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

Operation

Force
IorV

Sense

VorI

Source/Measure

Guard

Guard

Unit

HI

LO

HI

LO

Rows Columns

Signal

ua

G

Signal
Guard

S

ignal

uard

G

Signal
Guard

d

r

DUT

K.) Source/Measure Unit

Note: DUT shielding/guarding not shown. See Figures 2-20 and 2-21.

Figure 2-5

General instrument connections (cont.)

7174A

2-10

Operation

2.5.5 Keithley instrument connections

The following paragraphs outline connecting typical Kei­thley instruments to the Model 7174A 8 × 12 Low Current
Matrix Card. Other similar instruments can be connected
using the same cabling as long as their input/output configu­rations are the same. Instrument connections covered
include:

• Model 617 Electrometer/Source

• Model 196 DMM

• Model 230 Programmable Voltage Source

• Model 220 Programmable Current Source

• Model 590 CV Analyzer

• Model 236/237/238 Source Measure Unit

Model 617 electrometer connections

Connections for the Model 617 Electrometer are shown in
Figure 2-6. The electrometer INPUT and COM can be con-

6172 2-slot to 3-lug
Triax Adapter

Guard off

COM

INPUT

Model 617

nected to any row. Figure 2-6 shows connections to rows A
and B.

1. Connect one end of a Model 7078-TRX- (3, 10, or 20)
3-lug triaxial cable to row A of the Model 7174A.

2. Connect the other end of the triax cable to the Model
617 INPUT connector using a Model 6172 adapter.

3. Connect the triax end of a triax/banana cable to row B of
the Model 7174A.

4. Connect the banana plug end of the triax/banana cable
to the COM terminal of the Model 617. The shorting
link between COM and chassis ground should be re­moved for this application.

5. Place the GUARD switch in the OFF position.

6. T o connect the v oltage source to the Model 7174A, con­nect the V-SOURCE HI and LO connector of the Model
617 to the desired row connectors on the matrix card.
Figure 2-6 shows connections to rows C and D.

KEITHLEY

7174A

8x12LOW

CURRENT MATRIX

SIGNAL

200VP K

COLUMNS

200VPK

GUARD

200VP K

7078 - TRX Triax

237-BAN-3 o r Special Triax

237-BAN-3

ROWS

1

A

2

B

3

C

4

D

5

L

6

7

Voltage Source
Connections

Figure 2-6

Model 617 electrometer connections

237-BAN-3 o r Special Triax

Note: See paragraph 2.5.3 and Figure

2-4 f or special triax to banana
cable.

8

E

9

F

10

G

H

!

WARNING:

TIGHTENMOUNTINGSCREWS

TOENSUREPROPER

CHAS SIS GRO UND

11

12

7174A Matrix Card

2-11

Operation

Model 196 DMM connections

Connect the Model 196 or other similar DMM to the matrix
card using the general configuration shown in Figure 2-7.
The V OLTS OHMS HI and LO terminals should be connect­ed to the desired rows using triax/banana cables. For 4-wire
ohms measurements, the OHMS SENSE HI and LO termi-

237-BAN-3

237-BAN-3
or Special
Triax

HI

nals should be connected to two additional rows using the
same type of cables.

NOTE

For low-level voltage measurements, con­nect the inner shield of the HI cable to
VOLT OHMS LO to minimize noise.

KEITHLEY

7174A

8x12LOW

CURRENT MATRIX

SIGNAL

COLUMNS

200VP K

200VPK

GUARD

200VPK

ROWS

A

B

C

D

1

2

Note

3

4

5

L

6

: See paragraph 2.5.3

and Figur

special triax to banana

2-4 for

e

cable.

196 DMM

Connect inner shield to LO for
low-levelmeasurements.
(Modify the cable of Figure 2-4.)

Figure 2-7

Model 196 DMM connections

LO

7

8

E

F

G

H

TIGHTE N MOUNTING SCR EWS

WARNING:

TOENSUREPROPER

CHASSIS GROUND

9

10

11

12

!

7174A Matrix Card

2-12

Operation

Model 230 voltage source connections

Connect the Model 230 OUTPUT and COMMON terminal
to the desired rows using triax/banana plug cables, as shown

Common

230 C urrent Source

Note: See paragraph 2.5.3 and Figure

2-4 for special triax to banana cable.

Output

in Figure 2-8. For remote sensing applications, the SENSE
OUTPUT and SENSE COMMON connectors can be routed
through two additional rows using similar cables.

KEITHLEY

7174A

8x12LOW

CURRENT MATRIX

SIGNAL

COLUMNS

200VP K

200VP K

GUARD

200VPK

237-BAN-3 or Special Triax

237-BAN-3

ROWS

A

B

C

D

E

F

G

H

WARNING:

TIGHTENMOUNTING SCRE WS

TOE NSURE P R OPER

CHASSIS GROUND

1

2

3

4

5

6

7

8

9

10

11

12

!

Figure 2-8

Model 230 voltage source connections

7174A Matrix Card

2-13

Operation

Model 590 CV analyzer connections

The Model 590 CV analyzer can be connected to any row or
any column as shown in Figure 2-9. The BNC cables that are

. .

590 CV Analyzer

supplied with the Model 590 can be used; however, Model
7078-TRX-BNC adapters must be used at the Model 7174A
end.

7078-TRX-BNC

Triax-to-BNC

Adapters

7051 BNC Cables

KEITHLEY

8x12LOW

CURRENT MATRIX

SIGNAL

200VPK

200VPK

GUARD

200VP K

ROWS

A

B

C

D

E

F

G

H

WARNING :

TIGHTENMOUNTINGSCREWS

TOENSUREPROPER

CHASSISGROUND

7174A

COLUMNS

!

1

2

3

4

5

6

7

8

9

10

11

12

Figure 2-9

Model 590 CV analyzer connections

7174A Matrix Card

2-14

Operation

Model 220 current source connections

The Model 220 current source can be connected to the matrix
card using the Model 6167 Guarded Adapter, as shown in
Figure 2-10. This configuration guards the output signal to
minimize the effects of distributed capacitance and leakage
current.

NOTE

The Model 6167 adapter must be modified
by internally disconnecting the inner
shield connection of the input jack from
the GUARDED/UNGUARDED selection
switch. Otherwise, instrument LO will be

Model 6167

Guarded Adapter

connected to chassis ground through the
adapter.

1. Connect the Model 6167 adapter to the Model 220
OUTPUT jack.

2. Connect a Model 7078-TRX-(3, 10 or 20) triax cable
between the guarded adapter and the desired row of the
Model 7174A.

3. Connect the Model 220 GUARD output to GUARD
INPUT terminal of the adapter.

4. Connect the triax end of a triax/banana cable to the
desired row on the Model 7174A.

5. Connect the banana plug end of the triax/banana cable
to the OUTPUT COMMON jack of the Model 220.

KEITHLEY

7174A

8x12LOW

CURRENT MATRIX

SIGNAL

COLUMNS

200VP K

200VP K

GUARD

200VPK

7078-TRX T riax
237-BAN-3 or Special Triax

ROWS

1

A

2

B

3

C

4

D

5

6

Connect GUARD OUT

to GUARD

Note: See paragraph 2.5.3 and Figure

2-4 for special triax to banana cable.

Figure 2-10

Model 220 current source connections

220 C urrent Source

7

8

E

F

G

H

TIGHTENMOUNTING SCRE WS

WARNING:

TOE NSURE P R OPER

CHASSIS GROUND

9

10

11

12

!

7174A Matrix Card

2-15

Operation

Model 236/237/238 source measure unit connections

Source measure units are connected to the matrix card using
Model 7078-TRX cables. A Model 237-B AN-3 triax/banana
cable can also be used to connect the output low binding post
on the source measure unit to the matrix. Figure 2-11 shows
connections for remote and local sensing applications.

LINERATING

TRIGGER

MAXOUTPUT

KEITHLEY

GUARD

!

110V

MADEIN
U.S.A.

LO

HI

HI

OUTPUT

OUTPUT

SENSE

GUARD

A. Remote Sensing

OUT IN

OUTPUT

SENSE

LO

LO

LINEVOLTAGE

200V
MAX

SELECTED

LINEF USE
SLOWBLOW

INTERLOCK

50-60Hz

1

ACONLY

100VAMAX

2

IEEE-488INTERFACE

ADDRESSENTERED VIA
FRONTPANEL PROGRAM

CAL

ENABLE

7078-TRX Triax

7078-TRX Triax
7078-TRX Triax

CAUTION

Models 237 and 238 source measure
units can only be used within the speci­fied maximum signal levels of the Model
7174A (200V, 2A).

KEITHLEY

7174A

8x12LOW

CURRENTMATRIX

SIGNAL

200VPK

200VPK

COLUMNS

GUARD

200VPK

ROWS

1

A

2

B

3

C

4

D

5

6

7

8

E

9

F

10

G

11

H

12

WARNING:

!

TIGHTENMOUNTING SCREWS

TOENSUREPROPER

CHASSISGROUND

7174A Matrix Card

TRIGGER

OUT IN

MAXOUTPUT

KEITHLEY

GUARD

!

110V

MADEIN
U.S.A.

OUTPUT

OUTPUT

SENSE

LO

LO

LO

HI

HI

200V
MAX

OUTPUT

SENSE

GUARD

LINEVOLTAGE

SELECTED

LINEF USE
SLOWBLOW

INTERLOCK

ENABLE

B. Local Sensing

Figure 2-11

Model 236/237/238 source measure unit connections

7078-TRX Triax
237-BAN-3 or Special Triax

LINERATING

50-60Hz

1

ACONLY

100VAMAX

2

IEEE-488INTERFACE

ADDRESSENTERED VIA
FRONTPANELPROGRAM

CAL

Caution:

The models 237 and 238 Source Measure Units
can only be used within the specified maximum
signal levels of the Model 7174A (200V, 2A carry).

KEITHLEY

7174A

8x12LOW

CURRENTMATRIX

SIGNAL

COLUMNS

200VPK

200VPK

GUARD

200VPK

ROWS

1

A

2

B

3

C

4

D

5

6

7

8

E

9

F

10

G

11

H

12

!

WARNING:

TIGHTENMOUNTINGSCREWS

TOENSURE PROPER

CHASSISGROUND

7174A Matrix Card

2-16

Operation

2.5.6 T ypical test fixture connections

Typically, one or more test fixtures will be connected to
desired columns of the Model 7174A. Typically, the test fix-
tures will be equipped with card-edge connectors with wires
soldered to them. In some cases, the test fixture will be
equipped with triax connectors; for those types, Keithley
Model 7078-TRX-(3, 10, or 20) cables can be used, as shown
in Figure 2-12.

WARNING

Do not use BNC cables and adapters in
cases where hazardous voltages from
guard sources could be present on the
BNC cable shields.

KEI THLE Y

7174A

8x12LOW

CURRENTMATRIX

SIGNAL

COLUMNS

200VP K

200VP K

GUARD

200VP

K

ROWS

A

B

C

D

1

2

3

4

5

Internally, the test fixture should be wired as shown in the
equivalent circuit of Figure 2-13. SIGNAL should be con­nected to the probe or other device contact points, while
GUARD should be carried through as close to the device as
possible. If coaxial probes are to be used, connect GUARD
to the probe shield if the probe shield is insulated from the
fixture shield.

Usually, the chassis ground terminal of the triax connector
will automatically make contact with the fixture shield by
virtue of the mounting method. However, ground integrity
should be checked to ensure continued protection against
hazardous guard voltages.

3 - Lug Female

Test Fixture

Triax Connectors
(or run cables through strain
reliefs and connect internally)

6

7

8

E

F

G

H

TIGHT EN MOUNTING S CR EWS

WARNING:

TOENSUREPROPER

CHAS SIS GR OUND

9

10

11

12

!

7174A Matrix Card

Figure 2-12

Typical test fixture connections

®

Note: Teflon

-insulated connectors

recommended for specified
performance.

Warning:Donot use BNC connectors

to avoid possible shock
hazard.

2-17

Operation

Triax Cable

Signal

Probe

From

7174A

Card

Guard

Chassis
Ground

Figure 2-13

Equivalent circuit of test fixture connections

2.6 Matrix configuration

This section describes the matrix configuration of the Model
7174A. It also explains ways to expand the matrix by install­ing and connecting additional matrix cards in the Model
707A Switching Matrix.

2.6.1 Switching matrix

As shown in Figure 2-14, the Model 7174A is organized as
an 8 × 12 (8 rows by 12 columns) matrix. The rows on the
card are labeled A through H while the columns are num­bered 1 through 12. The actual column number to use when
programming depends on the slot and unit number (Table
2-3). For example, card column number 2 on a card in slot 5
of unit 1 is accessed as matrix column 50.

Wafer

Test Fixture Chassis

Each intersecting point in the matrix is called a crosspoint
that can be individually closed or opened by programming
the Model 707A mainframe. By closing the appropriate cros­spoint, required pathways and pins may be connected. All
crosspoints are configured for 2-pole switching, as shown in
Figure 2-14. SIGNAL and GUARD are switched separately
to any of the 12 columns on the card.

2.6.2 Path isolators

The path isolator relay switches shown in Figure 2-14 serve
to isolate a given path from the rest of the matrix when no
crosspoint (relay) is closed in that pathway. This topology
minimizes leakage current and capacitance to pathways
which are active. These isolators close automatically when
any crosspoint on the path is closed and open automatically
when all crosspoints on the path are opened.

2-18

Columns

HGC HG C HG C HGC HGC HGC HGC HG C HGC HGC HGC

Operation

HGC

User

connections

and expansion

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

Path Isolator
Relay Switch

Signal Guard

Row

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

Signal

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

Guard

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

Note: For schematic,

refer to Section 5.

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

H
G
C

H
G
C

H
G
C

H
G
C

H
G
C

H
G
C

H
G
C

H
G
C

Rows

Column

Figure 2-14

Matrix configuration

2-19

Operation

Table 2-3

Column numbering by slot and unit

Unit Slot Columns (1 through 12)

1

1
2
3
4
5
6

2

1
2
3
4
5
6

1

3

2
3
4
5
6

1

4

2
3
4
5
6

1
13
25
37
49
61

73
85
97

109
121
133

145
157
169
181
193
205

217
229
241
253
265
277

2
14
26
38
50
62

74
86
98

110
122
134

146
158
170
182
194
206

218
230
242
254
266
278

3
15
27
39
51
63

75
87
99

111
123
135

147
159
171
183
195
207

219
231
243
255
267
279

4
16
28
40
52
64

76
88

100
112
124
136

148
160
172
184
196
208

220
232
244
256
268
280

5
17
29
41
53
65

77
89

101
113
125
137

149
161
173
185
197
209

221
233
245
257
269
281

6
18
30
42
54
66

78
90

102
114
126
138

150
162
174
186
198
210

222
234

2446

258
270
282

7
19
31
43
55
67

79
91

103
115
127
139

151
163
175
187
199
211

223
235
247
259
271
283

8
20
32
44
56
68

80
92

104
116
128
140

152
164
176
188
200
212

224
236
248
260
272
284

9
21
33
45
57
69

81
93

105
117
129
141

153
165
177
189
201
213

225
237
249
261
273
285

10
22
34
46
58
70

82

94
106
118
130
142

154
166
178
190
202
214

226
238
250
262
274
286

11
23
35
47
59
71

83

95
107
119
131
143

155
167
179
191
203
215

227
239
251
263
275
287

12
24
36
48
60
72

84

96
108
120
132
144

156
168
180
192
204
216

228
240
252
264
276
288

2-20

289

1

5

301

2

313

3

325

4

337

5

349

6

290
302
314
326
338
350

291
303
315
327
339
351

292
304
316
328
340
352

293
305
317
329
341
353

294
306
318
330
342
354

295
307
319
331
343
355

296
308
320
332
344
356

297
309
321
333
345
357

298
310
322
334
346
358

299
311
323
335
347
359

300
312
324
336
348
360

Operation

2.6.3 Internal matrix expansion

Two to six Model 7174A cards can be connected together
within the mainframe to yield an 8 × N matrix, where N
depends on the number of cards. Figure 2-15 shows an inter­nally expanded matrix with three cards, resulting in an 8 × 36
(eight row by 36 column) matrix. As summarized in Table
2-3, the actual column number used when programming the
unit is determined by the slot.

WARNING

The shells of the row jumpers are at
guard potential. To avoid a possible
shock hazard, always disconnect all
cables from the row and column jacks
before removing or installing jumpers.

Internal

9

10

Paths Jumpers

12

11

131415

Paths

1
2
3
4
5
6
7
8

123

Slot 1 Slot 2 Slot 3

8

6

4

5

7

Because of critical signal paths, rows A-H are not jumpered
through the backplane. Instead, install the supplied coaxial
jumpers between appropriate connectors on Model 7174A
cards (for more critical signal paths, rows can be isolated
from other cards by not installing these cables). Each card
has two coaxial connectors for each row, allowing daisy
chaining of card rows. These connectors can be reached by
lifting the access door on the top of the mainframe; do not
remove cards to install the jumpers. This expansion is sho wn
schematically in Figure 2-15 for cards located in slots 1, 2
and 3.

Figure 2-16 shows the location of the connectors used for
this expansion. These connectors can be reached by lifting
the access door on the top of the Model 707A Switching
Matrix. The jumpers must be installed and removed before
installing or removing a Model 7174A from the 707A
Switching Matrix. Figure 2-17 shows how two cards can be
daisy chained together using the coaxial jumpers.

Internal

Paths Jumpers

18 19

20

212223

24 25 26 27 28

29 303132 333435

16 17

36

Figure 2-15

Connecting three cards for an 8 × 36 matrix

Figure 2-16

Jumper connector locations

ABCDEFGH

Measure

(For each path)

Warning:

Guard potential is on
coaxial jumper shields.

2-21

Operation

Figure 2-17

Two cards in daisy chain configuration

2.7 Measurement considerations

Most measurements made with the Model 7174A concern
low-level signals. Such measurements are subject to various
types of noise that can seriously affect low-level measure­ment accuracy. The following paragraphs discuss possible
noise sources that might affect these measurements.

keep the switching and measuring circuits a good distance
away from these potential noise sources.

2.7.2 Electromagnetic Interference (EMI)

The electromagnetic interference characteristics of the
Model 7174A comply with the electromagnetic compatibil­ity (EMC) requirements of the European Union (EU) direc­tives as denoted by the CE mark. However, it is still possible
for sensitive signals to be affected by external sources. In
these instances, special precautions may be required in the
test setup.

Sources of EMI include:

• Radio and TV broadcast transmitters.

• Communications transmitters, including cellular

phones and handheld radios.

• Devices incorporating microprocessors and high-speed
digital circuits.

• Impulse sources as in the case of arcing in high-voltage
environments.

The Model 7174A, signal source, measuring instrument, and
signal leads should be kept as far away as possible from any
EMI sources. Additional shielding of the card, signal leads,
sources, and measuring instruments will often reduce EMI to
an acceptable level. In extreme cases, a specially constructed
screen room may be required to sufficiently attenuate the
troublesome signal.

2.7.1 Magnetic fields

When a conductor cuts through magnetic lines of force, a
very small current is generated. This phenomenon will fre­quently cause unwanted signals to occur in the test leads of a
switching matrix system. If the conductor has sufficient
length, even weak magnetic fields like those of the earth can
create sufficient signals to affect low-level measurements.

Two ways to reduce these effects are: (1) reduce the lengths
of the test leads, and (2) minimize the exposed circuit area.
In extreme cases, magnetic shielding may be required. Spe­cial metals with high permeability at low flux densities (such
as mu metal) are effective at reducing these effects.

Even when the conductor is stationary, magnetically­induced signals may still be a problem. Fields can be
produced by various signals such as the AC power line
voltage. Large inductors such as power transformers can also
generate substantial magnetic fields, so care must be taken to

2-22

Many instruments incorporate internal filtering that may
help to reduce EMI effects in some situations. In other cases,
additional external filtering may be required. Keep in mind,
however, that filtering may have detrimental effects, such as
increased settling time, on the measurement.

2.7.3 Ground loops

When two or more instruments are connected together, care
must be taken to avoid unwanted signals caused by ground
loops. Ground Loops usually occur when sensitive instru­mentation is connected to other instrumentation with more
than one signal return path such as power line ground. As
shown in Figure 2-18, the resulting ground loop causes
unwanted signals to flow through the instrument LO signal
leads and then back through power line ground. This circu­lating current develops a small but undesirable voltage
between the LO terminals of the two instruments. This volt­age will be added to the source voltage, affecting the accu­racy of the measurement.

Operation

SIGNALLEADS

INSTRUMENT 1 INSTRUMENT 2 INSTRUMENT 3

GROUND

LOOP

CURRENT

POWER LINE GROUND

Figure 2-18

Power line ground loops

Figure 2-19 shows how to connect several instruments to­gether to eliminate this type of ground loop problem. Here,
there is only one connection to power line ground.

INSTRUMENT 1 INSTRUMENT 2 INSTRUMENT 3

these problems, never touch the connector insulating mate­rial. In addition, the matrix card should be used only in clean,
dry environments to avoid contamination.

If the connector insulators should become contaminated,
either by inadvertent touching or from air borne deposits,
they can be cleaned with a cotton swab dipped in clean meth­anol or an HCFC. After thorough cleaning, they should be
allowed to dry for several hours in a low-humidity environ­ment before use, or they can be dried more quickly using dry
nitrogen.

2.7.5 Noise currents caused by cable flexing

Noise currents can be generated by bending or flexing coax­ial, triaxial, or quadraxial cables. Such currents, known as
triboelectric currents, are generated by charges created
between a conductor and insulator caused by friction.

Low-noise cable can be used to minimize these effects. Such
cables have a special graphite coating under the shield to pro­vide lubrication and to provide a conduction path to equalize
charges.

POWER LINE GROUND

Figure 2-19

Eliminating ground loops

Ground loops are not normally a problem with instruments
having isolated LO terminals. However, all instruments in
the test setup may not be designed in this manner. When in
doubt, consult the manual for each instrument in the test set­up.

2.7.4 Keeping connectors clean

As is the case with any high-resistance device, the integrity
of connectors can be damaged if they are not handled prop­erly. If the connector insulation becomes contaminated, the
insulation resistance will be substantially reduced, affecting
high-impedance measurement paths.

Oils and salts from the skin can contaminate connector insu­lators, reducing their resistance. Also, contaminants present
in the air can be deposited on the insulator surface. To avoid

Even low-noise cable generates some noise current when
flexed or subjected to vibration. To minimize these effects,
keep the cables as short as possible, and do not subject them
to temperature variations that could cause expansion or con­traction. Tie down offending cables securely to avoid move­ment, and isolate or remove vibration sources such as motors
or pumps.

2.7.6 Shielding

Proper shielding of all unguarded signal paths and devices
under test is important to minimize noise pickup in virtually
any switching matrix system. Otherwise, interference from
such noise sources as line frequency and RF fields can seri­ously corrupt a measurement.

In order for shielding to be effective, the shield must com­pletely surround the source, measure and guard signals. It
must also have a low impedance path to chassis ground. This
is shown pictorially in Figure 2-20. The shield also functions
as a safety shield since it is connected to chassis ground.

WARNING

Hazardous voltage may be present if LO
on any instrument is floated above
ground potential.

2-23

Operation

To

7174A

Source

Measure

Guard

Chassis

Signal Source and Measure
(Probe or Contact Point)

Figure 2-20

Shielded and guarded

2.7.7 Guarding

Guarding is important in high-impedance circuits where
leakage resistance and capacitance could have degrading
effects on the measurement. Guarding consists of using a
shield surrounding a conductor that is carrying the high
impedance signal. This shield is driven by a low-impedance
amplifier to maintain the shield at signal potential.

Guarding minimizes leakage resistance effects by driving the
cable shield with a unity gain amplifier, as shown in Figure
2-21. Since the amplifier has a high input impedance, it min­imizes loading on the high-impedance signal lead. Also, the
low output impedance ensures that the shield remains at sig­nal potential, so that virtually no leakage current flows
through the leakage resistance, RL. Leakage between inner
and outer shields may be considerable, but that leakage is of
little consequence because that current is supplied by the
buffer amplifier rather than the signal itself.

DUT

Source or Measure

Signal

R

R

s

E

s

DUT

Figure 2-21

Guarded circuit

Inner Shield
(Guard or LO)

Outer S hield

(Chassis Ground)

Inner Shield

X1

Buffer

L

E

M

Guard

Measuring
Instrument

In a similar manner, guarding also reduces the effecti ve cable
capacitance, resulting in much faster measurements on high­impedance circuits. Because any distributed capacitance is
charged through the low impedance of the buffer amplifier
rather than by the source, settling times are shortened consid­erably by guarding.

In order to use guarding effectively with the Model 7174A,
the guard path of the matrix card should be connected to the
guard output of the sourcing or measuring instrument. Figure
2-20 shows typical connections. Guard should be properly
carried through the inner shield to the device under test to be
completely effective. The shielded, guarded test fixture
arrangement shown in Figure 2-20 is also recommended for
safety purposes (guard voltage may be hazardous with some
instruments).

2-24

2.7.8 Matrix expansion effects on card
specifications

Specifications such as those given for path isolation and off­set current are with a single Model 7174A card installed in
the mainframe. Expanding the matrix by internally connect­ing two or more Model 7174A cards together will degrade
system performance specifications (other types of cards do
not affect the specifications because they use different path­ways in the mainframe backplane). The extent depends on
how many cards are used, as well as the amount of cabling
used to connect them together.

With internal pathway expansion, isolation among paths is
increased, and offset current is decreased, although the isola­tor relays on the card do help to minimize these effects.

2.8 Coaxial jumper access

To gain access to jumpers, lift jumper across cover (Figure
2-22).

Operation

Figure 2-22

Coaxial jumper access

2-25

3

Applications

3.1 Introduction

This section covers typical applications for the Model 7174A
8 × 12 Low Current Matrix Card and is organized as follows:

3.2 CV measurements — Outlines the test configuration

and procedure for making quasistatic and high­frequency CV measurements.

3.3 Semiconductor test matrix — Details a semiconduc-

tor test matrix that can be used to perform a variety of
different tests on semiconductors such as FETs.

3.4 Resistivity measurements— Covers methods to mea-

sure the resistivity of semiconductor samples using the
van der Pauw method.

3.5 Semiconductor IV characterization — Covers the

basic scheme and connections used to generate an IV
curve of a bipolar or MOS transistor.

3.2 CV measurements

The Model 7174A can be used in conjunction with the
Keithley Model 590 CV Analyzer, and the Keithley Model
595 Quasistatic CV Meter to perform quasistatic and high­frequency CV (capacitance vs. voltage) test on
semiconductors. The resulting CV curves can be used to
calculate important semiconductor parameters such as
doping profile, band bending, and mobile ion concentration.

3.2.1 Stand alone system configuration

The stand alone system shown in Figure 3-1 can be used to
make CV measurements without the aid of a computer. Sys­tem components perform the following functions.

Model 590 CV Analyzer: Measures CV data at 100kHz and

1MHz and sends the resulting data to the plotter for
graphing.

Model 595 Quasistatic CV Meter: Measures quasistatic CV

data and sends the data to the plotter for graphing in real
time.

Model 707A Switching Matrix: Controls the semiconductor

matrix card to close and open the desired crosspoints at the
proper time.

Model 7174A 8 × 12 Low Current Matrix Card: Switches

the signa pathways to the six devices under test.

HP-GL Plotter: Plots CV and other curves directly from the

Models 590 and 595.

3.2.2 Computerized system configuration

Figure 3-2 shows a computerized version of the CV matrix
test system. The addition of a computer allows greater sys­tem versatility and easier instrument control. Also, analysis
functions such as doping profile and ion concentration can be
added to the software to expand CV analysis capabilities.

3-1

Applications

Devices Under

123456

A

B

C
D

E

F
G
H

7174A Matrix Card

707A Switching Matrix

Figure 3-1

Stand alone CV system configuration

Test

1112345678910 12

Triax

Cables

4801 Low-Noise Cables

S
G

S
G

7078-TRX-BNC
Triax BNC
Adapters

S
G

S
G

7051 BNC

Cables

Model 595

Quasistatic CV Meter

Meter Input

V-Source Output

IEEE-488

Bus

Output

Input

Model 590

CV Analyzer

Note:

Connect plotter to only one
instrument at a time.

HP-GL
Plotter

Devices Under

Test

123456

A

B

C

D

E

F
G

H

7174A Matrix Card

707A Switching Matrix

Triax
Cables

4801 Low-Noise Cables

S
G

S
G

7078-TRX-BNC

Triax BNC

Adapters

S
G

S
G

Model 595

Quasistatic CV Meter

Meter Input

V-Source Output

IEEE-488

Bus

Output

1112345678910 12

Input

7051 BNC

Cables

Model 590

CV Analyzer

IEEE-488 Bus

Note: Remove jumpers to other 7174A cards (if installed)

to optimize Model 595 measurement accuracy.

Computer

HP-GL
Plotter

Figure 3-2

Computerized CV system configuration

3-2

Applications

3.2.3 Optimizing CV measurement accuracy

For accurate CV measurements, each Model 590 CV mea­surement pathway must be corrected using the procedure
outlined in the Model 590 Instruction Manual. The pathways
to each DUT must be cable corrected separately.

Also, for best quasistatic CV results, the corrected capaci­tance feature of the Model 595 should be used. Corrected
capacitance compensates for any leakage currents present in
the cables, switching matrix, or test fixture. However, care
must be taken when using corrected capacitance to ensure
that the device remains in equilibrium throughout the test
sweep to avoid distorting the CV curves.

In order to minimize the effects of the switching network on
quasistatic CV measurements, cables to the Model 595 and
DUT should be kept as short as possible.

3.2.4 Basic CV test procedure

The fundamental CV test procedure is outlined below. Keep
in mind that this procedure does not address many consider­ations and aspects of CV testing, which is fairly complex.
The procedure given is for the stand alone system in Figure
3-1. Detailed instrument operating information may be
found in the pertinent instruction manuals.

7. Set up the Model 590 for the expected CV sweep.

8. Close the crosspoints necessary to connect the Model
590 to the device under test. For example, to test device
#1, close G1 and H2.

9. Run a high-frequency test sweep on the device to store
the CV data in the Model 590 buffer.

10. Disconnect the plotter from the Model 595 and connect
it to the Model 590.

11. Generate a plot from the data in the Model 590 buffer.

12. Repeat steps 2 through 11 for the remaining devices, as
required.

Table 3-1

CV test crosspoint summary

Closed crosspoints

Wafer #

1
2
3
4
5
6

Quasistatic (595) High frequency (590)

A1, B2
A3, B4
A5, B6
A7, B8

A9, B10

A11, B12

G1, H2
G3, H4
G5, H6
G7, H8

G9, H10

G11, H12

1. Connect the HP-GL plotter to the IEEE-488 bus connec­tor of the Model 595 only.

2. Set up the Model 595 for the expected CV sweep.

3. Close the crosspoints necessary to connect the Model
595 to the device under test, as summarized in Table 3-1.
For example, to test device #1, close A1 and B2.

4. Place the probes down on the wafer test dots.

5. Run a quasistatic sweep on the selected device and gen­erate a CV curve.

6. Open the crosspoints that are presently closed.

3.2.5 T ypical CV curves

Figure 3-3 and Figure 3-4 shows typical CV curves as
generated by the Model 595 and 590 respectively. The
quasistatic curve shows a fair amount of symmetry, while the
high-frequency curve is highly asymmetrical. The
asymmetrical nature of the high-frequency curve results
from the inability of minority carries to follow the high­frequency test signal.

3-3

Applications

+0.6E-10

+0.4E-10

-005.00

+005.00

KEITHLEY 595

Figure 3-3

Typical quasistatic CV curve generated by Model 595

1.50

1.42

1.35

9

0

-

^

0

1

1.27

X

)

d

a

r

a

1.20

F

(
e

c

n

a

t

1.12

i

c

a

p

a
C

1.05

0.97

0.90

0.82

0.75

- 4.99 - 3.99 - 2.99 - 1.99 - 0.99 0.00 1.00 1.99 2.99 3.9 9 4.99

Keithley 590: 00: 00: 10: 500 100KHz X1 Filter ------------- Para llel

Bias (Volt) X 10^+00

Figure 3-4

Typical high-frequency CV curve generated by Model 590

3-4

1112345678910 12

A

C

B

D

E

F
G
H

G

SGS G

SGS G

SGS GSG SGSG

G

G

G

G

G

G

S
S
S

S

S
S

HI

G

LO

LO

LO

617

I Measure

HI

HI

V Source

590

CV

HI HI HI LOLOLO

220

Current

Source

196

DMM

V Measure

230

V Source

Device Under Test

Source

Gate

Drain

7174A Matrix Card

707A Switching Matrix

Figure 3-5

Semiconductor test matrix

Applications

3.3 Semiconductor test matrix

Two important advantages of a matrix switching system are
the ability to connect a variety of instruments to the device or
devices under test, as well as the ability to connect any
instrument terminal to any device test node. The following
paragraphs discuss a typical semiconductor matrix test sys­tem and how to use that system to perform a typical test:
common-source characteristic testing of a typical JFET.

3.3.1 System configuration

Figure 3-5 shows the configuration for a typical multi­purpose semiconductor test matrix. Instruments in the
system perform the following functions.

Model 617 Electrometer/Source: Measures current, and

also could be used to measure voltages up to ±200VDC. The
DC voltage source can supply a maximum of ±100V at cur­rents up to 2mA.

Model 230 Voltage Source: Sources DC voltages up to

±101V at a maximum current of 100mA.

Model 590 CV Analyzer: Adds CV sweep measurement

capability to the system.

Model 220 Current Source: Used to source currents up to a

maximum of 101mA with a maximum compliance voltage
of 105V.

Model 196 DMM: Measure DC voltages in the range of

100nV to 300V. The Model 196 could also be used to mea­sure resistance in certain applications.

Device Under T est: A three-terminal picture for testing such

devices as bipolar transistors and FETs. Additional connec­tions could easily be added to test more complex devices, as
required.

3-5

Applications

617

Electrometer/Source

A12

HI

I

D

B9

Meter

(Current)

LO

D

F8 F10

HI

LO

Model 230

Voltage Source

= Closed Crosspoints on 7174A Card (Figure 3-5).

E9

E11

G

V

GS

S

Figure 3-6

System configuration for measuring common-emitter characteristics

3.3.2 T esting common-source characteristic of
FET s

The system shown in Figure 3-5 could be used to test a vari­ety of characteristics including I
and V

DS[OFF]

. To demonstrate a practical use for the system,
we will show how it can be used to generate common source
characteristic curves of a particular JFET.

In order to generate these curves, the instrument must be
connected to the JFET under test, as shown in Figure 3-6.
The advantage of using the matrix is, of course, that it is a
simple matter of closing specific crosspoints. The cross­points that must be closed are also indicated on the diagram.

GSS

, I

D[OFF]

, I

G[ON]

, I

DSS

,

V

DS

I

(µA)

D9

HI

Voltage

Source

LO

C11

100

90

V=0V

80
70
60

D

50
40
30
20
10

0

0 23456789

1

V(Volts)

DS

GS

V=-0.5V

GS

V=-1V

GS

10

To run the test, V
increments of 0.25V. At each V
voltage (V

DS

drain current, I

is set to specific values, for example in

GS

value, the drain-source

GS

) is stepped across the desired range, and the

, is measured at each value of V

D

. Once all

DS

data are compiled, it is a simple matter to generate the
common-source IV curves, an example of which is shown in
Figure 3-7. If the system is connected to a computer, the test
and graphing could all be done automatically.

3-6

Figure 3-7

Typical common-source FET IV characteristics

Applications

3.4 Resistivity measurements

The Model 7174A 8 × 12 Low Current Matrix Card can be
used in conjunction with a Model 220 Current Source and a
Model 196 DMM to perform resistivity measurements on
semiconductors. Such measurements can yield such impor­tant information as doping concentration.

3.4.1 T est configuration

Figure 3-8 shows the basic test configuration to make resis­tivity measurements on van der Pauw samples. The Model
220 sources current through the samples, while the Model
196 measures the voltage developed across the samples. The
matrix card, of course, switches the signal paths as neces­sary. In order to minimize sample loading, which will reduce
accuracy, the Model 196 DMM should be used only on the
300mV or 3V ranges. Also, this configuration is not recom-

1

3

due to the

2

4

mended for resistance measurements above 1M Ω
accuracy-degrading effects of DMM loading.

1

Sample 1

4

2

3

Sample 2 Sample 3

4

3.4.2 T est procedure

In order to make van der Pauw resistivity measurements,
four terminals of a sample of arbitrary shape are measured.
A current (from the Model 220) is applied to two terminals,
while the voltage is measured (by the Model 196) across the
two opposite terminals, as shown in Figure 3-9. A total of
eight such measurements on each sample are required, with
each possible terminal and current convention. The resulting
voltages are designated V1 through V8.

In order to source current into and measure the voltage
across the sample, specific crosspoints must be closed. Table
3-2 summarizes the crosspoints to close for each voltage
measurement on all three samples from the test configuration
shown in Figure 3-8.

1

2

3

SGSG

A

B

C

D

E

F

G

H

Figure 3-8

Resistivity test configuration

SG

SGSG SGSGSG

SG SGSGSG

7174A Matrix Card

707A Switching Matrix

1112345678910 12

S

G

S

G

S

G

S

G

HI
G

LO

220 Current Source
(Sources Current through Sample)

HI

LO

196 DMM
(Measures Voltage Across Sample)

3-7

Applications

I

12

43

V

(A)

V

3

(C) (D)

1

I

12

43

(B)

I

12

43

V

2

1

V

4

43

2

I

V

5

12

43

I

(E) (F)

1

43

I

(G) (H)

2

V

7

Figure 3-9

Resistivity measurement conventions

V

6

12

43

I

I

12

V

43

8

3-8

Table 3-2

Crosspoint summary for resistivity measurements

Crosspoint closed

Voltage

Applications

Current
between

Voltage

betweenSample #1 Sample #2 Sample #2

V
V
V
V
V
V
V
V

A1

B4

E3

F2

A5

B9

1

A4

B1

E3

F2

2

A4

B3

3

A3

4

A3

5

A2

6

A2

7

A1

8

B4
B2
B3
B1
B2

E2
E2
E1
E1
E4
E4

F1
F1
F4
F4
F3
F3

A8
A8
A7
A7
A6
A6
A5

B5
B7
B8
B6
B7
B5
B6

E7
E7
E6
E6
E5
E5
E8
E8

3.4.3 Resistivity calculations

Once the eight voltage measurements are known, the resis­tivity can be calculated. Two values of resistivity, ρ
are initially computed as follows:

1.1331 fAtSV2+V4–V1–V

------------------------------------------------------------------------ -=

ρ

A

1.1331 fBtSV6+V8–V5–V

------------------------------------------------------------------------ -=

ρ

B

()

I

()

I

3

7

and ρ

A

F6
F6
F5
F5
F8
F8
F7
F7

A9
A12
A12
A11
A11
A10
A10

A9

B12

B9
B11
B12
B10
B11

B9
B10

E11
E11
E10
E10

E9

E9
E12
E12

F10
F10

F9

F9
F12
F12
F11
F11

1-2
2-1
2-3
3-2
3-4
4-3
4-1
1-4

3-4
3-4
4-1
4-1
1-2
1-2
2-3
2-3

3.5 Semiconductor IV characterization

A source measure unit such as the Model 236, 237, or 238 is
used to test and characterize many types of devices. One of

B

these is semiconductor devices. The following paragraphs
explain the basic scheme and connections used to generate
an IV curve of a bipolar or MOS transistor. Figure 3-10
shows FET devices connected in a test fixture.

3.5.1 T est configuration

Rows A and B are used to switch the Model 237 Source Mea­sure Unit; rows C and D are used for the Model 236.

Where: ρ

and ρ

A

t

is the sample thickness in cm

S

V

1

are the resistivities in Ω -cm

B

through V

are the voltages measured by the

8

Model 196
I is the current through the sample in amperes
f

and f

are geometrical factors based on sample

B

=f

=1 for perfect symmetry).

A

B

are known, the average resistivity, ρ

B

Once ρ

A

symmetry (f

and ρ

A

can be determined as follows:

ρ

AVG

ρAρB+

------------------ -=

CAUTION

To prevent card damage, do not exceed
the 200 volt maximum rating of the
Model 7174A when switching the Model
237, which is capable of sourcing up to
1100 volts.

AVG

connected in a 4-wire sensing configuration. This connection

At the test fixture, the drain and source leads of the FETs are

,

scheme allows the Model 237 to use remote sensing to
accurately apply Vds to the FETs. The Model 236 uses local
sensing and is used to supply the bias to the gates of the

2

FETs. Since the gates are low current, remote sensing is not
necessary.

If more DUT pins are needed, the system is easily expanded
by adding more Model 7174A matrix cards. Each additional
card will add 12 columns to the system.

3-9

Applications

3.5.2 Cable connections

Source Measure Unit and test fixture connections to the
matrix card are accomplished using Model 7078-TRX.
These are three slot triax cables. On each Source Measure
Unit, the banana jack (5-way binding post) is used to access
OUTPUT LO. This connection is made using a Model 237-

Note:

Source Measure Units

Model 237 Model 236

DUT #1

Output HI/Guard

Sense HI/Guard

Sense LO/Output LO

Output LO

Output HI/Guard

Output LO

7078-TRX

Cables

123456789101112

Rows

A

X

B

X

C
D
E
F
G
H

X

X

X

•

•

X

X

X

•

•

123456789101112

BAN-3 or the special cable constructed using the informa­tion in Figure 2-4. This allows OUTPUT LO to be applied to
a signal pathway and independently switched. The guard
pathways of the matrix cards are used exclusively to extend
the driven guards of the Source Measure Units to the DUT to
eliminate the effects of leakage current.

Do not connect guards to the
DUT or short them together. If
guarding the inner panel, only
connect one guard line to it.

Test Fixture

DUT #2

DUT #3

Inner
Panel

Warning:

Columns

Test fixture chassis
must be connected
to a safety earth
ground.

7174A

Matrix Card

=

Model 237-BAN-3 or
Triax to banana plug
Modification (see Figure 2-4)

X

=

Crosspoints closed to
apply VDS to DUT #1

•

=

Crosspoints closed to
bias gate of DUT #1

Figure 3-10

Multi unit test system using Models 236 and 237 source measure units

3-10

7174A

Matrix Card

Signal
Guard

Signal

Crosspoint Switching
for all Rows

Guard

4

Service Information

4.1 Introduction

WARNING

The service 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 necessary to service the
Model 7174A Low Current Matrix Card and is arranged as
follows:

4.2 Handling and cleaning precautions — Discusses

handling precautions and methods to clean the card
should it become contaminated.

4.3 Principles of operation — Briefly discusses circuit

operation.

4.4 Troubleshooting — Presents some troubleshooting

tips for the Model 7174A.

4.5 Special handling of static-sensitive devices —

Reviews precautions necessary when handling static­sensitive devices.

4.6 Performance verification — Describes conditions

and provides references to determine if the card is op­erating properly.

4.7 Reed pack replacement — Provides a procedure for

replacing faulty reed packs.

4.2 Handling and cleaning precautions

Because of the high-impedance circuits on the Model
7174A, care should be taken when handling or servicing the
card to prevent possible contamination. The following pre­cautions should be taken when servicing the card.

1. Handle the card only by the edges and handle (do not
touch the edge connectors). Do not touch any board sur­faces or components not associated with the repair.

2. Do not store or operate the card in an environment
where dust could settle on the circuit board. Use dry ni­trogen gas to clean dust off the board if necessary.

3. When making repairs on the circuit board, use aqua core
solder and OA-based (organic acti v ated) flux. Use warm
deionized water along with clean cotton swabs or a
clean, soft brush to remove the flux. Take care not to
spread the flux to other areas of the circuit board. Once
the flux has been removed, blow dry the board with dry
nitrogen gas.

NOTE

Removal of skin oils and other non­organic contaminants can be done with
methanol or an HCFC.

4. After cleaning, the card should be placed in a 50°C low­humidity environment for several hours before use.

4-1

Service Information

4.3 Principles of operation

The following paragraphs discuss the basic operating princi­ples for the Model 7174A. A schematic diagram of the
matrix card may be found in drawings 9174-106 (mother
board) and 9174-126 (air matrix relay board) located at the
end of Section 5.

4.3.1 Block diagram

Figure 4-1 shows a simplified block diagram of the Model
7174A. Key elements include the buf fer (U410), ID data cir ­cuits (U406, U408, and U410), relay drivers (U101 through
U113), relays (K101-K204), and the power-on safe guard
(U409). The major elements are discussed below.

4.3.2 ID data circuits

At power up, the card identification data information from
each card is read by the mainframe. This ID data includes
such information as card ID, hardware settling time for the
card, and a relay configuration table, which tells the main­frame which relays to close for a specific crosspoint. This
configuration table is necessary because some cards (such as
the Model 7174A) require the closing of more than one relay
to close a specific crosspoint.

ID Data is contained within an on-card ROM, U406. In order
to read this information, the sequence below is performed
upon power up. Figure 4-2 shows the general timing of this
sequence.

1. The CARDSEL line is brought low, enabling the ROM
outputs. This line remains low throughout the ID data
transmission sequence.

2. The CLRADDR line is pulsed clearing the address
counter to zero. At this point, a ROM address of zero is
selected. This pulse occurs only once.

3. The NEXTADDR line is set low. NEXTADDR going
low increments the counter and enables parallel loading
of the parallel-to-serial converter. NEXTADDR is kept
low long enough for the counter to increment and the
ROM outputs to stabilize. This sequence functions
because the load input of the parallel-to-serial converter
is level sensitive rather than edge sensitive. The first
ROM address is location 1, not 0.

4. The CLK line clocks the parallel-to-serial converter to
shift all eight data bits from the converter to the main­frame via the IDDATA line.

The process in steps 3 and 4 repeats until all the necessary
ROM locations hav e been read. A total of 498 bytes of infor­mation are read by the mainframe during the card ID
sequence.

Address
Counter

U407

CLRADDR

To

Mainframe

Figure 4-1

Model 7174A block diagram

A0-A11

NEXTADDR

Buffer

U410

ROM

U406

CARDSEL

IDDATA

RELAYDATA

STROBE

Power-On

Safeguard

U409

D0-D7

CLK

NEXTADDR

Drivers

U101-U113

Output
Enable

Converter

U408

Relay

Parallel
to Serial

Relays

K101-K204

Columns

1-12

Rows
A-H

4-2

CARDSEL

CLRADDR

NEXTADDR

Service Information

CLK

IDDATA

HI-Z

Note: ID data sequence occurs on power-up only.

CLRADDR pulse occurs only once.

D7 D6 D5 D4 D3 D2 D1 D0

Figure 4-2

ID data timing

4.3.3 Relay control

The relays are controlled by serial data transmitted via the
RELAY DATA line. A total of 16 bytes for each card are
shifted in serial fashion into latches located in the 16 relay
drivers, (U101 through U113). The serial data is fed in
through the DATA lines under control of the CLK signal. As
data overflows one register, it is fed out the Q’s line of that
register to the next IC down the chain.

Once all 16 bytes have been shifted into each card in the
mainframe, the STROBE line is set high to latch the relay
information into the Q outputs of the relay drivers, and the
appropriate relays are energized (assuming the driver outputs
are enabled, as discussed below). Logic convention is such
that the corresponding relay driver output must be low to
energize the associated relay, while the output is high when
the relay is de-energized. For example, if the Q1 output of
U113 is low, relay K197 will be energized.

HI-Z

4.3.4 Power-on sequence

A power-on safeguard circuit, made up of U409 and associ­ated components, ensures that relays do not randomly ener­gize upon power-up. The tw o ANG gates, U409, make up an
R-S flip-flop. Initially, the Q output of the flip-flop (pin 3 of
U409) is set high upon power up. Since the OEN terminals
of the relay drivers (U101 through U113) are held high, their
outputs are disabled, and all relays remain de-energized
regardless of the relay data information preset at that time.

The first STROBE pulse that comes along (in order to load
relay data) clears the R-S flip-flop, setting the OEN lines of
the relay drivers low to enable their outputs. This action
allows the relays to be controlled by the transmitted relay
data information.

A hold-off period of approximately 470msec is included in
the safeguard circuit to guard against premature enabling of
the relays. The time constant of the hold-off period is deter­mined by the relative values of R419 and C419.

4-3

Service Information

4.3.5 Isolator relays

Row isolator relays are necessary in addition to the cross­point relays in order to ensure the integrity of signal path­ways. Path isolator relays include K198-K204. The
necessary isolator relay is closed in addition to the selected
crosspoint to complete the entire pathway. For example, if
crosspoint C10 (Row C, Column 10) is closed, relays K199
and K183 would be energized.

4.4 T roubleshooting

4.4.1 Recommended equipment

T able 4-1 summarizes the recommended equipment for gen­eral troubleshooting.

Table 4-1

Recommended troubleshooting equipment

Manufacturer

Description

5 ½ digit DMM
Oscilloscope
Extender card

and model Application

Keithley 199
TEK 2243
Keithley 7070

Measure DC voltages
View logic waveforms
Allow circuit access

4.4.2 Gaining circuit access

In order to gain access to the test points and other circuitry
on the Model 7174A, the card must be plugged into the
Model 7070 Extender Card, which, in turn, must be plugged
into the desired slot of the mainframe. The Model 7070 must
be configured as an extender card by placing the configura­tion jumper in the EXTEND position. See the documentation
supplied with the Model 7070 for complete details on using
the card.

NOTE

Do not use the Model 7070 for performing
verification tests because its presence will
affect the results.

4.4.3 T roubleshooting procedure

Table 4-2 summarizes the troubleshooting procedure for the
Model 7174A Low Current Matrix Card. Some of the trou­bleshooting steps refer to the ID data timing diagram shown
in Figure 4-2. Refer to paragraph 4.3 for an overview of oper ­ating principles.

Table 4-2

Troubleshooting procedure

Step Test point/component Required condition Comments

1

DGND

2

4-4

10

11

3
4
5
6
7
8
9

+6V
+5V
NXTADR
CLRADR
IDDATA
STRB
RLDAT
CLK
OE

U101-U113
pins 10-18

+6VDC
+5VDC
NEXT ADDR pulses
CLR ADDR pulse
ID data pulses
STROBE pulse
Relay data (128 bits)
CLK pulses
High on power up until first
STROBE sets low.
Low with relay energized,
high with relay de-energized.

All voltages referenced to DGND (digital
common)
Relay voltage
Logic voltage
Power up only (Fig. 4-2)
Power up only (Fig. 4-2)
Power up only (Fig. 4-2)
End of relay data sequence
Present when updating relays
Present during relay data or ID data (Fig. 4-2)
Power on safe guard

Relay driver outputs

Service Information

4.5 Special handling of static-sensitive devices

CMOS and other high-impedance devices are subject to pos­sible static discharge damage because of the high-impedance
levels in volved. When handling such devices, use the precau­tions listed below.

NOTE

In order to prevent damage, assume that all
parts are static sensitive.

1. Such devices should be transported and handled only in
containers specially designed to prevent or dissipate
static build-up. Typically , these devices will be received
in anti-static containers made of plastic or foam. Keep
these parts in their original containers until ready for in­stallation or use.

2. Remove the devices from their protective containers
only at a properly-grounded work station. Also ground
yourself with an appropriate wrist strap while working
with these devices.

3. Handle the devices only by the body; do not touch the
pins or terminals.

4. Any printed circuit board into which the device is to be
inserted must first be grounded to the bench or table.

5. Use only anti-static type de-soldering tools and
grounded-tip soldering irons.

4.6 Performance verification

The following paragraphs discuss performance verification
procedures for the Model 7174A, including relay testing,
contact resistance, contact potential, path isolation, and leak­age current.

4.6.1 Environment conditions

All verification measurements except for path isolation and
offset current should be made at an ambient temperature of
21°C-25°C and a relative humidity of less than 0% R.H. Path
isolation and offset current verification must be performed at
an ambient temperature of 23°C and a relative humidity of
less than 60% R.H. If the card has been subjected to temper­atures or humidities outside of this range for even a short
time, allow it to stabilize within these ranges for at least one
hour before performing any tests.

4.6.2 Recommended test equipment

Table 4-3 summarizes the equipment necessary to make the
performance verification tests, along with the application for
each item.

Table 4-3

Recommended verification equipment

Qty. Description Application

1

Model 617 Electrometer

1

Model 196 6½ Digit DMM

1

Model 707A Switching Matrix

4

Model 7078-TRX-10 triax cables*

2

Model 7078-TRX-3 triax cables

1

Model 6172 2-slot male to 3-lug female triaxial adapter

3

Model 7078-TRX-T triax tee adapter

5

Banana plugs (part #BG-10-2*)

1

Model 263 Calibrator/Source

1

BNC to Right-angle SMB Cable (part #CA-93-1)

1

BNC to Dual Banana Adapter (Pomona part #1269)

*These items are used to construct special cables; see text and Figure 4-9.

Offset current; path isolation
Path resistance; electrometer
All tests
Offset current; path resistance
Path isolation; offset current; electrometer
Offset current; electrometer
Path resistance
Path isolation and resistance
Electrometer
Electrometer
Electrometer

4-5

Service Information

4.6.3 Offset current verification

Recommended equipment

• Model 707A Switching Matrix

• Model 617 Electrometer

• Model 7078-TRX-3 Triax Cable

• Model 6172 2-slot male to 3-lug female triaxial adapter

Test connections

Figure 4-3 shows the test connections for offset current
verification. The Model 7174A row being tested is to be
connected to the Model 617 Electrometer input through the
triaxial cable and the triaxial adapter. Note that the
electrometer ground strap is to be removed, and the
electrometer should be operated in the unguarded mode.

Procedure

NOTE

The following procedure should be per­formed at an ambient temperature of 23°C
and at a relative humidity of less than
60%.

1. Turn on the Model 617 power and allow it to warm up
for two hours before beginning the verification
procedure

6172 2-Slot to

3-Lug Triax Adapter

Guard off

2. With the power off, install the Model 7174A in the
desired slot of the Model 707A Switching Matrix.
Remove all other cards from the instrument, and install
the slot covers.

3. After the prescribed warm up period, select the amps
function and the 2pA range on the Model 617. Zero cor­rect the instrument, and then select autoranging.

4. Connect the Model 617 to row A of the Model 7174A,
as shown in Figure 4-4.

5. Close crosspoint A1 by using the Model 707A front
panel controls.

6. Disable zero check on the Model 617, and allow the
reading to settle.

7. Verify that the offset current reading is <500fA.

8. Enable zero check on the Model 617, and open cross­point A1.

9. Repeat steps 5 through 8 for crosspoints A2 through
A12. Only one crosspoint at a time should be closed.

10. Disconnect the triax cable from row A, and connect it
instead to row B.

11. Repeat steps 5 through 8 for crosspoints B1 through
B12. Only one crosspoint at a time should be closed.

12. Connect the triax cable to each succeeding row and
repeat steps 5 through 8 for each of the row’s
crosspoints.

Connect Cable

to Row Under

Test

7078-TRX-3 Triax Cable

Ground Link

Removed

200VPK

200VPK

A

B

C

D

KEITHLEY

8x12LOW

CURRENT MATRIX

SIGNAL

200VPK

GUARD

ROWS

7174A

COLUMNS

1

2

3

4

5

617

7174A

A

Equivalent Circuit

Figure 4-3

Offset verification test connections

4-6

617 Electrometer

E

F

G

H

WARNING:

TIGHTENMOUNTING SCREWS

TOENSURE PROPER

CHASSISGROUN

Matrix Card7174A

6

7

8

9

10

11

12

!

D

Service Information

4.6.4 Path isolation verification

The procedure for verifying path isolation is discussed be­low. Should the card fail any of the tests, clean it using the
procedures outlined in paragraph 4.2.

Recommended equipment

• Model 707A Switching Matrix

• Model 617 Electrometer

• Model 7078-TRX-3 Triax Cable

• Unterminated 3-slot triaxial cable (cut connector off
7078-TRX-3)

• Banana plug (Keithley part #BG-10-2)

• #16-18AWG insulated stranded wire (6 in. length)

Test connections

Figure 4-4 shows the test connections for the path isolation
tests. One row being tested is to be connected to the Model
617 Electrometer input through a Model 6172 2-slot female

6172

Adapter

Guard off

to 3-lug male triaxial adapter. The other row is to be con­nected to the voltage source HI terminal using a specially
prepared 3-slot triax-to-banana plug cable, the construction
of which is shown in Figure 4-5. Note that both the inner
shield and the center conductor are to be connected to the
banana plug as shown.

COM and LO terminal of the electrometer voltage source
must be connected together as shown. Also, the ground link
between COM and chassis must be removed, and the Model
617 guard must be turned off for current measurements.

Procedure

WARNING

Hazardous voltage from the electrome­ter voltage source will be used in the fol­lowing steps. Take care not to contact
live circuits, which could cause personal
injury or death.

KEITHLEY

7174A

8x12LOW

CURRENT MATRIX

SIGNAL

200VPK

COLUMNS

200VPK

GUARD

200VPK

7078-TRX-3 Triax Cable

Ground Link

Removed

ROWS

1

A

2

B

3

C

4

D

5

617

7174A

A

F

Equivalent Circuit

Figure 4-4

Connections for path isolation verification

Row A

Row B

617 Electrometer

User-Prepared Triax Cable

(See Figure 4-5)

Warning: Hazardous voltage from

the electrometer source
may be present on terminals.

6

7

8

E

9

F

10

G

11

H

!

WARNING:

TIGHTENM OUNTINGSCREWS

TOENSURE PROPER

CHASSISGROUND

12

7174A Matrix Card

4-7

Service Information

Cut

(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.

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

(E) Screw on plastic cover.

Figure 4-5

Triaxial cable preparation

NOTE

The following procedure must be per­formed at an ambient temperature of 23°C
and at a relative humidity of less than
60%.

Cut

1. Turn on the Model 617 and allow it to warm up for two
hours for rated accuracy.

2. With the mainframe power turned off, plug the Model

1"

7174A into slot 1 of the mainframe. Remove all other
cards from the mainframe, and install the slot covers.

3. After the prescribed warm up period, select the Model
617 amps function, and enable zero check. Select the
2pA range, and zero correct the instrument.

4. Connect the Model 617 to rows A and B of the matrix
card, as shown in Figure 4-4.

5. Program the Model 617 voltage source for a value of
+100V, but do not yet turn on the voltage source output.

6. Close crosspoints A1 and B2 by using the switching ma­trix front panel controls.

7. With the Model 617 in amps, enable suppress after the
reading has settled.

8. Turn on the Model 617 voltage source output, and en­able the V/I ohms function on the electrometer.

9. After the reading has settled, verify that the resistance is
>67T Ω (6.7 × 10

13

Ω ).

10. Turn off the voltage source, and enable zero check.
Disable suppress, and select the amps function on the
electrometer.

11. Open crosspoints A1 and B2, and close crosspoints A3
and B4.

12. Repeat steps 7 through 11 for A3 and B4.

13. Repeat steps 7 through 12 for crosspoint pairs A5 and
B6, A7 and B8, A9 and B10, and A11 and B12.

14. Disconnect the electrometer from rows A and B, and
connect it instead to rows C and D.

15. Repeat steps 7 through 13 for rows C and D. The path
isolation for these rows should be 67T Ω (6.7 × 10

3

Ω ).

16. Repeat steps 7 through 14 for row pairs E and F, and G
and H. For each row pair, step through the crosspoint
pairs 1 and 2, 3 and 4, 5 and 6, 7 and 8, 9 and 10, and 11
and 12. The complete procedure outlined in steps 7
through 11 should be repeated for each crosspoint pair.
Each resistance measurement for rows E through H
should be 67T Ω (6.7 × 10

13

Ω ).

4-8

Service Information

4.6.5 Path resistance verification

The following paragraphs discuss the equipment, connec­tions, and procedure to check path resistance. Should a par­ticular pathway fail the resistance test, the relay (or relays)
for that particular crosspoint is probably defective. See the
schematic diagram at the end of Section 5 to determine
which relay is defective.

NOTE

The following procedure verifies the resis­tance of the HI signal path. To verify the
resistance of the GUARD path, modify the
cable of Figure 4-5 to connect the inner
shield to the banana plug and have no con­nection to the triax center conductor.

Recommended equipment

• Model 196 DMM

• 7078-TRX-T triax tee adapters (3)

• 237-BAN-3 triax to banana cables (4)

Connections

Figure 4-6 shows the connections for the path resistance
tests. The Model 196 is to be connected to the row and col­umn jacks using Model 237-BAN-3 triax/banana cables.
These cables differ from the one in Figure 4-5 in that the
inner shield and center conductor are not connected together.

7078-TRX-T

Triax Tee Adapters

237-BAN-3

Triax/Banana

196 DMM

Triax

Figure 4-6

Connections for path resistance verification

7174A

KEITHLEY

8x12LOW

CURRENT MATRIX

SIGNAL

COLUMNS

200VPK

200VPK

GUARD

200VPK

ROWS

B

C

D

E

F

G

H

!

WARNING:

TIGHTENM OUNTINGSCREWS

TOENSURE PROPER

CHASSISGROUND

7174A Matrix Card

4-9

Service Information

Procedure

1. Turn on the Model 196 DMM and allow it to warm up
for at least one hour before beginning the test.

2. With the po wer off, install the Model 7174A card in slot
1 of the mainframe.

3. Connect the four triaxial cables to the Model 196 and
the two triax tee adapters (Figure 4-6), but do not yet
connect the adapters to the Model 7174A.

4. Temporarily connect the two triax tee connectors to­gether using a third triax tee adapter, as shown in Figure
4-7.

5. Select the ohms function, 300 Ω range, and 6 ½ digit res­olution on the Model 196.

6. After the reading settles, enable zero on the Model 196
DMM. Leave zero enabled for the remainder of the tests.

7. Disconnect the two triax tee adapters from the shorting
adapter, and connect the two adapters with the cable to

To

196

the row A and column 1 connectors on the Model 7174A
(see Figure 4-6).

8. Close crosspoint A1, and allow the reading to settle.

9. Verify that the resistance reading is <1.5 Ω

.

10. Open the crosspoint, and disconnect the triax adapter
from column 1. Connect the adapter to column 2.

11. Repeat steps 8 through 10 for columns 2 through 12. In
each case, the column adapter must be connected to the
column under test, and the crosspoint must be closed.

12. Disconnect the row adapter from row A, and connect it
instead to row B.

13. Repeat steps 8 through 10 for row B. The crosspoints of
interest here are B1 through B12. Also, the row adapter
must be connected to the row being tested.

14. Repeat steps 8 through 13 for rows C through H. In each
case, the crosspoint to close is the one corresponding to
the row and column connections at that time. In all
cases, the measured resistance should be <1.5 Ω

.

To

196

Figure 4-7

Shorting measurement paths using triax tee adapter

4-10

Triax Tee

Adapters

Service Information

4.7 Reed pack replacement

If after performing troubleshooting or verification, a reed
switch is thought to be faulty , it should be replaced. Note that
reeds can only be replaced as a pack of three. The part num­ber for a reed pack is RL-179. A reed pack maintenance kit,
part number 9174-MK is also suggested.

Cross point relay

Use the following procedure and Figure 4-8 to replace cross
point relay reed packs.

NOTE

Repairs should only be done from the
component side of the board.

1. Remove the card and place on an anti-static surface.

2. Put on the gloves that came in the maintenance kit.

3. Carefully pry off the cover of the guard enclosure of the
crossbar that includes the suspect reed. Take care not to
break the wire that connects the cover to the front panel.

4. Carefully pry off the cross point interconnect board.
Take care not to break the wires that connect the inter­connect board to the front panel.

5. Using clean needle-noise pliers, carefully remove the
reed pack in question.

6. Inspect the relay coil. If there is any debris or
contamination, clean with methanol and blow out with
dry nitrogen.

NOTE

When inserting reed pack, make sure long
leads are inserted into relay coil (bobbin).

7. Using the reed pack insertion tool from the maintenance
kit, install the new reed pack into bobbin making sure
the long leads align with the holes at the base of the relay
coil (bobbin).

8. Reinstall any reed packs that may have been removed
when the cross point interconnect board was removed.

9. Reinstall the cross point interconnect board. Be sure that
it is properly seated.

10. Reinstall the guard enclosure cover.

11. Allow the card to stabilize for one hour.

12. Retest the card to verify operation and specifications.

Isolator relay

Use the following procedure and Figure 4-9 to replace isola­tor relay reed packs.

NOTE

Repairs should only be done from the
component side of the board.

1. Remove the card and place on an anti-static surface.

2. Put on the gloves that came in the maintenance kit.

3. Carefully pry off the cover of the guard enclosure. Take
care not to break wires connecting the relay to the path­way interconnect board.

4. Using clean needle nose pliers, carefully disconnect the
three wires that attach to the reed pack, taking note of
the locations for each.

5. Remove the reed pack in question.

6. Inspect the reed pack socket. If there is any debris or
contamination, clean with methanol and blow out with
dry nitrogen.

NOTE

When inserting reed pack, make sure long
leads are inserted into relay coil (bobbin).

7. Using the reed pack insertion tool from the maintenance
kit, install the new reed pack into bobbin making sure
the long leads align with the holes at the base of the relay
coil (bobbin).

8. Reconnect the wires to the top of the reed pack.

9. Reinstall the guard enclosure cover.

10. Allow the card to stabilize for one hour.

11. Retest the card to verify operations and specifications.

4-11

Service Information

Isolator

Relays (8)

N

ote

When inserting reed

:

pack, make sure long
leads are inserted into
bobbin.

Figure 4-8

Cross point relays

Clear

Triax

Connector

Yellow

TP1

Cross point

Relays (12 sets)

Bobbin

Cross point

Interconnect

Board

Cover

Crosspoint

Relay

Reed Pack

4-12

Pathway Interconnect Board

Service Information

Isolator

Relays (8)

Clear

Red

Bobbin

Isolator

Relay

Reed Pack

Note:

When inserting reed
pack, make sure long
leads are inserted into
bobbin.

Black

Red

Black
Yellow

Yellow

Clear

Figure 4-9

Isolator relays

Cross point

Relays (12 sets)

4-13

5

Replaceable Parts

5.1 Introduction

This section contains a list of replaceable electrical and
mechanical parts for the Model 7174A, as well as a compo­nent layout drawing and schematic diagram of the matrix
card.

5.2 Parts list

Electrical parts are listed in order of circuit designation in
Table 5-1. Table 5-2 summarizes mechanical parts.

5.3 Ordering information

To place an order, or to obtain information about replace­ment parts, contact your Keithley representative or the fac­tory (see the front of this manual for addresses). When
ordering parts, be sure to include the following information:

1. Matrix card model number 7174A.

2. Card serial number

3. Part description

4. Circuit designation, if applicable

5. Keithley part number

5.4 Factory service

If the matrix card is to be returned to Keithley Instruments
for repair, perform the following:

1. Call the Repair Department at 1-800-552-1115 for a
Return Authorization (RMA) number.

2. Complete the service form located at the back of this
manual, and include it with the unit.

3. Carefully pack the card in the original packing carton or
the equivalent.

4. Write ATTENTION REPAIR DEPARTMENT and the
RMA number on the shipping label. Note that it is not
necessary to return the matrix mainframe with the card.

5.5 Component layout and schematic diagram

Mother board

• Component layout — 9174-100

• Schematic — 9174-106

Relay board

• Component layout — 9174-120

• Schematic — 9174-126 (sheets 1 and 4 only)

Pathway interconnect board

• Component layout — 7174-160

• Schematic — 7174-166

5-1

Table 5-1

Model 7174A electrical parts list

Circuit Desig. Description Keithley Part No.

Replaceable Parts

C101-113
C415-418, 421
C413
C414, 425
C419
C420, 423
C422, 424

CR403
CR402

J1001
J1001-1003

K101-204
K101-204

R101-128
R417, 418
R419
R420
R421
R422
R423

CAP, .1µF, 20%, 50V, CERAMIC
CAP, .1µF, 20%, 50V, CERAMIC
CAP, .01µF, 10%, 1000V, CERAMIC
CAP, 10µF, -20+100%, 25V, ALUM ELEC
CAP, 47µF, 10%, 16V, ALUM ELEC
CAP, .01µF, 20%, 50V, CERAMIC
CAP, 270pF, 20%, 100V, CERAMIC/FERRITE

DIODE, SILICON, IN4148 (DO-35)
DIODE, SCHOTTKY, IN5711

CONNECTOR
CONNECTOR, MALE

REED PACK 3 FORM, DUAL GUARDED
RELAY, AIR MATRIX BOBBIN

RES, 22M, 5%, 1/4W, COMPOSITION OR FILM
RES, 10K, 5%, 1/4W, COMPOSITION OR FILM
RES, 47K, 5%, 1/4W, COMPOSITION OR FILM
RES, 200, 5%, 1/4W, COMPOSITION OR FILM
RES, 680, 5%, 1/4W, COMPOSITION OR FILM
RES, 120K, 5%, 1/4W, COMPOSITION OR FILM
RES, 11K, 5%, 1/4W, COMPOSITION OR FILM

C-365-.1
C-365-.1
C-64-.01
C-314-10
C-321-47
C-237-.01
C-386-270P

RF-28
RF-69

CS-598
CS-389-2

RL-179
RL-177

R-76-22M
R-76-10K
R-76-47K
R-76-200
R-76-680
R-76-120K
R-76-11K

U101-113
U406
U407
U408
U409
U410

W401

*Order present firmware revision level.

IC, 8-BIT SERIAL-IN LATCH DRIVER, 5841A
PROGRAM
IC, 12 STAGE BINARY COUNTER, 74HCT4040
IC, 8-BIT PARALLEL TO SERIAL, 74HCT165
IC, QUAD 2 INPUT NAND, 74HCT00
IC, OCTAL BUFFER/LINE DRIVER, 74HC244

STIFFENER, BOARD

IC-536
7174-800A02*
IC-545
IC-548
IC-399
IC-489

J-16

5-3

Replaceable Parts

Table 5-2

Model 7174A mechanical parts list

Description Keithley Part No.

#4-40X1/4 PHILLIPS PAN HD SEMS SCREW (9174-162 BOARD TO BRACKETS)
#6-32X3/8LG. PHIL FLAT HD SCR (HANDLE MTG)
#6-32X5/16PHIL PAN HED SEMS SCR (R. PANEL TO MB; BRKT TO BD)
#6-32 PEM NUT
8 POS INTERCONNECT
13 POS INTERCONNECT
BRACKET
BRACKET
CABLE
CABLE ASSEMBLY, 16 CONDUCTOR
CAP, PROTECTIVE
CONN, TEST POINT (DONE,IDDATA,NXTADR,OR,P,/F,RDAT,STRB)
CONN, TEST POINT (+5V, +VTH, -VTH,AGND,CLK,CLRADR,DGND)
CONNECTOR (ON SC-120-4)
FASTENER
FEMALE, BULKHEAD MOUNT RECEPTACLE
GROUND CLIP
GUARD TUBE, BASE
GUARD TUBE, LID
GUARD TUBE, BASE
GUARD TUBE, LID
GUARD TUBE, BASE
GUARD TUBE, LID
HANDLE
LOCKNUT (REL BD TO FASTENERS, BRKT TO BD)
LUG (ON SC-83, SC-120-4)
LUG (ON SC-120-4)
REAR PANEL ASSEMBLY
SOCKET (SOLDERED ON SC-83 AND SC-120-4)
SOCKET, I.C. 28 PIN (FOR U406)
SPACER, LID
STRIP TERMINAL (FOR SC-111)
SUPPORT
TEFLON TWISTED PAIR SHLD
TERMINAL, BIFURCATED (TEFLON)
TEST PIN
TRIAX CONNECTOR (FOR SC-111
WIRE, SINGLE CONDUCTOR

4-40X1/4PPHSEM
6-32X3/8PFH
6-32X5/16PPHSEM
FA-135
9174-315B
9174-314B
9174-307A
9174-308A
CA-121A
CA-27-13C
CAP-30-1
CS-553
CS-553
CS-236
FA-257-1
CS-824
9174-313A
9174-301A
9174-302A
9174-303A
9174-304A
9174-305A
9174-306A
HH-33-1
FA-226-1
LU-108-2
LU-108-2
7174A-301A
SO-144
SO-69
9174-316A
CS-812
9174-309A
SC-83
TE-119
TE-108
CS-827
SC-120-4

5-4

M1

Index

A

Applications 3-1

B

Basic CV test procedure 3-3
Block diagram 4-2

C

Cable connections 3-10
Card connectors 2-2
Card installation and removal 2-2
Coaxial jumper access 2-25
Component layout and schematic diagram

5-1
Computerized system configuration 3-1
Connections 2-2
CV measurements 3-1

E

Electromagnetic Interference (EMI) 2-22
Environment conditions 4-5
Environmental considerations 2-1

F

Factory service 5-1
Features 1-1

G

Gaining circuit access 4-4
General information 1-1
General instrument connections 2-5
Ground loops 2-22
Guarding 2-24

H

Handling and cleaning precautions 4-1
Handling precautions 2-1

I

ID data circuits 4-2
Inspection for damage 1-2
Instruction manual 1-2
Internal matrix expansion 2-21
Introduction 1-1, 2-1, 3-1, 4-1, 5-1
Isolator relays 4-4

K

Keeping connectors clean 2-23
Keithley instrument connections 2-11

M

Magnetic fields 2-22
Manual addenda 1-2
Matrix configuration 2-18
Matrix expansion effects on card specifica-

tions 2-24

Measurement considerations 2-22

N

Noise currents caused by cable flexing

2-23

O

Offset current verification 4-6
Operation 2-1
Optimizing CV measurement accuracy

3-3
Optional accessories 1-2
Ordering information 5-1

P

Packing for shipment 1-2
Parts list 5-1
Path isolation verification 4-7
Path isolators 2-18
Path resistance verification 4-9
Performance verification 4-5
Power-on sequence 4-3
Principles of operation 4-2

R

Recommended cables and adapters 2-3
Recommended equipment 4-4
Recommended test equipment 4-5
Reed pack replacement 4-11
Relay control 4-3
Replaceable parts 5-1
Resistivity calculations 3-9
Resistivity measurements 3-7

S

Safety symbols and terms 1-2
Semiconductor IV characterization 3-9
Semiconductor test matrix 3-5
Service information 4-1
Shielding 2-23
Shipment contents 1-2
Special handling of static-sensitive devices

4-5
Specifications 1-2
Stand alone system configuration 3-1
Switching matrix 2-18
System configuration 3-5

T

Test configuration 3-7, 3-9
Test procedure 3-7
Testing common-source characteristic of

FETs 3-6
Triax banana plug adapter 2-4

i-1

Troubleshooting 4-4
Troubleshooting procedure 4-4
Typical CV curves 3-3
Typical test fixture connections 2-17

U

Unpacking and inspection 1-2

W

Warranty information 1-1

i-2

Service Form

Model No. Serial No. Date
Name and Telephone No.
Company

List all control settings, describe problem and check boxes that apply to problem.

Intermittent

❏
❏

IEEE failure
Front panel operational

❏

Display or output (check one)

Drifts

❏

Unstable

❏
❏

Overload

❏

Calibration only
Data required

❏

(attach any additional sheets as necessary)
Show a block diagram of your measurement system including all instruments connected (whether power is turned on or not).

Also, describe signal source.

Analog output follows display

❏
❏

Obvious problem on power-up
All ranges or functions are bad

❏

Unable to zero

❏

Will not read applied input

❏

❏

Certificate of calibration required

Particular range or function bad; specify

❏
❏

Batteries and fuses are OK
Checked all cables

❏

Where is the measurement being performed? (factory, controlled laboratory, out-of-doors, etc.)

What power line voltage is used? Ambient temperature? °F

Relative humidity? Other?

Any additional information. (If special modifications have been made by the user, please describe.)

Be sure to include your name and phone number on this service form

.

Keithley Instruments, Inc.

28775 Aurora Road
Cleveland, Ohio 44139

Printed in the U.S.A.