Keithley 1801 User manual

Model 1801 Nanovolt Preamp
Instruction Manual
A GREATER MEASURE OF CONFIDENCE

WARRANTY
Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year
from date of shipment.
Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable
batteries, diskettes, and documentation.
During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.
To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Cleveland, Ohio.
You will be given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service
facility. Repairs will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for
the balance of the original warranty period, or at least 90 days.
LIMITATION OF WARRANTY
This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or
misuse of any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from
battery leakage, or problems arising from normal wear or failure to follow instructions.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY
IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PRO-
VIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.
NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT,
INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS
INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE
OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIM-
ITED TO: COSTS OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY
PERSON, OR DAMAGE TO PROPERTY.
Keithley Instruments, Inc. 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: [phone]
1-888-KEITHLEY (534-8453) • www.keithley.com
Sales Offices:BELGIUM: Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02-363 00 40 • Fax: [phone]
CHINA: Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-6202-2886 • Fax: [phone]
FINLAND: Tietäjäntie 2 • 02130 Espoo • Phone: [phone] • Fax: [phone]
FRANCE: 3, allée des Garays • 91127 Palaiseau Cédex • 01-64 53 20 20 • Fax: [phone]
GERMANY: Landsberger Strasse 65 • 82110 Germering • 089/84 93 07-40 • Fax: [phone]
GREAT BRITAIN: Unit 2 Commerce Park, Brunel Road • Theale • Berkshire RG7 4AB • 0118 929 7500 • Fax: [phone]
INDIA: Flat 2B, Willocrissa • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: [phone]
ITALY: Viale San Gimignano, 38 • 20146 Milano • 02-48 39 16 01 • Fax: [phone]
JAPAN: New Pier Takeshiba North Tower 13F • 11-1, Kaigan 1-chome • Minato-ku, Tokyo 105-0022 • 81-3-5733-7555 • Fax: [phone]
KOREA: FL., URI Building • 2-14 Yangjae-Dong • Seocho-Gu, Seoul 137-130 • 82-2-574-7778 • Fax: [phone]
NETHERLANDS: Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: [phone]
SWEDEN: c/o Regus Business Centre • Frosundaviks Allé 15, 4tr • 169 70 Solna • 08-509 04 679 • Fax: [phone]
SWITZERLAND: Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: [phone]
TAIWAN: 1FL., 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3-572-9077• Fax: [phone]
2/02

Model 1801 Nanovolt Preamp Instruction Manual
©1993, Keithley Instruments, Inc.
All rights reserved.
Third Printing April 1999
Cleveland, Ohio, U.S.A.
Document Number: 1801-901-01 Rev. C

Manual Print History
The print history shown below lists the printing dates of all Revisions and Addenda created for this manual. The
Revision Level letter increases alphabetically as the manual undergoes subsequent updates. Addenda, which are
released between Revisions, contain important change information that the user should incorporate immediately
into the manual. Addenda are numbered sequentially. When a new Revision is created, all Addenda associated
with the previous Revision of the manual are incorporated into the new Revision of the manual. Each new Revi-
sion includes a revised copy of this print history page.
Revision A (Document Number 1801-901-01)................................................................................ March 1993
Revision B (Document Number 1801-901-01).................................................................................... July 1995
Addendum B (Document Number 1801-901-02)........................................................................ October 1995
Revision C (Document Number 1801-901-01) .................................................................................April 1999
All Keithley product names are trademarks or registered trademarks of Keithley Instruments, Inc.
Other brand and product names are trademarks or registered trademarks of their respective holders.

Safety Precautions
The following safety precautions should be observed before using
this product and any associated instrumentation. Although some in-
struments and accessories would normally be used with non-haz-
ardous voltages, there are situations where hazardous conditions
may be present.
This product is intended for use by qualified personnel who recog-
nize shock hazards and are familiar with the safety precautions re-
quired to avoid possible injury. Read and follow all installation,
operation, and maintenance information carefully before using the
product. Refer to the manual for complete product specifications.
If the product is used in a manner not specified, the protection pro-
vided by the product may be impaired.
The types of product users are:
Responsible body is the individual or group responsible for the use
and maintenance of equipment, for ensuring that the equipment is
operated within its specifications and operating limits, and for en-
suring that operators are adequately trained.
Operators use the product for its intended function. They must be
trained in electrical safety procedures and proper use of the instru-
ment. They must be protected from electric shock and contact with
hazardous live circuits.
Maintenance personnel perform routine procedures on the product
to keep it operating properly, for example, setting the line voltage
or replacing consumable materials. Maintenance procedures are de-
scribed in the manual. The procedures explicitly state if the operator
may perform them. Otherwise, they should be performed only by
service personnel.
Service personnel are trained to work on live circuits, and perform
safe installations and repairs of products. Only properly trained ser-
vice personnel may perform installation and service procedures.
Keithley products are designed for use with electrical signals that
are rated Installation Category I and Installation Category II, as de-
scribed in the International Electrotechnical Commission (IEC)
Standard IEC 60664. Most measurement, control, and data I/O sig-
nals are Installation Category I and must not be directly connected
to mains voltage or to voltage sources with high transient over-volt-
ages. Installation Category II connections require protection for
high transient over-voltages often associated with local AC mains
connections. Assume all measurement, control, and data I/O con-
nections are for connection to Category I sources unless otherwise
marked or described in the Manual.
Exercise extreme caution when a shock hazard is present. Lethal
voltage may be present on cable connector jacks or test fixtures. The
American National Standards Institute (ANSI) states that a shock
hazard exists when voltage levels greater than 30V RMS, 42.4V
peak, or 60VDC are present. A good safety practice is to expect
that hazardous voltage is present in any unknown circuit before
measuring.
Operators of this product must be protected from electric shock at
all times. The responsible body must ensure that operators are pre-
vented access and/or insulated from every connection point. In
some cases, connections must be exposed to potential human con-
tact. Product operators in these circumstances must be trained to
protect themselves from the risk of electric shock. If the circuit is
capable of operating at or above 1000 volts, no conductive part of
the circuit may be exposed.
Do not connect switching cards directly to unlimited power circuits.
They are intended to be used with impedance limited sources.
NEVER connect switching cards directly to AC mains. When con-
necting sources to switching cards, install protective devices to lim-
it fault current and voltage to the card.
Before operating an instrument, make sure the line cord is connect-
ed to a properly grounded power receptacle. Inspect the connecting
cables, test leads, and jumpers for possible wear, cracks, or breaks
before each use.
When installing equipment where access to the main power cord is
restricted, such as rack mounting, a separate main input power dis-
connect device must be provided, in close proximity to the equip-
ment and within easy reach of the operator.
For maximum safety, do not touch the product, test cables, or any
other instruments while power is applied to the circuit under test.
ALWAYS remove power from the entire test system and discharge
any capacitors before: connecting or disconnecting cables or jump-
ers, installing or removing switching cards, or making internal
changes, such as installing or removing jumpers.
Do not touch any object that could provide a current path to the com-
mon side of the circuit under test or power line (earth) ground.Always
make measurements with dry hands while standing on a dry, insulated
surface capable of withstanding the voltage being measured.
The instrument and accessories must be used in accordance with its
specifications and operating instructions or the safety of the equip-
ment may be impaired.
Do not exceed the maximum signal levels of the instruments and ac-
cessories, as defined in the specifications and operating informa-
tion, and as shown on the instrument or test fixture panels, or
switching card.
When fuses are used in a product, replace with same type and rating
for continued protection against fire hazard.
Chassis connections must only be used as shield connections for
measuring circuits, NOT as safety earth ground connections.
If you are using a test fixture, keep the lid closed while power is ap-
plied to the device under test. Safe operation requires the use of a
lid interlock.
2/02

If a screw is present, connect it to safety earth ground using the
wire recommended in the user documentation.
The symbol on an instrument indicates that the user should re-
fer to the operating instructions located in the manual.
The symbol on an instrument shows that it can source or mea-
sure 1000 volts or more, including the combined effect of normal
and common mode voltages. Use standard safety precautions to
avoid personal contact with these voltages.
The WARNING heading in a manual explains dangers that might
result in personal injury or death. Always read the associated infor-
mation very carefully before performing the indicated procedure.
The CAUTION heading in a manual explains hazards that could
damage the instrument. Such damage may invalidate the warranty.
Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and
all test cables.
To maintain protection from electric shock and fire, replacement
components in mains circuits, including the power transformer, test
leads, and input jacks, must be purchased from Keithley Instru-
ments. Standard fuses, with applicable national safety approvals,
may be used if the rating and type are the same. Other components
that are not safety related may be purchased from other suppliers as
long as they are equivalent to the original component. (Note that se-
lected parts should be purchased only through Keithley Instruments
to maintain accuracy and functionality of the product.) If you are
unsure about the applicability of a replacement component, call a
Keithley Instruments office for information.
To clean an instrument, use a damp cloth or mild, water based
cleaner. Clean the exterior of the instrument only. Do not apply
cleaner directly to the instrument or allow liquids to enter or spill
on the instrument. Products that consist of a circuit board with no
case or chassis (e.g., data acquisition board for installation into a
computer) should never require cleaning if handled according to in-
structions. If the board becomes contaminated and operation is af-
fected, the board should be returned to the factory for proper
cleaning/servicing.
!

Table of Contents
i
1 General Information
1.1 Introduction ..................................................................................................................................................... 1-1
1.2 Features ........................................................................................................................................................... 1-1
1.3 Warranty information ...................................................................................................................................... 1-1
1.4 Manual addenda .............................................................................................................................................. 1-2
1.5 Safety symbols and terms ................................................................................................................................ 1-2
1.6 Specifications .................................................................................................................................................. 1-2
1.7 Unpacking and inspection ............................................................................................................................... 1-2
1.7.1 Inspection for damage ........................................................................................................................... 1-2
1.7.2 Shipment contents .................................................................................................................................. 1-2
1.7.3 Instruction manual ................................................................................................................................. 1-2
1.8 Repacking for shipment .................................................................................................................................. 1-2
1.9 Model 2001 compatibility ............................................................................................................................... 1-3
1.10 Optional accessories ........................................................................................................................................ 1-3
2 Installation
2.1 Introduction ..................................................................................................................................................... 2-1
2.2 Card configuration .......................................................................................................................................... 2-2
2.2.1 Preamplifier module .............................................................................................................................. 2-2
2.2.2 Power supply card ................................................................................................................................. 2-3
2.3 Power supply card preparation ........................................................................................................................ 2-4
2.4 Power supply card installation and removal ................................................................................................... 2-5
2.4.1 Card installation ..................................................................................................................................... 2-5
2.4.2 Card removal ......................................................................................................................................... 2-5
2.5 Connections ..................................................................................................................................................... 2-6
2.5.1 Power supply connections ..................................................................................................................... 2-6
2.5.2 Output connections to multimeter ......................................................................................................... 2-7
2.5.3 Input signal connections ........................................................................................................................ 2-7
2.6 Operating considerations ................................................................................................................................. 2-9
2.6.1 Using the thermal isolation container .................................................................................................... 2-9
2.6.2 Minimum operating distance ................................................................................................................. 2-9

ii
3 Operation
3.1 Introduction ..................................................................................................................................................... 3-1
3.2 Preamplifier operation .................................................................................................................................... 3-1
3.2.1 Power-up detection ................................................................................................................................ 3-1
3.2.2 Preamplifier configuration menu ........................................................................................................... 3-2
3.2.3 Enabling Model 1801 operation ............................................................................................................ 3-2
3.2.4 Preamp ON/OFF states .......................................................................................................................... 3-2
3.2.5 Preamplifier filtering ............................................................................................................................. 3-4
3.2.6 Operational differences ......................................................................................................................... 3-5
3.2.7 IEEE-488 bus operation ........................................................................................................................ 3-7
3.3 Measurements ................................................................................................................................................. 3-7
3.3.1 DC voltage measurements ..................................................................................................................... 3-7
3.3.2 AC voltage measurements ..................................................................................................................... 3-9
3.3.3 Four-wire resistance measurements .................................................................................................... 3-11
3.3.4 Frequency measurements .................................................................................................................... 3-11
3.3.5 Differential thermocouple temperature measurements ....................................................................... 3-14
3.4 Measurement considerations ......................................................................................................................... 3-18
3.4.1 Thermoelectric potentials .................................................................................................................... 3-18
3.4.2 Source resistance noise ........................................................................................................................ 3-20
3.4.3 Magnetic fields .................................................................................................................................... 3-21
3.4.4 Electromagnetic interference (EMI) .................................................................................................... 3-22
3.4.5 Ground loops ....................................................................................................................................... 3-22
3.4.6 Shielding .............................................................................................................................................. 3-22
4 Performance Verification
4.1 Introduction ..................................................................................................................................................... 4-1
4.2 Environmental conditions ............................................................................................................................... 4-1
4.3 Warm-up period .............................................................................................................................................. 4-2
4.4 Line power ...................................................................................................................................................... 4-2
4.5 Recommended test equipment ........................................................................................................................ 4-2
4.6 Verification limits ........................................................................................................................................... 4-2
4.7 Restoring default conditions ........................................................................................................................... 4-3
4.8 Verification procedures ................................................................................................................................... 4-3
4.8.1 DC volts verification ............................................................................................................................. 4-3
4.8.2 AC volts verification ............................................................................................................................. 4-6
4.8.3 Resistance verification .......................................................................................................................... 4-6
5 Service Information
5.1 Introduction ..................................................................................................................................................... 5-1
5.2 Calibration ...................................................................................................................................................... 5-1
5.2.1 Environmental conditions ..................................................................................................................... 5-1
5.2.2 Warm-up period .................................................................................................................................... 5-1
5.2.3 Line power ............................................................................................................................................. 5-2
5.2.4 Recommended calibration equipment ................................................................................................... 5-2
5.2.5 Offset adjustments ................................................................................................................................. 5-2
5.2.6 Normal calibration ................................................................................................................................. 5-4
5.2.7 Gain constants calibration ..................................................................................................................... 5-9

iii
5.3 Principles of operation .................................................................................................................................. 5-10
5.3.1 Block diagram ...................................................................................................................................... 5-10
5.3.2 Preamplifier module ............................................................................................................................ 5-10
5.3.3 Power supply cable .............................................................................................................................. 5-10
5.3.4 Power supply card ............................................................................................................................... 5-10
5.4 Special handling of static-sensitive devices .................................................................................................. 5-12
5.5 Troubleshooting ............................................................................................................................................ 5-12
5.5.1 Troubleshooting equipment ................................................................................................................. 5-12
5.5.2 Troubleshooting access ........................................................................................................................ 5-12
5.5.3 Troubleshooting procedure .................................................................................................................. 5-12
6 Replaceable Parts
6.1 Introduction ..................................................................................................................................................... 6-1
6.2 Parts lists ......................................................................................................................................................... 6-1
6.3 Ordering information ...................................................................................................................................... 6-1
6.4 Factory service ................................................................................................................................................ 6-1
6.5 Component layouts and schematic diagrams .................................................................................................. 6-1
A Specifications
B Calibration Programs
Introduction .................................................................................................................................................... B-1
Program requirements .................................................................................................................................... B-1
General program instructions ......................................................................................................................... B-1
C IEEE-488 Bus Command Summary

List of Illustrations
v
2 Installation
Figure 2-1 Preamplifier module configuration ..................................................................................................... 2-2
Figure 2-2 Power supply card configuration ........................................................................................................ 2-3
Figure 2-3 Power and output connections ............................................................................................................ 2-4
Figure 2-4 Typical analog output connections ..................................................................................................... 2-5
Figure 2-5 Power supply card installation ............................................................................................................ 2-6
Figure 2-6 Power supply connections .................................................................................................................. 2-7
Figure 2-7 Connections to multimeter input ........................................................................................................ 2-8
Figure 2-8 Input cable connections ...................................................................................................................... 2-8
Figure 2-9 Using the thermal isolator container ................................................................................................... 2-9
3 Operation
Figure 3-1 Filter frequency response curves ........................................................................................................ 3-5
Figure 3-2 Connections for DC voltage measurements ....................................................................................... 3-8
Figure 3-3 Connections for AC voltage measurements ..................................................................................... 3-10
Figure 3-4 Connections for 4-wire resistance measurements ............................................................................. 3-12
Figure 3-5 Connections for frequency measurements ........................................................................................ 3-13
Figure 3-6 Connections for differential temperature measurements .................................................................. 3-16
Figure 3-7 Thermal EMF generation .................................................................................................................. 3-19
Figure 3-8 Magnetic field generation ................................................................................................................. 3-21
Figure 3-9 Minimizing interference from magnetic loops ................................................................................. 3-21
Figure 3-10 Power line ground loops ................................................................................................................... 3-23
Figure 3-11 Eliminating ground loops ................................................................................................................. 3-24
4 Performance Verification
Figure 4-1 Connections for DC volts verification ................................................................................................ 4-4
Figure 4-2 Connections for AC volts verification ................................................................................................ 4-7
5 Service Information
Figure 5-1 Connections for offset voltage adjustment ......................................................................................... 5-3
Figure 5-2 Connections for offset current adjustment .......................................................................................... 5-3
Figure 5-3 Calibration connections ...................................................................................................................... 5-5
Figure 5-4 Block diagram ................................................................................................................................... 5-11

List of Tables
vii
3 Operation
Table 3-1 Power-up error messages .................................................................................................................... 3-2
Table 3-2 CONFIGURE PREAMP menu structure ............................................................................................ 3-3
Table 3-3 Preamp ON/OFF states ....................................................................................................................... 3-3
Table 3-4 Filter response parameters .................................................................................................................. 3-4
Table 3-5 Preamplifier measurement ranges ....................................................................................................... 3-6
Table 3-6 Factory default conditions .................................................................................................................. 3-6
Table 3-7 Preamplifier configuration commands ............................................................................................... 3-7
Table 3-8 CONFIG TEMPERATURE menu with Model 1801 enabled ......................................................... 3-14
Table 3-9 Differential temperature bus commands ........................................................................................... 3-18
Table 3-10 Thermoelectric coefficients .............................................................................................................. 3-18
4 Performance Verification
Table 4-1 Recommended test equipment for performance verification .............................................................. 4-2
Table 4-2 Limits for DC volts verification ......................................................................................................... 4-5
Table 4-3 Limits for AC voltage verification ..................................................................................................... 4-6
5 Service Information
Table 5-1 Recommended equipment for calibration ........................................................................................... 5-2
Table 5-2 Model 1801 IEEE-488 bus calibration commands ............................................................................. 5-7
Table 5-3 IEEE-488 bus calibration summary .................................................................................................... 5-7
Table 5-4 Preamplifier calibration errors ............................................................................................................ 5-9
Table 5-5 Recommended troubleshooting equipment ...................................................................................... 5-12
Table 5-6 Power supply card troubleshooting procedure ................................................................................. 5-13
6 Replaceable Parts
Table 6-1 Electrical, Parts List ............................................................................................................................ 6-2
Table 6-2 Mechanical, Parts List ........................................................................................................................ 6-3
C IEEE-488 Bus Command Summary
Table C-1 IEEE-488 bus command summary..................................................................................................... C-1

1
General Information
1-1
1.1 Introduction
This section contains general information about the
Model 1801 Nanovolt Preamp option for the Model 2001
Multimeter.The Model 1801adds20µV,200µV,and2mV
DC volts and 500µV RMS AC voltage measurement
ranges to the Model 2001 and includes 2m
Ω through
200
Ω 4-wire resistance ranges. The Model 1801 can also
be used for frequency and differential thermocouple tem-
perature measurements.
Section 1 is arranged in the following manner:
1.2 Features
1.3 Warranty information
1.4 Manual addenda
1.5 Safety symbols and terms
1.6 Specifications
1.7 Unpacking and inspection
1.8 Repacking for shipment
1.9 Model 2001 compatibility
1.10 Optional accessories
1.2 Features
The Model 1801 is designed to be used with the Model
2001 Multimeter. Key features include:
• High sensitivity: The Model 1801 increases the DC
voltage measurement sensitivity of the Model 2001
by a factor of 10,000.
• Low noise: Excellent noise rejection ensures minimal
noise effects on the measurement.
• Low-thermal input connections: Copper-to-copper
input connections are used to minimize offsets caused
by thermal EMFs.
• Thermal isolation enclosure: An insulated enclosure
is supplied for the preamplifier in order to minimize
the effects of temperature variations.
• Integrated operation: Automatic power-up detection
of the Model 1801 integrates range and function
selection and reading display from the Model 2001
Multimeter front panel. Model 1801 operation can be
enabledor disabledwith afrontpanelmenuselection.
1.3 Warranty information
Warranty information is located on the inside front cover
of this instruction manual. Should your Model 1801
require warranty service, contact the Keithley representa-
tive or authorized repair facility in your area for further
information. When returning the preamplifier for repair,
be sure to fill out and include the service form at the back
of this manual in order to provide the repair facility with
the necessary information.

General Information
1-2
1.4 Manual addenda
Any improvements or changes concerning the preampli-
fier or manual will be explained in an addendum included
with unit.
1.5 Safety symbols and terms
The following symbols and terms may be found on an
instrument or used in this manual.
The symbol on an instrument indicates that the user
should refer to the operating instructions located in the
instruction manual.
The
WARNING heading used in this manual explains
dangers that might result in personal injury or death.
Always read the associated information very carefully
before performing the indicated procedure.
The
CAUTION heading used in this manual explains
hazards that could damage the preamplifier. Such damage
may invalidate the warranty.
1.6 Specifications
Model 1801 specifications are located in Appendix A.
These specifications include Model 2001 Multimeter
specifications and assume that the Model 2001 is properly
calibrated.
1.7 Unpacking and inspection
1.7.1 Inspection for damage
Upon receiving the Model 1801, carefully unpack all
items from the shipping carton, and inspect for physical
damage. Report any such damage to the shipping agent
immediately. Save the packing carton in case the unit
must be shipped in the future.
NOTE
Be careful not to throw away the foam
thermal isolation enclosure, which is
intended for use with the preamplifier
module.
1.7.2 Shipment contents
The following items are included with every Model 1801
order:
• Power supply card
• Preamplifier module
• 3-meter power supply connecting cable
• 3-meter low-thermal input cable
• Low-thermal copper shorting strap
• Thermal isolation enclosure
• Model 1801 Instruction Manual
• Additional accessories as ordered
1.7.3 Instruction manual
If an additional Model 1801 Instruction Manual is
required, order the manual package, Keithley part number
1801-901-00. The manual package includes an instruction
manual and any pertinent addenda.
1.8 Repacking for shipment
Should it become necessary to return the Model 1801 for
repair, carefully pack the preamplifier, power supply card,
and power cable in the original packing carton or the
equivalent, and include the following information:
• Advise as to the warranty status of the unit.
• WriteATTENTION REPAIR DEPARTMENT on the
shipping label.
• Fill out and include the service form located at the
back of this manual.
!

General Information
1-3
1.9 Model 2001 compatibility
The Model 1801 can be used only with Model 2001 Mul-
timeters with main microcontroller revision B01 or later
firmware. The firmware revision level is displayed during
the power-up cycle (the main microcontroller firmware
revision level appears on the left). The firmware revision
level may also be displayed by using the front panel
MENU/GENERAL/SERIAL# selection.
If an earlier version is displayed (Ann), contact your
Keithley sales representative regarding an upgrade to your
Model 2001 DMM.
1.10 Optional accessories
Model 1483 Low-Thermal Connection Kit
The Model 1483 contains a crimp tool, pure copper lugs,
alligator clips, and assorted hardware.
Model 1484 Refill Kit
The Model 1484 includes the following replacement parts
for the Model 1483: pure copper lugs, alligator clips, and
assorted hardware.

2
Installation
2-1
2.1 Introduction
This section includes information on installing the Model
1801 in the Model 2001 Multimeter and making power
supply and output connections.
This section is arranged as follows:
2.2 Card configuration: Discusses the overall configu-
ration of both the preamplifier module and the
power supply card.
2.3 Power supply card preparation: Covers connect-
ing the power supply cable to the card and routing
the output leads through the cable clamp.
2.4 Card installation and removal: Gives the proce-
dure to install the power supply card assembly in
the Model 2001 Multimeter and describes how to
remove the card.
2.5 Connections: Covers the basics for connecting the
power supply to the preamplifier module, as well as
multimeter input connections and analog output
connections.
2.6 Operating considerations: Outlines use of the ther-
mal isolation enclosure and discusses minimum
operating distance.

Installation
2-2
2.2 Card configuration
2.2.1 Preamplifier module
Figure 2-1 shows the configuration of the preamplifier
module. Key items include:
❶
INPUT Terminals
The HI and LO INPUT terminals are pure copper studs
and nuts intended for connecting input signals to the
Model 1801. To minimize thermal EMFs, use only pure
copper lugs or wires for connections, and be sure that both
the terminals and connecting lugs are clean and free of
oxidation. See paragraph 2.4.4 for details on input
connections.
CAUTION
The maximum signal between
INPUTS HI and LO is 1V @ 100mA
peak (inputs over 2mV require one-
minute recovery). The maximum volt-
age between LO and chassis ground is
41V peak. Exceeding these limits may
result in damage.
❷
Offset Adjustments
V ZERO and I ZERO are externally accessible
adjustments for nulling voltage and current offsets
respectively. These controls need not be adjusted during
normal operation.
NOTE
Improper offset adjustments will
degrade performance. The offset adjust-
ments should only be performed using
the procedures covered in Section 5.
❸
Power Supply Connector
This connector attaches the preamplifier module to the
power supply card using the supplied cable. See para-
graph 2.4.1 for details.
1801 NANOVOLT PREAMP
INPUTS
HI
LO
41V
PEAK
VZERO
I ZERO
CAUTION:
NO INTERNAL OPERATOR SERVICEABLE PARTS,
SERVICE BY QUALIFIED PERSONNEL ONLY.
!
KEITHLEY
2mV
PEAK
Input
Terminals Zero
Adjustments Power Supply Connector
23 1
Figure 2-1
Preamplifier module configuration

Installation
2-3
2.2.2 Power supply card
Figure 2-2 shows the configuration of the power supply
card. Components include:
❶
Cover
The plastic cover shields circuit board parts from damage
and contamination. In order to open the cover, press in on
the cover latch, then swing the cover open on its hinges.
❷
Analog Output
The analog output terminals are intended for connecting
the preamplifier output to a monitoring device such as a
chart recorder. See paragraph 2.3 for details.
❸
Power Connector
The power connector and connecting cable supply power
and control signals to the preamplifier module. They also
feed the analog output signal back to the power supply
card.
❹
Cable Clamp
The cable clamp provides a strain relief for the output
leads and power cable.
❺
Output Leads
The two output leads are terminated with banana plugs
intended to connect to the multimeter input jacks. Red is
HI, and black is LO. See paragraph 2.5.2 for information
on output connections.
❻
Shield Jumper
This jumper allows you to connect the cable shield and
preamplifier shell either to earth ground or to input LO.
Installing the jumper in the earth ground position allows
the unit to meet its stated low common-mode current but
will degrade common-mode noise rejection (if anAC sig-
nal is floating on input LO). Installing the jumper in the
LO position will degrade the common-mode current but
will provide the specified common-mode noise rejection.
Power
connections
Cover
1Analog
Output
2
Shield Jumper
(W101)
6
Earth
LO
Cover
Latch
Output Leads
5
3Cable Clamp
4
Figure 2-2
Power supply card configuration

Installation
2-4
Analog output connections
The analog output terminals, which are located on the
power supply board, provide a 0-2V full scale output for
monitoring devices such as chart recorders.
Since the analog output signal is at a relatively high level
and has low source impedance, the type of wiring used for
connections is not critical. Standard stranded wire of the
type used for DMM test leads should be adequate in most
cases. Figure 2-4 shows typical analog output
connections.
Note that the common-mode current (from LO to earth
ground) of any device connected to the analog output ter-
minals will be added to that of the Model 1801/2001.Typ-
ical common-mode current levels for a DMM or chart
recorder are several micro amps or higher.
Power
Connections
Output Connections
To Preamp
Figure 2-3
Power and output connections
2.3 Power supply card preparation
Power and output connections
Before installing the power supply card in the multimeter,
make sure the power cable is connected to the power con-
nector (see Figure 2-3).
Shield jumper
The shield jumper connects the cable shield and preamp
shell either to earth ground or input LO. This jumper
should be installed as follows:
• If low common-mode current is more important than
common-mode noise rejection, place the jumper in
the earth ground position.
• If common-mode noise rejection is more important
than low common-mode current, place the jumper in
the LO position.

Installation
2-5
2.4 Power supply card installation and
removal
This paragraph explains how to install and remove the
Model 1801 power supply card assembly in the Model
2001 Multimeter.
2.4.1 Card installation
Perform the following steps, and refer to Figure 2-5 to
install the power supply card assembly in the Model 2001
Multimeter:
WARNING
Turn off the Model 2001 Multimeter,
and disconnect the line cord before inst
alling or removing the power supply
card.
1. Remove the cover plate labeled OPTION SLOT on
the rear panel of the Model 2001 Multimeter. To do
Analog output terminals
HI
LO
Monitoring device
(e.g., chart recorder)
Figure 2-4
Typical analog output connections
so, pry out the two fasteners, then remove the cover
plate.
2. Slide the power supply card edges into the guide rails
inside the multimeter.
3. With the ejector arms in the unlocked position, care-
fully push the card all the way forward until the arms
engage the ejector cups. Push both arms inward to
lock the card into the multimeter.
4. After installation, connect the power cable to the
preamp module and the output leads to the multime-
ter as discussed in paragraph 2.5 below.
2.4.2 Card removal
Follow the steps below to remove the power supply card
from the multimeter:
1. Unlock the card by pulling the latches outward.
2. Carefully slide the card out of the multimeter.
3. If the multimeter is to be operated without the power
supply card installed, install the OPTION SLOT
cover plate.

Installation
2-6
2.5 Connections
This paragraph provides the information necessary to
connect the preamplifier module to the power supply card
and multimeter.
Lock card
Ejector Arms (2)
Unlock card
Figure 2-5
Power supply card installation
2.5.1 Power supply connections
After installing the power supply in the multimeter, con-
nect the preamplifier to the power supply card using the
supplied connecting cable, as shown in Figure 2-6.