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