Keithley 228 Service manual

Model 228 Voltage/Current Source Instruction Manual

Contains Operating and Servicing Information

Publication Date: April 1986 Document Number: 228-901-01 Rev C

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. 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 instrument, transportation prepaid, to the indicated service facility. Repairs will be made and the instrument returned, transportation prepaid. Repaired

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 unauthorized

modification or misuse of any product or part. This warranty also does not apply to fuses, batteries, or damage from battery leakage.

This warranty is in lieu of all other warranties, expressed or implied, including any implied warranty of merchantability or fitness for a par-

ticular use. Keithley Instruments, Inc. shall not be liable for any indirect, special or consequential damages.

STATEMENT OF CALIBRATION

This instrument has been inspected and tested in accordance with

specifications published by Keithley Instruments, Inc. The accuracy and calibration of this instrument are traceable to the

National Bureau of Standards through equipment which is calibrated at

planned intervals by comparison to certified standards maintained in the Laboratories of Keithley Instruments, Inc.

KEITHLEY INSTRUMENTS, INC.

INSTRUMENT DIVISION I 28775 Aurora Road I Cleveland. Ohio 44139 / U.S.A. I 12161 248-0400 / Telex: 98-5469 WEST GERMANY: Keithley Instruments GmbH I Heiglhofstr. 5 I 8000 Mtinchen 70 / IO891 710020 / Telex: 52-12160 GREAT BRITAIN: Keithley Instruments. Ltd. / 1, Eoulton Road I Reading, Berkshire RG 2 ONL / (07341 86.12.87/88 /Telex: 84-7047 FRANCE: Keithley Instruments SARL / 2, 8is Rue Leon Blum ! 8.P. 60 / 91121 Palaiseau Cadex / (6) 011-51-55 /Telex: 600-933 NETHERLANDS: Keithley Instruments BV ! Arkelsedijk 4 I Postbus 559 / 4200 AN Gorinchem / 10) 1830-25577 /Telex: 24-684 SWITZERLAND: Keithley Instruments SA / Kriesbachstr. 4 / 8600 Dibendorf / 01/821-94-44 / Telex: 57-536 AUSTRIA: Keithlev Instruments Ges.m.b.H. / Doblinger Haupstr. 32 / 1190 Wien / 314 289 I Telex: 13-4500

Model 228

Voltage/Current Source

Instruction Manual

01986, Keithley Instruments, Inc.

Cleveland, Ohio, U.S.A.

Publication Date: April 1986

Document Number: 228-901-01 Rev. C

SPECIFICATIONS

AS A CONSTANT VOLTAGE SOURCE RANGE OVTPVT

ACCVRACY

MAXI- RESO.

MUM LUTION

loo” *,o,.o” lmm” *(o.l%+o.l “I *1.010 A ImA *K.l%+ ImA)

10” *,0.1Lw lam” *(o.l%+ lonw f10.10 A lomA *(o.s%+ 4cmA)

,1 YEAR1

W-WC Muhl LIJTION

I” *,.o,o” lnw *,0.1%+1.otr”~ *10.10.4 *on-A *w.s%+ 4omN

TEMPERAT”RE COEFF,CIENT (0”.1S”C a 28”.SO”0 f(0.1 Xapplic-

able acc”raw suwificationll”C.

NOISE:

1ov 2.OmV p-p

OUTPUT RESISTANCE (max.): lOOV Range: 1Omfl. 1OV Range: 1W pfl.

1v Range: ml pfl.

OUTPUT INDUCTANCE: l&$H typical.

SENSING: Rear panel witch selectable REMOTE and LOCAL sensing.

REMOTE SENSING: Corrects for up to 0.5V drop per ““t

im,,,,, s” per fence lead for rated accuracy. Maximum 0.5

for rated output resistance.

0.1.3oOHz 0.1~300kHz

5.omv p-p

0.7mV p-p

COMPLIANCE ,souru or Shk,

MAXI- RESO (1 YEAR)

*o.loloA k-m p.4 *,O.l%+4co #A) *l.oloA 1mA *ml%+ ImAl

*o.loloA m&A *KLl%+4m#A)

f1.010 A ,mA *,o.l%+ 4mA) *0.1010A ,MpA *:(0.l%+mpAl

15mV p-p 15nlv p-p 15mV p-p

AccmAcY

16’.WC

0.1.20MHz

mv P-P ‘YP. 25m” p-p typ.

25mV P-P w

“t lead. Max-

per sense lead

AS A CONSTANT CURRENT SOURCE

1 A *,.010A 1mA *~O.l%+l.cmA~ **o,.ov mmv *K.l%+mlrvl

0.1.4 *0.,0,0,4 ,MpA *(O.l%+O.,d~ *,o,.ov mlm” *~o.l%+mv~

‘Abave 0.4% of range.

TEMPERATURE COEFFICIENT (0”~ls”C dr 26”-50°C): f(O.l Xapplic-

able accuracy specificationl/“C.

NOISE:

OUTPUT RESISTANCE wn.1: IOA RanBe:

Range: lo*“. OUTPUT CAPACITANCE: 0.2rrF typical. OUTPUT LOAD: M”st be non-inductive.

“f,““A”

1 A O.lA 0.5mA D-D 3mA D-D Ml

0.1~300Hz

25 mA p-p

5 mA p-p

~,O.,O” lmn” *Ku%+ 4omVl *1.01ov

mm;;; mmv *ml%+ 4omVl

0.1~3OOkHz 0.1~MMHz 2smA p-p

Inl” *K%l%+ 4m”,

,mv *,O.*%+ h”,

;$ ;I:

lo4

iA Range: i&fl:b.lA

25* P-P typ. ‘OmA P-P tyP.

CURRENT MONITOR OUTPUT

SCALE FACTOR: 1” - 10% of range. ACCURACY: Same as constant currat mode. BANDWIDTH: 5kHz typical. OUTPUT RESISTANCE: lokIlo.

EXTERNAL MODULATION

INPUT RESISTANCE: 6.8M. SENSITIVITY: -lOV incraws magnitude of programmed output by

lW% of full scale; + 1OV decreaws magnitude of programmed output by

x0% of full scale. ACCURACY: 2% typical, dc to 6OHz. MAXIMUM MODULATION: Modulation and programmed settin should

not cause operation exceeding the range of zero to 101% of ful f scale.

MODULATION FREQUENCY: 6OOHz bandwidth.

IEEE-488 BUS IMPLEMENTATION (IEEE-4881978)

M~&IW&COMMANDSi DCL, LLO. SDC. GET, GTL. UNT. UNL. UNILINE COMMANDS: IFC, REN, EOI, SRQ, ATN.

INTERFACE FUNCTIONS: SHI. AHl, T6, TEO, L4, LEO, SRI. RLI. PPO.

DCl, DTl, CO, El.

PROGRAMMABLE PARAMETERS: Output (operate or standby), Range,

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

Dis lay Mode, Output Prefix (data format an readback), SRQ Mask,

EO , Terminator Characters, Status, Self Test, Memory Location (100 P

point memoryl, Dwell Time.

GENERAL

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

Standby and output value8 in Operate. READBACK ACCURACY: Same as o”tp”t accuracy FRONT PANEL PROGRAMS: COPY, SINK, IEEE address, MOD V,

MOD 1. TEST, RESET.

LOAD TRANSIENT RECOVERY TIME: With a resistive load the o”tp”t

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

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

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

changer within specified limits.

PROGRAM MEMORY (battery backed up): Stores up to 100 output set-

tings. Ra.nge of Dwell Time: 20mr to lw(k. Accuracy of Dwell Times:

* (0.05%+ 2msL

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

tion of data with “nit turned off. TRIGGER: IN and OUT ITL-compatible. RESPONSE TIME: 30,“s max. to 99% of programmed change. MAXIMUM COMMON MODE VOLTAGE ,o”tp”t “I o”tp”t common t”

chassis): IWV dc.

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 acd digital circ”its tested at power-on. Power sup-

plies. temperatures. and output continuously monitored.

WARMUP: 10 min”teS to rated accuracy.

POWER: 105.125 or 210.250 V ac (internally switch selectable), 50 or

6OHz. 500 VA maximum. COOLING: Internal fan for forced air coaling. ENVIRONMENTz Opratlng: O” to 50°C. less than 80% non-condensing

RH below 35°C. Storage: -25’ to 70°C.

DIMENSIONS, WEIGHT: 133mm high X 43Smm wide X 448mm deep

(5%

in. X 17Y. in. x 17% in.). Net weight 10.9kg (24 Ibs.).

ACCESSORIES AVAILABLE:

Model 2288: Fixed Rack Mounting Kit Model 2289: Slide Rack Mounting Kit Model 7008-3: IEEE-488 Cable (3 ft.) Model 7&X-6: IEEE-488 Cable (6 ft.)

TABLE OF CONTENTS

SECTION l-GENERAL INFORMATION

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

Introduction........................,...,.,,,..,.....,,............,,.,,.,,,,.,,,..,,......... 1-l

Features . . . . . . . . . . . . . . . . . . . . . ..~

Using the Instruction Manual Warranty Information

ManualAddenda...................,,...,..,,,,...,,.,.,...,......,.,..,.,,,,.,,,..,.....,.... l-2

SafetySymbolsandTerms........................................................,.......,..... 1-2

Specifications. l-2 Unpacking and Inspection Accessories, 1-3

SECTION 2-SAFETY AND GENERAL OPERATION

2.1

2.2

2.3

SafetyPr~autions............................................................................. 2-I

GeneralOperatingProcedure..................................................,.......,......... 2-l

StandbyModeNotes........................................................................... 2-3

SECTION 3-FRONT PANEL OPERATION

3.1

3.2

3.2.1

3.2.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

3.10

3.11

3.11.1

3.11.2

3.11.3

3.11.4

3.11.5

3.11.6

3.11.7

3.12

3.12.1

3.12.2

3.12.3

3.12.4

3.12.5

3.12.6

3.13

3.13.1

3.13.2

Introduction PreparationFor Use

Line Voltage Selection ........

FuseChecks

PowerUp

Wan,,Up

Environmental Conditions

OperatingInstructions

Front PanelDescription ........................................................................

RearPanelDescription

QuickDisconnect Board .......................................................................

RemoteandLocalSensing .....................................................................

FrontPanelPrograms .........................................................................

Program1Copy

Program2Sink ............................................................................

Program3lEEE.. ..........................................................................

Program 4 MOD V (Modulate Output Voltage) Program 5 MOD I (Modulate Output Current) Program 6 Test (Diagnostic Self Test)

Program9Reset ............................................................................

Loads ......................................................................................

Load Line Description, ResistiveLoads ReactiveLoads InductiveLoads

CapacitanceLoads ..........................................................................

LoadRegulation

Operating Examples ..........................................................................

Example 1: lO.OOV, lO.OOAOutput

Example2:100V,1AOutput .................................................................

.................................................................................. 3-1

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

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

................................................................................ 3-l

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

.................................................................................... 3-2

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

......................................................................... 3-2

........................................................................ 3-14

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

.................................................. 3-20

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

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

............................................................................. 3-24

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

............................................................................ 3-24

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

............................................................ 3-27

1-I l-2 1-2

l-2

3-1

3-l 3-2 3-7

3-16 3-18 3-18

3.18 3-19

3-19

3-21 3-21 3-21

3-22

3-24 3-26

3-26

3-27 3-28

3.13.3

3.13.4

3.13.5

3.13.6

3.13.7 Example 7: Using the External Trigger (Input and Output)

3.13.8 Example 8: Floating Operation (Extended Compliance)

3.14 Applications......................................................

3.14.1

3.14.2

3.14.3 External Modulation

3.14.4

3.14.5

Example 3: 1V. 10A. lsec: lOV, 10A Zsec; and lCOV, lA, 3sec Output

in the Continuous Memory Control Mode Example 4: Model 228 as an Active Load (Current Sink) Example 5: Operation as Source and Sink. Example 6: Fabricating Output Waveforms

Low Resistance Measurements BatteryTests

Ramp Generation Power Semiconductor Testing

SECTION 4-IEEE BUS OPERATION

4.1

4.1.1

4.1.2

4.1.3

4.1.4

4.2

4.2.1

4.2.2

4.2.3

4.3

4.4

4.4.1

4.4.2

4.4.3

4.5

4.5.1

4.5.2

4.5.3

4.5.4

4.5.5

4.5.6

4.5.7

4.5.8

4.5.9

4.5.10

4.5.11

4.5.12

4.5.13

4.5.14

4.6

4.6.1

4.6.2

4.6.3

Introduction. ............ .........

Software Considerations, ...........

Interface BASIC Programming Statements

Interface Function Codes ....................

Model 228 Interface Commands. ..............

IEEE-488 Bus Lines. ...........................

Bus Management Lines ......................

HandshakeLines.. .........................

Data Lines

System Set Up Procedure ......................

BusCommands.. ........ ...................

Uniline Commands .........................

Universal Commands .......................

Addressed Commands ......................

Device-Dependent Commands. .................

Display Mode (D) ..........................

Memory Control (I’) .......... .............

Prefix(G) .................................

SRQ Request Mode (M) .....................

TriggerModes .............................

Programmable Terminator(Y). ...............

Inputs(I,V,WandB). ......................

Function(F) .......... .........

Range(R)

External Modulation (A, C) ..................

Sink Mode (S) ... ........................

Status Word(U). ...........................

Self Test(J). ...................

EOI and Bus Hold-Off Modes (K) ..........

Front Panel Error Messages. ....................

IDDCError ...............................

IDDCO Error. .............................

No Remote Error ...........................

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

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

..... ...

.........

........

......

SECTION S-PERFORMANCE VERIFICATION

5.1

5.2

Introduction ...................................................................

Environmental Conditions .......................................................

5-l 5-l

5.3

5.4

5.5

5.5.1

5.5.2

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

Initial Conditions.

....... ..

Performance Verification Procedure

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

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

Voltage Mode Verification (IV, 1OV and 1OOV) Output Current Verification, ...

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

SECTION B-THEORY OF OPERATION

.........

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

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

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

........

.....

..........

5-l 5-l 5-1 5-l 5-2

6.1

6.2

6.2.1

6.2.2

6.3

6.4

6.5

Introduction. Power Supply

Linear Power Supply

Switching Power Supply

Analog Control

Digital Board

Display Board

SECTION ‘I-MAINTENANCE

7.1

7.2

7.3

7.4

7.4.1

7.4.2

7.4.3

7.4.4

7.5

7.5.1

7.5.2

7.5.3

7.6

7.6.1

7.6.2

7.6.3

7.6.4

7.6.5

7.6.6

7.6.7

7.6.8

7.7

Introduction. FuseReplacement Line Voltage Selection Disassembly

Removing the Top and Bottom Covers RemovetheRearPanel Digital Board, Mother Board and Power Supply Board Access. Heat Sink Assembly and Fan Access

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

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

DigitalSelfTest

Troubleshooting

Calibration

RecommendedTest Equipment ...............................................................

EnvironmentalConditions ...................................................................

warnlup .................................................................................

TopCoverRemoval ........................................................................

+15VSupplyAdjustment ...................................................................

TestSetup

+lV Reference Adjustment

Current Calibration

Special Handling of Static Sensitive Devices

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

6-l 6-l 6-l 6-2 6-2 6-6 6-6

7-1

7-l 7-l 7-2 7-2 7-3 7-3

7-3 7-10 7-10 7-10 7-10 7-13

7.13

7-13 7-13 7-13

7-14

7-14 7-14

7-14

7-15

SECTION 6-REPLACEABLE PARTS

8.1

8.2

8.3 a.4

8.5

Introduction ReplaceableParts Ordering Information Factory Service Schematic Diagram and Component Location Drawings

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

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

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

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

.........

.......

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

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

8-l 8-l 8-l

8-l 8-l

iii

LIST OF ILLUSTRATIONS

3-1 3-2 3-3

3-4 3-5 3-6

3-7 3-8

3-9 3-10 3-11 3-12 3-13 3-14 3-15

3-16 3-17 3-18 3-19 3-20 3-21 3-22 3-23 3-24 3-25 3-26 3-27 3-28 3-29 3-30

GraphofOperation

Model228FrontPanel

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

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

Model228RearPanel ............. ...................

QuickDisconnectBoard Quick Disconnect Board Installatmn Graph of Operation for External Modulation Load Line (Positive Line Shown) Resistive Load Connections Limiting Inductive Reaction Voltage InductiveLoadConnections Capacitive Load Connections Model 228 Recommended Operating Limits Model228AsAnActiveLoad.. Output Waveform External Trigger Connections Connections for Floating Operation Low Resistive Measurements

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Battery LifeTest .........................................................

Data Logging Configuration. Power Supply Protection Circuit

Connections for External Modulation

Typical Modulated Output.

RampGeneration

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

Ramp Characteristics Power Transistor Test Set Up. Power Transistor IC/VCE Curves

Automated Test Set Up.

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

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

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

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

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

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

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

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

FETTestSetUp .........................................................

FET Curves. ............................................................

Automated Test Set Up for FETs

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

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

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

.........

..........

3-2

,. 3-5

3-5 3-77 3-17 3-20 3-23 3-24 3-25 3-26 3-26 3-26 3-26 3-36

., 3-37

3-37 3-38 3-39 3-39 3-39 3-40 3-40 3-40 3-41 3-41 3-42 3-42 3-42 3-42

...,. 3-43

4-l 4-2 4-3 4-4 4-5 4-6 4-7 4-E 4-9

5-l 5-2

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

Bus Structure ...........................................................

Handshakesequence

Contact Assignments

Typical Bus Connector

General Format of SRQ Byte and Mask Format of SRQByte ErrorStatusWord

Status WordFormat IEEEDispIayErrorMessage..

Output Voltage Configuration Output Current Configuration.

Model 228 Block Diagram

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

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

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

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

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

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

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

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

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

....

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

Analog Control .............

Voltage Sensing .............

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

Current Sensing .............

Output Amplifier.

...........

A/D Converter .............

Display and Keyboard

.......

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

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

.....

4-4 4-5 4-6

4-6 4-19 4-19 4-27 4-28 4-29

s-2

5-2

6-I

b-3

6-4

6-5

7-l 7-2A 7-2B 7-3 7-4 7-5 7-6

TopandBottomCoverRemovaI .................................................................

RearPanelRemoval WiringInput

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

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

Model228ExplodedView ......................................................................

DetailofConnectors ...........................................................................

Heat Sink Assembly (Exploded View) CalibrationSetup

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

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

7-4 7-5

7-6 ‘,:;

7-11 7-17

8-l 8-2 8-3 8-4

8-5 8-6 8-7 8-8

Mother Board, Component Location Drawing, Dwg. No. 228-100 Mother Board, Schematic Diagram, Dwg. No. 228-106

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

Display Board, Component Location Drawing, Dwg. No. 228-110 Display Board, Schematic Diagram, Dwg. No. 228-116

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

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

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

Power Supply Board, Component Location Drawing, Dwg. No. 228-150. Power Supply Board, Schematic Drawing, Dwg. No. 228-156 Digital Board, Component Location Drawing, Dwg. No. 228-140

Digital Board, Component Location Drawing, Dwg. No. 228-146

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

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

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

8-6

8-7 8-15 8-17 8-22 8-23 8-27

8-29

LIST OF TABLES

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

4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 4-11 4-12

5-l 5-2 5-3

Line Voltage Setting .... ......... ......

Front Panel Controls ....................

Rear Panel Description .............

....

Front Panel Messages .. .................

Front Panel Messages and Prompts ........

Error Messages (Either Display)* ..........

Power Up Default Conditions. ............

Summary of Front Panel Programs

Maximum Inductive Reaction Voltage, HP-85 and IBM BASIC Statements

........

.....

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

Model 228 Interface Function Codes ............................

IEEE Command Groups. ......................................

IEEE Contact Designations ......

DCL and SDC Default Conditions

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

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

Device-Dependent Commands .................................

Device-Dependent Commands Not Available to the Front Panel.

Hierarchy of Command Execution ..............................

SRQMaskCommands .......................................

Input CommandSummary ....................................

RangeCommands ...........................................

HoldOFFTimes .............................................

Recommended Test Equipment. ........

Output Voltage Verification ...........

Output Current Verification ...........

....

3-1 3-3 3-4 3-a 3-a

3-8 3-10 3-18 3-26

4-2

4-3 4-3 4-6 4-8

4-11 4-13 4-14 4-19 4-22 4-24 4-29

5-l

5-2

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

8-l

8-2 8-3

8-4 8-5

Fuse Replacement ....................

Low Voltage Operation, Part Changes

Line Voltage Selection ................

Recommended Test Equipment. ........

Power Supply Checks ................

Analog Circuitry Checks. .............

Digital Circuitry Checks ..............

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

Recommended Calibration Equipment

Model 228 Static Sensitive Devices. .....

Mother Board Parts List. ..............

Display Board Parts List ..............

Power Supply Parts List. ..............

Digital Board Parts List ...............

Mechanical Parts List .................

7-1

7-2

7-10 7-11 7-11 7-12 7-13 7-13 7-15

8-2

8-13 8-19 8-25 8-31

SECTION 1

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 ob-

tained 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. Pronram 5 MOD 1 for modulatinn output current. Pro&m 6 Test for Model 228 self tes;,

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 configur-

ation 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 I*R lead drop by

maintaining regulation at the load instead of at the output

terminals of the Model 228.

l Four Quadrant 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).

1-1

. 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.

Section 3 contains front and rear panel descriptions, a

2. general operating procedure and specific operating examples showing how to use the Model 228.

Section 4 contains information pertaining to the IEEE-488

including primary address selection, device-

bus, dependent command programming, bus connection and several sample programs.

Section 5 includes a procedure to verify the performance

4. of the Model 228.

Section 6 contains theory of operation with detailed

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

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.

Section 8 gives replaceable parts information.

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.

1.6 SAFETY SYMBOLS AND TERMS

The following safety symbols and terms are used in this manual or found on the Model 228:

The symbol

should refer to the operating instructions in this manual.

The symbol /L* on the mstrument indicates that a lethal

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.

on the instrument indicates that the user

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.

1.6 UNPACKING AND INSPECTION

The Model 7.28 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-

mat. 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.

rewiring for each configuration, several quick disconnect boards could be wired for each unique configuration. The

Keithley part number of the quick disconnect board is 228-160. One quick disconnect board is supplied with each Model 228.

Model 2288 Fixed Rack Mount-The Model 2286 is a fixed or

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

1.9 ACCESSORIES

Quick Disconnect Board-The quick disconnect board con-

tains 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.

With all of the terminals on the board, many configurations

could be wired. To avoid cumbersome and time consuming

Model 2289 Slide Rack Mount-The Model 2269 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 700&j-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 700%6-The Model 7008-6 is a 2 meter (6 feet)

IEEE-466 cable. The cable has 24 stranded wire conductors and is terminated on each end with standard IEEE-488 connectors.

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 (“WC). 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 op-

poses the programmed polarity of the Model 228,

voltage has priority. where: Vs = Source Voltage (V~O~RCE) 1s = source Current (Iso”& RL = Load Resistance when:

vs + vzzs

is greater than the current setting of the

Model 228.

The standby mode programs the Model 228 for approximately O.OV, O.OA.

is + vz,, =

Therefore, 1s = VS/RL up to the limits of the output

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 mat-

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

when: Vs--lsR~ is greater than the voltage setting of

Before operation, ground the instrument through a pro-

oerlv earth mounded recentacle. Failure to mound the in-

‘, Y

strument may result in severe injury or even death in the event of a short circuit or malfunction.

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.

Never come into contact with the output connections

while the instrument is turned on. 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.

Use cables for the output that have appropriate current

and insulation rating. For example, if 1OV at 1OA 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.

Do not leave the instrument unattended when it is in the

operate made. Always place the instrument in standby after the measurement or test is completed.

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.

vs + 0

Model 228.

is greater than zero,

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

2-1

covered in the general procedure. Section 3 includes several specific examples of Model 228 operation.

NOTE Most of the front panel keys autorepeat 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 warm up. NOTE

To achieve rated accuracy, run Program 6 immediately after the lo-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 be-

ing 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. digit.

D. Press the increment or decrement keys (indicated by the D. Press the increment or decrement keys (indicated by the

up and down arrows) to modify the selected digit for up and down arrows) to modify the selected digit for

the desired memory location, 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

display the source voltage on the left display, or the

AMPS/DWELL TIME key to display the source current on the right display.

8. 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 OF 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 up-

dated continuously along with the display when using the increment or decrement keys.

Method 2: Proeram the Source

Press the VOLTS/MEMORY STEP key to display the source voltage, or the AMPS/DWELL TIME key to display the source current.

Dress 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.

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.

Press the SELECT key to select the left display. The selected display is indicated by the flashing bright digit.

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 undated continuouslv alone 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.

8. Press the SELECT key to select the left display. The selected digit is indicated by the flashing bright digit.

C. Enter the d+d dwell time using the DATA keys. D. Press ENTER.

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.

2-2

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 L $ is limited to the maximum compliance voltage of the

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 ex-. ample, 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 txned 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. l.OCOV selects the 1V range, 1V output. l.COV selects the 1OV range, 1V output. 0Ol.V selects the 1WV 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.

ls. After power on, the current range select relays remain

o P en until the operate key is pressed the first time. This e fectively open-circuits the output and may cause hansients on the output during auto cal and the first time operate is selected.

CAUTION

The MONITOR and MODULATION terminals re-

main connected to the Model 228’s internal clr-

cultry; therefore, lerge voltages or currents may exist between OUT+ and these tsrmlnels durIng callbretlon.

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, +O 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 bipressing 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. 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,

2-3

L 2, is limited to the maximum compliance voltage of the range. Table 3-4 lists the maximum inductive reaction voltage for each current range.

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 SV, 5A are programmed and the load is drawing 2.3A. then SV, 2.3A is displayed.

8. All of the front panel keys (except PROGRAM, CAN-

CEL, 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 100°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.

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

polarity).

2. OA ffour 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 OV setting does not change the current through

an inductor and the OA 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

226 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 21OV-25OV. 50Hz or 6OHz 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 instrw ment is internally selectable. Refer to Section 7 Maintenance,

for information on setting the line voltage.

CAUTION

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

attempt

to operate the instrument

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 line voltage was recently changed, the linear supply fuse (LINE FUSE 1) and the switching supply fuse (LINE FUSE 2) must also be changed to accomodate 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.

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.

3.3 POWER UP

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

to Section 7 Maintenance.

WARNING

Ground the instrument through a properly

earth grounded receptacle before operat-

ing. Failure to ground the instrument may result in severe injury or death in the event

of e short circuit or malfunction.

Table

Input Voltage (SW302l/ Fuse 1

sov-11ov* 115v 6.3A. 250v 1A. 250V

105V-125V 115V 5A. 250V 3/4A. 250V

IEOV-22OV” 230V 3.ljA. 250V 0.5A,‘250V

21OV-250V 230V 2.5A. 250V 3/8A, 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:

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

display segments by comparing the Model 228’s display

with the above figure.

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

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

3-l. Line Voltage Setting

1 Switch 1

Setting I

Fuss 2

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 RAh4 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 RAh4 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 5O”C, up to 35°C at

80% non-condensing relative humidity. Environmental con-

ditions 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 precautions 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 immedi-

ately after the lOminute warm-up period.

-I

L j

--- -_ B

---

I I

-V

--IG

3-2

Figure 3-I-Graph of Operation

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

Description

Turns the unit on or off.

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

terminals for OV, DA. Operate places the programmed value fvoltage 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 panel1 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 arrows1 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 con-

trol 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

Connectlon8/Controls

OUTPUTCONNECTOR

SENSE

CURRENT MONITOR TRIGGER IN TRIGGER OUT EXTERNAL MODULATION SENSING FUSE 1

FUSE 2 FUSE 3

IEEE-488 Connector LINE RECEPTACLE

Description

The outout 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 ara 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 lO@ec to initiate the selected memory mode.

The TRIGGER OUT connector outputs a TTL level negative going pulse of greater than lO@ec at the end of each programmed dwell time.

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

The REMOTE/LOCAL SENSING switch selects sensing from the sense terminals or the output terminals.

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 con-

nections to the line voltage.

3-4

3 !

lrlllllllll I

II II II II II

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 turned 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

VdWS.

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 20msec to 1000s~.

DISPLAY MODIFY GROUP (EDIT)

DECADE

III)

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.

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 in-

ductor 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.

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

by left and right arrows) select which digit on the display is to be modified. These keys wrap the cursor around to the opposite end (most significant) digit if attempting to go beyond the left most or right most (least significant) digit. The modify

digit is indicated by the “Lvight flashing” digit on the display.

The left and right keys autorepeat if held in. That is, the left

key when pressed and held in keeps advancing to the next digit to the left. The same is true for the right key except, of course, it advances to the right.

The increment and decrement keys (indicated by the up and

down arrows) increment and decrement the modify (bright) digit and therefore the displayed value. The modify digit is modified by one unit each time the increment or decrement

Table 3-4. Front Panel Messages

key is pressed. The increment/decrement keys are autorepeating. That is, pressing and holding in the increment key increments the display continually until the range limit is reached or the key is released. The same is true for the decrement key.

The incremenl key has the mathematical carry capability. This means that if the modify digit is a 9, pressing the increment key once sets the modify digit to 0 and the next significant digit is increased by one. If the display is at the maximum (IOIO), pressing the increment key causes an error message Lo be displayed for approximately one second. Refer

to Tables J-4,3-5 and 3-6 for front panel messages and Table 3-7 for the power up default conditions. The display then

returns to the previous condition.

Mssaage

Left Display

buF

-5

+15

-15

+115

-115

- 500 + 900

+ 1000

CAL

CAL CAL CAL

IEEE

buF

“0

Massage

ight Dlsplar

Err

Err Err Err Err Err Err Err Err

Err Err1 Err2 Err3 Err4

AdFb

Err

Pro

Err

End

IddC

IddCo

Comments Bad data was copied from the memory buffers.

+ 5V analog supply is outside of a f 50% range.

-5V analog supply is outside of a ~50% range. + 15V analog supply is outside of a f50% range.

- 15V analog supply is outside of a f50% range. + 115V analog supply is outside of a f 50% range.

- 115V analog supply is outside of a f50% range. Temperature sensor is not operating properly. Heat sink temperature has increased past 90°C. Turn sink mode on.

Temperature exceeds 100°C. The Model 228 turns off the switching supply and locks up the front panel. Turn off power and let it cool down.

Calibration error. Autocalibration cannot be performed. Voltage DAC (Digital to Analog Converter) gain is out of cal range.

Calibration error. Auto calibration cannot be performed. Voltage DAC (Digital to Analog Converter) offset is out of cal range.

Calibration error. Auto calibration cannot be performed. Current DAC (Digital to Analog Converters) gain is out of cal range.

Calibration error. Auto calibration cannot be performed. Current DAC (Digital to Analog Converter) offset is out of cal range.

No data transmits across the opt@isolators.

AID error. The AID does not read the 1V reference and ground properly.

No program exists. Illegal program number attempted. IEEE address error. An attempt to enter an illegal IEEE address was made.

The range of IEEE addresses is O-31.

Buffer end. The end of memory locations is reached. Maximum of 100 locations.

Illegal Device-Dependent Command

Illegal Device-Dependent Command Option No remote. The instrument wss not in remote when programmed.

3-9

Table 3-6. Front Panel Messages and Prompts

Message

.eft Display Right Display Comments

IEEE

Message

IEEE address, Address 11 shown. Front panel Program 3 activated or power

up sequence. rEU Pro 7

CAL

Software revision level. Revision A shown.

Prompt to enter the number of the desired front panel program.

Calibration, The Model 228 is going through the autocalibration sequence.

The Model 229 counts down from 20 to 0 during this sequence. This se-

quence may be bypassed by pressing the CANCEL key. However, the

previous cal will be valid.

U U

I Sill Sln

COP

Off

on OFF 002 Copy program enabled. Contents of memory location 1 duplicated into

External modulate V program is on. External modulate V program is off. External modulate I program is on. External modulate I program is off. Sink program on. Sink program off.

memory location 2.

Table 3-6. Error Messages (Either Display)*

Message Comments

oFL

Overflow. Attempt to output beyond the present range. Reading exceeds 1999 on any range.

Range. Attempt to program beyond the present range. Illegal range combination.

Err

Error. Exceeded 1010 limit or attempt to program below zero.

‘NOTE: These messages appear on the display where the error occurred.

3-g

Table 3-7. Power Up Default Conditions

Mode Value Status Display

DO Left Display=Volts, Right Display= Amps. Left Display ready for edit. Function FO Standby (output programmed to +4 counts on present range) Data Format

GO Prefix of buffer location contents. EOI KO Send EOI. SRQ

MO Disabled Program Mode PO Single Step Mode. Range Trigger Terminator

RO Autorange

T6 Stop on X

CR LF Carriage Return Line Feed

Buffer Location BOO1 Location #I

Voltage V

Current I Dwell Time w Sink Mode S External Modulation A

Program 1

Copy Disabled

Program 2

Dependent on previously programmed values of memory location I. Dependent on previously programmed values of memory location I. Dependent on previously programmed values of memon/ location 1, Dependent on previously programmed values of memory location I. Dependent on previously programmed values of memory locetion I. Dependent on previously programmed values of memory location I.

Sink Dependent on previously programmed values of memory location 1,

Program 3 IEEE Not affected

Program 4 Program 5 Porgram 6

Mod V Dependent on previously programmed values of memory location 1.

Mod I Dependent on previously programmed values of memory location 1.

Test Jl if passed; in status byte

J2 if failed; in status byte

Program 9 Reset Disabled

The decrement key has the mathematical borrow capability. This means that if the modify digit is 0, pressing the decrement key sets the modify digit to 9 and the next significant digit is decreased by one unit. If the display is 0000, pressing the decrement key causes an error message to be displayed for approximately one second. The display then returns to the previous condition.

Using the increment and decrement keys to change the sign of the displayed value causes and error message to be displayed for approximately one second. The display then returns to the previous condition.

The DECADE keys operate in the immediate mode. In the immediate mode, the output value is updated as the display is

3-10

updated. For example: If 95.OV is displayed and present on

the output, selecting the 5 digit and pressing the increment key increases the display to 96.OV. At the same time, the output is also changed to 96.OV.

ENTER-The ENTER key loads the displayed data into the present memory location. Pressing the ENTER key after modifying the displayed data, loads the new data into the present memory location. The display then reverts to normal intensity and the display modifying operation (edit) is terminated. The DATA keys do not affect the output until the ENTER key is pressed.

DATA GROUP

START/STOP-The START/STOP key serves three functions that are described as follows:

1. When the START/STOP key is pressed,

the selected

memory control mode (Single Step, Single Cycle or Con-

tinuous) is started.

2. Pressing the START/STOP key while the memory control mode is running stops

present memory location.

the memory control mode at the

3. In the single step memory control mode, pressing the

START/STOP key advances the instrument to the next programmed memory location.

The START/STOP LED is turned on while the single cycle

and continuous cle.

In the

memory control mode is going through its cy-

single step memory control mode, the START/ STOP LED is turned off for the duration of the programmed dwell time of the memory location.

DATA-The DATA keys have dual functions. In the enter

mode, these keys enter the desired number on the display. In the program mode, the keys activate the desired program. The front panel programs are described

paragraph 3.11. Entering data on the display using the DATA keys always start with the left most (most significant) digit on the display.,

MEMORY CONTROL GROUP

MEMORY CONTROL

STOP

[

STARl

When the Model 228 is in

the

standby mode (OPERATE LED is turned off) and either the single cycle or continuous memory control mode, the START/STOP key continues to control the buffer with no output present on output terminals, For example: The continuous mode keeps going on its cycle even though the Model 228 is in the standby

(STANDBY LED

on).

mode

SINGLE STEP-In the single step mode (SINGLE STEP LED is on), the memory

location

is advanced by one step each time the START/STOP key is pressed or the proper external trigger pulse is received. The voltage , current and dwell time may

different for each memory location. That is, the user

defines these parameters for each memory location.

At the completion of the programmed dwell time a pulse is sent out via the external trigger output connector. The START/STOP LED is turned off at this time. The pulse is a negative going TTL level pulse with a duration of greater than 10psec. The pulse could be used to trigger another instrument into its special function (e.g. chart recorder, DMM, etc).

Pressing the SINGLE STEP key when in the last programmed memory location and the single step mode causes the Model

228 to revert to memory location 1.

SINGLE STEP

f, SINGLE CYCLI

0 CONTINUOUS

A zero dwell time for any memory location causes the Model

228 to jump to memory location 1.

3-11

SINGLE CYCLE-In the single cycle mode (SINGLE CYCLE LED is on), and upon actuation of the START/STOP key or

upon receiving a proper external trigger pulse, the Model 228

advances to the next memory location. After the duration of

the dwell time for the memory location the Model 228 ad-

vances to

turned on. This cycle continues advancing through the pro-

grammed memory location until

tion is reached or stops at last memory location before zero dwell time. Pressing the START/STOP key jumps the Model 228 to memory location 1.

The voltage, current and dwell time parameters may be different for each memory location. That is, the user defines

these three parameters.

the

next memory location. START/STOP LED is

the last

programmed loca-

PROGRAM GROUP

PROGRAM CONTROL

PROGRAM

CANCEL

At the completion of each programmed dwell time, the Model 228 outputs a negative going TTL level pulse of greater than 10~s~ in duration. The pulse appears at the external trigger output connector on the rear panel. This pulse could be used to trigger another instrument into operation (e.g. DMM, con-

troller, etc.)

CONTINUOUS-In the continuous mode (CONTINUOUS LED is on) and upon actuation of the START/STOP key or after the proper external trigger pulse is received, the Model 228 advances to the next programmed memory location. After the duration of the present memory location the Model 228 advances to the next programmed memory location and remains there for its programmed dwell time. This cycle con-

tinues until the last programmed memory location is reached or a memory location with a zero dwell time is reached. At this point the Model 228 jumps to memory location 1. The cycle then repeats and continues repeating until it is stopped.

The voltage, current and dwell time parameters may be dif-

ferent for each memory location. That is, the user defines these three parameters. Just like the single step and single cy-

cle modes, in the continuous mode a negative going TTL level

pulse of greater than 10fisec appears at the external trigger output connector upon completion of each programmed dwell time. This pulse could be used to trigger another instru-

ment into its function in the system (e.g. start measurement cycle on DMM, inform a controller that the dwell time is ended, etc.). A zero dwell time for any memory location reverts

the Model 228 to memory location 1.

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

CANCEL-The CANCEL key has two levels of operation and they are described as follows:

1. Pressing the CANCEL key when a front panel program is running terminates the program mode and reverts the Model 228 to the previous mode of operation.

2. Pressing the CANCEL key during the entry of data in any of the programs, reverts the new data to the previous data, terminates the program and then terminates the program mode. The instrument is then reverted to the previous

mode of operation.

COMPLIANCE Graph-The COMPLIANCE graph indicates

the

state of the output. Refer to the front panel and/or following Figure. By noting the front panel COMPLIANCE graph four parameters concerning the output are known.

1. The polarity of the voltage.

2. The polarity of the current.

3. The controlling function (Voltage or Current)

4. Operation as a sink or source.

For example: If the LED just above the +I ( +Imd symbol is turned on, then four parameters are known.

1. The polarity of the voltage positive.

2. The polarity of the current is positive,

3. The controlling function is current.

4. The instrument is operating as a source.

3-12

The reason that the current is the controlling function is that

the line for that LED goes through the +I axis the current is

constant and the voltage is the parameter that varies. For line

intersecting the voltage axis it is the voltage that is the controlling function and the current is the parameter that varies.

LOCAL-In the remote mode (IEEE-488 bus operation) of

operation all front panel controls except LOCAL and

POWER ON/OFF are disabled. Pressing the LOCAL key

takes the Model 228 out of the remote mode and enables all of the front panel controls.

As another example consider that the LED just to the right of the -V(-VS~NK) symbol is turned on. As in the previous example, four parameters are known by noting the COMPLIANCE graph.

1. The polarity of the voltage is negative

2. The polarity of the current is positive.

3. Voltage is the controlling function.

4. The instrument is operating as an active load (current

-”

REMOTE LED-When the REMOTE LED is on, the Model 228 is in the remote mode of operation (IEEE-488 bus operation). When the REMOTE LED is off, the Model 228 is in the local mode of operation. Refer to Section 4 for more information concerning IEEE-486 bus operation.

TALK LED-When the TALK LED is on, the Model 228 is in the talk mode. Refer to Section 4 for more information concerning IEEE-bus operation.

LISTEN LED-When the LISTEN LED is on, the Model 228 is in the listen mode, Refer to Section 4 for more information concerning IEEE-488 bus operation.

MODULATE I-When the MODULATE I LED is on, external current modulation is enabled. An external AC signal can be superimposed on the ouput current through the external modulation connector on the rear panel. This assumes that current is the controlling function. Current is the controlling function when the Model 228 voltage (V) setting is greater than the product of the Model 228 current (I) setting and the user load.

MODULATE V-When the MODULATE V LED is on, the Model 228 is in the voltage modulation mode. An external AC signal up to the specified limits may be superimposed on

the output voltage through the quick disconnect board on the rear panel. This assumes that voltage is the controlling func-

tion. Voltage is the controlling function when the Model 228 voltage (V) setting is less than the product of the Model 228 current (I) setting and the user load.

STATUS GROUP

ILOCAL 0 REMOTE 1

------I

STATVS

0 TALK

0 MODULATE I

0 MODULATE V 0 SINK ONLY

q LlSTEN

SINK ONLY-When the SINK ONLY LED is on, the Model 228 is in the sink mode of operation. Take note of the front panel COMPLIANCE graph. The COMPLIANCE graph in-

dicates which quadrant of sink mode the Model 228 is

operating.

3.13

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