Keithley 7174A Service manual

I

nstruction Manua

l

Model 7174A

8×12 Low Current Matrix Card

Contains Operating and Servicing Information

7174A-901-01 Rev. A / 9-98

W ARRANTY

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 Keithle y headquarters in Cleveland, Ohio. Y ou 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.

LIMIT A TION OF W ARRANTY

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 PROVIDED 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 LIMITED 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, OH 44139 • 440-248-0400 • Fax: [phone] • http://www.keithley.com

CHINA: Keithley Instruments China • Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-62022886 • Fax: [phone]
FRANCE: Keithley Instruments SARL • BP 60 • 3 Allée des Garays • 91122 Palaiseau Cédex • 33-1-60-11-51-55 • Fax: [phone]
GERMANY: Keithley Instruments GmbH • Landsberger Strasse 65 • D-82110 Germering, Munich • 49-89-8493070 • Fax: [phone]
GREAT BRITAIN: Keithley Instruments, Ltd. • The Minster • 58 Portman Road • Reading, Berkshire, England RG3 1EA • 44-1189-596469 • Fax: [phone]
ITALY: Keithley Instruments SRL • Viale S. Gimignano 38 • 20146 Milano • 39-2-48303008 • Fax: [phone]
NETHERLANDS: Keithley Instruments BV • Avelingen West 49 • 4202 MS Gorinchem • 31-(0)183-635333 • Fax: [phone]
SWITZERLAND: Keithley Instruments SA • Kriesbachstrasse 4 • 8600 Dübendorf • 41-1-8219444 • Fax: [phone]
TAIWAN: Keithley Instruments Taiwan • 1FL., 85 Po Ai Street • Hsinchu, Taiwan • 886-3-572-9077 • Fax: [phone]

Model 7174A 8 × 12 Low Current Matrix Card

Instruction Manual

©1998, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

First Printing September 1998

Document Number: 7174A-901-01 Rev. A

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 Revision includes a revised copy of this print history page.

Revision A (Document Number 7174A-901-01)............................................................................ September 1998

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 in­struments and accessories would normally be used with non-haz­ardous voltages, there are situations where hazardous conditions
may be present.

This product is intended for use by qualified personnel who recog­nize shock hazards and are familiar with the safety precautions re­quired to avoid possible injury. Read the operating information
carefully before using the product.

The types of product users are:

Responsible body is the individual or group responsible for the use

and maintenance of equipment, and for ensuring 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 instru­ment. 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, for example, setting the line voltage or replac­ing consumable materials. Maintenance procedures are described 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 ser­vice personnel may perform installation and service procedures.

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.

that hazardous voltage is present in any unknown circuit before
measuring.

A good safety practice is to expect

Users of this product must be protected from electric shock at all
times. The responsible body must ensure that users are prevented
access and/or insulated from every connection point. In some cases,
connections must be exposed to potential human contact. Product
users 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,

exposed.

As described in the International Electrotechnical Commission
(IEC) Standard IEC 664, digital multimeter measuring circuits
(e.g., Keithley Models 175A, 199, 2000, 2001, 2002, and 2010) are
Installation Category II. All other instruments’ signal terminals are
Installation Category I and must not be connected to mains.

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 con­necting sources to switching cards, install protective devices to lim­it fault current and voltage to the card.

Before operating an instrument, make sure the line cord is connect­ed to a properly grounded power receptacle. Inspect the connecting
cables, test leads, and jumpers for possible wear, cracks, or breaks
before each use.

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 jump­ers, 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
common 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.

no conductive part of the circuit may be

Do not exceed the maximum signal levels of the instruments and ac­cessories, as defined in the specifications and operating informa­tion, 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 ap­plied to the device under test. Safe operation requires the use of a
lid interlock.

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 re­fer to the operating instructions located in the manual.

The symbol on an instrument shows that it can source or mea­sure 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. Alw ays read the associated infor ­mation very carefully before performing the indicated procedure.

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 Instru­ments. 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 se­lected 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 the 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.

The

CAUTION heading in a manual explains hazards that could

damage the instrument. Such damage may invalidate the warranty.

7174A 8×12 Low Current Matrix Card Specifications

MATRIX CONFIGURATION: Single 8 rows×12 columns. Expanding

the columns can be done internally by connecting the rows of
multiple 7174A cards together with coax jumpers.

CROSSPOINT CONFIGURATION: 2-pole Form A (Signal Guard).
CONNECTOR TYPE: 3-lug triax (Signal, Guard, Chassis).
MAXIMUM SIGNAL LEVEL:

Pin to Pin or Pin to Chassis: 200V. 2A carry current.

CONTACT LIFE: Cold Switching: 10

8

closures.

OFFSET CURRENT: 100fA max., 10fA typical (with 0V applied to

inputs and outputs).

ISOLATION: Path (Signal to Signal): >2×10

14

Ω, 1pF.

Common (Signal to Chassis): >1014Ω, <10pF.

SETTLING TIME: <2.5s to 400fA (all pathways) after 10V applied

(typical).

CROSSTALK (1MHz,50Ω Load): <–70dB.
INSERTION LOSS (1MHz, 50ΩLoad): <–0.2dB typical.
3dB BANDWIDTH:

(50Ω Load, 50Ω Source): 30MHz typical.
(1MΩ Load, 50Ω Source): 40MHz typical.

RELAY DRIVE CURRENT (per crosspoint): 17mA.
RELAY SETTLING TIME: <1ms.

ENVIRONMENT:

Offset Current and Path Isolation Specifications: 23°C, <60%

R.H.

Operating: 0° to 50°C, up to 35°C at 70% R.H.
Storage: –25° to +65°C.

MAXIMUM LEAKAGE:

Pin to Ground: 0.01pA/V. Pin to Pin: 0.005pA/V.

INSULATION RESISTANCE: 6.7×10

13

Ω minimum.

CAPACITANCE: (Guard Driven): Path to Ground: <10pF. Path to

Path: 1pF typical.

ACCESSORY SUPPLIED: Instruction manual and eight MCX expan-

sion cables.

ACCESSORIES AVAILABLE:

7078-TRX-TBC 3-Lug Triax to BNC Adapter
7078-TRX-T 3-Lug Triax Tee Adapter
7078-TRX-3 3-Lug Triax Cable, 0.9m (3 ft.)
7078-TRX-10 3-Lug Triax Cable, 3m (10 ft.)
7078-TBC 3-Lug Female Triax Bulkhead Connector with Cap
7078-CSHP Cable Set to Connect 7174 to HP 4145, 4155, 4156

Specifications are subject to change without notice.

Columns

HGCHGCHGCHGCHGCHGCHGCHGCHGCHGCHGCHGC

2

2

2

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2

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2

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2

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2

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User

connections

and expansion

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H
G
C

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H
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H
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Rows

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 Packing for shipment ........................................................................................................................................ 1-2

1.9 Optional accessories .......................................................................................................................................... 1-2

2 Operation

2.1 Introduction ....................................................................................................................................................... 2-1

2.2 Handling precautions ........................................................................................................................................ 2-1

2.3 Environmental considerations ........................................................................................................................... 2-1

2.4 Card installation and removal ........................................................................................................................... 2-2

2.5 Connections ....................................................................................................................................................... 2-2

2.5.1 Card connectors .......................................................................................................................................... 2-2

2.5.2 Recommended cables and adapters ............................................................................................................ 2-3

2.5.3 Triax banana plug adapter .......................................................................................................................... 2-4

2.5.4 General instrument connections ................................................................................................................. 2-5

2.5.5 Keithley instrument connections .............................................................................................................. 2-11

2.5.6 Typical test fixture connections ............................................................................................................... 2-17

2.6 Matrix configuration ....................................................................................................................................... 2-18

2.6.1 Switching matrix ...................................................................................................................................... 2-18

2.6.2 Path isolators ............................................................................................................................................ 2-18

2.6.3 Internal matrix expansion ......................................................................................................................... 2-21

2.7 Measurement considerations ........................................................................................................................... 2-22

2.7.1 Magnetic fields ........................................................................................................................................ 2-22

2.7.2 Electromagnetic Interference (EMI) ....................................................................................................... 2-22

2.7.3 Ground loops ........................................................................................................................................... 2-22

2.7.4 Keeping connectors clean ....................................................................................................................... 2-23

2.7.5 Noise currents caused by cable flexing ................................................................................................... 2-23

2.7.6 Shielding ................................................................................................................................................. 2-23

2.7.7 Guarding .................................................................................................................................................. 2-24

2.7.8 Matrix expansion effects on card specifications ..................................................................................... 2-24

2.8 Coaxial jumper access ..................................................................................................................................... 2-25

i

3 Applications

3.1 Introduction ........................................................................................................................................................ 3-1

3.2 CV measurements ............................................................................................................................................... 3-1

3.2.1 Stand alone system configuration ............................................................................................................... 3-1

3.2.2 Computerized system configuration ........................................................................................................... 3-1

3.2.3 Optimizing CV measurement accuracy ...................................................................................................... 3-3

3.2.4 Basic CV test procedure ............................................................................................................................. 3-3

3.2.5 Typical CV curves ...................................................................................................................................... 3-3

3.3 Semiconductor test matrix ................................................................................................................................. 3-5

3.3.1 System configuration .................................................................................................................................. 3-5

3.3.2 Testing common-source characteristic of FETs ......................................................................................... 3-6

3.4 Resistivity measurements ................................................................................................................................... 3-7

3.4.1 Test configuration ....................................................................................................................................... 3-7

3.4.2 Test procedure ............................................................................................................................................ 3-7

3.4.3 Resistivity calculations ............................................................................................................................... 3-9

3.5 Semiconductor IV characterization .................................................................................................................... 3-9

3.5.1 Test configuration ....................................................................................................................................... 3-9

3.5.2 Cable connections ..................................................................................................................................... 3-10

4 Service Information

4.1 Introduction ........................................................................................................................................................ 4-1

4.2 Handling and cleaning precautions .................................................................................................................... 4-1

4.3 Principles of operation ........................................................................................................................................ 4-2

4.3.1 Block diagram ............................................................................................................................................ 4-2

4.3.2 ID data circuits ........................................................................................................................................... 4-2

4.3.3 Relay control .............................................................................................................................................. 4-3

4.3.4 Power-on sequence ..................................................................................................................................... 4-3

4.3.5 Isolator relays ............................................................................................................................................. 4-4

4.4 Troubleshooting .................................................................................................................................................. 4-4

4.4.1 Recommended equipment .......................................................................................................................... 4-4

4.4.2 Gaining circuit access ................................................................................................................................. 4-4

4.4.3 Troubleshooting procedure ......................................................................................................................... 4-4

4.5 Special handling of static-sensitive devices ....................................................................................................... 4-5

4.6 Performance verification .................................................................................................................................... 4-5

4.6.1 Environment conditions .............................................................................................................................. 4-5

4.6.2 Recommended test equipment .................................................................................................................... 4-5

4.6.3 Offset current verification .......................................................................................................................... 4-6

4.6.4 Path isolation verification ........................................................................................................................... 4-7

4.6.5 Path resistance verification ......................................................................................................................... 4-9

4.7 Reed pack replacement...................................................................................................................................... 4-11

5 Replaceable Parts

5.1 Introduction ........................................................................................................................................................ 5-1

5.2 Parts list .............................................................................................................................................................. 5-1

5.3 Ordering information .......................................................................................................................................... 5-1

5.4 Factory service .................................................................................................................................................... 5-1

5.5 Component layout and schematic diagram ......................................................................................................... 5-1

ii

List of Illustrations

2 Operation

Figure 2-1 Model 7174A installation .......................................................................................................................... 2-2

Figure 2-2 Card connectors ......................................................................................................................................... 2-3

Figure 2-3 Triax connector configuration ................................................................................................................... 2-3

Figure 2-4 Triax cable preparation ............................................................................................................................. 2-4

Figure 2-5 General instrument connections ................................................................................................................ 2-6

Figure 2-6 Model 617 electrometer connections ...................................................................................................... 2-11

Figure 2-7 Model 196 DMM connections ................................................................................................................ 2-12

Figure 2-8 Model 230 voltage source connections ................................................................................................... 2-13

Figure 2-9 Model 590 CV analyzer connections ...................................................................................................... 2-14

Figure 2-10 Model 220 current source connections ................................................................................................... 2-15

Figure 2-11 Model 236/237/238 source measure unit connections ............................................................................ 2-16

Figure 2-12 Typical test fixture connections .............................................................................................................. 2-17

Figure 2-13 Equivalent circuit of test fixture connections .......................................................................................... 2-18

Figure 2-14 Matrix configuration ............................................................................................................................... 2-19

Figure 2-15 Connecting three cards for an 8 × 36 matrix ........................................................................................... 2-21

Figure 2-16 Jumper connector locations ..................................................................................................................... 2-21

Figure 2-17 Two cards in daisy chain configuration .................................................................................................. 2-22

Figure 2-18 Power line ground loops ......................................................................................................................... 2-23

Figure 2-19 Eliminating ground loops ........................................................................................................................ 2-23

Figure 2-20 Shielded and guarded .............................................................................................................................. 2-24

Figure 2-21 Guarded circuit ........................................................................................................................................ 2-24

Figure 2-22 Coaxial jumper access ............................................................................................................................. 2-25

3 Applications

Figure 3-1 Stand alone CV system configuration ........................................................................................................ 3-2

Figure 3-2 Computerized CV system configuration .................................................................................................... 3-2

Figure 3-3 Typical quasistatic CV curve generated by Model 595 ............................................................................. 3-4

Figure 3-4 Typical high-frequency CV curve generated by Model 590 ...................................................................... 3-4

Figure 3-5 Semiconductor test matrix ......................................................................................................................... 3-5

Figure 3-6 System configuration for measuring common-emitter characteristics ....................................................... 3-6

Figure 3-7 Typical common-source FET IV characteristics ........................................................................................ 3-6

Figure 3-8 Resistivity test configuration ..................................................................................................................... 3-7

Figure 3-9 Resistivity measurement conventions ........................................................................................................ 3-8

Figure 3-10 Multi-unit test system using Models 236 and 237 source measure units ................................................. 3-10

iii

4 Service Information

Figure 4-1 Model 7174A block diagram ...................................................................................................................... 4-2

Figure 4-2 ID data timing ............................................................................................................................................. 4-3

Figure 4-3 Offset verification test connections ............................................................................................................ 4-6

Figure 4-4 Connections for path isolation verification ................................................................................................ 4-7

Figure 4-5 Triaxial cable preparation ........................................................................................................................... 4-8

Figure 4-6 Connections for path resistance verification .............................................................................................. 4-9

Figure 4-7 Shorting measurement paths using triax tee adapter ................................................................................ 4-10

Figure 4-8 Cross point relays ..................................................................................................................................... 4-12

Figure 4-9 Isolator relays ........................................................................................................................................... 4-13

iv

List of Tables

2 Operation

Table 2-1 Recommended cables and adapters ............................................................................................................ 2-3

Table 2-2 Parts for special triaxial cable .................................................................................................................... 2-4

Table 2-3 Column numbering by slot and unit ......................................................................................................... 2-20

3 Applications

Table 3-1 CV test crosspoint summary ...................................................................................................................... 3-3

Table 3-2 Crosspoint summary for resistivity measurements .................................................................................... 3-9

4 Service Information

Table 4-1 Recommended troubleshooting equipment ................................................................................................ 4-4

Table 4-2 Troubleshooting procedure ........................................................................................................................ 4-4

Table 4-3 Recommended verification equipment ...................................................................................................... 4-5

5 Replaceable Parts

Table 5-1 Model 7174A electrical parts list ................................................................................................................5-3

Table 5-2 Model 7174A mechanical parts list ........................................................................................................... 5-4

v

1

General Information

1.1 Introduction

This section contains general information about the Model
7174A Low Current Matrix Card. The Model 7174A Low
Current Matrix Card is designed for semiconductor research,
development, and production applications that require high
quality and performance switching I-V (current versus volt­age) and C-V (capacitance versus voltage) signals. The
model 7174A is ideal for use with Keithley Model 236
Source Measure Unit for semiconductor testing and other
low current switching applications. Model 237 and Model
238 Source Measure Units can also be used below the maxi­mum signal level (200V, 2A carry) of the Model 7174A Low
Current Matrix Card (for full specifications, refer to para­graph 1.6). The Model 7174A also can be used with Models
590 and 595 C-V instruments.

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 Packing for shipment

1.9 Optional accessories

1.2 Features

Key features of the Model 7174A Low Current Matrix Card
include:

• Eight row by twelve column (8 × 12) switching matrix
configuration, with signal and guard switched at each
crosspoint

• Paths have offset currents of less than 100fA with typi­cal offset currents of 50fA

• Maximum Leakage Currents:
Pin to Ground -- 0.01 pA/V

Pin to Pin -- 0.005 pA/V

• 3-lug Triaxial Connectors (Signal, Guard, Chassis) for
all row and columns allow guarding of each signal path­way, minimizing effects of stray capacitance, leakage
current, and leakage resistance

• Model 7174A cards can be connected together inter­nally using the supplied SMB to SMB cables (jumpers)
to expand the number of columns in the matrix.

1.3 W arranty information

Warranty information is located on the inside front cover of
this manual. Should your Model 7174A require warranty
service, contact your Keithley representative or authorized
repair facility in your area for further information.

1-1

General Information

1.4 Manual addenda

Any improvements or changes concerning the matrix card or
manual will be explained in an addendum included with the
unit. Be sure to note these changes and incorporate them into
the manual before using or servicing the 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 symbol on an instrument shows that high voltage
may be present on the terminal(s). Use standard safety pre­cautions to avoid personal contact with these voltages.

The WARNINGS 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.

1.7.2 Shipment contents

The following items are included with every Model 7174A
order:

• Model 7174A Low Current Matrix Card.

• Model 7174A Instruction Manual.

• Coaxial jumper cables Model CA-121A (8) for matrix
expansion.

• Additional accessories as ordered.

1.7.3 Instruction manual

The Model 7174A Instruction Manual is three-hole drilled so
that it can be added to the system three-ring binder. After
removing the plastic wrapping, place the manual in the
binder after the mainframe instruction manual. Note that a
manual identification tab is included and should precede the
matrix card instruction manual.

If an additional manual is required, order the manual pack­age (Keithley part number 7174A-901-00). The manual
package includes an instruction manual and any pertinent
addenda.

The CAUTION heading used in this manual explains haz­ards that could damage the matrix card. Such damage may
invalidate the warranty.

1.6 Specifications

Model 7174A specifications may be found at the front of this
manual. These specifications are exclusiv e of the matrix card
file specifications, which are located in the Model 707A
Switching Matrix manual.

1.7 Unpacking and inspection

1.7.1 Inspection for damage

If you ordered the Model 7174A separately from a system,
carefully unpack it from its shipping carton and inspect the
card for any obvious signs of physical damage. Report any
such damage to the shipping agent immediately. Save the
original packing carton for possible future reshipment.

1.8 Packing for shipment

Should it become necessary to return the Model 7174A for
repair, carefully pack the card in its original packing carton
or the equivalent, and include the following information:

• Advise as to the warranty status of the matrix card.

• Write ATTENTION REPAIR DEPARTMENT on the
shipping label.

• Fill out and include the service form located at the back
of this manual.

1.9 Optional accessories

Cables

Model 7078-TRX-3 — A 0.9 m (3 ft.) triaxial cable termi-

nated at both ends with 3-slot male triax connectors. This
type of cable is also available in 10 ft. (Model 7078-TRX-10)
and 20 ft. (Model 7078-TRX-20) lengths.

Model CA-93-1 — BNC to right angle SMB (coaxial) cable.

1-2

General Information

Model 7078-CSHP — Is a cable set containing:

Eight 10 ft. (3m) cables — Cables to connect the Model
7174A to a HP-4145 Semiconductor Parameter Analyzer.

Four BNC to triax adapters — Used with eight cables
listed above

Four 3 slot triax cables— Cable set to connect the Model
7174A to Source Measurement Units

Four BNC to BNC coax cables — Adapt the measurement
and source modules in the HP-4145 to the connectors of
the Model 7174A.

Adapters

Model 7078-TRX-TBC — A 3-lug female triax bulkhead

connector (with cap). Use this connector for custom applica­tions and interface connections such as test fixtures.

Model 7078-TRX-T — 3-slot male to dual 3-lug female

triax tee adapter.

Model 237-BAN-3 — 3-slot male triax to male banana plug.

Model 237-ALG-2 — 3-slot male triax to alligator clips.

Model 7078-TRX-BNC — 3-slot male triax to BNC

adapter, connections to center and inner shell. For non­guarded applications, use Model 7078-TRX-GND.

Model 6171 — 3-slot male triax to 2-lug female triaxial

adapter.

Tools

Model 9172-314 — A tool designed to remove and install

internal coaxial jumpers between adjacent Model 7174A
Low Current Matrix Cards.

1-3

2

Operation

2.1 Introduction

WARNING

The installation and operation proce­dures in this section are intended for use
only by qualified service personnel. Do
not perform these procedures unless
qualified to do so. Failure to recognize
and observe normal safety precautions
could result in personal injury or death.

This section contains information on matrix card connec­tions, installation and matrix programming, and is arranged
as follows:

2.2 Handling precautions — Discusses precautions that

should be taken when handling the card to avoid con­tamination that could degrade performance.

2.3 Environmental considerations — Outlines environ-

mental aspects of using the Model 7174A.

2.4 Card installation and removal — Details installation

in and removal from the Model 707A Switching
Matrix.

2.7 Measurement considerations — Reviews a number

of considerations when making low-level current and
capacitance measurements.

2.8 Coaxial jumper access — Provides information on

jumper removal.

2.2 Handling precautions

To maintain high impedance isolation, care should be taken
when handling the matrix card to avoid contamination from
such foreign materials as body oils. Such contamination can
substantially lower leakage resistance, degrading perfor­mance. The areas of the card that are most sensitive to con­tamination are those associated with Teflon® insulators. To
avoid any possible contamination, always grasp the card by
the handle or the card edges. Do not touch board surfaces,
components, or card edge connectors.

Dirt and other particle build-up over a period of time are
other possible sources of contamination. To avoid this prob­lem, operate the mainframe and matrix card only in a clean
environment. If contamination is suspected, clean the card as
discussed in Section 4.

2.5 Connections — Discusses card connectors, cables

and adapters, and typical connections to other
instrumentation.

2.6 Matrix configuration — Discusses the switching

matrix, as well as matrix expansion by connecting two
or more cards together.

2.3 Environmental considerations

For rated performance, the card should be operated within
the temperature and humidity limits given in the specifica­tions at the front of this manual.

2-1

Operation

2.4 Card installation and removal

Before making connections, the Model 7174A should be
installed within the Model 707A Switching Matrix, as sum­marized below. Figure 2-1 shows the installation procedure.

WARNING

T urn off the system power before install­ing or removing matrix cards.

NOTE

The coaxial jumpers used to expand the
matrix with two or more Model 7174A
cards can not be installed before card
insertion; an access door on top of the
mainframe allows access to the connectors
after the card is installed.

2. With one hand grasping the handle, and the other hold­ing the bottom of the card, line up the card with the
tracks in the desired slot. Make certain that the compo­nent side of the card is facing the fan on the mainframe.

3. Slide the card into the mainframe until it is properly
seated in the edge connectors at the back of the slot.
Once the card is properly seated, secure it to the main­frame by finger tightening the spring-loaded screws.

WARNING

The mounting screws must be secured to
ensure proper chassis ground connec­tions between the card and the main­frame. Failure to properly secure this
ground connection may result in per­sonal injury or death due to electric
shock.

4. To remove a card, first turn off the system power. Dis­connect all external and internal jumper cables (internal
cables can be reached through the access door). Loosen
the mounting screws, then pull the card out of the main­frame by the handle. When the back edge of the card
clears the mainframe, support it by grasping the bottom
edge near the back or back edge.

Model 707A

Switching Matrix

Model 7174A Low

Current Matrix Card

Figure 2-1

Model 7174A installation

1. Before installing the card, make sure the access door on
top of the Model 707A Switching Matrix is fully closed
and secured. The access door contains tracks for the card
slots and must be in place to properly install the card.

CAUTION

Do not touch the card surfaces or any
components to avoid contamination
that could degrade card performance.

2.5 Connections

Card connectors, recommended cables and adapters, and
typical connections to test instruments are discussed in the
following paragraphs.

2.5.1 Card connectors

The card connectors are shown in Figure 2-2. Each pin is
equipped with a 3-lug triax connector. As shown in Figure
2-3, the center conductor is signal, the inner shield is guard,
and the outer shield is chassis ground.

CAUTION

Do not exceed 200V between any two
pins or between any pin and chassis.

The Model 7174A has 12 columns (labeled 1 through 12)
and 8 rows (labeled A through H).

2-2

Chassis
Ground

200V

Peak

Guard

200V Peak

Signal

200V

Peak

Caution:

Do not exceed maximum
voltage levels shown.

Figure 2-3

Triax connector configuration

Operation

Mounting

Screw

KEITHLEY

7174A

8x12LOW

CURRENT MATRIX

SIGNAL

200VPK

200VPK

Carrying
Handle

B

C

D

A

200VPK

ROWS

COLUMNS

GUARD

1

2

3

4

5

6

Caution:

Remove internal row
jumpers before removing
card.

Figure 2-2

Card connectors

Mounting

Screw

E

F

10

G

11

H

12

!

WARNING:

TIGHTEN MOUNTING SCREWS

TO ENSURE PROPER

CHASSIS GROUND

MADE INU.S.A.

7

2.5.2 Recommended cables and adapters

8

Table 2-1 summarizes the cables recommended for use with

9

the Model 7174A. Equivalent user-supplied items may be
substituted as long as they are of sufficient quality (low of fset
current, high leakage resistance). Using substandard cables
and connectors may degrade the integrity of the measure­ments made. See paragraph 2.7 for a discussion of measure­ment considerations.

Table 2-1

Recommended cables and adapters

Model Description

7078-TRX-x

3-slot male triax connectors on
both ends (x=3, 10 or 20 ft.)

237-BAN-3

3-slot male triax to male banana

plug
237-ALG-2
7078-TRX-BNC

3-slot male triax to alligator clips

3-slot male triax to BNC adapter,

connections to center and inner

shell
7078-TRX-GND

3-slot male triax to BNC adapter,

connections to center and outer

shell
7078-TRX-T

3-slot male to dual 3-lug female

triax tee adapter
6171

3-slot male triax to 2-lug female

triax adapter
CA-93-1

BNC to right angle SMB cable

2-3

Operation

2.5.3 T riax banana plug adapter

For instruments that use banana jacks, you need a triax cable
terminated with a 3-slot male triax and a single banana plug.
Use the Model 237-BAN-3 or prepare a special cable as out­lined below (Special triax to banana plug cable prepara-

tion) using the parts listed in Table 2-2.

Table 2-2

Parts for special triaxial cable

Keithley part or
model number Description

7078-TRX-3 triax cable*

BG-10-2

*One connector must be cut off

Figure 2-4 shows the conductors and insulation layers of a
triaxial cable. These layers must be carefully stripped back,
cleaned thoroughly and insulated with high insulation resis­tance material such as Teflon  to maintain the integrity of
the cable and measurement system. With the Model 237­BAN-3, the center conductor of the triax is connected to the
banana plug. The inner and outer shields have no connection.
With the special cable shown in Figure 2-4, the inner shield
is shorted to the center conductor. Which cable to use
depends on your application. The length of unshielded con­ductor that is connected to the banana plug should be mini­mized to maintain signal integrity. The topic of signal
integrity is also discussed in paragraph 2.7 Measurement
considerations.

Triax cable terminated with
3-slot male triax connectors
Red banana plug

4. Strip the insulator back 1/2 inch, then twist the strands
of the conductor together as shown in Figure 2-4(C).

5. Unscrew the cover from a banana plug, then slide the
cover over the conductor.

6. Insert the stripped center conductor through the hole in
the body of the banana plug, then wrap the wire around
the plug body as shown in Figure 2-4(D).

7. Screw on the plastic cover as shown in Figure 2-4(E).
Make certain the wire is secure by gently pulling on the
plug.

Cut

1"

(A) Cut off insulation with knife.

Cut off outer shield.

Insulation Over
Inner Shields

3/4"

(B) Strip insulation off inner shield.

(C) Twist inner shield then strip inner conductor.
Twister inner shield and center conductor together,

slip on plastic cover.

Cut

Note that you can use either an unterminated triax cable, or
cut a dual-connector cable (7078-TRX-10) in half to con­struct two special cables.

Special triax to banana plug cable preparation

The following steps outline a procedure for installing a
banana plug on the end of a triaxial cable (with inner shield
shorted to center conductor).

1. Using a knife, cut and strip back the jacket about 1-1/2
inches.

2. Remove the outer insulation, then cut away the outer
shield as far as the insulation is stripped as shown in Fig­ure 2-4(A).

3. Carefully strip away the insulation over the inner shield
one inch, then cut the inner shield and guard wire off
even with the stripped insulation as shown in Figure
2-4(B).

2-4

(D) Insert wires into hole and wrap around body.

(E) Screw on plastic cover.

Figure 2-4

Triax cable preparation

Operation

2.5.4 General instrument connections

The following paragraphs discuss connecting the Model
7174A to various general classes of instrumentation such as
DMMs, electrometers, sources, and source/measure units.
Because these configurations are generic in nature, some
modification of the connecting schemes may be necessary
for your particular instrumentation. Also, special cables or
adapters may be necessary. In all cases, 3-lug triax cables
must be used to make the connections.

WARNING

Do not use coaxial cables and adapters
because hazardous voltage from guard
sources may be present on the cable
shields.

Figure 2-5 shows the general instrument connections for the
discussions below. Note that DUT guarding or shielding are
not included here; see Figures 2-22 and 2-23 for shielding
and guarding information. As shown, all figure assume
instruments are connected to rows, and the DUT is con­nected to columns.

DMM connections

General DMM connections are shown in Figure 2-5 (A), (B),
and (C). Floating connections are shown in (A) with LO and
HI routed to two separate jacks on the Model 7174A. The
common LO connections in (Figure 2-5B) should be used
only for non-critical applications because the performance of
the GUARD pathway is not specified.

WARNING

Hazardous voltage from other guard
sources may be present on LO or the
DUT if other crosspoints are closed.

Electrometer connections

T ypical electrometer connections are shown in Figure 2-5(D)
through (G). The unguarded volts connections in (D) show
the HI signal path routed through one jack, and the LO path
goes through the other connector. Both GUARD pathways
are connected to electrometer LO. For guarded voltage (E),
Model 7174A GUARD is connected to electrometer
GUARD.

The connections for electrometer fast amps and resistance
measurements are shown in Figure 2-5(F) and (G). These
configurations are essentially the same as those discussed
above. For the case of fast amps, both GUARD paths are
connected to electrometer LO, while in the case of guarded
resistance, one GUARD path is connected to electrometer
GUARD, and the other GUARD path is connected to elec­trometer LO.

Source connections

Voltage and current source connections are shown in Figure
2-5(H) through (J). The HI and LO paths of the voltage
source (H) are routed through two jacks, with both card
GUARD pathways connected to voltage source LO. For the
unguarded current source connections (I), card GUARD is
again connected to source LO, with source HI and LO routed
through two pathways. In the case of the guarded current
source in (J), card GUARD of the HI signal path is connected
to source GUARD, and the other GUARD path is connected
to source LO.

Source/measure unit connections

Figure 2-5(K) shows typical connections for a source/mea­sure unit (SMU). In this instance, a remote-sensing type of a
SMU is shown, requiring a total of four signal pathways to
the DUT. For critical measurements, both source and sense
HI pathways would be guarded as shown, with two of the
four card GUARD pathways connected to SMU GUARD
terminals. As with other instrument connections, the LO card
GUARD pathways are connected to SMU LO terminals.

4-wire DMM connections are shown in Figure 2-5(C). In this
case, a total of four jacks are required; HI, LO, SENSE HI,
and SENSE LO.

2-5

Operation

Rows Columns

S

ignal

HI

LO

DMM

A.) DMM Floating

Rows Columns

HI

LO

DMM

Warning:Hazardous voltage from guard

sources may be present on LO.

Guard

Signal

Guard

Signa

Guard

7174A

l

7174A

DUT

DUT

Note: Use this configuration only for

non-critical measurements.

B.) DMM Common LO

Figure 2-5

General instrument connections

2-6

Operation

Sense HI
Sense LO

DMM

HI
LO

Rows Columns

Signal

Guard

Signal

Guard

DUT

Signal
Guard

Signal

Guard

C.) DMM 4-Wire

LO

Electrometer

D.) Electrometer, Unguarded Volts

Figure 2-5

General instrument connections (cont.)

HI

7174A

Rows Columns

Signal

Guard

DUT

Signal

Guard

7174A

2-7

Operation

Rows Columns

Signal

HI

Guard

LO

Electrometer

E.) Electrometer, Guarded Volts

HI

LO

Electrometer

Guard

DUT

Signal

Guard

7174A

Rows Columns

Signal
Guard

DUT

Signal
Guard

F.) Electrometer,Fast Current

HI
LO

Guard

Electrometer

G.) Electrometer, Resistance (Guarded)

Figure 2-5

General instrument connections (cont.)

7174A

Signal

Guard

DUT

Signal

Guard

7174A

2-8

ignal

S

Operation

HI
LO

Voltage
Source

H.) Voltage Source

HI
LO

Electrometer

Guard

DUT

Signal
Guard

7174A

Signal

Guard

DUT

Signal

Guard

I.) Current Source, Unguarded

Guard

Current Source

J.) Current Source, Guarded

Figure 2-5

General instrument connections (cont.)

HI
LO

7174A

Rows Columns

Signal
Guard

DUT

Signal
Guard

7174A

2-9