal Resistance Measurement
Current Measurement Between 2000mA and 20A
Current Measurements up to 2000mA
Typical ACV Frequency Response
SECTION 3 - Performance Verification
Figure 3-1
Figure 3-2
Figure 3-3
Figure 3-4
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Connections for DCV Verification .......................................................
Connections for ACV Verification .......................................................
Connections for 200R 2kQ and 2Okn Range Verification (4.terminal) ........................
Connections for 2OOkQ through Ma Ranges Verification (2-terminal) .........................
Connections for DC Current Verification (200pA to 2000mA) ................................
Connections for DC Current Verification (2000mA to 20A) ..................................
Connections for AC Current Verification (200pA to 2000mA) ................................
Connections for AC Current Verification (2000mA to SOA) ..................................
SECTION 4 - Maintenance
Figure 41
Figure 42
Figure 43
Figure 4-4
Figure 4-5
Figure 4-6
Model 197A Miscellaneous Parts .......................................................
Display Assembly Exploded View ......................................................
DC Voltage Calibration Configuration ..................................................
AC Voltage Calibration Configuration ..................................................
ZOO,2k and 20k Four Wire Resistance Calibration .........................................
2OOk, 2M and 20M Two Wire Resistance Calibration. ......................................
2-3
2-3
2-7
2-8
2-10
2-11
2.11
2-l 2
2-12
2.18
3-2
3-4
3-5
3-5
3-6
3-7
3-R
3-8
4-2
4-4
4-7
4-8
4-9
4-10

List of Tables
SECTION 2 - Bench Operation
Table 2-1 ErrorMessages ....................................................................... 2-5
Table 2-2 Model 197A Maximum Allowable Inputs ................................................. 2-6
Table 2-3 ResistanceRanges ..................................................................... 2-10
Table 2-4 dB Specifications for DC Volts (6000 Ref) ................................................. 2-13
Table 2-5 dB Specifications for AC Volts (6OOQ Ref) ................................................. 2-13
Table 2-6 Selectable Reference Impedances ........................................................ 2-13
Table 2-7 Levels for Other Reference Impedances .................................................. 2-14
Table 2-8 Comparison of Average and TRMS Meter Readings ........................................ 2-19
SECTION 3 -
Performance Verification
Table 3-l
Equipment Specifications ...........................................
.............
Table 3-2 Limits for DC Voltage Verification ...................................
.............
Table 3-3 Limits for AC Voltage Verification ...................................
.............
Table 3-4 Limits for Resistance Verification ....................................
.............
Table 3-5 Limits for DC Current Verification ...................................
.............
Table 3-6 Limits for AC Current Verification ...................................
.............
SECTION 4 - Maintenance
Table 4-l lnput Terminal Identification ........................................................... 4-3
Table 4-2 Recommended Calibration Equipment ................................................... 4-6
Table 4-3 DCVoltageCalibration ................................................................ 4-7
Table 4-4 ACVoltageCalibration ................................................................ 4-9
Table 4-5 ResistanceCalibration ................................................................. 4-9
3-2
3-3
3-3
3-4
3-7
3-9

SECTION 1
General Information
1.1 INTRODUCTION
The Model 197A is a six function, 5-l/2 digit resolution
autoranging digital multimeter with a ?220,000 count
LCD (Liquid Crystal Display). This A/D range is greater
than the normal +199,999count A/D used in many 5-l /2
digit DMMs. The 5-l /2 digit resolution allows the Model
197AtomeasureDC voltage for lpV/count to IOOOV.AC
voltage and current measurements are standard in the
Model 197A. TRMS ACV capability ranges from lpVv/
count to 750V.The Model 197A measuresres&ance from
1rnQ to 22OMQ on seven resistance ranges. The Model
197A has six current ranges that measure current from
1nA (WA) to 10A.
The dB function makes it possible to compress a large
range of readings into amuch smaller scope.Model 197A
dBm measurements can be referenced to 50,75,93,135,
300or 6OOQ(default), but canbe modified with the useof
the relative (REL) feature.
The Model 197Ahas two IEEE-488interface options: The
Model 1972Aand the Model 1973A.These optional inter-
facesenhance the capabilities of the Model 197A by al-
lowing programmed control over the IEEE-488bus. The
Model 1977-Aalso includes an analog output. The bus
commands arethe samefor eachinterface and respond to
IEEE-488protocol.
1.2 FEATURES
The Model 197A includes the following features:
1. Six Measurement Functions - DCV, ACV, DCA,
ACA, OHMS and dB all built in.
2. @EL) Relative Mode - The relative mode allows
offsets to be nulled out (e.g. test lead resistance for
low resistance measurements) and selectsa variety
of reference impedances for dB measurements.
3. Digital Calibration - A non-volatile RAM stores
calibration constants and canbe performed from the
front panel or over the IEEE-488bus.
4. Data Logger -A data storage buffer is included to
allow up to 100readings and minimum/maximwn
readings beintemallystored at auserselectablerate.
The buffer may beread and controlled from the front
panel or over the IEEE-488 bus. In the talk-only
mode, the output rate can also be programmed.
5. Autoranging - The Model 197A includes a fast
autoranging feature for easier measurements.
6. 5-l/2 Digit Resolution - The Model 197A has a
2220,000 count A/D that surpasses the more corn-
man 1199,999count A/D.
7. Four Terminal Ohms-These terminals are used to
eliminate the voltage from acrossthe current carry-
ing leads.
8. Sensitivity - The Model 197A has lpV, lmX2 and
1nA sensitivity. The 1pVof sensitivity allows minute
levels of offset, temperature etc.A ltisensitivity al-
lows low current measurements without special
equipment. Measure leakage, bias and offset CUP
l-1

SECTION 1
General Information
rent. A lma sensitivity allows easy low resistance
measurements.
9. Electroluminescent Display Backlight - An
electroluminescent display backlight is used to enhance
the liquid crystal display under low light or dark
conditions.
10. dB Reference Impedances - Selectable dB reference
impedances of 5OQ 754 930, 1354 3OOn and 6OOn
(default).
1.3ARRANTY INFORMATION
Warranty found on the inside front
cover of tit become necessary to
exercise the warranty,ntact your Keithley representative
or the factory to determine the proper course of action.
Keithley Instruments maintains service facilities in the
United States, United Kingdom and throughout Europe.
Information concerning the application, operation or
service of your instrument may be directed to the
applications engineer at any of these locations. Check the
inside front cover for sses.
1.4 MANUAL ADDENDA
information concerning improvements or changes to this
instrument which occur after the printing of this manual
will be found on an addendum sheet ined with this
manual. Be sure to review these changes before attempting
to operate or service the instrument.
1.5 SAFETY SYMBOLS AND TERMS
The following safety symbols and terms are used in this
manual or found on the Model 197A.
The symbol A on the instrument denotes the user
should refer to the operating instructions in this manual.
The symbol A on the instrument denotes that a poten-
tial of 1OOOVor more may be present on the terminal(s).
Standard safety practices should be observed when such
dangerous levels are encountered.
The WARNING heading used in this manual explains dan-
gers that could result in personal injury or death.
The CAUTION heading used in this manual explains haz-
ards that could damage the instrument.
1.6 SPECIFICATIONS
Detailed Model 197A specifications may be found preced-
ing the table of contents of this manual.
1.7 UNPACKING AND INSPECTION
The Model 197A Autoranging Microvolt DMM was care-
fully inspected, both electrically and mechanically before
shipment. Upon receiving the instrument, carefully unpack
all items from the shipping carton and check for any obvi-
ous signs of physical damage that may have occurred dur-
ing transit. Report any damage to the shipping agent.
Retain and use the original packing material in case reship-
ment is necessary. The following items are shipped with
every Model 197A order:
l Model 197A Autoranging DMM
. Model 197A User’s Manual
. Model 1751 Safety Shrouded Test Leads
l Additional accessories as ordered.
If an additional instruction manual is required, order the
manual package (K&Hey Part Number 197A-901-00). The
manual package includes an instruction manual and any
applicable addenda.
1.6 USING THE MODEL 197A MANUAL
This manual contains information necessary for operating
and servicing the Model 197A Autoranging Microvolt
DMM and the 1978 Rechargeable Battery Pack. This section
of the manual contains general information and an initial
operation procedure. The rest of the manual is organized as
follows:
Section 2 contains detailed bench operation information
for the Model 197A.
Section 3 contains the information needed to verify the
accuracy of the Model 197A. l’erformance verification
can be done upon receipt of the unit or whenever the
basic accuracy of the instrument is in question.
Section 4 contains information on maintenance and cal-
ibration for the Model 197A.
NOTE
The Models 1973A and 1972A IEEE-488 inter-
faces come supplied with their own manual.
1-2

SECTION 1
General Information
1.9 INITIAL OPERATION
Perform the following steps in sequence to acquaint your-
self with the basic operation of the Model 197A.
Verify that the instrument was not damaged in transit,
(see paragraph 1.7).
Carefully read over all safety information (see Section 2
Basic Operation).
Refer to paragraph 2.3 (Line Power) and set the line
voltage switch. Connect the female end of the power
cord to the AC receptacle on the rear of the Model 197A.
Plug the other end of the line cord into a properly
grounded receptacle. If the Model 1978 is installed, the
charging circuit is activated.
Acquaint yourself with the front panel controls as
follows:
1.
2.
3.
4.
5.
6.
7.
Turn on the instrument using the ON/OFF
button. All of the zeroes are briefly displayed.
Connect the supplied test leads to the HI and LO
input terminals. Connect the red test lead to the
HI terminal and the black test lead to the LO ter-
minal. Short the test leads together.
Select AC volts and autoranging by pressing in
the AC/DC, V, and AUTO buttons. The AC,
AUTO, and mV annunciators are displayed.
Pressing in any of the other range buttons acti-
vates manual ranging. This is indicated by the
absence of the AUTO annunciator.
Select DC volts by releasing (out position) the
AC/DC button. V is still selected. The AC annun-
ciator turns off.
Select the autoranging OHMS by pressing in the
AUTO, and a buttons. DC must still be selected.
The n (omega) symbol is displayed. Press the
AC/DC button in (means select AC) and note the
“Err” message is displayed. This indicates an
invalid mode.
Select AC or DC current by setting the AC/DC
button accordingly and pressing in the A button.
The annunciator that reflects the selected mode in
displayed. Note that current will not autorange.
The 10A and LO terminals must be used on the
10A range.
Select dB by selecting AC or DC volts and press-
ing the dB button. The dB annunciator will turn
on and the default reference impedance (600R)
will be displayed momentarily. Pressing dB a sec-
ond time disables the dB measurement mode. To
select an alternate dB reference impedance,
enable dB as previously described, but hold in the
dB button to scroll through the alternate imped-
ance selections. Release the dB button when the
desired dB reference impedance is displayed.
When finished, again press dB to exit the dB
mode.
The REL (relative) feature can be used with any
measurement function: Volts, Amps, Ohms, or
dB. For example, select the ohms function and
autorange. The display reads approximately
000.14OQ which is the test lead resistance. Press
the REL button. The REL annunciator is turned
on and the display reads OOO.OOOfi.The relative
level of 000.14n will be subtracted from all subse-
quent measurements. Press the REL button a sec-
ond time to cancel the REL level.
To activate the 100 point DATA LOGGER with
minimum/maximum, press and hold in the
STOiCLR button. When the reading rate r=O is
displayed release the STO/CLR button. The ST0
annunciator turns on. Press the RCL button and
the last data point is briefly displayed followed
by the reading (data). Other data points can be
displayed by holding in the RCL button. Turn off
the DATA LOGGER by pressing the STO/CLR
button again.
1.lO ACCESSORIES
The following accessories can be used with the Model
197A.
MODEL 1010 SINGLE RACK MOUNTING KIT - Used to
mount one Model 197A in a standard 5-l /2” x 19” rack.
MODEL 1017 DUAL RACK MOUNTING KIT - Used to
mount two Model 197As in a standard 5-l/4” x 19” rack.
MODEL 1301 TEMPERATURE PROBE - A rugged low
cost temperature probe designed to allow precision tem-
perature measurements from -55 to 150°C.
MODEL 1600A HIGH VOLTAGE PROBE -Extends DMM
measurements to 4OkV.
MODEL 1641 KELVIN TEST LEAD SET - Special clip
leads allow 4terminal measurements to be made while
making only two connections.
l-3

SECTION 1
General Information
MODEL 1651 50-AMPERE CURRENT SHUNT - The
external O.OOlQ il% 4.terminal shunt, permits current
measurements from 0 to 50A AC or DC.
MODEL 1681 CLIP ON TEST LEAD SET - Contains two
leads, 1.2m (48”) long terminated with banana plugs and
spring action clip probes.
MODEL 1682 R.F PROBE - Permits voltage measurements
from 1OkHz to 250MHz. AC to DC transfer accuracy is
ildB from 1OOkHz to 250MHz at IV, peak responding, cali-
brated in RMS of a sine wave.
MODEL 1684 HARD SHELL CARRYING CASE - Hard
vinyl case, 1OOmm x 3OOmm x 350mm (4” x 13” x 14”) has a
fitted foam insert with room for the Model 197A, an
instruction manual and small accessories.
MODEL 1685 CLAMP ON AC PROBE -Measure AC CUT-
rent by clamping on to a single conductor. Interruption of
the circuit is unnecessary. The Model 1685 detects currents
by sensing the changing magnetic produced by the current
flow.
MODEL 1751 SAFETY TEST LEADS-This test lead set is
supplied with every Model 197A. Finger guards and
shrouded banana plugs help minimize the chance of mak-
ing contact with live circuitry
MODEL 1754 UNIVERSAL TEST LEAD KIT - A 12 piece
test lead kit, with interchangeable plug-in accessories.
Included in the kit is one set of test leads (l-red, l-black),
two spade lugs, two standard banana plugs, two phone tips
(.06 DIA.) two hooks and miniature alligator clips (with
boots).
MODEL 1972A ANALOG OUTPUT IEEE-488 INTER-
FACE - The Model 1972A is an optional IEEE-488
interface that includes all of the logic necessary to interface
the Model 197A to the IEEE-488 bus. The Model 1972A is
similar to the Model 1973A however, it contains an analog
output. The analog output is a scaled output that follows
the display of the Model 197A. The Model 1972A is field
installable.
MODEL 1973A IEEE-488 INTERFACE -The Model 1973A
is an optional IEEE-488 interface for the Model 197A. This
interface adds extra versatility to the Model 197A by
allowing the hansmission of data and commands ova the
IEEE-486 bus. The interface provides all the logic necessary
to interface the Model 197A to the bus using standard
IEEE-488-1978 protocol. The Model 1973A is field
installable.
MODEL 1978 RECHARGEABLE BATTERY PACK - The
rechargeable battery pack allows off line or in the field
operation of the Model 197A. The pack typically provides
five hours operation from full charge. The battery pack
contains its own charging circuit and can be recharged
within 15 hours. The battery pack is field installable.
MODEL 7008 IEEE-488 DIGITAL CABLE -Useful for con-
necting the 1973 to the IEEE-488 bus. The Model 7008-3 is
0.9m (3 ft.) in length and has a standard IEEE-488 connec-
tor at each end. The Model 7008-6 is 1.8m (6 ft.) in length
and has a standard IEEE-488 connector at each end.
l-4

SECTION 2
Bench Operation
2.1 INTRODUCTION
This section contains the information needed to prepare and
operate the Model 197A as a bench DMM. Bench operation
consists of using the Model 197A to perform basic voltage,
current, resistance and dB measurements. Also, the opera-
tion of the data logger is covered. The capabilities of the
Model 197A can be enhanced with the addition of the
Model 1973A or Model 1972A IEEE-488 interface. IEEE
operation is covered in the Model 1973/1972 Manual. The
optional battery pack (Model 1978) is also covered in this
section.
2.2 HIGH ENERGY CIRCUIT SAFETY
PRECAUTIONS
To optimize safety when measuring voltage in high energy
distribution circuits, read and use the directions in the fol-
lowing warning.
WARNING
Dangerous arcs of an explosive nature in a high
energy circuit can cau8e *were personal injury
or death. If the meter is connected to a high
energy circuit when set to a current range, low
resistance range or any other low impedance
range, the circuit is virtually shorted. Dangerous
arcing can result even when the meter is set to a
voltage range if the minimum voltage spacing is
reduced.
When making measurements in high energy circuits use test
leads that meet the following requirements:
l Test leads should be fully insulated.
l Only use test leads that can be connected to the circuit
(e.g. alligator clips, spade lugs, etc.) for hands-off
measurements.
l Do not use test leads that decrease voltage spacing. This
diminishes arc protection and creates a hazardous
condition.
Use the following sequence when testing power circuits:
1. De-energize the circuit using the regular installed
connect-disconnect device such as the circuit breaker,
main switch, etc.
2. Attach the test leads to the circuit under test. Use appro-
priate safety rated test leads for this application.
3. Set the DMM to the proper function and range.
4. Energize the circuit using the installed connect-
disconnect device and make measurements without
disconnecting the DMM.
5. De-energize the circuit using the installed connect-
disconnect device.
6. Disconnect the test leads from the circuit under test.
CAUTION
The maximum common-mode input voltage (the
voltage behwen input LO and chassis ground)
is 500V peak. Exceeding this value may damage
the instrument.
2-l

SECTION 2
Bench Operation
2.3 PREPARATION FOR USE
2.3.1 Line Power
The Model 197A has a three-wire line cord which mates
with third-wire grounded receptacles. Connect the instru-
ment to AC line power as follows:
1. Set the LINE VOLTAGE switch on the back of the
instrument to correspond to line voltage available.
Ranges are 105V-125V or ZlOV-250V 50/60Hz AC.
CAUTION
Be sure that the power line voltage agrees with
the indicated range on the panel of the instru-
ment. Failure to observe this precaution may
result in instrument damage.
2. Connect the female end of the power cord to the AC
receptacle on the rear panel of the Model 197A. Plug in
the other end of the power cord into a properly
grounded receptacle.
WARNING
The Model 197A is equipped with a 3-wire
power cord that contains a separate ground
wire and is designed to be used with grounded
outlets. Failure to use a grounded outlet may
result in personal injury or death because of
electric shock.
2.3.2 Battery Pack Power
The Model 197A may be operated from rechargeable sealed
nickel-cadmium batteries contained in the optional Model
1978 Rechargeable Battery Pack. The battery pack will
operate the Model 197A for typically five hours. The BAT
annunciator turns on when the charge is insufficient to
maintain accurate readings.
2.3.3 Battery Charging
After the Model 1978 is installed in the Model 197A it can
be charged and recharged as follows:
1. Connect the instrument to line power as described in
paragraph 2.3.1.
2. The battery charge circuit is energized automatically
when the instrument is plugged into the AC line. The
of the power switch state. When the battery pack is first
installed, or if it is completely discharged, allow it to
charge for a minimum of 15 hours.
NOTE
For maximum battery efficiency only charge the
battery pack after it has become completely dis-
charged (BAT annunciator on). DO not make
measurements with BAT annunciator on as the
readings may be erroneous.
If the battery pack is not maintaining a charge (BAT off) for
five hours after a full 15 hour charge cycle, do the
following.
A.
8.
C.
D.
Disconnect the Model 197A from line power.
Turn on the Model 197A and leave it on to com-
pletely discharge the battery pack.
Connect the Model 197A to line power and charge
the battery pack for 15 hours with power off.
Repeat steps A through C three more times. The
battery pack should again be good for typically five
hours.
3. When the Model 197A is in use on line power, the bat-
tery charger maintains a trickle charge on the battery
pack.
NOTE
The IEEE options (Model 1972A and Model
1973A) do not run off of battery power.
2.4 FRONT AND REAR PANEL
FAMlLlARlZATlON
Figure 2-1, Figure 2-2 and the following paragraphs, pro-
vide a brief description of the display, front panel controls,
input terminals, and rear panel switches.
2.4.1 Display
The Model 197A has a 5-l/2 digit liquid crystal display
(LCD). Positive polarity is implied by the absence of the
minus (-) sign The following annunciators are displayed
rate at which the batteries charge is the same regardless on the LCU.
2-2

SECTION 2
Bench Operation
=y] 197A AUTORANGING MICROVOLT OMM
REL
OCY
DATA LOGGER
00
STOICLR RCL
Model 197A Front Panel
Figure 2-2. Model 197A Rear Panel
BAT-Low battery indicator for the Model 1978. C - Model 197A in calibration mode.
AC -AC selected (DC implied by the absence of the AC
annunciator). AUTO - Autorange.
REL - Relative.
mV or V-Millivolts or volts.
0, kQ or MR -Ohms, kilohms or megohms. dB -Decibel measurement mode
ST0 -Data being stored.
p, mA or A - Microamps, milliamps or amps. RCL - Data being recalled. RCL flashes when buffer is full
RMT (Remote) - Model 197A being controlled over the during logging cycle.
IEEE-468 bus (Model 1973A or Model 1972A installed).
2-3