Keithley 1801 Manuale utente

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: 440-248-6168

1-888-KEITHLEY (534-8453) • www.keithley.com

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CHINA: Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-6202-2886 • Fax: 8610-6202-2892

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TAIWAN: 1FL., 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3-572-9077• Fax: 886-3-572-9031

2/02

Model 1801 Nanovolt Preamp Instruction Manual

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

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

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

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