Keithley 177 User manual

DC VOLTAGE DC &TRMS AC CURRENT
ACCURACY (12 mo.l MAXIMUM
MAXIMUM 18“-28«C ALLOWABLE
RANGE READING ±i% rdg -i- digits) INPUT
20mV‘ 13.9S9 0.04% 4 2d 1200V momentary* ‘
200V’ 199.99 0.04% Id 1200V momentary”
2V 1.9999 0.03% +Id 1200V momentary”
20V 19.999 0.03% +Id 1200V
200V 199.99 0.03% + Id 1200V
t200V 1200,0 0.035% +Id 1200V
’Front penel zero
”Momentory“8/socond8/minuto at 1200V, 450V continuous.
TEMPERATURE COEFFICIENT (0°-18°C and 28°-55®C):
±(0.005% +0.1 digit)/°C except ±(0.005% +0.6 digitj/^C on the
20mV range
INPUT RESISTANCE: 10MQ ±0.5%
NMRR: Greater than 80dB on the 20mV range at 50Hz and 60Hz; greater
than 60dB on ail other range
CMRR (IkO unbalance): Greater than 120dB at DC, 50Hz &60Hz
AC VOLTAGE
ACCURACY (12 rno.l
18“-2B»C
±(% rdg 4- digits) MAXIMUM
RANGE MAXIMUM READING DC* AC 46Hz-‘IOkHz (above 2000 counta) VOLTAGE BURDEN
20»V\ 19.999 0,2% +2d 0,02V
200»iA 199.99 0.2% +Id 0.9% 415d 0.2V
2mA 1.9999 0.2% -(• Id 0.8% 4l6d 0.2V
20mA 19.999 0.2% +Id 0.8% 4- I6d 0.2V
200mA 199.99 0.2% +Id 0.8% 4- 15d 0.26V
2000mA 1999.9 0.2% +Id 0.8% 415d o.ev
’Front panel zero
MAXIMUM INPUT: 2A, 250V DC or rms (fuse protected)
TEMPERATURE COEFFICIENT (0°-18°C and 28°-55°C):
DC: ±(0.2 digits)/°C except ±(0.01% +0.6 digits)/°C on 20/tA range.
AC: ±(0.07% +2digits)/°C
CREST FACTOR: 3
RANGE MAXIMUM READING
ACCURACY (12 mo.l
(above 2(KX) counts)
18*-28'’C: lOOHz-IMtHz
±i% rdg +digits)
200mV 199.99 0.5% +15d
2V 1-9999 0.5% + 15d
20V 19.999 0,5% + 15d
200V 199.99 0.5% + 15d
1000V 1000,0 0.5% + 15d
EXTENDED FREQUENCY ACCURACY (45H2-20kHz): ±(0.7% +15
digits)
TEMPERATURE COEFFICIENT (0°-18°C &28«-55«C; 45Hz
~20kHz): ±(0.05% +2digits)/°C
RESPONSE: True root mean square
CREST FACTOR: 3
INPUT IMPEDANCE: KVIH ±1% shunted by less than 75pF.
MAXIMUM ALLOWABLE INPUT VOLTAGE: 1000V rms, 1400V peak,
10^»Hz maximum
CMRR (Ikfl unbalance): 60dB at DC, 50Hz and 60Hz
RESISTANCE
TEMPERATURE
RANGE MAXIMUM READING
ACCURACY (12 mo.)
18“-28“C
±{% rdg +digits!
COEFFICIENT
0»-18°C &M°-56°C
±{% rdg +dlgitsl/'C
NOMINAL
APPLIED
CURRENT
2on* 19.999 0.06% +3d 0,004% +0.6d 1mA
20on* 199.99 0.05% +2d 0.004% 40.2d 1mA
2kn 1.9999 0.04% +Id 0.004% 40.2d 1mA
20kO 19.999 0,04% +Id 0,004% 40.2d 100(iA
200k0 199.99 0.04% +Id 0.004% 40.2d lO^A
2000k() 1999.9 0.04% 4Id 0.005% 40.2d 1;xA
20MD 19.999 0.10% +1d 0,02% 40.2d O.l^iA
’Front panel zero
MAXIMUM ALLOWABLE INPUT: 350V peak
OPEN-CIRCUIT VOLTAGE: 5volts
GENERAL
DISPLAY: Five 0.5” LED digits, appropriate decimal point and polarity in-
dication
CONVERSION PERIOD: 400mS
OVERRANGE INDICATION: Display blinks all zeros above 19999 counts
MAXIMUM COMMON MODE VOLTAGE: 1400V peak
ANALOG OUTPUT; Output Voltage: IV =10,000 counts
Output Resistance: 5000Q
ENVIRONMENT: Operating: 0°C to 55°c; 0% to 80% relative humidity up
to 40°C.
Storage: —25°C to +65°C
CONNECTORS: Input; Binding posts
Output; Banana jacks
POWER: 105-125 or 210-250 volts (switch selected), 90-110V available.
50—60Hz, 8watts. Optional 6hour battery pack, Model 1788
DIMENSIONS WEIGHT: 85mm high x235mm wide x275mm deep
(3%" X9'A" X10%"). Net weight: 1.7kg (41b)
ACCESSORIES AVAILABLE:
Model 1010:
Model 1017:
Model 1301:
Model 1600A:
Model 1641:
Model 1651:
Model 1681:
Model 1682A:
Mode! 1683;
Model 1684:
Mode! 1685:
Model 1691;
Mode! 1779:
Model 1788;
Model 1792:
Model 1793:
Single Rack Mounting Kit
Dual Rack Mounting Kit
Temperature Probe
High Voltage Probe (40kV)
Kelvin Test Leads
50-Ampere Current Shunt
Clip-On Test Lead Set
RF Probe
Universal Test Lead Kit
Hard Shell Carrying Case
Clamp-On AC Probe
General Purpose Test Lead Set
Spare Parts Kit
Rechargeable Battery Pack
Isolated BCD Output
Isolated IEEE-488 Output
Specifications subject to change without notice.

Paragraph Title Page
SECTION 1-GENERAL INFORMATION
1.1 Introduction 1-1
1.2 Model 177 Features 1-1
1.3 Warranty Information 1-1
1.4 Manual Addenda 1-1
1.5 Safety Symbols and Terms 1-1
1.6 Safety Precautions 1-1
1.7 Specifications 1-1
1.8 Unpacking and Inspection 1-2
1.9 Scope of Model 177 Instruction Manual 1-2
1.10 Optional Accessories 1-2
1.10.1 PowerOptions 1-2
1.10.2 Cables and Connectors 1-2
1.10.3 Probes and Shunts 1-2
1.10.4 Carrying Case and Rack Mount 1-2
1.10.5 Output Options 1-2
SECTION 2-OPERATION
2.1 Introduction 2-1
2.2 Safety Precautions for High Energy Circuits 2-1
2.3 Preparation for Use 2-1
2.4 Operation on Line Power 2-1
2.5 Operation on Battery Pack Power 2-1
2.6 Battery Charging 2-1
2.7 Operating Instructions 2-3
2.8 Zero Adjustment 2-3
2.9 DC Voltage Measurement 2-3
2. 10 AC Voltage Measurement 2-5
2.11 Resistance (fi) Measurement 2-6
2.12 DC Current Measurement 2-7
2.13 AC Current Measurement 2-7
2.14 TRMS Measurements {AC +DC) 2-8
2.15 Analog Output 2-8
2.16 Tilt Bail Adjustment 2-8
SECTION 3-- PERFORMANCE VERIFICATION
3.1 Introduction 3-1
3.2 Recommended Test Equipment 3-1
3.3 Environmental Conditions 3-1
3.4 Performance Verification Procedure 3-1
3.4.1 Initial Conditions 3-1
3.4.2 DC Voltage Accuracy Check (2V to 1200V Ranges) 3-1
3.4.3 DC Voltage Accuracy Check (20mV and 200mV Ranges) 3-2
3.4.4 AC Voltage Accuracy Check 3-2
3.4.5 Resistance (fi Accuracy Check) 3-2
3.4.6 DC Current Accuracy Check 3-3
3.4.7 Analysis 3-3
SECTION 4-THEORY OF OPERATION
4.1 Introduction 4-1
4.2 Overall Operation 4-1
4.2.1 Signal Conditioning 4-1
i

4.2.2 A/D Converter 4-2
4.2.3 Range Switching 4-2
4.3 AC Converter 4-2
4.3.1 Scaling 4-2
4.3.2 AC Conversion 4-2
4.3.3 AC Current Measurements 4-2
4.4 DC Signal Conditioning 4-2
4.4.1 Input Attenuation 4-3
4.4.2 Chopper 4-3
4.5 Ohms Conversion 4-4
4.5.1 Floating Current Source 4-4
4.5.2 Chopper 4-4
4.5.3 Adjustments and Input Overload Protection 4-4
4.6 Analog Output 4-4
4.7 Clock 4-4
4.8 A/D Converter 4-4
4.8.1 Auto-Zero 4-5
4.8.2 Signal-Interface 4-5
4.8.3 Reference-Integrate 4-5
4.9 Display 4-6
4.10 AC Power Supply 4-6
4.11 Model 1788 Battery Pack 4-6
4.11.1 Battery Charging Circuit 4-6
4.11.2 Battery Operation and Shutdown Circuit 4-6
SECTION 5- MAINTENANCE
5.1 Introduction 5-1
5.2 Recommended Test Equipment 5-1
5.3 Environmental Conditions 5-1
5.4 Calibration Procedure 5-1
5.4.1 Calibration Shield Installation 5-1
5.4.2 Warm-Up 5-1
5.4.3 Calibration Instructions 5-1
5.5 Troubleshooting 5-2
5.6 Troubleshooting Procedure 5-2
5.6.1 Calibration Shield/ Battery Pack Removal 5-2
5.6.2 Line Power 5-4
5.6.3 Battery Power 5-4
5.6.4 Display and A/D Converter 5-4
5.6.5 AC Converter 5-4
5.6.6 Chopper Amplifier and Ohms Source 5-4
5.6.7 Current Shunts 5-4
5.7 Front Panel ZERO Knob Removal and Replacement 5-4
5.8 Fuse Replacement 5-5
5.9 Model 1788 Battery Pack Installation 5-6
SECTION 6-REPLACEABLE PARTS
6.1 Introduction 6-1
6.2 Parts List 6-1
6.3 Ordering Information 6-1
6.4 Factory Service 6-1
6.5 Component Location Drawings 6-1
6.6 Schematic Diagrams 6-1
6.7 Maintenance Kit 6-1

Figure Title Page
1-
1Model 177 Front Panel 1-0
2-
1Model 177 Rear View of Standard Line Voltage Instrument 2-2
2-2 Model 177 Rear View of Optional Line Voltage Instrument 2-2
2-
3Operating Controls 2-5
3-
1Test Circuit for 20mVDC Accuracy Check 3-2
4-
1Model 177 Simplified Signal Flow Block Diagram 4-1
4-2 Simplified Signal Conditioning 4-3
4-
3A/D Converter Function 4-5
5-
1Test Point Locations 5-3
5-2 integrator and Comparator Waveforms 5-4
5-3 Front Panel Zero Knob Removal 5-5
5-
4Battery Pack Installation 5-5
6-
1Model 177 Covers and Panels 6-2
6-2 Model 177 PC-476, Component Location Drawing, Dwg. No. 29474D 6-11
6-3 Display Board PC-475, Component Location Drawing, Dwg. No. 29652C 6-15
6-4 Model 1788 Battery Pack PC-451, Component Location Drawing, Dwg. No. 29007C 6-16
6-5 Model 1788 Battery Pack, Schematic Diagram, Dwg. No. 29659C 6-17
6-6 Model 177 4V2 Digit Multimeter, Schematic Diagram, Dwg. No. 29658E 6-19
LIST OF TABL
Table Title Page
2-1 Model 177 DMM Condensed Operating Instructions 2-4
2-
2Resistance Ranges 2-6
3-
1Recommended Test Equipment for Performance Verification 3-1
3-2 DC Voltage Performance Check (2V to 1200V Ranges) 3-2
3-3 AC Voltage Accuracy Check 3-2
3-4 Resistance Accuracy Check 3-3
3-
5DC Current Accuracy Check 3-3
4-
1Range Switch Correlation 4-2
4-2 AC Converter Attenuation Amplification 4-3
4-3 DC Signal Conditioning Attenuation and Gain 4-3
4-
4Ohms Conversion 4-4
5-
1Recommended Test Equipment for Calibration 5-1
5-2 Calibration Procedure 5-2
5-
3Line Power Checks 5-6
6-
4Battery Power Checks 5-7
5-5 Display 5-8
5-6 A/ DConverter 5-8
5-7 AC Converter 5-9
5-8 DC Attenuator and Chopper Amplifier 5-10
5-9 Ohms Source and Resistors 5-11
5-10 Current Shunts 5-11
5-
11 Adjustment of Battery Charge Voltage 5-12
6-
1Model 177 Spare Parts Kit 6-3
6-2 Mother Board, Parts List 6-4
6-3 Model 1788 Battery Pack, Parts List 6-8
6-4 Display Board, Parts List 6-9
lit

1.1 rNTRODUCTION
The Keithley Mode! 177 Microvolt DMM Is aversatile, highly
sensitive digital multimeter which is used for measurement of
DC and AC voltages, DC and AC currents, as well as
resistance. For acomplete 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 asingle set of front panel Input ter-
minals.
1.2 MODEL 177 FEATURES
1. 4V2 Digit LED Display— An easy to read 4H digit display
shows 20,000 counts of information with automatic polari-
ty indication.
2. VV/1mfi Resolution—The Model 177 is capable of
reading DC voltages as low as l/xV and resistances down
to 1mfl.
3. Front Panel Zero—The front panel zero control may be
used to compensate for thermal offsets or lead resistance
when making measurements.
4. Analog Output—An analog output of IV/ 10,000 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 use 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 on the instrument indicates that the user
should refer to the operating instructions.
The symboly^^n the instrument denotes that apotential
of 1000V 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 not
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 ashock hazard is present
at the instrument's input. The American National
Standards Institute (ANSI) states that ashock hazard ex-
ists when voltage levels greater than 30V rms or 42.4V
peak are present. Agood 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 test.
Turn the power off and discharge ail capacitors, before
connecting or disconnecting the instrument.
5. Do not touch any object which could provide acurrent
path to the common side of the circuit under test or power
line (earth) ground. Always make measurements with dry
hands while standing on adry, insulated surface, which is
capable of withstanding the voltage being measured.
6. Exercise extreme precaution when testing 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 Model 177 specifications are located at the front of
this manual.

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^'^lt 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 Bat-
tery Pack and is divided into the following sections.
1. Section 2contains 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.
The Model 177 can be powered by tine voltage (105-125V at
50-60HZ or 210-250V at 50-60Hz—standard ranges) or the
optional Model 1788 Rechargeable Battery Pack. (Optional
line voltage ranges are described in Section 2.) 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 1681 Clip-On Test Lead Set—This set contains two
1,2m (48 in.) leads with banana plugs at one end and spring-
action clip-on probes at the other end.
Model 1683 Universal Test Lead Kit—This kit contains
two 1m (40 In.) test leads and 14 screw-ln 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 the Model 177 to virtually
any source within its measurement range.
Model 1600A High Voltage Probe—The Model 1600A
High Voltage Probe extends the measurable DC voltage
range up to 40kV. It has a1000:1 division ratio, so that a
reading of 1Von the DMMcorresponds to 1kV (10OOV) .The
Model 1600A has abasic accuracy of ±25% and an input
resistance of 1000MQ.
Model 16S1 50-Ampere Shunt—The Model 1651
50-Ampere Shunt permits current measurements of up to
BOA AC or DC. The shunt has aresistance of 0.0010± 1%,
so that aBOA current will correspond to areading of BOmV
(0.0500V).
Model 1682A 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 1dB at IV, 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 asingle conductor, eliminating
the need to interrupt the current path. The Model 1685 has a
current conversion ratio of 0.1V/A with three ranges (2A,
20A, 200A). Accuracy is +4% at 60Hz (±6% at 50Hz).
1.10.4 Carrying Case and Rack Mounts
Model 1684 Carrying Case—The Model 1684 Carrying
Case is ahard vinyl case with afitted 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 (1010) or two (1017)
Model 177 DMMs in a19 inch rack for convenient viewing.
1.10.5 Output Options
Model 1792 isolated BCD 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'/i 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.

SECTIOW 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 meter is con-
nected to a high energy circuit when set to
acurrent 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 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-dlsconnect
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 athree-wire line cord which mates
with third-wire grounded receptacles. Connect the instru-
ment to AC line power as follows;
CAUTION
Connect only to the line voltage selected.
Application of incorrect voltage can
damage the instrument.
1. Set 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 2-1. Optional ranges of 90V to 110V and 180V 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 a3/16A fuse. See Section 5.
WARNING
Ground the Instrument through aproperly
earth-grounded receptacle before opera-
tion. Failure to ground the instrument can
result In severe Injury or death in the event
of short circuit or malfunction.
2. Plug the power cord into aproperly grounded outlet.
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 Model 1788, refer to Section
5.
2.6 BATTERY CHARGING
The Model 1788 Battery Pack contains an integral battery
charger. To charge the battery pack, install the battery 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.

These adjustments are used only for calibration.
Figure 2-1. Rear View Of Standard Line Voltage Instrument
These adjustments are used only for calibration.
Rear View Of Optional Lino Voltage Instrument