Keithley 177 User manual

Instruction Manual
Model 177 Microvolt DMM
and
Model 1788 Battery Pack
01978, Keithley Instruments. Inc.
Cleveland, Ohio, U.S.A.
Document Number 29683

Specifications
TEMPERATTURE COEFFlClENT VT-WC and m-55T.I:
*W305% + 0.1 di~itI/~C e~cepf *10.005% + 0.6 digifll°C on the
EXTENDED FREOUENCV ACCURACY ,45Hz--2OkW: i 10.7% + 15
diaitSl
TEtiPERATURE COEFFICIENT 10°-18pC Et ZW-55°C:
--2OkHz,: * ~0.05% + 2 digifs,PC
RESPONSE: True mot mean squsre
CREST FACTOR: 3
INPUT IMPEDANCE: IMO * 1% shunted by less than 75pF.
MnlyMUM *uOWABLE INPUT “OLT*GE: 1000” rms. ,400”
lO’+b maximum
CMRR Ilk0 unbalancel: SOdS at DC. 5OHz and SOHz
RESISTANCE
MAXIMVM ALLOWABLE INPUT: 350” peak
OPEN-CIRCUIT VOLTAGE: 5 volts
45Hz
peak
MAXIMUM INPUT: 2A. 250” DC or rms lfuse protected,
TEMPERATURE COEFFICIENT W-WC and 28D-550C,:
DC: f 10.2 digits)/°C except f 10.01% + 0.6 digitsl/“C on 2OpA range.
GENERAL
DISPLAY: Five 0.5” LED digits, appropriate decimal point and polarity ins
dicatio”
CONVERSION PERIOD: 400mS
OVERRANGE INDICATION: Display blinks all zems above 19999 counts
MAXlM”M COMMON MODE VOLTAGE: MOO” peak
ANALOG OUTPUT: Output Voltage: IV = 10,000 county
Output Resistance: 50000
ENVIRONMENT: Operating: O’C to SYc; 0% to 80% relative humidih/ up
to ‘WC.
storage: --25oc to ~+65T
CONNECTORS: In,,ut: Binding ,mst~
O”QJ”C smana jacks
POWER: IOS- 125 or 210-250 volts (switch selected), gOpllOV available.
506-6OHz. 8 warts. Optional 6 hour battery pack, Model 1788
DIMENSIONS WEIGHT: 85mm high x 235mm wide x 275mm deep
13%” x 9%” x 10%“). Net weight: l.,kg (4 lb,
ACCESSORlES *“VAILA.BLE:
Model ,010:
Model ,017:
Model ,301:
Model 1SOOA:
Model ,641:
Model 1651:
Model 1681:
Model 1mzA:
Model ,683:
Model ,684:
Model ,665:
Model ,m,:
Model ,779:
Model 1788:
Model 1792:
Made, ,793:
Single Rack Mounfing Kif
Dual Rack Mounting Kit
Tempereture Probe
High Voltage Probe 14OkVl
Kelvin Test Leads
50-Ampere Current Shunt
Clip-On Test Lead Set
RF Probe
Universal Test Lead Kit
Hard Shell Carving Case
Clamp~on AC Probe
Genersl Purpose Test Lead Set
Spare Paris Kit
Rechargeable Battery Pack
Isolated BCD OUtput
lsalsted IEEE-488 Output
Specifications subject to change without notice.

TABLE OF CONTENTS
Paragraoh Title Pan.3
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.10.1
1.102
1.10.3
1.10.4
1.10.5
SECTION I-GENERAL INFORMATION
Introduction .............................
Model 177 Features. ......................
Warranty Information .....................
ManualAddenda .........................
Safety Symbols and Terms. ................
Safety Precautions .......................
Specifications ...........................
Unpacking and Inspection .................
Scope of Model 177 Instruction Manual ......
Optional Accessories. .....................
Power Options. ........................
Cables and Connectors. .................
Probes and Shunts .....................
Carrying Case and Rack Mount ...........
Output Options ........................
......
......
......
......
......
......
......
......
......
......
......
......
......
......
......
l-l
l-l
1-l
1-l
1-l
1-l
., 1-l
1-2
., ., l-2
1-2
1-2
1-2
1-2
l-2
1-2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
2.12
2.13
2.14
2.15
2.16
3.1
3.2
3.3
3.4
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
3.4.6
3.4.7
4.1
4.2
4.2.1
SECTION 2-OPERATION
Introduction.. .....................................................................
Safety Precautions for High Energy Circuits ............................................
Preparation for Use .................................................................
Operationon LinePower ............................................................
Operation on Battery Pack Power .....................................................
Battery Charging ...................................................................
Operatinglnstructions ...............................................................
Zero Adjustment ...................................................................
DCVoltage Measurement ............................................................
ACVoltageMeasurement ............................................................
Resistance(O) Measurement .........................................................
DCCurrentMeasutement ............................................................
ACCurrentMeasurement ............................................................
TRMS Measurements (AC + DC) ....................................................
Analog Output .....................................................................
TiltBailAdjustment .................................................................
SECTION 3-PERFORMANCE VERIFICATION
Introduction.. .....................................................................
RecommendedTestEquipment .......................................................
Environmental Condltlons. ...........................................................
Performance Verification Procedure ...................................................
Initial Conditions .................................................................
DC Voltage Accuracy Check (2V to 12OOV Ranges) ....................................
DC Voltage Accuracy Check (20mV and 200mV Ranges) ..............................
ACVoltage Accuracy Check .......................................................
Resistance (n Accuracy Check) ....................................................
DCCurrentAccuracyCheck .......................................................
Analysis ........................................................................
SECTION 4-THEORY OF OPERATION
Introduction .......................................................................
OverallOperation ...................................................................
SignalConditioning ...............................................................
2-l
2-1
2-l
2-l
2-1
2-l
2-3
2-3
2-3
2-5
2-6
2-7
2-7
2-8
2-8
2-8
........... 3-l
3-l
3-l
........... 3-l
........... 3-1
........... 3-1
........... 3-2
........... 3-2
........... 3-2
........... 3-3
3-3
4-l
4-l
4-1

4.2.2
4.2.3
4.3
4.3.1
4.3.2
4.3.3
4.4
4.4.1
4.4.2
4.5
4.5.1
4.5.2
4.5.3
4.6
4.7
4.8
4.8.1
4.8.2
4.8.3
4.9
4.10
4.11
4.11.1
4.11.2
5.1
5.2
5.3
5.4
5.4.1
5.4.2
5.4.3
5.5
5.6
5.6.1
5.6.2
5.6.3
5.6.4
5.6.5
5.6.6
5.6.7
5.7
5.8
5.9
6.1
6.2
6.3
6.4
6.5
6.6
6.7
AIDConverter ..............................................................................
RangeSwitching ............................................................................
ACConverter .................................................................................
Scaling ....................................................................................
ACConversion ..............................................................................
ACCurrentMeasurements ....................................................................
DCSignalConditioning .........................................................................
InputAttenuation ...........................................................................
Chopper ...................................................................................
OhmsConversion .............................................................................
Floating Current Source
......................................................................
Chopper ...................................................................................
Adjustments and Input Overload Protection. .....................................................
AnalogOutput ................................................................................
Clock .......................................................................................
AIDConverter ................................................................................
Auto-Zero ..................................................................................
Signal-Interface .............................................................................
Reference-Integrate .........................................................................
Display ......................................................................................
ACPowerSupply
.............................................................................
Model17888atteryPack.. .....................................................................
BatteryChargingCircuit ......................................................................
Battery Operation and Shutdown Circuit ........................................................
SECTION 5-MAINTENANCE
Introduction ..................................................................................
RecommendedTestEquipment ..................................................................
EnvironmentalCondttlons.........................................................................
CalibrationProcedure ..........................................................................
Calibration Shield Installation ..................................................................
Warm-Up ..................................................................................
Calibration Instructions .......................................................................
Troubleshooting ...............................................................................
Troubleshootingprocedure .....................................................................
Calibration Shield/Batten/ Pack Removal .......................................................
LinePower .................................................................................
Battery Power ..............................................................................
DisplayandA/DConverter ...................................................................
ACConverter ...............................................................................
Chopper Amplifier and Ohms Source ...........................................................
CurrentShunts .............................................................................
Front Panel ZERO Knob Removal and Replacement ................................................
FuseReplacement .............................................................................
Model 1788 Battery Pack Installation. .............................................................
SECTION 6--REPLACEABLE PARTS
Introduction ..................................................................................
PartsList .....................................................................................
Orderinglnformation ............................................................................
FactoryService.. ..............................................................................
ComponentLocationDrawings ...................................................................
SchematicDiagrams ................................................................. ...........
MaintenanceKit ...............................................................................
4-2
4-2
4-2
4-2
4-2
4-2
4-2
4-3
4-3
4-4
4-4
4-4
4-4
4-4
4-4
4-4
4-5
4-5
4-5
4-6
4-6
4-6
4-6
4-6
5-l
5-1
5-1
5-1
5-1
5-l
5-l
5-2
5-2
5-2
5-4
5-4
5-4
5-4
5-4
5-4
5-4
5-5
5-6
6-l
6-l
6-l
6-l
6-1
6-l
6-l
ii

LIST OF FIGURES
Figure
1-l Title Page
2-1
2-2
2-3
3-1
4-l
4-2
4-3
5-l
5-2
5-3
5-4
6-l
6-2
6-3
6-4
6-5
6-6
Model177FrontPanel .......................................................................... 1-O
Model 177 Rear View of Standard Line Voltage Instrument ............................................ 2.2
Model 177 Rear View of Optional Line Voltage Instrument ............................................. 2-2
Operating Controls ............................................................................. 2-5
Test Circuitfor20mVDC Accuracy Check .......................................................... 3-2
Model 177 Simplified Signal Flow Block Diagram .................................................... 4-l
Simplified Signal Conditioning .................................................................... 4-3
AfDConverterFunction ......................................................................... 4~5
Test Point Locations ............................................................................ 5-3
Integrator and Comparator Waveforms. ............................................................ 5-4
Front Panel Zero Knob Removal .................................................................. 5-5
BatteryPacklnstallation ......................................................................... 5-5
Model177CoversandPanels ..................................................................... 6-2
Model 177 PC-476, Component Location Drawing, Dwg. No. 294740, ................................. 6-l 1
Display Board PC-475, Component Location Drawing, Dwg. No. 29652C ............................. 6-15
Model 1788 Battery Pack PC-451, Component Location Drawing, Dwg. No. 29007C ...................... 6-16
Model 1788 Battery Pack, Schematic Diagram, Dwg. No. 29659C ..................................... 6-17
Model 1774% Digit Multimeter, Schematic Diagram, Dwg. No. 29658E ................................ 6-19
LIST OF TABLES
Table Title Page
2-1 Model 177 DMM Condensed Operating Instructions .................................................. 2-4
2-2 Resistance Ranges ............................................................................. 2-6
3-1 Recommended Test Equipment for Performance Verification .......................................... 3-l
3-2 DC Voltage Performance Check (2V to 1200V Ranges). .............................................. 3-2
3-3 ACVoltage Accuracy Check ..................................................................... 3-2
3-4 Resistance Accuracy Check ...................................................................... 3-3
3-5 DCCurrentAccuracyCheck ..................................................................... 3-3
4-l Range Switch Correlation ........................................................................ 4-2
4-2 AC Converter Attenuation Amplification ........................................................... 4-3
4-3 DC Signal Conditioning Attenuation and Gain ....................................................... 4-3
4-4 OhmsConversion .............................................................................. 4-4
5-l Recommended Test Equipment for Calibration ...................................................... 5-l
5-2 Calibration Procedure ........................................................................... 5-2
5-3 Line Power Checks ............................................................................. 5-6
5-4 BatteryPowerChecks ........................................................................... 5-7
5-5 Display ....................................................................................... 5-8
5-6 A/DConverrer ................................................................................. 5-8
5-7 ACConverter .................................................................................. 5-9
5-8 DC Attenuator and Chopper Amplifier ............................................................ 5-10
5-9 OhmsSourceandResistors ..................................................................... 5-11
5-10 CurrantShunts .............................................................................. 5-11
5-11 Adjustment of Battery Charge Voltage ............................................................ 5-12
6-l Model177SparePartsKit ....................................................................... 6-3
6-2 Mother Board,
Parts List
......................................................................... 6-4
6-3 Modal 1788 Battery Pack, Parts List .............................................................. 6-8
6-4 Display Board,
Parts List
......................................................................... 6-9
iii

,’
Figure l-l. Model 177 Front Panel
1-o

SECTION 1
GENERAL INFORMATION
1.1 INTRODUCTION
The Keithley Model 177 Microvolt DMM is a versatile, highly
sensitive digital multimeter which is used for measurement of
DC and AC voltages, DC and AC currents, as well as
resistance. For a complete summary of ranges for each of
these five functions, refer to the specifications at the front of
this manual. Ranges and functions are easily selected with
front panel pushbuttons, while connections for all functions
are easily made with a single set of front panel input ter-
minals.
1.2 MODEL 177 FEATURES
1. 4% Digit LED Display-An easy to read 4% digit display
shows 20,000 counts of information with automatic polari-
ty indication.
2. l~V/lmQ Resolution-The Model 177 is capable of
reading DC voltages es low as 1wV and resistances down
to 1mR.
3. Front Panel Zero-The front panel zaro control may be
used to compensate for thermal offsets or lead resistance
when making measurements.
4. Analog Output-An analog output of lV/lO,OOO counts is
available on the rear panel.
1.3 WARRANTY INFORMATION
Warranty information may be found inside the front cover of
this manual. Should it become necessary to usa the warran-
ty, contact your nearest Keithley representative or the factory
to determine the correct course of action. Keithley Instru-
ments maintains service facilities in the United States, West
Germany, Great Britain, France, the Netherlands,
Switzerland and Austria. Information concerning the appli-
cation, operation or service of your instrument may be
directed to the applications engineer at any of these loca-
tions. Check inside the front cover of this manual for ad-
dresses.
1.4 MANUAL ADDENDA
Information concerning improvements or changes to the
instrument that occur after the printing of this manual will be
covered in an addendum sheet packed with the instrument.
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 may be found on the Model 177.
The symbol A on the instrument indicates that the user
should refer to the operating instructions.
The symbol #M on the instrument denotes that a potential
of 1OOOV or more may be found present on the terminals.
Standard safety practice should be observed when such
dangerous voltages are encountered.
The WARNING heading used in this manual explains
dangers that could result in personal injury or death if nor
handled properly. Be sure to read the WARNING informa-
tion carefully before performing the associated procedure.
The CAUTION heading is used in this manual explains
hazards that could damage the instrument.
1.6 SAFETY PRECAUTIONS
The following safety precautions should be observed before
operating any digital multimeter.
1. This instrument is intended for use by qualified personnel
who recognize shock hazards and are familiar with the
safetY precautions required to avoid possible injury. Read
over the manual carefully before operating this instrument.
2. Exercise extreme caution when a shock hazard is present
at the instrument’s input. The American National
Standards Institute (ANSI) states that a shock hazard ex-
ists when voltage levels greater than 30V rms or 42.4V
peak are present. A good safety practice is to expect that
hazardous voltage is present in any unknown circuit before
measuring.
3. Inspect the test leads for possible wear, cracks or breaks
before each use. If any defects are found, replace with test
leads that have the same measure of safety as those sup-
plied with the instrument.
4. For optimum safety do not touch the test leads of the
instrument while power is applied to the circuit under tast.
Turn the power off and discharge all capacitors, before
connecting or disconnecting the instrument.
5. Do not touch any object which could provide a current
path to the common side of the circuit under test or power
line (earth) ground. Always make meawrements with dry
hands while standing on a dry, insulated surface, which is
capable of withstanding the voltage being measured.
6. Exercise extreme precaution when tasting high energy
power circuits (AC line or mains, etc.). Refer to the oper-
ation section of the manual.
7. Do not exceed the instrument’s maximum allowable input
as defined in the specifications and operation section.
1.7 SPECIFICATIONS
Detailed Modal 177 specifications are located at the front of
this manual.
l-l

1.8 UNPACKING AND INSPECTION
The Model 177 was carefully inspected, both mechanically
and electrically, before shipment. Upon receiving the instru-
ment, carefully unpack it from the shipping carton and check
for any obvious signs of physical damage that might have oc-
curred during shipment. Report any damage to the shipping
agent at once. Retain the original packing materials in case
reshipment becomes necessary. The following items are in-
cluded with every Model 177 shipment.
1. Model 177 Micro\+t DMM
2. Model 177 Instruction Manual
3. Additional accessories as ordered.
1.9 SCOPE OF THE MODEL 177 INSTRUCTION
MANUAL
This manual contains information necessary to operate and
service both the Model 177 and the optional Model 1788 Sat-
tery Pack and is divided into the following sections.
1. Section 2 contains operating information.
2. Information necessary to verify that instrument per-
formance is within specified accuracy is located in Section
3.
3. Theory of operation is covered in Section 4.
4. Servicing information, including Model 1788 installation
instructions, may be found in Section 5.
5. Replaceable parts information, component layouts and
schematic diagrams are located in Section 6.
1.10 OPTIONAL ACCESSORIES
1.10.1 Power Options
The Model 177 can be powered by line voltage (105-125V at
50.60Hz or 210.250V at 50-GOHz--standard ranges) or the
optional Model 1788 Rechargeable Battery Pack. (Optional
line voltage rangas are described in Section 2.1 The Model
1788 is available factory-installed or is field-installable. Instal-
lation and operating instructions are given in Section 2.
1.10.2 Cables and Connectors
Model 1881 Clip-On Test Lead Set-This set contains two
1.2m (48 in.1 leads with banana plugs at one end and spring-
action clip-on probes at the other end.
Modal 1683 Universal Test Lead Kit-This kit contains
two Im (40 in.) test leads and 14 screw-in adapter tips. The
tips consist of two alligator tips with boots, four banana
plugs, phone tips, two spade lugs and four heavy duty tip
plugs which permit connection of theModel 177 to virtually
any source within its measurement range.
1.10.3 Probes and Shunts
Modal 1600A High Voltage Probe-The Model 1600A
High Voltage Probe extends the measurable DC voltage
range up to 40kV. It has a 1OOO:l division ratio, so that a
reading of 1V on the DMM corresponds to IkV IlOOOV). The
Model 1600A has a basic accuracy of lt25% and an input
resistance of IOOOMQ.
Model 1651 SO-Ampere Shunt-The Model 1651
50.Ampere Shunt permits current measurements of up to
50A AC or DC. The shunt has a resistance of O.OOlQ * 1%.
so that a 50A current will correspond to a reading of 50mV
I0.0500v).
Modal 1692A RF Probe-The Model 1682A RF Probe per-
mits measurement of AC voltages at frequencies of 20kHz to
250MHz. AC to DC transfer accuracy is Id6 at lV, and the
input voltage range is 0.25V to 15V rms.
Model 1685 Clamp-On AC Current Probe-The Model
1685 Clamp-On Current Probe permits measurement of AC
current by clamping around a single conductor, eliminating
the need to interrupt the current path. The Model 1685 has a
current conversion ratio of O.lV/A with three ranges (2A.
20A, 200A). Accuracy is +4% at 60Hz If6% at 50Hz).
1.10.4 Carrying Case and Rack Mounts
Modal 1684 Carrying Case-The Model 1684 Carrying
Case is a hard vinyl case with a fitted foam insert to help pro-
tect the Model 177 from damage. There is also room in the
case for the instruction manual and small accessories.
Models 1010 and 1017 Rack Mounting Kits-The rack
mounting kits permit mounting one 11010) or two (1017)
Model 177 DMMs in a 19 inch rack for convenient viewing.
1.10.5 Output Options
Model 1792 Isolated SCD Output-The Model 1792 con-
verts displayed reading to an electrically isolated, latched and
buffered parallel BCD format. Output data includes sign,
overrange and busy. It is compatible with Model 177 serial
number 14,500 and above, and can be either factory or field
installed. Installation of the 1792 precludes installation of
Models 1788 or 1793.
Model 1793 IEEE-488 Output-The Model 1793 converts
displayed readings to IEEE-488 bus compatible outputs to
permit automatic gathering of measurement data. Output in-
cludes 4% digit ASCII data, sign an overrange. It operates in
either talk-only or addressable modes. The Model 1793 is
compatible with Model 177s serial number 16,500 and above,
and can be either factory or field installed. Installation of the
1793 precludes installation of the Model 1788 or 1792.
1-2

SECTION 2
OPERATION
2.1 INTRODUCTION
This section provides information needed for preparation for
use and operation of the Model 177 and Model 1788.
2.2 SAFETY PRECAUTIONS FOR HIGH ENERGY
CIRCUITS
To optimize safety when measuring voltage in high energy
distribution circuits, read and observe the directions in the
following warning.
WARNING
Dangerous arcs of an explosive nature in a
high energy circuit can cause severe
personal injury or death. If the mater is con-
nected to a high energy circuit when sat 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 mater is set to a
voltage range if the minimum safety spac-
ing is reduced.
When making measurements in high energy circuits use test
leads that meet the following requirements:
1. Test leads should be fully insulated.
2. Only use test leads that can be connected to the circuit
(e.g. alligator or spade lugs) for a hands-off measurement.
3. Use test leads that do not reduce the arc protection by
decreasing the voltage spacing between conductors or
terminals.
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 ap-
propriate safety rated 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.
2.3 PREPARATION FOR USE
The Model 177 is shipped ready-to-use on line power. The
instrument may also be powered from rechargeable batteries
(when the optional Model 1788 Rechargeable Battery Set is
installed.)
2.4 OPERATION ON LINE POWER
The Model 177 DMM has a three-wire line cord which mates
with third-wire grounded receptacles. Connect the insfru-
ment to AC line power as follows:
1
CAUTION
Connect only to the line voltage selected.
Application of incorrect voltage can
damage the instrument.
Sat the LINE VOLTAGE switch on the back of the instru-
ment to correspond to the line voltage available. Standard
ranges are 105V to 125V and 210V to 250V AC as shown
in Figure 2-l. Optional ranges of 9OV to 11OV and 18OV to
220V AC are also available as shown in Figure 2-2. As in-
dicated on their respective rear panels, the standard line
voltage range instruments use an internal line fuse (F102)
of 1/8A rating and the optional line voltage range instru-
ments use a 3/16A fuse. See Section 5.
WARNING
Ground the instrument through a property
earth-grounded receptacle before opera-
tion. Failure to ground the instrument can
result in savera injury or death in the avant
of short circuit or malfunction.
2. Plug the power cord into a properly grounded outlat.
Operate the Model 177 DMM as described in paragraph
2.7.
2.5 OPERATION ON BATTERY PACK POWER
The Model 177 DMM may also be operated from
rechargeable sealed lead-acid batteries contained in the
optional Model 1788 Battery Pack. The battery pack will
operate the Model 177 DMM for up to six hours. Circuits
within the battery pack will automatically shut down the in-
strument when the battery charge is insufficient to maintain
accurate readings. To install the Modal 1788, refer to Section
5.
2.6 BATTERY CHARGING
The Modal 1788 Battery Pack contains an integral battery
charger. To charge the battery pack, install the battew pack
in the Model 177 DMM as described above and proceed as
follows:
1. Connect the instrument to line power as described in
paragraph 2.4.
2-1

These adjustments are used only for calibration.
They are not intended for adjustment during operation.
/
(JlOOS) LINE VOLTAGE
SELECT SWITC IP1007)
Figure 2-1. Rear View Of Standard Line Voltage Instrument
These adjustments are used only for calibration.
They we not intended for adjustment during operation.
/+J
H
,JlOO,: LINE VOLTAGL &x
SELECT SWITCH
(SlOll -v IP10071
Figure 2-2. Rear View Of Optional Line Voltage Instrument
2-2

2. With the power switch off, the battery charge circuitry is
automatically energized to charge the battery et the maxi-
mum rate. When the battev pack is first installed, or if it
has completely discharged, allow it to charge for at least 14
hours in this condition.
NOTE
For maximum battery life, do not allow the bat-
tery pack to remain completely discharged. Con-
stant charging will not harm either the battery
pack or the instrument. The Model 177 may be
operated up to six hours from fully charged bat-
teries. However, since 10 charge/discharge
cycles may be required to reach full batten/
capacity, less than six hours DMM operation can
be expected when the battery pack is first in-
stalled.
3. When the Model 177 DMM is in use on line power, the bat-
tery charger maintains a trickle charge on the battery pack.
2.7 OPERATING INSTRUCTIONS
The basic operating instructions for the Model 177 DMM are
outlined in the following steps, and condensed operating in-
structions are provided on the bottom cover of the instru-
ment and contained in Table 2-l. These instructions should
only be used after becoming completely familiar with the
operation of the Model 177 through day-to-day use. Until this
familiarity has been achieved, best performance and safest
operation will be obtained by using the individual instructions
provided in this section. Refer to Figure 2-3 and operate the
DMM es follows:
1. Turn on the power by depressing the ON/OFF pushbutton
and allow a 10 minute warm-up time. Allow additional
warm-up for zero stability on lowest DMM and Q ranges.
2. Select the function with the AC/DC, R, V, or A push-
buttons.
3. Select the range by depressing the appropriate push-
button.
4. Connect the source to the INPUT terminals. Accessories
described in Section 1 should be used as required.
CAUTION
Do not exceed the maximum input ratings
shown below.
DCV
ACV
DCA. ACA
R
QOmV, ZOmV, ZVI: 450V rms continuous;
1200V peak momentan/, for up to eight
seconds per minute maximum.
(20.12OOV): 12OOV peak.
;I ;;;ges): 1OOOV rms; 1400V peak;
.
(All Ranges): ZA, 250V DC or rms (fuse pro-
tected).
(All Ranges): 350V peak.
2.9 ZERO ADJUSTMENT
The front panel zero adjustment provides compensation for
test lead resistance and thermal EMFs generated in the cir-
cuits connected to the DMM input terminals. The zero adjusr-
ment is operative on the 20mV and 200mV ranges of DCV.
20 and 200R ranges and all DCA ranges. In general, the zero
must be readjusted whenever the function is changed and the
measurement is to be made on a range where the zero adjusts
ment is operative. The accuracy specifications assume that
zero is adjusted on the lowest range of the function. Where
applicable, a specific zero adjustment instruction is provided
in the description of how to make the particular function
measurement.
2.9 DC VOLTAGE MEASUREMENT
The Model 177 measures DC voltages from l,lV/digit to
12OOV. The maximum displayed reading is 19999. Overrange
is indicated by a flashing 0000 except on the 12COV range. On
the 1200V range, the display can read beyond the maximum
allowable input voltage. Use the Model 177 to measure DC
volts as follows:
CAUTION
Do not exceed the maximum input voltage
ratings, or instrument damage may occur.
1. Turn on power with ON/OFF pushbunon and select DC
with the AC/DC pushbutton.
2. Select the desired range from the six ranges available. The
decimal point is positioned by the range pushbuttons. The
1200V DC range is selected by the 1000 pushbutton.
NOTE
The 20M pushbutton is inoperative for DC volts.
If this pushbutton is inadvertantly depressed. the
Model 177 will read zero regardless of the
voltage applied and the eight second per minute
overload rating will apply.
3. Connect the signal to be measured between the INPUT HI
and LO binding posts. The binding posts accept wires,
spade lugs or banana plugs for ease of connecting the cir-
cuit to be measured. Low thermal cabling and connections
are recommended for measurements on the 20mV and
200mV ranges.
4. For the top four ranges. merely observe the displayed
digits, polarity sign and decimal point locations. The top
four ranges are direct-reading in volts. Nominal settling
time is located to within one digit of final reading.
5. For the 20mV and 200mV ranges, the front panel ZERO
must be adjusted to obtain rated accuracy. This adjust-
ment is necessary to compensate for thermal EMFs
generated by the connections to the circuit to be
measured. These voltages may be only a few microvolts or
several tens of microvolts. The zero adjustment span is set
up at the factory to allow at least f75,tV adjustment. To
adjust zero, proceed as follows:
2-3

Taba 2-1. Model 177 DMM Condensed Operating Instructions
Summary of Function, Ranges and Other lr
0.03% Rdg + 1D
0.5% Rdg +15D
lOOHz-10kHz
0.7% Rdg + 15D
0.2V Burden
0.8% Rdg +15D
ANALOG OUTPUT: f2V full scale. 5k0 outout resistance
Note 1: See manual fir detailed infbrmation.’
Note 2: Overrange is indicated by flashing 0000.
Note 3: True root mean square, crest factor = 3.
Note 4: Current fuse (installed internally) is 2A. 3AG normal blow. See Figure 5-4 for
location.
lrmation
Max. Input
(Note 1)
1200v
Momentary
1OOOV RMS
10WHz
2A. 250V
DC or rms
(Note 4)
2A. 250V
DC or rms
(Note 4)
350v
Peak
Front
Panel
Zero
Yk?S
1
No
No
YC?S
No
No
2-4

Polarity (Negative in indicated, positive is
implied when minus I-1 display is off.1
A.
Z:
D.
E.
F.
1. SET POWER ON 2. SELECT FUNCTION ‘3. SELECT RANGE 4. CONNECT SOURCE
Figure 2-3. Operating Controls
NOTE
Due to the long thermal time constant of the
20mV range zero, a one hour warm-up time may
be necessary to adjust zero to the final l@ set-
ting. Typically, only a one to three microvolt
zero shift can be expected during this warm-up
period, if the ambient temperature is within the
specified lfl” to 28% and the instrument has not
been subjected to temperature outside of this
range. Thus, since the expected zero shift is
both small and slow, normally zero can be ad-
justed and several measurements taken without
having to achieve the final zero setting.
Make connections to the Model 177 as described
above. For the best performance, connections should
be made to the binding posts rather than using banana
plugs.
Set the Model 177 to the 20mV range.
Disconnect the leads at the circuit to be measured and
short them.
Allow the thermal EMFs generated et the connections
to stabilize.
Adjust the front panel ZERO knob for a display indica-
tion of O.OOOmV (a flashing fO.OOlmV is permissible.)
NOTE
The ZERO control operates only on the 20mV
and 200mV ranges. It has no effect on the other
DC voltage ran&.
Make the measurements by applying the signal and
reading the mV on the display. Nominal settling time
G.
for the 20mV range is three seconds to within one digit
of final reading.
NOTE
An overload input to the Model 177 may cause
temporary zero shift due to thermal gradients.
The zero setting for the 20mV range will also be valid
for the 200mV range. Nominal setting time for the
200mV range is one second to within one digit of final
reading.
6. The optional Model 1600A High Voltage Probe can be
used with the Model 177 to measure DC voltage up to
40kV. at reduced accuracy.
2.10 AC VOLTAGE MEASUREMENT
The Model 177 measures AC voltages from 1OrV to 1OOOV.
The instrument measures the true root mean square (TRMSI
of a signal within the frequency range of 45Hz to 20kHz. The
maximum reading is 19999. Overrange is indicated by a
flashing 0000 except on the 1OOOV range. On the 1OOOV
range, the display can read beyond the maximum allowable
input voltage. The maximum crest factor for rated accuracy is
3. AC accuracy is specified for 2000 counts and above.
Nominal settling time for all AC voltage ranges is 2.5 second
to within 10 digits of final reading. Use the Model 177 DMM
to measure AC volts as follows:
1. Turn on power and set the AC/DC pushbutton to the in or
AC position. Depress the V pushbutton.
NOTE
The 20~ and 20M ranges are inoperative for AC
volts. If the 20~ pushbutton is inadvenantly
2-5

depressed, the display will read overrange,
signalling the user to go to the next higher
range. If 20M is depressed, the display will read
zero regardless of the voltage applied. The
method of calibrating the converter may yield an
offset up to 125 digits with the Model 177 input
shorted. This does not affect instrument ac-
curacy.
2. Select the desired range from the five ranges available.
CAUTION
MAXIMUM ALLOWABLE INPUTVOLTAGE
(All ranges): IOOOV rme, 1400V peak.
107V*Hz maximum. Do not exceed the max-
imum rating. Instrument damage may oc-
cur.
3. Connect signal to be measured between INPUT HI and LO
terminals. Observe the displayed digits and decimal point
location. The 200mV range is direct-reading in mV and the
remaining four ACV ranges are direct-reading in volts.
4. The crest factor (CFI is the ratio of the peak voltage to the
rms voltage as follows:
CFrVPEAK
VRMS
NOTE
There will be some additional measurement error
for signals with a crest factor greater than 3
fCF>3l.
Typical crest factors are as follows:
Sine Wave
Square Wave
rriangular Wave
Positive pulse train
(duty cycle CF = 3 is 0.11)
CF = 1.4
CF = 1
CF = 1.7
CF = \/l/duty cycle
5. The optional Model 1682A RF Probe can be used with the
Model 177 to measure 0.25V to 15V rrn.s AC signals with a
frequency of 2OkHz to 250MHz (and above at reduced ac-
curacy).
6. Refer to paragraph 2.14 for TRMS measurements of a
signal with both AC and DC components.
2.11 RESISTANCE KZ, MEASUREMENT
The Model 177 DMM measures resistance from lmD/digit to
20MD. See Table 2-2 for ranges. Nominal settling times to
within one digit of final reading are: three seconds on the 200
range; two seconds on the 2000kD and 20MD ranges; one se-
cond on the other four g ranges. Use the Model 177 to
measure resistance as follows:
1. Turn on power and depress the R pushbutton.
2-6
CAUTION
MAXIMUM ALLOWABLE INPUTVOLTAGE
(All ranaesl: 350V oeak. Do not exceed
maximum rating. l&trument damage may
occur.
2. Connect the circuit to be measured to the INPUT binding
posts and select the desired range from the seven
available.
?iii%gzm
x;
il binding post treol IS negatrve.
Range Maximum
Setting Reading
200*
19.999
2ooll*
199.99
2kD 1.9999
20kD 19.999
200kD
I
199.99
2000kR 1999.9
20MD 19.999
*Front
Panel
Zero
Table 2-2. Resistance Ranges
Full Scale
Voltage**
20mV
200mV
2v
2v
2v
2v
2v
All Ranges
Nominal
Applied
Current
1mA
1mA
1mA
1OOfiA
1Oj.cA
ld
O.lfiA
3. Observe the displayed digits and decimal point to measure
resistance using the 2k, 20k. 200k. 2000k and 20MR
ranges. The full scale voltage drop for these ranges is 2V
which is sufficient to cause forward conduction of
semiconductor junctions. The HI (Red) terminal is
negative. To measure a resistance in parallel with a
semiconductor junction without turning on the junction,
either reverse bias the junction or select the next higher D
range. The latter method is possible because of the one
decade reduction of applied test current, but will result in a
measurement with 3% digit accuracy. It is suggested that
the 2kg range be used for diode testing. This range has a
nominal 1mA test current and the displayed reading is the
forward voltage drop in volts.
NOTE
The front panel ZERO control operates only on
the 200 end 2OOD ranges. It has no effect on the
other resistance ranges.
4. Before making measurements on the 2051 or 200R ranges,
adjust front panel ZERO on the 20R range to compensate
for test lead resistance. Best performance will be obtained
on the low ohm ranges when test connections are made to
the binding posts, rather than using banana plugs. Adjust
ZERO and make resistance measurements as follows:

A. Select 200 range. D. Adjust front panel ZERO knob for a display indication of
B. Disconnect the test leads at the circuit to be measured O.OOO,rA * ,001 flashing.
and short them. If measurement is to be made right at 2. After adjusting ZERO, use the Model 177 to measure DC
the INPUT terminals (no test leads used) place a short, current as follows:
such as a piece of copper wire, across the binding
posts.
CAUTIONS
C. Adjust the front panel ZERO knob for a display indica-
Do not install e larger capacity fuse then
tion of 0.000 *O.OOlG (flashing). The nominal ZERO
the one originally supplied L?Al. Current
adjustment span is 200mD.
fuse FlOl (shown in Figure 5-4) protects the
instrument against over-current.
NOTE
The specified accuracy for the 2OD and 2OOG A. Select the desired range from the six ranges available.
ranges assumes that ZERO was adiusted on the 8. Connect the circuit to be measured to the INPUT ter-
20irange. Re-adjust zero on the 2dg range each
time that a different set of leads is used or
whenever measurements have been made on
minals.
C. Read the displayed polarity, digits and decimal point.
Select the next higher range if overrange is indicated.
either the two lowest DC voltage ranges or any
DC current range. The zero setting for those
measurements will be different than the zero set-
ting of ohms, Also, re-adjust zero whenever the
instrument is used outside the temperature
range of 18O to 28OC.
D. Reconnect the test leads to the circuit to be measured.
E. Select either 2OD range or 2000 range. Read the
displayed digits and decimal point.
NOTE
An input overload to the Model 177 may cause a
temporary zero shift due to thermal gradients.
2.12 DC CURRENT MEASUREMENT
2.13 AC CURRENT MEASUREMENT
The Model 177 measures AC current from 1OnAldigit to 2A.
over five ranges. (The’ 20r~A and 20M ranges are not
operative. See note below.1 The 200r~A range is direct-
reading in microamperes. The remaining AC current ranges
are direct-reading in milliamperes. The maximum reading is
19999. Overrange is indicated by a flashing 0000. Overload is
protected by fuse FlOl, a 2A, 3AG normal-blow fuse. The
instrument measures the true root mean square ITRMSj of
waveforms in the frequency range of 45 to 10kHz. Use the
Model 177 to measure AC current as follows:
1. Turn on power and set the AC/DC pushbunons to in or
AC position. Depress the A pushbunon.
CAUTION
The Model 177 measures DC current from lnA/digit to 2A.
over six ranges (the 20M range is not operative and the
Do not install a larger capacity fuse then
instrument will read zero if 20M pushbutton is depressed).
the one supplied. Current fuse FlM (shown
The maximum reading is 19999. Overrange is indicated by a
in Figure 5-41 protects the instrument
flashing 0000. Overload is protected by fuse FlOl, a 2A 3AG
against over current.
normal-blow fuse. Nominal settling time for DC current 2. Connect the circuit to be measured to the INPUT terminals
ranges is one second to within one digit of final reading ex- and select the desired range from the five ranges available.
cept three seconds on 20pA range.,
NOTE
1. Before making DC current measurements, the front panel
ZERO must be adjusted on the 20@ range. This adjust- The 20/1A and 20M ranges are not operative for
AC current measurements. If the 20uA push-
ment is necessary to remove any offset that was intr- button is inadvertently depressed, an overrange
oduced by adjusting ZERO for a low DC voltage measure-
mentor a low g measurement. This adjustment will also be will be indicated, signalling the user to go to the
necessary whenever the instrument is used outside of the next higher range. If the 20M pushbutton is de-
temperature range of 18O to 28Y. The specified accuracy pressed, the instrument will read zero.
for the DC current ranges assumes that ZERO was ad- 3. Read the displayed digits and decimal point.
justed on the 2OpA range. Adjust ZERO as follows:
A. Disconnect all circuits from the Model 177 INPUT ter-
NOTE
minals. The INPUT terminals must have an open cir- AC accuracy is specified for 2000 counts and
cuit~ above. The method of calibratina the converter
_-...
8. Turn on power and set the AC/DC pushbunon to the
out or DC position.
C. Depress A and 20~ pushbuttons.
may yield an offset up to 80 digits with the
Model 177 input shorted. This does not affect in-
strument accuracy. There will be some addi-
tional measurement error for signals with a crest
2-7

factor greater than 3 (CF>31.Refer to paragraph
2.10 for information on how to determine the
crest factor of a waveform.
4. Refer to paragraph 2.14 for TRMS measurements of a
signal with both AC and DC current components:
2.14 TRMS MEASUREMENTS (AC + DC)
The Model 177 measures the AC component of a waveform
and does not measure the DC component. Use the Model
177 to measure TRMS of a signal which has both AC and DC
components as follows:
1. Measure and record the AC and DC components separate-
lV.
A. Refer to paragraph 2.9 for DC voltage measurement.
6. Refer to paragraph 2.10 for AC voltage measurement.
C. Refer to paragraph 2.12 for DC current measurement.
D. Refer to paragraph 2.13 for AC current measurement.
2. Compute the TRMS value using the following equation:
ETRMS =“EDc~ + EACH OR lTRMS =‘IDC2 + lAC2
2.15 ANALOG OUTPUT
The rear panel accessible ANALOG OUTPUT provides a
f2V full scale DC signal IlOk counts = 1V). The ANALOG
OUTPUT is operable for all instrument ranges and functions.
The output polarity of the analog voltage is negative for the
ohms (0) function, positive for AC function and non-inverting
for DC functions. The effective analog output resistance is
5kR (4kn in series with the HI output to protect the Model 177
against externally applied voltage and 1k0 between input LO
and analog output LO to prevent a ground loop when con-
nection is made to a grounded load, oscilloscope or
recorder). The analog output voltage is compatible with most
modern analog recorders and may be used to determine
signal changes with respect to time or other variables. With
respect to the signal input and analog output, the Model 177
acts as an amplifier (for mV signals), an attenuator (for kV
signals) or a converter to DC volts (for AC current or
resistance signals). Output accuracy is the same as the
display except on ohms; up to *0.05% error can be ex-
pected due to the ratio-metric method used. The analog out-
put floats at input LO. For this reason, do not connect a
voltage source across INPUT LO and ANALOG LO. This will
result in a measurement error and may damage the Model
177 if the voltage is greater than 15V. When the instrument is
in an overrange condition, up to + 15V DC may be at the
ANALOG OUTPUT dependent upon the function, range and
level of the input signal.
2.16 TILT SAIL ADJUSTMENT
The tilt bail of the Model 177 may be used to elevate the in-
strument to a convenient viewing height. To adjust the bail,
pull the bail out from each side of the case and rotate it to the
desired position. Release the bail to allow it to lock into posi-
tion.
2-6

SECTION 3
PERFORMANCE VERIFICATION
3.1 INTRODUCTION
point, perform a complete calibration as described in Section
5, unless the instrument is still under warranty.
Performance verification may be performed upon receipt of
NOTE
the instrument to ensure that no damage or misadjustment
has occurred during transit. Verification may also be par- Performance verification should be performed
formed whenever ther is question of the instrument’s ac- by qualified personnel using accurate and
curacy, and following calibration, if desired. reliable test equipment.
3.4.1 Initial Conditions
NOTE
For instruments that are still under warranty (less
than 12 months Since date of shipment), if the Before beginning the verification procedure the instrument
instrument’s performance falls outside specifica- must meet the following conditions:
tions at any point, contact your Keithley 1. If the instrument has been subjected to extremes of
representative or the factory immediately. temperature, allow internal temperatures to stabilize for
one hour minimum at the environmental conditions
3.2 RECOMMENDED TEST EQUIPMENT
specififed in paragraph 3.3
2. Turn on the Model I77 and allow it to warm up for one
Recommended test equipment for performance verification is hour. The instrument may be operated from either line
listed in Table 3-1. Alternate test equipment may be used. power or from battery pack power, as long as the battety
However, if the accuracy of the alternate test equipment is pack has been fully charged as described in paragraph 2.6.
not at least IO times better than the instrument’s specifica-
tions, additional allowance must be made in the readings ob-
WARNING
tained. Some of the equipment listed in Table 3-I is not 10
Some procedures require the usa of high
times batter than the Model I77 specifications because such
voltage. Take care to prevent contact with
equipment is not readily available. In these instances, the
live circuits which could causa electrical
verification procedures indicate the equipment
shock resulting in injury or death.
manufacturer’s specified uncertainty, and include the uncsr-
tainty in determining the allowable reading for the Model 177.
3.4.2 DC Voltage Accuracy Check (2V to 1200V Ranges)
3.3 ENVIRONMENTAL CONDITIONS
I. Select DC voltage function with the AC/DC V push-
buttons.
All measurements should be made at an ambient temperature 2. Connect the DC calibrator to the instrument.
within the range of 18” to 28OC (65” to 62OFl. and a relative 3. Select the 2V range. and apply positive 2VDC to the
humidity of less than 80%. DMM. The reading must be within the limits specified in
Table 3-2.
3.4 PERFORMANCE VERIFICATION PROCEDURE
4. Select each remaining range and apply required voltage
specified in Table 3-2. Verify that the reading is within
Use the following procedures to verify the basic accuracy of specifications.
the Model 177 DMM for voltage, resistance and current
measursments. If the instrument is out of specification at any 5. Repeat all checks with negative voltage.
Table 3.1. Recommended Test Equipment For Perfomance Verification
Description
DC Calibrator
AC Calibrator
AC Amplifier
Decade Resistor
current source
1OOn Per Step 4-Terminal
Low Thermal Resistor
*0.002% or 2O@V
O.lV, 1v. IOV, IOOV 10.01%
1ooov @ 0.04%
1900, 1.9kQ. 19kQ. 190kn.
1.9MQ. IOMn, iO.OI%
100rA. lmA, lOmA, IOOmA, 1A
10:1 divider within 50 PPM
Mfr.
Fluke
Fluke
Fluke
ESI
Fluke
ESI
3-l

Table 3-2. DC Voltage Performance Check (2V to 1200V
Rangel
3.4.3 DC Voltage Accuracy Check (20mV and 200mV
Rangesl
1. Select DCV and 20mV range.
2. Disconnect test leads at the DC calibrator and short
them. Adjust Model 177 front panel ZERO for a display
indication of O.OOOmV *O.OOlmV flashina.
3. Connect the DC calibrator and select 200mV range.
4. Set the DC calibrator to an output of +O.l9OOOOV.
5. Verify that the Model 177 reading is between + 189.89 to
+ 190.11mV. Note that the allowable reading includes a
i2 digit allowance for the uncertainty of the DC
calibrator.
Table 3-3. AC Voltage Accuracy Check
Range
Applied
Voltage
@lkHz
lOO.OOmV
1.oooov
1o.ooov
1oo.oov
1ooo.ov
@45Hz
1o.ooov
@2OkHz
1o.ooov
Allowable Readings at
180 to 28Y.z
6. Repeat steps 4 and 5 with negative voltage.
7. Select 20mV M”Qc?.
8. Connect the DC calibrator, low thermal resistor and
Model 177 as shown in Figure 3-1.
9. Temporarily disconnect the leads from the DC calibrator
and short them. Adjust Model 177 front panel ZERO for a
display indication of 0.000 * O.OOlmV flashing.
10. Set the DC calibrator to an output of +O.l9OOOOV.
200mV
2v
2ov
2oov
1ooov
99.35 to 100.65mV
0.9935 to 1.0065V
9.935 to 10.065V
99.35 to 100.65V
993.5 to 1006.5V
2ov
2ov
9.915 to 10.085V
9.915 to 10.085V
11. Verify that the Model 177 readin is between + 18.987
3.4.5 Resistance KU Accuracy Check
~~^^_^ .,~
3. Set the DMM to the 200mV range and apply 1OOmV AC
to the DMM. The reading must be within the limits
specified in Table 3-3.
4. Select the 2,20 and 200mV ranges and apply the required
voltages as specified in Table 3-3. Verify that the readings
are within spcifications.
5. To check 1OOOV range, connect the AC calibrator
amplifier to the output of the AC calibrator per the
manufacturer’s instructions. Connect the amplifier output
to the Model 177 INPUT terminals. Set the AC calibrator
for amplifier output of lOOO.OOOV at 1kHz. Verify that the
DMM reading is within the specified limits in Table 3-3.
6. To check accuracy at 45kHz and 20kHz. select the 20V
range. Apply the voltage specified in Table 3-3 at 45Hr.
then repeat at 20kHz. Verify that the DMM readings are
within the specified limits.
1
I
ancl + IY.VIXnV. Note, that, the allowable reading in-
cludes *2 digits for DC calibrator uncertainty and * 1 1. Select resistance function by depressing n pushbuttons.
digit for low thermal resistor uncertainty.
2. Select 2000 range.
12. Repeat steps 10 and 11 with negative voltage. 3. Connect the decade resistor to the DMM.
4. Set the decade resistor to zero and compensate for lead
resistance by adjusting front panel ZERO for a display in-
THERMAL dication 00.10 f .OlQ flashing.
R6SlSTOR 5. Set the decade resistor to 190% Verify that the reading for
the 200R range is within the limits specified in Table 3.4.
6. Select the 2k0 ra”Qe.
7. Set the decade resistor to zero and measure the resistance
of the test leads. Subtract this reading from the displayed
reading in all of the following steps.
Figure 3-I. Test Circuit For 20mV DC Accuracy Check
8. Set the decade resistor to 1.900kfI. Verify that the reading
is within the limits specified in Table 3-4.
9. Continue by selecting the next range and measure the next
3.4.4 AC Voltage Accuracy Check
resistance as specified in Table 3-4. Test each item in the
1. Select AC voltage function with the AC/DC and V table and verify that each reading is within specifications.
pushbuttons.
2. Connect the AC calibrator to the DMM. Set the calibrator
frequency to 1kHz.
3-2

Table 3-4. Resistance Accuracy Check
Allowable Reading at
Range Resigtance 180 to
28%
l
2000 1900 189.86 to 190.140 * 2 diQits
2kQ 1.900kR 1.8989 to 1.9011 kO + 2 disits
20kR 19.000kfl 18.989 to 19.011kR + 2 digits
200kR 190.00kfI 189.89 to 190.11kfI +2 digits
2000kO 1900.0k0 1898.9 to 1901.lkR *2 digits
20MR lO.OOOMfl 9.988 to 10.012MR f 1 digit
*Manufacturer’s specified unceflainty of the decade resistor in
digits. This uncertainty has been added to the specified accuracy
of the Model 177 to obtain the allowable reading.
3.4.6 DC Current Accuracy Check
1. Select the DC current function with the AC/DC and A
pushbuttons.
2. Select the 20cA range. With an open circuit at the INPUT
terminals of the Model 177, adjust the front panel ZERO
for a display indication of 0.000 1tO.00l~A flashing.
3. Connect the DC current source to the DMM.
4. Select each range and apply the required current as
specified in Table 3-5. Verify that each reading is within
specification.
Table 3-5. DC Current Accuracy Check
Applied -
Current
lOO.OO~A --
L
1.OOOOmA
lO.OOOmA
lOO.OOmA
lOOO.OmA
I
0.9979 to 1.002imA
9.979 to 10.021mA
99.79 to 100.21mA
997.9 to 1002.lmA
3.4.7 Analysis
If the instrument is out of specified limits at any point in Table
3-2 through 3-5, calibrate the DMM as described in Section 5.
If the unit is still under warranty, refer to the ncate in
paraQraph 3.1.
NOTE
It is not necessary to specifically check the 20R
or 20uA ranaes. or a”” of the ACA ranaes. The
circuit components that determine th& accu-
racy have been checked elsewhere in the
verification procedure.
3-313-4