Keithley 224man schematic

Model 224 Programmable Current Source

Instruction Manual

A GREATER MEASURE OF CONFIDENCE

WARRANTY

Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year
from date of shipment.

Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable
batteries, diskettes, and documentation.

During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.

To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Cleveland, Ohio.
You will be given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service
facility. Repairs will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for
the balance of the original warranty period, or at least 90 days.

LIMITATION OF WARRANTY

This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or
misuse of any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from
battery leakage, or problems arising from normal wear or failure to follow instructions.

THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY
IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES 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 224 Programmable Current Source

Instruction Manual

Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

Fifth Printing, December 2001

Document Number: 224-901-01 Rev. E

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. A good safety practice is to expect

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

Operators of this product must be protected from electric shock at
all times. The responsible body must ensure that operators are 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, no conductive part of

the circuit may be exposed.

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

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. Always read the associated infor­mation 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

SPECIFICATIONS

ACCURACY

RANGE OUTPUT - 18z-280C SIZE ii=‘-18°C Et 28O-50°C

MAXIMUM +[%rdn + offset) STEP

IOOmA f101.00mA 0.1 % + 5OuA

1OmA I19.995mA 0.05% + l&A $A

ImA * 1.9995mA 0.05% + 1 pA 500nA 0.005% + 20nA

100 fi kl99.95 fi 0.05% + 100nA

IOfi kl9.995fi 0.05% + IOnA

OUTPUT RESISTANCE: Greater than lO’*g.
OUTPUT CAPACITANCE: Less than 2OpF.
LINE REGULATION: Less than 0.01% for AC power line changes within

specified limits.
VOLTAGE LIMIT: Bipolar, 1 to 105V in 1V programmable steps.
RESPONSE TIME: Less than 3ms to within 0.1% of programmed change.
TRANSIENT RECOVERY TIME: Less than 3ms to rated accuracy following

any change in compliance voltage.
NOISE

RANGE

IOOmA

IOfi to IOmA

GUARD OUTPUT: Maximum Load Capacitance: 10nF.

Maximum Load Current: Absolute total (Output + Guard) not to ex-

ceed 105mA.

Accuracy: * ImV (excluding output lead voltage drop).
INCREMENT/DECREMENT: Automatic, manual or trigger modes.

Range of Dwell Times: 50ms to 999.9s.

Accuracy of Dwell Times: f (0.05% + 20~s).
Step Size: Selected digit on a fixed range. Minimum step size 0.1% of

range.

Current Limit: Maximum is f (Full Scale) on range selected.
OUTPUT LOAD: Output load must be non-inductive
EXTERNAL TRIGGER: TTL-compatible EXTERNAL TRIGGER INPUT

and OUTPUT.

OUTPUT CONNECTIONS: Teflon@

Connector #30JRl21-I) for output; five way binding posts for GUARD

OUTPUT COMMON and CHASSIS; BNC (chassis isolated) connectors

for EXTERNAL TRIGGER INPUT and OUTPUT. All connections on

rear panel.

(1 YEAR)

5OU.A

50nA

NOISE

(p-p of range)

IOOppm
IOOppm

insulated triax connector (Specialty

TEMPERATURE

COEFFICIENT

f (%rda + offset)/OC

0.01 % + 2uA

0.005% + 20&A

0.005% + 2nA

5nA 0.005% + 20OpA

BANDWIDTH

0.1 Hz to 30kHz
O.lHz to 1OOHz

IEEE-488 BUS INTERFACE (ootion 22431

Multiline Commands: DCL, LLO, SDC, GET, GTL, UNT, UNL, SPE,

SPD.
Uniline Commands: IFC, REN, EOI, SRQ, ATN.
Interface Functions: SHl, AHI: T6, TEO, L4, LEO, SRl, RLI, PPO,

DCI, DTl, CO, El.
Output Connections: Amphenol or Cinch Series 87 IEEE and printed

circuit digital I/O port. All connections on rear panel.
Jnternal Programmable Parameters: Display Mode, Output,

(Prefix Data Format), EOI, SRQ (including mask for over V-limit),

Range, Terminator Character, Inputs (SOURCE, V-LIMIT, DWELL

TIME), Output Status.
Digital I/O Port: A separate I/O port consisting of four input and four

output lines as well as common (IEEE-4881 and +SVDC. Outputs will

drive one ‘ITL load. Inputs represent one TTL load. The 224 can be pro-

grammed to generate a “SRQ” upon any change in the four bit input

data. Mating connector supplied.

GENERAL

DISPLAY: 0.5” LED digits, 4%-digit signed mantissa, l-digit signed ex-

ponent.
OVER VOLTAGE LIMIT INDICATION: “V-LIMIT” LED will blink.
SELF TEST: Digital RAM,

upon power up.
WARMUP: 1 hour to rated accuracy.

POWER: 105125 or 210-250VAC (internal switch selected), 50 or 60H2,

60 watts maximum (80VA maximum). 90-105 or 180-210VAC operation

available.
COOLING: Internal fan for forced air cooling.

ENVIRONMENTAL LIMITS: Operating: O”-50°C; up to 35OC at 70%

non-condensing relative humidity. Storage: -25OC to 70°C.
DIMENSIONS, WEIGHT: 127mm high x 216mm wide x 359mm deep

(5-l/2” x &l/2” x 14-l/8”). Net weight 9 Ibs. 15 oz. (4.52kg).

MAXIMUM ALLOWABLE COMMON MODE VOLTAGE (OUTPUT

or OUTPUT COMMON to CHASSIS): 250V rms, DC to 60Hz.
ACCESSORIES SUPPLIED: Model 6011: Triaxial Test Lead (3 ft,)

ROM, and front panel LEDs

Specifications subject to change without notice.

TABLE OF CONTENTS

Para. Title Page

SECTION 1 — GENERAL INFORMATION

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 Unpacking and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.7 Repacking for Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.8 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.9 Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

SECTION 2 — OPERATION

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

2.2 Preparation for Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2.1 Correct Line Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2.2 Power Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2.3 Warm Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3 Operating lnstructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3.1 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3.2 Front Panel Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3.3 Rear Panel Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3.4 Output Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.3.5 Inductive Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.3.6 Response Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.3.7 General Operating Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.3.8 Front Panel Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2.3.9 Examples of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2.4 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2.4.1 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2.4.2 Resistivity Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2.4.3 Diode Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

2.4.4 Low Resistance “Lindeck” Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

2.5 Detailed Front Panel Controls Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

2.6 Detailed Rear Panel Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-l 5

SECTION 3 — PERFORMANCE VERIFICATION

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

3.2 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.3 Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.4 Initial Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.5 Performance Verification Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.5.1 100mA to 1mA Range Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.5.2 100µA and 10µA Range Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

SECTION 4 — THEORY OF OPERATION

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

4.2 Block Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.3 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.4 Analog Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.5 Digital Board (Microcomputer). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

i

TABLE OF CONTENTS CONT.

Para.

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.7.1

5.7.2

5.7.3

5.7.4

5.8

5.8.1

6.1

6.2

6.3

6.4

6.5

Title

SECTION 5-MAINTENANCE

Introduction
FuseReplacement
LineVoltageSelection

Disassembly......................................................~

FanFilterMaintenance
Special Handling of Static Sensitive Devices

Calibration ...................................................................................

RecommendedTestEquipment
Environmental Conditions.

Warmup.. ................................................................................

Calibration Adjustments

Troubleshooting ..............................................................................

DigitalSelfTest .............................................................................

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

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

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

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

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

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

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

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

SECTION 6-REPLACEABLE PARTS

Introduction

PartsList

Orderinglnformation

FactoryService..

Schematic Diagrams and Component Location Drawings

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

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

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

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

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

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

Page

5-l
5-l
5-1
5-2
5-2
52
5-4
5-4
5-4
5-4

5-4
5-5

5-5

6-l
6-l
6-l
6-l
6-1

ii

LIST OF ILLUSTRATIONS

Figure Title Page

2-1 Model 224 Front and Rear Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2-2 Output Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2-3 Limiting Inductive Reaction Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2-4 Response Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2-5 External Input and Output Trigger Pulse Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2-6 External Trigger Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

2-7 Unguarded Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

2-8 Guarded Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

2-9 Connections as a Current Sink with a Resistive Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2-10 Model 224 Recommended Operating Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2-11 Resistivity Measurement Using the Model 224 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

2-12 Diode Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

2-13 Diode Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

2-14 Low Resistance Measurement Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

3-1 100mA to 1mA Range Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

4-1 Analog Circuitry Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-2 Digital Circuitry Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4-3 Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

5-1 Model 224 Exploded View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5-2 Calibration Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5-3 Memory Chip Number Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

6-1 Fan Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6-2 Display Board, Component Location Drawing, Dwg. No. 220-110 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

6-3 Mother Board, Component Location Drawing, Dwg. No. 220-100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13

6-4 Analog Board, Component Location Drawing, Dwg. No. 224-120 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17

6-5 Display Board, Schematic Diagram, Dwg. No. 220-116 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21

6-6 Mother Board, Schematic Diagram, Dwg. No. 220-106 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23

6-7 Analog Board, Schematic Diagram, Dwg. No. 224-126 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-27

iii

LIST OF TABLES

Table
2-l
2-2
2-3

$2
3-l
3-2
5-l
5-2

5-3

5-4

5-5
5-6
5-7
5-8
5-9
5-10
6-l
6-2
6-3
6-4

LineVoltageSetting ...........................................................................

Power Up Default Conditions.

Front PanelControls.. .........................................................................

RearPanel Description .........................................................................

Front PanelMessages ..........................................................................

RecommendedTestEquipment.....................................: ............................

100mAtolmAVerification .....................................................................

FuseReplacement,3AG Size ....................................................................

FuseReplacement,5mmSize ...................................................................

LineVoltageSelection .........................................................................

Model 224 Static Sensitive Devices

RecommendedTestEquipment ..................................................................

Model224Calibration ..........................................................................

PowerSupplyChecks ..........................................................................

Analog BoardChecks.. ........................................................................

DigitalCircuitryChecks .........................................................................

Display Board Checks.. ........................................................................

Index of Model 224 Schematics and Component Layouts.

MotherBoard,PartsList ........................................................................

DisplayBoard,PartsList ........................................................................

AnalogBoard,PartsList ........................................................................

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

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

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

2-l
2-2
2-3
2-4
2-8
3-l
3-l
5-l
5-l
5-1
5-4
5-4
5-5
5-6
5-7

5-8

;:y

6-3
6-5
6-7

iv

SECTION 1

GENERAL INFORMATION

1.1 INTRODUCTION The Model 224 is a programmable current source with full

range current output of 20,uA to 101 mA. The smallest step of
output current is 5nA. The Model 224 has a selectable
voltage compliance of up to 105V in IV increments. The
value of output current can be modified in two ways: manual­ly or automatically. The automatically modified current value
is incremented or decremented by the programmed rate. The
time button allows the modification of the programmed auto
increment/decrement rate. The control of the current value
modification can be activated by an external trigger pulse ap­plied to the EXTERNAL TRIGGER INPUT. At the completion
of the current value modification (each digit) the Model 224
outputs a pulse that has the specifications shown in Figure
2-5. This pulse can be used to trigger another instrument

(printer, DMM, controller, etc.1 to start its programmed task.

With the Model 2243 IEEE-488 interface option installed, the

Model 224 can be used with any measurement system that

uses ?he IEEE-488 bus. For detailed operating instructions of
the Model 2243 IEEE-488 interface option, refer to the Model
2243 Instruction Manual

1.2 FEATURES

The Model 224 has several convenient and easy to use
features some of which are listed below.

@Selectable voltage compliance allows the user to select the

required voltage compliance.

04% digit display with appropriate exponent and decimal

point.

@The output current value can be modified either manually or

automatically.

*OPERATE button that places the display value of current at

the output connector on the rear panel. When not in operate
the Model 224’s output is set at O.OOO-6A while the display
remains the same.

@Data keys that allow the entry of numerical data onto the

display.

*External trigger input that when activated by the appropriate

signal instructs the Model 224 to increment or decrement
the displayed value of output current.

l

External trigger output places an output pulse at the external

trigger output connector upon completion of the increment

or decrement of the displayed current value.

@Guard terminal that allows guarded applications to be com-

pleted.

l

Selectable auto rate (TIME) of 50msec to 999.9sec.

aCANCEL button that momentarily blanks the display and

terminates the data modifying operation.

*I-LIMIT function that limits the output current between the

user programmed HI and LO current limits.

@IEEE-488 interface option allows the Model 224 to be incor-

porated into any system that uses programmed control
through the IEEE-488 bus.

1.3 WARRANTY INFORnhATlON

Warranty information is provided on the inside front cover of
this manual. If there is a need to exercise the warranty, con­tact the Keithley representative in your area to determine the

proper action to be taken, Keithley Instruments maintains

complete repair and calibration facilities in the United States,

United Kingdom and Europe. Information concerning the ap­plication, operation or service of your instrument should be
directed to the applications engineer in your area. Refer to the
inside front cover for address locations.

1.4 MANUAL ADDENDA

Improvements or changes to this manual will be explained on
an addendum sheet included with this manual.

1.5 SAFETY SYMBOLS AND TERMS

Safety symbols used throughout this manual are as follows:
The symbol ! A on the instrument denotes that the user

should refer to the operating instructions.
The symbol

voltage may be present on the output terminals.
The WARNING used in this manual explains dangers that

could result in personal injury or death.
The CAUTION used in this manual explains hazards that

could damage the instrument.

1.6 UNPACKING AND INSPECTION

The Model 224 is inspected both mechanically and electrically

before shipment. Upon receiving the Model 224 unpack all

items from the shipping container and check for any obvious

signs of damage that may have occurred during transit.

Report any damage to the shipping agent. Retain and use the

original packaging materials if reshipment is necessary. The

following items are shipped with all Model 224 orders:

Model 224 Programmable Current Source

Model 224 Instruction Manual

Model 6011 Triaxial Test Lead Set
Optional accessories as ordered.

If an additional instruction manual is required, order the
manual package (Keithley Part Number 224-901-00). The
manual package includes an instruction manual and all perti­nent addenda.

on the instrument denotes that high

AM

l-l

1.7 REPACKING FOR SHIPMENT

The Model 224 should be packed in its original carton. Before

packing, wrap the instrument in plastic. After it is placed in

the box, surround the instrument with Styrofoam packaging

material.
If the Model 224 is to be returned to Keithley Instruments for

calibration or repair include the following:
ATTENTION REPAIR DEPARTMENT on the address label.

Warranty status of the instrument.
Completed service form.

dard IEEE-488-1978 protocol. Additionally, the Model 2243
incorporates a separate digital I/O port that may be used to
interface the Model 224 to other digital instrumentation.

Model 6011 Triax Input Cable-The Model 6011 is a three
foot (1 meter) low noise triax cable terminated with alligator
clips at one end and a Teflon*

insulated triax connector at

the other end.
Model 6147 Triax to BlilC Adapter-The Model 6147 Triax to

BNC Adapter allows the Model 224 to be used with all
Keithley accessories and cables that require BNC connec­tions.

1.6 SPECIFICATIONS For Model 224 specifications, refer to the specifications that

precede this section.

1.9 ACCESSORIES

The following accessories are available from Keithley In-

struments to enhance the capabilities of the Model 224 Pro­grammable Current Source.

Model 1019A Universal Rack Mounting Kit-The Model
1019A Universal Rack Mounting Kit can accomodate one or
two Model 224’s. The dimensions are 133mm x 483mm
(5%in. x 19in.I.

Model 1019s is a slide type universal rack mounting kit. The
kit will accomodate up to two half rack size instruments (e.g.
Model 224) in a standard 5%” X 19” rack.

Model 2243 IEEE-488 Interface-The Model 2243 is an op­tional IEEE-488 interface for the Model 224 Programmable
Current Source. This interface adds extra versatility to the
Model 224 by allowing the transmission of data and com­mands over IEEE-488 bus. The interface provides all the logic
necessary to interface the Model 224 to the bus using stan-

Model 6167 Guarded Adapter-The Model 6167 Guarded
Adapter reduces effective cable capacity by driving the inner
shield of a triaxial cable at guard potential.

Model 7008-3 IEEE-488 Cable-The Model 7008-3 is a three
foot (1 meter) IEEE-488 cable. The cable has 24 stranded wire
conductors and is terminated with IEEE-488 standard con­nectors.

Model 7008-6 IEEE-488 Cable-The Model 7008-6 is a six
foot (2 meter) IEEE-488 cable. The cable has 24 stranded wire
conductors and is terminated with IEEE-488 standard con­nectors.

Model 7010 Cable Adapter-The Model 7010 is an IEEE-488

cable adapter. The adapter extends the IEEE-488 connector
by one connector width for easy access connections.

Model 7051-2-The Model 7051-2 is a BNC to BNC shielded

cable that is 2 feet long. This cable is especially useful when

utilizing the external input and output trigger connectors.

Model 7051-5-The Model 7051-5 is a BNC to BNC shielded

cable that is 5 feet long. This cable is especially useful when

utilizing the external input and output connectors.

1-2

SECTION 2

OPERATION

2.1 INTRODUCTION This section contains operating instructions for the Model

224 Programmable Current Source. The operating instruc­tions are divided into several categories including: prepara-

tion for use, operation, applications and detailed front and
rear panel descriptions.

For simple “getting started” information refer to paragraph

2.3.7 General Operating Procedure.
For front and rear panel illustrations of the Model 224 refer to

Figure 2-1.

2.2 PREPARATION FOR USE

2.2.1 Correct Line Voltage
Connect the Model 224 to a properly grounded power recep-

tacle. Refer to Table 2-l for the range of line voltage that the
Model 224 can operate on. For fuse replacement or line
voltage selection refer to Section 5 Maintenance.

WARNING
Ground the instrument through a properly earth
grounded receptacle before operation. Failure to
ground the instrument can result in severe per­sonal injury or death in the event of a short cir­cuit or malfunction.

Table 2-l. Line Voltage Setting

A. This is a display test. The operator can note inoperative

display segments by comparing the Model 224’s display
with the above figure.

B. In addition, the pushbutton and the TALK, LISTEN and

REMOTE indicators will light. All indicators will light

simultaneously if operating correctly.

2. After the display test is complete the Model 224 displays
the software revision level for approximately one second.
The following is an example of software revision level B

2.2.

Example:

3. If the Model 2243 IEEE interface is installed, the Model 224
displays the primary address for approximately one sec­cond. The primary address of the Model 2243 is factory
set at 19. If the Model 2243 is not installed in the Model

224, the power up sequence skips this step and goes on to

step 4.

4. At this point the Model 224 reverts to the default condi-

tions listed in Table 2-2.

2.2.3 Warm Up
To achieve rated accuracy the Model 224 requires one hour

for warm up.

2.3 OPERATING INSTRUCTIONS

2.3.1 Environmental Conditions
Operation of the Model 224 should be at an ambient

temperature within the range of O°C to 50°C, up to 35OC at

70% noncondensing relative humidity. Environmental condi-

tions for storage are from -25OC to 7OOC.

/---KF-j

For instruments equipped with low voltage

transformer TR-187.

2.2.2 Power Up
After the Model 224 is connected to a properly grounded

power source it can be powered up. When the instrument is
turned on it goes through a power up sequence that is out­lined as follows:

1. Immediately after turning on the Model 224 via the power
switch, the display will indicate the following for several
seconds.

2.3.2 Front Panel Controls
Model 224 front panel controls are listed in Table 2-3. Their

operation and function are briefly described in the table. For
detailed information concerning the Model 224 front panel
refer to paragraph 2.5 and Figure 2-1.

2.3.3 Rear Panel Description
The rear panel of the Model 224 has several terminals and

connectors. These are listed and described in Table 2-4. For
detailed information concerning the rear panel refer to
paragraph 2.6 and Figure 2-1.

2-1

Table 2-2. Power Up Default Conditions

Function
Power

output

Default Condition

On
Standby (OPERATE LED off). Programmed to
o.ooo-6A.

Auto
Trig
Source
V-limit

l-limit

Set to inactive (AUTO LED is off).
Set to inactive (TRIG LED is off).
Active (SOURCE LED is on).
Set to 3V.
HI Limit set to 0.000.
LO Limit set to 0.000.

Time Set to 50msec (50.00-3).

Digit
INCR

Set to inactive.
Set to inactive (INCR LED is off).

DECR Set to inactive (DECR LED is off).
Cancel
Enter
Exponent
Talk
Listen
Remote
Display

Set to inactive.
Not affected by power up.
Not affected by power up.
Talk function is disabled (TALK LED is off).
Listen function is disabled (LISTEN LED is off).
Remote function is disabled (REMOTE LED is off).

The 4% digit display is set to

2-2

Table 2-3. Front Panel Controls

Control

POWER ON/OFF

OPERATE

SOURCE

V-LIMIT

I-LIMIT

TIME

DIGIT

INCR

DECR

CANCEL
ENTER

EXPONENT
DATA
AUTO

TRIG

Description

Turns the instrument on or off.
When activated (LED on), the Model 224 outputs the displayed value of current.
When deactivated (LED off), the Model 224 is set to standby (O.OOO-6A is present
at the output).
When activated (LED on), the source data function is selected and displayed.
When deactivated (LED off), the source data is not displayed.
When activated (LED on), the voltage compliance is displayed. When deactivated
(LED off), the voltage compliance is not displayed.
I-LIMIT button selects the window of output current limit. Default value is

+ .OOOO-OA. When activated (LED on), the current (I) limit is displayed. The HI limit

is displayed first. When the l-limit button is pressed a second time the LO limit is
displayed. When deactivated (LED off), the l-limit is not displayed. This function
is used only in the auto mode.
When activated (LED on), the time function for the auto INCRIDECR is
displayed for inspection or modification.
Pressing the DIGIT button selects a display digit (c segment is flashing) for
alteration. Pressing the button while in the digit function selects the next digit
on the right for alteration. The DIGIT button wraps the modify digit around to the
most significant digit on the display if the DIGIT button is pressed when the cur­sor is on the next to least significant digit.
In the manual mode, each time the button is pressed the selected digit is in-

cremented by one count. In the auto mode, the selected digit is incremented and
therefore, the source value, automatically at the programmed time rate, When the
programmed HI limit is reached the error message is displayed and the display re­mains at the HI limit. This function has the mathematical capability of carry. The
least significant digit does not increment.

In the manual mode, each time the button is pressed the selected digit is
decremented by one count. In the auto mode, the selected digit is decremented

and therefore the source value, automatically at the programmed time rate. When
the programmed Ld limit is reached the error message is displayed and the display
remains at the LO limit. This function has the mathematical capability.
of borrow. The least significant digit does not decrement.
When activated, the CANCEL button momentarily blanks the display and ter­minates the data modifying operation.
The ENTER button loads the displayed data into the Model 224.
The EXPONENT allows entry of exponent data onto the display.
The data group of buttons allows the entry of numerical data onto the display.
When activated (LED on), the AUTO button selects the auto function for

INCR/DECR of the source data.
When activated (LED on), an external trigger pulse via the rear panel triggers
the instrument to increment or decrement the display digit. When deactivated
(LED off), the trigger function is disabled.

2-3

Table 2-4. Rear Panel Description

Connections

OUTPUT
GUARD

Description

The output connector is a Teflon@

insulated female triax connector.
The GUARD terminal provides a low impedance voltage source that is
equal to the output compliance voltage. The GUARD terminal is useful
in reducing leakage currents.

OUTPUT COMMON The OUTPUT COMMON connector provides easy access to the inner

shield of the OUTPUT connector.

CHASSIS GROUND

/ The chassis ground terminal provides easy access to chassis ground
I (earth ground).

EXTERNAL TRIGGER INPUT This input initiates the selected display digit to increment or decrement

(depending on which is enabled) upon receiving a TTL level negative

i transition with a minimum pulse width of lO@ec. Refer to Figure 2-5

for pulse specifications

EXTERNAL TRIGGER OUTPUT This output provides a negative going TTL level pulse of greater

! than lO@ec when the selected digit has been incremented or

decremented. Refer to Figure 2-5 for pulse specifications.

FUSE

This is the line power fuse and it is rated as listed in Table 5-l.

LINE RECEPTACLE This is the line power receptacle that mates with a three wire line cord.

Refer to Table 2-l for line power requirements.

“IEEE-488 INTERFACE This connector provides IEEE-488 bus connection to the Model 224.

The connector mates with the Model 7008-3 and 7008-6 IEEE cables.

*ADDRESS The address switches are used to set the primary address of the Model

2243 IEEE-488 interface. Factory set value is 19(10011 I.

*DIGITAL I/O The digital I/O port consists of four input and four output lines as well

as IEEE-488 common and +5VDC. The outputs will drive one TTL
load. The instrument can be programmed to generate an SRQ upon

any change in the four bit input data.

*These connectors are present only when the Model 2243 is installed in the Model 224.

For more information concerning these connectors refer to the Model 2243 Instruction Manual.

2-4

KEITHLEY

OUTPUT

OPERATE

POWER

ON
OFF

224 PROGRAMMABLE CURRENT SOURCE

CONTROL

AUTO TRIG

SOURCE

AMPS VOLTS AMPS SECONDS

DISPLAY MODIFY

DIGIT

INCR

DECR

TALK

LISTEN

REMOTE

DISPLAY

V - LIMIT I - LIMIT TIME

DATA ENTRY

CANCEL ENTER EXPONENT

IEEE-488 INTERFACE

SH1

AH1TETEOL4LEO

SR1

RL1

PP0

DC1COE1

DATA

7

8

9

4

5

6

1

2

3

0

1

A1

A2

A3

A4

+ / -

0

EXTERNAL

TRIGGER

INPUT

OUTPUT

FUSE

SLOWBLOW
3/4A 90-125V

3/8A 180/250V

Figure 2-1. Model 224 Front and Rear Panels

DIGITAL I/O

LINE RATING

50-60 Hz AC, 80 VA MAX

LINE VOLTAGE SELECTED

90-110V

105-125V

KEITHLEY

180-220V
210-250V

MADE IN

U.S.A.

2-5

(CENTER TRIAX CONDUCTOR)

OUTPUT HI

OUTPUT COMMON

(INNER TRIAX SHIELD)

CHASSIS COMMON

(OUTER TRIAX SHIELD)

Figure 2-2. Output Connector

250V

I

RMS MAX

f IOOV MAX

I

I

250V

RMS MAX

2.3.4 Output Connector
The output connector is a Teflon@

insulated triax connector

that is located on the rear panel. The maximum allowable

voltage potential between the HI and LO terminals is f 1OOV.
The maximum allowable common mode voltage between the
HI input terminal and the chassis common is 250Vrms DC to
60Hz. Refer to Figure 2-2.

2.3.5 Inductive Loads

In general, the output load connected to the Model 224
should be resistive. However, a small amount of inductance
can be tolerated if the inductive reaction voltage is limited to

less than 105V. Refer to Figure 2-3 for a suggested method
for limiting the inductive reaction voltage.

CAUTION

If the output load connected to the Model
224 is inductive, the inductive reaction
voltage MUST BE LIMITED to less than

105V. Otherwise instrument damage may

occur.

TWO BACK TO BACK

ZENER DIODES

~MOTOl?~CI~~~12OZ5lO~

LOAD

Figure 2-3. Limiting Inductive Reaction Voltage

2.3.6 Response Time
The response time is defined as the finite time difference be-

tween the actuation of the OUTPUT function and the output

reaching to within 0.1% of the programmed value. The ac­tuation of the OUTPUT function could be from an external
trigger pulse or by pressing the OPERATE button on the front
panel. The actual time difference is small, but in some ap­plications it may be helpful to know the response time. The
response time is depicted in Figure 2-4.

TIME -

TRIGGER

p=

OUTPUT

:-i-i 0.1% of final value
4

A :B!

,

Trigger Mode
“X’

EXTERNAL TRIGGER

INPUT

“A”

5.0mS
l.OmS

“B”

1 .OmS
1 .OmS

TOTAL

6.0mS

2.0mS

Figure 2-4. Response Time

2.3.7 General Operating Procedure
The Model 224 has several different operating parameters.

These parameters W-LIMIT, I-LIMIT, source value, time, etc)
are to be programmed into the Model 224 before actual
operation. The general procedure is designed to get the un-

familiar user familiar with the basic operation of the Model

224. Several programming examples follow the general pro­cedure. These programming examples show several various

ways to operate the Model 224.

1. Turn on the Model 224. Allow one hour warm up to

achieve rated accuracy.

2. Select the desired l-limits. HI and LO l-limits must be set
on the same range. (HI and LO are .0000-O at power up.)

A. Press I-LIMIT.

B. Press the numbers that correspond to the desired HI

limit. Maximum is lOl.OO-3A.
C. Press ENTER.
D. Press I-LIMIT.

E. Press the numbers that correspond to the desired LO

limit. Minimum is -101 .OO-3A.

F. Press ENTER.

I 3. Select the desired V-limit.

A. Press V-LIMIT.

-

2-6

B. Press the numbers that correspond to the desired

V-limit (Default is 3V.I

C. Press ENTER.

4. Select the desired source value. (Default is O.OOO-6A.)
There are two ways to select the source value: auto and
manual.

Manual Selection:
A. Press SOURCE.
B. Press the numbers (DATA keys) that correspond to the

desired source value. The source value ranges are from

-101 .OO-3A to O.OOO-6A to + 101.003A.
C. Press ENTER.
Auto Selection:
A. Press TIME. (Selects the output range mode. Default is

5Omsec. 1

B. Press the numbers that correspond to the desired in-

crement/decrement rate. The rate ranges from

50.00~3sec to 999.9sec.

C. Press ENTER.
D. Press SOURCE.
E. Press DIGIT the desired amount of times to select the

digit that is to be modified. The DIGIT button reverts
the modify digit to the most significant digit if the DIGIT
button is pressed when the cursor is presently on the
digit just before the least significant digit. The least

significant digit does not increment or decrement.
F. Press AUTO.
G. Press the INCR button to increment the displayed

value. Press DECR button to decrement the displayed

value.

NOTE

The INCR function has the mathematical carry

capability. The DECR function has the
mathematical borrow capability. The least
significant digit and the exponent digit do not in­crement or decrement. Use manual selection to
modify these digits.

H. Press AUTO to stop the display at the desired value.

5. Connect the appropriate load.

6. Press OPERATE to output the displayed value. The output
is programmed to O.OOO-6A when not in the operate mode
and the display remains the same.

NOTE

The output load must be noninductive. A small

amount of inductance in the load can be
tolerated if the inductive reaction voltage

(L $ 1 is limited to less than 105V. Refer to

paragraph 2.3.5.

2.3.8 Front Panel Messages
The Model 224 has several front panel messages. These

messages appear throughout the operation of the Model 224
and are listed in Table 2-5.

2.3.9 Examples of Operation
The following examples present several operating methods

and variations.

Example 1 Output 10mA: In this example the Model 224

will be programmed to output a source value of 10mA with a

compliance voltage of IOV.
Required Output: 10mA with 1OV compliance.
Use the following procedure to program the Model 224 to

output the preceding parameters.

1. Turn on the Model 224. Allow one hour for warm up.

2. Press SOURCE,l,O,EXPONENT,3,ENTER. (Programs a
source value of lOmA.

3. Press V-LIMIT,l,O,ENTER. (Programs V-LIMIT of 1OV).

4. Connect load.

5. Press OPERATE.
If the ENTER button is not pressed in the sequence indicated

the operation will not take place as intended. Upon the actua­tion of step 5 the Model 224 outputs 1OmA with a 1OV com­pliance limit. Press the SOURCE button to verify that the
1OmA was actually programmed into the Model 224. Press
the V-LIMIT button to verify that the 1OV limit was actually
programmed into the Model 224.

Example 2 Output POnA: In this example the Model 224 will
be programmed to output a source value of 20nA with a

compliance of 26V.

Required Output: 20nA with a 26V compliance limit.

Use the following procedure to program the Model 224 to
output the preceding parameters.

1. Turn on the Model 224 and allow one hour for warm up.

2. Press SOURCE,2,0,EXPONENT,S,ENTER. (Programs a
source value of 20nA.I

3. Press WLIMIT,2,6,ENTER. (Programs a 26V compliance

limit.)

4. Connect load.

5. Press OPERATE.

Example 3 Output 20nA: In this example the Model 224 will
be programmed to output a source value of 20nA with a
compliance voltage of 26V. This example is the same as Ex­ample 2 except for the method used to program the source
value.

Required Output: 20nA with a 26V compliance limit.
Use the following procedure to program the Model 224 to

output the preceding parameters.

1. Turn on the Model 224 and allow one hour for warm up.

2. Press SOURCE,O,.,0,2,EXPONENT,G,ENTER. (Programs
a source value of 20nA.I

2-7

3. Press VLIMIT,2,6,ENTER. (Programs a compliance
voltage of 26V.I

4. Connect load.

5. Press OPERATE.

Upon actuation of step 5 the Model 224 outputs 20nA with a
26V compliance limit. The end result of this example is the
same as the end result of Example 2. The only difference is

the method used to program the source value. Press the
SOURCE button to verify that 20nA was actually pro­grammed into the Model 224. Once the SOURCE button has
been activated the source value is displayed on the front

panel. Press the V-LIMIT button to verify that a 26V com­pliance limit was actually programmed into the Model 224.
Once the V-LIMIT button has been activated the V-limit is
displayed on the front panel.

Message

+H30fMd3 p

T-TITJ

m

p7c-j

b--

-7c-T-y

Err]

Example of the software revision level.

Factory set value of the IEEE-488 interface.

Error, one of the following conditions exists.
Selecting source value that is out of the range of the Model 224.

(Greater than 101 .OO-3A or less than -101 .OO-3A).
Selecting auto time of less than 50.00~3sec or greater than 999.9sec.
Selecting l-limit that is less than -101 .OO-3A or greater than 101 .OO-3A.

Table 2-5. Front Panel Messages

Description

ower up display segment test.

HI limit of the l-limit.

LO limit of the l-limit.

’

Selecting V-limit that is less than 1V or greater than 105V.
Selecting source value that is less than or greater than the programmed

limits. (Auto mode only)
Selected LO limit is higher than selected HI limit after auto is pressed.

When l-limit or full scale is reached in auto mode.

Example 4 Manual INCWDECR Operation: The value of
current can be modified either manually or automatically.
This example shows how to modify the current value manual-

IY.

Manual INCR/DECR Notes:

1. The DIGIT button must be pressed the desired number of
times to select the digit that is to be modified.

2. The term increment means that the increasing direction is
toward the positive current limit. The term decrement

‘means that the decreasing direction is toward the negative

current limit.

2-8

3. The displayed value is also the output value.

4. In this mode, the AUTO, INCR and DECR LED’s are
turned off.

5. The INCR function has the mathematical carry capability.

6. The DECR function has the mathematical borrow capabil­ity.

7. The least significant digit does not increment or decre­ment.

8. The exponent digit does not increment or decrement.

9. Only the source can be modified by INCR or DECR.

In this example we will choose the following parameters:

1. Output is 5pA.

2. Voltage compliance is 50V.
Use the following procedure to program the Model 224 to

output 5pA with a voltage compliance of 50V.

1. Turn on the Model 224 and allow one hour for warm up.

2. Press V-LIMIT,5,0,ENTER. (Programs a compliance limit

of 5OV.I

3. Press SOURCE. (Activates the source function.1

4. Press DIGIT,DIGIT. (Selects the digit that is to be

modified. Notice the C segment cursor is flashing.)

5. Press INCR,INCR,INCR,INCR,INCR,ENTER. (Modifies

the selected digit to numeral 5.1

6. Connect the load.

7. Press OUTPUT. (Outputs the displayed value of current to

the rear panel output connector.)

In this procedure it is easy to see how simple it is to program

the Model 224 to the exact value of current desired. The ex-

ample could also be used to decrement the value of current.

To do this change step 5 of the procedure to:

5. Press DECR,DECR,DECR,DECR,DECR,ENTER.
This causes the display to decrement the display to 0.000-6 if

it is done after the procedure was completed with the 5,uA
output. If this change is done before increment then the
display would go in the negative direction to -5.000-6A.

8. Decrementing a value lower or higher than the present
current range causes the ERR (error) message to be
displayed. The Model 224 will remain at the highest or
lowest value for that range.

9. Pressing the CANCEL button while in the auto mode will
abort the operation.

10. The least significant digit, or the exponent digit, does not
increment or decrement.

11. To auto step the source value from the HI l-limit to LO

l-limit without causing the error message to be displayed

and the auto step action to be stopped the l-limits (HI and

LO) must be set on the same range.
For example:
HI l-limit = + lOOE-3A on the lOOE-3A range

LO l-limit = - IOOE - 3A on the 100E - 3A range
These values are valid and allow the scan from HI to LO
or LO to HI to be completed.

Example of inappropriate values for the auto scan:

HI l-limit = + lOOE-3A on the IOOE-3A range
LO l-limit = + lOE-6A on the lOE-6A range
With these limits set, attempting to auto scan from the HI
to the LO limit causes the error message to be displayed,
scan operation to stop and the source value remains at
OO.OOE-3A. The same is true for scanning from the LO

limit to the HI limit. When the source value reaches

+ 19.00E-6A the error message is displayed, the scan

operation is stopped and the source value remains at

+ 19.00E - 6A.

Required Output: 33mA with a 1OOV compliance limit.

Example 5 Using the Auto Mode: In this example the
Model 224 will be programmed to output 33mA with a com­pliance limit of 1OOV using the auto mode. The auto mode
allows adjustment of the source value to be automatically in­cremented or decremented at a predetermined rate.

Auto Mode Notes:

1. The time (auto increment/decrement rate) must be pro­grammed to the desired value before using the auto
mode. Power up value of time is 50.00~3sec.

2. The SOURCE button must be activated before using the
auto mode.

3. The digit button cursor must be placed at the appropriate
digit on the display before the auto mode is activated.

4. The furthest digit on the left of the display is either a
blank or a “1”.

5. Incrementing a value higher than the HI limit causes the
Model 224 to display ERR, deactivate the auto mode and
remain at the HI l-limit.

6. Decrementing a value lower than the LO limit causes the
Model 224 to display ERR, deactivate the auto mode and
remain at the LO l-limit.

7. Pressing the AUTO button while the Model 224 is auto

incrementing/decrementing stops the auto increment/
decrement action. Pressing AUTO again resumes the
operation.

The auto rate will be programmed to one second. Use the
following procedure to program the Model 224 for the
preceding parameters.

1. Turn on the Model 224 and allow one hour for warm up.

2. Press I-LIMIT,l,O,O,EXPONENT,3,ENTER. (Programs HI
l-limit to lOOmA.

3. Press I-LIMIT, + /-,l,O,O,EXPONENT,B,ENTER. (Pro­grams the LO l-limit to -1OOmA.I

4. Press V-LIMIT,l,O,O,ENTER. (Programs a voltage com­pliance of 1OOV.I

5. Press TIME,l,U(PONENT,O,ENTER. (Programs the auto
rate to one second.)

6. Press SOURCE. (Selects the source function.1

7. Press DIGIT,DIGIT,DIGIT,AUTO,INCR. (Selects the

third digit on the left of the display, the auto function and
starts the automatic increment. When the display
reaches 3.3, press AUTO to stop the auto increment
function.)

8. Press CANCEL. (Deactivates the auto mode.1

9. Press EXPONENT,2,ENTER. (Programs the Model 224
for the 33mA value.)

10. Connect the Load.

11. Press OPERATE. (Outputs 33mA at the rear panel output
connector.)

2-9