Keithley 228A Service manual

Model 228AVoltage/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 228A Voltage/Current Source

Instruction Manual

All references to the Model 228 apply also to the Model 228A.

©1988, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

Fifth Printing, December 2000

Document Number: 228A-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

AS A CONSTANT VOLTAGE SOURCE

RANGE OUTPUT

MAXI- RESO- (1 YEAR)

MIJMLUnON

ACCURACY’ ACCURACY

184-28T

loOV rtlol.oV lC&nV ~t(O.l%+O.l V) k1.010 A lm.4 *(O.l%+ 4mA)

1OV ztlo.loV 1omV rt(O.l%+ 1omV) 3~10.10 A lomA rt(O.5%+ 4omA)

IV +l.OlOV ImV zt(O.l%+l.OmV) k10.10 A 1OmA ct(O.%%+ 4omA)

l

AboveO.4% range.

TEMPERATURE COEFFICIENT (OO-lS°C & 28”-50’0: +(O.l X apphc-

able accuracy specification)/°C.

NOISE: RANGE

OUTPUT RESISTANCE

1V Range: 100 PO.

lOOV

1ov

1V

0.1-3OOHz O.l-3OOkHz

5.omv p-p

2.OmV p-p 15mV p-p

0.7mV p-p

(max.):

1OOV Range: 1OmI-l. 1OV Range: 100 ~0

OUTPUT INDUCTANCE: lC+H typical.
SENSING: Rear panel switch selectable REMOTE and LOCAL sensing.
REMOTE SENSING: Corrects for up to OSV drop per output lead. Max-

imum 50 per sense lead for rated accuracy. Maximum 0.53 per sense lead

for rated output resistance.

COMPLIANCE (Source or Sink)

MAXI-

fO.lOlOA 100 pA f(0.1%+400 PAI

rt1.010 A 1mA k(O.l%+ 4mA)
+O.lOlOA 100 PA f(0.1%+400 pA)

3~1.010 A 1mA k(O.l%+ 4mA)
fO.lOlOA 100 pI rt(O.l%++400pA)

RESO (1YEAR)

MUM LUnON 180~2ST

0.1~20MHz

15mV p-p
15mV p-p

25mV p-p typ.

25mV

p-p typ.

25mV p-p typ.

AS A CONSTANT CURRENT SOURCE

RANGE OUTPUT (1 YR., 18”-28’C)

ACCURACY’ ACCURACY

MAXI- RESO

MlJTvI LUTION

10 A 3~10.10 A lOmA *(OS%+ lomA) 3zlO.lOV 1OmV +(O.l%+ 4OmV)

1 A +l.OlO A 1mA +(O.l%+l.OmA) flOl.OV 1CGmV ~t(O.l%+4OomV)

O.lA tO.lOlOA 100 pA +(0.1%+0.111~4)

(1 YEAR) MAXI- RE50- (1 YEAR)

IS”-28T

*Above 0.4% of range.

TEMPERATURE COEFFICIENT (O”-18°C 6~ 28”-50°C): +(O.l Xappiic-

able accuracy specification)/OC.

NOISE: RANGE

OUTPUT RESISTANCE (min.): 10A Range: 109. 1A Range: l&R. O.lA

Range: 109

10 A

1 A
O.lA

O.l-3OOHz

2.5 mA p-p 25mA p-p
5 mA P-P

OSmA p-p

OUTPUT CAPACITANCE: 0.2rF typical.
OUTPUT LOAD: Must be non-inductive.

COMPLIANCE (Source or Sink)

MUM LUTION

fl.OlOV

flO.lOV Khnv *(o.l%+ 4omV)
fl.OlOV

flOl.OV
*10.1ov

*1.01ov 1mV *(O.l%+ 4mV)

1mv f(o.l%+ 4mV)

1mv *(o.l%+ 4mV)

1WmV

1Omv zt(O.l%b 4omV)

la=28x

rt(O.l%+4OOmV)

O.l-3OOkHz O.l-20MHz

P-P

S-l-IA P-P typ.
mnL4 P-P typ.

3mA P-P typ.

5nL4 P-P

2m.4

CURRENT MONITOR OUTPUT

SCALE FACTOR: 1V =i 100% of range.
ACCURACY: Same as constant current mode.
BANDWIDTH: 5kHz typical.
OUTPUT RESISTANCE: 1okR.

EXTERNAL MODULATION

INPUT RESISTANCE: &SKI .
SENSITIVITY: - 1OV increases magnitude of programmed output by

100% of full scale; + 1OV decreases magnitude of programmed output by

100% of full scale.
ACCURACY: 2% typical, dc to 6OHz.
MAXIMUM MODULATION: Modulation and programmed settin

not cause operation exceeding the range of zero to 101% of fui

should

‘i scale.

MODULATION FREQUENCY: 6OOHz bandwidth.

IEEE-488 BUS IMPLEMENTATIoN (IElZE-48&1978)

M;I.;IL;;; COMMANDS: DCL, LLO, SDC, GET, GTL, UNT, UNL,
UNILINE COMMANDS: IFC, REN, EOI, SRQ, ATN.

INTERFACE FUNCTIONS: SHl, AHl, Tb, TEtJ, L4, LEO, SRI, RLl, PPO,

DCl. DTl. CO. El.
PROGRAMMABLE PARAMETERS: Output (operate or standby), Range,

Voltage, Current, Trigger Mode, Sink, Modulation (Voltage or Current),

Display Mode, Output Prefix (data format on readback), SRQ Mask,

EOI, Terminator Characters, Status, Self Test, Memory Location (100

point memory), Dwell Time.

GENERAL

DISPLAY: Dual 3i/,-digit LED (0.5 in.) indicate programmed values in

Standby and output values in Operate.
READBACK ACCURACY: Same as output accuracy.
FRONT PANEL PROGRAMS: COPY, SINK, IEEE address, MOD V,

MOD I, TEST, RESET.

LOAD TRANSIENT RECOVERY TIME: With a resistive load the output

will recover 90% of any load changes within Ims after end of changes,

provided the changes do not cause transfer to another control mode.

STANDBY: Programs ourput to OV, OA without changing ranges or polarity.
LINE REGULATION: Less than 0.01% output change for ac power line

changes within specified limits.
PROGRAM MEMORY (battery backed

tings. Range of Dwell Times: lOms to 1000s. Accuracy of Dwell Times:
*(O.O5%+2ms).

BATTERY BACKUP: Rechargeable 3.6V nickel-cadmium. 1 month reten-

tion of data with unit turned off.

TRIGGER: IN and OUT ‘I-IL-compatible.

PROGRAMMING RESPONSE TIME: Less than 1OOms on fixed range

(typical).

MAXIMUM

chassis): 1OOV dc.

COMMON

MODE VOLTAGE (output or output

OUTPUT CONNECTIONS: Quick disconnect card with screw terminals

for output, modulation, current monitor, and external sense. BNC

(chassis isolated) connectors for TRIGGER IN/OUT.

SELF TEST: Analog and digital circuits tested at power-on. Power sup-

plies, temperatures, and output continuously monitored.

WARMUP: 10 minutes to rated accuracy.
POWER: 10.5-125 or 210-250 V ac (internally switch selectable), 50 or

60Hz, 500 VA maximum.

COOLING: Internal fan for forced air cooling.
ENVIRONMENT:

RH below 35°C.

DIMENSIONS, WEIGHT: 133mm high X 435mm wide X 448mm deep

(51/r in. X 17% in. X 1736 in.). Net weight 10.9kg (24 Ibs.).

ACCESSORIES AVAILABLE:

Model 2288:

Model 2289:

Model 7008-3: IEEE-488 Cable (3 ft.)

Model 7008-6: IEEE-488 Cable (6 ft.)

Operating: 0”

Storage: -25“ to 70°C.

Fixed Rack Mounting Kit
Slide Rack Mounting Kit

up):

Stores up to 100 output set-

common to

to 50°C. less than 80% non-condensing

TABLE OF CONTENTS

SECTION 1 — GENERAL INFORMATION

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.3 Using the Instruction Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.4 Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.5 Manual Addenda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.6 Safety Symbols and Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.7 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.8 Unpacking and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.9 Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

SECTION 2 — SAFETY AND GENERAL OPERATION

2.1 Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 General Operating Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.3 General Operation Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.4 Standby Mode Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

SECTION 3 — FRONT PANEL OPERATION

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

3.2 Preparation For Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2.1 Line Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2.2 Fuse Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.3 Power Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.4 Warm Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3.5 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3.6 Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3.7 Front Panel Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3.8 Rear Panel Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

3.9 Quick Disconnect Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16

3.10 Remote/Local Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3.11 Front Panel Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3.11.1 Program 1 Copy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3.11.2 Program 2 Sink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19

3.11.3 Program 3 IEEE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19

3.11.4 Program 4 MOD V (Modulate Output Voltage) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20

3.11.5 Program 5 MOD I (Modulate Output Current) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20

3.11.6 Program 6 Test (Diagnostic Self Test) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

3.11.7 Program 9 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

3.12 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

3.12.1 Load Line Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-22

3.12.2 Resistive Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24

3.12.3 Reactive Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24

3.12.4 Inductive Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24

3.12.5 Capacitance Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3.12.6 Load Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3.12.7 Charging and Discharging Electrochemical Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27

3.13 Operating Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27

3.13.1 Example 1: 10.00V, 10.00A Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27

3.13.2 Example 2: 100V, 1A Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-29

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3.13.3 Example 3: 1V, 10A, 1sec; 10V, 10A 2sec; and 100V, 1A, 3sec Output in the

Continuous Memory Control Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-30

3.13.4 Example 4: Model 228 as an Active Load (Current Sink) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33

3.13.5 Example 5: Operation as Source and Sink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-35

3.13.6 Example 6: Fabricating Output Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-35

3.13.7 Example 7: Using the External Trigger (Input and Output) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36

3.13.8 Example 8: Floating Operation (Extended Compliance) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

3.14 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

3.14.1 Low Resistance Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

3.14.2 Battery Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-38

3.14.3 External Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3.14.4 Ramp Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3.14.5 Power Semiconductor Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

3.14.6 Compensation for Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-43

SECTION 4 — IEEE BUS OPERATION

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

4.1.1 Software Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1.2 Interface BASIC Programming Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1.3 Interface Function Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.1.4 Model 228 Interface Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.2 IEEE-488 Bus Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.2.1 Bus Management Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.2.2 Handshake Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.2.3 Data Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.3 System Set Up Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.4 Bus Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.4.1 Uniline Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.4.2 Universal Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.4.3 Addressed Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4.5 Device-Dependent Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4.5.1 Display Mode (D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

4.5.2 Memory Control Mode (P) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

4.5.3 Prefix (G) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

4.5.4 SRQ Response Mode (M) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19

4.5.5 Trigger Modes (T) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21

4.5.6 Programmable Terminator (Y) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21

4.5.7 Inputs (I, V, W and B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22

4.5.8 Function (F) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24

4.5.9 Range (R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24

4.5.10 External Modulation (A, C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26

4.5.11 Sink Mode (S) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26

4.5.12 Status Word (U) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26

4.5.13 Self Test (J) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28

4.5.14 EOI and Bus Hold-Off Modes (K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28

4.6 Front Panel Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-29

4.6.1 IDDC Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-30

4.6.2 IDDCO Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-30

4.6.3 No Remote Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-30

4.7 Response Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-31

SECTION 5 — PERFORMANCE VERIFICATION

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

5.2 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

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5.3 Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.4 Initial Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.5 Performance Verification Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.5.1 Voltage Mode Verification (1V, 10V and 100V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.5.2 Output Current Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

SECTION 6 — THEORY OF OPERATION

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2.1 Linear Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2.2 Switching Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6.3 Analog Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6.4 Digital Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6.5 Display Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

SECTION 7 — MAINTENANCE

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.2 Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.3 Line Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.4 Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7.4.1 Removing the Top and Bottom Covers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7.4.2 Remove the Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7.4.3 Digital Board, Mother Board and Power Supply Board Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7.4.4 Heat Sink Assembly and Fan Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7.5 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13

7.5.1 Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13

7.5.2 Digital Self Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13

7.5.3 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13

7.6 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.6.1 Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.6.2 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.6.3 Warm Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.6.4 Top Cover Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.6.5 +15V Supply Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17

7.6.6 Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17

7.6.7 +1V Reference Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17

7.6.8 Current Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17

7.7 Special Handling of Static Sensitive Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18

SECTION 8 — REPLACEABLE PARTS

8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.2 Replaceable Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.3 Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.4 Factory Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.5 Schematic Diagrams and Component Location Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

iii

iv

LIST OF ILLUSTRATIONS

3-1 Graph of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3-2 Model 228 Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3-3 Model 228 Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3-4 Quick Disconnect Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

3-5 Quick Disconnect Board Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

3-6 Graph of Operation for External Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20

3-7 Load Line (Positive Line Shown) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23

3-8 Resistive Load Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24

3-9 Limiting Inductive Reaction Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25

3-10 Inductive Load Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3-11 Capacitive Load Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3-12 Model 228 Recommended Operating Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-34

3-13 Model 228 as an Active Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-34

3-14 Output Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36

3-15 External Trigger Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

3-16 Connection for Floating Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

3-17 Low Resistance Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-38

3-18 Battery Life Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3-19 Data Logging Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3-20 Power Supply Protection Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3-21 Connections for External Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3-22 Typical Modulated Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3-23 Ramp Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3-24 Ramp Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

3-25 Power Transistor Test Set up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

3-26 Power Transistor I

3-27 Automated Test Set Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42

3-28 FET Test Set Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42

3-29 FET Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42

3-30 Automated Test Set Up for FETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-43

/V

Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42

C

CE

4-1 Bus Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4-2 Handshake Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4-3 Contact Assignments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4-4 Typical Bus Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4-5 Format of SRQ Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19

4-6 Format of SRQ Status Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19

4-7 Error Status Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27

4-8 Status Word Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27

4-9 IEEE Display Error Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-29

5-1 Output Voltage Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5-2 Output Current Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

6-1 Model 228 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6-2 Analog Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

6-3 A/D Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

6-4 Voltage Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

6-5 Current Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

6-6 Output Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

6-7 Display and Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

v

7-1 Top and Bottom Cover Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7-2A Rear Panel Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

7-2B Wiring Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

7-3 Model 228 Exploded View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7-4 Detail of Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9

7-5 Heat Sink Assembly (Exploded View) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11

7-6 Calibration Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17

8-1 Mother Board, Component Location Drawing, Dwg. No 228-100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6

8-2 Mother Board, Schematic Diagram, Dwg. No. 228-106 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

8-3 Display Board, Component Location Drawing, Dwg. No. 228-110 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15

8-4 Display Board, Schematic Diagram, Dwg. No. 228-116 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17

8-5 Power Supply Board, Component Location Drawing, Dwg. No. 228-150 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-22

8-6 Power Supply Board, Schematic Diagram, Dwg. No. 228-156 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23

8-7 Digital Board, Component Location Drawing, Dwg. No. 228-140 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27

8-8 Digital Board, Schematic Diagram, Dwg. No. 228-146 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29

vi

LIST OF TABLES

3-1 Line Voltage Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3-2 Front Panel Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3-3 Rear Panel Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3-4 Front Panel Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3-5 Front Panel Messages and Prompts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3-6 Error Messages (Either Display) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3-7 Power up Default Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

3-8 Summary of Front Panel Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3-9 Maximum Inductive Reaction Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

4-1 HP-85 and IBM BASIC Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4-2 Model 228 Interface Function Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-3 IEEE Command Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-4 IEEE Contact Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4-5 DCL and SDC Default Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4-6 Device-Dependent Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

4-7 Device-Dependent Commands Not Available to the Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

4-8 Hierarchy of Command Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

4-9 SRQ Mask Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19

4-10 Input Command Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22

4-11 Range Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24

4-12 Hold Off Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-29

4-13 Response Time (Voltage Changes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-31

4-14 Response Times (Other Control Changes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-31

5-1 Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5-2 Output Voltage Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5-3 Output Current Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

7-1 Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7-2 Low Voltage Operation Part Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7-3 Line Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7-4 Recommended Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13

7-5 Power Supply Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

7-6 Analog Circuitry Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

7-7 Digital Circuitry Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15

7-8 Display Board Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7-9 Recommended Calibration Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7-10 Model 228 Static Sensitive Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18

8-1 Mother Board Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2

8-2 Display Board Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13

8-3 Power Supply Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-19

8-4 Digital Board Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-25

8-5 Mechanical Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-33

vii

viii

SECTION I

GENERAL INFORMATION

1.1 INTRODUCTION

The Model 228 Voltage/Current Source is both a constant
voltage and constant current source with front panel and
IEEE operation. The Model 228 can be used as a constant
voltage source or a constant current source. It has four
quadrant operation. This means that the voltage or current
sources can operate as a source or a sink in either positive or
negative polarities. Full power capability of 1OOW may be ob­tained in any quadrant.

Parameter entry is done in one of two ways. Either using the
data keypad to enter the desired value into the display or us­ing the display modify function. The display modify function
allows the user to modify either display by selecting a digit of
the display and incrementing or decrementing that digit with
the appropriate keys. With the carry, borrow and autorepeat
capability, front panel operation is flexible and easy to pro­gram. The user selects the range with the decimal point.

The Model 228 has a 100 point data memory that allows the
user to store up to 100 unique values of current, voltage and
dwell time for future use. Once a particular level is stored in
the data memory, the user need not reprogram that level.

The output terminals are located on a quick disconnect board

that inserts into the rear panel of the mainframe. The output
is disconnected from the quick disconnect board when it is
removed from the mainframe.

1.2 FEATURES

The Model 228 includes the following features:

l Six ranges that allow a wide variety of voltage/current

values.

l Seven front panel programs. The programs include:

Program 1 Copy for duplicating memory location informa-

tion.
Program 2 Sink for sink only operation.
Program 3 IEEE for changing IEEE primary address.
Program 4 MOD V for modulating output voltage.
Program 5 MOD 1 for modulating output current.
Program 6 Test for Model 228 self test.
Program 9 Reset for resetting the Model 228 to factory set
values. See paragraph 3.13.7

l Dual displays for easy reference of the instrument’s status.

The left display has two display modes (voltage and mem-

ory step). The right display also has two display modes

amps and seconds).

l Two methods of modifying the source or sink value: Data

entry from the data keypad, and increment or decrement of

displayed valued using the decade keys.

l 100 point data memory to store up to 100 unique values of

voltage, current and dwell time. Each location also includes:

sink mode status and voltage current modulation status.

All information stored in a memory location is battery
backed up. This means that if the instrument is powered
down, the stored information (voltage, current and dwell

time parameters) remains in a particular location until

changed by the user.

l OPERATE/STANDBY switch that places the output in

either the operate mode (displayed value is present at out­put) or in the standby mode (output is programmed to ap­proximately zero).

l Compliance status is easy to read on the front panel com-

pliance graph. The graph shows the user at a glance how the
Model 228 is operating (source or sink polarity and voltage

or current compliance).

l IEEE-488 bus operation is standard. This enables the Model

228 to be incorporated into a system that uses programmed

control over the IEEE-488 bus.

l Single step, single cycle and continuous memory modes

control the sequence between data points in the 100 point

data memory. The program mode may be controlled in one
of three ways; using the front panel START/STOP key, the

external trigger pulse or by commands over the IEEE-488
bus.

l Output terminals are located on the quick disconnect board

for optimum safety. The output terminals, the sense ter-

minals, current monitor terminals and the external modula-

tion terminals are also located on the quick disconnect
board. Several quick disconnect boards may be wired with
their own unique wiring ‘configuration. When one configur­ation is required, simply insert into the mainframe. In this
way, cumbersome rewiring of one board is avoided.

l Remote and Local Sensing. This allows the user to sense at

the output terminals or at the load or source. Remote sens-

ing compensates for the effects of the l*R lead drop by
maintaining regulation at the load instead of at the output
terminals of the Model 228.

l Four Q,uadrant Operation. This means that the voltage or

current outputs can operate as a source or a load in either
positive or negative polarities. The front panel compliance

graph shows the user where the Model 228 is operating

(source or sink).

1-l

l Output Modulation. This feature allows the output signal

to be modulated from an external AC signal source. Voltage

or current may be modulated.

l Bipolar Output. This means that the polarity of the output

may be reversed by using front panel controls instead of

reversing the wires.

l Most of the front panel keys autorepeat if held in.

1.5 MANUAL ADDENDA

Information concerning improvements or changes to the in­strument which occur after the printing of this manual may
be found on an addendum sheet included with this manual.
Be sure to review these changes before attempting to operate
the instrument.

1.3 USING THE INSTRUCTION MANUAL

This manual contains information necessary for operating,
programming and servicing the Model 228 Voltage/Current

Source and is divided into the following sections:

Section 2 contains safety instructions and a general

1.
operating procedure.

2.

Section 3 contains front and rear panel descriptions, a
general operating procedure and specific operating ex­amples showing how to use the Model

3.

Section 4 contains information pertaining to the IEEE-488
bus, including primary address selection, device­dependent command programming, bus connection and
several sample programs.

4.

Section s includes a procedure to verify the performance
of the Model

5.

Section 6 contains theory of operation with detailed

228.

schematics and block diagrams. This section facilitates
understanding of the individual circuits of the Model 228.

6.

Section 7 contains servicing information for the Model

228. Calibration, troubleshooting, line voltage selection,
fuse replacement and static sensitive device information is
contained in this section.

7.

Section 8 gives replaceable parts information.

228.

If an additional manual is required, order the manual package
(Keithley Part Number 228-901-00). The manual package in­cludes an instruction manual and all pertinent addenda.

SAFETY SYMBOLS AND TERMS

1.6

following safety symbols and terms are used in this

The
manual or found on the Model 228:

The symbol !

on the instrument indicates that the user

A

--

should refer to the operating instructions in this manual.
The symbol

on the instrument indicates that a lethal

w
potential may be present at the output terminals. Standard
safety practices should be observed when such potentials are
encountered.

The

WARNING

heading used in this manual explains dangers

that could result in personal injury or death.
The

CAUTION

heading used in this manual explains hazards

that could damage the instrument.

1.7 SPECIFICATIONS

1.4 WARRANTY INFORMATION

Warranty information may be found inside the front cover of
this manual. Should it become necessary to exercise the war­ranty, contact your nearest Keithley representative or the fac­tory to determine the course of action. Keithley Instruments
maintains service facilities in the United States, United
Kingdom and throughout Europe. Addresses of these facilities
may be found inside the front cover of this manual. Informa­tion concerning the application, operation or service of your
instrument may be directed to the application engineer at any
of these locations.

1-2

Detailed Model 228 specifications may be found immediately
preceding this section of the manual.

1.8 UNPACKING AND INSPECTION

The Model 228 Voltage/Current Source was carefully in­spected, both electrically and mechanically before shipment.
Upon receiving the Model 228, carefully unpack all items
from the shipping containers and check for any obvious signs
for physical damage that may have occurred during ship-

ment. Report any damage to the shipping agent immediately.
Retain the original packing materials in case reshipment
becomes necessary. The following items are included with
every Model 228 order:

Model 228 Voltage/Current Source
Model 228 Instruction Manual, Reference and Program In-

structions and the Instruction Label.
Quick Disconnect Board
Additional accessories as ordered.

With all of the terminals on the board, many configurations could
be wired. To avoid cumbersome and time consuming rewiring
for each configuration, several quick disconnect boards could be
wired for each unique configuration. One quick disconnect board
is supplied with each Mode1 228.

Model 2288 Fixed Rack Mount- The Model 2288 is a fixed or

stationary rack mounting kit that mounts the Model 228 in a
standard 19 inch rack.

1.9 ACCESSORIES

Model 2286 Quick Disconnect Board - The quick disconnect
board contains output, sense, external modulation and current
monitor terminals. The quick disconnect board inserts into the
rear panel of the Model 228 mainframe. When the board is in
place, the terminals are connected to the actual potentials (if in
the operate mode). Removing the board from the mainframe
disconnects the terminals from the output. This is a safety feature
designed so the user should not have to come into contact with
a dangerous potential.

Model 2289 Slide Rack Mount- The Model 2289 is a sliding

rack mount kit. It enables one Model 228 to be rack mounted
with the added feature of sliding the instrument for fast ac­cess.

Model 7008-3-The Model 7008-3 is a 1 meter (3 feet)

IEEE-488 cable. The cable has 24 stranded wire conductors
and is terminated on each end with standard IEEE-488 con­nectors.

Model 7008-6-The Model 7008-6 is a 2 meter (6 feet)

IEEE-488 cable. The cable has 24 stranded wire conductors
and is terminated on each end with standard IEEE-488 con­nectors.

l-3/14

SECTION 2

SAFETY AND GENERAL OPERATION

2.1 SAFETY PRECAUTIONS

Safety information such as warnings and cautions are located
throughout this manual. The information is placed in the
appropriate places in the manual where a hazard may exist.
The warnings refer to a potentially dangerous situation
where personal injury or even death may occur. The cautions
refer to a potentially hazardous situation where the instru­ment may be damaged. Take the time to read and most of all
understand these warnings and cautions.

The following safety information is provided as a general
safety practice before, during and after operation of the
Model 228.

1. Do not operate the instrument with the top cover and/or
bottom cover removed. Lethal potentials are present
throughout the mainframe. The covers must also be in
place to allow proper air flow through the instrument.
Proper air flow is required to cool the instrument during
operation. If proper cooling is impeded the instrument
may overheat.

2. Never assume the output is at a safe potential while the
AC line is connected.

3. The Model 228 is capable of producing several times its
current rating for short periods of time (msec). Keep this
in mind when choosing a load. Brief bursts of high cur­rent are still enough to damage other instrumentation
and cause serious injury.

4. Using the Model 228 to sink power from an external
source requires some precautions that are outlined as
follows:

A. A temporary loss of line voltage resets the Model 228

output to a high impedance state. Therefore, a user
supplied voltage limiting circuit may be required to
control the external source. A zener diode placed
across the output is recommended.

B. When the voltage polarity of an external source

opposes the programmed polarity of the Model 228,
voltage has priority.

where:
V

= Source Voltage (V

S

= Source Current (I

I

S

= Load Resistance

R

L

when:
V

+ V

S

228

R

L

is greater than the current setting of the
Model 228.

SOURCE

SOURCE

)

)

The standby mode programs the Model 228 for
approximately 0.0V, 0.0A.

V

+ V

= V

= V

S

S

+ 0

is greater than zero.

L

/R

up to the limits of the output

S

L

S

228

R

R

L

Therefore, I
fuse. The output fuse is factory rated at 20A. In some

circuit applications it may be necessary to limit the
current with a resistor or select a lower rated output
fuse. The output fuse must have a minimum voltage
rating of 250V.

C. When the voltage polarity of an external source

matches the programmed polarity of the Model 228,
current has priority.

when:
V

— I

R

S

is greater than the voltage setting of

S

L

Model 228.

D. After using the Model 228 to charge a storage ele-

ment, such as an electrochemical cell or capacitor,
NEVER change the polarity of the source to dis­charge the cell. Doing so will damage the Model 228.
ALWAYS allow the cell to completely discharge
before changing the source polarity to charge it in
the opposite direction. The cell can be safely dis­charged with the source set to 0V. See paragraph

3.12.7 for details.

5. Before operation, ground the instrument through a prop­erly earth grounded receptacle. Failure to ground the
instrument may result in severe injury or even death in
the event of a short circuit or malfunction.

6. After extensive use of the Model 228, set the instrument
to standby and allow it to cool down for a few minutes
before turning off the power to the instrument.

7. Never come into contact with the output connections
while the instrument is turned on.

8. Observe proper polarity when operating in the sink
mode. A reversed polarity may allow the instrument to
operate at a current limit of the output fuse.

9. Use cables for the output that have appropriate current
and insulation rating. For example, if 10V at l0A is to be
produced or dissipated then the cables must be rated for
that amount. Also, use insulated lugs for connections on
the quick disconnect board.

10. Do not leave the instrument unattended when it is in the
operate mode. Always place the instrument in standby
after the measurement or test is completed.

11. Always set up the test circuit while the power is turned
off. Do not come into contact with any part of the test cir­cuit while power is on.

2-1

2.2 GENERAL OPERATING PROCEDURE

This is a general operating procedure to familiarize the user
with front panel operation of the Model 228. There are sev­eral operating parameters involved with Model 228 opera­tion. These parameters are taken into account in this
procedure. Of course, every detail of Model 228 operation is
not covered in the general procedure. Section 3 includes sev­eral specific examples of Model 228 operation.

NOTE

Most of the front panel keys auto-repeat if held
in. Refer to the operation notes at the end of this
procedure.

1. Turn on the Model 228 and allow 10 minutes for warm­up.

NOTE

To achieve rated accuracy, run Program 6 imme­diately after the 10-minute warm-up period.

2. Select the desired memory location. There are two meth­ods for selecting memory locations. This procedure cov­ers both methods.

NOTE

The unit powers up to memory location 1. This
need not be changed if memory control is not
being used.

Method 1: Select Memory Location

A. Press the VOLTS/MEMORY STEP key if not in the

memory step display. The present memory location
is displayed on the left display.

B. Press the SELECT key to select the display to be

modified (left or right). The selected display is indi­cated by the flashing bright digit.

C. Press the left or right key (indicated by the left and

right arrows) to select the digit that is to be modified.
The selected digit is indicated by the flashing bright
digit.

D. Press the increment or decrement keys (indicated by

the up and down arrows) to modify the selected
digit for the desired memory location.

Method 2: Select Memory Location

A. Press the VOLTS/MEMORY key to select MEMORY

STEP. The present memory location is displayed on
the left display.

B. Press the SELECT key to select the left display. The

selected display is indicated by the flashing bright
digit.

C. Enter the desired memory location number using

the DATA keys.

D. Press ENTER.

3. Program the desired source. There are two methods for
programming the source. The source may be voltage or
current.

Method 1: Program the Source

A. Press either the VOLTS/MEMORY STEP key to dis-

play the source voltage on the left display, or the
AMPS/DWELL TIME key to display the source cur­rent on the right display.

B. Press the SELECT key to select the display to be

modified. The left display is for voltage and the right
display is for current. The selected display is indi­cated by the flashing bright digit.

C. Press the left or right key to select which digit is to

be modified. The selected digit is indicated by the
flashing bright digit.

D. Press the increment or decrement key to modify the

selected digit and source value. The output value is
updated continuously along with the display when
using the increment or decrement keys.

Method 2: Program the Source

A. Press the VOLTS/MEMORY STEP key to display the

source voltage, or the AMPS/DWELL TIME key to
display the source current.

B. Press the SELECT key to select the left display; the

left display for voltage or the right display for cur­rent. The selected display is indicated by the flashing
bright digit.

C. Enter the desired source value on the display using

the DATA key.

D. Press ENTER.

4. Program the desired dwell time. This may be done by
one of two methods.

Method 1: Program Dwell Time

A. Press the AMPS/DWELL TIME key if dwell time is

not displayed. The present dwell time is displayed
on the right display.

B. Press the SELECT key to select the left display. The

selected display is indicated by the flashing bright
digit.

C. Press the left or right key to select the digit to be

modified. The selected digit is indicated by the flash­ing bright digit.

D. Press the increment or decrement key (indicated by

the up and down arrows) to modify the selected
digit and dwell time. The value is updated continu­ously along with the display when using the incre­ment or decrement keys.

Method 2: Program Dwell Time

A. Press the AMPS/DWELL TIME key if not in the

dwell time mode. The present dwell time is dis­played on the right display.

B. Press the SELECT key to select the left display. The

selected digit is indicated by the flashing bright
digit.

C. Enter the desired dwell time using the DATA keys.

D. Press ENTER.

2-2

5. Select the desired memory control mode (single step, sin­gle cycle or continuous).

6. Connect appropriate load.

7. Select remote or local sensing (rear panel switch).

8. Program the instrument to the operate mode by pressing
the OPERATE/STANDBY key.

9. If applicable press the START/STOP key to start the
selected memory control mode.

Notes

1. Using the increment or decrement keys to either exceed
the maximum value for that range or change sign, briefly
displays an error message and the last key pressed is
ignored. Refer to Tables 3-4, 3-5, and 3-6 for front panel
messages.

2. Using the increment and decrement keys to adjust the
most significant digit does not change the range. The
range error message is displayed for about one second
and the instrument remains at the previous setting.

3. During the edit mode, if no activity has happened on the
front panel for approximately 20 seconds or if the
ENTER key is pressed, the edit mode is cancelled and the
display returns to normal intensity.

4. For the current function the output load must be, in gen­eral, non-inductive. A small amount of inductance in the
load can be tolerated if the inductive reactive voltage

di

L is limited to the maximum compliance voltage of the

-----­dt

range. Table 3-9 lists the maximum inductive reaction
voltage for each current range. Refer to paragraph 3.12.3.

5. Operation of the Model 228 as a power sink produces
heat. The Model 228 employs a fan for forced air cooling.
Do not block the airflow of the fan. The instrument may
overheat and go into the thermal shut down mode.

6. When using the DATA keypad to modify the displayed
data, the actual value is not entered until the ENTER but­ton is pressed.

7. In the operate mode (OPERATE LED on), the actual volt­age and current are monitored and displayed. For exam­ple, if 5V, 5A are programmed and the load is drawing

2.3A, then 5V, 2.3A is displayed.

8. All of the front panel keys (except PROGRAM,
CANCEL, OPERATE and LOCAL) autorepeat if held in.

9. In the immediate mode (which uses DECADE keys and
output is updated along with the display), the ENTER
key need not be pressed. After approximately 20 seconds
the Model 228 cancels the edit mode and returns to the
previous operating mode. The new data remains.

10. The STANDBY LED is of amber color to distinguish it
from the OPERATE LED which is red.

11. If the internal operating temperature reaches over 100˚C,
the Model 228 displays an error message as shown in
Tables 3-4, 3-5, and 3-6. At this point the instrument locks
up and displays the error message. The Model 228 must

be turned off and allowed to cool down before continu­ing operation.

12. The Model 228 when first turned on, goes through a
power up sequence that is described in Section 3.

13. The Model 228 has a bipolar output. This means that the
polarity of the output may be reversed without having to
reverse the output leads.

14. All of the information programmed into the memory
locations is battery backed up. This means that if the
instrument is powered down, the information pro­grammed in the memory locations is not lost. The infor­mation remains in the memory location until changed by
the user.

15. Tables 3-4, 3-5, and 3-6 contain a complete list of front
panel messages and their definition. Included are error
and instrument status messages.

16. The user selects the range with the absolute location of
the decimal point. 1.000V selects the 1V range, 1V out­put. 1.00V selects the l0V range, 1V output. 001.V selects
the l00V range, 1V output.

17. Increment and decrement keys do not change the range
or polarity. These functions increase/decrease the mag­nitude of both positive and negative limits.

18. After power on, the current range select relays remain
open until the operate key is pressed the first time. This
effectively open-circuits the output and may cause tran­sients on the output during auto cal and the first time
operate is selected.

CAUTION
The MONITOR and MODULATION termi­nals remain connected to the Model 228’s
internal circuitry; therefore, large voltages
or currents may exist between OUT+ and
these terminals during calibration.

19. While in the standby mode, the output remains pro­grammed the same as when first programmed to
standby. Therefore range changes, source/sink status,
(etc.) take affect when operate is selected.

20. The front panel compliance graph may show multiple
LEDs. As an example; when current is zero, +0 and —0
are approximately the same magnitude so two LEDs will
show.

21. If the measured output current exceeds 200% of range,
the output is disconnected and the Model 228 is placed
in the standby mode. Normal operation returns by press­ing the OPERATE key.

2.3 GENERAL OPERATION NOTES

1. Using the increment or decrement keys to either exceed
the maximum value for that range or change sign, causes
the Model 228 to briefly display an error message. The last
key pressed is ignored. Refer to Tables 3-4, 3-5, and 3-6 for
front panel messages.

2-3

2. Using the increment or decrement key to adjust the most
significant digit does not change the range. The range
error message is displayed for about one second; and the
instrument remains at the maximum display for that
range or zero, whichever is programmed.

3. During the edit mode, if no activity has happened on the
front panel for approximately 20 seconds, or if the
ENTER key is pressed, the edit mode is cancelled. The
display returns to normal intensity.

4. For the current function, the output load must be, in gen­eral non-inductive. A small amount of inductance in the
load can be tolerated if the inductive reactive voltage

di

L , is limited to the maximum compliance voltage of

-----­dt

the range. Table 3-4 lists the maximum inductive reaction
voltage for each current range.

5. Operation of the Model 228 as a power sink produces
heat. The Model 228 employs a fan for forced air cooling.
Do not block the airflow of the fan. The instrument may
overheat and go into the thermal lock up mode.

6. When using the DATA keypad to modify the displayed
data, the actual value is not entered until the ENTER but­ton is pressed.

7. In the operate mode (OPERATE LED on), the actual volt­age and current are monitored and can be displayed. For
example, if 5V, 5A are programmed and the load is draw­ing 2.3A, then 5V, 2.3A is displayed.

8. All of the front panel keys (except PROGRAM,
CANCEL, OPERATE, and LOCAL) autorepeat if held in.

9. In the immediate mode (using DECADE keys and the
output is updated along with the display) the ENTER
key need not be pressed. After approximately 20 sec­onds, the Model 228 cancels the edit mode and returns to
the previous operating mode. The new data remains.

10. The STANDBY LED is of amber color to distinguish it
from the OPERATE LED which is red.

11. If the internal operating temperature reaches over l00˚C,
the Model 228 displays an error message as shown in
Table 3-4. At this point, the instrument locks up with the
error message displayed. The Model 228 must be turned
off and allowed to cool down before continuing
operation.

12. The Model 228 goes through an autocalibration cycle
when the instrument is powered on. Refer to the mainte­nance section for complete details.

13. The Model 228 has a bipolar output. This means that the
polarity of the output may be reversed without having to
reverse the output leads.

14. All of the information programmed into the memory
locations is battery backed up. This means that if the
instrument is powered down, the information pro­grammed in the memory locations is not lost. The infor­mation remains in the memory locations until changed
by the user.

15. Tables 3-5, 3-6, and 3-7, contain a complete list of front
panel messages and their definition. The messages
include: error messages and instrument status messages.

2.4 STANDBY MODE NOTES

The following situations depict when the Model 228 output is
electrically disconnected (via internal relays) from the
instrument.

1. Power is off.

2. During the auto calibration cycle. Upon power up, until
the end of the calibration cycle and during a portion of
front panel Program 6.

3. Within a few line cycles for low or missing line voltage. If
the microprocessor is reset, the normal power up
sequence occurs. If the microprocessor is not reset, the
next time the A/D is triggered (approximately six times
a second) or when the output is changed.

In the standby mode the Model 228 output is still active. The
standby mode has the same effect as programming the out­put for the following conditions:

1. 0V +four counts (on the same voltage range and same
polarity).

2. 0A +four counts (on the same current range and same
polarity).

3. MOD V off.

4. MOD I off.

The output is NOT disconnected. Programming the output
for the new values, ranges polarity, sink mode or modulation
does NOT change the output until the Model 228 is placed in
the operate mode.

Notes

1. Since the output is still active, the quick disconnect card
should be removed from the mainframe BEFORE any
wiring changes are to be made.

2. The Model 228 looks like a short or an open circuit to an
external source. This depends on whether the voltage
polarities oppose or match before the Model 228 is
placed in standby. Polarity changes do not affect the out­put until the Model 228 is placed in the operate mode.

3. Large reactive loads are not immediately discharged by
placing the Model 228 in the standby mode. This is
because the 0V setting does not change the current
through an inductor and the 0A setting does not change
the voltage across a capacitor. In reality, capacitors and
inductors discharge at approximately 0.4% of range
when the Model 228 is in the standby mode.

2-4

SECTION 3

FRONT PANEL OPERATION

3.1 INTRODUCTION

Information in this section concerns front panel operation of
the Model 228 and is divided into four categories: operating
instructions, operating examples, front panel programs, and
applications. Operating instructions include using the
Model 228 to source or sink, voltage or current, in the posi­tive or negative direction. Operating examples cover many
aspects of Model 228 operation. The front panel programs
section describes each program and gives a few examples of
Model 228 uses.

3.2 PREPARATION FOR USE

The following steps must be performed to prepare the
Model 228 for operation. These steps can be performed
quickly and will ensure proper line voltage and fuse
selection.

3.2.1 Line Voltage Selection

The Model 228 may be operated from either 105V-125V or
210V-250V, 50Hz or 60Hz power source. The instrument was
shipped from the factory set for an operating voltage that is
marked on the rear panel. The operating voltage of the
instrument is internally selectable. Refer to Section 7 Mainte­nance, for information on setting the line voltage.

CAUTION
Do not attempt to operate the instrument
on a supply voltage outside the indicated
range. Damage to the instrument may
occur.

3.2.2 Fuse Checks

It is important to check each of the three fuses for proper rat­ing before applying power to the Model 228. If the voltage
was recently changed, the linear supply fuse (LINE FUSE 1)
and the switching supply fuse (LINE FUSE 2) must also be
changed to accommodate the new line voltage. The output
fuse (OUTPUT FUSE) should also be checked for proper rat­ing. Refer to Section 7 Maintenance, for information on
proper fuse rating.

3.3 POWER UP

NOTE

To ensure compliance with EMI requirements,
the Model 228A should be connected to AC
power with the specified filtered power cord
provided with the unit.

Plug the Model 228 into the proper power source. (see Table
3-1.) For fuse replacement of line switch (S102) setting, refer
to Section 7 Maintenance.

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

Table 3-1. Line Voltage Setting

Switch

Setting

Input V oltage

090V - 110V*

105V - 125V*
180V - 220V*
210V - 250V*

* Operation at these input voltages requires power supply

modifications. Refer to the maintenance section of this manual for
more information.

Turn the instrument on. The Model 228 runs through a power
up sequence that is described as follows:

1. Immediately after turning on the Model 228 via the front
panel POWER switch, both displays indicate the
following for several seconds:

(SW302) Fuse 1 Fuse 2

115V
115V
230V
230V

6.3A, 250V
5A, 250V

3.15A, 250V

2.5A, 250V

1A, 250V
3/4A, 250V

0.5A, 250V
3/8A, 250V

+ +

CAUTION
Check all three fuses for appropriate
rating. The fuse ratings are listed in Tables
7-1 and 7-2, and they are also shown on
the rear panel. Incorrect rating may cause
damage to the instrument in case of short
circuit or malfunction.

A. This is a display test. The operator can note inopera-

tive display segments by comparing the Model 228’s
display with the above figure.

B. In addition, all LEDs are turned on for the same

period of time. The LEDs include: VOLTS, MEM STEP,
AMPS, SECONDS, STANDBY, OPERATE, STOP,

3-1

START, SINGLE MODULATE I, MODULATE V and
SINK ONLY. All of these LEDs light simultaneously if
operating properly.

C. While the display test is running, the Model 228 is per-

forming a digital self test on the RAM circuitry and
cyclic redundancy check (CRC) on the ROM circuitry.
If there is a problem, the Model 228 displays an error
message. For further information, refer to Section 7
Maintenance.

If the Model 228 did not pass the RAM test the following is
displayed.

If the Model 228 did not pass the ROM test the following is
displayed.

2. The Model 228 displays the software revision level. The
following is an example of software revision Al.

3.5 ENVIRONMENTAL CONDITIONS

Operate the Model 228 in an environment with an ambient
temperature within the range of 0°C to SO”C, up to 35°C at
80% non-condensing relative humidity. Environmental con­ditions for storage are from -25°C to 70°C.

3.6 OPERATING INSTRUCTIONS

The following instructions show how to operate the Model

228 using the front panel controls. In order to operate the

Model 228, the user must understand the front and rear panel

controls. It is important to read and follow the safety precau-

tions and warnings before operating the instrument. A brief
description of the front panel controls is provided in Table

3-2. A more detailed description of the front panel controls is
contained in paragraph 3.7. A brief description of the rear
panel terminals and controls is provided in Table 3-3. A more

detailed description of the rear panel controls is contained in
paragraph 3.8. Figure 3-2 shows the front panel of the Model

228. Figure 3-3 shows the rear panel of the Model 228. A
graph of operation is contained in Figure 1.

3. Next, the Model 228 displays the present primary address.
The following is an example of primary address set to 11.

3.4 WARM UP

In order to achieve rated accuracy, the Model 228 requires ten
minutes for warm up.

NOTE

To achieve rated accuracy, run Program 6 immedi­ately after the lOminute warm-up period.

-I

= +115V (DESTRUCTWE LIMIT1
= -CURRENT LIMIT I + PROGRAMMED)
= +VOLTAGE LlMlT (+PROGRAMMEDl I = -VOLTAGE LIMIT t - PROGRAMMEDI

= + CURRENT LIMIT (+ PROGRAMMED1 J = -CURRENT LIMIT (-PROGRAMMED)
E = -VOLTAGE LIMIT I + PROGRAMMED)
F = ZOA FUSE

G = - 115 IDESTRUCTlVE LIMIT)
H = + CURRENT LIMIT I -PROGRAMMED)

K = + VOLTAGE LIMIT I -PROGRAMMED)
L = 20A FUSE

Figure 3-l.Graph of Operation

3-2

Table 3-2. Front Panel Controls

Control
POWER ON/OFF
OPERATE/STANDBY

VOLTS/MEMORY STEP
AMPS/DWELL TIME

DISPLAY MODIFY GROUP
SELECT

DECADE

ENTER
DATA

MEMORY CONTROL GROUP

Descriotion

Turns the unit on or off.

Places the output in either standby or operate. Standby programs the output

terminals for OV, OA. Operate places the programmed value (voltage or cur-

rent) on the output terminals.
Places the left display (viewed from the front panel) in either the volts display

mode or the memory step mode.
Places the left display (viewed from the front panel) in either the amps display

mode or the dwell time display mode.

Determines which display (left or right) to modify.

The DECADE keys (left, right, up and down) modify the selected display. The

left and right keys (indicated by the left and right arrows) select which digit is
to be modified. The increment and decrement keys (indicated by the up and
down arrows) increment or decrement the value of the selected (bright) digit
and therefore the displayed value by one unit each time the key is pressed.
The output tracks the increment or decrement of the displayed value.

The ENTER key places the displayed data into the present memory location.
The DATA keys enter the desired value on the display. ENTER must be

pressed to update the value to the output. The DATA keys also activate the
desired front panel program. Refer to paragraph 3.11 for front panel pro­grams.

START/STOP
SINGLE STEP

SINGLE CYCLE

CONTINUOUS

PROGRAM CONTROL GROUF
PROGRAM

CANCEL

LOCAL

The START/STOP key enables or disables the memory control functions.

Selects the SINGLE STEP memory control function which allows the user to
step through the programmed memory locations one at a time. Each suc­cessive key pressed advances the unit to the next memory location. The

memory control mode must be activated in order for single step to operate.
Selects the single cycle memory control function which allows the user to run

through one complete cycle of the programmed memory location. The

memory control mode must be activated in order for Single Cycle to operate.
Selects the CONTINUOUS memory function which allows the user to run

through the programmed memory locations continuously. The memory con­trol mode must be activated in order for CONTINUOUS to operate.

The PROGRAM key is used as the first step in activating the front panel pro­grams.

The CANCEL key has two functions. In the program mode, the CANCEL key
takes the instrument out of the program mode. During entry of new data, the

CANCEL key terminates editing. The instrument is then returned to the

previous operating mode.
The LOCAL key enables front panel operation. In the remote mode (over

IEEE-488 bus), pressing the LOCAL key enables front panel operation and
takes the Model 228 out of the remote mode.

3-3

Table 3-3. Rear Panel Description

Connections/Controls

OUTPUT CONNECTOR

SENSE

CURRENT MONITOR
TRIGGER IN
TRIGGER OUT

EXTERNAL MODULATION
FUSE 1

FUSE 2
FUSE 3

IEEE-488 Connector
LINE RECEPTACLE

Description

The output connections are located on a card that is inserted into the

Model 228 mainframe. When the connector is removed from the mainframe

the output connections are disengaged from the actual output potentials.
The sense connectors are located on a card that is inserted into the Model

228 mainframe. The sense lines are used to sense the output at the output
connector (Local) or sense the output at the load (Remote).

This connection supplies a voltage proportional to the output current for
use with oscilloscopes or DMMs.

The TRIGGER IN connector accepts a TTL level negative going pulse of
greater than 10pec to initiate the selected memory mode.

The TRIGGER OUT connector outputs a lTL level negative going pulse of
greater than lO/rsec at the end of each programmed dwell time.

This connector allows the output (voltage or current) to be externally
modulated.

This is the line power fuse for the linear power supply on the analog board.
The fuse is rated as shown in Tables 7-1 and 7-2. If this fuse is blown the

Model 228 will not power up.

This is the switching supply fuse. It is rated as shown in Tables 7-1 and
7-2. If this fuse is blown there is no output present.

This is the output fuse. The fuse is rated at 20A.
This connector is used to connect the instrument to the IEEE-488 bus. The

IEEE interface functions are marked above the connector.

The line receptacle connects to a three wire line cord which provides con­nections to the line voltage.

3-4

3.7 FRONT PANEL DESCRIPTION

OPERATION GROUP

POWER ON/OFF-The ON/OFF switch operates on the
push-push principle. Depressing this switch turns the instru­ment on. Once the instrument is on, pressing (releasing) this
switch turns the instrument off. When the Model 228 is turn-

ed on, the output is programmed to about OV, OA and the

programmed settings are displayed. Note that the Model 228
does not change range polarity or sink status while in the
standby modes, and external modulation is disabled.

VOLTS/MEMORY STEP-The VOLTS/MEMORY STEP
key is an alternate action control which places the left display
in either the volts display mode or the memory step mode. In
the volts display mode, the voltage for the present memory
location (step) is displayed on the left display. In the memory
step mode, the present memory location is displayed on the
left display. This key allows the user to view either the pre­sent memory location or the voltage at the present memory
location. There are 100 memory locations (steps). Each
memory location contains five parameters (Voltage, Current,

Dwell Time, Modulation on or off and Sink Mode on or off).
These parameters are defined (programmed) by the user. This
means that each memory location may have its own unique
values.

OPERATE/STANDBY-The OPERATE/STANDBY key is
an alternate action control (toggle) which places the Model
228 in either the operate mode or the standby mode. In the
operate mode, the OPERATE LED is turned on and the pro­grammed source value is present on the output terminals. In
the standby mode, the STANDBY LED is turned on the out­put is programmed to approximately zero and the displayed
value remains the same.

In the standby mode the Model 228 is still active. The standby
mode has the same effect as programming the output for the
following conditions:

1. OV + four counts (on the same voltage range and polarity).

2. OA +four counts (on the same current range and same
polarity).

3. MOD V off.

4.. MOD I off.

The output is NOT disconnected. Programming the output
for a new value, range polarity, sink mode or modulation,

does not change the output until the Model 228 is placed in
the operate mode.

AMPS/DWELL TIME-The AMPS/DWELL TIME key is an
alternate action control which places the right display in
either the amps display mode or the dwell time display mode.
In the amps display mode, the current for the present memory
location is displayed on the right display. In the dwell time
display mode, the dwell time for the present memory location
is displayed on the right display. This key allows the user to
view either the dwell time for the present memory location or
the current for the present memory location. The dwell time
ranges from 1Omsec to 1000sec.

DISPLAY MODIFY GROUP (EDIT)

DISPLAY MODIFY

0

SELECT

0

A

ENTER

0

IO

DECADE

01)

Notes

1. Since the output is still active the quick disconnect board
should be removed from the mainframe before any wiring
changes are to be made.

2. The Model 228 looks like a short or an open circuit to an
external source. This depends on whether the voltage
polarities oppose or match before the Model 228 is placed
in standby. Polarity changes do not affect the output until

the Model 228 is placed in the operate mode.

3. Large reactive loads are not discharged immediately after
placing the Model 228 in the standby mode. This is because
the OV setting does not change the current through an in­ductor and the OA setting does not change the voltage
across a capacitor. In general, capacitors and inductors
discharge at approximately 0.4% of range when the Model
228 is in the standby mode.

0

‘I

SELECT-The SELECT key determines which display (left or
right) can be configured. Pressing the SELECT key once
selects the previously selected display for modification.
Subsequent key presses toggle the edit mode between
displays. Use the SELECT key before modifying the volts,

memory step, amps or dwell time functions.

DECADE-The DECADE keys (right, left, up and down)
modify the selected display. The left and right keys (indicated

3-7