Tektronix 7172 Instruction Manual

Model 7172Low Current 8 × 12 Matrix Card

Instruction Manual

A GREATER MEASURE OF CONFIDENCE

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 Keithley headquarters in Cle veland, Ohio.
You will be given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service
facility . Repairs will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for
the balance of the original warranty period, or at least 90 days.

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.

Sales Offices: BELGIUM: Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02-363 00 40 • Fax: [phone]

CHINA: Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-6202-2886 • Fax: [phone]
FINLAND: Tietäjäntie 2 • 02130 Espoo • Phone: [phone] • Fax: [phone]
FRANCE: 3, allée des Garays • 91127 Palaiseau Cédex • 01-64 53 20 20 • Fax: [phone]
GERMANY: Landsberger Strasse 65 • 82110 Germering • 089/84 93 07-40 • Fax: [phone]
GREAT BRITAIN: Unit 2 Commerce Park, Brunel Road • Theale • Berkshire RG7 4AB • 0118 929 7500 • Fax: [phone]
INDIA: Flat 2B, Willocrissa • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: [phone]
ITALY: Viale San Gimignano, 38 • 20146 Milano • 02-48 39 16 01 • Fax: [phone]
KOREA: FL., URI Building • 2-14 Yangjae-Dong • Seocho-Gu, Seoul 137-130 • 82-2-574-7778 • Fax: [phone]
NETHERLANDS: Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: [phone]
SWEDEN: c/o Regus Business Centre • Frosundaviks Allé 15, 4tr • 169 70 Solna • 08-509 04 679 • Fax: [phone]
SWITZERLAND: Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: [phone]
TAIWAN: 1FL., 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3-572-9077• Fax: [phone]

28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: [phone]

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

© Copyright 2001 Keithley Instruments, Inc.

Printed in the U.S.A.

11/01

Model 7172

Low Current 8

Instruction Manual

×

12 Matrix Card

©1991, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

Document Number: 7172-901-01 Rev. C

SAFETY PRECAUTIONS

The following safety precautions should be observed before using the Model 7172 and the associated instruments.

This matrix card is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety
precautions required to avoid possible injury. Read over this manual carefully before using the mati card.

Exercise extreme caution when a shock hazard is present at the test circuit. User-supplied lethal voltages may be present

on the card connector jacks. The American National Standards Institute (ANSI) states that a shock hazard exists when

voltage levels greater than 3OV RM!? or 42.4V peak are present. A good safety practice is to expect that hazardous voltage

is present in any unknown circuit before measuring.

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

Inspect the connecting cables and test leads for possible wear, cracks, or breaks before each use.

For maximum safety, do not touch the test cables or any instruments while power is applied to the circuit under test.
Turn off the power and discharge any capacitors before connecting or disconnecting cables from the matrix card.

Do not touch any object which 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 with-

standing the voltage being measured.

Do not exceed the maximum allowable input of the matrix card, as defined in the specifications and operation section of
this manual.

Instrumentation and accessories should not be connected to humans

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 and follow all installation,
operation, and maintenance information carefully before using the
product. Refer to the manual for complete product specifications.

If the product is used in a manner not specified, the protection pro­vided by the product may be impaired.

The types of product users are:

Responsible body is the individual or group responsible for the use

and maintenance of equipment, for ensuring that the equipment is
operated within its specifications and operating limits, and for 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 properly, 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.

Keithley products are designed for use with electrical signals that
are rated Installation Category I and Installation Category II, as de­scribed in the International Electrotechnical Commission (IEC)
Standard IEC 60664. Most measurement, control, and data I/O sig­nals are Installation Category I and must not be directly connected
to mains voltage or to voltage sources with high transient over -volt­ages. Installation Category II connections require protection for
high transient over-voltages often associated with local AC mains
connections. Assume all measurement, control, and data I/O con­nections are for connection to Category I sources unless otherwise
marked or described in the Manual.

Exercise extreme caution when a shock hazard is present. Lethal
voltage may be present on cable connector jacks or test fixtures. The
American National Standards Institute (ANSI) states that a shock
hazard exists when voltage levels greater than 30V RMS, 42.4V
peak, or 60VDC are present.

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

A good safety practice is to expect

Operators of this product must be protected from electric shock at
all times. The responsible body must ensure that operators are pre­vented access and/or insulated from every connection point. In
some cases, connections must be exposed to potential human con­tact. Product operators in these circumstances must be trained to
protect themselves from the risk of electric shock. If the circuit is
capable of operating at or above 1000 volts,

the circuit may be exposed.

Do not connect switching cards directly to unlimited power circuits.
They are intended to be used with impedance limited sources.
NEVER connect switching cards directly to AC mains. When 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.

When installing equipment where access to the main power cord is
restricted, such as rack mounting, a separate main input power dis­connect device must be provided, in close proximity to the equip­ment and within easy reach of the operator.

For maximum safety, do not touch the product, test cables, or any
other instruments while power is applied to the circuit under test.
ALWAYS remove power from the entire test system and discharge
any capacitors before: connecting or disconnecting cables or 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.

The instrument and accessories must be used in accordance with its
specifications and operating instructions or the safety of the equip­ment may be impaired.

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.

no conductive part of

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.

The

CAUTION heading in a manual explains hazards that could

damage the instrument. Such damage may invalidate the warranty.
Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and

all test cables.

To maintain protection from electric shock and fire, replacement
components in mains circuits, including the power transformer, test
leads, and input jacks, must be purchased from Keithley 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 an instrument, use a damp cloth or mild, water based
cleaner. Clean the exterior of the instrument only. Do not apply
cleaner directly to the instrument or allow liquids to enter or spill
on the instrument. Products that consist of a circuit board with no
case or chassis (e.g., data acquisition board for installation into a
computer) should never require cleaning if handled according to in­structions. If the board becomes contaminated and operation is af­fected, the board should be returned to the factory for proper
cleaning/servicing.

11/01

7172 8×12 Low Current Matrix Card

MATRIX CONFIGURATION: Single 8 rows×12 columns. Expanding

the columns can be done internally by connecting the rows of mul­tiple 7172 cards together with coax jumpers.

OFFSET CURRENT SELF TEST: An onboard electrometer circuit

measures offset current when the rear panel switch is pushed.
Pass/fail LEDs indicate if offset is above or below 500fA. The on­board SMB connector outputs voltage proportional to current
(1mV/10fA).

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. 1A

carry/0.5A switched, 10VA.

CONTACT LIFE: Cold Switching: 10

8

closures. At Maximum Signal

Level: 10

5

closures.

PATH RESISTANCE (Per Conductor): <1.0Ω initial, <1.5Ω at end of

contact life.

CONTACT POTENTIAL: Differential (Signal to Guard): <30µV.

Single ended (Guard to Guard or Signal to Signal): <60µV.

OFFSET CURRENT: <500fA, 150fA typical.

ISOLATION:

Path (Signal to Signal): >10

13

Ω, 0.4pF typical.

Differential (Signal to Guard): >10

9

Ω, 170pF typical.

Common (Signal and Guard to Chassis): >10

9

Ω, 430pF typical.

CROSSTALK (1MHz,50Ω Load): <–70dB.
INSERTION LOSS (1MHz, 50ΩLoad): 0.22dB typical.
3dB BANDWIDTH (50ΩLoad, 50Ω Source): 30MHz typical.
RELAY DRIVE CURRENT (Per Crosspoint): 30mA.
RELAY SETTLING TIME: <2ms.
EMC: Conforms to European Union Directive 89/336/EEC.
SAFETY: Conforms to European Union Directive 73/23/EEC (meets

EN61010-1/IEC 1010).

ENVIRONMENT:

Offset Current and Path Isolation Specifications: 23°C,

<50% R.H.

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

ACCESSORY SUPPLIED: Instruction manual and eight SMB expan-

sion cables (C99-1A).

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Offset current

self test

Contains information on Model 7172 features, specifica­tions, and accessories.

Details installation of the Model 7172 Low Current 8 x 12
Matrix Card within the Model 707 Switching Matrix, cov­ers card connections, and also discusses measurement
considerations.

Gives four typical applications for the Model 7172, includ­ing combined quasistatic and high-frequency CV meas­urements, van der Pauw resistivity measurements, and
semiconductor parameter analysis.

SECTION 1

General Information

SECTION 3

Applications

Contains performance verification procedures, trouble­shooting information and principles of operation for the
matrix card.

Lists replacement parts, and also includes component lay­out and schematic drawings for the Model 7172.

SECTION 4

Service Information

SECTION 5

Replaceable Parts

Table of Contents

SECTION 1 —

1.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2 FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.3 WARRANTY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.4 MANUAL ADDENDA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.5 SAFETY SYMBOLS AND TERMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.6 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 Instrument Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.8 REPACKING FOR SHIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.9 OPTIONAL ACCESSORIES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.10 COAXIAL JUMPER ACCESS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

SECTION 2 —

2.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 HANDLING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3 ENVIRONMENTAL CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.4 CARD INSTALLATION AND REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.5 CONNECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.5.1 Card Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.5.2 Recommended Cables and Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.5.3 Triaxial to Banana Plug Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

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 Row Isolators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

2.6.3 Internal Matrix Expansion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

2.6.4 External Matrix Expansion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23

2.7 MEASUREMENT CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

2.7.1 Magnetic Fields. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

2.7.2 Electromagnetic Interference (EMI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

2.7.3 Ground Loops. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

2.7.4 Keeping Connectors Clean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

2.7.5 Noise Currents Caused by Cable Flexing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

2.7.6 Shielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

2.7.7 Guarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

2.7.8 Matrix Expansion Effects on Card SpeciÞcations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

General Information

Operation

SECTION 3 —

3.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2 CV MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2.1 Stand Alone System ConÞguration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2.2 Computerized System ConÞguration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2.3 Optimizing CV Measurement Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.2.4 Basic CV Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.2.5 Typical CV Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.3 SEMICONDUCTOR TEST MATRIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3.3.1 System ConÞguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3.3.2 Testing Common-Source Characteristic of FETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3.4 RESISTIVITY MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3.4.1 Test ConÞguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3.4.2 Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3.4.3 Resistivity Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3.5 SEMICONDUCTOR IV CHARACTERIZATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3.5.1 Test ConÞguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3.5.2 Cable Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3.6 SEMICONDUCTOR PARAMETER ANALYSIS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3.6.1 System ConÞguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

3.6.2 Cable Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

3.6.3 SPA Measurement Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

3.6.4 Typical Test Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

Applications

SECTION 4 —

4.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2 HANDLING AND CLEANING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.3 OFFSET CURRENT SELF-TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.4 PERFORMANCE VERIFICATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.4.1 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.4.2 Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.4.3 Offset Current VeriÞcation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.4.4 Path Isolation VeriÞcation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.4.5 Path Resistance VeriÞcation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.4.6 Electrometer VeriÞcation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

4.5 SPECIAL HANDLING OF STATIC-SENSITIVE DEVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

4.6 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

4.6.1 Recommended Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

4.6.2 Using the Extender Card. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

4.6.3 Troubleshooting Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

4.7 PRINCIPLES OF OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15

4.7.1 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15

4.7.2 ID Data Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15

4.7.3 Relay Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

4.7.4 Power-on Safeguard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

4.7.5 Isolator Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

4.7.6 Electrometer Circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

Service Information

SECTION 5 –

5.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.2 PARTS LISTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.3 ORDERING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.4 FACTORY SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.5 COMPONENT LAYOUT AND SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Replaceable Parts

List of Illustrations

SECTION 2 -

Figure 2-l
Figure 2-2

Figure 2-3 TriaxConnectorConfigumtion.. .............................................

Figure 2-4 TriaxialCablePreparation ...................................................

Figure 2-5 General Instrument Connections
Figure Z-6 Model 617 Electrometer Connections

Figure 2-7 Mode1196DMMConnections ................................................

Figure 2-8
Figure 2-9
Figure Z-10 Model 220 Current Source Connections
Figure 2-l 1 Model 236/237/m Source Measure Unit Connections
Figure 2-12 Typical Test Fixture Connections
Figure 2-13
Figure 2-14
Figure 2-15
Figure 2-16
Figure 2-17
Figure 2-18
Figure 2-19
Figure 2-20 PowerLineGromdLoops
Figure 2-21
Figure 2-22
Figure 2-23
Figure 2-24
Figure 2-25

Operation

Model7172Installation .....................................................

CardConnectors ..........................................................

..............................................

........................................... 2-11

Model 230 Voltage Source Connections
Model 590 CV Analyzer Connections

Equivalent Circuit of Test Fixture Connections

Model7172MatrixOrganization ..............................................

Conn&ingTbreeCardsfor8x36Matrix

JumperCo~~orLoca~ons .................................................

ThreeCardsinDaisyChainConfiguration ......................................

l6x36MatrixConstructedbyExtemalJumpering

Using Triax Tee Adapters to Daisy Chain Cards

..................................................

FkninatingGroundLoops ..................................................

Shi&iingExample ........................................................

DualShieldTestFiiture ....................................................

GuardedCircuit
Typical Guarded Signal Connections

..........................................................

......................................... 2-13

.......................................... 2-14

.........................................

............................. 2-16

.............................................

................................... 2-18

....................................... 2-21

................................ 2-23

.................................. 2-24

...........................................

2-2
2-3
2-4
24
2-6

2-12

2-15

Z-17

2-19

2-21
2-22

2-25

2-25

2-27

2-27

2-28

2-29

SECTION 3

Figure 3-l Stand Alone CV System Configuration
Figure 3-2 computerized CV system configuration

Figure 3-3
Figure 3-4 Typical High-frequency CV Curve Generated by Model 590
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9 Resistivity Measurement Conventions
Figure 3-10
Figure 3-11 Semiconductor Parameter Analysis Switching System
Figure 3-12

Figure 3-13
Figure 3-14

- Applications

...............................

.............................

Typical Quasistatic 07 Curve Generated by Model 595

Semiconductor Test M&ix
System Configuration for Me

Typical Common-Same FET IV Cbaractexistics

Resisti~~TestConfiguration ......................................

Multi Unit Test System Using Models 236 and 237 Source Measure Units.

Sl’ACo~eciions ...............................................

System Configuration for JPET Test

TypicalJFETPlot ...............................................

........................................ 3-7

aswing Common-Emitter Characteristics

...............................

..................................

...................

........................

....................

...............

.......

.....

3-2

3-3

3-5

3-6

3-8
3-9
3-10
3-11
3-13
3-14
3-16

3-17
3-18

SECTION 4 - Service

Information

Figure 4-l
Figure &2
Figure 4-3 Offset Verification Test Connections

Figure 44 Conmctions for Path Isolation Verification ...............

Figure 4-5
Figure 4-6
Figure 4-7
Figure 48
Figure 4-9
Figure 4-10
Figure 4-11
Figure 4-12

switch for offset Current Self-test

DMMConnectiontoSMBofMode17172 .................

Triaxial Cable Preparation

Connections for path Resistance Verification ..............

Shorting Measurement Paths Using Trim Tee Adapter ......

Verificatin of On-board Electrometer
IDDataTiming
Model 7172 Block Diagram

Simplified Schematic of On-Board Electrometer. ...........

Siiplified Model of Current to Voltage Converter ..........

.....................................

............................

......................

....................

....................

...........................

4-l
4-3
46
4-7
4-8
4-9
4-10
4-12
4-14
4-15
4-17
4-18

List of Tables

SECTION

Table 2-l Recommended Cables and Adapters
Table 2-2 PartsforSpecialTriaxialCable
Table 2-3 Column Numbering by Slot and Unit

SECTION

Table 3-l CV Test Crosspoint Summary . . . .

Table 52

Table 3-3 Crosspoint Summary for JFET Test . . . . .

SECTION

Table 4-l
Table 42
Table 43

2 - Operation

...........

...............

..........

3 - Applications

Crosspoint summary

for Resistivity Measurements

4 - Service Information

Recommended Verification Equipment . .
Recommended Troubleshooting Equipment

Troubleshooting Procedure . . . . .

...........

...........

...........

...........

...........

...........

...........

...........

...........

24
24
Z-20

34
3-10
3-15

44
4-13
4-14

SECTION 1

General Information

1 .l INTRODUCTION

This section contains general information about the

Model 7172 Low Current 8 x 12 Ma&ix Card. The Model
7172 is designed to complement the Model 236 Source
Measure Unit in semiconductor testing and other low
current switching applications. (The Models 737 and 238
Source Measure Units can also be used, within the speci­fied maximum signal levels of the Model 7172.)

Section 1 is armnged in the following manner:

1.2 Features
13 warranty Informaticm

1.4 Manual Addenda

1.5 Safety Symbols and Terms

1.6 Specifications

1.7 Unpacking and Inspection

1.8 Repacking for Shipment

1.9 Optional Accessories

effects of stray capacitance, leakage current, and leak­age resistance.

.

Model 7l72 cards can be internally connected together
or to Model 7072 cards using supplied SMB to SMB

2.p.w to expand the number of columns in the ma-

1.3 WARRANTY INFORMATION

Warranty information is located on the inside front cover
of this instruction manual. Should your Model 7172 re­quire warranty service, contact the Keithley representa­tive or authorized repair facility in your area for further
information. when returning the matrix card for repair,
be sure to fill out and include the service form at the back
of this manual in order to provide the repair facility with

the necessary information.

1.4 MANUAL ADDENDA

Any improvements or changes concerning the matrix

card or manual will be explained in an addendum in­cluded with the the unit. Be sure to note these changes
and incorporate them into the manual before using or
servicing the unit.

1.10 Coaxial Jumper Access

1.2 FEATURES

Keyfeatoresof theModel7172LowCurrent8x12Matrix
Card in&de:

. 8 x 12 (eight row by 12 column) switching matrix.

l AII paths have <5OOfA of offset current and typical val-

ues of 150fA.

. Electrometer to measure the offset current on the card

as a self-test. Front panelLED givepass/fail informa-

tion or PCB connector gives voltage proportional to

off& (lmV=lOfA).

. Threelug triax connectors for all row and columns al-

low guarding of each signal pathway to minimize the

1.5 SAFETY SYMBOLS AND TERMS

The following symbols and terms may be found on an in­strument or used in this marmat.

Then

user should refer to the operating instnxtions located in
the instrLlction manual.

ti

The
may be present on the terminal(s). Use standard safety
precautions to avoid personal contact with these volt­ages.

symbol on an in&rument indicates that the

symbol on an instrument shows that high voltage

1-l

SECTION I
General Information

The WARNING heading used in this manual explains
dangers that might result in personal injury or death. Al­ways read the associated information very carefully be
fore performing the indicated procedure.

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 7172 specifications may be found at the front of
thismanual. These specifications are exclusive of the ma­trix mainframe specifications, which are located in the

Model 707 Instruction Manual.

1.7 UNPACKING AND INSPECTION

1.7.1

Upon receiving the Model 7172, 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.

Inspection for Damage

manual package includes an instruction manual and any
pertinent addenda.

1.8 REPACKING FOR SHIPMENT

Should it become necessary to return the Model 7172 for
repair, carefully pack the card in its original packing car­ton or the equivalent, and include the following informa­ti0l-l:

. Advise as to the warranty status of the matrix card.
. Write ATTENTION REPAIR DEl’ARTMEiVT on the

shipping label.

. Fill out and include the service form located at the back

of this manual.

1.9 OPTIONAL ACCESSORIES

Model 237.ALG-2 -A 2m (2.4 ft.) low noise hiax cable
terminated with a 3-&t male triax connector and alliga­tor clips.

Model 237-BAN-3 -A 3 ft. low noise tiax cable tern%
nated with a 3slot male triax connector and a banana

plug.

1.7.2

The following items are included with every Model 7172

order:
. Model 7172 Low Current 8 x 12 Matrix Card.

l Model 7172 Instruction Manual.
l Coaxial jumper cables (8) for matrix expansion.

. Additional accessories as ordered.

Shipment Contents

1.7.3 Instruction Manual

The Model 7172 Ji~~trwtion Manual is three-hole drilled
so that it can be added to the three-ring binder of the
Model 707 Switching
removing the plastic wrapping, place the manual in the
binder after the mainframe insfxuction manual. Note that
a manual identification tab is included and should pre­cede the matrix card instruction manual.

If an additional instruction manual is required, order the
manual package, Keithley part number 7172-901-00. The

Matrix Instiction

Manual. After

Models 237.TRX-T and 7078-m-T - These are 3slot
male to dual 3-lug female triax tee adapters. The Model
237-TRX-T is for high voltage applications.

Model 707%TRX-3 -A 3 ft low noise triax cable termi­nated with 3slot male triax connectors. Also available in
10 and 20 ft. lengths as Models 7078-TRX-10 and

7078-TRX-20.

Models 7078-TRX-BNC and 707%TRXGND - These are
3-slot male triax to female BNC adapters. The Model
7078-TRX-GND is for non-guarded applications.

Model 707%TBC 3-Lug Female Triw Bulkhead Connec­tor with Cap-The Model 7078-TBC can be used for ap­plications such as test fixtures.

Model 7078-CSHl’ Cable Set-The Model 7078-CSHp
Cable Set includes the necessary cables and adapters to
connect the Model 7172 to the Hewlett-Packard Model
4145 Semiconductor Parameter Analyzer. The Model

l-2

General

SECTION 1

Information

7078CSHP includes four Model 707%TRX-10 loft. 3-lug
triaxial cables, four Model 7051-10 loft. BNC cables, and
four Model 707%TRX-BNC 34ug triax to BNC adapters.

Recommended cables and adapters are summarized in
Table 2-l.

1 .lO COAXIAL JUMPER ACCESS

Coaxial jumpers can be installed to expand rows A-H of

the matrix using two or more Model 7172 Cards. An ac­cess door on the mainframe allows access to these jump-

ers. To allow access when the Model 707 is mounted in a
rack, it is recommended that the Model 7079 Slide Rack
Mount Kit be used.

l-3

SECTION 2

Operation

2.1 INTRODUCTION

This section contains information on mati card connec­tions, installation and matrix programming,
ranged 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 environ­mental aspects of using the Model 7172.

2.4 Card Installation and Removal: Details installation
in and removal from the Model 707 Switching Matrix

and is ar-

mainframe.

2.5 Connections: Discusses card connectors, cables and
adapters, and typical connections to other instrumenta­tion.

26 Matrix Configuration: Discusses the switchingma­ti, as well as matrix expansion by connecting two or
more cards together.

2.7 Measurement Considerations: Reviews a number
of considerations when making low-level current and ca­pacitance measurements.

the mainframe and matrix card only in a clean environ­ment. If contamination is suspected, clean the card as dis­cussed in Section 4. Also, the performance verification
procedures in Section 4 can be used to test the card for
low leakage resistances that could signal contamination.

2.3 ENVIRONMENTAL CONSIDERATIONS

For rated performance, the card should be operated
within the temperature and humidity limits given in the
specifkations at the front of this manual. Note that cur­rent offset and path isolation values are spekfied within a
lower range of limits than the general operating environ­ment.

2.4 CARD INSTALLATION AND REMOVAL

Before making connections, the Model 7172 should be ir­stalled within the Model 707 Switching Matrix, as sum­marized below. Figure 2-l shows the installation proce­dure.

WARNING
Turn off the
nect the line cord before installing orremov­ing matrix cards.

mainframe

power and discon-

2.2 HANDLING PRECAUTIONS

To maintain high impedance isolation, care should be
taken when handling the mati card to avoid contami­nation from such foreign materials as body oils. Such
contamination can substantially lower leakage resis­tances, degrading performance. The areas of the card that
are most sensitive to contamination are those associated
with the 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 build-up over a period of time is another possible
source of contamination. To avoid this problem, operate

NOTE
The coaxial jumpers used to expand the ma­hiw with two or more Model 7172 cards are
not installed before card insertion; an access
door on top of the mainframe allows access to
the connectors after the card is installed.

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

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.

2-l

SECTION 2
Operation

Fimre 2-l. Model 7172 Installation

CAUTION
Do not touch the card surfaces or any compo- properly secure this ground connection may
nents to avoid contamination that could de- result in personal injury or death due to elec­grade card performance. tric shock.

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

?.cTews.

The mounting screws must be secured to en­sure a proper chassis ground connection be-

2-2

by finger tightening the spring-loaded

WARNING

tween the card and the mainframe. Failure to

4. To remove a card, first turn off the power and dis­connect the line cord from the mainframe. Discon­nect all external and internal 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

tom

mainframe,

edge near the back edge.

support it by grasping the bot-

2.5 CONNECTIONS

SECTION 2

Operation

Card connectors, recommended cables and adapters, and

typical connections to test instruments are discussed in
the following paragraphs.

2.5.1

The card connectors are shown in Figure 2-Z. Each row

and column is equipped with a 3-lug female hiax connec­tor. As shown in Figure 2-3, the center conductor is SIG-

NAL, the inner shield is GUARD, and the outer shield, or

shell is chassis ground. Note that slug connectors are

wed to avoid possible damage from inadvertently at-

tempting to connect BNC cables.

The Model 7172 has 12 cohmms that are labeled 1

through 12, as well as eight rows, A through H.

Card Connectors

CAUTION

Do not

between any pin and chassis.

exceed 2OOV between any two pins or

Mounting

screw

I

2.5.2 Recommended Cables and
Adapters

Table 2-1 summarizes the cables and adapters recom­mended~ for use with the Model 7172. Equivalent user­supplied items may be substituted as long as they are of
sufficient quality (low offset current, high leakage resis­tance). Using substandard cables and adapters may de­grade the integrity of the measurements made using the
matrix card. See paragraph 2.7 for a discussion of meas­urement considerations.

2.5.3

For instruments that use banana
cable terminated with a 3-&t male triax and a single ba­nana plug. Use the Model 237-BAN-3 or prepare a special
cable as outlined below using the parts listed in Table 2-2.

With the Model 237-BAN-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.

Triaxial to Banana Plug Adapter

jacks, you need a triax

Mounting

screw

+ure 2-2.

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.

Card Connectors

2-3

SECTION 2
Operation

Chassis
Ground

2oov -

Peak

Caution : Do not Exceed Maximum

Voltage

Levels Shown

Table 2-2. Parts for Special Triaxial Cable

Keithley Part or
Model Number Description

7078.TRX-3 triax Triax cable terminated with
cable*
Part # BG-10-2

3-slot male triax connectors
Red banana plug

F” P,

I I

r

I_ 1”---4

I

Figure 2-3.

Table 2-1. Recommended Cables and Adapters

Model
7078-TRX-x
237-BAN-3
237-ALG2

7078-TRX-BNC

7078-TRX-GND

707%TRX-T
6171
CA-93-l

Pomona 1269

Trim Connector Configuration

Description
3-slot male triax connectors on

both ends (x = 3,lO or 20 ft.)
3-slot male triax to male banana

Plug
3-&t male triax to alligator clips

3-slot male triax to BNC adapter,
connections to center and inner
shell
3slot male triax to BNC adapter,
connections to center and outer
shell
3slot male to dual 3-lug female
triax tee adapter
3slot male tiax to Z-lug female
triax adapter
BNC to right angle SMB cable
Female BNC to female banana
adapter.

(A) Cut off insulation with knife.

Cut off outer shield.

Insulation Over
Inner Shield

I

(6) Strip insulation off inner shield

(C) Twist inner shield then strip inner conductor.

Twist inner shield and center conductor together,

slip on plastic cover.

(D) Insert wires into hole and wrap around

body.

2-4

(E) Screw on plastic cover.

Fifflre 24. Trimial Cable Preparation

SECTION2

Operation

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

2. Remove the outer insulation, then cut away the outer
shield back as far as the insulation is shipped.

3. carefully strip away the insulation over the inner
shield one inch, then cut the inner shield off even
with the stripped insulation.

4. Strip the inner conductor l/2 inch, then twist the
strands together.

5. Unscrew the cover from a banana plug, then slide
the cover over the center conductor of the triax cable.

6. Insert the stripped center conductor through the
hole in the body of the banana plug, then wrap the
wire around the plug body.

7. Screw on the plastic cover, and make certain the wire
is secure by gently pulling on the plug.

2.5.4 General Instrument Connections

The following paragraphs discuss connecting the Model
7172 to various general classes of iwhumentation 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 inshumentation. Also, spe
cial cables or adapters may be necessary. Jn all cases,
3-lug triax cables must be used to make the connections.

WARNING

Hazardous voltage from other guard sources

may be present on LO or the DUT if other

crosspoints are closed.

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

Electrometer Connections
Typical 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 7172 GUARD is connected to elec­trometer GUARD.

The connections for elecmmeter fast amps and resis-

tame measurements are shown in Figure 2-5 (F) and (G).
These configurations are essentialIy 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 con-

nected to electmmeter LO.

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

Figure 2-5 shows the general instrument comwztions for

the discussions below. Note that DUT guarding or
shielding are not indicated here; see Figures 2-21 and 2-24
for shielding and guarding information. As shown, alI
figures 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 (0. Floating connections are shown in (A), with
LO and HI routed to two separate jacks on the Model

7172. The common LO conmxtions in (B) should be used
only for non-critical applications because the perform­ance of the GUARD pathway is not specified.

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 sauce co~ectiom (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 (T) shows typical connections for a source/

measure unit (Siviu). 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.

2-5

SECTION 2
Operation

Rows

A.) DMM Floating

Warning : Hazardous voltage from guard

so”rces may be pres*“t on LO.

r----

L----J

7172

7172

-j

Columns

U

Note : Use this configuration only for

non-critical measurements.

Figure Z-5.

B.) DMM Common LO

GeneralInstrument Connections (A-B)

2-6

SECTION 2

Operation

C.) DMM 4Wre

Flows

r - - - - 7 Columns

DUT

L-----l

7172

Figure 2-5.

ROWS

D.) Electrometer. Unguarded Volts

General Instrument Connections (C-D)

r----i

(cont.)

Columns

DUT

2-7

SECTION 2
Operation

E.) Electrometer, Guarded ‘Job

-3 r-

F.) Electmmetsr. Fast Current

7172

L----A

7172

Figure 2-5.

2-8

-7-J J-i-+-

G.) Electrometer. Resistance (Guarded)

General Instrument Connections (E-G)

L----A

7172

(cont.)

H.) Voltage Source

SECTION 2

Operation

-7-J $-+-

L----A

7172

-7-2 Jr+-

I.) current source, unguarded

J.) Current Source, Guarded

Figure 2-S. General Instrument Connections (H-I) (cont.)

L----A

7172

7172

2-9

SECTION 2

Operation

DUT

KJ SourcelMeasure Unit

Notes : DtJT shielding/guarding not shown. See Figures 2-21 and 2-24.

Figure 2-5. General Instrument Connections (K) (cont.)

L-----l

7172

Z-10

SECTION 2

Operation

2.5.5

Keithley Instrument Connections

The following paragraphs outline connecting typical
Keithley instruments to the Model 7172 Low Current 8 x

12 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:

l Model 617 Electrometer/Source
l Model 196 DMM
l Model 230 l’rogmmmable Voltage Source
l Model 220 Programma
l Model 590 CV Analyzer
l Model 236/237/238 Source Measure Unit

ble Current Source

Model 617 Electrometer Connections
ComwctionsfortheMode1617Electrometerareshownin

Figure 2-6. Tlw electrometer INPUT and COM can be

connected to any row. Figure 24 shows connections to
rows A and B.

1. Connect one end of a Model 7078-TRX-3 or -10 3-lug
triaxial cable to row A of the Model 7172.

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

3. Connect

the trim end of a t&w/banana cable to row

B of the Model 7172.

4.

Connect the banana plug end of the t&x/banana ca­ble to the COM terminal of the Model 617. The short­ing link between COM and chassis qound should be
removed for this application.

5.

Place the GUARD switch in the OFF position.

6. To connect the voltage source to the Model 7172,
connect the V-SOURCE HI and LO connectors of the
Model 617 to the desired row connectors on the ma­trix card. Fiwre 2-6 shows connections to rows C
andD. -

Figure 2-6.

6172 2-Slot to 3-h \
Triax Adapter -

Note : See Figure 2-4 for special triax

ii-“’

to banana cable.

Model 617 Electrometer Connections

\ II

237~BAN-3 1

7172

Matrix Card

2-11

SECTION2
Operation

Model 196 DMM Connections

Connect the Model 196 or other similar DMM to the ma­trix card using the general configuration shown in
FigureZ-7. The VOLTS OHMS HI and LO terminals
should be connected to the desired rows using triax/ba­nana cables. For 4-w& ohms measurements, the OHMS
SENSE Hl and LO terminals 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.

Model 230 Voltage Source Connections
Connect the Model 230 OUTPUT and COMMON termi-

nals to the desired rows using t&x/banana plug cables,

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

Model 590 CV Analyzer Connections

The Model 590 CV Analyzer can be connected to any KXV

or any column as shown in Figure 2-9. The BNC cables
that are supplied with the Model 590 can be used; how­ever, Model 707%TRX-BNC triax-to-BNC adapters must

be used at the Model 7172 end.

Figure

196 DMM

Connect inner shield to LO for
low-level measurements.

(Modify the

2-7.

cable

of Figure 2-4.)

Model 196 DMM Connections

-A

L

Note : See Figure 2-4

for special triax
to banana cable.

LO

7 ‘172 Matrix Card

-

2-12

SECTION 2

Operation

Figure 2-8.

Common 7

Note : See Figure 24 for special

triax to banana cable.

//II

/- Output

Model 230 Voltage Source Connections

7172

Matrix Card

2-13

SECTION 2
Operation

590 C’J Analyzer

7078.TRX-BNC
Triax-to-BNC \

r

‘igure 2-9.

Model 590 CVAnalyzer Connections

Model 220 Current Source Connections

The Model 220 Current Source can be connecied 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
TheModel6167Adaptermustbemodified by
internally disconnecting the inner shield con­nection of the input jack from the
GUARDED/UNGUARDED selection switch.
Otherwise, instrument LO will be connected
to chassis ground through the adapter.

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

7172 Matrix Card

2. Connect a Model 7078TRX-3 or -10 triax cable be­tween the guarded adapter and the desired row of
the Model 7172.

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

4.

Connect the triax end of a tiax/banana cable to the
desired row on the Model 7172.

5.

Connect the banana plug end of the t&x/banana ca­ble to the OUTPUT COMMON jack of the Model

220.

Model 236/237/238 Source Measure Unit Connections

Source measure units are connected to the matrix card us­ing Model 7078TRX cables. A Model 237-BAN-3 Triax/
Banana cable can also be used to connect the output low
binding post on the source measure unit to the matrix.
FigureZ11 shows connections for remote and local sens­ing applications.

2-14

SECTION 2

Operation

Figure Z-10.

Note : See Figure Z-4

Model 220

I

for special

trim to banana cable.

Current Source Connections

7078-TF

7172

Matrix Card

2-15

SECTION 2

Opdi0?l

I II

707s-TRX Tax
707BTRXTriax

707%TRX Triax

I

I r

A. Remote Sensing

II

6. Local Sensing

Y

I

, I

71-n Matrix Card

‘igure Z-11.

2-16

Model 236/237/238 Source Measure Unit Connections

SECTION2

Operation

2.5.6 Typical Test Fixture Connections

Typically, one or more test fixtures will be connected to

desired columns of &Mode17172 Typically, the test fix-

twes wiJl be equipped titb card-edge connedors with
wires soldered to them. In some cases, the test f%&ue will
be equipped with triax connectors; for those types, Keith­ley Model 707~TRX-3 or -10 cables can be used, as
shown in Figure Z-12.

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

Intemlly, the test fixture should be wired as shown in

the equivalent circuit of Figure Z-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 in­s&ted from the fixture shield.

Usually, the chassis ground terminal of the !xiax conmc­tar will automatically make contact with the fixture
shield by virtue of the mounting method. However,
ground integrity should be checked to ensure co&im.wd
protection against hazardous guard voltages.

Triax connectors

7172 Matrix Card

3gure Z-12. Typical Test Fixture Connections

II II II II

Note : Teflon@ - insulated connectors

recommended for specified
petforrnance.

hazard.

2-17

SECTION2
Operation

Triax Cable

From
7172
Card

Figure 2-13. Equivalent Circuit

of

Test Fixture Connections

2.6 MATRIX CONFIGURATION

The following paragraphs discuss the switching matrix
of the Model 7172 as well as how to expand the matrix by
connecting two or more cards together.

2.6.1

L.“. I Gmv,rr;r,,,q

As shown in Figure Z-14, the Model 7172 is organized as

As shown in Figure Z-14, the k
an 8 x 12 (eight row by 12 column) matrix. The rows are

an 8 x 12 (eight row by 12 column) matrix. The rows are
labeled A through H, while the columns on the card are labeled A through H, while the columns on the card are

Switching Matrix

r----

Test Fixture Chassis

numbered 1 through 12. The actual column number to
use when progr amming depends on the slot and unit
number, as summarized in Table 2-3. For example, card
column number 2 on a card in slot 5 of unit 1 is accessed as
ma&ix columl62.

Eachintersectingpointinthematriwiscalledacrosspoint
that can be individually closed or opened by progmn-

I

ming the Model 707 mainframe. All crosspoints are con­figured for 2-pole switching, as shown in Figure 2-14.
SIGNAI SIGNAL and GUARD are switched separately to any of
the 12 Cc.luvUO “1, ULC c-u. the 12 columns on the card.

1

-----

2-18

SECTION2

Operation

Figure 2-14.

Model 7172 Matrix Organization

2-19

SECTION 2

0pZti0ll

Table2-3. Column Numbering by Slot and

unit

Columns (l-l.3

1
2
3 25-36
4 3748
5 49-60
6 61-72

1 73-84
2 85-96
3 97-108
4 109-120
5 121-132
6 133-144

1 145-156
2
3 169-180
4
5 193204
6 205-216

1
2
3
4
5
6

-

l-12

13-24

157-168
181-192

217-228
229-240
241-252
253-264
265-276
277-288

289-300
301312
313-324
325-336
337-348
349-360

Row isolator relays isolate one card from the next when
expanded using row jumpers. This greatly reduces the

offset current, noise current, and capacitive effects of a

muIti-card matrix.

2.6.3

Two to six Model 7272 cards can be connected together

within the mainframe to yield an 8 x N matrix, where N
depends on the number of cards. Figure 2-15 shows an
internalIy expanded matrix with three cards, resulting in

an 8 x 36 (eight row by 36 column) matrix. As summa­rized in Table 2-3, the achml column number used when
progmnming the unit is determined by the slot.

Because of critical signal paths, rows A-H are not jum-

pered through the backplane. Instead, you must install
the supplied coaxial jumpers between appropriate con­nectors on Model 7172 cards (for more critical signal
paths, rows can be Isolated from other cards by not in-

stalling these cables). Each card has hvo coaxial connec-

tars 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; it is not necessary to re­move cards to install the jumpers. Figure 2-16 shows a
side view of the jumper connectors with row numbers
marked for convenience. Figure 2-17 demonstrates how

three cards can be daisy chained together using the coax­ial jumpers.

Internal Matrix Expansion

NOTE
Coax&d jumpers can also be used to extend
any Model 7172 row to the Model 7072 Semi­conductor Ma&ix Card (rows A, B, G, and H)
and the Model 7072~HV High Voltage Semi­conductor Matrix Card (rows G and H). Since
the offset current specified on the Model 7072
and 7072-I-W is greater than the Model 7172,
ordy extend less critical signals to these rows.

2.6.2 Row Isolators

Row isolator relays isolate the crosspoint relays from a
given row to minimize leakage current and capacitance.
The row isolator relay closes when any crosspoint relay
associated with that row is dosed.

2-20

WARNING
The shells of the row jumpers are at guard
potential. To avoid a possible shock hazard,
always disconnect all cables from the row
andcolumn jacksbeforeremovingorinstall­*g jumpers.

Note : Rows A - H require installation of coaxial jumpers (shown shaded)

SECTTON 2

Operation

cigure 2-16.

-

Jumper

Warning : Guard potential is on

coaxial jumper shields

Connector Locations

2-21

SECTZON 2
Operatibn

ipre 2-l 7.

ntree Cards in Daisy Chain Configuration

2-22

SECTION 2

Operation

2.6.4

External jumper cables must be used to expand the nun­ber of rows in the matrix, or to connect between columns
of cards installed in different mainframes. An example of
such an expanded matrix is shown in Figure Z-18. Here,
siucardsareconfiguredasa16x36matriw.Sincetherows
are internally jumpered, only columns must be jumped
extemauy in this configuration.

External Matrix Expansion

Triax tee adapters (Model 707%TRX-T or Model
237-TRX-T) can be used to provide daisy chain capability
between the triax input connectors. Figure Z-19 shows a
typical arrangement between two Model 7172 cards. Ide­ally, custom-length tiax cables should be used to avoid

the cable “jungle” that would OCCUT with longer, Stan­dard-length cables.

Figure 2-18.

16 x 36 Matrix Constructed by External Jumpming

Z-23

SECTION 2
Operation

Matrix

input I Output

707%TRX-T or 237-TRX-T

Triax Tee Adapters

-

{-

Figure

2-19. Using Trim Tee Adapters to Daisy Chain Cards

2.7 MEASUREMENT CONSIDERATIONS

Many measurements made with the Model 7172 concern
low-level signals. Such mea~~ments are subject to vari­ous types of noise that can serioIlsly a&fect low-level
measurement accuracy. The following paragraphs dis­cuss possible noise smmxs that might affect these meas-

uremenrs.

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 mati 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 metal with high permeability at low

flw densities (such as mu metal) are effective at redudng
these effects.

Even when the conductor is stationary, magnetically-in­duced signals may still be a problem. Fields can be pro-

duced by various signals such as the AC power line volt-

age. Large inductors such as power transformers can
generate substantial magnetic fields, so care must be

taken to keep the switching and measuring circuits a

good distance away from these potential noise sources.

2-24

SECTION 2

Operation

2.7.2 Electromagnetic Interference (EMI)

The electromagnetic interference characteristics of the
Model 7172 Low Current 8

×

12 Matrix Card comply with
the electromagnetic compatibility (EMC) requirements
of the European Union as denoted by the CE mark.
However, it is still possible for sensitive measurements
to be affected by external sources. In these instances,
special precautions may be required in the measure­ment setup.

Sources of EMI include:

INSTRUMENT 1

SIGNAL LEADS

INSTRUMENT 2 INSTRUMENT 3

GROUND

LOOP

CURRENT

POWER LINE GROUND

•

radio and television 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 high­voltage environments

The effect on instrument performance can be consider­able if enough of the unwanted signal is present. A com­mon problem is the rectiÞcation by semiconductor
junctions of RF picked up by the leads.

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

Many instruments incorporate internal Þltering that
may help to reduce RFI effects in some situations. In
some cases, external Þltering may also be required. Such
Þltering, however, may have detrimental effects on the
desired signal.

Figure 2-20. Power Line Ground Loops

Figure 2-21 shows how to connect several instruments
together to eliminate this type of ground loop problem.
Here, only one instrument is connected to power line
ground.

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.

INSTRUMENT 1

INSTRUMENT 2 INSTRUMENT 3

POWER LINE GROUND

Figure 2-21. Eliminating Ground Loops

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 2-20, the
resulting ground loop causes current to ßow 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.

2.7.4 Keeping Connectors Clean

As is the case with any high-resistance device, the integ­rity of triaxial and other 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 sur-

2-25

SECTION 2
Operation

face. To avoid 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. After thorough cleaning, they should be
allowed to dry for several hours in a low-humidity awi­ronment 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 or triaial cables. Such currents, which are known as
triboelectric currents, are generated by charges created
between a conductor and insulator caused by friction.

2.7.6 Shielding

Proper shielding of all unguarded signal paths and de­vices under test is important to minimize noise pickup in
virhmlly 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 surround­ing the HI signal path should be connected to signal LO
(or chassis ground for instruments without isolated LO
temimls). Since most Model 7172 matrix applications
cdl for separately switching LO, a separate connection
from LO to the cable shield at the source or measurement
end must be provided, as in the example of Figure 2-22.
Here, weareusingtheGUARD path of the Model 7172 to
carry the shield out to the device under test. Needless to
say, this arrangement should not be used with guarding,
as GUARD and LO should not be connected together.

WARNING
Hazardous voltage may be present if LO on
;nytiFtmment is floated above ground po-

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

Even low-noise cable generates some noise currents
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.

If the device under test is to be shielded, the shield should
be connected to the LO terminal. If you are using the
GUARD comwction as shield, care should be taken to in­sulate the outer ring of the triiudal connector mounted on

the test fixture from the test fixture

will be connected to chassis ground, possibly resulting in
a ground loop. An alternative is to use two shields, one
mounted within (and insulated from) the other. In this
case, the GUARD path would be connected to the inner
shield, while the outer shield would be chassis grounded.
This arrangement is shown in Figure 2-23. Incidentally,
this configuration is also recommended for guarded ap­plications, with the inner shield as guard, and the outer
shield acting as a safety shield.

itself.

Otherwise,

LO

SECTION 2

Operation

Inner Shield of HI Ttiax
Connected to LO

1

Cigure 2-22. Shielding Example

r-----

-----

7172 Card

Columns

1

Triax

Triax

inner Shield
Connected to LO

r

---

r----------l

L _ _ - - - - _ _ - _ -I+- Outer Shield

(Chassis Ground)

2-27

SECTION 2
opemtion

2.7.7

Guarding is important in high-impedance circuits where
leakage resistance and capacitance could have degrading
effects on the measurement. Guarding consists of wing a
shield surrounding a conductor that is carrying the high­impedance signal. This shield is driven by a low-imped­ante amplifier to maintain the shield at signal potential.
For triaxial cables, the inner shield is used as guard.

Guarding minimizes leakage resistance effects by driv­ing the cable shield with a unity gain amplifier, as shown
in Figure Z-24. Since the amplifier has a high input im­pedance, it
signal lead. Also, the low output impedance ensures that
the shield remains at signal potential, so that virhmlly no
leakage current flows through the leakage resistance, RL.
Leakagebetweeninneradoutershieldsmaybeco~ider­able, but that leakage is of little consequence because that
current is supplied by the buffer amplifier rather than the

signal itself.

Guarding

minimizes loading on the high-impedance

In a similar manner, guarding also reduces the effective
cable capadtance, resulting in much faster measure­ments on high-impedance circuits. Because any distrib-

uted capacitance is charged through the low impedance

of the buffer amplifier rather than by the source, settling
times are shortened considerably by guarding.

Jn order to use guarding effectively with the Model 7172,
the GUARD path of the matrix card should be connected
to the guard output of the sourcing or measuring instru­mat. Figure 2-25 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 2-23 is recommended for safety purposes (guard

voltage may be hazardous with some instruments). With

most instruments, special adapters or cables may be re­quired to connect guard to the inner shield, and at the

same time route signal LO through a separate cable.

Figure2-24. Guarded Circuit

2-28

Measuring
Instrument

DUT

SECTION 2

Operation

3iarre 2-25. Tvoical Guarded Sisal Connections

------

7172 Matrix Card

Columns

Warning: Outer fixture must be --J

used to avoid possible
shock hazard from guard.

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 7172 Card installed
in the mainframe. Expanding the matrix by internally or
externally comeding two or more Model 7172 Cards tc­gether will degrade system performance specifications
(other types of cards do not affect the specifications be­came 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 row expansion, isolation among rows is in-

creased, and offset current is decreased, although the iso­lator relays on the card do help to minimize these effects.
With external row or column expansion, isolation and

offset current specifications are degraded because of the

additional parallel paths and relays present on each sig-

nal line.

2-29

SECTION 3

Applications

3.1 INTRODUCTION

This section covers typical applications for the Model
7172 Low Current 8 x 12 Matrix Card and is organized as
follows:

3.2 cv Measurements: chltlines the test configuration
and procedure for making quasistatic and high-fre­quency CV measurements.

3.3 Semiconductor Test Matrix Details a semiconduc­tor 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
measure the resistivity of semiconductor samples using
the van der Pauw method.

3.5 Semiconductor Parameter Analysis: Discusses us­ing the Model 7l72 in conjunction with an HI’ 41458
Semiconductor Parameter Analyzer.

3.2 CV MEASUREMENTS

The Model 7172 can be used in conjunction the Keithley

Model 590 CV Analyzer, and the Keithley Model 595

Quasistatic CV Meter to perform quasistatic and high-

frequency CV kapa&nce vs. voltage) tests on sernicon­ductors. The resulting CV curve 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-I can be used
to make CV measurements without the aid of a com-

puter. System components perform the following func­tions.

Model 590 CV Analyzer:
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 707 Switching Matrix Controls the semiconduc­tor matrix card to close and open the desired crosspoints
at the proper time.

Model 7l72 Low Current 8 x 12 Matrix Card: Switches
the signal pathways to the six wafers under test.

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

the Models 590 and 595.

Measures

CV data at 1OOkH.z

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-l

SECTION 3
Applications

Wafers Under

Test

..___. -__

Quasistatic CV Meter

707%TRX-BNC

iH
I
I

1 2 3 4 5 6 7 8 9 10 1, 12) I I

I
L-

----------

7172 Matrix Card

707 Switching Matrix

I

-I

7051 BNC

Cables

HP-GL
PIOtter

0

Input

Model 590

CV Analyzer

Note : Connect plotter to only one

instrument at a time.

3-2

Wafers Under

Test

A

1

2 3 4 5 6

SECTION 3

Applications

Model 595

Quasistatic CV Meter

IH
I
I

1 2 3 4

I
I
L

--------

Figure 3-2.

5 6 7 8 9 10 1, 12 I

7172

Matrix Card

707 Switching Matrix

Note : Remove jumpers to other 7172 cards (if installed)

Computerized CV System Configuration

CV Analyzer

IEEE-488 Bus

to optimize Model 595 measurement accuracy.

HP-GL
PIOtter

3-3

SECTION 3
Applications

3.2.3 Optimizing CV Measurement
Accuracy

For accurate CV measurements, each Model 590 CV
measurement pathway must be cable 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 compeIwates for any leakage currents pre­sent in the cables, switching matrix, or test fixture. How­ever, care must be taken when using corrected capad­tance to ensure that the device remains in equilibrium
throughout the test sweep to avoid distorting the CV
CUIV~S.

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

minimize the effects of the switching network

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, wbicb is fairly

complex. The procedure given is for the stand alone sys­tem in Figure 3-l. Detailed instrument operating infor­mation may be found in the pertinent instnwtion manu-

al?..

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.

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 #l, close Gl 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-l.

Wafer # Quasistatic (595) 1 High Frequency (590)

I

1

2

I
3 A<, 86
4
5 A9, BlO
6 All, B12

3.2.5 Typical CV Curves

CV Test Crosspoint Summary

Closed Crosspoints

I
Al, B2
A3, B4

A7,B8

I

Gl, HZ
G3, H4
G5, H6
G7, H8

G9, H10

Gil, H12

\

I

1. Connect the HP-GL plotter to the IEEE488 bus con­nector of the Model 595 only.

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

3. Close the cmsspoints necessary to connect the Model
595 to the device under test, as summarized in
Table 3-1. For example, to test device #l, close Al
and 82.

3-4

Figure 3-3 and Figure 34 show typical CV curves as gen-

erated by the Models 595 and 590 respectively. The
quasistatic curve shows a fair amount of symmetry,

while the the high-frequency curve is highly asymmetri-

cal. The asymmetrical nature of the high-frequency curve
results from the inability of the minority carriers to follow
the high-frequency test signal.

+0&E-10

SECTION 3

Applications

I

+0.4E-10

-005.00

I

I I

I I

Figure 3-3. Typical Quasistatic CV Curve Generated by Model 595

I I I

+005.00

KEITHLEY 595

3-5

SECTION 3
Applications

$

5 1.35
x

6 1.27

2

v 1.20

8
5

.$j 1.12

Fi

0” 1.05

-

1.50

1.42

0.97

0.90

‘igure 34.

0.82

0.75 : :

: : : : : : : : ! ! : :

590: 00: 00: 10: 500 IOOKHZ

Keithley

Typical High-frequency CV Cum Generated by Model 590

: ! : : : : : : : : :

x1 Filter --------. Parallel

: : : : : : : : : : : :

: : :

3-6

SECTION 3
Applications

3.3 SEMICONDUCTOR TEST MATRIX

Two important advantages of a matrix switching system
are the ability to connect a variety instruments to the de­vice or devices under test, as well as the ability to connect
my 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 charactelistic testing of a
typical JFET.

3.3.1 System Configuration

Figure 3-5

purpose semiconductor test matrix. Instruments in the
system perform the follwing functions.

Model 617 Electrometer/Source: Measures current, and
also could be used to measure voltages up to k2OOVDC.
The DC voltage sxlrce can supply a maximum of ~1OOV
at currents up to ZmA.

shows the configuration for a typical multi-

Figure 3-5.

1 2 3 4 5 6 7

7172 Matrix

707 Switching

Semiconductor Test Matrix

8 9 10 11 12

Card

Matrix

3-7

SEC27ON 3
Aaalications

Model 230 Voltage Source: Sources DC voltages up to
+101v at a mawimum current of lOOmA.

Model 590 CV Analyzer: Adds CV sweep measurement
capability to the system.

Model 220

Current Source:

Used to source currents up to
amaximumof 1OlmAwith amaximumcompliancevolt­age of 105v.

Model 196 DMM: Measure DC voltages in the range of

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

Device Under Test: A three-terminal fixture for testing

such devices as bipolar transistors and FETs. Additional

connections could easily be added to test more complex
devices, as required.

3.3.2

Testing Common-Source Charac-

teristic of FETs

The system shown in Figure 3-5 could be used to test a
variety of characteristics including IGSS, Iorom, IGONI, Ims,

and Vm[om. 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 JET.

In order to generate these curves, the instruments must
be connected to the JFET under test, as shown in
Figwe3-6. 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.

LO

Model 230

Voltage source

@=

Closed Crosspoints on 7172 Card (Figure 3-5).

HI

0

Electrometer/Source

617

A12

_._._._._,_,._._...........~. - .

0 HI

Voltage
source

0 LO

Figure 3-6. System Configuration

343

for

Measuring Common-Emitter Characteristics

SECTION 3
Applications

Tonmthetest,Vcsisset to~pedficvalues,forexamplein
increments of OZV. At each Vcs value, the drain-source
voltage (Vos) is stepped aaoss the desired range, and the
drain current, IO, is measured at each value of Vos. Once
all 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.

Figure 3-7.

Typical Common-Source FET IV Charac­teristics

on semiconductors. Such measurements can yield such
important information as doping concentration.

3.4.1

Figure3-8 shows the basic test configuration to make
resistivity measurements on van der Pauw samples. The
Model 220 sources cement 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 3OOmV or 3V ranges. Also, this con-

figuration is not recommended for resistance measure-

ments above 1MQ due to the accuracy-degrading effects

of DMM loading.

3.4.2

In order tomakevanderPauwresistivitymeasurernents,
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
Vl through V8.

Test Configuration

Test Procedure

3.4 RESISTIVITY MEASUREMENTS

The Model 717’2 Low Current 8 x 12 Matrix Card can be
used in conjunction with a Model 220 Current Source and
a Model 196 DMM to perform resistivity measurements

In order to source current into and measure the voltage

across the sample, specific crosspoints must be closed.
Table 3-Z summarizes the crosspoints to close for each

voltage

configuration shown in Figure 3-8.

measurement on all three

samples from the test

3-9

SECTION 3
Applications

SGsGsGSGSGSGSGSGSGSGSGSy

r; ( ( ( , , , , , ,

A I

I

---------_

1 2 3 4 5 6 7 8 9101112

7172 Matrix Card

707 Switching Matrix

,

220 Current Source

(Sources Current through Sample)

196 DMM
(Measures Voltage Across Sample)

:i,mre

3-10

3-8. Resistivitu Test Configuration

Table 3-Z. Crosspoint Summary for Resistivity Measurements

Voltage

VI
VZ
V3
Va
VS
V6
V7
VS

r

Sample #l

Al B4 E3 F2 A5 B9 E7 F6 A9 812 El1 F10
A4 Bl E3 F2 A8 85 E7 F6 A12 B9 El1 FIO 2-l
A4 B3 E2 Fl A8 87 E6 F5 Al2 Bll El0 F9 2-3
A3 B4 E2 Fl A7 B8 E6 F5 All 812 El0 F9
A3 B2 El F4 A7 86 E5 F8 All BIO E9 F12 3-4
A2 B3 El F4 A6 B7 ES F8 Al0 Bll E9 FlZ
A2 Bl E4 F3 A6 85 E8 F7 A10 B9 El2 Fll 4-I
Al B2 E4 F3 A5 B6 ES l-7 A9 BlO El2 Fll 14

1 Sample #2 1 Sample #3

Crosspoint

Closed

Current Voltage

Between

l-2

3-2

4-3

Between

SECTION 3
Applications

Ygure 3-9.

0

(E)

I-+

(G)

R&tidy Measurement Conventions

3-11

SECTION 3
Applications

3.4.3 Resistivity Calculations

Once the eight voltage measurements are known, the
resistivity can be calculated. Two values of resistivity, PA

and pe are initially computed as follows:

1.1331 f* ts (V2 + v4 - v, - V3)

PA=

1.1331 f6 ts i.ve + v.9 - vs - V7)

pa =

Where: pa and pi are the resistivities in Q-cm

ts is the sample tllic!aess in cm
VI through Vs are the voltages measured by
the Model 196
I is the current through the sample in amperes
fA and fs are geometrical factors based on sm.
ple symmetry (f* = fs = 1 for perfect sym
IXWtI$.

Once pi, and ps are known, the average resistivity,
can be determined as follows:

p*“G= -

I

I

~AVG,

2

3.5 Semiconductor IV Characterization

CAUTION
To prevent card damage, do not exceed the
200 volt maximum rating of the Model 7172
when switching the Model 237, which is ca­pable of sourcing up to 1100 volts.

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

are connected in a 4-wire sensing configuration. This con­nection scheme aUows 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 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 7172 matrix cards. Each
additional card will add 12 columns to the system.

3.5.2

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-BAN-3 or 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.

Cable Connections

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

3-12

3.6 SEMICONDUCTOR PARAMETER

ANALYSIS

One or more Model 7172 Low Current 8 x 12 Matrix
CardscanbeusedinconjunctionwithanHP4145BSemi­conductor Parameter Analyzer (SPA) to provide a versa­tile switching system capable of complete DC characteri­zation of semiconductors. The following paragraphs dk­cuss system configuration, connections using the
7078CSHP Cable Set, and SPA measurement considera­tions.

SECTION 3

Applications

Figure

3-20.

MuIti Unit Test System Using Models 236 and 237 Source Measure Units

3-13

SECTION 3
Applications

3.6.1

System Configuration

Figure S-11 shows the general configuration of the SPA
switching system. The components of the system per­form the following functions:

SMUl ---------A

HP 41458

Semiconductor

Parameter

AllalyZer

SMU 2 B
SMU 3 C
SMU 4

Vsl

vs

2

HP 4145B3 Has four SMUs (Source/Measure

Units), two

voltage sources, and two voltage measurement ports.
The unit can automatically run a variety of tests on semi­conductors and plot data on a built-in CRT.

Test Fixture

DUT Pins

c---

1...12 13e.24
?

T

I...12

; ~~~ I

A

13...24

7172

Card

---Y

25...36

T 1

25...36

I ‘c’,:d’

Columns

>

:: v j--;;m;myalnx---

A

HP9000 or IBM PC/AT

Note : Connecting cables included in 707%CSHP cable set

Finwe 3-11.

Semiconductor Parameter Atulvsis Switchim Svstem

Rows’

system Controller

A

IEEE-488 Bus

3-14

SECTION 3
Applications

Model 707 Switching Matrix Controls the matrix card to
open and dose signal paths as required.

Model 7l72 Low Current 8 x 12 Matrix Card: Switches
the test pathways to the device under test. In this particu­lar application, three Model 7172 cards provide 36-pin
test capability. A total of six cards can be installed in a sin­gle mainframe, providing up to 72.pin capability in one
mainframe.

System Controller: Controls the SPA and switching ma­trix with user-written software. Typical controlkers for
this application are Hr9000 Series 200 or300 (with HP-E3
interface), and IBM PC, AT or compatible computers
(equipped with an IEEE-488 interface).

Test Fixhue: Provides the interface between the device
under test and the matrix card. Typically, the test fixture
will be equipped with tiax connectors for ease of connec­tions.

3.6.2 Cable Connections

Any switching system can degrade low-level signals, and

the same holds true for the system shown in Figure 3-10.

Safety considerations are also a concern when connecting
instmments to a switching matrix. Therefore, it is

strongly recommended that you carefully read the HI’

4145B manual before wing the system.

WARNING
Hazardous voltage may be present on the
outer conductors of the connecting cables

when the HP 4145B is set up for floating

measurements.

3.6.4 Typical Test Procedure

The following paragraphs outline the procedure for us­ing the SPA/m&ix system to perform a typical test: VDS­IO (common-source) curves of a typical JFET. The proce-

due uses one of the four standard setups that are part of
the applications package supplied with the HP 4145B.

Figure 312 shows how to connect the HP 4145B to the
Model 7172 using the optional Keithley Model
7078-CSI-P Cable Set. The four SMU ports are to be con­nected with the triax cables (707%TRX-lo), while the two
voltage source and voltage measurement ports (Vs and
Vm) are to be connected using BNC cables (7051-10) and
t&x-BNC adapters (707%TRX-BNC). Typically, the SPA
will be connected to the rows, as shown in Figure 3-12.

Connections to a user-supplied test fixture should be
made using triax cables in order to maintain path integ­rity and safety. BNC cables and adapters should not be
used in case hazardous potential appears on guard terml­Ids.

3.6.3 SPA Measurement Considerations

A complete discussion of SPA measurements is well be­yond the scope of this manual. However, there are a few
points that should be kept in mind when using this ar­rangement. Additional measurement considerations
may be found in Section 2, paragraph 2.7 of this instruc­tion manual.

System Configuration

Figure 3-13 shows the configuration and connections for
this example. Only three of the four SMUs are required
for the test, as indicated in the figure. A total of four FETs
can be connected to a single card, as shown on the dia­gmm. In all cases, hiax cabling should be used. The cross­points to close to test a specific FET are summarized in
Table 3-3.

Table 3-3. Crosspoint Summary for JFET Test

2
3
4

‘Crosspoints from Figure Z-13.

A5, C4, B6
A8, C7, B9

All, ClO, 812

3-15

SECTION 3
Applications

HP 4145 Semiconductor Parameter

All&Z3

TO
Test
Fixture

‘igure 3-12. SPA Connections

7172 Math Card

Triax-BNC

Adapters

_I

3-16

FETs Under

Test

A

SECTION 3

Applications

Triax

Cables

IH
I

I

1 a 3 4 5 6 7 l3 9 10 11 12’

I
I

L~~---~~----~

Figure 3-23. System Configuration for JFET Test

Procedure

1. Connect the system and devices together, as shown
in Figure 3-13.

2. Turn on the HP 41458 and allow it to go through its

boot-up routine.

3. Turn on the Model 707 Switching M&ix.

4. From the HP 4145B main menu, select the channel
definition page, then choose the FET Vm-ID applica­tion.

5. Press the PAGE NEXT key, and program the
parameters, as required.

7172 Matrix Card

707 Switching Matrix

SOUTC~

HP 41456 Semiconductor

Parameter Analyzer

I

6. Press the PAGE NEXT key, and program the re­quired graphing parameters.

7. Press the PAGE NEXT key to display the gnph for­mat.

8. From the front panel of the Model 707, close the
aosspoints necessary to connect the FET being
tested to the SMUs (see Table 3-3).

9. Press the MEASUREMENT

SINGLE key to initiate
the sweep. The SPA will generate the IO vs. Vos
cwves at specified VGS values.

10. Open the crosspoints presently closed.

11. Repeat steps 8 and 9 for the remaining devices, as re­quired.

3-17

SECTION 3
Applications

Typical Plot
Figure 3-14 shows a typical plot made using the proce-

due above. The device tested was a 2N4392 N-channel

ID

(W

3.50(
ldb

JFET. For the graphs, Vos was swept from OV to 1OV in

0.W increments, and Vcs was stepped from 0 to -10.25V.

Variable 1 :

VDS -Ch2

Linear *weep

Variable 2 :

VG -Ch2
start

%OP
Step

Constant :

vs -Chl

Fiwre 3-24.

Tvaical JFET Plot

VDS l.OOO/div (V)

10.00

3-18

REFERENCES

SECTION3
Applications

ASTM, F76-84. “Standard Method of Measuring Hall Mobility
Crystals.” Am 1986: 10.05 155.

Coyle, G. et al. Switchinz Handbook, 2nd edition. Keithley Instmment.s Inc., Cleveland, (1989).
NicolIian, E.H. and Brews, J.R. MOS Phvsics and Technolovv. Wiley, New York (1982)
Sze, S.M. Phvsics of Semiconductor Devices. 2nd edition. Wiley, New York (1985).

Van der Pauw, L.J. “A Method of Measuring Specific Resistivity and Hall Effects of Discs of Arbitrary Shape.” PhiliDs
Rec. Rem., 1958: 13 1.

OperationandServiceManual,Mode14145ASemiconductorParameterAnalvzer,Yokogawa-Hewlett-PackardLtd,T0-

kyo, Japan (1982).

and Hail Coefficient in Extrinsic Semiconductor Single

3-19

SECTION 4

Service Information

4.1 INTRODUCTION

This section contains information necessary to service the

Model 7172 Low Current 8 x 12 Matrix Card and is ar­ranged as follows:

43 Handling and Cleaning Precautions: Discusses
handling precautions and methods to clean the card
should it become contaminated.

4.3 Offset Current Self-test: Describes a confidence test
of the offset currents on the Model 7172.

4.4 Performance Verification: Covers the procedures
necessary to determine if the card is operating properly.

4.5 Special Handling of Static-Sensitive Devices: Re­views precautions necessay when handling staticsensi­tive devices.

4.6 Troubleshooting: Presents some troubleshooting
tips for the Model 7172.

4.7 Principles of Operation: Briefly discusses circuit
operation.

Once the fly has been removed, blow dry the board
with dry nitrogen gas.

4. After cleaning, the card should be placed in a 5O’C
low-humidity environment for several hours before
use.

4.3 OFFSET CURRENT SELF-TEST

The Model 7172 has an on-board electrometer circuit that
measures offset current and gives you a pass/fail indica­tion. This measurement is a confidence test only.

With this self-test, you canlocate contaminated &iax con­nectors, a common cause of excessive offset current. Use
the offset current verification procedure of paragraph

4.4.3 to locate a contaminated area of the PC board, or a
leaky relay.

The on-board measurement is performed whenever you
press the switch marked OFFSET CURRENT SELF TEST,
as shown in Figure 41. The test continues until you press
the switch a second time (push-on/push-off actuation).

4.2 HANDLING AND CLEANING PRECAUTIONS

Because of the high-impedance circuits on the Model
7172, care should be taken when handling or servidng
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

where dust could settle on the circuit board. Use dry
nitrogen gas to dean dust off the board if necessary.

3. When making repairs on the circuit board, use aqua

core solder and OA-based (organic activated) flw.
Use warm water along with clean cotton swabs or a
clean, soft brush to remove the flu. Take care not to
spread the fhrx to other areas of the circuit board.

card in an environment

Pushbutton Switch

LEDs

41

SECTION 4
Service

Information

After the OFFSET CURRENT SELF TEST switch is
pressed, the yellow LED marked TESTING lights. This
closes a relay to connect an electrometer circuit to Row H
and begins measuring the offset current. After approxi­mately 40 seconds, a comparator portion of the circuit
turns on the green (PASS) or red (FAIL) LED. If the test
passes, the offset current is below 500fA.

If a crosspoint is closed after the test has run, the red or
green LED will go out and the electrometer circuit meas­ures the offset current again.

Quantifying the Offset Current

To quantify the offset current, use a 4-l/2 digit DMM ca­pable of floating measurements with a sensitivity of at
least IOOpV. (The Keithley Model 196 is used here be-

cause it is needed later in this section to verify path resis­tance.) Again, this is intended as a confidence test, not as
a substitute for the offset current verification procedure.

A DMM connected to SMB connector J1037, as shown in
Figure 4-2, measures the output of a current to voltage

converter, where a 1mV measurement is the equivalent
of 1OfA offset current.

row and column triax connectors. Also disconnect all
jumpers to other cards from the SMB connectors.
Turn on the Modle 707 and allow the Model 7172 to

2.
warm up for one hour.

3.

Close all crosspoints in Column 1 (Al, Bl, Hl).
This will check all rows and Column 1.

NOTE

The offset current of the M [ode1 7172 is speci-

fied with one crosspoint closed. Hence, with
all crosspoints in a column closed, this is a
more stringent test.

4. Press the OFFSET CURRENT SELF TEST switch,

CAUTION
Use a l/&inch flat blade screwdriver with an
insulated shaft to press the OFFSET CUR­RENT SELF TEST switch. The use of other
tools may electrically damage the circuit
board.

Verify that the green LED (PASS) comes on after ap-

5.
proximately 40 seconds. Then open all crosspoints.

Test Procedure

NOTE
The on-board electrometer is sensitive to your
movements when crosspoint relays are
closed. Remain still when testing the offset
current and do not stand directly in front of

the triax connectors. As described previously,
a DMM can be used to perform the self-test

more remotely.

As a quick test of the offset current, follow this procedure:

1. With the mainframe power tuned off, plug the
Model 7172 into a slot. Disconnect all cables from the

If the red LED (FAIL) comes on, isolate the row by
using a binary search (run test with Al through Dl
closed, then run with El through Hl closed). It may
turn out that with fewer than eight relays closed the
green LED comes on. Continue the binary search un­til it narrows down to one row. Suspect the triax con­nector first and perform the cleaning procedure that
follows.

6.

Close all crosspoints in Row H (Hl, H2,. H12). This
will check all columns and Row H.

7.

Again verify that the green LED comes on after 40
seconds. Then open all crosspoints.

If the self-test fails, use a binary search to isolate the col­umn connector, then perform the cleaning procedure
that follows.

4-2

SECTION 4

Service Information

‘igure 4-2.

DMM Connections to SMB

of

the Model 7172

4-3

SECTION 4
Service

Information

T&x Connector Cleaning

Contaminated t&x connectors are often the cause of ex­cessive offset current on the Model 7172. Connector insu­lation must be kept clean to avoid reducing its leakage re­sistance. Avoid touching the insulating material and
keep unused connectors capped to prevent contamina­tion. If the connectors become contaminated, they can be
cleaned with the following procedure:

l Disassemble the connector

l Swab generously with methanol.
l Dry the connector for one hour at 50°C.
l Reassemble the connector.

If the offset current self-test fails after cleaning the con­nectors, perform the offset current verification procedure
of paragraph 4.4.3 to isolate the PC board contamination
or leaky relay. As a general rule, a card out of the main­frame will exhibit excessive offset current when it is con­taminated; a card with a bad relay will not.

4.4 PERFORMANCE VERIFICATION

The foIlowing paragraphs discuss performance verifica­tion procedures for the Model 7172, including relay test­ing, contact resistance, contact potential, path isolation,
and leakage current.

4.4.1

AU verification measurements except for path isolation
and offset current should be made at an ambient tem­perature between 0°C and 35°C and at a relative humid­ity of less than 70%. Path isolation and offset current veri­fication must be performed at an ambient temperature of
23°C and at a relative humidity of less than 60%. If the
matrix card has be subjected to temperature or humidity
extremes, allow the card to environmentally stabilize for
at least one hour before performing any tests.

4.4.2

Environmental Conditions

Recommended Test Equipment

Table 4-1 summarizes the equipment necessary to make
the performance verification tests, along with the appli­cation for each item.

Table 4-l.

2ty. Description

1

Model 617 Electrometer

1

Model 196 6-l /2 Digit DMM Path resistance; electrometer

1

Model 707 Switching Matrix All tests
4 Model 7078-TRX-10 t&x cables’
2

Model 707sTRX3 hiax cables

1

Model 6172 2-&t male to 3-lug female hiaxial adapter
3 Model 707~TR&T hiax tee adapter
5

Banana plugs (part # BG-lo-2*) Path isolation and resistance

1

Model 263 Calibrator/Source

1 BNC to Right-angle SMB Cable (part #CA-93-l)
1 BNC to Dual Banana Adapter (Pomona

Recommended Verification Equipment

Application
Offset current; path isolation

Offset current; path resistance
path isolation; offset current; electrometer
Offset current; electrometer
Path resistance

Electrometer
Electrometer

part #1269)

Electrometer

4-4

SECTION 4

Service Information

4.4.3 Offset Current Verification

Recommended Equipment

•

Model 707 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
veriÞcation. The Model 7172 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 50%.

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 7172,
as shown in Figure 4-3.

5. Close crosspoint A1 by using the Model 707 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.

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

2. With the power off, install the Model 7172 in the
desired slot of the Model 707 Switching Matrix.
Remove all other cards from the instrument, and
install the slot covers.

4.4.4 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.

4-5

SECTION 4
Service

Information

?72 2 Slot to

3-Lug Triax Adapter

Guard off \

617 I 7172 -

--F

I- Ground Link

617 Electrometer

Connect

lo Row Under

Cable

Equivalent Circuit

Figure 4-3.

Recommended Equipment

. Model 707 Switching Matrix
. Model 617 Electrometer
. Model 7078TRX-3 triaxial cable
. Unterminated 3-&t triaxial cable (cut connector off

707B-TRX-3)
. Banana plug (Keithley part #BG-10-2)
. #16-ISAWG insulated stranded wire (6 in. length)

Test Commotions

Figure 44 shows the test connections for the path isola­tion tests. One row being tested is to be connected to the
Model 617 Electmmeter input through a Model 6172

2-&t female to 3-lug male tiaxial adapter. The other row

is to be connected to the voltage source HI terminal using
a specially prepared 3slot trim-to-banana plug cable, the

Offset Verification Test Connections

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 the 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.

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.

4-6

617 1 7172 -

SECTION4

Service Jnformation

Figure 44.

‘RowB

Warning : Hazardous voltage from

Equivalent Circuit

Connections for Path Isolation Verification

I’

user-Pre

pared Triax Cable
? Fiaure 4-5)

(Set _

the electrometer source

may be present on terminals.

I

;

I

7172 Matrix Card

4-7

SECTION 4

Service Information

NOTE

Cut

Cut

The following procedure must be performed
at an ambient temperature of 23°C and at a
relative humidity of less than 50%.

1”

(A) Cut off insulation with knife.

Cut off outer shield.

Insulation Over
Inner Shield

3/4”

(B) Strip insulation off inner shield.

(C) Twist inner shield then strip inner conductor.

Twist 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

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 7172 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 >10T

Ω

(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 >10T

13

(10

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 >10T

Ω

(10

13

Ω

).

Ω

4-8

SECTION 4

Service Information

4.4.5

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.

Path Resistance Verification

hiax c&&r conductor. gether.

Triax Tee Adapters

7078-TRX-T -k

RecommendedEquipment

. Model 196 DMM
. 7078-m-T triax tee adapters (3)
. 237-BAN-3 triax to banana cables (4)

Comections

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

Figure 4-6.

196 DMM

7172 Matrix Card

connections for Path Resistance Verification

4-9

SECTION 4
Service

Information

Procedure

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

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

2. With the power off, install the Model 7172 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 7172.

4. Temporarily connect the two triax tee connectors to­gether using a third hiax tee adapter, as shown in
Figure 47.

5. Select the ohms function, 3OOQ range, and 6-l/2
digit resolution on the Model 196.

6. After the reading settles, enable zero on the Model
196 Dh4h4. Leave zero enabled for the remainder of
the tests.

7. Disconnect the two kiax tee adapters from the short­ing adapter, and connect the &o adapters with the <1.5!2.

9. Verify that the resistance reading is <1.5Q.

10. Open the mosspoint, and disconnect the triax adapt-

11. Repeat steps 8 through 10 for columns 2 through 12.

12. DisconnecttherowadapterfromrowA,andconnect

13. Repeat steps 8 through 10 for row B. The crosspoints

14. Repeat steps 8 through 13 for rows C through H. In

cable to the row A and column 1 connectors on the
Model 7172 (see Figure 4-6).

er from colwnn 1. Connect the adapter to column 2.

In each case, the column adapter must be connected
to the column under test, and the crosspoint must be

ClOSd.

it instead to row B.
of interest here are Bl through 812. Also, the row

adapter must be connected to the row being tested.
each case, the crosspoint to close is the one corre-

sponding to the row and column connections at that
time. In all cases. the measured resistance should be

To

196

2

t

Figure 4-7. Shorting Measurement Paths Using Trim Tee Adapter

410

SECTION 4

Service Information

4.4.6

Recommended Equipment

Model 707 Switching Matrix
Model 263 Calibrator/Source
Model 196 DMM
Model 707%TRX-3 Triax Cable
Model 61722slot male to 3-lugfemak+auiaadapter

BNC to Right-angle SMB Cable (Keithley part #
CA-93-l)
BNC to Dual Banana Adapter O’omona part # 1269)

CONldiOlW

Figure 4-8 shows the connections for on-board elec­trometer verification. The Model 196 connects to SMB
connector J1037 on the Model 7172. The Model 263 Cali­brator Source connect.s to the Row H triax. The ground
link on the Model 263 rear panel is removed.

Procedure

1.

2.

3.

4.

Electrometer Verification

With the power off, install the Model 7172 in the

mainframe. Remove all other cards from the main­frame and install the slot covers.
Connect the cables between the Model 7172 and test
instruments.
Turn on the Model 707 and keep all crosspoint~

open.
Press the OFFSET CURRENT
the Model 7172.

CAUTION
Use a l/S-inch flat blade screwdriver with an
insulated shaft to press the OFFSET CUR-

SELF TEST switch on

RENT SELF TEST switch. The use of other
tools may electrically damage the circuit
board.

TumontheModel196DMMandMode1263Calibra-

5.
tor/Souce. Allow them to warm up for at least one

hour before beginning the verification test.

Select the volts function and the 3OOmV range on the

6.
Model 196.
With the Model 263 in standby, select the active

7.
amps function, 2pA range, and +0.5pA output.
To reduce Model 263 offsets, perform the foBowing:

8.

A. Set the Model 263 for zero by pressing ZERO,

and source zero current to the circuit by pressing
OPERATE.

B. The DMM measurement is the offset of the cir-

cuit and Model 263. When the measurement set­tles, press ZERO on the Model 196 to store the
offset value. This will be sub&acted from subse­quent readings.

Source +0.50pA to the circuit by again pressing

9,

ZERO on the Model 263. The Model 196 measure­ment should be 48mV to 52mV. (The state of the
LEDs is not important within this range.)
PuttheMode1263instandbybypressingOl’ERATE.

10

Select an output level of -0.50pA.
Source-OSOpA to tlw circuit by pressing OPERATE.

11.
The Model 196 measurement should be -48mV to

-52mV. (The state of the LEDs is not important
within this range.)

Use the adjust feature of the Model 263 to find the

12.
threshold of the Model 7172 comparator circuit. The
green LED should light at absolute levels below

46mV. The red LED should light at absolute levels
above 54mV.

4-u

SECTION 4
Service

Information

‘igure 48.

4-12

Verification

of

On-Board Electrometer

Seroice

SECTION4

Information

4.5 SPECIAL HANDLING OF STATIC­SENSITIVE DEVICES

CMOS

possible static discharge damage because of the high-im­pedance levels involved. When handling such devices,
use the precautions listed below.

and

other high-impedance

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.
Remove the devices from their protective containers

2.
only at a properly-grounded work station. Also
ground yourself with an appropriate wrist strap
while working with these devices.
Handle the devices only by the body; do not touch

3.
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.

devices are subject to

4.6 TROUBLESHOOTING

4.6.1

Table 4-2 summ arizes the recommended equipment for
general troubleshooting.

4.6.2

In order to gain access to the test points and other cir­cuitry cm the Model 7172, 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.

4.6.3

Table 4-3 summarizes the troubleshooting procedure for

the Model 7172 Low Current 8 x 12 Matrix Card. Some of
the troubleshooting steps refer to the ID data timing dia­gram shown in Figure 4-9. In addition to the procedure
shown, the relay tests outlined in paragraph 4.3.3 can be
used to aid in troubleshooting. Also, refer to paragraph

4.6 for an overview of operating prindples.

Recommended Equipment

Using the Extender Card

NOTE

The Model 7070 cannot be used for perform-

ing the verification tests because its presence
will affect the results.

Troubleshooting Procedure

Table 4-2 Recommended Troubleshooting Equipment

4-13

SECTION 4
Service Infomtion

Table 43. Troubleshooting Procedure

step Test point/Component

1 lxxm

+6V

2

+5v

3

4 NXTADR

5 CLRADR
6 IDDATA

STRB

7

8 RLDAT
9 CLK

10 OE
11

UIOO-U106, U108, Ulll,
U113, U114, U116, Ull7,

pins lo-18

CARDSEL

CLRADDR

Required Condition

+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.

rl

comments

All voltages referenced to DGND

kiigital common)
Relay voltage
Logic voltage
Power up only (Fig. 4-8)
Power up only (Fig. 4-8)
Power up only (Fig. 4-8)
End of relay data sequence.
Present when updating relays.
Present during relay data or ID data.
Power on safe guard.

Relay driver outputs

NEXTADDR

CLK

IDDATA

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

CLRADDR pulse occurs only once.

Figure 4-9. ID Data Timing

414

SECTlON

Service Information

4

4.7 PRINCIPLES OF QPERATION

The following paragraphs discuss the basic operating
principlesfortheModel71~. Aschematicdiagmmof the
matrix card may be found in drawing number 7172-106
(six sheets), located at the end of Section 5.

4.7.1

Figwe4-10 shows a simplified block diagram of the
Model 7172. Key elements include the buffer W122), ID
data circuits (U119, U118, and UlZO), relay drivers

(UlOO-LJ106, UlO8, Ulll, U113, U114, Ul16, U117) and
relays (KlCO-K2C4), and power-on safe guard (U121). The
major elements are discussed below.

Block Diagram

Address
counter

AO-Al 1

ROM

DO-D7

4.7.2

ID Data Circuits

Upon power up, the card identification data information

from each card is read by the mainframe. This ID data in-

dudes 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 7172) require the closing
of more than one relay to close a specific cro.sspoint.

ID data is contained within an on-card ROM, U118. In or­der to read this information, the sequence below is per­formed upon power up. Figure 4-9 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.

ParallI?l

to Serial

C0fWHter

CLRADDR

TO

W&frame

u119

NEXTADDR _

Buffer <

u122

U118

CARDSEL

IDDATA

RELAYDATA

STROBE

Power-On

Safeguard

V

u121

CLK - >

output

Enable

u120

Relay

DIiVWS

“1cc-“106,
“tc8.ull7,
“113. “114.

>

“116.“117

A

! Y

>To self-test circuit

Relays

>

KIOO-Kz04

Columns

l-12

c--3 A-H

Rows

Figure 4-10. Model 7172 Block Diagram

SECTION 4

ServiceInformation

The CLRADDR line is pulsed high to clear the ad-

dress counter and set it to zero. At this point, a ROM
address of zero is selected. This putse occurs only

once.
The NEXTADDR line is set low. NFXTADDR going
low increments the counter and enables par&l
loading of the paraIIel-tmerial converter. NEX­TADDR is kept low long enough for the counter to
increment and the ROM outputs to stabilize. This se-

quence functions because the load input of the pm­l&to-serial converter is level sensitive rather than

edge sensitive. The tist ROM address is location 1,
not 0.
The CLK line docks the pm&-to-serial converter

to shift aU eight data bits from the converter to the

mainframe via the IDDATA line.

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

sequence.

4.7.3 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, WOO-U106, U108, IJIll, LJ113, U114,
U116, U117). The serial data is fed in through the DATA
lines under control of the CLK signal. As data overfIc~s
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 Ql output of IJ117 is low, relay K199
will be energized.

4.7.4

A power-on safeguard circuit, made up of U121 and asso-

ciate components, ensures that relays do not randomly
energize upon power-up. The two AND gates, U121,
make up an R-S flip-flop. Initially, the Q output of the

flip-flop (pin 3 of U121) is set high upon power up. Since

the OEN terminals of the relay drivers (UlOO-U106, U108,
Ulll, Ul13, U114, U116, U117) are held high, their out­puts are disabled, and alI relays remain de-energized re­gardless of the relay data information present at that

time.

The first STROBE pulse that comes along (in order to load

relay data) dears the R-S flip-flop, setting the OEN lines

of the relay drivers low to enable their outputs. This ac-

tion aIlows the relays to be contmlIed by the transmitted

relay data information.

A hold-off period of approximately 470msec in incIuded

in the safeguard circuit to guard against premahm ena-

bling of the relays. The time constant of the hold-off pe-

riod is determined by the relative values of R121 and

c130.

Power-on Safeguard

4.7.6 Isolator Relays

Row isolator relays are necessary in addition to the

crosspoint relays in order to ensure the integrity of low­level signal pathways. Row isolator relays include KlOO,
K113, K126, K139, K152, K165, K178, and K192. The nec­essary isolator relay is dosed in addition to the selected
crosspoint to complete the entire pathway. For example,
if crosspoint Cl0 is dosed, relays K136 and K126 would
be energized.

4.7.6

The electrometer circuitry is composed of a current to

voltage converter, a comparator circuit, and a timer. Re­fer to Figure 4-11 for a simplified schematic.

Electrometer Circuitry

4-16

SECTION 4

Service Information

Figure 4-12. Simplified Schematic of On-Board Electrometer

4-17

SECTION 4
Service Information

Current to Voltage converter

A simplified model of the current to voltage converter
portion of the electrometer circuit is shown in Figure
4-12. The offset current IIN is from contamination between
signal high and guard. Since no current flows into the (-)
terminal of the op amp, 1~ = IN, where IF is the current
flowing through the feedback resistor RF. The negative
feedback configuration and high-gain op amp make the
in&p;; voltage equal to the input offset vos of the op amp.

VOUT

=-IFRF+vos
=-Ii?4RF+Vo?

For example, the output voltage with 500fA of offset cur­rent is:

VOUr

= (-5OOfA) ( 100GR) + 3mV
= 47mv

The offset voltage can be easily subtracted by zeroing a

DMM with the offset current self-test switch (5100) open.

CAUTION

Do not connect A (analog) ground to chassis

or digital ground. If looking at signals with a
scope, do not connect the scope ground to A
bnalog) ground, since the scope ground is at
chassis potential. The shell of SMB connec­tor J1037 is at a (analog) ground potential.

When SlOO is closed, the yellow TESTING LED comes on

and removes the CLR signal from the timer U107. This
causes the DONE signal to go low while the timer is run­ning. This keeps the PASS and FAIL LEDs off.

After approximately 40 seconds, the DONE signal goes
true or high. Since TESTlNG and DONE are true the l’,F

signal is gated to the PASS/FAIL LEDs and one of the

LEDs comes on. A toggle on the CLK or TESTING line

causes the timer to stat running again, causing DONE to
go low and waiting40 more seconds. The timer is a retrig­gerable one-shot, so repeated changes on the CLK or
TESTING line could keep the red and green LEDs off for-

Comparators

Resistors R130, R118, R115, and R116 generate +Vth and

-Vm and A (analog) ground. +VUI and -Vth are used by the
window comparator U112. The output of the com-

parators are high if the output of the I to V converter is be­tween +Vm and -Vth, which corresponds to +5OOfA and

-500fA.

The A (analog) ground is three volts from chassis ground,
but this is still used as a ground for the I to V converter. In

other words, consider the single-ended 6-volt supply as a
differential +3V supply with A (analog) ground as the
ground.

Figure 4-12. Simplified Model of Current to Voltage

CO?lWrte7

4-18

SECTION 5

Replaceable Parts

5.1 INTRODUCTION

This section contains a list of replaceable electrical and

mechanical parts for the Model 7172, as welI as a compo­nent layout drawing and schematic diagram of the ma­ti card.

5.2 PARTS LISTS

Electrical parts are listed in order of circuit designation in
Table 5-1. Table 5-2 summarizes mechanicaI 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 inside front cover of this manual for ad­dresses). When ordering parts, be sure to include the fol­lowing information:

1. Matrix card model number (7172)

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 rehuned to Keithley Instn­ments for repair, perform the following:

1. Complete the service form located at the back of thii
manual, and include it with the tit.

2. Caddy pack the card in the original packing car­ton or the equivalent.

3. Write ATTENTION REPAIR DEPARTMENT 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

7172-100 is the component layout for the Model 7172.
7172-106 shows a schematic diagram of the card on six

separate sheets.

5-l

Table 1. Model 7172 Parts List

Circuit
Desig.

ClOl-123
C124,125

C126,127
C128,129
Cl30
Cl31
C132,133
Cl34
Cl35
C136,137

CRlOO,lOZ
CR101

DSlOO
DS102
DS103

J1021-1028
J1029-1037

KlOO-190,

192-204

K191

Description

CAP,.lUF,20%,50V,CERAMIC
CAl’,.OlUF,20%,50V,CERAMIC
CAP, lOUF,-20+100%,25V,ALUM ELEC
CAP,22UF.-20+100%,25V,ALUM ELEC
CAP; 47LJE,10%,16V;ALLiM ELEC
CAP, 33UF, 20%, 6.3V, ALUM ELEC
CAP.270PF.20%.100V.CERAMIC/FERRITE

CAI’;.01Lk,10%,1006V,CERAMIC
CAP,.01UE,20%,50V,CERAMIC

DIODE,SILICON,lN4148 (DO-35)
DIODE,SCHOTTKY, lN5711

PILOT LIGHT, AMBER, LED
PILOT LIGHT; RED, LED
PILOT LIGHT, GREEN, LED

CONN, SMB, MALE (22 BUSS-8 PER 3/4”)
CONN,SMB,MALE,I’.C. MOUNT

RELAY, REED
RELAY, REED

Keithley
Part No.

C-365-.1
C-237-.01
c-314-10
c-314-22
C-321-47
c-333-330
C-386-27OI’
c-405-8P
C-64-.01
C-365-.01

RF-28

RF-69

PL-75-1
EL-77
PL-78

CS-580
cs-545

RL-106
RL-143

R103
R104-106,109,

120
R107,113
R108,112
RllO,lll
R114
R115,118
R116,117
R119
R121
R122
R123
R124
R125

SlOO

RES,27OK,5%,1/4W, COMPOSITION OR FILM
RES,lOK,5%,1/4W,COMPOSlTION OR FILM

RES,lK,5%,1/4W,COMPOSlTION OR FILM
RES, l.O7K,l%,l/SW METAL FILM
RES,1.5M,5%,1/4W,COMEOSITION OR FILM
RES; lOti, 2%,~1.5ti, HY MEG
RES, 2.2,5%, 1/4W, COMPOSITION OR FILM
RES, 130,1%, 1/8W,METAL FILM
RES,22M,5%,1/4W,COMI’OSITION OR FILM
RES,47K,5%,1/4W,COh4l’OSITION OR FILM
RES,~OO,~%,~ /4W,COMEDSITION OR FILM
RES,~~~,~%,~/~,COMPOS~TION OR FILM
RES,12OK,5%,1/4W,COMPOSl-TION OR FILM
RES,l1K,5%,l/4W,COMFOSITION OR FILM

SWITCH, MINIATURE PUSHBUTTON (DPDT)

R-76-270K
R-76-10K

R-76-1K

R-88-l .07K
R-76-1.5M
R-289-100G
R-76-2.2
R-88-130
R-76-2.2M
R-76-47K
R-76-200
R-76-680
R-76-120K
R-76.1lK

SW-488

WOO-106,108,

IC, 8 STAGE SHIFT/STORE UCN5841
111,113,114,
116,117

u107

IC,RBTRIG MONO MULTMB,74HC123
u109 IC, TRIPLE 3 INPUT NAND, 74HClO
UllO IC,QUAD 2 INPUT NAND,74HCOO
u112 QUAD COMPARATOR, LM339 AN
u115 IC,OI=‘-AMP,AD549L
U118

EPROM PROGRAM
u119 IC, 12 STAGE BINARY COUNTER,74HCT4040
u120 IC,8BIT PARALLEL TO SERIAL,74HCT165
U121
u122

IC, QUAD 2 INPUT NAND, 74HCTOO

IC, OCTAL BUFFER/LINE DRNBR, 74HC244

K-536

IC-492
IC-341
IC-351
IC-859
K-542

7172.800-*
IC-545
IC-548
IC-399

K-489
VRlOl DIODE, ZENER 6.8V, IN53424 (CASE 17)
WlOO

STIFFENER,BoARD

* Order current firmware revision level.

DZ-77

J-16

Table 2. Model 7172 Miscellaneous Mechanical, Parts List

Qty

1
2
1
98

:0

1
1

8

1

16
32
2
3 6-32x5/16 PHIL PAN HD SEMS SCR (PANEL TO BOARD)

Description
CABLE ASSEMBLY (SUFPLIBD ACCES., SMB/SMB)

CAP, PROTECTIVE
EXTRUSION, REAR PANEL
FASTENER
HANDLE
JUMPER CABLE, BOTTOM CABLE ASSEMBLY
JUMPER WIRE (BLOCK TO BLOCK)
JUMPER WIRE (TERMINAL TO TERMINAL)
REAR PANEL ASSFMBLY
SHIELD, BOTTOM
SHIELD, TOP
SOCKET,I.C. 28 PIN (FOR U118)
TPl-16 CONN,TESI FOINT
44X1/4 PHILLIPS PAN HD SEMS SCREW (SHIELD MOUNTING)
6-32X3/8 LG. PHIL FLAT I-ID SCR (HANDLE MOUNTING)

Keithley

Part No.
CA-99-1A

CAP-30-l
707-318
PA-154-l
HH-33-1

CA-98-1A
J-19-1
J-19-2

7172-301

7070307

7172.302
SO-69
cs-553
4-40X1/4PPHSEM
6-32X3/8PFH
6-32X5/16PPHSEM

M3

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

❏

❏

CertiÞcate 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 modiÞcations have been made by the user, please describe.)

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

.

Specifications are subject to change without notice.
All Keithley trademarks and trade names are the property of Keithley Instruments, Inc. All other

trademarks and trade names are the property of their respective companies.

Keithley Instruments, Inc. 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: [phone]

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

BELGIUM: Keithley Instruments B.V. Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02/363 00 40 • Fax: [phone]
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© Copyright 2000 Keithley Instruments, Inc. No. 2193
Printed in the U.S.A. 2/2000